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Sample records for carbon transverse relaxation

  1. Transverse Spin Relaxation in Liquid X

    SciTech Connect

    Romalis, M. V.; Ledbetter, M. P.

    2001-08-06

    Using spin-echo NMR techniques we study the transverse spin relaxation of hyperpolarized liquid X{sup 129}e in a spherical cell. We observe an instability of the transverse magnetization due to dipolar fields produced by liquid X{sup 129}e , and find that imperfections in the {pi} pulses of the spin-echo sequence suppress this instability. A simple perturbative model of this effect is in good agreement with the data. We obtain a transverse spin relaxation time of 1300sec in liquid X{sup 129}e , and discuss applications of hyperpolarized liquid X{sup 129}e as a sensitive magnetic gradiometer and for a permanent electric dipole moment search.

  2. Fat Emulsification Measured Using NMR Transverse Relaxation

    NASA Astrophysics Data System (ADS)

    Marciani, L.; Ramanathan, C.; Tyler, D. J.; Young, P.; Manoj, P.; Wickham, M.; Fillery-Travis, A.; Spiller, R. C.; Gowland, P. A.

    2001-11-01

    This paper presents a novel method of measuring the droplet size in oil-in-water emulsions. It is based on changes in the NMR transverse relaxation rate due to the effect of microscopic magnetic susceptibility differences between fat droplets and the surrounding water. The longitudinal and transverse relaxation rates of a series of emulsions with constant oil volume fraction and five different mean droplet sizes, in the range 0.4-20.9 μm, were measured in vitro at 37°C using EPI. While the longitudinal relaxation rate 1/T1 did not change significantly, 1/T2 was observed to increase with mean droplet size. The measured changes in 1/T2 were found to be in good agreement with results predicted from proton random walk simulations, and were also consistent with analytical solutions based on an outer sphere relaxation model. Measurements of 1/T2 on emulsions with a higher oil volume fraction, and on emulsions of a fixed size where the water phase was doped with gadolinium to modulate the susceptibility difference between the phases, also showed the predicted behavior. As part of this study the susceptibility difference between olive oil and water was measured to be 1.55 ppm.

  3. Transverse relaxation of scalar-coupled protons.

    PubMed

    Segawa, Takuya F; Baishya, Bikash; Bodenhausen, Geoffrey

    2010-10-25

    In a preliminary communication (B. Baishya, T. F. Segawa, G. Bodenhausen, J. Am. Chem. Soc. 2009, 131, 17538-17539), we recently demonstrated that it is possible to obtain clean echo decays of protons in biomolecules despite the presence of homonuclear scalar couplings. These unmodulated decays allow one to determine apparent transverse relaxation rates R(2) (app) of individual protons. Herein, we report the observation of R(2) (app) for three methyl protons, four amide H(N) protons, and all 11 backbone H(α) protons in cyclosporin A. If the proton resonances overlap, their R(2) (app) rates can be measured by transferring their magnetization to neighboring (13)C nuclei, which are less prone to overlap. The R(2) (app) rates of protons attached to (13)C are faster than those attached to (12)C because of (13)C-(1)H dipolar interactions. The differences of these rates allow the determination of local correlation functions. Backbone H(N) and H(α) protons that have fast decay rates R(2) (app) also feature fast longitudinal relaxation rates R(1) and intense NOESY cross peaks that are typical of crowded environments. Variations of R(2) (app) rates of backbone H(α) protons in similar amino acids reflect differences in local environments.

  4. Correlation of transverse relaxation time with structure of biological tissue.

    PubMed

    Furman, Gregory B; Meerovich, Victor M; Sokolovsky, Vladimir L

    2016-09-01

    Transverse spin-spin relaxation of liquids entrapped in nanocavities with different orientational order is theoretically investigated. Based on the bivariate normal distribution of nanocavities directions, we have calculated the anisotropy of the transverse relaxation time for biological systems, such as collagenous tissues, articular cartilage, and tendon. In the framework of the considered model, the dipole-dipole interaction is determined by a single coupling constant. The calculation results for the transverse relaxation time explain the angular dependence observed in MRI experiments with biological objects. The good agreement with the experimental data is obtained by adjustment of only one parameter which characterizes the disorder in fiber orientations. The relaxation time is correlated with the degree of ordering in biological tissues. Thus, microstructure of the tissues can be revealed from the measurement of relaxation time anisotropy. The clinical significance of the correlation, especially in the detection of damage must be evaluated in a large prospective clinical trials.

  5. Correlation of transverse relaxation time with structure of biological tissue

    NASA Astrophysics Data System (ADS)

    Furman, Gregory B.; Meerovich, Victor M.; Sokolovsky, Vladimir L.

    2016-09-01

    Transverse spin-spin relaxation of liquids entrapped in nanocavities with different orientational order is theoretically investigated. Based on the bivariate normal distribution of nanocavities directions, we have calculated the anisotropy of the transverse relaxation time for biological systems, such as collagenous tissues, articular cartilage, and tendon. In the framework of the considered model, the dipole-dipole interaction is determined by a single coupling constant. The calculation results for the transverse relaxation time explain the angular dependence observed in MRI experiments with biological objects. The good agreement with the experimental data is obtained by adjustment of only one parameter which characterizes the disorder in fiber orientations. The relaxation time is correlated with the degree of ordering in biological tissues. Thus, microstructure of the tissues can be revealed from the measurement of relaxation time anisotropy. The clinical significance of the correlation, especially in the detection of damage must be evaluated in a large prospective clinical trials.

  6. Transverse quasilinear relaxation in an inhomogeneous magnetic field

    NASA Astrophysics Data System (ADS)

    Lyutikov, Maxim

    1998-08-01

    Transverse quasilinear relaxation of the cyclotron Cherenkov instability of an ultrarelativistic beam propagating along a strong, inhomogeneous magnetic field in a pair plasma is considered. We find a quasilinear state in which the kinetic-type instability is saturated by the force arising in the inhomogeneous field due to the conservation of the adiabatic invariant. The resulting wave intensities generally have a non-power-law frequency dependence, but in a broad frequency range can be well approximated by a power law with a spectral index -2. The emergent spectra and fluxes are consistent with the one observed from radio pulsars.

  7. A fast determination method for transverse relaxation of spin-exchange-relaxation-free magnetometer

    SciTech Connect

    Lu, Jixi Qian, Zheng; Fang, Jiancheng

    2015-04-15

    We propose a fast and accurate determination method for transverse relaxation of the spin-exchange-relaxation-free (SERF) magnetometer. This method is based on the measurement of magnetic resonance linewidth via a chirped magnetic field excitation and the amplitude spectrum analysis. Compared with the frequency sweeping via separate sinusoidal excitation, our method can realize linewidth determination within only few seconds and meanwhile obtain good frequency resolution. Therefore, it can avoid the drift error in long term measurement and improve the accuracy of the determination. As the magnetic resonance frequency of the SERF magnetometer is very low, we include the effect of the negative resonance frequency caused by the chirp and achieve the coefficient of determination of the fitting results better than 0.998 with 95% confidence bounds to the theoretical equation. The experimental results are in good agreement with our theoretical analysis.

  8. A fast determination method for transverse relaxation of spin-exchange-relaxation-free magnetometer.

    PubMed

    Lu, Jixi; Qian, Zheng; Fang, Jiancheng

    2015-04-01

    We propose a fast and accurate determination method for transverse relaxation of the spin-exchange-relaxation-free (SERF) magnetometer. This method is based on the measurement of magnetic resonance linewidth via a chirped magnetic field excitation and the amplitude spectrum analysis. Compared with the frequency sweeping via separate sinusoidal excitation, our method can realize linewidth determination within only few seconds and meanwhile obtain good frequency resolution. Therefore, it can avoid the drift error in long term measurement and improve the accuracy of the determination. As the magnetic resonance frequency of the SERF magnetometer is very low, we include the effect of the negative resonance frequency caused by the chirp and achieve the coefficient of determination of the fitting results better than 0.998 with 95% confidence bounds to the theoretical equation. The experimental results are in good agreement with our theoretical analysis.

  9. Nuclear magnetic resonance transverse relaxation in muscle water.

    PubMed Central

    Fung, B M; Puon, P S

    1981-01-01

    The origin of the nonexponentiality of proton spin echoes of skeletal muscle has been carefully examined. It is shown that the slowly decaying part of the proton spin echoes is not due to extracellular water. First, for muscle from mice with in vivo deuteration, the deuteron spin echoes were also nonexponential, but the slowly decaying part had a larger weighing factor. Second, for glycerinated muscle in which cell membranes were disrupted, the proton spin echoes were similar to those in intact muscle. Third, the nonexponentiality of the proton spin echoes in intact muscle increased when postmortem rigor set in. Finally, when the lifetimes of extracellular water and intracellular water were taken into account in the exchange, it was found that the two types of water would not give two resolvable exponentials with the observed decay constants. It is suggested that the unusually short T2's and the nonexponential character of the spin echoes of proton and deuteron in muscle water are mainly due to hydrogen exchange between water and functional groups in the protein filaments. These groups have large dipolar or quadrupolar splittings, and undergo hydrogen exchange with water at intermediate rates. The exchange processes and their effects on the spin echoes are pH-dependent. The dependence of transverse relaxation of pH was observed in glycerinated rabbit psoas muscle fibers. PMID:7272437

  10. Effects of frozen storage and sample temperature on water compartmentation and multiexponential transverse relaxation in cartilage.

    PubMed

    Reiter, David A; Peacock, Andrew; Spencer, Richard G

    2011-05-01

    Multiexponential transverse relaxation in tissue has been interpreted as a marker of water compartmentation. Articular cartilage has been reported to exhibit such relaxation in several studies, with the relative contributions of tissue heterogeneity and tissue microstructure remaining unspecified. In bovine nasal cartilage, conflicting data regarding the existence of multiexponential relaxation have been reported. Imaging and analysis artifacts as well as rapid chemical exchange between tissue compartments have been identified as potential causes for this discrepancy. Here, we find that disruption of cartilage microstructure by freeze-thawing can greatly alter the character of transverse relaxation in this tissue. We conclude that fresh cartilage exhibits multiexponential relaxation based upon its microstructural water compartments, but that multiexponentiality can be lost or rendered undetectable by freeze-thawing. In addition, we find that increasing chemical exchange by raising sample temperature from 4°C to 37°C does not substantially limit the ability to detect multiexponential relaxation. Published by Elsevier Inc.

  11. Combined Diffusion Tensor Imaging and Apparent Transverse Relaxation Rate Differentiate Parkinson Disease and Atypical Parkinsonism.

    PubMed

    Du, G; Lewis, M M; Kanekar, S; Sterling, N W; He, L; Kong, L; Li, R; Huang, X

    2017-05-01

    Both diffusion tensor imaging and the apparent transverse relaxation rate have shown promise in differentiating Parkinson disease from atypical parkinsonism (particularly multiple system atrophy and progressive supranuclear palsy). The objective of the study was to assess the ability of DTI, the apparent transverse relaxation rate, and their combination for differentiating Parkinson disease, multiple system atrophy, progressive supranuclear palsy, and controls. A total of 106 subjects (36 controls, 35 patients with Parkinson disease, 16 with multiple system atrophy, and 19 with progressive supranuclear palsy) were included. DTI and the apparent transverse relaxation rate measures from the striatal, midbrain, limbic, and cerebellar regions were obtained and compared among groups. The discrimination performance of DTI and the apparent transverse relaxation rate among groups was assessed by using Elastic-Net machine learning and receiver operating characteristic curve analysis. Compared with controls, patients with Parkinson disease showed significant apparent transverse relaxation rate differences in the red nucleus. Compared to those with Parkinson disease, patients with both multiple system atrophy and progressive supranuclear palsy showed more widespread changes, extending from the midbrain to striatal and cerebellar structures. The pattern of changes, however, was different between the 2 groups. For instance, patients with multiple system atrophy showed decreased fractional anisotropy and an increased apparent transverse relaxation rate in the subthalamic nucleus, whereas patients with progressive supranuclear palsy showed an increased mean diffusivity in the hippocampus. Combined, DTI and the apparent transverse relaxation rate were significantly better than DTI or the apparent transverse relaxation rate alone in separating controls from those with Parkinson disease/multiple system atrophy/progressive supranuclear palsy; controls from those with Parkinson

  12. Electron spin relaxation in carbon nanotubes: Dyakonov-Perel mechanism

    NASA Astrophysics Data System (ADS)

    Semenov, Yuriy; Zavada, John; Kim, Ki Wook

    2010-03-01

    The long standing problem of unaccountable short spin relaxation in carbon nanotubes (CNT) meets a disclosure in terms of curvature-mediated spin-orbital interaction that leads to spin fluctuating precession analogous to Dyakonov-Perel mechanism. Strong anisotropy imposed by arbitrary directed magnetic field has been taken into account in terms of extended Bloch equations. Especially, stationary spin current through CNT can be controlled by spin-flip processes with relaxation time as less as 150 ps, the rate of transversal polarization (i.e. decoherence) runs up to 1/(70 ps) at room temperature while spin interference of the electrons related to different valleys can be responsible for shorter spin dephasing. Dependencies of spin-relaxation parameters on magnetic field strength and orientation, CNT curvature and chirality have been analyzed.

  13. Transverse relaxation in the rotating frame induced by chemical exchange

    NASA Astrophysics Data System (ADS)

    Michaeli, Shalom; Sorce, Dennis J.; Idiyatullin, Djaudat; Ugurbil, Kamil; Garwood, Michael

    2004-08-01

    In the presence of radiofrequency irradiation, relaxation of magnetization aligned with the effective magnetic field is characterized by the time constant T1 ρ. On the other hand, the time constant T2 ρ characterizes the relaxation of magnetization that is perpendicular to the effective field. Here, it is shown that T2 ρ can be measured directly with Carr-Purcell sequences composed of a train of adiabatic full-passage (AFP) pulses. During adiabatic rotation, T2 ρ characterizes the relaxation of the magnetization, which under adiabatic conditions remains approximately perpendicular to the time-dependent effective field. Theory is derived to describe the influence of chemical exchange on T2 ρ relaxation in the fast-exchange regime, with time constant defined as T2 ρ,ex . The derived theory predicts the rate constant R 2ρ, ex (=1/T 2ρ, ex) to be dependent on the choice of amplitude- and frequency-modulation functions used in the AFP pulses. Measurements of R2 ρ,ex of the water/ethanol exchanging system confirm the predicted dependence on modulation functions. The described theoretical framework and adiabatic methods represent new tools to probe exchanging systems.

  14. General solution to gradient-induced transverse and longitudinal relaxation of spins undergoing restricted diffusion

    NASA Astrophysics Data System (ADS)

    Zheng, W.; Gao, H.; Liu, J.-G.; Zhang, Y.; Ye, Q.; Swank, C.

    2011-11-01

    We develop an approach, by calculating the autocorrelation function of spins, to derive the magnetic field gradient-induced transverse (T2) relaxation of spins undergoing restricted diffusion. This approach is an extension to the method adopted by McGregor. McGregor's approach solves the problem only in the fast diffusion limit; however, our approach yields a single analytical solution suitable in all diffusion regimes, including the intermediate regime. This establishes a direct connection between the well-known slow diffusion result of Torrey and the fast diffusion result. We also perform free induction decay measurements on spin-exchange optically polarized 3He gas with different diffusion constants. The measured transverse relaxation profiles are compared with the theory and satisfactory agreement has been found throughout all diffusion regimes. In addition to the transverse relaxation, this approach is also applicable to solving the longitudinal relaxation (T1) regardless of the diffusion limits. It turns out that the longitudinal relaxation in the slow diffusion limit differs by a factor of 2 from that in the fast diffusion limit.

  15. Transverse relaxivity of iron oxide nanocrystals clustered in nanoemulsions: Experiment and theory.

    PubMed

    Hak, Sjoerd; Goa, Pål Erik; Stenmark, Sebastian; Bjerkholt, Frøydis F; Haraldseth, Olav

    2015-09-01

    To compare experimental transverse relaxivities of iron oxide nanocrystals (IONC) as a function of clustering and magnetic field strength with different theoretical model predictions. Well-defined IONC clusters in nanoemulsions (NEs) of which both size and IONC loading could be judiciously tuned were developed. Transverse relaxivities were measured as a function of NE size and IONC loading at 20 and 300 MHz and compared with four theoretical model predictions. Polydispersity of the NEs was measured and taken into account in the theoretical calculations. Experimentally observed relaxivities were in between theoretical predictions from the fast diffusion regime and the static dephasing regimen. NE polydispersity significantly affected the theoretical T2 relaxivity. The effect of both the number of IONCs inside each droplet as well as the radius of the droplet itself was correctly described by a fast diffusion loose aggregate model, while the effect of increased magnetic field was in agreement with a static dephasing model. The results suggest that both fast diffusion, originating from bulk water, and static dephasing phenomena, perhaps originating from water associated with the NE, play a role in transverse relaxivities of IONC aggregates. The developed aggregate system represents a powerful tool to further study these phenomena. © 2014 Wiley Periodicals, Inc.

  16. Measurement of the true transverse nuclear magnetic resonance relaxation in the presence of field gradients.

    PubMed

    Mitchell, J; Chandrasekera, T C; Gladden, L F

    2013-08-21

    A measure of the nuclear spin transverse relaxation time T2, as determined using the nuclear magnetic resonance Carr-Purcell Meiboom-Gill (CPMG) experiment, provides unique information characterizing the microstructure of porous media which are themselves ubiquitous across fields of petrophysics, biophysics, and chemical engineering. However, the CPMG measurement is sensitive to diffusion in large magnetic field gradients. Under such conditions an effective relaxation time T2,eff is observed instead, described by a combination of relaxation and diffusion exponents. The relaxation exponent always varies as nte (where n is the number, and te is the temporal separation, of spin echoes). The diffusion exponent varies as nte (k), where 1 < k ≤ 3, although the exact analytic form is often unknown. Here we present a general approach to separating the influence of relaxation and diffusion by utilizing a composite diffusion exponent. Any T2,eff component with a power of k > 1 is removed to provide a measure of the true T2 relaxation time distribution from CPMG data acquired in the presence of a strong background gradient. We apply the technique to discriminate between the effects of relaxation and diffusion in porous media using catalysts and rocks as examples. The method is generally applicable to any CPMG measurements conducted in the presence of a static magnetic field gradient.

  17. An approximate analytical expression for the nuclear quadrupole transverse relaxation rate of half-integer spins in liquids.

    PubMed

    Wu, Gang

    2016-08-01

    The nuclear quadrupole transverse relaxation process of half-integer spins in liquid samples is known to exhibit multi-exponential behaviors. Within the framework of Redfield's relaxation theory, exact analytical expressions for describing such a process exist only for spin-3/2 nuclei. As a result, analyses of nuclear quadrupole transverse relaxation data for half-integer quadrupolar nuclei with spin >3/2 must rely on numerical diagonalization of the Redfield relaxation matrix over the entire motional range. In this work we propose an approximate analytical expression that can be used to analyze nuclear quadrupole transverse relaxation data of any half-integer spin in liquids over the entire motional range. The proposed equation yields results that are in excellent agreement with the exact numerical calculations.

  18. Toward understanding transverse relaxation in human brain through its field dependence.

    PubMed

    Mitsumori, Fumiyuki; Watanabe, Hidehiro; Takaya, Nobuhiro; Garwood, Michael; Auerbach, Edward J; Michaeli, Shalom; Mangia, Silvia

    2012-09-01

    Apparent transverse-relaxation rate constants (R₂⁺ = 1/T₂⁺) were measured in various regions of the healthy human brain using a multiecho adiabatic spin-echo sequence at five different magnetic fields, 1.5, 1.9, 3, 4.7, and 7 T. The R₂⁺ values showed a clear dependence on magnetic field strength (B(0) ). The regional distribution of the R ₂⁺ was well explained by the sum of three components: (1) regional nonhemin iron concentration ([Fe]), (2) regional macromolecular mass fraction (f(M) ), and (3) a region-independent factor. Accordingly, R₂⁺ = α[Fe] + βf(M) + γ, where coefficients α, β, and γ were experimentally determined at each magnetic field by a least square fitting method using multiple regression analysis. Although the coefficient α linearly increased with B(0) , β showed a quadratic dependence on top of a field-independent component. The coefficient γ also increased slightly with B(0) on top of a field-independent component. The linear dependence of α on B(0) was consistent with that observed for the transverse-relaxation rate of water protons in ferritin solutions as found previously by others. The quadratic dependence of β on B(0) was accounted for by isochronous and anisochronous exchange mechanisms using intrinsic-relaxation parameters obtained from the literature. Copyright © 2011 Wiley Periodicals, Inc.

  19. Maximizing MR signal for 2D UTE slice selection in the presence of rapid transverse relaxation.

    PubMed

    Carl, Michael; Chiang, Jing-Tzyh Alan; Du, Jiang

    2014-10-01

    Ultrashort TE (UTE) sequences allow direct visualization of tissues with very short T2 relaxation times, such as tendons, ligaments, menisci, and cortical bone. In this work, theoretical calculations, simulations, and phantom studies, as well as in vivo imaging were performed to maximize signal-to-noise ratio (SNR) for slice selective RF excitation for 2D UTE sequences. The theoretical calculations and simulations were based on the Bloch equations, which lead to analytic expressions for the optimal RF pulse duration and amplitude to maximize magnetic resonance signal in the presence of rapid transverse relaxation. In steady state, it was found that the maximum signal amplitude was not obtained at the classical Ernst angle, but at an either lower or higher flip angle, depending on whether the RF pulse duration or amplitude was varied, respectively.

  20. Experimental validation of a T2 ρ transverse relaxation model using LASER and CPMG acquisitions

    NASA Astrophysics Data System (ADS)

    Nikolova, Simona; Bowen, Chris V.; Bartha, Robert

    2006-07-01

    The transverse relaxation rate (R2 = 1/T2) of many biological tissues are altered by endogenous magnetized particles (i.e., ferritin, deoxyhemoglobin), and may be sensitive to the pathological progression of neurodegenerative disorders associated with altered brain-iron stores. R2 measurements using Carr-Purcell-Meiboom-Gill (CPMG) acquisitions are sensitive to the refocusing pulse interval (2τcp), and have been modeled as a chemical exchange (CE) process, while R2 measurements using a localization by adiabatic selective refocusing (LASER) sequence have an additional relaxation rate contribution that has been modeled as a R2ρ process. However, no direct comparison of the R2 measured using these two sequences has been described for a controlled phantom model of magnetized particles. The three main objectives of this study were: (1) to compare the accuracy of R2 relaxation rate predictions from the CE model with experimental data acquired using a conventional CPMG sequence, (2) to compare R2 estimates obtained using LASER and CPMG acquisitions, and (3) to determine whether the CE model, modified to account for R2ρ relaxation, adequately describes the R2 measured by LASER for a full range of τcp values. In all cases, our analysis was confined to spherical magnetic particles that satisfied the weak field regime. Three phantoms were produced that contained spherical magnetic particles (10 μm diameter polyamide powders) suspended in Gd-DTPA (1.0, 1.5, and 2.0 mmol/L) doped gel. Mono-exponential R2 measurements were made at 4 T as a function of refocusing pulse interval. CPMG measurements of R2 agreed with CE model predictions while significant differences in R2 estimates were observed between LASER and CPMG measurements for short τcp acquisitions. The discrepancy between R2 estimates is shown to be attributable to contrast enhancement in LASER due to T2ρ relaxation.

  1. A theoretical and numerical consideration of the longitudinal and transverse relaxations in the rotating frame.

    PubMed

    Murase, Kenya

    2013-11-01

    We previously derived a simple equation for solving time-dependent Bloch equations by a matrix operation. The purpose of this study was to present a theoretical and numerical consideration of the longitudinal (R1ρ=1/T1ρ) and transverse relaxation rates in the rotating frame (R2ρ=1/T2ρ), based on this method. First, we derived an equation describing the time evolution of the magnetization vector (M(t)) by expanding the matrix exponential into the eigenvalues and the corresponding eigenvectors using diagonalization. Second, we obtained the longitudinal magnetization vector in the rotating frame (M1ρ(t)) by taking the inner product of M(t) and the eigenvector with the smallest eigenvalue in modulus, and then we obtained the transverse magnetization vector in the rotating frame (M2ρ(t)) by subtracting M1ρ(t) from M(t). For comparison, we also computed the spin-locked magnetization vector. We derived the exact solutions for R1ρ and R2ρ from the eigenvalues, and compared them with those obtained numerically from M1ρ(t) and M2ρ(t), respectively. There was excellent agreement between them. From the exact solutions for R1ρ and R2ρ, R2ρ was found to be given by R2ρ=(2R2+R1)/2-R1ρ/2, where R1 and R2 denote the conventional longitudinal and transverse relaxation rates, respectively. We also derived M1ρ(t) and M2ρ(t) for bulk water protons, in which the effect of chemical exchange was taken into account using a 2-pool chemical exchange model, and we compared the R1ρ and R2ρ values obtained from the eigenvalues and those obtained numerically from M1ρ(t) and M2ρ(t). There was also excellent agreement between them. In conclusion, this study will be useful for better understanding of the longitudinal and transverse relaxations in the rotating frame and for analyzing the contrast mechanisms in T1ρ- and T2ρ-weighted MRI.

  2. Benchmarking transverse spin relaxation based oxygenation measurements in the brain during hypercapnia and hypoxia.

    PubMed

    Ni, Wendy W; Christen, Thomas; Zaharchuk, Greg

    2017-09-01

    To simultaneously assess reproducibility of three MRI transverse relaxation parameters ( R2', R2*, and R2 ) for brain tissue oxygenation mapping and to assess changes in these parameters with inhalation of gases that increase and decrease oxygenation, to identify the most sensitive parameter for imaging brain oxygenation. Forty-eight healthy subjects (25 male, ages 35 ± 8 years) were scanned at 3.0 Tesla, each with one of four gases (mildly and strongly hypercapnic and hypoxic) administered in a challenge paradigm, using a gas delivery setup designed for patient use. Cerebral blood flow mapping with arterial spin labeling, and simultaneous R2', R2*, and R2 mapping with gradient-echo sampling of free induction decay and echo (GESFIDE) were performed. Reproducibility in air and gas-induced changes were evaluated using nonparametric analysis with correction for multiple comparisons. Our gas delivery setup achieved stable gas challenges as shown by physiological monitoring. Test-retest variability of R2', R2*, and R2 were found to be 0.24 s(-1) (8.6% of mean), 0.24 s(-1) (1.3% of mean), and 0.15 s(-1) (1.0% of mean), respectively. Strong hypoxia produced the most conclusive oxygenation-driven relaxation change, inducing increases in R2' (25 ± 13%, P = 0.03), R2* (5 ± 2%, P = 0.02), and R2 (2 ± 2%, NS). We benchmarked the intra-scan test-retest variability in GESFIDE-based transverse relaxation rate mapping. Using a reliable framework for gas challenge paradigms, we recommend strong hypoxia for validating oxygenation mapping methods, and the use of tissue R2' change, instead of R2* or R2 , as a metric for studying brain tissue oxygenation using transverse relaxation methods. 1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:704-714. © 2017 International Society for Magnetic Resonance in Medicine.

  3. Detection of intermolecular homonuclear dipolar coupling in organic rich shale by transverse relaxation exchange

    NASA Astrophysics Data System (ADS)

    Washburn, Kathryn E.; Cheng, Yuesheng

    2017-05-01

    The mechanism behind surface relaxivity within organic porosity in shales has been an unanswered question. Here, we present results that confirm the existence of intermolecular homonuclear dipolar coupling between solid and liquid phases in sedimentary organic matter. Transverse magnetization exchange measurements were performed on an organic-rich shale saturated with liquid hydrocarbon. Liquid and solid constituents were identified through both sample resaturation and through their T1/T2 ratios. Extensive cross peaks are observed in the T2-T2 exchange spectra between the solid and liquid constituents, indicating an exchange of magnetization between the two phases. This result cannot arise from physical molecular diffusion, and the dissolution energies are too high for chemical exchange, such that the magnetization exchange must arise from intermolecular homonuclear dipolar coupling. These results both confirm a possible source of surface relaxivity in organic matter and emphasize caution in the use of standard porous media interpretations of relaxation results in shales because of coupling between different magnetization environments.

  4. Detection of intermolecular homonuclear dipolar coupling in organic rich shale by transverse relaxation exchange.

    PubMed

    Washburn, Kathryn E; Cheng, Yuesheng

    2017-03-04

    The mechanism behind surface relaxivity within organic porosity in shales has been an unanswered question. Here, we present results that confirm the existence of intermolecular homonuclear dipolar coupling between solid and liquid phases in sedimentary organic matter. Transverse magnetization exchange measurements were performed on an organic-rich shale saturated with liquid hydrocarbon. Liquid and solid constituents were identified through both sample resaturation and through their T1/T2 ratios. Extensive cross peaks are observed in the T2-T2 exchange spectra between the solid and liquid constituents, indicating an exchange of magnetization between the two phases. This result cannot arise from physical molecular diffusion, and the dissolution energies are too high for chemical exchange, such that the magnetization exchange must arise from intermolecular homonuclear dipolar coupling. These results both confirm a possible source of surface relaxivity in organic matter and emphasize caution in the use of standard porous media interpretations of relaxation results in shales because of coupling between different magnetization environments.

  5. Electromechanical behavior of carbon nanotube fibers under transverse compression

    NASA Astrophysics Data System (ADS)

    Li, Yuanyuan; Lu, Weibang; Sockalingam, Subramani; Gu, Bohong; Sun, Baozhong; Gillespie, John W.; Chou, Tsu-Wei

    2017-03-01

    Although in most cases carbon nanotube (CNT) fibers experience axial stretch or compression, they can also be subjected to transverse compression, for example, under impact loading. In this paper, the electromechanical properties of both aerogel-spun and dry-spun CNT fibers under quasi-static transverse compressive loading are investigated for the first time. Transverse compression shows a nonlinear and inelastic behavior. The compressive modulus/strength of the aerogel-spun and dry-spun CNT fibers are about 0.21 GPa/0.796 GPa and 1.73 GPa/1.036 GPa, respectively. The electrical resistance goes through three stages during transverse compressive loading/unloading: initially it decreases, then it increases during the loading, and finally it decreases upon unloading. This study extends our knowledge of the overall properties of CNT fibers, and will be helpful in promoting their engineering applications.

  6. Muonium spin relaxation in carbon monoxide

    NASA Astrophysics Data System (ADS)

    Arseneau, D. J.; Pan, J. J.; Senba, M.; Shelley, M.; Fleming, D. G.

    1997-04-01

    The spin relaxation of Mu was measured in mixtures of CO and Ar at pressures up to 270 atm and at various magnetic fields. The relaxation rate increased with magnetic field in the way expected for electron spin-exchange processes, though the effect declined at high pressures. We describe the results in terms of spin relaxation of Mu-formyl radicals, MuCO, which break up to give depolarized Mu at low pressures, but are increasingly stabilized at higher pressures.

  7. Transverse Relaxation of Cu Nuclear Spins in YBa2Cu3O6.98

    NASA Astrophysics Data System (ADS)

    Itoh, Yutaka; Yasuoka, Hiroshi; Ueda, Yutaka

    1990-10-01

    We have measured the transverse relaxation of the planar Cu(2) nuclear spins in an oriented powder sample of YBa2Cu3O6.98 (Tc{=}92 K) by using the nuclear quadrupole resonance (NQR) technique. Above Tc, after subtraction of the Tl process, the spin echo envelope decay follows a Gaussian form, and its time constant is almost independent of temperature. In the vicinity of Tc, however, the Gaussian line shape is gradually narrowed. The calculated value (TG{=}149 μsec) for the Gaussian time constant based on the direct nuclear dipole-dipole interaction is comparable to the experimental one (TG{=}131± 2 μsec) at 297 K. Hence, the nuclear indirect coupling proposed previously may not be needed. Below Tc, the Gaussian line shape was found to be narrowed depending on Hl, and especially, it is sharply narrowed at 35 K and 87 K.

  8. Practical Aspects of 1H Transverse Paramagnetic Relaxation Enhancement Measurements on Macromolecules

    PubMed Central

    Iwahara, Junji; Tang, Chun; Clore, G. Marius

    2007-01-01

    The use of 1H transverse paramagnetic relaxation enhancement (PRE) has seen a resurgence in recent years as method for providing long-range distance information for structural studies and as a probe of large amplitude motions and lowly populated transient intermediates in macromolecular association. In this paper we discuss various practical aspects pertaining to accurate measurement of PRE 1H transverse relaxation rates (Γ2). We first show that accurate Γ2 rates can be obtained from a two time-point measurement without requiring any fitting procedures or complicated error estimations, and no additional accuracy is achieved from multiple time-point measurements recorded in the same experiment time. Optimal setting of the two time-points that minimize experimental errors is also discussed. Next we show that the simplistic single time-point measurement that has been commonly used in the literature, can substantially underestimate the true value of Γ2, unless a relatively long repetition delay is employed. We then examine the field dependence of Γ2, and show that Γ2 exhibits only a very weak field dependence at high magnetic fields typically employed in macromolecular studies. The theoretical basis for this observation is discussed. Finally, we investigate the impact of contamination of the paramagnetic sample by trace amounts (≤5%) of the corresponding diamagnetic species on the accuracy of Γ2 measurements. Errors in Γ2 introduced by such diamagnetic contamination are potentially sizeable, but can be significantly reduced by using a relatively short time interval for the two time-point Γ2 measurement. PMID:17084097

  9. Practical aspects of (1)H transverse paramagnetic relaxation enhancement measurements on macromolecules.

    PubMed

    Iwahara, Junji; Tang, Chun; Marius Clore, G

    2007-02-01

    The use of (1)H transverse paramagnetic relaxation enhancement (PRE) has seen a resurgence in recent years as method for providing long-range distance information for structural studies and as a probe of large amplitude motions and lowly populated transient intermediates in macromolecular association. In this paper we discuss various practical aspects pertaining to accurate measurement of PRE (1)H transverse relaxation rates (Gamma(2)). We first show that accurate Gamma(2) rates can be obtained from a two time-point measurement without requiring any fitting procedures or complicated error estimations, and no additional accuracy is achieved from multiple time-point measurements recorded in the same experiment time. Optimal setting of the two time-points that minimize experimental errors is also discussed. Next we show that the simplistic single time-point measurement that has been commonly used in the literature, can substantially underestimate the true value of Gamma(2), unless a relatively long repetition delay is employed. We then examine the field dependence of Gamma(2), and show that Gamma(2) exhibits only a very weak field dependence at high magnetic fields typically employed in macromolecular studies. The theoretical basis for this observation is discussed. Finally, we investigate the impact of contamination of the paramagnetic sample by trace amounts (5%) of the corresponding diamagnetic species on the accuracy of Gamma(2) measurements. Errors in Gamma(2) introduced by such diamagnetic contamination are potentially sizeable, but can be significantly reduced by using a relatively short time interval for the two time-point Gamma(2) measurement.

  10. Measurement of longitudinal and transverse spin relaxation rates using the ground-state Hanle effect

    SciTech Connect

    Castagna, N.; Weis, A.

    2011-11-15

    We present a theoretical and experimental study of the resonant circularly-polarized-light-induced Hanle effect in the ground state of Cs vapor atoms in a paraffin-coated cell. The effect manifests itself as a narrow resonance (centered at B=0) in the dependence of the optical transmission coefficient of the vapor on the magnitude of an external magnetic field B(vector sign). We develop a theoretical model that yields an algebraic expression for the shape of these resonances for arbitrary field orientations and arbitrary angular momenta of the states coupled by the exciting light, provided that the light power is kept sufficiently small. An experimental procedure for assessing the range of validity of the model is given. Experiments were carried out on the laser-driven Cs D{sub 1} transition both in longitudinal and transverse field geometries, and the observed line shapes of the corresponding bright and dark resonances give an excellent confirmation of the model predictions. The method is applied for determining the intrinsic longitudinal and transverse relaxation rates of the vector magnetization in the vapor and their dependence on light power.

  11. Measurement of longitudinal and transverse spin relaxation rates using the ground-state Hanle effect

    NASA Astrophysics Data System (ADS)

    Castagna, N.; Weis, A.

    2011-11-01

    We present a theoretical and experimental study of the resonant circularly-polarized-light-induced Hanle effect in the ground state of Cs vapor atoms in a paraffin-coated cell. The effect manifests itself as a narrow resonance (centered at B=0) in the dependence of the optical transmission coefficient of the vapor on the magnitude of an external magnetic field B⃗. We develop a theoretical model that yields an algebraic expression for the shape of these resonances for arbitrary field orientations and arbitrary angular momenta of the states coupled by the exciting light, provided that the light power is kept sufficiently small. An experimental procedure for assessing the range of validity of the model is given. Experiments were carried out on the laser-driven Cs D1 transition both in longitudinal and transverse field geometries, and the observed line shapes of the corresponding bright and dark resonances give an excellent confirmation of the model predictions. The method is applied for determining the intrinsic longitudinal and transverse relaxation rates of the vector magnetization in the vapor and their dependence on light power.

  12. Dysprosium-bearing red cells as potential transverse relaxation agents for MRI.

    PubMed

    Johnson, K M; Tao, J Z; Kennan, R P; Gore, J C

    2001-05-01

    The cytosol of intact human red blood cells was loaded with 28.1 +/- 3.4 mM of dysprosium DTPA-BMA using a hypoosmotic technique. When loaded cells were diluted with saline and control cells to give an average dysprosium concentration of 3.3 +/- 0.5 mM, the transverse relaxation rate constants R(*)(2) and R(2) increased. R(*)(2) increased from 7.5 +/- 0.9 sec(-1) to 356 +/- 50 sec(-1), and R(2) increased from 7.4 +/- 0.7 sec(-1) to 148 +/- 40 sec(-1). After lysing, R(*)(2) was 6.0 +/- 0.6 sec(-1) in the control and 13.4 +/- 1.5 sec(-1) in the mixture; R(2) was 6.4 +/- 1.1 sec(-1) and 9.8 +/- 2.4 sec(-1), respectively. Thus, the relaxivity effects were enhanced by sequestration of the dysprosium within intact red cells, and this effect was lost after lysis. At a circulating whole-blood concentration of 0.81 +/- 0.15 mM in rats, the liver signal intensity dropped 29.9% +/- 3.7% and kidney signal intensity dropped 19.4% +/- 8.7%. Dysprosium-loaded cells might be useful in the study of perfusion and tissue blood volume.

  13. The effect of diffusion in internal gradients on nuclear magnetic resonance transverse relaxation measurements

    SciTech Connect

    Muncaci, S.; Ardelean, I.; Boboia, S.

    2013-11-13

    In the present work we study the internal gradient effects on diffusion attenuation of the echo train appearing in the well-known Carr-Purcell-Meiboom-Gill (CPMG) technique, extensively used for transverse relaxation measurements. Our investigations are carried out on two porous ceramics, prepared with the same amount of magnetic impurities (Fe{sub 2}O{sub 3}) but different pore sizes. It is shown that diffusion effects on the CPMG echo train attenuation are strongly influenced by the pore size for the same magnetic susceptibility of the two samples. The experimental results were compared with a theoretical model taking into account the limit of free or restricted diffusion on echo train attenuation. The NMR experiments were performed on water filled samples using a low-field NMR instrument. The porous ceramics were prepared using both the replica technique and the powder compression technique. Magnetic susceptibility measurements indicated close values of the susceptibility constant for the two samples whereas the SEM images indicated different pore sizes. The results reported here may have impact in the interpretation of NMR relaxation measurements of water in soils or concrete samples.

  14. Molecular dynamics simulations of proton transverse relaxation times in suspensions of magnetic nanoparticles.

    PubMed

    Panczyk, Tomasz; Konczak, Lukasz; Zapotoczny, Szczepan; Szabelski, Pawel; Nowakowska, Maria

    2015-01-01

    In this work we have analyzed the influence of various factors on the transverse relaxation times T2 of water protons in suspension of magnetic nanoparticles. For that purpose we developed a full molecular dynamics force field which includes the effects of dispersion interactions between magnetic nanoparticles and water molecules, electrostatic interactions between charged nanoparticles and magnetic dipole-dipole and dipole-external field interactions. We also accounted for the magnetization reversal within the nanoparticles body frames due to finite magnetic anisotropy barriers. The force field together with the Langevin dynamics imposed on water molecules and the nanoparticles allowed us to monitor the dephasing of water protons in real time. Thus, we were able to determine the T2 relaxation times including the effects of the adsorption of water on the nanoparticles' surfaces, thermal fluctuations of the orientation of nanoparticles' magnetizations as well as the effects of the core-shell architecture of nanoparticles and their agglomeration into clusters. We found that there exists an optimal cluster size for which T2 is minimized and that the retardation of water molecules motion, due to adsorption on the nanoparticles surfaces, has some effect in the measured T2 times. The typical strengths of the external magnetic fields in MRI are enough to keep the magnetizations fixed along the field direction, however, in the case of low magnetic fields, we observed significant enhancement of T2 due to thermal fluctuations of the orientations of magnetizations. Copyright © 2014 Elsevier Inc. All rights reserved.

  15. Transverse Relaxation and Magnetization Transfer in Skeletal Muscle: Effect of pH

    PubMed Central

    Louie, Elizabeth A.; Gochberg, Daniel F.; Does, Mark D.; Damon, Bruce M.

    2008-01-01

    Exercise increases the intracellular T2 (T2,i) of contracting muscles. The mechanism(s) for the T2,i increase have not been fully described, and may include increased intracellular free water and acidification. These changes may alter chemical exchange processes between intracellular free water and proteins. In this study, the hypotheses were tested that 1) pH changes T2,i by affecting the rate of magnetization transfer (MT) between free intracellular water and intracellular proteins and 2) the magnitude of the T2,i effect depends on acquisition mode (localized or non-localized) and echo spacing. Frog gastrocnemius muscles were excised and their intracellular pH was either kept at physiological pH (7.0) or modified to model exercising muscle (pH 6.5). The intracellular transverse relaxation rate (R2,i =1/T2,i) always decreased in the acidic muscles, but the changes were greater when measured using more rapid refocusing rates. The MT rate from the macromolecular proton pool to the free water proton pool, its reverse rate, and the spin-lattice relaxation rate of water decreased in acidic muscles. It is concluded that intracellular acidification alters the R2,i of muscle water in a refocusing rate-dependent manner and that the R2,i changes are correlated with changes in the MT rate between macromolecules and free intracellular water. PMID:19097244

  16. Effect of the cross-relaxation rate on the transverse radiation dynamics of a wide-aperture laser

    SciTech Connect

    Zaikin, A P; Molevich, N E

    2004-08-31

    The effect of a finite polarisation relaxation time on the transverse structure of the optical field of a wide-aperture laser is considered. The conditions are found for the emergence of periodic autowaves for positive and negative frequency detuning. These conditions are shown to depend strongly on the cross-relaxation rate. It is established that the dynamics of finite-aperture lasers at high cross-relaxation rates is satisfactorily described by simplified models in which the polarisation is adiabatically eliminated. (lasers)

  17. An in vivo study of the orientation-dependent and independent components of transverse relaxation rates in white matter.

    PubMed

    Gil, Rita; Khabipova, Diana; Zwiers, Marcel; Hilbert, Tom; Kober, Tobias; Marques, José P

    2016-12-01

    Diffusion-weighted imaging (DWI) provides information that allows the estimation of white-matter (WM) fibre orientation and distribution, but it does not provide information about myelin density, fibre concentration or fibre size within each voxel. On the other hand, quantitative relaxation contrasts (like the apparent transverse relaxation, R2∗) offer iron and myelin-related contrast, but their dependence on the orientation of microstructure with respect to the applied magnetic field, B0 , is often neglected. The aim of this work was to combine the fibre orientation information retrieved from the DWI acquisition and the sensitivity to microstructural information from quantitative relaxation parameters. The in vivo measured quantitative transverse relaxation maps (R2 and R2∗) were decomposed into their orientation-dependent and independent components, using the DWI fibre orientation information as prior knowledge. The analysis focused on major WM fibre bundles such as the forceps major (FMj), forceps minor (FMn), cingulum (CG) and corticospinal tracts (CST). The orientation-dependent R2 parameters, despite their small size (0-1.5 Hz), showed higher variability across different fibre populations, while those derived from R2∗, although larger (3.1-4.5 Hz), were mostly bundle-independent. With this article, we have, for the first time, attempted the in vivo characterization of the orientation-(in)dependent components of the transverse relaxation rates and demonstrated that the orientation of WM fibres influences both R2 and R2∗ contrasts.

  18. The effect of magnetically induced linear aggregates on proton transverse relaxation rates of aqueous suspensions of polymer coated magnetic nanoparticles.

    PubMed

    Saville, Steven L; Woodward, Robert C; House, Michael J; Tokarev, Alexander; Hammers, Jacob; Qi, Bin; Shaw, Jeremy; Saunders, Martin; Varsani, Rahi R; St Pierre, Tim G; Mefford, O Thompson

    2013-03-07

    It has been recently reported that for some suspensions of magnetic nanoparticles the transverse proton relaxation rate, R(2), is dependent on the time that the sample is exposed to an applied magnetic field. This time dependence has been linked to the formation of linear aggregates or chains in an applied magnetic field via numerical modeling. It is widely known that chain formation occurs in more concentrated ferrofluids systems and that this has an affect on the ferrofluid properties. In this work we examine the relationships between colloidal stability, the formation of these linear structures, and changes observed in the proton transverse relaxation rate of aqueous suspensions of magnetic particles. A series of iron oxide nanoparticles with varying stabilizing ligand brush lengths were synthesized. These systems were characterized with dynamic light scattering, transmission electron microscopy, dark-field optical microscopy, and proton transverse relaxation rate measurements. The dark field optical microscopy and R(2) measurements were made in similar magnetic fields over the same time scale so as to correlate the reduction of the transverse relaxivity with the formation of linear aggregates. Our results indicate that varying the ligand length has a direct effect on the colloidal arrangement of the system in a magnetic field, producing differences in the rate and size of chain formation, and hence systematic changes in transverse relaxation rates over time. With increasing ligand brush length, attractive inter-particle interactions are reduced, which results in slower aggregate formation and shorter linear aggregate length. These results have implications for the stabilization, characterization and potentially the toxicity of magnetic nanoparticle systems used in biomedical applications.

  19. Understanding generalized inversions of nuclear magnetic resonance transverse relaxation time in porous media

    NASA Astrophysics Data System (ADS)

    Mitchell, J.; Chandrasekera, T. C.

    2014-12-01

    The nuclear magnetic resonance transverse relaxation time T2, measured using the Carr-Purcell-Meiboom-Gill (CPMG) experiment, is a powerful method for obtaining unique information on liquids confined in porous media. Furthermore, T2 provides structural information on the porous material itself and has many applications in petrophysics, biophysics, and chemical engineering. Robust interpretation of T2 distributions demands appropriate processing of the measured data since T2 is influenced by diffusion through magnetic field inhomogeneities occurring at the pore scale, caused by the liquid/solid susceptibility contrast. Previously, we introduced a generic model for the diffusion exponent of the form -ant_e^k (where n is the number and te the temporal separation of spin echoes, and a is a composite diffusion parameter) in order to distinguish the influence of relaxation and diffusion in CPMG data. Here, we improve the analysis by introducing an automatic search for the optimum power k that best describes the diffusion behavior. This automated method is more efficient than the manual trial-and-error grid search adopted previously, and avoids variability through subjective judgments of experimentalists. Although our method does not avoid the inherent assumption that the diffusion exponent depends on a single k value, we show through simulation and experiment that it is robust in measurements of heterogeneous systems that violate this assumption. In this way, we obtain quantitative T2 distributions from complicated porous structures and demonstrate the analysis with examples of ceramics used for filtration and catalysis, and limestone of relevance to the construction and petroleum industries.

  20. Understanding generalized inversions of nuclear magnetic resonance transverse relaxation time in porous media

    SciTech Connect

    Mitchell, J.; Chandrasekera, T. C.

    2014-12-14

    The nuclear magnetic resonance transverse relaxation time T{sub 2}, measured using the Carr-Purcell-Meiboom-Gill (CPMG) experiment, is a powerful method for obtaining unique information on liquids confined in porous media. Furthermore, T{sub 2} provides structural information on the porous material itself and has many applications in petrophysics, biophysics, and chemical engineering. Robust interpretation of T{sub 2} distributions demands appropriate processing of the measured data since T{sub 2} is influenced by diffusion through magnetic field inhomogeneities occurring at the pore scale, caused by the liquid/solid susceptibility contrast. Previously, we introduced a generic model for the diffusion exponent of the form −ant{sub e}{sup k} (where n is the number and t{sub e} the temporal separation of spin echoes, and a is a composite diffusion parameter) in order to distinguish the influence of relaxation and diffusion in CPMG data. Here, we improve the analysis by introducing an automatic search for the optimum power k that best describes the diffusion behavior. This automated method is more efficient than the manual trial-and-error grid search adopted previously, and avoids variability through subjective judgments of experimentalists. Although our method does not avoid the inherent assumption that the diffusion exponent depends on a single k value, we show through simulation and experiment that it is robust in measurements of heterogeneous systems that violate this assumption. In this way, we obtain quantitative T{sub 2} distributions from complicated porous structures and demonstrate the analysis with examples of ceramics used for filtration and catalysis, and limestone of relevance to the construction and petroleum industries.

  1. Induced Clustered Nanoconfinement of Superparamagnetic Iron Oxide in Biodegradable Nanoparticles Enhances Transverse Relaxivity for Targeted Theranostics

    PubMed Central

    Ragheb, Ragy R. T.; Kim, Dongin; Bandyopadhyay, Arunima; Chahboune, Halima; Bulutoglu, Beyza; Ezaldein, Harib; Criscione, Jason M.; Fahmy, Tarek M.

    2013-01-01

    Purpose Combined therapeutic and diagnostic agents, “theranostics” are emerging valuable tools for noninvasive imaging and drug delivery. Here, we report on a solid biodegradable multifunctional nanoparticle that combines both features. Methods Poly(lactide-co-glycolide) nanoparticles were engineered to confine superparamagnetic iron oxide contrast for magnetic resonance imaging while enabling controlled drug delivery and targeting to specific cells. To achieve this dual modality, fatty acids were used as anchors for surface ligands and for encapsulated iron oxide in the polymer matrix. Results We demonstrate that fatty acid modified iron oxide prolonged retention of the contrast agent in the polymer matrix during degradative release of drug. Antibody-fatty acid surface modification facilitated cellular targeting and subsequent internalization in cells while inducing clustering of encapsulated fatty-acid modified superparamagnetic iron oxide during particle formulation. This induced clustered confinement led to an aggregation within the nanoparticle and, hence, higher transverse relaxivity, r2, (294 mM−1 s−1) compared with nanoparticles without fatty-acid ligands (160 mM−1 s−1) and higher than commercially available superparamagnetic iron oxide nanoparticles (89 mM−1 s−1). Conclusion Clustering of superparamagnetic iron oxide in poly(lactide-co-glycolide) did not affect the controlled release of encapsulated drugs such as methotrexate or clodronate and their subsequent pharmacological activity, thus highlighting the full theranostic capability of our system. PMID:23401099

  2. Translational diffusion of macromolecular assemblies measured using transverse relaxation-optimized PFG-NMR

    PubMed Central

    Horst, Reto; Horwich, Arthur L.

