WorldWideScience

Sample records for relaxation properties t1

  1. Amide proton transfer (APT) imaging of brain tumors at 7 T : The role of tissue water T1 -Relaxation properties

    NARCIS (Netherlands)

    Khlebnikov, V; Polders, Daniel; Hendrikse, J; Robe, Pierre A.; Voormolen, Eduard H; Luijten, Peter R; Klomp, DWJ; Hoogduin, Hans

    PURPOSE: To provide insight into the effect of water T1 relaxation (T1wat ) on amide proton transfer (APT) contrast in tumors. Three different metrics of APT contrast-magnetization transfer ratio (MTRRex ), relaxation-compensated MTRRex (AREX), and traditional asymmetry (MTRasym )-were compared in

  2. NMR relaxation in natural soils: Fast Field Cycling and T1-T2 Determination by IR-MEMS

    Science.gov (United States)

    Haber-Pohlmeier, S.; Pohlmeier, A.; Stapf, S.; van Dusschoten, D.

    2009-04-01

    Soils are natural porous media of highest importance for food production and sustainment of water resources. For these functions, prominent properties are their ability of water retainment and transport, which are mainly controlled by pore size distribution. The latter is related to NMR relaxation times of water molecules, of which the longitudinal relaxation time can be determined non-invasively by fast-field cycling relaxometry (FFC) and both are obtainable by inversion recovery - multi-echo- imaging (IR-MEMS) methods. The advantage of the FFC method is the determination of the field dependent dispersion of the spin-lattice relaxation rate, whereas MRI at high field is capable of yielding spatially resolved T1 and T2 times. Here we present results of T1- relaxation time distributions of water in three natural soils, obtained by the analysis of FFC data by means of the inverse Laplace transformation (CONTIN)1. Kaldenkirchen soil shows relatively broad bimodal distribution functions D(T1) which shift to higher relaxation rates with increasing relaxation field. These data are compared to spatially resolved T1- and T2 distributions, obtained by IR-MEMS. The distribution of T1 corresponds well to that obtained by FFC.

  3. Quantitative Study of Longitudinal Relaxation (T 1) Contrast Mechanisms in Brain MRI

    Science.gov (United States)

    Jiang, Xu

    Longitudinal relaxation (T1) contrast in MRI is important for studying brain morphology and is widely used in clinical applications. Although MRI only detects signals from water hydrogen ( 1H) protons (WPs), T1 contrast is known to be influenced by other species of 1H protons, including those in macromolecules (MPs), such as lipids and proteins, through magnetization transfer (MT) between WPs and MPs. This complicates the use and quantification of T1 contrast for studying the underlying tissue composition and the physiology of the brain. MT contributes to T1 contrast to an extent that is generally dependent on MT kinetics, as well as the concentration and NMR spectral properties of MPs. However, the MP spectral properties and MT kinetics are both difficult to measure directly, as the signal from MPs is generally invisible to MRI. Therefore, to investigate MT kinetics and further quantify T1 contrast, we first developed a reliable way to indirectly measure the MP fraction and their exchange rate with WPs, with minimal dependence on the spectral properties of MPs. For this purpose, we used brief, highpower radiofrequency (RF) NMR excitation pulses to almost completely saturate the magnetization of MPs. Based on this, both MT kinetics and the contribution of MPs to T1 contrast through MT were studied. The thus obtained knowledge allowed us to subsequently infer the spectral properties of MPs by applying low-power, frequencyselective off-resonance RF pulses and measuring the offset-frequency dependent effect of MPs on the WP MRI signal. A two-pool exchange model was used in both cases to account for direct effects of the RF pulse on WP magnetization. Consistent with earlier works using MRI at low-field and post-mortem analysis of brain tissue, our novel measurement approach found that MPs constitute an up to 27% fraction of the total 1H protons in human brain white matter, and their spectrum follows a super-Lorentzian line with a T2 of 9.6+/-0.6 mus and a resonance

  4. Effects of pulmonary inhalation on hyperpolarized krypton-83 magnetic resonance T1 relaxation.

    Science.gov (United States)

    Stupic, K F; Elkins, N D; Pavlovskaya, G E; Repine, J E; Meersmann, T

    2011-07-07

    The (83)Kr magnetic resonance (MR) relaxation time T(1) of krypton gas in contact with model surfaces was previously found to be highly sensitive to surface composition, surface-to-volume ratio, and surface temperature. The work presented here explored aspects of pulmonary (83)Kr T(1) relaxation measurements in excised lungs from healthy rats using hyperpolarized (hp) (83)Kr with approximately 4.4% spin polarization. MR spectroscopy without spatial resolution was applied to the ex vivo lungs that actively inhale hp (83)Kr through a custom designed ventilation system. Various inhalation schemes were devised to study the influence of anatomical dead space upon the measured (83)Kr T(1) relaxation times. The longitudinal (83)Kr relaxation times in the distal airways and the respiratory zones were independent of the lung inhalation volume, with T(1) = 1.3 s and T(1) = 1.0 s, depending only on the applied inhalation scheme. The obtained data were highly reproducible between different specimens. Further, the (83)Kr T(1) relaxation times in excised lungs were unaffected by the presence of up to 40% oxygen in the hp gas mixture. The results support the possible importance of (83)Kr as a biomarker for evaluating lung function.

  5. Prolonged T1 relaxation of the hemopoietic bone marrow in patients with chronic leukemia

    International Nuclear Information System (INIS)

    Jensen, K.E.; Soerensen, P.G.; Thomsen, C.; Christoffersen, P.; Henriksen, O.; Karle, H.; Hvidovre Hospital; Hvidovre Hospital; Gentofte Hospital

    1990-01-01

    Eleven patients with chronic leukemia (7 with chronic lymphocytic leukemia and 4 with chronic myeloid leukemia) were evaluated with magnetic resonance (MR) imaging and T1 relaxation time measurements by use of a 1.5 tesla whole body MR scanner. Bone marrow biopsies were obtained from the posterior iliac crest (within 72 hours of the MR examination) in order to provide data on bone marrow cellularity and differential counts. The patients with chronic leukemia all showed a significant prolongation of the T1 relaxation times compared with the normal range for hemopoietic bone marrow. (orig.)

  6. Prolonged bone marrow T1-relaxation in patients with polycythemia vera

    DEFF Research Database (Denmark)

    Jensen, K E; Grube, T; Thomsen, C

    1988-01-01

    In vitro as well as in vivo studies have shown prolonged T1 relaxation times in patients with acute leukemia. The mechanism behind this finding is not known. In order to evaluate if this was specific for leukemia we examined eight patients with polycythemia vera, representing a condition with a r......In vitro as well as in vivo studies have shown prolonged T1 relaxation times in patients with acute leukemia. The mechanism behind this finding is not known. In order to evaluate if this was specific for leukemia we examined eight patients with polycythemia vera, representing a condition...

  7. Prolonged T1 relaxation of the hemopoietic bone marrow in patients with chronic leukemia

    DEFF Research Database (Denmark)

    Jensen, K E; Sørensen, P G; Thomsen, C

    1990-01-01

    Eleven patients with chronic leukemia (7 with chronic lymphocytic leukemia and 4 with chronic myeloid leukemia) were evaluated with magnetic resonance (MR) imaging and T1 relaxation time measurements by use of a 1.5 tesla whole body MR scanner. Bone marrow biopsies were obtained from the posterior...

  8. TOMROP: a sequence for determining the longitudinal relaxation time T1 in NMR

    International Nuclear Information System (INIS)

    Graumann, R.; Barfuss, H.; Fischer, H.; Hentschel, D.; Oppelt, A.

    1987-01-01

    We developed the pulse sequence TOMROP (T One by Multiple Read Out Pulses) for determining precisely the spatial distribution of the longitudinal relaxation time T 1 in nuclear magnetic resonance (NMR): a series of small-angle selection pulses is used to read out longitudinal magnetization from its initial state till thermal equilibrium. Hence, one measurement will produce several images with different T 1 weightings whose pixel brilliance depends exponentially from read-out time. T 1 can be determined from these independent of initial magnetization and selection pulse angle. The measuring time corresponds to the time needed in multi-echo imaging for the determination of the transversal relaxation time T 2 . We demonstrate this new method using head images of volunteers produced with a 0.23 T test facility. (orig./HP) [de

  9. The interplay of T1- and T2-relaxation on T1-weighted MRI of hMSCs induced by Gd-DOTA-peptides.

    Science.gov (United States)

    Cao, Limin; Li, Binbin; Yi, Peiwei; Zhang, Hailu; Dai, Jianwu; Tan, Bo; Deng, Zongwu

    2014-04-01

    Three Gd-DOTA-peptide complexes with different peptide sequence are synthesized and used as T1 contrast agent to label human mesenchymal stem cells (hMSCs) for magnetic resonance imaging study. The peptides include a universal cell penetrating peptide TAT, a linear MSC-specific peptide EM7, and a cyclic MSC-specific peptide CC9. A significant difference in labeling efficacy is observed between the Gd-DOTA-peptides as well as a control Dotarem. All Gd-DOTA-peptides as well as Dotarem induce significant increase in T1 relaxation rate which is in favor of T1-weighted MR imaging. Gd-DOTA-CC9 yields the maximum labeling efficacy but poor T1 contrast enhancement. Gd-DOTA-EM7 yields the minimum labeling efficacy but better T1 contrast enhancement. Gd-DOTA-TAT yields a similar labeling efficacy as Gd-DOTA-CC9 and similar T1 contrast enhancement as Gd-DOTA-EM7. The underlying mechanism that governs T1 contrast enhancement effect is discussed. Our results suggest that T1 contrast enhancement induced by Gd-DOTA-peptides depends not only on the introduced cellular Gd content, but more importantly on the effect that Gd-DOTA-peptides exert on the T1-relaxation and T2-relaxation processes/rates. Both T1 and particularly T2 relaxation rate have to be taken into account to interpret T1 contrast enhancement. In addition, the interpretation has to be based on cellular instead of aqueous longitudinal and transverse relaxivities of Gd-DOTA-peptides. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Instrumentation problems in the measurement of relaxation time T1 in MRI

    International Nuclear Information System (INIS)

    Leroy-Willig, A.; Roucayrol, J.C.; Bittoun, J.; Courtieu, J.

    1986-01-01

    Longitudinal relaxation (T 1 ) of protons is a sensitive though non specific tool of tissue characterization. T 1 measurement from magnetic resonance images is unprecise, due to several phenomena that we review: time intervals shorter than in spectroscopic sequences; flip angle inhomogeneity; slice selection and spin echoes. In vivo the molecular inhomogeneity can prevent to measure a true T 1 ; motion and blood flow are important causes of errors. The relative effects of these factors are examined from in vitro and in vivo images acquired at 1.5 T. From a mono-echo single-slice saturation sequence reliable values of T 1 are obtained in vitro, the measurement time being compatible with clinical imaging. In vivo, problems due to various causes of motions are still unresolved [fr

  11. Molecular order and T1-relaxation, cross-relaxation in nitroxide spin labels

    Science.gov (United States)

    Marsh, Derek

    2018-05-01

    Interpretation of saturation-recovery EPR experiments on nitroxide spin labels whose angular rotation is restricted by the orienting potential of the environment (e.g., membranes) currently concentrates on the influence of rotational rates and not of molecular order. Here, I consider the dependence on molecular ordering of contributions to the rates of electron spin-lattice relaxation and cross relaxation from modulation of N-hyperfine and Zeeman anisotropies. These are determined by the averages and , where θ is the angle between the nitroxide z-axis and the static magnetic field, which in turn depends on the angles that these two directions make with the director of uniaxial ordering. For saturation-recovery EPR at 9 GHz, the recovery rate constant is predicted to decrease with increasing order for the magnetic field oriented parallel to the director, and to increase slightly for the perpendicular field orientation. The latter situation corresponds to the usual experimental protocol and is consistent with the dependence on chain-labelling position in lipid bilayer membranes. An altered dependence on order parameter is predicted for saturation-recovery EPR at high field (94 GHz) that is not entirely consistent with observation. Comparisons with experiment are complicated by contributions from slow-motional components, and an unexplained background recovery rate that most probably is independent of order parameter. In general, this analysis supports the interpretation that recovery rates are determined principally by rotational diffusion rates, but experiments at other spectral positions/field orientations could increase the sensitivity to order parameter.

  12. In vivo measurements of T1 relaxation times of 31P-metabolites in human skeletal muscle

    DEFF Research Database (Denmark)

    Thomsen, C; Jensen, K E; Henriksen, O

    1989-01-01

    The T1 relaxation times were estimated for 31P-metabolites in human skeletal muscle. Five healthy volunteers were examined in a 1.5 Tesla wholebody imaging system using an inversion recovery pulse sequence. The calculated T1 relaxation times ranged from 5.517 sec for phosphocreatine to 3.603 sec...

  13. T1 nuclear magnetic relaxation dispersion of hyperpolarized sodium and cesium hydrogencarbonate-13 C.

    Science.gov (United States)

    Martínez-Santiesteban, Francisco M; Dang, Thien Phuoc; Lim, Heeseung; Chen, Albert P; Scholl, Timothy J

    2017-09-01

    In vivo pH mapping in tissue using hyperpolarized hydrogencarbonate- 13 C has been proposed as a method to study tumor growth and treatment and other pathological conditions related to pH changes. The finite spin-lattice relaxation times (T 1 ) of hyperpolarized media are a significant limiting factor for in vivo imaging. Relaxation times can be measured at standard magnetic fields (1.5 T, 3.0 T etc.), but no such data are available at low fields, where T 1 values can be significantly shorter. This information is required to determine the potential loss of polarization as the agent is dispensed and transported from the polarizer to the MRI scanner. The purpose of this study is to measure T 1 dispersion from low to clinical magnetic fields (0.4 mT to 3.0 T) of different hyperpolarized hydrogencarbonate formulations previously proposed in the literature for in vivo pH measurements. 13 C-enriched cesium and sodium hydrogencarbonate preparations were hyperpolarized using dynamic nuclear polarization, and the T 1 values of different samples were measured at different magnetic field strengths using a fast field-cycling relaxometer and a 3.0 T clinical MRI system. The effects of deuterium oxide as a dissolution medium for sodium hydrogencarbonate were also analyzed. This study finds that the cesium formulation has slightly shorter T 1 values compared with the sodium preparation. However, the higher solubility of cesium hydrogencarbonate- 13 C means it can be polarized at greater concentration, using less trityl radical than sodium hydrogencarbonate- 13 C. This study also establishes that the preparation and handling of sodium hydrogencarbonate formulations in relation to cesium hydrogencarbonate is more difficult, due to the higher viscosity and lower achievable concentrations, and that deuterium oxide significantly increases the T 1 of sodium hydrogencarbonate solutions. Finally, this work also investigates the influence of pH on the spin-lattice relaxation of cesium

  14. In vivo measurements of the T1 relaxation processes in the bone marrow in patients with myelodysplastic syndrome

    International Nuclear Information System (INIS)

    Jensen, K.E.; Nielsen, H.; Thomsen, C.; Soerensen, P.G.; Karle, H.; Christoffersen, P.; Henriksen, O.; Hvidovre Hospital, Copenhagen; Hvidovre Hospital, Copenhagen

    1989-01-01

    Nine patients with myelodysplastic syndrome (MDS) were examined with magnetic resonance imaging and in vivo T1 relaxation time measurements of the vertebral bone marrow in a 1.5 tesla whole body scanner. Two patients underwent transformation to acute myeloid leukemia and were evaluated at follow-up examinations. At the time of diagnosis the T1 relaxation times of the vertebral bone marrow were significantly prolonged compared with normal values. The T1 relaxation times of the vertebral bone marrow in patients with MDS showed significantly lower values compared with patients with acute leukemia and did not differ from patients with polycythemia vera. (orig.)

  15. TU-EF-BRA-02: Longitudinal Proton Spin Relaxation and T1-Imaging

    International Nuclear Information System (INIS)

    Lemen, L.

    2015-01-01

    NMR, and Proton Density MRI of the 1D Patient - Anthony Wolbarst Net Voxel Magnetization, m(x,t). T1-MRI; The MRI Device - Lisa Lemen ‘Classical’ NMR; FID Imaging in 1D via k-Space - Nathan Yanasak Spin-Echo; S-E/Spin Warp in a 2D Slice - Ronald Price Magnetic resonance imaging not only reveals the structural, anatomic details of the body, as does CT, but also it can provide information on the physiological status and pathologies of its tissues, like nuclear medicine. It can display high-quality slice and 3D images of organs and vessels viewed from any perspective, with resolution better than 1 mm. MRI is perhaps most extraordinary and notable for the plethora of ways in which it can create unique forms of image contrast, reflective of fundamentally different biophysical phenomena. As with ultrasound, there is no risk from ionizing radiation to the patient or staff, since no X-rays or radioactive nuclei are involved. Instead, MRI harnesses magnetic fields and radio waves to probe the stable nuclei of the ordinary hydrogen atoms (isolated protons) occurring in water and lipid molecules within and around cells. MRI consists, in essence, of creating spatial maps of the electromagnetic environments around these hydrogen nuclei. Spatial variations in the proton milieus can be related to clinical differences in the biochemical and physiological properties and conditions of the associated tissues. Imaging of proton density (PD), and of the tissue proton spin relaxation times known as T1 and T2, all can reveal important clinical information, but they do so with approaches so dissimilar from one another that each is chosen for only certain clinical situations. T1 and T2 in a voxel are determined by different aspects of the rotations and other motions of the water and lipid molecules involved, as constrained by the local biophysical surroundings within and between its cells – and they, in turn, depend on the type of tissue and its state of health. Three other common

  16. TU-EF-BRA-02: Longitudinal Proton Spin Relaxation and T1-Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Lemen, L. [Univ Cincinnati (United States)

    2015-06-15

    NMR, and Proton Density MRI of the 1D Patient - Anthony Wolbarst Net Voxel Magnetization, m(x,t). T1-MRI; The MRI Device - Lisa Lemen ‘Classical’ NMR; FID Imaging in 1D via k-Space - Nathan Yanasak Spin-Echo; S-E/Spin Warp in a 2D Slice - Ronald Price Magnetic resonance imaging not only reveals the structural, anatomic details of the body, as does CT, but also it can provide information on the physiological status and pathologies of its tissues, like nuclear medicine. It can display high-quality slice and 3D images of organs and vessels viewed from any perspective, with resolution better than 1 mm. MRI is perhaps most extraordinary and notable for the plethora of ways in which it can create unique forms of image contrast, reflective of fundamentally different biophysical phenomena. As with ultrasound, there is no risk from ionizing radiation to the patient or staff, since no X-rays or radioactive nuclei are involved. Instead, MRI harnesses magnetic fields and radio waves to probe the stable nuclei of the ordinary hydrogen atoms (isolated protons) occurring in water and lipid molecules within and around cells. MRI consists, in essence, of creating spatial maps of the electromagnetic environments around these hydrogen nuclei. Spatial variations in the proton milieus can be related to clinical differences in the biochemical and physiological properties and conditions of the associated tissues. Imaging of proton density (PD), and of the tissue proton spin relaxation times known as T1 and T2, all can reveal important clinical information, but they do so with approaches so dissimilar from one another that each is chosen for only certain clinical situations. T1 and T2 in a voxel are determined by different aspects of the rotations and other motions of the water and lipid molecules involved, as constrained by the local biophysical surroundings within and between its cells – and they, in turn, depend on the type of tissue and its state of health. Three other common

  17. Changes in T1 relaxation processes in the bone marrow following treatment in children with acute lymphoblastic leukemia

    International Nuclear Information System (INIS)

    Jensen, K.E.; Thomsen, C.; Henriksen, O.; Hertz, H.; Johansen, H.K.; Yssing, M.

    1990-01-01

    Magnetic resonance imaging (MRI) and T 1 relaxation time measurements of the vertebral bone marrow were performed in 11 children with acute lymphoblastic leukemia (ALL) at diagnosis. Nine of the children were re-examined after chemotherapeutic treatment. The results were compared with histological data from bone marrow biopsies obtained in close association to the MR examinations. Ten age matched children were examined as a control group. A 1.5 Tesla whole body scanner was used for the measurements. The pretreatment T 1 relaxation times of the bone marrow were significantly prolonged, compared to the age matched controls. After chemotherapy the T 1 relaxation times of the children with ALL decreased significantly towards or into the normal range. A significant correlation was found between the T 1 relaxation time and the content of malignant blast cells in the bone marrow. (orig.)

  18. Prolonged bone marrow T1-relaxation in acute leukaemia. In vivo tissue characterization by magnetic resonance imaging

    DEFF Research Database (Denmark)

    Thomsen, C; Sørensen, P G; Karle, H

    1987-01-01

    In vivo tissue characterization by measurement of T1- and T2-relaxation processes is one of the greatest potentials of magnetic resonance imaging (MRI). This may be especially useful in the evaluation of bone marrow disorders as the MRI-signal from bone marrow is not influenced by the overlying...... osseous tissue. Nine patients with acute leukaemia, one patient with myelodysplastic syndrome, and ten normal volunteers were included in the study. The T1- and T2-relaxation processes were measured in the lumbar spine bone marrow using a wholebody superconductive MR-scanner operating at 1.5 Tesla.......38-0.60 sec.). No significant difference was seen in the T2-relaxation process. In relation to chemotherapy T1 decreased towards the normal range in the patients who obtained complete remission, whereas T1 remained prolonged in the patients who did not respond successfully to the treatment. The results...

  19. Intraindividual comparison of T1 relaxation times after gadobutrol and Gd-DTPA administration for cardiac late enhancement imaging

    Energy Technology Data Exchange (ETDEWEB)

    Doeblin, Patrick, E-mail: Patrick.doeblin@charite.de [Department of Cardiology, Charité – Universitätsmedizin Berlin, Charité Campus Benjamin Franklin, Berlin (Germany); Schilling, Rene, E-mail: rene.schilling@charite.de [Department of Radiology, Charité – Universitätsmedizin Berlin, Charité Campus Mitte, Berlin (Germany); Wagner, Moritz, E-mail: moritz.wagner@charite.de [Department of Radiology, Charité – Universitätsmedizin Berlin, Charité Campus Mitte, Berlin (Germany); Luhur, Reny, E-mail: renyluhur@yahoo.com [Department of Radiology, Charité – Universitätsmedizin Berlin, Charité Campus Mitte, Berlin (Germany); Huppertz, Alexander, E-mail: alexander.huppertz@charite.de [Department of Radiology, Charité – Universitätsmedizin Berlin, Charité Campus Mitte, Berlin (Germany); Imaging Science Institute, Charité, Berlin (Germany); Hamm, Bernd, E-mail: bernd.hamm@charite.de [Department of Radiology, Charité – Universitätsmedizin Berlin, Charité Campus Mitte, Berlin (Germany); Taupitz, Matthias, E-mail: matthias.taupitz@harite.de [Department of Radiology, Charité – Universitätsmedizin Berlin, Charité Campus Mitte, Berlin (Germany); and others

    2014-04-15

    Purpose: To evaluate T1-relaxation times of chronic myocardial infarction (CMI) using gadobutrol and gadopentetate dimeglumine (Gd-DTPA) over time and to determine the optimal imaging window for late enhancement imaging with both contrast agents. Material and methods: Twelve patients with CMI were prospectively included and examined on a 1.5 T magnetic resonance (MR) system using relaxivity-adjusted doses of gadobutrol (0.15 mmol/kg) and Gd-DTPA (0.2 mmol/kg) in random order. T1-relaxation times of remote myocardium (RM), infarcted myocardium (IM), and left ventricular cavity (LVC) were assessed from short-axis TI scout imaging using the Look–Locker approach and compared intraindividually using a Wilcoxon paired signed-rank test (α < 0.05). Results: Within 3 min of contrast agent administration (CA), IM showed significantly lower T1-relaxation times than RM with both contrast agents, indicating beginning cardiac late enhancement. Differences between gadobutrol and Gd-DTPA in T1-relaxation times of IM and RM were statistically not significant through all time points. However, gadobutrol led to significantly higher T1-relaxation times of LVC than Gd-DTPA from 6 to 9 min (220 ± 15 ms vs. 195 ± 30 ms p < 0.01) onwards, resulting in a significantly greater ΔT1 of IM to LVC at 9–12 min (−20 ± 35 ms vs. 0 ± 35 ms, p < 0.05) and 12–15 min (−25 ± 45 ms vs. −10 ± 60 ms, p < 0.05). Using Gd-DTPA, comparable ΔT1 values were reached only after 25–35 min. Conclusion: This study indicates good delineation of IM to RM with both contrast agents as early as 3 min after administration. However, we found significant differences in T1 relaxation times with greater ΔT1 IM–LVC using 0.15 mmol/kg gadobutrol compared to 0.20 mmol/kg Gd-DTPA after 9–15 min post-CA suggesting earlier differentiability of IM and LVC using gadobutrol.

  20. Structural relaxation: low temperature properties

    International Nuclear Information System (INIS)

    Cruz, F. de la

    1984-01-01

    We discuss the changes in transport and superconducting properties of amorphous Zr 70 Cu 30 , induced by thermal relaxation. The experimental results are used to investigate the relation between the microscopic parameters and the observed physical properties. It is shown that the density of eletronic states determines the shift Tc as well as the variation of the electrical resistivity. It is necessary to assume strong hybridization between s and d bands to understand the eletrodynamic response of the superconductor. (Author) [pt

  1. In-vivo measurement of proton relaxation time (T1 and T2) in paediatric brain by MRI

    International Nuclear Information System (INIS)

    Masumura, Michio

    1986-01-01

    The clinical application of MRI led to the detailed imaging of the three-dimentional structure of the brain. Thus, significant information has been obtained with respect to the diagnosis of various diseases, rating severity, evaluation of curative effects, etc. On the other hand, the proportion of the comparative length of the relaxation time to the signal intensity of the images (especially the Spin-Echo image) was not necessarily linear. Consquently, the evaluation of severity was not easy to make. However, if we can obtain T 1 and T 2 precisely as the parameters costituting the images, it will be possible to overcome the above-mentioned difficulties. Further, the usefulness of MRI in activities such as determining the water metabolism of the brain is expected to increase even more. By means of VISTA-MR (0.15 Tesla, resistive magnet ; Picker International Co.) we measured the proton relaxation time (spin-lattice relaxation time (T 1 ) and spin-spin relaxation time (T 2 )) of various intracerebral lesions in paediatric cases. As the control group, 43 children, 4 adolescents and 6 adults were used. The T 1 and T 2 in the normal infantile cases prolonged significantly as compared with adult case. Thereafter, they become shortened by aging. In the age of two or three years, they reach the normal level of adult case. In the cases of degenerative disease, brain tumor, and cerebral contusion, the remarkable prolongation of both T 1 and T 2 , compared with normal value of the same age was observed. In the cases of brain atrophy and epilepsy, T 1 and T 2 were slightly short or within normal value of the same age. In the cases of intracerebral hemorrhage, T 1 was shortened. The in-vivo proton relaxation time obtained by MRI have various limits, but they can be a noninvasive and useful index in evaluation of severity or curative effects in various cerebral diseases. (author)

  2. The influence of temperature, viscosity and pH on the relaxation time T1 in flowing liquids

    International Nuclear Information System (INIS)

    Toczylowska, B.

    1995-01-01

    The designed and constructed at the Institute of Biocybernetics and Biomedical Engineering facility for the relaxation time (T 1 ) measurements of liquids flow has been presented. The influence of temperature, viscosity and pH has been determined for several liquids, especially physiological fluids

  3. Medial meniscal posterior root/horn radial tears correlate with cartilage degeneration detected by T1ρ relaxation mapping

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Kenji, E-mail: Kenji-am@nms.ac.jp [Department of Orthopaedic Surgery, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603 (Japan); Hashimoto, Sanshiro, E-mail: info@msorc.jp [Minami-Shinjuku Orthopaedic Rehabilitation Clinic, 2-16-7 Yoyogi, Shibuya-ku, Tokyo 151-0053 (Japan); Nakamura, Hiroshi, E-mail: nakamura@nms.ac.jp [Department of Orthopaedic Surgery, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603 (Japan); Mori, Atsushi, E-mail: atsu@nms.ac.jp [Department of Orthopaedic Surgery, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603 (Japan); Sato, Akiko, E-mail: akiko-sato@nms.ac.jp [Department of Orthopaedic Surgery, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603 (Japan); Majima, Tokifumi, E-mail: tkmajima@iuhw.ac.jp [Department of Orthopaedic Surgery, International University of Health and Welfare Hospital, 537-3 Iguchi, Nasu-shiobara, Tochigi 329-2763 (Japan); Takai, Shinro, E-mail: takai-snr@nms.ac.jp [Department of Orthopaedic Surgery, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603 (Japan)

    2015-06-15

    Highlights: • Posterior radial tears in medial meniscus associate T1ρ values of cartilage. • Posterior radial tears relate to cartilage degeneration even in early-stage osteoarthritis. • Abnormalities in meniscus on MRI are useful for screening early-stage osteoarthritis. - Abstract: Objective: This study aimed to identify factors on routine pulse sequence MRI associated with cartilage degeneration observed on T1ρ relaxation mapping. Materials and methods: This study included 137 subjects with knee pain. T1ρ values were measured in the regions of interest on the surface layer of the cartilage on mid-coronal images of the femorotibial joint. Assessment of cartilage, subchondral bone, meniscus and ligaments was performed using routine pulse sequence MRI. Radiographic evaluation for osteoarthritis was also performed. Results: Multiple regression analysis revealed posterior root/horn tears to be independent factors increasing the T1ρ values of the cartilage in the medial compartment of the femorotibial joint. Even when adjusted for radiographically defined early-stage osteoarthritis, medial posterior meniscal radial tears significantly increased the T1ρ values. Conclusions: This study showed that posterior root/horn radial tears in the medial meniscus are particularly important MRI findings associated with cartilage degeneration observed on T1ρ relaxation mapping. Morphological factors of the medial meniscus on MRI provide findings useful for screening early-stage osteoarthritis.

  4. Medial meniscal posterior root/horn radial tears correlate with cartilage degeneration detected by T1ρ relaxation mapping

    International Nuclear Information System (INIS)

    Takahashi, Kenji; Hashimoto, Sanshiro; Nakamura, Hiroshi; Mori, Atsushi; Sato, Akiko; Majima, Tokifumi; Takai, Shinro

    2015-01-01

    Highlights: • Posterior radial tears in medial meniscus associate T1ρ values of cartilage. • Posterior radial tears relate to cartilage degeneration even in early-stage osteoarthritis. • Abnormalities in meniscus on MRI are useful for screening early-stage osteoarthritis. - Abstract: Objective: This study aimed to identify factors on routine pulse sequence MRI associated with cartilage degeneration observed on T1ρ relaxation mapping. Materials and methods: This study included 137 subjects with knee pain. T1ρ values were measured in the regions of interest on the surface layer of the cartilage on mid-coronal images of the femorotibial joint. Assessment of cartilage, subchondral bone, meniscus and ligaments was performed using routine pulse sequence MRI. Radiographic evaluation for osteoarthritis was also performed. Results: Multiple regression analysis revealed posterior root/horn tears to be independent factors increasing the T1ρ values of the cartilage in the medial compartment of the femorotibial joint. Even when adjusted for radiographically defined early-stage osteoarthritis, medial posterior meniscal radial tears significantly increased the T1ρ values. Conclusions: This study showed that posterior root/horn radial tears in the medial meniscus are particularly important MRI findings associated with cartilage degeneration observed on T1ρ relaxation mapping. Morphological factors of the medial meniscus on MRI provide findings useful for screening early-stage osteoarthritis

  5. Relaxation properties in classical diamagnetism

    Science.gov (United States)

    Carati, A.; Benfenati, F.; Galgani, L.

    2011-06-01

    It is an old result of Bohr that, according to classical statistical mechanics, at equilibrium a system of electrons in a static magnetic field presents no magnetization. Thus a magnetization can occur only in an out of equilibrium state, such as that produced through the Foucault currents when a magnetic field is switched on. It was suggested by Bohr that, after the establishment of such a nonequilibrium state, the system of electrons would quickly relax back to equilibrium. In the present paper, we study numerically the relaxation to equilibrium in a modified Bohr model, which is mathematically equivalent to a billiard with obstacles, immersed in a magnetic field that is adiabatically switched on. We show that it is not guaranteed that equilibrium is attained within the typical time scales of microscopic dynamics. Depending on the values of the parameters, one has a relaxation either to equilibrium or to a diamagnetic (presumably metastable) state. The analogy with the relaxation properties in the Fermi Pasta Ulam problem is also pointed out.

  6. Gadolinium-based magnetic resonance contrast agents at 7 Tesla: in vitro T1 relaxivities in human blood plasma.

    Science.gov (United States)

    Noebauer-Huhmann, Iris M; Szomolanyi, Pavol; Juras, Vladimír; Kraff, Oliver; Ladd, Mark E; Trattnig, Siegfried

    2010-09-01

    PURPOSE/INTRODUCTION: The aim of this study was to determine the T1 relaxivities (r1) of 8 gadolinium (Gd)-based MR contrast agents in human blood plasma at 7 Tesla, compared with 3 Tesla. Eight commercially available Gd-based MR contrast agents were diluted in human blood plasma to concentrations of 0, 0.25, 0.5, 1, and 2 mmol/L. In vitro measurements were performed at 37 degrees C, on a 7 Tesla and on a 3 Tesla whole-body magnetic resonance imaging scanner. For the determination of T1 relaxation times, Inversion Recovery Sequences with inversion times from 0 to 3500 ms were used. The relaxivities were calculated. The r1 relaxivities of all agents, diluted in human blood plasma at body temperature, were lower at 7 Tesla than at 3 Tesla. The values at 3 Tesla were comparable to those published earlier. Notably, in some agents, a minor negative correlation of r1 with a concentration of up to 2 mmol/L could be observed. This was most pronounced in the agents with the highest protein-binding capacity. At 7 Tesla, the in vitro r1 relaxivities of Gd-based contrast agents in human blood plasma are lower than those at 3 Tesla. This work may serve as a basis for the application of Gd-based MR contrast agents at 7 Tesla. Further studies are required to optimize the contrast agent dose in vivo.

  7. Relationship between aging and T1 relaxation time in deep gray matter: A voxel-based analysis.

    Science.gov (United States)

    Okubo, Gosuke; Okada, Tomohisa; Yamamoto, Akira; Fushimi, Yasutaka; Okada, Tsutomu; Murata, Katsutoshi; Togashi, Kaori

    2017-09-01

    To investigate age-related changes in T 1 relaxation time in deep gray matter structures in healthy volunteers using magnetization-prepared 2 rapid acquisition gradient echoes (MP2RAGE). In all, 70 healthy volunteers (aged 20-76, mean age 42.6 years) were scanned at 3T magnetic resonance imaging (MRI). A MP2RAGE sequence was employed to quantify T 1 relaxation times. After the spatial normalization of T 1 maps with the diffeomorphic anatomical registration using the exponentiated Lie algebra algorithm, voxel-based regression analysis was conducted. In addition, linear and quadratic regression analyses of regions of interest (ROIs) were also performed. With aging, voxel-based analysis (VBA) revealed significant T 1 value decreases in the ventral-inferior putamen, nucleus accumbens, and amygdala, whereas T 1 values significantly increased in the thalamus and white matter as well (P time vary by location in deep gray matter. 2 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:724-731. © 2017 International Society for Magnetic Resonance in Medicine.

  8. Surface-NMR measurements of the longitudinal relaxation time T1 in a homogeneous sandy aquifer in Skive, Denmark

    Science.gov (United States)

    Walbrecker, J.; Behroozmand, A.

    2011-12-01

    Efficient groundwater management requires reliable means of characterizing shallow groundwater aquifers. One key parameter in this respect is hydraulic conductivity. Surface nuclear magnetic resonance (NMR) is a geophysical exploration technique that can potentially provide this type of information in a noninvasive, cost-effective way. The technique is based on measuring the precession of nuclear spins of protons in groundwater molecules. It involves large loop antennas deployed on Earth's surface to generate electromagnetic pulses tuned to specifically excite and detect groundwater proton spins. Naturally, the excited state of spins is transitory - once excited, spins relax back to their equilibrium state. This relaxation process is strongly influenced by the spin environment, which, in the case of groundwater, is defined by the aquifer. By employing empirical relations, changes in relaxation behavior can be used to identify changes in aquifer hydraulic conductivity, making the NMR relaxation signal a very important piece of information. Particularly, efforts are made to record the longitudinal relaxation parameter T1, because it is known from laboratory studies that it often reliably correlates with hydraulic conductivity, even in the presence of magnetic species. In surface NMR, T1 data are collected by recording the NMR signal amplitude following two sequential excitation pulses as a function of the delay time τ between the two pulses. In conventional acquisition, the two pulses have a mutual phase shift of π. Based on theoretical arguments it was recently shown that T1 times acquired according to this conventional surface-NMR scheme are systematically biased. It was proposed that the bias can be minimized by cycling the phase of the two pulses between π and zero in subsequent double-pulse experiments, and subtracting the resulting signal amplitudes (phase-cycled pseudosaturation recovery scheme, pcPSR). We present the first surface-NMR T1 data set recorded

  9. Magnetic resonance imaging of the bone marrow in patients with acute leukemia during and after chemotherapy. Changes in T1 relaxation

    DEFF Research Database (Denmark)

    Jensen, K E; Grundtvig Sørensen, P; Thomsen, C

    1990-01-01

    Twenty-seven patients with acute leukemia were examined at the time of diagnosis with MR imaging and in vivo T1 relaxation time measurements of the hemopoietic bone marrow. A 1.5 T whole body magnetic resonance scanner was used. Twenty of the patients had follow-up examinations in relation...... to chemotherapy. Bone marrow biopsies from the posterior iliac crest were obtained within a short time interval of all MR examinations. At the time of diagnosis, T1 relaxation times were increased significantly in all the leukemic patients, compared with 24 age-matched controls. A decrease in T1 relaxation time......, also showed prolongation of T1 relaxation time in relation to leukemic relapse. The results indicate that changes observed in T1 relaxation times of the hemopoietic bone marrow in patients with acute leukemia reflect changes in disease activity, and, that serial measurements of T1 values may provide...

  10. In vivo relaxation time measurements on a murine tumor model--prolongation of T1 after photodynamic therapy.

    Science.gov (United States)

    Liu, Y H; Hawk, R M; Ramaprasad, S

    1995-01-01

    RIF tumors implanted on mice feet were investigated for changes in relaxation times (T1 and T2) after photodynamic therapy (PDT). Photodynamic therapy was performed using Photofrin II as the photosensitizer and laser light at 630 nm. A home-built proton solenoid coil in the balanced configuration was used to accommodate the tumors, and the relaxation times were measured before, immediately after, and up to several hours after therapy. Several control experiments were performed untreated tumors, tumors treated with Photofrin II alone, or tumors treated with laser light alone. Significant increases in T1s of water protons were observed after PDT treatment. In all experiments, 31P spectra were recorded before and after the therapy to study the tumor status and to confirm the onset of PDT. These studies show significant prolongation of T1s after the PDT treatment. The spin-spin relaxation measurements, on the other hand, did not show such prolongation in T2 values after PDT treatment.

  11. Topographical Variation of Human Femoral Articular Cartilage Thickness, T1rho and T2 Relaxation Times Is Related to Local Loading during Walking.

    Science.gov (United States)

    Van Rossom, Sam; Wesseling, Mariska; Van Assche, Dieter; Jonkers, Ilse

    2018-01-01

    Objective Early detection of degenerative changes in the cartilage matrix composition is essential for evaluating early interventions that slow down osteoarthritis (OA) initiation. T1rho and T2 relaxation times were found to be effective for detecting early changes in proteoglycan and collagen content. To use these magnetic resonance imaging (MRI) methods, it is important to document the topographical variation in cartilage thickness, T1rho and T2 relaxation times in a healthy population. As OA is partially mechanically driven, the relation between these MRI-based parameters and localized mechanical loading during walking was investigated. Design MR images were acquired in 14 healthy adults and cartilage thickness and T1rho and T2 relaxation times were determined. Experimental gait data was collected and processed using musculoskeletal modeling to identify weight-bearing zones and estimate the contact force impulse during gait. Variation of the cartilage properties (i.e., thickness, T1rho, and T2) over the femoral cartilage was analyzed and compared between the weight-bearing and non-weight-bearing zone of the medial and lateral condyle as well as the trochlea. Results Medial condyle cartilage thickness was correlated to the contact force impulse ( r = 0.78). Lower T1rho, indicating increased proteoglycan content, was found in the medial weight-bearing zone. T2 was higher in all weight-bearing zones compared with the non-weight-bearing zones, indicating lower relative collagen content. Conclusions The current results suggest that medial condyle cartilage is adapted as a long-term protective response to localized loading during a frequently performed task and that the weight-bearing zone of the medial condyle has superior weight bearing capacities compared with the non-weight-bearing zones.

  12. Real T1 relaxation time measurement and diurnal variation analysis of intervertebral discs in a healthy population of 50 volunteers

    International Nuclear Information System (INIS)

    Galley, J.; Maestretti, G.; Koch, G.; Hoogewoud, H-M.

    2017-01-01

    Purpose: To measure the real T1 relaxation time of the lumbar intervertebral discs in a young and healthy population, using different inversion recovery times, and assess diurnal variation. Material and methods: Intervertebral discs from D12 to S1 of 50 healthy volunteers from 18 to 25 years old were evaluated twice the same day, in the morning and in the late afternoon. Dedicated MRI sequences with different inversion recovery times (from 100 to 2500 ms) were used to calculate the real T1 relaxation time. Three regions of interest (ROIs) were defined in each disc, the middle representing the nucleus pulposus (NP) and the outer parts the annulus fibrosus (AF) anterior and posterior. Diurnal variation and differences between each disc level were analyzed. Results: T1 mean values in the NP were 1142 ± 12 ms in the morning and 1085 ± 13 ms in the afternoon, showing a highly significant decrease of 57 ms (p < 0.001). A highly significant difference between the levels of the spine was found. The mean T1 of the anterior part of the AF was 577 ± 9 ms in the morning and 554 ± 8 ms in the afternoon. For the posterior part, the mean values were 633 ± 8 ms in the morning and 581 ± 7 ms in the evening. It shows a highly significant decrease of 23 ms for the anterior part and 51 ms for the posterior part (all p < 0.001). Conclusion: T1 mapping is a promising method of intervertebral disc evaluation. Significant diurnal variation and difference between levels of the lumbar spine were demonstrated. A potential use for longitudinal study in post-operative follow up or sport medicine needs to be evaluated.

  13. Real T1 relaxation time measurement and diurnal variation analysis of intervertebral discs in a healthy population of 50 volunteers

    Energy Technology Data Exchange (ETDEWEB)

    Galley, J., E-mail: galleyjulien@gmail.com [Department of Radiology, HFR Fribourg, Hôpital Cantonal (Switzerland); Maestretti, G. [Department of Orthopedic Surgery, HFR Fribourg, Hôpital Cantonal (Switzerland); Koch, G.; Hoogewoud, H-M. [Department of Radiology, HFR Fribourg, Hôpital Cantonal (Switzerland)

    2017-02-15

    Purpose: To measure the real T1 relaxation time of the lumbar intervertebral discs in a young and healthy population, using different inversion recovery times, and assess diurnal variation. Material and methods: Intervertebral discs from D12 to S1 of 50 healthy volunteers from 18 to 25 years old were evaluated twice the same day, in the morning and in the late afternoon. Dedicated MRI sequences with different inversion recovery times (from 100 to 2500 ms) were used to calculate the real T1 relaxation time. Three regions of interest (ROIs) were defined in each disc, the middle representing the nucleus pulposus (NP) and the outer parts the annulus fibrosus (AF) anterior and posterior. Diurnal variation and differences between each disc level were analyzed. Results: T1 mean values in the NP were 1142 ± 12 ms in the morning and 1085 ± 13 ms in the afternoon, showing a highly significant decrease of 57 ms (p < 0.001). A highly significant difference between the levels of the spine was found. The mean T1 of the anterior part of the AF was 577 ± 9 ms in the morning and 554 ± 8 ms in the afternoon. For the posterior part, the mean values were 633 ± 8 ms in the morning and 581 ± 7 ms in the evening. It shows a highly significant decrease of 23 ms for the anterior part and 51 ms for the posterior part (all p < 0.001). Conclusion: T1 mapping is a promising method of intervertebral disc evaluation. Significant diurnal variation and difference between levels of the lumbar spine were demonstrated. A potential use for longitudinal study in post-operative follow up or sport medicine needs to be evaluated.

  14. Magnetic resonance fingerprinting using echo-planar imaging: Joint quantification of T1 and T2∗ relaxation times.

    Science.gov (United States)

    Rieger, Benedikt; Zimmer, Fabian; Zapp, Jascha; Weingärtner, Sebastian; Schad, Lothar R

    2017-11-01

    To develop an implementation of the magnetic resonance fingerprinting (MRF) paradigm for quantitative imaging using echo-planar imaging (EPI) for simultaneous assessment of T 1 and T2∗. The proposed MRF method (MRF-EPI) is based on the acquisition of 160 gradient-spoiled EPI images with rapid, parallel-imaging accelerated, Cartesian readout and a measurement time of 10 s per slice. Contrast variation is induced using an initial inversion pulse, and varying the flip angles, echo times, and repetition times throughout the sequence. Joint quantification of T 1 and T2∗ is performed using dictionary matching with integrated B1+ correction. The quantification accuracy of the method was validated in phantom scans and in vivo in 6 healthy subjects. Joint T 1 and T2∗ parameter maps acquired with MRF-EPI in phantoms are in good agreement with reference measurements, showing deviations under 5% and 4% for T 1 and T2∗, respectively. In vivo baseline images were visually free of artifacts. In vivo relaxation times are in good agreement with gold-standard techniques (deviation T 1 : 4 ± 2%, T2∗: 4 ± 5%). The visual quality was comparable to the in vivo gold standard, despite substantially shortened scan times. The proposed MRF-EPI method provides fast and accurate T 1 and T2∗ quantification. This approach offers a rapid supplement to the non-Cartesian MRF portfolio, with potentially increased usability and robustness. Magn Reson Med 78:1724-1733, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  15. In vivo measurements of the T1 relaxation processes in the bone marrow in patients with myelodysplastic syndrome. A magnetic resonance imaging study

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, K.E.; Nielsen, H.; Thomsen, C.; Soerensen, P.G.; Karle, H.; Christoffersen, P.; Henriksen, O. (Hvidovre Hospital, Copenhagen (Denmark). Dept. of Magnetic Resonance; Hvidovre Hospital, Copenhagen (Denmark). Dept. of Hematology; Hvidovre Hospital, Copenhagen (Denmark). Dept. of Pathology)

    Nine patients with myelodysplastic syndrome (MDS) were examined with magnetic resonance imaging and in vivo T1 relaxation time measurements of the vertebral bone marrow in a 1.5 tesla whole body scanner. Two patients underwent transformation to acute myeloid leukemia and were evaluated at follow-up examinations. At the time of diagnosis the T1 relaxation times of the vertebral bone marrow were significantly prolonged compared with normal values. The T1 relaxation times of the vertebral bone marrow in patients with MDS showed significantly lower values compared with patients with acute leukemia and did not differ from patients with polycythemia vera. (orig.).

  16. The application of T1 and T2 relaxation time and magnetization transfer ratios to the early diagnosis of patellar cartilage osteoarthritis

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Weiwu; Qu, Nan; Lu, Zhihua; Yang, Shixun [Shanghai Jiaotong University, Department of Radiology, Shanghai (China)

    2009-11-15

    We compare the T1 and T2 relaxation times and magnetization transfer ratios (MTRs) of normal subjects and patients with osteoarthritis (OA) to evaluate the ability of these techniques to aid in the early diagnosis and treatment of OA. The knee joints in 11 normal volunteers and 40 patients with OA were prospectively evaluated using T1 relaxation times as measured using delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), T2 relaxation times (multiple spin-echo sequence, T2 mapping), and MTRs. The OA patients were further categorized into mild, moderate, and severe OA. The mean T1 relaxation times of the four groups (normal, mild OA, moderate OA, and severe OA) were: 487.3{+-}27.7, 458.0{+-}55.9, 405.9{+-}57.3, and 357.9{+-}36.7 respectively (p<0.001). The mean T2 relaxation times of the four groups were: 37.8{+-}3.3, 44.0{+-}8.5, 50.9{+-}9.5, and 57.4{+-}4.8 respectively (p<0.001). T1 relaxation time decreased and T2 relaxation time increased with worsening degeneration of patellar cartilage. The result of the covariance analysis showed that the covariate age had a significant influence on T2 relaxation time (p<0.001). No significant differences between the normal and OA groups using MTR were noted. T1 and T2 relaxation times are relatively sensitive to early degenerative changes in the patellar cartilage, whereas the MTR may have some limitations with regard to early detection of OA. In addition, The T1 and T2 relaxation times negatively correlate with each other, which is a novel finding. (orig.)

  17. Relaxation property of the fractional Brownian particle

    International Nuclear Information System (INIS)

    Wang Litan; Lung, C.W.

    1988-08-01

    Dynamic susceptibility of a diffusion system associated with the fractional Brownian motion (fBm) was examined for the fractal property of the Non-Debye relaxation process. The comparisons between fBm and other approaches were made. Anomalous diffusion and the Non-Debye relaxation processes were discussed with this approach. (author). 8 refs, 1 fig

  18. Biologically aggressive regions within glioblastoma identified by spin-lock contrast T1 relaxation in the rotating frame (T1ρ MRI

    Directory of Open Access Journals (Sweden)

    Ramon Francisco Barajas, Jr., MD

    2017-12-01

    Full Text Available Spin-lattice relaxation in the rotating frame magnetic resonance imaging allows for the quantitative assessment of spin-lock contrast within tissues. We describe the utility of spin-lattice relaxation in the rotating frame metrics in characterizing glioblastoma biological heterogeneity. A 84-year-old man presented to our institution with a right frontal temporal mass. Prior tissue sampling from a peripheral nonenhancing lesion was nondiagnostic. Stereotactic image-guided tissue sampling of the nonenhancing T2-fluid-attenuated inversion recovery hyperintense region involving the anterior cingulate gyrus with elevated spin-lattice relaxation in the rotating frame metrics provided a pathologic diagnosis of glioblastoma. This case illustrates the utility of spin-lattice relaxation in the rotating frame magnetic resonance imaging in identifying biologically aggressive regions within glioblastoma.

  19. The impact of fibre orientation on T1-relaxation and apparent tissue water content in white matter.

    Science.gov (United States)

    Schyboll, Felix; Jaekel, Uwe; Weber, Bernd; Neeb, Heiko

    2018-02-20

    Recent MRI studies have shown that the orientation of nerve fibres relative to the main magnetic field affects the R 2 *(= 1/T 2 *) relaxation rate in white matter (WM) structures. The underlying physical causes have been discussed in several studies but are still not completely understood. However, understanding these effects in detail is of great importance since this might serve as a basis for the development of new diagnostic tools and/or improve quantitative susceptibility mapping techniques. Therefore, in addition to the known angular dependence of R 2 *, the current study investigates the relationship between fibre orientation and the longitudinal relaxation rate, R 1 (= 1/T 1 ), as well as the apparent water content. For a group of 16 healthy subjects, a series of gradient echo, echo-planar and diffusion weighted images were acquired at 3T from which the decay rates, the apparent water content and the diffusion direction were reconstructed. The diffusion weighted data were used to determine the angle between the principle fibre direction and the main magnetic field to examine the angular dependence of R 1 and apparent water content. The obtained results demonstrate that both parameters depend on the fibre orientation and exhibit a positive correlation with the angle between fibre direction and main magnetic field. These observations could be helpful to improve and/or constrain existing biophysical models of brain microstructure by imposing additional constraints resulting from the observed angular dependence R 1 and apparent water content in white matter.

  20. Gd-DTPA T1 relaxivity in brain tissue obtained by convection-enhanced delivery, magnetic resonance imaging and emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Haar, Peter J [Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, VA (United States); Broaddus, William C; Chen Zhijian; Gillies, George T [Department of Neurosurgery, Virginia Commonwealth University, Richmond, VA (United States); Fatouros, Panos P; Corwin, Frank D, E-mail: wbroaddus@mcvh-vcu.ed [Department of Radiology, Virginia Commonwealth University, Richmond, VA (United States)

    2010-06-21

    A common approach to quantify gadolinium (Gd) contrast agents involves measuring the post-contrast change in T1 rate and then using the constant T1 relaxivity R to determine the contrast agent concentration. Because this method is fast and non-invasive, it could be potentially valuable in many areas of brain research. However, to accurately measure contrast agent concentrations in the brain, the T1 relaxivity R of the specific agent must be accurately known. Furthermore, the macromolecular content and compartmentalization of the brain extracellular space (ECS) are expected to significantly alter R from values measured in aqueous solutions. In this study, the T1 relaxivity R of gadolinium-diethylene-triamine penta-acetic acid (Gd-DTPA) was measured following direct interstitial infusions of three different contrast agent concentrations to the parenchyma of rat brains. Changes in magnetic resonance (MR) T1 values were compared to brain slice concentrations determined with inductively coupled plasma atomic emission spectroscopy (ICP-AES) to determine R in 15 rats. Additionally, samples of cerebrospinal fluid, blood and urine were analyzed to evaluate possible Gd-DTPA clearance from the brain. The T1 relaxivity R of Gd-DTPA in the brain ECS was measured to be 5.35 (mM s){sup -1} in a 2.4 T field. This value is considerably higher than estimations used in studies by other groups. Measurements of brain Gd-DTPA tissue concentrations using MRI and ICP-AES demonstrated a high degree of coincidence. Clearance of Gd-DTPA was minimal at the time point immediately after infusion. These results suggest that the environment of the brain does in fact significantly affect Gd T1 relaxivity, and that MRI can accurately measure contrast agent concentrations when this relaxivity is well characterized.

  1. Gd-DTPA T1 relaxivity in brain tissue obtained by convection-enhanced delivery, magnetic resonance imaging and emission spectroscopy

    Science.gov (United States)

    Haar, Peter J.; Broaddus, William C.; Chen, Zhi-jian; Fatouros, Panos P.; Gillies, George T.; Corwin, Frank D.

    2010-06-01

    A common approach to quantify gadolinium (Gd) contrast agents involves measuring the post-contrast change in T1 rate and then using the constant T1 relaxivity R to determine the contrast agent concentration. Because this method is fast and non-invasive, it could be potentially valuable in many areas of brain research. However, to accurately measure contrast agent concentrations in the brain, the T1 relaxivity R of the specific agent must be accurately known. Furthermore, the macromolecular content and compartmentalization of the brain extracellular space (ECS) are expected to significantly alter R from values measured in aqueous solutions. In this study, the T1 relaxivity R of gadolinium-diethylene-triamine penta-acetic acid (Gd-DTPA) was measured following direct interstitial infusions of three different contrast agent concentrations to the parenchyma of rat brains. Changes in magnetic resonance (MR) T1 values were compared to brain slice concentrations determined with inductively coupled plasma atomic emission spectroscopy (ICP-AES) to determine R in 15 rats. Additionally, samples of cerebrospinal fluid, blood and urine were analyzed to evaluate possible Gd-DTPA clearance from the brain. The T1 relaxivity R of Gd-DTPA in the brain ECS was measured to be 5.35 (mM s)-1 in a 2.4 T field. This value is considerably higher than estimations used in studies by other groups. Measurements of brain Gd-DTPA tissue concentrations using MRI and ICP-AES demonstrated a high degree of coincidence. Clearance of Gd-DTPA was minimal at the time point immediately after infusion. These results suggest that the environment of the brain does in fact significantly affect Gd T1 relaxivity, and that MRI can accurately measure contrast agent concentrations when this relaxivity is well characterized.

  2. Gd-DTPA T1 relaxivity in brain tissue obtained by convection-enhanced delivery, magnetic resonance imaging and emission spectroscopy

    International Nuclear Information System (INIS)

    Haar, Peter J; Broaddus, William C; Chen Zhijian; Gillies, George T; Fatouros, Panos P; Corwin, Frank D

    2010-01-01

    A common approach to quantify gadolinium (Gd) contrast agents involves measuring the post-contrast change in T1 rate and then using the constant T1 relaxivity R to determine the contrast agent concentration. Because this method is fast and non-invasive, it could be potentially valuable in many areas of brain research. However, to accurately measure contrast agent concentrations in the brain, the T1 relaxivity R of the specific agent must be accurately known. Furthermore, the macromolecular content and compartmentalization of the brain extracellular space (ECS) are expected to significantly alter R from values measured in aqueous solutions. In this study, the T1 relaxivity R of gadolinium-diethylene-triamine penta-acetic acid (Gd-DTPA) was measured following direct interstitial infusions of three different contrast agent concentrations to the parenchyma of rat brains. Changes in magnetic resonance (MR) T1 values were compared to brain slice concentrations determined with inductively coupled plasma atomic emission spectroscopy (ICP-AES) to determine R in 15 rats. Additionally, samples of cerebrospinal fluid, blood and urine were analyzed to evaluate possible Gd-DTPA clearance from the brain. The T1 relaxivity R of Gd-DTPA in the brain ECS was measured to be 5.35 (mM s) -1 in a 2.4 T field. This value is considerably higher than estimations used in studies by other groups. Measurements of brain Gd-DTPA tissue concentrations using MRI and ICP-AES demonstrated a high degree of coincidence. Clearance of Gd-DTPA was minimal at the time point immediately after infusion. These results suggest that the environment of the brain does in fact significantly affect Gd T1 relaxivity, and that MRI can accurately measure contrast agent concentrations when this relaxivity is well characterized.

  3. Non-invasive evaluation of blood oxygen saturation and hematocrit from T1 and T2 relaxation times: In-vitro validation in fetal blood.

    Science.gov (United States)

    Portnoy, Sharon; Seed, Mike; Sled, John G; Macgowan, Christopher K

    2017-12-01

    We propose an analytical method for calculating blood hematocrit (Hct) and oxygen saturation (sO 2 ) from measurements of its T 1 and T 2 relaxation times. Through algebraic substitution, established two-compartment relationships describing R1=T1-1 and R2=T2-1 as a function of hematocrit and oxygen saturation were rearranged to solve for Hct and sO 2 in terms of R 1 and R 2 . Resulting solutions for Hct and sO 2 are the roots of cubic polynomials. Feasibility of the method was established by comparison of Hct and sO 2 estimates obtained from relaxometry measurements (at 1.5 Tesla) in cord blood specimens to ground-truth values obtained by blood gas analysis. Monte Carlo simulations were also conducted to assess the effect of T 1 , T 2 measurement uncertainty on precision of Hct and sO 2 estimates. Good agreement was observed between estimated and ground-truth blood properties (bias = 0.01; 95% limits of agreement = ±0.13 for Hct and sO 2 ). Considering the combined effects of biological variability and random measurement noise, we estimate a typical uncertainty of ±0.1 for Hct, sO 2 estimates. Results demonstrate accurate quantification of Hct and sO 2 from T 1 and T 2 . This method is applicable to noninvasive fetal vessel oximetry-an application where existing oximetry devices are unusable or require risky blood-sampling procedures. Magn Reson Med 78:2352-2359, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  4. A general model to calculate the spin-lattice (T1) relaxation time of blood, accounting for haematocrit, oxygen saturation and magnetic field strength.

    Science.gov (United States)

    Hales, Patrick W; Kirkham, Fenella J; Clark, Christopher A

    2016-02-01

    Many MRI techniques require prior knowledge of the T1-relaxation time of blood (T1bl). An assumed/fixed value is often used; however, T1bl is sensitive to magnetic field (B0), haematocrit (Hct), and oxygen saturation (Y). We aimed to combine data from previous in vitro measurements into a mathematical model, to estimate T1bl as a function of B0, Hct, and Y. The model was shown to predict T1bl from in vivo studies with a good accuracy (± 87 ms). This model allows for improved estimation of T1bl between 1.5-7.0 T while accounting for variations in Hct and Y, leading to improved accuracy of MRI-derived perfusion measurements. © The Author(s) 2015.

  5. Quantum process tomography with informational incomplete data of two J-coupled heterogeneous spins relaxation in a time window much greater than T1

    Science.gov (United States)

    Maciel, Thiago O.; Vianna, Reinaldo O.; Sarthour, Roberto S.; Oliveira, Ivan S.

    2015-11-01

    We reconstruct the time dependent quantum map corresponding to the relaxation process of a two-spin system in liquid-state NMR at room temperature. By means of quantum tomography techniques that handle informational incomplete data, we show how to properly post-process and normalize the measurements data for the simulation of quantum information processing, overcoming the unknown number of molecules prepared in a non-equilibrium magnetization state (Nj) by an initial sequence of radiofrequency pulses. From the reconstructed quantum map, we infer both longitudinal (T1) and transversal (T2) relaxation times, and introduce the J-coupling relaxation times ({T}1J,{T}2J), which are relevant for quantum information processing simulations. We show that the map associated to the relaxation process cannot be assumed approximated unital and trace-preserving for times greater than {T}2J.

  6. Electron relaxation properties of Ar magnetron plasmas

    Science.gov (United States)

    Xinjing, CAI; Xinxin, WANG; Xiaobing, ZOU

    2018-03-01

    An understanding of electron relaxation properties in plasmas is of importance in the application of magnetrons. An improved multi-term approximation of the Boltzmann equation is employed to study electron transport and relaxation properties in plasmas. Elastic, inelastic and nonconservative collisions between electrons and neutral particles are considered. The expressions for the transport coefficients are obtained using the expansion coefficients and the collision operator term. Numerical solutions of the matrix equations for the expansion coefficients are also investigated. Benchmark calculations of the Reid model are presented to demonstrate the accuracy of the improved multi-term approximation. It is shown that the two-term approximation is generally not accurate enough and the magnetic fields can reduce the anisotropy of the velocity distribution function. The electron relaxation properties of Ar plasmas in magnetrons for various magnetic fields are studied. It is demonstrated that the energy parameters change more slowly than the momentum parameters.

  7. T1 and T2 relaxivity of intracellular and extracellular USPIO at 1.5T and 3T clinical MR scanning

    International Nuclear Information System (INIS)

    Simon, Gerhard H.; Bauer, Jan; Saborovski, Olaf; Fu, Yanjun; Wendland, Michael F.; Daldrup-Link, Heike E.; Corot, Claire

    2006-01-01

    In this study we evaluated the effects of intracellular compartmentalization of the ultrasmall superparamagnetic iron oxide (USPIO) ferumoxtran-10 on its proton T1 and T2 relaxivities at 1.5 and 3T. Monocytes were labeled with ferumoxtran-10 by simple incubation. Decreasing quantities of ferumoxtran-10-labeled cells (2.5 x 10 7 -0.3 x 10 7 cells/ml) and decreasing concentrations of free ferumoxtran-10 (without cells) in Ficoll solution were evaluated with 1.5 and 3T clinical magnetic resonance (MR) scanners. Pulse sequences comprised axial spin echo (SE) sequences with multiple TRs and fixed TE and SE sequences with fixed TR and increasing TEs. Signal intensity measurements were used to calculate T1 and T2 relaxation times of all samples, assuming a monoexponential signal decay. The iron content in all samples was determined by inductively coupled plasma atomic emission spectrometry and used for calculating relaxivities. Measurements at 1.5T and 3T showed higher T1 and T2 relaxivity values of free extracellular ferumoxtran-10 as opposed to intracellularly compartmentalized ferumoxtran-10, under the evaluated conditions of homogeneously dispersed contrast agents/cells in Ficoll solution and a cell density of up to 2.5 x 10 7 cells/ml. At 3T, differences in T1-relaxivities between intra- and extracellular USPIO were smaller, while differences in USPIO T2-relaxivities were similar compared with 1.5T. In conclusion, cellular compartmentalization of ferumoxtran-10 changes proton relaxivity. (orig.)

  8. Multiscale approach to mechanical behavior of polymeric nanocomposites: an application of T1.rho.(13C) relaxation experiments at variable spin-locking fields

    Czech Academy of Sciences Publication Activity Database

    Kotek, Jiří; Brus, Jiří

    2014-01-01

    Roč. 59, č. 9 (2014), s. 662-666 ISSN 0032-2725 R&D Projects: GA ČR(CZ) GA13-29009S Institutional support: RVO:61389013 Keywords : polyamide 6 * nanocomposite * T1ρ(13C) relaxation Subject RIV: JI - Composite Materials Impact factor: 0.633, year: 2014

  9. In vivo measurements of the T1 relaxation processes in the bone marrow in patients with myelodysplastic syndrome. A magnetic resonance imaging study

    DEFF Research Database (Denmark)

    Jensen, K E; Nielsen, H; Thomsen, C

    1989-01-01

    Nine patients with myelodysplastic syndrome (MDS) were examined with magnetic resonance imaging and in vivo T1 relaxation time measurements of the vertebral bone marrow in a 1.5 tesla whole body scanner. Two patients underwent transformation to acute myeloid leukemia and were evaluated at follow-...... not differ from patients with polycythemia vera....

  10. Changes in T1 relaxation processes in the bone marrow following treatment in children with acute lymphoblastic leukemia. A magnetic resonance imaging study

    DEFF Research Database (Denmark)

    Jensen, K E; Thomsen, C; Henriksen, O

    1990-01-01

    data from bone marrow biopsies obtained in close association to the MR examinations. Ten age matched children were examined as a control group. A 1.5 Tesla whole body scanner was used for the measurements. The pretreatment T1 relaxation times of the bone marrow were significantly prolonged, compared...

  11. T1rho and T2 relaxation times of the normal adult knee meniscus at 3T: analysis of zonal differences.

    Science.gov (United States)

    Takao, Shoichiro; Nguyen, Tan B; Yu, Hon J; Hagiwara, Shigeo; Kaneko, Yasuhito; Nozaki, Taiki; Iwamoto, Seiji; Otomo, Maki; Schwarzkopf, Ran; Yoshioka, Hiroshi

    2017-05-18

    Prior studies describe histological and immunohistochemical differences in collagen and proteoglycan content in different meniscal zones. The aim of this study is to evaluate horizontal and vertical zonal differentiation of T1rho and T2 relaxation times of the entire meniscus from volunteers without symptom and imaging abnormality. Twenty volunteers age between 19 and 38 who have no knee-related clinical symptoms, and no history of prior knee surgeries were enrolled in this study. Two T1rho mapping (b-FFE T1rho and SPGR T1rho) and T2 mapping images were acquired with a 3.0-T MR scanner. Each meniscus was divided manually into superficial and deep zones for horizontal zonal analysis. The anterior and posterior horns of each meniscus were divided manually into white, red-white and red zones for vertical zonal analysis. Zonal differences of average relaxation times among each zone, and both inter- and intra-observer reproducibility were statistically analyzed. In horizontal zonal analysis, T1rho relaxation times of the superficial zone tended to be higher than those of the deep zone, and this difference was statistically significant in the medial meniscal segments (84.3 ms vs 76.0 ms on b-FFE, p meniscus (88.4 ms vs 77.1 ms on b-FFE, p meniscus, p = 0.011). T2 relaxation times of the white zone were significantly higher than those of the red zone in the medial meniscus posterior horn (96.8 ms vs 84.3 ms, p meniscus anterior horn (104.6 ms vs 84.2 ms, p 0.74) or good (0.60-0.74) in all meniscal segments on both horizontal and vertical zonal analysis, except for inter-class correlation coefficients of the lateral meniscus on SPGR. Compared with SPGR T1rho images, b-FFE T1rho images demonstrated more significant zonal differentiation with higher inter- and intra-observer reproducibility. There are zonal differences in T1rho and T2 relaxation times of the normal meniscus.

  12. Influence of Free Radicals on the Intrinsic MRI Relaxation Properties.

    Science.gov (United States)

    Tain, Rong-Wen; Scotti, Alessandro M; Li, Weiguo; Zhou, Xiaohong Joe; Cai, Kejia

    2017-01-01

    Free radicals are critical contributors in various conditions including normal aging, Alzheimer's disease, cancer, and diabetes. Currently there is no non-invasive approach to image tissue free radicals based on endogenous contrast due to their extremely short lifetimes and low in vivo concentrations. In this study we aim at characterizing the influence of free radicals on the MRI relaxation properties. Phantoms containing free radicals were created by treating egg white with various H 2 O 2 concentrations and scanned on a 9.4 T MRI scanner at room temperature. T 1 and T 2 relaxation maps were generated from data acquired with an inversion recovery sequence with varied inversion times and a multi-echo spin echo sequence with varied echo times (TEs), respectively. Results demonstrated that free radicals express a strong shortening effect on T 1 , which was proportional to the H 2 O 2 concentration, and a relatively small reduction in T 2 (free radicals was estimated to be in the pM range that is within the physiological range of in vivo free radical expression. In conclusion, the free radicals show a strong paramagnetic effect that may be utilized as an endogenous MRI contrast for its non-invasive in vivo imaging.

  13. Microwave Amplitude Modulation Technique to Measure Spin-Lattice (T 1) and Spin-Spin (T 2) Relaxation Times

    Science.gov (United States)

    Misra, Sushil K.

    The measurement of very short spin-lattice, or longitudinal, relaxation (SLR) times (i.e., 10-10 Misra, 1998), and polymer resins doped with rare-earth ions (Pescia et al., 1999a; Pescia et al. 1999b). The ability to measure such fast SLR data on amorphous Si and copper-chromium-tin spinel led to an understanding of the role of exchange interaction in affecting spin-lattice relaxation, while the data on polymer resins doped with rare-earth ions provided evidence of spin-fracton relaxation (Pescia et al., 1999a, b). But such fast SLR times are not measurable by the most commonly used techniques of saturation- and inversion-recovery (Poole, 1982; Alger, 1968), which only measure spin-lattice relaxation times longer than 10-6 s. A summary of relevant experimental data is presented in Table 1.

  14. Diagnostic value of T1 and T2 * relaxation times and off-resonance saturation effects in the evaluation of Achilles tendinopathy by MRI at 3T.

    Science.gov (United States)

    Grosse, Ulrich; Syha, Roland; Hein, Tobias; Gatidis, Sergios; Grözinger, Gerd; Schabel, Christoph; Martirosian, Petros; Schick, Fritz; Springer, Fabian

    2015-04-01

    To evaluate and compare the diagnostic value of T1 , T2 * relaxation times and off-resonance saturation ratios (OSR) in healthy controls and patients with different clinical and morphological stages of Achilles tendinopathy. Forty-two healthy Achilles tendons and 34 tendons of 17 patients with symptomatic and asymptomatic tendinopathy were investigated clinically with conventional magnetic resonance imaging (MRI) sequences on a 3T whole-body MR scanner and a dynamic ultrasound examination. In addition, T1 and T2 * relaxation times were assessed using an ultrashort echo time (UTE) imaging sequence with flip angle and echo time variation. For the calculation of OSR values a Gaussian off-resonance saturation pulse (frequency offset: 750-5000 Hz) was used. The diagnostic value of the derived MR values was assessed and compared using receiver operating characteristic (ROC) curves. ROC curves demonstrate the highest overall test performance for OSR values at 2000 Hz off-resonance in differentiating slightly (OSR-2000 [AUC: 0.930] > T2 * [AUC: 0.884] > T1 [AUC: 0.737]) and more severe pathologically altered tendon areas (OSR-2000 [AUC: 0.964] > T2 * [AUC: 0.917] > T1 [AUC: 0.819]) from healthy ones. OSR values at a frequency offset of 2000 Hz demonstrated a better sensitivity and specificity for detecting mild and severe stages of tendinopathy compared to T2 * and particularly when compared to T1 relaxation times. © 2014 Wiley Periodicals, Inc.

  15. Relaxation times T1, T2, and T2* of apples, pears, citrus fruits, and potatoes with a comparison to human tissues

    International Nuclear Information System (INIS)

    Werz, Karin; Braun, Hans; Vitha, Dominik; Bruno, Graziano; Martirosian, Petros; Steidle, Guenter; Schick, Fritz

    2011-01-01

    The aim of the project was a systematic assessment of relaxation times of different fruits and vegetables and a comparison to values of human tissues. Results provide an improved basis for selection of plant phantoms for development of new MR techniques and sequences. Vessels filled with agar gel are mostly used for this purpose, preparation of which is effortful and time-consuming. In the presented study apples, (malus, 8 species), pears, (pyrus, 2 species), citrus fruits (citrus, 5 species) and uncooked potatoes (solanum tuberosum, 8 species) from the supermarket were examined which are easily available nearly all-the-year. T1, T2 and T2 * relaxation times of these nature products were measured on a 1.5 Tesla MR system with adapted examination protocols and mono-exponential fitting, and compared to literature data of human parenchyma tissues, fatty tissue and body fluid (cerebrospinal fluid). Resulting values were as follows: apples: T1: 1486 - 1874 ms, T2: 163 - 281 ms, T2 * : 2,3 - 3,2 ms; pears: T1: 1631 - 1969 ms, T2: 119 - 133 ms, T2 * : 10,1 - 10,6 ms, citrus fruits (pulp) T1: 2055 - 2632 ms, T2: 497 - 998 ms, T2 * : 151 - 182 ms; citrus fruits (skin) T1: 561 - 1669 ms, T2: 93 - 119 ms; potatoes: T1: 1011 - 1459 ms, T2: 166 - 210 ms, T2 * : 20 - 30 ms. All T1-values of the examined objects (except for potatoes and skins of citrus fruits) were longer than T1 values of human tissues. Also T2 values (except for pears and skins of citrus fruits) of the fruits and the potatoes tended to be longer. T2 * values of apples, pears and potatoes were shorter than in healthy human tissue. Results show relaxation values of many fruits to be not exactly fitting to human tissue, but with suitable selection of the fruits and optionally with an adaption of measurement parameters one can achieve suitable contrast and signal characteristics for some purposes. (orig.)

  16. Heteronuclear relaxation in time-dependent spin systems: 15N-T1ρ dispersion during adiabatic fast passage

    International Nuclear Information System (INIS)

    Konrat, Robert; Tollinger, Martin

    1999-01-01

    A novel NMR experiment comprising adiabatic fast passage techniques for the measurement of heteronuclear self-relaxation rates in fully 15N-enriched proteins is described. Heteronuclear self-relaxation is monitored by performing adiabatic fast passage (AFP) experiments at variable adiabaticity (e.g., variation of RF spin-lock field intensity). The experiment encompasses gradient- selection and sensitivity-enhancement. It is shown that transverse relaxation rates derived with this method are in good agreement with the ones measured by the classical Carr-Purcell-Meiboom-Gill (CPMG) sequences. An application of this method to the study of the carboxyl-terminal LIM domain of quail cysteine and glycine-rich protein qCRP2(LIM2) is presented

  17. Combined Fat Imaging/Look Locker for mapping of lipid spin-lattice (T1) relaxation time

    Science.gov (United States)

    Jihyun Park, Annie; Yung, Andrew; Kozlowski, Piotr; Reinsberg, Stefan

    2012-10-01

    Tumor hypoxia is a main problem arising in the treatment of cancer due to its resistance to cytotoxic therapy such as radiation and chemotherapy, and selection for more aggressive tumor phenotypes. Attempts to improve and quantify tumor oxygenation are in development and tools to assess the success of such schemes are required. Monitoring oxygen level with MRI using T1 based method (where oxygen acts as T1 shortening agent) is a dynamic and noninvasive way to study tumor characteristics. The method's sensitivity to oxygen is higher in lipids than in water due to higher oxygen solubility in lipid. Our study aims to develop a time-efficient method to spatially map T1 of fat inside the tumor. We are combining two techniques: Fat/Water imaging and Look Locker (a rapid T1 measurement technique). Fat/Water Imaging is done with either Dixon or Direct Phase Encoding (DPE) method. The combination of these techniques poses new challenges that are tackled using spin dynamics simulations as well as experiments in vitro and in vivo.

  18. Comparison of different pulse sequences for in vivo determination of T1 relaxation times in the human brain

    DEFF Research Database (Denmark)

    Kjaer, L; Henriksen, O

    1988-01-01

    ). T1 measurements were performed on the human brain using a whole body MR scanner operating at 1.5 tesla. Three different pulse sequences were compared including two 6-points inversion recovery (IR) sequences with TR = 2.0 s and 4.0, respectively, and a 12-points partial saturation inversion recovery...

  19. Optical properties, morphology and elemental composition of atmospheric particles at T1 supersite on MILAGRO campaign

    Science.gov (United States)

    Carabali, G.; Mamani-Paco, R.; Castro, T.; Peralta, O.; Herrera, E.; Trujillo, B.

    2012-03-01

    Atmospheric particles were sampled at T1 supersite during MILAGRO campaign, in March 2006. T1 was located at the north of Mexico City (MC). Aerosol sampling was done by placing copper grids for Transmission Electron Microscope (TEM) on the last five of an 8-stage MOUDI cascade impactor. Samples were obtained at different periods to observe possible variations on morphology. Absorption and scattering coefficients, as well as particle concentrations (0.01-3 μm aerodynamic diameter) were measured simultaneously using a PSAP absorption photometer, a portable integrating nephelometer, and a CPC particle counter. Particle images were acquired at different magnifications using a CM 200 Phillips TEM-EDAX system, and then calculated the border-based fractal dimension. Also, Energy Dispersive X-Ray Spectroscopy (EDS) was used to determine the elemental composition of particles. The morphology of atmospheric particles for two aerodynamic diameters (0.18 and 1.8 μm) was compared using border-based fractal dimension to relate it to the other particle properties, because T1-generated particles have optical, morphological and chemical properties different from those transported by the MC plume. Particles sampled under MC pollution influence showed not much variability, suggesting that more spherical particles (border-based fractal dimension close to 1.0) are more common in larger sizes (d50 = 1.8 μm), which may be attributed to aerosol aging and secondary aerosol formation. Between 06:00 and 09:00 a.m., smaller particles (d50 = 0.18 μm) had more irregular shapes resulting in higher border-based fractal dimensions (1.2-1.3) for samples with more local influence. EDS analysis in d50 = 0.18 μm particles showed high contents of carbonaceous material, Si, Fe, K, and Co. Perhaps, this indicates an impact from industrial and vehicle emissions on atmospheric particles at T1.

  20. Spatial characterization of T1 and T2 relaxation times and the water apparent diffusion coefficient in rabbit Achilles tendon subjected to tensile loading.

    Science.gov (United States)

    Wellen, J; Helmer, K G; Grigg, P; Sotak, C H

    2005-03-01

    Tendons exhibit viscoelastic mechanical behavior under tensile loading. The elasticity arises from the collagen chains that form fibrils, while the viscous response arises from the interaction of the water with the solid matrix. Therefore, an understanding of the behavior of water in response to the application of a load is crucial to the understanding of the origin of the viscous response. Three-dimensional MRI mapping of rabbit Achilles tendons was performed at 2.0 T to characterize the response of T(1) and T(2) relaxation times and the apparent diffusion coefficient (ADC) of water to tensile loading. The ADC was measured in directions both parallel (ADC( parallel)) and perpendicular (ADC( perpendicular)) to the long axis of the tendon. At a short diffusion time (5.8 ms) MR parameter maps showed the existence of two regions, here termed "core" and "rim", that exhibited statistically significant differences in T(1), T(2), and ADC( perpendicular) under the baseline loading condition. MR parameter maps were also generated at a second loading condition of approximately 1 MPa. At a diffusion time of 5.8 ms, there was a statistically significant increase in the rim region for both ADC( perpendicular) (57.5%) and ADC( parallel) (20.5%) upon tensile loading. The changes in core ADC(( perpendicular), ( parallel)), as well as the relaxation parameters in both core and rim regions, were not statistically significant. The effect of diffusion time on the ADC(( perpendicular), ( parallel)) values was investigated by creating maps at three additional diffusion times (50.0, 125.0, 250.0 ms) using a diffusion-weighted, stimulated-echo (DW-STE) pulse sequence. At longer diffusion times, ADC(( perpendicular), ( parallel)) values increased rather than approaching a constant value. This observation was attributed to T(1) spin-editing during the DW-STE pulse sequence, which resulted in the loss of short-T(1) components (with correspondingly lower ADCs) at longer diffusion times

  1. Ultrashort Echo Time Magnetic Resonance Imaging of the Lung Using a High-Relaxivity T1 Blood-Pool Contrast Agent

    Directory of Open Access Journals (Sweden)

    Joris Tchouala Nofiele

    2014-10-01

    Full Text Available The lung remains one of the most challenging organs to image using magnetic resonance imaging (MRI due to intrinsic rapid signal decay. However, unlike conventional modalities such as computed tomography, MRI does not involve radiation and can provide functional and morphologic information on a regional basis. Here we demonstrate proof of concept for a new MRI approach to achieve substantial gains in a signal to noise ratio (SNR in the lung parenchyma: contrast-enhanced ultrashort echo time (UTE imaging following intravenous injection of a high-relaxivity blood-pool manganese porphyrin T1 contrast agent. The new contrast agent increased relative enhancement of the lung parenchyma by over 10-fold compared to gadolinium diethylene triamine pentaacetic acid (Gd-DTPA, and the use of UTE boosted the SNR by a factor of 4 over conventional T1-weighted gradient echo acquisitions. The new agent also maintains steady enhancement over at least 60 minutes, thus providing a long time window for obtaining high-resolution, high-quality images and the ability to measure a number of physiologic parameters.

  2. Local NMR relaxation rates T1-1 and T2-1 depending on the d -vector symmetry in the vortex state of chiral and helical p -wave superconductors

    Science.gov (United States)

    Tanaka, Kenta K.; Ichioka, Masanori; Onari, Seiichiro

    2018-04-01

    Local NMR relaxation rates in the vortex state of chiral and helical p -wave superconductors are investigated by the quasiclassical Eilenberger theory. We calculate the spatial and resonance frequency dependences of the local NMR spin-lattice relaxation rate T1-1 and spin-spin relaxation rate T2-1. Depending on the relation between the NMR relaxation direction and the d -vector symmetry, the local T1-1 and T2-1 in the vortex core region show different behaviors. When the NMR relaxation direction is parallel to the d -vector component, the local NMR relaxation rate is anomalously suppressed by the negative coherence effect due to the spin dependence of the odd-frequency s -wave spin-triplet Cooper pairs. The difference between the local T1-1 and T2-1 in the site-selective NMR measurement is expected to be a method to examine the d -vector symmetry of candidate materials for spin-triplet superconductors.

  3. Mechanical properties of plant cell walls probed by relaxation spectra

    DEFF Research Database (Denmark)

    Hansen, Steen Laugesen; Ray, Peter Martin; Karlsson, Anders Ola

    2011-01-01

    Relax, that deduces relaxation spectra from appropriate rheological measurements is presented and made accessible through a Web interface. BayesRelax models the cell wall as a continuum of relaxing elements, and the ability of the method to resolve small differences in cell wall mechanical properties is demonstrated......Transformants and mutants with altered cell wall composition are expected to display a biomechanical phenotype due to the structural role of the cell wall. It is often quite difficult, however, to distinguish the mechanical behavior of a mutant's or transformant's cell walls from that of the wild...... type. This may be due to the plant’s ability to compensate for the wall modification or because the biophysical method that is often employed, determination of simple elastic modulus and breakstrength, lacks the resolving power necessary for detecting subtle mechanical phenotypes. Here, we apply...

  4. Relaxation and transport properties of liquid n-triacontane

    International Nuclear Information System (INIS)

    Kondratyuk, N D; Lankin, A V; Norman, G E; Stegailov, V V

    2015-01-01

    Molecular modelling is used to calculate transport properties and to study relaxation of liquid n-triacontane (C 30 H 62 ). The problem is important in connection with the behavior of liquid isolators in a pre-breakdown state. Two all-atom models and a united-atom model are used. Shear viscosity is calculated using the Green-Kubo formula. The force fields are compared with each other using the following criteria: the required time for one molecular dynamics step, the compliance of the main physical and transport properties with experimental values. The problem of the system equilibration is considered. The united-atom potential is used to model the n-triacontane liquid with an initial directional orientation. The time of relaxation to the disordered state, when all molecules orientations are randomized, are obtained. The influence of the molecules orientations on the shear viscosity value and the shear viscosity relaxation are treated. (paper)

  5. Molecular dynamics study on the relaxation properties of bilayered ...

    Indian Academy of Sciences (India)

    2017-08-31

    Aug 31, 2017 ... Abstract. The influence of defects on the relaxation properties of bilayered graphene (BLG) has been studied by molecular dynamics simulation in nanometre sizes. Type and position of defects were taken into account in the calculated model. The results show that great changes begin to occur in the ...

  6. Calcium signaling properties of a thyrotroph cell line, mouse TαT1 cells.

    Science.gov (United States)

    Tomić, Melanija; Bargi-Souza, Paula; Leiva-Salcedo, Elias; Nunes, Maria Tereza; Stojilkovic, Stanko S

    2015-12-01

    T1 cells are mouse thyrotroph cell line frequently used for studies on thyroid-stimulating hormone beta subunit gene expression and other cellular functions. Here we have characterized calcium-signaling pathways in TαT1 cells, an issue not previously addressed in these cells and incompletely described in native thyrotrophs. TαT1 cells are excitable and fire action potentials spontaneously and in response to application of thyrotropin-releasing hormone (TRH), the native hypothalamic agonist for thyrotrophs. Spontaneous electrical activity is coupled to small amplitude fluctuations in intracellular calcium, whereas TRH stimulates both calcium mobilization from intracellular pools and calcium influx. Non-receptor-mediated depletion of intracellular pool also leads to a prominent facilitation of calcium influx. Both receptor and non-receptor stimulated calcium influx is substantially attenuated but not completely abolished by inhibition of voltage-gated calcium channels, suggesting that depletion of intracellular calcium pool in these cells provides a signal for both voltage-independent and -dependent calcium influx, the latter by facilitating the pacemaking activity. These cells also express purinergic P2Y1 receptors and their activation by extracellular ATP mimics TRH action on calcium mobilization and influx. The thyroid hormone triiodothyronine prolongs duration of TRH-induced calcium spikes during 30-min exposure. These data indicate that TαT1 cells are capable of responding to natively feed-forward TRH signaling and intrapituitary ATP signaling with acute calcium mobilization and sustained calcium influx. Amplification of TRH-induced calcium signaling by triiodothyronine further suggests the existence of a pathway for positive feedback effects of thyroid hormones probably in a non-genomic manner. Published by Elsevier Ltd.

  7. The influence of microvascular injury on native T1 and T2* relaxation values after acute myocardial infarction: implications for non-contrast-enhanced infarct assessment.

    Science.gov (United States)

    Robbers, Lourens F H J; Nijveldt, Robin; Beek, Aernout M; Teunissen, Paul F A; Hollander, Maurits R; Biesbroek, P Stefan; Everaars, Henk; van de Ven, Peter M; Hofman, Mark B M; van Royen, Niels; van Rossum, Albert C

    2018-02-01

    Native T1 mapping and late gadolinium enhancement (LGE) imaging offer detailed characterisation of the myocardium after acute myocardial infarction (AMI). We evaluated the effects of microvascular injury (MVI) and intramyocardial haemorrhage on local T1 and T2* values in patients with a reperfused AMI. Forty-three patients after reperfused AMI underwent cardiovascular magnetic resonance imaging (CMR) at 4 [3-5] days, including native MOLLI T1 and T2* mapping, STIR, cine imaging and LGE. T1 and T2* values were determined in LGE-defined regions of interest: the MI core incorporating MVI when present, the core-adjacent MI border zone (without any areas of MVI), and remote myocardium. Average T1 in the MI core was higher than in the MI border zone and remote myocardium. However, in the 20 (47%) patients with MVI, MI core T1 was lower than in patients without MVI (MVI 1048±78ms, no MVI 1111±89ms, p=0.02). MI core T2* was significantly lower in patients with MVI than in those without (MVI 20 [18-23]ms, no MVI 31 [26-39]ms, pvalues. T2* mapping suggested that this may be the result of intramyocardial haemorrhage. These findings have important implications for the interpretation of native T1 values shortly after AMI. • Microvascular injury after acute myocardial infarction affects local T1 and T2* values. • Infarct zone T1 values are lower if microvascular injury is present. • T2* mapping suggests that low infarct T1 values are likely haemorrhage. • T1 and T2* values are complimentary for correctly assessing post-infarct myocardium.

  8. Design and Synthesis of Novel and Selective Glycine Transporter-1 (GlyT1) Inhibitors with Memory Enhancing Properties.

    Science.gov (United States)

    Santora, Vincent J; Almos, Theresa A; Barido, Richard; Basinger, Jillian; Bellows, Chris L; Bookser, Brett Carder; Breitenbucher, J Guy; Broadbent, Nicola J; Cabebe, Clifford; Chai, Chih-Kun; Chen, Mi; Chow, Stephine; Chung, De Michael; Crickard, Lindsay; Danks, Anne M; Freestone, Graeme; Gitnick, Dany; Gupta, Varsha; Hoffmaster, Christine; Hudson, Andrew R; Kaplan, Alan P; Kennedy, Michael R; Lee, Dong; Limberis, James; Ly, Kiev; Mak, Chi Ching; Masatsugu, Brittany; Morse, Andrew C; Na, Jim; Neul, David; Nikpur, John; Peters, Marco; Petroski, Robert E; Renick, Joel; Sebring, Kristen; Sevidal, Samantha; Tabatabaei, Ali; Wen, Jenny; Yan, Yingzhuo; Yoder, Zachary W; Zook, Douglas

    2018-06-11

    We report here the identification and optimization of a novel series of potent GlyT1 inhibitors. A ligand design campaign that utilized known GlyT1 inhibitors as starting points led to the identification of a novel series of pyrrolo[3,4-c]pyrazoles amides (21-50) with good in vitro potency. Subsequent optimization of physicochemical and in vitro ADME properties produced several compounds with promising pharmacokinetic profiles. In vivo inhibition of GlyT1 was demonstrated for select compounds within this series by measuring the elevation of glycine in the cerebrospinal fluid (CSF) of rats after a single oral dosing of 10 mg/kg. Ultimately, an optimized lead, compound 46, demonstrated in vivo efficacy in a rat Novel Object Recognition (NOR) assay after oral dosing at 0.1, 1, and 3 mg/kg.

  9. The influence of microvascular injury on native T1 and T2* relaxation values after acute myocardial infarction. Implications for non-contrast-enhanced infarct assessment

    Energy Technology Data Exchange (ETDEWEB)

    Robbers, Lourens F.H.J.; Nijveldt, Robin; Beek, Aernout M.; Teunissen, Paul F.A.; Hollander, Maurits R.; Biesbroek, P.S.; Everaars, Henk; Royen, Niels van; Rossum, Albert C. van [VU University Medical Centre, Department of Cardiology, Amsterdam (Netherlands); Ven, Peter M. van de [VU University Medical Centre, Department of Clinical Epidemiology and Biostatistics, Amsterdam (Netherlands); Hofman, Mark B.M. [VU University Medical Centre, Department of Physics and Medical Technology, Amsterdam (Netherlands)

    2018-02-15

    Native T1 mapping and late gadolinium enhancement (LGE) imaging offer detailed characterisation of the myocardium after acute myocardial infarction (AMI). We evaluated the effects of microvascular injury (MVI) and intramyocardial haemorrhage on local T1 and T2* values in patients with a reperfused AMI. Forty-three patients after reperfused AMI underwent cardiovascular magnetic resonance imaging (CMR) at 4 [3-5] days, including native MOLLI T1 and T2* mapping, STIR, cine imaging and LGE. T1 and T2* values were determined in LGE-defined regions of interest: the MI core incorporating MVI when present, the core-adjacent MI border zone (without any areas of MVI), and remote myocardium. Average T1 in the MI core was higher than in the MI border zone and remote myocardium. However, in the 20 (47%) patients with MVI, MI core T1 was lower than in patients without MVI (MVI 1048±78ms, no MVI 1111±89ms, p=0.02). MI core T2* was significantly lower in patients with MVI than in those without (MVI 20 [18-23]ms, no MVI 31 [26-39]ms, p<0.001). The presence of MVI profoundly affects MOLLI-measured native T1 values. T2* mapping suggested that this may be the result of intramyocardial haemorrhage. These findings have important implications for the interpretation of native T1 values shortly after AMI. (orig.)

  10. Rapid parametric mapping of the longitudinal relaxation time T1 using two-dimensional variable flip angle magnetic resonance imaging at 1.5 Tesla, 3 Tesla, and 7 Tesla.

    Science.gov (United States)

    Dieringer, Matthias A; Deimling, Michael; Santoro, Davide; Wuerfel, Jens; Madai, Vince I; Sobesky, Jan; von Knobelsdorff-Brenkenhoff, Florian; Schulz-Menger, Jeanette; Niendorf, Thoralf

    2014-01-01

    Visual but subjective reading of longitudinal relaxation time (T1) weighted magnetic resonance images is commonly used for the detection of brain pathologies. For this non-quantitative measure, diagnostic quality depends on hardware configuration, imaging parameters, radio frequency transmission field (B1+) uniformity, as well as observer experience. Parametric quantification of the tissue T1 relaxation parameter offsets the propensity for these effects, but is typically time consuming. For this reason, this study examines the feasibility of rapid 2D T1 quantification using a variable flip angles (VFA) approach at magnetic field strengths of 1.5 Tesla, 3 Tesla, and 7 Tesla. These efforts include validation in phantom experiments and application for brain T1 mapping. T1 quantification included simulations of the Bloch equations to correct for slice profile imperfections, and a correction for B1+. Fast gradient echo acquisitions were conducted using three adjusted flip angles for the proposed T1 quantification approach that was benchmarked against slice profile uncorrected 2D VFA and an inversion-recovery spin-echo based reference method. Brain T1 mapping was performed in six healthy subjects, one multiple sclerosis patient, and one stroke patient. Phantom experiments showed a mean T1 estimation error of (-63±1.5)% for slice profile uncorrected 2D VFA and (0.2±1.4)% for the proposed approach compared to the reference method. Scan time for single slice T1 mapping including B1+ mapping could be reduced to 5 seconds using an in-plane resolution of (2×2) mm2, which equals a scan time reduction of more than 99% compared to the reference method. Our results demonstrate that rapid 2D T1 quantification using a variable flip angle approach is feasible at 1.5T/3T/7T. It represents a valuable alternative for rapid T1 mapping due to the gain in speed versus conventional approaches. This progress may serve to enhance the capabilities of parametric MR based lesion detection and

  11. Relaxation times T1, T2, and T2{sup *} of apples, pears, citrus fruits, and potatoes with a comparison to human tissues; T1-, T2- und T2{sup *}-Relaxationswerte von Aepfeln, Birnen, Zitrusfruechten und Kartoffeln im Vergleich zu menschlichen Geweben

    Energy Technology Data Exchange (ETDEWEB)

    Werz, Karin; Braun, Hans; Vitha, Dominik; Bruno, Graziano; Martirosian, Petros; Steidle, Guenter; Schick, Fritz [Tuebingen Univ. (Germany). Sektion fuer Experimentelle Radiologie

    2011-07-01

    The aim of the project was a systematic assessment of relaxation times of different fruits and vegetables and a comparison to values of human tissues. Results provide an improved basis for selection of plant phantoms for development of new MR techniques and sequences. Vessels filled with agar gel are mostly used for this purpose, preparation of which is effortful and time-consuming. In the presented study apples, (malus, 8 species), pears, (pyrus, 2 species), citrus fruits (citrus, 5 species) and uncooked potatoes (solanum tuberosum, 8 species) from the supermarket were examined which are easily available nearly all-the-year. T1, T2 and T2{sup *} relaxation times of these nature products were measured on a 1.5 Tesla MR system with adapted examination protocols and mono-exponential fitting, and compared to literature data of human parenchyma tissues, fatty tissue and body fluid (cerebrospinal fluid). Resulting values were as follows: apples: T1: 1486 - 1874 ms, T2: 163 - 281 ms, T2{sup *}: 2,3 - 3,2 ms; pears: T1: 1631 - 1969 ms, T2: 119 - 133 ms, T2{sup *}: 10,1 - 10,6 ms, citrus fruits (pulp) T1: 2055 - 2632 ms, T2: 497 - 998 ms, T2{sup *}: 151 - 182 ms; citrus fruits (skin) T1: 561 - 1669 ms, T2: 93 - 119 ms; potatoes: T1: 1011 - 1459 ms, T2: 166 - 210 ms, T2{sup *}: 20 - 30 ms. All T1-values of the examined objects (except for potatoes and skins of citrus fruits) were longer than T1 values of human tissues. Also T2 values (except for pears and skins of citrus fruits) of the fruits and the potatoes tended to be longer. T2{sup *} values of apples, pears and potatoes were shorter than in healthy human tissue. Results show relaxation values of many fruits to be not exactly fitting to human tissue, but with suitable selection of the fruits and optionally with an adaption of measurement parameters one can achieve suitable contrast and signal characteristics for some purposes. (orig.)

  12. Universal properties of relaxation and diffusion in condensed matter

    International Nuclear Information System (INIS)

    Ngai K L

    2017-01-01

    By and large the research communities today are not fully aware of the remarkable universality in the dynamic properties of many-body relaxation/diffusion processes manifested in experiments and simulations on condensed matter with diverse chemical compositions and physical structures. I shall demonstrate the universality first from the dynamic processes in glass-forming systems. This is reinforced by strikingly similar properties of different processes in contrasting interacting systems all having nothing to do with glass transition. The examples given here include glass-forming systems of diverse chemical compositions and physical structures, conductivity relaxation of ionic conductors (liquid, glassy, and crystalline), translation and orientation ordered phase of rigid molecule, and polymer chain dynamics. Universality is also found in the change of dynamics when dimension is reduced to nanometer size in widely different systems. The remarkable universality indicates that many-body relaxation/diffusion is governed by fundamental physics to be unveiled. One candidate is classical chaos on which the coupling model is based, Universal properties predicted by this model are in accord with diverse experiments and simulations. (paper)

  13. In vitro properties and tumorigenicity of radiation-transformed clones of mouse 10T1/2 cells

    International Nuclear Information System (INIS)

    Otsu, Hiroshi; Yasukawa, Mieko; Terasima, Toyozo

    1983-01-01

    Nineteen radiation-induced and one spontaneously developed transformed foci were cloned from mouse 10T1/2 cells. Each clone was grown with normal 10T1/2 cells, and typing (types II and III) was carried out by making reference to the description of Reznikoff et al. Morphological characteristics of foci and their response to co-cultured normal counterparts are described. Some in vitro properties of the clones were examined and the relationship to each focus type is discussed. A reduced serum requirement of transformed clones was not recognized. Soft agar colonies were produced exclusively by type III clones. Tumorigenicity testing of the clones revealed that 93 % of type III clones were tumorigenic upon inoculation into syngeneic mice in an immunosuppressed condition. From these findings, it can be concluded that the tumorigenic potential of radiation-induced transformed cells can be predicted from the ability of the cells to form colonies in agar. (author)

  14. Relaxation Mechanisms, Structure and Properties of Semi-Coherent Interfaces

    Directory of Open Access Journals (Sweden)

    Shuai Shao

    2015-10-01

    Full Text Available In this work, using the Cu–Ni (111 semi-coherent interface as a model system, we combine atomistic simulations and defect theory to reveal the relaxation mechanisms, structure, and properties of semi-coherent interfaces. By calculating the generalized stacking fault energy (GSFE profile of the interface, two stable structures and a high-energy structure are located. During the relaxation, the regions that possess the stable structures expand and develop into coherent regions; the regions with high-energy structure shrink into the intersection of misfit dislocations (nodes. This process reduces the interface excess potential energy but increases the core energy of the misfit dislocations and nodes. The core width is dependent on the GSFE of the interface. The high-energy structure relaxes by relative rotation and dilatation between the crystals. The relative rotation is responsible for the spiral pattern at nodes. The relative dilatation is responsible for the creation of free volume at nodes, which facilitates the nodes’ structural transformation. Several node structures have been observed and analyzed. The various structures have significant impact on the plastic deformation in terms of lattice dislocation nucleation, as well as the point defect formation energies.

  15. Study on properties of stress relaxation for NiTiNb shape memory alloy

    International Nuclear Information System (INIS)

    Zhou Xuchang; Mo Huaqiang; Zeng Guangting; Shen Baoluo; Huo Yongzhong

    2002-01-01

    Stress relaxation tests at high temperature are performed for NiTiNb shape memory alloy to obtain the properties of stress relaxation. The relaxation curve fitted with the expression, which is deduced based on the relation between the relaxation and the creep. With the aid of experimental data, relaxation characteristic coefficient and remaining stress ratio are obtained, which characterize the relaxation behavior. The results of the study show that stress relaxation would be more evident with the higher temperature and/or greater initial stress. NiTiNb alloy has good relaxation resistance in the temperature range 300-400 degree C and the initial stress range 260-360 MPa. NiTiNb has better properties to resist relaxation than NiTiFe, therefore it is more applicable to work at high temperature

  16. Repeatability and reliability of muscle relaxation properties induced by motor cortical stimulation.

    Science.gov (United States)

    Molenaar, Joery P; Voermans, Nicol C; de Jong, Lysanne A; Stegeman, Dick F; Doorduin, Jonne; van Engelen, Baziel G

    2018-03-15

    Impaired muscle relaxation is a feature of many neuromuscular disorders. However, there are few tests available to quantify muscle relaxation. Transcranial magnetic stimulation (TMS) of the motor cortex can induce muscle relaxation by abruptly inhibiting corticospinal drive. The aim of our study is to investigate if repeatability and reliability of TMS-induced relaxation is greater than voluntary relaxation. Furthermore, effects of sex, cooling and fatigue on muscle relaxation properties were studied. Muscle relaxation of deep finger flexors was assessed in twenty-five healthy subjects (14 M and 11 F, aged 39.1{plus minus}12.7 and 45.3{plus minus}8.7 years old, respectively) using handgrip dynamometry. All outcome measures showed greater repeatability and reliability in TMS-induced relaxation compared to voluntary relaxation. The within-subject coefficient of variability of normalized peak relaxation rate was lower in TMS-induced relaxation than in voluntary relaxation (3.0 vs 19.7% in men, and 6.1 vs 14.3% in women). The repeatability coefficient was lower (1.3 vs 6.1 s -1 in men and 2.3 vs 3.1 s -1 in women), and the intraclass correlation coefficient was higher (0.95 vs 0.53 in men and 0.78 vs 0.69 in women), for TMS-induced relaxation compared to voluntary relaxation. TMS enabled to demonstrate slowing effects of sex, muscle cooling, and muscle fatigue on relaxation properties that voluntary relaxation could not. In conclusion, repeatability and reliability of TMS-induced muscle relaxation was greater compared to voluntary muscle relaxation. TMS-induced muscle relaxation has the potential to be used in clinical practice for diagnostic purposes and therapy effect monitoring in patients with impaired muscle relaxation.

  17. T1 relaxation time constants, influence of oxygen, and the oxygen transfer function of the human lung at 1.5 T—A meta-analysis

    Energy Technology Data Exchange (ETDEWEB)

    Dietrich, Olaf, E-mail: od@dtrx.net [Josef Lissner Laboratory for Biomedical Imaging, Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, Munich (Germany); Gaass, Thomas [Josef Lissner Laboratory for Biomedical Imaging, Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, Munich (Germany); Comprehensive Pneumology Center, German Center for Lung Research, Munich (Germany); Reiser, Maximilian F. [Josef Lissner Laboratory for Biomedical Imaging, Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, Munich (Germany)

    2017-01-15

    Purpose: To pool and summarize published data from magnetic resonance longitudinal relaxation measurements of the human lung at 1.5 T to provide a reliable basis of T{sub 1} relaxation time constants of healthy lung tissue both under respiration of room air and of pure oxygen. In particular, the oxygen-induced shortening of T{sub 1} was evaluated. Materials and methods: The PubMed database was comprehensively searched up to June 2016 for original publications in English containing quantitative T{sub 1} data (at least mean values and standard deviations) of the lung parenchyma of healthy subjects (minimum subject number: 3) at 1.5 T. From all included publications, T{sub 1} values of the lung of healthy subjects were extracted (inhaling room air and, if available, inhaling pure oxygen). Weighted mean values and standard deviations of all extracted data and the oxygen transfer function (OTF) were calculated. Results: 22 publications were included with a total number of 188 examined healthy subjects. 103 of these subjects (from 13 studies) were examined while breathing pure oxygen and room air; 85 subjects were examined only under room-air conditions. The weighted mean value (weighted sample standard deviation) of the room-air T{sub 1} values over all 22 studies was 1196 ms (152 ms). Based on studies with room-air and oxygen results, the mean T{sub 1} value at room-air conditions was 1172 ms (161 ms); breathing pure oxygen, the mean T{sub 1} value was reduced to 1054 ms (138 ms). This corresponds to a mean T{sub 1} reduction by 118 ms (35 ms) or 10.0 % (2.3 %) and to a mean OTF value of 1.22 (0.32) × 10{sup −3} s{sup −1}/(%O{sub 2}). Conclusion: This meta-analysis with data from 188 subjects indicates that the average T{sub 1} relaxation time constant of healthy lung tissue at 1.5 T is distributed around 1200 ms with a standard deviation of about 150 ms; breathing pure oxygen reduces this value significantly by 10 % to about 1050 ms.

  18. Properties of charmed particle nonleptonic interactions following from Δ T=1/2 rule for usual mesons and baryons

    International Nuclear Information System (INIS)

    Arbuzov, B.A.; Cartasheva, V.G.; Tikhonin, F.F.

    1978-01-01

    A version of weak interaction has been considered in the frame of the model of 4-colour quarks with integer charges. The white part of the nonleptonic Lagrangian, responsible for the weak decay of usual particles, is constructed in such a way, that the ΔT=1/2 rule be fulfilled. This requirement fixed in a certain way the set of the parameters of full weak hadronic current. Parameters obtained in such a way give a complete description of the part of the Lagrangian with c-quark. The properties of the latter one reproduce to a certain extent those of the Lagrangian obtained in the GIM model, however the Lagrangian obtained in this work contains additional terms, that cannot be derived in the GIM model

  19. Proton conductivity and relaxation properties of chitosan-acetate films

    International Nuclear Information System (INIS)

    Prokhorov, E.; Luna-Bárcenas, G.; González-Campos, J.B.; Kovalenko, Yu.; García-Carvajal, Z.Y.; Mota-Morales, J.

    2016-01-01

    Graphical abstract: Temperature dependence of conductivity, the number of density and proton mobility in chitosan-acetate film. - Highlights: • DD, conductivity, Vogel temperature dependent on the concentration of acetic acid. • Proton conductivity of CS-acetate films interpreted using two Grotthuss mechanisms. • Transformation between two mechanisms observed at the glass transition temperature. - Abstract: The effect of aqueous acetic acid solution concentration during the preparation of chitosan-acetate (CS-acetate) films on the conductivity and relaxation properties were studied by dielectric and FTIR spectroscopies, TGA measurements and X-Ray diffraction. Analyses of the experimental results on the degree of deacetylation, water absorption, conductivity, Vogel temperature and activation energy demonstrate a strong dependence of these parameters on the concentration of the acid acetic solutions from which the films have been obtained. The proton conductivity and relaxation properties of CS-acetate films have been interpreted using two Grotthuss “structural diffusion” and “pack-acid” mechanisms. The transformation between these two mechanisms observed at temperature higher than CS-acetate glass transition temperature is due to an increase in the thermal motion of CS chains, water evaporation, hydrogen bond between water molecules and side groups of CS breaking and formation of new bonds between NH 3 + and acetate ions. Additionally, application of the Rice and Roth model allowed estimating the temperature dependence of proton number and their mobility in CS-acetate films. A systematic interpretation on the appropriate conductivity mechanism will help trigger the design of smart materials used in flexible electronic, solid polymer electrolytes for fuel cells and solid polymer batteries based on CS-acetate films.

  20. Transport and relaxation properties of superfluid 3He. I. Kinetic equation and Bogoliubov quasiparticle relaxation rate

    International Nuclear Information System (INIS)

    Einzel, D.; Woelfle, P.

    1978-01-01

    The kinetic equation for Bogoliubov quasiparticles for both the A and B phases of superfluid 3 He is derived from the general matrix kinetic equation. A condensed expression for the exact spin-symmetric collision integral is given. The quasiparticle relaxation rate is calculated for the BW state using the s--p approximation for the quasiparticle scattering amplitude. By using the results for the quasiparticle relaxation rate, the mean free path of Bogoliubov quasiparticles is calculated for all temperatures

  1. Synthesis of Tumor-avid Photosensitizer-Gd(III)DTPA conjugates: impact of the number of gadolinium units in T1/T2 relaxivity, intracellular localization, and photosensitizing efficacy.

    Science.gov (United States)

    Goswami, Lalit N; White, William H; Spernyak, Joseph A; Ethirajan, Manivannan; Chen, Yihui; Missert, Joseph R; Morgan, Janet; Mazurchuk, Richard; Pandey, Ravindra K

    2010-05-19

    To develop novel bifunctional agents for tumor imaging (MR) and photodynamic therapy (PDT), certain tumor-avid photosensitizers derived from chlorophyll-a were conjugated with variable number of Gd(III)aminobenzyl DTPA moieties. All the conjugates containing three or six gadolinium units showed significant T(1) and T(2) relaxivities. However, as a bifunctional agent, the 3-(1'-hexyloxyethyl)pyropheophorbide-a (HPPH) containing 3Gd(III) aminophenyl DTPA was most promising with possible applications in tumor-imaging and PDT. Compared to HPPH, the corresponding 3- and 6Gd(III)aminobenzyl DTPA conjugates exhibited similar electronic absorption characteristics with a slightly decreased intensity of the absorption band at 660 nm. However, compared to HPPH, the excitation of the broad "Soret" band (near 400 nm) of the corresponding 3Gd(III)aminobenzyl-DTPA analogues showed a significant decrease in the fluorescence intensity at 667 nm.

  2. Calorimetric and relaxation properties of xylitol-water mixtures

    Science.gov (United States)

    Elamin, Khalid; Sjöström, Johan; Jansson, Helén; Swenson, Jan

    2012-03-01

    We present the first broadband dielectric spectroscopy (BDS) and differential scanning calorimetry study of supercooled xylitol-water mixtures in the whole concentration range and in wide frequency (10-2-106 Hz) and temperature (120-365 K) ranges. The calorimetric glass transition, Tg, decreases from 247 K for pure xylitol to about 181 K at a water concentration of approximately 37 wt. %. At water concentrations in the range 29-35 wt. % a plentiful calorimetric behaviour is observed. In addition to the glass transition, almost simultaneous crystallization and melting events occurring around 230-240 K. At higher water concentrations ice is formed during cooling and the glass transition temperature increases to a steady value of about 200 K for all higher water concentrations. This Tg corresponds to an unfrozen xylitol-water solution containing 20 wt. % water. In addition to the true glass transition we also observed a glass transition-like feature at 220 K for all the ice containing samples. However, this feature is more likely due to ice dissolution [A. Inaba and O. Andersson, Thermochim. Acta, 461, 44 (2007)]. In the case of the BDS measurements the presence of water clearly has an effect on both the cooperative α-relaxation and the secondary β-relaxation. The α-relaxation shows a non-Arrhenius temperature dependence and becomes faster with increasing concentration of water. The fragility of the solutions, determined by the temperature dependence of the α-relaxation close to the dynamic glass transition, decreases with increasing water content up to about 26 wt. % water, where ice starts to form. This decrease in fragility with increasing water content is most likely caused by the increasing density of hydrogen bonds, forming a network-like structure in the deeply supercooled regime. The intensity of the secondary β-relaxation of xylitol decreases noticeably already at a water content of 2 wt. %, and at a water content above 5 wt. % it has been replaced by a

  3. Properties and genomic analysis of Lactococcus garvieae lysogenic bacteriophage PLgT-1, a new member of Siphoviridae, with homology to Lactococcus lactis phages.

    Science.gov (United States)

    Hoai, Truong Dinh; Nishiki, Issei; Yoshida, Terutoyo

    2016-08-15

    The lysogenic phage PLgT-1 is highly prevalent in Lactococcus garvieae, which is a serious bacterial pathogen in marine fish. Therefore, information regarding this phage is one of the key factors to predict the evolution of this bacterium. However, many properties of this phage, its complete genome sequence, and its relationship with other viral communities has not been investigated to date. Here, we demonstrated that the phage PLgT-1 was not only induced by an induction agent (Mitomycin C), but could be released frequently during cell division in a nutrient-rich environment or in natural seawater. Integration of PLgT-1 into non-lysogenic bacteria via transduction changed the genotype, resulting in the diversification of L. garvieae. The complete DNA sequence of PLgT-1 was also determined. This phage has a dsDNA genome of 40,273bp with 66 open reading frames (ORFs). Of these, the biological functions of 24 ORFs could be predicted but those of 42 ORFs are unknown. Thus, PLgT-1 is a novel phage with several novel proteins encoded in its genome. The strict MegaBLAST search program for the PLgT-1 genome revealed that this phage had no similarities with other previously investigated phages specific to L. garvieae (WP-2 and GE1). Notably, PLgT-1 was relatively homologous with several phages of Lactococcus lactis and 17 of the 24 predicted proteins encoded in PLgT-1 were homologous with the deduced proteins of various phages from these dairy bacteria. Comparative genome analysis revealed that the L. garvieae phage PLgT-1 was most closely related to the L. lactis phage TP712. However, they differed from each other in genome size and gene arrangement. The results obtained in this study suggest that the lysogenic phage PLgT-1 is a new member of the family Siphoviridae and has been involved in horizontal gene exchange with microbial communities, especially with L. lactis and its phages. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Optical properties, morphology and elemental chemical composition of atmospheric particles at T1 supersite on MILAGRO campaign

    Science.gov (United States)

    Carabali, G.; Mamani-Paco, R.; Castro, T.; Peralta, O.; Herrera, E.; Trujillo, B.

    2011-05-01

    Atmospheric particles were sampled at T1 supersite (19°43' N latitude, 98°58' W longitude, and 2340 m above sea level) during MILAGRO campaign. T1 was located at the north of Mexico City Metropolitan Area (MCMA). Aerosol sampling was done by placing transmission electron microscope (TEM) copper grids on the last 5 stages of an 8-stage MOUDI cascade impactor (d50 = 1.8, 1.0, 0.56, 0.32, and 0.18 μm). Samples were obtained at morning (06:00-09:00), noon (11:00-14:00), afternoon (16:00-19:00) and evening (21:00-24:00) local time. Absorption and scattering coefficients, and particles concentration (0.01-3 μm aerodynamic diameter) were measured simultaneously using a PASP absorption photometer (operated at 550 nm), a portable integrating nephelometer (at 530 nm) and a CNI particle counter. TEM images of particles were acquired at different magnifications using a CM 200 Phillips TEM-EDAX system. The morphology of atmospheric particles for two aerodynamic diameters (0.18 and 1.8 μm) was compared using border-based fractal dimension. Particles sampled under Mexico City pollution influence showed not much variability, suggesting the presence of more compact particles in smaller sizes (d50 = 1.8 μm) at the site. The presence of higher numbers of compact particles can be attributed to aerosol aging and secondary aerosol formation, among others. Under early morning conditions, smaller particles (d50 = 0.18 μm) had more irregular features resulting in a higher average fractal dimension. Energy dispersive X-ray spectroscopy (EDS) was used to determine the elemental composition of particles. EDS analysis in particles with d50 = 0.18 μm showed a higher content of carbonaceous material and relevant amounts of Si, Fe, K, and Co. This may indicate an impact from industrial and vehicle's emissions on atmospheric particles.

  5. Study on Relaxation Damage Properties of High Viscosity Asphalt Sand under Uniaxial Compression

    Directory of Open Access Journals (Sweden)

    Yazhen Sun

    2018-01-01

    Full Text Available Laboratory investigations of relaxation damage properties of high viscosity asphalt sand (HVAS by uniaxial compression tests and modified generalized Maxwell model (GMM to simulate viscoelastic characteristics coupling damage were carried out. A series of uniaxial compression relaxation tests were performed on HVAS specimens at different temperatures, loading rates, and constant levels of input strain. The results of the tests show that the peak point of relaxation modulus is highly influenced by the loading rate in the first half of an L-shaped curve, while the relaxation modulus is almost constant in the second half of the curve. It is suggested that for the HVAS relaxation tests, the temperature should be no less than −15°C. The GMM is used to determine the viscoelastic responses, the Weibull distribution function is used to characterize the damage of the HVAS and its evolution, and the modified GMM is a coupling of the two models. In this paper, the modified GMM is implemented through a secondary development with the USDFLD subroutine to analyze the relaxation damage process and improve the linear viscoelastic model in ABAQUS. Results show that the numerical method of coupling damage provides a better approximation of the test curve over almost the whole range. The results also show that the USDFLD subroutine can effectively predict the relaxation damage process of HVAS and can provide a theoretical support for crack control of asphalt pavements.

  6. Formulation, Characterization, and Antitumor Properties of Trans- and Cis-Citral in the 4T1 Breast Cancer Xenograft Mouse Model.

    Science.gov (United States)

    Zeng, San; Kapur, Arvinder; Patankar, Manish S; Xiong, May P

    2015-08-01

    Citral is composed of a random mixture of two geometric stereoisomers geranial (trans-citral) and neral (cis-citral) yet few studies have directly compared their in vivo antitumor properties. A micelle formulation was therefore developed. Geranial and neral were synthesized. Commercially-purchased citral, geranial, and neral were formulated in PEG-b-PCL (block sizes of 5000:10,000, Mw/Mn 1.26) micelles. In vitro degradation, drug release, cytotoxicity, flow cytometry, and western blot studies were conducted. The antitumor properties of drug formulations (40 and 80 mg/kg based on MTD studies) were evaluated on the 4T1 xenograft mouse model and tumor tissues were analyzed by western blot. Micelles encapsulated drugs with >50% LE at 5-40% drug to polymer (w/w), displayed sustained release (t1/2 of 8-9 h), and improved drug stability at pH 5.0. The IC50 of drug formulations against 4T1 cells ranged from 1.4 to 9.9 μM. Western blot revealed that autophagy was the main cause of cytotoxicity. Geranial at 80 mg/kg was most effective at inhibiting tumor growth. Geranial is significantly more potent than neral and citral at 80 mg/kg (p < 0.001) and western blot of tumor tissues confirms that autophagy and not apoptosis is the major mechanism of tumor growth inhibition in p53-null 4T1 cells.

  7. The CAP Theorem Versus Databases with Relaxed ACID properties

    DEFF Research Database (Denmark)

    Frank, Lars; Pedersen, Rasmus Ulslev; Havnø Frank, Christian

    2014-01-01

    data from different locations can have at most two of the three desirable CAP properties [5]. The NoSQL movement has applied the CAP theorem as an argument against tradi- tional ACID (atomicity, consistency, isolation, and durabil- ity) databases, which prioritize consistency and partition- tolerance...

  8. The structural relaxation effect on the nanomechanical properties of a Ti-based bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yongjiang, E-mail: yjhuang@hit.edu.cn [State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001 (China); School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Key Laboratory of Micro-Systems and Micro-Structures Manufacturing, Harbin Institute of Technology, Ministry of Education, Harbin 150001 (China); Zhou, Binjun [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Chiu, YuLung, E-mail: y.chiu@bham.ac.uk [School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Fan, Hongbo [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wang, Dongjun [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Key Laboratory of Micro-Systems and Micro-Structures Manufacturing, Harbin Institute of Technology, Ministry of Education, Harbin 150001 (China); Sun, Jianfei; Shen, Jun [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2014-09-01

    Highlights: • The effect of structural relaxation on the nano-mechanical behaviors of BMGs is studied. • The indent load at first pop-in event, the hardness and Young’s modulus are enhanced after annealing. • The differences in nanomechanical properties can be attributed to their different atomic structure. - Abstract: Indentation experiments were performed on the as-cast and the annealed Ti-based bulk metallic glass samples to investigate the effect of structural relaxation on the nanomechanical behaviors of the material. The onset of pop-in event, Young’s modulus, and hardness were found to be sensitive to the structural relaxation of the testing material. The difference in nanomechanical properties between the as-cast and annealed BMG samples is interpreted in terms of free volume theory.

  9. The structural relaxation effect on the nanomechanical properties of a Ti-based bulk metallic glass

    International Nuclear Information System (INIS)

    Huang, Yongjiang; Zhou, Binjun; Chiu, YuLung; Fan, Hongbo; Wang, Dongjun; Sun, Jianfei; Shen, Jun

    2014-01-01

    Highlights: • The effect of structural relaxation on the nano-mechanical behaviors of BMGs is studied. • The indent load at first pop-in event, the hardness and Young’s modulus are enhanced after annealing. • The differences in nanomechanical properties can be attributed to their different atomic structure. - Abstract: Indentation experiments were performed on the as-cast and the annealed Ti-based bulk metallic glass samples to investigate the effect of structural relaxation on the nanomechanical behaviors of the material. The onset of pop-in event, Young’s modulus, and hardness were found to be sensitive to the structural relaxation of the testing material. The difference in nanomechanical properties between the as-cast and annealed BMG samples is interpreted in terms of free volume theory

  10. T1ρ magnetic resonance: basic physics principles and applications in knee and intervertebral disc imaging

    NARCIS (Netherlands)

    Wáng, Yì-Xiáng J.; Zhang, Qinwei; Li, Xiaojuan; Chen, Weitian; Ahuja, Anil; Yuan, Jing

    2015-01-01

    T1ρ relaxation time provides a new contrast mechanism that differs from T1- and T2-weighted contrast, and is useful to study low-frequency motional processes and chemical exchange in biological tissues. T1ρ imaging can be performed in the forms of T1ρ-weighted image, T1ρ mapping and T1ρ dispersion.

  11. Managing Consistency Anomalies in Distributed Integrated Databases with Relaxed ACID Properties

    DEFF Research Database (Denmark)

    Frank, Lars; Ulslev Pedersen, Rasmus

    2014-01-01

    In central databases the consistency of data is normally implemented by using the ACID (Atomicity, Consistency, Isolation and Durability) properties of a DBMS (Data Base Management System). This is not possible if distributed and/or mobile databases are involved and the availability of data also...... has to be optimized. Therefore, we will in this paper use so called relaxed ACID properties across different locations. The objective of designing relaxed ACID properties across different database locations is that the users can trust the data they use even if the distributed database temporarily...... is inconsistent. It is also important that disconnected locations can operate in a meaningful way in socalled disconnected mode. A database is DBMS consistent if its data complies with the consistency rules of the DBMS's metadata. If the database is DBMS consistent both when a transaction starts and when it has...

  12. Improved optical properties of InAs quantum dots for intermediate band solar cells by suppression of misfit strain relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Xie, H. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, Arizona 85287-6106 (United States); Prioli, R. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); Departamento de Física, Pontificia Universidade Católica do Rio de Janeiro, Marques de São Vicente 225, Rio de Janeiro 22452-900 RJ (Brazil); Fischer, A. M.; Ponce, F. A., E-mail: ponce@asu.edu [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); Kawabata, R. M. S.; Pinto, L. D.; Souza, P. L. [LabSem, CETUC, Pontificia Universidade Católica do Rio de Janeiro, Marques de São Vicente 225, Rio de Janeiro 22452-900 RJ (Brazil); Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutores – DISSE – PUC-Rio, RJ (Brazil); Jakomin, R. [Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutores – DISSE – PUC-Rio, RJ (Brazil); Campus de Xerem, UFRJ, Duque de Caxias-RJ (Brazil); Pires, M. P. [Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutores – DISSE – PUC-Rio, RJ (Brazil); Instituto de Física, UFRJ, Rio de Janeiro-RJ (Brazil)

    2016-07-21

    The properties of InAs quantum dots (QDs) have been studied for application in intermediate band solar cells. It is found that suppression of plastic relaxation in the QDs has a significant effect on the optoelectronic properties. Partial capping plus annealing is shown to be effective in controlling the height of the QDs and in suppressing plastic relaxation. A force balancing model is used to explain the relationship between plastic relaxation and QD height. A strong luminescence has been observed from strained QDs, indicating the presence of localized states in the desired energy range. No luminescence has been observed from plastically relaxed QDs.

  13. A model of magnetic and relaxation properties of the mononuclear [Pc2Tb](-)TBA+ complex.

    Science.gov (United States)

    Reu, O S; Palii, A V; Ostrovsky, S M; Tregenna-Piggott, P L W; Klokishner, S I

    2012-10-15

    The present work is aimed at the elaboration of the model of magnetic properties and magnetic relaxation in the mononuclear [Pc(2)Tb](-)TBA(+) complex that displays single-molecule magnet properties. We calculate the Stark structure of the ground (7)F(6) term of the Tb(3+) ion in the exchange charge model of the crystal field, taking account for covalence effects. The ground Stark level of the complex possesses the maximum value of the total angular momentum projection, while the energies of the excited Stark levels increase with decreasing |M(J)| values, thus giving rise to a barrier for the reversal of magnetization. The one-phonon transitions between the Stark levels of the Tb(3+) ion induced by electron-vibrational interaction are shown to lead to magnetization relaxation in the [Pc(2)Tb](-)TBA(+) complex. The rates of all possible transitions between the low-lying Stark levels are calculated in the temperature range 14 Krelaxation time of magnetization, we solve the set of master equations for the populations of the Stark levels. The relaxation time is shown to diminish from 3.2 × 10(-2) s to 1.52 × 10(-4) s as the temperature increases from 27 K to 40 K. The obtained values of the relaxation time are in satisfactory agreement with the observed ones. The developed model also provides satisfactory description of the dc-magnetic data and paramagnetic shifts.

  14. The study of magnetic properties and relaxation processes in Co/Au bimetallic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hrubovčák, Pavol [Department of Condensed Matter Physics, P.J. Šafárik University, Park Angelinum 9, Košice (Slovakia); Zeleňáková, Adriana, E-mail: adriana.zelenakova@upjs.sk [Department of Condensed Matter Physics, P.J. Šafárik University, Park Angelinum 9, Košice (Slovakia); Zeleňák, Vladimir [Department of Inorganic Chemistry, P.J. Šafárik University, Moyzesova 11, Košice (Slovakia); Kováč, Jozef [Institute of Experimental Physics, SAS, Watsonova 41, Košice (Slovakia)

    2015-11-15

    Co/Au bimetallic fine nanoparticles were prepared employing the method of microemulsion using reverse micelle as nanoreactor, controlling the particles size. Magnetic and structural properties of two different samples Co/Au1 and Co/Au2 with almost comparable size of Co core and different size of Au layer were studied. The investigation of magnetic relaxation processes present in the particles was carried out by means of ac and dc magnetization data obtained at different temperatures and magnitudes of magnetic field. We observed the existence of superspin glass state characterized by the strong inter-particle interactions in the nanoparticle systems. In this paper, we discuss the attributes of novel superspin glass magnetic state reflected on various features (saturated FC magnetization at low temperatures, shift of the Cole–Cole arc downwards) and calculated parameters (relaxation time, critical exponent zv ∼ 10 and frequency dependent criterion p < 0.05). Comparison of the magnetic properties of two studied samples show that the thickness of diamagnetic Au shell significantly influences the magnetic interactions and change the relaxation dynamics. - Highlights: • Co/Au fine nanoparticles prepared by reverse micelle as nanoreactor, controlling the size. • Existence of superspin glass state confirmed from ac magnetic susceptibility study. • Individual particles exhibit the collective behavior below glass temperature T{sub SSG}. • Influence of diamagnetic shell on the magnetic properties of core–shell nanoparticles.

  15. Sodium and T1rho MRI for molecular and diagnostic imaging of articular cartilage.

    Science.gov (United States)

    Borthakur, Arijitt; Mellon, Eric; Niyogi, Sampreet; Witschey, Walter; Kneeland, J Bruce; Reddy, Ravinder

    2006-11-01

    In this article, both sodium magnetic resonance (MR) and T1rho relaxation mapping aimed at measuring molecular changes in cartilage for the diagnostic imaging of osteoarthritis are reviewed. First, an introduction to structure of cartilage, its degeneration in osteoarthritis (OA) and an outline of diagnostic imaging methods in quantifying molecular changes and early diagnostic aspects of cartilage degeneration are described. The sodium MRI section begins with a brief overview of the theory of sodium NMR of biological tissues and is followed by a section on multiple quantum filters that can be used to quantify both bi-exponential relaxation and residual quadrupolar interaction. Specifically, (i) the rationale behind the use of sodium MRI in quantifying proteoglycan (PG) changes, (ii) validation studies using biochemical assays, (iii) studies on human OA specimens, (iv) results on animal models and (v) clinical imaging protocols are reviewed. Results demonstrating the feasibility of quantifying PG in OA patients and comparison with that in healthy subjects are also presented. The section concludes with the discussion of advantages and potential issues with sodium MRI and the impact of new technological advancements (e.g. ultra-high field scanners and parallel imaging methods). In the theory section on T1rho, a brief description of (i) principles of measuring T1rho relaxation, (ii) pulse sequences for computing T1rho relaxation maps, (iii) issues regarding radio frequency power deposition, (iv) mechanisms that contribute to T1rho in biological tissues and (v) effects of exchange and dipolar interaction on T1rho dispersion are discussed. Correlation of T1rho relaxation rate with macromolecular content and biomechanical properties in cartilage specimens subjected to trypsin and cytokine-induced glycosaminoglycan depletion and validation against biochemical assay and histopathology are presented. Experimental T1rho data from osteoarthritic specimens, animal models

  16. Estimation of magnetic relaxation property for CVD processed YBCO-coated conductors

    International Nuclear Information System (INIS)

    Takahashi, Y.; Kiuchi, M.; Otabe, E.S.; Matsushita, T.; Shikimachi, K.; Watanabe, T.; Kashima, N.; Nagaya, S.

    2010-01-01

    Ion Beam Assist Deposition/Chemical Vapor Deposition(IBAD/CVD)-processed YBCO-coated conductors with high critical current density J c at high magnetic fields are expected to be applied to superconducting equipments such as superconducting magnetic energy storage (SMES). For application to superconducting magnet in SMES one of the most important properties for superconductors is the relaxation property of superconducting current. In this paper, the relaxation property is investigated for IBAD/CVD-processed YBCO-coated conductors of the superconducting layer in the range of 0.18-0.90 μm. This property can be quantitatively characterized by the apparent pinning potential, U 0 *. It is found that U 0 * takes a smaller value due to the two-dimensional pinning mechanism at high magnetic fields for conductor with thinner superconducting layer. Although U 0 * decreases with increasing thickness at low magnetic fields at 20 K, it increases at high magnetic fields. The results are theoretically explained by the model of the flux creep and flow based on the dimensionality of flux pinning. Scaling analysis is examined for the dependence of U 0 * on the magnetic field, temperature and the layer thickness.

  17. Relaxation dynamics and thermophysical properties of vegetable oils using time-domain reflectometry.

    Science.gov (United States)

    Sonkamble, Anil A; Sonsale, Rahul P; Kanshette, Mahesh S; Kabara, Komal B; Wananje, Kunal H; Kumbharkhane, Ashok C; Sarode, Arvind V

    2017-04-01

    Dielectric relaxation studies of vegetable oils are important for insights into their hydrogen bonding and intermolecular dynamics. The dielectric relaxation and thermo physical properties of triglycerides present in some vegetable oils have been measured over the frequency range of 10 MHz to 7 GHz in the temperature region 25 to 10 °C using a time-domain reflectometry approach. The frequency and temperature dependence of dielectric constants and dielectric loss factors were determined for coconut, peanut, soya bean, sunflower, palm, and olive oils. The dielectric permittivity spectra for each of the studied vegetable oils are explained using the Debye model with their complex dielectric permittivity analyzed using the Havriliak-Negami equation. The dielectric parameters static permittivity (ε 0 ), high-frequency limiting static permittivity (ε ∞ ), average relaxation time (τ 0 ), and thermodynamic parameters such as free energy (∆F τ ), enthalpy (∆H τ ), and entropy of activation (∆S τ ) were also measured. Calculation and analysis of these thermodynamic parameters agrees with the determined dielectric parameters, giving insights into the temperature dependence of the molecular dynamics of these systems.

  18. Comparison of Property-Oriented Basis Sets for the Computation of Electronic and Nuclear Relaxation Hyperpolarizabilities.

    Science.gov (United States)

    Zaleśny, Robert; Baranowska-Łączkowska, Angelika; Medveď, Miroslav; Luis, Josep M

    2015-09-08

    In the present work, we perform an assessment of several property-oriented atomic basis sets in computing (hyper)polarizabilities with a focus on the vibrational contributions. Our analysis encompasses the Pol and LPol-ds basis sets of Sadlej and co-workers, the def2-SVPD and def2-TZVPD basis sets of Rappoport and Furche, and the ORP basis set of Baranowska-Łączkowska and Łączkowski. Additionally, we use the d-aug-cc-pVQZ and aug-cc-pVTZ basis sets of Dunning and co-workers to determine the reference estimates of the investigated electric properties for small- and medium-sized molecules, respectively. We combine these basis sets with ab initio post-Hartree-Fock quantum-chemistry approaches (including the coupled cluster method) to calculate electronic and nuclear relaxation (hyper)polarizabilities of carbon dioxide, formaldehyde, cis-diazene, and a medium-sized Schiff base. The primary finding of our study is that, among all studied property-oriented basis sets, only the def2-TZVPD and ORP basis sets yield nuclear relaxation (hyper)polarizabilities of small molecules with average absolute errors less than 5.5%. A similar accuracy for the nuclear relaxation (hyper)polarizabilites of the studied systems can also be reached using the aug-cc-pVDZ basis set (5.3%), although for more accurate calculations of vibrational contributions, i.e., average absolute errors less than 1%, the aug-cc-pVTZ basis set is recommended. It was also demonstrated that anharmonic contributions to first and second hyperpolarizabilities of a medium-sized Schiff base are particularly difficult to accurately predict at the correlated level using property-oriented basis sets. For instance, the value of the nuclear relaxation first hyperpolarizability computed at the MP2/def2-TZVPD level of theory is roughly 3 times larger than that determined using the aug-cc-pVTZ basis set. We link the failure of the def2-TZVPD basis set with the difficulties in predicting the first-order field

  19. Relaxation dynamics in the presence of pulse multiplicative noise sources with different correlation properties

    Science.gov (United States)

    Kargovsky, A. V.; Chichigina, O. A.; Anashkina, E. I.; Valenti, D.; Spagnolo, B.

    2015-10-01

    The relaxation dynamics of a system described by a Langevin equation with pulse multiplicative noise sources with different correlation properties is considered. The solution of the corresponding Fokker-Planck equation is derived for Gaussian white noise. Moreover, two pulse processes with regulated periodicity are considered as a noise source: the dead-time-distorted Poisson process and the process with fixed time intervals, which is characterized by an infinite correlation time. We find that the steady state of the system is dependent on the correlation properties of the pulse noise. An increase of the noise correlation causes the decrease of the mean value of the solution at the steady state. The analytical results are in good agreement with the numerical ones.

  20. Correlation between physical properties and ultrasonic relaxation parameters in transition metal tellurite glasses

    Science.gov (United States)

    Abd El-Moneim, A.

    2003-07-01

    The correlation between activation energy of ultrasonic relaxation process through the temperature range from 140 to 300 K and some physical properties has been investigated in pure TeO 2 and transition metal TeO 2-V 2O 5 and TeO 2-MoO 3 glasses according to Bridge and Patel's theory. The oxygen density (loss centers), number of two-well systems, hopping distance and mechanical relaxation time have been calculated in these glasses from the data of density, bulk modulus and stretching force constant of the glass. It has been found that the acoustic activation energy increased linearly with both the oxygen density and the number of two-well systems. The correlation between the acoustic activation energy and bulk modulus was achieved through the stretching force constant of the network and other structural parameters. Moreover, the experimental values of activation energy (V) agree well with those calculated from an empirical equation presented in this study in the form V=2.9×10 -7 F( F/ K) 3.37, where F is the stretching force constant of the glass and K is the experimental bulk modulus.

  1. Elastic properties, reaction kinetics, and structural relaxation of an epoxy resin polymer during cure

    Science.gov (United States)

    Heili, Manon; Bielawski, Andrew; Kieffer, John

    The cure kinetics of a DGEBA/DETA epoxy is investigated using concurrent Raman and Brillouin light scattering. Raman scattering allows us to monitor the in-situ reaction and quantitatively assess the degree of cure. Brillouin scattering yields the elastic properties of the system, providing a measure of network connectivity. We show that the adiabatic modulus evolves non-uniquely as a function of cure degree, depending on the cure temperature and the molar ratio of the epoxy. Two mechanisms contribute to the increase in the elastic modulus of the material during curing. First, there is the formation of covalent bonds in the network during the curing process. Second, following bond formation, the epoxy undergoes structural relaxation toward an optimally packed network configuration, enhancing non-bonded interactions. We investigate to what extent the non-bonded interaction contribution to structural rigidity in cross-linked polymers is reversible, and to what extent it corresponds to the difference between adiabatic and isothermal moduli obtained from static tensile, i.e. the so-called relaxational modulus. To this end, we simultaneously measure the adiabatic and isothermal elastic moduli as a function of applied strain and deformation rate.

  2. Influence of strain relaxation in axial [Formula: see text] nanowire heterostructures on their electronic properties.

    Science.gov (United States)

    Marquardt, Oliver; Krause, Thilo; Kaganer, Vladimir; Martín-Sánchez, Javier; Hanke, Michael; Brandt, Oliver

    2017-05-26

    We present a systematic theoretical study of the influence of elastic strain relaxation on the built-in electrostatic potentials and the electronic properties of axial [Formula: see text] nanowire (NW) heterostructures. Our simulations reveal that for a sufficiently large ratio between the thickness of the [Formula: see text] disk and the diameter of the NW, the elastic relaxation leads to a significant reduction of the built-in electrostatic potential in comparison to a planar system of similar layer thickness and In content. In this case, the ground state transition energies approach constant values with increasing thickness of the disk and only depend on the In content, a behavior usually associated to that of a quantum well free of built-in electrostatic potentials. We show that the structures under consideration are by no means field-free, and the built-in potentials continue to play an important role even for ultrathin NWs. In particular, strain and the resulting polarization potentials induce complex confinement features of electrons and holes, which depend on the In content, shape, and dimensions of the heterostructure.

  3. Enhanced AC conductivity and dielectric relaxation properties of polypyrrole nanoparticles irradiated with Ni12+ swift heavy ions

    International Nuclear Information System (INIS)

    Hazarika, J.; Kumar, A.

    2014-01-01

    In this paper, we report the 160 MeV Ni 12+ swift heavy ions (SHIs) irradiation effects on AC conductivity and dielectric relaxation properties of polypyrrole (PPy) nanoparticles in the frequency range of 42 Hz–5 MHz. Four ion fluences of 5 × 10 10 , 1 × 10 11 , 5 × 10 11 and 1 × 10 12 ions/cm 2 have been used for the irradiation purpose. Transport properties in the pristine and irradiated PPy nanoparticles have been investigated with permittivity and modulus formalisms to study the polarization effects and conductivity relaxation. With increasing ion fluence, the relaxation peak in imaginary modulus (M ″ ) plots shifts toward high frequency suggesting long range motion of the charge carriers. The AC conductivity studies suggest correlated barrier hopping as the dominant transport mechanism. The hopping distance (R ω ) of the charge carriers decreases with increasing the ion fluence. Binding energy (W m ) calculations depict that polarons are the dominant charge carriers

  4. Temperature-Induced Lattice Relaxation of Perovskite Crystal Enhances Optoelectronic Properties and Solar Cell Performance

    KAUST Repository

    Banavoth, Murali

    2016-12-14

    Hybrid organic-inorganic perovskite crystals have recently become one of the most important classes of photoactive materials in the solar cell and optoelectronic communities. Albeit improvements have focused on state-of-the-art technology including various fabrication methods, device architectures, and surface passivation, progress is yet to be made in understanding the actual operational temperature on the electronic properties and the device performances. Therefore, the substantial effect of temperature on the optoelectronic properties, charge separation, charge recombination dynamics, and photoconversion efficiency are explored. The results clearly demonstrated a significant enhancement in the carrier mobility, photocurrent, charge carrier lifetime, and solar cell performance in the 60 ± 5 °C temperature range. In this temperature range, perovskite crystal exhibits a highly symmetrical relaxed cubic structure with well-aligned domains that are perpendicular to a principal axis, thereby remarkably improving the device operation. This finding provides a new key variable component and paves the way toward using perovskite crystals in highly efficient photovoltaic cells.

  5. Composition effect of potassium-borate glasses on their relaxation properties

    International Nuclear Information System (INIS)

    Lomovskoj, V.A.; Bartenev, G.M.

    1995-01-01

    Relaxation processes in potassium-borate glasses have been investigated in detail for the first time. It is shown that low-temperature β-process of relaxation relating to rotational mobility of the B-O bond is the same for all potassium-borate glasses and B 2 O 3 . The process of β k -relaxation related to diffusion mobility of potassium ions depends on the composition of the glasses in the same way as α-relaxation (glass formation).12 refs., 10 figs., 2 tabs

  6. Correlation between structural relaxation enthalpy and superconducting properties of amorphous Zr70Cu30 and Zr70Ni30 alloys

    International Nuclear Information System (INIS)

    Inoue, A.; Matsuzaki, K.; Toyota, N.; Chen, H.S.; Masumoto, T.; Fukase, T.

    1985-01-01

    The anneal-induced change in the superconducting properties together with the irrecoverable relaxation enthalpy (ΔHsub(i,exo)) and recoverable relaxation enthalpy (ΔHsub(r,endo)) of amorphous Zr 70 Cu 30 and Zr 70 Ni 30 alloys was examined. The increase in ΔHsub(i,exo) and the degradation of Tsub(c) progress logarithmically with annealing time tsub(a) in a temperature range of 373 to 523 K. The activation energy and the attempted frequency were respectively estimated to be 1.5 eV and 6.6 x 10 13 sec -1 for the increase in ΔHsub(i,exo) and 1.5 eV and 1.9 x 10 14 sec -1 for the degradation of Tsub(c). The recoverable structure relaxation exerts little effect on Tsub(c). Based on the agreement between the kinetic parameters for the changes of ΔHsub(i,exo) and Tsub(c), it appears that the degradation of Tsub(c) on annealing is associated with the irrecoverable structural relaxation as a result of the annihilation of frozen-in defects and the topological and compositional atomic rearrangement. The values of the attempted frequency being of the order of Debye frequency suggest that the irrecoverable structural relaxation processes occur more or less independently from each other. (author)

  7. Acute effects of 15min static or contract-relax stretching modalities on plantar flexors neuromuscular properties.

    Science.gov (United States)

    Babault, Nicolas; Kouassi, Blah Y L; Desbrosses, Kevin

    2010-03-01

    The present study aimed to investigate the immediate effects of 15 min static or sub-maximal contract-relax stretching modalities on the neuromuscular properties of plantar flexor muscles. Ten male volunteers were tested before and immediately after 15 min static or contract-relax stretching programs of plantar flexor muscles (20 stretches). Static stretching consisted in 30s stretches to the point of discomfort. For the contract-relax stretching modality, subjects performed 6s sub-maximal isometric plantar flexion before 24s static stretches. Measurements included maximal voluntary isometric torque (MVT) and the corresponding electromyographic activity of soleus (SOL) and medial gastrocnemius (MG) muscles (RMS values), as well as maximal peak torque (Pt) elicited at rest by single supramaximal electrical stimulation of the tibial nerve. After 15 min stretching, significant MVT and SOL RMS decreases were obtained (-6.9+/-11.6% and -6.5+/-15.4%, respectively). No difference was obtained between stretching modalities. Pt remained unchanged after stretching. MG RMS changes were significantly different between stretching modalities (-9.4+/-18.3% and +3.5+/-11.6% after static and contract-relax stretching modalities, respectively). These findings indicated that performing 15 min static or contract-relax stretching had detrimental effects on the torque production capacity of plantar flexor muscles and should be precluded before competition. Mechanisms explaining this alteration seemed to be stretch modality dependent. Copyright 2009 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  8. An instant photo-excited electrons relaxation on the photo-degradation properties of TiO2-x films

    CSIR Research Space (South Africa)

    Nkosi, SS

    2014-11-01

    Full Text Available of Photochemistry and Photobiology A: Chemistry 293 (2014) 72–80 An instant photo-excited electrons relaxation on the photo- degradation properties of TiO2−x films S.S. Nkosi a,b,∗, I. Kortidis d, D.E. Motaungc,∗, P.R. Makgwanec, O.M. Ndwandwe b, S.S. Rayc, G...

  9. The effects of strain relaxation on the dielectric properties of epitaxial ferroelectric Pb(Zr0.2Ti0.8)TiO3 thin films

    Science.gov (United States)

    Khan, Asif Islam; Yu, Pu; Trassin, Morgan; Lee, Michelle J.; You, Long; Salahuddin, Sayeef

    2014-07-01

    We study the effects of strain relaxation on the dielectric properties of epitaxial 40 nm Pb(Zr0.2Ti0.8)TiO3 (PZT) films. A significant increase in the defect and dislocation density due to strain relaxation is observed in PZT films with tetragonality c/a fatigue in ferroelectric materials.

  10. Effect of alkali ion on relaxation properties of binary alkali-borate glasses

    International Nuclear Information System (INIS)

    Lomovskoj, V.A.; Bartenev, G.M.

    1992-01-01

    Method of relaxation spectrometry were used to analyze the data on internal friction spectra of lithium, sodium, potassium and rubidium alkali-borate glasses in wide range of temperatures and frequencies. The nature of two relaxation processes was clarified: β m -process, related with mobility of alkaline metal cations, and α-process (vitrification), conditioned by system transformation from viscous-flow to vitreous state. It is shown that atomic-molecular mechanism of vitrification process changes when passing from vitreous B 2 O 3 to alkali-borate glasses

  11. Enhanced AC conductivity and dielectric relaxation properties of polypyrrole nanoparticles irradiated with Ni{sup 12+} swift heavy ions

    Energy Technology Data Exchange (ETDEWEB)

    Hazarika, J.; Kumar, A., E-mail: ask@tezu.ernet.in

    2014-08-15

    In this paper, we report the 160 MeV Ni{sup 12+} swift heavy ions (SHIs) irradiation effects on AC conductivity and dielectric relaxation properties of polypyrrole (PPy) nanoparticles in the frequency range of 42 Hz–5 MHz. Four ion fluences of 5 × 10{sup 10}, 1 × 10{sup 11}, 5 × 10{sup 11} and 1 × 10{sup 12} ions/cm{sup 2} have been used for the irradiation purpose. Transport properties in the pristine and irradiated PPy nanoparticles have been investigated with permittivity and modulus formalisms to study the polarization effects and conductivity relaxation. With increasing ion fluence, the relaxation peak in imaginary modulus (M{sup ″}) plots shifts toward high frequency suggesting long range motion of the charge carriers. The AC conductivity studies suggest correlated barrier hopping as the dominant transport mechanism. The hopping distance (R{sub ω}) of the charge carriers decreases with increasing the ion fluence. Binding energy (W{sub m}) calculations depict that polarons are the dominant charge carriers.

  12. Transport properties in amorphous U/sub x/-T1/sub -//sub x/ films (T = Fe, Ni, Gd, Tb, and Yb) (invited)

    International Nuclear Information System (INIS)

    Freitas, P.P.; Plaskett, T.S.; Moreira, J.M.; Amaral, V.S.