    2012-01-01

    In structural biology, pulsed field gradient (PFG) NMR for characterization of size and hydrodynamic parameters of macromolecular solutes has the advantage over other techniques that the measurements can be recorded with identical solution conditions as used for NMR structure determination or for crystallization trials. This paper describes two transverse relaxation-optimized (TRO) 15N-filtered PFG stimulated-echo (STE) experiments for studies of macromolecular translational diffusion in solution, 1H-TRO-STE and 15N-TRO-STE, which include CRINEPT and TROSY elements. Measurements with mixed micelles of the Escherichia coli outer membrane protein X (OmpX) and the detergent Fos-10 were used for a systematic comparison of 1H-TRO-STE and 15N-TRO-STE with conventional 15N-filtered STE experimental schemes. The results provide an extended platform for evaluating the NMR experiments available for diffusion measurements in structural biology projects with molecular particles of different size ranges. An initial application of the 15N-TRO-STE experiment with very long diffusion delays showed that the tedradecamer structure of the 800 kDa Thermus thermophilus chaperonin GroEL is preserved in aqueous solution over the temperature range 25–60°C. PMID:21919531

  3. Translational diffusion of macromolecular assemblies measured using transverse-relaxation-optimized pulsed field gradient NMR.

    PubMed

    Horst, Reto; Horwich, Arthur L; Wüthrich, Kurt

    2011-10-19

    In structural biology, pulsed field gradient (PFG) NMR spectroscopy for the characterization of size and hydrodynamic parameters of macromolecular solutes has the advantage over other techniques that the measurements can be recorded with identical solution conditions as used for NMR structure determination or for crystallization trials. This paper describes two transverse-relaxation-optimized (TRO) (15)N-filtered PFG stimulated-echo (STE) experiments for studies of macromolecular translational diffusion in solution, (1)H-TRO-STE and (15)N-TRO-STE, which include CRINEPT and TROSY elements. Measurements with mixed micelles of the Escherichia coli outer membrane protein X (OmpX) and the detergent Fos-10 were used for a systematic comparison of (1)H-TRO-STE and (15)N-TRO-STE with conventional (15)N-filtered STE experimental schemes. The results provide an extended platform for evaluating the NMR experiments available for diffusion measurements in structural biology projects involving molecular particles with different size ranges. An initial application of the (15)N-TRO-STE experiment with very long diffusion delays showed that the tedradecamer structure of the 800 kDa Thermus thermophilus chaperonin GroEL is preserved in aqueous solution over the temperature range 25-60 °C.

  4. Bone marrow segmentation based on a combined consideration of transverse relaxation processes and Dixon oscillations.

    PubMed

    Balasubramanian, Mukund; Jarrett, Delma Y; Mulkern, Robert V

    2016-05-01

    The aim of this study was to demonstrate that gradient-echo sampling of single spin echoes can be used to isolate the signal from trabecular bone marrow, with high-quality segmentation and surface reconstructions resulting from the application of simple post-processing strategies. Theoretical expressions of the time-domain single-spin-echo signal were used to simulate signals from bone marrow, non-bone fatty deposits and muscle. These simulations were compared with and used to interpret signals obtained by the application of the gradient-echo sampling of a spin-echo sequence to image the knee and surrounding tissues at 1.5 T. Trabecular bone marrow has a much higher reversible transverse relaxation rate than surrounding non-bone fatty deposits and other musculoskeletal tissues. This observation, combined with a choice of gradient-echo spacing that accentuates Dixon-type oscillations from chemical-shift interference effects, enabled the isolation of bone marrow signal from surrounding tissues through the use of simple image subtraction and thresholding. Three-dimensional renderings of the marrow surface were then readily generated with this approach - renderings that may prove useful for bone morphology assessment, e.g. for the measurement of femoral anteversion. In conclusion, understanding the behavior of signals from bone marrow and surrounding tissue as a function of time through a spin echo facilitates the segmentation and reconstruction of bone marrow surfaces using straightforward post-processing strategies that are typically available on modern radiology workstations.

  5. MRI of bone marrow in the distal radius: in vivo precision of effective transverse relaxation times

    NASA Technical Reports Server (NTRS)

    Grampp, S.; Majumdar, S.; Jergas, M.; Lang, P.; Gies, A.; Genant, H. K.

    1995-01-01

    The effective transverse relaxation time T2* is influenced by the presence of trabecular bone, and can potentially provide a measure of bone density as well as bone structure. We determined the in vivo precision of T2* in repeated bone marrow measurements. The T2* measurements of the bone marrow of the distal radius were performed twice within 2 weeks in six healthy young volunteers using a modified water-presaturated 3D Gradient-Recalled Acquisition at Steady State (GRASS) sequence with TE 7, 10, 12, 20, and 30; TR 67; flip angle (FA) 90 degrees. An axial volume covering a length of 5.6 cm in the distal radius was measured. Regions of interest (ROIs) were determined manually and consisted of the entire trabecular bone cross-section extending proximally from the radial subchondral endplate. Reproducibility of T2* and area measurements was expressed as the absolute precision error (standard deviation [SD] in ms or mm2) or as the relative precision error (SD/mean x 100, or coefficient of variation [CV] in %) between the two-point measurements. Short-term precision of T2* and area measurements varied depending on section thickness and location of the ROI in the distal radius. Absolute precision errors for T2* times were between 1.3 and 2.9 ms (relative precision errors 3.8-9.5 %) and for area measurements between 20 and 55 mm2 (relative precision errors 5.1-16.4%). This MR technique for quantitative assessment of trabecular bone density showed reasonable reproducibility in vivo and is a promising future tool for the assessment of osteoporosis.

  6. Changes in transverse relaxation time of quadriceps femoris muscles after active recovery exercises with different intensities.

    PubMed

    Mukaimoto, Takahiro; Semba, Syun; Inoue, Yosuke; Ohno, Makoto

    2014-01-01

    The purpose of this study was to examine the changes in the metabolic state of quadriceps femoris muscles using transverse relaxation time (T2), measured by muscle functional magnetic resonance (MR) imaging, after inactive or active recovery exercises with different intensities following high-intensity knee-extension exercise. Eight healthy men performed recovery sessions with four different conditions for 20 min after high-intensity knee-extension exercise on separate days. During the recovery session, the participants conducted a light cycle exercise for 20 min using a cycle (50%, 70% and 100% of the lactate threshold (LT), respectively: active recovery), and inactive recovery. The MR images of quadriceps femoris muscles were taken before the trial and after the recovery session every 30 min for 120 min. The percentage changes in T2 for the rectus femoris and vastus medialis muscles after the recovery session in 50% LT and 70% LT were significantly lower than those in either inactive recovery or 100% LT. There were no significant differences in those for vastus lateralis and vastus intermedius muscles among the four trials. The percentage changes in T2 of rectus femoris and vastus medialis muscles after the recovery session in 50% LT and 70% LT decreased to the values before the trial faster than those in either inactive recovery or 100% LT. Those of vastus lateralis and vastus intermedius muscles after the recovery session in 50% LT and 70% LT decreased to the values before the trial faster than those in 100% LT. Although the changes in T2 after active recovery exercises were not uniform in exercised muscles, the results of this study suggest that active recovery exercise with the intensities below LT are more effective to recover the metabolic state of quadriceps femoris muscles after intense exercise than with either intensity at LT or inactive recovery.

  7. Mechanical Impedance of the Non-loaded Lower Leg with Relaxed Muscles in the Transverse Plane

    PubMed Central

    Ficanha, Evandro Maicon; Ribeiro, Guilherme Aramizo; Rastgaar, Mohammad

    2015-01-01

    This paper describes the protocols and results of the experiments for the estimation of the mechanical impedance of the humans’ lower leg in the External–Internal direction in the transverse plane under non-load bearing condition and with relaxed muscles. The objectives of the estimation of the lower leg’s mechanical impedance are to facilitate the design of passive and active prostheses with mechanical characteristics similar to the humans’ lower leg, and to define a reference that can be compared to the values from the patients suffering from spasticity. The experiments were performed with 10 unimpaired male subjects using a lower extremity rehabilitation robot (Anklebot, Interactive Motion Technologies, Inc.) capable of applying torque perturbations to the foot. The subjects were in a seated position, and the Anklebot recorded the applied torques and the resulting angular movement of the lower leg. In this configuration, the recorded dynamics are due mainly to the rotations of the ankle’s talocrural and the subtalar joints, and any contribution of the tibiofibular joints and knee joint. The dynamic mechanical impedance of the lower leg was estimated in the frequency domain with an average coherence of 0.92 within the frequency range of 0–30 Hz, showing a linear correlation between the displacement and the torques within this frequency range under the conditions of the experiment. The mean magnitude of the stiffness of the lower leg (the impedance magnitude averaged in the range of 0–1 Hz) was determined as 4.9 ± 0.74 Nm/rad. The direct estimation of the quasi-static stiffness of the lower leg results in the mean value of 5.8 ± 0.81 Nm/rad. An analysis of variance shows that the estimated values for the stiffness from the two experiments are not statistically different. PMID:26697424

  8. NMR permeability estimators in 'chalk' carbonate rocks obtained under different relaxation times and MICP size scalings

    NASA Astrophysics Data System (ADS)

    Rios, Edmilson Helton; Figueiredo, Irineu; Moss, Adam Keith; Pritchard, Timothy Neil; Glassborow, Brent Anthony; Guedes Domingues, Ana Beatriz; Bagueira de Vasconcellos Azeredo, Rodrigo

    2016-07-01

    The effect of the selection of different nuclear magnetic resonance (NMR) relaxation times for permeability estimation is investigated for a set of fully brine-saturated rocks acquired from Cretaceous carbonate reservoirs in the North Sea and Middle East. Estimators that are obtained from the relaxation times based on the Pythagorean means are compared with estimators that are obtained from the relaxation times based on the concept of a cumulative saturation cut-off. Select portions of the longitudinal (T1) and transverse (T2) relaxation-time distributions are systematically evaluated by applying various cut-offs, analogous to the Winland-Pittman approach for mercury injection capillary pressure (MICP) curves. Finally, different approaches to matching the NMR and MICP distributions using different mean-based scaling factors are validated based on the performance of the related size-scaled estimators. The good results that were obtained demonstrate possible alternatives to the commonly adopted logarithmic mean estimator and reinforce the importance of NMR-MICP integration to improving carbonate permeability estimates.

  9. Strange metal from Gutzwiller correlations in infinite dimensions: Transverse transport, optical response, and rise of two relaxation rates

    NASA Astrophysics Data System (ADS)

    Ding, Wenxin; Žitko, Rok; Shastry, B. Sriram

    2017-09-01

    Using two approaches to strongly correlated systems, the extremely correlated Fermi liquid theory and the dynamical mean field theory, we compute the transverse transport coefficients, namely, the Hall constants RH and Hall angles θH, and the longitudinal and transverse optical response of the U =∞ Hubbard model in the limit of infinite dimensions. We focus on two successive low-temperature regimes, the Gutzwiller-correlated Fermi liquid (GCFL) and the Gutzwiller-correlated strange metal (GCSM). We find that the Hall angle cotθH is proportional to T2 in the GCFL regime, while upon warming into the GCSM regime it first passes through a downward bend and then continues as T2. Equivalently, RH is weakly temperature dependent in the GCFL regime, but becomes strongly temperature dependent in the GCSM regime. Drude peaks are found for both the longitudinal optical conductivity σx x(ω ) and the optical Hall angles tanθH(ω ) below certain characteristic energy scales. By comparing the relaxation rates extracted from fitting to the Drude formula, we find that in the GCFL regime there is a single relaxation rate controlling both longitudinal and transverse transport, while in the GCSM regime two different relaxation rates emerge. We trace the origin of this behavior to the dynamical particle-hole asymmetry of the Dyson self-energy, arguably a generic feature of doped Mott insulators.

  10. Determination of transverse relaxation rates in systems with scalar-coupled spins: The role of antiphase coherences

    NASA Astrophysics Data System (ADS)

    Segawa, Takuya F.; Bodenhausen, Geoffrey

    2013-12-01

    Homogeneous line-widths that arise from transverse relaxation tend to be masked by B0 field inhomogeneity and by multiplets due to homonuclear J-couplings. Besides well-known spin-locking sequences that lead to signals that decay with a rate R1ρ without any modulations, alternative experiments allow one to determine the transverse relaxation rates R2 in systems with scalar-coupled spins. We evaluate three recent strategies by experiment and simulation: (i) moderate-amplitude SITCOM-CPMG sequences (Dittmer and Bodenhausen, 2006 [2]), (ii) multiple-quantum filtered (MQF) sequences (Barrère et al., 2011 [4]) and (iii) PROJECT sequences (Aguilar et al., 2012 [5]). Experiments where the J-evolution is suppressed by spin-locking measure the pure relaxation rate R2(Ix) of an in-phase component. Experiments based on J-refocusing yield a mixture of in-phase rates R2(Ix) and antiphase rates R2(2IySz), where the latter are usually faster than the former. Moderate-amplitude SITCOM-CPMG and PROJECT methods can be applied to systems with many coupled spins, but applications of MQF sequences are limited to two-spin systems since modulations in larger systems can only partly be suppressed.

  11. Analysis of 31P MAS NMR spectra and transversal relaxation of bacteriophage M13 and tobacco mosaic virus.

    PubMed Central

    Magusin, P C; Hemminga, M A

    1994-01-01

    Phosphorus magic angle spinning nuclear magnetic resonance (NMR) spectra and transversal relaxation of M13 and TMV are analyzed by use of a model, which includes both local backbone motions of the encapsulated nucleic acid molecules and overall rotational diffusion of the rod-shaped virions about their length axis. Backbone motions influence the sideband intensities by causing a fast restricted reorientation of the phosphodiesters. To evaluate their influence on the observed sideband patterns, we extend the model that we used previously to analyze nonspinning 31P NMR lineshapes (Magusin, P.C.M.M., and M. A. Hemminga. 1993a. Biophys. J. 64:1861-1868) to magic angle spinning NMR experiments. Backbone motions also influence the conformation of the phosphodiesters, causing conformational averaging of the isotropic chemical shift, which offers a possible explanation for the various linewidths of the centerband and the sidebands observed for M13 gels under various conditions. The change of the experimental lineshape of M13 as a function of temperature and hydration is interpreted in terms of fast restricted fluctuation of the dihedral angles between the POC and the OCH planes on both sides of the 31P nucleus in the nucleic acid backbone. Backbone motions also seem to be the main cause of transversal relaxation measured at spinning rates of 4 kHz or higher. At spinning rates less than 2 kHz, transversal relaxation is significantly faster. This effect is assigned to slow, overall rotation of the rod-shaped M13 phage about its length axis. Equations are derived to simulate the observed dependence of T2e on the spinning rate. PMID:8038391

  12. Creep and inverse stress relaxation behaviors of carbon nanotube yarns.

    PubMed

    Misak, H E; Sabelkin, V; Miller, L; Asmatulu, R; Mall, S

    2013-12-01

    Creep, creep recovery and inverse stress relaxation behaviors of carbon nanotube yarns that consisted of 1-, 30-, and 100-yarn(s) were characterized. Primary and secondary creep stages were observed over the duration of 336 h. The primary creep stage lasted for about 4 h at an applied load equal to 75% of the ultimate tensile strength. The total strain in the primary stage was significantly larger in the carbon nanotube multi-yarn than in the carbon nanotube 1-yarn. In the secondary stage, 1-yarn also had a smaller steady state strain rate than the multi-yarn, and it was independent of number of yarns in multi-yarn. Strain response under cyclic creep loading condition was comparable to its counterpart in non-cyclic (i.e., standard) creep test except that strain response during the first cycle was slightly different from the subsequent cycles. Inverse creep (i.e., strain recovery) was observed in the 100-yarn during the cyclic creep tests after the first unloading cycle. Furthermore, inverse stress relaxation of the multi-yarns was characterized. Inverse stress relaxation was larger and for longer duration with the larger number of yarns.

  13. The Effect of Magnetic Field Inhomogeneity on the Transverse Relaxation of Quadrupolar Nuclei Measured by Multiple Quantum Filtered NMR

    NASA Astrophysics Data System (ADS)

    Eliav, U.; Kushnir, T.; Knubovets, T.; Itzchak, Y.; Navon, G.

    1997-09-01

    The effects of magnetic fieldsB0andB1inhomogeneities on techniques which are commonly used for the measurements of triple-quantum-filtered (TQF) NMR spectroscopy of23Na in biological tissues are analyzed. The results of measurements by pulse sequences with and without refocusing ofB0inhomogeneities are compared. It is shown that without refocusing the errors in the measurement of the transverse relaxation times by TQF NMR spectroscopy may be as large as 100%, and thus, refocusing of magnetic field inhomogeneity is mandatory. Theoretical calculations demonstrate that without refocusingB0inhomogeneities the spectral width and phase depend on the interpulse time intervals, thus, leading to errors in the measured relaxation times. It is shown that pulse sequences that were used for the refocusing of the magnetic field (B0) inhomogeneity also reduce the sensitivity of the experimental results to radiofrequency (B1) magnetic field inhomogeneity.

  14. Dielectric relaxation of near-percolated carbon nanofiber polypropylene composites

    NASA Astrophysics Data System (ADS)

    Paleo, A. J.; Zille, A.; Van Hattum, F. W.; Ares-Pernas, A.; Agostinho Moreira, J.

    2017-07-01

    In this work, the morphological, structural and dielectric analysis of near-percolated polypropylene (PP) composites containing carbon nanofibers (CNF) processing by melt-mixing are investigated. Whereas the morphological analysis shows that CNF exhibit some tendency to agglomerate within the PP matrix, the structural analysis showed first a general decrease in the intensity of the IR bands as a consequence of the interaction between carbon nanofibers and PP matrix and second an increase of the crystallinity degree of the PP/CNF composites when compared to the pure PP. The dielectric analysis demonstrates enhanced dielectric constants (from 2.97 for neat polymer to 9.7 for 1.9 vol% loaded composites at 200 Hz) and low dielectric losses. Furthermore, the dielectric relaxation for composites with concentrations in the vicinity of percolation is evidenced and well described by the generalized polydispersive Cole-Cole model from which the values of static dielectric constant (εs) , high frequency dielectric constant (ε∞) , distribution of relaxation time (α) and mean relaxation time (τo), are determined, suggesting that this latter analysis constitutes a strong tool for understanding the relationships between microstructure and dielectric properties in this type of polymer composites.

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    Hydrothermal synthesis of Mn1-xZnxFe2O4 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 B0=0.5 T, reveal high transverse relaxivity (r2(20 °C)=450 s-1 mmol(Me3O4)-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.

  16. Assessing tumor cytoarchitecture using multi-echo DSC-MRI derived measures of the Transverse Relaxivity at Tracer Equilibrium (TRATE)

    PubMed Central

    Semmineh, Natenael B; Xu, Junzhong; Skinner, Jack T; Xie, Jingping; Li, Hua; Ayers, Gregory; Quarles, C Chad

    2014-01-01

    Purpose In brain tumor dynamic susceptibility contrast (DSC)-MRI studies, multi-echo acquisition methods are used to quantify the dynamic changes in T1 and T2* that occur when contrast agent (CA) extravasates. Such methods also enable the estimation of the effective tissue CA transverse relaxivity. The goal of this study was to evaluate the sensitivity of the Transverse Relaxivity at Tracer Equilibrium (TRATE) to tumor cytoarchitecture. Theory and Methods Computational and in vitro studies were used to evaluate the biophysical basis of TRATE. In 9L, C6 and human brain tumors, TRATE, the apparent diffusion coefficient (ADC), the CA transfer constant (Ktrans), the extravascular extracellular volume fraction (ve) and histological data were compared. Results Simulations and in vitro results indicate that TRATE is highly sensitive to variations in cellular properties such as cell size and density. The histologic cell density and TRATE values were significantly higher in 9L tumors as compared to C6 tumors. In animal and human tumors, a voxel-wise comparison of TRATE with ADC, ve, and Ktrans maps showed low spatial correlation. Conclusion The assessment of TRATE is clinically feasible and its sensitivity to tissue cytoarchitectural features not present in other imaging methods indicate that it could potentially serve as a unique structural signature or “trait” of cancer. PMID:25227668

  17. The effect of polymer coatings on proton transverse relaxivities of aqueous suspensions of magnetic nanoparticles.

    PubMed

    Carroll, Matthew R J; Huffstetler, Phillip P; Miles, William C; Goff, Jonathon D; Davis, Richey M; Riffle, Judy S; House, Michael J; Woodward, Robert C; St Pierre, Timothy G

    2011-08-12

    Iron oxide magnetic nanoparticles are good candidates for magnetic resonance imaging (MRI) contrast agents due to their high magnetic susceptibilities. Here we investigate 19 polyether-coated magnetite nanoparticle systems comprising three series. All systems were synthesized from the same batch of magnetite nanoparticles. A different polyether was used for each series. Each series comprised systems with systematically varied polyether loadings per particle. A highly significant (p < 0.0001) linear correlation (r = 0.956) was found between the proton relaxivity and the intensity-weighted average diameter measured by dynamic light scattering in the 19 particle systems studied. The intensity-weighted average diameter measured by dynamic light scattering is sensitive to small number fractions of larger particles/aggregates. We conclude that the primary effect leading to differences in proton relaxivity between systems arises from the small degree of aggregation within the samples, which appears to be determined by the nature of the polymer and, for one system, the degree of polymer loading of the particles. For the polyether coatings used in this study, any changes in relaxivity from differences in water exclusion or diffusion rates caused by the polymer are minor in comparison with the changes in relaxivity resulting from variations in the degree of aggregation.

  18. Graphene oxide-Fe3O4 nanoparticle composite with high transverse proton relaxivity value for magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Venkatesha, N.; Poojar, Pavan; Qurishi, Yasrib; Geethanath, Sairam; Srivastava, Chandan

    2015-04-01

    The potential of graphene oxide-Fe3O4 nanoparticle (GO-Fe3O4) composite as an image contrast enhancing material in magnetic resonance imaging has been investigated. Proton relaxivity values were obtained in three different homogeneous dispersions of GO-Fe3O4 composites synthesized by precipitating Fe3O4 nanoparticles in three different reaction mixtures containing 0.01 g, 0.1 g, and 0.2 g of graphene oxide. A noticeable difference in proton relaxivity values was observed between the three cases. A comprehensive structural and magnetic characterization revealed discrete differences in the extent of reduction of the graphene oxide and spacing between the graphene oxide sheets in the three composites. The GO-Fe3O4 composite framework that contained graphene oxide with least extent of reduction of the carboxyl groups and largest spacing between the graphene oxide sheets provided the optimum structure for yielding a very high transverse proton relaxivity value. It was found that the GO-Fe3O4 composites possessed good biocompatibility with normal cell lines, whereas they exhibited considerable toxicity towards breast cancer cells.

  19. Estimating the apparent transverse relaxation time (R2*) from images with different contrasts (ESTATICS) reduces motion artifacts

    PubMed Central

    Weiskopf, Nikolaus; Callaghan, Martina F.; Josephs, Oliver; Lutti, Antoine; Mohammadi, Siawoosh

    2014-01-01

    Relaxation rates provide important information about tissue microstructure. Multi-parameter mapping (MPM) estimates multiple relaxation parameters from multi-echo FLASH acquisitions with different basic contrasts, i.e., proton density (PD), T1 or magnetization transfer (MT) weighting. Motion can particularly affect maps of the apparent transverse relaxation rate R2*, which are derived from the signal of PD-weighted images acquired at different echo times. To address the motion artifacts, we introduce ESTATICS, which robustly estimates R2* from images even when acquired with different basic contrasts. ESTATICS extends the fitted signal model to account for inherent contrast differences in the PDw, T1w and MTw images. The fit was implemented as a conventional ordinary least squares optimization and as a robust fit with a small or large confidence interval. These three different implementations of ESTATICS were tested on data affected by severe motion artifacts and data with no prominent motion artifacts as determined by visual assessment or fast optical motion tracking. ESTATICS improved the quality of the R2* maps and reduced the coefficient of variation for both types of data—with average reductions of 30% when severe motion artifacts were present. ESTATICS can be applied to any protocol comprised of multiple 2D/3D multi-echo FLASH acquisitions as used in the general research and clinical setting. PMID:25309307

  20. Polarized Alkali-Metal Vapor with Minute-Long Transverse Spin-Relaxation Time

    SciTech Connect

    Balabas, M. V.; Karaulanov, T.; Ledbetter, M. P.; Budker, D.

    2010-08-13

    We demonstrate lifetimes of Zeeman populations and coherences in excess of 60 sec in alkali-metal vapor cells with inner walls coated with an alkene material. This represents 2 orders of magnitude improvement over the best paraffin coatings. We explore the temperature dependence of cells coated with this material and investigate spin-exchange relaxation-free magnetometry in a room-temperature environment, a regime previously inaccessible with conventional coating materials.

  1. Quantitative Measurement of Longitudinal and Transverse Cross-Relaxation Rates: An Application to the Analysis of the Internal Dynamics of Ranalexin in Water and Trifluoroethanol

    NASA Astrophysics Data System (ADS)

    Malliavin, T. E.; Desvaux, H.; Aumelas, A.; Chavanieu, A.; Delsuc, M. A.

    1999-09-01

    We describe a quantitative processing method which gives access to the longitudinal and transverse cross-relaxation rates from off-resonance ROESY intensities. This method takes advantage of the dependence of the off-resonance ROESY experiments at any mixing time and any spin-lock angle θ on two relaxation matrices, the longitudinal and the transverse ones. This allows one to take into account multistep magnetization transfers even if the measurements are performed only at one or two mixing times. The ratio of the longitudinal to transverse cross-relaxation rates can then be used as a local indicator of the internal dynamics, without assuming a structure or a model of motion. After validation of this processing method by numerical simulations, it is applied to the analysis of the dynamics of the peptide ranalexin dissolved in pure water and in water/TFE.

  2. Quantitative measurement of longitudinal and transverse cross-relaxation rates: an application to the analysis of the internal dynamics of ranalexin in water and trifluoroethanol.

    PubMed

    Malliavin, T E; Desvaux, H; Aumelas, A; Chavanieu, A; Delsuc, M A

    1999-09-01

    We describe a quantitative processing method which gives access to the longitudinal and transverse cross-relaxation rates from off-resonance ROESY intensities. This method takes advantage of the dependence of the off-resonance ROESY experiments at any mixing time and any spin-lock angle θ on two relaxation matrices, the longitudinal and the transverse ones. This allows one to take into account multistep magnetization transfers even if the measurements are performed only at one or two mixing times. The ratio of the longitudinal to transverse cross-relaxation rates can then be used as a local indicator of the internal dynamics, without assuming a structure or a model of motion. After validation of this processing method by numerical simulations, it is applied to the analysis of the dynamics of the peptide ranalexin dissolved in pure water and in water/TFE. Copyright 1999 Academic Press.

  3. NOTE: Detection limits for ferrimagnetic particle concentrations using magnetic resonance imaging based proton transverse relaxation rate measurements

    NASA Astrophysics Data System (ADS)

    Pardoe, H.; Chua-anusorn, W.; St. Pierre, T. G.; Dobson, J.

    2003-03-01

    A clinical magnetic resonance imaging (MRI) system was used to measure proton transverse relaxation rates (R2) in agar gels with varying concentrations of ferrimagnetic iron oxide nanoparticles in a field strength of 1.5 T. The nanoparticles were prepared by coprecipitation of ferric and ferrous ions in the presence of either dextran or polyvinyl alcohol. The method of preparation resulted in loosely packed clusters (dextran) or branched chains (polyvinyl alcohol) of particles containing of the order of 600 and 400 particles, respectively. For both methods of particle preparation, concentrations of ferrimagnetic iron in agar gel less than 0.01 mg ml-1 had no measurable effect on the value of R2 for the gel. The results indicate that MRI-based R2 measurements using 1.5 T clinical scanners are not quite sensitive enough to detect the very low concentrations of nanoparticulate biogenic magnetite reported in human brain tissue.

  4. Ultrafast direct modulation of transverse-mode coupled-cavity VCSELs far beyond the relaxation oscillation frequency

    NASA Astrophysics Data System (ADS)

    Dalir, Hamed; Koyama, Fumio

    2014-02-01

    A novel approach for bandwidth augmentation for direct modulation of VCSELs using transverse-coupled-cavity (TCC) scheme is raised, which enables us to tailor the modulation-transfer function. The base structure is similar to that of 3QW VCSELs with 980 nm wavelength operation. While the bandwidth of conventional VCSELs was limited by 9-10 GHz, the 3-dB bandwidth of TCC VCSEL with aperture diameters of 8.5×8.5μm2 and 3×3μm2 are increased by a factor of 3 far beyond the relaxation-oscillation frequency. Our current bandwidth achievement on the larger aperture size is 29 GHz which is limited by the used photo-detector. To the best of our knowledge this is the fastest 980 nm VCSEL.

  5. SU-E-I-64: Transverse Relaxation Time in Methylene Protons of Non-Alcoholic Fatty Liver Disease Rats

    SciTech Connect

    Song, K-H; Lee, D-W; Choe, B-Y

    2015-06-15

    Purpose: The aim of this study was to evaluate transverse relaxation time of methylene resonance compared to other lipid resonances. Methods: The examinations were performed using a 3.0 T scanner with a point — resolved spectroscopy (PRESS) sequence. Lipid relaxation time in a lipid phantom filled with canola oil was estimated considering repetition time (TR) as 6000 msec and echo time (TE) as 40 — 550 msec. For in vivo proton magnetic resonance spectroscopy ({sup 1}H — MRS), eight male Sprague — Dawley rats were given free access to a normal - chow (NC) and eight other male Sprague-Dawley rats were given free access to a high — fat (HF) diet. Both groups drank water ad libitum. T{sub 2} measurements in the rats’ livers were conducted at a fixed TR of 6000 msec and TE of 40 – 220 msec. Exponential curve fitting quality was calculated through the coefficients of determination (R{sup 2}). Results: A chemical analysis of phantom and liver was not performed but a T{sub 2} decay curve was acquired. The T{sub 2} relaxation time of methylene resonance was estimated as follows: NC rats, 37.07 ± 4.32 msec; HF rats, 31.43 ± 1.81 msec (p < 0.05). The extrapolated M0 values were higher in HF rats than in NC rats (p < 0.005). Conclusion: This study of {sup 1}H-MRS led to sufficient spectral resolution and signal — to — noise ratio differences to characterize all observable resonances for yielding T{sub 2} relaxation times of methylene resonance. {sup 1}H — MRS relaxation times may be useful for quantitative characterization of various liver diseases, including fatty liver disease. This study was supported by grant (2012-007883 and 2014R1A2A1A10050270) from the Mid-career Researcher Program through the NRF funded by Ministry of Science. In addition, this study was supported by the Industrial R&D of MOTIE/KEIT (10048997, Development of the core technology for integrated therapy devices based on real-time MRI-guided tumor tracking)

  6. Magnetic susceptibility matching at the air-tissue interface in rat lung by using a superparamagnetic intravascular contrast agent: influence on transverse relaxation time of hyperpolarized helium-3.

    PubMed

    Vignaud, Alexandre; Maître, Xavier; Guillot, Geneviève; Durand, Emmanuel; de Rochefort, Ludovic; Robert, Philippe; Vivès, Véronique; Santus, Robin; Darrasse, Luc

    2005-07-01

    Transverse relaxation of hyperpolarized helium-3 magnetization in respiratory airways highly depends on local magnetic field gradients induced by the magnetic susceptibility difference between gas and pulmonary tissue. Fast transverse relaxation is known to be an important feature that yields information about lung microstructure and function, but it is also an essential limitation in designing efficient strategies for lung imaging. Using intravascular injections of a superparamagnetic contrast agent in rats, it was possible to increase the overall susceptibility of the perfused lung tissues and hence to match it with the gas susceptibility. The transverse decay time constant of inhaled hyperpolarized helium-3 was measured in multiple-spin-echo experiments at 1.5 T as a function of the superparamagnetic contrast agent concentration in the animal blood. The time constant was increased by a factor of 3 when an optimal concentration was reached as predicted for susceptibility matching by combining intrinsic susceptibilities of tissue, blood, and gas.

  7. The heterogeneity of segmental dynamics of filled EPDM by 1H transverse relaxation NMR

    NASA Astrophysics Data System (ADS)

    Moldovan, D.; Fechete, R.; Demco, D. E.; Culea, E.; Blümich, B.; Herrmann, V.; Heinz, M.

    2011-01-01

    Residual second moment of dipolar interactions M∼2 and correlation time segmental dynamics distributions were measured by Hahn-echo decays in combination with inverse Laplace transform for a series of unfilled and filled EPDM samples as functions of carbon-black N683 filler content. The fillers-polymer chain interactions which dramatically restrict the mobility of bound rubber modify the dynamics of mobile chains. These changes depend on the filler content and can be evaluated from distributions of M∼2. A dipolar filter was applied to eliminate the contribution of bound rubber. In the first approach the Hahn-echo decays were fitted with a theoretical relationship to obtain the average values of the 1H residual second moment and correlation time <τc>. For the mobile EPDM segments the power-law distribution of correlation function was compared to the exponential correlation function and found inadequate in the long-time regime. In the second approach a log-Gauss distribution for the correlation time was assumed. Furthermore, using an averaged value of the correlation time, the distributions of the residual second moment were determined using an inverse Laplace transform for the entire series of measured samples. The unfilled EPDM sample shows a bimodal distribution of residual second moments, which can be associated to the mobile polymer sub-chains (M∼2≅6.1 rad s) and the second one associated to the dangling chains M∼2≅5.4 rad s). By restraining the mobility of bound rubber, the carbon-black fillers induce diversity in the segmental dynamics like the apparition of a distinct mobile component and changes in the distribution of mobile and free-end polymer segments.

  8. The heterogeneity of segmental dynamics of filled EPDM by (1)H transverse relaxation NMR.

    PubMed

    Moldovan, D; Fechete, R; Demco, D E; Culea, E; Blümich, B; Herrmann, V; Heinz, M

    2011-01-01

    Residual second moment of dipolar interactions M(2) and correlation time segmental dynamics distributions were measured by Hahn-echo decays in combination with inverse Laplace transform for a series of unfilled and filled EPDM samples as functions of carbon-black N683 filler content. The fillers-polymer chain interactions which dramatically restrict the mobility of bound rubber modify the dynamics of mobile chains. These changes depend on the filler content and can be evaluated from distributions of M(2). A dipolar filter was applied to eliminate the contribution of bound rubber. In the first approach the Hahn-echo decays were fitted with a theoretical relationship to obtain the average values of the (1)H residual second moment and correlation time <τ(c)>. For the mobile EPDM segments the power-law distribution of correlation function was compared to the exponential correlation function and found inadequate in the long-time regime. In the second approach a log-Gauss distribution for the correlation time was assumed. Furthermore, using an averaged value of the correlation time, the distributions of the residual second moment were determined using an inverse Laplace transform for the entire series of measured samples. The unfilled EPDM sample shows a bimodal distribution of residual second moments, which can be associated to the mobile polymer sub-chains (M(2) ≅ 6.1 rad (2) s(-2)) and the second one associated to the dangling chains M(2) ≅ 5.4 rad(2) s(-2)). By restraining the mobility of bound rubber, the carbon-black fillers induce diversity in the segmental dynamics like the apparition of a distinct mobile component and changes in the distribution of mobile and free-end polymer segments. Copyright © 2010 Elsevier Inc. All rights reserved.

  9. A theoretical study of rotational diffusion models for rod-shaped viruses. The influence of motion on 31P nuclear magnetic resonance lineshapes and transversal relaxation.

    PubMed Central

    Magusin, P C; Hemminga, M A

    1993-01-01

    Information about the interaction between nucleic acids and coat proteins in intact virus particles may be obtained by studying the restricted backbone dynamics of the incapsulated nucleic acids using 31P nuclear magnetic resonance (NMR) spectroscopy. In this article, simulations are carried out to investigate how reorientation of a rod-shaped virus particle as a whole and isolated nucleic acid motions within the virion influence the 31P NMR lineshape and transversal relaxation dominated by the phosphorus chemical shift anisotropy. Two opposite cases are considered on a theoretical level. First, isotropic rotational diffusion is used as a model for mobile nucleic acids that are loosely or partially bound to the protein coat. The effect of this type of diffusion on lineshape and transversal relaxation is calculated by solving the stochastic Liouville equation by an expansion in spherical functions. Next, uniaxial rotational diffusion is assumed to represent the mobility of phosphorus in a virion that rotates as a rigid rod about its length axis. This type of diffusion is approximated by an exchange process among discrete sites. As turns out from these simulations, the amplitude and the frequency of the motion can only be unequivocally determined from experimental data by a combined analysis of the lineshape and the transversal relaxation. In the fast motional region both the isotropic and the uniaxial diffusion model predict the same transversal relaxation as the Redfield theory. For very slow motion, transversal relaxation resembles the nonexponential relaxation as observed for water molecules undergoing translational diffusion in a magnetic field gradient. In this frequency region T2e is inversely proportional to the cube root of the diffusion coefficient. In addition to the isotropic and uniaxial diffusion models, a third model is presented, in which fast restricted nucleic acid backbone motions dominating the lineshape are superimposed on a slow rotation of the

  10. Transverse spin relaxation and diffusion-constant measurements of spin-polarized 129Xe nuclei in the presence of a magnetic field gradient

    PubMed Central

    Liu, Xiaohu; Chen, Chang; Qu, Tianliang; Yang, Kaiyong; Luo, Hui

    2016-01-01

    The presence of a magnetic field gradient in a sample cell containing spin-polarized 129Xe atoms will cause an increased relaxation rate. We measured the transverse spin relaxation time of 129Xe verse the applied magnetic field gradient and the cell temperature. We then compared the different transverse spin relaxation behavior of dual isotopes of xenon (129Xe and 131Xe) due to magnetic field gradient in the same cell. The experiment results show the residual magnetic field gradient can be measured and compensated by applying a negative magnetic gradient in the sample cell. The transverse spin relaxation time of 129Xe could be increased 2–7 times longer when applying an appropriate magnetic field gradient. The experiment results can also be used to determine the diffusion constant of 129Xe in H2 and N2 to be 0.4 ± 0.26 cm2/sec and 0.12 ± 0.02 cm2/sec. The results are close with theoretical calculation. PMID:27049237

  11. NMR T1 relaxation time measurements and calculations with translational and rotational components for liquid electrolytes containing LiBF4 and propylene carbonate

    NASA Astrophysics Data System (ADS)

    Richardson, P. M.; Voice, A. M.; Ward, I. M.

    2013-12-01

    Longitudinal relaxation (T1) measurements of 19F, 7Li, and 1H in propylene carbonate/LiBF4 liquid electrolytes are reported. Comparison of T1 values with those for the transverse relaxation time (T2) confirm that the measurements are in the high temperature (low correlation time) limit of the T1 minimum. Using data from pulsed field gradient measurements of self-diffusion coefficients and measurements of solution viscosity measured elsewhere, it is concluded that although in general there are contributions to T1 from both translational and rotational motions. For the lithium ions, this is mainly translational, and for the fluorine ions mainly rotational.

  12. NMR T1 relaxation time measurements and calculations with translational and rotational components for liquid electrolytes containing LiBF4 and propylene carbonate.

    PubMed

    Richardson, P M; Voice, A M; Ward, I M

    2013-12-07

    Longitudinal relaxation (T1) measurements of (19)F, (7)Li, and (1)H in propylene carbonate/LiBF4 liquid electrolytes are reported. Comparison of T1 values with those for the transverse relaxation time (T2) confirm that the measurements are in the high temperature (low correlation time) limit of the T1 minimum. Using data from pulsed field gradient measurements of self-diffusion coefficients and measurements of solution viscosity measured elsewhere, it is concluded that although in general there are contributions to T1 from both translational and rotational motions. For the lithium ions, this is mainly translational, and for the fluorine ions mainly rotational.

  13. Dielectric relaxation of ethylene carbonate and propylene carbonate from molecular dynamics simulations

    SciTech Connect

    Chaudhari, Mangesh I.; You, Xinli; Pratt, Lawrence R.; Rempe, Susan B.

    2015-11-24

    Ethylene carbonate (EC) and propylene carbonate (PC) are widely used solvents in lithium (Li)-ion batteries and supercapacitors. Ion dissolution and diffusion in those media are correlated with solvent dielectric responses. Here, we use all-atom molecular dynamics simulations of the pure solvents to calculate dielectric constants and relaxation times, and molecular mobilities. The computed results are compared with limited available experiments to assist more exhaustive studies of these important characteristics. As a result, the observed agreement is encouraging and provides guidance for further validation of force-field simulation models for EC and PC solvents.

  14. Effects of Mesoporous Silica Coating and Post-Synthetic Treatment on the Transverse Relaxivity of Iron Oxide Nanoparticles

    PubMed Central

    Hurley, Katie R.; Lin, Yu-Shen; Zhang, Jinjin; Egger, Sam M.; Haynes, Christy L.

    2013-01-01

    Mesoporous silica nanoparticles have the capacity to load and deliver therapeutic cargo and incorporate imaging modalities, making them prominent candidates for theranostic devices. One of the most widespread imaging agents utilized in this and other theranostic platforms is nanoscale superparamagnetic iron oxide. Although several core-shell magnetic mesoporous silica nanoparticles presented in the literature have provided high T2 contrast in vitro and in vivo, there is ambiguity surrounding which parameters lead to enhanced contrast. Additionally, there is a need to understand the behavior of these imaging agents over time in biologically relevant environments. Herein, we present a systematic analysis of how the transverse relaxivity (r2) of magnetic mesoporous silica nanoparticles is influenced by nanoparticle diameter, iron oxide nanoparticle core synthesis, and the use of a hydrothermal treatment. This work demonstrates that samples which did not undergo a hydrothermal treatment experienced a drop in r2 (75% of original r2 within 8 days of water storage), while samples with hydrothermal treatment maintained roughly the same r2 for over 30 days in water. Our results suggest that iron oxide oxidation is the cause of the r2 loss, and this oxidation can be prevented both during synthesis and storage by the use of deoxygenated conditions during nanoparticle synthesis. The hydrothermal treatment also provides colloidal stability, even in acidic and highly salted solutions, and a resistance against acid degradation of the iron oxide nanoparticle core. The results of this study show the promise of multifunctional mesoporous silica nanoparticles but will also likely inspire further investigation into multiples types of theranostic devices, taking into consideration their behavior over time and in relevant biological environments. PMID:23814377

  15. Slow magnetic relaxation induced by a large transverse zero-field splitting in a Mn(II)Re(IV)(CN)2 single-chain magnet.

    PubMed

    Feng, Xiaowen; Liu, Junjie; Harris, T David; Hill, Stephen; Long, Jeffrey R

    2012-05-02

    The model compounds (NBu(4))(2)[ReCl(4)(CN)(2)] (1), (DMF)(4)ZnReCl(4)(CN)(2) (2), and [(PY5Me(2))(2)Mn(2)ReCl(4)(CN)(2)](PF(6))(2) (3) have been synthesized to probe the origin of the magnetic anisotropy barrier in the one-dimensional coordination solid (DMF)(4)MnReCl(4)(CN)(2) (4). High-field electron paramagnetic resonance spectroscopy reveals the presence of an easy-plane anisotropy (D > 0) with a significant transverse component, E, in compounds 1-3. These findings indicate that the onset of one-dimensional spin correlations within the chain compound 4 leads to a suppression of quantum tunneling of the magnetization within the easy plane, resulting in magnetic bistability and slow relaxation behavior. Within this picture, it is the transverse E term associated with the Re(IV) centers that determines the easy axis and the anisotropy energy scale associated with the relaxation barrier. The results demonstrate for the first time that slow magnetic relaxation can be achieved through optimization of the transverse anisotropy associated with magnetic ions that possess easy-plane anisotropy, thus providing a new direction in the design of single-molecule and single-chain magnets. © 2012 American Chemical Society

  16. Effects of in-pulse transverse relaxation in 3D ultrashort echo time sequences: analytical derivation, comparison to numerical simulation and experimental application at 3T.

    PubMed

    Springer, Fabian; Steidle, Günter; Martirosian, Petros; Claussen, Claus D; Schick, Fritz

    2010-09-01

    The introduction of ultrashort-echo-time-(UTE)-sequences to clinical whole-body MR scanners has opened up the field of MR characterization of materials or tissues with extremely fast signal decay. If the transverse relaxation time is in the range of the RF-pulse duration, approximation of the RF-pulse by an instantaneous rotation applied at the middle of the RF-pulse and immediately followed by free relaxation will lead to a distinctly underestimated echo signal. Thus, the regular Ernst equation is not adequate to correctly describe steady state signal under those conditions. The paper presents an analytically derived modified Ernst equation, which correctly describes in-pulse relaxation of transverse magnetization under typical conditions: The equation is valid for rectangular excitation pulses, usually applied in 3D UTE sequences. Longitudinal relaxation time of the specimen must be clearly longer than RF-pulse duration, which is fulfilled for tendons and bony structures as well as many solid materials. Under these conditions, the proposed modified Ernst equation enables adequate and relatively simple calculation of the magnetization of materials or tissues. Analytically derived data are compared to numerical results obtained by using an established Runge-Kutta-algorithm based on the Bloch equations. Validity of the new approach was also tested by systematical measurements of a solid polymeric material on a 3T whole-body MR scanner. Thus, the presented modified Ernst equation provides a suitable basis for T1 measurements, even in tissues with T2 values as short as the RF-pulse duration: independent of RF-pulse duration, the 'variable flip angle method' led to consistent results of longitudinal relaxation time T1, if the T2 relaxation time of the material of interest is known as well.

  17. Transverse water relaxation in whole blood and erythrocytes at 3T, 7T, 9.4T, 11.7T and 16.4T; determination of intracellular hemoglobin and extracellular albumin relaxivities.

    PubMed

    Grgac, Ksenija; Li, Wenbo; Huang, Alan; Qin, Qin; van Zijl, Peter C M

    2017-05-01

    Blood is a physiological substance with multiple water compartments, which contain water-binding proteins such as hemoglobin in erythrocytes and albumin in plasma. Knowing the water transverse (R2) relaxation rates from these different blood compartments is a prerequisite for quantifying the blood oxygenation level-dependent (BOLD) effect. Here, we report the Carr-Purcell-Meiboom-Gill (CPMG) based transverse (R2CPMG) relaxation rates of water in bovine blood samples circulated in a perfusion system at physiological temperature in order to mimic blood perfusion in humans. R2CPMG values of blood plasma, lysed packed erythrocytes, lysed plasma/erythrocyte mixtures, and whole blood at 3 T, 7 T, 9.4 T, 11.7 T and 16.4 T were measured as a function of hematocrit or hemoglobin concentration, oxygenation, and CPMG inter-echo spacing (τcp). R2CPMG in lysed cells showed a small τcp dependence, attributed to the water exchange rate between free and hemoglobin-bound water to be much faster than τcp. This was contrary to the tangential dependence in whole blood, where a much slower exchange between cells and blood plasma applies. Whole blood data were fitted as a function of τcp using a general tangential correlation time model applicable for exchange as well as diffusion contributions to R2CPMG, and the intercept R20blood at infinitely short τcp was determined. The R20blood values at different hematocrit and the R2CPMG values of lysed erythrocyte/plasma mixtures at different hemoglobin concentration were used to determine the relaxivity of hemoglobin inside the erythrocyte (r2Hb) and albumin (r2Alb) in plasma. The r2Hb values obtained from lysed erythrocytes and whole blood were comparable at full oxygenation. However, while r2Hb determined from lysed cells showed a linear dependence on oxygenation, this dependence became quadratic in whole blood. This possibly suggests an additional relaxation effect inside intact cells, perhaps due to hemoglobin proximity to the

  18. THE EXCRETION OF CARBON DIOXIDE BY RELAXED AND CONTRACTED SEA ANEMONES

    PubMed Central

    Parker, G. H.

    1922-01-01

    1. The metabolism of the sea anemone Metridium marginatum Edw. was measured in four states, relaxed, relaxing, contracted, and contracting, by means of an Osterhout respiratory apparatus. The basis of measurement was the number of hundred-thousandths of a milligram of carbon dioxide excreted per second by a gram of living sea anemone. 2. In the relaxed state this varied from 6.1 to 4.4+ and averaged 5.43–. 3. In a comparison of the relaxed and contracted states the amount of carbon dioxide excreted was found to beabout the same; in one instance in relaxation 4.2 and in contraction 4.1+; in another in relaxation 7.8+ and 7.9– and in contraction 8.1–. 4. In a comparison of the three states relaxed, relaxing, and contracting, the first two were found to average about the same, 4.8+ and 4.6– respectively and the last proved to be appreciably higher 7.1–. 5. It is, therefore, concluded that the process of relaxing and the states of relaxation and of contraction are accompanied by no unusual metabolism, but that in the operation of contracting the metabolism becomes about half again as intense as that characteristic of the other states. 6. The maintenance of the contracted state in Metridium for days at a time without an increase of metabolism indicates that its musculature is of the type known as tonus muscle. 7. In tonus muscle, contraction is accomplished by an active shortening of the myofibrils, extension by a passive drawing out of these fibrils through the distension of the adjacent cavities, etc., and the continued maintenance of any particular state of shortening by some form of catch mechanism in the muscle, such, possibly, as the gelation of its sarcoplasm. PMID:19871978

  19. Vibrational relaxation of carbon monoxide studied by two-wavelength infrared emission

    NASA Technical Reports Server (NTRS)

    Chackerian, C., Jr.

    1973-01-01

    Experimental results are presented for the vibrational relaxation of pure carbon monoxide behind incident shock waves over the temperature range 4000 to 6300 K. The data were obtained as infrared emission from the fundamental and overtone vibrational band systems (in some of the experiments the two-band systems were recorded simultaneously). The data are consistent with present theories for the vibrational relaxation of diatomic molecules and can be interpreted in terms of an initial Boltzmann vibrational distribution relaxing toward final equilibrium via a continuous sequence of intermediate Boltzmann distributions.