    1988-01-01

    We describe the competing magnetic, localization, and phonon effects on the transport properties of amorphous magnetic U/sub x/T/sub 1-//sub x/ films, with T = Fe, Ni, Gd, Tb, and Yb. Amorphous U/sub x/Fe/sub 1-//sub x/ films change from collinear to random ferromagnetism as x increases, and the temperature dependence of the resistivity denotes the competing effects of spin-flip and non-spin-flip exchange scattering processes. The resistivity has a minimum at T/sub f/ rising sharply below this temperature. The sign of the magnetic resistivity and the magnetoresistance indicates >0, while the anisotropic magnetoresistance indicates a local exchange gap. Amorphous U/sub x/Gd/sub 1-//sub x/ and a-U/sub x/Tb/sub 1-//sub x/ are, respectively, spin glasses and random anisotropy dominated systems. The resistivity increases smoothly through T/sub f/ and has a slight upturn at low temperatures that we associate with weak localization. The magnetoresistance is negative in both systems and the anisotropic magnetoresistance is null, although the applied field induces anisotropic behavior in the Tb containing films (asperomagnets). All samples show quadratic and positive field dependence of magnetoresistance well inside the paramagnetic regime, and a linear regime below T/sub f/. At low temperatures and in the a-U/sub x/Gd/sub 1-//sub x/ films, negative (H)/sup 1/2/ and H 2 regimes occur and are associated with weak localization processes dominated by the inelastic mean free path

  13. Evaluation of MRI sequences for quantitative T1 brain mapping

    Science.gov (United States)

    Tsialios, P.; Thrippleton, M.; Glatz, A.; Pernet, C.

    2017-11-01

    T1 mapping constitutes a quantitative MRI technique finding significant application in brain imaging. It allows evaluation of contrast uptake, blood perfusion, volume, providing a more specific biomarker of disease progression compared to conventional T1-weighted images. While there are many techniques for T1-mapping there is a wide range of reported T1-values in tissues, raising the issue of protocols reproducibility and standardization. The gold standard for obtaining T1-maps is based on acquiring IR-SE sequence. Widely used alternative sequences are IR-SE-EPI, VFA (DESPOT), DESPOT-HIFI and MP2RAGE that speed up scanning and fitting procedures. A custom MRI phantom was used to assess the reproducibility and accuracy of the different methods. All scans were performed using a 3T Siemens Prisma scanner. The acquired data processed using two different codes. The main difference was observed for VFA (DESPOT) which grossly overestimated T1 relaxation time by 214 ms [126 270] compared to the IR-SE sequence. MP2RAGE and DESPOT-HIFI sequences gave slightly shorter time than IR-SE (~20 to 30ms) and can be considered as alternative and time-efficient methods for acquiring accurate T1 maps of the human brain, while IR-SE-EPI gave identical result, at a cost of a lower image quality.

  14. T1 value of hyperplastic and hypoplastic bone marrow

    International Nuclear Information System (INIS)

    Asai, Sae; Yoshida, Hideo; Yoshikawa, Hiroki; Yashiro, Naofumi; Iio, Masahiro; Takaku, Fumimaro

    1985-01-01

    Magnetic resonance (MR) images of the bone marrow of 18 patients (11 normal control, 4 aplastic anemia, 2 chronic myelocytic leukemia, 1 polycythemia vera) were discussed. MR imager had 0.15T registive system. Sagittal section of the body was obtained with inversion recovery (TR1,000, 1,600/TI 350, 450/TE 13, 40 msec) and saturation recovery (TR 1,000, 2,000/TE 13,40 msec) sequences. T 1 relaxation time was calculated from those images. T 1 value of the thoracic and lumbar vertebral bone marrow which contains red marrow even in elderly patients was measured. The results were as follows: 1) T 1 values of chronic myelocytic leukemia (CML) and polycythemia vera were longer than that of normal. 2) T 1 values of four aplastic anemia were all shorter than normal. CML and polycythemia vera can be called myeloproliferative disease and their bone marrows are hyperplastic, which may explain elongated T 1 . The bone marrow of aplasticanemia is hypoplastic and shows fatty change which may have decreased T 1 . Our results suggest T 1 value of bone marrow is useful to evaluate hematological disorders. (author)

  15. Extracting energy and structure properties of glass-forming liquids from structural relaxation time.

    Science.gov (United States)

    Wang, Lianwen

    2012-04-18

    A comprehensive examination of the kinetic liquid model (Wang et al 2010 J. Phys.: Condens. Matter 22 455104) is carried out by fitting the structural relaxation time of 26 different glass-forming liquids in a wide temperature range, including most of the well-studied materials. Careful analysis of the compiled reported data reveals that experimental inaccuracies should not be overlooked in any 'benchmark test' of relating theories or models (e.g. in Lunkenheimer et al 2010 Phys. Rev. E 81 051504). The procedure, accuracy, ability, and efficiency of the kinetic liquid model are discussed in detail and in comparison with other available fitting methods. In general, the kinetic liquid model could be verified by 17 of the 26 compiled data sets and can serve as a meaningful approximative method for analyzing these liquids. Nonetheless, further experimental examinations in a wide temperature range are needed and are called for. Through fitting, the microscopic details of these liquids are extracted, namely, the enthalpy, entropy, and cooperativity in structural relaxation, which may facilitate further quantitative analysis to both the liquidus and glassy states of these materials.

  16. Electrical Properties and Dipole Relaxation Behavior of Zinc-Substituted Cobalt Ferrite

    Science.gov (United States)

    Supriya, Sweety; Kumar, Sunil; Kar, Manoranjan

    2017-12-01

    Co1- x Zn x Fe2O4 ceramics with x = 0.00, 0.05, 0.10, 0.15 and 0.20 were synthesized by a modified citric acid sol-gel method. The crystalline phase of the samples was characterized by the powder x-ray diffraction technique (XRD) and the Rietveld analysis of the XRD patterns. The morphology and particle size were studied using field emission scanning electron microscopy. Fourier transform infrared spectroscopy studies were consistent with the XRD results. The impedance measurements were carried out from 100 Hz to 10 MHz at different temperatures from 40°C to 300°C. The frequency dispersion of dielectric was analyzed with a modified Debye equation. The activation energy derived from the dielectric constant and the impedance follows the Arrhenius law and are comparable with each other. The dielectric relaxation and impedance relaxation are correlated in terms of activation energy, show a good temperature stability of the dielectrics and are useful for their applications in microelectronic devices such as filters, capacitors, resonators, etc.

  17. Study of the water content and relaxation properties of the uterine junctional zone

    International Nuclear Information System (INIS)

    McCarthy, S.; Scott, G.; Majumdar, S.; Thompson, S.; Shapiro, B.; Lange, R.; Gore, J.

    1988-01-01

    Nine hysterectomy specimens were imaged at 1.5T (General Electric Sigma), 5-mm single section, repetition time msec/echo time msec = 2,000/ 20, 40, 60, 80; and 500/20. With the use of tissue thickness measured from the images, weighed samples of myometrium, junctional zone, and endometrium were excised for determination of T1 and T2 in a 20-MHz spectrometer and then dried for determination of water content. The remainder of the uterus, examined with special histopathologic stains, demonstrated no significant difference in the number of blood vessels, smooth muscle cells, fibroblasts, elastin, iron, collagen, mucin, polysaccharide, or amyloid. The junctional zone water content (79.28%) was significantly lower than those of endometrium (82.88%; P = .004) and myometrium (8.05%; P = .0046). The T1 of the junctional zone (643) was significantly lower than those of endometrium (836, P = .004) and myometrium (709; P = .0114). Junctional zone T2 (58) was significantly lower than those of endometrium (87; P = .0114) and myometrium (66.7; P = .006)

  18. Structural Relaxations and Thermodynamic Properties of Molecular Amorphous Solids by Mechanical Milling

    Science.gov (United States)

    Tsukushi, I.; Yamamuro, O.; Matsuo, T.

    The organic crystals of tri-O-methyl-β-cyclodextrin (TMCD) and its three clathrate compounds containing benzoic acid (BA), p-nitrobenzoic acid (NBA) and p-hydroxybenzoic acid (HBA), sucrose (SUC), salicin (SAL), phenolphthalein (PP), 1,3,5-tri-α-naphthylbenzene (TNB) were amorphized by milling with a vibrating mill for 2 ˜ 16 hours at room temperature. The amorphization was checked by differential scanning calorimetry (DSC) and X-ray powder diffraction. The heat capacities of crystals, liquid quenched glasses (LQG), and mechanically-milled amorphous solid (MMAS) of TMCD and TNB were measured with an adiabatic calorimeter in the temperature range between 12 and 375 K. For both compounds, the enthalpy relaxation of MMAS appeared in the wide temperature range below Tg and the released configurational enthalpy was much larger than that of LQG, indicating that MMAS is more disordered and strained than LQG.

  19. Quantum close coupling calculation of transport and relaxation properties for Hg-H_2 system

    International Nuclear Information System (INIS)

    Nemati-Kande, Ebrahim; Maghari, Ali

    2016-01-01

    Highlights: • Several relaxation cross sections are calculated for Hg-H_2 van der Waals complex. • These cross sections are calculated from exact close-coupling method. • Energy-dependent SBE cross sections are calculated for ortho- and para-H_2 + Hg systems. • Viscosity and diffusion coefficients are calculated using Mason-Monchick approximation. • The results obtained by Mason-Monchick approximation are compared to the exact close-coupling results. - Abstract: Quantum mechanical close coupling calculation of the state-to-state transport and relaxation cross sections have been done for Hg-H_2 molecular system using a high-level ab initio potential energy surface. Rotationally averaged cross sections were also calculated to obtain the energy dependent Senftleben-Beenakker cross sections at the energy range of 0.005–25,000 cm"−"1. Boltzmann averaging of the energy dependent Senftleben-Beenakker cross sections showed the temperature dependency over a wide temperature range of 50–2500 K. Interaction viscosity and diffusion coefficients were also calculated using close coupling cross sections and full classical Mason-Monchick approximation. The results were compared with each other and with the available experimental data. It was found that Mason-Monchick approximation for viscosity is more reliable than diffusion coefficient. Furthermore, from the comparison of the experimental diffusion coefficients with the result of the close coupling and Mason-Monchick approximation, it was found that the Hg-H_2 potential energy surface used in this work can reliably predict diffusion coefficient data.

  20. Quantum close coupling calculation of transport and relaxation properties for Hg-H{sub 2} system

    Energy Technology Data Exchange (ETDEWEB)

    Nemati-Kande, Ebrahim; Maghari, Ali, E-mail: maghari@ut.ac.ir

    2016-11-10

    Highlights: • Several relaxation cross sections are calculated for Hg-H{sub 2} van der Waals complex. • These cross sections are calculated from exact close-coupling method. • Energy-dependent SBE cross sections are calculated for ortho- and para-H{sub 2} + Hg systems. • Viscosity and diffusion coefficients are calculated using Mason-Monchick approximation. • The results obtained by Mason-Monchick approximation are compared to the exact close-coupling results. - Abstract: Quantum mechanical close coupling calculation of the state-to-state transport and relaxation cross sections have been done for Hg-H{sub 2} molecular system using a high-level ab initio potential energy surface. Rotationally averaged cross sections were also calculated to obtain the energy dependent Senftleben-Beenakker cross sections at the energy range of 0.005–25,000 cm{sup −1}. Boltzmann averaging of the energy dependent Senftleben-Beenakker cross sections showed the temperature dependency over a wide temperature range of 50–2500 K. Interaction viscosity and diffusion coefficients were also calculated using close coupling cross sections and full classical Mason-Monchick approximation. The results were compared with each other and with the available experimental data. It was found that Mason-Monchick approximation for viscosity is more reliable than diffusion coefficient. Furthermore, from the comparison of the experimental diffusion coefficients with the result of the close coupling and Mason-Monchick approximation, it was found that the Hg-H{sub 2} potential energy surface used in this work can reliably predict diffusion coefficient data.

  1. Preparation of Mn-Zn ferrite nanoparticles and their silica-coated clusters: Magnetic properties and transverse relaxivity

    Energy Technology Data Exchange (ETDEWEB)

    Kaman, Ondřej, E-mail: kamano@seznam.cz [Institute of Physics, AS CR, Cukrovarnická 10, 162 00 Praha 6 (Czech Republic); Kuličková, Jarmila [Institute of Physics, AS CR, Cukrovarnická 10, 162 00 Praha 6 (Czech Republic); Herynek, Vít [Institute for Clinical and Experimental Medicine, Vídeňská 1958/9, 140 21 Praha 4 (Czech Republic); Koktan, Jakub [Institute of Physics, AS CR, Cukrovarnická 10, 162 00 Praha 6 (Czech Republic); University of Chemistry and Technology, Prague, Technická 5, 166 28 Praha 6 (Czech Republic); Maryško, Miroslav [Institute of Physics, AS CR, Cukrovarnická 10, 162 00 Praha 6 (Czech Republic); Dědourková, Tereza [Institute of Physics, AS CR, Cukrovarnická 10, 162 00 Praha 6 (Czech Republic); University of Pardubice, Doubravice 41, 532 10 Pardubice (Czech Republic); Knížek, Karel; Jirák, Zdeněk [Institute of Physics, AS CR, Cukrovarnická 10, 162 00 Praha 6 (Czech Republic)

    2017-04-01

    Hydrothermal synthesis of Mn{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} nanoparticles followed by direct encapsulation of the as-grown material into silica is demonstrated as a fast and facile method for preparation of efficient negative contrast agents based on clusters of ferrite crystallites. At first, the hydrothermal procedure is optimized to achieve strictly single-phase magnetic nanoparticles of Mn-Zn ferrites in the compositional range of x≈0.2–0.6 and with the mean size of crystallites ≈10 nm. The products are characterized by powder X-ray diffraction, X-ray fluorescence spectroscopy, and SQUID magnetometry, and the composition close to x=0.4 is selected for the preparation of silica-coated clusters with the mean diameter of magnetic cores ≈25 nm. Their composite structure is studied by means of transmission electron microscopy combined with detailed image analysis and magnetic measurements in DC fields. The relaxometric studies, performed in the magnetic field of B{sub 0}=0.5 T, reveal high transverse relaxivity (r{sub 2}(20 °C)=450 s{sup −1} mmol(Me{sub 3}O{sub 4}){sup −1} L) with a pronounced temperature dependence, which correlates with the observed temperature dependence of magnetization and is ascribed to a mechanism of transverse relaxation similar to the motional averaging regime. - Highlights: • Mn-Zn ferrite particles with size of ≈10 nm are synthesized by hydrothermal method. • Their structure and magnetic properties are analysed in dependence on composition. • Silica-coated clusters with the size ≈26 nm are prepared as contrast agent for MRI. • Their transverse relaxivity shows strong temperature dependence.

  2. Mechanical relaxation in glasses

    International Nuclear Information System (INIS)

    Hiki, Y.

    2004-01-01

    The basic properties of glasses and the characteristics of mechanical relaxation in glasses were briefly reviewed, and then our studies concerned were presented. Experimental methods adopted were viscosity, internal friction, ultrasonic attenuation, and Brillouin scattering measurements. The specimens used were several kinds of inorganic, organic, and metallic glasses. The measurements were mainly carried out from the room temperature up to the glass transition temperature, and the relaxation time was determined as a function of temperature. The 'double relaxation' composed of two Arrhenius-type relaxations was observed in many materials. In both relaxations, the 'compensation effect' showing a correlation of the pre-exponential factor and the activation energy was observed. These results were explained by considering the 'complex relaxation' due to cooperative motions of atoms or group of atoms. Values of activation energy near the glass transition determined by the various experimental methods were compared with each other

  3. Ab initio study on the effect of structural relaxation on the electronic and optical properties of P-doped Si nanocrystals

    International Nuclear Information System (INIS)

    Pi, Xiaodong; Ni, Zhenyi; Yang, Deren; Delerue, Christophe

    2014-01-01

    In contrast to the conventional doping of bulk silicon (Si), the doping of Si nanocrystals (NCs) that are often smaller than 5 nm in diameter may lead to serious structural changes. Since the electronic and optical properties of Si NCs are intimately associated with their structures, it is critical to understand how doping impacts the structures of Si NCs. By means of ab initio calculation we now compare 1.4 nm phosphorus (P)-doped Si NCs without structural relaxation and those with structural relaxation. Structural changes induced by structural relaxation are manifested by the stretching and compressing of bonds and apparent variations in bond angles. With the increase of the concentration of P structural changes induced by structural relaxation become more serious. It is found that structural relaxation makes differences in the energy-level schemes of P-doped Si NCs. Structural relaxation also causes the binding energy of an electron in a P-doped Si NC to more significantly increase as the concentration of P increases. With the increase of the concentration of P structural relaxation leads to more pronounced changes in the optical absorption of P-doped Si NCs

  4. Properties of the relaxation time distribution underlying the Kohlrausch-Williams-Watts photoionization of the DX centers in Cd1-xMnxTe mixed crystals

    International Nuclear Information System (INIS)

    Trzmiel, J; Weron, K; Placzek-Popko, E; Janczura, J

    2009-01-01

    In this paper we clarify the relationship between the relaxation rate and relaxation time distributions underlying the Kohlrausch-Williams-Watts (KWW) photoconductivity build-ups in indium- and gallium-doped Cd 1-x Mn x Te mixed crystals. We discuss the role of asymptotic properties of the corresponding probability density functions. We show that the relaxation rate distribution, as a completely asymmetric α-stable distribution, leads to an infinite mean value of the effective relaxation rate. In contrast, the relaxation time distribution related to it leads to a finite mean value of the effective relaxation time. It follows from the experimental data analysis that for all the investigated samples the KWW exponent α decreases linearly with increasing photon flux in the range of (0.6-0.99) and its values are more spread in the case of gallium-doped material. We also observe a linear dependence of the mean relaxation time on the characteristic material time constant, which is consistent with the theoretical model.

  5. MR imaging differentiation of Fe{sup 2+} and Fe{sup 3+} based on relaxation and magnetic susceptibility properties

    Energy Technology Data Exchange (ETDEWEB)

    Dietrich, Olaf [Ludwig-Maximilians-University Hospital Munich, Josef Lissner Laboratory for Biomedical Imaging, Institute for Clinical Radiology, Munich (Germany); Levin, Johannes [Ludwig-Maximilians-University Hospital Munich, Department of Neurology, Munich (Germany); German Center for Neurodegenerative Diseases (DZNE), Munich (Germany); Ahmadi, Seyed-Ahmad; Plate, Annika; Boetzel, Kai [Ludwig-Maximilians-University Hospital Munich, Department of Neurology, Munich (Germany); Reiser, Maximilian F.; Ertl-Wagner, Birgit [Ludwig-Maximilians-University Hospital Munich, Institute for Clinical Radiology, Munich (Germany); Giese, Armin [Ludwig-Maximilians-University Munich, Center for Neuropathology and Prion Research, Munich (Germany)

    2017-04-15

    The aim of this study is to evaluate the MR imaging behavior of ferrous (Fe{sup 2+}) and ferric (Fe{sup 3+}) iron ions in order to develop a noninvasive technique to quantitatively differentiate between both forms of iron. MRI was performed at 3 T in a phantom consisting of 21 samples with different concentrations of ferrous and ferric chloride solutions (between 0 and 10 mmol/L). A multi-echo spoiled gradient-echo pulse sequence with eight echoes was used for both T{sub 2}* and quantitative susceptibility measurements. The transverse relaxation rate, R{sub 2}* = 1/T{sub 2}*, was determined by nonlinear exponential fitting based on the mean signals in each sample. The susceptibilities, χ, of the samples were calculated after phase unwrapping and background field removal by fitting the spatial convolution of a unit dipole response to the measured internal field map. Relaxation rate changes, ΔR{sub 2}*(c{sub Fe}), and susceptibility changes, Δχ(c{sub Fe}), their linear slopes, as well as the ratios ΔR{sub 2}*(c{sub Fe}) / Δχ(c{sub Fe}) were determined for all concentrations. The linear slopes of the relaxation rate were (12.5 ± 0.4) s{sup -1}/(mmol/L) for Fe{sup 3+} and (0.77 ± 0.09) s{sup -1}/(mmol/L) for Fe{sup 2+} (significantly different, z test P < 0.0001). The linear slopes of the susceptibility were (0.088 ± 0.003) ppm/(mmol/L) for Fe{sup 3+} and (0.079 ± 0.006) ppm/(mmol/L) for Fe{sup 2+}. The individual ratios ΔR{sub 2}*/Δχ were greater than 40 s{sup -1}/ppm for all samples with ferric solution and lower than 20 s{sup -1}/ppm for all but one of the samples with ferrous solution. Ferrous and ferric iron ions show significantly different relaxation behaviors in MRI but similar susceptibility patterns. These properties can be used to differentiate ferrous and ferric samples. (orig.)

  6. Understanding Structure-Property Relations of Compressed Glasses through Relaxation Studies

    DEFF Research Database (Denmark)

    Smedskjær, Morten Mattrup; Svenson, Mouritz Nolsøe; Youngman, Randall E.

    under high pressure from both scientific and technological perspectives, since the glass structures frozen-in under elevated pressure may give rise to properties unattainable under ambient pressure. However, the structural and topological origins of the pressure-induced changes in macroscopic properties...

  7. Overview of the Benefits and Costs og Integrating Heterogeneous Applications by Using Relaxed ACID Properties

    DEFF Research Database (Denmark)

    Frank, Lars

    2012-01-01

    In central databases the consistency of data is normally implemented by using the ACID (Atomicity, Consistency, Isolation and Durability) properties of a DBMS (Data Base Management System). In practice, it is not possible to implement the ACID properties if heterogeneous or distributed databases ...

  8. Interpreting equilibrium-conductivity and conductivity-relaxation measurements to establish thermodynamic and transport properties for multiple charged defect conducting ceramics.

    Science.gov (United States)

    Zhu, Huayang; Ricote, Sandrine; Coors, W Grover; Kee, Robert J

    2015-01-01

    A model-based interpretation of measured equilibrium conductivity and conductivity relaxation is developed to establish thermodynamic, transport, and kinetics parameters for multiple charged defect conducting (MCDC) ceramic materials. The present study focuses on 10% yttrium-doped barium zirconate (BZY10). In principle, using the Nernst-Einstein relationship, equilibrium conductivity measurements are sufficient to establish thermodynamic and transport properties. However, in practice it is difficult to establish unique sets of properties using equilibrium conductivity alone. Combining equilibrium and conductivity-relaxation measurements serves to significantly improve the quantitative fidelity of the derived material properties. The models are developed using a Nernst-Planck-Poisson (NPP) formulation, which enables the quantitative representation of conductivity relaxations caused by very large changes in oxygen partial pressure.

  9. Influence of Nanodisperse Metal Fillers on the Viscoelastic Properties and Processes of Mechanical Relaxation of Polymer Systems

    Science.gov (United States)

    Kolupav, B. B.; Kolupaev, B. S.; Levchuk, V. V.; Maksimtsev, Yu. R.; Sidletskii, V. A.

    2017-05-01

    The results of research into the viscoelastic properties and processes of mechanical relaxation of polyvinylchloride (PVC) containing Cu nanoparticles obtained by means of electroerosion crushing and electrohydraulic destruction of agglomerates of disperse Cu in the presence of an ultrasonic field are presented. It is shown that, in the case of longitudinal shear deformation at a frequency of 0.4 × 106 s-1 over a wide range of temperatures and content of ingredients, viscoelastic phenomena depending on structural changes in the PVC system occur. An analysis of quantitative results of the elastic and viscoelastic deformation of a body is carried out taking into account the energy and entropy components of interaction of the polymer and filler at their interface.

  10. Electrokinetic properties and conductance relaxation of polystyrene and silver iodide plugs

    NARCIS (Netherlands)

    Hoven, van den J.J.

    1984-01-01

    This thesis describes an experimental study on the electrokinetic and electrical properties of concentrated polystyrene and silver iodide dispersions. The purpose of the study is to obtain information on the structure of the electrical double layer at the solid-liquid interface. Special

  11. Osteosarcoma: correlation of T1 map and histology map

    International Nuclear Information System (INIS)

    Suh, Jin Suck; Yun, Mi Jin; Jeong, Eun Kee; Shin, Kyoo Ho; Yang, Woo Ick

    1999-01-01

    To determine whether T1 mapping shows regional differences between viable and necrotic regions of osteosarcomas after anticancer chemotherapy and to assess whether this mapping is able to express the characteristics of various intramural tissue components. Eleven of 20 osteosarcomas were included in this study, while the remaining nine were excluded because the tumor site was inappropriate for comparison of T1 map and tumor macrosection. All patients underwent MR imaging for the purpose of T1 mapping, followed by pre-operative chemotherapy and subsequent limb-salvage surgery. Spin echo pulse sequencing was used with varying TR (100, 200, 400, 800, 1600, and 2400 msec) and a constant TE of 20 msec. Using a C-language software program, T1 relaxation time was calculated on a pixel-by-pixel basis and then a T1 map was generated by using a post-processing program, NIH Image. We attempted correlation of the T1 map and histologic findings, particularly in regions of interest(ROI) if certain areas were different from other regions on either the T1 or histologic map. Value was expressed as an average of the ratio of T1 of ROI and T1 of fat tissue, and this was used as an internal reference for normalization of the measurement. Tumor necrosis was 100 %(Grade IV) in six specimens, and over 90 % (Grade III) in five. Viable tumor cells were found mostly in regions with chondroid matrix and seldom in regions with osteoid matrix. Regardless of cell viability, values ranged from 0.9 to 9.87(mean, 4.02) in tumor necrotic area with osteoid matrices, and from 3.04 to 3.9(mean, 3.55) in areas with chondroid matrices. Other regions with fibrous tissue proliferation, hemorrhage, and fatty necrosis showed values of 2.92-9.83(mean, 7.20), 2.65-5.96(mean,3.59), and 1.43-3.11(mean, 2.68) respectively. The values of various tissues overlapped. No statistically significant difference was found between regions in which tumors were viable and those with tumor necrosis. Although we hypothesized

  12. Photovoltaic Properties and Ultrafast Plasmon Relaxation Dynamics of Diamond-Like Carbon Nanocomposite Films with Embedded Ag Nanoparticles.

    Science.gov (United States)

    Meškinis, Šarūnas; Peckus, Domantas; Vasiliauskas, Andrius; Čiegis, Arvydas; Gudaitis, Rimantas; Tamulevičius, Tomas; Yaremchuk, Iryna; Tamulevičius, Sigitas

    2017-12-01

    Ultrafast relaxation dynamics of diamond-like carbon (DLC) films with embedded Ag nanoparticles (DLC:Ag) and photovoltaic properties of heterojunctions consisting of DLC:Ag and crystalline silicon (DLC:Ag/Si) were investigated by means of transient absorption (TAS) spectroscopy and photovoltaic measurements. The heterojunctions using both p type and n type silicon were studied. It was found that TAS spectra of DLC:Ag films were dependent on the used excitation wavelength. At wavelengths where Ag nanoparticles absorbed light most intensively, only DLC signal was registered. This result is in good accordance with an increase of the DLC:Ag/Si heterojunction short circuit current and open circuit voltage with the excitation wavelength in the photovoltaic measurements. The dependence of the TAS spectra of DLC:Ag films and photovoltaic properties of DLC:Ag/Si heterostructures on the excitation wavelength was explained as a result of trapping of the photoexcited hot charge carriers in DLC matrix. The negative photovoltaic effect was observed for DLC:Ag/p-Si heterostructures and positive ("conventional") for DLC:Ag/n-Si ones. It was explained by the excitation of hot plasmonic holes in the Ag nanoparticles embedded into DLC matrix. Some decrease of DLC:Ag/Si heterostructures photovoltage as well as photocurrent with DLC:Ag film thickness was observed, indicating role of the interface in the charge transfer process of photocarriers excited in Ag nanoparticles.

  13. Effect of lanthanum substitution on dielectric relaxation, impedance response, conducting and magnetic properties of strontium hexaferrite

    Energy Technology Data Exchange (ETDEWEB)

    Want, Basharat, E-mail: bawant@kashmiruniversity.ac.in; Bhat, Bilal Hamid; Ahmad, Bhat Zahoor

    2015-04-05

    Highlights: • The substitution of La affects the dielectric and magnetic properties of strontium hexaferrite. • The electric behaviour of the compound follows the Koop’s phenomenological theory. • The impedance study shows the role of grain boundaries to the electric properties of the compound. • The substitution of La to strontium hexaferrite reduces the resistive nature of grain boundaries. - Abstract: Lanthanum strontium hexaferrite Sr{sub 1−x}La{sub x}Fe{sub 12}O{sub 19} (x = 0, 0.08, 0.13 , 0.18) has been successfully synthesized by using citrate-precursor method and characterized by different techniques. The X-ray diffraction results revealed that the sample is crystalline in nature and is of single phase with the space group P63/mmc. The dielectric, conducting and impedance related studies have been carried out as a function of frequency and concentration of lanthanum in the frequency ranges of 20 Hz–3 MHz. Impedance studies were performed in the frequency domain to distinguish between bulk and grain boundary contributions of the material to the overall dielectric response. The electric response of the material was also modeled by an equivalent circuit and different circuit parameters were calculated. Magnetic characterization of the material was also performed and the effect of lanthanum concentration was studied. The hysteresis loop obtained from the magnetometer showed that with the increase of lanthanum concentration, the saturation magnetisation decreases while as coercivity increases.

  14. NMR relaxation induced by iron oxide particles: testing theoretical models.

    Science.gov (United States)

    Gossuin, Y; Orlando, T; Basini, M; Henrard, D; Lascialfari, A; Mattea, C; Stapf, S; Vuong, Q L

    2016-04-15

    Superparamagnetic iron oxide particles find their main application as contrast agents for cellular and molecular magnetic resonance imaging. The contrast they bring is due to the shortening of the transverse relaxation time T 2 of water protons. In order to understand their influence on proton relaxation, different theoretical relaxation models have been developed, each of them presenting a certain validity domain, which depends on the particle characteristics and proton dynamics. The validation of these models is crucial since they allow for predicting the ideal particle characteristics for obtaining the best contrast but also because the fitting of T 1 experimental data by the theory constitutes an interesting tool for the characterization of the nanoparticles. In this work, T 2 of suspensions of iron oxide particles in different solvents and at different temperatures, corresponding to different proton diffusion properties, were measured and were compared to the three main theoretical models (the motional averaging regime, the static dephasing regime, and the partial refocusing model) with good qualitative agreement. However, a real quantitative agreement was not observed, probably because of the complexity of these nanoparticulate systems. The Roch theory, developed in the motional averaging regime (MAR), was also successfully used to fit T 1 nuclear magnetic relaxation dispersion (NMRD) profiles, even outside the MAR validity range, and provided a good estimate of the particle size. On the other hand, the simultaneous fitting of T 1 and T 2 NMRD profiles by the theory was impossible, and this occurrence constitutes a clear limitation of the Roch model. Finally, the theory was shown to satisfactorily fit the deuterium T 1 NMRD profile of superparamagnetic particle suspensions in heavy water.

  15. Spin wave relaxation and magnetic properties in [M/Cu] super-lattices; M=Fe, Co and Ni

    International Nuclear Information System (INIS)

    Fahmi, A.; Qachaou, A.

    2009-01-01

    In this work, we study the elementary excitations and magnetic properties of the [M/Cu] super-lattices with: M=Fe, Co and Ni, represented by a Heisenberg ferromagnetic system with N atomic planes. The nearest neighbour (NN), next nearest neighbour (NNN) exchange, dipolar interactions and surface anisotropy effects are taken into account and the Hamiltonian is studied in the framework of the linear spin wave theory. In the presence of the exchange alone, the excitation spectrum E(k) and the magnetization z >/S analytical expressions are obtained using the Green's function formalism. The obtained relaxation time of the magnon populations is nearly the same in the Fe and Co-based super-lattices, while these magnetic excitations would last much longer in the Ni-based super lattice. A numerical study of the surface anisotropy and long-ranged dipolar interaction combined effects are also reported. The exchange integral values deduced from a comparison with experience for the three super-lattices are coherent.

  16. Atomic level structural modulation during the structural relaxation and its effect on magnetic properties of Fe81Si4B10P4Cu1 nanocrystalline alloy

    Science.gov (United States)

    Cao, C. C.; Zhu, L.; Meng, Y.; Zhai, X. B.; Wang, Y. G.

    2018-06-01

    The evolution of local structure and defects in the Fe81Si4B10P4Cu1 amorphous alloy during the structural relaxation has been investigated by Mössbauer spectroscopy, positron annihilation lifetime spectroscopy and transmission electron microscopy to explore their effects on magnetic properties of the nanocrystalline. The atomic rearrangements at the early stage of the structural relaxation cause the density increase of the amorphous matrix, but the subsequent atomic rearrangements contribute to the transformation of Fe3B-like atomic arrangements to FeB-like ones with the temperature increasing. As the structural relaxation processes, the released Fe atoms both from Fe3B- and Fe3P-like atomic arrangements result in the formation of new Fe clusters and the increase of Fe-Fe coordination number in the existing Fe clusters and the nucleation sites for α-Fe gradually increase, both of which promote the crystallization. However, the homogeneity of amorphous matrix will be finally destroyed under excessive relaxation temperature, which coarsens nanograins during the crystallization instead. Therefore, soft magnetic properties of the Fe81Si4B10P4Cu1 nanocrystalline alloy can be improved by pre-annealing the amorphous precursor at an appropriate temperature due to the atomic level structural optimization.

  17. Rapid T1 quantification based on 3D phase sensitive inversion recovery

    Directory of Open Access Journals (Sweden)

    Warntjes Marcel JB

    2010-08-01

    Full Text Available Abstract Background In Contrast Enhanced Magnetic Resonance Imaging fibrotic myocardium can be distinguished from healthy tissue using the difference in the longitudinal T1 relaxation after administration of Gadolinium, the so-called Late Gd Enhancement. The purpose of this work was to measure the myocardial absolute T1 post-Gd from a single breath-hold 3D Phase Sensitivity Inversion Recovery sequence (PSIR. Equations were derived to take the acquisition and saturation effects on the magnetization into account. Methods The accuracy of the method was investigated on phantoms and using simulations. The method was applied to a group of patients with suspected myocardial infarction where the absolute difference in relaxation of healthy and fibrotic myocardium was measured at about 15 minutes post-contrast. The evolution of the absolute R1 relaxation rate (1/T1 over time after contrast injection was followed for one patient and compared to T1 mapping using Look-Locker. Based on the T1 maps synthetic LGE images were reconstructed and compared to the conventional LGE images. Results The fitting algorithm is robust against variation in acquisition flip angle, the inversion delay time and cardiac arrhythmia. The observed relaxation rate of the myocardium is 1.2 s-1, increasing to 6 - 7 s-1 after contrast injection and decreasing to 2 - 2.5 s-1 for healthy myocardium and to 3.5 - 4 s-1 for fibrotic myocardium. Synthesized images based on the T1 maps correspond very well to actual LGE images. Conclusions The method provides a robust quantification of post-Gd T1 relaxation for a complete cardiac volume within a single breath-hold.

  18. Low-Field NMR Spectrometry of Chalk and Argillaceous Sandstones: Rock-Fluid Affinity Assessed from T-1/T-2 Ratio

    DEFF Research Database (Denmark)

    Katika, Konstantina; Saidian, Milad; Prasad, Manika

    2017-01-01

    greensand shows different behavior for small and large pores. Small pores (fast-relaxing components) have T-1/T-2 = 2.0 when water saturated, but T-1/T-2 = 3.8 when oil saturated, indicating oil-affinity of chlorite. By contrast, large pores (slow-relaxing components) have significant preference for water...

  19. Investigation of Temperature Change under Influence of Ultrashort Laser Pulses Taking into Account Relaxation Properties of Materials

    Science.gov (United States)

    Eremin, A. V.; Kudinov, V. A.; Stefanyuk, E. V.; Kudinov, I. V.

    2018-03-01

    By using the modified Fourier law’s formula considering the relaxation of heat flow and temperature gradient, a mathematical model of the local non-equilibrium process of plate heating with ultrashort laser pulses was developed. The research showed that consideration of non-locality results in the delayed plate heat up irrespective of the laser radiation flow intensity. It was also shown that in consideration of the relaxation phenomena, the boundary conditions may not be fulfilled immediately – they may be set only within a definite range of the initial time.

  20. Relaxation System

    Science.gov (United States)

    1987-01-01

    Environ Corporation's relaxation system is built around a body lounge, a kind of super easy chair that incorporates sensory devices. Computer controlled enclosure provides filtered ionized air to create a feeling of invigoration, enhanced by mood changing aromas. Occupant is also surrounded by multidimensional audio and the lighting is programmed to change colors, patterns, and intensity periodically. These and other sensory stimulators are designed to provide an environment in which the learning process is stimulated, because research has proven that while an individual is in a deep state of relaxation, the mind is more receptive to new information.

  1. Longitudinal evaluation of T1ρ and T2 spatial distribution in osteoarthritic and healthy medial knee cartilage.

    Science.gov (United States)

    Schooler, J; Kumar, D; Nardo, L; McCulloch, C; Li, X; Link, T M; Majumdar, S

    2014-01-01

    To investigate longitudinal changes in laminar and spatial distribution of knee articular cartilage magnetic resonance imaging (MRI) T1ρ and T2 relaxation times, in individuals with and without medial compartment cartilage defects. All subjects (at baseline n = 88, >18 years old) underwent 3-Tesla knee MRI at baseline and annually thereafter for 3 years. The MR studies were evaluated for presence of cartilage defects (modified Whole-Organ Magnetic Resonance Imaging Scoring - mWORMS), and quantitative T1ρ and T2 relaxation time maps. Subjects were segregated into those with (mWORMS ≥2) and without (mWORMS ≤1) cartilage lesions at the medial tibia (MT) or medial femur (MF) at each time point. Laminar (bone and articular layer) and spatial (gray level co-occurrence matrix - GLCM) distribution of the T1ρ and T2 relaxation time maps were calculated. Linear regression models (cross-sectional) and Generalized Estimating Equations (GEEs) (longitudinal) were used. Global T1ρ, global T2 and articular layer T2 relaxation times at the MF, and global and articular layer T2 relaxation times at the MT, were higher in subjects with cartilage lesions compared to those without lesions. At the MT global T1ρ relaxation times were higher at each time point in subjects with lesions. MT T1ρ and T2 became progressively more heterogeneous than control compartments over the course of the study. Spatial distribution of T1ρ and T2 relaxation time maps in medial knee OA using GLCM technique may be a sensitive indicator of cartilage deterioration, in addition to whole-compartment relaxation time data. Copyright © 2013 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

  2. T1 hyperintense disc in alkaptonuria.

    Science.gov (United States)

    Sag, Alan A; Silbergleit, Richard; Olson, Rick E; Wilson, Jon; Krishnan, Anant

    2012-10-01

    Case report. To report a rare case of alkaptonuria presenting as a T1-hyperintense disc herniation. A 46-year-old man without previous diagnosis of alkaptonuria underwent evaluation for progressive back pain revealing a T1-hyperintense disc herniation at the L3-L4 level. Discectomy recovered a blackened disc that was pathologically confirmed to be nucleus pulposus with alkaptonuric involvement. The differential diagnosis of a T1-hyperintense, T2-hypointense disc on magnetic resonance imaging is discussed, with emphasis on the pathophysiology of alkaptonuria. A single patient is reported. Pathologically proven patient presentation with radiological and pathological images. We report a rare case of alkaptonuria presenting as a T1-hyperintense disc herniation.

  3. Preparation of Mn-Zn ferrite nanoparticles and their silica-coated clusters: magnetic properties and transverse relaxivity

    Czech Academy of Sciences Publication Activity Database

    Kaman, Ondřej; Kuličková, Jarmila; Herynek, Vít; Koktan, Jakub; Maryško, Miroslav; Dědourková, T.; Knížek, Karel; Jirák, Zdeněk

    2017-01-01

    Roč. 427, Apr (2017), s. 251-257 ISSN 0304-8853 Institutional support: RVO:68378271 ; RVO:68378041 Keywords : magnetic nanoparticles * Mn-Zn ferrite * hydrothermal synthesis * magnetic resonance imaging * transverse relaxivity Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.630, year: 2016

  4. Isotropic morphometry and multicomponent T1 ρ mapping of human knee articular cartilage in vivo at 3T.

    Science.gov (United States)

    Baboli, Rahman; Sharafi, Azadeh; Chang, Gregory; Regatte, Ravinder R

    2018-05-02

    The progressive loss of hyaline articular cartilage due to osteoarthritis (OA) changes the functional and biochemical properties of cartilage. Measuring the T 1 ρ along with the morphological assessment can potentially be used as noninvasive biomarkers in detecting early-stage OA. To correlate the biochemical and morphological data, submillimeter isotropic resolution for both studies is required. To implement a high spatial resolution 3D-isotropic-MRI sequence for simultaneous assessment of morphological and biexponential T 1 ρ relaxometry of human knee cartilage in vivo. Prospective. Ten healthy volunteers with no known inflammation, trauma, or pain in the knee. Standard FLASH sequence and customized Turbo-FLASH sequence to acquire 3D-isotropic-T 1 ρ-weighted images on a 3T MRI scanner. The mean volume and thickness along with mono- and biexponential T 1 ρ relaxations were assessed in the articular cartilage of 10 healthy volunteers. Nonparametric rank-sum tests. Bland-Altman analysis and coefficient of variation. The mean monoexponential T 1 ρ relaxation was 40.7 ± 4.8 msec, while the long and short components were 58.2 ± 3.9 msec and 6.5 ± 0.6 msec, respectively. The mean fractions of long and short T 1 ρ relaxation components were 63.7 ± 5.9% and 36.3 ± 5.9%, respectively. Statistically significant (P ≤ 0.03) differences were observed in the monoexponential and long components between some of the regions of interest (ROIs). No gender differences between biexponential components were observed (P > 0.05). Mean cartilage volume and thickness were 25.9 ± 6.4 cm 3 and 2.2 ± 0.7 mm, respectively. Cartilage volume (P = 0.01) and thickness (P = 0.03) were significantly higher in male than female participants across all ROIs. Bland-Altman analysis showed agreement between two morphological methods with limits of agreement between -1000 mm 3 and +1100 mm 3 for volume, and -0.78 mm and +0.46 mm for

  5. Cerebral abnormalities: use of calculated T1 and T2 magnetic resonance images for diagnosis

    International Nuclear Information System (INIS)

    Mills, C.M.; Crooks, L.E.; Kaufman, L.; Brant-Zawadzki, M.

    1984-01-01

    The potential clinical importance of T1 and T2 relaxation times in distinguishing normal and pathologic tissue with magnetic resonance (MR) is discussed and clinical examples of cerebral abnormalities are given. Five patients with cerebral infarction, 15 with multiple sclerosis, two with Wilson disease, and four with tumors were imaged. Hemorrhagic and ischemic cerebrovascular accidents were distinguished using the spin echo technique. In the patients with multiple sclerosis, lesions had prolonged T1 and T2 times, but the definition of plaque was limited by spatial resolution. No abnormalities in signal intensity were seen in the patient with Wilson disease who was no longer severly disabled; abnormal increased signal intensity in the basal ganglia was found in the second patient with Wilson disease. Four tumors produced abnormal T1 and T2 relaxation times but these values alone were not sufficient for tumor characterization

  6. Influence of anisotropic strain relaxation on the magnetoresistance properties of epitaxial Fe3O4 (110) films

    Science.gov (United States)

    Sofin, R. G. S.; Wu, Han-Chun; Ramos, R.; Arora, S. K.; Shvets, I. V.

    2015-11-01

    We studied Fe3O4 (110) films grown epitaxially on MgO (110) substrates using oxygen plasma assisted molecular beam epitaxy. The films with thickness of 30-200 nm showed anisotropic in-plane partial strain relaxation. Magneto resistance (MR) measurements with current and magnetic field along ⟨001⟩ direction showed higher MR compared to ⟨1 ¯ 10 ⟩ direction. Maximum value of MR was measured at Verwey transition temperature for both directions. We explain the observed anisotropy in the MR on the basis of the effects of anisotropic misfit strain, and the difference between the density of antiferromagnetically coupled antiphase boundaries formed along ⟨001⟩ and ⟨1 ¯ 10 ⟩ crystallographic directions, suggesting the dependence of spin polarisation on the anisotropic strain relaxation along the said crystallographic directions.

  7. Interpretation of NMR relaxation properties of Pin1, a two-domain protein, based on Brownian dynamic simulations

    International Nuclear Information System (INIS)

    Bernado, Pau; Fernandes, Miguel X.; Jacobs, Doris M.; Fiebig, Klaus; Garcia de la Torre, Jose; Pons, Miquel

    2004-01-01

    Many important proteins contain multiple domains connected by flexible linkers. Inter-domain motion is suggested to play a key role in many processes involving molecular recognition. Heteronuclear NMR relaxation is sensitive to motions in the relevant time scales and could provide valuable information on the dynamics of multi-domain proteins. However, the standard analysis based on the separation of global tumbling and fast local motions is no longer valid for multi-domain proteins undergoing internal motions involving complete domains and that take place on the same time scale than the overall motion.The complexity of the motions experienced even for the simplest two-domain proteins are difficult to capture with simple extensions of the classical Lipari-Szabo approach. Hydrodynamic effects are expected to dominate the motion of the individual globular domains, as well as that of the complete protein. Using Pin1 as a test case, we have simulated its motion at the microsecond time scale, at a reasonable computational expense, using Brownian Dynamic simulations on simplified models. The resulting trajectories provide insight on the interplay between global and inter-domain motion and can be analyzed using the recently published method of isotropic Reorientational Mode Dynamics which offer a way of calculating their contribution to heteronuclear relaxation rates. The analysis of trajectories computed with Pin1 models of different flexibility provides a general framework to understand the dynamics of multi-domain proteins and explains some of the observed features in the relaxation rate profile of free Pin1

  8. Interpretation of NMR relaxation properties of Pin1, a two-domain protein, based on Brownian dynamic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Bernado, Pau [Institut de Biologie Structurale, Jean Pierre Ebel (France); Fernandes, Miguel X. [Universidad de Murcia, Departamento de Quimica Fisica, Facultad de Quimica (Spain); Jacobs, Doris M. [Johann Wolfgang Goethe-Universitaet Frankfurt, Institut fuer Organische Chemie und Chemische Biologie (Germany); Fiebig, Klaus [Affinium Pharmaceuticals (Canada); Garcia de la Torre, Jose [Universidad de Murcia, Departamento de Quimica Fisica, Facultad de Quimica (Spain); Pons, Miquel [Laboratori de RMN de Biomolecules, Parc Cientific de Barcelona (Spain)], E-mail: mpons@ub.edu

    2004-05-15

    Many important proteins contain multiple domains connected by flexible linkers. Inter-domain motion is suggested to play a key role in many processes involving molecular recognition. Heteronuclear NMR relaxation is sensitive to motions in the relevant time scales and could provide valuable information on the dynamics of multi-domain proteins. However, the standard analysis based on the separation of global tumbling and fast local motions is no longer valid for multi-domain proteins undergoing internal motions involving complete domains and that take place on the same time scale than the overall motion.The complexity of the motions experienced even for the simplest two-domain proteins are difficult to capture with simple extensions of the classical Lipari-Szabo approach. Hydrodynamic effects are expected to dominate the motion of the individual globular domains, as well as that of the complete protein. Using Pin1 as a test case, we have simulated its motion at the microsecond time scale, at a reasonable computational expense, using Brownian Dynamic simulations on simplified models. The resulting trajectories provide insight on the interplay between global and inter-domain motion and can be analyzed using the recently published method of isotropic Reorientational Mode Dynamics which offer a way of calculating their contribution to heteronuclear relaxation rates. The analysis of trajectories computed with Pin1 models of different flexibility provides a general framework to understand the dynamics of multi-domain proteins and explains some of the observed features in the relaxation rate profile of free Pin1.

  9. Gluon fragmentation in T(1S) decays

    International Nuclear Information System (INIS)

    Bienlein, J.K.

    1983-05-01

    In T(1S) decays most observables (sphericity, charged multiplicity, photonic energy fraction, inclusive spectra) can be understood assuming that gluons fragment like quarks. New results from LENA use the (axis-independent) Fox-Wolfram moments for the photonic energy deposition. Continuum reactions show 'standard' Field-Feynman fragmentation. T(1S) decays show a significant difference in the photonic energy topology. It is more isotropic than with the Field-Feynman fragmentation scheme. Gluon fragmentation into isoscalar mesons (a la Peterson and Walsh) is excluded. But if one forces the leading particle to be isoscalar, one gets good agreement with the data. (orig.)

  10. Magnetic Resonance Fingerprinting with short relaxation intervals.

    Science.gov (United States)

    Amthor, Thomas; Doneva, Mariya; Koken, Peter; Sommer, Karsten; Meineke, Jakob; Börnert, Peter

    2017-09-01

    The aim of this study was to investigate a technique for improving the performance of Magnetic Resonance Fingerprinting (MRF) in repetitive sampling schemes, in particular for 3D MRF acquisition, by shortening relaxation intervals between MRF pulse train repetitions. A calculation method for MRF dictionaries adapted to short relaxation intervals and non-relaxed initial spin states is presented, based on the concept of stationary fingerprints. The method is applicable to many different k-space sampling schemes in 2D and 3D. For accuracy analysis, T 1 and T 2 values of a phantom are determined by single-slice Cartesian MRF for different relaxation intervals and are compared with quantitative reference measurements. The relevance of slice profile effects is also investigated in this case. To further illustrate the capabilities of the method, an application to in-vivo spiral 3D MRF measurements is demonstrated. The proposed computation method enables accurate parameter estimation even for the shortest relaxation intervals, as investigated for different sampling patterns in 2D and 3D. In 2D Cartesian measurements, we achieved a scan acceleration of more than a factor of two, while maintaining acceptable accuracy: The largest T 1 values of a sample set deviated from their reference values by 0.3% (longest relaxation interval) and 2.4% (shortest relaxation interval). The largest T 2 values showed systematic deviations of up to 10% for all relaxation intervals, which is discussed. The influence of slice profile effects for multislice acquisition is shown to become increasingly relevant for short relaxation intervals. In 3D spiral measurements, a scan time reduction of 36% was achieved, maintaining the quality of in-vivo T1 and T2 maps. Reducing the relaxation interval between MRF sequence repetitions using stationary fingerprint dictionaries is a feasible method to improve the scan efficiency of MRF sequences. The method enables fast implementations of 3D spatially

  11. Is the T1ρ MRI profile of hyaline cartilage in the normal hip uniform?

    Science.gov (United States)

    Rakhra, Kawan S; Cárdenas-Blanco, Arturo; Melkus, Gerd; Schweitzer, Mark E; Cameron, Ian G; Beaulé, Paul E

    2015-04-01

    T1ρ MRI is an imaging technique sensitive to proteoglycan (PG) content of hyaline cartilage. However, normative T1ρ values have not been established for the weightbearing cartilage of the hip, and it is not known whether it is uniform or whether there is topographic variation. Knowledge of the T1ρ profile of hyaline cartilage in the normal hip is important for establishing a baseline against which comparisons can be made to experimental and clinical arthritic subjects. In this diagnostic study, we determined (1) the T1ρ MRI values of hyaline cartilage of the normal hip; and (2) whether the T1ρ MRI profile of the normal hip hyaline cartilage is uniform. Fourteen asymptomatic volunteers (11 men, three women; mean age, 35 years) prospectively underwent 1.5-T T1ρ MRI of a single hip. The weightbearing hyaline cartilage bilayer of the acetabulum and femoral head was evaluated on sagittal images and segmented into four zones: (1) anterior; (2) anterosuperior; (3) posterosuperior; and (4) and posterior. For the full region of interest and within each zone and each sagittal slice, we calculated the mean T1ρ relaxation value, a parameter that indirectly quantifies PG content, where T1ρ is inversely related to PG concentration. There was variation in the T1ρ relaxation values depending on zone (anterior to posterior) and slice (medial to lateral). When combining the most anterior quadrants (Zones 1 and 2), the T1ρ relaxation values were lower than those in the combined posterior quadrants (Zones 3 and 4) (30.4 msec versus 32.2 msec, respectively; p = 0.002), reflecting higher PG concentration. There was a difference between the T1ρ relaxation values of the sagittal slices (p = 0.038), most pronounced anteriorly in Zone 1 (26.6 msec, p = 0.001). With a selective combination of zones and slices, there were lower mean T1ρ values in the anterolateral-most region compared with the remainder of the weightbearing portion of the hip (28.6 msec versus 32.2 msec

  12. Average beta measurement in EXTRAP T1

    International Nuclear Information System (INIS)

    Hedin, E.R.

    1988-12-01

    Beginning with the ideal MHD pressure balance equation, an expression for the average poloidal beta, Β Θ , is derived. A method for unobtrusively measuring the quantities used to evaluate Β Θ in Extrap T1 is described. The results if a series of measurements yielding Β Θ as a function of externally applied toroidal field are presented. (author)

  13. Single-shot T1 mapping of the corpus callosum: A rapid characterization of fiber bundle anatomy

    Directory of Open Access Journals (Sweden)

    Sabine eHofer

    2015-05-01

    Full Text Available Using diffusion-tensor MRI and fiber tractography the topographic organization of the corpus callosum (CC has been described to comprise 5 segments with fibers projecting into prefrontal (I, premotor and supplementary motor (II, primary motor (III, and primary sensory areas (IV, as well as into parietal, temporal, and occipital cortical areas (V. In order to more rapidly characterize the underlying anatomy of these segments, this study used a novel single-shot T1 mapping method to quantitatively determine T1 relaxation times in the human CC. A region-of-interest analysis revealed a tendency for the lowest T1 relaxation times in the genu and the highest T1 relaxation times in the somatomotor region of the CC. This observation separates regions dominated by myelinated fibers with large diameters (somatomotor area from densely packed smaller axonal bundles (genu with less myelin. The results indicate that characteristic T1 relaxation times in callosal profiles provide an additional means to monitor differences in fiber anatomy, fiber density, and gray matter in respective neocortical areas. In conclusion, rapid T1 mapping allows for a characterization of the axonal architecture in an individual CC in less than 10 s. The approach emerges as a valuable means for studying neocortical brain anatomy with possible implications for the diagnosis of neurodegenerative processes.

  14. Structurally Oriented Nano-Sheets in Co Thin Films: Changing Their Anisotropic Physical Properties by Thermally-Induced Relaxation.

    Science.gov (United States)

    Vergara, José; Favieres, Cristina; Magén, César; de Teresa, José María; Ibarra, Manuel Ricardo; Madurga, Vicente

    2017-12-05

    We show how nanocrystalline Co films formed by separated oblique nano-sheets display anisotropy in their resistivity, magnetization process, surface nano-morphology and optical transmission. After performing a heat treatment at 270 °C, these anisotropies decrease. This loss has been monitored measuring the resistivity as a function of temperature. The resistivity measured parallel to the direction of the nano-sheets has been constant up to 270 °C, but it decreases when measured perpendicular to the nano-sheets. This suggests the existence of a structural relaxation, which produces the change of the Co nano-sheets during annealing. The changes in the nano-morphology and the local chemical composition of the films at the nanoscale after heating above 270 °C have been analysed by scanning transmission electron microscopy (STEM). Thus, an approach and coalescence of the nano-sheets have been directly visualized. The spectrum of activation energies of this structural relaxation has indicated that the coalescence of the nano-sheets has taken place between 1.2 and 1.7 eV. In addition, an increase in the size of the nano-crystals has occurred in the samples annealed at 400 °C. This study may be relevant for the application in devices working, for example, in the GHz range and to achieve the retention of the anisotropy of these films at higher temperatures.

  15. Influence of strain relaxation on the optical properties of InGaN/GaN multiple quantum well nanorods

    International Nuclear Information System (INIS)

    Wang, Q; Bai, J; Gong, Y P; Wang, T

    2011-01-01

    Optical investigation has been carried out on InGaN/GaN nanorod structures with different indium compositions, fabricated from InGaN/GaN multiple quantum well (MQW) epitaxial wafers using a self-organized nickel nano-mask and subsequent dry etching techniques. In comparison with the as-grown InGaN/GaN MQWs, the internal quantum efficiencies of the nanorods are significantly improved, in particular, for the green InGaN/GaN nanorods with a high indium composition, the internal quantum efficiency is enhanced by a factor of 8, much larger than the enhancement factor of 3.4 for the blue InGaN/GaN nanorods. X-ray reciprocal space mapping (RSM) measurements have been performed in order to quantitatively evaluate the stain relaxation in the nanorods, demonstrating that the majority of strain in InGaN/GaN MQWs can be relaxed as a result of fabrication into nanorods. The excitation-power-dependent photoluminescence measurements have also clearly shown that a significant reduction in the strain-induced quantum confined stark effect has occurred to the nanorod structures.

  16. Structurally Oriented Nano-Sheets in Co Thin Films: Changing Their Anisotropic Physical Properties by Thermally-Induced Relaxation

    Directory of Open Access Journals (Sweden)

    José Vergara

    2017-12-01

    Full Text Available We show how nanocrystalline Co films formed by separated oblique nano-sheets display anisotropy in their resistivity, magnetization process, surface nano-morphology and optical transmission. After performing a heat treatment at 270 °C, these anisotropies decrease. This loss has been monitored measuring the resistivity as a function of temperature. The resistivity measured parallel to the direction of the nano-sheets has been constant up to 270 °C, but it decreases when measured perpendicular to the nano-sheets. This suggests the existence of a structural relaxation, which produces the change of the Co nano-sheets during annealing. The changes in the nano-morphology and the local chemical composition of the films at the nanoscale after heating above 270 °C have been analysed by scanning transmission electron microscopy (STEM. Thus, an approach and coalescence of the nano-sheets have been directly visualized. The spectrum of activation energies of this structural relaxation has indicated that the coalescence of the nano-sheets has taken place between 1.2 and 1.7 eV. In addition, an increase in the size of the nano-crystals has occurred in the samples annealed at 400 °C. This study may be relevant for the application in devices working, for example, in the GHz range and to achieve the retention of the anisotropy of these films at higher temperatures.

  17. Gd-Complexes of New Arylpiperazinyl Conjugates of DTPA-Bis(amides: Synthesis, Characterization and Magnetic Relaxation Properties

    Directory of Open Access Journals (Sweden)

    Abdullah O. Ba-Salem

    2015-04-01

    Full Text Available Two new DTPA-bis(amide based ligands conjugated with the arylpiperazinyl moiety were synthesized and subsequently transformed into their corresponding Gd(III complexes 1 and 2 of the type [Gd(LH2O]·nH2O. The relaxivity (R1 of these complexes was measured, which turned out to be comparable with that of Omniscan®, a commercially available MRI contrast agent. The cytotoxicity studies of these complexes indicated that they are non-toxic, which reveals their potential and physiological suitability as MRI contrast agents. All the synthesized ligands and complexes were characterized with the aid of analytical and spectroscopic methods, including elemental analysis, 1H-NMR, FT-IR, XPS and fast atom bombardment (FAB mass spectrometry.

  18. T1 value of hyperplastic and hypoplastic bone marrow. Preliminary report

    Energy Technology Data Exchange (ETDEWEB)

    Asai, Sae; Yoshida, Hideo; Yoshikawa, Hiroki; Yashiro, Naofumi; Iio, Masahiro; Takaku, Fumimaro

    1985-03-01

    Magnetic resonance (MR) images of the bone marrow of 18 patients (11 normal control, 4 aplastic anemia, 2 chronic myelocytic leukemia, 1 polycythemia vera) were discussed. MR imager had 0.15T registive system. Sagittal section of the body was obtained with inversion recovery (TR1,000, 1,600/TI 350, 450/TE 13, 40 msec) and saturation recovery (TR 1,000, 2,000/TE 13,40 msec) sequences. T1 relaxation time was calculated from those images. T1 value of the thoracic and lumbar vertebral bone marrow which contains red marrow even in elderly patients was measured. T1 values of chronic myelocytic leukemia (CML) and polycythemia vera were longer than that of normal. T1 values of four aplastic anemia were all shorter than normal. CML and polycythemia vera can be called myeloproliferative disease and their bone marrows are hyperplastic, which may explain elongated T1. The bone marrow of aplasticanemia is hypoplastic and shows fatty change which may have decreased T1. Our results suggest T1 value of bone marrow is useful to evaluate hematological disorders. (author).

  19. Influence of strain relaxation in axial {{In}}_{x}{{Ga}}_{1-x}{\\rm{N}}/{GaN} nanowire heterostructures on their electronic properties

    Science.gov (United States)

    Marquardt, Oliver; Krause, Thilo; Kaganer, Vladimir; Martín-Sánchez, Javier; Hanke, Michael; Brandt, Oliver

    2017-05-01

    We present a systematic theoretical study of the influence of elastic strain relaxation on the built-in electrostatic potentials and the electronic properties of axial {{In}}x{{Ga}}1-x{{N}}/{GaN} nanowire (NW) heterostructures. Our simulations reveal that for a sufficiently large ratio between the thickness of the {{In}}x{{Ga}}1-x{{N}} disk and the diameter of the NW, the elastic relaxation leads to a significant reduction of the built-in electrostatic potential in comparison to a planar system of similar layer thickness and In content. In this case, the ground state transition energies approach constant values with increasing thickness of the disk and only depend on the In content, a behavior usually associated to that of a quantum well free of built-in electrostatic potentials. We show that the structures under consideration are by no means field-free, and the built-in potentials continue to play an important role even for ultrathin NWs. In particular, strain and the resulting polarization potentials induce complex confinement features of electrons and holes, which depend on the In content, shape, and dimensions of the heterostructure.

  20. Properties of the relaxation time distribution underlying the Kohlrausch-Williams-Watts photoionization of the DX centers in Cd{sub 1-x}Mn{sub x}Te mixed crystals

    Energy Technology Data Exchange (ETDEWEB)

    Trzmiel, J; Weron, K; Placzek-Popko, E [Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Janczura, J [Hugo Steinhaus Center for Stochastic Methods and Institute of Mathematics and Computer Science, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland)

    2009-08-26

    In this paper we clarify the relationship between the relaxation rate and relaxation time distributions underlying the Kohlrausch-Williams-Watts (KWW) photoconductivity build-ups in indium- and gallium-doped Cd{sub 1-x}Mn{sub x}Te mixed crystals. We discuss the role of asymptotic properties of the corresponding probability density functions. We show that the relaxation rate distribution, as a completely asymmetric alpha-stable distribution, leads to an infinite mean value of the effective relaxation rate. In contrast, the relaxation time distribution related to it leads to a finite mean value of the effective relaxation time. It follows from the experimental data analysis that for all the investigated samples the KWW exponent alpha decreases linearly with increasing photon flux in the range of (0.6-0.99) and its values are more spread in the case of gallium-doped material. We also observe a linear dependence of the mean relaxation time on the characteristic material time constant, which is consistent with the theoretical model.

  1. Distinct human and mouse membrane trafficking systems for sweet taste receptors T1r2 and T1r3.

    Science.gov (United States)

    Shimizu, Madoka; Goto, Masao; Kawai, Takayuki; Yamashita, Atsuko; Kusakabe, Yuko

    2014-01-01

    The sweet taste receptors T1r2 and T1r3 are included in the T1r taste receptor family that belongs to class C of the G protein-coupled receptors. Heterodimerization of T1r2 and T1r3 is required for the perception of sweet substances, but little is known about the mechanisms underlying this heterodimerization, including membrane trafficking. We developed tagged mouse T1r2 and T1r3, and human T1R2 and T1R3 and evaluated membrane trafficking in human embryonic kidney 293 (HEK293) cells. We found that human T1R3 surface expression was only observed when human T1R3 was coexpressed with human T1R2, whereas mouse T1r3 was expressed without mouse T1r2 expression. A domain-swapped chimera and truncated human T1R3 mutant showed that the Venus flytrap module and cysteine-rich domain (CRD) of human T1R3 contain a region related to the inhibition of human T1R3 membrane trafficking and coordinated regulation of human T1R3 membrane trafficking. We also found that the Venus flytrap module of both human T1R2 and T1R3 are needed for membrane trafficking, suggesting that the coexpression of human T1R2 and T1R3 is required for this event. These results suggest that the Venus flytrap module and CRD receive taste substances and play roles in membrane trafficking of human T1R2 and T1R3. These features are different from those of mouse receptors, indicating that human T1R2 and T1R3 are likely to have a novel membrane trafficking system.

  2. Usefulness of T1 mapping on Gd-EOB-DTPA-enhanced MR imaging in assessment of non-alcoholic fatty liver disease

    International Nuclear Information System (INIS)

    Ding, Ying; Rao, Sheng-Xiang; Meng, Tao; Chen, Caizhong; Li, Renchen; Zeng, Meng-Su

    2014-01-01

    This study evaluates the value of Gd-EOB-DTPA-enhanced MRI for diagnosis and staging of non-alcoholic fatty liver disease (NAFLD) in an animal model by T 1 relaxation time measurement. Thirty-four rabbits were divided into the control group (n = 10) and NAFLD group, which was split into four groups (n = 6) with a high-fat diet for an interval of 3 weeks. A dual flip angle was performed before and at the hepatobiliary phase (HBP). T 1 relaxation times of the liver parenchyma and the decrease rate (∇%) were calculated. Histological findings according to semi-quantitative scoring of steatosis, activity and fibrosis were the standard of reference. HBP and ∇% T 1 relaxation time measurement showed significant differences between normal and NAFLD groups, between non-alcoholic steatohepatitis (NASH) and NAFLD without NASH (p = 0.000-0.049), between fibrosis groups (p = 0.000-0.019), but no difference between F1 and F2 (p = 0.834). The areas under the receiver operating characteristic curves (AUCs) of T 1 relaxation time for HBP and ∇% were 0.86-0.93 for the selection of NASH and activity score ≥2, and 0.86-0.95 for the selection of F ≥ 1, 2, 3. No significant difference was found for diagnostic performance between HBP and ∇% T 1 relaxation time. HBP T 1 relaxation time measurement of Gd-EOB-DTPA-enhanced MRI was useful to evaluate NAFLD according to the SAF score. HBP T 1 relaxation time measurement was as accurate as ∇% T 1 relaxation time. (orig.)

  3. Simultaneous acquisition for T2 -T2 Exchange and T1 -T2 correlation NMR experiments

    Science.gov (United States)

    Montrazi, Elton T.; Lucas-Oliveira, Everton; Araujo-Ferreira, Arthur G.; Barsi-Andreeta, Mariane; Bonagamba, Tito J.

    2018-04-01

    The NMR measurements of longitudinal and transverse relaxation times and its multidimensional correlations provide useful information about molecular dynamics. However, these experiments are very time-consuming, and many researchers proposed faster experiments to reduce this issue. This paper presents a new way to simultaneously perform T2 -T2 Exchange and T1 -T2 correlation experiments by taking the advantage of the storage time and the two steps phase cycling used for running the relaxation exchange experiment. The data corresponding to each step is either summed or subtracted to produce the T2 -T2 and T1 -T2 data, enhancing the information obtained while maintaining the experiment duration. Comparing the results from this technique with traditional NMR experiments it was possible to validate the method.

  4. Evolution of the electrical properties of amorphous Ni24Zr76 and Ni35Ti65 as a result of structural relaxation and crystallization

    International Nuclear Information System (INIS)

    Pelletier, J.M.; Fouquet, F.; Hillairet, J.

    1986-01-01

    Experimental results are given for the resistivity and the thermopower of two metallic glasses, Ni 24 Zr 76 and Ni 35 Ti 65 , together with the temperature dependences of these physical parameters, between 4 K (or 78 K) and crystallization temperature. In the as-quenched state the observed profiles are in qualitative agreement with the Mooij empirical law, but they agree only in part with the Ziman theory. The modifications which occur in response to successive thermal treatments are analyzed in terms of structural relaxation and crystallization processes. As expected the respective evolutions of the two electrical properties studied are found to be very closely related. It is shown that they can adequately be used to monitor the evolution of the volume fraction of crystallinity during the aging of amorphous metallic alloys. (author)

  5. Dynamic Properties of Glass-Formers Governed by the Frequency Dispersion of the Structural α-Relaxation: Examples from Prilocaine.

    Science.gov (United States)

    Wojnarowska, Z; Rams-Baron, M; Knapik, J; Ngai, K L; Kruk, D; Paluch, M

    2015-10-01

    General and fundamental properties of glass-formers of various chemical bonding and physical structures have been found in the recent past. These important findings should be key to gain basic understanding of the dynamics at all time scales leading to glass transition. However, the entirety of these general properties has not been found in a single glass-former. For others to appreciate the importance of these properties, they need to collect the supporting experimental data from different glass-formers scattered over many publications. This hurdle may account for the current lack of universal recognition of the importance of these general properties by the research community. In this paper we present experimental studies of the dynamic processes over a broad range of time scales of a single glass-former, prilocaine. Practically the entire collection of fundamental properties has been found in this system. The advance should heighten the awareness of the importance of these properties in anyone's effort to solve the glass transition problem.

  6. QM/MM studies on the excited-state relaxation mechanism of a semisynthetic dTPT3 base.

    Science.gov (United States)

    Guo, Wei-Wei; Zhang, Teng-Shuo; Fang, Wei-Hai; Cui, Ganglong

    2018-02-14

    Semisynthetic alphabets can potentially increase the genetic information stored in DNA through the formation of unusual base pairs. Recent experiments have shown that near-visible-light irradiation of the dTPT3 chromophore could lead to the formation of a reactive triplet state and of singlet oxygen in high quantum yields. However, the detailed excited-state relaxation paths that populate the lowest triplet state are unclear. Herein, we have for the first time employed the QM(MS-CASPT2//CASSCF)/MM method to explore the spectroscopic properties and excited-state relaxation mechanism of the aqueous dTPT3 chromophore. On the basis of the results, we have found that (1) the S 2 ( 1 ππ*) state of dTPT3 is the initially populated excited singlet state upon near-visible light irradiation; and (2) there are two efficient relaxation pathways to populate the lowest triplet state, i.e. T 1 ( 3 ππ*). In the first one, the S 2 ( 1 ππ*) system first decays to the S 1 ( 1 nπ*) state near the S 2 /S 1 conical intersection, which is followed by an efficient S 1 → T 1 intersystem crossing process at the S 1 /T 1 crossing point; in the second one, an efficient S 2 → T 2 intersystem crossing takes place first, and then, the T 2 ( 3 nπ*) system hops to the T 1 ( 3 ππ*) state through an internal conversion process at the T 2 /T 1 conical intersection. Moreover, an S 2 /S 1 /T 2 intersection region is found to play a vital role in the excited-state relaxation. These new mechanistic insights help in understanding the photophysics and photochemistry of unusual base pairs.

  7. Coherence transfer and electron T1-, T2-relaxation in nitroxide spin labels

    DEFF Research Database (Denmark)

    Marsh, Derek

    2017-01-01

    -hyperfine anisotropies of isolated nitroxide spin labels. Results compatible with earlier treatments by Redfield theory are obtained without specifically evaluating matrix elements. Extension to single-transition operators for isolated nitroxides predicts electron coherence transfer by pseudosecular electron...

  8. T1- Thresholds in Black Holes Increase Clinical-Radiological Correlation in Multiple Sclerosis Patients.

    Science.gov (United States)

    Thaler, Christian; Faizy, Tobias; Sedlacik, Jan; Holst, Brigitte; Stellmann, Jan-Patrick; Young, Kim Lea; Heesen, Christoph; Fiehler, Jens; Siemonsen, Susanne

    2015-01-01

    Magnetic Resonance Imaging (MRI) is an established tool in diagnosing and evaluating disease activity in Multiple Sclerosis (MS). While clinical-radiological correlations are limited in general, hypointense T1 lesions (also known as Black Holes (BH)) have shown some promising results. The definition of BHs is very heterogeneous and depends on subjective visual evaluation. We aimed to improve clinical-radiological correlations by defining BHs using T1 relaxation time (T1-RT) thresholds to achieve best possible correlation between BH lesion volume and clinical disability. 40 patients with mainly relapsing-remitting MS underwent MRI including 3-dimensional fluid attenuated inversion recovery (FLAIR), magnetization-prepared rapid gradient echo (MPRAGE) before and after Gadolinium (GD) injection and double inversion-contrast magnetization-prepared rapid gradient echo (MP2RAGE) sequences. BHs (BHvis) were marked by two raters on native T1-weighted (T1w)-MPRAGE, contrast-enhancing lesions (CE lesions) on T1w-MPRAGE after GD and FLAIR lesions (total-FLAIR lesions) were detected separately. BHvis and total-FLAIR lesion maps were registered to MP2RAGE images, and the mean T1-RT were calculated for all lesion ROIs. Mean T1 values of the cortex (CTX) were calculated for each patient. Subsequently, Spearman rank correlations between clinical scores (Expanded Disability Status Scale and Multiple Sclerosis Functional Composite) and lesion volume were determined for different T1-RT thresholds. Significant differences in T1-RT were obtained between all different lesion types with highest T1 values in visually marked BHs (BHvis: 1453.3±213.4 ms, total-FLAIR lesions: 1394.33±187.38 ms, CTX: 1305.6±35.8 ms; p1500 ms (Expanded Disability Status Scale vs. lesion volume: rBHvis = 0.442 and rtotal-FLAIR = 0.497, p<0.05; Multiple Sclerosis Functional Composite vs. lesion volume: rBHvis = -0.53 and rtotal-FLAIR = -0.627, p<0.05). Clinical-radiological correlations in MS patients are

  9. Enhancement of relaxation rates in the normal state of superconductor PuRhGa5:NQR relaxation study

    International Nuclear Information System (INIS)

    Sakai, H.; Kambe, S.; Tokunaga, Y.; Fujimoto, T.; Walstedt, R.E.; Yasuoka, H.; Aoki, D.; Homma, Y.; Yamamoto, E.; Nakamura, A.; Shiokawa, Y.; Nakajima, K.; Arai, Y.; Matsuda, T.D.; Haga, Y.; Onuki, Y.

    2007-01-01

    The spin-lattice relaxation rates (1/T 1 ) have been measured under zero field using nuclear quadrupole resonance (NQR) lines in superconductor PuRhGa 5 and Pauli-paramagnet LuCoGa 5 . In the reference LuCoGa 5 with fully-occupied 4f shell, the 1/T 1 shows the constant behavior of (T 1 T) -1 =0.495+/-0.002(sK) -1 . On the other hand, in PuRhGa 5 , 1/T 1 is much larger than in LuCoGa 5 and the 1/T 1 ∝T behavior below ∼30K is seen, where its (T 1 T) -1 value is 3.27+/-0.005(sK) -1 . These results suggest a development of coherent Fermi liquid state incorporated with 5f electrons below ∼30K in PuRhGa 5

  10. MHD activity during RFP startup in Extrap T1

    International Nuclear Information System (INIS)

    Drake, J.R.; Brzozowski, J.; Mazur, S.; Nordlund, P.

    1993-04-01

    During the startup phase of a reversed field pinch discharge (RFP), the configuration undergoes relaxation which is the dynamic process by which the configuration evolves to states near the minimum magnetic energy thus realising improved stability. A high loop voltage and a high level of level of m =1 poloidal mode activity is observed while this process occurs. After the RFP configuration is established, there is a substantial decrease in both the m = 1 activity and the loop voltage. In addition in the Extrap T1 device, under unfavourable conditions characterised by a pinch parameter θ less than about 1.5 at the time of reversal, the loop voltage can further increase substantially resulting in a suppressed plasma current level. Simultaneous with the loop voltage increase there is an observed increase in poloidal m = 0 mode activity. This occurs just when field reversal first is established as the surface with zero toroidal field is produced at the plasma edge. The increased loop voltage is believed to be the result of m = 0 tearing modes resonant at the reversal surface and driven by a large parallel current gradient at the edge which become particularly pathological when the θ, is comparatively low

  11. Extrap mode operation on Extrap T1-U

    International Nuclear Information System (INIS)

    Scheffel, J.; Brzozowski, J.; Hellblom, G.; Hoerling, P.; Welander, A.

    1995-02-01

    An extensive series of experiments in the Extrap mode has been carried out on Extrap T1-U in an attempt to obtain hot, collisionless discharges. Performance has, however, been limited to low temperatures (≤15 eV) and low currents (≤20 kA) at high loop voltages ≤1.4 kV, leading to energy confinement times of only a few μs or Alfven times. The discharge length is typically of order >100 Alfven times. The poor confinement is attributed to the absence of an axial magnetic field, generating strong instability- induced fluctuations and related transport in the core plasma. A turbulence core plasma transport model is suggested, based on theoretical evidence of linear instability in the kinetic regime. Experiments show that nonlinear saturation prevents the discharge from quenching on a time scale of a few Alfven times. Relaxation to RFP-like states is prevented from by a sufficiently strong octupole magnetic field. Edge transport appears to be strongly influenced by particle diffusion and heat conduction along open field lines (X-points) to the wall. 43 refs, 11 figs

  12. In vitro and in vivo aphrodisiac properties of the seed extract from Allium tuberosum on corpus cavernosum smooth muscle relaxation and sexual behavior parameters in male Wistar rats.

    Science.gov (United States)

    Tang, Xingli; Olatunji, Opeyemi J; Zhou, Yifeng; Hou, Xilin

    2017-12-01

    Allium tuberosum is a well-known spice as well as a herb in traditional Chinese medicine, used for increasing libido and treating erectile dysfunction. However, not many studies have been done to evaluate the sexual enhancing properties of A. tuberosum. The aim of this study was to evaluate the aphrodisiac and vasorelaxant properties of A. tuberosum on corpus cavernosum smooth muscle (CCSM) as well as checking the effect on enhancing male rat sexual behavior, libido, potency as well as its spermatogenic properties. The seeds were powdered and sequentially extracted with hexane, ethyl acetate and butanol. Male Wistar rats were administered with graded doses of the n-BuOH extracts (ATB) of A. tuberosum (50, 100, 200 and 400 mg/kg) and Viagra was used as the positive control drug. The extract/drug was administered by gastric probe once daily for 45 days and the sexual behavior was analyzed by exposing the male rats to female rats in the estrus period. ATB relaxed corpus cavernosum smooth muscle (68.9%) at a concentration of 200 μg/ml. The results obtained from the animal studies indicated that ATB significantly increased mount frequency (MF), intromission frequency (IF), ejaculation frequency (EF), ejaculation latency (EL) and markedly reduced post ejaculatory interval (PEI), mount latency (ML), and intromission latency (IL). Furthermore, a remarkable increase in the test for potency was observed as witnessed by marked increase in erections, quick flips, long flips and total reflex. In addition, ATB significantly improved the sperm viability and count as well as increased the concentrations of testosterone, follicle stimulating hormone (FSH), and phosphatases in the treated animals. Thus our results suggest that A. tuberosum could stimulate sexual arousal and enhance sexual execution in male rats, thus providing valuable experimental evidence that A. tuberosum possesses sexual enhancing properties.

  13. 7 Tesla quantitative hip MRI: T1, T2 and T2* mapping of hip cartilage in healthy volunteers

    Energy Technology Data Exchange (ETDEWEB)

    Lazik, Andrea; Theysohn, Jens M.; Geis, Christina [University Hospital Essen, Department of Diagnostic and Interventional Radiology and Neuroradiology, Essen (Germany); Johst, Soeren; Kraff, Oliver [University of Duisburg-Essen, Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen (Germany); Ladd, Mark E. [University Hospital Essen, Department of Diagnostic and Interventional Radiology and Neuroradiology, Essen (Germany); University of Duisburg-Essen, Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen (Germany); German Cancer Research Center (DKFZ), Medical Physics in Radiology, Heidelberg (Germany); Quick, Harald H. [University of Duisburg-Essen, Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen (Germany); University Hospital Essen, High Field and Hybrid MR Imaging, Essen (Germany)

    2016-05-15

    To evaluate the technical feasibility and applicability of quantitative MR techniques (delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), T2 mapping, T2* mapping) at 7 T MRI for assessing hip cartilage. Hips of 11 healthy volunteers were examined at 7 T MRI with an 8-channel radiofrequency transmit/receive body coil using multi-echo sequences for T2 and T2* mapping and a dual flip angle gradient-echo sequence before (T1{sub 0}) and after intravenous contrast agent administration (T1{sub Gd}; 0.2 mmol/kg Gd-DTPA{sup 2-} followed by 0.5 h of walking and 0.5 h of rest) for dGEMRIC. Relaxation times of cartilage were measured manually in 10 regions of interest. Pearson's correlations between R1{sub delta} = 1/T1{sub Gd} - 1/T1{sub 0} and T1{sub Gd} and between T2 and T2* were calculated. Image quality and the delineation of acetabular and femoral cartilage in the relaxation time maps were evaluated using discrete rating scales. High correlations were found between R1{sub delta} and T1{sub Gd} and between T2 and T2* relaxation times (all p < 0.01). All techniques delivered diagnostic image quality, with best delineation of femoral and acetabular cartilage in the T2* maps (mean 3.2 out of a maximum of 4 points). T1, T2 and T2* mapping of hip cartilage with diagnostic image quality is feasible at 7 T. To perform dGEMRIC at 7 T, pre-contrast T1 mapping can be omitted. (orig.)

  14. Contributions of chemical exchange to T1ρ dispersion in a tissue model.

    Science.gov (United States)

    Cobb, Jared G; Xie, Jingping; Gore, John C

    2011-12-01

    Variations in T(1ρ) with locking-field strength (T(1ρ) dispersion) may be used to estimate proton exchange rates. We developed a novel approach utilizing the second derivative of the dispersion curve to measure exchange in a model system of cross-linked polyacrylamide gels. These gels were varied in relative composition of comonomers, increasing stiffness, and in pH, modifying exchange rates. Magnetic resonance images were recorded with a spin-locking sequence as described by Sepponen et al. These measurements were fit to a mono-exponential decay function yielding values for T(1ρ) at each locking-field measured. These values were then fit to a model by Chopra et al. for estimating exchange rates. For low stiffness gels, the calculated exchange values increased by a factor of 4 as pH increased, consistent with chemical exchange being the dominant contributor to T(1ρ) dispersion. Interestingly, calculated chemical exchange rates also increased with stiffness, likely due to modified side-chain exchange kinetics as the composition varied. This article demonstrates a new method to assess the structural and chemical effects on T(1ρ) relaxation dispersion with a suitable model. These phenomena may be exploited in an imaging context to emphasize the presence of nuclei of specific exchange rates, rather than chemical shifts. Copyright © 2011 Wiley Periodicals, Inc.

  15. Influence of age, BMI, gender and lumbar level on T1ρ magnetic resonance imaging of lumbar discs in healthy asymptomatic adults

    Energy Technology Data Exchange (ETDEWEB)

    Guebitz, Raphael [Asklepios Hospital Altona, Hamburg (Germany). Dept. of Radiology and Neuroradiology; Lange, Tobias; Gosheger, Georg [University Hospital Muenster (Germany). Dept. of Orthopaedics and Tumor Orthopaedics; Heindel, Walter; Allkemper, Thomas [University Hospital Muenster (Germany). Dept. of Clinical Radiology; Stehling, Christoph [Sankt-Barbara Hospital Ham-Heessen, Hamm (Germany). Clinic for Radiology and Neuroradiology; Gerss, Joachim [Muenster Univ. (Germany). Inst. of Biostatistics and Clinical Research; Kanthak, Christian [Fraunhofer MEVIS, Bremen (Germany). Inst. for Medical Image Computing; Schulte, Tobias L. [Bochum Univ. St. Josef Hospital (Germany). Dept. of Orthopaedics and Trauma Surgery

    2018-02-15

    To assess the T1ρ range of lumbar intervertebral discs in healthy asymptomatic individuals at 1.5 T and to investigate the influence of age, body mass index (BMI), gender, and lumbar level on T1ρ relaxation. In a prospective study, a total of 81 volunteers aged 20 - 80 years were included in this study and divided into three age groups (A: 20 - 39y; B: 40 - 59y; C: 60 - 80y). All of the volunteers underwent magnetic resonance imaging (MRI) at 1.5 T with acquisition of sagittal T1ρ images. The calculated T1ρ relaxation times were correlated with age, BMI, gender, and lumbar level relative to the total disc, the annulus fibrosus, and the nucleus pulposus. Age had a significant influence on T1ρ relaxation times at all lumbar levels, with increasing age being associated with reduced relaxation times. There was also a significant difference between age groups A vs. C and B vs. C (P = 0.0008 and P = 0.0149, respectively). No significant differences in T1ρ relaxation time were observed between men and women (P > 0.05). BMI showed a significant negative correlation with T1ρ relaxation times (P < 0.0001). Analysis of the lumbar level revealed a significant decrease in relaxation times from L1/2 to L5 / S1 (P = 0.0013). Increasing age correlated significantly with advanced lumbar disc degeneration in asymptomatic individuals, particularly in those aged 60 or older. Increasing BMI correlated significantly with increasing degeneration. The lower discs showed more degeneration than the upper ones.

  16. Influence of age, BMI, gender and lumbar level on T1ρ magnetic resonance imaging of lumbar discs in healthy asymptomatic adults

    International Nuclear Information System (INIS)

    Guebitz, Raphael; Lange, Tobias; Gosheger, Georg; Heindel, Walter; Allkemper, Thomas; Stehling, Christoph; Gerss, Joachim; Kanthak, Christian; Schulte, Tobias L.

    2018-01-01

    To assess the T1ρ range of lumbar intervertebral discs in healthy asymptomatic individuals at 1.5 T and to investigate the influence of age, body mass index (BMI), gender, and lumbar level on T1ρ relaxation. In a prospective study, a total of 81 volunteers aged 20 - 80 years were included in this study and divided into three age groups (A: 20 - 39y; B: 40 - 59y; C: 60 - 80y). All of the volunteers underwent magnetic resonance imaging (MRI) at 1.5 T with acquisition of sagittal T1ρ images. The calculated T1ρ relaxation times were correlated with age, BMI, gender, and lumbar level relative to the total disc, the annulus fibrosus, and the nucleus pulposus. Age had a significant influence on T1ρ relaxation times at all lumbar levels, with increasing age being associated with reduced relaxation times. There was also a significant difference between age groups A vs. C and B vs. C (P = 0.0008 and P = 0.0149, respectively). No significant differences in T1ρ relaxation time were observed between men and women (P > 0.05). BMI showed a significant negative correlation with T1ρ relaxation times (P < 0.0001). Analysis of the lumbar level revealed a significant decrease in relaxation times from L1/2 to L5 / S1 (P = 0.0013). Increasing age correlated significantly with advanced lumbar disc degeneration in asymptomatic individuals, particularly in those aged 60 or older. Increasing BMI correlated significantly with increasing degeneration. The lower discs showed more degeneration than the upper ones.

  17. Effects of the strain relaxation of an AlGaN barrier layer induced by various cap layers on the transport properties in AlGaN/GaN heterostructures

    International Nuclear Information System (INIS)

    Liu Zi-Yang; Zhang Jin-Cheng; Duan Huan-Tao; Xue Jun-Shuai; Lin Zhi-Yu; Ma Jun-Cai; Xue Xiao-Yong; Hao Yue

    2011-01-01

    The strain relaxation of an AlGaN barrier layer may be influenced by a thin cap layer above, and affects the transport properties of AlGaN/GaN heterostructures. Compared with the slight strain relaxation found in AlGaN barrier layer without cap layer, it is found that a thin cap layer can induce considerable changes of strain state in the AlGaN barrier layer. The degree of relaxation of the AlGaN layer significantly influences the transport properties of the two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures. It is observed that electron mobility decreases with the increasing degree of relaxation of the AlGaN barrier, which is believed to be the main cause of the deterioration of crystalline quality and morphology on the AlGaN/GaN interface. On the other hand, both GaN and AlN cap layers lead to a decrease in 2DEG density. The reduction of 2DEG caused by the GaN cap layer may be attributed to the additional negative polarization charges formed at the interface between GaN and AlGaN, while the reduction of the piezoelectric effect in the AlGaN layer results in the decrease of 2DEG density in the case of AlN cap layer. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  18. Doping effects on the relaxation of frustration and magnetic properties of YMn0.9Cu0.1O3

    Science.gov (United States)

    Xiao, L. X.; Xia, Z. C.; Wang, X.; Ni, Y.; Yu, W.; Shi, L. R.; Jin, Z.; Xiao, G. L.

    2017-12-01

    The crystal structure and magnetic properties of hexagonal YMn0.9Cu0.1O3 single crystal are systematically investigated. The refinement results of XRD show the lattice constant decreases, which is unusually due to the doped Cu2+ ion has a larger ionic radius than the Mn3+ ions. The XPS results show that the coexistence of Mn2+, Mn3+ and Mn4+ ions in YMn0.9Cu0.1O3 single crystal. Magnetization measurements show that Cu doped YMn0.9Cu0.1O3 and parent YMnO3 have almost the same antiferromagnetic transition temperature TN, which indicates the AFM interaction is robust in the geometry frustrated system. Because doping directly destroy some of the Mn3+ ions nets, the relaxation of frustration of Mn in-plane 2D triangular geometry network leads to the significantly decrease of Mn3+ ions AFM interaction. In addition, the coexistence and competition between the ferromagnetic and antiferromagnetic interactions among the Mn2+, Mn3+ and Mn4+ ions lead to a complicated and irreversible magnetization behavior in YMn0.9Cu0.1O3 single crystal.

  19. Measuring hepatic functional reserve using T1 mapping of Gd-EOB-DTPA enhanced 3T MR imaging: A preliminary study comparing with 99mTc GSA scintigraphy and signal intensity based parameters.

    Science.gov (United States)

    Nakagawa, Masataka; Namimoto, Tomohiro; Shimizu, Kie; Morita, Kosuke; Sakamoto, Fumi; Oda, Seitaro; Nakaura, Takeshi; Utsunomiya, Daisuke; Shiraishi, Shinya; Yamashita, Yasuyuki

    2017-07-01

    To determine the utility of liver T1-mapping on gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic acid (Gd-EOB-DTPA) enhanced magnetic resonance (MR) imaging for the measurement of liver functional reserve compared with the signal intensity (SI) based parameters, technetium-99m-galactosyl serum albumin ( 99m Tc-GSA) scintigraphy and indocyanine green (ICG) clearance. This retrospective study included 111 patients (Child-Pugh-A 90; -B 21) performed with both Gd-EOB-DTPA enhanced liver MR imaging and 99m Tc-GSA (76 patients with ICG). Receiver operating characteristic (ROC) curve analysis was performed to compare diagnostic performances of T1-relaxation-time parameters [pre-(T1pre) and post-contrast (T1hb) Gd-EOB-DTPA], SI based parameters [relative enhancement (RE), liver-to-muscle-ratio (LMR), liver-to-spleen-ratio (LSR)] and 99m Tc-GSA scintigraphy blood clearance index (HH15)] for Child-Pugh classification. Pearson's correlation was used for comparisons among T1-relaxation-time parameters, SI-based parameters, HH15 and ICG. A significant difference was obtained for Child-Pugh classification with T1hb, ΔT1, all SI based parameters and HH15. T1hb had the highest AUC followed by RE, LMR, LSR, ΔT1, HH15 and T1pre. The correlation coefficients with HH15 were T1pre 0.22, T1hb 0.53, ΔT1 -0.38 of T1 relaxation parameters; RE -0.44, LMR -0.45, LSR -0.43 of SI-based parameters. T1hb was highest for correlation with HH15. The correlation coefficients with ICG were T1pre 0.29, T1hb 0.64, ΔT1 -0.42 of T1 relaxation parameters; RE -0.50, LMR -0.61, LSR -0.58 of SI-based parameters; 0.64 of HH15. Both T1hb and HH15 were highest for correlation with ICG. T1 relaxation time at post-contrast of Gd-EOB-DTPA (T1hb) was strongly correlated with ICG clearance and moderately correlated HH15 with 99m Tc-GSA. T1hb has the potential to provide robust parameter of liver functional reserve. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. An open-source software tool for the generation of relaxation time maps in magnetic resonance imaging

    International Nuclear Information System (INIS)

    Messroghli, Daniel R; Rudolph, Andre; Abdel-Aty, Hassan; Wassmuth, Ralf; Kühne, Titus; Dietz, Rainer; Schulz-Menger, Jeanette

    2010-01-01

    In magnetic resonance (MR) imaging, T1, T2 and T2* relaxation times represent characteristic tissue properties that can be quantified with the help of specific imaging strategies. While there are basic software tools for specific pulse sequences, until now there is no universal software program available to automate pixel-wise mapping of relaxation times from various types of images or MR systems. Such a software program would allow researchers to test and compare new imaging strategies and thus would significantly facilitate research in the area of quantitative tissue characterization. After defining requirements for a universal MR mapping tool, a software program named MRmap was created using a high-level graphics language. Additional features include a manual registration tool for source images with motion artifacts and a tabular DICOM viewer to examine pulse sequence parameters. MRmap was successfully tested on three different computer platforms with image data from three different MR system manufacturers and five different sorts of pulse sequences: multi-image inversion recovery T1; Look-Locker/TOMROP T1; modified Look-Locker (MOLLI) T1; single-echo T2/T2*; and multi-echo T2/T2*. Computing times varied between 2 and 113 seconds. Estimates of relaxation times compared favorably to those obtained from non-automated curve fitting. Completed maps were exported in DICOM format and could be read in standard software packages used for analysis of clinical and research MR data. MRmap is a flexible cross-platform research tool that enables accurate mapping of relaxation times from various pulse sequences. The software allows researchers to optimize quantitative MR strategies in a manufacturer-independent fashion. The program and its source code were made available as open-source software on the internet

  1. An open-source software tool for the generation of relaxation time maps in magnetic resonance imaging

    Directory of Open Access Journals (Sweden)

    Kühne Titus

    2010-07-01

    Full Text Available Abstract Background In magnetic resonance (MR imaging, T1, T2 and T2* relaxation times represent characteristic tissue properties that can be quantified with the help of specific imaging strategies. While there are basic software tools for specific pulse sequences, until now there is no universal software program available to automate pixel-wise mapping of relaxation times from various types of images or MR systems. Such a software program would allow researchers to test and compare new imaging strategies and thus would significantly facilitate research in the area of quantitative tissue characterization. Results After defining requirements for a universal MR mapping tool, a software program named MRmap was created using a high-level graphics language. Additional features include a manual registration tool for source images with motion artifacts and a tabular DICOM viewer to examine pulse sequence parameters. MRmap was successfully tested on three different computer platforms with image data from three different MR system manufacturers and five different sorts of pulse sequences: multi-image inversion recovery T1; Look-Locker/TOMROP T1; modified Look-Locker (MOLLI T1; single-echo T2/T2*; and multi-echo T2/T2*. Computing times varied between 2 and 113 seconds. Estimates of relaxation times compared favorably to those obtained from non-automated curve fitting. Completed maps were exported in DICOM format and could be read in standard software packages used for analysis of clinical and research MR data. Conclusions MRmap is a flexible cross-platform research tool that enables accurate mapping of relaxation times from various pulse sequences. The software allows researchers to optimize quantitative MR strategies in a manufacturer-independent fashion. The program and its source code were made available as open-source software on the internet.

  2. Dielectric Relaxation of Water: Theory and Experiment

    International Nuclear Information System (INIS)

    Adhikari, Narayan Prasad; Paudyal, Harihar; Johri, Manoj

    2010-06-01

    We have studied the hydrogen bond dynamics and methods for evaluation of probability and relaxation time for hydrogen bond network. Further, dielectric relaxation time has been calculated by using a diagonalization procedure by obtaining eigen values (inverse of relaxation time) of a master equation framed on the basis of Fokker-Planck equations. Microwave cavity spectrometer has been described to make measurements of relaxation time. Slater's perturbation equations are given for the analysis of the data. A comparison of theoretical and experimental data shows that there is a need for improvements in the theoretical model and experimental techniques to provide exact information about structural properties of water. (author)

  3. Alterations of the cerebellum and basal ganglia in bipolar disorder mood states detected by quantitative T1ρ mapping.

    Science.gov (United States)

    Johnson, Casey P; Christensen, Gary E; Fiedorowicz, Jess G; Mani, Merry; Shaffer, Joseph J; Magnotta, Vincent A; Wemmie, John A

    2018-01-07

    Quantitative mapping of T1 relaxation in the rotating frame (T1ρ) is a magnetic resonance imaging technique sensitive to pH and other cellular and microstructural factors, and is a potentially valuable tool for identifying brain alterations in bipolar disorder. Recently, this technique identified differences in the cerebellum and cerebral white matter of euthymic patients vs healthy controls that were consistent with reduced pH in these regions, suggesting an underlying metabolic abnormality. The current study built upon this prior work to investigate brain T1ρ differences across euthymic, depressed, and manic mood states of bipolar disorder. Forty participants with bipolar I disorder and 29 healthy control participants matched for age and gender were enrolled. Participants with bipolar disorder were imaged in one or more mood states, yielding 27, 12, and 13 imaging sessions in euthymic, depressed, and manic mood states, respectively. Three-dimensional, whole-brain anatomical images and T1ρ maps were acquired for all participants, enabling voxel-wise evaluation of T1ρ differences between bipolar mood state and healthy control groups. All three mood state groups had increased T1ρ relaxation times in the cerebellum compared to the healthy control group. Additionally, the depressed and manic groups had reduced T1ρ relaxation times in and around the basal ganglia compared to the control and euthymic groups. The study implicated the cerebellum and basal ganglia in the pathophysiology of bipolar disorder and its mood states, the roles of which are relatively unexplored. These findings motivate further investigation of the underlying cause of the abnormalities, and the potential role of altered metabolic activity in these regions. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  4. Evaluation of MR imaging with T1 and T2* mapping for the determination of hepatic iron overload.

    Science.gov (United States)

    Henninger, B; Kremser, C; Rauch, S; Eder, R; Zoller, H; Finkenstedt, A; Michaely, H J; Schocke, M

    2012-11-01

    To evaluate MRI using T1 and T2* mapping sequences in patients with suspected hepatic iron overload (HIO). Twenty-five consecutive patients with clinically suspected HIO were retrospectively studied. All underwent MRI and liver biopsy. For the quantification of liver T2* values we used a fat-saturated multi-echo gradient echo sequence with 12 echoes (TR = 200 ms, TE = 0.99 ms +  n × 1.41 ms, flip angle 20°). T1 values were obtained using a fast T1 mapping sequence based on an inversion recovery snapshot FLASH sequence. Parameter maps were analysed using regions of interest. ROC analysis calculated cut-off points at 10.07 ms and 15.47 ms for T2* in the determination of HIO with accuracy 88 %/88 %, sensitivity 84 %/89.5 % and specificity 100 %/83 %. MRI correctly classified 20 patients (80 %). All patients with HIO only had decreased T1 and T2* relaxation times. There was a significant difference in T1 between patients with HIO only and patients with HIO and steatohepatitis (P = 0.018). MRI-based T2* relaxation diagnoses HIO very accurately, even at low iron concentrations. Important additional information may be obtained by the combination of T1 and T2* mapping. It is a rapid, non-invasive, accurate and reproducible technique for validating the evidence of even low hepatic iron concentrations. • Hepatic iron overload causes fibrosis, cirrhosis and increases hepatocellular carcinoma risk. • MRI detects iron because of the field heterogeneity generated by haemosiderin. • T2* relaxation is very accurate in diagnosing hepatic iron overload. • Additional information may be obtained by T1 and T2* mapping.

  5. Measurement of Myocardial T1ρ with a Motion Corrected, Parametric Mapping Sequence in Humans.

    Directory of Open Access Journals (Sweden)

    Sebastian Berisha

    Full Text Available To develop a robust T1ρ magnetic resonance imaging (MRI sequence for assessment of myocardial disease in humans.We developed a breath-held T1ρ mapping method using a single-shot, T1ρ-prepared balanced steady-state free-precession (bSSFP sequence. The magnetization trajectory was simulated to identify sources of T1ρ error. To limit motion artifacts, an optical flow-based image registration method was used to align T1ρ images. The reproducibility and accuracy of these methods was assessed in phantoms and 10 healthy subjects. Results are shown in 1 patient with pre-ventricular contractions (PVCs, 1 patient with chronic myocardial infarction (MI and 2 patients with hypertrophic cardiomyopathy (HCM.In phantoms, the mean bias was 1.0 ± 2.7 msec (100 msec phantom and 0.9 ± 0.9 msec (60 msec phantom at 60 bpm and 2.2 ± 3.2 msec (100 msec and 1.4 ± 0.9 msec (60 msec at 80 bpm. The coefficient of variation (COV was 2.2 (100 msec and 1.3 (60 msec at 60 bpm and 2.6 (100 msec and 1.4 (60 msec at 80 bpm. Motion correction improved the alignment of T1ρ images in subjects, as determined by the increase in Dice Score Coefficient (DSC from 0.76 to 0.88. T1ρ reproducibility was high (COV < 0.05, intra-class correlation coefficient (ICC = 0.85-0.97. Mean myocardial T1ρ value in healthy subjects was 63.5 ± 4.6 msec. There was good correspondence between late-gadolinium enhanced (LGE MRI and increased T1ρ relaxation times in patients.Single-shot, motion corrected, spin echo, spin lock MRI permits 2D T1ρ mapping in a breath-hold with good accuracy and precision.

  6. Characterization of structural relaxation in inorganic glasses using length dilatometry

    Science.gov (United States)

    Koontz, Erick

    characterization technique is comprised of three main components: experimental measurements, fitting of configurational length change, and description of glass behavior by analysis of fitting parameters. N-BK7 optical glass from Schott was used as the proof of concept glass but the main scientific interest was in three chalcogenide glasses: As40Se 60, As20Se80, and Ge17.9As19.7 Se62.4. The dilatometric experiments were carried out using a thermomechanical analyzer (TMA) on glass sample that were synthesized by the author, in all cases except N-BK7. Isothermal structural relaxation measurements were done on (12 mm tall x 3 mm x 3 mm) beams placed vertically in the TMA. The samples were equilibrated at a starting temperature (T 0) until structural equilibrium was reached then a temperature down step was initiated to the final temperature (T 1) and held isothermally until relaxation concluded. The configurational aspect of length relaxation, and therefore volume relaxation was extracted and fit with a Prony series. The Prony series parameters indicated a number of relaxation events occurring within the glass on timescales typically an order of magnitude apart in time. The data analysis showed as many as 4 discrete relaxation times at lower temperatures. The number of discrete relaxation decreased as the temperature increased until just one single relaxation was left in the temperature range just at or above Tg. In the case of N-BK7 these trends were utilized to construct a simple model that could be applied to glass manufacturing in the areas of annealing or PGM. A future development of a rather simple finite element model (FEM) would easily be able to use this model to predict the exponential-like, temperature and time dependent relaxation behaviors of the glass. The predictive model was not extended to the chalcogenide glass studied here, but could easily be applied to them in the future. The relaxation time trends versus temperature showed a definite region of transition between a

  7. Evidence for conformational flexibility in the Tat-TAR recognition motif of cyclin T1

    International Nuclear Information System (INIS)

    Das, Chandreyee; Edgcomb, Stephen P.; Peteranderl, Ralph; Chen, Lily; Frankel, Alan D.

    2004-01-01

    Cyclin T1 (CycT1) is a cellular transcription elongation factor that also participates in Tat-mediated activation of several lentiviral promoters. In human immunodeficiency virus (HIV), CycT1 is required for Tat to bind tightly to TAR and interacts in the ternary complex via its Tat-TAR recognition motif (TRM). In the related bovine immunodeficiency virus (BIV), Tat recognizes its cognate TAR element with high affinity and specificity in the absence of CycT1. At both promoters, CycT1 recruits the Cdk9 kinase, which phosphorylates RNA polymerase II to generate processive transcription complexes. To examine the physical properties of CycT1, we purified a functional domain corresponding to residues 1-272 and found that it possesses a stably folded core, as judged by partial proteolysis and circular dichroism experiments. Interestingly, the C-terminal 20 residues corresponding to the TRM appear conformationally flexible or disordered. The TRM of the bovine CycT1 (bCycT1) is similarly sensitive to proteolysis yet differs in sequence from the human protein. In particular, bCycT1 lacks a cysteine at residue 261 known to be critical for HIV but not BIV ternary complex formation, and mutagenesis data are consistent with a proposed role for this cysteine in metal binding. The apparent flexibility of the TRM suggests that conformational rearrangements may accompany formation of CycT1-Tat-TAR ternary complexes and may contribute to different TAR recognition strategies in different lentiviruses

  8. Breathing and Relaxation

    Science.gov (United States)

    ... Find a Doctor Relaxation is the absence of tension in muscle groups and a minimum or absence ... Drill Meditation Progressive Muscle Relaxation Minimizing Shortness of Breath Visualization This information has been approved by Shelby ...

  9. NMR relaxation of the orientation of single segments in semiflexible dendrimers

    International Nuclear Information System (INIS)

    Markelov, Denis A.; Gotlib, Yuli Ya.; Dolgushev, Maxim; Blumen, Alexander

    2014-01-01

    We study the orientational properties of labeled segments in semiflexible dendrimers making use of the viscoelastic approach of Dolgushev and Blumen [J. Chem. Phys. 131, 044905 (2009)]. We focus on the segmental orientational autocorrelation functions (ACFs), which are fundamental for the frequency-dependent spin-lattice relaxation times T 1 (ω). We show that semiflexibility leads to an increase of the contribution of large-scale motions to the ACF. This fact influences the position of the maxima of the [1/T 1 ]-functions. Thus, going from outer to inner segments, the maxima shift to lower frequencies. Remarkably, this feature is not obtained in the classical bead-spring model of flexible dendrimers, although many experiments on dendrimers manifest such a behavior

  10. In vivo determination of T1 and T2 in the brain of patients with severe but stable multiple sclerosis

    DEFF Research Database (Denmark)

    Larsson, H B; Frederiksen, J; Kjaer, L

    1988-01-01

    investigated, using a whole-body superconductive MR scanner, operating at 1.5 T. By employing 12-point (or 6-point) partial saturation inversion recovery (PSIR) and 32-echo multiple spin-echo sequences we measured T1 and T2 in MS plaques, white matter, and cortical gray matter. We also focused on the issue......, whether T1 and T2 relaxation processes in fact were monoexponential. T1 and T2 in plaques were found to cover a wide range, which could be explained only by inherent biophysical dissimilarity of the plaques, possibly due to differences in disease activity, edema and gliosis. T1 appeared monoexponential...... in all the plaques, but in seven cases T2 showed biexponential behavior. This was found to be most pronounced near the cerebrospinal fluid of the ventricles, probably caused by partial volume effects or increased free water content. The T2 of apparently normal white matter was significantly longer in MS...

  11. Relaxations in spin glasses: Similarities and differences from ordinary glasses

    International Nuclear Information System (INIS)

    Ngai, K.L.; Rajagopal, A.K.; Huang, C.Y.

    1984-01-01

    Relaxation phenomena have become a major concern in the physics of spin glasses. There are certain resemblances of these relaxation properties to those of ordinary glasses. In this work, we compare the relaxation properties of spin glasses near the freezing temperature with those of glasses near the glass transition temperature. There are similarities between the two types of glasses. Moreover, the relaxation properties of many glasses and spin glasses are in conformity with two coupled ''universality'' relations predicted by a recent model of relaxations in condensed matter

  12. Proton NMR relaxation in hydrous melts

    International Nuclear Information System (INIS)

    Braunstein, J.; Bacarella, A.L.; Benjamin, B.M.; Brown, L.L.; Girard, C.

    1976-01-01

    Pulse and continuous wave NMR measurements are reported for protons in hydrous melts of calcium nitrate at temperatures between -4 and 120 0 C. Although measured in different temperature ranges, spin-lattice (T 1 ) and spin-spin (T 2 ) relaxation times appear to be nearly equal to each other and proportional to the self-diffusion coefficients of solute metal cations such as Cd 2+ . At temperatures near 50 0 C, mean Arrhenius coefficients Δ H/sub T 1 / (kcal/mol) are 7.9, 7.3, and 4.8, respectively, for melts containing 2.8, 4.0, and 8.0 moles of water per mole of calcium nitrate, compared to 4.6 kcal/mol for pure water. Temperature dependence of T 1 and T 2 in Ca(NO 3 ) 2 -2.8 H 2 O between -4 and 120 0 C are non-Arrhenius and can be represented by a Fulcher-type equation with a ''zero mobility temperature'' (T 0 ) of 225 0 K, close to the value of T 0 for solute diffusion, electrical conductance and viscosity. Resolution of the relaxation rates into correlation times for intramolecular (rotational) and intermolecular (translational) diffusional motion is discussed in terms of the Bloembergen-Purcell-Pound and more recent models for dipolar relaxation

  13. Proton NMR relaxivity of blood samples in the presence of some gadolinium and dysprosium compounds

    International Nuclear Information System (INIS)

    Coroiu, I.; Darabont, Al.; Bogdan, M.

    1999-01-01

    The use of some new compounds in MRI tissue and blood characterisation based on nuclear spin relaxation time measurements cannot be sustained until the molecular sources of these variations are understood. Tissues and blood are complex molecular systems with complex NMR properties. A better comprehension of the molecular basis of relaxation offers the possibility to predict the changes expected for a given pathology. The purpose of this contribution is to evidence the different relaxation characteristics of some gadolinium and dysprosium compounds in the presence and absence of the blood and to give a possible explanation about the molecular processes that cause occurrence of changes. Some gadolinium and dysprosium compounds such as: Gd-CIT (gadolinium citrate), Dy-DTPA (DTPA-diethylenetriamine pentaacetic acid), iron oxide - gadolinium oxide (or dysprosium oxide)- dextran complexes were prepared. The longitudinal T 1 -1 and transverse T 2 -1 'relaxation rates' measurements have been carried out as a function of molar concentrations. All measurements have been made at room temperature (about 25 deg.C) and the proton Larmor frequency ν o = 90 MHz. The pulsed NMR spectrometer utilised was a commercial Bruker SXP4/100 spectrometer. Transverse relaxation rate measurements have been made using the Carr-Purcell method, while longitudinal relaxation rate measurements using the inversion recovery pulse sequence, 180 angle-τ-90 angle. The accuracy was about 2-3% for the longitudinal relaxation rates and about 5-7% for the transverse relaxation rates. R 1 and R 2 relaxivities, in mM -1 s -1 were determined from the least square determination of the slopes of plots 1/T 1,2 versus compound molar concentration, using at least five independent measurements at several concentrations between 0 and 2 mM. Increased R 2 relaxivity observed for dysprosium compounds in the blood presence can be explained by PRE effect. The largest gain in R 2 relaxivity seems to imply a noncovalent

  14. Dynamics of helicity transport and Taylor relaxation

    International Nuclear Information System (INIS)

    Diamond, P.H.; Malkov, M.

    2003-01-01

    A simple model of the dynamics of Taylor relaxation is derived using symmetry principles alone. No statistical closure approximations are invoked or detailed plasma model properties assumed. Notably, the model predicts several classes of nondiffusive helicity transport phenomena, including traveling nonlinear waves and superdiffusive turbulent pulses. A universal expression for the scaling of the effective magnetic Reynolds number of a system undergoing Taylor relaxation is derived. Some basic properties of intermittency in helicity transport are examined

  15. Quantitative assessment of hepatic function: modified look-locker inversion recovery (MOLLI) sequence for T1 mapping on Gd-EOB-DTPA-enhanced liver MR imaging

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Jeong Hee [Seoul National University Hospital, Department of Radiology, Seoul (Korea, Republic of); Lee, Jeong Min; Han, Joon Koo; Choi, Byung Ihn [Seoul National University Hospital, Department of Radiology, Seoul (Korea, Republic of); Seoul National University College of Medicine, Institute of Radiation Medicine, Jongno-gu, Seoul (Korea, Republic of); Paek, Munyoung [Siemens Healthcare, Seoul (Korea, Republic of)

    2016-06-15

    To determine whether multislice T1 mapping of the liver using a modified look-locker inversion recovery (MOLLI) sequence on gadoxetic acid-enhanced magnetic resonance imaging (MRI) can be used as a quantitative tool to estimate liver function and predict the presence of oesophageal or gastric varices. Phantoms filled with gadoxetic acid were scanned three times using MOLLI sequence to test repeatability. Patients with chronic liver disease or liver cirrhosis who underwent gadoxetic acid-enhanced liver MRI including MOLLI sequence at 3 T were included (n = 343). Pre- and postcontrast T1 relaxation times of the liver (T1liver), changes between pre- and postcontrast T1liver (ΔT1liver), and adjusted postcontrast T1liver (postcontrast T1liver-T1spleen/T1spleen) were compared among Child-Pugh classes. In 62 patients who underwent endoscopy, all T1 parameters and spleen sizes were correlated with varices. Phantom study showed excellent repeatability of MOLLI sequence. As Child-Pugh scores increased, pre- and postcontrast T1liver were significantly prolonged (P < 0.001), and ΔT1liver and adjusted postcontrast T1liver decreased (P< 0.001). Adjusted postcontrast T1liver and spleen size were independently associated with varices (R{sup 2} = 0.29, P < 0.001). T1 mapping of the liver using MOLLI sequence on gadoxetic acid-enhanced MRI demonstrated potential in quantitatively estimating liver function, and adjusted postcontrast T1liver was significantly associated with varices. (orig.)

  16. Proton relaxation relationships of human and animal tissues in vitro. Changes due to autolysis and fixing

    International Nuclear Information System (INIS)

    Grodd, W.; Schmitt, W.G.H.

    1983-01-01

    The results of measurements of proton relaxation times of various tissues from rats, pigs and humans are reported; these were obtained by a resonance spectroscope at 20 MHz and 40 0 C. There were specific differences in both relaxation times (T 1 and T 2 ) of the liver and spleen. There was a difference of more than 150 ms in the longitudinal relaxation time between grey and white cerebral tissue. Autolytic changes show an increase in both relaxation times. Fixation produced a reduction in T 1 only. The significance of these findings for NMR tomography is discussed. (orig.) [de

  17. Evaluation of biexponential relaxation processes by magnetic resonance imaging. A phantom study

    DEFF Research Database (Denmark)

    Kjaer, L; Thomsen, C; Larsson, H B

    1988-01-01

    Despite the complexity of biologic tissues, a monoexponential behaviour is usually assumed when estimating relaxation processes in vivo by magnetic resonance imaging (MRI). This study was designed to evaluate the potential of biexponential decomposition of T1 and T2 relaxation curves obtained at 1...... echoes. Applying biexponential curve analysis, a significant deviation from a monoexponential behaviour was recognized at a ratio of corresponding relaxation rates of about 3 and 2, estimating T1 and T2 relaxation, respectively (p less than 0.01, F-test). Requiring an SD less than or equal to 10 per cent...

  18. Relaxation parameter estimation and comparison of NLS and LLS methods for DCE MRI in the cervix

    DEFF Research Database (Denmark)

    Mariager, Christian; Kallehauge, Jesper; Tanderup, Kari

    Dynamic Contrast Enhanced (DCE) MRI is a promising tool for tumor treatment planning. However, prior knowledge of the T1 value within each tumor voxel is needed to utilize this technique. Therefore, a T1 relaxation measurement is performed before the DCE experiment to establish a baseline, before...... any injection of contrast agent. This T1 relaxation measurement is often performed using a variable flip angle spoiled gradient recalled echo (SPGR) sequence. T1 can then be estimated using either a linear least squares (LLS) or a non-linear least squares (NLS) fitting algorithm....

  19. Quantitative plasma spectroscopy at JET and Extrap-T1

    International Nuclear Information System (INIS)

    Zastrow, K.D.

    1993-01-01

    Studies in quantitative plasma spectroscopy are performed on the Joint European Torus (JET) in Culham, Great-Britain and on the Extrap-T1 reversed-field pinch (RFP) in Stockholm. The model concepts that form the basis of these studies are reviewed. At JET, spectra of He-like nickel are observed with a high-resolution X-ray crystal spectrometer. The experimental line intensity ratios of satellite lines to the resonance line are compared with theoretical data. The agreement is found to be good, with the exception of the excitation of dipole-forbidden lines. The spectrum is also used to derive central ion temperature, central toroidal rotation and nickel concentration based upon a model for the radial emission. The results are compared with those from an independent diagnostic, charge-exchange recombination spectroscopy (CWRS). Theoretically predicted cross section effects on the CXRS data are verified. On Extrap-T1, vacuum ultraviolet (VUV) spectra and visible spectra are analysed. From these, thermodynamic quantities of the plasma are derived, like electron temperature, impurity concentrations and particle fluxes. The oxygen ionization balance is measured and compared to calculations with a collisional-dielectronic model with metastable resolution, both in 0-dimensional time-dependent and transport model calculations. The performance of the RFP discharges investigated in terms of radiative power loss and energy and particle confinement properties. The scaling of the energy confinement time with plasma current, pinch parameter and electron density is found to be dominated by the dynamo activity needed to sustain the RFP configuration. The scaling of the particle confinement time, on the other hand, is dominated by pressure-driven activity associated with the regulation of β

  20. Relaxation of nuclear spin on holes in semiconductors

    International Nuclear Information System (INIS)

    Gr'ncharova, E.I.; Perel', V.I.

    1977-01-01

    The longitudienal relaxation time T 1 of nuclear spins due to dipole-dipole interaction with holes in semiconductors is calculated. Expressions for T 1 in cubic and uniaxial semiconductors are obtained for non-degenerate and degenerate cases. On the basis of comparison with available experimental data for silicon the agreement with the theoretical results is obtained. It is demonstrated that in uniaxial semiconductors the time of relaxation on holes for a nuclear spin directed along the c axis is considerably greater than that for a spin in the normal direction

  1. Native T1 mapping of the heart - a pictorial review.

    Science.gov (United States)

    Germain, Philippe; El Ghannudi, Soraya; Jeung, Mi-Young; Ohlmann, Patrick; Epailly, Eric; Roy, Catherine; Gangi, Afshin

    2014-01-01

    T1 mapping is now a clinically feasible method, providing pixel-wise quantification of the cardiac structure's T1 values. Beyond focal lesions, well depicted by late gadolinium enhancement sequences, it has become possible to discriminate diffuse myocardial alterations, previously not assessable by noninvasive means. The strength of this method includes the high reproducibility and immediate clinical applicability, even without the use of contrast media injection (native or pre-contrast T1). The two most important determinants of native T1 augmentation are (1) edema related to tissue water increase (recent infarction or inflammation) and (2) interstitial space increase related to fibrosis (infarction scar, cardiomyopathy) or to amyloidosis. Conversely, lipid (Anderson-Fabry) or iron overload diseases are responsible for T1 reduction. In this pictorial review, the main features provided by native T1 mapping are discussed and illustrated, with a special focus on the awaited clinical purpose of this unique, promising new method.

  2. Structural relaxation and thermal conductivity coefficient of liquids

    International Nuclear Information System (INIS)

    Abdurasulov, A.

    1992-01-01

    Present article is devoted to structural relaxation and thermal conductivity coefficient of liquids. The thermoelastic properties of liquids were studied taking into account the contribution of translational and structural relaxation. The results of determination of dynamic coefficient of thermal conductivity of liquids taking into account the contribution of translational and structural relaxation are presented.

  3. Measurements of T1 and T2 over time in formalin-fixed human whole-brain specimens

    International Nuclear Information System (INIS)

    Tovi, M.; Ericsson, A.

    1992-01-01

    T1 and T2 were measured in 5 formalin-fixed human whole-brain specimens as a function of time. Gray matter/white matter contrast reversal was observed around the 4th day and was considered to be due to the greater decrease in T1 in gray than in white matter. A possible explanation for this is that the decomposition of the myelin phospholipid structure by formalin somewhat counteracts the general reductive effect of the fixation procedure on relaxation times. (orig.)

  4. Structure relaxation effect on superconductive properties of amorphous metallic ZrΛ9Λ0BΛ3SiΛ7 alloy

    International Nuclear Information System (INIS)

    Zolotukhin, I.V.; Zheleznyj, V.S.; Rudyj, S.D.; Fedorov, V.M.

    1985-01-01

    The effect of structural relaxation on electronand phonon spectra and electron-phonon interaction of Zr 90 B 3 Si 7 amorphous alloy is investigated. The specific electric conductivity rho 293 , superconducting transition temperature Tsub(c), critical magnetic field Bsub(c) (near Tsub(c)) and the Young modulus E 293 were measured. The Debye temperature THETA sub(D), electron state density on the Fermi surface N(O electron-phonon interaction constant lambda) mean square of a matrix element and the Hopfeld parameter were calculated. Experimental data show that Tsub(c) decreases during the structural relaxation of amorphous alloy in spite of increasing THETA sub(D) and N(O). However, the calculations show that during the structural relaxation the matrix element of the electron-phonon inte raction decreases with a simultaneous lambda decrease and an insignificant change in the Hopfeld parameter

  5. Relaxation of structural parameters and potential coefficients of nonrigid molecules. General symmetry properties and application to ab initio study of 1,2-difluoroethane

    Science.gov (United States)

    Ha, T.-K.; Günthard, H. H.

    1989-07-01

    Structural parameters like bond length, bond angles, etc. and harmonic and anharmonic potential coefficients of molecules with internal rotation, inversion or puckering modes are generally assumed to vary with the large amplitude internal coordinates in a concerted manner (relaxation). Taking the coordinate vectors of the nuclear configuration of semirigid molecules with relaxation (SRMRs) as functions of relaxing structural parameters and finite amplitude internal coordinate, the isometric group of SRMRs is discussed and the irreducible representations of the latter are shown to classify into engendered and nonengendered ones. On this basis a concept of equivalent sets of nuclei SRMRs is introduced and an analytical expression is derived which defines the most general functional form of relaxation increments of all common types of structural parameters compatible with isometric symmetry. This formula is shown to be a close analog of an analytical expression defining the transformations induced by the isometric group of infinitesimal internal coordinates associated with typical structural parameters. Furthermore analogous formulae are given for the most general form of the relaxation of harmonic potential coefficients as a function of finite internal coordinates. The general relations are illustrated by ab initio calculations for 1,2-difluoroethane at the MP4/DZP//HF/4-31G* level for twelve values of the dihedral angle including complete structure optimization. The potential to internal rotation is found to be in essential agreement with experimentally derived data. For a complete set of ab initio structural parameters the associated relaxation increments are represented as Fourier series, which are shown to confirm the form predicted by the general formula and the isometric group of 1,2-difluoroethane. Depending on type of the structural parameters (bond length, bond angles, etc.), the associated relaxation increments appear to follow some simple rules. Similarly

  6. Time-Dependent Changes in T1 during Fracture Healing in Juvenile Rats: A Quantitative MR Approach.

    Directory of Open Access Journals (Sweden)

    Katharina Baron

    Full Text Available Quantitative magnetic resonance imaging (qMRI offers several advantages in imaging and determination of soft tissue alterations when compared to qualitative imaging techniques. Although applications in brain and muscle tissues are well studied, its suitability to quantify relaxation times of intact and injured bone tissue, especially in children, is widely unknown. The objective observation of a fracture including its age determination can become of legal interest in cases of child abuse or maltreatment. Therefore, the aim of this study is the determination of time dependent changes in intact and corresponding injured bones in immature rats via qMRI, to provide the basis for an objective and radiation-free approach for fracture dating. Thirty-five MR scans of 7 Sprague-Dawley rats (male, 4 weeks old, 100 ± 5 g were acquired on a 3T MRI scanner (TimTrio, Siemens AG, Erlangen, Germany after the surgical infliction of an epiphyseal fracture in the tibia. The images were taken at days 1, 3, 7, 14, 28, 42 and 82 post-surgery. A proton density-weighted and a T1-weighted 3D FLASH sequence were acquired to calculate the longitudinal relaxation time T1 of the fractured region and the surrounding tissues. The calculation of T1 in intact and injured bone resulted in a quantitative observation of bone development in intact juvenile tibiae as well as the bone healing process in the injured tibiae. In both areas, T1 decreased over time. To evaluate the differences in T1 behaviour between the intact and injured bone, the relative T1 values (bone-fracture were calculated, showing clear detectable alterations of T1 after fracture occurrence. These results indicate that qMRI has a high potential not only for clinically relevant applications to detect growth defects or developmental alterations in juvenile bones, but also for forensically relevant applications such as the dating of fractures in cases of child abuse or maltreatment.

  7. Anomalous enhancement of nuclear spin relaxation rates of 109Ag and 115In at low temperatures in cubic Γ3 ground-state system PrAg2In. First observation of octupole fluctuations of f-electrons

    International Nuclear Information System (INIS)

    Tanida, Hiroshi; Takagi, Shigeru; Suzuki, Hiroyuki S.; Satoh, Isamu; Komatsubara, Takemi

    2006-01-01

    Microscopic properties have been investigated on a cubic nonmagnetic non-Kramers Γ 3 doublet ground-state (GS) system PrAg 2 In by complementarily utilizing 115 In (I=9/2) and 109 Ag (I=1/2) NMR with particular emphasis on the low-frequency (low-ω) dipole and multipole (octupole and/or quadrupole) fluctuations of f-electrons as probed by the nuclear spin relaxation rates 1/ 115 T 1 and 1/ 109 T 1 . We show that 1/ 115 T 1 and 1/ 109 T 1 are anomalously enhanced respectively below≅50 K and ≅100K over those expected for the low-ω dipole fluctuations of the excited magnetic Γ 4 and Γ 5 states in a simple crystalline-electric-field model for a Γ 3 GS system. By comparing 1/( 115 T 1 T) and 1/( 109 T 1 T) and also by considering an invariant form of the hyperfine and/or quadrupole couplings of Γ 3 octupole and/or quadrupole moments with Ag/In nuclear dipole and/or quadrupole moments, we show that Γ 3 octupole fluctuations dominate 1/ 109 T 1 and quadrupole ones can possibly contribute to 1/ 115 T 1 at low T. (author)

  8. Ovarian chocolate cysts. Staging with relaxation time in MR imaging

    Energy Technology Data Exchange (ETDEWEB)

    Sugimura, Kazuro; Ishida, Tetsuya; Takemori, Masayuki; Kitagaki, Hajime; Tanaka, Yutaka; Yamasaki, Katsuhito; Shimizu, Tadafumi; Kono, Michio

    1988-10-01

    Accurate preoperative staging of ovarian chocolate cysts is very important because recent hormonal therapy has been effective in low stage patients. However, it has been difficult to assess the preoperative stage of ovarian chocolate cysts. We evaluated the diagnostic potential of MRI in preoperative staging of 15 overian chocolate cysts. It was well known that the older the ovarian chocolate cyst was the more iron content it had. We examined the iron contents effect on T1 and T2 relaxation times in surgically confirmed chocolate cysts (stage II: 3 cases, stage III: 3 cases and stage IV: 9 cases by AFS classification, 1985) employing the 0.15-T MR system and 200 MHz spectrometer. There was a positive linear relation between T1 of the lesion using the MR system (T1) and T1 of the resected contents using the spectrometer (sp-T1); r = 0.93. The same relation was revealed between T2 and sp-T2; r = 0.87. It was indicated that T1 and T2 using the MR system was accurate. There was a negative linear relation between T1 and the iron contents ( r = -0.81) but no relation between T2 and the iron contents. T1 was 412 +- 91 msec for stage II, 356 +- 126 msec for stage III and 208 +- 30 msec for stage IV. T1 for stage IV was shorter than that for stage II and III, statistically significant differences were noted (p < 0.05). Thus, T1 was useful in differentiating a fresh from an old ovarian chocolate cyst. We concluded that T1 relaxation time using the MR system was useful for the staging of an ovarian chocolate cyst without surgery.

  9. Nonlinear Relaxation in Population Dynamics

    Science.gov (United States)

    Cirone, Markus A.; de Pasquale, Ferdinando; Spagnolo, Bernardo

    We analyze the nonlinear relaxation of a complex ecosystem composed of many interacting species. The ecological system is described by generalized Lotka-Volterra equations with a multiplicative noise. The transient dynamics is studied in the framework of the mean field theory and with random interaction between the species. We focus on the statistical properties of the asymptotic behaviour of the time integral of the ith population and on the distribution of the population and of the local field.

  10. Rotational dynamics of benzene and water in an ionic liquid explored via molecular dynamics simulations and NMR T1 measurements.

    Science.gov (United States)

    Yasaka, Yoshiro; Klein, Michael L; Nakahara, Masaru; Matubayasi, Nobuyuki

    2012-02-21

    The rotational dynamics of benzene and water in the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride are studied using molecular dynamics (MD) simulation and NMR T(1) measurements. MD trajectories based on an effective potential are used to calculate the (2)H NMR relaxation time, T(1) via Fourier transform of the relevant rotational time correlation function, C(2R)(t). To compensate for the lack of polarization in the standard fixed-charge modeling of the IL, an effective ionic charge, which is smaller than the elementary charge is employed. The simulation results are in closest agreement with NMR experiments with respect to the temperature and Larmor frequency dependencies of T(1) when an effective charge of ±0.5e is used for the anion and the cation, respectively. The computed C(2R)(t) of both solutes shows a bi-modal nature, comprised of an initial non-diffusive ps relaxation plus a long-time ns tail extending to the diffusive regime. Due to the latter component, the solute dynamics is not under the motional narrowing condition with respect to the prevalent Larmor frequency. It is shown that the diffusive tail of the C(2R)(t) is most important to understand frequency and temperature dependencies of T(1) in ILs. On the other hand, the effect of the initial ps relaxation is an increase of T(1) by a constant factor. This is equivalent to an "effective" reduction of the quadrupolar coupling constant (QCC). Thus, in the NMR T(1) analysis, the rotational time correlation function can be modeled analytically in the form of aexp (-t/τ) (Lipari-Szabo model), where the constant a, the Lipari-Szabo factor, contains the integrated contribution of the short-time relaxation and τ represents the relaxation time of the exponential (diffusive) tail. The Debye model is a special case of the Lipari-Szabo model with a = 1, and turns out to be inappropriate to represent benzene and water dynamics in ILs since a is as small as 0.1. The use of the Debye model would result in

  11. Time course of NMR images and T1 values associated with hypertensive intracerebral hematoma

    International Nuclear Information System (INIS)

    Inao, Suguru; Furuse, Masahiro; Saso, Katsuyoshi; Yoshida, Kazuo; Motegi, Yoshimasa; Kaneoke, Yoshiki; Kamata, Noriko; Izawa, Akira

    1986-01-01

    The present study describes time courses in tissue T 1 values, as well as in NMR imagings, associated with hypertensive intracerebral hematoma (ICH). Non-operative 21 cases of ICH were examined by FONAR QED 80-α NMR system, which possessed dual modes of image display and focal T 1 measurement (static magnetic field : 433 gauss). As the first step of examination SSFP images are displayed and then, at the regions of interest, absolute values of T 1 are measured by field focusing technique. The extent of ICH was revealed as high density zone in NMR imaging, occasionally represented much wider extent of high density area than the finding on X-ray CT. Prolonged T 1 values were obtained from such high density zone. This widespread high density area was regarded to reflect the spread of perifocal brain edema. T 1 value of the hematoma itself was rather shortened in its initial phase within 2 weeks, thereafter followed by prolongation in the time lapse. This seemed to reflect the alterations in the properties of hematoma such as clot formation in earlier phase and resolution in later phase. On the contrary, T 1 in the brain tissue surrounded to hematoma was apparently prolonged in the early phase within 2 weeks, representing the maximal values of 312 msec arround 2 to 4 weeks after the onset, and then gradually normalized in the period over 1 month. This alteration in tissue T 1 likely represents the processes of edema formation and its regression in perifocal zone. T 1 values measured in perifocal region might be available for the evaluation of edema state in association with cerebrovascular accident. (author)

  12. T1-mapping for assessment of ischemia-induced acute kidney injury and prediction of chronic kidney disease in mice

    Energy Technology Data Exchange (ETDEWEB)

    Hueper, Katja; Gutberlet, Marcel; Wacker, Frank; Hartung, Dagmar [Hannover Medical School, Department of Radiology, Hannover (Germany); Hannover Medical School, REBIRTH Cluster of Excellence, Hannover (Germany); Peperhove, Matti; Tewes, Susanne; Barrmeyer, Amelie [Hannover Medical School, Department of Radiology, Hannover (Germany); Rong, Song [Hannover Medical School, Department of Nephrology, Hannover (Germany); Zunyi Medical College, Laboratory of Organ Transplantation, Zunyi (China); Gerstenberg, Jessica; Haller, Herman; Gueler, Faikah [Hannover Medical School, Department of Nephrology, Hannover (Germany); Mengel, Michael [University of Alberta, Department of Laboratory Medicine and Pathology, Edmonton (Canada); Meier, Martin [Hannover Medical School, REBIRTH Cluster of Excellence, Hannover (Germany); Hannover Medical School, Institute for Animal Science, Hannover (Germany); Chen, Rongjun [Hannover Medical School, Department of Nephrology, Hannover (Germany); Zhejiang University, The Kidney Disease Center of the First Affiliated Hospital, Hangzhou (China)

    2014-09-15

    To investigate whether T1-mapping allows assessment of acute kidney injury (AKI) and prediction of chronic kidney disease (CKD) in mice. AKI was induced in C57Bl/6N mice by clamping of the right renal pedicle for 35 min (moderate AKI, n = 26) or 45 min (severe AKI, n = 23). Sham animals served as controls (n = 9). Renal histology was assessed in the acute (day 1 + day 7; d1 + d7) and chronic phase (d28) after AKI. Furthermore, longitudinal MRI-examinations (prior to until d28 after surgery) were performed using a 7-Tesla magnet. T1-maps were calculated from a fat-saturated echoplanar inversion recovery sequence, and mean and relative T1-relaxation times were determined. Renal histology showed severe tubular injury at d1 + d7 in both AKI groups, whereas, at d28, only animals with prolonged 45-min ischemia showed persistent signs of AKI. Following both AKI severities T1-values significantly increased and peaked at d7. T1-times in the contralateral kidney without AKI remained stable. At d7 relative T1-values in the outer stripe of the outer medulla were significantly higher after severe than after moderate AKI (138 ± 2 % vs. 121 ± 3 %, p = 0.001). T1-elevation persisted until d28 only after severe AKI. Already at d7 T1 in the outer stripe of the outer medulla correlated with kidney volume loss indicating CKD (r = 0.83). T1-mapping non-invasively detects AKI severity in mice and predicts further outcome. (orig.)

  13. T1-mapping for assessment of ischemia-induced acute kidney injury and prediction of chronic kidney disease in mice

    International Nuclear Information System (INIS)

    Hueper, Katja; Gutberlet, Marcel; Wacker, Frank; Hartung, Dagmar; Peperhove, Matti; Tewes, Susanne; Barrmeyer, Amelie; Rong, Song; Gerstenberg, Jessica; Haller, Herman; Gueler, Faikah; Mengel, Michael; Meier, Martin; Chen, Rongjun

    2014-01-01

    To investigate whether T1-mapping allows assessment of acute kidney injury (AKI) and prediction of chronic kidney disease (CKD) in mice. AKI was induced in C57Bl/6N mice by clamping of the right renal pedicle for 35 min (moderate AKI, n = 26) or 45 min (severe AKI, n = 23). Sham animals served as controls (n = 9). Renal histology was assessed in the acute (day 1 + day 7; d1 + d7) and chronic phase (d28) after AKI. Furthermore, longitudinal MRI-examinations (prior to until d28 after surgery) were performed using a 7-Tesla magnet. T1-maps were calculated from a fat-saturated echoplanar inversion recovery sequence, and mean and relative T1-relaxation times were determined. Renal histology showed severe tubular injury at d1 + d7 in both AKI groups, whereas, at d28, only animals with prolonged 45-min ischemia showed persistent signs of AKI. Following both AKI severities T1-values significantly increased and peaked at d7. T1-times in the contralateral kidney without AKI remained stable. At d7 relative T1-values in the outer stripe of the outer medulla were significantly higher after severe than after moderate AKI (138 ± 2 % vs. 121 ± 3 %, p = 0.001). T1-elevation persisted until d28 only after severe AKI. Already at d7 T1 in the outer stripe of the outer medulla correlated with kidney volume loss indicating CKD (r = 0.83). T1-mapping non-invasively detects AKI severity in mice and predicts further outcome. (orig.)

  14. Repeatability of magnetic resonance fingerprinting T1 and T2 estimates assessed using the ISMRM/NIST MRI system phantom.

    Science.gov (United States)

    Jiang, Yun; Ma, Dan; Keenan, Kathryn E; Stupic, Karl F; Gulani, Vikas; Griswold, Mark A

    2017-10-01

    The purpose of this study was to evaluate accuracy and repeatability of T 1 and T 2 estimates of a MR fingerprinting (MRF) method using the ISMRM/NIST MRI system phantom. The ISMRM/NIST MRI system phantom contains multiple compartments with standardized T 1 , T 2 , and proton density values. Conventional inversion-recovery spin echo and spin echo methods were used to characterize the T 1 and T 2 values in the phantom. The phantom was scanned using the MRF-FISP method over 34 consecutive days. The mean T 1 and T 2 values were compared with the values from the spin echo methods. The repeatability was characterized as the coefficient of variation of the measurements over 34 days. T 1 and T 2 values from MRF-FISP over 34 days showed a strong linear correlation with the measurements from the spin echo methods (R 2  = 0.999 for T 1 ; R 2  = 0.996 for T 2 ). The MRF estimates over the wide ranges of T 1 and T 2 values have less than 5% variation, except for the shortest T 2 relaxation times where the method still maintains less than 8% variation. MRF measurements of T 1 and T 2 are highly repeatable over time and across wide ranges of T 1 and T 2 values. Magn Reson Med 78:1452-1457, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  15. Myocardial T1 mapping and determination of partition coefficients at 3 tesla: comparison between gadobenate dimeglumine and gadofosveset trisodium

    Directory of Open Access Journals (Sweden)

    Marcelo Souto Nacif

    2018-01-01

    Full Text Available Abstract Objective: To compare an albumin-bound gadolinium chelate (gadofosveset trisodium and an extracellular contrast agent (gadobenate dimeglumine, in terms of their effects on myocardial longitudinal (T1 relaxation time and partition coefficient. Materials and Methods: Study subjects underwent two imaging sessions for T1 mapping at 3 tesla with a modified look-locker inversion recovery (MOLLI pulse sequence to obtain one pre-contrast T1 map and two post-contrast T1 maps (mean 15 and 21 min, respectively. The partition coefficient was calculated as ΔR1myocardium /ΔR1blood , where R1 is 1/T1. Results: A total of 252 myocardial and blood pool T1 values were obtained in 21 healthy subjects. After gadolinium administration, the myocardial T1 was longer for gadofosveset than for gadobenate, the mean difference between the two contrast agents being −7.6 ± 60 ms (p = 0.41. The inverse was true for the blood pool T1, which was longer for gadobenate than for gadofosveset, the mean difference being 56.5 ± 67 ms (p < 0.001. The partition coefficient (λ was higher for gadobenate than gadofosveset (0.41 vs. 0.33, indicating slower blood pool washout for gadofosveset than for gadobenate. Conclusion: Myocardial T1 times did not differ significantly between gadobenate and gadofosveset. At typical clinical doses of the contrast agents, partition coefficients were significantly lower for the intravascular contrast agent than for the extravascular agent.

  16. Relaxation characteristics of hastelloy X

    International Nuclear Information System (INIS)

    Suzuki, Kazuhiko

    1980-02-01

    Relaxation diagrams of Hastelloy X (relaxation curves, relaxation design diagrams, etc.) were generated from the creep constitutive equation of Hastelloy X, using inelastic stress analysis code TEPICC-J. These data are in good agreement with experimental relaxation data of ORNL-5479. Three typical inelastic stress analyses were performed for various relaxation behaviors of the high-temperature structures. An attempt was also made to predict these relaxation behaviors by the relaxation curves. (author)

  17. Simultaneous Imaging of CBF Change and BOLD with Saturation-Recovery-T1 Method.

    Directory of Open Access Journals (Sweden)

    Xiao Wang

    Full Text Available A neuroimaging technique based on the saturation-recovery (SR-T1 MRI method was applied for simultaneously imaging blood oxygenation level dependence (BOLD contrast and cerebral blood flow change (ΔCBF, which is determined by CBF-sensitive T1 relaxation rate change (ΔR1CBF. This technique was validated by quantitatively examining the relationships among ΔR1CBF, ΔCBF, BOLD and relative CBF change (rCBF, which was simultaneously measured by laser Doppler flowmetry under global ischemia and hypercapnia conditions, respectively, in the rat brain. It was found that during ischemia, BOLD decreased 23.1±2.8% in the cortical area; ΔR1CBF decreased 0.020±0.004s-1 corresponding to a ΔCBF decrease of 1.07±0.24 ml/g/min and 89.5±1.8% CBF reduction (n=5, resulting in a baseline CBF value (=1.18 ml/g/min consistent with the literature reports. The CBF change quantification based on temperature corrected ΔR1CBF had a better accuracy than apparent R1 change (ΔR1app; nevertheless, ΔR1app without temperature correction still provides a good approximation for quantifying CBF change since perfusion dominates the evolution of the longitudinal relaxation rate (R1app. In contrast to the excellent consistency between ΔCBF and rCBF measured during and after ischemia, the BOLD change during the post-ischemia period was temporally disassociated with ΔCBF, indicating distinct CBF and BOLD responses. Similar results were also observed for the hypercapnia study. The overall results demonstrate that the SR-T1 MRI method is effective for noninvasive and quantitative imaging of both ΔCBF and BOLD associated with physiological and/or pathological changes.

  18. Field dependence of T1 for hyperpolarized [1-13C]pyruvate

    DEFF Research Database (Denmark)

    Chattergoon, N.; Martnez-Santiesteban, F.; Handler, W. B.

    2013-01-01

    conformation and properties of the dissolution media such as buffer composition, solution pH, temperature and magnetic field. We have measured the magnetic field dependence of the spin–lattice relaxation time of hyperpolarized [1-13C]pyruvate using field-cycled relaxometry. [1-13C]pyruvate was hyperpolarized...

  19. 1.48 GHz (34.8 T) ^1H NMR measurements of SDW fluctuations in (TMTSF)_2PF_6

    Science.gov (United States)

    Clark, W. G.; Vonlanthen, P.; Goto, A.; Tanaka, K. B.; Alavi, B.; Kuhns, P.; Reyes, A. P.; Moulton, W. G.

    2001-03-01

    We report ^1H spin-lattice relaxation rate (T_1-1) measurements that probe the spin-density-wave (SDW) fluctuations in the quasi 1-d system (TMTSF)_2PF6 up to 1.48 GHz (34.8 T) in the NHMFL hybrid magnet. In the critical regime above the SDW transition near 12 K, T_1-1 has no frequency dependence and the angular dependence of T_1-1 attributed to the spin-flop condition in the ordered phase is absent. These results indicate that amplitude fluctuations of the SDW drive T_1-1 in the critical regime and that the SDW critical fluctuation correlation time is <1× 10-10 s. Somewhat below the transition, T_1-1 continues the decrease with increasing NMR frequency observed at lower frequencies. We attribute it to the power spectrum of the SDW phason fluctuations. The dependence of T_1-1 upon the field orientation in this phase reflects the spin-flop condition, but with parameters that are different from the expected ones. The UCLA part of this work was supported by NSF Grants DMR-9705369 and DMR-0072524.

  20. Meniscal T1rho and T2 measured with 3.0T MRI increases directly after running a marathon

    Energy Technology Data Exchange (ETDEWEB)

    Stehling, Christoph [University of California, Musculoskeletal and Quantitative Imaging Group (MQIR), Department of Radiology and Biomedical Imaging, San Francisco, CA (United States); University of Muenster, Department of Clinical Radiology, Muenster (Germany); Luke, Anthony [University of California, Department of Orthopedic Surgery, San Francisco, CA (United States); Stahl, Robert [University of California, Musculoskeletal and Quantitative Imaging Group (MQIR), Department of Radiology and Biomedical Imaging, San Francisco, CA (United States); Ludwig Maximilians University of Munich, Department of Clinical Radiology, Munich (Germany); Baum, Thomas; Joseph, Gabby; Pan, Judong; Link, Thomas M. [University of California, Musculoskeletal and Quantitative Imaging Group (MQIR), Department of Radiology and Biomedical Imaging, San Francisco, CA (United States)

    2011-06-15

    To prospectively evaluate changes in T1rho and T2 relaxation time in the meniscus using 3.0 T MRI in asymptomatic knees of marathon runners and to compare these findings with those of age-matched healthy subjects. Thirteen marathon runners underwent 3.0 T MRI including T1rho and T2 mapping sequences before, 48-72 h after, and 3 months after competition. Ten controls were examined at baseline and after 3 months. All images were analyzed by two musculoskeletal radiologists identifying and grading cartilage, meniscal, ligamentous. and other knee abnormalities with WORMS scores. Meniscal segmentation was performed to generate T1rho and T2 maps in six compartments. No differences in morphological knee abnormalities were found before and after the marathon. However, all marathon runners showed a significant increase in T1rho and T2 values after competition in all meniscus compartments (p < 0.0001), which may indicate changes in the biochemical composition of meniscal tissue. While T2 values decreased after 3 months T1rho values remained at a high level, indicating persisting changes in the meniscal matrix composition after a marathon. T2 values in menisci have the potential to be used as biomarkers for identifying reversible meniscus matrix changes indicating potential tissue damage. T1rho values need further study, but may be a valuable marker for diagnosing early, degenerative changes in the menisci following exercise. (orig.)

  1. Effects of aging on T1, T∗2, and QSM MRI values in the subcortex

    NARCIS (Netherlands)

    Keuken, M.C.; Bazin, P.-L.; Backhouse, K.; Beekhuizen, S.; Himmer, L.; Kandola, A.; Lafeber, J.J.; Prochazkova, L.; Trutti, A.; Schäfer, A.; Turner, R.; Forstmann, B.U.

    The aging brain undergoes several anatomical changes that can be measured with Magnetic Resonance Imaging (MRI). Early studies using lower field strengths have assessed changes in tissue properties mainly qualitatively, using T1 - or T∗2 - weighted images to provide image contrast. With the

  2. Correlation between right ventricular T1 mapping and right ventricular dysfunction in non-ischemic cardiomyopathy.

    Science.gov (United States)

    Jellis, Christine L; Yingchoncharoen, Teerapat; Gai, Neville; Kusunose, Kenya; Popović, Zoran B; Flamm, Scott; Kwon, Deborah

    2018-01-01

    Right ventricular (RV) fibrosis is increasingly recognized as the underlying pathological substrate in a variety of clinical conditions. We sought to employ cardiac magnetic resonance (CMR) techniques of strain imaging and longitudinal relaxation time (T 1 ) mapping to better examine the relationship between RV function and structure. Our aim was to initially evaluate the feasibility of these techniques to evaluate the right ventricle. We then sought to explore the relationship between RV function and underlying fibrosis, along with examining the evolution of RV remodeling according to the amount of baseline fibrosis. Echocardiography was performed in 102 subjects with non-ischemic cardiomyopathy. Right ventricular parameters were assessed including: fractional area change (FAC) and longitudinal strain. The same cohort underwent CMR. Post-contrast T 1 mapping was performed as a marker of fibrosis with a Look-Locker technique using inversion recovery imaging. Mid-ventricular post-contrast T 1 values of the RV free wall, RV septum and lateral LV were calculated using prototype analysis software. Biventricular volumetric data including ejection fraction was measured by CMR using a cine short axis stack. CMR strain analysis was also performed to assess 2D RV longitudinal and radial strain. Simultaneous biochemical and anthropometric data were recorded. Subjects were followed over a median time of 29 months (IQR 20-37 months) with echocardiography to evaluate temporal change in RV FAC according to baseline post-contrast T 1 values. Longitudinal data analysis was performed to adjust for patient loss during follow-up. Subjects (62% men, 51 ± 15 years) had mild to moderately impaired global RV systolic function (RVEF = 39 ± 15%; RVEDV = 187 ± 69 ml; RVESV = 119 ± 68 ml) and moderate left ventricular dysfunction at baseline (LVEF 30 ± 17%). Good correlation was observed between mean LV and RV post-contrast T 1 values (r = 0.652, p

  3. Dynamic Quantitative T1 Mapping in Orthotopic Brain Tumor Xenografts

    Directory of Open Access Journals (Sweden)

    Kelsey Herrmann

    2016-04-01

    Full Text Available Human brain tumors such as glioblastomas are typically detected using conventional, nonquantitative magnetic resonance imaging (MRI techniques, such as T2-weighted and contrast enhanced T1-weighted MRI. In this manuscript, we tested whether dynamic quantitative T1 mapping by MRI can localize orthotopic glioma tumors in an objective manner. Quantitative T1 mapping was performed by MRI over multiple time points using the conventional contrast agent Optimark. We compared signal differences to determine the gadolinium concentration in tissues over time. The T1 parametric maps made it easy to identify the regions of contrast enhancement and thus tumor location. Doubling the typical human dose of contrast agent resulted in a clearer demarcation of these tumors. Therefore, T1 mapping of brain tumors is gadolinium dose dependent and improves detection of tumors by MRI. The use of T1 maps provides a quantitative means to evaluate tumor detection by gadolinium-based contrast agents over time. This dynamic quantitative T1 mapping technique will also enable future quantitative evaluation of various targeted MRI contrast agents.