  20. Bi-exponential proton transverse relaxation rate (R2) image analysis using RF field intensity-weighted spin density projection: potential for R2 measurement of iron-loaded liver.

    PubMed

    Clark, Paul R; Chua-anusorn, Wanida; St Pierre, Timothy G

    2003-06-01

    A bi-exponential proton transverse relaxation rate (R(2)) image analysis technique has been developed that enables the discrimination of dual compartment transverse relaxation behavior in systems with rapid transverse relaxation enhancement. The technique is particularly well suited to single spin-echo imaging studies where a limited number of images are available for analysis. The bi-exponential R(2) image analysis is facilitated by estimation of the initial proton spin density signal within the region of interest weighted by the RF field intensities. The RF field intensity-weighted spin density map is computed by solving a boundary value problem presented by a high spin density, long T(2) material encompassing the region for analysis. The accuracy of the bi-exponential R(2) image analysis technique is demonstrated on a simulated dual compartment manganese chloride phantom system with relaxation rates and relative population densities between the two compartments similar to the bi-exponential transverse relaxation behavior expected of iron loaded liver. Results from analysis of the phantoms illustrate the potential of bi-exponential R(2) image analysis with RF field intensity-weighted spin density projection for quantifying transverse relaxation enhancement as it occurs in liver iron overload.

  1. Incorporating reversible and irreversible transverse relaxation effects into Steady State Free Precession (SSFP) signal intensity expressions for fMRI considerations.

    PubMed

    Mulkern, Robert V; Balasubramanian, Mukund; Orbach, Darren B; Mitsouras, Dimitrios; Haker, Steven J

    2013-04-01

    Among the multiple sequences available for functional magnetic resonance imaging (fMRI), the Steady State Free Precession (SSFP) sequence offers the highest signal-to-noise ratio (SNR) per unit time as well as distortion free images not feasible with the more commonly employed single-shot echo planar imaging (EPI) approaches. Signal changes occurring with activation in SSFP sequences reflect underlying changes in both irreversible and reversible transverse relaxation processes. The latter are characterized by changes in the central frequencies and widths of the inherent frequency distribution present within a voxel. In this work, the well-known frequency response of the SSFP signal intensity is generalized to include the widths and central frequencies of some common frequency distributions on SSFP signal intensities. The approach, using a previously unnoted series expansion, allows for a separation of reversible from irreversible transverse relaxation effects on SSFP signal intensity changes. The formalism described here should prove useful for identifying and modeling mechanisms associated with SSFP signal changes accompanying neural activation. Copyright © 2013 Elsevier Inc. All rights reserved.

  2. 1H metabolite relaxation times at 3.0 tesla: Measurements of T1 and T2 values in normal brain and determination of regional differences in transverse relaxation.

    PubMed

    Träber, Frank; Block, Wolfgang; Lamerichs, Rolf; Gieseke, Jürgen; Schild, Hans H

    2004-05-01

    To measure 1H relaxation times of cerebral metabolites at 3 T and to investigate regional variations within the brain. Investigations were performed on a 3.0-T clinical whole-body magnetic resonance (MR) system. T2 relaxation times of N-acetyl aspartate (NAA), total creatine (tCr), and choline compounds (Cho) were measured in six brain regions of 42 healthy subjects. T1 relaxation times of these metabolites and of myo-inositol (Ins) were determined in occipital white matter (WM), the frontal lobe, and the motor cortex of 10 subjects. T2 values of all metabolites were markedly reduced with respect to 1.5 T in all investigated regions. T2 of NAA was significantly (P < 0.001) shorter in the motor cortex (247 +/- 13 msec) than in occipital WM (301 +/- 18 msec). T2 of the tCr methyl resonance showed a corresponding yet less pronounced decrease (162 +/- 16 msec vs. 178 +/- 9 msec, P = 0.021). Even lower T2 values for all metabolites were measured in the basal ganglia. Metabolite T1 relaxation times at 3.0 T were not significantly different from the values at 1.5 T. Transverse relaxation times of the investigated cerebral metabolites exhibit an inverse proportionality to magnetic field strength, and especially T2 of NAA shows distinct regional variations at 3 T. These can be attributed to differences in relative WM/gray matter (GM) contents and to local paramagnetism. Copyright 2004 Wiley-Liss, Inc.

  3. Effects of initial stress on transverse wave propagation in carbon nanotubes based on Timoshenko laminated beam models

    NASA Astrophysics Data System (ADS)

    Cai, H.; Wang, X.

    2006-01-01

    Based on Timoshenko laminated beam models, this paper investigates the influence of initial stress on the vibration and transverse wave propagation in individual multi-wall carbon nanotubes (MWNTs) under ultrahigh frequency (above 1 THz), in which the initial stress in the MWNTs can occur due to thermal or lattice mismatch between different materials. Considering van der Waals force interaction between two adjacent tubes and effects of rotary inertia and shear deformation, results show that the initial stress in individual multi-wall carbon nanotubes not only affects the number of transverse wave speeds and the magnitude of transverse wave speeds, but also terahertz critical frequencies at which the number of wave speeds changes. When the initial stress in individual multi-wall carbon nanotubes is the compressive stress, transverse wave speeds decrease and the vibration amplitude ratio of two adjacent tubes increases. When the initial stress in individual multi-wall carbon nanotubes is the tensile stress, transverse wave speeds increase and the vibration amplitude ratio of two adjacent tubes decreases. The investigation of the effects of initial stress on transverse wave propagation in carbon nanotubes may be used as a useful reference for the application and the design of nanoelectronic and nanodrive devices, nano-oscillators, and nanosensors, in which carbon nanotubes act as basic elements.

  4. Measurement of transverse relaxation times of J-coupled metabolites in the human visual cortex at 4 T.

    PubMed

    Deelchand, Dinesh Kumar; Henry, Pierre-Gilles; Uǧurbil, Kâmil; Marjańska, Małgorzata

    2012-04-01

    Accurate quantification of (1) H NMR spectra often requires knowledge of the relaxation times to correct for signal losses due to relaxation and saturation. In human brain, T(2) values for singlets such as N-acetylaspartate, creatine, and choline have been reported, but few T(2) values are available for J-coupled spin systems. The purpose of this study was to measure the T(2) relaxation times of J-coupled metabolites in the human occipital lobe using the LASER sequence. Spectra were acquired at multiple echo times and were analyzed with an LCModel using basis sets simulated at each echo time. Separate basis spectra were used for resonances of protons belonging to the same molecule but having very different T(2) values (e.g., two separate basis spectra were used for the singlet and multiplet signal in N-acetylaspartate). The T(2) values for the N-acetylaspartate multiplet (149 ± 12 ms), glutamate (125 ± 10 ms), myo-inositol (139 ± 20 ms), and taurine (196 ± 28 ms) were successfully measured in the human visual cortex at 4 T. These measured T(2) relaxation times have enabled the accurate and absolute quantification of cerebral metabolites at longer echo times. Copyright © 2011 Wiley-Liss, Inc.

  5. Mixed quantum-classical simulations of the vibrational relaxation of photolyzed carbon monoxide in a hemoprotein

    NASA Astrophysics Data System (ADS)

    Schubert, Alexander; Falvo, Cyril; Meier, Christoph

    2016-08-01

    We present mixed quantum-classical simulations on relaxation and dephasing of vibrationally excited carbon monoxide within a protein environment. The methodology is based on a vibrational surface hopping approach treating the vibrational states of CO quantum mechanically, while all remaining degrees of freedom are described by means of classical molecular dynamics. The CO vibrational states form the "surfaces" for the classical trajectories of protein and solvent atoms. In return, environmentally induced non-adiabatic couplings between these states cause transitions describing the vibrational relaxation from first principles. The molecular dynamics simulation yields a detailed atomistic picture of the energy relaxation pathways, taking the molecular structure and dynamics of the protein and its solvent fully into account. Using the ultrafast photolysis of CO in the hemoprotein FixL as an example, we study the relaxation of vibrationally excited CO and evaluate the role of each of the FixL residues forming the heme pocket.

  6. Mixed quantum-classical simulations of the vibrational relaxation of photolyzed carbon monoxide in a hemoprotein.

    PubMed

    Schubert, Alexander; Falvo, Cyril; Meier, Christoph

    2016-08-07

    We present mixed quantum-classical simulations on relaxation and dephasing of vibrationally excited carbon monoxide within a protein environment. The methodology is based on a vibrational surface hopping approach treating the vibrational states of CO quantum mechanically, while all remaining degrees of freedom are described by means of classical molecular dynamics. The CO vibrational states form the "surfaces" for the classical trajectories of protein and solvent atoms. In return, environmentally induced non-adiabatic couplings between these states cause transitions describing the vibrational relaxation from first principles. The molecular dynamics simulation yields a detailed atomistic picture of the energy relaxation pathways, taking the molecular structure and dynamics of the protein and its solvent fully into account. Using the ultrafast photolysis of CO in the hemoprotein FixL as an example, we study the relaxation of vibrationally excited CO and evaluate the role of each of the FixL residues forming the heme pocket.

  7. Second harmonic generation in carbon nanotubes induced by transversal electrostatic field.

    PubMed

    Trolle, Mads Lund; Pedersen, Thomas Garm

    2013-08-14

    Carbon nanotubes (CNTs) of armchair and zigzag type contain an inversion centre, and are thus intrinsically unable to generate dipole even-order nonlinearities, such as second harmonic generation (SHG). Breaking the inversion symmetry by application of an external voltage transversal to the CNT axis will, however, induce a second harmonic response. Similarly, additional non-vanishing second harmonic tensor elements will be induced in chiral tubes already displaying an intrinsic response. Many geometries realizing such a setup can be envisaged, e.g., an experimental gate setup or deposition of CNTs on, or integration in, strongly polarized host media, perhaps facilitating a tunable second harmonic response. In this work, we calculate the SHG signal from CNTs under transversally applied electric fields based on a tight-binding model.

  8. Scaling Effects in Carbon/Epoxy Laminates Under Transverse Quasi-Static Loading

    NASA Technical Reports Server (NTRS)

    Nettles, Alan T.; Douglas, Michael J.; Estes, Eric E.

    1999-01-01

    Scaling effects were considered for 8, 16, 32, and 64 ply IM-7/8551-7 carbon/epoxy composites plates transversely loaded to the first significant load drop by means of both a quasi-static and an equivalent impact force. The resulting damage was examined by x-ray and photomicroscopy analysis. Load-deflection curves were generated for the quasi-static tests and the resulting indentation depth was measured. Results showed that the load-deflection data scaled well for most of the various thicknesses of plates. However, damage did not scale as well. No correlation could be found between dent depth and any of the other parameters measured in this study. The impact test results showed that significantly less damage was formed compared to the quasi- static results for a given maximum transverse load. The criticality of ply-level scaling (grouping plies) was also examined.

  9. Transverse Coefficient of Thermal Expansion Measurements of Carbon Fibers Using ESEM at High Temperatures

    NASA Technical Reports Server (NTRS)

    Ochoa, O.; Jiang, J.; Putnam, D.; Lo, Z.; Ellis, A.; Effinger, Michael

    2003-01-01

    The transverse coefficient of thermal expansion (CTE) of single IM7, T1000, and P55 carbon fibers are measured at elevated temperatures. The specimens are prepared by press-fitting fiber tows into 0.7mm-diameter cavity in a graphite disk of 5mm in diameter and 3mm high. The specimens are placed on a crucible in an ESEM, and images of the fiber cross section are taken as the fibers are heated up to 800 C. Holding time, heating and cool down cycles are also introduced. The geometrical changes are measured using a graphics tablet. The change in area/perimeter is calculated to determine the strain and transverse CTE for each fiber. In a complimentary computational effort, displacements and stresses are calculated with finite element models.

  10. Transverse Coefficient of Thermal Expansion Measurements of Carbon Fibers Using ESEM at High Temperatures

    NASA Technical Reports Server (NTRS)

    Ochoa, O.; Jiang, J.; Putnam, D.; Lo, Z.; Ellis, A.; Effinger, Michael

    2003-01-01

    The transverse coefficient of thermal expansion (CTE) of single IM7, T1000, and P55 carbon fibers are measured at elevated temperatures. The specimens are prepared by press-fitting fiber tows into 0.7mm-diameter cavity in a graphite disk of 5mm in diameter and 3mm high. The specimens are placed on a crucible in an ESEM, and images of the fiber cross section are taken as the fibers are heated up to 800 C. Holding time, heating and cool down cycles are also introduced. The geometrical changes are measured using a graphics tablet. The change in area/perimeter is calculated to determine the strain and transverse CTE for each fiber. In a complimentary computational effort, displacements and stresses are calculated with finite element models.

  11. Graphene oxide-Fe{sub 3}O{sub 4} nanoparticle composite with high transverse proton relaxivity value for magnetic resonance imaging

    SciTech Connect

    Venkatesha, N.; Srivastava, Chandan; Poojar, Pavan; Geethanath, Sairam; Qurishi, Yasrib

    2015-04-21

    The potential of graphene oxide–Fe{sub 3}O{sub 4} nanoparticle (GO-Fe{sub 3}O{sub 4}) composite as an image contrast enhancing material in magnetic resonance imaging has been investigated. Proton relaxivity values were obtained in three different homogeneous dispersions of GO-Fe{sub 3}O{sub 4} composites synthesized by precipitating Fe{sub 3}O{sub 4} nanoparticles in three different reaction mixtures containing 0.01 g, 0.1 g, and 0.2 g of graphene oxide. A noticeable difference in proton relaxivity values was observed between the three cases. A comprehensive structural and magnetic characterization revealed discrete differences in the extent of reduction of the graphene oxide and spacing between the graphene oxide sheets in the three composites. The GO-Fe{sub 3}O{sub 4} composite framework that contained graphene oxide with least extent of reduction of the carboxyl groups and largest spacing between the graphene oxide sheets provided the optimum structure for yielding a very high transverse proton relaxivity value. It was found that the GO-Fe{sub 3}O{sub 4} composites possessed good biocompatibility with normal cell lines, whereas they exhibited considerable toxicity towards breast cancer cells.

  12. Assessment of chemical exchange in tryptophan-albumin solution through (19)F multicomponent transverse relaxation dispersion analysis.

    PubMed

    Lin, Ping-Chang

    2015-06-01

    A number of NMR methods possess the capability of probing chemical exchange dynamics in solution. However, certain drawbacks limit the applications of these NMR approaches, particularly, to a complex system. Here, we propose a procedure that integrates the regularized nonnegative least squares (NNLS) analysis of multiexponential T2 relaxation into Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion experiments to probe chemical exchange in a multicompartmental system. The proposed procedure was validated through analysis of (19)F T2 relaxation data of 6-fluoro-DL-tryptophan in a two-compartment solution with and without bovine serum albumin. Given the regularized NNLS analysis of a T2 relaxation curve acquired, for example, at the CPMG frequency υ CPMG  = 125, the nature of two distinct peaks in the associated T2 distribution spectrum indicated 6-fluoro-DL-tryptophan either retaining the free state, with geometric mean */multiplicative standard deviation (MSD) = 1851.2 ms */1.51, or undergoing free/albumin-bound interconversion, with geometric mean */MSD = 236.8 ms */1.54, in the two-compartment system. Quantities of the individual tryptophan species were accurately reflected by the associated T2 peak areas, with an interconversion state-to-free state ratio of 0.45 ± 0.11. Furthermore, the CPMG relaxation dispersion analysis estimated the exchange rate between the free and albumin-bound states in this fluorinated tryptophan analog and the corresponding dissociation constant of the fluorinated tryptophan-albumin complex in the chemical-exchanging, two-compartment system.

  13. High performance current and spin diode of atomic carbon chain between transversely symmetric ribbon electrodes

    PubMed Central

    Dong, Yao-Jun; Wang, Xue-Feng; Yang, Shuo-Wang; Wu, Xue-Mei

    2014-01-01

    We demonstrate that giant current and high spin rectification ratios can be achieved in atomic carbon chain devices connected between two symmetric ferromagnetic zigzag-graphene-nanoribbon electrodes. The spin dependent transport simulation is carried out by density functional theory combined with the non-equilibrium Green's function method. It is found that the transverse symmetries of the electronic wave functions in the nanoribbons and the carbon chain are critical to the spin transport modes. In the parallel magnetization configuration of two electrodes, pure spin current is observed in both linear and nonlinear regions. However, in the antiparallel configuration, the spin-up (down) current is prohibited under the positive (negative) voltage bias, which results in a spin rectification ratio of order 104. When edge carbon atoms are substituted with boron atoms to suppress the edge magnetization in one of the electrodes, we obtain a diode with current rectification ratio over 106. PMID:25142376

  14. NMR T{sub 1} relaxation time measurements and calculations with translational and rotational components for liquid electrolytes containing LiBF{sub 4} and propylene carbonate

    SciTech Connect

    Richardson, P. M. Voice, A. M. Ward, I. M.

    2013-12-07

    Longitudinal relaxation (T{sub 1}) measurements of {sup 19}F, {sup 7}Li, and {sup 1}H in propylene carbonate/LiBF{sub 4} liquid electrolytes are reported. Comparison of T{sub 1} values with those for the transverse relaxation time (T{sub 2}) confirm that the measurements are in the high temperature (low correlation time) limit of the T{sub 1} minimum. Using data from pulsed field gradient measurements of self-diffusion coefficients and measurements of solution viscosity measured elsewhere, it is concluded that although in general there are contributions to T{sub 1} from both translational and rotational motions. For the lithium ions, this is mainly translational, and for the fluorine ions mainly rotational.

  15. Differences in patellar cartilage thickness, transverse relaxation time, and deformational behavior: a comparison of young women with and without patellofemoral pain.

    PubMed

    Farrokhi, Shawn; Colletti, Patrick M; Powers, Christopher M

    2011-02-01

    The origin of patellofemoral pain (PFP) may be associated with the inability of the patellofemoral joint cartilage to absorb and distribute patellofemoral joint forces. When compared with a pain-free control group, young active women with PFP will demonstrate differences in their baseline patellar cartilage thickness and transverse (T2) relaxation time, as well as a less adaptive response to an acute bout of joint loading. Controlled laboratory study; Level of evidence, 3. Ten women between the ages of 23 to 37 years with PFP and 10 sex-, age-, and activity-matched pain-free controls participated. Quantitative magnetic resonance imaging of the patellofemoral joint was performed at baseline and after participants performed 50 deep knee bends. Differences in baseline cartilage thickness and T2 relaxation time, as well as the postexercise change in patellar cartilage thickness and T2 relaxation time, were compared between groups. Individuals with PFP demonstrated reductions in baseline cartilage thickness of 14.0% and 14.1% for the lateral patellar facet and total patellar cartilage, respectively. Similarly, individuals with PFP exhibited significantly lower postexercise cartilage thickness change for the lateral patellar facet (2.1% vs 8.9%) and the total patellar cartilage (4.4% vs 10.0%) when compared with the control group. No group differences in baseline or postexercise change in T2 relaxation time were found. The findings suggest that a baseline reduction in patellar cartilage thickness and a reduced deformational behavior of patellar cartilage following an acute bout of loading are associated with presence of PFP symptoms.

  16. Longitudinal waves in carbon nanotubes in the presence of transverse magnetic field and elastic medium

    NASA Astrophysics Data System (ADS)

    Liu, Hu; Liu, Hua; Yang, Jialing

    2017-09-01

    In the present paper, the coupling effect of transverse magnetic field and elastic medium on the longitudinal wave propagation along a carbon nanotube (CNT) is studied. Based on the nonlocal elasticity theory and Hamilton's principle, a unified nonlocal rod theory which takes into account the effects of small size scale, lateral inertia and radial deformation is proposed. The existing rod theories including the classic rod theory, the Rayleigh-Love theory and Rayleigh-Bishop theory for macro solids can be treated as the special cases of the present model. A two-parameter foundation model (Pasternak-type model) is used to represent the elastic medium. The influence of transverse magnetic field, Pasternak-type elastic medium and small size scale on the longitudinal wave propagation behavior of the CNT is investigated in detail. It is shown that the influences of lateral inertia and radial deformation cannot be neglected in analyzing the longitudinal wave propagation characteristics of the CNT. The results also show that the elastic medium and the transverse magnetic field will also affect the longitudinal wave dispersion behavior of the CNT significantly. The results obtained in this paper are helpful for understanding the mechanical behaviors of nanostructures embedded in an elastic medium.

  17. Effect of low concentrations of carbon nanotubes on electric dipole relaxation in a polyurethane elastomer

    NASA Astrophysics Data System (ADS)

    Rabenok, E. V.; Novikov, G. F.; Estrin, Ya. I.; Badamshina, E. R.

    2015-03-01

    The effect of small (up to 0.018 wt %) additions of single-walled carbon nanotubes (SWNTs) on the complex electric modulus M*= M' - jM″ and the spectrum of the relaxation times G(τ) of a cross-linked polyurethane elastomer containing ˜10 vol % of polyamide-6 dispersed in the polyurethane matrix and incompatible with it was studied. The measurements were conducted in the range of electric field frequencies 10-3-105 Hz at temperatures from 133 to 413 K. Based on the shape analysis of the M″( M') diagrams, the contributions of electric conductivity and dielectric relaxation to complex dielectric permittivity ɛ* = ɛ' - jɛ″ were separated and the effect of additions on α and β relaxation for both polyurethane and polyamide phases was analyzed in accordance with the peculiarities of phase-separated systems. The introduction of SWNTs in the composite affected the dielectric properties of the material; the maximum effect was observed at concentrations of 0.002-0.008 wt %; at higher SWNT concentrations, the scatter of data increased and did not allow us to evaluate the effect. The effect of SWNTs on G(τ) in the main phase was opposite to that in the polyamide phase. In the temperature range of α relaxation of the polyurethane phase, the relaxation times increased after the introduction of SWNTs evidently because of the decrease in the free volume that determines the α relaxation times of polyurethane. In contrast, for the polyamide phase in the range of α relaxation, the relaxation times decreased after the introduction of SWNTs. The results agree with the literature data on the effect of ultrasmall SWNT concentrations on the physicomechanical characteristics of the polyurethane elastomer and its electric conductivity.

  18. Thermal relaxation kinetics of defects in single-wall carbon nanotubes

    SciTech Connect

    Uchida, Takashi; Tachibana, Masaru; Kojima, Kenichi

    2007-04-15

    The defects in single-wall carbon nanotubes irradiated with a 248 nm pulsed excimer laser were studied using Raman spectroscopy. The thermal relaxation kinetics of the laser-induced defects was examined at sample temperatures from 296 to 698 K. Two relaxation processes are revealed; one is the fast process with an activation energy of 0.4 eV and the other is the slow process with an activation energy of 0.7 eV. These two processes can correspond to vacancy-interstitial recombination and vacancy migration along the tube axis, respectively.

  19. Transverse spin relaxation and magnetic correlation in Pr1-xCaxMnO3: Influence of particle size variation and chemical doping

    NASA Astrophysics Data System (ADS)

    Shukla, Vinay Kumar; Mukhopadhyay, Soumik

    2017-03-01

    The short ranged magnetic correlations and dynamics of hole doped Pr1-xCaxMnO3 (0.33 < x < 0.5) of different crystallite sizes have been investigated using electron spin resonance spectroscopy. The major contribution to the temperature dependence of paramagnetic line-width is attributed to the spin-lattice relaxation dominated by thermally activated hopping of small polarons with the typical activation energy of 20-50 meV. Irrespective of the crystallite size and dopant concentration, the transverse spin relaxation time (t2) follows a universal scaling behaviour of the type t 2 ˜ ( T / T 0 ) n in the paramagnetic regime, where T0 and n are the scaling parameters. Using the temperature dependence of t2, we construct a phase diagram which shows that near half-doping, the magnetic correlations associated with charge ordering not only survives even down to the crystallite size of 22 nm but is also actually enhanced. We conclude that the eventual suppression of charge ordering with reduction in the particle size is possibly more to do with the greater influence of chemical disorder than any intrinsic effect.

  20. Conductivity analysis of epoxy/carbon nanotubes composites by dipole relaxation and hopping models

    NASA Astrophysics Data System (ADS)

    Ramos, Airton; Pezzin, Sergio H.; Farias, Heric Denis; Becker, Daniela; Bello, Roger H.; Coelho, Luiz A. F.

    2016-10-01

    In this study it was used a numerical technique of successive approximations to estimate parameters of a conductivity model that includes the hopping process and the dipole relaxation for the purpose of describing the behavior of the conductivity measured on nanocomposites with carbon nanotubes in epoxy resin in the range of frequency of 100 Hz to 40 MHz. Two relaxation bands were detected, one with a response below 10 kHz and one above 10 MHz. For the first band, it was observed that the nanocomposites become more conductive, and its conductivity less temperature dependent, as the nanotube content increases. The second band is characterized by a large spread in relaxation time. The results show that the percolation threshold is below 0.15 vol% and that 'ac' hopping is the main transport process above 100 kHz, becoming dominant with respect to percolation at higher temperatures (>340 K).

  1. Electrical transport in transverse direction through silicon carbon alloy multilayers containing regular size silicon quantum dots

    NASA Astrophysics Data System (ADS)

    Mandal, Aparajita; Kole, Arindam; Dasgupta, Arup; Chaudhuri, Partha

    2016-11-01

    Electrical transport in the transverse direction has been studied through a series of hydrogenated silicon carbon alloy multilayers (SiC-MLs) deposited by plasma enhanced chemical vapor deposition method. Each SiC-ML consists of 30 cycles of the alternating layers of a nearly amorphous silicon carbide (a-SiC:H) and a microcrystalline silicon carbide (μc-SiC:H) that contains high density of silicon quantum dots (Si-QDs). A detailed investigation by cross sectional TEM reveals preferential growth of densely packed Si-QDs of regular sizes ∼4.8 nm in diameter in a vertically aligned columnar structure within the SiC-ML. More than six orders of magnitude increase in transverse current through the SiC-ML structure were observed for decrease in the a-SiC:H layer thickness from 13 nm to 2 nm. The electrical transport mechanism was established to be a combination of grain boundary or band tail hopping and Frenkel-Poole (F-P) type conduction depending on the temperature and externally applied voltage ranges. Evaluation of trap concentration within the multilayer structures from the fitted room temperature current voltage characteristics by F-P function shows reduction up-to two orders of magnitude indicating an improvement in the short range order in the a-SiC:H matrix for decrease in the thickness of a-SiC:H layer.

  2. Ab initio determination of the nuclear relaxation contribution to the second hyperpolarizability of carbon disulfide

    NASA Astrophysics Data System (ADS)

    Champagne, Benoı̂t

    1998-04-01

    Although basis set saturation, electron correlation and frequency dispersion have been addressed thoroughly, the electronic second hyperpolarizability of carbon disulfide computed by K. Ohta, T. Sakaguchi, K. Kamada and T. Fukumi (Chem. Phys. Lett. 274 (1997) 306) is not in agreement with experiment. In this Letter the potentially substantial nuclear relaxation contribution is evaluated within the Møller-Plesset scheme limited to second order by using the 6-31G * basis set augmented by three diffuse functions (1p and 2d). Within the enhanced approximation, the nuclear relaxation contribution to the static, dc-Kerr and ESHG second hyperpolarizability turns out to amount to 26.5%, 6.8% and -0.8% of the pure static electronic counterpart, respectively. The remaining gap between theory and experiment suggests new experiments should be carried out.

  3. Two-dimensional longitudinal and transverse relaxation time correlation as a low-resolution nuclear magnetic resonance characterization of ancient ceramics

    NASA Astrophysics Data System (ADS)

    Casieri, Cinzia; Terenzi, Camilla; De Luca, Francesco

    2009-02-01

    Longitudinal and transverse relaxation time correlation (T1-T2) is employed as a nuclear magnetic resonance noninvasive characterization tool for archeological ceramics. This paper is aimed at investigating whether the most relevant firing-induced changes in ceramics, including those involving pore space properties and paramagnetic mineral structures, could be used as markers of the firing process and therefore of ceramics themselves. Ancient ceramics are made up of naturally available clays, often rich in iron impurities, which undergo relevant modifications of pore distribution upon firing. The firing process also assists chemical and physical rearrangement of iron-bearing species, yielding mineral structures with different magnetic properties. That being so, T1-T2 maps are expected to show the interdependence between ceramic structure and firing technology. T1 and T2 distributions are basically proportional to pore-size distribution, but T2, which is also sensitive to magnetic susceptibility effects, may give information on the porous matrix composition as well. Such a methodology has first been employed on laboratory-prepared ceramic samples, with different paramagnetic compositions and controlled firing temperatures, in order to tackle the problem of model-ceramic selection. Then, the T1-T2 correlation approach has been used on medieval ceramic findings in order to get information about their thermal and compositional history. The information obtained by means of two-dimensional correlation maps proves coherent with archeological dating, thus illustrating the capabilities of this method.

  4. Investigating the Relationship between Transverse Relaxation Rate (R2) and Interecho Time in MagA-Expressing, Iron-Labeled Cells.

    PubMed

    Lee, Casey Y; Thompson, R Terry; Prato, Frank S; Goldhawk, Donna E; Gelman, Neil

    2015-01-01

    Reporter gene-based labeling of cells with iron is an emerging method of providing magnetic resonance imaging contrast for long-term cell tracking and monitoring cellular activities. This report investigates 9.4 T nuclear magnetic resonance properties of mammalian cells overexpressing MagA, a putative iron transport protein from magnetotactic bacteria. MagA-expressing MDA-MB-435 cells were cultured in the presence and absence of iron supplementation and compared to the untransfected control. The relationship between the transverse relaxation rate (R2) and interecho time was investigated using the Carr-Purcell-Meiboom-Gill sequence. This relationship was analyzed using a model based on water diffusion in weak magnetic field inhomogeneities (Jensen-Chandra model) as well as a fast-exchange model (Luz-Meiboom model). Increases in R2 with increasing interecho time were larger in the iron-supplemented, MagA-expressing cells compared to other cells. The dependence of R2 on interecho time in these iron-supplemented, MagA-expressing cells was better represented by the Jensen-Chandra model compared to the Luz-Meiboom model, whereas the Luz-Meiboom model performed better for the remaining cell types. Our findings provide an estimate of the distance scale of microscopic magnetic field variations in MagA-expressing cells, which is thought to be related to the size of iron-containing vesicles.

  5. Lung Parenchymal Signal Intensity in MRI: A Technical Review with Educational Aspirations Regarding Reversible Versus Irreversible Transverse Relaxation Effects in Common Pulse Sequences.

    PubMed

    Mulkern, Robert; Haker, Steven; Mamata, Hatsuho; Lee, Edward; Mitsouras, Dimitrios; Oshio, Koichi; Balasubramanian, Mukund; Hatabu, Hiroto

    2014-03-01

    Lung parenchyma is challenging to image with proton MRI. The large air space results in ~l/5th as many signal-generating protons compared to other organs. Air/tissue magnetic susceptibility differences lead to strong magnetic field gradients throughout the lungs and to broad frequency distributions, much broader than within other organs. Such distributions have been the subject of experimental and theoretical analyses which may reveal aspects of lung microarchitecture useful for diagnosis. Their most immediate relevance to current imaging practice is to cause rapid signal decays, commonly discussed in terms of short T2(*) values of 1 ms or lower at typical imaging field strengths. Herein we provide a brief review of previous studies describing and interpreting proton lung spectra. We then link these broad frequency distributions to rapid signal decays, though not necessarily the exponential decays generally used to define T2(*) values. We examine how these decays influence observed signal intensities and spatial mapping features associated with the most prominent torso imaging sequences, including spoiled gradient and spin echo sequences. Effects of imperfect refocusing pulses on the multiple echo signal decays in single shot fast spin echo (SSFSE) sequences and effects of broad frequency distributions on balanced steady state free precession (bSSFP) sequence signal intensities are also provided. The theoretical analyses are based on the concept of explicitly separating the effects of reversible and irreversible transverse relaxation processes, thus providing a somewhat novel and more general framework from which to estimate lung signal intensity behavior in modern imaging practice.

  6. Surface structure and relaxation during the oxidation of carbon monoxide on Pt Pd bimetallic surfaces

    NASA Astrophysics Data System (ADS)

    Lucas, C. A.; Markovic, N. M.; Ball, M.; Stamenkovic, V.; Climent, V.; Ross, P. N.

    2001-05-01

    The atomic structure and surface relaxation of Pd monolayer on Pt(1 1 1) has been studied by surface X-ray scattering, in an aqueous environment under electrostatic potential control, during the adsorption and oxidation of carbon monoxide. The results show that the Pd-Pt layer spacing contracts at the onset of CO oxidation before the Pd adlayer forms an oxide structure that is incommensurate with the Pt lattice. Both the oxide formation and the lattice contraction are fully reversible over many cycles of the applied electrode potential.

  7. Carbon-13 chemical shift anisotropy in DNA bases from field dependence of solution NMR relaxation rates.

    PubMed

    Ying, Jinfa; Grishaev, Alexander; Bax, Ad

    2006-03-01

    Knowledge of (13)C chemical shift anisotropy (CSA) in nucleotide bases is important for the interpretation of solution-state NMR relaxation data in terms of local dynamic properties of DNA and RNA. Accurate knowledge of the CSA becomes particularly important at high magnetic fields, prerequisite for adequate spectral resolution in larger oligonucleotides. Measurement of (13)C relaxation rates of protonated carbons in the bases of the so-called Dickerson dodecamer, d(CGCGAATTCGCG)(2), at 500 and 800 MHz (1)H frequency, together with the previously characterized structure and diffusion tensor yields CSA values for C5 in C, C6 in C and T, C8 in A and G, and C2 in A that are closest to values previously reported on the basis of solid-state FIREMAT NMR measurements, and mostly larger than values obtained by in vacuo DFT calculations. Owing to the noncollinearity of dipolar and CSA interactions, interpretation of the NMR relaxation rates is particularly sensitive to anisotropy of rotational diffusion, and use of isotropic diffusion models can result in considerable errors.

  8. Stress Relaxation Behavior of Unidirectional Carbon/Epoxy Composites at Elevated Temperature and Analysis Using Viscoplasticity Model

    NASA Astrophysics Data System (ADS)

    Kawai, Masamichi; Kazama, Takeshi; Masuko, Yoichi; Tsuda, Hiroshi; Takahashi, Jun; Kemmochi, Kiyoshi

    Off-axis stress relaxation behavior of unidirectional T800H/3631 carbon/epoxy composite exposed to high temperature is examined at relatively high tensile strain levels, and a phenomenological viscoplasticity model is tested on the capability to describe the time-dependent response observed. First, stress relaxation tests are performed at 100°C on plain coupon specimens with different fiber orientations, θ=0, 10, 30, 45, and 90°. For each of the fiber orientations, in principle, stress relaxation tests are carried out at three different strain levels. The relaxation of axial stress in the unidirectional composite is clearly observed, regardless of the fiber orientation. Just after the total strain hold, the axial stress quickly relaxes with time in a short period. The stress relaxation rate of the composite tends to become zero, irrespective of the fiber orientation. The associated relaxation modulus depends on the level of strain. The entire process of the prior instantaneous tensile response and the subsequent off-axis stress relaxation behavior is simulated using a macromechanical viscoplasticity model based on an overstress concept. It is demonstrated that the model succeeds in adequately reproducing the off-axis stress relaxation behavior of the unidirectional composite laminate.

  9. My starting point: the discovery of an NMR method for measuring blood oxygenation using the transverse relaxation time of blood water.

    PubMed

    Thulborn, Keith R

    2012-08-15

    This invited personal story, covering the period from 1979 to 2010, describes the discovery of the dependence of the transverse relaxation time of water in blood on the oxygenation state of hemoglobin in the erythrocytes. The underlying mechanism of the compartmentation of the different magnetic susceptibilities of hemoglobin in its different oxygenation states also explains the mechanism that underlies blood oxygenation level dependent contrast used in fMRI. The story begins with the initial observation of line broadening during ischemia in small rodents detected by in vivo 31P NMR spectroscopy at high field. This spectroscopic line broadening or T2* relaxation effect was demonstrated to be related to the oxygenation state of blood. The effect was quantified more accurately using T2 values measured by the Carr-Purcell-Meiboom-Gill method. The effect was dependent on the integrity of the erythrocytes to compartmentalize the different magnetic susceptibilities produced by the changing spin state of the ferrous iron of hemoglobin in its different oxygenation states between the erythrocytes and the suspending solution. The hematocrit and magnetic field dependence, the requirement for erythrocyte integrity and lack of T1 dependence confirmed that the magnetic susceptibility effect explained the oxygenation state dependence of T2* and T2. This T2/T2* effect was combined with T1 based measurements of blood flow to measure oxygen consumption in animals. This blood oxygenation assay and its underlying magnetic susceptibility gradient mechanism was published in the biochemistry literature in 1982 and largely forgotten. The observation was revived to explain evolving imaging features of cerebral hematoma as MR imaging of humans increased in field strength to 1.5 T by the mid 1980s. Although the imaging version of this assay was used to measure a global metabolic rate of cerebral oxygen consumption in humans at 1.5-T by 1991, the global measurement had little clinical value

  10. Relaxation lifetimes of plasmonically enhanced hybrid gold-carbon nanotubes systems

    NASA Astrophysics Data System (ADS)

    Glaeske, M.; Kumar, M.; Bisswanger, T.; Vaitiekenas, S.; Soci, C.; Narula, R.; Bruno, A.; Setaro, A.

    2017-06-01

    Recently, we introduced a novel hybridization route for carbon nanotubes using gold nanoparticles, whose close proximity neatly enhances their radiative emission. Here we investigate the mechanisms behind the enhancement by monitoring the de-excitation dynamics of our π-hybrids through two-color pump-probe time-resolved spectroscopy. The de-excitation process reveals a fast component and a slow component. We find that the presence of gold prominently affects the fast processes, indicating a stronger influence of the gold nanoparticle on the intra-band non-radiative relaxation than on the inter-band recombination of the single-walled carbon nanotube. By evaluating the de-excitation times, we estimate the balance between near-field pumping and the faster metal-induced de-excitation contributions, proving the enhanced pumping to be the leading mechanism.

  11. Transversal thermal transport in single-walled carbon nanotube bundles: influence of axial stretching and intertube bonding.

    PubMed

    Gharib-Zahedi, Mohammad Reza; Tafazzoli, Mohsen; Böhm, Michael C; Alaghemandi, Mohammad

    2013-11-14

    Using reverse nonequilibrium molecular dynamics simulations the influence of intermolecular bridges on the thermal conductivity (λ) in carbon nanotube (CNT) bundles has been investigated. The chosen cross linkers (CH2, O, CO) strengthen the transversal energy transport relative to the one in CNT bundles without bridges. The results showed that λ does not increase linearly with the linker density. The efficiency of the heat transport is determined by the number of linkers in the direction of the heat flux, the type of the linker, and their spatial ordering. The influence of a forced axial stress on the transversal λ has been also studied. The observed λ reduction with increasing axial stretching in a neat CNT bundle can be (over)compensated by cross linkers. The present computational data emphasize the contribution of phonons to the transversal heat transport in CNT bundles with intertube bonds.

  12. Lung Parenchymal Signal Intensity in MRI: A Technical Review with Educational Aspirations Regarding Reversible Versus Irreversible Transverse Relaxation Effects in Common Pulse Sequences

    PubMed Central

    MULKERN, ROBERT; HAKER, STEVEN; MAMATA, HATSUHO; LEE, EDWARD; MITSOURAS, DIMITRIOS; OSHIO, KOICHI; BALASUBRAMANIAN, MUKUND; HATABU, HIROTO

    2014-01-01

    Lung parenchyma is challenging to image with proton MRI. The large air space results in ~l/5th as many signal-generating protons compared to other organs. Air/tissue magnetic susceptibility differences lead to strong magnetic field gradients throughout the lungs and to broad frequency distributions, much broader than within other organs. Such distributions have been the subject of experimental and theoretical analyses which may reveal aspects of lung microarchitecture useful for diagnosis. Their most immediate relevance to current imaging practice is to cause rapid signal decays, commonly discussed in terms of short T2* values of 1 ms or lower at typical imaging field strengths. Herein we provide a brief review of previous studies describing and interpreting proton lung spectra. We then link these broad frequency distributions to rapid signal decays, though not necessarily the exponential decays generally used to define T2* values. We examine how these decays influence observed signal intensities and spatial mapping features associated with the most prominent torso imaging sequences, including spoiled gradient and spin echo sequences. Effects of imperfect refocusing pulses on the multiple echo signal decays in single shot fast spin echo (SSFSE) sequences and effects of broad frequency distributions on balanced steady state free precession (bSSFP) sequence signal intensities are also provided. The theoretical analyses are based on the concept of explicitly separating the effects of reversible and irreversible transverse relaxation processes, thus providing a somewhat novel and more general framework from which to estimate lung signal intensity behavior in modern imaging practice. PMID:25228852

  13. Reduced white matter MRI transverse relaxation rate in cognitively normal H63D-HFE human carriers and H67D-HFE mice.

    PubMed

    Meadowcroft, Mark D; Wang, Jianli; Purnell, Carson J; Peters, Douglas G; Eslinger, Paul J; Neely, Elizabeth B; Gill, David J; Vasavada, Megha; Ali-Rahmani, Fatima; Yang, Qing X; Connor, James R

    2016-12-01

    Mutations within the HFE protein gene sequence have been associated with increased risk of developing a number of neurodegenerative disorders. To this effect, an animal model has been created which incorporates the mouse homologue to the human H63D-HFE mutation: the H67D-HFE knock-in mouse. These mice exhibit alterations in iron management proteins, have increased neuronal oxidative stress, and a disruption in cholesterol regulation. However, it remains undetermined how these differences translate to human H63D carriers in regards to white matter (WM) integrity. To this endeavor, MRI transverse relaxation rate (R2) parametrics were employed to test the hypothesis that WM alterations are present in H63D human carriers and are recapitulated in the H67D mice. H63D carriers exhibit widespread reductions in brain R2 compared to non-carriers within white matter association fibers in the brain. Similar R2 decreases within white matter tracts were observed in the H67D mouse brain. Additionally, an exacerbation of age-related R2 decrease is found in the H67D animal model in white matter regions of interest. The decrease in R2 within white matter tracts of both species is speculated to be multifaceted. The R2 changes are hypothesized to be due to alterations in axonal biochemical tissue composition. The R2 changes observed in both the human-H63D and mouse-H67D data suggest that modified white matter myelination is occurring in subjects with HFE mutations, potentially increasing vulnerability to neurodegenerative disorders.

  14. Detailing magnetic field strength dependence and segmental artifact distribution of myocardial effective transverse relaxation rate at 1.5, 3.0, and 7.0 T.

    PubMed

    Meloni, Antonella; Hezel, Fabian; Positano, Vincenzo; Keilberg, Petra; Pepe, Alessia; Lombardi, Massimo; Niendorf, Thoralf

    2014-06-01

    Realizing the challenges and opportunities of effective transverse relaxation rate (R2 *) mapping at high and ultrahigh fields, this work examines magnetic field strength (B0 ) dependence and segmental artifact distribution of myocardial R2 * at 1.5, 3.0, and 7.0 T. Healthy subjects were considered. Three short-axis views of the left ventricle were examined. R2 * was calculated for 16 standard myocardial segments. Global and mid-septum R2 * were determined. For each segment, an artifactual factor was estimated as the deviation of segmental from global R2 * value. The global artifactual factor was significantly enlarged at 7.0 T versus 1.5 T (P = 0.010) but not versus 3.0 T. At 7.0 T, the most severe susceptibility artifacts were detected in the inferior lateral wall. The mid-septum showed minor artifactual factors at 7.0 T, similar to those at 1.5 and 3.0 T. Mean R2 * increased linearly with the field strength, with larger changes for global heart R2 * values. At 7.0 T, segmental heart R2 * analysis is challenging due to macroscopic susceptibility artifacts induced by the heart-lung interface and the posterior vein. Myocardial R2 * depends linearly on the magnetic field strength. The increased R2 * sensitivity at 7.0 T might offer means for susceptibility-weighted and oxygenation level-dependent MR imaging of the myocardium. Copyright © 2013 Wiley Periodicals, Inc.

  15. On the lorentzian versus Gaussian character of time-domain spin-echo signals from the brain as sampled by means of gradient-echoes: Implications for quantitative transverse relaxation studies.

    PubMed

    Mulkern, Robert V; Balasubramanian, Mukund; Mitsouras, Dimitrios

    2014-07-30

    To determine whether Lorentzian or Gaussian intra-voxel frequency distributions are better suited for modeling data acquired with gradient-echo sampling of single spin-echoes for the simultaneous characterization of irreversible and reversible relaxation rates. Clinical studies (e.g., of brain iron deposition) using such acquisition schemes have typically assumed Lorentzian distributions. Theoretical expressions of the time-domain spin-echo signal for intra-voxel Lorentzian and Gaussian distributions were used to fit data from a human brain scanned at both 1.5 Tesla (T) and 3T, resulting in maps of irreversible and reversible relaxation rates for each model. The relative merits of the Lorentzian versus Gaussian model were compared by means of quality of fit considerations. Lorentzian fits were equivalent to Gaussian fits primarily in regions of the brain where irreversible relaxation dominated. In the multiple brain regions where reversible relaxation effects become prominent, however, Gaussian fits were clearly superior. The widespread assumption that a Lorentzian distribution is suitable for quantitative transverse relaxation studies of the brain should be reconsidered, particularly at 3T and higher field strengths as reversible relaxation effects become more prominent. Gaussian distributions offer alternate fits of experimental data that should prove quite useful in general. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc. © 2014 Wiley Periodicals, Inc.

  16. Relaxation NMR as a tool to study the dispersion and formulation behavior of nanostructured carbon materials.

    PubMed

    Fairhurst, David; Cosgrove, Terence; Prescott, Stuart W

    2016-06-01

    Solvent relaxation NMR has been used to estimate the surface areas and wettability of various types of nanostructured carbon materials in a range of solvents including water, ethanol, and tetrahydrofuran. We illustrate the application of the technique through several short case studies using samples including nanocarbon blacks, graphene oxide, nanographites, and porous graphenes. The technique is shown to give a good measure of surface area, correlating well with conventional surface area estimates obtained by nitrogen adsorption, transmission electron microscopy, or light scattering for the non-porous samples. NMR relaxation has advantages in terms of speed of analysis and being able to use concentrated, wet, and opaque samples. For samples that are porous, two distinct surface areas can be estimated assuming the two environments ('inner' and 'outer') have the same surface chemistry, and that there is a slow exchange of solvent molecules between them. Furthermore, we show that differences in wettability and dispersability between samples dispersed in water, ethanol, and cyclopentanone can be observed, along with changes to the surface chemistry of the interface. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  17. Dielectric hysteresis, relaxation dynamics, and nonvolatile memory effect in carbon nanotube dispersed liquid crystal

    NASA Astrophysics Data System (ADS)

    Basu, Rajratan; Iannacchione, Germano S.

    2009-12-01

    Self-organizing nematic liquid crystals (LCs) impart their orientational order onto dispersed carbon nanotubes (CNTs) and obtain CNT-self-assembly on a macroscopic dimension. The nanotube-long axis, being coupled to the nematic director, enables orientational manipulation via the LC nematic reorientation. Electric-field-induced director rotation of a nematic LC+CNT system is of potential interest due to its possible application as a nanoelectromechanical system. Electric field and temperature dependence of dielectric properties of a LC+CNT composite system have been investigated to understand the principles governing CNT assembly mediated by the LC. In the LC+CNT nematic phase, the dielectric relaxation on removing the applied field follows a single-exponential decay, exhibiting a faster decay response than the pure LC above a threshold field. The observed dielectric behaviors on field cycling in the nematic phase for the composite indicates an electromechanical hysteresis effect of the director field due to the LC-CNT anchoring mechanism. Observations in the isotropic phase coherently combine to confirm the presence of anisotropic pseudonematic domains stabilized by the LC-CNT anchoring energy. These polarized domains maintain local directors and respond to external fields, but do not relax back to the original state on switching the field off, showing nonvolatile memory effect.

  18. Microwave permittivity and dielectric relaxation of a high surface area activated carbon

    NASA Astrophysics Data System (ADS)

    Atwater, J. E.; Wheeler, R. R., Jr.

    Carbonaceous materials are amenable to microwave heating to varying degrees. The primary indicator of susceptibility is the complex permittivity (ɛ*), of which, the real component correlates with polarization, and the imaginary term represents dielectric loss. For a given material, the complex permittivity is dependent upon both frequency and temperature. Here we report the complex permittivity of a high surface area coconut shell activated carbon which is commonly used in analytical chemistry and a wide variety of industrial separations. Associated polarization-relaxation phenomena are also characterized. Broadband measurements were made using a high temperature compatible open-ended coaxial dielectric probe at frequencies between 0.2 and 26 GHz, and across the temperature region between 24 °C and 191 °C.

  19. Magnetic Field Strength Dependence of Transverse Relaxation and Signal-to-Noise Ratio for Hyperpolarized Xenon-129 and Helium-3 Gas Magnetic Resonance Imaging of Lungs

    NASA Astrophysics Data System (ADS)

    Dominguez-Viqueira, William

    Magnetic resonance (MR) imaging with hyperpolarized noble gases (HNG), 3He or 129Xe, has become a promising approach for studying lung anatomy and function. Unlike conventional MR imaging, the magnetization in HNG MR is independent of the magnetic field strength. This means that no improvement in signal-to-noise ratio (SNR) is expected with increasing clinical field strength above ˜0.25T. Furthermore, it has been predicted that the SNR may decline at clinical field strength due to decreases in the apparent transverse relaxation time (T2*), caused by the increased magnetic susceptibility induced field gradients at the air-tissue interface. In this thesis the magnetic field strength dependence of T2* and SNR in HNG MR is investigated experimentally in rodent and human lungs. For rodent imaging, a novel broad-band (0.1-100MHz) variable field strength MR imaging system for rodents was built. This system permitted imaging of 129Xe, 3He and 1H at low magnetic field strengths (3-73.5mT) to experimentally investigate the field dependence of HNG imaging SNR in rodent lungs. In vivo 129Xe and 3He signals were acquired at 73.5mT and T 2* was estimated to be approximately 180+/-8 ms, in good agreement with previously reported values. At 73.5mT, image noise is dominated by losses originated from the radiofrequency (RF) coils. To address this issue, RF coils were built using different types of copper wire and compared in phantoms and in vivo in rat lungs using hyperpolarized 3He and 129Xe gas. An SNR improvement of up to 200% was obtained with Litz wire compared to conventional copper wire. This improvement demonstrated the feasibility of HNG lung imaging in rodents at 73.5mT with SNR comparable to that obtained at clinical field strengths. To verify the SNR field dependence in humans, hyperpolarized 3He lung imaging at two commonly used clinical field strengths (1.5T and 3T) was performed in the same volunteers and compared. No significant differences in SNR were obtained

  20. Intra- and inter-tube exciton relaxation dynamics in high purity semiconducting and metallic single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Ichida, Masao; Saito, Shingo; Miyata, Yasumitsu; Yanagi, Kazuhiro; Kataura, Hiromichi; Ando, Hiroaki

    2013-02-01

    We have measured the exciton and carrier dynamics in the high purity semiconducting (S-) and metallic (M-) single-walled carbon nanotubes (SWNTs) in the isolated and aggregated (bundled) forms. The exciton relaxation decay times are measured by using the pump-probe spectroscopy. For bundled samples, the relaxation time becomes shorter than that for isolated SWNTs sample, because of the existence of inter-tube relaxation. We estimate the relaxation rates from S-SWNT to S-SWNT and S-SWNT to M-SWNT using the decay times for isolated SWNTs, high purity S-SWNTs bundle, and doped S-SWNTs in high purity M-SWNTs bundle. For S-SWNTs, inter-tube relaxation plays an important role in the relaxation dynamics. However, for M-SWNTs, the inter-tube relaxation is not so important, and the transition energy and intensity of exciton in M-SWNTs is strongly affected by the photoexcited carriers which plays like as photo doping.