  4. TEACHING NEUROMUSCULAR RELAXATION.

    Science.gov (United States)

    NORRIS, JEANNE E.; STEINHAUS, ARTHUR H.

    THIS STUDY ATTEMPTED TO FIND OUT WHETHER (1) THE METHODS FOR ATTAINING NEUROMUSCULAR RELAXATION THAT HAVE PROVED FRUITFUL IN THE ONE-TO-ONE RELATIONSHIP OF THE CLINIC CAN BE SUCCESSFULLY ADAPTED TO THE TEACHER-CLASS RELATIONSHIP OF THE CLASSROOM AND GYMNASIUM, AND (2) NEUROMUSCULAR RELAXATION CAN BE TAUGHT SUCCESSFULLY BY AN APPROPRIATELY TRAINED…

  5. Relaxation of Anisotropic Glasses

    DEFF Research Database (Denmark)

    Deubener, Joachim; Martin, Birgit; Wondraczek, Lothar

    2004-01-01

    . When the load was removed at room temperature a permanent optical anisotropy (birefringence) was observed only perpendicular to cylinder axis and the pressure direction indicating complete elimination of thermal stresses. Relaxation of structural anisotropy was studied from reheating experiments using...... the energy release, thermo-mechanical and optical relaxation behaviour are drawn....

  6. Relaxation techniques for stress

    Science.gov (United States)

    ... raise your heart rate. This is called the stress response. Relaxation techniques can help your body relax and lower your blood pressure ... also many other types of breathing techniques you can learn. In many cases, you do not need much ... including those that cause stress. Meditation has been practiced for thousands of years, ...

  7. T1-T2 dual-modal MRI of brain gliomas using PEGylated Gd-doped iron oxide nanoparticles.

    Science.gov (United States)

    Xiao, Ning; Gu, Wei; Wang, Hao; Deng, Yunlong; Shi, Xin; Ye, Ling

    2014-03-01

    To overcome the negative contrast limitations of iron oxide-based contrast agents and to improve the biocompatibility of Gd-chelate contrast agents, PEGylated Gd-doped iron oxide (PEG-GdIO) NPs as a T1-T2 dual-modal contrast agent were synthesized by the polyol method. The transverse relaxivity (r2) and longitudinal relaxivity (r1) of PEG-GdIO were determined to be 66.9 and 65.9 mM(-1) s(-1), respectively. The high r1 value and low r2/r1 ratio make PEG-GdIO NPs suitable as a T1-T2 dual-modal contrast agent. The in vivo MRI demonstrated a brighter contrast enhancement in T1-weighted image and a simultaneous darken effect in T2-weighted MR image compared to the pre-contrast image in the region of glioma. Furthermore, the biocompatibility of PEG-GdIO NPs was confirmed by the in vitro MTT cytotoxicity and in vivo histological analyses (H&E). Therefore, PEG-GdIO NPs hold great potential in T1-T2 dual-modal imaging for the diagnosis of brain glioma. Copyright © 2013 Elsevier Inc. All rights reserved.

  8. Nuclear spin-lattice relaxation in nitroxide spin-label EPR

    DEFF Research Database (Denmark)

    Marsh, Derek

    2016-01-01

    that the definition of nitrogen nuclear relaxation rate Wn commonly used in the CW-EPR literature for 14N-nitroxyl spin labels is inconsistent with that currently adopted in time-resolved EPR measurements of saturation recovery. Redefinition of the normalised 14N spin-lattice relaxation rate, b = Wn/(2We), preserves...... of spin-lattice relaxation in this three-level system. Expressions for CW-saturation EPR with the revised definitions are summarised. Data on nitrogen nuclear spin-lattice relaxation times are compiled according to the three-level scheme for 14N-relaxation: T1 n = 1/Wn. Results are compared and contrasted...

  9. Optimized co-solute paramagnetic relaxation enhancement for the rapid NMR analysis of a highly fibrillogenic peptide

    International Nuclear Information System (INIS)

    Oktaviani, Nur Alia; Risør, Michael W.; Lee, Young-Ho; Megens, Rik P.; Jong, Djurre H. de; Otten, Renee; Scheek, Ruud M.; Enghild, Jan J.; Nielsen, Niels Chr.; Ikegami, Takahisa; Mulder, Frans A. A.

    2015-01-01

    Co-solute paramagnetic relaxation enhancement (PRE) is an attractive way to speed up data acquisition in NMR spectroscopy by shortening the T 1 relaxation time of the nucleus of interest and thus the necessary recycle delay. Here, we present the rationale to utilize high-spin iron(III) as the optimal transition metal for this purpose and characterize the properties of its neutral chelate form Fe(DO3A) as a suitable PRE agent. Fe(DO3A) effectively reduces the T 1 values across the entire sequence of the intrinsically disordered protein α-synuclein with negligible impact on line width. The agent is better suited than currently used alternatives, shows no specific interaction with the polypeptide chain and, due to its high relaxivity, is effective at low concentrations and in ‘proton-less’ NMR experiments. By using Fe(DO3A) we were able to complete the backbone resonance assignment of a highly fibrillogenic peptide from α 1 -antitrypsin by acquiring the necessary suite of multidimensional NMR datasets in 3 h

  10. The electrical properties and relaxation behavior of AgNb{sub 1/2}Ta{sub 1/2}O{sub 3} ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, K.Ganga, E-mail: kotagirigangaprasad@gmail.com; Niranjan, Manish K.; Asthana, Saket

    2017-02-01

    Polycrystalline AgNb{sub 1/2}Ta{sub 1/2}O{sub 3} powder was prepared by solid state reaction method. Preliminary x-ray diffractogram analysis of some aspects of crystal structure showed that a single phase compound formed exhibiting a monoclinic system. Impedance spectroscopy showed the presence of both bulk and grain boundary effects in the material. The relaxation behavior was studied by fitting electric modulus with Bergman function confirms us the existence of non-Debye type of relaxation the material. The ac conductivity spectrum obeyed Funke's double power law and fitting in results, the hopping parameters n{sub 1},n{sub 2} were indicating the existence of small and large range polaron hopping in the material. The band gap of the material 3.02 eV measured by using UV visible spectroscopy.

  11. Relaxation and Diffusion in Complex Systems

    CERN Document Server

    Ngai, K L

    2011-01-01

    Relaxation and Diffusion in Complex Systems comprehensively presents a variety of experimental evidences of universal relaxation and diffusion properties in complex materials and systems. The materials discussed include liquids, glasses, colloids, polymers, rubbers, plastic crystals and aqueous mixtures, as well as carbohydrates, biomolecules, bioprotectants and pharmaceuticals. Due to the abundance of experimental data, emphasis is placed on glass-formers and the glass transition problem, a still unsolved problem in condensed matter physics and chemistry. The evidence for universal properties of relaxation and diffusion dynamics suggests that a fundamental physical law is at work. The origin of the universal properties is traced to the many-body effects of the interaction, rigorous theory of which does not exist at the present time. However, using solutions of simplified models as guides, key quantities have been identified and predictions of the universal properties generated. These predictions from Ngai’...

  12. Evaluation of multi-exponential relaxation processes: In vitro and in vivo studies

    International Nuclear Information System (INIS)

    Henriksen, O.; Thomsen, C.; Kjaer, L.; Ring, P.

    1986-01-01

    T1 and T2 relaxation values obtained at 1.5 T were measured on 12 inversion-recovery (IR) sequences and a multiple spin-echo (SE) sequence with 32 echoes. Phantom studies were carried out for different CuSO/sub 4/ solutions, using MR imaging and reference spectrometry. The correlation was excellent (r=.98, P>.01;r=1.00, P>.01). T1 and T2 values varied less than 10% in the imaging plane. Then two-compartment phantoms were examined. For T1 and T2, the ratios T1(compartment A)/T1 (compartment B)>6 ant T2(c.A)/T2(c.B) > 6 were essential for reliable estimation. Studies on the normal brain indicate a multiexponential T1 and T2 relaxation process in gray matter

  13. T1 glottis radiotherapy: functional results and patients satisfaction

    International Nuclear Information System (INIS)

    Azoury, F.; Nasr, E.; Nehme Nasr, D.; Ghorra, C.; Fares, G.; Tabchy, B.; Ghorra, C.; Haddad, A.

    2009-01-01

    This retrospective series confirms the efficiency of the radical radiotherapy for the T1 glottal cancers as well as its satisfying tolerance with a low toxicity; most of patients were satisfied of their voice quality. (N.C.)

  14. Corroborative evidences of TV γ -scaling of the α-relaxation originating from the primitive relaxation/JG β relaxation

    Science.gov (United States)

    Ngai, K. L.; Paluch, M.

    2017-12-01

    Successful thermodynamic scaling of the structural alpha-relaxation time or transport coefficients of glass-forming liquids determined at various temperatures T and pressures P means the data conform to a single function of the product variable TVgamma, where V is the specific volume and gamma is a material specific constant. In the past two decades we have witnessed successful TVgamma-scaling in many molecular, polymeric, and even metallic glass-formers, and gamma is related to the slope of the repulsive part of the intermolecular potential. The advances made indicate TVgamma-scaling is an important aspect of the dynamic and thermodynamic properties of glass-formers. In this paper we show the origin of TVgamma-scaling is not from the structural alpha-relaxation time. Instead it comes from its precursor, the Johari-Goldstein beta-relaxation or the primitive relaxation of the Coupling Model and their relaxation times or tau_0 respectively. It is remarkable that all relaxation times are functions of TVgamma with the same gama, as well as the fractional exponent of the Kohlrausch correlation function of the structural alpha-relaxation. We arrive at this conclusion convincingly based on corroborative evidences from a number of experiments and molecular dynamics simulations performed on a wide variety of glass-formers and in conjunction with consistency with the predictions of the Coupling Model.

  15. SU-D-303-03: Impact of Uncertainty in T1 Measurements On Quantification of Dynamic Contrast Enhanced MRI

    Energy Technology Data Exchange (ETDEWEB)

    Aryal, M; Cao, Y [The University of Michigan, Ann Arbor, MI (United States)

    2015-06-15

    Purpose: Quantification of dynamic contrast enhanced (DCE) MRI requires native longitudinal relaxation time (T1) measurement. This study aimed to assess uncertainty in T1 measurements using two different methods. Methods and Materials: Brain MRI scans were performed on a 3T scanner in 9 patients who had low grade/benign tumors and partial brain radiotherapy without chemotherapy at pre-RT, week-3 during RT (wk-3), end-RT, and 1, 6 and 18 months after RT. T1-weighted images were acquired using gradient echo sequences with 1) 2 different flip angles (50 and 150), and 2) 5 variable TRs (100–2000ms). After creating quantitative T1 maps, average T1 was calculated in regions of interest (ROI), which were distant from tumors and received a total of accumulated radiation doses < 5 Gy at wk-3. ROIs included left and right normal Putamen and Thalamus (gray matter: GM), and frontal and parietal white matter (WM). Since there were no significant or even a trend of T1 changes from pre-RT to wk-3 in these ROIs, a relative repeatability coefficient (RC) of T1 as a measure of uncertainty was estimated in each ROI using the data pre-RT and at wk-3. The individual T1 changes at later time points were evaluated compared to the estimated RCs. Results: The 2-flip angle method produced small RCs in GM (9.7–11.7%) but large RCs in WM (12.2–13.6%) compared to the saturation-recovery (SR) method (11.0–17.7% for GM and 7.5–11.2% for WM). More than 81% of individual T1 changes were within T1 uncertainty ranges defined by RCs. Conclusion: Our study suggests that the impact of T1 uncertainty on physiological parameters derived from DCE MRI is not negligible. A short scan with 2 flip angles is able to achieve repeatability of T1 estimates similar to a long scan with 5 different TRs, and is desirable to be integrated in the DCE protocol. Present study was supported by National Institute of Health (NIH) under grant numbers; UO1 CA183848 and RO1 NS064973.

  16. Assessment of demyelination, edema, and gliosis by in vivo determination of T1 and T2 in the brain of patients with acute attack of multiple sclerosis

    DEFF Research Database (Denmark)

    Larsson, H B; Frederiksen, J; Petersen, J

    1989-01-01

    -body superconductive MR-scanner, operating at 1.5 T. The measurements were repeated several times, from onset of the disease and during remission by use of six-point partial saturation inversion recovery and 32-echo multiple spin-echo sequences, giving T1 and T2, respectively. We also focused on the issue, whether T1....... Hendriksen, and J. Olesen, Magn. Reson. Med. 7, 43 (1988)). In some of the acute plaques a slight initial increase in T1 and T2 was seen, when the measurement was repeated in about 10 days. Thereafter T1 decreased slowly in all but one patient as a function of days. In all cases the T1 relaxation process...

  17. Repair of damage induced by ultraviolet radiation in mutator T-1 Escherichia coli transductants

    International Nuclear Information System (INIS)

    Sideropoulos, A.S.; Greenberg, J.; Warren, G.

    1975-01-01

    To ascertain whether a relationship commonly exists between azide resistance, ultraviolet (uv) resistance, and the mutator property (mut T-1), we performed uv survival and mutation frequency determinations with and without caffeine (2.571 mM) in nonmutator azide resistant (azi/sup r/) and phage mediated mut T-1 transductants of Escherichia coli K-12, B/r, B/r T-, Bs-1, and Bs-8. The strains constructed were assumed to be ''co-isogenic'' except for the mutator factor. The frequency of mutation to streptomycin resistance (str/sup r/) was relatively constant and approximated 2 x 10- 7 . Transductants carrying the azide marker with or without the mut T-1 gene had the same level of uv survival as the parent with the same mutator phenotype. Dark repair of the prelethal uv lesion is equally caffeine sensitive in the nonmutator and mutator HCR+ strains. Our results indicated that the mut T-1 strains possess an efficient dark repair system for uv damage and that the mechanism of mut T-1 action is independent of uv dark repair processes. (auth)

  18. The relaxation time approximation

    International Nuclear Information System (INIS)

    Gairola, R.P.; Indu, B.D.

    1991-01-01

    A plausible approximation has been made to estimate the relaxation time from a knowledge of the transition probability of phonons from one state (r vector, q vector) to other state (r' vector, q' vector), as a result of collision. The relaxation time, thus obtained, shows a strong dependence on temperature and weak dependence on the wave vector. In view of this dependence, relaxation time has been expressed in terms of a temperature Taylor's series in the first Brillouin zone. Consequently, a simple model for estimating the thermal conductivity is suggested. the calculations become much easier than the Callaway model. (author). 14 refs

  19. Cardiac MOLLI T1 mapping at 3.0 T: comparison of patient-adaptive dual-source RF and conventional RF transmission.

    Science.gov (United States)

    Rasper, Michael; Nadjiri, Jonathan; Sträter, Alexandra S; Settles, Marcus; Laugwitz, Karl-Ludwig; Rummeny, Ernst J; Huber, Armin M

    2017-06-01

    To prospectively compare image quality and myocardial T 1 relaxation times of modified Look-Locker inversion recovery (MOLLI) imaging at 3.0 T (T) acquired with patient-adaptive dual-source (DS) and conventional single-source (SS) radiofrequency (RF) transmission. Pre- and post-contrast MOLLI T 1 mapping using SS and DS was acquired in 27 patients. Patient wise and segment wise analysis of T 1 times was performed. The correlation of DS MOLLI measurements with a reference spin echo sequence was analysed in phantom experiments. DS MOLLI imaging reduced T 1 standard deviation in 14 out of 16 myocardial segments (87.5%). Significant reduction of T 1 variance could be obtained in 7 segments (43.8%). DS significantly reduced myocardial T 1 variance in 16 out of 25 patients (64.0%). With conventional RF transmission, dielectric shading artefacts occurred in six patients causing diagnostic uncertainty. No according artefacts were found on DS images. DS image findings were in accordance with conventional T 1 mapping and late gadolinium enhancement (LGE) imaging. Phantom experiments demonstrated good correlation of myocardial T 1 time between DS MOLLI and spin echo imaging. Dual-source RF transmission enhances myocardial T 1 homogeneity in MOLLI imaging at 3.0 T. The reduction of signal inhomogeneities and artefacts due to dielectric shading is likely to enhance diagnostic confidence.

  20. Relaxation of coupled nuclear spin systems

    International Nuclear Information System (INIS)

    Koenigsberger, E.

    1985-05-01

    The subject of the present work is the relaxation behaviour of scalarly coupled spin-1/2 systems. In the theoretical part the semiclassical Redfield equations are used. Dipolar (D), Chemical Shift Anisotropy (CSA) and Random Field (RF) interactions are considered as relaxation mechanisms. Cross correlations of dipolar interactions of different nuclei pairs and those between the D and the CSA mechanisms are important. The model of anisotropic molecular rotational relaxation and the extreme narrowing approximation are used to obtain the spectral density functions. The longitudinal relaxation data are analyzed into normal modes following Werbelow and Grant. The time evolution of normal modes is derived for the AX system with D-CSA cross terms. In the experimental part the hypothesis of dimerization in the cinnamic acid and the methyl cinnamate - AMX systems with DD cross terms - is corroborated by T 1 -time measurements and a calculation of the diffusion constants. In pentachlorobenzene - an AX system - taking into account of D-CSA cross terms enables the complete determination of movements anosotropy and the determination of the sign of the indirect coupling constant 1 Jsub(CH). (G.Q.)

  1. Assessment of myocardial fibrosis with T1 mapping MRI

    International Nuclear Information System (INIS)

    Everett, R.J.; Stirrat, C.G.; Semple, S.I.R.; Newby, D.E.; Dweck, M.R.; Mirsadraee, S.

    2016-01-01

    Myocardial fibrosis can arise from a range of pathological processes and its presence correlates with adverse clinical outcomes. Cardiac magnetic resonance (CMR) can provide a non-invasive assessment of cardiac structure, function, and tissue characteristics, which includes late gadolinium enhancement (LGE) techniques to identify focal irreversible replacement fibrosis with a high degree of accuracy and reproducibility. Importantly the presence of LGE is consistently associated with adverse outcomes in a range of common cardiac conditions; however, LGE techniques are qualitative and unable to detect diffuse myocardial fibrosis, which is an earlier form of fibrosis preceding replacement fibrosis that may be reversible. Novel T1 mapping techniques allow quantitative CMR assessment of diffuse myocardial fibrosis with the two most common measures being native T1 and extracellular volume (ECV) fraction. Native T1 differentiates normal from infarcted myocardium, is abnormal in hypertrophic cardiomyopathy, and may be particularly useful in the diagnosis of Anderson–Fabry disease and amyloidosis. ECV is a surrogate measure of the extracellular space and is equivalent to the myocardial volume of distribution of the gadolinium-based contrast medium. It is reproducible and correlates well with fibrosis on histology. ECV is abnormal in patients with cardiac failure and aortic stenosis, and is associated with functional impairment in these groups. T1 mapping techniques promise to allow earlier detection of disease, monitor disease progression, and inform prognosis; however, limitations remain. In particular, reference ranges are lacking for T1 mapping values as these are influenced by specific CMR techniques and magnetic field strength. In addition, there is significant overlap between T1 mapping values in healthy controls and most disease states, particularly using native T1, limiting the clinical application of these techniques at present.

  2. Assessment of myocardial fibrosis with T1 mapping MRI.

    Science.gov (United States)

    Everett, R J; Stirrat, C G; Semple, S I R; Newby, D E; Dweck, M R; Mirsadraee, S

    2016-08-01

    Myocardial fibrosis can arise from a range of pathological processes and its presence correlates with adverse clinical outcomes. Cardiac magnetic resonance (CMR) can provide a non-invasive assessment of cardiac structure, function, and tissue characteristics, which includes late gadolinium enhancement (LGE) techniques to identify focal irreversible replacement fibrosis with a high degree of accuracy and reproducibility. Importantly the presence of LGE is consistently associated with adverse outcomes in a range of common cardiac conditions; however, LGE techniques are qualitative and unable to detect diffuse myocardial fibrosis, which is an earlier form of fibrosis preceding replacement fibrosis that may be reversible. Novel T1 mapping techniques allow quantitative CMR assessment of diffuse myocardial fibrosis with the two most common measures being native T1 and extracellular volume (ECV) fraction. Native T1 differentiates normal from infarcted myocardium, is abnormal in hypertrophic cardiomyopathy, and may be particularly useful in the diagnosis of Anderson-Fabry disease and amyloidosis. ECV is a surrogate measure of the extracellular space and is equivalent to the myocardial volume of distribution of the gadolinium-based contrast medium. It is reproducible and correlates well with fibrosis on histology. ECV is abnormal in patients with cardiac failure and aortic stenosis, and is associated with functional impairment in these groups. T1 mapping techniques promise to allow earlier detection of disease, monitor disease progression, and inform prognosis; however, limitations remain. In particular, reference ranges are lacking for T1 mapping values as these are influenced by specific CMR techniques and magnetic field strength. In addition, there is significant overlap between T1 mapping values in healthy controls and most disease states, particularly using native T1, limiting the clinical application of these techniques at present. Copyright © 2016 The Royal College

  3. Analytical properties of an Ostrovsky-Whitham type dynamical system for a relaxing medium with spatial memory and its integrable regularization

    International Nuclear Information System (INIS)

    Bogoliubov, N.N. Jr.; Prykarpatsky, A.K.; Gucwa, I.; Golenia, J.

    2007-12-01

    Short-wave perturbations in a relaxing medium, governed by a special reduction of the Ostrovsky evolution equation, and later derived by Whitham, are studied using the gradient-holonomic integrability algorithm.The bi-Hamiltonicity and complete integrability of the corresponding dynamical system is stated and an infinite hierarchy of commuting to each other conservation laws of dispersive type are found. The two- and four-dimensional invariant reductions are studied in detail. The well defined regularization of the model is constructed and its Lax type integrability is discussed. (author)

  4. CONDENSED MATTER: STRUCTURE, MECHANICAL, AND THERMAL PROPERTIES: Observation of β-Relaxation in Sub-Tg Isothermally Annealed Al-Based Metallic Glasses

    Science.gov (United States)

    Yang, Hong-Wang; Tong, Wei-Ping; Zhao, Xiang; Zuo, Liang; Wang, Jian-Qiang

    2008-09-01

    Al85 Ni5 Y8 C02 and Al 85 Ni5 Y6 C02 Fe2 metallic glasses are fabricated by melt spinning. A kink or a small exothermic peak is observed for both the samples isothermally annealed at sub-glass transition temperatures. Temperature modulated differential scanning calorimetry (TMDSC) data disapprove amorphous phase separation. The activation energies derived from Kissinger plots of the exothermic process on DSC curve around glass transition temperature are consistent with those of β -relaxation of metallic glasses.

  5. Relaxed Poisson cure rate models.

    Science.gov (United States)

    Rodrigues, Josemar; Cordeiro, Gauss M; Cancho, Vicente G; Balakrishnan, N

    2016-03-01

    The purpose of this article is to make the standard promotion cure rate model (Yakovlev and Tsodikov, ) more flexible by assuming that the number of lesions or altered cells after a treatment follows a fractional Poisson distribution (Laskin, ). It is proved that the well-known Mittag-Leffler relaxation function (Berberan-Santos, ) is a simple way to obtain a new cure rate model that is a compromise between the promotion and geometric cure rate models allowing for superdispersion. So, the relaxed cure rate model developed here can be considered as a natural and less restrictive extension of the popular Poisson cure rate model at the cost of an additional parameter, but a competitor to negative-binomial cure rate models (Rodrigues et al., ). Some mathematical properties of a proper relaxed Poisson density are explored. A simulation study and an illustration of the proposed cure rate model from the Bayesian point of view are finally presented. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Measurements of spin-lattice relaxation time in mixed alkali halide crystals

    International Nuclear Information System (INIS)

    Tannus, A.

    1983-01-01

    Using magneto-optic techniques the ground state spin-lattice relaxation times (T1) of 'F' centers in mixed Alkali Halide cristals (KCl-KBr), was studied. A computer assisted system to optically measure short relaxation times (approx. = 1mS), was described. The technique is based on the measurement of the Magnetic Circular Dicroism (MCD) presented by F centers. The T1 magnetic field dependency at 2 K (up to 65 KGauss), was obtained as well as the MCD spectra for different relative concentration at the mixed matrices. The theory developed by Panepucci and Mollenauer for F centers spin-lattice relaxation in pure matrices was modified to explain the behaviour of T1 in mixed cristals. The Direct Process results (T approx. = 2.0 K) compared against that theory shows that the main relaxation mecanism, up to 25 KGauss, continues to be phonon modulation of the hiperfine iteraction between F electrons and surrounding nuclei. (Author) [pt

  7. Quantifying NMR relaxation correlation and exchange in articular cartilage with time domain analysis

    Science.gov (United States)

    Mailhiot, Sarah E.; Zong, Fangrong; Maneval, James E.; June, Ronald K.; Galvosas, Petrik; Seymour, Joseph D.

    2018-02-01

    Measured nuclear magnetic resonance (NMR) transverse relaxation data in articular cartilage has been shown to be multi-exponential and correlated to the health of the tissue. The observed relaxation rates are dependent on experimental parameters such as solvent, data acquisition methods, data analysis methods, and alignment to the magnetic field. In this study, we show that diffusive exchange occurs in porcine articular cartilage and impacts the observed relaxation rates in T1-T2 correlation experiments. By using time domain analysis of T2-T2 exchange spectroscopy, the diffusive exchange time can be quantified by measurements that use a single mixing time. Measured characteristic times for exchange are commensurate with T1 in this material and so impacts the observed T1 behavior. The approach used here allows for reliable quantification of NMR relaxation behavior in cartilage in the presence of diffusive fluid exchange between two environments.

  8. Nuclear Spin relaxation mediated by Fermi-edge electrons in n-type GaAs

    Science.gov (United States)

    Kotur, M.; Dzhioev, R. I.; Kavokin, K. V.; Korenev, V. L.; Namozov, B. R.; Pak, P. E.; Kusrayev, Yu. G.

    2014-03-01

    A method based on the optical orientation technique was developed to measure the nuclear-spin lattice relaxation time T 1 in semiconductors. It was applied to bulk n-type GaAs, where T 1 was measured after switching off the optical excitation in magnetic fields from 400 to 1200 G at low (< 30 K) temperatures. The spin-lattice relaxation of nuclei in the studied sample with n D = 9 × 1016 cm-3 was found to be determined by hyperfine scattering of itinerant electrons (Korringa mechanism) which predicts invariability of T 1 with the change in magnetic field and linear dependence of the relaxation rate on temperature. This result extends the experimentally verified applicability of the Korringa relaxation law in degenerate semiconductors, previously studied in strong magnetic fields (several Tesla), to the moderate field range.

  9. Resistive switching properties and low resistance state relaxation in Al/Pr0.7Ca0.3MnO3/Pt junctions

    International Nuclear Information System (INIS)

    Li Songlin; Liao, Z L; Li, J; Gang, J L; Zheng, D N

    2009-01-01

    Metal/insulator/metal structures composed of active Al top electrodes (TEs) and oxygen-deficient Pr 0.7 Ca 0.3 MnO 3 (PCMO) insulator layers are prepared on platinized silicon substrates. The junction resistance exhibits an obvious negative differential resistance region in the first bias sweep and an irreversible increase from 2 to 100 MΩ in repeated ±4 V sweeps. The pulse duration needed to fully switch the junctions is found to be on the order of milliseconds. When 100-500 μs negative pulses are used, the junctions show an incomplete switch to the low resistance state (LRS) which exhibits fluctuating resistances. The fluctuation in the LRS is suppressed and the high-to-low resistance ratio increases gradually when the negative pulse duration is increased from 100 to 500 μs. For relaxed junctions, pulse switching experiments reveal that the LRS undergoes a dynamically stable process at the beginning and then reaches a lower and metastable resistance value. Resistance retention tests also indicate that the high resistance state is very stable, while the metastable LRS gradually relaxes to higher resistance values. The experimental results are discussed with the formation and dissociation of an interfacial AlO x layer at the interface between Al TEs and PCMO layers.

  10. Structure of the two-dimensional relaxation spectra seen within the eigenmode perturbation theory and the two-site exchange model.

    Science.gov (United States)

    Bytchenkoff, Dimitri; Rodts, Stéphane

    2011-01-01

    The form of the two-dimensional (2D) NMR-relaxation spectra--which allow to study interstitial fluid dynamics in diffusive systems by correlating spin-lattice (T(1)) and spin-spin (T(2)) relaxation times--has given rise to numerous conjectures. Herein we find analytically a number of fundamental structural properties of the spectra: within the eigen-modes formalism, we establish relationships between the signs and intensities of the diagonal and cross-peaks in spectra obtained by various 1 and 2D NMR-relaxation techniques, reveal symmetries of the spectra and uncover interdependence between them. We investigate more specifically a practically important case of porous system that has sets of T(1)- and T(2)-eigenmodes and eigentimes similar to each other by applying the perturbation theory. Furthermore we provide a comparative analysis of the application of the, mathematically more rigorous, eigen-modes formalism and the, rather more phenomenological, first-order two-site exchange model to diffusive systems. Finally we put the results that we could formulate analytically to the test by comparing them with computer-simulations for 2D porous model systems. The structural properties, in general, are to provide useful clues for assignment and analysis of relaxation spectra. The most striking of them--the presence of negative peaks--underlines an urgent need for improvement of the current 2D Inverse Laplace Transform (ILT) algorithm used for calculation of relaxation spectra from NMR raw data. Copyright © 2010 Elsevier Inc. All rights reserved.

  11. A novel enterocin T1 with anti-Pseudomonas activity produced by Enterococcus faecium T1 from Chinese Tibet cheese.

    Science.gov (United States)

    Liu, Hui; Zhang, Lanwei; Yi, Huaxi; Han, Xue; Gao, Wei; Chi, Chunliang; Song, Wei; Li, Haiying; Liu, Chunguang

    2016-02-01

    An enterocin-producing Enterococcus faecium T1 was isolated from Chinese Tibet cheese. The enterocin was purified by SP-Sepharose and reversed phase HPLC. It was identified as unique from other reported bacteriocins based on molecular weight (4629 Da) and amino acid compositions; therefore it was subsequently named enterocin T1. Enterocin T1 was stable at 80-100 °C and over a wide pH range, pH 3.0-10.0. Protease sensitivity was observed to trypsin, pepsin, papain, proteinase K, and pronase E. Importantly, enterocin T1 was observed to inhibit the growth of numerous Gram-negative and Gram-positive bacteria including Pseudomonas putida, Pseudomonas aeruginosa, Pseudomonas fluorescens, Escherichia coli, Salmonella typhimurium, Shigella flexneri, Shigella sonnei, Staphylococcus aureus, Listeria monocytogenes. Take together, these results suggest that enterocin T1 is a novel bacteriocin with the potential to be used as a bio-preservative to control Pseudomonas spp. in food.

  12. Acoustic noise reduction in T 1- and proton-density-weighted turbo spin-echo imaging.

    Science.gov (United States)

    Ott, Martin; Blaimer, Martin; Breuer, Felix; Grodzki, David; Heismann, Björn; Jakob, Peter

    2016-02-01

    To reduce acoustic noise levels in T 1-weighted and proton-density-weighted turbo spin-echo (TSE) sequences, which typically reach acoustic noise levels up to 100 dB(A) in clinical practice. Five acoustic noise reduction strategies were combined: (1) gradient ramps and shapes were changed from trapezoidal to triangular, (2) variable-encoding-time imaging was implemented to relax the phase-encoding gradient timing, (3) RF pulses were adapted to avoid the need for reversing the polarity of the slice-rewinding gradient, (4) readout bandwidth was increased to provide more time for gradient activity on other axes, (5) the number of slices per TR was reduced to limit the total gradient activity per unit time. We evaluated the influence of each measure on the acoustic noise level, and conducted in vivo measurements on a healthy volunteer. Sound recordings were taken for comparison. An overall acoustic noise reduction of up to 16.8 dB(A) was obtained by the proposed strategies (1-4) and the acquisition of half the number of slices per TR only. Image quality in terms of SNR and CNR was found to be preserved. The proposed measures in this study allowed a threefold reduction in the acoustic perception of T 1-weighted and proton-density-weighted TSE sequences compared to a standard TSE-acquisition. This could be achieved without visible degradation of image quality, showing the potential to improve patient comfort and scan acceptability.

  13. Relaxation rates of low-field gas-phase ^129Xe storage cells

    Science.gov (United States)

    Limes, Mark; Saam, Brian

    2010-10-01

    A study of longitudinal nuclear relaxation rates T1 of ^129Xe and Xe-N2 mixtures in a magnetic field of 3.8 mT is presented. In this regime, intrinsic spin relaxation is dominated by the intramolecular spin-rotation interaction due to persistent xenon dimers, a mechanism that can be quelled by introducing large amounts of N2 into the storage cell. Extrinsic spin relaxation is dominated by the wall-relaxation rate, which is the primary quantity of interest for the various low-field storage cells and coatings that we have tested. Previous group work has shown that extremely long gas-phase relaxation times T1 can be obtained, but only at large magnetic fields and low xenon densities. The current work is motivated by the practical benefits of retaining hyperpolarized ^129Xe for extended periods of time in a small magnetic field.

  14. Nuclear spin relaxation due to chemical shift anisotropy of gas-phase 129Xe.

    Science.gov (United States)

    Hanni, Matti; Lantto, Perttu; Vaara, Juha

    2011-08-14

    Nuclear spin relaxation provides detailed dynamical information on molecular systems and materials. Here, first-principles modeling of the chemical shift anisotropy (CSA) relaxation time for the prototypic monoatomic (129)Xe gas is carried out, both complementing and predicting the results of NMR measurements. Our approach is based on molecular dynamics simulations combined with pre-parametrized ab initio binary nuclear shielding tensors, an "NMR force field". By using the Redfield relaxation formalism, the simulated CSA time correlation functions lead to spectral density functions that, for the first time, quantitatively determine the experimental spin-lattice relaxation times T(1). The quality requirements on both the Xe-Xe interaction potential and binary shielding tensor are investigated in the context of CSA T(1). Persistent dimers Xe(2) are found to be responsible for the CSA relaxation mechanism in the low-density limit of the gas, completely in line with the earlier experimental findings.

  15. Nuclear magnetic resonance relaxation times for human lung cancer and lung tissues

    International Nuclear Information System (INIS)

    Matsuura, Yoshifumi; Shioya, Sumie; Kurita, Daisaku; Ohta, Takashi; Haida, Munetaka; Ohta, Yasuyo; Suda, Syuichi; Fukuzaki, Minoru.

    1994-01-01

    We investigated the nuclear magnetic resonance (NMR) relaxation times, T 1 and T 2 , for lung cancer tissue, and other samples of lung tissue obtained from surgical specimens. The samples were nine squamous cell carcinomas, five necrotic squamous cell carcinomas, 15 adenocarcinomas, two benign mesotheliomas, and 13 fibrotic lungs. The relaxation times were measured with a 90 MHz NMR spectrometer and the results were correlated with histological changes. The values of T 1 and T 2 for squamous cell carcinoma and mesothelioma were significantly longer than those of adenocarcinoma and fibrotic lung tissue. There were no significant differences in values of T 1 and T 2 between adenocarcinoma and lung tissue. The values of T 1 and T 2 for benign mesothelioma were similar to those of squamous cell carcinoma, which suggested that increases in T 1 and T 2 are not specific to malignant tissues. (author)

  16. Anti-cytokine therapies in T1D

    DEFF Research Database (Denmark)

    Nepom, Gerald T; Ehlers, Mario; Mandrup-Poulsen, Thomas

    2013-01-01

    Therapeutic targeting of proinflammatory cytokines is clinically beneficial in several autoimmune disorders. Several of these cytokines are directly implicated in the pathogenesis of type 1 diabetes, suggesting opportunities for design of clinical trials in type 1 diabetes that incorporate select...... suitable for modulating the immune response in T1D....

  17. OWEZ pelagic fish, progress report and progression after T1

    NARCIS (Netherlands)

    Ybema, M.S.; Gloe, D.; Lambers, R.H.L.

    2009-01-01

    This report presents the current status of pelagic fish research in the Offshore Windfarm Egmond aan Zee (OWEZ) after having finalized the T0 baseline survey in 2003 and the T1 survey after construction of the wind farm in 2007. The T0 study indicated a highly dynamic pelagic fish community along

  18. A macrocyclic ellagitannin trimer, oenotherin T(1), from Oenothera species.

    Science.gov (United States)

    Taniguchi, Shoko; Imayoshi, Yoko; Yabu-uchi, Ryoko; Ito, Hideyuki; Hatano, Tsutomu; Yoshida, Takashi

    2002-01-01

    Oenotherin T(1) was isolated from leaves of Oenothera tetraptera as a major ellagitannin. Its structure, that of a macrocyclic trimer with a new acyl group, an isodehydrovaloneoyl group, was established. This compound was also produced by callus tissues induced from O. laciniata leaves.

  19. Relaxation of synchronization on complex networks.

    Science.gov (United States)

    Son, Seung-Woo; Jeong, Hawoong; Hong, Hyunsuk

    2008-07-01

    We study collective synchronization in a large number of coupled oscillators on various complex networks. In particular, we focus on the relaxation dynamics of the synchronization, which is important from the viewpoint of information transfer or the dynamics of system recovery from a perturbation. We measure the relaxation time tau that is required to establish global synchronization by varying the structural properties of the networks. It is found that the relaxation time in a strong-coupling regime (K>Kc) logarithmically increases with network size N , which is attributed to the initial random phase fluctuation given by O(N-1/2) . After elimination of the initial-phase fluctuation, the relaxation time is found to be independent of the system size; this implies that the local interaction that depends on the structural connectivity is irrelevant in the relaxation dynamics of the synchronization in the strong-coupling regime. The relaxation dynamics is analytically derived in a form independent of the system size, and it exhibits good consistency with numerical simulations. As an application, we also explore the recovery dynamics of the oscillators when perturbations enter the system.

  20. Relaxivity of Ferumoxytol at 1.5 T and 3.0 T.

    Science.gov (United States)

    Knobloch, Gesine; Colgan, Timothy; Wiens, Curtis N; Wang, Xiaoke; Schubert, Tilman; Hernando, Diego; Sharma, Samir D; Reeder, Scott B

    2018-05-01

    The aim of this study was to determine the relaxation properties of ferumoxytol, an off-label alternative to gadolinium-based contrast agents, under physiological conditions at 1.5 T and 3.0 T. Ferumoxytol was diluted in gradually increasing concentrations (0.26-4.2 mM) in saline, human plasma, and human whole blood. Magnetic resonance relaxometry was performed at 37°C at 1.5 T and 3.0 T. Longitudinal and transverse relaxation rate constants (R1, R2, R2*) were measured as a function of ferumoxytol concentration, and relaxivities (r1, r2, r2*) were calculated. A linear dependence of R1, R2, and R2* on ferumoxytol concentration was found in saline and plasma with lower R1 values at 3.0 T and similar R2 and R2* values at 1.5 T and 3.0 T (1.5 T: r1saline = 19.9 ± 2.3 smM; r1plasma = 19.0 ± 1.7 smM; r2saline = 60.8 ± 3.8 smM; r2plasma = 64.9 ± 1.8 smM; r2*saline = 60.4 ± 4.7 smM; r2*plasma = 64.4 ± 2.5 smM; 3.0 T: r1saline = 10.0 ± 0.3 smM; r1plasma = 9.5 ± 0.2 smM; r2saline = 62.3 ± 3.7 smM; r2plasma = 65.2 ± 1.8 smM; r2*saline = 57.0 ± 4.7 smM; r2*plasma = 55.7 ± 4.4 smM). The dependence of relaxation rates on concentration in blood was nonlinear. Formulas from second-order polynomial fittings of the relaxation rates were calculated to characterize the relationship between R1blood and R2 blood with ferumoxytol. Ferumoxytol demonstrates strong longitudinal and transverse relaxivities. Awareness of the nonlinear relaxation behavior of ferumoxytol in blood is important for ferumoxytol-enhanced magnetic resonance imaging applications and for protocol optimization.

  1. Tumour T1 changes in vivo are highly predictive of response to chemotherapy and reflect the number of viable tumour cells – a preclinical MR study in mice

    International Nuclear Information System (INIS)

    Weidensteiner, Claudia; Allegrini, Peter R; Sticker-Jantscheff, Melanie; Romanet, Vincent; Ferretti, Stephane; McSheehy, Paul MJ

    2014-01-01

    Effective chemotherapy rapidly reduces the spin–lattice relaxation of water protons (T 1 ) in solid tumours and this change (ΔT 1 ) often precedes and strongly correlates with the eventual change in tumour volume (TVol). To understand the biological nature of ΔT 1 , we have performed studies in vivo and ex vivo with the allosteric mTOR inhibitor, everolimus. Mice bearing RIF-1 tumours were studied by magnetic resonance imaging (MRI) to determine TVol and T 1 , and MR spectroscopy (MRS) to determine levels of the proliferation marker choline and levels of lipid apoptosis markers, prior to and 5 days (endpoint) after daily treatment with vehicle or everolimus (10 mg/kg). At the endpoint, tumours were ablated and an entire section analysed for cellular and necrotic quantification and staining for the proliferation antigen Ki67 and cleaved-caspase-3 as a measure of apoptosis. The number of blood-vessels (BV) was evaluated by CD31 staining. Mice bearing B16/BL6 melanoma tumours were studied by MRI to determine T 1 under similar everolimus treatment. At the endpoint, cell bioluminescence of the tumours was measured ex vivo. Everolimus blocked RIF-1 tumour growth and significantly reduced tumour T 1 and total choline (Cho) levels, and increased polyunsaturated fatty-acids which are markers of apoptosis. Immunohistochemistry showed that everolimus reduced the %Ki67 + cells but did not affect caspase-3 apoptosis, necrosis, BV-number or cell density. The change in T 1T 1 ) correlated strongly with the changes in TVol and Cho and %Ki67 + . In B16/BL6 tumours, everolimus also decreased T 1 and this correlated with cell bioluminescence; another marker of cell viability. Receiver-operating-characteristic curves (ROC) for everolimus on RIF-1 tumours showed that ΔT 1 had very high levels of sensitivity and specificity (ROC AUC = 0.84) and this was confirmed for the cytotoxic patupilone in the same tumour model (ROC AUC = 0.97). These studies suggest that ΔT 1 is not a

  2. Quantitative Renal Cortical Perfusion in Human Subjects with Magnetic Resonance Imaging Using Iron-Oxide Nanoparticles: Influence of T1 Shortening

    Energy Technology Data Exchange (ETDEWEB)

    Morell, A.; Ahlstrom, H.; Schoenberg, S.O.; Abildgaard, A.; Bock, M.; Bjoernerud, A. (Dept. of Diagnostic Radiology, Uppsala Univ. Hospital, Uppsala (Sweden))

    2008-10-15

    Background: Using conventional contrast agents, the technique of quantitative perfusion by observing the transport of a bolus with magnetic resonance imaging (MRI) is limited to the brain due to extravascular leakage. Purpose: To perform quantitative perfusion measurements in humans with an intravascular contrast agent, and to estimate the influence of the T1 relaxivity of the contrast agent on the first-pass response. Material and Methods: Renal cortical perfusion was measured quantitatively in six patients with unilateral renal artery stenosis using a rapid gradient double-echo sequence in combination with an intravenous bolus injection of NC100150 Injection, an intravascular contrast agent based on iron-oxide nanoparticles. The influence of T1 relaxivity was measured by comparing perfusion results based on single- and double-echo data. Results: The mean values of cortical blood flow, cortical blood volume, and mean transit time in the normal kidneys were measured to 339+-60 ml/min/100 g, 41+-8 ml/100 g, and 7.3+-1.0 s, respectively, based on double-echo data. The corresponding results based on single-echo data, which are not compensated for the T1 relaxivity, were 254+-47 ml/min/100 g, 27+-3 ml/100 g, and 6+-1.2 s, respectively. Conclusion: The use of a double-echo sequence enabled elimination of confounding T1 effects and consequent systematic underestimation of the perfusion.

  3. Modern pulsed spectrometer EPR for longitudinal relaxation time (T1) investigation - computer programs for measurement and data analysis

    International Nuclear Information System (INIS)

    Ilnicki, J.; Koziol, J.; Galinski, W.; Oles, T.; Kostrzewa, J.; Froncisz, W.

    1994-01-01

    The computerized control and data processing systems for new spectrometer designed for nuclear magnetic resonance studies of biological samples are presented. Both programs were written for INTEL 386 processor and they works under the Windows 3.0 environment

  4. Measurements of T1 and T2 relaxation times of colon cancer metastases in rat liver at 7 T

    NARCIS (Netherlands)

    Gambarota, G.; Veltien, A.; van Laarhoven, H.; Philippens, M.; Jonker, A.; Mook, O. R.; Frederiks, W. M.; Heerschap, A.

    2004-01-01

    The purpose of this study was to investigate the magnetic resonance imaging (MRI) characteristics of colon cancer metastases in rat liver at 7 T. A dedicated RF microstrip coil of novel design was built in order to increase the signal-to-noise ratio and, in combination with respiratory triggering,

  5. Relaxed Binaural LCMV Beamforming

    NARCIS (Netherlands)

    Koutrouvelis, A.; Hendriks, R.C.; Heusdens, R.; Jensen, Jesper Rindom

    2017-01-01

    In this paper, we propose a new binaural beamforming technique, which can be seen as a relaxation of the linearly constrained minimum variance (LCMV) framework. The proposed method can achieve simultaneous noise reduction and exact binaural cue preservation of the target source, similar to the

  6. T1 Shortening in the Globus Pallidus after Multiple Administrations of Gadobutrol: Assessment with a Multidynamic Multiecho Sequence.

    Science.gov (United States)

    Kang, Koung Mi; Choi, Seung Hong; Hwang, Moonjung; Yun, Tae Jin; Kim, Ji-Hoon; Sohn, Chul-Ho

    2018-04-01

    Purpose To determine the association between the administration of the macrocyclic contrast medium gadobutrol and T1 relaxation time in the brains of patients with normal renal function by using multidynamic multiecho (MDME) magnetic resonance (MR) imaging sequences. Materials and Methods The institutional review board approved this retrospective study, and the need to obtain written informed consent was waived. This study included 46 patients (revealed by an electronic medical record search) who had received one or more gadobutrol injections and a maximum of one MR imaging contrast medium injection other than gadobutrol before MDME sequence acquisition. One radiologist performed quantitative analyses of regions of interest on quantitative T1 maps twice to cover the normal-appearing globus pallidus (GP), frontal white matter, frontal cortex, and thalamus. The number of administrations and the cumulative dose of gadobutrol, age, intervals between administrations, sex, and treatment were investigated. Univariable and multivariable linear regression analyses of the T1 values in four brain regions and the GP-to-thalamus signal intensity (SI) ratio were performed. P values of less than the Bonferroni-corrected value of .01 were considered to indicate significant differences. Results Intraobserver reproducibility was good to excellent (intraclass correlation coefficients, 0.62-0.81). Because of high multicollinearity between the number of gadobutrol administrations and accumulated dose (r = 0.96, P .01). Conclusion Multiple exposures to gadobutrol are associated with T1 shortening in the GP. © RSNA, 2017 Online supplemental material is available for this article.

  7. Preoperative staging and treatment options in T1 rectal adenocarcinoma

    DEFF Research Database (Denmark)

    Baatrup, Gunnar; Endreseth, Birger H; Isaksen, Vidar

    2009-01-01

    . Results. Local treatment of T1 cancers combined with close follow-up, early salvage surgery or later radical resection of local recurrences or with chemo-radiation may lead to fewer severe complications and comparable, or even better, long-term survival. Accurate preoperative staging and careful selection...... of patients for local or non-operative treatment are mandatory. As preoperative staging, at present, is not sufficiently accurate, strategies for completion, salvage or rescue surgery is important, and must be accepted by the patient before local treatment for cure is initiated. Recommendations......Background. Major rectal resection for T1 rectal cancer offers more than 95% cancer specific five-year survival to patients surviving the first 30 days after surgery. A significant further improvement by development of the surgical technique may not be possible. Improvements in the total survival...

  8. Towards quantification of butadiene content in styrene-butadiene block copolymers and their blends with general purpose polystyrene (GPPS) and the relation between mechanical properties and NMR relaxation times

    Energy Technology Data Exchange (ETDEWEB)

    Nestle, Nikolaus [BASF Aktiengesellschaft, GKP/P-G 201, D-67056 Ludwigshafen (Germany)], E-mail: nikolaus.nestle@basf.com; Heckmann, Walter; Steininger, Helmut; Knoll, Konrad [BASF Aktiengesellschaft, GKP/P-G 201, D-67056 Ludwigshafen (Germany)

    2007-11-26

    The properties of styrene-butadiene-styrene (SBS) block copolymers do not only depend on the butadiene content and the degree of polymerisation but also on their chain architecture. In this contribution we present the results of a low-field time domain (TD) NMR study in which the transverse relaxation behaviour of different SBS block copolymers was analysed and correlated with findings from mechanical testing on pure and blended materials and transmission electron microscopy data which provide information on the microphase separation. The results indicate that while a straightforward determination of the butadiene content as in blended materials like ABS is not possible for these materials, the TD-NMR results correlate quite well with the mechanical performance of blends from SBS block copolymers with general purpose polystyrene (GPPS), i.e. industrial grade homopolymer polystyrene. Temperature-dependent experiments on pure and blended materials revealed a slight reduction in the softening temperature of the GPPS fraction in the blends.

  9. Moessbauer and muon spin relaxation investigation of magnetic and superconducting properties of Ca{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Materne, Philipp; Bubel, Sirko; Maeter, Hemke; Sarkar, Rajib; Klauss, Hans-Henning [Institut fuer Festkoerperphysik, Technische Universitaet Dresden, 01062 Dresden (Germany); Harnagea, Luminita; Wurmehl, Sabine; Buechner, Bernd [IFW Dresden, Postfach 270016, 01171 Dresden (Germany); Luetkens, Hubertus [Paul-Scherrer-Institut, 5232 Villigen (Switzerland)

    2013-07-01

    The antiferromagnetic parent compound, CaFe{sub 2}As{sub 2}, shows a supression of the spin density wave and a subsequent superconducting state upon partial substitution of Ca by Na. Along the substitution series, superconducting transition temperatures up to ∼35 K were found. We studied the electronic phase diagram of Ca{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2} using Moessbauer spectroscopy and muon spin relaxation experiments. We have analyzed the data in terms of magnetic and superconducting properties and possible coexistence of superconductivity and spin density wave order. We compared our results with recently published data of Ba{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2}.

  10. A study of spin-lattice relaxation rates of glucose, fructose, sucrose and cherries using high-T c SQUID-based NMR in ultralow magnetic fields

    Science.gov (United States)

    Liao, Shu-Hsien; Wu, Pei-Che

    2017-08-01

    We study the concentration dependence of spin-lattice relaxation rates, T 1 -1, of glucose, fructose, sucrose and cherries by using high-T c SQUID-based NMR at magnetic fields of ˜97 μT. The detected NMR signal, Sy (T Bp), is fitted to [1 - exp(-T Bp/T 1)] to derive T 1 -1, where Sy (T Bp) is the strength of the NMR signal, T Bp is the duration of pre-polarization and T 1 -1 is the spin-lattice relaxation rate. It was found that T 1 -1 increases as the sugar concentrations increase. The increased T 1 -1 is due to the presence of more molecules in the surroundings, which increases the spin-lattice interaction and in turn enhances T 1 -1. The T 1 -1 versus degrees Brix curve provides a basis for determining unknown Brix values for cherries as well as other fruits.

  11. HER-2 immunohistochemical expression as prognostic marker in high-grade T1 bladder cancer (T1G3

    Directory of Open Access Journals (Sweden)

    Luca Bongiovanni

    2013-06-01

    Full Text Available Objectives: To evaluate if the Human epidermal growth factor receptor 2 (HER-2 expression levels may be used as potential prognostic marker in high grade T1 blad- der cancer (T1G3 Methods: Specimens from transurethral resection of bladder tumour (TURBT of 103 patients with high-grade T1 bladder cancer were collected. This pathologic database was reviewed. Four-year follow-up data were matched with pathologic data. Eighty-three patients entered the study. HER-2 staining was performed. Patients were grouped for HER-2 status. Statistical analysis included Kaplan Meier survival analysis and Log-rank test. Results: Pathological review of TURBT specimens confirmed high-grade T1 transitional cell bladder cancer in all patients. Median follow-up was 12 months (mean 23,5; range 3-48. Twenty-one patients (25.4% present strong HER-2 expression (3+, 28 (33.7% moderate expression (2+, 26 (33.7% weak staining (1+ and 8 (9.6% negative expression (0. Thirty- one patients of 83 (37.4% had not evidence of disease, 41 (49.4% recurred, 11 (13.2% had a progression of disease. Forty-one patients had high grade T1 recurrence. Patients with HER-2 status 0 did not showed progression of disease. Patients with HER-2 status 3+, undergoing cys- tectomy because progression of disease, had a pathological stage > pT2 and a nodal involve- ment. Median Disease-Free Survival (DFS for all patients was 12 months (DFS probability (pDFS = 49.3%; 95% CI, -11.1/+10.1. Median DFS in HER-2 groups was 8 (pDFS 37.5%; 95% CI,-28.8/+29.9, 24 (pDFS 46.1%; 95% CI,-19.5/+17.5, 20 (pDFS 46.4%; 95% CI,-18.8/+16.9 and 10 months (pDFS 47.6%; 95% CI,-21.9/+19.1 respectively in HER-2 status 0,1+,2+,3+. Log-Rank test is not statistically significant (p = 0,39. Conclusions: This study showed that HER-2 expression does not represent a prognostic mark- er of recurrence/progression of disease in high-grade T1 bladder cancer.

  12. Relaxation Time of High-Density Amorphous Ice

    Science.gov (United States)

    Handle, Philip H.; Seidl, Markus; Loerting, Thomas

    2012-06-01

    Amorphous water plays a fundamental role in astrophysics, cryoelectron microscopy, hydration of matter, and our understanding of anomalous liquid water properties. Yet, the characteristics of the relaxation processes taking place in high-density amorphous ice (HDA) are unknown. We here reveal that the relaxation processes in HDA at 110-135 K at 0.1-0.2 GPa are of collective and global nature, resembling the alpha relaxation in glassy material. Measured relaxation times suggest liquid-like relaxation characteristics in the vicinity of the crystallization temperature at 145 K. By carefully relaxing pressurized HDA for several hours at 135 K, we produce a state that is closer to the ideal glass state than all HDA states discussed so far in literature.

  13. MR T1{rho} as an imaging biomarker for monitoring liver injury progression and regression: an experimental study in rats with carbon tetrachloride intoxication

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Feng; Wang, Yi-Xiang J.; Yuan, Jing; Deng, Min; Ahuja, Anil T. [Chinese University of Hong Kong, Department of Imaging and Interventional Radiology, Prince of Wales Hospital, Hong Kong SAR (China); Wong, Hing Lok [School of Public Health and Primary Care, Prince of Wales Hospital, The Chinese University of Hong Kong, Jockey Club Centre for Osteoporosis Care and Control, Hong Kong SAR (China); Chu, Eagle S.H.; Go, Minnie Y.Y.; Yu, Jun [Chinese University of Hong Kong, Institute of Digestive Disease and Department of Medicine and Therapeutics, Li Ka Shing Institute of Health Sciences, Hong Kong SAR (China); Teng, Gao-Jun [Southeast University, Department of Radiology, Zhongda Hospital, Nanjing (China)

    2012-08-15

    Recently it was shown that the magnetic resonance imaging (MRI) T1{rho} value increased with the severity of liver fibrosis in rats with bile duct ligation. Using a rat carbon tetrachloride (CCl{sub 4}) liver injury model, this study further investigated the merit of T1{rho} relaxation for liver fibrosis evaluation. Male Sprague-Dawley rats received intraperitoneal injection of 2 ml/kg CCl{sub 4} twice weekly for up to 6 weeks. Then CCl{sub 4} was withdrawn and the animals were allowed to recover. Liver T1{rho} MRI and conventional T2-weighted images were acquired. Animals underwent MRI at baseline and at 2 days, 2 weeks, 4 weeks and 6 weeks post CCl{sub 4} injection, and they were also examined at 1 week and 4 weeks post CCl{sub 4} withdrawal. Liver histology was also sampled at these time points. Liver T1{rho} values increased slightly, though significantly, on day 2, and then increased further and were highest at week 6 post CCl{sub 4} insults. The relative liver signal intensity change on T2-weighted images followed a different time course compared with that of T1{rho}. Liver T1{rho} values decreased upon the withdrawal of the CCl{sub 4} insult. Histology confirmed the animals had typical CCl{sub 4} liver injury and fibrosis progression and regression processes. MR T1{rho} imaging can monitor CCl{sub 4}-induced liver injury and fibrosis. (orig.)

  14. Simultaneous multislice triple-echo steady-state (SMS-TESS) T1 , T2 , PD, and off-resonance mapping in the human brain.

    Science.gov (United States)

    Heule, Rahel; Celicanin, Zarko; Kozerke, Sebastian; Bieri, Oliver

    2018-02-21

    To investigate the ability of simultaneous multislice triple-echo steady-state (SMS-TESS) imaging to provide quantitative maps of multiple tissue parameters, i.e., longitudinal and transverse relaxation times (T 1 and T 2 ), proton density (PD), and off-resonance (ΔB 0 ), in the human brain at 3T from a single scan. TESS acquisitions were performed in 2D mode to reduce motion sensitivity and accelerated by an SMS excitation scheme (CAIPIRINHA) with SENSE reconstruction. SMS-acceleration factors (R) of 2 and 4 were evaluated. The in vitro and in vivo validation process included standard reference scans to analyze the accuracy of T 1 , T 2 , and ΔB 0 estimates, as well as single-slice TESS measurements. For R = 2, the quantification of T 1 , T 2 , PD, and ΔB 0 was overall reliable with marginal noise enhancement. T 1 and T 2 values were in good agreement with the reference measurements and single-slice TESS. For R = 4, the agreement of ΔB 0 with the standard reference was excellent and the determination of T 1 , T 2 , and PD was reproducible; however, increased variations in T 1 and T 2 values with respect to single-slice TESS were observed. SMS-TESS has shown potential to offer rapid simultaneous T 1 , T 2 , PD, and ΔB 0 mapping of human brain tissues. © 2018 International Society for Magnetic Resonance in Medicine.

  15. Multi-Quanta Spin-Locking Nuclear Magnetic Resonance Relaxation Measurements: An Analysis of the Long-Time Dynamical Properties of Ions and Water Molecules Confined within Dense Clay Sediments

    Directory of Open Access Journals (Sweden)

    Patrice Porion

    2017-11-01

    Full Text Available Solid/liquid interfaces are exploited in various industrial applications because confinement strongly modifies the physico-chemical properties of bulk fluids. In that context, investigating the dynamical properties of confined fluids is crucial to identify and better understand the key factors responsible for their behavior and to optimize their structural and dynamical properties. For that purpose, we have developed multi-quanta spin-locking nuclear magnetic resonance relaxometry of quadrupolar nuclei in order to fill the gap between the time-scales accessible by classical procedures (like dielectric relaxation, inelastic and quasi-elastic neutron scattering and obtain otherwise unattainable dynamical information. This work focuses on the use of quadrupolar nuclei (like 2H, 7Li and 133Cs, because quadrupolar isotopes are the most abundant NMR probes in the periodic table. Clay sediments are the confining media selected for this study because they are ubiquitous materials implied in numerous industrial applications (ionic exchange, pollutant absorption, drilling, waste storing, cracking and heterogeneous catalysis.

  16. NMR relaxation times in human brain tumors (preliminary results)

    International Nuclear Information System (INIS)

    Benoist, L.; Certaines, J. de; Chatel, M.; Menault, F.

    1981-01-01

    Since the early work of Damadian in 1971, proton NMR studies of tumors has been well documented. Present study concerns the spin-lattice T 1 and spin-spin T 2 relaxation times of normal dog brain according to the histological differentiation and of 35 human benignant or malignant tumors. The results principally show T 2 important variations between white and gray substance in normal brain but no discrimination between malignant and benignant tumors [fr

  17. Hair Dye and Hair Relaxers

    Science.gov (United States)

    ... For Consumers Consumer Information by Audience For Women Hair Dye and Hair Relaxers Share Tweet Linkedin Pin it More sharing ... products. If you have a bad reaction to hair dyes and relaxers, you should: Stop using the ...

  18. Experiments in paramagnetic relaxation

    International Nuclear Information System (INIS)

    Lijphart, E.E.

    1976-01-01

    This thesis presents two attempts to improve the resolving power of the relaxation measurement technique. The first attempt reconsiders the old technique of steady state saturation. When used in conjunction with the pulse technique, it offers the possibility of obtaining additional information about the system in which all-time derivatives are zero; in addition, non-linear effects may be distinguished from each other. The second attempt involved a systematic study of only one system: Cu in the Tutton salts (K and Rb). The systematic approach, the high accuracy of the measurement and the sheer amount of experimental data for varying temperature, magnetic field and concentration made it possible in this case to separate the prevailing relaxation mechanisms reliably

  19. Relaxation from particle production

    Energy Technology Data Exchange (ETDEWEB)

    Hook, Anson; Marques-Tavares, Gustavo [Stanford Institute for Theoretical Physics, Stanford University, Stanford, CA 94305 (United States)

    2016-12-20

    We consider using particle production as a friction force by which to implement a “Relaxion” solution to the electroweak hierarchy problem. Using this approach, we are able to avoid superplanckian field excursions and avoid any conflict with the strong CP problem. The relaxation mechanism can work before, during or after inflation allowing for inflationary dynamics to play an important role or to be completely decoupled.

  20. Evaluation of biexponential relaxation behaviour in the human brain by magnetic resonance imaging

    DEFF Research Database (Denmark)

    Kjaer, L; Thomsen, C; Henriksen, O

    1989-01-01

    Quantitative estimation of individual biologic components in relaxation curves obtained in vivo may increase the specificity of tissue characterization by magnetic resonance imaging. In this study, the potential of biexponential curve analysis was evaluated in T1 and T2 measurements on the human...... brain at 1.5 tesla. Optimal experimental conditions were carefully observed, including the use of long TR values and a very small voxel size. T1 determination was based on a 12-points partial saturation inversion recovery pulse sequence. T2 determination involved a multiple spin echo sequence with 32...... echoes. No genuine biexponentiality was demonstrated in the T1 and T2 relaxation processes of white matter, cortical grey matter, or cerebrospinal fluid. Thus, a monoexponential model seems adequate for description of the relaxation behaviour in these cases. Furthermore, the results suggest...

  1. Magnetic relaxation in anisotropic magnets

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker

    1971-01-01

    The line shape and the kinematic and thermodynamic slowing down of the critical and paramagnetic relaxation in axially anisotropic materials are discussed. Kinematic slowing down occurs only in the longitudinal relaxation function. The thermodynamic slowing down occurs in either the transverse...... or longitudinal relaxation function depending on the sign of the axial anisotropy....

  2. Momentum constraint relaxation

    International Nuclear Information System (INIS)

    Marronetti, Pedro

    2006-01-01

    Full relativistic simulations in three dimensions invariably develop runaway modes that grow exponentially and are accompanied by violations of the Hamiltonian and momentum constraints. Recently, we introduced a numerical method (Hamiltonian relaxation) that greatly reduces the Hamiltonian constraint violation and helps improve the quality of the numerical model. We present here a method that controls the violation of the momentum constraint. The method is based on the addition of a longitudinal component to the traceless extrinsic curvature A ij -tilde, generated by a vector potential w i , as outlined by York. The components of w i are relaxed to solve approximately the momentum constraint equations, slowly pushing the evolution towards the space of solutions of the constraint equations. We test this method with simulations of binary neutron stars in circular orbits and show that it effectively controls the growth of the aforementioned violations. We also show that a full numerical enforcement of the constraints, as opposed to the gentle correction of the momentum relaxation scheme, results in the development of instabilities that stop the runs shortly

  3. The TOTEM T1 read out card motherboard

    OpenAIRE

    Minutoli, S; Lo Vetere, M; Robutti, E

    2010-01-01

    This article describes the Read Out Card (ROC) motherboard, which is the main component of the T1 forward telescope front-end electronic system. The ROC main objectives are to acquire tracking data and trigger information from the detector. It performs data conversion from electrical to optical format and transfers the data streams to the next level of the system and it implements Slow Control modules which are able to receive, decode and distribute the LHC machine low jitter clock and fast c...

  4. The relaxation phenomena of radicals induced in irradiated fresh mangoes

    International Nuclear Information System (INIS)

    Kikuchi, Masahiro; Morishita, Norio; Kobayashi, Yasuhiko; Ogawa, Hideyuki; Shimoyama, Yuhei; Ukai, Mitsuko

    2009-01-01

    Using the γ-irradiated fresh mangoes followed by freeze-drying and powderization, electron spin resonance spectrometry of specimens was performed. As a result, a strong single peak in the flesh, the pericarp and the seed was observed at g=2.004 and attributed to organic free radicals. When relaxation times of the peak was calculated using the method of Lund et al., T 2 showed dose responses according to increasing doses while T 1 was almost constant. Dose responsibility of the relaxation time T 2 obtained from flesh specimens of the mangoes could be measured regardless of the preservation period of 1 to 9 days following γ-irradiation. Therefore, there might be possible to detect the irradiation treatment of fresh mangoes using relaxation time T 2 . (author)

  5. Connexin 43-targeted T1 contrast agent for MRI diagnosis of glioma.

    Science.gov (United States)

    Abakumova, Tatiana; Abakumov, Maxim; Shein, Sergey; Chelushkin, Pavel; Bychkov, Dmitry; Mukhin, Vladimir; Yusubalieva, Gaukhar; Grinenko, Nadezhda; Kabanov, Alexander; Nukolova, Natalia; Chekhonin, Vladimir

    2016-01-01

    Glioblastoma multiforme is the most aggressive form of brain tumor. Early and accurate diagnosis of glioma and its borders is an important step for its successful treatment. One of the promising targets for selective visualization of glioma and its margins is connexin 43 (Cx43), which is highly expressed in reactive astrocytes and migrating glioma cells. The purpose of this study was to synthesize a Gd-based contrast agent conjugated with specific antibodies to Cx43 for efficient visualization of glioma C6 in vivo. We have prepared stable nontoxic conjugates of monoclonal antibody to Cx43 and polylysine-DTPA ligands complexed with Gd(III), which are characterized by higher T1 relaxivity (6.5 mM(-1) s(-1) at 7 T) than the commercial agent Magnevist® (3.4 mM(-1) s(-1)). Cellular uptake of Cx43-specific T1 contrast agent in glioma C6 cells was more than four times higher than the nonspecific IgG-contrast agent, as detected by flow cytometry and confocal analysis. MRI experiments showed that the obtained agents could markedly enhance visualization of glioma C6 in vivo after their intravenous administration. Significant accumulation of Cx43-targeted contrast agents in glioma and the peritumoral zone led not only to enhanced contrast but also to improved detection of the tumor periphery. Fluorescence imaging confirmed notable accumulation of Cx43-specific conjugates in the peritumoral zone compared with nonspecific IgG conjugates at 24 h after intravenous injection. All these features of Cx43-targeted contrast agents might be useful for more precise diagnosis of glioma and its borders by MRI. Copyright © 2015 John Wiley & Sons, Ltd.

  6. Bilateral hyperintense basal ganglia on T1-weighted image

    International Nuclear Information System (INIS)

    Baik, Seung Kug; Ahn, Woo Hyun; Choi, Han Yong; Kim, Bong Gi

    1994-01-01

    Bilateral high signal intensity in basal ganglia on T1-weighted images is unusual, the purpose of this study is to describe the pattern of high signal intensity and underlying disease. During the last three years, 8 patients showed bilateral high signal intensity in basal ganglia on T1-weighted image, as compared with cerebral white matter. Authors analyzed the images and underlying causes retrospectively. Of 8 patients, 5 were male and 3 were female. The age ranged from 15 days to 79 years. All patient were examined by a 0.5T superconductive MRI. Images were obtained by spin echo multislice technique. Underlying causes were 4 cases of hepatopathy, 2 cases of calcium metabolism disorder, and one case each of neurofibromatosis and hypoxic brain injury. These process were bilateral in all cases and usually symmetric. In all cases the hyperintense areas were generally homogenous without mass effect or edema, although somewhat nodular appearance was seen in neurofibromatosis. Lesions were located in the globus pallidus and internal capsule in hepatopathy and neurofibromatosis, head of the caudate nucleus in disorder of calcum metabolism, and the globus pallidus in hypoxic brain injury. Although this study is limited by its patient population, bilateral hyperintense basal ganglia is associated with various disease entities. On analysis of hyperintense basal ganglia lesion, the knowledge of clinical information improved diagnostic accuracy

  7. Mapping pathological changes in brain structure by combining T1- and T2-weighted MR imaging data

    International Nuclear Information System (INIS)

    Ganzetti, Marco; Mantini, Dante; Wenderoth, Nicole

    2015-01-01

    A workflow based on the ratio between standardized T1-weighted (T1-w) and T2-weighted (T2-w) MR images has been proposed as a new tool to study brain structure. This approach was previously used to map structural properties in the healthy brain. Here, we evaluate whether the T1-w/T2-w approach can support the assessment of structural impairments in the diseased brain. We use schizophrenia data to demonstrate the potential clinical utility of the technique. We analyzed T1-w and T2-w images of 36 schizophrenic patients and 35 age-matched controls. These were collected for the Function Biomedical Informatics Research Network (fBIRN) collaborative project, which had an IRB approval and followed the HIPAA guidelines. We computed T1-w/T2-w images for each individual and compared intensities in schizophrenic and control groups on a voxel-wise basis, as well as in regions of interest (ROIs). Our results revealed that the T1-w/T2-w image permits to discriminate brain regions showing group-level differences between patients and controls with greater accuracy than conventional T1-w and T2-w images. Both the ROIs and the voxel-wise analysis showed globally reduced gray and white matter values in patients compared to controls. Significantly reduced values were found in regions such as insula, primary auditory cortex, hippocampus, inferior longitudinal fasciculus, and inferior fronto-occipital fasciculus. Our findings were consistent with previous meta-analyses in schizophrenia corroborating the hypothesis of a potential ''disconnection'' syndrome in conjunction with structural alterations in local gray matter regions. Overall, our study suggested that the T1-w/T2-w technique permits to reliably map structural differences between the brains of patients and healthy individuals. (orig.)

  8. Mapping pathological changes in brain structure by combining T1- and T2-weighted MR imaging data

    Energy Technology Data Exchange (ETDEWEB)

    Ganzetti, Marco; Mantini, Dante [ETH Zurich, Neural Control of Movement Laboratory, Department of Health Sciences and Technology, Zurich (Switzerland); University of Oxford, Department of Experimental Psychology, Oxford (United Kingdom); Wenderoth, Nicole [ETH Zurich, Neural Control of Movement Laboratory, Department of Health Sciences and Technology, Zurich (Switzerland); KU Leuven, Laboratory of Movement Control and Neuroplasticity, Faculty of Kinesiology and Rehabilitation Sciences, Leuven (Belgium)

    2015-09-15

    A workflow based on the ratio between standardized T1-weighted (T1-w) and T2-weighted (T2-w) MR images has been proposed as a new tool to study brain structure. This approach was previously used to map structural properties in the healthy brain. Here, we evaluate whether the T1-w/T2-w approach can support the assessment of structural impairments in the diseased brain. We use schizophrenia data to demonstrate the potential clinical utility of the technique. We analyzed T1-w and T2-w images of 36 schizophrenic patients and 35 age-matched controls. These were collected for the Function Biomedical Informatics Research Network (fBIRN) collaborative project, which had an IRB approval and followed the HIPAA guidelines. We computed T1-w/T2-w images for each individual and compared intensities in schizophrenic and control groups on a voxel-wise basis, as well as in regions of interest (ROIs). Our results revealed that the T1-w/T2-w image permits to discriminate brain regions showing group-level differences between patients and controls with greater accuracy than conventional T1-w and T2-w images. Both the ROIs and the voxel-wise analysis showed globally reduced gray and white matter values in patients compared to controls. Significantly reduced values were found in regions such as insula, primary auditory cortex, hippocampus, inferior longitudinal fasciculus, and inferior fronto-occipital fasciculus. Our findings were consistent with previous meta-analyses in schizophrenia corroborating the hypothesis of a potential ''disconnection'' syndrome in conjunction with structural alterations in local gray matter regions. Overall, our study suggested that the T1-w/T2-w technique permits to reliably map structural differences between the brains of patients and healthy individuals. (orig.)