  1. Relaxivity enhancement of aquated Tris(β-diketonate)gadolinium(III) chelates by confinement within ultrashort single-walled carbon nanotubes.

    PubMed

    Law, Justin J; Guven, Adem; Wilson, Lon J

    2014-01-01

    Ultrashort single-walled carbon nanotubes loaded with gadolinium ions (gadonanotubes) have been previously shown to exhibit extremely high T1 -weighted relaxivities (>100 mm(-1) s(-1) ). To further examine the effect of nanoconfinement on the relaxivity of gadolinium-based contrast agents for magnetic resonance imaging, a series of ultrashort single-walled carbon nanotube (US-tube) materials internally loaded with gadolinium chelates have been prepared and studied. US-tubes were loaded with Gd(acac)3  · 2H2 O, Gd(hfac)3  · 2H2 O, and Gd(thd)3 (acac = acetylacetone, hfac = hexafluoroacetylacetone, thd = tetramethylheptanedione). The longitudinal relaxivities of the prepared materials determined at 25°C in a 1.5 T field were 103 mm(-1) s(-1) for Gd(acac)3  · 2H2 O@US-tubes, 105 mm(-1) s(-1) for Gd(hfac)3  · 2H2 O@US-tubes and 26 mm(-1) s(-1) for Gd(thd)3 @US-tubes. Compared with the relaxivities obtained for the unloaded chelates (<10 mm(-1) s(-1) ) as well as accounting for the T1 reduction observed for the empty US-tubes, the boost in relaxivity for chelate-loaded US-tubes is attributed to confinement within the nanotube and depends on the number of coordinated water molecules.

  2. Unsnarling Excitation, Relaxation and Scattering Dynamics in Multi-Chiral Distributions of Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Ames, Jessica Nicole

    relevant nanotube species. These dynamical equations are fit to multiple data sets for a range of excitation intensities. Second, additional relaxation measurements are taken for an atypical strong probe. The strong probe provides access to the dependence of nanotube dynamics on their excited state transitions. With this additional information the contributions from various nanotubes can be distinguished and quantified. Across all data sets we found, within 20% error, lowest energy bright exciton lifetimes of 175fs, exciton-exciton annihilation rates of 0.19/ps and that 80% of second excited state excitons decayed non-radiatively into the first bright exciton. Fitting results, however, showed wide, unexpected variation in one bright state lifetime and the coupling between one of the second excitons to the first. This hot probe technique has, therefore, uncovered additional physics not fully described by a discrete-level rate equation model. Variations in rate equation solutions are partly attributed to coherent interaction of both pump and probe fields with the nanotubes. To test the coherence hypothesis an alternative density matrix approach is proposed that accounts for strong pump and probe as well as decay and dephasing. Results of this model are highly sensitive to both pump and probe intensities and can only generally reproduce the expected population behavior and differential absorption signatures seen in the data. The coherent model, however, predicts non-linear pump-probe interaction just beyond the measured power ranges providing for testable verification in the future. Both models therefore lead to the conclusion that the existing discrete-level models for carbon nanotube dynamics are incomplete, and a full microscopic theory of optical interaction will be required.

  3. Penetration Characteristics of Air, Carbon Dioxide and Helium Transverse Sonic Jets in Mach 5 Cross Flow

    PubMed Central

    Erdem, Erinc; Kontis, Konstantinos; Saravanan, Selvaraj

    2014-01-01

    An experimental investigation of sonic air, CO2 and Helium transverse jets in Mach 5 cross flow was carried out over a flat plate. The jet to freestream momentum flux ratio, J, was kept the same for all gases. The unsteady flow topology was examined using high speed schlieren visualisation and PIV. Schlieren visualisation provided information regarding oscillating jet shear layer structures and bow shock, Mach disc and barrel shocks. Two-component PIV measurements at the centreline, provided information regarding jet penetration trajectories. Barrel shocks and Mach disc forming the jet boundary were visualised/quantified also jet penetration boundaries were determined. Even though J is kept the same for all gases, the penetration patterns were found to be remarkably different both at the nearfield and the farfield. Air and CO2 jet resulted similar nearfield and farfield penetration pattern whereas Helium jet spread minimal in the nearfield. PMID:25494348

  4. Transverse flowmetry of carbon particles based on photoacoustic Doppler standard deviation using an auto-correlation method

    NASA Astrophysics Data System (ADS)

    Lu, Tao; Sun, Li-jun

    2015-05-01

    In order to measure the flow velocity of carbon particle suspension perpendicular to the receiving axis of ultrasound transducer, the standard deviation of photoacoustic Doppler frequency spectrum is used to estimate the bandwidth broadening, and the spectrum standard deviation is calculated by an auto-correlation method. A 532 nm pulsed laser with the repetition rate of 20 Hz is used as a pumping source to generate photoacoustic signal. The photoacoustic signals are detected using a focused PZT ultrasound transducer with the central frequency of 10 MHz. The suspension of carbon particles is driven by a syringe pump. The complex photoacoustic signal is calculated by Hilbert transformation from time domain signal before auto-correlation. The standard deviation of the Doppler bandwidth broadening is calculated by averaging the auto-correlation results of several individual A scans. The feasibility of the proposed method is demonstrated by measuring the spectrum standard deviation of the transversal carbon particle flow from 5.0 mm/s to 8.4 mm/s. The experimental results show that the auto-correlation result is approximately linearly distributed within the measuring range.

  5. Anomalous nuclear Overhauser effects in carbon-substituted aziridines: scalar cross-relaxation of the first kind.

    PubMed

    Kuprov, Ilya; Hodgson, David M; Kloesges, Johannes; Pearson, Christopher I; Odell, Barbara; Claridge, Timothy D W

    2015-03-16

    Anomalous NOESY cross-peaks that cannot be explained by dipolar cross-relaxation or chemical exchange are described for carbon-substituted aziridines. The origin of these is identified as scalar cross-relaxation of the first kind, as demonstrated by a complete theoretical description of this relaxation process and by computational simulation of the NOESY spectra. It is shown that this process relies on the stochastic modulation of J-coupling by conformational transitions, which in the case of aziridines arise from inversion at the nitrogen center. The observation of scalar cross-relaxation between protons does not appear to have been previously reported for NOESY spectra. Conventional analysis would have assigned the cross-peaks as being indicative of a chemical exchange process occurring between correlated spins, were it not for the fact that the pairs of nuclei displaying them cannot undergo such exchange. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

  6. Variational principles for transversely vibrating multiwalled carbon nanotubes based on nonlocal Euler-Bernoulli beam model.

    PubMed

    Adali, Sarp

    2009-05-01

    Variational principles are derived for multiwalled carbon nanotubes undergoing vibrations. Derivations are based on the continuum modeling with the Euler-Bernoulli beam representing the nanotubes and small scale effects taken into account via the nonlocal elastic theory. Hamilton's principle for multiwalled nanotubes is given and Rayleigh's quotient for the frequencies is derived for nanotubes undergoing free vibrations. Natural and geometric boundary conditions are derived which lead to a set of coupled boundary conditions due to nonlocal effects.

  7. Spectrochemical analysis of powdered biological samples using transversely excited atmospheric carbon dioxide laser plasma excitation

    NASA Astrophysics Data System (ADS)

    Zivkovic, Sanja; Momcilovic, Milos; Staicu, Angela; Mutic, Jelena; Trtica, Milan; Savovic, Jelena

    2017-02-01

    The aim of this study was to develop a simple laser induced breakdown spectroscopy (LIBS) method for quantitative elemental analysis of powdered biological materials based on laboratory prepared calibration samples. The analysis was done using ungated single pulse LIBS in ambient air at atmospheric pressure. Transversely-Excited Atmospheric pressure (TEA) CO2 laser was used as an energy source for plasma generation on samples. The material used for the analysis was a blue-green alga Spirulina, widely used in food and pharmaceutical industries and also in a few biotechnological applications. To demonstrate the analytical potential of this particular LIBS system the obtained spectra were compared to the spectra obtained using a commercial LIBS system based on pulsed Nd:YAG laser. A single sample of known concentration was used to estimate detection limits for Ba, Ca, Fe, Mg, Mn, Si and Sr and compare detection power of these two LIBS systems. TEA CO2 laser based LIBS was also applied for quantitative analysis of the elements in powder Spirulina samples. Analytical curves for Ba, Fe, Mg, Mn and Sr were constructed using laboratory produced matrix-matched calibration samples. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used as the reference technique for elemental quantification, and reasonably well agreement between ICP and LIBS data was obtained. Results confirm that, in respect to its sensitivity and precision, TEA CO2 laser based LIBS can be successfully applied for quantitative analysis of macro and micro-elements in algal samples. The fact that nearly all classes of materials can be prepared as powders implies that the proposed method could be easily extended to a quantitative analysis of different kinds of materials, organic, biological or inorganic.

  8. Fabrication of uniform graphene discs via transversal cutting of carbon nanofibers.

    PubMed

    Long, Donghui; Hong, Jin-Yong; Li, Wei; Miyawaki, Jin; Ling, Licheng; Mochida, Isao; Yoon, Seong-Ho; Jang, Jyongsik

    2011-08-23

    The graphene discs with well-defined shape are successfully fabricated using a simple oxidation and exfoliation process of high-crystalline carbon nanofibers (CNFs). To control the shapes of graphene discs, two different types of CNFs (platelet and herringbone-type) are used as starting materials. The CNFs are formed by the perpendicular stacking of graphene discs, resulting in free edges on the external surface and ready access to interlay spaces. Interestingly, the diameter and shape of the graphene discs can be controlled by selectively designing the morphology of starting materials and optimizing the cutting method. In addition, a mechanical reduction method for oxidized graphene discs is also proposed in order to combine the high recovery of π-conjugated electronic structure with the solution processability of graphene discs. The reduced graphene discs can be formed without any additives, such as reducing agent, and are highly dispersed in different solvents with a high content of graphene discs. This novel strategy offers great possibility for fabricating various graphene-based nanomaterials with rational nanostructure design. © 2011 American Chemical Society

  9. Dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with ethylene carbonate

    SciTech Connect

    Pal, P.; Ghosh, A.

    2016-07-28

    In this paper, we have studied the dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with ethylene carbonate. Structural and thermal properties have been examined using X-ray diffraction and differential scanning calorimetry, respectively. We have analyzed the complex conductivity spectra by using power law model coupled with the contribution of electrode polarization at low frequencies and high temperatures. The temperature dependence of the ionic conductivity and crossover frequency exhibits Vogel-Tammann-Fulcher type behavior indicating a strong coupling between the ionic and the polymer chain segmental motions. The scaling of the ac conductivity indicates that relaxation dynamics of charge carriers follows a common mechanism for all temperatures and ethylene carbonate concentrations. The analysis of the ac conductivity also shows the existence of a nearly constant loss in these polymer electrolytes at low temperatures and high frequencies. The fraction of free anions and ion pairs in polymer electrolyte have been obtained from the analysis of Fourier transform infrared spectra. It is observed that these quantities influence the behavior of the composition dependence of the ionic conductivity.

  10. Dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with ethylene carbonate

    NASA Astrophysics Data System (ADS)

    Pal, P.; Ghosh, A.

    2016-07-01

    In this paper, we have studied the dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with ethylene carbonate. Structural and thermal properties have been examined using X-ray diffraction and differential scanning calorimetry, respectively. We have analyzed the complex conductivity spectra by using power law model coupled with the contribution of electrode polarization at low frequencies and high temperatures. The temperature dependence of the ionic conductivity and crossover frequency exhibits Vogel-Tammann-Fulcher type behavior indicating a strong coupling between the ionic and the polymer chain segmental motions. The scaling of the ac conductivity indicates that relaxation dynamics of charge carriers follows a common mechanism for all temperatures and ethylene carbonate concentrations. The analysis of the ac conductivity also shows the existence of a nearly constant loss in these polymer electrolytes at low temperatures and high frequencies. The fraction of free anions and ion pairs in polymer electrolyte have been obtained from the analysis of Fourier transform infrared spectra. It is observed that these quantities influence the behavior of the composition dependence of the ionic conductivity.

  11. Investigation of ligand binding and protein dynamics in Bacillus subtilis chorismate mutase by transverse relaxation optimized spectroscopy-nuclear magnetic resonance.

    PubMed

    Eletsky, Alexander; Kienhöfer, Alexander; Hilvert, Donald; Pervushin, Konstantin

    2005-05-10

    The structural and dynamical consequences of ligand binding to a monofunctional chorismate mutase from Bacillus subtilis have been investigated by solution NMR spectroscopy. TROSY methods were employed to assign 98% of the backbone (1)H(N), (1)H(alpha), (15)N, (13)C', and (13)C(alpha) resonances as well as 86% of the side chain (13)C resonances of the 44 kDa trimeric enzyme at 20 degrees C. This information was used to map chemical shift perturbations and changes in intramolecular mobility caused by binding of prephenate or a transition state analogue to the X-ray structure. Model-free interpretation of backbone dynamics for the free enzyme and its complexes based on (15)N relaxation data measured at 600 and 900 MHz showed significant structural consolidation of the protein in the presence of a bound ligand. In agreement with earlier structural and biochemical studies, substantial ordering of 10 otherwise highly flexible residues at the C-terminus is particularly notable. The observed changes suggest direct contact between this protein segment and the bound ligand, providing support for the proposal that the C-terminus can serve as a lid for the active site, limiting diffusion into and out of the pocket and possibly imposing conformational control over substrate once bound. Other regions of the protein that experience substantial ligand-induced changes also border the active site or lie along the subunit interfaces, indicating that the enzyme adapts dynamically to ligands by a sort of induced fit mechanism. It is believed that the mutase-catalyzed chorismate-to-prephenate rearrangement is partially encounter controlled, and backbone motions on the millisecond time scale, as seen here, may contribute to the reaction barrier.

  12. Carbon segregation as a strain relaxation mechanism in thin germanium-carbon layers deposited directly on silicon

    NASA Astrophysics Data System (ADS)

    Garcia-Gutierrez, D. I.; José-Yacamán, M.; Lu, Shifeng; Kelly, D. Q.; Banerjee, S. K.

    2006-08-01

    We report experimental evidence for the segregation and preferential localization of C atoms at the surface and substrate interfaces in thin Ge1-xCx films deposited directly on Si (100). The results are interpreted in the context of C segregation providing a mechanism for strain relaxation. Four different experimental techniques, including energy-dispersive spectroscopy, electron energy loss spectroscopy (EELS), energy-filtering transmission electron microscopy, and secondary ion mass spectrometry, support our claims. The EELS analyses showed that the C bonding near the Ge1-xCx/Si substrate interface presented a higher sp3 character than in the central region or at the surface. Two interpretations are given for this observation; one is that structural relaxation occurs when C atoms occupy substitutional sites in the Ge crystal closer to the Ge1-xCx/Si substrate interface; the other is that the higher sp3 character of the C atoms might be an indication that C-containing tetrahedral interstitial complexes form at the interface (chemical relaxation).

  13. Efficient stress-relaxation in InGaN/GaN light-emitting diodes using carbon nanotubes.

    PubMed

    Park, Ah Hyun; Seo, Tae Hoon; Chandramohan, S; Lee, Gun Hee; Min, Kyung Hyun; Lee, Seula; Kim, Myung Jong; Hwang, Yong Gyoo; Suh, Eun-Kyung

    2015-10-07

    A facile method to facilitate epitaxial lateral overgrowth (ELO) of gallium nitride (GaN) was developed by using single-walled carbon nanotubes (SWCNTs). High-quality GaN was achieved on sapphire by simply coating the SWCNTs as an intermediate layer for stress and defect mitigation. SWCNTs maintained their integrity at high reaction temperature and led to suppression of edge dislocations and biaxial stress relaxation by up to 0.32 GPa in a GaN template layer. InGaN/GaN multi-quantum-well light-emitting diodes (LEDs) on this high-quality GaN template offered enhanced internal quantum efficiency and light output power with reduced efficiency droop. The method developed here has high potential to replace current ELO methods such as patterned sapphire substrates or buffer layers like SiO2 and SiNx.

  14. Efficient stress-relaxation in InGaN/GaN light-emitting diodes using carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Park, Ah Hyun; Seo, Tae Hoon; Chandramohan, S.; Lee, Gun Hee; Min, Kyung Hyun; Lee, Seula; Kim, Myung Jong; Hwang, Yong Gyoo; Suh, Eun-Kyung

    2015-09-01

    A facile method to facilitate epitaxial lateral overgrowth (ELO) of gallium nitride (GaN) was developed by using single-walled carbon nanotubes (SWCNTs). High-quality GaN was achieved on sapphire by simply coating the SWCNTs as an intermediate layer for stress and defect mitigation. SWCNTs maintained their integrity at high reaction temperature and led to suppression of edge dislocations and biaxial stress relaxation by up to 0.32 GPa in a GaN template layer. InGaN/GaN multi-quantum-well light-emitting diodes (LEDs) on this high-quality GaN template offered enhanced internal quantum efficiency and light output power with reduced efficiency droop. The method developed here has high potential to replace current ELO methods such as patterned sapphire substrates or buffer layers like SiO2 and SiNx.A facile method to facilitate epitaxial lateral overgrowth (ELO) of gallium nitride (GaN) was developed by using single-walled carbon nanotubes (SWCNTs). High-quality GaN was achieved on sapphire by simply coating the SWCNTs as an intermediate layer for stress and defect mitigation. SWCNTs maintained their integrity at high reaction temperature and led to suppression of edge dislocations and biaxial stress relaxation by up to 0.32 GPa in a GaN template layer. InGaN/GaN multi-quantum-well light-emitting diodes (LEDs) on this high-quality GaN template offered enhanced internal quantum efficiency and light output power with reduced efficiency droop. The method developed here has high potential to replace current ELO methods such as patterned sapphire substrates or buffer layers like SiO2 and SiNx. Electronic supplementary information (ESI) available. See DOI: 10.1039/C5NR04239A

  15. NMR relaxation of neritic carbonates: An integrated petrophysical and petrographical approach

    NASA Astrophysics Data System (ADS)

    Vincent, Benoit; Fleury, Marc; Santerre, Yannick; Brigaud, Benjamin

    2011-05-01

    A set of carbonate outcrop samples, covering a wide range of the sedimentary textures and depositional environments existing on carbonate systems, was studied through an integrated petrographical and petrophysical approach. With the aim of improving the understanding of the NMR (Nuclear Magnetic Resonance) signal of carbonates, this work is: 1) providing an atlas for various carbonate reservoir rock-types, 2) providing a workflow for integrating geological and petrophysical data and, 3) documenting common shortfalls in NMR/MICP analyses in carbonates. The petrographical investigation includes thin section and SEM (Secondary Electron Microscope) observations, whereas petrophysical investigation includes porosity (Φ), permeability (K), NMR, MICP (Mercury Injection Capillary Pressure), and specific surface area (BET) measurements. On the basis of NMR and MICP data, 4 groups of samples were identified: (1) microporous samples, (2) micro-mesoporous samples, (3) wide multimodal samples, and (4) atypical samples. The microporous samples allow us to define a maximum NMR threshold for microporosity at a T 2 of 200 ms. NMR and MICP response of the investigated carbonates are often comparable in terms of modal distribution (microporous, micro-mesoporous and wide multimodal samples). In particular, micritization, a well known but underestimated early diagenetic process, tends to homogenize the NMR signal of primarily different sedimentary facies. A grainstone with heavily micritized grains can display well sorted unimodal NMR and MICP signatures very similar, even identical, to a mudstone-wackestone. Their signatures are comparable to that of a simple sphere packing model. On the contrary, several samples (labeled atypical samples) show a discrepancy between NMR and MICP response. This discrepancy is explained by the fact that MICP can be affected by the physical connectivity of the pore network, in case of disseminated and isolated molds in a micrite matrix for instance

  16. Enhanced NMR Relaxation of Tomonaga-Luttinger Liquids and the Magnitude of the Carbon Hyperfine Coupling in Single-Wall Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Kiss, A.; Pályi, A.; Ihara, Y.; Wzietek, P.; Simon, P.; Alloul, H.; Zólyomi, V.; Koltai, J.; Kürti, J.; Dóra, B.; Simon, F.

    2011-10-01

    Recent transport measurements [Churchill et al. Nature Phys.NPAHAX1745-2473 5, 321 (2009)10.1038/nphys1247] found a surprisingly large, 2-3 orders of magnitude larger than usual C13 hyperfine coupling (HFC) in C13 enriched single-wall carbon nanotubes. We formulate the theory of the nuclear relaxation time in the framework of the Tomonaga-Luttinger liquid theory to enable the determination of the HFC from recent data by Ihara et al. [Europhys. Lett. 90, 17 004 (2010)EULEEJ0295-507510.1209/0295-5075/90/17004]. Though we find that 1/T1 is orders of magnitude enhanced with respect to a Fermi-liquid behavior, the HFC has its usual, small value. Then, we reexamine the theoretical description used to extract the HFC from transport experiments and show that similar features could be obtained with HFC-independent system parameters.

  17. Vibrational population relaxation of carbon monoxide in the heme pocket of photolyzed carbonmonoxy myoglobin: Comparison of time-resolved mid-IR absorbance experiments and molecular dynamics simulations

    PubMed Central

    Sagnella, Diane E.; Straub, John E.; Jackson, Timothy A.; Lim, Manho; Anfinrud, Philip A.

    1999-01-01

    The vibrational energy relaxation of carbon monoxide in the heme pocket of sperm whale myoglobin was studied by using molecular dynamics simulation and normal mode analysis methods. Molecular dynamics trajectories of solvated myoglobin were run at 300 K for both the δ- and ɛ-tautomers of the distal His-64. Vibrational population relaxation times of 335 ± 115 ps for the δ-tautomer and 640 ± 185 ps for the ɛ-tautomer were estimated by using the Landau–Teller model. Normal mode analysis was used to identify those protein residues that act as the primary “doorway” modes in the vibrational relaxation of the oscillator. Although the CO relaxation rates in both the ɛ- and δ-tautomers are similar in magnitude, the simulations predict that the vibrational relaxation of the CO is faster in the δ-tautomer with the distal His playing an important role in the energy relaxation mechanism. Time-resolved mid-IR absorbance measurements were performed on photolyzed carbonmonoxy hemoglobin (Hb13CO). From these measurements, a T1 time of 600 ± 150 ps was determined. The simulation and experimental estimates are compared and discussed. PMID:10588704

  18. Relaxation in quantum glasses

    NASA Astrophysics Data System (ADS)

    Ancona Torres, Carlos E.

    The Ising model in transverse field provides the simplest description of a quantum glass. I study two systems that are realizations of the Ising model in transverse field, LiHoxY1-- xF4 and Rb1-- x(NH4)xH2PO 4. In the spin glass LiHoxY1-- xF4, applying a magnetic field Ht transverse to the Ising direction introduces tunneling between the bare Ising eigenstates. In addition, the coupling between the transverse dipolar interaction and the transverse field introduces entanglement or tunable random fields depending on the concentration. By comparing the classical and quantum transitions in LiHo0.198Y0.802F4 and LiHo 0.167Y0.833F4, I characterize the crossover from random field dominated behavior in the 19.8% sample to entanglement dominated behavior in the 16.7% sample. The quantum transition in the 19.8% sample is dominated by the limit on its correlation length caused by the random fields, while the dominant effect in the 16.7% sample is the enhanced tunneling rate introduced by entanglement. The proton glass Rb1--x(NH 4)xH2PO4 relaxes through tunneling of protons in the hydrogen bonds of the crystal, yielding an effective Ising model in transverse field. Since this field cannot be tuned directly, I combine bulk dielectric susceptibility measurements with neutron Compton scattering measurements of the local tunneling potential in two different concentrations, x = 35% and 72%. I find that tunneling drives the fastest relaxation processes at temperatures as high as 20 K and explicitly calculate the tunneling rate from the tunneling potential of the hydrogen bond. Moreover, the structural mechanism for the glassy relaxation allows a real-space picture of the relaxation dynamics to be correlated to the free energy description of aging. I find that the glassy relaxation is driven by the sequential diffusion of defects called Takagi configurations with a classical to quantum crossover in the relaxation at 3 K. I relate the relaxation rate to the quantum action of tunneling

  19. Transversely isotropic elastic properties of single-walled carbon nanotubes by a rectangular beam model for the C C bonds

    NASA Astrophysics Data System (ADS)

    Li, Haijun; Guo, Wanlin

    2008-05-01

    Continuum mechanics modeling of carbon nanotubes has long been an attractive issue, but how to reflect exactly the physics essential of the atomic bonds still remains to be a challenging problem. To capture the distinguishing in-plane σ-σ and out-of-plane σ-π bond angle bending rigidities of C C bonds in carbon nanotubes, an equivalent beam element with rectangular section is proposed and a corresponding frame structure model for a single-walled carbon nanotube (SWNT) is developed. By using the model, the five independent elastic moduli of SWNTs with arbitrary chirality and diameter are evaluated systematically. It is found that the elastic properties of the SWNTs are transversely isotropic when the tube diameter is small. The smaller the tube diameter is, the stronger the dependence of the elastic properties on the tube size and chirality is, while when the tube diameter is large enough, the SWNTs degenerate from transversely isotropic to isotropic and the elastic moduli tend to that of a graphite sheet. The present model can be incorporated into any standard finite element software directly, providing an extremely versatile and powerful tool for the study of nanostructures that beyond the computational capability of current atomistic approaches.

  20. Mechanisms of Gadographene-Mediated Proton Spin Relaxation

    PubMed Central

    Hung, Andy H.; Duch, Matthew C.; Parigi, Giacomo; Rotz, Matthew W.; Manus, Lisa M.; Mastarone, Daniel J.; Dam, Kevin T.; Gits, Colton C.; MacRenaris, Keith W.; Luchinat, Claudio; Hersam, Mark C.; Meade, Thomas J.

    2013-01-01

    Gd(III) associated with carbon nanomaterials relaxes water proton spins at an effectiveness that approaches or exceeds the theoretical limit for a single bound water molecule. These Gd(III)-labeled materials represent a potential breakthrough in sensitivity for Gd(III)-based contrast agents used for magnetic resonance imaging (MRI). However, their mechanism of action remains unclear. A gadographene library encompassing GdCl3, two different Gd(III)-complexes, graphene oxide (GO), and graphene suspended by two different surfactants and subjected to varying degrees of sonication was prepared and characterized for their relaxometric properties. Gadographene was found to perform comparably to other Gd(III)-carbon nanomaterials; its longitudinal (r1) and transverse (r2) relaxivity is modulated between 12–85 mM−1s−1 and 24–115 mM−1s−1, respectively, depending on the Gd(III)-carbon backbone combination. The unusually large relaxivity and its variance can be understood under the modified Florence model incorporating the Lipari-Szabo approach. Changes in hydration number (q), water residence time (τM), molecular tumbling rate (τR), and local motion (τfast) sufficiently explain most of the measured relaxivities. Furthermore, results implicated the coupling between graphene and Gd(III) as a minor contributor to proton spin relaxation. PMID:24298299

  1. Direct imaging of the structure, relaxation, and sterically constrained motion of encapsulated tungsten polyoxometalate lindqvist ions within carbon nanotubes.

    PubMed

    Sloan, Jeremy; Matthewman, Gemma; Dyer-Smith, Clare; Sung, A-Young; Liu, Zheng; Suenaga, Kazu; Kirkland, Angus I; Flahaut, Emmanuel

    2008-05-01

    The imaging properties and observation of the sterically regulated translational motion of discrete tungsten polyoxometalate Linqvist ions (i.e., [W(6)O(19)](2-)) within carbon nanotubes of specific internal diameter are reported. The translational motion of the nonspheroidal anion within the nanotube capillary is found to be impeded by its near-perfect accommodation to the internal van der Waals surface of the nanotube wall. Rotational motion of the anion about one remaining degree of freedom permits translational motion of the anion along the nanotube followed by locking in at sterically favorable positions in a mechanism similar to a molecular ratchet. This steric locking permits the successful direct imaging of the constituent octahedral cation template of individual [W(6)O(19)](2-) anions by high resolution transmission electron microscopy thereby permitting meterological measurements to be performed directly on the anion. Direct imaging of pairs of equatorial W(2) atoms within the anion reveal steric relaxation of the anion contained within the nanotube capillary relative to the bulk anion structure.

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

    PubMed

    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.

  3. Transversity 2005

    NASA Astrophysics Data System (ADS)

    Barone, Vincenzo; Ratcliffe, Philip G.

    Introduction. Purpose and status of the Italian Transversity Project / F. Bradamante -- Opening lecture. Transversity / M. Anselmino -- Experimental lectures. Azimuthal single-spin asymmetries from polarized and unpolarized hydrogen targets at HERMES / G. Schnell (for the HERMES Collaboration). Collins and Sivers asymmetries on the deuteron from COMPASS data / I. Horn (for the COMPASS Collaboration). First measurement of interference fragmentation on a transversely polarized hydrogen target / P. B. van der Nat (for the HERMES Collaboration). Two-hadron asymmetries at the COMPASS experiment / A. Mielech (for the COMPASS Collaboration). Measurements of chiral-odd fragmentation functions at Belle / R. Seidl ... [et al.]. Lambda asymmetries / A. Ferrero (for the COMPASS Collaboration). Transverse spin at PHENIX: results and prospects / C. Aidala (for the PHENIX Collaboration). Transverse spin and RHIC / L. Bland. Studies of transverse spin effects at JLab / H. Avakian ... [et al.] (for the CLAS Collaboration). Neutron transversity at Jefferson Lab / J. P. Chen ... [et al.] (for the Jefferson Lab Hall A Collaboration). PAX: polarized antiproton experiments / M. Contalbrigo. Single and double spin N-N interactions at GSI / M. Maggiora (for the ASSIA Collaboration). Spin filtering in storage rings / N. N. Nikolaev & F. F. Pavlov -- Theory lectures. Single-spin asymmetries and transversity in QCD / S. J. Brodsky. The relativistic hydrogen atom: a theoretical laboratory for structure functions / X. Artru & K. Benhizia. GPD's and SSA's / M. Burkardt. Time reversal odd distribution functions in chiral models / A. Drago. Soffer bound and transverse spin densities from lattice QCD / M. Diehl ... [et al.]. Single-spin asymmetries and Qiu-Sterman effect(s) / A. Bacchetta. Sivers function: SIDIS data, fits and predictions / M. Anselmino ... [et al.]. Twist-3 effects in semi-inclusive deep inelastic scattering / M. Schlegel, K. Goeke & A. Metz. Quark and gluon Sivers functions / I

  4. Transversity 2008

    NASA Astrophysics Data System (ADS)

    Giuseppe, Ciullo; Paolo, Lenisa; Marco, Contalbrigo; Delia, Hasch

    2009-04-01

    Purpose and status of the Italian transversity project / F. Bradamante -- Transversity asymmetries / D. Boer -- The transverse angular momentum sum rule / E. Leader -- Measurement of Collins and Sivers asymmetries at HERMES / L. L. Pappalardo (for the HERMES collaboration) -- Review of SSA results on deuteron at COMPASS / A. Richter (for the COMPASS collaboration) -- Single spin asymmetries on a transversely polarized proton target at COMPASS / S. Levorato (for the COMPASS collaboration) -- New preliminary results on the transversity distribution and the Collins fragmentation functions / M. Anselmino ... [et al.] -- Sivers effect in SIDIS pion and kaon production / M. Anselmino ... [et al.] -- Spin-orbit correlations / M. Burkardt -- Correlation functions in hard and (semi)-inclusive processes / M. Schlegel, S. Mei[symbol]ner and A. Metz -- Transversity via exclusive [pie symbol]-electroproduction / G. R. Goldstein, S. Liuti and S. Ahmad -- Estimate of the Sivers asymmetry at intermediate energies with rescattering extracted from exclusive processes / A. Bianconi -- Exclusively produced p[symbol] asymmetries on the deuteron and future GPD measurements at COMPASS / C. Schill (for the COMPASS collaboration) -- Transversity and transverse-momentum-dependent distribution measurements from PHENIX and BRAHMS / C. Aidala (for the PHENIX and BRAHMS collaborations) -- Sivers and Collins effects in polarized pp scattering processes / M. Anselmino ... [et al.] -- Sivers function in constituent quark models / S. Scopetta ... [et al.] -- Sivers, Boer-Mulders and transversity in Drell-Yan processes / M. Anselmino ... [et al.] -- TMDs and Drell-Yan experiments at Fermilab and J-PARC / J.-C. Peng -- Double polarisation observables at PAX / M. Nekipelov (for the PAX collaboration) -- Future Drell-Yan measurement @ COMPASS / M. Colantoni (for the COMPASS collaboration) -- Measurements of unpolarized azimuthal asymmetries at COMPASS / W. Käfer (for the COMPASS collaboration

  5. A carbon-13 NMR spin-lattice relaxation study of the molecular conformation of the nootropic drug 2-oxopyrrolidin-1-ylacetamide

    NASA Astrophysics Data System (ADS)

    Baldo, M.; Grassi, A.; Guidoni, L.; Nicolini, M.; Pappalardo, G. C.; Viti, V.

    The spin-lattice relaxation times ( T1) of carbon-13 resonances of the drug 2-oxopyrrolidin- 1-ylacetamide ( 2OPYAC) were determined in CDCl 3 + DMSO and H 2O solutions to investigate the internal conformational flexibility. The measured T1s for the hydrogen-bearing carbon atoms of the 2-pyrrolidone ring fragment were diagnostic of a rigid conformation with respect to the acetamide linked moiety. The model of anisotropic reorientation of a rigid body was used to analyse the measured relaxation data in terms of a single conformation. Owing to the small number of T1 data available the fitting procedure for each of the possible conformations failed. The structure corresponding to the rigid conformation was therefore considered to be the one that is strongly stabilized by internal hydrogen bonding as predicted on the basis of theoretical MO ab initio quantum chemical calculations.

  6. Unexpectedly broad photoelectron spectrum as a signature of ultrafast electronic relaxation of Rydberg states of carbon dioxide

    NASA Astrophysics Data System (ADS)

    Adachi, Shunsuke; Sato, Motoki; Suzuki, Toshinori; Grebenshchikov, Sergy Yu.

    2017-03-01

    The dynamics of CO2 excited into Rydberg states lying 0.2 eV below the ionization threshold is studied by means of time resolved photoelectron imaging. Over 3 eV broad photoelectron spectra are measured for all pump-probe delay times. Quantum mechanical calculations demonstrate that the spectral broadening is due to ultrafast electronic relaxation of Rydberg states and identify the likely relaxation pathways. Experiment and theory bracket the relaxation time between 15 and 65 fs. A weak time independent ionization signal is attributed to CO2 trapped in near-threshold triplet states.

  7. Improvement of the relaxation time and the order parameter of nematic liquid crystal using a hybrid alignment mixture of carbon nanotube and polyimide

    SciTech Connect

    Lee, Hyojin; Yang, Seungbin; Lee, Ji-Hoon; Soo Park, Young

    2014-05-12

    We examined the electrooptical properties of a nematic liquid crystal (LC) sample whose substrates were coated with a mixture of carbon nanotube (CNT) and polyimide (PI). The relaxation time of the sample coated with 1.5 wt. % CNT mixture was about 35% reduced compared to the pure polyimide sample. The elastic constant and the order parameter of the CNT-mixture sample were increased and the fast relaxation of LC could be approximated to the mean-field theory. We found the CNT-mixed polyimide formed more smooth surface than the pure PI from atomic force microscopy images, indicating the increased order parameter is related to the smooth surface topology of the CNT-polyimide mixture.

  8. Optical Emission Studies of Copper Plasma Induced Using Infrared Transversely Excited Atmospheric (IR TEA) Carbon Dioxide Laser Pulses.

    PubMed

    Momcilovic, Milos; Kuzmanovic, Miroslav; Rankovic, Dragan; Ciganovic, Jovan; Stoiljkovic, Milovan; Savovic, Jelena; Trtica, Milan

    2015-04-01

    Spatially resolved, time-integrated optical emission spectroscopy was applied for investigation of copper plasma produced by a nanosecond infrared (IR) transversely excited atmospheric (TEA) CO2 laser, operating at 10.6 μm. The effect of surrounding air pressure, in the pressure range 0.1 to 1013 mbar, on plasma formation and its characteristics was investigated. A linear dependence of intensity threshold for plasma formation on logarithm of air pressure was found. Lowering of the air pressure reduces the extent of gas breakdown, enabling better laser-target coupling and thus increases ablation. Optimum air pressure for target plasma formation was 0.1 mbar. Under that pressure, the induced plasma consisted of two clearly distinguished and spatially separated regions. The maximum intensity of emission, with sharp and well-resolved spectral lines and negligibly low background emission, was obtained from a plasma zone 8 mm from the target surface. The estimated excitation temperature in this zone was around 7000 K. The favorable signal to background ratio obtained in this plasma region indicates possible analytical application of TEA CO2 laser produced copper plasma. Detection limits of trace elements present in the Cu sample were on the order of 10 ppm (parts per million). Time-resolved measurements of spatially selected plasma zones were used to find a correlation between the observed spatial position and time delay.

  9. Relaxed heaps

    SciTech Connect

    Driscoll, J.R. ); Gabow, H.N.; Shrairman, R. ); Tarjan, R.E. )

    1988-11-01

    The relaxed heap is a priority queue data structure that achieves the same amortized time bounds as the Fibonacci heap - a sequence of m decrease key and n delete min operations takes time O(m + n log n). A variant of relaxed heaps achieves similar bounds in the worst case - O(1) time for decrease key and O(log n) for delete min. Relaxed heaps give a processor-efficient parallel implementation of Dijkstra's shortest path algorithm, and hence other algorithms in network optimization. A relaxed heap is a type of binomial queue that allows heap order to be violated.

  10. The influence of external transverse magnetic field in propagation of electrostatic oscillations in single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Abdikian, Alireza

    2016-10-01

    Propagation of an electrostatic oscillation by using the linearized quantum hydrodynamic model in conjunction with Maxwell's equations was studied. The dispersion relation of a system of electron plasma in single-walled carbon nanotubes in the presence of an external magnetic field B 0 by considering the exchange-correlation effects in 2D cylindrical geometry is derived here. The uniform static magnetic field is assumed to be normal to the cylindrical surface (Voigt configuration). Distribution of the electrons and ions are considered uniformly over the cylindrical surface of a nanotube. It is found that the external magnetic field has significant impact on the wave in the longer wavelength. The influence of variation in azimuthal index and radius of the nanotube on dispersion relation is also discussed. It is tried to plot some schemes and analyze numerically in different limits of cylindrical and planar geometries. The results can be important in the study of collective phenomena in nanostructures.

  11. Uranyl Carbonate Complexes in Aqueous Solution and Their Ligand NMR Chemical Shifts and (17)O Quadrupolar Relaxation Studied by ab Initio Molecular Dynamics.

    PubMed

    Marchenko, Alex; Truflandier, Lionel A; Autschbach, Jochen

    2017-07-03

    Dynamic structural effects, NMR ligand chemical shifts, and (17)O NMR quadrupolar relaxation rates are investigated in the series of complexes UO2(2+), UO2(CO3)3(4-), and (UO2)3(CO3)6(6-). Car-Parrinello molecular dynamics (CPMD) is used to simulate the dynamics of the complexes in water. NMR properties are computed on clusters extracted from the CPMD trajectories. In the UO2(2+) complex, coordination at the uranium center by water molecules causes a decrease of around 300 ppm for the uranyl (17)O chemical shift. The final value of this chemical shift is within 40 ppm of the experimental range. The UO2(CO3)3(4-) and (UO2)3(CO3)6(6-) complexes show a solvent dependence of the terminal carbonate (17)O and (13)C chemical shifts that is less pronounced than that for the uranyl oxygen atom. Corrections to the chemical shift from hybrid functionals and spin-orbit coupling improve the accuracy of chemical shifts if the sensitivity of the uranyl chemical shift to the uranyl bond length (estimated at 140 ppm per 0.1 Å from trajectory data) is taken into consideration. The experimentally reported trend in the two unique (13)C chemical shifts is correctly reproduced for (UO2)3(CO3)6(6-). NMR relaxation rate data support large (17)O peak widths, but remain below those noted in the experimental literature. Comparison of relaxation data for solvent-including versus solvent-free models suggest that carbonate ligand motion overshadows explicit solvent effects.

  12. Ingestion of a carbonated beverage decreases lower esophageal sphincter pressure and increases frequency of transient lower esophageal sphincter relaxation in normal subjects.

    PubMed

    Shukla, Akash; Meshram, Megha; Gopan, Amrit; Ganjewar, Vaibhav; Kumar, Praveen; Bhatia, Shobna J

    2012-06-01

    Transient lower esophageal sphincter relaxation (tLESR) and decreased basal lower esophageal sphincter (LES) pressure are postulated mechanisms of gastroesophageal reflux (GER). There is conflicting evidence on the effect of carbonated drinks on lower esophageal sphincter function. This study was conducted to assess the effect of a carbonated beverage on tLESR and LES pressure. High resolution manometry tracings (16 channel water-perfused, Trace 1.2, Hebbard, Australia) were obtained in 18 healthy volunteers (6 men) for 30 min each at baseline, and after 200 mL of chilled potable water and 200 mL of chilled carbonated cola drink (Pepsi [Pepsico India Ltd]). The sequence of administration of the drinks was determined by random number method generated by a computer. The analysis of tracings was done using TRACE 1.2 software by a physician who was unaware of the sequence of administration of fluids. The mean (SD) age of the participant was 37.3 (12.9) years. The median (range) frequency of tLESr was higher after the carbonated beverage (10.5 [0-26]) as compared to baseline (0 [0-3], p = 0.005) as well as after water (1 [0-14], p = 0.010). The LES pressure decreased after ingestion of the carbonated beverage (18.5 [11-37] mmHg) compared to baseline (40.5 [25-66] mmHg, p = 0.0001) and after water (34 [15-67] mmHg, p = 0.003). Gastric pressure was not different in the three groups. Ingestion of a carbonated beverage increases tLESr and lowers LES pressure in healthy subjects.

  13. Role of carbon monoxide in electrically induced non-adrenergic, non-cholinergic relaxations in the guinea-pig isolated whole trachea

    PubMed Central

    Dellabianca, A; Sacchi, M; Anselmi, L; De Amici, E; Cervio, E; Agazzi, A; Tonini, S; Sternini, C; Tonini, M; Candura, S M

    2006-01-01

    Background and purpose: Nitric oxide (NO) and vasoactive intestinal peptide (VIP) are considered transmitters of non-adrenergic, non-cholinergic (NANC) relaxations in guinea-pig trachea, whereas the role of carbon monoxide (CO) is unknown. This study was designed to assess the participation of CO, and to investigate the localization of haem oxygenase-2 (HO-2), the CO-producing enzyme, in tracheal neurons. Experimental approach: NANC responses to electrical field stimulation (EFS) at 3 and 10 Hz were evaluated in epithelium-free whole tracheal segments as intraluminal pressure changes. Drugs used were: L-nitroarginine methyl ester (L-NAME, 100 μ M) to inhibit NO synthase (NOS), α-chymotrypsin (2 U ml−1) to inactivate VIP, zinc protoporphyrin-IX (ZnPP-IX, 10 μM) to inhibit HO-2, and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10 μM), a soluble guanylyl cyclase inhibitor. For immunohistochemistry, tissues were exposed to antibodies to PGP 9.5, a general neuronal marker, HO-2 and NOS, and processed with an indirect immunofluorescence method. Key results: α-Chymotrypsin did not affect NANC relaxations. ODQ inhibited NANC responses by about 60%, a value similar to that obtained by combining L-NAME and ZnPP-IX. The combination of ODQ, L-NAME and ZnPP-IX reduced the responses by 90%. Subpopulations of HO-2 positive neurons containing NOS were detected in tracheal sections. Conclusions and Implications: In the guinea-pig trachea, NANC inhibitory responses at 3 and 10 Hz use NO and CO as main transmitters. Their participation is revealed following inhibition of NOS, HO-2 and soluble guanylyl cyclase. The involvement of CO as a relaxing transmitter paves the way for novel therapeutic approaches in the treatment of airway obstruction. PMID:17179955

  14. Dielectric relaxation and ac conductivity behavior of carboxyl functionalized multiwalled carbon nanotubes/poly (vinyl alcohol) composites

    NASA Astrophysics Data System (ADS)

    Amrin, Sayed; Deshpande, V. D.

    2017-03-01

    We study the dielectric relaxation and ac conductivity behavior of MWCNT-COOH/Polyvinyl alcohol nanocomposite films in the temperature (T) range 303-423 K and in the frequency (f) range 0.1 Hz-1 MHz. The dielectric constant increases with an increase in temperature and also with an increase in MWCNT-COOH loading into the polymer matrix, as a result of interfacial polarization. The permittivity data were found to fit well with the modified Cole-Cole equation. Temperature dependent values of the relaxation times, free charge carrier conductivity and space charge carrier conductivity were extracted from the equation. An observed increment in the ac conductivity for the nanocomposites was analysed by a Jonscher power law which suggests that the correlated barrier hopping is the dominant charge transport mechanism for the nanocomposite films. The electric modulus study revealed deviations from ideal Debye-type behavior which are explained by considering a generalized susceptibility function. XRD and DSC results show an increase in the degree of crystallinity.

  15. The change of longitudinal relaxation rate in oxygen enhanced pulmonary MRI depends on age and BMI but not diffusing capacity of carbon monoxide in healthy never-smokers.

    PubMed

    Kindvall, Simon Sven Ivan; Diaz, Sandra; Svensson, Jonas; Wollmer, Per; Olsson, Lars E

    2017-01-01

    Oxygen enhanced pulmonary MRI is a promising modality for functional lung studies and has been applied to a wide range of pulmonary conditions. The purpose of this study was to characterize the oxygen enhancement effect in the lungs of healthy, never-smokers, in light of a previously established relationship between oxygen enhancement and diffusing capacity of carbon monoxide in the lung (DL,CO) in patients with lung disease. In 30 healthy never-smoking volunteers, an inversion recovery with gradient echo read-out (Snapshot-FLASH) was used to quantify the difference in longitudinal relaxation rate, while breathing air and 100% oxygen, ΔR1, at 1.5 Tesla. Measurements were performed under multiple tidal inspiration breath-holds. In single parameter linear models, ΔR1 exhibit a significant correlation with age (p = 0.003) and BMI (p = 0.0004), but not DL,CO (p = 0.33). Stepwise linear regression of ΔR1 yields an optimized model including an age-BMI interaction term. In this healthy, never-smoking cohort, age and BMI are both predictors of the change in MRI longitudinal relaxation rate when breathing oxygen. However, DL,CO does not show a significant correlation with the oxygen enhancement. This is possibly because oxygen transfer in the lung is not diffusion limited at rest in healthy individuals. This work stresses the importance of using a physiological model to understand results from oxygen enhanced MRI.

  16. Simulated carbon and nitrogen flows of the planktonic food web during an upwelling relaxation period in St Helena Bay (southern Benguela ecosystem) [review article

    NASA Astrophysics Data System (ADS)

    Touratier, Franck; Field, John G.; Moloney, Coleen L.

    2003-07-01

    A vertically resolved ecosystem model is developed to simulate the dynamics of the pelagic food web in St Helena Bay during a representative period of relaxation after an upwelling event. The proposed model aims at coupling three biogeochemical cycles (carbon, nitrogen and silicon), using several recently developed concepts of the stoichiometric approach. A consequence of this approach is that important qualitative aspects are introduced, such as indicators of phytoplankton physiological state or variable food C:N ratios. For instance, the sedimentation and exudation rates for phytoplankton vary according to physiological state. An attempt is made to parameterize and simulate the diel cycles for vertical migration and feeding rhythms of large zooplankton, two important mesoscale processes that are thought to influence the overall dynamics of the huge phytoplankton blooms in the region. Observations of the Anchor Station Experiment 1987 (ASE’87) are used to assess the quality of the model. There is overall agreement between observations and the corresponding simulated results. The timing, the magnitude, and the vertical structure of the phytoplankton bloom are well reproduced. The balances for carbon and nitrogen flows and stocks compare well to the numerous estimates found from the literature for the southern Benguela region. On the basis of the model results, the origin of the new nutrients, the fate of the carbon fixed by phytoplankton, and the importance of the microheterotrophic pathways are discussed. It is concluded that sediments of the St Helena Bay and surrounding areas may play a crucial role in increasing the level of phytoplankton production. The results also suggest that exudation is the main process by which the carbon fixed by phytoplankton would have been lost, and that microheterotrophic pathways would have been intense during the experiment.

  17. Relaxation System

    NASA Technical Reports Server (NTRS)

    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.

  18. Fluid mixing technique increases the gain and output power of carbon dioxide laser systems

    NASA Technical Reports Server (NTRS)

    Cool, T. A.

    1970-01-01

    High speed flowing gas system provides uniform mixing in short times compared to flow transit times and carbon dioxide vibrational relaxation times. This system minimizes the effects of surrounding surfaces and provides a uniformly high gain that is independent of dimensions transverse to the flow direction.