  9. Nuclear spin-lattice relaxation in nitroxide spin-label EPR.

    Science.gov (United States)

    Marsh, Derek

    2016-11-01

    Nuclear relaxation is a sensitive monitor of rotational dynamics in spin-label EPR. It also contributes competing saturation transfer pathways in T 1 -exchange spectroscopy, and the determination of paramagnetic relaxation enhancement in site-directed spin labelling. A survey shows that the definition of nitrogen nuclear relaxation rate W n commonly used in the CW-EPR literature for 14 N-nitroxyl spin labels is inconsistent with that currently adopted in time-resolved EPR measurements of saturation recovery. Redefinition of the normalised 14 N spin-lattice relaxation rate, b=W n /(2W e ), preserves the expressions used for CW-EPR, whilst rendering them consistent with expressions for saturation recovery rates in pulsed EPR. Furthermore, values routinely quoted for nuclear relaxation times that are deduced from EPR spectral diffusion rates in 14 N-nitroxyl spin labels do not accord with conventional analysis of spin-lattice relaxation in this three-level system. Expressions for CW-saturation EPR with the revised definitions are summarised. Data on nitrogen nuclear spin-lattice relaxation times are compiled according to the three-level scheme for 14 N-relaxation: T 1 n =1/W n . Results are compared and contrasted with those for the two-level 15 N-nitroxide system. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Contrast-enhanced 3T MR perfusion of musculoskeletal tumours. T1 value heterogeneity assessment and evaluation of the influence of T1 estimation methods on quantitative parameters

    Energy Technology Data Exchange (ETDEWEB)

    Gondim Teixeira, Pedro Augusto; Leplat, Christophe; Verbizier, Jacques de; Blum, Alain [Hopital Central, CHRU-Nancy, Service d' Imagerie Guilloz, Nancy (France); Chen, Bailiang; Beaumont, Marine [Universite de Lorraine, Laboratoire IADI, UMR S 947, Nancy (France); Badr, Sammy; Cotten, Anne [CHRU Lille Centre de Consultations et d' Imagerie de l' Appareil Locomoteur, Department of Radiology and Musculoskeletal Imaging, Lille (France)

    2017-12-15

    To evaluate intra-tumour and striated muscle T1 value heterogeneity and the influence of different methods of T1 estimation on the variability of quantitative perfusion parameters. Eighty-two patients with a histologically confirmed musculoskeletal tumour were prospectively included in this study and, with ethics committee approval, underwent contrast-enhanced MR perfusion and T1 mapping. T1 value variations in viable tumour areas and in normal-appearing striated muscle were assessed. In 20 cases, normal muscle perfusion parameters were calculated using three different methods: signal based and gadolinium concentration based on fixed and variable T1 values. Tumour and normal muscle T1 values were significantly different (p = 0.0008). T1 value heterogeneity was higher in tumours than in normal muscle (variation of 19.8% versus 13%). The T1 estimation method had a considerable influence on the variability of perfusion parameters. Fixed T1 values yielded higher coefficients of variation than variable T1 values (mean 109.6 ± 41.8% and 58.3 ± 14.1% respectively). Area under the curve was the least variable parameter (36%). T1 values in musculoskeletal tumours are significantly different and more heterogeneous than normal muscle. Patient-specific T1 estimation is needed for direct inter-patient comparison of perfusion parameters. (orig.)

  11. ΔT=1/2 rule in quark models with unconfined colour

    International Nuclear Information System (INIS)

    Arbuzov, B.A.; Kompaneetz, F.F.; Tikhonin, F.F.

    1977-01-01

    In the triplet quark model with unconfined colour a weak hadronic current is obtained with the following properties: a) it satisfies weak SU(2) algebra; b) the neutral current is completely diagonal and coincides with electromagnetic one in the quark structure ; c) the ''white'' part of the current possesses the properties of the Cabbibo current. The properties of the ''white'' part of nonleptonic Lagrangian derived from this current are : a)between the coefficients of the transition amplitudes ΔT=1/2 and ΔT=3/2 there is a ratio approximately 25 corresponding to experiment; b) there are no transitions ΔS=2; c) the values for the transitions ΔT=0,1,2 of the Lagrangian without changes of strangeness are compatible with each other

  12. Contrast-enhanced 3T MR Perfusion of Musculoskeletal Tumours: T1 Value Heterogeneity Assessment and Evaluation of the Influence of T1 Estimation Methods on Quantitative Parameters.

    Science.gov (United States)

    Gondim Teixeira, Pedro Augusto; Leplat, Christophe; Chen, Bailiang; De Verbizier, Jacques; Beaumont, Marine; Badr, Sammy; Cotten, Anne; Blum, Alain

    2017-12-01

    To evaluate intra-tumour and striated muscle T1 value heterogeneity and the influence of different methods of T1 estimation on the variability of quantitative perfusion parameters. Eighty-two patients with a histologically confirmed musculoskeletal tumour were prospectively included in this study and, with ethics committee approval, underwent contrast-enhanced MR perfusion and T1 mapping. T1 value variations in viable tumour areas and in normal-appearing striated muscle were assessed. In 20 cases, normal muscle perfusion parameters were calculated using three different methods: signal based and gadolinium concentration based on fixed and variable T1 values. Tumour and normal muscle T1 values were significantly different (p = 0.0008). T1 value heterogeneity was higher in tumours than in normal muscle (variation of 19.8% versus 13%). The T1 estimation method had a considerable influence on the variability of perfusion parameters. Fixed T1 values yielded higher coefficients of variation than variable T1 values (mean 109.6 ± 41.8% and 58.3 ± 14.1% respectively). Area under the curve was the least variable parameter (36%). T1 values in musculoskeletal tumours are significantly different and more heterogeneous than normal muscle. Patient-specific T1 estimation is needed for direct inter-patient comparison of perfusion parameters. • T1 value variation in musculoskeletal tumours is considerable. • T1 values in muscle and tumours are significantly different. • Patient-specific T1 estimation is needed for comparison of inter-patient perfusion parameters. • Technical variation is higher in permeability than semiquantitative perfusion parameters.

  13. Variational formulation of relaxed and multi-region relaxed magnetohydrodynamics

    Science.gov (United States)

    Dewar, R. L.; Yoshida, Z.; Bhattacharjee, A.; Hudson, S. R.

    2015-12-01

    > Ideal magnetohydrodynamics (IMHD) is strongly constrained by an infinite number of microscopic constraints expressing mass, entropy and magnetic flux conservation in each infinitesimal fluid element, the latter preventing magnetic reconnection. By contrast, in the Taylor relaxation model for formation of macroscopically self-organized plasma equilibrium states, all these constraints are relaxed save for the global magnetic fluxes and helicity. A Lagrangian variational principle is presented that leads to a new, fully dynamical, relaxed magnetohydrodynamics (RxMHD), such that all static solutions are Taylor states but also allows state with flow. By postulating that some long-lived macroscopic current sheets can act as barriers to relaxation, separating the plasma into multiple relaxation regions, a further generalization, multi-region relaxed magnetohydrodynamics (MRxMHD) is developed.

  14. Effect of Temper Condition on Stress Relaxation Behavior of an Aluminum Copper Lithium Alloy

    Science.gov (United States)

    Mishra, Sumeet; Beura, Vikrant Kumar; Singh, Amit; Yadava, Manasij; Nayan, Niraj

    2018-04-01

    Deformation behavior of an Al-Cu-Li alloy in different temper conditions (solutionized and T8) is investigated using stress relaxation tests. Fundamental parameters such as the apparent and physical activation volume, strain rate sensitivity, effective stress, and exhaustion rate of mobile dislocation density are determined from single and multiple relaxation tests. It was found that dislocation-dislocation interaction controls the kinetics of plastic deformation in the solutionized sample, whereas dislocation-precipitate interaction is the overriding factor in the presence of T1 precipitates. The apparent activation volume was found to be significantly lower in the presence of T1 precipitates compared with solutionized samples. Strain rate sensitivity and effective stress were found to be higher in the presence of T1 precipitates. In addition, multiple relaxation tests showed that irrespective of microstructural features (solutes, semi-coherent precipitates), the mobile dislocation density reduces during the relaxation period. Further evidence regarding reduction in mobile dislocation density is obtained from uniaxial tensile tests carried out after stress relaxation tests, where both solutionized and T8 samples show an increase in strength. Additional discussion on relaxation strain is included to provide a complete overview regarding the time-dependent deformation behavior of the Al-Cu-Li alloy in different temper conditions.

  15. Plasma position from ring current measurements in Extrap T1

    International Nuclear Information System (INIS)

    Brunsell, P.; Jin Li.

    1989-11-01

    The inductive coupling between the plasma and the four octupole field coils in the Extrap T1 device is utilized as a means of estimating the plasma position. The current in each octupole ring as well as the plasma current is measured by a Rogowski coil and the ring - plasma mutual inductance is then computed assuming axisymmetric plasma displacements. The obtained position is in agreement with internal magnetic probe measurements. The time - evolution of the plasma position for different external vertical and toroidal field strengths is studied. For the present discharge parameter a vertical field of about .008 T is found to give an almost radially stationary plasma. The results are compared with a simple equilibrium model

  16. Visible spectroscopy at the Extrap-T1 pinch experiment

    International Nuclear Information System (INIS)

    Bengtsson, P.; Brzozowski, J.H.; Kaellne, E.; Zaztrow, K.D.

    1991-06-01

    A wide range UV to visible spectrum from 2450 to 8050 Angstrom has been acquired and analysed for the EXTRAP-T1 plasma. The impurity lines in the spectrum are mainly from carbon and oxygen species up to four times ionized, but also nitrogen lines are present. No traces of metal impurity are observed. We have identified most of the spectral lines and compare intensities from several multiplets with predicted values. A spectral range free from line emission is found which is suitable for continuum measurements. Furthermore, line strictures are identified as originating from the CH molecule and are observed both using a center chord line of sight and an edge chord line-of-sight through the plasma. (au)

  17. Determination of the magnetic impurities contribution to the nuclear relaxation in metals

    International Nuclear Information System (INIS)

    Cohen, A.M.

    1982-01-01

    The renormalization group techniques developed by Wilson for the Kondo problem are applied, for the first time, to the calculation of nuclear spin relaxation rates in dilute magnetic alloys. A procedure that calculates the longitudinal relaxation time T 1 over the entire temperature range 0 B T 1 is derived; for distances R between the impurity and the nucleus large compared to the inverse Fermi momentum H f , the result is identical to Korringa's expression for the nuclear spin relaxation rate in the pure metal. For smaller k F R, T 1 increases and becomes infinite as k F R→0. A numerical approach, capable of calculating T 1 at finite temperatures, is presented and tested by calculating T 1 for T→0; the numerical results are in excellent agreement with the analytical expression discussed above. Only for k F R→ infinity do the results for T 1 at T=0 agree with those found by Roshen and Saam, who recently analysed this problem in the light of Nozieres's Fermi liquid theory. The reasons for the discrepancy for finite k F R are discussed. (author) [pt

  18. Oxygen Mapping within Healthy and Acutely Infarcted Brain Tissue in Humans Using the NMR Relaxation of Lipids: A Proof-Of-Concept Translational Study.

    Science.gov (United States)

    Colliez, Florence; Safronova, Marta M; Magat, Julie; Joudiou, Nicolas; Peeters, André P; Jordan, Bénédicte F; Gallez, Bernard; Duprez, Thierry

    2015-01-01

    The clinical applicability of brain oxygenation mapping using the MOBILE (Mapping of Oxygen By Imaging Lipids relaxation Enhancement) magnetic resonance (MR) technique was assessed in the clinical setting of normal brain and of acute cerebral ischemia as a founding proof-of-concept translational study. Changes in the oxygenation level within healthy brain tissue can be detected by analyzing the spin-lattice proton relaxation ('Global T1' combining water and lipid protons) because of the paramagnetic properties of molecular oxygen. It was hypothesized that selective measurement of the relaxation of the lipid protons ('Lipids T1') would result in enhanced sensitivity of pO2 mapping because of higher solubility of oxygen in lipids than in water, and this was demonstrated in pre-clinical models using the MOBILE technique. In the present study, 12 healthy volunteers and eight patients with acute (48-72 hours) brain infarction were examined with the same clinical 3T MR system. Both Lipids R1 (R1 = 1/T1) and Global R1 were significantly different in the infarcted area and the contralateral unaffected brain tissue, with a higher statistical significance for Lipids R1 (median difference: 0.408 s-1; pbrain tissue of stroke patients were not significantly different from the R1 values calculated in the brain tissue of healthy volunteers. The main limitations of the present prototypic version of the MOBILE sequence are the long acquisition time (4 min), hampering robustness of data in uncooperative patients, and a 2 mm slice thickness precluding accurate measurements in small infarcts because of partial volume averaging effects.

  19. Dynamics of relaxed inflation

    Science.gov (United States)

    Tangarife, Walter; Tobioka, Kohsaku; Ubaldi, Lorenzo; Volansky, Tomer

    2018-02-01

    The cosmological relaxation of the electroweak scale has been proposed as a mechanism to address the hierarchy problem of the Standard Model. A field, the relaxion, rolls down its potential and, in doing so, scans the squared mass parameter of the Higgs, relaxing it to a parametrically small value. In this work, we promote the relaxion to an inflaton. We couple it to Abelian gauge bosons, thereby introducing the necessary dissipation mechanism which slows down the field in the last stages. We describe a novel reheating mechanism, which relies on the gauge-boson production leading to strong electro-magnetic fields, and proceeds via the vacuum production of electron-positron pairs through the Schwinger effect. We refer to this mechanism as Schwinger reheating. We discuss the cosmological dynamics of the model and the phenomenological constraints from CMB and other experiments. We find that a cutoff close to the Planck scale may be achieved. In its minimal form, the model does not generate sufficient curvature perturbations and additional ingredients, such as a curvaton field, are needed.

  20. Impurity deposition on surface probes during different operation modes at EXTRAP T1

    International Nuclear Information System (INIS)

    Gudowska, I.; Bergsaker, H.; Hellblom, G.

    1991-01-01

    Surface probes were used in the impurity control program during initial operation of the EXTRAP T1 device. The EXTRAP concept, design and operation characteristics are given elsewhere. The dimensions of the device are R/a=0.5m/0.06m. Four different modes of operation were studied: pure EXTRAP, mixed EXTRAP, RFP and ULQ. Briefly, all four are toroidal plasma discharges, with poloidal magnetic field due to the toroidal plasma current. In the ULQ case, a relatively strong external toroidal magnetic field is applied. In the RFP, and in the mixed mode, an external toroidal field is applied early in the discharge, and the plasma subsequently relaxes into a state with self-generated toroidal field. In the EXTRAP and mixed EXTRAP modes, an additional strong external octupole field is applied, breaking the poloidal symmetry. Throughout the initial period of operation of the device, the plasma performance was largely dominated by impurities, in particular fluorine, which was present due to an accidental contamination of the vessel. Probes have been exposed in wall/liner position, and the objective has been to measure erosion and deposition and try to identify which mechanisms are mainly responsible for impurity production. (author) 5 refs., 2 figs., 1 tab

  1. Spin transport and relaxation in graphene

    International Nuclear Information System (INIS)

    Han Wei; McCreary, K.M.; Pi, K.; Wang, W.H.; Li Yan; Wen, H.; Chen, J.R.; Kawakami, R.K.

    2012-01-01

    We review our recent work on spin injection, transport and relaxation in graphene. The spin injection and transport in single layer graphene (SLG) were investigated using nonlocal magnetoresistance (MR) measurements. Spin injection was performed using either transparent contacts (Co/SLG) or tunneling contacts (Co/MgO/SLG). With tunneling contacts, the nonlocal MR was increased by a factor of ∼1000 and the spin injection/detection efficiency was greatly enhanced from ∼1% (transparent contacts) to ∼30%. Spin relaxation was investigated on graphene spin valves using nonlocal Hanle measurements. For transparent contacts, the spin lifetime was in the range of 50-100 ps. The effects of surface chemical doping showed that for spin lifetimes in the order of 100 ps, charged impurity scattering (Au) was not the dominant mechanism for spin relaxation. While using tunneling contacts to suppress the contact-induced spin relaxation, we observed the spin lifetimes as long as 771 ps at room temperature, 1.2 ns at 4 K in SLG, and 6.2 ns at 20 K in bilayer graphene (BLG). Furthermore, contrasting spin relaxation behaviors were observed in SLG and BLG. We found that Elliot-Yafet spin relaxation dominated in SLG at low temperatures whereas Dyakonov-Perel spin relaxation dominated in BLG at low temperatures. Gate tunable spin transport was studied using the SLG property of gate tunable conductivity and incorporating different types of contacts (transparent and tunneling contacts). Consistent with theoretical predictions, the nonlocal MR was proportional to the SLG conductivity for transparent contacts and varied inversely with the SLG conductivity for tunneling contacts. Finally, bipolar spin transport in SLG was studied and an electron-hole asymmetry was observed for SLG spin valves with transparent contacts, in which nonlocal MR was roughly independent of DC bias current for electrons, but varied significantly with DC bias current for holes. These results are very important for

  2. Preoperative differentiation between T1a and ≥T1b gallbladder cancer: combined interpretation of high-resolution ultrasound and multidetector-row computed tomography

    International Nuclear Information System (INIS)

    Joo, Ijin; Baek, Jee Hyun; Kim, Jung Hoon; Han, Joon Koo; Choi, Byung Ihn; Lee, Jae Young; Park, Hee Sun

    2014-01-01

    To determine the diagnostic value of combined interpretation of high-resolution ultrasound (HRUS) and multidetector-row computed tomography (MDCT) for preoperative differentiation between T1a and ≥T1b gallbladder (GB) cancer. Eighty-seven patients with pathologically confirmed GB cancers (T1a, n = 15; ≥T1b, n = 72), who preoperatively underwent both HRUS and MDCT, were included in this retrospective study. Two reviewers independently determined the T-stages of the GB cancers on HRUS and MDCT using a five-point confidence scale (5, definitely T1a; 1, definitely ≥T1b). For individual modality interpretation, the lesions with scores ≥4 were classified as T1a, and, for combined modality interpretation, the lesions with all scores ≥4 in both modalities were classified as T1a. The McNemar test was used to compare diagnostic performance. The diagnostic accuracy of differentiation between T1a and ≥T1b GB cancer was higher using combined interpretation (90.8 % and 88.5 % for reviewers 1 and 2, respectively) than individual interpretation of HRUS (82.8 % and 83.9 %) or MDCT (74.7 % and 82.8 %) (P < 0.05, reviewer 1). Combined interpretations demonstrated 100 % specificity for both reviewers, which was significantly higher than individual interpretations (P < 0.05, both reviewers). Combined HRUS and MDCT interpretation may improve the diagnostic accuracy and specificity for differentiating between T1a and ≥T1b GB cancers. circle Differentiating between T1a and ≥T1b gallbladder cancer can help surgical planning. (orig.)

  3. Under which conditions does T1 difficulty affect T2 performance in the attentional blink?

    DEFF Research Database (Denmark)

    Nielsen, Simon; Petersen, Anders; Andersen, Tobias Søren

    2009-01-01

    When two visual targets (T1 & T2) are presented in rapid succession, performance of T2 suffers up to 900 ms. One theory of this attentional blink (Raymond, Shapiro, & Arnell, 1992) propose that T1 and T2 compete for limited processing resources (Chun & Potter, 1995), and predict that prolonging...... processing time for T1 by increasing its perceptual difficulty will induce a larger blink. Several studies have tested this prediction without reaching a consistent answer. McLaughlin, Shore, & Klein (2001) found no effect of the exposure duration of T1 on the attentional blink. Christmann & Leuthold (2004...... duration. In the hard condition, T1 exposure duration was 10 ms while T1 contrast was adjusted individually to reach 50% correct T1 identification. In the long duration condition, T1 exposure duration was increased to reach approximately 90% correct T1 identification. In the high contrast condition, T1...

  4. Communication: Relaxation-limited electronic currents in extended reservoir simulations

    Science.gov (United States)

    Gruss, Daniel; Smolyanitsky, Alex; Zwolak, Michael

    2017-10-01

    Open-system approaches are gaining traction in the simulation of charge transport in nanoscale and molecular electronic devices. In particular, "extended reservoir" simulations, where explicit reservoir degrees of freedom are present, allow for the computation of both real-time and steady-state properties but require relaxation of the extended reservoirs. The strength of this relaxation, γ, influences the conductance, giving rise to a "turnover" behavior analogous to Kramers turnover in chemical reaction rates. We derive explicit, general expressions for the weak and strong relaxation limits. For weak relaxation, the conductance increases linearly with γ and every electronic state of the total explicit system contributes to the electronic current according to its "reduced" weight in the two extended reservoir regions. Essentially, this represents two conductors in series—one at each interface with the implicit reservoirs that provide the relaxation. For strong relaxation, a "dual" expression-one with the same functional form-results, except now proportional to 1/γ and dependent on the system of interest's electronic states, reflecting that the strong relaxation is localizing electrons in the extended reservoirs. Higher order behavior (e.g., γ2 or 1/γ2) can occur when there is a gap in the frequency spectrum. Moreover, inhomogeneity in the frequency spacing can give rise to a pseudo-plateau regime. These findings yield a physically motivated approach to diagnosing numerical simulations and understanding the influence of relaxation, and we examine their occurrence in both simple models and a realistic, fluctuating graphene nanoribbon.

  5. Irradiation creep, stress relaxation and a mechanical equation of state

    International Nuclear Information System (INIS)

    Foster, J.P.

    1976-01-01

    Irradiation creep and stress relaxation data are available from the United Kingdom for 20 percent CW M316, 20 percent CW FV 548 and FHT PE16 using pure torsion in the absence of swelling at 300 0 C. Irradiation creep models were used to calculate the relaxation and permanent deflection of the stress relaxation tests. Two relationships between irradiation creep and stress relaxation were assessed by comparing the measured and calculated stress relaxation and permanent deflection. The results show that for M316 and FV548, the stress relaxation and deflection may be calculated using irradiation creep models when the stress rate term arising from the irradiation creep model is set equal to zero. In the case of PE16, the inability to calculate the stress relaxation and permanent deflection from the irradiation creep data was attributed to differences in creep behavior arising from lot-to-lot variations in alloying elements and impurity content. A modification of the FV548 and PE16 irradiation creep coefficients was necessary in order to calculate the stress relaxation and deflection. The modifications in FV548 and PE16 irradiation creep properties reduces the large variation in the transient or incubation parameter predicted by irradiation creep tests for M316, FV548 and PE16

  6. Evaluation of clinical state of patients with acute leukemia, multiple myeloma and malignant lymphoma by means of in vitro T1 and T2 measurements in serum

    International Nuclear Information System (INIS)

    Kuliszkiewicz-Janus, M.; Urbaniak-Kujda, D.; Burczak, K.

    1995-01-01

    A dynamic relaxation times T1 and T2 in vitro study has been performed in the human sera of patients with haematological malignant diseases to monitor their clinical state. Two hundred studies were performed in 20 healthy volunteers and in 180 patients with different malignancies, mostly: acute leukemia, Hodgkin's disease, non-Hodgkin's lymphomas, multiple myeloma. Determinations were performed in active phase of disease and in remission. Measurements were carried out on spectrometer Minispect PC 20B (Bruker; 20 MHz) in 27 C. Additionally, serum proteins of all patients were examined, including total protein content, serum electrophoresis and measurement of Ig classes. Remarkable increase of T1 values in active phase of the disease was found (compared to healthy volunteers) in all malignancies, except multiple myeloma. It was associated with the severeness of the illness, not with diagnose. During remission T1 values did not differ significantly from those of healthy persons. All sera of patients with multiple myeloma in active phase of the disease showed strongly reduced values of T1, associated with the high level of pathological proteins. In 45 patients the measurements were repeated up to 4 times before and during chemotherapy. During treatment resulting in remission, mean T1 values progressively decreased (from 1560 ms to 1394 ms) except of those patients with multiple myeloma. In persons non-responding to therapy these mean values were prolonged (from 1474 ms to 1620 ms) during therapy. In patients with multiple myeloma we noted the reverse changes of mean T1 values in comparison with other malignancies: those responding to the treatment revealed prolonged T1 (from 1165 to 1303 ms) while in those non-responding were decreased (from 1184 ms to 1158 ms). Statistically significant negative correlation was observed between the T1 and total protein content, percentage of gamma-globulin, especially of IgG class. Moreover, a remarkable positive correlation of T1

  7. T1 Colorectal Cancer with Synchronous Liver Metastasis

    Directory of Open Access Journals (Sweden)

    Kiichi Sugimoto

    2013-06-01

    Full Text Available The patient was a 68-year-old man who was admitted to our hospital with a liver tumor. Abdominal ultrasonography and computed tomography revealed a liver tumor 30 mm in diameter. On colonoscopy, a pedunculated tumor with a central depression (20 mm in diameter was observed in the ascending colon, and this tumor was considered to be invading deeply into the submucosal layer. Right hemicolectomy with D3 lymphadenectomy and partial hepatectomy were performed simultaneously. On histopathological examination of the resected specimen, the tumor was a well-differentiated tubular adenocarcinoma with 3,000 μm invasion of the submucosal layer. The liver tumor showed histological findings similar to those of the primary colorectal carcinoma. The pathological stage according to the 7th edition of the TNM classification was stage IV (T1N0M1. Nine months after the operation, computed tomography revealed hepatic hilar lymph node metastases and a great deal of ascites. The patient ultimately died 14 months after the operation.

  8. Relaxed Bell inequalities and Kochen-Specker theorems

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Michael J. W. [Theoretical Physics, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

    2011-08-15

    The combination of various physically plausible properties, such as no signaling, determinism, and experimental free will, is known to be incompatible with quantum correlations. Hence, these properties must be individually or jointly relaxed in any model of such correlations. The necessary degrees of relaxation are quantified here via natural distance and information-theoretic measures. This allows quantitative comparisons between different models in terms of the resources, such as the number of bits of randomness, communication, and/or correlation, that they require. For example, measurement dependence is a relatively strong resource for modeling singlet-state correlations, with only 1/15 of one bit of correlation required between measurement settings and the underlying variable. It is shown how various ''relaxed'' Bell inequalities may be obtained, which precisely specify the complementary degrees of relaxation required to model any given violation of a standard Bell inequality. The robustness of a class of Kochen-Specker theorems, to relaxation of measurement independence, is also investigated. It is shown that a theorem of Mermin remains valid unless measurement independence is relaxed by 1/3. The Conway-Kochen ''free will'' theorem and a result of Hardy are less robust, failing if measurement independence is relaxed by only 6.5% and 4.5%, respectively. An appendix shows that existence of an outcome-independent model is equivalent to existence of a deterministic model.

  9. Comparison of T1-weighted fast spin-echo and T1-weighted fluid-attenuated inversion recovery images of the lumbar spine at 3.0 Tesla

    International Nuclear Information System (INIS)

    Lavdas, Eleftherios; Vlychou, Marianna; Arikidis, Nikos; Kapsalaki, Eftychia; Roka, Violetta; Fezoulidis, Ioannis V.

    2010-01-01

    Background: T1-weighted fluid-attenuated inversion recovery (FLAIR) sequence has been reported to provide improved contrast between lesions and normal anatomical structures compared to T1-weighted fast spin-echo (FSE) imaging at 1.5T regarding imaging of the lumbar spine. Purpose: To compare T1-weighted FSE and fast T1-weighted FLAIR imaging in normal anatomic structures and degenerative and metastatic lesions of the lumbar spine at 3.0T. Material and Methods: Thirty-two consecutive patients (19 females, 13 males; mean age 44 years, range 30-67 years) with lesions of the lumbar spine were prospectively evaluated. Sagittal images of the lumbar spine were obtained using T1-weighted FSE and fast T1-weighted FLAIR sequences. Both qualitative and quantitative analyses measuring the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and relative contrast (ReCon) between degenerative and metastatic lesions and normal anatomic structures were conducted, comparing these sequences. Results: On quantitative evaluation, SNRs of cerebrospinal fluid (CSF), nerve root, and fat around the root of fast T1-weighted FLAIR imaging were significantly lower than those of T1-weighted FSE images (P<0.001). CNRs of normal spinal cord/CSF and disc herniation/ CSF for fast T1-weighted FLAIR images were significantly higher than those for T1-weighted FSE images (P<0.001). ReCon of normal spinal cord/CSF, disc herniation/CSF, and vertebral lesions/CSF for fast T1-weighted FLAIR images were significantly higher than those for T1-weighted FSE images (P<0.001). On qualitative evaluation, it was found that CSF nulling and contrast at the spinal cord (cauda equina)/CSF interface for T1-weighted FLAIR images were significantly superior compared to those for T1-weighted FSE images (P<0.001), and the disc/spinal cord (cauda equina) interface was better for T1-weighted FLAIR images (P<0.05). Conclusion: The T1-weighted FLAIR sequence may be considered as the preferred lumbar spine imaging

  10. Disruptive chemical doping in a ferritin-based iron oxide nanoparticle to decrease r2 and enhance detection with T1-weighted MRI.

    Science.gov (United States)

    Clavijo Jordan, M Veronica; Beeman, Scott C; Baldelomar, Edwin J; Bennett, Kevin M

    2014-01-01

    Inorganic doping was used to create flexible, paramagnetic nanoparticle contrast agents for in vivo molecular magnetic resonance imaging (MRI) with low transverse relaxivity (r2). Most nanoparticle contrast agents formed from superparamagnetic metal oxides are developed with high r2. While sensitive, they can have limited in vivo detection due to a number of constraints with T2 or T2*-weighted imaging. T1-weighted imaging is often preferred for molecular MRI, but most T1-shortening agents are small chelates with low metal payload or are nanoparticles that also shorten T2 and limit the range of concentrations detectable with T1-weighting. Here we used tungsten and iron deposition to form doped iron oxide crystals inside the apoferritin cavity to form a WFe nanoparticle with a disordered crystal and un-coupled atomic magnetic moments. The atomic magnetic moments were thus localized, resulting in a principally paramagnetic nanoparticle. The WFe nanoparticles had no coercivity or saturation magnetization at 5 K and sweeping up to ± 20,000 Oe, while native ferritin had a coercivity of 3000 Oe and saturation at ± 20,000 Oe. This tungsten-iron crystal paramagnetism resulted in an increased WFe particle longitudinal relaxivity (r1) of 4870 mm(-1) s(-1) and a reduced transverse relaxivity (r2) of 9076 mm(-1) s(-1) compared with native ferritin. The accumulation of the particles was detected with T1-weighted MRI in concentrations from 20 to 400 nm in vivo, both injected in the rat brain and targeted to the rat kidney glomerulus. The WFe apoferritin nanoparticles were not cytotoxic up to 700 nm particle concentrations, making them potentially important for targeted molecular MRI. Copyright © 2014 John Wiley & Sons, Ltd.

  11. Musculoskeletal MRI at 3.0 T and 7.0 T: A comparison of relaxation times and image contrast

    International Nuclear Information System (INIS)

    Jordan, Caroline D.; Saranathan, Manojkumar; Bangerter, Neal K.; Hargreaves, Brian A.; Gold, Garry E.

    2013-01-01

    Objective: The purpose of this study was to measure and compare the relaxation times of musculoskeletal tissues at 3.0 T and 7.0 T, and to use these measurements to select appropriate parameters for musculoskeletal protocols at 7.0 T. Materials and methods: We measured the T 1 and T 2 relaxation times of cartilage, muscle, synovial fluid, bone marrow and subcutaneous fat at both 3.0 T and 7.0 T in the knees of five healthy volunteers. The T 1 relaxation times were measured using a spin-echo inversion recovery sequence with six inversion times. The T 2 relaxation times were measured using a spin-echo sequence with seven echo times. The accuracy of both the T 1 and T 2 measurement techniques was verified in phantoms at both magnetic field strengths. We used the measured relaxation times to help design 7.0 T musculoskeletal protocols that preserve the favorable contrast characteristics of our 3.0 T protocols, while achieving significantly higher resolution at higher SNR efficiency. Results: The T 1 relaxation times in all tissues at 7.0 T were consistently higher than those measured at 3.0 T, while the T 2 relaxation times at 7.0 T were consistently lower than those measured at 3.0 T. The measured relaxation times were used to help develop high resolution 7.0 T protocols that had similar fluid-to-cartilage contrast to that of the standard clinical 3.0 T protocols for the following sequences: proton-density-weighted fast spin-echo (FSE), T 2 -weighted FSE, and 3D-FSE-Cube. Conclusion: The T 1 and T 2 changes were within the expected ranges. Parameters for musculoskeletal protocols at 7.0 T can be optimized based on these values, yielding improved resolution in musculoskeletal imaging with similar contrast to that of standard 3.0 T clinical protocols

  12. Spin-Relaxation Anisotropy in a GaAs Quantum Dot

    NARCIS (Netherlands)

    Scarlino, P.; Kawakami, E.; Stano, P.; Shafiei, M.; Reichl, C.; Wegscheider, W.; Vandersypen, L.M.K.

    2014-01-01

    We report that the electron spin-relaxation time T1 in a GaAs quantum dot with a spin-1/2 ground state has a 180° periodicity in the orientation of the in-plane magnetic field. This periodicity has been predicted for circular dots as being due to the interplay of Rashba and Dresselhaus spin orbit

  13. Spin dynamics of the itinerant helimagnet MnSi studied by positive muon spin relaxation

    International Nuclear Information System (INIS)

    Kadono, R.; Matsuzaki, T.; Yamazaki, T.; Kreitzman, S.R.; Brewer, J.H.

    1990-03-01

    The local magnetic fields and spin dynamics of the itinerant helimagnet MnSi(T c ≅ 29.5 K) have been studied experimentally using positive muon spin rotation/relaxation (μ + SR) methods. In the ordered phase (T c ), zero-field μSR was used to measure the hyperfine fields at the muon sites as well as the muon spin-lattice relaxation time T 1 μ . Two magnetically inequivalent interstitial μ + sites were found with hyperfine coupling constants A hf (1) = -3.94 kOe/μ B and A hf (2) = -6.94 kOe/μ B , respectively. In the paramagnetic phase (T > T c ), the muon-nuclear spin double relaxation technique was used to simultaneously but independently determine the spin-lattice relaxation time T 1 Mn of 55 Mn spins and that of positive muons (T 1 μ ) over a wide temperature range (T c 1 Mn and T 1 μ in both phases shows systematic deviations from the predictions of self-consistent renormalization (SCR) theory. (author)

  14. Hydration water dynamics in biopolymers from NMR relaxation in the rotating frame.

    Science.gov (United States)

    Blicharska, Barbara; Peemoeller, Hartwig; Witek, Magdalena

    2010-12-01

    Assuming dipole-dipole interaction as the dominant relaxation mechanism of protons of water molecules adsorbed onto macromolecule (biopolymer) surfaces we have been able to model the dependences of relaxation rates on temperature and frequency. For adsorbed water molecules the correlation times are of the order of 10(-5)s, for which the dispersion region of spin-lattice relaxation rates in the rotating frame R(1)(ρ)=1/T(1)(ρ) appears over a range of easily accessible B(1) values. Measurements of T(1)(ρ) at constant temperature and different B(1) values then give the "dispersion profiles" for biopolymers. Fitting a theoretical relaxation model to these profiles allows for the estimation of correlation times. This way of obtaining the correlation time is easier and faster than approaches involving measurements of the temperature dependence of R(1)=1/T(1). The T(1)(ρ) dispersion approach, as a tool for molecular dynamics study, has been demonstrated for several hydrated biopolymer systems including crystalline cellulose, starch of different origins (potato, corn, oat, wheat), paper (modern, old) and lyophilized proteins (albumin, lysozyme). Copyright © 2010 Elsevier Inc. All rights reserved.

  15. Total water, phosphorus relaxation and inter-atomic organic to inorganic interface are new determinants of trabecular bone integrity.

    Directory of Open Access Journals (Sweden)

    Ratan Kumar Rai

    Full Text Available Bone is the living composite biomaterial having unique structural property. Presently, there is a considerable gap in our understanding of bone structure and composition in the native state, particularly with respect to the trabecular bone, which is metabolically more active than cortical bones, and is readily lost in post-menopausal osteoporosis. We used solid-state nuclear magnetic resonance (NMR to compare trabecular bone structure and composition in the native state between normal, bone loss and bone restoration conditions in rat. Trabecular osteopenia was induced by lactation as well as prolonged estrogen deficiency (bilateral ovariectomy, Ovx. Ovx rats with established osteopenia were administered with PTH (parathyroid hormone, trabecular restoration group, and restoration was allowed to become comparable to sham Ovx (control group using bone mineral density (BMD and µCT determinants. We used a technique combining (1H NMR spectroscopy with (31P and (13C to measure various NMR parameters described below. Our results revealed that trabecular bones had diminished total water content, inorganic phosphorus NMR relaxation time (T1 and space between the collagen and inorganic phosphorus in the osteopenic groups compared to control, and these changes were significantly reversed in the bone restoration group. Remarkably, bound water was decreased in both osteopenic and bone restoration groups compared to control. Total water and T1 correlated strongly with trabecular bone density, volume, thickness, connectivity, spacing and resistance to compression. Bound water did not correlate with any of the microarchitectural and compression parameters. We conclude that total water, T1 and atomic space between the crystal and organic surface are altered in the trabecular bones of osteopenic rats, and PTH reverses these parameters. Furthermore, from these data, it appears that total water and T1 could serve as trabecular surrogates of micro-architecture and

  16. Anomalous NMR Relaxation in Cartilage Matrix Components and Native Cartilage: Fractional-Order Models

    Science.gov (United States)

    Magin, Richard L.; Li, Weiguo; Velasco, M. Pilar; Trujillo, Juan; Reiter, David A.; Morgenstern, Ashley; Spencer, Richard G.

    2011-01-01

    We present a fractional-order extension of the Bloch equations to describe anomalous NMR relaxation phenomena (T1 and T2). The model has solutions in the form of Mittag-Leffler and stretched exponential functions that generalize conventional exponential relaxation. Such functions have been shown by others to be useful for describing dielectric and viscoelastic relaxation in complex, heterogeneous materials. Here, we apply these fractional-order T1 and T2 relaxation models to experiments performed at 9.4 and 11.7 Tesla on type I collagen gels, chondroitin sulfate mixtures, and to bovine nasal cartilage (BNC), a largely isotropic and homogeneous form of cartilage. The results show that the fractional-order analysis captures important features of NMR relaxation that are typically described by multi-exponential decay models. We find that the T2 relaxation of BNC can be described in a unique way by a single fractional-order parameter (α), in contrast to the lack of uniqueness of multi-exponential fits in the realistic setting of a finite signal-to-noise ratio. No anomalous behavior of T1 was observed in BNC. In the single-component gels, for T2 measurements, increasing the concentration of the largest components of cartilage matrix, collagen and chondroitin sulfate, results in a decrease in α, reflecting a more restricted aqueous environment. The quality of the curve fits obtained using Mittag-Leffler and stretched exponential functions are in some cases superior to those obtained using mono- and bi-exponential models. In both gels and BNC, α appears to account for microstructural complexity in the setting of an altered distribution of relaxation times. This work suggests the utility of fractional-order models to describe T2 NMR relaxation processes in biological tissues. PMID:21498095

  17. Tuning the non-covalent confinement of Gd(III) complexes in silica nanoparticles for high T1-weighted MR imaging capability.

    Science.gov (United States)

    Fedorenko, Svetlana V; Grechkina, Svetlana L; Mustafina, Asiya R; Kholin, Kirill V; Stepanov, Alexey S; Nizameev, Irek R; Ismaev, Ildus E; Kadirov, Marsil K; Zairov, Rustem R; Fattakhova, Alfia N; Amirov, Rustem R; Soloveva, Svetlana E

    2017-01-01

    The present work introduces deliberate synthesis of Gd(III)-doped silica nanoparticles with high relaxivity at magnetic field strengths below 1.5T. Modified microemulsion water-in-oil procedure was used in order to achieve superficial localization of Gd(III) complexes within 40-55nm sized silica spheres. The relaxivities of the prepared nanoparticles were measured at 0.47, 1.41 and 1.5T with the use of both NMR analyzer and whole body NMR scanner. Longitudinal relaxivities of the obtained silica nanoparticles reveal significant dependence on the confinement mode, changing from 4.1 to 49.6mM -1 s -1 at 0.47T when the localization of Gd(III) complexes changes from core to superficial zones of the silica spheres. The results highlight predominant contribution of the complexes located close to silica/water interface to the relaxivity of the nanoparticles. Low effect of blood proteins on the relaxivity in the aqueous colloids of the nanoparticles was exemplified by serum bovine albumin. T 1 - weighted MRI data indicate that the nanoparticles provide strong positive contrast at 1.5T, which along with low cytotoxicity effect make a good basis for their application as contrast agents. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Comparison of Trifecta and Pentafecta Outcomes between T1a and T1b Renal Masses following Robot-Assisted Partial Nephrectomy (RAPN with Minimum One Year Follow Up: Can RAPN for T1b Renal Masses Be Feasible?

    Directory of Open Access Journals (Sweden)

    Dae Keun Kim

    Full Text Available To investigate the feasibility of RAPN on T1b renal mass by assessment of Trifecta and Pentafecta rate between T1a and T1b renal mass.We retrospectively reviewed the medical records of 277 cases of RPN performed from 2006 to 2015. Sixty patients with clinically T1b renal masses (> 4 cm and ≤ 7 cm were identified, and from 180 patients with clinically T1a renal mass, 60 patients were matched with T1b renal mass by propensity score. Tumor complexity was investigated according to R.E.N.A.L nephrometry score. "Pentafecta" was defined as achievement of Trifecta (negative surgical margin, no postoperative complications and warm ischemia time of ≤ 25 minutes with addition of over 90% estimated GFR preservation and no chronic kidney disease stage upgrading at 1 year postoperative period. Propensity score matching was performed by OneToManyMTCH. Logistic regression models were used to identify the variables which predict the Trifecta, and Pentafecta ac.Preoperative variables (age, sex, body mass index, ASA score were similar between T1a and T1b after propensity score matching. The median R.E.N.A.L. nephrometry score was 8 vs 9 for T1a and T1b respectively (p<0.001. The median warm ischemia time was 20.1 min vs 26.2 min (p<0.001. Positive surgical margin rate was 5% vs 6.6% (p = 0.729 and overall complication rate of 13.3%. vs 15% (p = 0.793. The rate of achievement of Trifecta rate were 65.3% vs 43.3% (p = 0.017 and Pentafecta rate were 38.3% vs 26.7% (p = 0.172. For achievement of Pentafecta, R.E.N.A.L nephrometry score (HR 0.80; 95% CI (0.67-0.97; p = 0.031 was significant predictor of achieving Pentafecta. Subanalyis to assess the component of R.E.N.A.L nephrometry score, L component (location relative to the polar lines, HR 0.63; 95% CI (0.38-1.03; P = 0.064 was relatively important component for Pentafecta achievement.The rate of Pentafecta after RAPN was comparable between T1a and T1b renal masses. RAPN is a feasible modality with excellent

  19. Time course of action and endotracheal intubating conditions of Org 9487, a new short-acting steroidal muscle relaxant; a comparison with succinylcholine

    NARCIS (Netherlands)

    Wierda, JMKH; van den Broek, L; Proost, JH; Verbaan, BW; Hennis, PJ

    In a randomized study, we evaluated lag time (time from the end of injection of muscle relaxant until the first depression of the train-of-four response [TOF]), onset time (time from the end of injection of muscle relaxant until the maximum depression of the first twitch of the TOF [T1]),

  20. Relaxation in the XX quantum chain

    International Nuclear Information System (INIS)

    Platini, Thierry; Karevski, Dragi

    2007-01-01

    We present the results obtained on the magnetization relaxation properties of an XX quantum chain in a transverse magnetic field. We first consider an initial thermal kink-like state where half of the chain is initially thermalized at a very high temperature T b while the remaining half, called the system, is put at a lower temperature T s . From this initial state, we derive analytically the Green function associated with the dynamical behaviour of the transverse magnetization. Depending on the strength of the magnetic field and on the temperature of the system, different regimes are obtained for the magnetic relaxation. In particular, with an initial droplet-like state, that is a cold subsystem of the finite size in contact at both ends with an infinite temperature environment, we derive analytically the behaviour of the time-dependent system magnetization

  1. Milrinone relaxes pulmonary veins in guinea pigs and humans.

    Directory of Open Access Journals (Sweden)

    Annette D Rieg

    Full Text Available INTRODUCTION: The phosphodiesterase-III inhibitor milrinone improves ventricular contractility, relaxes pulmonary arteries and reduces right ventricular afterload. Thus, it is used to treat heart failure and pulmonary hypertension (PH. However, its action on pulmonary veins (PVs is not defined, although particularly PH due to left heart disease primarily affects the pulmonary venous bed. We examined milrinone-induced relaxation in PVs from guinea pigs (GPs and humans. MATERIAL AND METHODS: Precision-cut lung slices (PCLS were prepared from GPs or from patients undergoing lobectomy. Milrinone-induced relaxation was studied by videomicroscopy in naïve PVs and in PVs pre-constricted with the ETA-receptor agonist BP0104. Baseline luminal area was defined as 100%. Intracellular cAMP was measured by ELISA and milrinone-induced changes of segmental vascular resistances were studied in the GP isolated perfused lung (IPL. RESULTS: In the IPL (GP, milrinone (10 µM lowered the postcapillary resistance of pre-constricted vessels. In PCLS (GP, milrinone relaxed naïve and pre-constricted PVs (120% and this relaxation was attenuated by inhibition of protein kinase G (KT 5823, adenyl cyclase (SQ 22536 and protein kinase A (KT 5720, but not by inhibition of NO-synthesis (L-NAME. In addition, milrinone-induced relaxation was dependent on the activation of K ATP-, BK Ca (2+- and Kv-channels. Human PVs also relaxed to milrinone (121%, however only if pre-constricted. DISCUSSION: Milrinone relaxes PVs from GPs and humans. In GPs, milrinone-induced relaxation is based on K ATP-, BK Ca (2+- and Kv-channel-activation and on cAMP/PKA/PKG. The relaxant properties of milrinone on PVs lead to reduced postcapillary resistance and hydrostatic pressures. Hence they alleviate pulmonary edema and suggest beneficial effects of milrinone in PH due to left heart disease.

  2. Milrinone relaxes pulmonary veins in guinea pigs and humans.

    Science.gov (United States)

    Rieg, Annette D; Suleiman, Said; Perez-Bouza, Alberto; Braunschweig, Till; Spillner, Jan W; Schröder, Thomas; Verjans, Eva; Schälte, Gereon; Rossaint, Rolf; Uhlig, Stefan; Martin, Christian

    2014-01-01

    The phosphodiesterase-III inhibitor milrinone improves ventricular contractility, relaxes pulmonary arteries and reduces right ventricular afterload. Thus, it is used to treat heart failure and pulmonary hypertension (PH). However, its action on pulmonary veins (PVs) is not defined, although particularly PH due to left heart disease primarily affects the pulmonary venous bed. We examined milrinone-induced relaxation in PVs from guinea pigs (GPs) and humans. Precision-cut lung slices (PCLS) were prepared from GPs or from patients undergoing lobectomy. Milrinone-induced relaxation was studied by videomicroscopy in naïve PVs and in PVs pre-constricted with the ETA-receptor agonist BP0104. Baseline luminal area was defined as 100%. Intracellular cAMP was measured by ELISA and milrinone-induced changes of segmental vascular resistances were studied in the GP isolated perfused lung (IPL). In the IPL (GP), milrinone (10 µM) lowered the postcapillary resistance of pre-constricted vessels. In PCLS (GP), milrinone relaxed naïve and pre-constricted PVs (120%) and this relaxation was attenuated by inhibition of protein kinase G (KT 5823), adenyl cyclase (SQ 22536) and protein kinase A (KT 5720), but not by inhibition of NO-synthesis (L-NAME). In addition, milrinone-induced relaxation was dependent on the activation of K ATP-, BK Ca (2+)- and Kv-channels. Human PVs also relaxed to milrinone (121%), however only if pre-constricted. Milrinone relaxes PVs from GPs and humans. In GPs, milrinone-induced relaxation is based on K ATP-, BK Ca (2+)- and Kv-channel-activation and on cAMP/PKA/PKG. The relaxant properties of milrinone on PVs lead to reduced postcapillary resistance and hydrostatic pressures. Hence they alleviate pulmonary edema and suggest beneficial effects of milrinone in PH due to left heart disease.

  3. Evaluation of bone marrow by opposed phase T1-weighted images and enhanced MR imaging

    International Nuclear Information System (INIS)

    Amano, Yasuo; Tanabe, Yoshihiro; Miyashita, Tsuguhiro; Hayashi, Hiromitsu; Horiuchi, Junichi; Nomura, Takeo; Kumazaki, Tatsuo

    1994-01-01

    We investigated bone marrow in a control group, cases of aplastic anemia and post-irradiation patients by examining T1-weighted (T1W1), short T1 inversion recovery (STIR), opposed phase T1W1 (op-T1W1) and Gd-DTPA enhanced op-T1W1 images obtained by 0.5 T MRI. Bone marrow was classified into four types based on MR findings. Normal marrow showed low intensity on op-T1W1 and STIR images without enhancement (I). Fatty marrow, which showed high intensity on T1W1 and op-T1W1 images was observed in aplastic anemia and post-irradiation patients (II). Hematopoietic marrow (III) showed low intensity on op-T1W1 and enhanced, while active hematopoietic marrow (IV) revealed high intensity on both STIR and op-T1W1 images and was enhanced following Gd-DTPA infusion. Aplastic anemia of moderate grade included types II, III and IV. Enhanced MR was needed to differentiate between types I and III since both types showed low intensity on op-T1W1 images. Furthermore, type IV was considered as hyperplastic compared with type III. Enhanced MR and op-T1W1 images were useful in evaluating hematopoiesis of bone marrow. (author)

  4. Evaluation of bone marrow by opposed phase T1-weighted images and enhanced MR imaging

    Energy Technology Data Exchange (ETDEWEB)

    Amano, Yasuo; Tanabe, Yoshihiro; Miyashita, Tsuguhiro; Hayashi, Hiromitsu; Horiuchi, Junichi; Nomura, Takeo; Kumazaki, Tatsuo (Nippon Medical School, Tokyo (Japan))

    1994-09-01

    We investigated bone marrow in a control group, cases of aplastic anemia and post-irradiation patients by examining T1-weighted (T1W1), short T1 inversion recovery (STIR), opposed phase T1W1 (op-T1W1) and Gd-DTPA enhanced op-T1W1 images obtained by 0.5 T MRI. Bone marrow was classified into four types based on MR findings. Normal marrow showed low intensity on op-T1W1 and STIR images without enhancement (I). Fatty marrow, which showed high intensity on T1W1 and op-T1W1 images was observed in aplastic anemia and post-irradiation patients (II). Hematopoietic marrow (III) showed low intensity on op-T1W1 and enhanced, while active hematopoietic marrow (IV) revealed high intensity on both STIR and op-T1W1 images and was enhanced following Gd-DTPA infusion. Aplastic anemia of moderate grade included types II, III and IV. Enhanced MR was needed to differentiate between types I and III since both types showed low intensity on op-T1W1 images. Furthermore, type IV was considered as hyperplastic compared with type III. Enhanced MR and op-T1W1 images were useful in evaluating hematopoiesis of bone marrow. (author).

  5. The impact of reliable prebolus T 1 measurements or a fixed T 1 value in the assessment of glioma patients with dynamic contrast enhancing MRI.

    Science.gov (United States)

    Tietze, Anna; Mouridsen, Kim; Mikkelsen, Irene Klærke

    2015-06-01

    Accurate quantification of hemodynamic parameters using dynamic contrast enhanced (DCE) MRI requires a measurement of tissue T 1 prior to contrast injection (T 1). We evaluate (i) T 1 estimation using the variable flip angle (VFA) and the saturation recovery (SR) techniques and (ii) investigate if accurate estimation of DCE parameters outperform a time-saving approach with a predefined T 1 value when differentiating high- from low-grade gliomas. The accuracy and precision of T 1 measurements, acquired by VFA and SR, were investigated by computer simulations and in glioma patients using an equivalence test (p > 0.05 showing significant difference). The permeability measure, K trans, cerebral blood flow (CBF), and - volume, V p, were calculated in 42 glioma patients, using fixed T 1 of 1500 ms or an individual T 1 measurement, using SR. The areas under the receiver operating characteristic curves (AUCs) were used as measures for accuracy to differentiate tumor grade. The T 1 values obtained by VFA showed larger variation compared to those obtained using SR both in the digital phantom and the human data (p > 0.05). Although a fixed T 1 introduced a bias into the DCE calculation, this had only minor impact on the accuracy differentiating high-grade from low-grade gliomas, (AUCfix = 0.906 and AUCind = 0.884 for K trans; AUCfix = 0.863 and AUCind = 0.856 for V p; p for AUC comparison > 0.05). T 1 measurements by VFA were less precise, and the SR method is preferable, when accurate parameter estimation is required. Semiquantitative DCE values, based on predefined T 1 values, were sufficient to perform tumor grading in our study.

  6. Cartilage quality in rheumatoid arthritis: comparison of T2* mapping, native T1 mapping, dGEMRIC, ΔR1 and value of pre-contrast imaging

    International Nuclear Information System (INIS)

    Buchbender, Christian; Scherer, Axel; Kroepil, Patric; Quentin, Michael; Reichelt, Dorothea C.; Lanzman, Rotem S.; Mathys, Christian; Blondin, Dirk; Wittsack, Hans-Joerg; Antoch, Gerald; Miese, Falk; Koerbl, Birthe; Bittersohl, Bernd; Zilkens, Christoph; Hofer, Matthias; Schneider, Matthias; Ostendorf, Benedikt

    2012-01-01

    To prospectively evaluate four non-invasive markers of cartilage quality - T2* mapping, native T1 mapping, dGEMRIC and ΔR1 - in healthy volunteers and rheumatoid arthritis (RA) patients. Cartilage of metacarpophalangeal (MCP) joints II were imaged in 28 consecutive subjects: 12 healthy volunteers [9 women, mean (SD) age 52.67 (9.75) years, range 30-66] and 16 RA patients with MCP II involvement [12 women, mean (SD) age 58.06 (12.88) years, range 35-76]. Sagittal T2* mapping was performed with a multi-echo gradient-echo on a 3 T MRI scanner. For T1 mapping the dual flip angle method was applied prior to native T1 mapping and 40 min after gadolinium application (delayed gadolinium-enhanced MRI of cartilage, dGEMRIC, T1 Gd ). The difference in the longitudinal relaxation rate induced by gadolinium (ΔR1) was calculated. The area under the receiver operating characteristic curve (AROC) was used to test for differentiation of RA patients from healthy volunteers. dGEMRIC (AUC 0.81) and ΔR1 (AUC 0.75) significantly differentiated RA patients from controls. T2* mapping (AUC 0.66) and native T1 mapping (AUC 0.66) were not significantly different in RA patients compared to controls. The data support the use of dGEMRIC for the assessment of MCP joint cartilage quality in RA. T2* and native T1 mapping are of low diagnostic value. Pre-contrast T1 mapping for the calculation of ΔR1 does not increase the diagnostic value of dGEMRIC. (orig.)

  7. In-vivo Intervertebral Disc Characterization using Magnetic Resonance Spectroscopy and T1ρ Imaging: Association with Discography and Oswestry Disability Index and SF-36

    Science.gov (United States)

    Zuo, Jin; Joseph, Gabby B.; Li, Xiaojuan; Link, Thomas M.; Hu, Serena S.; Berven, Sigurd H.; Kurhanewitz, John; Majumdar, Sharmila

    2011-01-01

    Study Design An in vivo study of intervertebral disc degeneration using quantitative MRI and MRS. Objective To quantify water and proteoglycan (PG) content in the intervertebral disc using in vivo magnetic resonance spectroscopy (MRS), and to evaluate the relationship between MRS- quantified water/PG content, T1ρ, Pfirrmann score, clinical self-assessment, and discography. Summary of Background Data Previous in vitro studies have investigated the relationship between MRS-quantified water/PG content, and degenerative grade using cadaveric intervertebral discs. T1ρ has been shown to relate to Pfirmann grade and clinical self-assessment. However, the associations between MRS-quantified water/PG content, MR imaging-based T1ρ, self-assessment of health status and clinical response to discography have not been studied in vivo. Methods MRS and MR imaging were performed in 26 patients (70 discs) with symptomatic intervertebral degenerative disc (IVDD) and 23 controls (41 discs). Patients underwent evaluation of intervertebral discs with provocative discography. All subjects completed the SF-36 Health Survey and Oswestry Disability Index questionnaires. Results The water/PG peak area ratio was significantly elevated in a) patients (compared to controls) and in b) discs with positive discography (compared to negative discography). MR T1ρ exhibited similar trends. A significant association was found between T1ρ and normalized PG content (R2 = 0.61, p 0.05). The water/PG peak area ratio, normalized water, normalized PG, and Pfirrmann grade were significantly associated with patient self-assessment of disability and physical composite score, while disc height was not. Conclusion This study demonstrated a relationship between in vivo MRS spectroscopy (water content, PG content), imaging parameters (T1ρ, Pfirrmann Grade), discography results, and clinical self-assessment, suggesting that MRS-quantified water, PG and MR T1ρ relaxation time may potentially serve as

  8. In vivo intervertebral disc characterization using magnetic resonance spectroscopy and T1ρ imaging: association with discography and Oswestry Disability Index and Short Form-36 Health Survey.

    Science.gov (United States)

    Zuo, Jin; Joseph, Gabby B; Li, Xiaojuan; Link, Thomas M; Hu, Serena S; Berven, Sigurd H; Kurhanewitz, John; Majumdar, Sharmila

    2012-02-01

    An in vivo study of intervertebral disc degeneration by using quantitative magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). To quantify water and proteoglycan (PG) content in the intervertebral disc by using in vivo MRS and to evaluate the relationship between MRS-quantified water/PG content, T1ρ, Pfirrmann score, clinical self-assessment, and discography. Previous in vitro studies have investigated the relationship between MRS-quantified water/PG content and degenerative grade by using cadaveric intervertebral discs. T1ρ has been shown to relate to Pfirrmann grade and clinical self-assessment. However, the associations between MRS-quantified water/PG content, MRI-based T1ρ, self-assessment of health status, and clinical response to discography have not been studied in vivo. MRS and MRI were performed in 26 patients (70 discs) with symptomatic intervertebral degenerative disc (IVDD) and 23 controls (41 discs). Patients underwent evaluation of intervertebral discs with provocative discography. All subjects completed the Short Form-36 Health Survey and Oswestry Disability Index questionnaires. The water/PG peak area ratio was significantly elevated in (a) patients (compared with controls) and in (b) discs with positive discography (compared with negative discography). Magnetic resonance (MR) T1ρ exhibited similar trends. A significant association was found between T1ρ and normalized PG content (R = 0.61, P 0.05). The water/PG peak area ratio, normalized water, normalized PG, and Pfirrmann grade were significantly associated with patient self-assessment of disability and physical composite score, while disc height was not. This study demonstrated a relationship between in vivo MRS spectroscopy (water content and PG content), imaging parameters (T1ρ and Pfirrmann grade), discography results, and clinical self-assessment, suggesting that MRS-quantified water, PG, and MR T1ρ relaxation time may potentially serve as biomarkers of

  9. Cartilage quality in rheumatoid arthritis: comparison of T2* mapping, native T1 mapping, dGEMRIC, {delta}R1 and value of pre-contrast imaging

    Energy Technology Data Exchange (ETDEWEB)

    Buchbender, Christian; Scherer, Axel; Kroepil, Patric; Quentin, Michael; Reichelt, Dorothea C.; Lanzman, Rotem S.; Mathys, Christian; Blondin, Dirk; Wittsack, Hans-Joerg; Antoch, Gerald; Miese, Falk [University Duesseldorf, Department of Diagnostic and Interventional Radiology, Medical Faculty, Duesseldorf (Germany); Koerbl, Birthe [Heinrich-Heine-University, Department of Endocrinology, Diabetology and Rheumatology, Medical Faculty, Duesseldorf (Germany); Heinrich-Heine-University, Leibniz Centre for Diabetes Research, Institute of Biometrics and Epidemiology, German Diabetes Centre, Duesseldorf (Germany); Bittersohl, Bernd; Zilkens, Christoph [Heinrich-Heine-University, Department of Orthopaedics, Medical Faculty, Duesseldorf (Germany); Hofer, Matthias [Heinrich-Heine-University, Medical Education Group, Medical School, Duesseldorf (Germany); Schneider, Matthias; Ostendorf, Benedikt [Heinrich-Heine-University, Department of Endocrinology, Diabetology and Rheumatology, Medical Faculty, Duesseldorf (Germany)

    2012-06-15

    To prospectively evaluate four non-invasive markers of cartilage quality - T2* mapping, native T1 mapping, dGEMRIC and {delta}R1 - in healthy volunteers and rheumatoid arthritis (RA) patients. Cartilage of metacarpophalangeal (MCP) joints II were imaged in 28 consecutive subjects: 12 healthy volunteers [9 women, mean (SD) age 52.67 (9.75) years, range 30-66] and 16 RA patients with MCP II involvement [12 women, mean (SD) age 58.06 (12.88) years, range 35-76]. Sagittal T2* mapping was performed with a multi-echo gradient-echo on a 3 T MRI scanner. For T1 mapping the dual flip angle method was applied prior to native T1 mapping and 40 min after gadolinium application (delayed gadolinium-enhanced MRI of cartilage, dGEMRIC, T1{sub Gd}). The difference in the longitudinal relaxation rate induced by gadolinium ({delta}R1) was calculated. The area under the receiver operating characteristic curve (AROC) was used to test for differentiation of RA patients from healthy volunteers. dGEMRIC (AUC 0.81) and {delta}R1 (AUC 0.75) significantly differentiated RA patients from controls. T2* mapping (AUC 0.66) and native T1 mapping (AUC 0.66) were not significantly different in RA patients compared to controls. The data support the use of dGEMRIC for the assessment of MCP joint cartilage quality in RA. T2* and native T1 mapping are of low diagnostic value. Pre-contrast T1 mapping for the calculation of {delta}R1 does not increase the diagnostic value of dGEMRIC. (orig.)

  10. T1 mapping of the myocardium: Intra-individual assessment of the effect of field strength, cardiac cycle and variation by myocardial region

    Directory of Open Access Journals (Sweden)

    Kawel Nadine

    2012-05-01

    Full Text Available Abstract Background Myocardial T1 relaxation time (T1 time and extracellular volume fraction (ECV are altered in the presence of myocardial fibrosis. The purpose of this study was to evaluate acquisition factors that may result in variation of measured T1 time and ECV including magnetic field strength, cardiac phase and myocardial region. Methods 31 study subjects were enrolled and underwent one cardiovascular MR exam at 1.5 T and two exams at 3 T, each on separate days. A Modified Look-Locker Inversion Recovery (MOLLI sequence was acquired before and 5, 10, 12, 20, 25 and 30 min after administration of 0.15 mmol/kg gadopentetate dimeglumine (Gd-DTPA; Magnevist at 1.5 T (exam 1. For exam 2, MOLLI sequences were acquired at 3 T both during diastole and systole, before and after administration of Gd-DTPA (0.15 mmol/kg Magnevist.Exam 3 was identical to exam 2 except gadobenate dimeglumine was administered (Gd-BOPTA; 0.1 mmol/kg Multihance. T1 times were measured in myocardium and blood. ECV was calculated by (ΔR1myocardium/ΔR1blood*(1-hematocrit. Results Before gadolinium, T1 times of myocardium and blood were significantly greater at 3 T versus 1.5 T (28% and 31% greater, respectively, p  Conclusion ECV is similar at field strengths of 1.5 T and 3 T. Due to minor variations in T1 time and ECV during the cardiac cycle and in different myocardial regions, T1 measurements should be obtained at the same cardiac phase and myocardial region in order to obtain consistent results.

  11. Electronic relaxation processes in polyatomic molecules. Progress report, October 1, 1975--September 30, 1976

    International Nuclear Information System (INIS)

    Lim, E.C.

    1976-09-01

    Excitation energy dependence of radiationless decay rate under collision-free conditions was utilized as a probe of intramolecular vibrational relaxation in tetracene and pentacene. The results give evidence of vibrational relaxation which competes with electronic relaxation. The substitution dependence of T 1 (nπ*) → S 0 radiationless transition in monocyclic diazines and the temperature dependence of S 1 non-radiative decay rate in alcoholic solutions of polycyclic monoazines indicate that the vibronic interaction between the lowest energy nπ* and ππ* states leads to a rapid radiationless deactivation of the lower of the two electronic states. Finally, a photon-counting spectrofluorometer of very high sensitivity was constructed, and it was used to record T 2 → T 1 fluorescence in bromoanthracenes and S 2 → S 1 fluorescence in azulene. These spectra represent the first bona-fide, or the most convincing, observation of fluorescence between excited electronic states

  12. Impact of liver fibrosis and fatty liver on T1rho measurements: A prospective study

    International Nuclear Information System (INIS)

    Xie, Shuang Shuang; Li, Qing; Cheng, Yue; Shen, Wen; Zhang, Yu; Zhuo, Zhi Zheng; Zhao, Guiming

    2017-01-01

    To investigate the liver T1rho values for detecting fibrosis, and the potential impact of fatty liver on T1rho measurements. This study included 18 healthy subjects, 18 patients with fatty liver, and 18 patients with liver fibrosis, who underwent T1rho MRI and mDIXON collections. Liver T1rho, proton density fat fraction (PDFF) and T2* values were measured and compared among the three groups. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the T1rho values for detecting liver fibrosis. Liver T1rho values were correlated with PDFF, T2* values and clinical data. Liver T1rho and PDFF values were significantly different (p 0.05). T1rho MRI is useful for noninvasive detection of liver fibrosis, and may not be affected with the presence of fatty liver

  13. Reversed field pinch magnetic equilibrium and profile dynamics in Extrap T1-upgrade

    International Nuclear Information System (INIS)

    Nordlund, P.; Mazur, S.; Drake, J.R.

    1992-05-01

    An eight station insertable magnetic probe has been installed on the Extrap T1-U machine. The structure of the reversed field pinch magnetic equilibrium and the time evolution of the profiles has been studied. The probe was inserted into sustained high current density RFP plasma, typically 12-16 MA/m 2 on axis. When the probe was inserted there was a somewhat shorter pulse duration and a slightly decaying current. The magnetic field profiles are shift corrected and expressed in a cylindrically symmetric form. All quantities are then derived from cylindrically symmetric equations. In the beginning of the sustainment phase, where the best reproducibility is achieved, we have been able to obtain estimates of the pressure profile consistent with independent measurements of the central pressure. Values of βθ approx = 0.19 and approx = 0.09 are found leading to an estimation of the energy confinement time, with the probe inserted, of τε approx = 5 μs. Profiles of the effective parallel conductivity clearly indicates the presence of a 'dynamo mechanism' sustaining the field configuration. Higher Θ discharges usually exhibit large oscillations in the F-Θ plane. We find that these oscillations represents macroscopic redistribution of the current in the plasma. A cyclic process is found where the parallel current density (μ-profile) tends to peak in the center and then relax towards a flatter and broader configuration. Towards the end of the discharge there is an increasing fluctuation level along with an increasing V loop /I p - Here we find a relative increase in the current density in the edge region resulting in a hollow μ-profile. (au) (15 refs., 31 figs.)

  14. Taste information derived from T1R-expressing taste cells in mice.

    Science.gov (United States)

    Yoshida, Ryusuke; Ninomiya, Yuzo

    2016-03-01

    The taste system of animals is used to detect valuable nutrients and harmful compounds in foods. In humans and mice, sweet, bitter, salty, sour and umami tastes are considered the five basic taste qualities. Sweet and umami tastes are mediated by G-protein-coupled receptors, belonging to the T1R (taste receptor type 1) family. This family consists of three members (T1R1, T1R2 and T1R3). They function as sweet or umami taste receptors by forming heterodimeric complexes, T1R1+T1R3 (umami) or T1R2+T1R3 (sweet). Receptors for each of the basic tastes are thought to be expressed exclusively in taste bud cells. Sweet (T1R2+T1R3-expressing) taste cells were thought to be segregated from umami (T1R1+T1R3-expressing) taste cells in taste buds. However, recent studies have revealed that a significant portion of taste cells in mice expressed all T1R subunits and responded to both sweet and umami compounds. This suggests that sweet and umami taste cells may not be segregated. Mice are able to discriminate between sweet and umami tastes, and both tastes contribute to behavioural preferences for sweet or umami compounds. There is growing evidence that T1R3 is also involved in behavioural avoidance of calcium tastes in mice, which implies that there may be a further population of T1R-expressing taste cells that mediate aversion to calcium taste. Therefore the simple view of detection and segregation of sweet and umami tastes by T1R-expressing taste cells, in mice, is now open to re-examination. © 2016 Authors; published by Portland Press Limited.

  15. The effects of bone on proton NMR relaxation times of surrounding liquids

    Science.gov (United States)

    Davis, C. A.; Genant, H. K.; Dunham, J. S.

    1986-01-01

    Preliminary attempts by our group at UCSF to assess fat content of vertebral marrow in the lumbar spine using relaxation time information demonstrated that the presence of trabecular bone affects relaxation times. The objective of this work was a thorough study of the effects of bone on NMR relaxation characteristics of surrounding liquids. Trabecular bone from autopsy specimens was ground up and sifted into a series of powders with graded densities ranging from 0.3 gm/cc to 0.8 gm/cc. Each powder was placed first in n-saline and then in cottonseed oil. With spectroscopy, spin-lattice relaxation times (T1) and effective spin-spin relaxation times (T2*) were measured for each liquid in each bone powder. As bone density and surface to volume ratio increased, T1 decreased faster for saline than for oil. T2* decreased significantly for both water and oil as the surface to volume ratio increased. It was concluded that effects of water on T1 could be explained by a surface interaction at the bone/liquid interface, which restricted rotational and translational motion of nearby molecules. The T1s of oil were not affected since oil molecules are nonpolar, do not participate in significant intermolecular hydrogen bonding, and therefore would not be expected to interact strongly with the bone surface. Effects on T2* could be explained by local magnetic field inhomogeneities created by discontinuous magnetic susceptibility near the bone surface. These preliminary results suggest that water in contact with trabecular bone in vivo will exhibit shortened relaxation times.

  16. 13C NMR relaxation times of hepatic glycogen in vitro and in vivo

    International Nuclear Information System (INIS)

    Zang, Lihsin; Laughlin, M.R.; Rothman, D.L.; Shulman, R.G.

    1990-01-01

    The field dependence of relaxation times of the C-1 carbon of glycogen was studied in vitro by natural-abundance 13 C NMR. T 1 is strongly field dependent, while T 2 does not change significantly with magnetic field. T 1 and T 2 were also measured for rat hepatic glycogen enriched with [1- 13 C]glucose in vivo at 4.7 T, and similar relaxation times were observed as those obtained in vitro at the same field. The in vitro values of T 1 were 65 ± 5 ms at 2.1 T, 142 ± 10 ms at 4.7 T, and 300 ± 10 ms at 8.4 T, while T 2 values were 6.7 ± 1 ms at 2.1 T, 9.4 ± 1 ms at 4.7 T, and 9.5 ± 1 ms at 8.4 T. Calculations based on the rigid-rotor nearest-neighbor model give qualitatively good agreement with the T 1 field dependence with a best-fit correlation time of 6.4 x 10 -9 s, which is significantly smaller than τ M , the estimated overall correlation time for the glycogen molecule (ca. 10 -5 s). A more accurate fit of T 1 data using a modified Lipari and Szabo approach indicates that internal fast motions dominate the T 1 relaxation in glycogen. On the other hand, the T 2 relaxation is dominated by the overall correlation time τ M while the internal motions are almost but not completely unrestricted

  17. Relaxed states with plasma flow

    International Nuclear Information System (INIS)

    Avinash, K.; Taylor, J.B.

    1991-01-01

    In the theory of relaxation, a turbulent plasma reaches a state of minimum energy subject to constant magnetic helicity. In this state the plasma velocity is zero. Attempts have been made by introducing a number of different constraints, to obtain relaxed states with plasma flow. It is shown that these alternative constraints depend on two self-helicities, one for ions, and one for electrons. However, whereas there are strong arguments for the effective invariance of the original magnetic-helicity, these arguments do not apply to the self-helicities. Consequently the existence of relaxed states with flow remains in doubt. (author)

  18. The impact of reliable pre-bolus T1 measurements or a fixed T1 value in the assessment of glioma patients with Dynamic Contrast Enhancing MRI

    DEFF Research Database (Denmark)

    Tietze, Anna; Mouridsen, Kim; Mikkelsen, Irene Klærke

    2015-01-01

    ) investigate if accurate estimation of DCE parameters outperform a time-saving approach with a pre-defined T1 value when differentiating high- from low-grade gliomas. Methods: (i) The accuracy and precision of T1 measurements, acquired by VFA and SR was investigated by computer simulations and in glioma...... to differentiate tumor grade. Results: The T1 values obtained by VFA showed larger variation compared to those obtained using SR both in the digital phantom and the human data (p > 0.05). Although a fixed T1 introduced a bias into the DCE calculation, this had only minor impact on the accuracy differentiating high......-quantitative DCE values, based on pre-defined T1 values, were sufficient to perform tumor grading in our study....

  19. On aggregation of relaxed T-indistinguishability operators

    Energy Technology Data Exchange (ETDEWEB)

    Fuster-Parra, P.