  19. Relaxation Techniques.

    DTIC Science & Technology

    1985-04-01

    FUNDING/SPONSORING 18b. OFFICE SYMBOL 9. PROCUREMENT INSTRUMENT IDENTIFICATION NUMBER ORGANIZATION (If applicable) 8c ADDRESS f( t’, State and ZIP Code) 10...inhaling and exhaling to promote a feeling of relaxation that is used in yoga, LaMaze childbirth, and hypnosis . The sccond is progressive muscle

  20. Transverse Myelitis Association

    MedlinePlus

    ... Acute Flaccid Myelitis) REGISTER TODAY! The Transverse Myelitis Association Registry The NIH/NCATS GRDR® Program Global Rare ... be followed via electronic surveys THE TRANSVERSE MYELITIS ASSOCIATION ADVOCATING FOR THOSE WITH ACUTE DISSEMINATED ENCEPHALOMYELITIS, NEUROMYELITIS ...

  1. Uncovering the intrinsic permittivity of the carbonaceous phase in carbon black filled polymers from broadband dielectric relaxation

    NASA Astrophysics Data System (ADS)

    Essone Mezeme, M.; El Bouazzaoui, S.; Achour, M. E.; Brosseau, C.

    2011-04-01

    An outstanding experimental issue in the physics of composites concerns the reliable extraction of the intrinsic dielectric characteristics from effective permittivity measurements of heterostructures. Though recent analytical and numerical models have made progress in tackling this question, their applicability is typically limited by the lack of information about the structural organization of the filler phase. As a follow-up of our earlier work [S. El Bouazzaoui et al. J. Appl. Phys. 106, 104 (2009), we report in this paper a systematic study of the intrinsic permittivity ɛ2 of the carbonaceous phase in carbon black (CB) loaded polymers. A variety of authors has suggested very early that ɛ2 can be modeled with a simple free-electron (Drude) metal model with static disorder. Despite the interest in the physics of carbonaceous materials, there have been few experimental tests of this assumption, in part, due to the experimental challenge of measuring ɛ2. Here, this interpretation is questioned by an analysis of the frequency-dependent complex effective permittivity of these lossy conductor-insulator composites using the Hashin-Shtrikman bounds of the effective medium approximation. For the materials investigated over the range of frequencies explored (10-104 kHz) it is found that ɛ2 can be written as ɛ2=ɛ2'-iɛ2'' with ɛ2''>>|ɛ2'|. We critically evaluate the possibility that the estimates of ɛ2 are related to Drude model. We found that the intrinsic permittivity of the carbonaceous phase dispersed in the composite materials investigated is consistent with the dielectric response described by the Drude metal model in a percolative morphology. The sensitivity of this method is fundamentally related to the complexity of the morphological changes which occur during mechanical mixing, i.e., interphase formation, CB particles aggregation. Such knowledge can be used to determine the role of the conducting states at the interface between insulating polymer chains

  2. Transverse vibration of nematic elastomer Timoshenko beams

    NASA Astrophysics Data System (ADS)

    Zhao, Dong; Liu, Ying; Liu, Chuang

    2017-01-01

    Being a rubber-like liquid crystalline elastomer, a nematic elastomer (NE) is anisotropic viscoelastic, and displays dynamic soft elasticity. In this paper, the transverse vibration of a NE Timoshenko beam is studied based on the linear viscoelasticity theory of nematic elastomers. The governing equation of motion for the transverse vibration of a NE Timoshenko beam is derived. A complex modal analysis method is used to obtain the natural frequencies and decrement coefficients of NE beams. The influences of the nematic director rotation, the rubber relaxation time, and the director rotation time on the vibration characteristic of NE Timoshenko beams are discussed in detail. The sensitivity of the dynamic performance of NE beams to director initial angle and relaxation times provides a possibility of intelligent controlling of their dynamic performance.

  3. Transverse vibration of nematic elastomer Timoshenko beams.

    PubMed

    Zhao, Dong; Liu, Ying; Liu, Chuang

    2017-01-01

    Being a rubber-like liquid crystalline elastomer, a nematic elastomer (NE) is anisotropic viscoelastic, and displays dynamic soft elasticity. In this paper, the transverse vibration of a NE Timoshenko beam is studied based on the linear viscoelasticity theory of nematic elastomers. The governing equation of motion for the transverse vibration of a NE Timoshenko beam is derived. A complex modal analysis method is used to obtain the natural frequencies and decrement coefficients of NE beams. The influences of the nematic director rotation, the rubber relaxation time, and the director rotation time on the vibration characteristic of NE Timoshenko beams are discussed in detail. The sensitivity of the dynamic performance of NE beams to director initial angle and relaxation times provides a possibility of intelligent controlling of their dynamic performance.

  4. Natural relaxation

    NASA Astrophysics Data System (ADS)

    Marzola, Luca; Raidal, Martti

    2016-11-01

    Motivated by natural inflation, we propose a relaxation mechanism consistent with inflationary cosmology that explains the hierarchy between the electroweak scale and Planck scale. This scenario is based on a selection mechanism that identifies the low-scale dynamics as the one that is screened from UV physics. The scenario also predicts the near-criticality and metastability of the Standard Model (SM) vacuum state, explaining the Higgs boson mass observed at the Large Hadron Collider (LHC). Once Majorana right-handed neutrinos are introduced to provide a viable reheating channel, our framework yields a corresponding mass scale that allows for the seesaw mechanism as well as for standard thermal leptogenesis. We argue that considering singlet scalar dark matter extensions of the proposed scenario could solve the vacuum stability problem and discuss how the cosmological constant problem is possibly addressed.

  5. La relaxation en pedagogie (Relaxation in Teaching).

    ERIC Educational Resources Information Center

    Dufeu, Bernard

    1989-01-01

    A discussion of the use of relaxation techniques in the language classroom outlines the reasons for their use and specifies procedures for relaxation either lying down or seated as a prelude to instruction. (MSE)

  6. Breathing and Relaxation

    MedlinePlus

    ... Home Health Insights Stress & Relaxation Breathing and Relaxation Breathing and Relaxation Make an Appointment Ask a Question ... level is often dependent on his or her breathing pattern. Therefore, people with chronic lung conditions may ...

  7. Relaxation Assessment with Varied Structured Milieu (RELAX).

    ERIC Educational Resources Information Center

    Cassel, Russell N.; Cassel, Susie L.

    1983-01-01

    Describes Relaxation Assessment with Varied Structured Milieu (RELAX), a clinical program designed to assess the degree to which an individual is able to demonstrate self-control for overall general relaxation. The program is designed for use with the Cassel Biosensors biofeedback equipment. (JAC)

  8. Relaxation Assessment with Varied Structured Milieu (RELAX).

    ERIC Educational Resources Information Center

    Cassel, Russell N.; Cassel, Susie L.

    1983-01-01

    Describes Relaxation Assessment with Varied Structured Milieu (RELAX), a clinical program designed to assess the degree to which an individual is able to demonstrate self-control for overall general relaxation. The program is designed for use with the Cassel Biosensors biofeedback equipment. (JAC)

  9. TRANSVERSITY SINGLE SPIN ASYMMETRIES.

    SciTech Connect

    BOER,D.

    2001-04-27

    The theoretical aspects of two leading twist transversity single spin asymmetries, one arising from the Collins effect and one from the interference fragmentation functions, are reviewed. Issues of factorization, evolution and Sudakov factors for the relevant observables are discussed. These theoretical considerations pinpoint the most realistic scenarios towards measurements of transversity.

  10. Transverse gravity versus observations

    SciTech Connect

    Álvarez, Enrique; Faedo, Antón F.; López-Villarejo, J.J. E-mail: anton.fernandez@uam.es

    2009-07-01

    Theories of gravity invariant under those diffeomorphisms generated by transverse vectors, ∂{sub μ}ξ{sup μ} = 0 are considered. Such theories are dubbed transverse, and differ from General Relativity in that the determinant of the metric, g, is a transverse scalar. We comment on diverse ways in which these models can be constrained using a variety of observations. Generically, an additional scalar degree of freedom mediates the interaction, so the usual constraints on scalar-tensor theories have to be imposed. If the purely gravitational part is Einstein-Hilbert but the matter action is transverse, the models predict that the three a priori different concepts of mass (gravitational active and gravitational passive as well as inertial) are not equivalent anymore. These transverse deviations from General Relativity are therefore tightly constrained, actually correlated with existing bounds on violations of the equivalence principle, local violations of Newton's third law and/or violation of Local Position Invariance.

  11. Transverse instability of dunes.

    PubMed

    Parteli, Eric J R; Andrade, José S; Herrmann, Hans J

    2011-10-28

    The simplest type of dune is the transverse one, which propagates with invariant profile orthogonally to a fixed wind direction. Here we show, by means of numerical simulations, that transverse dunes are unstable with respect to along-axis perturbations in their profile and decay on the bedrock into barchan dunes. Any forcing modulation amplifies exponentially with growth rate determined by the dune turnover time. We estimate the distance covered by a transverse dune before fully decaying into barchans and identify the patterns produced by different types of perturbation.

  12. Transversity measurements at HERMES

    SciTech Connect

    Diefenthaler, Markus

    2005-10-06

    Azimuthal single-spin asymmetries (SSA) in semi-inclusive electroproduction of charged pions in deep-inelastic scattering (DIS) of positrons on a transversely polarised hydrogen target are presented. Azimuthal moments for both the Collins and the Sivers mechanism are extracted. In addition the subleading-twist contribution due to the transverse spin component from SSA on a longitudinally polarised hydrogen target is evaluated.

  13. Molecular motions of [Beta]-carotene and a carotenoporphyrin dyad in solution. A carbon-13 NMR spin-lattice relaxation time study

    SciTech Connect

    Li, S.; Swindle, S.L.; Smith, S.K.; Nieman, R.A.; Moore, A.L.; Moore, T.A.; Gust, D. )

    1995-03-09

    Analysis of [sup 13]C NMR spin-lattice relaxation times (T[sub 1]) yields information concerning both overall tumbling of molecules in solution and internal rotations about single bonds. Relaxation time and nuclear Overhauser effect data have been obtained for [Beta]-carotene and two related molecules, squalane and squalene, for zinc meso-tetraphenylporphyrin, and for a dyad consisting of a porphyrin covalently linked to a carotenoid polyene through a trimethylene bridge. Squalane and squalene, which lack conjugated double bonds, behave essentially as limp string, with internal rotations at least as rapid as overall isotropic tumbling motions. In contrast, [Beta]-carotene reorients as a rigid rod, with internal motions which are too slow to affect relaxation times. Modeling it as an anisotropic rotor yields a rotational diffusion coefficient for motion about the major axis which is 14 times larger than that for rotation about axes perpendicular to that axis. The porphyrin reorients more nearly isotropically and features internal librational motions about the single bonds to the phenyl groups. The relaxation time data for the carotenoporphyrin are consistent with internal motions similar to those of a medieval military flail. 31 refs., 3 figs., 5 tabs.

  14. Relaxation magnétique nucléaire du carbone-13 et dynamique des molécules de chlorpromazine associées en solution aqueuse

    NASA Astrophysics Data System (ADS)

    Compère, S.; Thévand, A.

    1998-02-01

    13C relaxation times and heteronuclear NOE enhancements have been measured for chlorpromazine hydrochloride salt in chloroform and water. The dipolar contribution to 13C ^1H spin systems relaxation rates were extracted and allowed us to characterize the molecular reorientation in the two solvents. The correlation times are on either side of “T1 minimum". The values agree with the size of the molecule and show an association by stacking of 11 monomeric entities. Les temps de relaxation des 13C et les accroissements par effet Overhauser 1Hto13C ont été mesurés parallèlement sur la molécule de chlorhydrate de chlorpromazine non associée dans le chloroforme et auto-associée dans l'eau. L'extraction de la contribution dipolaire aux constantes de vitesse de relaxation des systèmes 13C 1H de la molécule a permis de caractériser la réorientation de la molécule dans les deux cas. Les temps de corrélation obtenus qui se situent de part et d'autre du “T1 minimum" sont en accord avec la taille de la molécule isolée et montrent que l'agrégat est formé par empilement de 11 molécules.

  15. Transverse spin and transverse momentum in scattering of plane waves.

    PubMed

    Saha, Sudipta; Singh, Ankit K; Ray, Subir K; Banerjee, Ayan; Gupta, Subhasish Dutta; Ghosh, Nirmalya

    2016-10-01

    We study the near field to the far field evolution of spin angular momentum (SAM) density and the Poynting vector of the scattered waves from spherical scatterers. The results show that at the near field, the SAM density and the Poynting vector are dominated by their transverse components. While the former (transverse SAM) is independent of the helicity of the incident circular polarization state, the latter (transverse Poynting vector) depends upon the polarization state. It is further demonstrated that the interference of the transverse electric and transverse magnetic scattering modes enhances both the magnitudes and the spatial extent of the transverse SAM and the transverse momentum components.

  16. Molecular factors that determine Curie spin relaxation in dysprosium complexes.

    PubMed

    Caravan, P; Greenfield, M T; Bulte, J W

    2001-11-01

    Dysprosium complexes can serve as transverse relaxation (T(2)) agents for water protons through chemical exchange and the Curie spin relaxation mechanism. Using a pair of matched dysprosium(III) complexes, Dy-L1 (contains one inner-sphere water) and Dy-L2 (no inner-sphere water), it is shown that the transverse relaxation of bulk water is predominantly an inner-sphere effect. The kinetics of water exchange at Dy-L1 were determined by (17)O NMR. Proton transverse relaxation by Dy-L1 at high fields is governed primarily through a large chemical shift difference between free and bound water. Dy-L1 forms a noncovalent adduct with human serum albumin which dramatically lengthens the rotational correlation time, tau(R), causing the dipole-dipole component of the Curie spin mechanism to become significant and transverse relaxivity to increase by 3-8 times that of the unbound chelate. These findings aid in the design of new molecular species as efficient r(2) agents.

  17. Latent Period of Relaxation.

    PubMed

    Kobayashi, M; Irisawa, H

    1961-10-27

    The latent period of relaxation of molluscan myocardium due to anodal current is much longer than that of contraction. Although the rate and the grade of relaxation are intimately related to both the stimulus condition and the muscle tension, the latent period of relaxation remains constant, except when the temperature of the bathing fluid is changed.

  18. Charge relaxation resistance at atomic scale: An ab initio calculation

    NASA Astrophysics Data System (ADS)

    Wang, Bin; Wang, Jian

    2008-06-01

    We report an investigation of ac quantum transport properties of a nanocapacitor from first principles. At low frequencies, the nanocapacitor is characterized by a static electrochemical capacitance Cμ and the charge relaxation resistance Rq . We carry out a first principle calculation within the nonequilibrium Green’s function formalism. In particular, we investigate charge relaxation resistance of a single carbon atom as well as two carbon atoms in a nanocapacitor made of a capped carbon nanotube (CNT) and an alkane chain connected to a bulk Si. The nature of charge relaxation resistance is predicted for this nanocapacitor. Specifically, we find that the charge relaxation resistance shows resonant behavior and it becomes sharper as the distance between plates of nanocapacitor increases. If there is only one transmission channel dominating the charge transport through the nanocapacitor, the charge relaxation resistance Rq is half of resistance quantum h/2e2 . This result shows that the theory of charge relaxation resistance applies at atomic scale.

  19. Digital transversal filter architecture

    NASA Astrophysics Data System (ADS)

    Greenberger, A. J.

    1985-01-01

    A fast and efficient architecture is described for the realization of a pipelined, fully parallel digital transversal filter in VLSI. The order of summation is changed such that no explicit multiplication is seen, gated accumulators are used, and the coefficients are circulated. Estimates for the number of transistors needed for a CMOS implementation are given.

  20. ô Electroproduction and Transversity

    NASA Astrophysics Data System (ADS)

    Liuti, Simonetta

    2008-10-01

    Exclusive ô electroproduction from the proton is suggested for extracting the tensor charge and other quantities related to transversity from experimental data [1]. A connection between a description based on partonic degrees of freedom, given in terms of Generalized Parton Distributions (GPDs), and Regge phenomenology is discussed. Pion electroproduction is described in terms of the chiral odd (spin flip) GPDs for both longitudinal and transverse virtual photon polarizations. A mechanism for the Q^2-dependence of the &*circ;ô vertex is proposed that, by treating separately natural and unnatural parity exchanges at this vertex, allows one to separate the transverse and longitudinal virtual photon contributions, the latter being dominated by unnatural exchanges. A study of the sensitivity of different observables in both unpolarized and polarized scattering to both the tensor charge and the transverse anomalous magnetic moment [2], is presented with the aim of providing a practical method for extracting the latter. Future investigations using a variety of targets (proton, deuteron and ^4He) and probes -- both electron and neutrino scattering as well as hadronic reactions will be discussed. [1] S. Ahmad, G. R. Goldstein and S. Liuti, arXiv:0805.3568 [hep-ph] [2] M. Burkardt, Phys. Lett. B 639, 462 (2006).

  1. Spontaneous transverse colon volvulus

    PubMed Central

    Sana, Landolsi; Ali, Gassara; Kallel, Helmi; Amine, Baklouti; Ahmed, Saadaoui; Mohamed Ali, Elouer; Wajdi, Chaeib; Saber, Mannaï

    2013-01-01

    We report a case of spontaneous transverse colon volvulus in a young healthy woman. It constitutes an unusual case since it occurred in a young healthy woman with a subacute onset and no aetiological factor has been found. Its diagnosis is still challenging. Prompt recognition with emergency intervention constitutes the key to successful outcome. PMID:23785565

  2. Spontaneous transverse colon volvulus.

    PubMed

    Sana, Landolsi; Ali, Gassara; Kallel, Helmi; Amine, Baklouti; Ahmed, Saadaoui; Ali, Elouer Mohamed; Wajdi, Chaeib; Saber, Mannaï

    2013-01-01

    We report a case of spontaneous transverse colon volvulus in a young healthy woman. It constitutes an unusual case since it occurred in a young healthy woman with a subacute onset and no aetiological factor has been found. Its diagnosis is still challenging. Prompt recognition with emergency intervention constitutes the key to successful outcome.

  3. Characterization of spin relaxation anisotropy in Co using spin pumping

    NASA Astrophysics Data System (ADS)

    Li, Yi; Cao, Wei; Bailey, W. E.

    2016-11-01

    Ferromagnets are believed to exhibit strongly anisotropic spin relaxation, with relaxation lengths for spin longitudinal to the magnetization significantly longer than those for spin transverse to the magnetization. Here, we characterize the anisotropy of spin relaxation in Co using the spin pumping contribution to Gilbert damping in noncollinearly magnetized Py1 -xCux /Cu/Co trilayer structures. The static magnetization angle between Py1 -xCux and Co, adjusted under field bias perpendicular to film planes, controls the projections of longitudinal and transverse spin current pumped from Py1 -xCux into Co. We find nearly isotropic absorption of pure spin current in Co using this technique; fits to a diffusive transport model yield the longitudinal spin relaxation length <2 nm in Co. The longitudinal spin relaxation lengths found are an order of magnitude smaller than those determined by current-perpendicular-to-planes giant magnetoresistance measurements, but comparable with transverse spin relaxation lengths in Co determined by spin pumping.

  4. Relaxation-relaxation exchange experiments in porous media with portable Halbach-Magnets.

    NASA Astrophysics Data System (ADS)

    Haber, A.; Haber-Pohlmeier, S.; Casanova, F.; Blümich, B.

    2009-04-01

    Mobile NMR became a powerful tool following the development of portable NMR sensors for well logging. By now there are numerous applications of mobile NMR in materials analysis and chemical engineering where, for example, unique information about the structure, morphology and dynamics of polymers is obtained, and new opportunities are provided for geo-physical investigations [1]. In particular, dynamic information can be retrieved by two-dimensional Laplace exchange NMR, where the initial NMR relaxation environment is correlated with the final relaxation environment of molecules migrating from one environment to the other within a so-called NMR mixing time tm [2]. Relaxation-relaxation exchange experiments of water in inorganic porous media were performed at low and moderately inhomogeneous magnetic field with a simple, portable Halbach-Magnet. By conducting NMR transverse relaxation exchange experiments for several mixing times and converting the results to 2D T2 distributions (joint probability densities of transverse relaxation times T2) with the help of the inverse 2D Laplace Transformation (ILT), we obtained characteristic exchange times for different pore sizes. The results of first experiments on soil samples are reported, which reveal information about the complex pore structure of soil and the moisture content. References: 1. B. Blümich, J. Mauler, A. Haber, J. Perlo, E. Danieli, F. Casanova, Mobile NMR for Geo-Physical Analysis and Material Testing, Petroleum Science, xx (2009) xxx - xxx. 2. K. E. Washburn, P.T. Callaghan, Tracking pore to pore exchange using relaxation exchange spectroscopy, Phys. Rev. Lett. 97 (2006) 175502.

  5. Partonic Transverse Momentum Distributions

    SciTech Connect

    Rossi, Patrizia

    2010-08-04

    In recent years parton distributions have been generalized to account also for transverse degrees of freedom and new sets of more general distributions, Transverse Momentum Dependent (TMD) parton distributions and fragmentation functions were introduced. Different experiments worldwide (HERMES, COMPASS, CLAS, JLab-Hall A) have measurements of TMDs in semi-inclusive DIS processes as one of their main focuses of research. TMD studies are also an important part of the present and future Drell-Yan experiments at RICH and JPARC and GSI, respectively, Studies of TMDs are also one of the main driving forces of the Jefferson Lab (JLab) 12 GeV upgrade project. Progress in phenomenology and theory is flourishing as well. In this talk an overview of the latest developments in studies of TMDs will be given and newly released results, ongoing activities, as well as planned near term and future measurements will be discussed.

  6. [Ettore Majoran's transversal epistemology].

    PubMed

    Bontems, Vincent

    2013-01-01

    « Il valore delle leggi statistiche nella fisica e nelle scienze sociali » is Ettore Majorana's only work on science. It offers a critique of classical determinism, establishing an analogy between the laws of quantum mechanics and social science and arguing that both are intrinsically linked to probability. This article first studies this argument from the standpoing of metaphysics, physics, and sociology, and then assesses the significance of this transversal epistemology.

  7. Tunable Microwave Transversal Filters.

    DTIC Science & Technology

    1984-05-01

    GOVT ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER AFOSR-TR. 84-0977 S4. TI TLE (and Subtitle) 5. TYP ?FE&T&PEO OEE U!NABLE MICROWAVE TRANSVERSAL FILTERS...this goal through magnetostatic waves MSW propagating at microwave frequency in magnetically biased, liquid phase epitaxial films of yttrium iron...garnet (YIG) grown on gadolinium gallium garnet (GGG). This technology has a number of advantages; low loss (greater than 30db/usec at xband), tunable by

  8. Transverse Spin Physics: Recent Developments

    SciTech Connect

    Yuan, Feng

    2008-12-10

    Transverse-spin physics has been very active and rapidly developing in the last few years. In this talk, I will briefly summarize recent theoretical developments, focusing on the associated QCD dynamics in transverse spin physics.

  9. Clarification of the measurement of surface spin relaxation via conduction electron spin resonance

    NASA Astrophysics Data System (ADS)

    Eigler, D. M.; Schultz, S.

    1982-12-01

    We clarify the parameterization of the probability of transverse conduction electron spin relaxation. ɛ, at the surface of a metal. Using Walker's boundary condition on the transverse spin magnetization, we have calculated the ɛ and thickness dependence of the spin resonance linewidth. The results are discussed in simple physical terms. The recent work of Allam and Vigouroux is shown to contain errors.

  10. Modified Statistical Dynamical Diffraction Theory: A Novel Metrological Analysis Method for Partially Relaxed and Defective Carbon-doped Silicon and Silicon Germanium Heterostructures

    NASA Astrophysics Data System (ADS)

    Shreeman, Paul K.

    The statistical dynamical diffraction theory, which has been initially developed by late Kato remained in obscurity for many years due to intense and difficult mathematical treatment that proved to be quite challenging to implement and apply. With assistance of many authors in past (including Bushuev, Pavlov, Pungeov, and among the others), it became possible to implement this unique x-ray diffraction theory that combines the kinematical (ideally imperfect) and dynamical (the characteristically perfect diffraction) into a single system of equations controlled by two factors determined by long range order and correlation function within the structure. The first stage is completed by the publication (Shreeman and Matyi, J. Appl. Cryst., 43, 550 (2010)) demonstrating the functionality of this theory with new modifications hence called modified statistical dynamical diffraction theory (mSDDT). The foundation of the theory is also incorporated into this dissertation, and the next stage of testing the model against several ion-implanted SiGe materials has been published: (Shreeman and Matyi, physica status solidi (a)208(11), 2533-2538, 2011). The dissertation with all the previous results summarized, dives into comprehensive analysis of HRXRD analyses complete with several different types of reflections (symmetrical, asymmetrical and skewed geometry). The dynamical results (with almost no defects) are compared with well-known commercial software. The defective materials, to which commercially available modeling software falls short, is then characterized and discussed in depth. The results will exemplify the power of the novel approach in the modified statistical dynamical diffraction theory: Ability to detect and measure defective structures qualitatively and quantitatively. The analysis will be compared alongside with TEM data analysis for verification and confirmation. The application of this theory will accelerate the ability to quickly characterize the relaxed

  11. Ideas in Transverse Spin Physics

    NASA Astrophysics Data System (ADS)

    Sivers, Dennis

    2015-01-01

    Three simple ideas about transverse spin observables are presented for the purpose of stimulating discussion. The manuscript is based on a presentation at the Transversity 2014 Workshop in Torre Chia, Sardinia, Italy on June 9-13, 2014 where approximately sixty experts on transverse spin physics had gathered to share recent results in an atmosphere of sun-drenched intensity.

  12. PARAMAGNETIC RELAXATION IN CRYSTALS.

    DTIC Science & Technology

    CRYSTALS, PARAMAGNETIC RESONANCE, RELAXATION TIME , CRYSTAL DEFECTS, QUARTZ, GLASS, STRAIN(MECHANICS), TEMPERATURE, NUCLEAR SPINS, HYDROGEN, CALCIUM COMPOUNDS, FLUORIDES, COLOR CENTERS, PHONONS, OXYGEN.

  13. Neutron Transversity at Jefferson Lab

    SciTech Connect

    Jian-Ping Chen; Xiaodong Jiang; Jen-chieh Peng; Lingyan Zhu

    2005-09-07

    Nucleon transversity and single transverse spin asymmetries have been the recent focus of large efforts by both theorists and experimentalists. On-going and planned experiments from HERMES, COMPASS and RHIC are mostly on the proton or the deuteron. Presented here is a planned measurement of the neutron transversity and single target spin asymmetries at Jefferson Lab in Hall A using a transversely polarized {sup 3}He target. Also presented are the results and plans of other neutron transverse spin experiments at Jefferson Lab. Finally, the factorization for semi-inclusive DIS studies at Jefferson Lab is discussed.

  14. Transverse Spin Diffusion

    NASA Astrophysics Data System (ADS)

    Mullin, William

    2014-05-01

    Transverse spin diffusion is a relatively new transport coefficient and a review of its history and physical basis will be presented. In NMR spin diffusion is often measured by spin echo techniques, which involve spin currents perpendicular to the direction of the magnetization, in contrast with the usual longitudinal case where the current is parallel to the magnetization. The first indication that this involved new physics was the Leggett-Rice effect (1970) in which spin waves, new spin-echo behavior, and an altered spin diffusion coefficient were predicted in liquid 3He. This effect gave the possibility of the first measurement of F1a, the parameter of the Landau Fermi-liquid theory mean-field responsible for the effect. In 1982 Lhuillier and Laloe found a transport equation very similar to the Leggett equation, but valid for highly-polarized dilute Boltzmann Bose and Fermi gases, and describing the ``identical spin rotation effect'' (ISRE), the analog of a Landau mean field. Coincidentally Bashkin and Meyerovich had also given equivalent descriptions of transport in polarized Boltzmann gases. That a mean-field effect could exists in dilute Boltzmann gases was theoretically surprising, but was confirmed experimentally. At low polarization the basic transverse diffusion constant D⊥ coincides with the longitudinal value D∥ however Meyerovich first pointed out that they could differ in highly polarized degenerate gases. Indeed detailed calculations (Jeon and Mullin) showed that, while D∥ is proportional to T-2, D⊥ approaches a constant (depending on polarization) at low T. Considerable controversy existed until experimental verification was achieved in 2004. The importance of ISRE again arose in 2008 as the basis of ``anomalous spin-state segregation'' in Duke and JILA experiments. More recently application of the ideas of transverse spin diffusion to strongly interacting Fermi gases has resulted in the observation of the diffusion constants at the quantum

  15. Entangled transverse optical vortex.

    PubMed

    Chui, S T; Lin, Zhifang

    2014-10-01

    We discuss a new kind of optical vortex with the angular momentum perpendicular to the flow direction and entangled in that it is a coherent combination of different orbital angular momentum states of the same sign. This entangled state exhibits many unexpected physical properties. The transverse optical vortex can be generated from the reflection of an electromagnetic wave off an array of ferrite rods. Its vorticity can be reversed by switching the direction of the magnetization of the rods, which usually takes only a nanosecond.

  16. [Transverse ectopic testis].

    PubMed

    Jouini, Riadh; Lefi, Mounir; Sami, Chelly; Manef, Gesmi; Mohsen, Belguith; Nouri, Abdellatif

    2002-09-01

    Transverse ectopic testis (TET) is a rare form of ectopic testis. The authors report the case of a 2-month-old infant presenting with right inguinoscrotal hernia and ectopic left testis with an impalpable testis. Opening of the hernia sac revealed two testes with two distally fused vasa deferentes. The contralateral testis was easily descended by translocation through the other inguinal canal. A favourable result was obtained with two testes situated in a normal position. In the light of this case, the authors emphasize the clinical and therapeutic features of this anomaly.

  17. Transverse field focused system

    DOEpatents

    Anderson, Oscar A.

    1986-01-01

    A transverse field focused (TFF) system for transport or acceleration of an intense sheet beam of negative ions in which a serial arrangement of a plurality of pairs of concentric cylindrical-arc electrodes is provided. Acceleration of the sheet beam can be achieved by progressively increasing the mean electrode voltage of successive electrode pairs. Because the beam is curved by the electrodes, the system can be designed to transport the beam through a maze passage which is baffled to prevent line of sight therethrough. Edge containment of the beam can be achieved by shaping the side edges of the electrodes to produce an electric force vector directed inwardly from the electrode edges.

  18. Transverse axis fluid turbine

    SciTech Connect

    Brenneman, B.

    1983-11-15

    A fluid turbine, the rotation axis of which is transverse to the direction of fluid flow, has at least two blade assemblies mounted for rotation about the rotation axis. Each blade assembly includes a streamlined elongated blade having a span parallel to the rotation axis. Each blade is pivotable about a pivot axis parallel to and spaced from the rotation axis. The pivot axis is located circumferentially ahead of the blade center of pressure with respect to the direction of turbine rotation. Each blade assembly is so constructed that its center of mass is located either at its pivot axis or circumferentially at its pivot axis and radially outboard of its pivot axis.

  19. TEACHING NEUROMUSCULAR RELAXATION.

    ERIC Educational Resources Information Center

    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…

  20. Relaxation of magnetotail plasmas

    NASA Technical Reports Server (NTRS)

    Bhattacharjee, A.

    1987-01-01

    A quasi-thermodynamic model is presented for the relaxation of magnetotail plasmas during substorms, followed by quiet times. It is proposed that the plasma relaxes to a state of low-potential energy subject to a small number of global constraints. The constraints are exactly preserved by all ideal motions and, approximately, by a wide class of motions of the plasma undergoing magnetic reconnection. A variational principle which minimizes the free energy predicts the relaxed state. Exact, two-dimensional solutions of the relaxed state are obtained. A universal feature of the exact solutions is a chain of magnetic islands along the tail axis. Sufficient conditions for the stability of relaxed states are obtained from the second variation of the free-energy functional.

  1. The influence of nanofiller alignment on transverse percolation and conductivity.

    PubMed

    Tallman, T N; Wang, K W

    2015-01-16

    Nanocomposites have unprecedented potential for conductivity-based damage identification when used as matrices in structural composites. Recent research has investigated nanofiller alignment in structural composites, but because damage identification often requires in-plane measurements, percolation and conductivity transverse to the alignment direction become crucial considerations. We herein contribute indispensable guidance to the development of nanocomposites with aligned nanofiller networks and insights into percolation trends transverse to the alignment direction by studying the influence of alignment on transverse critical volume fraction, conductivity, and rate of transition from non-percolating to percolating in three-dimensional carbon nanotube composite systems.

  2. Transverse Compression of Tendons.

    PubMed

    Salisbury, S T Samuel; Buckley, C Paul; Zavatsky, Amy B

    2016-04-01

    A study was made of the deformation of tendons when compressed transverse to the fiber-aligned axis. Bovine digital extensor tendons were compression tested between flat rigid plates. The methods included: in situ image-based measurement of tendon cross-sectional shapes, after preconditioning but immediately prior to testing; multiple constant-load creep/recovery tests applied to each tendon at increasing loads; and measurements of the resulting tendon displacements in both transverse directions. In these tests, friction resisted axial stretch of the tendon during compression, giving approximately plane-strain conditions. This, together with the assumption of a form of anisotropic hyperelastic constitutive model proposed previously for tendon, justified modeling the isochronal response of tendon as that of an isotropic, slightly compressible, neo-Hookean solid. Inverse analysis, using finite-element (FE) simulations of the experiments and 10 s isochronal creep displacement data, gave values for Young's modulus and Poisson's ratio of this solid of 0.31 MPa and 0.49, respectively, for an idealized tendon shape and averaged data for all the tendons and E = 0.14 and 0.10 MPa for two specific tendons using their actual measured geometry. The compression load versus displacement curves, as measured and as simulated, showed varying degrees of stiffening with increasing load. This can be attributed mostly to geometrical changes in tendon cross section under load, varying according to the initial 3D shape of the tendon.

  3. Nuclear relaxation in an electric field enables the determination of isotropic magnetic shielding

    NASA Astrophysics Data System (ADS)

    Garbacz, Piotr

    2016-08-01

    It is shown that in contrast to the case of nuclear relaxation in a magnetic field B, simultaneous application of the magnetic field B and an additional electric field E causes transverse relaxation of a spin-1/2 nucleus with the rate proportional to the square of the isotropic part of the magnetic shielding tensor. This effect can contribute noticeably to the transverse relaxation rate of heavy nuclei in molecules that possess permanent electric dipole moments. Relativistic quantum mechanical computations indicate that for 205Tl nucleus in a Pt-Tl bonded complex, Pt(CN)5Tl, the transverse relaxation rate induced by the electric field is of the order of 1 s-1 at E = 5 kV/mm and B = 10 T.

  4. High Transverse Energy Proton - Nuclear Interactions

    SciTech Connect

    Rice, James Allen

    1983-06-01

    A study of high transverse energy events resulting from 400 GeV protons scattering from targets of hydrogen, carbon, aluminum, copper, tin, and lead has been performed with the E609 apparatus at Fermilab. Wire chambers and a highly segmented calorimeter detect secondary particles. The use of efficient jet collecting triggers and of a beam jet calorimeter have been originally applied to nuclear target studies in this thesis. $A^{\\alpha}$ scaling with hydrogen deviations is observed for $E_T$ and planarity. The data provide evidence that $A^{\\alpha}$ scaling results from multiple scattering.Evidence for hadron jets is seen with a large solid angle calorimeter for all the targets when triggers requiring two high $E_T$ single particles are employed. Jet cross-sections for nuclei are approximately determined herein. Jet event angular distributions possibly indicate that low and high transverse energy particles in jets from nuclei may result, in part, from different types of interactions.

  5. Dynamic postures of the transverse metacarpal arch during typing.

    PubMed

    Baker, Nancy A; Xiu, Kaihua; Moehling, Krissy; Li, Zong-Ming

    2013-12-01

    The purpose of this paper is to describe the transverse metacarpal arch (TMA) during a dynamic typing task. Static/relaxed and dynamic typing TMA were collected from 36 right-handed females with musculoskeletal discomfort using a motion capture system. While the angle of right TMA static/relaxed posture (10.1° ± 5.5°) was significantly larger than the left (8.5° ± 5.6°) (P < .05), the right dynamic posture (10.6° ± 4.3°) was not significantly different from the left (10.3° ± 5.5°) (P = .66). Within both these mean scores, there was considerable individual variation, with some subjects demonstrating very flat TMA, and some very curved. The results indicate that TMA angular postures both for static/relaxed and dynamic typing are highly variable both between individuals and between individual hands.

  6. Rehabilitation in transverse myelitis.

    PubMed

    Sadowsky, Cristina L; Becker, Daniel; Bosques, Glendaliz; Dean, Janet M; McDonald, John W; Recio, Albert; Frohman, Elliot M

    2011-08-01

    The consequences of neurologic injuries related to transverse myelitis (TM) are long-lasting and require rehabilitative interventions in about two-thirds of cases. Because numerous neural repair mechanisms are dependent on maintenance of an optimal amount of activity both above and below the injury level, rehabilitation and exercise are useful not only for compensatory functional purposes but also as tools in neural system restoration. The application of established neurophysiologic principles to post-TM rehabilitation has substantial impact on optimizing residual functional capabilities while facilitating the processes of central plasticity and reorganization of sensory and motor programming. The process of neurorehabilitation thereby serves both to treat the patient with TM and to help physicians interrogate and dissect the mechanisms involved in spinal cord injury, neuroprotection, and, ultimately, recovery. Post-TM rehabilitation is lifelong and should be integrated into daily living in a home setting as part of the global management of paralysis, a chronic condition with significant comorbidities.

  7. Transverse Wobbling in 135Pr

    NASA Astrophysics Data System (ADS)

    Matta, J. T.; Garg, U.; Li, W.; Frauendorf, S.; Ayangeakaa, A. D.; Patel, D.; Schlax, K. W.; Palit, R.; Saha, S.; Sethi, J.; Trivedi, T.; Ghugre, S. S.; Raut, R.; Sinha, A. K.; Janssens, R. V. F.; Zhu, S.; Carpenter, M. P.; Lauritsen, T.; Seweryniak, D.; Chiara, C. J.; Kondev, F. G.; Hartley, D. J.; Petrache, C. M.; Mukhopadhyay, S.; Lakshmi, D. Vijaya; Raju, M. Kumar; Madhusudhana Rao, P. V.; Tandel, S. K.; Ray, S.; Dönau, F.

    2015-02-01

    A pair of transverse wobbling bands is observed in the nucleus 135Pr . The wobbling is characterized by Δ I =1 , E 2 transitions between the bands, and a decrease in the wobbling energy confirms its transverse nature. Additionally, a transition from transverse wobbling to a three-quasiparticle band comprised of strong magnetic dipole transitions is observed. These observations conform well to results from calculations with the tilted axis cranking model and the quasiparticle rotor model.

  8. Transverse Spin Effects at COMPASS

    SciTech Connect

    Wollny, H.

    2009-08-04

    The measurement of transverse spin effects in semi-inclusive deep-inelastic scattering (SIDIS) is an important part of the COMPASS physics program. In the years 2002-2004 data was taken by scattering a 160 GeV/c muon beam off a transversely polarized deuteron target. In 2007, additional data was collected on a transversely polarized proton target. New preliminary results for the Collins and Sivers asymmetries from the analysis of the proton data are presented.

  9. Relaxation Techniques for Health

    MedlinePlus

    ... for posttraumatic stress disorder have had inconsistent results. Rheumatoid Arthritis There’s limited evidence that biofeedback or other relaxation ... might be valuable additions to treatment programs for rheumatoid arthritis. Ringing in the Ears (Tinnitus) Only a few ...

  10. Relaxation techniques for stress

    MedlinePlus

    ... problems such as high blood pressure, stomachaches, headaches, anxiety, and depression. Using relaxation techniques can help you feel calm. These exercises can also help you manage stress and ease ...

  11. Paramagnetic nanoparticles as potential MRI contrast agents: characterization, NMR relaxation, simulations and theory.

    PubMed

    Vuong, Quoc Lam; Van Doorslaer, Sabine; Bridot, Jean-Luc; Argante, Corradina; Alejandro, Gabriela; Hermann, Raphaël; Disch, Sabrina; Mattea, Carlos; Stapf, Siegfried; Gossuin, Yves

    2012-12-01

    Paramagnetic nanoparticles, mainly rare earth oxides and hydroxides, have been produced these last few years for use as MRI contrast agents. They could become an interesting alternative to iron oxide particles. However, their relaxation properties are not well understood. Magnetometry, (1)H and (2)H NMR relaxation results at different magnetic fields and electron paramagnetic resonance are used to investigate the relaxation induced by paramagnetic particles. When combined with computer simulations of transverse relaxation, they allow an accurate description of the relaxation induced by paramagnetic particles. For gadolinium hydroxide particles, both T(1) and T(2) relaxation are due to a chemical exchange of protons between the particle surface and bulk water, called inner sphere relaxation. The inner sphere is also responsible for T(1) relaxation of dysprosium, holmium, terbium and erbium containing particles. However, for these latter compounds, T(2) relaxation is caused by water diffusion in the field inhomogeneities created by the magnetic particle, the outer-sphere relaxation mechanism. The different relaxation behaviors are caused by different electron relaxation times (estimated by electron paramagnetic resonance). These findings may allow tailoring paramagnetic particles: ultrasmall gadolinium oxide and hydroxide particles for T(1) contrast agents, with shapes ensuring the highest surface-to-volume ratio. All the other compounds present interesting T(2) relaxation performance at high fields. These results are in agreement with computer simulations and theoretical predictions of the outer-sphere and static dephasing regime theories. The T(2) efficiency would be optimum for spherical particles of 40-50 nm radius.

  12. Panic attacks during relaxation and relaxation-induced anxiety: a hyperventilation interpretation.

    PubMed

    Ley, R

    1988-12-01

    This paper explains how a hyperventilation theory of panic disorder accounts for panic attacks during relaxation and relaxation-induced anxiety. The explanation is based on the observation that chronic hyperventilators maintain a steady state of low pCO2 (arterial carbon dioxide tension) and are, therefore, sensitive to relatively small increases in ventilation when metabolism is low and to relatively sudden reductions in metabolism when ventilation is relatively constant. Thus, if minute volume of air breathed remains constant while the metabolic production of CO2 decreases, as in the case of one who sits down or lies down to relax, respiratory hypocapnea may increase in intensity until it produces the familiar sensations which mark the panic attack. Data from relevant studies of panic attacks during relaxation support the hyperventilation interpretation.

  13. General formulation of transverse hydrodynamics

    SciTech Connect

    Ryblewski, Radoslaw; Florkowski, Wojciech

    2008-06-15

    General formulation of hydrodynamics describing transversally thermalized matter created at the early stages of ultrarelativistic heavy-ion collisions is presented. Similarities and differences with the standard three-dimensionally thermalized relativistic hydrodynamics are discussed. The role of the conservation laws as well as the thermodynamic consistency of two-dimensional thermodynamic variables characterizing transversally thermalized matter is emphasized.

  14. Molecular determinants for drug-receptor interactions. 8. Anisotropic and internal motions in morphine, nalorphine, oxymorphone, naloxone and naltrexone in aqueous solution by carbon-13 NMR spin-lattice relaxation times

    NASA Astrophysics Data System (ADS)

    Grassi, Antonio; Perly, Bruno; Pappalardo, Giuseppe C.

    1989-02-01

    Carbon-13 NMR spin-lattice relaxation times ( T1) were measured for morphine, oxymorphone, nalorphine, naloxone and naltrexone as hydrochloride salts in 2H 2O solution. The data refer to the molecules in the N-equatorial configuration. The experimental T1 values were interpreted using a model of anisotropic reorientation of a rigid body with superimposed internal motions of the flexible N-methyl, N-methyl-allyl and N-methyl-cyclopropyl fragments. The calculated internal motional rates were found to markedly decrease on passing from agonists to mixed (nalorphine) and pure (naloxone, naltrexone) antagonists. For these latter the observed trend of the internal flexibility about NC and CC bonds of the N-substituents is discussed in terms of a correlation with their relative antagonistic potencies. In fact, such an evidence of decreasing internal conformational dynamics in the order nalorphine, naloxone, naltrexone, appeared interestingly in line with the "two-state" model of opiate receptor operation mode proposed by Snyder.

  15. Classical Weyl transverse gravity

    NASA Astrophysics Data System (ADS)

    Oda, Ichiro

    2017-05-01

    We study various classical aspects of the Weyl transverse (WTDiff) gravity in a general space-time dimension. First of all, we clarify a classical equivalence among three kinds of gravitational theories, those are, the conformally invariant scalar tensor gravity, Einstein's general relativity and the WTDiff gravity via the gauge-fixing procedure. Secondly, we show that in the WTDiff gravity the cosmological constant is a mere integration constant as in unimodular gravity, but it does not receive any radiative corrections unlike the unimodular gravity. A key point in this proof is to construct a covariantly conserved energy-momentum tensor, which is achieved on the basis of this equivalence relation. Thirdly, we demonstrate that the Noether current for the Weyl transformation is identically vanishing, thereby implying that the Weyl symmetry existing in both the conformally invariant scalar tensor gravity and the WTDiff gravity is a "fake" symmetry. We find it possible to extend this proof to all matter fields, i.e. the Weyl-invariant scalar, vector and spinor fields. Fourthly, it is explicitly shown that in the WTDiff gravity the Schwarzschild black hole metric and a charged black hole one are classical solutions to the equations of motion only when they are expressed in the Cartesian coordinate system. Finally, we consider the Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmology and provide some exact solutions.

  16. Transverse electron resonance accelerator

    SciTech Connect

    Csonka, P.L.

    1985-01-01

    Transverse (to the velocity, v, of the particles to be accelerated) electron oscillations are generated in high (e.g. solid) density plasmas by either an electromagnetic wave or by the field of charged particles traveling parallel to v. The generating field oscillates with frequency ..omega.. = ..omega../sub p/, where ..omega../sub p/ is the plasma frequency. The plasma is confined to a sequence of microstructures with typical dimensions of d approx. = 2..pi..c/..omega../sub p/, allowing the generating fields to penetrate. Since ..omega../sub p/ is now high, the time scales, T, are correspondingly reduced. The microstructures are allowed to explode after t = T, until then they are confined by ion inertia. As a result of resonance, the electric field, E, inside the microstructures can exceed the generating field E/sub L/. The generating force is proportional to E/sub L/ (as opposed to E/sub L//sup 2/). Phase matching of particles is possible by appropriate spacing of the microstructures or by a gas medium. The generating beam travels outside the plasma, filamentation is not a problem. The mechanism is relatively insensitive to the exact shape and position of the microstructures. This device contains features of various earlier proposed acceleration mechanisms and may be considered as the limiting case of several of those for small d, T and high E.

  17. Johari-Goldstein secondary relaxation in methylated alkanes

    NASA Astrophysics Data System (ADS)

    Ngai, K. L.

    2005-06-01

    Dielectric relaxation measurements of the methylated alkanes, 3-methylpentane, 3-methylheptane, 4-methylheptane, 2,3-dimethylpentane, and 2,4,6-trimethylheptane by S. Shahriari, A. Mandanici, L-M Wang, and R. Richert [J. Chem. Phys. 121, 8960 (2004)] have found a primary α relaxation of these glass-forming liquids and a slow secondary β relaxation that are in close proximity to each other on the frequency scale. These glass formers have one or more methyl groups individually attached to various carbons on the alkane chain. They cannot contribute to such a slow secondary relaxation. Hence the observed secondary relaxations is not intramolecular in origin and, similar to secondary relaxations found in rigid molecules by Johari and Goldstein, they are potentially important in the consideration of a mechanism for the glass transition. These secondary relaxations in the methylated alkanes are special and belong to the class of Johari-Goldstein in a generalized sense. The coupling model has predicted that its primitive relaxation time should be approximately the same as the relaxation time of the secondary relaxation if the latter is of the Johari-Goldstein kind. This prediction has been shown to hold in many other glass formers. The published data of the methylated alkanes provide an opportunity to test this prediction once more. The results of this work confirm the prediction.

  18. Kinesthetic Transverse Wave Demonstration

    NASA Astrophysics Data System (ADS)

    Pantidos, Panagiotis; Patapis, Stamatis

    2005-09-01

    This is a variation on the String and Sticky Tape demonstration "The Wave Game," suggested by Ron Edge. A group of students stand side by side, each one holding a card chest high with both hands. The teacher cues the first student to begin raising and lowering his card. When he starts lowering his card, the next student begins to raise his. As succeeding students move their cards up and down, a wave such as that shown in the figure is produced. To facilitate the process, students' motions were synchronized with the ticks of a metronome (without such synchronization it was nearly impossible to generate a satisfactory wave). Our waves typically had a frequency of about 1 Hz and a wavelength of around 3 m. We videotaped the activity so that the students could analyze the motions. The (17-year-old) students had not received any prior instruction regarding wave motion and did not know beforehand the nature of the exercise they were about to carry out. During the activity they were asked what a transverse wave is. Most of them quickly realized, without teacher input, that while the wave propagated horizontally, the only motion of the transmitting medium (them) was vertical. They located the equilibrium points of the oscillations, the crests and troughs of the waves, and identified the wavelength. The teacher defined for them the period of the oscillations of the motion of a card to be the total time for one cycle. The students measured this time and then several asserted that it was the same as the wave period. Knowing the length of the waves and the number of waves per second, the next step can easily be to find the wave speed.

  19. NMR relaxation rate studies of molecular motions in NaSn, the Laves-phase metal hydride C15-ZrCr(2)H(x) and carbon/epoxy composite materials

    NASA Astrophysics Data System (ADS)

    Stoddard, Ronald Dean

    Here I present studies of molecular motions in three very different systems: NaSn, which exhibits motion characteristic of both a superionic conductor and a rotor crystal; C15-ZrCrsb2Hsbx (x < 0.5), a metal hydride which exhibits unusual characteristics in its hydrogen motion; and, finally a study of the relationship between Tsb2 and the degree of cure of carbon/epoxy materials. NaSn is characterized by Nasp+ ions and stable (Snsb4)sp{4-} tetrahedra. At high temperatures NaSn displays a disordered solid phase (alpha-NaSn). The presence of Nasp+ ions suggests that alpha-NaSn may be a superionic conductor (translationally disordered) and the presence of stable Snsb4 tetrahedra suggests it may be a rotor crystal (organizationally disordered). The purpose of this study is to gain better understanding of the motions in alpha-NaSn by monitoring Na and Sn motion using sp{23}Na and sp{119}Sn NMR, respectively. C15-ZrCrsb2Hsbx (x < 0.5) is a Laves phase metal hydride which displays extremely rapid hydrogen motion and a Tsb1 peak which cannot be explained by a model employing a single correlation time for the motion. A model employing a Gaussian distribution of correlation times has been used to successfully fit Tsb1, but the origin of this distribution in a crystalline solid solution is not known. The purpose of this study is to better understand the low temperature hydrogen motions occurring in C15-ZrCrsb2Hsbx by extending the previous NMR measurements using Tsb1p and Tsb1D, experiments which effectively push the relaxation peak to lower temperatures. New techniques for manufacturing carbon/epoxy components are under development which require partial curing of the material. At present, no method for monitoring partial curing exists. Tsb2 is a promising monitor of degree of cure because of its sensitivity to changes rates of molecular motions. The purpose of this study is to demonstrate the sensitivity of Tsb2 to changes in molecular motion due to curing, and to find a

  20. Transversity and SIDIS at CLAS

    SciTech Connect

    Avagyan, Harutyun; Rossi, Patrizia

    2009-01-01

    The single-spin asymmetries (SSA) in semi-inclusive DIS have emerged as a powerful tool to access transverse momentum distributions of partons and to give access to the spin-orbit correlations. SSA enable measurements of some essentially unexplored physical observables, including transversity, {\\it time-reversal odd} distribution and fragmentation functions. In this talk we present an overview of the latest studies of transverse spin effects and discuss newly released results, ongoing activities, as well as planned near term and future measurements of spin-orbit correlations at CLAS.