    2017-07-01

    The notion of T -indistinguishability operator was introduced by E. Trillas in [7] with the aim of fuzzifying the classical (crisp) notion of equivalence relation. Relaxed metrics and indistinguishability operators are closely related. Indeed, in [1] it has been stated that the logical counterpart for relaxed metrics is, in some sense, a generalized indistinguishability operator (relaxed T -indistinguishability operator). Notice that the notion of T -indistinguishability operator is retrieved as a particular case of relaxed T -indistinguishability operator whenever the relaxed T - indistinguishability operator satisfies also the reflexivity. In fact, a relaxed indistinguishability operator is a indistinguishability operator if and only if it holds the reflexivity. The same occurs when we consider T -indistinguishability operator that separates points. Several authors have studied the aggregation of some classes of fuzzy relations (see [3, 4, 5, 6]), where it is stated that transitivity is one of the most important properties of a fuzzy relation. In [5] a study of aggregation of T-indistinguishability operators is presented, motivated by this work the aim of this study is to analyze the case of aggregating relaxed T-indistinguishability operators. (Author)

  20. State resolved vibrational relaxation modeling for strongly nonequilibrium flows

    Science.gov (United States)

    Boyd, Iain D.; Josyula, Eswar

    2011-05-01

    Vibrational relaxation is an important physical process in hypersonic flows. Activation of the vibrational mode affects the fundamental thermodynamic properties and finite rate relaxation can reduce the degree of dissociation of a gas. Low fidelity models of vibrational activation employ a relaxation time to capture the process at a macroscopic level. High fidelity, state-resolved models have been developed for use in continuum gas dynamics simulations based on computational fluid dynamics (CFD). By comparison, such models are not as common for use with the direct simulation Monte Carlo (DSMC) method. In this study, a high fidelity, state-resolved vibrational relaxation model is developed for the DSMC technique. The model is based on the forced harmonic oscillator approach in which multi-quantum transitions may become dominant at high temperature. Results obtained for integrated rate coefficients from the DSMC model are consistent with the corresponding CFD model. Comparison of relaxation results obtained with the high-fidelity DSMC model shows significantly less excitation of upper vibrational levels in comparison to the standard, lower fidelity DSMC vibrational relaxation model. Application of the new DSMC model to a Mach 7 normal shock wave in carbon monoxide provides better agreement with experimental measurements than the standard DSMC relaxation model.

  1. Can T1 w/T2 w ratio be used as a myelin-specific measure in subcortical structures? Comparisons between FSE-based T1 w/T2 w ratios, GRASE-based T1 w/T2 w ratios and multi-echo GRASE-based myelin water fractions.

    Science.gov (United States)

    Uddin, Md Nasir; Figley, Teresa D; Marrie, Ruth Ann; Figley, Chase R

    2018-03-01

    suggests that the two T 1 w/T 2 w ratio approaches measure similar facets of subcortical tissue microstructure, whereas T 1 w/T 2 w ratios and MWFs appear to be sensitized to different microstructural properties. On this basis, we conclude that multi-echo GRASE sequences can be used in future studies to efficiently elucidate both general (T 1 w/T 2 w ratio) and myelin-specific (MWF) tissue characteristics. Copyright © 2018 John Wiley & Sons, Ltd.

  2. Articular cartilage lesions increase early cartilage degeneration in knees treated by anterior cruciate ligament reconstruction: T1ρ mapping evaluation and 1-year follow-up.

    Science.gov (United States)

    Hirose, Jun; Nishioka, Hiroaki; Okamoto, Nobukazu; Oniki, Yasunari; Nakamura, Eiichi; Yamashita, Yasuyuki; Usuku, Koichiro; Mizuta, Hiroshi

    2013-10-01

    Articular cartilage degeneration can develop after anterior cruciate ligament reconstruction (ACLR). Although radiological studies have identified risk factors for the progression of degenerative cartilage changes in the long term, risk factors in the early postoperative period remain to be documented. Cartilage lesions that are present at surgery progress to cartilage degeneration in the early phase after ACLR. Case series; Level of evidence, 4. T1ρ is the spin-lattice relaxation in the rotating frame magnetic resonance imaging. Sagittal T1ρ maps of the femorotibial joint were obtained before and 1 year after ACLR in 23 patients with ACL injuries. Four regions of interest (ROIs) were placed on images of the cartilage in the medial and lateral femoral condyle (MFC, LFC) and the medial and lateral tibia plateau (MTP, LTP). Changes in the T1ρ value (milliseconds) of each ROI were recorded, and differences between patients with and without cartilage lesions were evaluated. The relationship between changes in the T1ρ value and meniscal tears was also studied. Arthroscopy at ACLR detected cartilage lesions in 15 MFCs, 7 LFCs, and 2 LTPs. The baseline T1ρ value of the MFC and LFC was significantly higher in patients with cartilage lesions (MFC, 40.7 ms; LFC, 42.2 ms) than in patients without cartilage lesions (MFC, 38.0 ms, P = .025; LFC, 39.4 ms, P = .010). At 1-year follow-up, the T1ρ value of the MFC and LFC was also significantly higher in patients with lesions (MFC, 43.1 ms; LFC, 42.7 ms) than in patients without such lesions (MFC, 39.1 ms, P = .002; LFC, 40.4 ms, P = .023, respectively). In patients with cartilage injury, the T1ρ value of the MFC increased during the year after treatment (P = .002). There was no significant difference in the baseline and follow-up T1ρ value in patients with or without meniscal tears on each side although the T1ρ value of the MFC, MTP, and LFC increased during the first year after surgery regardless of the presence or

  3. An analysis of the NMR-CT image by the measurement of proton-relaxation times in tissue

    International Nuclear Information System (INIS)

    Naruse, Shoji; Horikawa, Yoshiharu; Tanaka, Chuzo; Hirakawa, Kimiyoshi; Nishikawa, Hiroyasu; Shimizu, Koji; Kiri, Motosada.

    1984-01-01

    NMR-CT images were analyzed by measuring the proton-relaxation times in tissues. The NMR-CT images were obtained in 10 normal volunteers and 16 patients with brain tumors with a prototype superconducting magnet (Shimadzu Corp., Japan) operating at 0.2 T and 0.375 T. A smooth T 1 relaxation curve was obtained in each part of the brain and the brain tumor by the use of the data of the NMR-CT image; consequently, the in vivo T 1 value was proved to be reliable. The in vivo T 1 value showed the specific value corresponding to each region of the normal brain in all cases. Cerebral gray matter normally had the longest T 1 value, followed by the medulla oblongata, the pons, and white matter. The T 1 value of each region of the brain varied to the same degree in proportion to the strength of the static magnetic field. The in vivo T 1 values of the brain tumor varied with the histological type. All were longer than any part of the brain parenchyma, being between 480 and 780 msec at 0.2 T. The prolongation of the T 1 value does not always correspond to the degree of the malignancy in a tumor. The in vitro T 1 and T 2 values were also prolonged in all tumors. Although the absolute value of T 1 did not coincide between the in vitro and in vivo data, the tendency of the prolongation was the same between them. This result indicated that the NMR-CT images could be analysed by the use of the data of the in vitro T 1 and T 2 values in the tumor tissues. It is important to analyse the NMR-CT image by both in vivo and in vitro examinations of the relaxation times. (J.P.N.)

  4. NMR relaxation rates and Knight shifts in MgB2 and AlB2: theory versus experiments

    International Nuclear Information System (INIS)

    Pavarini, E; Baek, S H; Suh, B J; Borsa, F; Bud'ko, S L; Canfield, P C

    2003-01-01

    We have performed 11 B NMR measurements in 11 B enriched MgB 2 powder sample in the normal phase. The Knight shift was accurately determined by using the magic angle spinning technique. Results for 11 B and 27 Al Knight shifts (K) and relaxation rates (1/T 1 ) are also reported for AlB 2 . The data show a dramatic decrease of both K and 1/T 1 for 11 B in AlB 2 with respect to MgB 2 . We compare experimental results with ab initio calculated NMR relaxation rates and Knight shifts. The experimental values for 1/T 1 and K are in most cases in good agreement with the theoretical results. We show that the decrease of K and 1/T 1 for 11 B is consistent with a drastic drop of the density of states at the boron site in AlB 2 with respect to MgB 2

  5. A statistical correlation investigation for the role of surface spins to the spin relaxation of nitrogen vacancy centers

    Directory of Open Access Journals (Sweden)

    Xuerui Song

    2014-04-01

    Full Text Available We investigated the influence of spins on surface of nanodiamonds (NDs to the longitudinal relaxation time (T1 and transverse relaxation time (T2 of nitrogen vacancy (NV centers in ND. A spherical model of the NDs was suggested to account for the experimental results of T1 and T2, and the density of surface spins was roughly estimated based on the statistical analysis of experimental results of 72 NDs containing a single NV center. For NDs studied here, the T1 of NV center inside is highly dependent to the surface spins of the NDs. However, for the T2 of NV center, intrinsic contributions must be much pronounced than that by surface spins. In other words, T1 of an NV center in NDs is more sensitive to the change of the surface spin density than T2.

  6. Electron spin relaxation in cryptochrome-based magnetoreception

    DEFF Research Database (Denmark)

    Kattnig, Daniel R; Solov'yov, Ilia A; Hore, P J

    2016-01-01

    The magnetic compass sense of migratory birds is thought to rely on magnetically sensitive radical pairs formed photochemically in cryptochrome proteins in the retina. An important requirement of this hypothesis is that electron spin relaxation is slow enough for the Earth's magnetic field to have...... this question for a structurally characterized model cryptochrome expected to share many properties with the putative avian receptor protein. To this end we combine all-atom molecular dynamics simulations, Bloch-Redfield relaxation theory and spin dynamics calculations to assess the effects of spin relaxation...... on the performance of the protein as a compass sensor. Both flavin-tryptophan and flavin-Z˙ radical pairs are studied (Z˙ is a radical with no hyperfine interactions). Relaxation is considered to arise from modulation of hyperfine interactions by librational motions of the radicals and fluctuations in certain...

  7. Relaxed states of tokamak plasmas

    International Nuclear Information System (INIS)

    Kucinski, M.Y.; Okano, V.

    1993-01-01

    The relaxed states of tokamak plasmas are studied. It is assumed that the plasma relaxes to a quasi-steady state which is characterized by a minimum entropy production rate, compatible with a number of prescribed conditions and pressure balance. A poloidal current arises naturally due to the anisotropic resistivity. The minimum entropy production theory is applied, assuming the pressure equilibrium as fundamental constraint on the final state. (L.C.J.A.)

  8. Negative magnetic relaxation in superconductors

    Directory of Open Access Journals (Sweden)

    Krasnoperov E.P.

    2013-01-01

    Full Text Available It was observed that the trapped magnetic moment of HTS tablets or annuli increases in time (negative relaxation if they are not completely magnetized by a pulsed magnetic field. It is shown, in the framework of the Bean critical-state model, that the radial temperature gradient appearing in tablets or annuli during a pulsed field magnetization can explain the negative magnetic relaxation in the superconductor.

  9. Relaxation effects in ferrous complexes

    International Nuclear Information System (INIS)

    Nicolini, C.; Mathieu, J.P.; Chappert, J.

    1976-01-01

    The slow relaxation mechanism of the Fe 2+ ion in the tri-fluorinated TF(acac) and hexafluorinated HF(acac) complexes of Fe(II) acetylacetonate was investigated. The 300K and 77K Moessbauer spectra for TF(acac) consist in a slightly asymmetric quadrupole doublet. On the contrary, at 4.2K the higher energy line is strongly widened; that is typical of a slowing down in the electron relaxation frequency [fr

  10. Comparison of axial T1 spin-echo and T1 fat-saturation magnetic resonance imaging techniques in the diagnosis of chondromalacia patellae.

    Science.gov (United States)

    Vanarthos, W J; Pope, T L; Monu, J U

    1994-12-01

    To test the diagnostic value of T1 spin-echo and T1 fat-saturated magnetic resonance images (MRIs), we reviewed axial T1-weighted images with and without fat saturation in 20 patients with clinically suspected chondromalacia of the patella. All scans were obtained on 1.5-MR units. The scans were randomly ordered and reviewed independently at different times by two radiologists without knowledge of the arthroscopy results. The sensitivity of the individual techniques for detecting grade 3 or 4 chondromalacia patellae was 92% for fat-saturated axial T1-weighted images alone, and 67% for axial T1-weighted images without fat saturation. The sensitivity of the combined techniques was 100% for grades 3 and 4 and 90% for all grades (0 to 4). Chondromalacia patellae is diagnosed more accurately by using T1 fat saturation than by using T1 spin-echo images. With a combination of the two techniques, accuracy is 90% to 100%.

  11. T1rho mapping of entire femoral cartilage using depth- and angle-dependent analysis

    Energy Technology Data Exchange (ETDEWEB)

    Nozaki, Taiki; Kaneko, Yasuhito; Yu, Hon J.; Yoshioka, Hiroshi [University of California Irvine, Department of Radiological Sciences, Orange, CA (United States); Kaneshiro, Kayleigh [University of California Irvine, School of Medicine, Irvine, CA (United States); Schwarzkopf, Ran [University of California Irvine, Department of Orthopedic Surgery, Irvine, CA (United States); Hara, Takeshi [Gifu University Graduate School of Medicine, Department of Intelligent Image Information, Division of Regeneration and Advanced Medical Sciences, Gifu (Japan)

    2016-06-15

    To create and evaluate normalized T1rho profiles of the entire femoral cartilage in healthy subjects with three-dimensional (3D) angle- and depth-dependent analysis. T1rho images of the knee from 20 healthy volunteers were acquired on a 3.0-T unit. Cartilage segmentation of the entire femur was performed slice-by-slice by a board-certified radiologist. The T1rho depth/angle-dependent profile was investigated by partitioning cartilage into superficial and deep layers, and angular segmentation in increments of 4 over the length of segmented cartilage. Average T1rho values were calculated with normalized T1rho profiles. Surface maps and 3D graphs were created. T1rho profiles have regional and depth variations, with no significant magic angle effect. Average T1rho values in the superficial layer of the femoral cartilage were higher than those in the deep layer in most locations (p < 0.05). T1rho values in the deep layer of the weight-bearing portions of the medial and lateral condyles were lower than those of the corresponding non-weight-bearing portions (p < 0.05). Surface maps and 3D graphs demonstrated that cartilage T1rho values were not homogeneous over the entire femur. Normalized T1rho profiles from the entire femoral cartilage will be useful for diagnosing local or early T1rho abnormalities and osteoarthritis in clinical applications. (orig.)

  12. T1rho mapping of entire femoral cartilage using depth- and angle-dependent analysis

    International Nuclear Information System (INIS)

    Nozaki, Taiki; Kaneko, Yasuhito; Yu, Hon J.; Yoshioka, Hiroshi; Kaneshiro, Kayleigh; Schwarzkopf, Ran; Hara, Takeshi

    2016-01-01

    To create and evaluate normalized T1rho profiles of the entire femoral cartilage in healthy subjects with three-dimensional (3D) angle- and depth-dependent analysis. T1rho images of the knee from 20 healthy volunteers were acquired on a 3.0-T unit. Cartilage segmentation of the entire femur was performed slice-by-slice by a board-certified radiologist. The T1rho depth/angle-dependent profile was investigated by partitioning cartilage into superficial and deep layers, and angular segmentation in increments of 4 over the length of segmented cartilage. Average T1rho values were calculated with normalized T1rho profiles. Surface maps and 3D graphs were created. T1rho profiles have regional and depth variations, with no significant magic angle effect. Average T1rho values in the superficial layer of the femoral cartilage were higher than those in the deep layer in most locations (p < 0.05). T1rho values in the deep layer of the weight-bearing portions of the medial and lateral condyles were lower than those of the corresponding non-weight-bearing portions (p < 0.05). Surface maps and 3D graphs demonstrated that cartilage T1rho values were not homogeneous over the entire femur. Normalized T1rho profiles from the entire femoral cartilage will be useful for diagnosing local or early T1rho abnormalities and osteoarthritis in clinical applications. (orig.)

  13. Study of magnetic properties and relaxation in amorphous Fe73.9Nb3.1Cu0.9Si13.2B8.9 thin films produced by ion beam sputtering

    International Nuclear Information System (INIS)

    Celegato, F.; Coiesson, M.; Magni, A.; Tiberto, P.; Vinai, F.; Kane, S. N.; Modak, S. S.; Gupta, A.; Sharma, P.

    2007-01-01

    Amorphous Fe 73.9 Nb 3.1 Cu 0.9 Si 13.2 B 8.9 thin films have been produced by ion beam sputtering with two different beam energies (500 and 1000 eV). Magnetic measurements indicate that the samples display a uniaxial magnetic anisotropy, especially for samples prepared with the lower beam energy. Magnetization relaxation has been measured on both films with an alternating gradient force magnetometer and magneto-optical Kerr effect. Magnetization relaxation occurs on time scales of tens of seconds and can be described with a single stretched exponential function. Relaxation intensity turns out to be higher when measured along the easy magnetization axis

  14. Spin Diffusion and Spin Lattice Relaxation of Dipolar Order in Solids Containing Paramagnetic Impurities

    International Nuclear Information System (INIS)

    Furman, G.B.; Panich, A.M.; Goren, S.D.

    1998-01-01

    The phenomena of spin diffusion and spin lattice relaxation of nuclear dipolar order in solids containing paramagnetic impurities (PI) is considered. We show that at the beginning of the relaxation process the diffusion vanishing regime realizes with non-exponential time dependence, R(t) ∼ exp [- (t/T 1d ) α ], where T 1d ∼ C p -1/α , C p is PI's concentration. For a homogeneous distribution of Pis and nuclear spins, α=Q/6, where Q is the sample dimensionality; for an inhomogeneous distribution, the sample is divided into q-dimensional subsystems, each containing one PI, yield- ing α= (Q + q) /6. This result coincides with experimental data for CaF 2 doped with 0.8 - 10 -3 ωt % of Mn 2+ , where the non-exponential decay of the dipolar signal with α= 0.83 has been observed [3]. Fitting the experimental data yields a good agreement with T 1d = 66 ms . For another independent check of the obtained results we use dependence of the relaxation time on impurities concentration. In accordance that 1/α=1.2 , we have T 1d ∼ C p -1 '. 2 . Exactly this dependence on impurity concentration of the relaxation time has been found in the experiment. Then the relaxation regime starts as a non-exponential time dependent, proceed asymptotically to an to an exponential function of time, to so called diffusion limited relaxation regime with relaxation time T 1d D is inversely depends on impurities concentration. This kind of relaxation behavior of the dipolar order takes place in the experiment [2]. Using experimental results [2] from this two regime we can estimate the diffusion coefficient of the nuclear dipolar order in CaF 2 , which gives for typical values of impurity concentration C p ∼ 10 18 cm 3 the diffusion coefficient of dipolar order in the interval D ∼ 10 -11 -i- 10 -12 cm 2 /sec which is coincide to the case of Zeeman energy spin diffusion

  15. Butyrate transcriptionally enhances peptide transporter PepT1 expression and activity.

    Directory of Open Access Journals (Sweden)

    Guillaume Dalmasso

    Full Text Available BACKGROUND: PepT1, an intestinal epithelial apical di/tripeptide transporter, is normally expressed in the small intestine and induced in colon during chronic inflammation. This study aimed at investigating PepT1 regulation by butyrate, a short-chain fatty acid produced by commensal bacteria and accumulated inside inflamed colonocyte. RESULTS: We found that butyrate treatment of human intestinal epithelial Caco2-BBE cells increased human PepT1 (hPepT1 promoter activity in a dose- and time-dependent manner, with maximal activity observed in cells treated with 5 mM butyrate for 24 h. Under this condition, hPepT1 promoter activity, mRNA and protein expression levels were increased as assessed by luciferase assay, real-time RT-PCR and Western blot, respectively. hPepT1 transport activity was accordingly increased by approximately 2.5-fold. Butyrate did not alter hPepT1 mRNA half-life indicating that butyrate acts at the transcriptional level. Molecular analyses revealed that Cdx2 is the most important transcription factor for butyrate-induced increase of hPepT1 expression and activity in Caco2-BBE cells. Butyrate-activated Cdx2 binding to hPepT1 promoter was confirmed by gel shift and chromatin immunoprecipitation. Moreover, Caco2-BBE cells overexpressing Cdx2 exhibited greater hPepT1 expression level than wild-type cells. Finally, treatment of mice with 5 mM butyrate added to drinking water for 24 h increased colonic PepT1 mRNA and protein expression levels, as well as enhanced PepT1 transport activity in colonic apical membranes vesicles. CONCLUSIONS: Collectively, our results demonstrate that butyrate increases PepT1 expression and activity in colonic epithelial cells, which provides a new understanding of PepT1 regulation during chronic inflammation.

  16. Modelling Creep (Relaxation of the Urinary Bladder

    Directory of Open Access Journals (Sweden)

    Zdravkovic Nebojsa

    2017-12-01

    Full Text Available We first present the results of an experiment in which the passive properties of the urinary bladder were investigated using strips of rabbit bladder. Under the assumption that the urinary bladder had orthopaedic characteristics, the strips were taken in the longitudinal and in the circumferential directions. The material was subjected to uniaxial tension, and stress-stretch curves were generated for various rates of deformation. We found that the rates did not have a significantly effect on the passive response of the material. Additionally, the stress-stretch dependence during relaxation of the material when exposed to isometric conditions was determined experimentally.

  17. Stretched exponential relaxation and ac universality in disordered dielectrics

    DEFF Research Database (Denmark)

    Milovanov, Alexander V.; Rypdal, Kristoffer; Juul Rasmussen, Jens

    2007-01-01

    This paper is concerned with the connection between the properties of dielectric relaxation and alternating-current (ac) conduction in disordered dielectrics. The discussion is divided between the classical linear-response theory and a self-consistent dynamical modeling. The key issues are stretc......This paper is concerned with the connection between the properties of dielectric relaxation and alternating-current (ac) conduction in disordered dielectrics. The discussion is divided between the classical linear-response theory and a self-consistent dynamical modeling. The key issues...

  18. Relaxation time T/sub 1/ and bound water fraction of muscle by NMR imager

    Energy Technology Data Exchange (ETDEWEB)

    Fukuda, N.; Ikehira, H.; Yamane, T.; Tateno, Y.; Torii, S.; Matsumura, K.

    1986-05-01

    In order to establish the efficacy of NMR-CT in the diagnostic investigation of muscle disorders, proton NMR-CT imaging was performed and muscle longitudinal relaxation (T1) times were measured in 20 Duchenne muscular dystrophy (DMD) patients and normal controls (NC). In addition, the bound water fraction (BWF) was calculated from the measured T1 value in appropriate cases. Results show that in DMD muscle T1 values were above normal in the early clinical stages, declined rapidly with progress of the disease, and reached the same low level as the subcutaneous fat. This decrease of T1 values was not uniform for all muscles, being most prominent in gluteus maximus and least in sartorius and gracilis. In NC muscle BWF increased with maturation under the age of 10 years, and became fixed beyond that. In the early stages of DMD, BWF was below normal.

  19. T1 changes of canine brain in hyponatremic hypoosmosis induced by peritoneal dialysis with water

    International Nuclear Information System (INIS)

    Tsuji, Takayuki; Fujimoto, Toshiro; Fujii, Masatoshi; Nakano, Toshihiko; Shimooki, Susumu.

    1991-01-01

    Changes of canine brain T 1 s measured in right and left white (W-T 1 ) and gray (G-T 1 ) matter, thalamus (T-T 1 ), and caudate nucleus (C-T 1 ) in coronal view with a head coil was studied in anesthesized and automatically ventilated 11 mongrel dogs (9.2±2.2 kg) using 0.1 T MR imager (Mark-J, Siemens-Asahi Meditech) before and every 30 minutes after infusion of distilled water warmed at 37degC into abdominal cavity (192±50 ml/kg) up to 120 minute later. Hemolysis (2→85 mg/dl: before→after 120 min) increased in association with total protein (5.9→8.0 g/dl) while sodium (147→122 mEq/l) and osmolarity (302→263 mOsm/kg) decreased. G-T 1 (388→394 ms) and W-T 1 (287→305 ms) did not change significantly, but T-T 1 prolonged early (331→349 ms) at 60 min (p 1 (356→376 ms) did at 90 min (p 1 (363 ms) and C-T 1 (382 ms) elongated from initial each T 1 significantly (p<0.01) 7% and 6% at 120 min, respectively. Basal nuclei, especially thalamus, in canine brain became edematous at the early stage of hyponatremic hypoosmosis induced by peritoneal dialysis with water. (author)

  20. Fully automatic detection of deep white matter T1 hypointense lesions in multiple sclerosis

    Science.gov (United States)

    Spies, Lothar; Tewes, Anja; Suppa, Per; Opfer, Roland; Buchert, Ralph; Winkler, Gerhard; Raji, Alaleh

    2013-12-01

    A novel method is presented for fully automatic detection of candidate white matter (WM) T1 hypointense lesions in three-dimensional high-resolution T1-weighted magnetic resonance (MR) images. By definition, T1 hypointense lesions have similar intensity as gray matter (GM) and thus appear darker than surrounding normal WM in T1-weighted images. The novel method uses a standard classification algorithm to partition T1-weighted images into GM, WM and cerebrospinal fluid (CSF). As a consequence, T1 hypointense lesions are assigned an increased GM probability by the standard classification algorithm. The GM component image of a patient is then tested voxel-by-voxel against GM component images of a normative database of healthy individuals. Clusters (≥0.1 ml) of significantly increased GM density within a predefined mask of deep WM are defined as lesions. The performance of the algorithm was assessed on voxel level by a simulation study. A maximum dice similarity coefficient of 60% was found for a typical T1 lesion pattern with contrasts ranging from WM to cortical GM, indicating substantial agreement between ground truth and automatic detection. Retrospective application to 10 patients with multiple sclerosis demonstrated that 93 out of 96 T1 hypointense lesions were detected. On average 3.6 false positive T1 hypointense lesions per patient were found. The novel method is promising to support the detection of hypointense lesions in T1-weighted images which warrants further evaluation in larger patient samples.

  1. Predictors of associated autoimmune diseases (AAID) in families with type 1 diabetes (T1D). Results from the Type 1 Diabetes Genetics Consortium (T1DGC)

    Science.gov (United States)

    Wägner, Ana M; Santana, Ángelo; Hernández, Marta; Wiebe, Julia C; Nóvoa, Javier; Mauricio, Didac

    2011-01-01

    Background Type 1 diabetes (T1D) is a clinically heterogeneous disease. The presence of associated autoimmune diseases (AAID) may represent a distinct form of autoimmune diabetes, with involvement of specific mechanisms. The aim of this study was to find predictors of AAID in the Type 1 Diabetes Genetics Consortium (T1DGC) data set. Methods 3263 families with at least 2 siblings with T1D were included. Clinical information was obtained using questionnaires, anti-GAD and anti-IA-2 were measured and HLA-genotyping was performed. Siblings with T1D with and without AAID were compared and a multivariate regression analysis was performed to find predictors of AAID. T1D-associated HLA haplotypes were defined as the 4 most susceptible and protective, respectively. Results AAID was present in 14.4% of the T1D affected siblings. Age of diabetes onset, current age and time since diagnosis were higher, and there was a female predominance and more family history of AAID in the group with AAID, as well as more frequent anti-GAD and less frequent anti-IA2 positivity. Risk and protective HLA haplotype distributions were similar, though DRB1*0301-DQA1*0501-DQB1*0201 was more frequent in the group with AAID. In the multivariate analysis, female gender, age of onset, family history of AAID, time since diagnosis and anti-GAD positivity were significantly associated with AAID. Conclusions In patients with T1D, the presence of AAID is associated with female predominance, more frequent family history of AAID, later onset of T1D and more anti-GAD antibodies, despite longer duration of the disease. The predominance of certain HLA haplotypes suggests that specific mechanisms of disease may be involved. PMID:21744463

  2. Detection of maltodextrin and its discrimination from sucrose are independent of the T1R2 + T1R3 heterodimer.

    Science.gov (United States)

    Smith, Kimberly R; Spector, Alan C

    2017-10-01

    Maltodextrins, such as Maltrin and Polycose, are glucose polymer mixtures of varying chain lengths that are palatable to rodents. Although glucose and other sugars activate the T1R2 + T1R3 "sweet" taste receptor, recent evidence from T1R2- or T1R3-knockout (KO) mice suggests that maltodextrins, despite their glucose polymer composition, activate a separate receptor mechanism to generate a taste percept qualitatively distinguishable from that of sweeteners. However, explicit discrimination of maltodextrins from prototypical sweeteners has not yet been psychophysically tested in any murine model. Therefore, mice lacking T1R2 + T1R3 and wild-type controls were tested in a two-response taste discrimination task to determine whether maltodextrins are 1 ) detectable when both receptor subunits are absent and 2 ) perceptually distinct from that of sucrose irrespective of viscosity, intensity, and hedonics. Most KO mice displayed similar Polycose sensitivity as controls. However, some KO mice were only sensitive to the higher Polycose concentrations, implicating potential allelic variation in the putative polysaccharide receptor or downstream pathways unmasked by the absence of T1R2 + T1R3. Varied Maltrin and sucrose concentrations of approximately matched viscosities were then presented to render the oral somatosensory features, intensity, and hedonic value of the solutions irrelevant. Although both genotypes competently discriminated Maltrin from sucrose, performance was apparently driven by the different orosensory percepts of the two stimuli in control mice and the presence of a Maltrin but not sucrose orosensory cue in KO mice. These data support the proposed presence of an orosensory receptor mechanism that gives rise to a qualitatively distinguishable sensation from that of sucrose. Copyright © 2017 the American Physiological Society.

  3. Sugar-induced cephalic-phase insulin release is mediated by a T1r2+T1r3-independent taste transduction pathway in mice.

    Science.gov (United States)

    Glendinning, John I; Stano, Sarah; Holter, Marlena; Azenkot, Tali; Goldman, Olivia; Margolskee, Robert F; Vasselli, Joseph R; Sclafani, Anthony

    2015-09-01

    Sensory stimulation from foods elicits cephalic phase responses, which facilitate digestion and nutrient assimilation. One such response, cephalic-phase insulin release (CPIR), enhances glucose tolerance. Little is known about the chemosensory mechanisms that activate CPIR. We studied the contribution of the sweet taste receptor (T1r2+T1r3) to sugar-induced CPIR in C57BL/6 (B6) and T1r3 knockout (KO) mice. First, we measured insulin release and glucose tolerance following oral (i.e., normal ingestion) or intragastric (IG) administration of 2.8 M glucose. Both groups of mice exhibited a CPIR following oral but not IG administration, and this CPIR improved glucose tolerance. Second, we examined the specificity of CPIR. Both mouse groups exhibited a CPIR following oral administration of 1 M glucose and 1 M sucrose but not 1 M fructose or water alone. Third, we studied behavioral attraction to the same three sugar solutions in short-term acceptability tests. B6 mice licked more avidly for the sugar solutions than for water, whereas T1r3 KO mice licked no more for the sugar solutions than for water. Finally, we examined chorda tympani (CT) nerve responses to each of the sugars. Both mouse groups exhibited CT nerve responses to the sugars, although those of B6 mice were stronger. We propose that mice possess two taste transduction pathways for sugars. One mediates behavioral attraction to sugars and requires an intact T1r2+T1r3. The other mediates CPIR but does not require an intact T1r2+T1r3. If the latter taste transduction pathway exists in humans, it should provide opportunities for the development of new treatments for controlling blood sugar. Copyright © 2015 the American Physiological Society.

  4. T1 Gd-enhanced compared with CISS sequences in retinoblastoma: superiority of T1 sequences in evaluation of tumour extension

    Energy Technology Data Exchange (ETDEWEB)

    Gizewski, Elke R.; Wanke, Isabel; Guengoer, Ali-Riza; Forsting, Michael [University Hospital, Department of Diagnostic and Interventional Neuroradiology, Essen (Germany); Jurklies, Christine [University Hospital Essen, Department of Ophthalmology (Germany)

    2005-01-01

    Background As adequate therapy for retinoblastoma in young children depends on infiltration of extra-retinal structures, diagnostic modalities play an essential role. Methods: In this widely extended study, 80 children with retinoblastoma were studied with MRI (standard fat-suppressed Gd-enhanced T1, T2 thin-slice sequences (additionally with small loop surface coil), constructive interference in steady state (CISS) sequence covering the orbita). The images were analysed by two blinded neuroradiologists. Histology was used as the gold standard. MRI assumed infiltration of extra-retinal structures in 13 of 80 patients of which ten were confirmed by histology. Affected extra-retinal structures were: optic nerve (five, of which two were on CISS and three on T1 with higher image resolution using the surface coil), scleral infiltration (five, of which four on CISS and T1) and ciliary body infiltration (one on CISS and T1). Another 61 enucleated patients did not have any extra-retinal infiltration in histology. The CISS sequence with multiplanar reconstruction was mainly helpful in revealing exact three-dimensional tumour extension with excellent clinical acceptance and pre-surgical planning but T1 fat-suppressed Gd-enhanced images were superior in revealing exact tumour extension. CISS sequences allow to produce excellent anatomical images and to perform multiplanar reconstruction to better demonstrate tumour extension. However, T1-weighted sequences after contrast application are more sensitive (60 versus 40%) in detecting infiltration of the optic nerve but equal in detecting scleral infiltration. (orig.)

  5. Closed-form expressions for flip angle variation that maximize total signal in T1-weighted rapid gradient echo MRI.

    Science.gov (United States)

    Drobnitzky, Matthias; Klose, Uwe

    2017-03-01

    Magnetization-prepared rapid gradient-echo (MPRAGE) sequences are commonly employed for T1-weighted structural brain imaging. Following a contrast preparation radiofrequency (RF) pulse, the data acquisition proceeds under nonequilibrium conditions of the relaxing longitudinal magnetization. Variation of the flip angle can be used to maximize total available signal. Simulated annealing or greedy algorithms have so far been published to numerically solve this problem, with signal-to-noise ratios optimized for clinical imaging scenarios by adhering to a predefined shape of the signal evolution. We propose an unconstrained optimization of the MPRAGE experiment that employs techniques from resource allocation theory. A new dynamic programming solution is introduced that yields closed-form expressions for optimal flip angle variation. Flip angle series are proposed that maximize total transverse magnetization (Mxy) for a range of physiologic T1 values. A 3D MPRAGE sequence is modified to allow for a controlled variation of the excitation angle. Experiments employing a T1 contrast phantom are performed at 3T. 1D acquisitions without phase encoding permit measurement of the temporal development of Mxy. Image mean signal and standard deviation for reference flip angle trains are compared in 2D measurements. Signal profiles at sharp phantom edges are acquired to access image blurring related to nonuniform Mxy development. A novel closed-form expression for flip angle variation is found that constitutes the optimal policy to reach maximum total signal. It numerically equals previously published results of other authors when evaluated under their simplifying assumptions. Longitudinal magnetization (Mz) is exhaustively used without causing abrupt changes in the measured MR signal, which is a prerequisite for artifact free images. Phantom experiments at 3T verify the expected benefit for total accumulated k-space signal when compared with published flip angle series. Describing

  6. STrategically Acquired Gradient Echo (STAGE) imaging, part I: Creating enhanced T1 contrast and standardized susceptibility weighted imaging and quantitative susceptibility mapping.

    Science.gov (United States)

    Chen, Yongsheng; Liu, Saifeng; Wang, Yu; Kang, Yan; Haacke, E Mark

    2018-02-01

    To provide whole brain grey matter (GM) to white matter (WM) contrast enhanced T1W (T1WE) images, multi-echo quantitative susceptibility mapping (QSM), proton density (PD) weighted images, T1 maps, PD maps, susceptibility weighted imaging (SWI), and R2* maps with minimal misregistration in scanning times creating enhanced GM/WM contrast (the T1WE). The proposed T1WE image was created from a combination of the proton density weighted (6°, PDW) and T1W (24°) images and corrected for RF transmit field variations. Prior to the QSM calculation, a multi-echo phase unwrapping strategy was implemented using the unwrapped short echo to unwrap the longer echo to speed up computation. R2* maps were used to mask deep grey matter and veins during the iterative QSM calculation. A weighted-average sum of susceptibility maps was generated to increase the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR). The proposed T1WE image has a significantly improved CNR both for WM to deep GM and WM to cortical GM compared to the acquired T1W image (the first echo of 24° scan) and the T1MPRAGE image. The weighted-average susceptibility maps have 80±26%, 55±22%, 108±33% SNR increases across the ten subjects compared to the single echo result of 17.5ms for the putamen, caudate nucleus, and globus pallidus, respectively. STAGE imaging offers the potential to create a standardized brain imaging protocol providing four pieces of quantitative tissue property information and multiple types of qualitative information in just 5min. Published by Elsevier Inc.

  7. Interface relaxation and band gap shift in epitaxial layers

    Directory of Open Access Journals (Sweden)

    Ziming Zhu

    2012-12-01

    Full Text Available Although it is well known that the interface relaxation plays the crucial role for the electronic properties in semiconductor epitaxial layers, there is lack of a clear definition of relationship between interfacial bond-energy variation and interface bond-nature-factor (IBNF in epitaxial layers before and after relaxation. Here we establish an analytical method to shed light on the relationship between the IBNF and the bond-energy change, as well as the relation with band offset in epitaxial layers from the perspective of atomic-bond-relaxation consideration and continuum mechanics. The theoretical predictions are consistent with the available evidences, which provide an atomistic understanding on underlying mechanism of interface effect in epitaxial nanostructures. Thus, it will be helpful for opening up to tailor physical-chemical properties of the epitaxial nanostructures to the desired specifications.

  8. Relaxation cracking in the process industry, an underestimated problem

    Energy Technology Data Exchange (ETDEWEB)

    Wortel, J.C. van [TNO Institute of Industrial Technology, Apeldoorn (Netherlands)

    1998-12-31

    Austenitic components, operating between 500 and 750 deg C, can fail within 1 year service while the ordinary mechanical properties after failure are still within the code requirements. The intergranular brittle failures are situated in the welded or cold deformed areas. This type of cracking has many names, showing the uncertainty concerning the mechanism for the (catastrophical) failures. A just finished investigation showed that it is a relaxation crack problem, introduced by manufacturing processes, especially welding and cold rolling. Cracking/failures can be expected after only 0.1- 0.2 % relaxation strain. These low strain values can already be generated during relaxation of the welding stresses. Especially coarse grained `age hardening` materials are susceptible. Stabilising and Postweld Heat Treatments are very effective to avoid relaxation crack problems during operation. After these heat treatments the components can withstand more than 2 % relaxation strain. At temperatures between 500 and 750 deg C relaxation cracking is the predominant factor for the safety and lifetime of welded austenitic components. (orig.) 12 refs.

  9. Relaxation cracking in the process industry, an underestimated problem

    Energy Technology Data Exchange (ETDEWEB)

    Wortel, J.C. van [TNO Institute of Industrial Technology, Apeldoorn (Netherlands)

    1999-12-31

    Austenitic components, operating between 500 and 750 deg C, can fail within 1 year service while the ordinary mechanical properties after failure are still within the code requirements. The intergranular brittle failures are situated in the welded or cold deformed areas. This type of cracking has many names, showing the uncertainty concerning the mechanism for the (catastrophical) failures. A just finished investigation showed that it is a relaxation crack problem, introduced by manufacturing processes, especially welding and cold rolling. Cracking/failures can be expected after only 0.1- 0.2 % relaxation strain. These low strain values can already be generated during relaxation of the welding stresses. Especially coarse grained `age hardening` materials are susceptible. Stabilising and Postweld Heat Treatments are very effective to avoid relaxation crack problems during operation. After these heat treatments the components can withstand more than 2 % relaxation strain. At temperatures between 500 and 750 deg C relaxation cracking is the predominant factor for the safety and lifetime of welded austenitic components. (orig.) 12 refs.

  10. Effects of thermal relaxation on an amorphous superconducting Zr--Rh alloy

    International Nuclear Information System (INIS)

    Drehman, A.J.; Johnson, W.L.

    1978-05-01

    The electronic and superconducting properties of an amorphous transition metal alloy are used to evaluate the effects of low temperature annealing. It is observed that the superconducting transition temperature and the electrical resistivity relax exponentially in time from their initial value to a final relaxed value. From this an activation energy for the relaxation process is derived and an explanation is suggested which involves internal stress

  11. Measurement of brain oxygenation changes using dynamic T1-weighted imaging

    DEFF Research Database (Denmark)

    Haddock, Bryan; Larsson, Henrik B W; Hansen, Adam E

    2013-01-01

    Magnetic resonance imaging (MRI) has proven useful in evaluating oxygenation in several types of tissue and blood. This study evaluates brain tissue oxygenation changes between normoxia and hyperoxia in healthy subjects using dynamic T1 and T2*-weighted imaging sequences. The change in FiO2 induced...... by hyperoxia caused a significant decrease in T1. A model to determine changes in tissue oxygen tension from the T1-weighted MRI signal is presented based on previous findings that T1 is sensitive to oxygen tension whereas T2* is sensitive to blood saturation. The two sequences produce results with different...... regional and temporal dynamics. These differences combined with results from simulations of the T1 signal intensities, indicate an increase in extravascular oxygen tension during hyperoxia. This study concludes that T1 and T2* responses to FiO2 serve as independent biomarkers of oxygen physiology...

  12. Peeling mode relaxation ELM model

    International Nuclear Information System (INIS)

    Gimblett, C. G.

    2006-01-01

    This paper discusses an approach to modelling Edge Localised Modes (ELMs) in which toroidal peeling modes are envisaged to initiate a constrained relaxation of the tokamak outer region plasma. Relaxation produces both a flattened edge current profile (which tends to further destabilise a peeling mode), and a plasma-vacuum negative current sheet which has a counteracting stabilising influence; the balance that is struck between these two effects determines the radial extent (rE) of the ELM relaxed region. The model is sensitive to the precise position of the mode rational surfaces to the plasma surface and hence there is a 'deterministic scatter' in the results that has an accord with experimental data. The toroidal peeling stability criterion involves the edge pressure, and using this in conjunction with predictions of rE allows us to evaluate the ELM energy losses and compare with experiment. Predictions of trends with the edge safety factor and collisionality are also made

  13. Anisotropy of the nuclear magnetic relaxation times induced in solid 3He by modulation of the dipolar interactions

    International Nuclear Information System (INIS)

    Deville, G.

    1976-01-01

    Anisotropic nuclear relaxation times have been measured in solid 3 He samples grown at constant pressure, in the Larmor frequency range 1.5MHz-5MHz where the main relaxation mechanism is the modulation of the dipolar interaction by exchange or by motion of the vacancies. The second order calculation made by Harris for the exchange induced relaxation regime is extended to the regime where vacancy motion dominates. The theory is further refined by considering the fourth moment anisotropy effect on the spectral densities. This latter calculation yields a frequency dependent anisotropic contribution to T 1 which agrees qualitatively with the data, unlike the simpler results by Harris [fr

  14. Increased native T1-values at the interventricular insertion regions in precapillary pulmonary hypertension.

    Science.gov (United States)

    Spruijt, Onno A; Vissers, Loek; Bogaard, Harm-Jan; Hofman, Mark B M; Vonk-Noordegraaf, Anton; Marcus, J Tim

    2016-03-01

    Cardiac magnetic resonance imaging of the pressure overloaded right ventricle (RV) of precapillary pulmonary hypertension (PH) patients, exhibits late gadolinium enhancement at the interventricular insertion regions, a phenomenon which has been linked to focal fibrosis. Native T1-mapping is an alternative technique to characterize myocardium and has the advantage of not requiring the use of contrast agents. The aim of this study was to characterize the myocardium of idiopathic pulmonary arterial hypertension (IPAH), systemic scleroderma related PH (PAH-Ssc) and chronic thromboembolic PH (CTEPH) patients using native T1-mapping and to see whether native T1-values were related to disease severity. Furthermore, we compared native T1-values between the different precapillary PH categories. Native T1-mapping was performed in 46 IPAH, 14 PAH-SSc and 10 CTEPH patients and 10 control subjects. Native T1-values were assessed using regions of interest at the RV and LV free wall, interventricular septum and interventricular insertion regions. In PH patients, native T1-values of the interventricular insertion regions were significantly higher than the native T1-values of the RV free wall, LV free wall and interventricular septum. Native T1-values at the insertion regions were significantly related to disease severity. Native T1-values were not different between IPAH, PAH-Ssc and CTEPH patients. Native T1-values of the interventricular insertion regions are significantly increased in precapillary PH and are related to disease severity. Native T1-mapping can be developed as an alternative technique for the characterization of the interventricular insertion regions and has the advantage of not requiring the use of contrast agents.

  15. The advantage of high relaxivity contrast agents in brain perfusion

    International Nuclear Information System (INIS)

    Cotton, F.; Hermier, M.

    2006-01-01

    Accurate MRI characterization of brain lesions is critical for planning therapeutic strategy, assessing prognosis and monitoring response to therapy. Conventional MRI with gadolinium-based contrast agents is useful for the evaluation of brain lesions, but this approach primarily depicts areas of disruption of the blood-brain barrier (BBB) rather than tissue perfusion. Advanced MR imaging techniques such as dynamic contrast agent-enhanced perfusion MRI provide physiological information that complements the anatomic data available from conventional MRI. We evaluated brain perfusion imaging with gadobenate dimeglumine (Gd-BOPTA, MultiHance; Bracco Imaging, Milan, Italy). The contrast-enhanced perfusion technique was performed on a Philips Intera 1.5-T MR system. The technique used to obtain perfusion images was dynamic susceptibility contrast-enhanced MRI, which is highly sensitive to T2* changes. Combined with PRESTO perfusion imaging, SENSE is applied to double the temporal resolution, thereby improving the signal intensity curve fit and, accordingly, the accuracy of the derived parametric images. MultiHance is the first gadolinium MR contrast agent with significantly higher T1 and T2 relaxivities than conventional MR contrast agents. The higher T1 relaxivity, and therefore better contrast-enhanced T1-weighted imaging, leads to significantly improved detection of BBB breakdown and hence improved brain tumor conspicuity and delineation. The higher T2 relaxivity allows high-quality T2*-weighted perfusion MRI and the derivation of good quality relative cerebral blood volume (rCBV) maps. We determined the value of MultiHance for enhanced T2*-weighted perfusion imaging of histologically proven (by surgery or stereotaxic biopsy) intraaxial brain tumors (n=80), multiple sclerosis lesions (n=10), abscesses (n=4), neurolupus (n=15) and stroke (n=16). All the procedures carried out were safe and no adverse events occurred. The acquired perfusion images were of good quality in

  16. Wettability of Chalk and Argillaceous Sandstones Assessed from T1/T2 Ratio

    DEFF Research Database (Denmark)

    Katika, Konstantina; Saidian, M.; Fabricius, Ida Lykke

    ratio can quantify the affinity between the rock and wetting pore fluid. The affinity is a measure directly linked to wettability. In order to investigate the T2-shortening, we performed T1-T2 NMR experiments on different samples of chalk, Berea sandstone, and chloritic greensand, saturated either...... with water, oil or oil/water at irreducible water saturation. The T1/T2 ratio obtained from T1-T2 maps reflects the T2-shortening. We compare the T1/T2 ratio for the same type of rock, saturated with different fluids. The chalk shows high affinity for water, Berea sandstone has no clear preference for oil...

  17. [Results of conservative surgery in T1 breast carcinoma. Our experience in 66 treated cases].

    Science.gov (United States)

    Barillari, P; Leuzzi, R; Nardi, M; Cerasi, A; Calcaterra, D; Cesareo, S; Brandimarte, A; Manetti, G; Bovino, A; Sammartino, P

    1994-11-01

    Between 1989 and 1991, 66 women affected by breast cancer smaller than 2 cm in diameter, were treated with conservative procedure plus radiotherapy. Conservative procedure consisted in quadrantectomy and axillary dissection of the 3 axillary nodes levels. Neoplasms were grouped according to TNM classification. Eleven were classified as Tis, 9 as T1aN0M0, 12 as T1bN0M0, one case T1bN1M0, 24 as T1cN0M0 and finally 9 as T1cN1M0. Actuarial 5-year survival rate was related to TNM. It has been reported to be 100% in Tis and T1aN0M0 neoplasms; 91.7% in pT1bN0M0 tumors, 95.8% in pT1cN0M0 neoplasms, 55.6% in patients affected with pT1cN1M0 tumors. According to the relationship between receptor status of the neoplasm and survival, this was 88.9% in ER+ and 77.8% in ER- tumors, and 97.1% against 71.4% (p < 0.05) in PR+ and PR- neoplasms respectively. Two patients presented (3%) local recurrence which were treated by means of a tumorectomy and radiotherapy. Both patients are still living and disease free after 6 and 9 months from re-operation.

  18. T1 bright appendix sign to exclude acute appendicitis in pregnant women.

    Science.gov (United States)

    Shin, Ilah; An, Chansik; Lim, Joon Seok; Kim, Myeong-Jin; Chung, Yong Eun

    2017-08-01

    To evaluate the diagnostic value of the T1 bright appendix sign for the diagnosis of acute appendicitis in pregnant women. This retrospective study included 125 pregnant women with suspected appendicitis who underwent magnetic resonance (MR) imaging. The T1 bright appendix sign was defined as a high intensity signal filling more than half length of the appendix on T1-weighted imaging. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the T1 bright appendix sign for normal appendix identification were calculated in all patients and in those with borderline-sized appendices (6-7 mm). The T1 bright appendix sign was seen in 51% of patients with normal appendices, but only in 4.5% of patients with acute appendicitis. The overall sensitivity, specificity, PPV, and NPV of the T1 bright appendix sign for normal appendix diagnosis were 44.9%, 95.5%, 97.6%, and 30.0%, respectively. All four patients with borderline sized appendix with appendicitis showed negative T1 bright appendix sign. The T1 bright appendix sign is a specific finding for the diagnosis of a normal appendix in pregnant women with suspected acute appendicitis. • Magnetic resonance imaging is increasingly used in emergency settings. • Acute appendicitis is the most common cause of acute abdomen. • Magnetic resonance imaging is widely used in pregnant population. • T1 bright appendix sign can be a specific sign representing normal appendix.

  19. Effects of Cluster Porosity on the Tensile Properties of Butt-Weldments in T-1 Steel

    Science.gov (United States)

    1974-11-01

    measured both in terms ol the actual total area ol pores and the area ol ihe clustei (including metal ligaments, or webs , that connect pores...8217hat a nearly linear con elation exists between the J integral value at maximum load. JM=J<^max,> aml tne Product °im max < Wix - Hcrt’ <W\\ is the

  20. Dependence of Brownian and Néel relaxation times on magnetic field strength

    International Nuclear Information System (INIS)

    Deissler, Robert J.; Wu, Yong; Martens, Michael A.

    2014-01-01

    Purpose: In magnetic particle imaging (MPI) and magnetic particle spectroscopy (MPS) the relaxation time of the magnetization in response to externally applied magnetic fields is determined by the Brownian and Néel relaxation mechanisms. Here the authors investigate the dependence of the relaxation times on the magnetic field strength and the implications for MPI and MPS. Methods: The Fokker–Planck equation with Brownian relaxation and the Fokker–Planck equation with Néel relaxation are solved numerically for a time-varying externally applied magnetic field, including a step-function, a sinusoidally varying, and a linearly ramped magnetic field. For magnetic fields that are applied as a step function, an eigenvalue approach is used to directly calculate both the Brownian and Néel relaxation times for a range of magnetic field strengths. For Néel relaxation, the eigenvalue calculations are compared to Brown's high-barrier approximation formula. Results: The relaxation times due to the Brownian or Néel mechanisms depend on the magnitude of the applied magnetic field. In particular, the Néel relaxation time is sensitive to the magnetic field strength, and varies by many orders of magnitude for nanoparticle properties and magnetic field strengths relevant for MPI and MPS. Therefore, the well-known zero-field relaxation times underestimate the actual relaxation times and, in particular, can underestimate the Néel relaxation time by many orders of magnitude. When only Néel relaxation is present—if the particles are embedded in a solid for instance—the authors found that there can be a strong magnetization response to a sinusoidal driving field, even if the period is much less than the zero-field relaxation time. For a ferrofluid in which both Brownian and Néel relaxation are present, only one relaxation mechanism may dominate depending on the magnetic field strength, the driving frequency (or ramp time), and the phase of the magnetization relative to the

  1. Thermally induced magnetic relaxation in square artificial spin ice

    Science.gov (United States)

    Andersson, M. S.; Pappas, S. D.; Stopfel, H.; Östman, E.; Stein, A.; Nordblad, P.; Mathieu, R.; Hjörvarsson, B.; Kapaklis, V.

    2016-11-01

    The properties of natural and artificial assemblies of interacting elements, ranging from Quarks to Galaxies, are at the heart of Physics. The collective response and dynamics of such assemblies are dictated by the intrinsic dynamical properties of the building blocks, the nature of their interactions and topological constraints. Here we report on the relaxation dynamics of the magnetization of artificial assemblies of mesoscopic spins. In our model nano-magnetic system - square artificial spin ice - we are able to control the geometrical arrangement and interaction strength between the magnetically interacting building blocks by means of nano-lithography. Using time resolved magnetometry we show that the relaxation process can be described using the Kohlrausch law and that the extracted temperature dependent relaxation times of the assemblies follow the Vogel-Fulcher law. The results provide insight into the relaxation dynamics of mesoscopic nano-magnetic model systems, with adjustable energy and time scales, and demonstrates that these can serve as an ideal playground for the studies of collective dynamics and relaxations.

  2. Universal binding energy relation for cleaved and structurally relaxed surfaces

    International Nuclear Information System (INIS)

    Srirangarajan, Aarti; Datta, Aditi; Gandi, Appala Naidu; Ramamurty, U; Waghmare, U V

    2014-01-01

    The universal binding energy relation (UBER), derived earlier to describe the cohesion between two rigid atomic planes, does not accurately capture the cohesive properties when the cleaved surfaces are allowed to relax. We suggest a modified functional form of UBER that is analytical and at the same time accurately models the properties of surfaces relaxed during cleavage. We demonstrate the generality as well as the validity of this modified UBER through first-principles density functional theory calculations of cleavage in a number of crystal systems. Our results show that the total energies of all the relaxed surfaces lie on a single (universal) energy surface, that is given by the proposed functional form which contains an additional length-scale associated with structural relaxation. This functional form could be used in modelling the cohesive zones in crack growth simulation studies. We find that the cohesive law (stress–displacement relation) differs significantly in the case where cracked surfaces are allowed to relax, with lower peak stresses occurring at higher displacements. (paper)

  3. Universal binding energy relation for cleaved and structurally relaxed surfaces.

    Science.gov (United States)

    Srirangarajan, Aarti; Datta, Aditi; Gandi, Appala Naidu; Ramamurty, U; Waghmare, U V

    2014-02-05

    The universal binding energy relation (UBER), derived earlier to describe the cohesion between two rigid atomic planes, does not accurately capture the cohesive properties when the cleaved surfaces are allowed to relax. We suggest a modified functional form of UBER that is analytical and at the same time accurately models the properties of surfaces relaxed during cleavage. We demonstrate the generality as well as the validity of this modified UBER through first-principles density functional theory calculations of cleavage in a number of crystal systems. Our results show that the total energies of all the relaxed surfaces lie on a single (universal) energy surface, that is given by the proposed functional form which contains an additional length-scale associated with structural relaxation. This functional form could be used in modelling the cohesive zones in crack growth simulation studies. We find that the cohesive law (stress-displacement relation) differs significantly in the case where cracked surfaces are allowed to relax, with lower peak stresses occurring at higher displacements.

  4. 31-P Relaxation times of metabolic compounds in tumors grafted in nude mice

    International Nuclear Information System (INIS)

    Remy, C.; Benabid, A.L.; Jacrot, M.; Riondel, J.; Albrand, J.P.; Decorps, M.

    1985-08-01

    The observation that water proton relaxation rates were longer in tumors than in normal tissues provided a basis for the detection of human tumors by the NMR imaging technique. To evaluate the potentiality of 31-P NMR spectroscopy as a diagnostic tool of the pathological state of tissues, T1 and T2 relaxation times have been measured for the phosphates of ATP, inorganic phosphate (Pi), phosphomonoesters (PME) and phosphocreatine (PCr) in the 31-P NMR spectra obtained in vivo for normal rat brain and rat brain tumors implanted in nude mice

  5. Relaxation time measurements of white and grey matter in multiple sclerosis patients

    International Nuclear Information System (INIS)

    Rinck, P.A.; Appel, B.; Moens, E.; Academisch Ziekenhuis Middelheim, Antwerp

    1987-01-01

    In a patient population of some 450 with definite, probable, and possible multiple sclerosis referred to us for MRI, some 40 suffering from definite MS were chosen randomly for relaxation time measurements of plaque-free grey and white matter. T 1 values could not be used for diagnostic purposes owing to their broad standard deviation. Overall white matter T 2 was slightly higher in MS patients than in a non-MS population (94 ms versus 89 ms). Because these changes are not visible in MR images, relaxation time measurements may prove valuable for differential diagnosis. (orig.) [de

  6. Analysis of the backbone dynamics of capsicein using 15N NMR relaxation rate measurements

    International Nuclear Information System (INIS)

    Van Heijenoort, C.; Bouaziz, S.; Guittet, E.

    1994-01-01

    15 N relaxation times T 1 and T 1ρ , and heteronuclear steady state nOes, were measured on capsicein, a 98 residue protein. The classical analysis of these data using directly the Lipari and Szabo formalism was shown to give incoherent results, probably due to the presence of a slow exchange along the whole protein. This global exchange broadening made the usual preliminary evaluation of the overall correlation time of capsicein using the Lipari and Szabo expression for the spectral densities impossible. (authors). 2 figs., 23 refs

  7. Hydrogen-1 NMR relaxation time studies in membrane: anesthetic systems

    International Nuclear Information System (INIS)

    Pinto, L.M.A.; Fraceto, L.; Paula, E. de; Franzoni, L.; Spisni, A.

    1997-01-01

    The study of local anesthetics'(LA) interaction with model phospholipid membranes is justified by the direct correlation between anesthetic's hydrophobicity and its potency/toxicity. By the same reason, uncharged LA species seems to play a crucial role in anesthesia. Most clinically used LA are small amphiphilics with a protonated amine group (pKa around 8). Although both charged (protonated) and uncharged forms can coexist at physiological pH, it has been shown (Lee, Biochim. Biophys. Acta 514:95, 1978; Screier et al. Biochim. Biophys. Acta 769:231, 1984) that the real anesthetic pka can be down-shifted, due to differential partition into membranes, increasing the ratio of uncharged species at pH 7.4. We have measured 1 H-NMR longitudinal relaxation times (T 1 ) for phospholipid and three local anesthetics (tetracaine, lidocaine, benzocaine), in sonicated vesicles at a 3:1 molar ratio. All the LA protons have shown smaller T 1 in this system than in isotropic phases, reflecting LA immobilization caused by insertion in the membrane. T 1 values for the lipid protons in the presence of LA were analyzed, in an attempt to identify specific LA:lipid contact regions. (author)

  8. Onsager relaxation of toroidal plasmas

    International Nuclear Information System (INIS)

    Samain, A.; Nguyen, F.

    1997-01-01

    The slow relaxation of isolated toroidal plasmas towards their thermodynamical equilibrium is studied in an Onsager framework based on the entropy metric. The basic tool is a variational principle, equivalent to the kinetic equation, involving the profiles of density, temperature, electric potential, electric current. New minimization procedures are proposed to obtain entropy and entropy production rate functionals. (author)

  9. Anisotropic spin relaxation in graphene

    NARCIS (Netherlands)

    Tombros, N.; Tanabe, S.; Veligura, A.; Jozsa, C.; Popinciuc, M.; Jonkman, H. T.; van Wees, B. J.

    2008-01-01

    Spin relaxation in graphene is investigated in electrical graphene spin valve devices in the nonlocal geometry. Ferromagnetic electrodes with in-plane magnetizations inject spins parallel to the graphene layer. They are subject to Hanle spin precession under a magnetic field B applied perpendicular

  10. Stochastic and Chaotic Relaxation Oscillations

    NARCIS (Netherlands)

    Grasman, J.; Roerdink, J.B.T.M.

    1988-01-01

    For relaxation oscillators stochastic and chaotic dynamics are investigated. The effect of random perturbations upon the period is computed. For an extended system with additional state variables chaotic behavior can be expected. As an example, the Van der Pol oscillator is changed into a

  11. Tensions relaxation in Zircaloy-4

    International Nuclear Information System (INIS)

    Cuniberti, A.M.; Picasso, A.C.

    1990-01-01

    Traction and stress relaxation studies were performed on polycrystalline Zry-4 at room temperature. The effect of loading velocity on the plastic behaviour of the material is discussed, analysing log σ vs. log dε/dt at different deformation levels. The contribution introduced by the testing machine was taken into account in data evaluation. (Author). 7 refs., 3 figs., 3 tabs

  12. 1H NMR relaxometry and quadrupole relaxation enhancement as a sensitive probe of dynamical properties of solids—[C(NH2)3]3Bi2I9 as an example

    International Nuclear Information System (INIS)

    Florek-Wojciechowska, M.; Wojciechowski, M.; Brym, Sz.; Kruk, D.; Jakubas, R.

    2016-01-01

    1 H nuclear magnetic resonance relaxometry has been applied to reveal information on dynamics and structure of Gu 3 Bi 2 I 9 ([Gu = C(NH 2 ) 3 ] denotes guanidinium cation). The data have been analyzed in terms of a theory of quadrupole relaxation enhancement, which has been extended here by including effects associated with quadrupole ( 14 N) spin relaxation caused by a fast fluctuating component of the electric field gradient tensor. Two motional processes have been identified: a slow one occurring on a timescale of about 8 × 10 −6 s which has turned out to be (almost) temperature independent, and a fast process in the range of 10 −9 s. From the 1 H- 14 N relaxation contribution (that shows “quadrupole peaks”) the quadrupole parameters, which are a fingerprint of the arrangement of the anionic network, have been determined. It has been demonstrated that the magnitude of the quadrupole coupling considerably changes with temperature and the changes are not caused by phase transitions. At the same time, it has been shown that there is no evidence of abrupt changes in the cationic dynamics and the anionic substructure upon the phase transitions

  13. 1H NMR relaxometry and quadrupole relaxation enhancement as a sensitive probe of dynamical properties of solids—[C(NH2)3]3Bi2I9 as an example

    Science.gov (United States)

    Florek-Wojciechowska, M.; Wojciechowski, M.; Jakubas, R.; Brym, Sz.; Kruk, D.

    2016-02-01

    1H nuclear magnetic resonance relaxometry has been applied to reveal information on dynamics and structure of Gu3Bi2I9 ([Gu = C(NH2)3] denotes guanidinium cation). The data have been analyzed in terms of a theory of quadrupole relaxation enhancement, which has been extended here by including effects associated with quadrupole (14N) spin relaxation caused by a fast fluctuating component of the electric field gradient tensor. Two motional processes have been identified: a slow one occurring on a timescale of about 8 × 10-6 s which has turned out to be (almost) temperature independent, and a fast process in the range of 10-9 s. From the 1H-14N relaxation contribution (that shows "quadrupole peaks") the quadrupole parameters, which are a fingerprint of the arrangement of the anionic network, have been determined. It has been demonstrated that the magnitude of the quadrupole coupling considerably changes with temperature and the changes are not caused by phase transitions. At the same time, it has been shown that there is no evidence of abrupt changes in the cationic dynamics and the anionic substructure upon the phase transitions.

  14. Enhancement effects and relaxivities of gadolinium-DTPA at 1.5 versus 3 tesla. A phantom study

    International Nuclear Information System (INIS)

    Sasaki, Makoto; Shibata, Eri; Kanbara, Yoshiyuki; Ehara, Shigeru

    2005-01-01

    The purpose of this study was to investigate the difference in enhancement effects and relaxivities of the gadolinium chelate at 1.5 and 3 Tesla (T) and to elucidate the contribution of the high magnetic field to contrast enhancement in spin-echo (SE) and gradient-echo (GRE) images. Phantoms containing water with or without gadopentetate dimeglumine (Gd-DTPA) at different concentrations were scanned using 1.5T and 3T MRI scanners of the same manufacturer and under the same temperature conditions and scanning parameters. Relaxivities of gadolinium, R 1 and R 2 , were estimated from serial T 1 and T 2 values of the phantoms using linear regression. Contrast enhancement ratios in SE and GRE T 1 -weighted images were compared at 1.5 and 3T. The R 1 and R 2 of Gd-DTPA at 1.5 and 3T were 4.79 and 5.14, and 4.50 and 5.09, respectively. Although the relaxivities at 3T were slightly lower than those at 1.5T, the contrast enhancement ratio improved in both SE and GRE images as a result of T 1 prolongation of the water at 3T. The decrease in relaxivities of the Gd-DTPA at 3T appears to be so small that T 1 prolongation of the water improves contrast enhancement, suggesting a potential clinical advantage in administration of Gd-DTPA at high field strength. (author)

  15. Sleep, Stress & Relaxation: Rejuvenate Body & Mind

    Science.gov (United States)

    Sleep, Stress & Relaxation: Rejuvenate Body & Mind; Relieve Stress; best ways to relieve stress; best way to relieve stress; different ways to relieve stress; does smoking relieve stress; does tobacco relieve stress; how can I relieve stress; how can you relieve stress; how do I relieve stress; reduce stress; does smoking reduce stress; how can I reduce stress; how to reduce stress; reduce stress; reduce stress levels; reducing stress; smoking reduce stress; smoking reduces stress; stress reducing techniques; techniques to reduce stress; stress relief; best stress relief; natural stress relief; need stress relief; relief for stress; relief from stress; relief of stress; smoking and stress relief; smoking for stress relief; smoking stress relief; deal with stress; dealing with stress; dealing with anger; dealing with stress; different ways of dealing with stress; help dealing with stress; how to deal with anger; how to deal with stress; how to deal with stress when quitting smoking; stress management; free stress management; how can you manage stress; how do you manage stress; how to manage stress; manage stress; management of stress; management stress; managing stress; strategies for managing stress; coping with stress; cope with stress; copeing with stress; coping and stress; coping skills for stress; coping strategies for stress; coping strategies with stress; coping strategy for stress; coping with stress; coping with stress and anxiety; emotional health; emotional health; emotional health article; emotional health articles; deep relaxation; deep breathing relaxation techniques; deep muscle relaxation; deep relaxation; deep relaxation meditation; deep relaxation technique; deep relaxation techniques; meditation exercises; mindful exercises; mindful meditation exercises; online relaxation exercises; relaxation breathing exercises; relaxation exercise; relaxation exercises; stress relaxation; methods of relaxation for stress; relax stress; relax techniques stress

  16. Fat fraction bias correction using T1 estimates and flip angle mapping.

    Science.gov (United States)

    Yang, Issac Y; Cui, Yifan; Wiens, Curtis N; Wade, Trevor P; Friesen-Waldner, Lanette J; McKenzie, Charles A

    2014-01-01

    To develop a new method of reducing T1 bias in proton density fat fraction (PDFF) measured with iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL). PDFF maps reconstructed from high flip angle IDEAL measurements were simulated and acquired from phantoms and volunteer L4 vertebrae. T1 bias was corrected using a priori T1 values for water and fat, both with and without flip angle correction. Signal-to-noise ratio (SNR) maps were used to measure precision of the reconstructed PDFF maps. PDFF measurements acquired using small flip angles were then compared to both sets of corrected large flip angle measurements for accuracy and precision. Simulations show similar results in PDFF error between small flip angle measurements and corrected large flip angle measurements as long as T1 estimates were within one standard deviation from the true value. Compared to low flip angle measurements, phantom and in vivo measurements demonstrate better precision and accuracy in PDFF measurements if images were acquired at a high flip angle, with T1 bias corrected using T1 estimates and flip angle mapping. T1 bias correction of large flip angle acquisitions using estimated T1 values with flip angle mapping yields fat fraction measurements of similar accuracy and superior precision compared to low flip angle acquisitions. Copyright © 2013 Wiley Periodicals, Inc.

  17. T1 bright appendix sign to exclude acute appendicitis in pregnant women

    International Nuclear Information System (INIS)

    Shin, Ilah; An, Chansik; Lim, Joon Seok; Kim, Myeong-Jin; Chung, Yong Eun

    2017-01-01

    To evaluate the diagnostic value of the T1 bright appendix sign for the diagnosis of acute appendicitis in pregnant women. This retrospective study included 125 pregnant women with suspected appendicitis who underwent magnetic resonance (MR) imaging. The T1 bright appendix sign was defined as a high intensity signal filling more than half length of the appendix on T1-weighted imaging. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the T1 bright appendix sign for normal appendix identification were calculated in all patients and in those with borderline-sized appendices (6-7 mm). The T1 bright appendix sign was seen in 51% of patients with normal appendices, but only in 4.5% of patients with acute appendicitis. The overall sensitivity, specificity, PPV, and NPV of the T1 bright appendix sign for normal appendix diagnosis were 44.9%, 95.5%, 97.6%, and 30.0%, respectively. All four patients with borderline sized appendix with appendicitis showed negative T1 bright appendix sign. The T1 bright appendix sign is a specific finding for the diagnosis of a normal appendix in pregnant women with suspected acute appendicitis. (orig.)

  18. T1 bright appendix sign to exclude acute appendicitis in pregnant women

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Ilah; An, Chansik; Lim, Joon Seok; Kim, Myeong-Jin; Chung, Yong Eun [Yonsei University College of Medicine, Department of Radiology, Research Institute of Radiological Science, Severance Hospital, 50-1 Yonsei-ro, Seodaemun-gu, Seoul (Korea, Republic of)

    2017-08-15

    To evaluate the diagnostic value of the T1 bright appendix sign for the diagnosis of acute appendicitis in pregnant women. This retrospective study included 125 pregnant women with suspected appendicitis who underwent magnetic resonance (MR) imaging. The T1 bright appendix sign was defined as a high intensity signal filling more than half length of the appendix on T1-weighted imaging. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the T1 bright appendix sign for normal appendix identification were calculated in all patients and in those with borderline-sized appendices (6-7 mm). The T1 bright appendix sign was seen in 51% of patients with normal appendices, but only in 4.5% of patients with acute appendicitis. The overall sensitivity, specificity, PPV, and NPV of the T1 bright appendix sign for normal appendix diagnosis were 44.9%, 95.5%, 97.6%, and 30.0%, respectively. All four patients with borderline sized appendix with appendicitis showed negative T1 bright appendix sign. The T1 bright appendix sign is a specific finding for the diagnosis of a normal appendix in pregnant women with suspected acute appendicitis. (orig.)

  19. T1 and T2 Mapping in Cardiology: "Mapping the Obscure Object of Desire".

    Science.gov (United States)

    Mavrogeni, Sophie; Apostolou, Dimitris; Argyriou, Panayiotis; Velitsista, Stella; Papa, Lilika; Efentakis, Stelios; Vernardos, Evangelos; Kanoupaki, Mikela; Kanoupakis, George; Manginas, Athanassios

    The increasing use of cardiovascular magnetic resonance (CMR) is based on its capability to perform biventricular function assessment and tissue characterization without radiation and with high reproducibility. The use of late gadolinium enhancement (LGE) gave the potential of non-invasive biopsy for fibrosis quantification. However, LGE is unable to detect diffuse myocardial disease. Native T1 mapping and extracellular volume fraction (ECV) provide knowledge about pathologies affecting both the myocardium and interstitium that is otherwise difficult to identify. Changes of myocardial native T1 reflect cardiac diseases (acute coronary syndromes, infarction, myocarditis, and diffuse fibrosis, all with high T1) and systemic diseases such as cardiac amyloid (high T1), Anderson-Fabry disease (low T1), and siderosis (low T1). The ECV, an index generated by native and post-contrast T1 mapping, measures the cellular and extracellular interstitial matrix (ECM) compartments. This myocyte-ECM dichotomy has important implications for identifying specific therapeutic targets of great value for heart failure treatment. On the other hand, T2 mapping is superior compared with myocardial T1 and ECM for assessing the activity of myocarditis in recent-onset heart failure. Although these indices can significantly affect the clinical decision making, multicentre studies and a community-wide approach (including MRI vendors, funding, software, contrast agent manufacturers, and clinicians) are still missing. © 2017 S. Karger AG, Basel.

  20. Metastatic spinal tumor. Assessment with fat-saturation T1-weighted MR imaging

    International Nuclear Information System (INIS)

    Kasai, Toshifumi; Sugimura, Kazuro; Uchida, Nobue; Kawamitsu, Hideaki; Komatsu, Akio; Okui, Shouji; Kimino, Katsuji.

    1994-01-01

    The purpose of this study was to compare conventional T1-weighted imaging (T1-WI) and chemical shift fat-saturation T1-weighted imaging (fat-sat T1-WI) by a diagnosis of the bone metastases. Thirty-two patients (143 vertebrae) with non-neoplastic lesions (normal group) and 32 patients (82 vertebrae) with spinal metastases (metastatic group) were evaluated using both images. The signal intensity (SI) distribution of both groups regarding T1-WI provided various patterns, and the SI measurements were not significantly different between the two groups ; however, the metastases which were mixed, showed a low SI. Regarding fat-sat T1-WI, all non-neoplastic lesions had a low-intensity homogeneous appearance ; however, the metastases were mixed to a high SI. The SI measurement data of the metastatic group was significantly higher than that of the normal group. In conclusion, fat-sat T1-WI was useful for evaluating the vertebral metastases. When fat-sat T1-WI demonstrated a mixed to high SI in patients suspected of having vertebral metastasis, Gd-DTPA enhancement was thought to be the problem. (author)

  1. T1 ρ mapping for the evaluation of high intensity focused ultrasound tumor treatment

    NARCIS (Netherlands)

    Hectors, Stefanie J. C. G.; Moonen, Rik P. M.; Strijkers, Gustav J.; Nicolay, Klaas

    2015-01-01

    This study was aimed to assess the effects of High Intensity Focused Ultrasound (HIFU) thermal ablation on tumor T1ρ . In vivo T1ρ measurements of murine tumors at various spin-lock amplitudes (B1 = 0-2000 Hz) were performed before (n = 13), directly after (n = 13) and 3 days (n = 7) after HIFU

  2. Ultra-low q and reversed field pinch experiments in Extrap T1 with a resistive shell

    International Nuclear Information System (INIS)

    Brunsell, P.; Drake, J.R.; Mazur, S.; Nordlund, P.