  1. Design of self-refocused pulses under short relaxation times.

    PubMed

    Issa, Bashar

    2009-06-01

    The effect of using self-refocused RF pulses of comparable duration to relaxation times is studied in detail using numerical simulation. Transverse magnetization decay caused by short T2 and longitudinal component distortion due to short T1 are consistent with other studies. In order to design new pulses to combat short T1 and T2 the relaxation terms are directly inserted into the Bloch equations. These equations are inverted by searching the RF solution space using simulated annealing global optimization technique. A new T2-decay efficient excitation pulse is created (SDETR: single delayed excursion T2 resistive) which is also energy efficient. Inversion pulses which improve the inverted magnetization profile and achieve better suppression of the remaining transverse magnetization are also created even when both T1 and T2 are short. This is achieved, however, on the expense of a more complex B1 shape of larger energy content.

  2. The origin of biexponential T2 relaxation in muscle water

    NASA Technical Reports Server (NTRS)

    Cole, W. C.; LeBlanc, A. D.; Jhingran, S. G.

    1993-01-01

    Two theories have been proposed to explain the multiexponential transverse relaxation of muscle water protons: "anatomical" and "chemical" compartmentation. In an attempt to obtain evidence to support one or the other of these two theories, interstitial and intracellular macromolecular preparations were studied and compared with rat muscle tissue by proton NMR transverse relaxation (T2) measurements. All macromolecule preparations displayed monoexponential T2 decay. Membrane alteration with DMSO/glycerin did not eliminate the biexponential T2 decay of muscle tissue. Maceration converted biexponential T2 decay of muscle tissue to single exponential decay. It is concluded that the observed two component exponential T2 decay of muscle represents anatomical compartmentation of tissue water, probably intracellular versus extracellular.

  3. The origin of biexponential T2 relaxation in muscle water

    NASA Technical Reports Server (NTRS)

    Cole, W. C.; LeBlanc, A. D.; Jhingran, S. G.

    1993-01-01

    Two theories have been proposed to explain the multiexponential transverse relaxation of muscle water protons: "anatomical" and "chemical" compartmentation. In an attempt to obtain evidence to support one or the other of these two theories, interstitial and intracellular macromolecular preparations were studied and compared with rat muscle tissue by proton NMR transverse relaxation (T2) measurements. All macromolecule preparations displayed monoexponential T2 decay. Membrane alteration with DMSO/glycerin did not eliminate the biexponential T2 decay of muscle tissue. Maceration converted biexponential T2 decay of muscle tissue to single exponential decay. It is concluded that the observed two component exponential T2 decay of muscle represents anatomical compartmentation of tissue water, probably intracellular versus extracellular.

  4. Transverse correlations in multiphoton entanglement

    NASA Astrophysics Data System (ADS)

    Wen, Jianming; Rubin, Morton H.; Shih, Yanhua

    2007-10-01

    We have analyzed the transverse correlation in multiphoton entanglement. The generalization of quantum ghost imaging is extended to the N -photon state. The Klyshko’s two-photon advanced-wave picture is generalized to the N -photon case.

  5. Transverse correlations in multiphoton entanglement

    SciTech Connect

    Wen Jianming; Rubin, Morton H.; Shih Yanhua

    2007-10-15

    We have analyzed the transverse correlation in multiphoton entanglement. The generalization of quantum ghost imaging is extended to the N-photon state. The Klyshko's two-photon advanced-wave picture is generalized to the N-photon case.

  6. [Transverse myelitis in immunocompetent children].

    PubMed

    Oñate Vergara, E; Sota Busselo, I; García-Santiago, J; Gaztañaga Expósito, R; Nogués Pérez, A; Ruiz Benito, M A

    2004-08-01

    Acute transverse myelitis is an acute inflammatory medullar disease characterized by acute or subacute motor, sensory and autonomic dysfunction. The incidence is low and is estimated at 1-4 cases/10(6) inhabitants per year. In Spain, the disorder is exceptional and most reported cases have occurred in immunodepressed patients. We describe two new cases of transverse myelitis in immunocompetent children and review the etiopathogenesis, diagnosis and outcome of this disorder.

  7. Nuclear Spin Relaxation and Water Self-diffusion in Hardening Magnesium Oxychloride Cement

    NASA Astrophysics Data System (ADS)

    Nestle, Nikolaus; Galvosas, Petrik; Zimmermann, Christian; Dakkouri, Marwan; Kärger, Jörg

    2001-08-01

    In this contribution, we report the results of NMR studies of the behaviour of water in a hydrating Sorel cement paste with a composition close to the stoichiometric optimum. Both the transverse spin-relaxation behaviour and water self-diffusion were studied in two separate experiments performed on samples on the basis of the same formulation. While there is a very strong initial decrease in the transverse relaxation time of the water in the paste, the diffusion coefficient is found to decrease mainly at later times of the hydration process where the decrease of the transverse relaxation time has already strongly slowed down. After about 6 h of the hardening process, the signal intensity available for a pulsed gradient diffusometry experiment is not sufficient any more for reliable measurements of the diffusion coefficients

  8. Transverse Mode Dynamics and Ultrafast Modulation of Vertical-Cavity Surface-Emitting Lasers

    NASA Technical Reports Server (NTRS)

    Ning, Cun-Zheng; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    We show that multiple transverse mode dynamics of VCSELs (Vertical-Cavity Surface-Emitting Lasers) can be utilized to generate ultrafast intensity modulation at a frequency over 100 GHz, much higher than the relaxation oscillation frequency. Such multimode beating can be greatly enhanced by taking laser output from part of the output facet.

  9. Magnetic field dependence of the longitudinal and transverse spin correlation in the Blume-Hubbard theory

    NASA Technical Reports Server (NTRS)

    Sung, C. C.

    1973-01-01

    The longitudinal and transverse spin-correlation functions of local paramagnetic impurities are solved in the long-time limit on the basis of the Blume-Hubbard theory. The magnetic field dependence of the nuclear spin-lattice relaxation via paramagnetic centers is in good agreement with the experimental data by McHenry et al.

  10. Combined Diffusion Tensor Imaging and Transverse Relaxometry in Early-Onset Bipolar Disorder

    ERIC Educational Resources Information Center

    Gonenc, Atilla; Frazier, Jean A.; Crowley, David J.; Moore, Constance M.

    2010-01-01

    Objective: Transverse relaxation time (T2) imaging provides the opportunity to examine membrane fluidity, which can affect a number of cellular functions. The objective of the present work was to examine T2 abnormalities in children with unmodified DSM-IV-TR bipolar disorder (BD) in bilateral cingulate-paracingulate (CPC) white matter. Method: A…

  11. Combined Diffusion Tensor Imaging and Transverse Relaxometry in Early-Onset Bipolar Disorder

    ERIC Educational Resources Information Center

    Gonenc, Atilla; Frazier, Jean A.; Crowley, David J.; Moore, Constance M.

    2010-01-01

    Objective: Transverse relaxation time (T2) imaging provides the opportunity to examine membrane fluidity, which can affect a number of cellular functions. The objective of the present work was to examine T2 abnormalities in children with unmodified DSM-IV-TR bipolar disorder (BD) in bilateral cingulate-paracingulate (CPC) white matter. Method: A…

  12. TRANSVERSE OSCILLATIONS IN CHROMOSPHERIC MOTTLES

    SciTech Connect

    Kuridze, D.; Mathioudakis, M.; Jess, D. B.; Keenan, F. P.; Morton, R. J.; Erdelyi, R.; Dorrian, G. D.

    2012-05-01

    A number of recent investigations have revealed that transverse waves are ubiquitous in the solar chromosphere. The vast majority of these have been reported in limb spicules and active region fibrils. We investigate long-lived, quiet-Sun, on-disk features such as chromospheric mottles (jet-like features located at the boundaries of supergranular cells) and their transverse motions. The observations were obtained with the Rapid Oscillations in the Solar Atmosphere instrument at the Dunn Solar Telescope. The data set is comprised of simultaneous imaging in the H{alpha} core, Ca II K, and G band of an on-disk quiet-Sun region. Time-distance techniques are used to study the characteristics of the transverse oscillations. We detect over 40 transverse oscillations in both bright and dark mottles, with periods ranging from 70 to 280 s, with the most frequent occurrence at {approx}165 s. The velocity amplitudes and transverse displacements exhibit characteristics similar to limb spicules. Neighboring mottles oscillating in-phase are also observed. The transverse oscillations of individual mottles are interpreted in terms of magnetohydrodynamic kink waves. Their estimated periods and damping times are consistent with phase mixing and resonant mode conversion.

  13. Spin-orbit coupling and spin relaxation in phosphorene: Intrinsic versus extrinsic effects

    NASA Astrophysics Data System (ADS)

    Kurpas, Marcin; Gmitra, Martin; Fabian, Jaroslav

    2016-10-01

    First-principles calculations of the essential spin-orbit and spin relaxation properties of phosphorene are performed. Intrinsic spin-orbit coupling induces spin mixing with the probability of b2≈10-4 , exhibiting a large anisotropy, following the anisotropic crystalline structure of phosphorene. For realistic values of the momentum relaxation times, the intrinsic (Elliott-Yafet) spin relaxation times are hundreds of picoseconds to nanoseconds. Applying a transverse electric field (simulating gating and substrates) generates extrinsic C2 v symmetric spin-orbit fields in phosphorene, which activate the D'yakonov-Perel' mechanism for spin relaxation. It is shown that this extrinsic spin relaxation also has a strong anisotropy and can dominate over the Elliott-Yafet one for strong enough electric fields. Phosphorene on substrates can thus exhibit an interesting interplay of both spin-relaxation mechanisms, whose individual roles could be deciphered using our results.

  14. T2 relaxation time abnormalities in bipolar disorder and schizophrenia.

    PubMed

    Ongür, Dost; Prescot, Andrew P; Jensen, J Eric; Rouse, Elizabeth D; Cohen, Bruce M; Renshaw, Perry F; Olson, David P

    2010-01-01

    There are substantial abnormalities in the number, density, and size of cortical neurons and glial cells in bipolar disorder and schizophrenia. Because molecule-microenvironment interactions modulate metabolite signals characteristics, these cellular abnormalities may impact transverse (T2) relaxation times. We measured T2 relaxation times for three intracellular metabolites (N-acetylaspartate+N-acetylaspartylglutamate, creatine+phosphocreatine, and choline-containing compounds) in the anterior cingulate cortex and parieto-occipital cortex from 20 healthy subjects, 15 patients with bipolar disorder, and 15 patients with schizophrenia at 4 T. Spectra used in T2 quantification were collected from 8-cc voxels with varying echo times (30 to 500 ms, in 10-ms steps). Both bipolar disorder and schizophrenia groups had numerically shorter T2 relaxation times than the healthy subjects group in both regions; these differences reached statistical significance for creatine+phosphocreatine and choline-containing compounds in bipolar disorder and for choline-containing compounds in schizophrenia. Metabolite T2 relaxation time shortening is consistent with reduced cell volumes and altered macromolecule structures, and with prolonged water T2 relaxation times reported in bipolar disorder and schizophrenia. These findings suggest that metabolite concentrations reported in magnetic resonance spectroscopy studies of psychiatric conditions may be confounded by T2 relaxation and highlight the importance of measuring and correcting for this variable.

  15. Studies on Enhancing Transverse Thermal Conductivity Carbon/Carbon Composites

    DTIC Science & Technology

    2007-07-06

    control of matrix microstructure and to study influence of nanocarbon reinforcement addition to the carbonaceous precursors on the microstructure of the...of nanocarbon reinforcement addition to the carbonaceous precursors on the microstructure of the matrix as well as on the thermal properties of the

  16. Comment on ``Field dependence of the transverse spin freezing transition''

    NASA Astrophysics Data System (ADS)

    Kaptás, D.; Kiss, L. F.; Balogh, J.; Vincze, I.

    2002-05-01

    Transverse spin freezing temperature of amorphous Fe100-xZrx (x=7,8,9) is determined by 57Fe Mössbauer spectroscopy as a function of the applied magnetic field, and the results are compared to those obtained by longitudinal field muon spin relaxation [D.H. Ryan et al., Phys. Rev. B 63, 140405 (2001)] (LF-μSR) for amorphous Fe92Zr8. The Mössbauer results are at variance with the LF-μSR results for x=8 and do not support the proposed inverse field dependence.

  17. Effect of Mesoporous Nano Water Reservoir on MR Relaxivity.

    PubMed

    Sharmiladevi, Palani; Haribabu, Viswanathan; Girigoswami, Koyeli; Sulaiman Farook, Abubacker; Girigoswami, Agnishwar

    2017-09-11

    In the present work, an attempt was made to engineer a mesoporous silica coated magnetic nanoparticles (MNF@mSiO2) for twin mode contrast in magnetic resonance imaging (MRI) with reduced toxicity. Superparamagnetic manganese ferrite nanoparticles were synthesized with variable mesoporous silica shell thickness to control the water molecules interacting with metal oxide core. 178 nm was the optimum hydrodynamic diameter of mesoporous ferrite core-shell nanoparticles that showed maximum longitudinal relaxation time (T1) and transverse relaxation time (T2) in MRI due to the storage of water molecules in mesoporous silica coating. Besides the major role of mesoporous silica in controlling relaxivity, mesoporous silica shell also reduces the toxicity and enhances the bioavailability of superparamagnetic manganese ferrite nanoparticles. The in vitro toxicity assessment using HepG2 liver carcinoma cells shows that the mesoporous silica coating over ferrite nanoparticles could exert less toxicity compared to the uncoated particle.

  18. Evaluation of sandstone surface relaxivity using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Washburn, Kathryn E.; Sandor, Magdalena; Cheng, Yuesheng

    2017-02-01

    Nuclear magnetic resonance (NMR) relaxometry is a common technique used to assess the pore size of fluid-filled porous materials in a wide variety of fields. However, the NMR signal itself only provides a relative distribution of pore size. To calculate an absolute pore size distribution from the NMR data, the material's surface relaxivity needs to be known. Here, a method is presented using laser-induced breakdown spectroscopy (LIBS) to evaluate surface relaxivity in sandstones. NMR transverse and longitudinal relaxation was measured on a set of sandstone samples and the surface relaxivity was calculated from the pore size distribution determined with MICP measurements. Using multivariate analysis, it was determined that the LIBS data can predict with good accuracy the longitudinal (R2 ∼ 0.84) and transverse (R2 ∼ 0.79) surface relaxivity. Analysis of the regression coefficients shows significant influence from several elements. Some of these are elements previously established to have an effect on surface relaxivity, such as iron and manganese, while others are not commonly associated with surface relaxivity, such as cobalt and titanium. Furthermore, LIBS provides advantages compared to current methods to calibrate surface relaxivity in terms of speed, portability, and sample size requirements. While this paper focuses on geological samples, the method could potentially be expanded to other types of porous materials.

  19. Evaluation of sandstone surface relaxivity using laser-induced breakdown spectroscopy.

    PubMed

    Washburn, Kathryn E; Sandor, Magdalena; Cheng, Yuesheng

    2017-02-01

    Nuclear magnetic resonance (NMR) relaxometry is a common technique used to assess the pore size of fluid-filled porous materials in a wide variety of fields. However, the NMR signal itself only provides a relative distribution of pore size. To calculate an absolute pore size distribution from the NMR data, the material's surface relaxivity needs to be known. Here, a method is presented using laser-induced breakdown spectroscopy (LIBS) to evaluate surface relaxivity in sandstones. NMR transverse and longitudinal relaxation was measured on a set of sandstone samples and the surface relaxivity was calculated from the pore size distribution determined with MICP measurements. Using multivariate analysis, it was determined that the LIBS data can predict with good accuracy the longitudinal (R(2)∼0.84) and transverse (R(2)∼0.79) surface relaxivity. Analysis of the regression coefficients shows significant influence from several elements. Some of these are elements previously established to have an effect on surface relaxivity, such as iron and manganese, while others are not commonly associated with surface relaxivity, such as cobalt and titanium. Furthermore, LIBS provides advantages compared to current methods to calibrate surface relaxivity in terms of speed, portability, and sample size requirements. While this paper focuses on geological samples, the method could potentially be expanded to other types of porous materials.

  20. Structural and Dielectric Relaxations in Vitreous and Liquid State of Monohydroxy Alcohol at High Pressure.

    PubMed

    Danilov, I V; Pronin, A A; Gromnitskaya, E L; Kondrin, M V; Lyapin, A G; Brazhkin, V V

    2017-08-31

    2-Ethyl-1-hexanol monoalcohol is a well-known molecular glassformer, which for a long time attracts attention of researchers. As in all other monohydroxy alcohols, its dielectric relaxation reveals two distinct relaxation processes attributed to the structural relaxation and another more intense process, which gives rise to a low-frequency Debye-like relaxation. In this monoalcohol, the frequency separation between these two processes reaches an extremely high value of 3 orders of magnitude, which makes this substance a rather convenient object for studies of mechanisms (supposedly common to all monoalcohols) leading to vitrification of this type of liquids. In this work, we apply two experimental techniques, dielectric spectroscopy and ultrasonic measurements (in both longitudinal and transverse polarizations) at high pressure, to study interference between different relaxation mechanisms occurring in this liquid, which could shed light on both structural and dielectric relaxation processes observed in a supercooled liquid and a glass state. Application of high pressure in this case leads to the simplification of the frequency spectrum of dielectric relaxation, where only one asymmetric feature is observed. Nonetheless, the maximum attenuation of the longitudinal wave in ultrasonic experiments at high pressure is observed at temperatures ≈50 K above the corresponding temperature for the transverse wave. This might indicate different mechanisms of structural relaxation in shear and bulk elasticities in this liquid.

  1. Determining the relaxivity values of protein cage-templated nanoparticles using magnetic resonance imaging.

    PubMed

    Sana, Barindra; Lim, Sierin

    2015-01-01

    The application of magnetic resonance imaging (MRI) is often limited by low magnetic relaxivity of currently used contrast agents. This problem can be addressed by developing more sensitive contrast agents by synthesizing new types of metal complex or metallic nanoparticles. Protein cage has been used as a template in biological synthesis of magnetic nanoparticles. The magnetic nanoparticle-protein cage composites have been reported to have high magnetic relaxivity, which implies their potential application as an MRI contrast agent. The magnetic relaxivity is determined by measuring longitudinal and transverse magnetic relaxivities of the potential agent. The commonly performed techniques are field-cycling NMR relaxometry (also known as variable field relaxometry or nuclear magnetic relaxation dispersion (NMRD) profiling) and in vitro or in vivo MRI relaxometry. Here, we describe techniques for the synthesis of nanoparticle-protein cage composite and determination of their magnetic relaxivities by in vitro MR image acquisition and data processing. In this method, longitudinal and transverse relaxivities are calculated by measuring relaxation rates of water hydrogen nuclei at different nanoparticle-protein cage composite concentrations.

  2. Interatomic relaxation effects in double core ionization of chain molecules

    NASA Astrophysics Data System (ADS)

    Kryzhevoi, Nikolai V.; Tashiro, Motomichi; Ehara, Masahiro; Cederbaum, Lorenz S.

    2012-10-01

    Core vacancies created on opposite sides of a molecule operate against each other in polarizing the environment between them. Consequently, the relaxation energy associated with the simultaneous creation of these two core holes turns out to be smaller than the sum of the relaxation energies associated with each individual single core vacancy created independently. The corresponding residual, termed interatomic relaxation energy, is sensitive to the environment. In the present paper we explore how the interatomic relaxation energy depends on the length and type of carbon chains bridging two core ionized nitrile groups (-C≡N). We have uncovered several trends and discuss them with the help of simple electrostatic and quantum mechanical models. Namely, the absolute value of the interatomic relaxation energy depends strongly on the orbital hybridization in carbons being noticeably larger in conjugated chains (sp and sp2 hybridizations) possessing highly mobile electrons in delocalized π-type orbitals than in saturated chains (sp3 hybridization) where only σ bonds are available. The interatomic relaxation energy decreases monotonically with increasing chain length. The corresponding descent is determined by the energetics of the molecular bridge, in particular, by the HOMO-LUMO gap. The smallest HOMO-LUMO gap is found in molecules with the sp2-hybridized backbone. Here, the interatomic relaxation energy decreases slowest with the chain length.

  3. Transverse deformations of extreme horizons

    NASA Astrophysics Data System (ADS)

    Li, Carmen; Lucietti, James

    2016-04-01

    We consider the inverse problem of determining all extreme black hole solutions to the Einstein equations with a prescribed near-horizon geometry. We investigate this problem by considering infinitesimal deformations of the near-horizon geometry along transverse null geodesics. We show that, up to a gauge transformation, the linearised Einstein equations reduce to an elliptic PDE for the extrinsic curvature of a cross-section of the horizon. We deduce that for a given near-horizon geometry there exists a finite dimensional moduli space of infinitesimal transverse deformations. We then establish a uniqueness theorem for transverse deformations of the extreme Kerr horizon. In particular, we prove that the only smooth axisymmetric transverse deformation of the near-horizon geometry of extreme Kerr, such that cross-sections of the horizon are marginally trapped surfaces, corresponds to that of the extreme Kerr black hole. Furthermore, we determine all smooth and biaxisymmetric transverse deformations of the near-horizon geometry of the five-dimensional extreme Myers-Perry black hole with equal angular momenta. We find a three parameter family of solutions such that cross-sections of the horizon are marginally trapped, which is more general than the known black hole solutions. We discuss the possibility that they correspond to new five-dimensional vacuum black holes.

  4. Relaxation in Physical Education Curricula.

    ERIC Educational Resources Information Center

    Coville, Claudia A.

    1979-01-01

    A theoretical framework for incorporating relaxation instruction in the physical education curriculum is presented based on the assumption that relaxation is a muscular-skeletal skill benefitting general motor skill acquisition. Theoretical principles, a definition of relaxation, and an analysis of stages of skill development are also used in the…

  5. A Comparison of Relaxation Strategies.

    ERIC Educational Resources Information Center

    Matthews, Doris B.

    Some researchers argue that all relaxation techniques produce a single relaxation response while others support a specific-effects hypothesis which suggests that progressive relaxation affects the musculoskeletal system and that guided imagery affects cognitive changes. Autogenics is considered a technique which is both somatic and cognitive. This…

  6. Relaxation from particle production

    NASA Astrophysics Data System (ADS)

    Hook, Anson; Marques-Tavares, Gustavo

    2016-12-01

    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.

  7. Relaxation from particle production

    SciTech Connect

    Hook, Anson; Marques-Tavares, Gustavo

    2016-12-20

    Here, 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.

  8. Transverse discrete breathers in unstrained graphene

    NASA Astrophysics Data System (ADS)

    Barani, Elham; Lobzenko, Ivan P.; Korznikova, Elena A.; Soboleva, Elvira G.; Dmitriev, Sergey V.; Zhou, Kun; Marjaneh, Aliakbar Moradi

    2017-02-01

    Discrete breathers (DB) are spatially localized vibrational modes of large amplitude in defect-free nonlinear lattices. The search for DBs in graphene is of high importance, taking into account that this one atom thick layer of carbon is promising for a number of applications. There exist several reports on successful excitation of DBs in graphene, based on molecular dynamics and ab initio simulations. In a recent work by Hizhnyakov with co-authors the possibility to excite a DB with atoms oscillating normal to the graphene sheet has been reported. In the present study we use a systematic approach for finding initial conditions to excite transverse DBs in graphene. The approach is based on the analysis of the frequency-amplitude dependence for a delocalized, short-wavelength vibrational mode. This mode is a symmetry-dictated exact solution to the dynamic equations of the atomic motion, regardless the mode amplitude and regardless the type of interatomic potentials used in the simulations. It is demonstrated that if the AIREBO potential is used, the mode frequency increases with the amplitude bifurcating from the upper edge of the phonon spectrum for out-of-plane phonons. Then a bell-shaped function is superimposed on this delocalized mode to obtain a spatially localized vibrational mode, i.e., a DB. Placing the center of the bell-shaped function at different positions with respect to the lattice sites, three different DBs are found. Typically, the degree of spatial localization of DBs increases with the DB amplitude, but the transverse DBs in graphene reported here demonstrate the opposite trend. The results are compared to those obtained with the use of the Savin interatomic potential and no transverse DBs are found in this case. The results of this study contribute to a better understanding of the nonlinear dynamics of graphene and they call for the ab initio simulations to verify which of the two potentials used in this study is more precise.

  9. Flutter analysis using transversality theory

    NASA Technical Reports Server (NTRS)

    Afolabi, D.

    1993-01-01

    A new method of calculating flutter boundaries of undamped aeronautical structures is presented. The method is an application of the weak transversality theorem used in catastrophe theory. In the first instance, the flutter problem is cast in matrix form using a frequency domain method, leading to an eigenvalue matrix. The characteristic polynomial resulting from this matrix usually has a smooth dependence on the system's parameters. As these parameters change with operating conditions, certain critical values are reached at which flutter sets in. Our approach is to use the transversality theorem in locating such flutter boundaries using this criterion: at a flutter boundary, the characteristic polynomial does not intersect the axis of the abscissa transversally. Formulas for computing the flutter boundaries and flutter frequencies of structures with two degrees of freedom are presented, and extension to multi-degree of freedom systems is indicated. The formulas have obvious applications in, for instance, problems of panel flutter at supersonic Mach numbers.

  10. Transversity Physics Results from PHENIX

    SciTech Connect

    Chiu, M.

    2005-10-06

    During the 2001-2002 proton run at RHIC, PHENIX collected an integrated luminosity of 0.15 pb-1 of transversely polarized proton collisions at a {radical}(s) = 200GeV/c. With this dataset the transverse single-spin asymmetry AN for {pi}0 and non-identified charged hadrons at xF = 0 has been measured up to p perpendicular = 5 GeV/c. Transverse Single Spin Asymmetries (SSA) are thought to come from at least three mechanisms, and in the future PHENIX will be able to decouple contributions to SSA from the Sivers function by measuring asymmetries in the back-to-back correlation in azimuthal angle of two high-p perpendicular hadrons.

  11. Probabilities of transversions and transitions.

    PubMed

    Vol'kenshtein, M V

    1976-01-01

    The values of the mean relative probabilities of transversions and transitions have been refined on the basis of the data collected by Jukes and found to be equal to 0.34 and 0.66, respectively. Evolutionary factors increase the probability of transversions to 0.44. The relative probabilities of individual substitutions have been determined, and a detailed classification of the nonsense mutations has been given. Such mutations are especially probable in the UGG (Trp) codon. The highest probability of AG, GA transitions correlates with the lowest mean change in the hydrophobic nature of the amino acids coded.

  12. Cosmology in Weyl transverse gravity

    NASA Astrophysics Data System (ADS)

    Oda, Ichiro

    2016-11-01

    We study the Friedmann-Lemaître-Robertson-Walker (FLRW) cosmology in the Weyl-transverse (WTDiff) gravity in a general spacetime dimension. The WTDiff gravity is invariant under both the local Weyl (conformal) transformation and the volume preserving diffeormorphisms (transverse diffeomorphisms) and is believed to be equivalent to general relativity at least at the classical level (perhaps, even in the quantum regime). It is explicitly shown by solving the equations of motion that the FLRW metric is a classical solution in the WTDiff gravity only when the spatial metric is flat, that is, the Euclidean space, and the lapse function is a nontrivial function of the scale factor.

  13. Indentation of Transversely Isotropic Materials

    NASA Astrophysics Data System (ADS)

    Bhat, Talapady Srivatsa

    Instrumented indentation, as a tool for characterization of mechanical properties, has well been established in the past decades. Studies have been conducted to understand the behavior of isotropic materials under indentation and techniques to accurately predict isotropic material properties have also been reported. Further, within the isotropic regime, work has been done to predict the indentation hardness without having to investigate the area of contact during indentation. Studies have also reported the prospect of utilizing indentation to predict the fatigue behavior of isotropic materials. This dissertation is made with the intent of extending the use of indentation, as a characterization tool, to the anisotropic regime. The effect of transverse isotropy on the indentation response of materials is systematically studied here. Extensive computational analysis is performed to elucidate the underlying deformation mechanics of indentation of transversely isotropic materials. Owing to the anisotropy, indentation may be performed parallel or perpendicular to the plane of isotropy of the specimen. It is observed that the indentation response varies significantly for each of these cases. The two cases are treated as unique and an identical systematic analysis is carried for both. The indentation orientations shall henceforth be referred to as transverse and longitudinal indentation for indentation parallel and perpendicular to the plane of isotropy respectively. A technique is developed capable of extracting the elastic-plastic properties of transversely isotropic materials from interpretation of indentation response in either direction. The technique is rigorously tested for its robustness, accuracy and uniqueness of results. A sensitivity analysis is performed to determine how sensitive the technique is to errors in experimental results. Rigorous studies are performed to understand the variation in pile-up or sink-in during indentation with varying anisotropy in the

  14. Hemorrhagic Longitudinally Extensive Transverse Myelitis.

    PubMed

    Wu, Chris Y; Riangwiwat, Tanawan; Nakamoto, Beau K

    2016-01-01

    Longitudinally extensive transverse myelitis (LETM) may be associated with viral triggers, including both infections and vaccinations. We present a case of a healthy immunocompetent 33-year-old woman who developed a hemorrhagic LETM 2 weeks after seasonal influenza vaccination. Hemorrhagic LETM has not to our knowledge been reported after influenza vaccination. It may represent a forme fruste variant of acute hemorrhagic leukoencephalitis.

  15. Transverse effects in UV FELs

    SciTech Connect

    Small, D.W.; Wong, R.K.; Colson, W.B.

    1995-12-31

    In an ultraviolet Free Electron Laser (UV FEL), the electron beam size can be approximately the same as the optical mode size. The performance of a UV FEL is studied including the effect of emittance, betatron focusing, and external focusing of the electron beam on the transverse optical mode. The results are applied to the Industrial Laser Consortium`s UV FEL.

  16. Transverse Magnetic Field Propellant Isolator

    NASA Technical Reports Server (NTRS)

    Foster, John E.

    2000-01-01

    An alternative high voltage isolator for electric propulsion and ground-based ion source applications has been designed and tested. This design employs a transverse magnetic field that increases the breakdown voltage. The design can greatly enhance the operating range of laboratory isolators used for high voltage applications.

  17. An evaluation of the contributions of diffusion and exchange in relaxation enhancement by MRI contrast agents

    NASA Astrophysics Data System (ADS)

    Gossuin, Yves; Roch, Alain; Muller, Robert N.; Gillis, Pierre

    2002-09-01

    Magnetic compounds are known to enhance water proton relaxation, either by diffusion or by proton exchange. An experimental procedure to distinguish both mechanisms is proposed and validated by relaxation measurements made in water-methanol solutions of Dy 3+, Ni 2+, Gd 3+, Tempo, and AMI-25. The test discriminates according to the character of the transverse relaxation in water-methanol solutions: a mono-exponential decay corresponds to diffusion, while a bi-exponential decay indicates the contribution of a proton exchange. The study of ferritin and akaganeite particle solutions confirms the occurrence of a proton exchange between protons belonging to hydroxyl groups of the particle surface and free water protons.

  18. Progressive muscle relaxation, yoga stretching, and ABC relaxation theory.

    PubMed

    Ghoncheh, Shahyad; Smith, Jonathan C

    2004-01-01

    This study compared the psychological effects of progressive muscle relaxation (PMR) and yoga stretching (hatha) exercises. Forty participants were randomly divided into two groups and taught PMR or yoga stretching exercises. Both groups practiced once a week for five weeks and were given the Smith Relaxation States Inventory before and after each session. As hypothesized, practitioners of PMR displayed higher levels of relaxation states (R-States) Physical Relaxation and Disengagement at Week 4 and higher levels of Mental Quiet and Joy as a posttraining aftereffect at Week 5. Contrary to what was hypothesized, groups did not display different levels of R-States Energized or Aware. Results suggest the value of supplementing traditional somatic conceptualizations of relaxation with the psychological approach embodied in ABC relaxation theory. Clinical and research implications are discussed.

  19. Differentiable McCormick relaxations

    DOE PAGES

    Khan, Kamil A.; Watson, Harry A. J.; Barton, Paul I.

    2016-05-27

    McCormick's classical relaxation technique constructs closed-form convex and concave relaxations of compositions of simple intrinsic functions. These relaxations have several properties which make them useful for lower bounding problems in global optimization: they can be evaluated automatically, accurately, and computationally inexpensively, and they converge rapidly to the relaxed function as the underlying domain is reduced in size. They may also be adapted to yield relaxations of certain implicit functions and differential equation solutions. However, McCormick's relaxations may be nonsmooth, and this nonsmoothness can create theoretical and computational obstacles when relaxations are to be deployed. This article presents a continuously differentiablemore » variant of McCormick's original relaxations in the multivariate McCormick framework of Tsoukalas and Mitsos. Gradients of the new differentiable relaxations may be computed efficiently using the standard forward or reverse modes of automatic differentiation. Furthermore, extensions to differentiable relaxations of implicit functions and solutions of parametric ordinary differential equations are discussed. A C++ implementation based on the library MC++ is described and applied to a case study in nonsmooth nonconvex optimization.« less

  20. Differentiable McCormick relaxations

    SciTech Connect

    Khan, Kamil A.; Watson, Harry A. J.; Barton, Paul I.

    2016-05-27

    McCormick's classical relaxation technique constructs closed-form convex and concave relaxations of compositions of simple intrinsic functions. These relaxations have several properties which make them useful for lower bounding problems in global optimization: they can be evaluated automatically, accurately, and computationally inexpensively, and they converge rapidly to the relaxed function as the underlying domain is reduced in size. They may also be adapted to yield relaxations of certain implicit functions and differential equation solutions. However, McCormick's relaxations may be nonsmooth, and this nonsmoothness can create theoretical and computational obstacles when relaxations are to be deployed. This article presents a continuously differentiable variant of McCormick's original relaxations in the multivariate McCormick framework of Tsoukalas and Mitsos. Gradients of the new differentiable relaxations may be computed efficiently using the standard forward or reverse modes of automatic differentiation. Furthermore, extensions to differentiable relaxations of implicit functions and solutions of parametric ordinary differential equations are discussed. A C++ implementation based on the library MC++ is described and applied to a case study in nonsmooth nonconvex optimization.

  1. Evaluation of brain edema using magnetic resonance proton relaxation times

    SciTech Connect

    Fu, Y.; Tanaka, K.; Nishimura, S. )

    1990-01-01

    Experimental and clinical studies on the evaluation of water content in cases of brain edema were performed in vivo, using MR proton relaxation times (longitudinal relaxation time, T1; transverse relaxation time, T2). Brain edema was produced in the white matter of cats by the direct infusion method. The correlations between proton relaxation times obtained from MR images and the water content of white matter were studied both in autoserum-infused cats and in saline-infused cats. The correlations between T1 as well as T2 and the water content in human vasogenic brain edema were also examined and compared with the data obtained from the serum group. T1 and T2 showed good correlations with the water content of white matter not only in the experimental animals but also in the clinical cases. The quality of the edema fluid did not influence relaxation time and T1 seemed to represent almost solely the water content of the tissue. T2, however, was affected by the nature of existence of water and was more sensitive than T1 in detecting extravasated edema fluid. It seems feasible therefore to evaluate the water content of brain edema on the basis of T1 values.

  2. Transverse force on transversely polarized quarks in longitudinally polarized nucleons

    NASA Astrophysics Data System (ADS)

    Abdallah, Manal; Burkardt, Matthias

    2016-11-01

    We study the semiclassical interpretation of the x3 and x4 moments of twist-3 parton distribution functions (PDFs). While no semiclassical interpretation for the higher moments of gT(x ) and e (x ) was found, the x3 moment of the chirally odd spin-dependent twist-3 PDF hL3(x ) can be related to the longitudinal gradient of the transverse force on transversely polarized quarks in longitudinally polarized nucleons in a deep-inelastic scattering experiment. We discuss how this result relates to the torque acting on a quark in the same experiment. This has further implications for comparisons between the Jaffe-Manohar and the Ji decompositions of the nucleon spin.

  3. Grueneisen Relaxation Photoacoustic Microscopy

    NASA Astrophysics Data System (ADS)

    Wang, Lidai; Zhang, Chi; Wang, Lihong V.

    2014-10-01

    The temperature-dependent property of the Grueneisen parameter has been employed in photoacoustic imaging mainly to measure tissue temperature. Here we explore this property using a different approach and develop Grueneisen relaxation photoacoustic microscopy (GR-PAM), a technique that images nonradiative absorption with confocal optical resolution. GR-PAM sequentially delivers two identical laser pulses with a microsecond-scale time delay. The first laser pulse generates a photoacoustic signal and thermally tags the in-focus absorbers. When the second laser pulse excites the tagged absorbers within the thermal relaxation time, a photoacoustic signal stronger than the first one is produced, owing to the temperature dependence of the Grueneisen parameter. GR-PAM detects the amplitude difference between the two colocated photoacoustic signals, confocally imaging the nonradiative absorption. We greatly improved axial resolution from 45 μm to 2.3 μm and, at the same time, slightly improved lateral resolution from 0.63 μm to 0.41 μm. In addition, the optical sectioning capability facilitates the measurement of the absolute absorption coefficient without fluence calibration.

  4. Measuring the relaxation time of the xenon atoms and the rubidium atoms

    NASA Astrophysics Data System (ADS)

    Jiang, Peng; Wang, Zhi-Guo; Li, Ying-Ying; Jiang, Qi-Yuan; Luo, Hui

    2016-11-01

    In a nuclear-magnetic-resonance gyroscope (NMRG), the polarization of nuclear spins and the detection of motional information are usually achieved by utilizing the atomic spins of alkali atoms. The parameters of the atomic spins are mainly evaluated by the relaxation time. Relaxation time is very important and can influence signal-to-noise ratio, dynamic range, start time, and other gyroscope parameters. Therefore, its accurate measurement is critical in the study of NMRG performance. In this study, we evaluate a variety of methods to measure the transverse and longitudinal relaxation times. First we examine the free-induction-decay method, which is the industry standard for measuring spin relaxation time. Second we investigate the improved free-induction-decay, fitting-ratio, and magnetic-resonance-broadening- fitting methods for measuring the transverse relaxation time, and the flipped polarization method for measuring the longitudinal relaxation time. By changing the experimental conditions, we obtain the longitudinal relaxation time using the flipped polarization method under a variety of conditions. Finally, by comparing these measurement methods, we propose the best measurement methods under different conditions.

  5. Generalized extended Navier-Stokes theory: multiscale spin relaxation in molecular fluids.

    PubMed

    Hansen, J S

    2013-09-01

    This paper studies the relaxation of the molecular spin angular velocity in the framework of generalized extended Navier-Stokes theory. Using molecular dynamics simulations, it is shown that for uncharged diatomic molecules the relaxation time decreases with increasing molecular moment of inertia per unit mass. In the regime of large moment of inertia the fast relaxation is wave-vector independent and dominated by the coupling between spin and the fluid streaming velocity, whereas for small inertia the relaxation is slow and spin diffusion plays a significant role. The fast wave-vector-independent relaxation is also observed for highly packed systems. The transverse and longitudinal spin modes have, to a good approximation, identical relaxation, indicating that the longitudinal and transverse spin viscosities have same value. The relaxation is also shown to be isomorphic invariant. Finally, the effect of the coupling in the zero frequency and wave-vector limit is quantified by a characteristic length scale; if the system dimension is comparable to this length the coupling must be included into the fluid dynamical description. It is found that the length scale is independent of moment of inertia but dependent on the state point.

  6. Effect of Paramagnetic Ions on NMR Relaxation of Fluids at Solid Surfaces

    NASA Astrophysics Data System (ADS)

    Foley, I.; Farooqui, S. A.; Kleinberg, R. L.

    Proton NMR longitudinal and transverse relaxation times of water-saturated powder packs have been measured. The powders were a series of synthetic calcium silicates with known concentrations of iron or manganese paramagnetic ions. The rate of water proton relaxation has been found to be linearly proportional to the concentration of paramagnetic ion. The constant of proportionality is used to determine the electron relaxation time of ions at the fluid-solid interface. A substantial relaxivity is found in the absence of paramagnetic ions. Thus the oxide surface itself is an unexpectedly good relaxer of fluid-borne nuclear spins. The results answer some long-standing questions connected with the NMR properties of fluid-saturated sedimentary rocks.

  7. New approach for understanding experimental NMR relaxivity properties of magnetic nanoparticles: focus on cobalt ferrite.

    PubMed

    Rollet, Anne-Laure; Neveu, Sophie; Porion, Patrice; Dupuis, Vincent; Cherrak, Nadine; Levitz, Pierre

    2016-12-07

    Relaxivities r1 and r2 of cobalt ferrite magnetic nanoparticles (MNPs) have been investigated in the aim of improving the models of NMR relaxation induced by magnetic nanoparticles. On one hand a large set of relaxivity data has been collected for cobalt ferrite MNP dispersions. On the other hand the relaxivity has been calculated for dispersions of cobalt ferrite MNPs with size ranging from 5 to 13 nm, without using any fitting procedure. The model is based on the magnetic dipolar interaction between the magnetic moments of the MNPs and the (1)H nuclei. It takes into account both the longitudinal and transversal contributions of the magnetic moments of MNPs leading to three contributions in the relaxation equations. The comparison of the experimental and theoretical data shows a good agreement of the NMR profiles as well as the temperature dependence.

  8. Ultrafast Relaxation in Conjugated Polymers

    NASA Astrophysics Data System (ADS)

    Kobayashi, Takayoshi

    The following sections are included: * INTRODUCTION * EXPERIMENTAL * Samples * Femtosecond experimental apparatus * RESULTS AND DISCUSSION * Poly(phenylacetylenes) * Blue-phase PDA-3BCMU * Red-phase PDA-4BCMU * Blue-phase PDA-DFMP * P3MT * P3DT * PTV * RELAXATION MECHANISMS * Review of the previous works * Symmetry of the lower electronic excited states * Primary relaxation processes * Theoretical studies of nonlinear excitations * Mechanism of relaxation in polymers with a weakly nondegenerate ground state (poly(phenylacetylene)s) * Dual peak component with power-law decay * Single-peak component with an exponential decay * Hot self-trapped exciton * Transition to the electron-hole threshold * Transition to a biexciton state * Mechanism of relaxation in polymers with a strongly or moderately nondegenerate ground state * Classifications of polymers * Femtosecond relaxation * Picosecond relaxation * CONCLUSION * Acknowledgments * REFERENCES

  9. Relaxing music for anxiety control.

    PubMed

    Elliott, Dave; Polman, Remco; McGregor, Richard

    2011-01-01

    The purpose of this investigation was to determine the characteristics of relaxing music for anxiety control. Undergraduate students (N=84) were instructed to imagine themselves in an anxiety producing situation while listening to a selection of 30 music compositions. For each composition, level of relaxation, the factors that either enhanced or detracted from its relaxing potential and the emotional labels attached were assessed. Participants were also asked to state which music components (e.g., tempo, melody) were most conducive to relaxation. Additional information was obtained through the use of a focus group of 6 undergraduate music students. This paper presents details on the characteristics of relaxing-music for anxiety control and emotional labels attached to the relaxing compositions. Furthermore, an importance value has been attached to each of the music components under scrutiny, thus providing an indication of which music components should receive greatest attention when selecting music for anxiety control.

  10. ABC relaxation theory and the factor structure of relaxation states, recalled relaxation activities, dispositions, and motivations.

    PubMed

    Smith, J C; Wedell, A B; Kolotylo, C J; Lewis, J E; Byers, K Y; Segin, C M

    2000-06-01

    ABC Relaxation Theory proposes 15 psychological relaxation-related states (R-States): Sleepiness, Disengagement, Physical Relaxation, Mental Quiet, Rested/Refreshed, At Ease/At Peace, Energized, Aware, Joy, Thankfulness and Love, Prayerfulness, Childlike Innocence, Awe and Wonder, Mystery, and Timeless/Boundless/Infinite. The present study summarizes the results of 13 separate factor analyses of immediate relaxation-related states, states associated with recalled relaxation activities, relaxation dispositions, and relaxation motivations on a combined sample of 1,904 individuals (group average ages ranged from 28-40 yr.). Four exploratory factor analyses of Smith Relaxation Inventories yielded 15 items that most consistently and exclusively load (generally at least .70) on six replicated factors. These items included happy, joyful, energized, rested, at peace, warm, limp, silent, quiet, dozing, drowsy, prayerful, mystery, distant, and indifferent. Subsequent factor analyses restricted to these items and specifying six factors were performed on 13 different data sets. Each yielded the same six-factor solution: Factor 1: Centered Positive Affect, Factor 2: Sleepiness, Factor 3: Disengagement, Factor 4: Physical Relaxation, Factor 5: Mental Quiet, and Factor 6: Spiritual. Implications for ABC Relaxation Theory are discussed.

  11. State resolved vibrational relaxation modeling for strongly nonequilibrium flows

    NASA Astrophysics Data System (ADS)

    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.

  12. Transverse shape of the electron

    SciTech Connect

    Hoyer, Paul; Kurki, Samu

    2010-01-01

    We study the charge density, form factors and spin distributions of the electron induced by its |e{gamma}> light-front Fock state in impact parameter space. Only transversally compact Fock states contribute to the leading behavior of the Dirac and Pauli form factors as the momentum transfer tends to infinity. Power suppressed contributions are not compact, and distributions weighted by the transverse size have endpoint contributions. The Fock state conserves the spin of the parent electron locally, but the separate contributions of the electron, photon, and orbital angular momentum depend on longitudinal momentum and impact parameter. The sign of the anomalous magnetic moment of the electron may be understood intuitively from the density distribution, addressing a challenge by Feynman.

  13. Transverse Bragg resonance laser amplifier.

    PubMed

    Yariv, Amnon; Xu, Yong; Mookherjea, Shayan

    2003-02-01

    We propose and analyze a new type of optical amplifier that is formed by addition of gain in the periodic cladding of a transverse Bragg resonance waveguide [Opt. Lett. 27, 936 (2002)]. Using the coupled-wave formalism, we calculate the mode profiles, the exponential gain constant, and, for comparison, the gain enhancement compared with those of conventional semiconductor optical amplifiers. In contrast with coupled-mode theory, in one-dimensional structures (e.g., the distributed-feedback laser) the exponential gain constant in the longitudinal direction is involved in both longitudinal and transverse confinement, and its solution has to be achieved self-consistently, together with the quantized guiding channel width.

  14. Transverse angular momentum of photons

    SciTech Connect

    Aiello, Andrea

    2010-05-15

    We develop the quantum theory of transverse angular momentum of light beams. The theory applies to paraxial and quasiparaxial photon beams in vacuum and reproduces the known results for classical beams when applied to coherent states of the field. Both the Poynting vector, alias the linear momentum, and the angular-momentum quantum operators of a light beam are calculated including contributions from first-order transverse derivatives. This permits a correct description of the energy flow in the beam and the natural emergence of both the spin and the angular momentum of the photons. We show that for collimated beams of light, orbital angular-momentum operators do not satisfy the standard commutation rules. Finally, we discuss the application of our theory to some concrete cases.

  15. Hemorrhagic Longitudinally Extensive Transverse Myelitis

    PubMed Central

    Wu, Chris Y.; Riangwiwat, Tanawan

    2016-01-01

    Longitudinally extensive transverse myelitis (LETM) may be associated with viral triggers, including both infections and vaccinations. We present a case of a healthy immunocompetent 33-year-old woman who developed a hemorrhagic LETM 2 weeks after seasonal influenza vaccination. Hemorrhagic LETM has not to our knowledge been reported after influenza vaccination. It may represent a forme fruste variant of acute hemorrhagic leukoencephalitis. PMID:27847660

  16. [Ulcer of the transverse colon].

    PubMed

    Constantinescu, C; Stoichiţa, S; Vasilescu, D; Strutenschi, T; Lake, D

    1979-01-01

    This very rare affection of unknown origin, achieves a macroscopic and microscopic aspect similar to that described by Cruveillhier at the level of the stomach. The authors present a case of ulcer located on the transverse colon, at the free margin, with stenosing evolution and coexisting with duodenal ulceration of chronic character. The patient also had portal hypertension in the third stage and arteriopathy that had been diagnosed previously.

  17. Spin-relaxation time in materials with broken inversion symmetry and large spin-orbit coupling.

    PubMed

    Szolnoki, Lénárd; Kiss, Annamária; Dóra, Balázs; Simon, Ferenc

    2017-08-30

    We study the spin-relaxation time in materials where a large spin-orbit coupling (SOC) is present which breaks the spatial inversion symmetry. Such a spin-orbit coupling is realized in zincblende structures and heterostructures with a transversal electric field and the spin relaxation is usually described by the so-called D'yakonov-Perel' (DP) mechanism. We combine a Monte Carlo method and diagrammatic calculation based approaches in our study; the former tracks the time evolution of electron spins in a quasiparticle dynamics simulation in the presence of the built-in spin-orbit magnetic fields and the latter builds on the spin-diffusion propagator by Burkov and Balents. Remarkably, we find a parameter free quantitative agreement between the two approaches and it also returns the conventional result of the DP mechanism in the appropriate limit. We discuss the full phase space of spin relaxation as a function of SOC strength, its distribution, and the magnitude of the momentum relaxation rate. This allows us to identify two novel spin-relaxation regimes; where spin relaxation is strongly non-exponential and the spin relaxation equals the momentum relaxation. A compelling analogy between the spin-relaxation theory and the NMR motional narrowing is highlighted.

  18. Relaxation Techniques for Trauma.

    PubMed

    Scotland-Coogan, Diane; Davis, Erin

    2016-01-01

    Physiological symptoms of posttraumatic stress disorder (PTSD) manifest as increased arousal and reactivity seen as anger outburst, irritability, reckless behavior with no concern for consequences, hypervigilance, sleep disturbance, and problems with focus (American Psychiatric Association, 2013 ). In seeking the most beneficial treatment for PTSD, consideration must be given to the anxiety response. Relaxation techniques are shown to help address the physiological manifestations of prolonged stress. The techniques addressed by the authors in this article include mindfulness, deep breathing, yoga, and meditation. By utilizing these techniques traditional therapies can be complemented. In addition, those who are averse to the traditional evidence-based practices or for those who have tried traditional therapies without success; these alternative interventions may assist in lessening physiological manifestations of PTSD. Future research studies assessing the benefits of these treatment modalities are warranted to provide empirical evidence to support the efficacy of these treatments.

  19. 40 Gbps modulation of transverse coupled cavity VCSEL with push-pull modulation scheme

    NASA Astrophysics Data System (ADS)

    Dalir, Hamed; Koyama, Fumio

    2014-09-01

    The push-pull modulation of a transverse coupled cavity VCSEL with a bow-tie-shaped oxide aperture is demonstrated. We experimentally show the transverse-mode switching of laterally coupled VCSELs, which potentially offers a novel push-pull modulation concept. The calculated results of small-signal responses indicate an extreme expansion of the modulation bandwidth regardless of the relaxation oscillation frequency. The small-signal response was measured by tuning the RF phase of the modulation current in one cavity. A clear eye opening up to 40 Gbps with push-pull modulation has been obtained, whereas the eye pattern with the single-cavity modulation is completely closed.

  20. Transverse spin effects at COMPASS

    SciTech Connect

    Pesaro, G.

    2009-03-23

    The COMPASS experiment at the CERN SPS has a broad physics program focused on the nucleon spin structure and on hadron spectroscopy, using both muon and hadron beams. One of the main objectives for the spin program with the muon beam is the measurement of transverse spin effects in semi inclusive deep inelastic scattering. A longitudinally polarized 160 GeV/c muon beam is impinging on a transversely polarized target: from 2002 to 2004 a {sup 6}LiD(deuteron) target has been used, while during 2007 data taking a NH{sub 3}(proton) target was put in place. All measured transverse asymmetries on deuteron have been found to be small, and compatible with zero, within the few percent statistical errors. These results, which are currently used as input for global fits, can be interpreted as cancellation between u and d quark contribution in the deuteron. The first results for the Collins and Sivers asymmetries for charged hadrons from the 2007 proton COMPASS data are also presented and discussed.

  1. Comet Bursting Through Relaxation

    NASA Astrophysics Data System (ADS)

    Jacobson, Seth A.; Scheeres, D. J.

    2012-10-01

    Comets may be excited and occupy non-principal axis (complex) rotation states for a large fraction of their lifetimes. Many comet nuclei have been identified or are suspected to occupy non-principal axis (complex) rotation [Belton 2005, etc.] as well as have evolving rotation rates [Belton 2011, etc.]. Comet orbits drive these rotation states through cycles of excitation due to surface jets and relaxation due to time variable internal stresses that dissipate energy in the anelastic comet interior. Furthermore, relaxation from complex rotation can increase the loads along the symmetry axis of prolate comets. These loads stretch the body along the symmetry axis and may be the cause of the characteristic ``bowling pin’’ shape and eventually may lead to failure. This is an alternative model for comet bursting. Each cycle deposits only a small amount of energy and stress along the axis, but this process is repeated every orbit during which jets are activated. Our model for the evolution of comet nuclei includes torques due to a number of discrete jets located on the surface based on Neishtadt et al. [2002]. The model also includes internal dissipation using an approach developed by Sharma et al. [2005] and Vokrouhlicky et al. [2009]. These equations are averaged over the instantaneous spin state and the heliocentric orbit so the long-term evolution of the comet can be determined. We determine that even after the inclusion of internal dissipation there still exist non-principal axis equilibrium states for certain jet geometries. For ranges of dissipation factors and jet geometries, prolate comets are found to occupy states that have time variable internal loads over long time periods. These periodic loadings along the symmetry axis may lead to ``necking’’ as the body extends along the axis to release the stress and eventually disruption.

  2. QCD Evolution of Helicity and Transversity TMDs

    SciTech Connect

    Prokudin, Alexei

    2014-01-01

    We examine the QCD evolution of the helicity and transversity parton distribution functions when including also their dependence on transverse momentum. Using an appropriate definition of these polarized transverse momentum distributions (TMDs), we describe their dependence on the factorization scale and rapidity cutoff, which is essential for phenomenological applications.

  3. Development of relaxation turbulence models

    NASA Technical Reports Server (NTRS)

    Hung, C. M.

    1976-01-01

    Relaxation turbulence models have been intensively studied. The complete time dependent mass averaged Navier-Stokes equations have been solved for flow into a two dimensional compression corner. A new numerical scheme has been incorporated into the developed computed code with an attendant order of magnitude reduction in computation time. Computed solutions are compared with experimental measurements of Law for supersonic flow. Details of the relaxation process have been studied; several different relaxation models, including different relaxation processes and varying relaxation length, are tested and compared. Then a parametric study has been conducted in which both Reynolds number and wedge angle are varied. To assess effects of Reynolds number and wedge angle, the parametric study includes the comparison of computed separation location and upstream extent of pressure rise; numerical results are also compared with the measurements of surface pressure, skin friction and mean velocity field.

  4. Phenomenological extraction of Transverse Momentum Dependent distributions

    SciTech Connect

    Prokudin, Alexei

    2011-10-24

    We discuss phenomenological extraction of Transverse Momentum Dependent Distributions (TMDs) from experimental data. At leading twist spin structure of spin-1/2 hadron can be described by 8 TMDs. TMDs reveal three-dimensional distribution of partons inside polarised nucleon. Experimentally these functions can be studied in polarised experiments using Spin Asymmetries in particular Single Spin Asymmetries (SSAs). We discuss transversity that measures distribution of transversely polarised quarks in a transversely polarised nucleon and Sivers distribution function that describes distribution of unpolarised quarks in a transversely polarised nucleon.

  5. Electron Ion Collider transverse spin physics

    SciTech Connect

    Prokudin, Alexei

    2011-07-01

    Electron Ion Collider is a future high energy facility for studies of the structure of the nucleon. Three-dimensional parton structure is one of the main goals of EIC. In momentum space Transverse Momentum Dependent Distributions (TMDs) are the key ingredients to map such a structure. At leading twist spin structure of spin-1/2 hadron can be described by 8 TMDs. Experimentally these functions can be studied in polarised SIDIS experiments. We discuss Sivers distribution function that describes distribution of unpolarised quarks in a transversely polarised nucleon and transversity that measures distribution of transversely polarised quarks in a transversely polarised nucleon

  6. Electron Ion Collider transverse spin physics

    SciTech Connect

    Prokudin, Alexei

    2011-07-15

    Electron Ion Collider is a future high energy facility for studies of the structure of the nucleon. Three-dimensional parton structure is one of the main goals of EIC. In momentum space Transverse Momentum Dependent Distributions (TMDs) are the key ingredients to map such a structure. At leading twist spin structure of spin-1/2 hadron can be described by 8 TMDs. Experimentally these functions can be studied in polarised SIDIS experiments. We discuss Sivers distribution function that describes distribution of unpolarised quarks in a transversely polarised nucleon and transversity that measures distribution of transversely polarised quarks in a transversely polarised nucleon.

  7. Nonequilibrium quantum relaxation across a localization-delocalization transition

    NASA Astrophysics Data System (ADS)

    Roósz, Gergő; Divakaran, Uma; Rieger, Heiko; Iglói, Ferenc

    2014-11-01

    We consider the one-dimensional X X model in a quasiperiodic transverse field described by the Harper potential, which is equivalent to a tight-binding model of spinless fermions with a quasiperiodic chemical potential. For weak transverse field (chemical potential), h hc . We study the nonequilibrium relaxation of the system by applying two protocols: a sudden change of h (quench dynamics) and a slow change of h in time (adiabatic dynamics). For a quench into the delocalized (localized) phase, the entanglement entropy grows linearly (saturates) and the order parameter decreases exponentially (has a finite limiting value). For a critical quench the entropy increases algebraically with time, whereas the order parameter decreases with a stretched exponential. The density of defects after an adiabatic field change through the critical point is shown to scale with a power of the rate of field change and a scaling relation for the exponent is derived.

  8. Influence of Specimen Preparation and Specimen Size on Composite Transverse Tensile Strength and Scatter

    NASA Technical Reports Server (NTRS)

    OBrien, T. Kevin; Chawan, Arun D.; DeMarco, Kevin; Paris, Isabelle

    2001-01-01

    The influence of specimen polishing, configuration, and size on the transverse tension strength of two glass-epoxy materials, and one carbon-epoxy material, loaded in three and four point bending was evaluated. Polishing machined edges, arid/or tension side failure surfaces, was detrimental to specimen strength characterization instead of yielding a higher, more accurate, strength as a result of removing inherent manufacture and handling flaws. Transverse tension strength was typically lower for longer span lengths due to the classical weakest link effect. However, strength was less sensitive to volume changes achieved by increasing specimen width. The Weibull scaling law typically over-predicted changes in transverse tension strengths in three point bend tests and under-predicted changes in transverse tension strengths in four point bend tests. Furthermore, the Weibull slope varied with specimen configuration, volume, and sample size. Hence, this scaling law was not adequate for predicting transverse tension strength of heterogeneous, fiber-reinforced, polymer matrix composites.

  9. Investigation of transverse oscillation method.

    PubMed

    Udesen, Jesper; Jensen, Jørgen Arendt

    2006-05-01

    Conventional ultrasound scanners can display only the axial component of the blood velocity vector, which is a significant limitation when vessels nearly parallel to the skin surface are scanned. The transverse oscillation (TO) method overcomes this limitation by introducing a TO and an axial oscillation in the pulse echo field. The theory behind the creation of the double oscillation pulse echo field is explained as well as the theory behind the estimation of the vector velocity. A parameter study of the method is performed, using the ultrasound simulation program Field II. A virtual linear-array transducer with center frequency 7 MHz and 128 active elements is created, and a virtual blood vessel of radius 6.4 mm is simulated. The performance of the TO method is found around an initial point in the parameter space. The parameters varied are: flow angle, transmit focus depth, receive apodization, pulse length, transverse wave length, number of emissions, signal-to-noise ratio (SNR), and type of echo-canceling filter used. Using an experimental scanner, the performance of the TO method is evaluated. An experimental flowrig is used to create laminar parabolic flow in a blood mimicking fluid, and the fluid is scanned under different flow-to-beam angles. The relative standard deviation on the transverse velocity estimate is found to be less than 10% for all angles between 50 degrees and 90 degrees. Furthermore, the TO method is evaluated in the flowrig using pulsatile flow, which resembles the flow in the femoral artery. The estimated volume flow as a function of time is compared to the volume flow derived from a conventional axial method at a flow-to-beam angle of 60 degrees. It is found that the method is highly sensitive to the angle between the flow and the beam direction. Also, the choice of echo canceling filter affects the performance significantly.

  10. Liquid-state paramagnetic relaxation from first principles

    NASA Astrophysics Data System (ADS)

    Rantaharju, Jyrki; Vaara, Juha

    2016-10-01

    We simulate nuclear and electron spin relaxation rates in a paramagnetic system from first principles. Sampling a molecular dynamics trajectory with quantum-chemical calculations produces a time series of the instantaneous parameters of the relevant spin Hamiltonian. The Hamiltonians are, in turn, used to numerically solve the Liouville-von Neumann equation for the time evolution of the spin density matrix. We demonstrate the approach by studying the aqueous solution of the Ni2 + ion. Taking advantage of Kubo's theory, the spin-lattice (T1) and spin-spin (T2) relaxation rates are extracted from the simulations of the time dependence of the longitudinal and transverse magnetization, respectively. Good agreement with the available experimental data is obtained by the method.

  11. Suppression of sodium nuclear magnetic resonance double-quantum coherence by chemical shift and relaxation reagents

    NASA Astrophysics Data System (ADS)

    Hutchison, Robert B.; Huntley, James J. A.; Jin, Haoran; Shapiro, Joseph I.

    1992-12-01

    An investigation into the signal suppression behavior of the paramagnetic shift and relaxation reagents, Dy(P3O10)27- and Gd(P3O10)27-, with regard to their use in the nuclear magnetic resonance spectroscopic study of sodium has been performed. Measurements of T1 and T2 relaxation time constants of sodium in normal saline, Krebs-Henseleit buffer, and human blood serum, as a function of concentration of these reagents showed that, although closely coupled in the saline and K-H buffer environments, in plasma T1 and T2 become decoupled, transverse relaxation dominating in comparison to longitudinal relaxation. Linewidth measurements further suggest that relaxation in the plasma milieu is controlled primarily by inherent T2 relaxation, rather than by field inhomogeneity or diffusion effects. Quantitative single-quantum (1Q) and double-quantum (2Q) intensity measurements, biexponential T2 relaxation measurements, and parametric studies of the preparation time of the 2Q pulse sequence, were obtained in suspensions of bovine serum albumin and human erythrocytes. The observed suppression of sodium 2Q coherence by paramagnetic shift and relaxation reagents was found to exhibit a complex behavior in albumin solutions, involving the biexponential T2 decay to be expected during the preparation time of the 2Q filter pulse sequence, as well as the optimum preparation time for production of the double-quantum coherence itself. The controlling factor for both of these effects is the biexponential amplitude function in the expression for the transverse magnetization observed following application of the 2Q pulse sequence. This in turn is determined entirely by the values for the slow and fast components of biexponential relaxation in sodium, which themselves depend upon the concentration of the macromolecular binding sites for quadrupolar interaction. A similar behavior has been observed in suspensions of human erythrocytes.

  12. TRANSVERSE ECHO MEASUREMENTS IN RHIC.

    SciTech Connect

    FISCHER, W.

    2005-09-18

    Diffusion counteracts cooling and the knowledge of diffusion rates is important for the calculation of cooling times and equilibrium beam sizes. Echo measurements are a potentially sensitive method to determine diffusion rates, and longitudinal measurements were done in a number of machines. We report on transverse echo measurements in RHIC and the observed dependence of echo amplitudes on a number of parameters for beams of gold and copper ions, and protons. In particular they examine the echo amplitudes of gold and copper ion bunches of varying intensity, which exhibit different diffusion rates from intrabeam scattering.

  13. A Transversely Isotropic Thermoelastic Theory

    NASA Technical Reports Server (NTRS)

    Arnold, S. M.

    1989-01-01

    A continuum theory is presented for representing the thermoelastic behavior of composites that can be idealized as transversely isotropic. This theory is consistent with anisotropic viscoplastic theories being developed presently at NASA Lewis Research Center. A multiaxial statement of the theory is presented, as well as plane stress and plane strain reductions. Experimental determination of the required material parameters and their theoretical constraints are discussed. Simple homogeneously stressed elements are examined to illustrate the effect of fiber orientation on the resulting strain distribution. Finally, the multiaxial stress-strain relations are expressed in matrix form to simplify and accelerate implementation of the theory into structural analysis codes.

  14. Optical Isolators With Transverse Magnets

    NASA Technical Reports Server (NTRS)

    Fan, Yuan X.; Byer, Robert L.

    1991-01-01

    New design for isolator includes zigzag, forward-and-backward-pass beam path and use of transverse rather than longitudinal magnetic field. Design choices produce isolator with as large an aperture as desired using low-Verdet-constant glass rather than more expensive crystals. Uses commercially available permanent magnets in Faraday rotator. More compact and less expensive. Designed to transmit rectangular beam. Square cross section of beam extended to rectangular shape by increasing one dimension of glass without having to increase magnetic field. Potentially useful in laser systems involving slab lasers and amplifiers. Has applications to study of very-high-power lasers for fusion research.

  15. Ultrasound Devulcanization of Natural Rubber, Studied by NMR Relaxation and Diffusion

    NASA Astrophysics Data System (ADS)

    von Meerwall, E.

    2005-03-01

    In support of recycling of industrial rubbers, we have studied the effect of intense ultrasound on unfilled natural rubber networks using proton and carbon transverse NMR relaxation and diffusion, sol extraction, and bulk characterization. At 70.5^o C the proton echo decay exhibits three components, due to entangled sol and crosslinked network; unentangled polymeric sol plus dangling chain ends; and oligomer remnants. Contrary to the 13C results which indicate backbone mobilities decreasing with sonication (hence with increasing sol fraction), all 1H component T2 values, hence intermolecular mobilities, increase by similar modest factors; the network component amplitude decreases strongly. Diffusion of unentangled sol is sharply bimodal, arising from intermediate fractions and unreactive oligomers. Both diffusion rates decrease slightly with sonication in spite of plasticization by sol, because degradation adds sol primarily of intermediate molecular weights. We compare these results with our earlier work in SBR. Although ultrasound devulcanization does not recover many properties of the virgin melt, recyclability is not compromised.

  16. Anomalous T2 relaxation in normal and degraded cartilage.

    PubMed

    Reiter, David A; Magin, Richard L; Li, Weiguo; Trujillo, Juan J; Pilar Velasco, M; Spencer, Richard G

    2016-09-01

    To compare the ordinary monoexponential model with three anomalous relaxation models-the stretched Mittag-Leffler, stretched exponential, and biexponential functions-using both simulated and experimental cartilage relaxation data. Monte Carlo simulations were used to examine both the ability of identifying a given model under high signal-to-noise ratio (SNR) conditions and the accuracy and precision of parameter estimates under more modest SNR as would be encountered clinically. Experimental transverse relaxation data were analyzed from normal and enzymatically degraded cartilage samples under high SNR and rapid echo sampling to compare each model. Both simulation and experimental results showed improvement in signal representation with the anomalous relaxation models. The stretched exponential model consistently showed the lowest mean squared error in experimental data and closely represents the signal decay over multiple decades of the decay time (e.g., 1-10 ms, 10-100 ms, and >100 ms). The stretched exponential parameter αse showed an inverse correlation with biochemically derived cartilage proteoglycan content. Experimental results obtained at high field suggest potential application of αse as a measure of matrix integrity. Simulation reflecting more clinical imaging conditions, indicate the ability to robustly estimate αse and distinguish between normal and degraded tissue, highlighting its potential as a biomarker for human studies. Magn Reson Med 76:953-962, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  17. Progressive muscle relaxation, breathing exercises, and ABC relaxation theory.

    PubMed

    Matsumoto, M; Smith, J C

    2001-12-01

    This study compared the psychological effects of Progressive Muscle Relaxation (PMR) and breathing exercises. Forty-two students were divided randomly into two groups and taught PMR or breathing exercises. Both groups practiced for five weeks and were given the Smith Relaxation States Inventory before and after each session. As hypothesized, PMR practitioners displayed greater increments in relaxation states (R-States) Physical Relaxation and Disengagement, while breathing practitioners displayed higher levels of R-State Strength and Awareness. Slight differences emerged at Weeks 1 and 2; major differences emerged at Weeks 4 and 5. A delayed and potentially reinforcing aftereffect emerged for PMR only after five weeks of training--increased levels of Mental Quiet and Joy. Clinical and theoretical implications are discussed.

  18. Quasiparticle relaxation in superconducting nanostructures

    NASA Astrophysics Data System (ADS)

    Savich, Yahor; Glazman, Leonid; Kamenev, Alex

    2017-09-01

    We examine energy relaxation of nonequilibrium quasiparticles in "dirty" superconductors with the electron mean free path much shorter than the superconducting coherence length. Relaxation of low-energy nonequilibrium quasiparticles is dominated by phonon emission. We derive the corresponding collision integral and find the quasiparticle relaxation rate. The latter is sensitive to the breaking of time reversal symmetry (TRS) by a magnetic field (or magnetic impurities). As a concrete application of the developed theory, we address quasiparticle trapping by a vortex and a current-biased constriction. We show that trapping of hot quasiparticles may predominantly occur at distances from the vortex core, or the constriction, significantly exceeding the superconducting coherence length.

  19. Can Black Hole Relax Unitarily?

    NASA Astrophysics Data System (ADS)

    Solodukhin, S. N.

    2005-03-01

    We review the way the BTZ black hole relaxes back to thermal equilibrium after a small perturbation and how it is seen in the boundary (finite volume) CFT. The unitarity requires the relaxation to be quasi-periodic. It is preserved in the CFT but is not obvious in the case of the semiclassical black hole the relaxation of which is driven by complex quasi-normal modes. We discuss two ways of modifying the semiclassical black hole geometry to maintain unitarity: the (fractal) brick wall and the worm-hole modification. In the latter case the entropy comes out correctly as well.

  20. Stress relaxation in heterogeneous polymers

    NASA Astrophysics Data System (ADS)

    Witten, T. A.

    1992-05-01

    When heterogeneous polymers such as diblock copolymers form a microdomain phase, an imposed strain gives rise to stress from two sources, and several mechanisms of stress relaxation. The release of stress by disentanglement is strongly influenced by the effective confinement of the junction points to the domain boundaries and by the stretching of the chains. Using accepted notions of entangled chain kinetics, it is argued that the relaxation time for sliding stress is exponential in the chainlength to the 7/9 power. A method for calculating the frequency-dependent dynamic modulus is sketched. Despite the slow relaxation implied by these mechanisms, it appears possible to create domains of high energy.

  1. Dynamics of the transverse Ising model with next-nearest-neighbor interactions.

    PubMed

    Guimarães, P R C; Plascak, J A; de Alcantara Bonfim, O F; Florencio, J

    2015-10-01

    We study the effects of next-nearest-neighbor (NNN) interactions on the dynamics of the one-dimensional spin-1/2 transverse Ising model in the high-temperature limit. We use exact diagonalization to obtain the time-dependent transverse correlation function and the corresponding spectral density for a tagged spin. Our results for chains of 13 spins with periodic boundary conditions produce results which are valid in the infinite-size limit. In general we find that the NNN coupling produces slower dynamics accompanied by an enhancement of the central mode behavior. Even in the case of a strong transverse field, if the NNN coupling is sufficiently large, then there is a crossover from collective mode to central mode behavior. We also obtain several recurrants for the continued fraction representation of the relaxation function.

  2. From Strong to Fragile Glass Formers: Secondary Relaxation in Polyalcohols

    NASA Astrophysics Data System (ADS)

    Döß, A.; Paluch, M.; Sillescu, H.; Hinze, G.

    2002-03-01

    We have studied details of the molecular origin of slow secondary relaxation near Tg in a series of neat polyalcohols by means of dielectric spectroscopy and 2H NMR. From glycerol to threitol, xylitol, and sorbitol the appearance of the secondary relaxation changes gradually from a wing-type scenario to a pronounced β peak. It is found that in sorbitol the dynamics of the whole molecule contributes equally to the β process, while in glycerol the hydrogen bond forming OH groups remain rather rigid compared to the hydrogens bonded to the carbon skeleton.

  3. Transverse Domain Wall Profile for Spin Logic Applications

    PubMed Central

    Goolaup, S.; Ramu, M.; Murapaka, C.; Lew, W. S.

    2015-01-01

    Domain wall (DW) based logic and memory devices require precise control and manipulation of DW in nanowire conduits. The topological defects of Transverse DWs (TDW) are of paramount importance as regards to the deterministic pinning and movement of DW within complex networks of conduits. In-situ control of the DW topological defects in nanowire conduits may pave the way for novel DW logic applications. In this work, we present a geometrical modulation along a nanowire conduit, which allows for the topological rectification/inversion of TDW in nanowires. This is achieved by exploiting the controlled relaxation of the TDW within an angled rectangle. Direct evidence of the logical operation is obtained via magnetic force microscopy measurement. PMID:25900455

  4. Stress Relaxation of Interim Restoratives.

    DTIC Science & Technology

    1978-05-18

    unmodified zinc oxide- eugenol cement were more favorable than those of IRM and Cavit. The plastic behavior of gutta-percha temporary stopping precluded assessment of its relaxation at temperatures in excess of 22P C. (Author)

  5. Relaxation Pathways in Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Gallino, Isabella; Busch, Ralf

    2017-09-01

    At temperatures below the glass transition temperature, physical properties of metallic glasses, such as density, viscosity, electrical resistivity or enthalpy, slowly evolve with time. This is the process of physical aging that occurs among all types of glasses and leads to structural changes at the microscopic level. Even though the relaxation pathways are ruled by thermodynamics as the glass attempts to re-attain thermodynamic equilibrium, they are steered by sluggish kinetics at the microscopic level. Understanding the structural and dynamic pathways of the relaxing glassy state is still one of the grand challenges in materials physics. We review some of the recent experimental advances made in understanding the nature of the relaxation phenomenon in metallic glasses and its implications to the macroscopic and microscopic properties changes of the relaxing glass.

  6. Relaxation labeling using modular operators

    SciTech Connect

    Duncan, J.S.; Frei, W.

    1983-01-01

    Probabilistic relaxation labeling has been shown to be useful in image processing, pattern recognition, and artificial intelligence. The approaches taken to date have been encumbered with computationally extensive summations which generally prevent real-time operation and/or easy hardware implementation. The authors present a new and unique approach to the relaxation labeling problem using modular, VLSI-oriented hierarchical complex operators. One of the fundamental concepts of this work is the representation of the probability distribution of the possible labels for a given object (pixel) as an ellipse, which may be summed with neighboring object's distribution ellipses, resulting in a new, relaxed label space. The mathematical development of the elliptical approach will be presented and compared to more classical approaches, and a hardware block diagram that shows the implementation of the relaxation scheme using vlsi chips will be presented. Finally, results will be shown which illustrate applications of the modular scheme, iteratively, to both edges and lines. 13 references.

  7. Relaxation behavior of glassy selenium

    NASA Astrophysics Data System (ADS)

    Svoboda, Roman; Pustková, Pavla; Málek, Jiří

    2007-05-01

    The dynamics of the glass transition of amorphous selenium was investigated by using differential scanning calorimeter. The heat capacity data were analyzed applying the phenomenological Tool Narayanaswamy Moynihan (TNM) model in order to describe the relaxation behavior of a-Se. The TNM parameters were evaluated by fitting the enthalpic cycles and also one isothermal experiment. Furthermore, peak-shift method and several other methods of evaluating the TNM parameters were applied to confirm the results of curve fitting. The results are compared with the other published enthalpy and viscosity data, volume and enthalpy relaxation are compared on account of our previous mercury dilatometry measurements. We found out that the pre-exponential factor A and the apparent activation energy Δh* of structural relaxation are similar for volume and enthalpy relaxation and Δh* is very close to the activation energy of viscous flow.

  8. Relaxation Dynamics in Heme Proteins.

    NASA Astrophysics Data System (ADS)

    Scholl, Reinhard Wilhelm

    A protein molecule possesses many conformational substates that are likely arranged in a hierarchy consisting of a number of tiers. A hierarchical organization of conformational substates is expected to give rise to a multitude of nonequilibrium relaxation phenomena. If the temperature is lowered, transitions between substates of higher tiers are frozen out, and relaxation processes characteristic of lower tiers will dominate the observational time scale. This thesis addresses the following questions: (i) What is the energy landscape of a protein? How does the landscape depend on the environment such as pH and viscosity, and how can it be connected to specific structural parts? (ii) What relaxation phenomena can be observed in a protein? Which are protein specific, and which occur in other proteins? How does the environment influence relaxations? (iii) What functional form best describes relaxation functions? (iv) Can we connect the motions to specific structural parts of the protein molecule, and are these motions important for the function of the protein?. To this purpose, relaxation processes after a pressure change are studied in carbonmonoxy (CO) heme proteins (myoglobin-CO, substrate-bound and substrate-free cytochrome P450cam-CO, chloroperoxidase-CO, horseradish peroxidase -CO) between 150 K and 250 K using FTIR spectroscopy to monitor the CO bound to the heme iron. Two types of p -relaxation experiments are performed: p-release (200 to ~eq40 MPa) and p-jump (~eq40 to 200 MPa) experiments. Most of the relaxations fall into one of three groups and are characterized by (i) nonexponential time dependence and non-Arrhenius temperature dependence (FIM1( nu), FIM1(Gamma)); (ii) exponential time dependence and non-Arrhenius temperature dependence (FIM0(A_{i}to A_{j})); exponential time dependence and Arrhenius temperature dependence (FIMX( nu)). The influence of pH is studied in myoglobin-CO and shown to have a strong influence on the substate population of the

  9. Transitions, transversions, and the molecular evolutionary clock.

    PubMed

    Jukes, T H

    1987-01-01

    Nucleotide substitutions in the form of transitions (purine-purine or pyrimidine-pyrimidine interchanges) and transversions (purine-pyrimidine interchanges) occur during evolution and may be compiled by aligning the sequences of homologous genes. Referring to the genetic code tables, silent transitions take place in third positions of codons in family boxes and two-codon sets. Silent transversions in third positions occur only in family boxes, except for A = C transversions between AGR and CGR arginine codons (R = A or G). Comparisons of several protein genes have been made, and various subclasses of transitional and transversional nucleotide substitutions have been compiled. Considerable variations occur among the relative proportions of transitions and transversions. Such variations could possibly be caused by mutator genes, favoring either transitions or, conversely, transversions, during DNA replication. At earlier stages of evolutionary divergence, transitions are usually more frequent, but there are exceptions. No indication was found that transversions usually originate from multiple substitutions in transitions.

  10. Relaxation processes in Aeolian transport

    NASA Astrophysics Data System (ADS)

    Selmani, Houssem; Valance, Alexandre; Ould El Moctar, Ahmed; Dupont, Pascal; Zegadi, Rabah

    2017-06-01

    We investigate experimentally the relaxation process toward the equilibrium regime of saltation transport in the context of spatial inhomogeneous conditions. The relaxation length associated to this process is an important length in aeolian transport. This length stands for the distance needed for the particle flux to adapt to a change in flow conditions or in the boundary conditions at the bed. Predicting the value of this length under given conditions of transport remains an open and important issue. We conducted wind tunnel experiments to document the influence of the upstream particle flux and wind speed on the relaxation process toward the saturated transport state. In the absence of upstream particle flux, data show that the relaxation length is independent of the wind strength (except close to the threshold of transport). In contrast, in the case of a finite upstream flux, the relaxation length exhibits a clear increase with increasing air flow velocity. Moreover, in the latter the relaxation is clearly non-monotonic and presents an overshoot.

  11. Vacancy Relaxation in Cubic Crystals

    NASA Technical Reports Server (NTRS)

    Girifalco, L. A.; Weizer, V. G.

    1960-01-01

    The configuration of the atoms surrounding a vacancy in four face-centered cubic and three body-centered cubic metals has been computed, using a pairwise, central-force model in which the energy of interaction between two atoms was taken to have the form of a Morse function. Only radial relaxations were considered. The first and second nearest-neighbor relaxations for the face-centered systems were found to be: Pb (1.42,-0.43), Ni (2.14,-0.39), Cu(2.24,-0.40) and Ca (2.73,-0.41, expressed in percentages of normal distances. For the body-centered systems the relaxations out to the fourth nearest neighbors to the vacancy were: Fe (6.07,-2.12, -0.25, -), Ba (7.85, -2.70, 0.70, -0.33) and Na (10.80, -3.14, 3.43, -0.20). The positive signs indicate relaxation toward the vacancy and the negative signs indicate relaxation away from the vacancy. The energies of relaxation (eV) are: Pb (0.162), Ni (0.626), Cu (0.560), Ca (0.400), Fe (1.410), Ba (0.950) and Na (0.172).

  12. Transverse shift in Andreev reflection

    NASA Astrophysics Data System (ADS)

    Liu, Ying; Yu, Zhi-Ming; Yang, Shengyuan A.

    2017-09-01

    An incoming electron is reflected back as a hole at a normal-metal-superconductor interface, a process known as Andreev reflection. We predict that there exists a universal transverse shift in this process due to the effect of spin-orbit coupling in the normal metal. Particularly, using both the scattering approach and the argument of angular momentum conservation, we demonstrate that the shifts are pronounced for lightly doped Weyl semimetals, and are opposite for incoming electrons with different chirality, generating a chirality-dependent Hall effect for the reflected holes. The predicted shift is not limited to Weyl systems, but exists for a general three-dimensional spin-orbit-coupled metal interfaced with a superconductor.

  13. Transversal magnetoresistance in Weyl semimetals

    NASA Astrophysics Data System (ADS)

    Klier, J.; Gornyi, I. V.; Mirlin, A. D.

    2015-11-01

    We explore theoretically the magnetoresistivity of three-dimensional Weyl and Dirac semimetals in transversal magnetic fields within two alternative models of disorder: (i) short-range impurities and (ii) charged (Coulomb) impurities. Impurity scattering is treated using the self-consistent Born approximation. We find that an unusual broadening of Landau levels leads to a variety of regimes of the resistivity scaling in the temperature-magnetic field plane. In particular, the magnetoresistance is nonmonotonous for the white-noise disorder model. For H →0 the magnetoresistance for short-range impurities vanishes in a nonanalytic way as H1 /3. In the limits of strongest magnetic fields H , the magnetoresistivity vanishes as 1 /H for pointlike impurities, while it is linear and positive in the model with Coulomb impurities.

  14. Transverse section radionuclide scanning system

    DOEpatents

    Kuhl, David E.; Edwards, Roy Q.

    1976-01-01

    This invention provides a transverse section radionuclide scanning system for high-sensitivity quantification of brain radioactivity in cross-section picture format in order to permit accurate assessment of regional brain function localized in three-dimensions. High sensitivity crucially depends on overcoming the heretofore known raster type scanning, which requires back and forth detector movement involving dead-time or partial enclosure of the scan field. Accordingly, this invention provides a detector array having no back and forth movement by interlaced detectors that enclose the scan field and rotate as an integral unit around one axis of rotation in a slip ring that continuously transmits the detector data by means of laser emitting diodes, with the advantages that increased amounts of data can be continuously collected, processed and displayed with increased sensitivity according to a suitable computer program.

  15. Transverse-longitudinal integrated resonator

    DOEpatents

    Hutchinson, Donald P [Knoxville, TN; Simpson, Marcus L [Knoxville, TN; Simpson, John T [Knoxville, TN

    2003-03-11

    A transverse-longitudinal integrated optical resonator (TLIR) is disclosed which includes a waveguide, a first and a second subwavelength resonant grating in the waveguide, and at least one photonic band gap resonant structure (PBG) in the waveguide. The PBG is positioned between the first and second subwavelength resonant gratings. An electro-optic waveguide material may be used to permit tuning the TLIR and to permit the TLIR to perform signal modulation and switching. The TLIR may be positioned on a bulk substrate die with one or more electronic and optical devices and may be communicably connected to the same. A method for fabricating a TLIR including fabricating a broadband reflective grating is disclosed. A method for tuning the TLIR's transmission resonance wavelength is also disclosed.

  16. Transverse patterning and human amnesia.

    PubMed

    Rickard, Timothy C; Verfaellie, Mieke; Grafman, Jordan

    2006-10-01

    The transverse patterning (TP) task (A+ B-, B+ C-, C+ A-) has played a central role in testing the hypothesis that medial-temporal (and, in particular, hippocampal) brain damage selectively impairs learning on at least some classes of configural (i.e., nonlinear) learning tasks. Results in the animal and human literature generally support that hypothesis. Reed and Squire [Impaired transverse patterning in human amnesia is a special case of impaired memory for two-choice discrimination tasks. Behavioral Neuroscience, 113, 3-9, 1999], however, advanced an alternative account in which impaired TP performance in amnesia reflects a generic scaling artifact arising from the greater difficulty of the TP task compared to the elemental (i.e., linear) control task that is typically used. We begin with a critique of Reed and Squire, countering their conceptual arguments and showing that their results, when analyzed appropriately, support the configural deficit hypothesis. We then report results from eight new amnesic patients and controls on an improved version of the TP task. Despite substantial practice, accuracy of patients with bilateral hippocampal damage due to anoxia reached and maintained an asymptote of only 54% correct, well below the maximum accuracy obtainable (67%) in the absence of configural learning. A patient with selective bilateral damage to the anterior thalamic nuclei exhibited a TP accuracy asymptote that was near 67%, a pattern of two out of three correct consecutive trials, and a pattern of nearly always answering correctly for two of the three TP item pairs. These results are consistent with a set of unique and parameter-free predictions of the configural deficit hypothesis.

  17. All-Aluminum Transverse Platelet Injector

    DTIC Science & Technology

    1978-01-25

    to the low density material. The 1xx$nafter described lightweight platelet injector includes an aluminum transverse platelet faceplate joined to an... aluminum body 15 with the electron beam 20 welds 21. This allows the fabrication of an all aluminum transverse platelet iinjector capable of replacing the...1 87 1-93 Serial No _ 872,?193 Filing 1)’ 25Jan 78( * Inventg/ Samuel E./Adair --: i - ------ NOC E . . . / All- Aluminum Transverse Platelet

  18. TRANSVERSE POLARIZATION DISTRIBUTION AND FRAGMENTATION FUNCTIONS

    SciTech Connect

    BOER,D.

    2000-04-11

    The authors discuss transverse polarization distribution and fragmentation functions, in particular, T-odd functions with transverse momentum dependence, which might be relevant for the description of single transverse spin asymmetries. The role of intrinsic transverse momentum in the expansion in inverse powers of the hard scale is elaborated upon. The sin {phi} single spin asymmetry in the process e {rvec p} {r_arrow} e{prime} {pi}{sup +} X as recently reported by the HERMES Collaboration is investigated, in particular, by using the bag model.

  19. Relaxation schemes for Chebyshev spectral multigrid methods

    NASA Technical Reports Server (NTRS)

    Kang, Yimin; Fulton, Scott R.

    1993-01-01

    Two relaxation schemes for Chebyshev spectral multigrid methods are presented for elliptic equations with Dirichlet boundary conditions. The first scheme is a pointwise-preconditioned Richardson relaxation scheme and the second is a line relaxation scheme. The line relaxation scheme provides an efficient and relatively simple approach for solving two-dimensional spectral equations. Numerical examples and comparisons with other methods are given.

  20. A three-dimensional constitutive model for the stress relaxation of articular ligaments.

    PubMed

    Davis, Frances M; De Vita, Raffaella

    2014-06-01

    A new nonlinear constitutive model for the three-dimensional stress relaxation of articular ligaments is proposed. The model accounts for finite strains, anisotropy, and strain-dependent stress relaxation behavior exhibited by these ligaments. The model parameters are identified using published uniaxial stress-stretch and stress relaxation data on human medial collateral ligaments (MCLs) subjected to tensile tests in the fiber and transverse to the fiber directions (Quapp and Weiss in J Biomech Eng Trans ASME 120:757-763, 1998; Bonifasi-Lista et al. in J Orthop Res 23(1):67-76, 2005). The constitutive equation is then used to predict the nonlinear elastic and stress relaxation response of ligaments subjected to shear deformations in the fiber direction and transverse to the fiber direction, and an equibiaxial extension. A direct comparison with stress relaxation data collected by subjecting human MCLs to shear deformation in the fiber direction is presented in order to demonstrate the predictive capabilities of the model.

  1. Nanoscale relaxation oscillator

    DOEpatents

    Zettl, Alexander K.; Regan, Brian C.; Aloni, Shaul

    2009-04-07

    A nanoscale oscillation device is disclosed, wherein two nanoscale droplets are altered in size by mass transport, then contact each other and merge through surface tension. The device may also comprise a channel having an actuator responsive to mechanical oscillation caused by expansion and contraction of the droplets. It further has a structure for delivering atoms between droplets, wherein the droplets are nanoparticles. Provided are a first particle and a second particle on the channel member, both being made of a chargeable material, the second particle contacting the actuator portion; and electrodes connected to the channel member for delivering a potential gradient across the channel and traversing the first and second particles. The particles are spaced apart a specified distance so that atoms from one particle are delivered to the other particle by mass transport in response to the potential (e.g. voltage potential) and the first and second particles are liquid and touch at a predetermined point of growth, thereby causing merging of the second particle into the first particle by surface tension forces and reverse movement of the actuator. In a preferred embodiment, the channel comprises a carbon nanotube and the droplets comprise metal nanoparticles, e.g. indium, which is readily made liquid.

  2. The influence of the counterion on the relaxation of polyacrylate deuterons

    NASA Astrophysics Data System (ADS)

    Van Rijn, C. J. M.; Maat, A. J.; De Bleijser, J.; Leyte, J. C.

    1987-03-01

    Relaxation rates of 2H methylene polyacrylate solutions have been determined for five different types of monovalent counter-ions: tetramethylammonium (TMA) and four alkali ions, Li, Na, K and Cs. TMA influences the polymer 2H relaxation rates in a way that differs qualitatively from the effect of the alkali counterions. In the presence of TMA the transverse rates of the polymer nuclei are increased relative to their values in the presence of alkali ions. For the longitudinal rates another effect is observed, the rates are larger for Li and Na and essentially the same for K, Cs and TMA.

  3. Nuclear magnetic relaxation by the dipolar EMOR mechanism: Multi-spin systems.

    PubMed

    Chang, Zhiwei; Halle, Bertil

    2017-08-28

    In aqueous systems with immobilized macromolecules, including biological tissues, the longitudinal spin relaxation of water protons is primarily induced by exchange-mediated orientational randomization (EMOR) of intra- and intermolecular magnetic dipole-dipole couplings. Starting from the stochastic Liouville equation, we have previously developed a rigorous EMOR relaxation theory for dipole-coupled two-spin and three-spin systems. Here, we extend the stochastic Liouville theory to four-spin systems and use these exact results as a guide for constructing an approximate multi-spin theory, valid for spin systems of arbitrary size. This so-called generalized stochastic Redfield equation (GSRE) theory includes the effects of longitudinal-transverse cross-mode relaxation, which gives rise to an inverted step in the relaxation dispersion profile, and coherent spin mode transfer among solid-like spins, which may be regarded as generalized spin diffusion. The GSRE theory is compared to an existing theory, based on the extended Solomon equations, which does not incorporate these phenomena. Relaxation dispersion profiles are computed from the GSRE theory for systems of up to 16 protons, taken from protein crystal structures. These profiles span the range from the motional narrowing limit, where the coherent mode transfer plays a major role, to the ultra-slow motion limit, where the zero-field rate is closely related to the strong-collision limit of the dipolar relaxation rate. Although a quantitative analysis of experimental data is beyond the scope of this work, it is clear from the magnitude of the predicted relaxation rate and the shape of the relaxation dispersion profile that the dipolar EMOR mechanism is the principal cause of water-(1)H low-field longitudinal relaxation in aqueous systems of immobilized macromolecules, including soft biological tissues. The relaxation theory developed here therefore provides a basis for molecular-level interpretation of endogenous

  4. Nuclear magnetic relaxation by the dipolar EMOR mechanism: Multi-spin systems

    NASA Astrophysics Data System (ADS)

    Chang, Zhiwei; Halle, Bertil

    2017-08-01

    In aqueous systems with immobilized macromolecules, including biological tissues, the longitudinal spin relaxation of water protons is primarily induced by exchange-mediated orientational randomization (EMOR) of intra- and intermolecular magnetic dipole-dipole couplings. Starting from the stochastic Liouville equation, we have previously developed a rigorous EMOR relaxation theory for dipole-coupled two-spin and three-spin systems. Here, we extend the stochastic Liouville theory to four-spin systems and use these exact results as a guide for constructing an approximate multi-spin theory, valid for spin systems of arbitrary size. This so-called generalized stochastic Redfield equation (GSRE) theory includes the effects of longitudinal-transverse cross-mode relaxation, which gives rise to an inverted step in the relaxation dispersion profile, and coherent spin mode transfer among solid-like spins, which may be regarded as generalized spin diffusion. The GSRE theory is compared to an existing theory, based on the extended Solomon equations, which does not incorporate these phenomena. Relaxation dispersion profiles are computed from the GSRE theory for systems of up to 16 protons, taken from protein crystal structures. These profiles span the range from the motional narrowing limit, where the coherent mode transfer plays a major role, to the ultra-slow motion limit, where the zero-field rate is closely related to the strong-collision limit of the dipolar relaxation rate. Although a quantitative analysis of experimental data is beyond the scope of this work, it is clear from the magnitude of the predicted relaxation rate and the shape of the relaxation dispersion profile that the dipolar EMOR mechanism is the principal cause of water-1H low-field longitudinal relaxation in aqueous systems of immobilized macromolecules, including soft biological tissues. The relaxation theory developed here therefore provides a basis for molecular-level interpretation of endogenous soft

  5. Evolution of the helicity and transversity Transverse-Momentum-Dependent parton distributions

    SciTech Connect

    Prokudin, Alexey; Bacchetta, Alessandro

    2013-10-01

    We examine the QCD evolution of the helicity and transversity parton distribution functions when including also their dependence on transverse momentum. Using an appropriate definition of these polarized transverse momentum distributions (TMDs), we describe their dependence on the factorization scale and rapidity cutoff, which is essential for phenomenological applications.

  6. Evolution of the helicity and transversity Transverse-Momentum-Dependent parton distributions

    SciTech Connect

    Prokudin, Alexei; Bacchetta, Alessandro

    2013-07-01

    We examine the QCD evolution of the helicity and transversity parton distribution functions when including also their dependence on transverse momentum. Using an appropriate definition of these polarized transverse momentum distributions (TMDs), we describe their dependence on the factorization scale and rapidity cutoff, which is essential for phenomenological applications.

  7. Ultraviolet and visible Brillouin scattering study of viscous relaxation in 3-methylpentane down to the glass transition

    NASA Astrophysics Data System (ADS)

    Benassi, P.; Nardone, M.; Giugni, A.

    2012-09-01

    Brillouin light scattering spectra from transverse and longitudinal acoustic waves in liquid and supercooled 3-methylpentane have been collected from room temperature down to 80 K, just above the glass transition. Spectra at different wave vectors have been obtained using 532 nm and 266 nm excitation. We found evidence of a shear relaxation with a characteristic time of 100 s at the glass transition which only partly accounts for the relaxation observed in the propagation and attenuation of the longitudinal modes. The inclusion of a relaxing bulk viscosity contribution with a relaxation time of the order of 102 ns at the glass transition is found to adequately reproduce the experimental data including transient grating data at a much lower frequency. A consistent picture of relaxed shear and bulk moduli as a function of temperature is derived. These two quantities are found to be related by a linear relation suggesting that a Cauchy-like relation holds also above the glass transition.

  8. Cladding For Transversely-Pumped Laser Rod

    NASA Technical Reports Server (NTRS)

    Byer, Robert L.; Fan, Tso Yee

    1989-01-01

    Combination of suitable dimensioning and cladding of neodymium:yttrium aluminum garnet of similar solid-state laser provides for more efficient utilization of transversely-incident pump light from diode lasers. New design overcomes some of limitations of longitudinal- and older transverse-pumping concepts and promotes operation at higher output powers in TEM00 mode.

  9. Transverse instability at the recycler ring

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2004-10-01

    Sporadic transverse instabilities have been observed at the Fermilab Recycler Ring leading to increase in transverse emittances and beam loss. The driving source of these instabilities has been attributed to the resistive-wall impedance with space-charge playing an important role in suppressing Landau damping. Growth rates of the instabilities are computed. Remaining problems are discussed.

  10. Cladding For Transversely-Pumped Laser Rod

    NASA Technical Reports Server (NTRS)

    Byer, Robert L.; Fan, Tso Yee

    1989-01-01

    Combination of suitable dimensioning and cladding of neodymium:yttrium aluminum garnet of similar solid-state laser provides for more efficient utilization of transversely-incident pump light from diode lasers. New design overcomes some of limitations of longitudinal- and older transverse-pumping concepts and promotes operation at higher output powers in TEM00 mode.

  11. Acute transverse myelopathy complicating systemic lupus erythematosus.

    PubMed Central

    Propper, D J; Bucknall, R C

    1989-01-01

    A sixteen year old girl with systemic lupus erythematosus developed acute transverse myelopathy. She was treated with high dose steroids, cyclophosphamide, and plasma exchange and regained partial neurological function. Previous descriptions of transverse myelopathy complicating systemic lupus erythematosus are reviewed, with particular reference to the efficacy of high dose steroid treatment. PMID:2662918

  12. Transverse impedance localization using intensity dependent optics

    SciTech Connect

    Calaga,R.; Arduini, G.; Metral, E.; Papotti, G.; Quatraro, D.; Rumolo, G.; Salvant, B.; Tomas, R.

    2009-05-04

    Measurements of transverse impedance in the SPS to track the evolution over the last few years show discrepancies compared to the analytical estimates of the major contributors. Recent measurements to localize the major sources of the transverse impedance using intensity dependent optics are presented. Some simulations using HEADTAIL to understand the limitations of the reconstruction and related numerical aspects are also discussed.

  13. Laparoscopic correction of right transverse colostomy prolapse.

    PubMed

    Gundogdu, Gokhan; Topuz, Ufuk; Umutoglu, Tarik

    2013-08-01

    Colostomy prolapse is a frequently seen complication of transverse colostomy. In one child with recurrent stoma prolapse, we performed a loop-to-loop fixation and peritoneal tethering laparoscopically. No prolapse had recurred at follow-up. Laparoscopic repair of transverse colostomy prolapse seems to be a less invasive method than other techniques.

  14. Transverse Mercator Projection Via Elliptic Integrals

    NASA Technical Reports Server (NTRS)

    Wallis, David E.

    1992-01-01

    Improved method of construction of U.S. Army's universal transverse Mercator grid system based on Gauss-Kruger transverse Mercator projection and on use of elliptic integrals of second kind. Method can be used to map entire northern or southern hemisphere with respect to single principal meridian.

  15. Unravelling the mechanisms of vibrational relaxation in solution.

    PubMed

    Grubb, Michael P; Coulter, Philip M; Marroux, Hugo J B; Orr-Ewing, Andrew J; Ashfold, Michael N R

    2017-04-01

    We present a systematic study of the mode-specific vibrational relaxation of NO2 in six weakly-interacting solvents (perfluorohexane, perfluoromethylcyclohexane, perfluorodecalin, carbon tetrachloride, chloroform, and d-chloroform), chosen to elucidate the dominant energy transfer mechanisms in the solution phase. Broadband transient vibrational absorption spectroscopy has allowed us to extract quantum state-resolved relaxation dynamics of the two distinct NO2 fragments produced from the 340 nm photolysis of N2O4 → NO2(X) + NO2(A) and their separate paths to thermal equilibrium. Distinct relaxation pathways are observed for the NO2 bending and stretching modes, even at energies as high as 7000 cm(-1) above the potential minimum. Vibrational energy transfer is governed by different interaction mechanisms in the various solvent environments, and proceeds with timescales ranging from 20-1100 ps. NO2 relaxation rates in the perfluorocarbon solvents are identical despite differences in acceptor mode state densities, infrared absorption cross sections, and local solvent structure. Vibrational energy is shown to be transferred to non-vibrational solvent degrees of freedom (V-T) through impulsive collisions with the perfluorocarbon molecules. Conversely, NO2 relaxation in chlorinated solvents is reliant on vibrational resonances (V-V) while V-T energy transfer is inefficient and thermal excitation of the surrounding solvent molecules inhibits faster vibrational relaxation through direct complexation. Intramolecular vibrational redistribution allows the symmetric stretch of NO2 to act as a gateway for antisymmetric stretch energy to exit the molecule. This study establishes an unprecedented level of detail for the cooling dynamics of a solvated small molecule, and provides a benchmark system for future theoretical studies of vibrational relaxation processes in solution.