    1991-02-01

    The Extrap T1 device is a high aspect ratio toroidal pinch with the dimensions R/a = 0.5 m/0.057 m. In the experiments described here, the stainless steel bellows vacuum vessels was surrounded by a resistive shell with a perpendicular field penetration time of 75 μs. The ULQ discharges, with toroidal currents in the range 20-50 kA and pulse lengths up to 2 ms, showed the typical step-wise decay of the plasma current. The current steps corresponded to transitions of the edge q-value across rational values 1/4, 1/3, 1/2, and 1. During a step through a rational q value, there was an increase in the fluctuation activity and a corresponding increase in the plasma resistance. As part of the ULQ studies, discharges with four poloidal field nulls were produced by applying an octupole magnetic field, thus demonstrating that it is possible to sustain ULQ equilibria with poloidal field x-points and a magnetic separatix. In another study, the transition from ULQ discharges to relaxed state discharges was investigated. When the initial bias toroidal field was reduced so that q was less than about 1/6, which corresponded to a pinch parameter of about 0.6, a change in the discharge character was observed. The loop voltage required to sustain a given current increased and stochastic fluctuations were seen. Toroidal flux was generated and relaxed state equilibira developed. For higher pinch parameter, in the range of 1.5 to 2.0, a reversed field pinch could be set up if the toroidal field power supply provided a reversed current in the coils. The plasma resistivity was again lower and the pulse lengths in the RFP mode were up to 1 ms, corresponding to over 10 shell penetration times. (au)

  3. Gradient-induced longitudinal relaxation of hyperpolarized noble gases in the fringe fields of superconducting magnets used for magnetic resonance.

    Science.gov (United States)

    Zheng, Wangzhi; Cleveland, Zackary I; Möller, Harald E; Driehuys, Bastiaan

    2011-02-01

    When hyperpolarized noble gases are brought into the bore of a superconducting magnet for magnetic resonance imaging (MRI) or spectroscopy studies, the gases must pass through substantial field gradients, which can cause rapid longitudinal relaxation. In this communication, we present a means of calculating this spatially dependent relaxation rate in the fringe field of typical magnets. We then compare these predictions to experimental measurements of (3)He relaxation at various positions near a medium-bore 2-T small animal MRI system. The calculated and measured relaxation rates on the central axis of the magnet agree well and show a maximum (3)He relaxation rate of 3.83×10(-3) s(-1) (T(1)=4.4 min) at a distance of 47 cm from the magnet isocenter. We also show that if this magnet were self-shielded, its minimum T(1) would drop to 1.2 min. In contrast, a typical self-shielded 1.5-T clinical MRI scanner will induce a minimum on-axis T(1) of 12 min. Additionally, we show that the cylindrically symmetric fields of these magnets enable gradient-induced relaxation to be calculated using only knowledge of the on-axis longitudinal field, which can either be measured directly or calculated from a simple field model. Thus, while most MRI magnets employ complex and proprietary current configurations, we show that their fringe fields and the resulting gradient-induced relaxation are well approximated by simple solenoid models. Finally, our modeling also demonstrates that relaxation rates can increase by nearly an order of magnitude at radial distances equivalent to the solenoid radius. Copyright © 2010 Elsevier Inc. All rights reserved.

  4. Superdomain dynamics in ferroelectric-ferroelastic films: Switching, jamming, and relaxation

    Science.gov (United States)

    Scott, J. F.; Hershkovitz, A.; Ivry, Y.; Lu, H.; Gruverman, A.; Gregg, J. M.

    2017-12-01

    Recent experimental work shows that ferroelectric switching can occur in large jumps in which ferroelastic superdomains switch together, rather than having the numerous smaller ferroelectric domains switch within them. In this sense, the superdomains play a role analogous to that of Abrikosov vortices in thin superconducting films under the Kosterlitz-Thouless framework, which control the dynamics more than individual Cooper pairs within them do. Here, we examine the dynamics of ferroelastic superdomains in ferroelastic ferroelectrics and their role in switching devices such as memories. Jamming of ferroelectric domains in thin films has revealed an unexpected time dependence of t-1/4 at long times (hours), but it is difficult to discriminate between power-law and exponential relaxation. Other aspects of this work, including spatial period doubling of domains, led to a description of ferroelastic domains as nonlinear processes in a viscoelastic medium, which produce folding and metastable kinetically limited states. This ¼ exponent is a surprising agreement with the well-known value of ¼ for coarsening dynamics in viscoelastic media. We try to establish a link between these two processes, hitherto considered unrelated, and with superdomains and domain bundles. We note also that high-Tc superconductors share many of the ferroelastic domain properties discussed here and that several new solar cell materials and metal-insulator transition systems are ferroelastic.

  5. Promoting effect of bile acids on neoplastic transformation of x-irradiated 10T1/2 cells

    International Nuclear Information System (INIS)

    Han, A.; Hill, C.K.

    1984-01-01

    Experimental studies have raised a concern about a role of bile acids in colo-rectal carcinogenesis. Studies in vivo suggest that bile acids may act as tumor promoters. Using 10T1/2 mouse cells as a model system, the authors explored the effects of cholic and cheno-deoxycholic acid on x-ray-induced neoplastic transformation in these cells. Addition of either cheno-deoxycholic acid or cholic acid to 10T1/2 cells, 24 hours after exposure to x-rays (50kv) increases significantly the frequencies of transformation. The compounds were present in the medium throughout the entire postirradiation refeeding period. At the concentrations used (0.5μg/ml), neither acid was cytotoxic and did not have any effect on cell survival. The enhancement of radiation-induced transformation seems to be greater in the presence of cholic acid, as compared to the effect of cheno-deoxycholic acid. Increase in transformation was relatively greater after low compared to high doses of radiation. The effect of bile acids on transformation of 10T1/2 cells is similar to that of a known tumor promoter TPA. The authors' observations support the conclusion that promotional effect of bile acids is not because of their specific effect on colonic epithelium, but rather due to their general properties as tumor promoters

  6. Measurement of myocardial native T1 in cardiovascular diseases and norm in 1291 subjects.

    Science.gov (United States)

    Liu, Joanna M; Liu, Alexander; Leal, Joana; McMillan, Fiona; Francis, Jane; Greiser, Andreas; Rider, Oliver J; Myerson, Saul; Neubauer, Stefan; Ferreira, Vanessa M; Piechnik, Stefan K

    2017-09-28

    Native T1-mapping provides quantitative myocardial tissue characterization for cardiovascular diseases (CVD), without the need for gadolinium. However, its translation into clinical practice is hindered by differences between techniques and the lack of established reference values. We provide typical myocardial T1-ranges for 18 commonly encountered CVDs using a single T1-mapping technique - Shortened Look-Locker Inversion Recovery (ShMOLLI), also used in the large UK Biobank and Hypertrophic Cardiomyopathy Registry study. We analyzed 1291 subjects who underwent CMR (1.5-Tesla, MAGNETOM-Avanto, Siemens Healthcare, Erlangen, Germany) between 2009 and 2016, who had a single CVD diagnosis, with mid-ventricular T1-map assessment. A region of interest (ROI) was placed on native T1-maps in the "most-affected myocardium", characterized by the presence of late gadolinium enhancement (LGE), or regional wall motion abnormalities (RWMA) on cines. Another ROI was placed in the "reference myocardium" as far as possible from LGE/RWMA, and in the septum if no focal abnormality was present. To further define normality, we included native T1 of healthy subjects from an existing dataset after sub-endocardial pixel-erosions. Native T1 of patients with normal CMR (938 ± 21 ms) was similar compared to healthy subjects (941 ± 23 ms). Across all patient groups (57 ± 19 yrs., 65% males), focally affected myocardium had significantly different T1 value compared to reference myocardium (all p Fabry disease (863 ± 23 ms) had the lowest native reference T1 (all p < 0.001). Future studies designed to detect the large T1 differences between affected and reference myocardium are estimated to require small sample-sizes (n < 50). However, studies designed to detect the small T1 differences between reference myocardium in CVDs and healthy controls can require several thousand of subjects. We provide typical T1-ranges for common clinical cardiac conditions in the largest cohort

  7. MR imaging of the stomach and relaxation measurement with intraluminal hyperpolarized 129Xenon gas

    International Nuclear Information System (INIS)

    Yanagawa, Yasuhiro; Kimura, Atsuomi; Fujiwara, Hideaki; Kinoshita, Yoshimasa; Hattori, Mineyuki; Hiraga, Takashi; Iida, Hidehiro

    2001-01-01

    Using laser optical pumping, the nuclear spin polarization of noble gases can be strongly enhanced. The purpose of this study was to make a simple apparatus that can provide hyperpolarized 129 Xe gas, which can then be used in an attempt to obtain magnetic resonance imaging (MRI). We would also like to study the relaxation behavior of hyperpolarized 129 Xe gas through the measurement of the relaxation time. First, we demonstrated that hyperpolarized 129 Xe gas can be applied to magnetic resonance imaging of the stomach, by using a rat as a model. This was performed under a 4.7 T magnet field using the following imaging parameters for the hyperpolarized 129 Xe gas: TR=50 ms, TE=15 ms, FOV=10 x 10 cm 2 , matrix size 64 x 64, THK=2.54 cm. By using these parameters, we were able to obtain a hyperpolarized image of the stomach in rats for the first time. Next, we measured the relaxation times of the hyperpolarized 129 Xe gas enclosed in cavities such as the stomach of rats as well as in phantoms created by glass and gelatin bulbs. The cavity size dependency of the relaxation time was analyzed on the basis of the kinetic theory of gases. This analysis showed a linear relationship between the relaxation rate (1/T 1 ) and a square inverse of the cavity diameter (1/d 2 ). From this relationship, the wall effect on the 129 Xe relaxation can be estimated in the novel parameter t 1 , wall . This shows drastic dependency on the material of the wall, suggesting a potential use of the relaxation experiment as a diagnostic tool for organ surfaces in the future. (author)

  8. Relationship Between T1 Slope and Cervical Alignment Following Multilevel Posterior Cervical Fusion Surgery: Impact of T1 Slope Minus Cervical Lordosis.

    Science.gov (United States)

    Hyun, Seung-Jae; Kim, Ki-Jeong; Jahng, Tae-Ahn; Kim, Hyun-Jib

    2016-04-01

    Retrospective study. To assess the relationship between sagittal alignment of the cervical spine and patient-reported health-related quality-of-life scores following multilevel posterior cervical fusion, and to explore whether an analogous relationship exists in the cervical spine using T1 slope minus C2-C7 lordosis (T1S-CL). A recent study demonstrated that, similar to the thoracolumbar spine, the severity of disability increases with sagittal malalignment following cervical reconstruction surgery. From 2007 to 2013, 38 consecutive patients underwent multilevel posterior cervical fusion for cervical stenosis, myelopathy, and deformities. Radiographic measurements included C0-C2 lordosis, C2-C7 lordosis, C2-C7 sagittal vertical axis (SVA), T1 slope, and T1S-CL. Pearson correlation coefficients were calculated between pairs of radiographic measures and health-related quality-of-life. C2-C7 SVA positively correlated with neck disability index (NDI) scores (r = 0.495). C2-C7 lordosis (P = 0.001) and T1S-CL (P = 0.002) changes correlated with NDI score changes after surgery. For significant correlations between C2-C7 SVA and NDI scores, regression models predicted a threshold C2-C7 SVA value of 50 mm, beyond which correlations were most significant. The T1S-CL also correlated positively with C2-C7 SVA and NDI scores (r = 0.871 and r = 0.470, respectively). Results of the regression analysis indicated that a C2-C7 SVA value of 50 mm corresponded to a T1S-CL value of 26.1°. This study showed that disability of the neck increased with cervical sagittal malalignment following surgical reconstruction and a greater T1S-CL mismatch was associated with a greater degree of cervical malalignment. Specifically, a mismatch greater than 26.1° corresponded to positive cervical sagittal malalignment, defined as C2-C7 SVA greater than 50 mm. 3.

  9. Ultralow-field and spin-locking relaxation dispersion in postmortem pig brain.

    Science.gov (United States)

    Dong, Hui; Hwang, Seong-Min; Wendland, Michael; You, Lixing; Clarke, John; Inglis, Ben

    2017-12-01

    To investigate tissue-specific differences, a quantitative comparison was made between relaxation dispersion in postmortem pig brain measured at ultralow fields (ULF) and spin locking at 7 tesla (T). The goal was to determine whether ULF-MRI has potential advantages for in vivo human brain imaging. Separate specimens of gray matter and white matter were investigated using an ULF-MRI system with superconducting quantum interference device (SQUID) signal detection to measure T1ULF at fields from 58.7 to 235.0 μT and using a commercial MRI scanner to measure T1ρ7T at spin-locking fields from 5.0 to 235.0 μT. At matched field strengths, T1ρ7T is 50 to 100% longer than T1ULF. Furthermore, dispersion in T1ULF is close to linear between 58.7 and 235 µT, whereas dispersion in T1ρ7T is highly nonlinear over the same range. A subtle elbow in the T1ULF dispersion at approximately 140 µT is tentatively attributed to the local dipolar field of macromolecules. It is suggested that different relaxation mechanisms dominate each method and that ULF-MRI has a fundamentally different sensitivity to the macromolecular structure of neural tissue. Ultralow-field MRI may offer distinct, quantitative advantages for human brain imaging, while simultaneously avoiding the severe heating limitation imposed on high-field spin locking. Magn Reson Med 78:2342-2351, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  10. SirT1 regulates energy metabolism and response to caloric restriction in mice.

    Directory of Open Access Journals (Sweden)

    Gino Boily

    Full Text Available The yeast sir2 gene and its orthologues in Drosophila and C. elegans have well-established roles in lifespan determination and response to caloric restriction. We have studied mice carrying two null alleles for SirT1, the mammalian orthologue of sir2, and found that these animals inefficiently utilize ingested food. These mice are hypermetabolic, contain inefficient liver mitochondria, and have elevated rates of lipid oxidation. When challenged with a 40% reduction in caloric intake, normal mice maintained their metabolic rate and increased their physical activity while the metabolic rate of SirT1-null mice dropped and their activity did not increase. Moreover, CR did not extend lifespan of SirT1-null mice. Thus, SirT1 is an important regulator of energy metabolism and, like its orthologues from simpler eukaryotes, the SirT1 protein appears to be required for a normal response to caloric restriction.

  11. Characterization of the transverse relaxation rates in lipid bilayers

    International Nuclear Information System (INIS)

    Watnick, P.I.; Dea, P.; Chan, S.I.

    1990-01-01

    The 2H NMR transverse relaxation rates of a deuterated phospholipid bilayer reflect slow motions in the bilayer membrane. A study of dimyristoyl lecithin specifically deuterated at several positions of the hydrocarbon chains indicates that these motions are cooperative and are confined to the hydrocarbon chains of the lipid bilayer. However, lipid head group interactions do play an important role in modulating the properties of the cooperative fluctuations of the hydrocarbon chains (director fluctuations), as evidenced by the effects of various lipid additives on the 2H NMR transverse relaxation rates of the dimyristoyl lecithin bilayer

  12. Methyl group rotation and nuclear relaxation at low temperatures

    International Nuclear Information System (INIS)

    Zweers, A.E.

    1976-01-01

    This thesis deals with the proton spin-lattice relaxation of some methyl group compounds at liquid helium temperatures. In these molecular crystals, an energy difference between the ground and first rotational state of the methyl group occurs, the so-called tunnelling splitting, which is of the order of a few degrees Kelvin. This means that the high temperature approximation is inappropriate for the description of the occupation densities of the two lowest rotational levels. A description of the properties of the methyl group in connection with relaxation

  13. Continuous monitoring of the zinc-phosphate acid-base cement setting reaction by proton nuclear magnetic relaxation

    International Nuclear Information System (INIS)

    Apih, T.; Lebar, A.; Pawlig, O.; Trettin, R.

    2001-01-01

    Proton nuclear magnetic relaxation is a well-established technique for continuous and non destructive monitoring of hydration of conventional Portland building cements. Here, we demonstrate the feasibility of nuclear magnetic resonance (NMR) monitoring of the setting reaction of zinc-phosphate acid-base dental cements, which harden in minutes as compared to days, as in the case of Portland cements. We compare the setting of cement powder (mainly, zinc oxide) prepared with clinically used aluminum-modified orthophosphoric acid solution with the setting of a model system where cement powder is mixed with pure orthophosphoric acid solution. In contrast to previously published NMR studies of setting Portland cements, where a decrease of spin-lattice relaxation time is attributed to enhanced relaxation at the growing internal surface, spin-lattice relaxation time T 1 increases during the set of clinically used zinc-phosphate cement. Comparison of these results with a detailed study of diffusion, viscosity, and magnetic-field dispersion of T 1 in pure and aluminum-modified orthophosphoric acid demonstrates that the increase of T 1 in the setting cement is connected with the increase of molecular mobility in the residual phosphoric acid solution. Although not taken into account so far, such effects may also significantly influence the relaxation times in setting Portland cements, particularly when admixtures with an effect on water viscosity are used. [copyright] 2001 American Institute of Physics

  14. Robust T1-weighted structural brain imaging and morphometry at 7T using MP2RAGE.

    Directory of Open Access Journals (Sweden)

    Kieran R O'Brien

    Full Text Available PURPOSE: To suppress the noise, by sacrificing some of the signal homogeneity for numerical stability, in uniform T1 weighted (T1w images obtained with the magnetization prepared 2 rapid gradient echoes sequence (MP2RAGE and to compare the clinical utility of these robust T1w images against the uniform T1w images. MATERIALS AND METHODS: 8 healthy subjects (29.0 ± 4.1 years; 6 Male, who provided written consent, underwent two scan sessions within a 24 hour period on a 7T head-only scanner. The uniform and robust T1w image volumes were calculated inline on the scanner. Two experienced radiologists qualitatively rated the images for: general image quality; 7T specific artefacts; and, local structure definition. Voxel-based and volume-based morphometry packages were used to compare the segmentation quality between the uniform and robust images. Statistical differences were evaluated by using a positive sided Wilcoxon rank test. RESULTS: The robust image suppresses background noise inside and outside the skull. The inhomogeneity introduced was ranked as mild. The robust image was significantly ranked higher than the uniform image for both observers (observer 1/2, p-value = 0.0006/0.0004. In particular, an improved delineation of the pituitary gland, cerebellar lobes was observed in the robust versus uniform T1w image. The reproducibility of the segmentation results between repeat scans improved (p-value = 0.0004 from an average volumetric difference across structures of ≈ 6.6% to ≈ 2.4% for the uniform image and robust T1w image respectively. CONCLUSIONS: The robust T1w image enables MP2RAGE to produce, clinically familiar T1w images, in addition to T1 maps, which can be readily used in uniform morphometry packages.

  15. Temperature dependence of relaxation times in proton components of fatty acids

    International Nuclear Information System (INIS)

    Kuroda, Kagayaki; Iwabuchi, Taku; Saito, Kensuke; Obara, Makoto; Honda, Masatoshi; Imai, Yutaka

    2011-01-01

    We examined the temperature dependence of relaxation times in proton components of fatty acids in various samples in vitro at 11 tesla as a standard calibration data for quantitative temperature imaging of fat. The spin-lattice relaxation time, T 1 , of both the methylene (CH 2 ) chain and terminal methyl (CH 3 ) was linearly related to temperature (r>0.98, P 2 signal for calibration and observed the signal with 18% of CH 3 to estimate temperature. These findings suggested that separating the fatty acid components would significantly improve accuracy in quantitative thermometry for fat. Use of the T 1 of CH 2 seems promising in terms of reliability and reproducibility in measuring temperature of fat. (author)

  16. Relaxation time of normal breast tissues. Changes with age and variations during the menstrual cycle

    International Nuclear Information System (INIS)

    Dean, K.I.; Majurin, M.L.; Komu, M.

    1994-01-01

    The influence of age on the relaxation times of normal breast parenchyma and its surrounding fatty tissue were evaluated, and the variations during a normal menstrual cycle were analyzed using an ultra low field 0.02 T imager. Thirty-nine healthy volunteers aged 21 to 59 years were examined to determine T1 and T2 relaxation times, and 8 of these volunteers were studied once weekly during one menstrual cycle. The only significant trend was an increase in the T2 of breast parenchyma with increasing age. During the menstrual cycle there was a slight but insignificant (p=0.10) increase in T1 of the breast parenchyma values during the latter half of the menstrual cycle, and a corresponding increase in T2 values between the 2nd and 3rd weeks of the menstrual cycle, which was significant. (orig.)

  17. Relaxation time of normal breast tissues. Changes with age and variations during the menstrual cycle

    Energy Technology Data Exchange (ETDEWEB)

    Dean, K.I. (University Central Hospital, Turku (Finland). Dept. of Diagnostic Radiology); Majurin, M.L. (University Central Hospital, Turku (Finland). Dept. of Diagnostic Radiology); Komu, M. (University Central Hospital, Turku (Finland). Dept. of Diagnostic Radiology)

    1994-05-01

    The influence of age on the relaxation times of normal breast parenchyma and its surrounding fatty tissue were evaluated, and the variations during a normal menstrual cycle were analyzed using an ultra low field 0.02 T imager. Thirty-nine healthy volunteers aged 21 to 59 years were examined to determine T1 and T2 relaxation times, and 8 of these volunteers were studied once weekly during one menstrual cycle. The only significant trend was an increase in the T2 of breast parenchyma with increasing age. During the menstrual cycle there was a slight but insignificant (p=0.10) increase in T1 of the breast parenchyma values during the latter half of the menstrual cycle, and a corresponding increase in T2 values between the 2nd and 3rd weeks of the menstrual cycle, which was significant. (orig.).

  18. Evaluation of relaxation time measurements by magnetic resonance imaging. A phantom study

    DEFF Research Database (Denmark)

    Kjaer, L; Thomsen, C; Henriksen, O

    1987-01-01

    Several circumstances may explain the great variation in reported proton T1 and T2 relaxation times usually seen. This study was designed to evaluate the accuracy of relaxation time measurements by magnetic resonance imaging (MRI) operating at 1.5 tesla. Using a phantom of nine boxes with different...... concentrations of CuSO4 and correlating the calculated T1 and T2 values with reference values obtained by two spectrometers (corrected to MRI-proton frequency = 64 MHz) we found a maximum deviation of about 10 per cent. Measurements performed on a large water phantom in order to evaluate the homogeneity...... in the imaging plane showed a variation of less than 10 per cent within 10 cm from the centre of the magnet in all three imaging planes. Changing the gradient field strength apparently had no influence on the T2 values recorded. Consequently diffusion processes seem without significance. It is concluded...

  19. Eu, Gd-Codoped Yttria Nanoprobes for Optical and T1-Weighted Magnetic Resonance Imaging

    Directory of Open Access Journals (Sweden)

    Timur Sh Atabaev

    2017-02-01

    Full Text Available Nanoprobes with multimodal functionality have attracted significant interest recently because of their potential applications in nanomedicine. This paper reports the successful development of lanthanide-doped Y2O3 nanoprobes for potential applications in optical and magnetic resonance (MR imaging. The morphology, structural, and optical properties of these nanoprobes were characterized by transmission electron microscope (TEM, field emission scanning electron microscope (FESEM, X-ray diffraction (XRD, energy-dispersive X-ray (EDX, and photoluminescence (PL. The cytotoxicity test showed that the prepared lanthanide-doped Y2O3 nanoprobes have good biocompatibility. The obvious contrast enhancement in the T1-weighted MR images suggested that these nanoprobes can be used as a positive contrast agent in MRI. In addition, the clear fluorescence images of the L-929 cells incubated with the nanoprobes highlight their potential for optical imaging. Overall, these results suggest that prepared lanthanide-doped Y2O3 nanoprobes can be used for simultaneous optical and MR imaging.

  20. Microencapsulation of Islets for the Treatment of Type 1 Diabetes Mellitus (T1D).

    Science.gov (United States)

    Calafiore, Riccardo; Basta, Giuseppe; Montanucci, Pia

    2017-01-01

    Microencapsulation technology, based on use of alginic acid biopolymers, has been devised many years ago. However, when intended for enveloping human islets for transplantation purposes, the method needs to be up-scaled and implemented with care being taken to comply with simple but important measures. It is almost indispensable to rely on an ultrapurified alginic polymers: in fact, any, even minimal, alginate contamination with endotoxins, pyrogens, and proteins could provoke the host's inflammatory reaction upon graft, with heavy adverse consequences on the capsules immunoprotective properties, hence on graft survival per se. Care should be taken in ensuring fabrication of reproducible microspheres, in terms not only of shape and size, but also consistency of the peripheral layers around the central alginate gel core, where the islets are immobilized. Once the product is well defined and stable, care should also be taken in accurately selecting patients with T1D that are candidate for encapsulated islet cell transplantation with no general immunosuppression. A series of pre- and post-intraperitoneal transplant metabolic, chemical, and immunological parameters are to be monitored, in conjunction with image analysis of the abdomen, in order to assess efficacy of the intervention according to well defined grading scale.

  1. Relaxed metrics and indistinguishability operators: the relationship

    Energy Technology Data Exchange (ETDEWEB)

    Martin, J.

    2017-07-01

    In 1982, the notion of indistinguishability operator was introduced by E. Trillas in order to fuzzify the crisp notion of equivalence relation (/cite{Trillas}). In the study of such a class of operators, an outstanding property must be pointed out. Concretely, there exists a duality relationship between indistinguishability operators and metrics. The aforesaid relationship was deeply studied by several authors that introduced a few techniques to generate metrics from indistinguishability operators and vice-versa (see, for instance, /cite{BaetsMesiar,BaetsMesiar2}). In the last years a new generalization of the metric notion has been introduced in the literature with the purpose of developing mathematical tools for quantitative models in Computer Science and Artificial Intelligence (/cite{BKMatthews,Ma}). The aforementioned generalized metrics are known as relaxed metrics. The main target of this talk is to present a study of the duality relationship between indistinguishability operators and relaxed metrics in such a way that the aforementioned classical techniques to generate both concepts, one from the other, can be extended to the new framework. (Author)

  2. Relaxation creep model of impending earthquake

    Energy Technology Data Exchange (ETDEWEB)

    Morgounov, V. A. [Russian Academy of Sciences, Institute of Physics of the Earth, Moscow (Russian Federation)

    2001-04-01

    The alternative view of the current status and perspective of seismic prediction studies is discussed. In the problem of the ascertainment of the uncertainty relation Cognoscibility-Unpredictability of Earthquakes, priorities of works on short-term earthquake prediction are defined due to the advantage that the final stage of nucleation of earthquake is characterized by a substantial activation of the process while its strain rate increases by the orders of magnitude and considerably increased signal-to-noise ratio. Based on the creep phenomenon under stress relaxation conditions, a model is proposed to explain different images of precursors of impending tectonic earthquakes. The onset of tertiary creep appears to correspond to the onset of instability and inevitably fails unless it unloaded. At this stage, the process acquires the self-regulating character to the greatest extent the property of irreversibility, one of the important components of prediction reliability. Data in situ suggest a principal possibility to diagnose the process of preparation by ground measurements of acoustic and electromagnetic emission in the rocks under constant strain in the condition of self-relaxed stress until the moment of fracture are discussed in context. It was obtained that electromagnetic emission precedes but does not accompany the phase of macrocrak development.

  3. Creep and stress relaxation behavior of two soft denture liners.

    Science.gov (United States)

    Salloum, Alaa'a M

    2014-03-01

    Numerous investigators stated the indications of soft denture lining materials; but no one determined the indications of these materials according to their chemical structure. The purpose of this investigation was to evaluate the viscoelastic properties of acrylic and silicon lining materials. This study investigated and compared viscoelastic properties of two resilient denture lining materials. Tested materials were laboratory processed; one of them was silicone-based liner product (Molloplast-B), and the other was plasticized acrylic resin (Vertex™ Soft). Twenty cylindrical specimens (10-20 mm in length, 11.55 mm in diameter) were fabricated in an aluminum mold from each material for creep and stress relaxation testing (the study of viscoelastic properties). Tests were performed by using the universal testing machine DY-34. Collected data were analyzed with t test statistics for statistically significant differences at the 95 % confidence level. There was a clear difference in creep and stress relaxation behavior between acrylic and silicone liners. Statistical study of Young's moduli illustrated that Vertex™ Soft was softer than Molloplast-B. On the other hand, the results explained that the recovery of silicone material was better than of acrylic one. The creep test revealed that the plasticized acrylic resin lining material exhibited considerable creep, whereas silicone-based liner exhibited elastic behavior. Besides, the stress relaxation test showed that relaxation of the plasticized acrylic resin material was bigger than of the silicone-based liner.

  4. Disagreement between splenic switch-off and myocardial T1-mapping after caffeine intake.

    Science.gov (United States)

    Kuijpers, Dirkjan; van Dijk, Randy; van Assen, Marly; Kaandorp, Theodorus A M; van Dijkman, Paul R M; Vliegenthart, Rozemarijn; van der Harst, Pim; Oudkerk, Matthijs

    2018-04-01

    Caffeine is an adenosine receptor antagonist and a possible cause of inadequate stress perfusion. Splenic switch-off (SSO) and splenic rest-stress T1-mapping have been proposed as indicators of stress adequacy during perfusion cardiac magnetic resonance (CMR). We compared myocardial rest-stress T1-mapping with SSO and splenic rest-stress T1-mapping in patients with and without recent coffee intake. We analyzed 344 consecutive patients suspected of myocardial ischemia with adenosine perfusion CMR. All 146 normal CMR studies with a normal T1-rest of the myocardium, used as standard of reference, were included and divided in two groups. 22 patients accidentally ingested coffee < 4 h before CMR, compared to control group of 124 patients without self-reported coffee intake. Two independent readers graded SSO visually. T1-reactivity (ΔT1) was defined as percentual difference in T1-rest and T1-stress. Follow-up data were extracted from electronic patients records. In patients with recent coffee intake SSO was identified in 96%, which showed no significant difference with SSO in controls (94%, p = 0.835), however event rates were significantly different (13.6 and 0.8%, respectively (p < 0.001), median FU 17 months). Myocardial ΔT1 in the coffee group (- 5.2%) was significantly lower compared to control (+ 4.0%, p < 0.001), in contrast to the splenic ΔT1 (- 3.7 and - 4.0%, p = 0.789). The splenic T1-mapping results failed to predict false negative results. SSO and splenic rest-stress T1-mapping are not reliable indicators of stress adequacy in patients with recent coffee intake. Therefore, the dark spleen sign does not indicate adequate myocardial stress in patients with recent caffeine intake. Myocardial rest-stress T1-mapping is an excellent indicator of stress adequacy during adenosine perfusion CMR.

  5. A suite of Mathematica notebooks for the analysis of protein main chain 15N NMR relaxation data

    International Nuclear Information System (INIS)

    Spyracopoulos, Leo

    2006-01-01

    A suite of Mathematica notebooks has been designed to ease the analysis of protein main chain 15 N NMR relaxation data collected at a single magnetic field strength. Individual notebooks were developed to perform the following tasks: nonlinear fitting of 15 N-T 1 and -T 2 relaxation decays to a two parameter exponential decay, calculation of the principal components of the inertia tensor from protein structural coordinates, nonlinear optimization of the principal components and orientation of the axially symmetric rotational diffusion tensor, model-free analysis of 15 N-T 1 , -T 2 , and { 1 H}- 15 N NOE data, and reduced spectral density analysis of the relaxation data. The principle features of the notebooks include use of a minimal number of input files, integrated notebook data management, ease of use, cross-platform compatibility, automatic visualization of results and generation of high-quality graphics, and output of analyses in text format

  6. The water proton spin-lattice relaxation times in virus-infected cells

    International Nuclear Information System (INIS)

    Valensin, G.; Gaggelli, E.; Tiezzi, E.; Valensin, P.E.; Bianchi Bandinelli, M.L.

    1979-01-01

    The water proton spin-lattice relaxation times in HEp-2 cell cultures were determined immediately after 1 h of polio-virus adsorption. The shortening of the water T 1 was closely related to the multiplicity of infection, allowing direct inspections of the virus-cell interaction since the first steps of the infectious cycle. Virus-induced structural and conformational changes of cell constituents were suggested to be detectable by NMR investigation of cell water. (Auth.)

  7. T(2) relaxation time of hyaline cartilage in presence of different gadolinium-based contrast agents.

    Science.gov (United States)

    Wiener, Edzard; Settles, Marcus; Diederichs, Gerd

    2010-01-01

    The transverse relaxation time, T(2), of native cartilage is used to quantify cartilage degradation. T(2) is frequently measured after contrast administration, assuming that the impact of gadolinium-based contrast agents on cartilage T(2) is negligible. To verify this assumption the depth-dependent variation of T(2) in the presence of gadopentetate dimeglumine, gadobenate dimeglumine and gadoteridol was investigated. Furthermore, the r(2)/r(1) relaxivity ratios were quantified in different cartilage layers to demonstrate differences between T(2) and T(1) relaxation effects. Transverse high-spatial-resolution T(1)- and T(2)-maps were simultaneously acquired on a 1.5 T MR scanner before and after contrast administration in nine bovine patellae using a turbo-mixed sequence. The r(2)/r(1) ratios were calculated for each contrast agent in cartilage. Profiles of T(1), T(2) and r(2)/r(1) across cartilage thickness were generated in the absence and presence of contrast agent. The mean values in different cartilage layers were compared for global variance using the Kruskal-Wallis test and pairwise using the Mann-Whitney U-test. T(2) of unenhanced cartilage was 98 +/- 5 ms at 1 mm and 65 +/- 4 ms at 3 mm depth. Eleven hours after contrast administration significant differences (p cartilage thickness were close to 1.0 (range 0.9-1.3). At 1.5 T, T(2) decreased significantly in the presence of contrast agents, more pronounced in superficial than in deep cartilage. The change in T(2) relaxation rate was similar to the change in T(1). Cartilage T(2) measurements after contrast administration will lead to systematic errors in the quantification of cartilage degradation. 2010 John Wiley & Sons, Ltd.

  8. Toward real-time temperature monitoring in fat and aqueous tissue during magnetic resonance-guided high-intensity focused ultrasound using a three-dimensional proton resonance frequency T1 method.

    Science.gov (United States)

    Diakite, Mahamadou; Odéen, Henrik; Todd, Nick; Payne, Allison; Parker, Dennis L

    2014-07-01

    To present a three-dimensional (3D) segmented echoplanar imaging (EPI) pulse sequence implementation that provides simultaneously the proton resonance frequency shift temperature of aqueous tissue and the longitudinal relaxation time (T1 ) of fat during thermal ablation. The hybrid sequence was implemented by combining a 3D segmented flyback EPI sequence, the extended two-point Dixon fat and water separation, and the double flip angle T1 mapping techniques. High-intensity focused ultrasound (HIFU) heating experiments were performed at three different acoustic powers on excised human breast fat embedded in ex vivo porcine muscle. Furthermore, T1 calibrations with temperature in four different excised breast fat samples were performed, yielding an estimate of the average and variation of dT1 /dT across subjects. The water only images were used to mask the complex original data before computing the proton resonance frequency shift. T1 values were calculated from the fat-only images. The relative temperature coefficients were found in five fat tissue samples from different patients and ranged from 1.2% to 2.6%/°C. The results demonstrate the capability of real-time simultaneous temperature mapping in aqueous tissue and T1 mapping in fat during HIFU ablation, providing a potential tool for treatment monitoring in organs with large fat content, such as the breast. Copyright © 2013 Wiley Periodicals, Inc.

  9. Dielectric relaxation of glass particles with conductive nano-coatings

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, Shahid [Applied Technologies Department, QinetiQ Limited, Cody Technology Park, Farnborough, Hampshire, GU14 0LX (United Kingdom)

    2009-03-21

    This research focuses on the dielectric properties of particles consisting of glass cores with nanometre conductive coatings. The effects of the core glass particle shape (sphere, flake and fibre) and size are investigated for different coating characteristics over the frequency range 0.5-18 GHz. Experimental results for the coated glass particle combinations show the existence of a dielectric loss peak. This feature is associated with interfacial relaxation between the insulating core glass particle and the nanoscale conductive coating. The relaxation mechanism provides enhanced loss that is not observed in conventional solid metal particle composites. The results are fitted to a model, which shows that the relaxation frequency increases with increasing coating conductivity and thickness, with additional parameters identified for further particle optimizations.

  10. Efficient relaxed-Jacobi smoothers for multigrid on parallel computers

    Science.gov (United States)

    Yang, Xiang; Mittal, Rajat

    2017-03-01

    In this Technical Note, we present a family of Jacobi-based multigrid smoothers suitable for the solution of discretized elliptic equations. These smoothers are based on the idea of scheduled-relaxation Jacobi proposed recently by Yang & Mittal (2014) [18] and employ two or three successive relaxed Jacobi iterations with relaxation factors derived so as to maximize the smoothing property of these iterations. The performance of these new smoothers measured in terms of convergence acceleration and computational workload, is assessed for multi-domain implementations typical of parallelized solvers, and compared to the lexicographic point Gauss-Seidel smoother. The tests include the geometric multigrid method on structured grids as well as the algebraic grid method on unstructured grids. The tests demonstrate that unlike Gauss-Seidel, the convergence of these Jacobi-based smoothers is unaffected by domain decomposition, and furthermore, they outperform the lexicographic Gauss-Seidel by factors that increase with domain partition count.

  11. Relaxation Techniques to Manage IBS Symptoms

    Science.gov (United States)

    ... for 15–20 seconds and then begin again. Progressive Muscle Relaxation This method of relaxation focuses on ... helpful, please consider supporting IFFGD with a small tax- deductible donation. Make Donation Adapted from IFFGD Publication # ...

  12. Relaxation and Distraction in Experimental Desensitization.

    Science.gov (United States)

    Weir, R. O.; Marshall, W. L.

    1980-01-01

    Compared experimental desensitization with a procedure that replaced relaxation with a distraction task and with an approach that combined both relaxation and distraction. Desensitization generally was more effective than the other two procedures. (Author)

  13. Relaxation as a Factor in Semantic Desensitization

    Science.gov (United States)

    Bechtel, James E.; McNamara, J. Regis

    1975-01-01

    Relaxation and semantic desensitization were used to alleviate the fear of phobic females. Results showed that semantic desensitization, alone or in combination with relaxation, failed to modify the evaluative meanings evoked by the feared object. (SE)

  14. Plasmon-mediated energy relaxation in graphene

    Energy Technology Data Exchange (ETDEWEB)

    Ferry, D. K. [School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287-5706 (United States); Somphonsane, R. [Department of Physics, King Mongkut' s Institute of Technology, Ladkrabang, Bangkok 10520 (Thailand); Ramamoorthy, H.; Bird, J. P. [Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260-1500 (United States)

    2015-12-28

    Energy relaxation of hot carriers in graphene is studied at low temperatures, where the loss rate may differ significantly from that predicted for electron-phonon interactions. We show here that plasmons, important in the relaxation of energetic carriers in bulk semiconductors, can also provide a pathway for energy relaxation in transport experiments in graphene. We obtain a total loss rate to plasmons that results in energy relaxation times whose dependence on temperature and density closely matches that found experimentally.

  15. F19 relaxation in non-magnetic hexafluorides

    International Nuclear Information System (INIS)

    Rigny, P.

    1969-01-01

    The interesting properties of the fluorine magnetic resonance in the hexafluorides of molybdenum, tungsten and uranium, are very much due to large anisotropies of the chemical shift tensors. In the solid phases these anisotropies, the values of which are deduced from line shape studies, allow one to show that the molecules undergo hindered rotations about the metal atom. The temperature and frequency dependence of the fluorine longitudinal relaxation times shows that the relaxation is due to the molecular motion. The dynamical parameters of this motion are then deduced from the complete study of the fluorine relaxation in the rotating frame. In the liquid phases, the existence of anisotropies allows an estimation of the different contributions to the relaxation. In particular, the frequency and temperature dependence of the relaxation shows it to be dominated by the spin-rotation interaction. We have shown that the strength of this interaction can be deduced from the chemical shifts, and the angle through which the molecule rotates quasi-freely can be determined. In the hexafluorides, this angle is roughly one radian at 70 C, and with the help of this value, the friction coefficients which describe the intermolecular interactions are discussed. (author) [fr

  16. Assessment of acute kidney injury with T1 mapping MRI following solid organ transplantation

    Energy Technology Data Exchange (ETDEWEB)

    Peperhove, Matti; Vo Chieu, Van Dai; Gutberlet, Marcel; Hartung, Dagmar; Tewes, Susanne; Wacker, Frank; Hueper, Katja [Hannover Medical School, Diagnostic and Interventional Radiology, Hannover (Germany); Jang, Mi-Sun; Gwinner, Wilfried; Haller, Hermann; Gueler, Faikah [Nephrology, Hannover Medical School, Hannover (Germany); Warnecke, Gregor; Fegbeutel, Christiane; Haverich, Axel [Hannover Medical School, Cardiothoracic, Transplantation and Vascular Surgery, Hannover (Germany); Lehner, Frank [Hannover Medical School, General, Abdominal and Transplant Surgery, Hannover (Germany); Braesen, Jan Hinrich [Pathology, Hannover Medical School, Hannover (Germany)

    2018-01-15

    To evaluate T1 mapping as a non-invasive, functional MRI biomarker in patients shortly after solid organ transplantation to detect acute postsurgical kidney damage and to correlate T1 times with renal function. 101 patients within 2 weeks after solid organ transplantation (49 kidney transplantation, 52 lung transplantation) and 14 healthy volunteers were examined by MRI between July 2012 and April 2015 using the modified Look-Locker inversion recovery (MOLLI) sequence. T1 times in renal cortex and medulla and the corticomedullary difference were compared between groups using one-way ANOVA adjusted for multiple comparison with the Tukey test, and T1 times were correlated with renal function using Pearson's correlation. Compared to healthy volunteers T1 times were significantly increased after solid organ transplantation in the renal cortex (healthy volunteers 987 ± 102 ms; kidney transplantation 1299 ± 101 ms, p < 0.001; lung transplantation 1058 ± 96 ms, p < 0.05) and to a lesser extent in the renal medulla. Accordingly, the corticomedullary difference was diminished shortly after solid organ transplantation. T1 changes were more pronounced following kidney compared to lung transplantation, were associated with the stage of renal impairment and significantly correlated with renal function. T1 mapping may be helpful for early non-invasive assessment of acute kidney injury and renal pathology following major surgery such as solid organ transplantation. (orig.)

  17. Lumbosacral lipoma : gadolinium-enhanced fat saturation T1 weighted MR image is necessary?

    International Nuclear Information System (INIS)

    Yoon, Man Won; Kim, Hyun Chul; Chung, Tae Woong; Seo, Jeong Jin; Chung, Gwang Woo; Kim, Yun Hyeon; Kim, Jae Kyu; Park, Jin Gyoon; Kang, Heoung Keun

    1999-01-01

    To evaluate the usefulness of contrast-enhanced fat saturation T1-weighted imaging for the evaluation of spinal lipoma, compared with clinical symptoms and surgical findings. Ten patients with lipomyelomeningocele, confirmed by surgery, were included in this study. In all cases, conventional spin echo T1-and T2-weighted MR imaging, and contrast-enhanced fat saturation T1-weighted imaging was performed to evaluate clinical symptoms, the position of the conus medullaris, the presence of cord tethering, and associated anomalies, and to compare the relative usefulness of the techniques. All ten patients were suffering from lipomyelomeningocele without filum terminale fibrolipoma or intradural lipoma. All cases were associated with cord tethering. As associated anomalies, there were seven cases of syringomyelia without hydrocephalus or anorectal anomaly. To evaluate the position of the spinal conus and the presence of cord tethering, conventional T1-weighted imaging was more useful than the contrast-enhanced fat saturation equivalent. In patients with early-stage spinal lipoma, MRI is useful for evaluation of the causes and position of cord tethering and associated anomalies Our results suggest that contrast-enhanced fat saturation T1-weighted images do not provide additional information concerning spinal lipoma, and that for the diagnosis of this condition, conventional T1 and T2-weighted images are more useful than those obtained by contrast-enhanced fat saturation T1-weighted imaging

  18. NMR images and in vivo T1 values associated with cerebrovascular diseases

    International Nuclear Information System (INIS)

    Furuse, Kazuhiro; Sao, Katsuyoshi; Inao, Motohide; Motegi, Yoshimasa; Kimura, Hiroaki; Kasai, Akira.

    1983-01-01

    NMR images and T 1 values, which were obtained by a Fonar QED 80-α system, were investigated in patients with cerebrovascular disease. In patients with intracerebral hemorrhage, hematoma was seen as high density area on steady state free precession images, and the extension of hematoma and its surrounding edema was also visualized frequently at the onset. T 1 values are generally high in the area of edema. T 1 values and their changes are thus considered useful in selecting the method of treatment. In patients with cerebral infarction, lesions were seen as high density areas. This was noted in serious cases, i.e., the areas corresponding to low density areas on CT were visualized as high density areas on NMR imaging. T 1 values were high especially in the center part of the infarct area, and tended to be prolonged with time. Prolongation of T 1 during the chronic stage seems to provide information concerning degeneration of tissues. Local T 1 values, as well as image findings, have a great significance for the clinical application of NMR technique. Sequential observations of T 1 values seem to make a large contribution to the pathological elucidation. (Namekawa, K.)

  19. Assessment of acute kidney injury with T1 mapping MRI following solid organ transplantation

    International Nuclear Information System (INIS)

    Peperhove, Matti; Vo Chieu, Van Dai; Gutberlet, Marcel; Hartung, Dagmar; Tewes, Susanne; Wacker, Frank; Hueper, Katja; Jang, Mi-Sun; Gwinner, Wilfried; Haller, Hermann; Gueler, Faikah; Warnecke, Gregor; Fegbeutel, Christiane; Haverich, Axel; Lehner, Frank; Braesen, Jan Hinrich

    2018-01-01

    To evaluate T1 mapping as a non-invasive, functional MRI biomarker in patients shortly after solid organ transplantation to detect acute postsurgical kidney damage and to correlate T1 times with renal function. 101 patients within 2 weeks after solid organ transplantation (49 kidney transplantation, 52 lung transplantation) and 14 healthy volunteers were examined by MRI between July 2012 and April 2015 using the modified Look-Locker inversion recovery (MOLLI) sequence. T1 times in renal cortex and medulla and the corticomedullary difference were compared between groups using one-way ANOVA adjusted for multiple comparison with the Tukey test, and T1 times were correlated with renal function using Pearson's correlation. Compared to healthy volunteers T1 times were significantly increased after solid organ transplantation in the renal cortex (healthy volunteers 987 ± 102 ms; kidney transplantation 1299 ± 101 ms, p < 0.001; lung transplantation 1058 ± 96 ms, p < 0.05) and to a lesser extent in the renal medulla. Accordingly, the corticomedullary difference was diminished shortly after solid organ transplantation. T1 changes were more pronounced following kidney compared to lung transplantation, were associated with the stage of renal impairment and significantly correlated with renal function. T1 mapping may be helpful for early non-invasive assessment of acute kidney injury and renal pathology following major surgery such as solid organ transplantation. (orig.)

  20. The Effects of Suggestibility on Relaxation.

    Science.gov (United States)

    Rickard, Henry C.; And Others

    1985-01-01

    Selected undergraduates (N=32) on the basis of Creative Imagination Scale scores and randomly assigned high and low suggestibility subjects to progressive relaxation (PR) and suggestions of relaxation (SR) training modes. Results revealed a significant pre-post relaxation effect, and main efffects for both suggestibility and training mode. (NRB)

  1. Magnetic resonance imaging (MRI) and relaxation time mapping of concrete

    Science.gov (United States)

    Beyea, Steven Donald

    2001-07-01

    The use of Magnetic Resonance Imaging (MRI) of water in concrete is presented. This thesis will approach the problem of MR imaging of concrete by attempting to design new methods, suited to concrete materials, rather than attempting to force the material to suit the method. A number of techniques were developed, which allow the spatial observation of water in concrete in up to three dimensions, and permits the determination of space resolved moisture content, as well as local NMR relaxation times. These methods are all based on the Single-Point Imaging (SPI) method. The development of these new methods will be described, and the techniques validated using phantom studies. The study of one-dimensional moisture transport in drying concrete was performed using SPI. This work examined the effect of initial mixture proportions and hydration time on the drying behaviour of concrete, over a period of three months. Studies of drying concrete were also performed using spatial mapping of the spin-lattice (T1) and effective spin-spin (T2*) relaxation times, thereby permitting the observation of changes in the water occupied pore surface-to-volume ratio (S/V) as a function of drying. Results of this work demonstrated changes in the S/V due to drying, hydration and drying induced microcracking. Three-dimensional MRI of concrete was performed using SPRITE (Single-Point Ramped Imaging with T1 Enhancement) and turboSPI (turbo Single Point Imaging). While SPRITE allows for weighting of MR images using T 1 and T2*, turboSPI allows T2 weighting of the resulting images. Using relaxation weighting it was shown to be possible to discriminate between water contained within a hydrated cement matrix, and water in highly porous aggregates, used to produce low-density concrete. Three dimensional experiments performed using SPRITE and turboSPI examined the role of self-dessication, drying, initial aggregate saturation and initial mixture conditions on the transport of moisture between porous

  2. Arresting relaxation in Pickering Emulsions

    Science.gov (United States)

    Atherton, Tim; Burke, Chris

    2015-03-01

    Pickering emulsions consist of droplets of one fluid dispersed in a host fluid and stabilized by colloidal particles absorbed at the fluid-fluid interface. Everyday materials such as crude oil and food products like salad dressing are examples of these materials. Particles can stabilize non spherical droplet shapes in these emulsions through the following sequence: first, an isolated droplet is deformed, e.g. by an electric field, increasing the surface area above the equilibrium value; additional particles are then adsorbed to the interface reducing the surface tension. The droplet is then allowed to relax toward a sphere. If more particles were adsorbed than can be accommodated by the surface area of the spherical ground state, relaxation of the droplet is arrested at some non-spherical shape. Because the energetic cost of removing adsorbed colloids exceeds the interfacial driving force, these configurations can remain stable over long timescales. In this presentation, we present a computational study of the ordering present in anisotropic droplets produced through the mechanism of arrested relaxation and discuss the interplay between the geometry of the droplet, the dynamical process that produced it, and the structure of the defects observed.

  3. Vibrational relaxation in OCS mixtures

    International Nuclear Information System (INIS)

    Simpson, C.J.S.M.; Gait, P.D.; Simmie, J.M.

    1976-01-01

    Experimental measurements are reported of vibrational relaxation times which may be used to show whether there is near resonant vibration-rotation energy transfer between OCS and H 2 , D 2 or HD. Vibrational relaxation times have been measured in OCS and OCS mixtures over the temperature range 360 to 1000 K using a shock tube and a laser schlieren system. The effectiveness of the additives in reducing the relaxation time of OCS is in the order 4 He 3 He 2 2 and HD. Along this series the effect of an increase in temperature changes from the case of speeding up the rate with 4 He to retarding it with D 2 , HD and H 2 . There is no measurable difference in the effectiveness of n-D 2 and o-D 2 and little, or no, difference between n-H 2 and p-H 2 . Thus the experimental results do not give clear evidence for rotational-vibration energy transfer between hydrogen and OCS. This contrasts with the situation for CO 2 + H 2 mixtures. (author)

  4. Relaxed plasma-vacuum systems

    International Nuclear Information System (INIS)

    Spies, G.O.; Lortz, D.; Kaiser, R.

    2001-01-01

    Taylor's theory of relaxed toroidal plasmas (states of lowest energy with fixed total magnetic helicity) is extended to include a vacuum between the plasma and the wall. In the extended variational problem, one prescribes, in addition to the helicity and the magnetic fluxes whose conservation follows from the perfect conductivity of the wall, the fluxes whose conservation follows from the assumption that the plasma-vacuum interface is also perfectly conducting (if the wall is a magnetic surface, then one has the toroidal and the poloidal flux in the vacuum). Vanishing of the first energy variation implies a pressureless free-boundary magnetohydrostatic equilibrium with a Beltrami magnetic field in the plasma, and in general with a surface current in the interface. Positivity of the second variation implies that the equilibrium is stable according to ideal magnetohydrodynamics, that it is a relaxed state according to Taylor's theory if the interface is replaced by a wall, and that the surface current is nonzero (at least if there are no closed magnetic field lines in the interface). The plane slab, with suitable boundary conditions to simulate a genuine torus, is investigated in detail. The relaxed state has the same double symmetry as the vessel if, and only if, the prescribed helicity is in an interval that depends on the prescribed fluxes. This interval is determined in the limit of a thin slab

  5. Regularized Label Relaxation Linear Regression.

    Science.gov (United States)

    Fang, Xiaozhao; Xu, Yong; Li, Xuelong; Lai, Zhihui; Wong, Wai Keung; Fang, Bingwu

    2018-04-01

    Linear regression (LR) and some of its variants have been widely used for classification problems. Most of these methods assume that during the learning phase, the training samples can be exactly transformed into a strict binary label matrix, which has too little freedom to fit the labels adequately. To address this problem, in this paper, we propose a novel regularized label relaxation LR method, which has the following notable characteristics. First, the proposed method relaxes the strict binary label matrix into a slack variable matrix by introducing a nonnegative label relaxation matrix into LR, which provides more freedom to fit the labels and simultaneously enlarges the margins between different classes as much as possible. Second, the proposed method constructs the class compactness graph based on manifold learning and uses it as the regularization item to avoid the problem of overfitting. The class compactness graph is used to ensure that the samples sharing the same labels can be kept close after they are transformed. Two different algorithms, which are, respectively, based on -norm and -norm loss functions are devised. These two algorithms have compact closed-form solutions in each iteration so that they are easily implemented. Extensive experiments show that these two algorithms outperform the state-of-the-art algorithms in terms of the classification accuracy and running time.

  6. Real-time relaxation and kinetics in hot scalar QED: Landau damping

    International Nuclear Information System (INIS)

    Boyanovsky, D.; Vega, H.J. de; Holman, R.; Kumar, S.P.; Pisarski, R.D.

    1998-01-01

    The real time evolution of non-equilibrium expectation values with soft length scales ∼k -1 >(eT) -1 is solved in hot scalar electrodynamics, with a view towards understanding relaxational phenomena in the QGP and the electroweak plasma. We find that the gauge invariant non-equilibrium expectation values relax via power laws to asymptotic amplitudes that are determined by the quasiparticle poles. The long time relaxational dynamics and relevant time scales are determined by the behavior of the retarded self-energy not at the small frequencies, but at the Landau damping thresholds. This explains the presence of power laws and not of exponential decay. In the process we rederive the HTL effective action using non-equilibrium field theory. Furthermore we obtain the influence functional, the Langevin equation and the fluctuation-dissipation theorem for the soft modes, identifying the correlators that emerge in the classical limit. We show that a Markovian approximation fails to describe the dynamics both at short and long times. We find that the distribution function for soft quasiparticles relaxes with a power law through Landau damping. We also introduce a novel kinetic approach that goes beyond the standard Boltzmann equation by incorporating off-shell processes and find that the distribution function for soft quasiparticles relaxes with a power law through Landau damping. We find an unusual dressing dynamics of bare particles and anomalous (logarithmic) relaxation of hard quasiparticles. copyright 1998 The American Physical Society

  7. Multi-Phonon Relaxation of H^- Local Modes in CaF_2

    Science.gov (United States)

    Davison, C. P.; Happek, U.; Campbell, J. A.; Engholm, J. R.; Schwettman, H. A.

    1998-03-01

    Local modes play an important role in the relaxation of vibrational modes of small molecules in solids (J.R. Engholm, C.W. Rella, H.A. Schwettman, and U. Happek; Phys. Rev. Lett. 77), 1302 (1996)., but only few attempts have been reported to study the relaxation of these local modes. Here we report on experiments to investigate the non-radiative relaxation of H^- local modes in CaF_2. Using a pump-probe technique, saturation experiments on the H^- local modes, both interstitial and substitutional, were performed at the Stanford Free Electron Laser Center. At low temperature we find a relaxation time T1 of 45 psec for the substitutional H^- local mode, and a more rapid relaxation for the interstitial H^- local modes next to La^3+ and Lu^3+ impurities. Information on the decay channels of the local modes are obtained from the characteristic temperature dependence of the relaxation rates. This work is supported in part by the ONR, Grant No. N00014-94-1024.

  8. Methods of fast, multiple-point in vivo T1 determination

    International Nuclear Information System (INIS)

    Zhang, Y.; Spigarelli, M.; Fencil, L.E.; Yeung, H.N.

    1989-01-01

    Two methods of rapid, multiple-point determination of T1 in vivo have been evaluated with a phantom consisting of vials of gel in different Mn + + concentrations. The first method was an inversion-recovery- on-the-fly technique, and the second method used a variable- tip-angle (α) progressive saturation with two sub- sequences of different repetition times. In the first method, 1/T1 was evaluated by an exponential fit. In the second method, 1/T1 was obtained iteratively with a linear fit and then readjusted together with α to a model equation until self-consistency was reached

  9. Error reduction and parameter optimization of the TAPIR method for fast T1 mapping.

    Science.gov (United States)

    Zaitsev, M; Steinhoff, S; Shah, N J

    2003-06-01

    A methodology is presented for the reduction of both systematic and random errors in T(1) determination using TAPIR, a Look-Locker-based fast T(1) mapping technique. The relations between various sequence parameters were carefully investigated in order to develop recipes for choosing optimal sequence parameters. Theoretical predictions for the optimal flip angle were verified experimentally. Inversion pulse imperfections were identified as the main source of systematic errors in T(1) determination with TAPIR. An effective remedy is demonstrated which includes extension of the measurement protocol to include a special sequence for mapping the inversion efficiency itself. Copyright 2003 Wiley-Liss, Inc.

  10. 31P spin-lattice relaxation time measurements in biological systems

    International Nuclear Information System (INIS)

    Suzuki, Eiji; Maeda, Munehiro; Kuki, Satoru; Tsukamoto, Kenji; Kawakami, Tsuyoshi; Seo, Yoshiteru; Murakami, Masataka; Watari, Hiroshi

    1989-01-01

    Spin-lattice relaxation time (T 1 ) of phosphorus compounds in the perfused heart, liver, kidney and erythrocytes of rats were measured by the DESPOT (Driven-equilibrium single-pulse observation of T 1 ) method at 8.45 T. This method is a rapid and accurate technique for the measurement of T 1 values. T 1 values of phosphomonoesters (PME), 2, 3-diphosphoglycerate (DPG), inorganic phosphate (Pi), phosphodiesters (PDE), phosphocreatine (PCr) and three phosphates of ATP were ranged from 0.15±0.02 sec (β-ATP in the liver) to 8.5±1.6 sec (PDE in the kidney). T 1 value of β-ATP in the liver was 1/4-1/5 of those in the mandibular gland, heart, erythrocytes and kidney. T 1 values obtained from biological materials are useful for selecting the optimal pulse repetition times and pulse angles to maximize the signal-to-noise ratio of 13 P spectra, and for correcting distortions of signal intensities in the spectra. (author)

  11. Under which conditions does T1 difficulty affect T2 performance in the attentional blink?

    DEFF Research Database (Denmark)

    Nielsen, Simon; Petersen, Anders; Andersen, Tobias

    When two visual targets (T1 & T2) are presented in rapid succession, performance of T2 suffers up to 900 ms. One theory of this attentional blink (Raymond, Shapiro, & Arnell, 1992) propose that T1 and T2 compete for limited processing resources (Chun & Potter, 1995), and predict that prolonging...... processing time for T1 by increasing its perceptual difficulty will induce a larger blink. Several studies have tested this prediction without reaching a consistent answer. McLaughlin, Shore, & Klein (2001) found no effect of the exposure duration of T1 on the attentional blink. Christmann & Leuthold (2004...... duration. In the hard condition, T1 exposure duration was 10 ms while T1 contrast was adjusted individually to reach 50% correct T1 identification. In the long duration condition, T1 exposure duration was increased to reach approximately 90% correct T1 identification. In the high contrast condition, T1...

  12. Relaxations to Sparse Optimization Problems and Applications

    Science.gov (United States)

    Skau, Erik West

    Parsimony is a fundamental property that is applied to many characteristics in a variety of fields. Of particular interest are optimization problems that apply rank, dimensionality, or support in a parsimonious manner. In this thesis we study some optimization problems and their relaxations, and focus on properties and qualities of the solutions of these problems. The Gramian tensor decomposition problem attempts to decompose a symmetric tensor as a sum of rank one tensors.We approach the Gramian tensor decomposition problem with a relaxation to a semidefinite program. We study conditions which ensure that the solution of the relaxed semidefinite problem gives the minimal Gramian rank decomposition. Sparse representations with learned dictionaries are one of the leading image modeling techniques for image restoration. When learning these dictionaries from a set of training images, the sparsity parameter of the dictionary learning algorithm strongly influences the content of the dictionary atoms.We describe geometrically the content of trained dictionaries and how it changes with the sparsity parameter.We use statistical analysis to characterize how the different content is used in sparse representations. Finally, a method to control the structure of the dictionaries is demonstrated, allowing us to learn a dictionary which can later be tailored for specific applications. Variations of dictionary learning can be broadly applied to a variety of applications.We explore a pansharpening problem with a triple factorization variant of coupled dictionary learning. Another application of dictionary learning is computer vision. Computer vision relies heavily on object detection, which we explore with a hierarchical convolutional dictionary learning model. Data fusion of disparate modalities is a growing topic of interest.We do a case study to demonstrate the benefit of using social media data with satellite imagery to estimate hazard extents. In this case study analysis we

  13. Predicting the effect of relaxation during frequency-selective adiabatic pulses

    Science.gov (United States)

    Pfaff, Annalise R.; McKee, Cailyn E.; Woelk, Klaus

    2017-11-01

    Adiabatic half and full passages are invaluable for achieving uniform, B1-insensitive excitation or inversion of macroscopic magnetization across a well-defined range of NMR frequencies. To accomplish narrow frequency ranges with adiabatic pulses (computer-calculated data with experimental results demonstrates that, in non-viscous, small-molecule fluids, it is possible to model magnetization and relaxation by considering standard T1 and T2 relaxation in the traditional rotating frame. The proposed model is aimed at performance optimizations of applications in which these pulses are employed. It differs from previous reports which focused on short high-power adiabatic pulses and relaxation that is governed by dipole-dipole interactions, cross polarization, or chemical exchange.

  14. The time-dependence of exchange-induced relaxation during modulated radio frequency pulses.

    Science.gov (United States)

    Sorce, Dennis J; Michaeli, Shalom; Garwood, Michael

    2006-03-01

    The problem of the relaxation of identical spins 1/2 induced by chemical exchange between spins with different chemical shifts in the presence of time-dependent RF irradiation (in the first rotating frame) is considered for the fast exchange regime. The solution for the time evolution under the chemical exchange Hamiltonian in the tilted doubly rotating frame (TDRF) is presented. Detailed derivation is specified to the case of a two-site chemical exchange system with complete randomization between jumps of the exchanging spins. The derived theory can be applied to describe the modulation of the chemical exchange relaxation rate constants when using a train of adiabatic pulses, such as the hyperbolic secant pulse. Theory presented is valid for quantification of the exchange-induced time-dependent rotating frame longitudinal T1rho,ex and transverse T2rho,ex relaxations in the fast chemical exchange regime.

  15. Relaxation behavior and dose dependence of radiation induced radicals in irradiated mango

    International Nuclear Information System (INIS)

    Kameya, Hiromi; Kakita, Daisuke; Kaimori, Yoshihiko; Ukai, Mitsuko; Kikuchi, Masahiro; Kobayashi, Yasuhiko; Shimoyama, Yuhei

    2010-01-01

    Mangoes are imported to Japan after treated with hot water. Recently, irradiated mangoes imported to U. S. are widely used. This paper reports on the ESR method for analyzing the radiation induced radicals of irradiated mangoes. Upon the γ ray irradiation, a strong single peak in the flesh and skin of mangoes was observed at g=2.004. This singlet peak may be attributed to organic free radicals. The ESR spectra of the flesh and skin of mangoes showed the radiation induced radicals due to cellulose by irradiation over 12 kGy. The relaxation times (T 1 and T 2 ) of the singlet signal were calculated. T 2 showed dose response according to increasing the irradiation dose levels, while T 1 was almost constant. The value of (T 1 T 2 ) 1/2 showed the dependence of irradiation dose level. (author)

  16. Capturing molecular multimode relaxation processes in excitable gases based on decomposition of acoustic relaxation spectra

    Science.gov (United States)

    Zhu, Ming; Liu, Tingting; Wang, Shu; Zhang, Kesheng

    2017-08-01

    Existing two-frequency reconstructive methods can only capture primary (single) molecular relaxation processes in excitable gases. In this paper, we present a reconstructive method based on the novel decomposition of frequency-dependent acoustic relaxation spectra to capture the entire molecular multimode relaxation process. This decomposition of acoustic relaxation spectra is developed from the frequency-dependent effective specific heat, indicating that a multi-relaxation process is the sum of the interior single-relaxation processes. Based on this decomposition, we can reconstruct the entire multi-relaxation process by capturing the relaxation times and relaxation strengths of N interior single-relaxation processes, using the measurements of acoustic absorption and sound speed at 2N frequencies. Experimental data for the gas mixtures CO2-N2 and CO2-O2 validate our decomposition and reconstruction approach.

  17. Characterization of a novel telomerase-immortalized human endometrial stromal cell line, St-T1b

    Directory of Open Access Journals (Sweden)

    Brosens Jan J

    2009-07-01

    Full Text Available Abstract Background Coordinated differentiation of the endometrial compartments in the second half of the menstrual cycle is a prerequisite for the establishment of pregnancy. Endometrial stromal cells (ESC decidualize under the influence of ovarian progesterone to accommodate implantation of the blastocyst and support establishment of the placenta. Studies into the mechanisms of decidualization are often hampered by the lack of primary ESC. Here we describe a novel immortalized human ESC line. Methods Primary ESC were immortalized by the transduction of telomerase. The resultant cell line, termed St-T1b, was characterized for its morphological and biochemical properties by immunocytochemistry, RT-PCR and immunoblotting. Its progestational response was tested using progesterone and medroxyprogesterone acetate with and without 8-Br-cAMP, an established inducer of decidualization in vitro. Results St-T1b were positive for the fibroblast markers vimentin and CD90 and negative for the epithelial marker cytokeratin-7. They acquired a decidual phenotype indistinguishable from primary ESC in response to cAMP stimulation. The decidual response was characterized by transcriptional activation of marker genes, such as PRL, IGFBP1, and FOXO1, and enhanced protein levels of the tumor suppressor p53 and the metastasis suppressor KAI1 (CD82. Progestins alone had no effect on St-T1b cells, but medroxyprogesterone acetate greatly enhanced the cAMP-stimulated expression of IGFBP-1 after 3 and 7 days. Progesterone, albeit more weakly, also augmented the cAMP-induced IGFBP-1 production but only after 7 days of treatment. The cell line remained stable in continuous culture for more than 150 passages. Conclusion St-T1b express the appropriate phenotypic ESC markers and their decidual response closely mimics that of primary cultures. Decidualization is efficiently induced by cAMP analog and enhanced by medroxyprogesterone acetate, and, to a lesser extent, by natural

  18. Sandpile model for relaxation in complex systems

    International Nuclear Information System (INIS)

    Vazquez, A.; Sotolongo-Costa, O.; Brouers, F.

    1997-10-01

    The relaxation in complex systems is, in general, nonexponential. After an initial rapid decay the system relaxes slowly following a long time tail. In the present paper a sandpile moderation of the relaxation in complex systems is analysed. Complexity is introduced by a process of avalanches in the Bethe lattice and a feedback mechanism which leads to slower decay with increasing time. In this way, some features of relaxation in complex systems: long time tails relaxation, aging, and fractal distribution of characteristic times, are obtained by simple computer simulations. (author)

  19. Myocardial T1 and T2 mapping: Techniques and clinical applications

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Pan Ki; Hong, Yoo Jin; Im, Dong Jin [Dept. of Radiology and Research Institute of Radiological Science, Severance Hospital, Yonsei University College of Medicine, Seoul (Korea, Republic of); and others

    2017-01-15

    Cardiac magnetic resonance (CMR) imaging is widely used in various medical fields related to cardiovascular diseases. Rapid technological innovations in magnetic resonance imaging in recent times have resulted in the development of new techniques for CMR imaging. T1 and T2 image mapping sequences enable the direct quantification of T1, T2, and extracellular volume fraction (ECV) values of the myocardium, leading to the progressive integration of these sequences into routine CMR settings. Currently, T1, T2, and ECV values are being recognized as not only robust biomarkers for diagnosis of cardiomyopathies, but also predictive factors for treatment monitoring and prognosis. In this study, we have reviewed various T1 and T2 mapping sequence techniques and their clinical applications.

  20. Responses of mRNA expression of PepT1 in small intestine to ...

    African Journals Online (AJOL)

    STORAGESEVER

    2009-05-04

    May 4, 2009 ... 2National Key Laboratory of Animal Nutrition, Beijing, 100193, China. 3College ... porters are present in tissues of sheep, cows, pigs and .... PepT1; Peptide transporter, GAPDH; Glyceraldehyde-3-phosphate dehydrogenase.

  1. T1 pseudohyperintensity on fat-suppressed MRI: A potential diagnostic pitfall

    Science.gov (United States)

    Huynh, Tuan N.; Johnson, D. Thor; Poder, Liina; Joe, Bonnie N.; Webb, Emily M.; Coakley, Fergus V.

    2011-01-01

    MRI findings in two patients with misleading T1 hyperintensity seen only on fat-suppressed images are presented, one with a renal cell carcinoma that was misinterpreted as a hemorrhagic cyst and the other with an ovarian serous cystadenocarcinoma that was misinterpreted as a complicated endometrioma. The apparent T1 hyperintensity on fat suppressed images in these cases was likely due to varying perception of image signal dependent on local contrast, an optical effect known as the checker-shadow illusion. T1 pseudohyperintensity should be considered when apparently high T1 signal intensity is seen only on fat-suppressed images; review of non fat-suppressed images may help prevent an erroneous diagnoses of blood-containing lesions. PMID:21765301

  2. Impact of liver fibrosis and fatty liver on T1rho measurements: A prospective study

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Shuang Shuang; Li, Qing; Cheng, Yue; Shen, Wen [Dept. of Radiology, Tianjin First Center Hospital, Tianjin (China); Zhang, Yu; Zhuo, Zhi Zheng [Clinical Science, Philips Healthcare, Beijing (China); Zhao, Guiming [Dept. of Hepatology, Tianjin Second People' s Hospital, Tianjin (China)

    2017-11-15

    To investigate the liver T1rho values for detecting fibrosis, and the potential impact of fatty liver on T1rho measurements. This study included 18 healthy subjects, 18 patients with fatty liver, and 18 patients with liver fibrosis, who underwent T1rho MRI and mDIXON collections. Liver T1rho, proton density fat fraction (PDFF) and T2* values were measured and compared among the three groups. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the T1rho values for detecting liver fibrosis. Liver T1rho values were correlated with PDFF, T2* values and clinical data. Liver T1rho and PDFF values were significantly different (p < 0.001), whereas the T2* (p = 0.766) values were similar, among the three groups. Mean liver T1rho values in the fibrotic group (52.6 ± 6.8 ms) were significantly higher than those of healthy subjects (44.9 ± 2.8 ms, p < 0.001) and fatty liver group (45.0 ± 3.5 ms, p < 0.001). Mean liver T1rho values were similar between healthy subjects and fatty liver group (p = 0.999). PDFF values in the fatty liver group (16.07 ± 10.59%) were significantly higher than those of healthy subjects (1.43 ± 1.36%, p < 0.001) and fibrosis group (1.07 ± 1.06%, p < 0.001). PDFF values were similar in healthy subjects and fibrosis group (p = 0.984). Mean T1rho values performed well to detect fibrosis at a threshold of 49.5 ms (area under the ROC curve, 0.855), had a moderate correlation with liver stiffness (r = 0.671, p = 0.012), and no correlation with PDFF, T2* values, subject age, or body mass index (p > 0.05). T1rho MRI is useful for noninvasive detection of liver fibrosis, and may not be affected with the presence of fatty liver.

  3. Dynamical properties of the S =1/2 random Heisenberg chain

    Science.gov (United States)

    Shu, Yu-Rong; Dupont, Maxime; Yao, Dao-Xin; Capponi, Sylvain; Sandvik, Anders W.

    2018-03-01

    We study dynamical properties at finite temperature (T ) of Heisenberg spin chains with random antiferromagnetic exchange couplings, which realize the random singlet phase in the low-energy limit, using three complementary numerical methods: exact diagonalization, matrix-product-state algorithms, and stochastic analytic continuation of quantum Monte Carlo results in imaginary time. Specifically, we investigate the dynamic spin structure factor S (q ,ω ) and its ω →0 limit, which are closely related to inelastic neutron scattering and nuclear magnetic resonance (NMR) experiments (through the spin-lattice relaxation rate 1 /T1 ). Our study reveals a continuous narrow band of low-energy excitations in S (q ,ω ) , extending throughout the q space, instead of being restricted to q ≈0 and q ≈π as found in the uniform system. Close to q =π , the scaling properties of these excitations are well captured by the random-singlet theory, but disagreements also exist with some aspects of the predicted q dependence further away from q =π . Furthermore we also find spin diffusion effects close to q =0 that are not contained within the random-singlet theory but give non-negligible contributions to the mean 1 /T1 . To compare with NMR experiments, we consider the distribution of the local relaxation rates 1 /