  16. Electrodeposited, Transverse Nanowire Electroluminescent Junctions.

    PubMed

    Qiao, Shaopeng; Xu, Qiang; Dutta, Rajen K; Le Thai, Mya; Li, Xiaowei; Penner, Reginald M

    2016-09-27

    The preparation by electrodeposition of transverse nanowire electroluminescent junctions (tn-ELJs) is described, and the electroluminescence (EL) properties of these devices are characterized. The lithographically patterned nanowire electrodeposition process is first used to prepare long (millimeters), linear, nanocrystalline CdSe nanowires on glass. The thickness of these nanowires along the emission axis is 60 nm, and the width, wCdSe, along the electrical axis is adjustable from 100 to 450 nm. Ten pairs of nickel-gold electrical contacts are then positioned along the axis of this nanowire using lithographically directed electrodeposition. The resulting linear array of nickel-CdSe-gold junctions produces EL with an external quantum efficiency, EQE, and threshold voltage, Vth, that depend sensitively on wCdSe. EQE increases with increasing electric field and also with increasing wCdSe, and Vth also increases with wCdSe and, therefore, the electrical resistance of the tn-ELJs. Vth down to 1.8(±0.2) V (for wCdSe ≈ 100 nm) and EQE of 5.5(±0.5) × 10(-5) (for wCdSe ≈ 450 nm) are obtained. tn-ELJs produce a broad EL emission envelope, spanning the wavelength range from 600 to 960 nm.

  17. Nuclear magnetic relaxation studies of semiconductor nanocrystals and solids

    SciTech Connect

    Sachleben, Joseph Robert

    1993-09-01

    Semiconductor nanocrystals, small biomolecules, and 13C enriched solids were studied through the relaxation in NMR spectra. Surface structure of semiconductor nanocrystals (CdS) was deduced from high resolution 1H and 13C liquid state spectra of thiophenol ligands on the nanocrystal surfaces. The surface coverage by thiophenol was found to be low, being 5.6 and 26% for nanocrystal radii of 11.8 and 19.2 Å. Internal motion is estimated to be slow with a correlation time > 10-8 s-1. The surface thiophenol ligands react to form a dithiophenol when the nanocrystals were subjected to O2 and ultraviolet. A method for measuring 14N-1H J-couplings is demonstrated on pyridine and the peptide oxytocin; selective 2D T1 and T2 experiments are presented for measuring relaxation times in crowded spectra with overlapping peaks in 1D, but relaxation effects interfere. Possibility of carbon-carbon cross relaxation in 13C enriched solids is demonstrated by experiments on zinc acetate and L-alanine.

  18. Nuclear magnetic relaxation studies of semiconductor nanocrystals and solids

    NASA Astrophysics Data System (ADS)

    Sachleben, J. R.

    1993-09-01

    Semiconductor nanocrystals, small biomolecules, and C-13 enriched solids were studied through the relaxation in NMR spectra. Surface structure of semiconductor nanocrystals (CdS) was deduced from high resolution H-1 and C-13 liquid state spectra of thiophenol ligands on the nanocrystal surfaces. The surface coverage by thiophenol was found to be low, being 5.6 and 26% for nanocrystal radii of 11.8 and 19.2 angstrom. Internal motion is estimated to be slow with a correlation time greater than 10(exp -8) s(exp -1). The surface thiophenol ligands react to form a dithiophenol when the nanocrystals were subjected to O2 and ultraviolet. A method for measuring (N-14)-(H-1) J-couplings is demonstrated on pyridine and the peptide oxytocin; selective 2D T(sub 1) and T(sub 2) experiments are presented for measuring relaxation times in crowded spectra with overlapping peaks in 1D, but relaxation effects interfere. Possibility of carbon-carbon cross relaxation in C-13 enriched solids is demonstrated by experiments on zinc acetate and L-alanine.

  19. Density matrix solutions for the susceptibilities of a three-level system with arbitrary relaxation rates and field strengths

    NASA Technical Reports Server (NTRS)

    Ryan, J. C.; Lawandy, N. M.

    1986-01-01

    The susceptibilities for a three-level system with arbitrary pump and signal field strengths are derived for arbitrary longitudinal and transverse relaxation rates. The results are of interest in connection with the calculation of the Raman gain in systems where resonance enhancement plays a dominant role.

  20. Transversity from two pion interference fragmentation

    SciTech Connect

    She Jun; Huang Yang; Barone, Vincenzo; Ma Boqiang

    2008-01-01

    We present calculation on the azimuthal spin asymmetries for pion pair production in semi-inclusive deep inelastic scattering (SIDIS) process at both HERMES and COMPASS kinematics, with transversely polarized proton, deuteron, and neutron targets. We calculate the asymmetry by adopting a set of parametrization of the interference fragmentation functions and two different models for the transversity. We find that the result for the proton target is insensitive to the approaches of the transversity but more helpful to understand the interference fragmentation functions. However, for the neutron target, which can be obtained through using deuteron and {sup 3}He targets, we find different predictions for different approaches to the transversity. Thus probing the two pion interference fragmentation from the neutron can provide us more interesting information on the transversity.

  1. Transverse Spin Effects in SIDIS at COMPASS

    SciTech Connect

    Joosten, Rainer

    2009-12-17

    The measurement of single spin asymmetries in semi-inclusive deep-inelastic scattering (SIDIS) on a transversely polarized target is an important part of the COMPASS physics program. It allows us to investigate the transversity distribution functions as well as transverse momentum dependent distribution functions by measuring azimuthal asymmetries in the hadron production. After COMPASS took data in the years 2002-2004 by scattering a 160 GeV/c muon beam off a transversely polarized deuteron ({sup 6}LiD) target, in 2007 additional data was collected on a transversely polarized proton (NH{sub 3}) target. In this contribution, the latest results on the Collins and Sivers asymmetries in single hadron production as well as two-hadron asymmetries from the analysis of the proton data are presented and compared with existing model predictions.

  2. Recent COMPASS Results on Transverse Physics

    SciTech Connect

    Iwata, Takahiro; Collaboration: COMPASS Collaboration

    2011-12-14

    The investigation of transverse spin and transverse momentum dependent effects in deep inelastic scattering of muons off nucleons is one of the key physics programs of the COMPASS collaboration at CERN. We have investigated the effects from the data obtained with a polarized proton target. In order to access the transversity distribution function, following channels have been analyzed: The azimuthal distribution of single hadrons, the azimuthal dependence of the plane containing hadron pairs, and the measurement of the transverse polarization of lambda hyperons in the final state. The Sivers distribution function which is one of the transverse momentum dependent functions has been investigated also from the azimuthal distribution of single hadrons. Azimuthal asymmetries in unpolarized deep inelastic scattering give important information on the inner structure of the nucleon to access the so-far unmeasured Boer-Mulders function. We have measured these asymmetries using spin-averaged {sup 6}L{sub i}D.

  3. Relaxed Poisson cure rate models.

    PubMed

    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.

  4. Ellipsoidal Relaxation of Deformed Vesicles

    NASA Astrophysics Data System (ADS)

    Yu, Miao; Lira, Rafael B.; Riske, Karin A.; Dimova, Rumiana; Lin, Hao

    2015-09-01

    Theoretical analysis and experimental quantification on the ellipsoidal relaxation of vesicles are presented. The current work reveals the simplicity and universal aspects of this process. The Helfrich formula is shown to apply to the dynamic relaxation of moderate-to-high tension membranes, and a closed-form solution is derived which predicts the vesicle aspect ratio as a function of time. Scattered data are unified by a time scale, which leads to a similarity behavior, governed by a distinctive solution for each vesicle type. Two separate regimes in the relaxation are identified, namely, the "entropic" and the "constant-tension" regimes. The bending rigidity and the initial membrane tension can be simultaneously extracted from the data analysis, posing the current approach as an effective means for the mechanical analysis of biomembranes.

  5. Multigrid Methods for Mesh Relaxation

    SciTech Connect

    O'Brien, M J

    2006-06-12

    When generating a mesh for the initial conditions for a computer simulation, you want the mesh to be as smooth as possible. A common practice is to use equipotential mesh relaxation to smooth out a distorted computational mesh. Typically a Laplace-like equation is set up for the mesh coordinates and then one or more Jacobi iterations are performed to relax the mesh. As the zone count gets really large, the Jacobi iteration becomes less and less effective and we are stuck with our original unrelaxed mesh. This type of iteration can only damp high frequency errors and the smooth errors remain. When the zone count is large, almost everything looks smooth so relaxation cannot solve the problem. In this paper we examine a multigrid technique which effectively smooths out the mesh, independent of the number of zones.

  6. Peeling mode relaxation ELM model

    SciTech Connect

    Gimblett, C. G.

    2006-11-30

    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.

  7. A mixed relaxed clock model

    PubMed Central

    2016-01-01

    Over recent years, several alternative relaxed clock models have been proposed in the context of Bayesian dating. These models fall in two distinct categories: uncorrelated and autocorrelated across branches. The choice between these two classes of relaxed clocks is still an open question. More fundamentally, the true process of rate variation may have both long-term trends and short-term fluctuations, suggesting that more sophisticated clock models unfolding over multiple time scales should ultimately be developed. Here, a mixed relaxed clock model is introduced, which can be mechanistically interpreted as a rate variation process undergoing short-term fluctuations on the top of Brownian long-term trends. Statistically, this mixed clock represents an alternative solution to the problem of choosing between autocorrelated and uncorrelated relaxed clocks, by proposing instead to combine their respective merits. Fitting this model on a dataset of 105 placental mammals, using both node-dating and tip-dating approaches, suggests that the two pure clocks, Brownian and white noise, are rejected in favour of a mixed model with approximately equal contributions for its uncorrelated and autocorrelated components. The tip-dating analysis is particularly sensitive to the choice of the relaxed clock model. In this context, the classical pure Brownian relaxed clock appears to be overly rigid, leading to biases in divergence time estimation. By contrast, the use of a mixed clock leads to more recent and more reasonable estimates for the crown ages of placental orders and superorders. Altogether, the mixed clock introduced here represents a first step towards empirically more adequate models of the patterns of rate variation across phylogenetic trees. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’. PMID:27325829

  8. A mixed relaxed clock model.

    PubMed

    Lartillot, Nicolas; Phillips, Matthew J; Ronquist, Fredrik

    2016-07-19

    Over recent years, several alternative relaxed clock models have been proposed in the context of Bayesian dating. These models fall in two distinct categories: uncorrelated and autocorrelated across branches. The choice between these two classes of relaxed clocks is still an open question. More fundamentally, the true process of rate variation may have both long-term trends and short-term fluctuations, suggesting that more sophisticated clock models unfolding over multiple time scales should ultimately be developed. Here, a mixed relaxed clock model is introduced, which can be mechanistically interpreted as a rate variation process undergoing short-term fluctuations on the top of Brownian long-term trends. Statistically, this mixed clock represents an alternative solution to the problem of choosing between autocorrelated and uncorrelated relaxed clocks, by proposing instead to combine their respective merits. Fitting this model on a dataset of 105 placental mammals, using both node-dating and tip-dating approaches, suggests that the two pure clocks, Brownian and white noise, are rejected in favour of a mixed model with approximately equal contributions for its uncorrelated and autocorrelated components. The tip-dating analysis is particularly sensitive to the choice of the relaxed clock model. In this context, the classical pure Brownian relaxed clock appears to be overly rigid, leading to biases in divergence time estimation. By contrast, the use of a mixed clock leads to more recent and more reasonable estimates for the crown ages of placental orders and superorders. Altogether, the mixed clock introduced here represents a first step towards empirically more adequate models of the patterns of rate variation across phylogenetic trees.This article is part of the themed issue 'Dating species divergences using rocks and clocks'.

  9. Changes in Porcine Muscle Water Characteristics during Growth—An in Vitro Low-Field NMR Relaxation Study

    NASA Astrophysics Data System (ADS)

    Bertram, Hanne Christine; Rasmussen, Marianne; Busk, Hans; Oksbjerg, Niels; Karlsson, Anders Hans; Andersen, Henrik Jørgen

    2002-08-01

    This study investigates the effects of developmental stage and muscle type on the mobility and distribution of water within skeletal muscles, using low-field 1H-NMR transverse relaxation measurements in vitro on four different porcine muscles ( M. longissimus dorsi, M. semitendinosus, M. biceps femoris, M. vastus intermedius) from a total of 48 pigs slaughtered at various weight classes between 25 kg and 150 kg. Principal component analysis (PCA) revealed effects of both slaughter weight and muscle type on the transverse relaxation decay. Independent of developmental stage and muscle type, distributed exponential analysis of the NMR T 2 relaxation data imparted the existence of three distinct water populations, T 2b, T 21, and T 22, with relaxation times of approximately 1-10, 45-120, and 200-500 ms, respectively. The most profound change during muscle growth was a shift toward faster relaxation in the intermediate time constant, T 21. It decreased by approx. 24% in all four muscle types during the period from 25 to 150 kg live weight. Determination of dry matter, fat, and protein content in the muscles showed that the changes in relaxation time of the intermediate time constant, T 21, during growth should be ascribed mainly to a change in protein content, as the protein content explained 77% of the variation in the T 21 time constant. Partial least squares (PLS) regression revealed validated correlations in the region of 0.58 to 0.77 between NMR transverse relaxation data and muscle development for all the four muscle types, which indicates that NMR relaxation measurements may be used in the prediction of muscle developmental stage.

  10. CPMG relaxation rate dispersion in dipole fields around capillaries.

    PubMed

    Kurz, F T; Kampf, T; Buschle, L R; Heiland, S; Schlemmer, H-P; Bendszus, M; Ziener, C H

    2016-09-01

    Transverse relaxation rates for Carr-Purcell-Meiboom-Gill (CPMG) sequences increase with inter-echo time in presence of microscopic magnetic field inhomogeneities due to nuclear spin diffusion. For a weak field approximation that includes diffusion effects, the CPMG relaxation rate shift for proton diffusion around capillaries in muscle tissue can be expressed in terms of a frequency correlation function and the inter-echo time. The present work provides an analytical expression for the local relaxation rate shift that is dependent on local blood volume fraction, diffusion coefficient, capillary radius, susceptibility difference and inter-echo time. Asymptotic regions of the model are in agreement with previous modeling results of Brooks et al., Luz et al. and Ziener et al. In comparison with simulation data, the model shows an equal or better accuracy than established approximations. Also, model behavior coincides with experimental data for rat heart and skeletal muscle. The present work provides analytical tools to extract sub-voxel information about uniform capillary networks that can be used to study capillary organization or micro-circulatory remodeling.

  11. Leptogenesis via Higgs condensate relaxation

    NASA Astrophysics Data System (ADS)

    Yang, Louis; Pearce, Lauren; Kusenko, Alexander

    2015-08-01

    An epoch of Higgs relaxation may occur in the early universe during or immediately following postinflationary reheating. It has recently been pointed out that leptogenesis may occur in minimal extensions of the standard model during this epoch [A. Kusenko, L. Pearce, and L. Yang, Phys. Rev. Lett. 114, 061302 (2015)]. We analyze Higgs relaxation taking into account the effects of perturbative and nonperturbative decays of the Higgs condensate, and we present a detailed derivation of the relevant kinetic equations and of the relevant particle interaction cross sections. We identify the parameter space in which a sufficiently large asymmetry is generated.

  12. Analog circuits for relaxation networks.

    PubMed

    Card, H

    1993-12-01

    Selected examples are presented of recent advances, primarily from the U.S. and Canada, in analog circuits for relaxation networks. Relaxation networks having feedback connections exhibit potentially greater computational power per neuron than feedforward networks. They are also more poorly understood especially with respect to learning algorithms. Examples are described of analog circuits for (i) supervised learning in deterministic Boltzmann machines, (ii) unsupervised competitive learning and feature maps and (iii) networks with resistive grids for vision and audition tasks. We also discuss recent progress on in-circuit learning and synaptic weight storage mechanisms.

  13. Nuclear Spin Relaxation and Molecular Interactions of a Novel Triazolium-Based Ionic Liquid

    SciTech Connect

    Allen, Jesse J; Schneider, Yanika; Kail, Brian W; Luebke, David R; Nulwala, Hunaid; Damodaran, Krishnan

    2013-04-11

    Nuclear spin relaxation, small-angle X-ray scattering (SAXS), and electrospray ionization mass spectrometry (ESI-MS) techniques are used to determine supramolecular arrangement of 3-methyl-1-octyl-4-phenyl-1H-triazol-1,2,3-ium bis(trifluoromethanesulfonyl)imide [OMPhTz][Tf{sub 2}N], an example of a triazolium-based ionic liquid. The results obtained showed first-order thermodynamic dependence for nuclear spin relaxation of the anion. First-order relaxation dependence is interpreted as through-bond dipolar relaxation. Greater than first-order dependence was found in the aliphatic protons, aromatic carbons (including nearest neighbors), and carbons at the end of the aliphatic tail. Greater than first order thermodynamic dependence of spin relaxation rates is interpreted as relaxation resulting from at least one mechanism additional to through-bond dipolar relaxation. In rigid portions of the cation, an additional spin relaxation mechanism is attributed to anisotropic effects, while greater than first order thermodynamic dependence of the octyl side chain’s spin relaxation rates is attributed to cation–cation interactions. Little interaction between the anion and the cation was observed by spin relaxation studies or by ESI-MS. No extended supramolecular structure was observed in this study, which was further supported by MS and SAXS. nuclear Overhauser enhancement (NOE) factors are used in conjunction with spin–lattice relaxation time (T{sub 1}) measurements to calculate rotational correlation times for C–H bonds (the time it takes for the vector represented by the bond between the two atoms to rotate by one radian). The rotational correlation times are used to represent segmental reorientation dynamics of the cation. A combination of techniques is used to determine the segmental interactions and dynamics of this example of a triazolium-based ionic liquid.

  14. Angular momentum relaxation in atom-diatom dilute gas mixtures

    NASA Astrophysics Data System (ADS)

    Evans, Glenn T.

    1987-04-01

    The angular momentum relaxation cross sections for a diatomic molecule in a dilute atomic gas are estimated subject to the assumption that the intermolecular torque is dominated by the hard, impulsive contribution (evaluated using Boltzmann kinetic theory for nonspherical molecules). For carbon monoxide in a variety of gases, the kinetic theory derived contribution to the angular momentum cross section is in qualitative agreement with the experimental results of Jameson, Jameson, and Buchi.

  15. Transverse plane motion at the ankle joint.

    PubMed

    Nester, Christopher J; Findlow, Andrew F; Bowker, Peter; Bowden, Peter D

    2003-02-01

    The ankle is often considered to have little or no capacity to move in the transverse plane. This is clear in the persistent concept that it is the role of the subtalar joint to accommodate the transverse plane motion of the leg while the foot remains in a fixed transverse plane position on the floor. We present data from noninvasive in vivo study of the ankle subtalar complex during standing internal and external rotation of the leg and study of the ankle subtalar complex during walking. These data reinforce the results of cadaver study and invasive in vivo study of the ankle/subtalar complex. We suggest that the ankle is capable of considerable movement in the transverse plane (generally greater than 15 degrees) and that its role in the mechanism that allows the foot to remain in a fixed transverse plane position on the floor while the leg rotates in the transverse plane, is not simply the transfer of the transverse plane moment to the subtalar joint, but is accommodation of some of the necessary movement.

  16. Theory of nuclear magnetic relaxation

    NASA Technical Reports Server (NTRS)

    Mcconnell, J.

    1983-01-01

    A theory of nuclear magnetic interaction is based on the study of the stochastic rotation operator. The theory is applied explicitly to relaxation by anisotropic chemical shift and to spin-rotational interactions. It is applicable also to dipole-dipole and quadrupole interactions.

  17. "Stressing" Relaxation in the Classroom.

    ERIC Educational Resources Information Center

    Prager-Decker, Iris

    A rationale is offered for incorporating relaxation training in elementary school classroom activities. Cited are research studies which focus on the reaction of children to stressful life changes and resulting behavioral and physical disorders. A list is given of significant life events which may be factors in causing diseases or misbehavior in…

  18. Relaxation properties in classical diamagnetism

    NASA Astrophysics Data System (ADS)

    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.

  19. Distributed Relaxation for Conservative Discretizations

    NASA Technical Reports Server (NTRS)

    Diskin, Boris; Thomas, James L.

    2001-01-01

    A multigrid method is defined as having textbook multigrid efficiency (TME) if the solutions to the governing system of equations are attained in a computational work that is a small (less than 10) multiple of the operation count in one target-grid residual evaluation. The way to achieve this efficiency is the distributed relaxation approach. TME solvers employing distributed relaxation have already been demonstrated for nonconservative formulations of high-Reynolds-number viscous incompressible and subsonic compressible flow regimes. The purpose of this paper is to provide foundations for applications of distributed relaxation to conservative discretizations. A direct correspondence between the primitive variable interpolations for calculating fluxes in conservative finite-volume discretizations and stencils of the discretized derivatives in the nonconservative formulation has been established. Based on this correspondence, one can arrive at a conservative discretization which is very efficiently solved with a nonconservative relaxation scheme and this is demonstrated for conservative discretization of the quasi one-dimensional Euler equations. Formulations for both staggered and collocated grid arrangements are considered and extensions of the general procedure to multiple dimensions are discussed.

  20. Relaxation times estimation in MRI

    NASA Astrophysics Data System (ADS)

    Baselice, Fabio; Caivano, Rocchina; Cammarota, Aldo; Ferraioli, Giampaolo; Pascazio, Vito

    2014-03-01

    Magnetic Resonance Imaging is a very powerful techniques for soft tissue diagnosis. At the present, the clinical evaluation is mainly conducted exploiting the amplitude of the recorded MR image which, in some specific cases, is modified by using contrast enhancements. Nevertheless, spin-lattice (T1) and spin-spin (T2) relaxation times can play an important role in many pathology diagnosis, such as cancer, Alzheimer or Parkinson diseases. Different algorithms for relaxation time estimation have been proposed in literature. In particular, the two most adopted approaches are based on Least Squares (LS) and on Maximum Likelihood (ML) techniques. As the amplitude noise is not zero mean, the first one produces a biased estimator, while the ML is unbiased but at the cost of high computational effort. Recently the attention has been focused on the estimation in the complex, instead of the amplitude, domain. The advantage of working with real and imaginary decomposition of the available data is mainly the possibility of achieving higher quality estimations. Moreover, the zero mean complex noise makes the Least Square estimation unbiased, achieving low computational times. First results of complex domain relaxation times estimation on real datasets are presented. In particular, a patient with an occipital lesion has been imaged on a 3.0T scanner. Globally, the evaluation of relaxation times allow us to establish a more precise topography of biologically active foci, also with respect to contrast enhanced images.

  1. "Stressing" Relaxation in the Classroom.

    ERIC Educational Resources Information Center

    Prager-Decker, Iris

    A rationale is offered for incorporating relaxation training in elementary school classroom activities. Cited are research studies which focus on the reaction of children to stressful life changes and resulting behavioral and physical disorders. A list is given of significant life events which may be factors in causing diseases or misbehavior in…

  2. Ferroelectric Cathodes in Transverse Magnetic Fields

    SciTech Connect

    Alexander Dunaevsky; Yevgeny Raitses; Nathaniel J. Fisch

    2002-07-29

    Experimental investigations of a planar ferroelectric cathode in a transverse magnetic field up to 3 kGs are presented. It is shown that the transverse magnetic field affects differently the operation of ferroelectric plasma cathodes in ''bright'' and ''dark'' modes in vacuum. In the ''bright'' mode, when the surface plasma is formed, the application of the transverse magnetic field leads to an increase of the surface plasma density. In the ''dark'' mode, the magnetic field inhibits the development of electron avalanches along the surface, as it does similarly in other kinds of surface discharges in the pre-breakdown mode.

  3. Transverse Emittance Reduction with Tapered Foil

    SciTech Connect

    Jiao, Yi; Chao, Alex; Cai, Yunhai; /SLAC

    2011-12-09

    The idea of reducing transverse emittance with tapered energy-loss foil is proposed by J.M. Peterson in 1980s and recently by B. Carlsten. In this paper, we present the physical model of tapered energy-loss foil and analyze the emittance reduction using the concept of eigen emittance. The study shows that, to reduce transverse emittance, one should collimate at least 4% of particles which has either much low energy or large transverse divergence. The multiple coulomb scattering is not trivial, leading to a limited emittance reduction ratio. Small transverse emittances are of essential importance for the accelerator facilities generating free electron lasers, especially in hard X-ray region. The idea of reducing transverse emittance with tapered energy-loss foil is recently proposed by B. Carlsten [1], and can be traced back to J.M. Peterson's work in 1980s [2]. Peterson illustrated that a transverse energy gradient can be produced with a tapered energy-loss foil which in turn leads to transverse emittance reduction, and also analyzed the emittance growth from the associated multiple coulomb scattering. However, what Peterson proposed was rather a conceptual than a practical design. In this paper, we build a more complete physical model of the tapered foil based on Ref. [2], including the analysis of the transverse emittance reduction using the concept of eigen emittance and confirming the results by various numerical simulations. The eigen emittance equals to the projected emittance when there is no cross correlation in beam's second order moments matrix [3]. To calculate the eigen emittances, it requires only to know the beam distribution at the foil exit. Thus, the analysis of emittance reduction and the optics design of the subsequent beam line section can be separated. In addition, we can combine the effects of multiple coulomb scattering and transverse energy gradient together in the beam matrix and analyze their net effect. We find that,when applied to an

  4. Transverse Colon Diverticulitis with Calcified Fecalith

    PubMed Central

    Solak, Aynur; Solak, Ilhami; Genç, Berhan; Sahin, Neslin; Yalaz, Seyhan

    2013-01-01

    Left colonic diverticula are common in Western populations, whereas right colonic diverticulosis primarily occurs in Oriental populations. Diverticulitis of the transverse colon is very rare, with very few cases reported in the literature. Herein, we report a case of transverse colon diverticulitis caused by a calcified stone in a 69-year-old female. This was a solitary diverticulum. The signs and symptoms of the disease are similar to acute pancreatitis. To the best of our knowledge, this is the first report describing the MRI findings of a patient with trans-verse colon diverticulitis caused by a calcified stone. PMID:25610254

  5. TRANSVERSE SPIN AT PHENIX AND FUTURE PLANS.

    SciTech Connect

    MAKDISI,Y.

    2005-01-28

    The PHENIX experiment took data with transversely polarized proton beams in 2001-2002 and measured the transverse single spin asymmetries in inclusive neutral pion and non-identified charge hadrons at midrapidity and {radical} s = 200 GeV. The data near X{sub F} {approx} 0 cover a transverse momentum range from 0.5 to 5.0 GeV/c. The observed asymmetries are consistent with zero with good statistical accuracy. This paper presents the current work in light of earlier measurements at lower energies in this kinematic region and the future plans of the PHENIX detector.

  6. Transverse single bunch instability study on BEPC

    NASA Astrophysics Data System (ADS)

    Gao, J.; Sun, Y. P.

    2007-04-01

    In recent years, a lot of experiments were done on ESRF and ELETTRA to study the single bunch transverse instability. To prevent such instabilities on BEPCII in the future, experiments were made on the single bunch transverse instability threshold current versus the chromaticity on BEPC. By analyzing the experimental data based on the theory developed in [J. Gao, Nucl. Instr. and Meth. A 416 (1998) 186 (see also PAC97, Vancouver, Canada, 1997, p. 1605).], the transverse loss factor of BEPC and the corresponding scaling law are obtained.

  7. Relaxation processes in non-Debye dielectrics

    NASA Astrophysics Data System (ADS)

    Turik, A. V.; Bogatin, A. S.; Andreev, E. V.

    2011-12-01

    The specific features of the relaxation processes in non-Debye dielectrics have been investigated. The nature of the difference between the relaxation frequencies of the dielectric constant and dielectric loss (conductivity) has been explained. It has been shown that the average relaxation frequency of the conductivity is considerably (in some cases, by several orders of magnitude) higher than the relaxation frequency of the dielectric constant owing to an increase in the conductivity spectra of the statistical weight of the relaxation processes with short relaxation times.

  8. Novel itinerant transverse spin waves

    NASA Astrophysics Data System (ADS)

    Feldmann, John Delaney

    In 1956, Lev Davidovich Landau put forth his theory on systems of interacting fermions, or fermi liquids. A year later, Viktor Pavlovich Silin described spin waves that such a system of fermions would support. The treatment of the contribution of the molecular field to the spin wave dispersion was a novel aspect of these spin waves. Silin predicted that there would exist a hierarchy of spin waves in a fermi liquid, one for each component of the spherical harmonic expansion of the fermi surface. In 1968, Anthony J. Leggett and Michael J. Rice derived from fermi liquid theory how the behavior of the spin diffusion coefficient of a fermi liquid could be directly experimentally observable via the spin echo effect [24]. Their prediction, that the diffusion coefficient of a fermi liquid would not decay exponentially with temperature, but rather would have a maximum at some non-zero temperature, was a direct consequence of the fermi liquid molecular field and spin wave phenomena, and this was corroborated by experiment in 1971 by Corruccini, et al. [13]. A parallel advancement in the theory of fermi liquid spin waves came with the extension of the theory to describe weak ferromagnetic metals. In 1959, Alexei Abrikosov and I. E. Dzyaloshiski put forth a theoretical description of a ferromagnetic fermi liquid [1]. In 2001, Kevin Bedell and Krastan Blagoev showed that a non-trivial contribution to the dispersion of the ferromagnetic current spin wave arises from the necessary consideration of higher harmonic moments in the distortion of the fermi surface from its ground state [8]. In the chapters to follow, the author presents new results for transverse spin waves in a fermi liquid, which arise from a novel ground state of a fermi liquid-one in which an l = 1 harmonic distortion exists in the ground state polarization. It is shown that such an instability can lead to spin waves with dispersions that are characterized by a linear dependence on the wave number at long

  9. Differentiation of transverse sinus thrombosis from congenitally atretic cerebral transverse sinus with CT.

    PubMed

    Chik, Yolanda; Gottesman, Rebecca F; Zeiler, Steven R; Rosenberg, Jason; Llinas, Rafael H

    2012-07-01

    Transverse sinus thrombosis can have nonspecific clinical and radiographic signs. We hypothesized that the novel "sigmoid notch sign" (on head CT) can help differentiate transverse sinus thrombosis from a congenitally atretic sinus among individuals with absent signal in 1 transverse sinus by MR venography. We retrospectively evaluated 53 subjects with a unilaterally absent transverse sinus signal on MR venography. Eleven had true transverse sinus thrombosis and 42 had an atretic transverse sinus. Reviewers were trained in the sigmoid notch sign: "positive" if 1 of the sigmoid notches was asymmetrically smaller than the other, consistent with a congenitally absent transverse sinus on that side. This sign was scored on CT scans by 2 blinded reviewers to determine if signal dropout was clot or atretic sinus. A consensus rating was reached when the reviewers disagreed. Characteristics of the sigmoid notch sign as a diagnostic test were compared with a gold standard of full chart review by an independent reviewer. Each reviewer had a sensitivity of 91% (detecting 10 of 11 clots based on a negative sigmoid notch sign) and specificity of 71% to 81%; consensus specificity increased to 86% (36 of 42 individuals with an atretic sinus had a positive notch sign, detecting atretic sinuses based on presence of the sign). Asymmetries of the sigmoid notches on noncontrast brain CT is a very sensitive and specific measure of differentiating transverse sinus thrombosis from an atretic transverse sinus when absence of transverse sinus flow is visualized on MR venography.

  10. Equivalent Relaxations of Optimal Power Flow

    SciTech Connect

    Bose, S; Low, SH; Teeraratkul, T; Hassibi, B

    2015-03-01

    Several convex relaxations of the optimal power flow (OPF) problem have recently been developed using both bus injection models and branch flow models. In this paper, we prove relations among three convex relaxations: a semidefinite relaxation that computes a full matrix, a chordal relaxation based on a chordal extension of the network graph, and a second-order cone relaxation that computes the smallest partial matrix. We prove a bijection between the feasible sets of the OPF in the bus injection model and the branch flow model, establishing the equivalence of these two models and their second-order cone relaxations. Our results imply that, for radial networks, all these relaxations are equivalent and one should always solve the second-order cone relaxation. For mesh networks, the semidefinite relaxation and the chordal relaxation are equally tight and both are strictly tighter than the second-order cone relaxation. Therefore, for mesh networks, one should either solve the chordal relaxation or the SOCP relaxation, trading off tightness and the required computational effort. Simulations are used to illustrate these results.

  11. Development of Transverse Modes Damped DLA Structure

    SciTech Connect

    Jing, C.; Kanareykin, A.; Schoessow, P.; Gai, W.; Konecny, R.; Power, J. G.; Conde, M.

    2009-01-22

    As the dimensions of accelerating structures become smaller and beam intensities higher, the transverse wakefields driven by the beam become quite large with even a slight misalignment of the beam from the geometric axis. These deflection modes can cause inter-bunch beam breakup and intra-bunch head-tail instabilities along the beam path, and thus BBU control becomes a critical issue. All new metal based accelerating structures, like the accelerating structures developed at SLAC or power extractors at CLIC, have designs in which the transverse modes are heavily damped. Similarly, minimizing the transverse wakefield modes (here the HEMmn hybrid modes in Dielectric-Loaded Accelerating (DLA) structures) is also very critical for developing dielectric based high energy accelerators. In this paper, we present the design of a 7.8 GHz transverse mode damped DLA structure currently under construction, along with plans for the experimental program.

  12. Transversally periodic solitary gravity-capillary waves.

    PubMed

    Milewski, Paul A; Wang, Zhan

    2014-01-08

    When both gravity and surface tension effects are present, surface solitary water waves are known to exist in both two- and three-dimensional infinitely deep fluids. We describe here solutions bridging these two cases: travelling waves which are localized in the propagation direction and periodic in the transverse direction. These transversally periodic gravity-capillary solitary waves are found to be of either elevation or depression type, tend to plane waves below a critical transverse period and tend to solitary lumps as the transverse period tends to infinity. The waves are found numerically in a Hamiltonian system for water waves simplified by a cubic truncation of the Dirichlet-to-Neumann operator. This approximation has been proved to be very accurate for both two- and three-dimensional computations of fully localized gravity-capillary solitary waves. The stability properties of these waves are then investigated via the time evolution of perturbed wave profiles.

  13. Transversally periodic solitary gravity–capillary waves

    PubMed Central

    Milewski, Paul A.; Wang, Zhan

    2014-01-01

    When both gravity and surface tension effects are present, surface solitary water waves are known to exist in both two- and three-dimensional infinitely deep fluids. We describe here solutions bridging these two cases: travelling waves which are localized in the propagation direction and periodic in the transverse direction. These transversally periodic gravity–capillary solitary waves are found to be of either elevation or depression type, tend to plane waves below a critical transverse period and tend to solitary lumps as the transverse period tends to infinity. The waves are found numerically in a Hamiltonian system for water waves simplified by a cubic truncation of the Dirichlet-to-Neumann operator. This approximation has been proved to be very accurate for both two- and three-dimensional computations of fully localized gravity–capillary solitary waves. The stability properties of these waves are then investigated via the time evolution of perturbed wave profiles. PMID:24399922

  14. Transverse impedances of cavities and collimators

    SciTech Connect

    Kheifets, S.A.; Bane, K.L.F.; Bizek, H.

    1987-03-01

    Field matching has been used to compute the transverse impedance of simple, cylindrically symmetric, perfectly conducting structures, the subregions of which are separated by radial cuts. The method is briefly described, and some early results are presented. (LEW)

  15. Transverse optical forces for manipulating nanoparticles

    NASA Astrophysics Data System (ADS)

    Zharov, Alexander A.; Zharov, Alexander A.; Shadrivov, Ilya V.; Zharova, Nina A.

    2016-12-01

    We study optical forces acting on a subwavelength particle with anisotropic polarizability and discover an optomechanical effect that resembles the Hall effect for electrons. While in the classical Hall effect the transverse Lorentz force and the transverse voltage appear due to the static magnetic field which induces the nondiagonal components of the electric conductivity tensor; in our case the imaginary parts of the nondiagonal elements of the polarizability tensor are responsible for the transverse scattering force. We calculate this force for the examples of the ellipsoidal plasmonic nanoparticles and the spherical particle with gyromagnetic properties, and show that the transverse force depends on the physical origin of the anisotropy of the polarizability, and on the electromagnetic wave structure around the particle. Moreover, this force primarily occurs in the inhomogeneous field only.

  16. Transverse-longitudinal coupling in intense beams

    SciTech Connect

    Wang, T.S.F.; Smith, L.

    1981-03-01

    The coupling between transverse and longitudinal perturbations is studied self-consistently by considering a beam of K-V distribution. The analysis is carried out within the context of linearized Vlasov-Maxwell equations and electrostatic approximation. The perturbation is assumed to be azimuthally symmetric but axially non-uniform (k/sub z/ is not equal to 0). It is shown that the coupling affects both the longitudinal and transverse modes significantly in the high density and low frequency region. Two new classes of longitudinal modes are found which would not exist if the transverse motions of particles are neglected. The effect of resistive wall impedance on beam stability is also studied. It is found that the longitudinal impedance can cause the transverse modes also to be weakly unstable.

  17. Pressure-induced emergence of unusually high-frequency transverse excitations in a liquid alkali metal: Evidence of two types of collective excitations contributing to the transverse dynamics at high pressures

    SciTech Connect

    Bryk, Taras; Ruocco, G.; Scopigno, T.

    2015-09-14

    Unlike phonons in crystals, the collective excitations in liquids cannot be treated as propagation of harmonic displacements of atoms around stable local energy minima. The viscoelasticity of liquids, reflected in transition from the adiabatic to elastic high-frequency speed of sound and in absence of the long-wavelength transverse excitations, results in dispersions of longitudinal (L) and transverse (T) collective excitations essentially different from the typical phonon ones. Practically, nothing is known about the effect of high pressure on the dispersion of collective excitations in liquids, which causes strong changes in liquid structure. Here dispersions of L and T collective excitations in liquid Li in the range of pressures up to 186 GPa were studied by ab initio simulations. Two methodologies for dispersion calculations were used: direct estimation from the peak positions of the L/T current spectral functions and simulation-based calculations of wavenumber-dependent collective eigenmodes. It is found that at ambient pressure, the longitudinal and transverse dynamics are well separated, while at high pressures, the transverse current spectral functions, density of vibrational states, and dispersions of collective excitations yield evidence of two types of propagating modes that contribute strongly to transverse dynamics. Emergence of the unusually high-frequency transverse modes gives evidence of the breakdown of a regular viscoelastic theory of transverse dynamics, which is based on coupling of a single transverse propagating mode with shear relaxation. The explanation of the observed high-frequency shift above the viscoelastic value is given by the presence of another branch of collective excitations. With the pressure increasing, coupling between the two types of collective excitations is rationalized within a proposed extended viscoelastic model of transverse dynamics.

  18. 1H and 19F NMR relaxation studies of fleroxacin with Micrococcus luteus.

    PubMed

    Waibel, Benjamin; Holzgrabe, Ulrike

    2007-04-11

    In order to investigate and characterize interaction processes between the fluoroquinolone fleroxacin and bacterial cells we used non-selective (all resonances are excited), selective (observed resonance is excited) spin-lattice relaxation rates and spin-spin relaxation measurements. The signals of three hydrogens at different moieties of the fleroxacin molecule were considered to get an insight in the complexation behavior. The enhancement of selective relaxation rates was observed with increasing fleroxacin concentrations and keeping the bacterial mass constant. The obtained relaxation rates of the affected hydrogens were analyzed via a Lineweaver-Burk-plot to determine the KD values. Furthermore, 19F NMR spectra were recorded and spin-spin relaxation rates (R2) were determined by a Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence. Because of the dependency of the line width of NMR peaks on transversal relaxation time T2, we compared the line width at half-height at different fleroxacin concentrations in order to investigate the involvement of fluorine atoms in different positions in the complexation. All findings point to core quinolone moiety to be involved in the interaction with bacterial cells.

  19. Exploring the transverse spin structure of the nucleon

    SciTech Connect

    D'Alesio, Umberto

    2008-10-13

    We discuss our present understanding of the transverse spin structure of the nucleon and of related properties originating from parton transverse motion. Starting from the transversity distribution and the ways to access it, we then address the role played by spin and transverse momentum dependent (TMD) distributions in azimuthal and transverse single spin asymmetries. The latest extractions of the Sivers, Collins and transversity functions are also presented.

  20. Soft dynamics and transverse momenta in QCD

    NASA Astrophysics Data System (ADS)

    Trentadue, L.

    1987-03-01

    We analyze transverse momentum distributions in QCD. We focus on the small and intermediate transverse momentum range where the form factor represents a universal quantity. The relation between the shape of the distributions and the underlying theory is emphasized. Results from analytical and numerical analyses are compared. On leave of absence from Dipartimento di Fisica, Università di Parma, Parma, Italy and Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Parma, Sezione di Milano, Milan, Italy.

  1. The Effects of Transverse Stress on Magnetization.

    DTIC Science & Technology

    1982-01-01

    because of the --greater population of stress active walls. *This inequality causes the magnetic behavior in tension to be ’amplified’ in comparison...AD-R124 229 THE EFFECTS OF TRANSVERSE STRESS ON MAGNETIZATION(U) 1/1 I NAVAL ACADEMY ANNAPOLIS ND J N RICHARDSON 1982 USNA-TSPR-ii9 UNCLASSIFIED F/G...THE EFFECTS OF TRANSVERSE STRESS ON MAGNETIZATION UNITED STATES NAVAL ACADEMY ANNAPOLIS, MARYLAND 1982 This document has been approved for public LL

  2. Acute transverse myelitis complicating breakthrough varicella infection.

    PubMed

    Aslan, Asli; Kurugol, Zafer; Gokben, Sarenur

    2014-11-01

    We report a 10-year-old girl who presented with acute transverse myelitis after breakthrough varicella infection. The diagnosis was based on the development of motor weakness, paraparesis and bladder dysfunction, spinal magnetic resonance imaging findings and detection of anti-varicella zoster virus IgG antibody in the cerebrospinal fluid. This case report highlights that breakthrough varicella can result in serious complications such as acute transverse myelitis.

  3. Chiral dynamics and peripheral transverse densities

    SciTech Connect

    Granados, Carlos G.; Weiss, Christian

    2014-01-01

    In the partonic (or light-front) description of relativistic systems the electromagnetic form factors are expressed in terms of frame-independent charge and magnetization densities in transverse space. This formulation allows one to identify the chiral components of nucleon structure as the peripheral densities at transverse distances b = O(M{sub {pi}}{sup -1}) and compute them in a parametrically controlled manner. A dispersion relation connects the large-distance behavior of the transverse charge and magnetization densities to the spectral functions of the Dirac and Pauli form factors near the two--pion threshold at timelike t = 4 M{ sub {pi}}{sup 2}, which can be computed in relativistic chiral effective field theory. Using the leading-order approximation we (a) derive the asymptotic behavior (Yukawa tail) of the isovector transverse densities in the "chiral" region b = O(M{sub {pi}}{sup -1}) and the "molecular" region b = O(M{sub N}{sup 2}/M{sub {pi}}{sup 3}); (b) perform the heavy-baryon expansion of the transverse densities; (c) explain the relative magnitude of the peripheral charge and magnetization densities in a simple mechanical picture; (d) include Delta isobar intermediate states and study the peripheral transverse densities in the large-N{ sub c} limit of QCD; (e) quantify the region of transverse distances where the chiral components of the densities are numerically dominant; (f) calculate the chiral divergences of the b{sup 2}-weighted moments of the isovector transverse densities (charge and anomalous magnetic radii) in the limit M{sub {pi}} -> 0 and determine their spatial support. Our approach provides a concise formulation of the spatial structure of the nucleon's chiral component and offers new insights into basic properties of the chiral expansion. It relates the information extracted from low-t elastic form factors to the generalized parton distributions probed in peripheral high-energy scattering processes.

  4. Transverse flat plate heat pipe experiment

    NASA Technical Reports Server (NTRS)

    Edelstein, F.

    1978-01-01

    This paper describes a Shuttle-launched flight experiment to evaluate the performance of a transverse flat plate heat pipe that serves as an integral temperature control/mounting panel for electronic equipment. A transverse heat pipe is a gas-controlled variable conductance heat pipe that can handle relatively large thermal loads. An experiment designed to flight test the concept over a 6-9 month period is self-sufficient with respect to electrical power, timing sequences, and data storage.

  5. Results from the AGS Booster transverse damper

    SciTech Connect

    Russo, D.; Brennan, M.; Meth, M.; Roser, T.

    1993-06-01

    To reach the design intensity of 1.5 {times} 10{sup 13} protons per pulse in the AGS Booster, transverse coupled bunch instabilities with an estimated growth rate of 1500s{sup {minus}1} have to be dampened. A prototype transverse damper has been tested successfully using a one turn digital delay and closed orbit suppression implemented in a programmable gate array. An updated damper, which includes an algorithm to optimize damping for a changing betatron rune, will also be presented.

  6. Results from the AGS Booster transverse damper

    SciTech Connect

    Russo, D.; Brennan, M.; Meth, M.; Roser, T.

    1993-01-01

    To reach the design intensity of 1.5 [times] 10[sup 13] protons per pulse in the AGS Booster, transverse coupled bunch instabilities with an estimated growth rate of 1500s[sup [minus]1] have to be dampened. A prototype transverse damper has been tested successfully using a one turn digital delay and closed orbit suppression implemented in a programmable gate array. An updated damper, which includes an algorithm to optimize damping for a changing betatron rune, will also be presented.

  7. Schwarzschild solution from Weyl transverse gravity

    NASA Astrophysics Data System (ADS)

    Oda, Ichiro

    2017-01-01

    We study classical solutions in the Weyl-transverse (WTDiff) gravity. The WTDiff gravity is invariant under both the local Weyl (conformal) transformation and the volume preserving diffeomorphisms (Diff) (transverse diffeomorphisms (TDiff)) and is known to be equivalent to general relativity at least at the classical level. In particular, we find that in a general spacetime dimension, the Schwarzschild metric is a classical solution in the WTDiff gravity when it is expressed in the Cartesian coordinate system.

  8. Organic semiconductors: What makes the spin relax?

    NASA Astrophysics Data System (ADS)

    Bobbert, Peter A.

    2010-04-01

    Spin relaxation in organic materials is expected to be slow because of weak spin-orbit coupling. The effects of deuteration and coherent spin excitation show that the spin-relaxation time is actually limited by hyperfine fields.

  9. Relaxation and Distraction in Experimental Desensitization.

    ERIC Educational Resources Information Center

    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)

  10. Relaxation as a Factor in Semantic Desensitization

    ERIC Educational Resources Information Center

    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)

  11. Transverse structure of the QCD string

    SciTech Connect

    Meyer, Harvey B.

    2010-11-15

    The characterization of the transverse structure of the QCD string is discussed. We formulate a conjecture as to how the stress-energy tensor of the underlying gauge theory couples to the string degrees of freedom. A consequence of the conjecture is that the energy density and the longitudinal-stress operators measure the distribution of the transverse position of the string, to leading order in the string fluctuations, whereas the transverse-stress operator does not. We interpret recent numerical measurements of the transverse size of the confining string and show that the difference of the energy and longitudinal-stress operators is a particularly natural probe at next-to-leading order. Second, we derive the constraints imposed by open-closed string duality on the transverse structure of the string. We show that a total of three independent ''gravitational'' form factors characterize the transverse profile of the closed string, and obtain the interpretation of recent effective string theory calculations: the square radius of a closed string of length {beta} defined from the slope of its gravitational form factor, is given by (d-1/2{pi}{sigma})log({beta}/4r{sub 0}) in d space dimensions. This is to be compared with the well-known result that the width of the open string at midpoint grows as (d-1/2{pi}{sigma})log(r/r{sub 0}). We also obtain predictions for transition form factors among closed-string states.

  12. The Effects of Dissolved Oxygen upon Amide Proton Relaxation and Chemical Shift in a Perdeuterated Protein

    NASA Astrophysics Data System (ADS)

    Ulmer, Tobias S.; Campbell, Iain D.; Boyd, Jonathan

    2002-08-01

    The effects of dissolved molecular oxygen upon amide proton ( 1H N) longitudinal and transverse relaxation rates and chemical shifts were studied for a small protein domain, the second type 2 module of fibronectin ( 2F2)—isotopically enriched to 99% 2H, 98% 15N. Longitudinal relaxation rate enhancements, R O 2( 1H N), of individual backbone 1H N nuclei varied up to 14 fold between a degassed and oxygenated (1 bar) solution, indicating that the oxygen distribution within the protein is inhomogeneous. On average, smaller relaxation rate enhancements were observed for 1H N nuclei associated with the core of the protein compared to 1H N nuclei closer to the surface, suggesting restricted oxygen accessibility to some regions. In agreement with an O 2- 1H N hyperfine interaction in the extreme narrowing limit, the 1H N transverse relaxation rates showed no significant change, up to an oxygen pressure of 9.5 bar (the maximum pressure used in this study). For most 1H N resonances, small Δδ O 2( 1H N) hyperfine chemical shifts could be detected between oxygen pressures of 1 bar and 9.5 bar.

  13. A nonlinear constitutive model for stress relaxation in ligaments and tendons.

    PubMed

    Davis, Frances M; De Vita, Raffaella

    2012-12-01

    A novel constitutive model that describes stress relaxation in transversely isotropic soft collagenous tissues such as ligaments and tendons is presented. The model is formulated within the nonlinear integral representation framework proposed by Pipkin and Rogers (J. Mech. Phys. Solids. 16:59-72, 1968). It represents a departure from existing models in biomechanics since it describes not only the strain dependent stress relaxation behavior of collagenous tissues but also their finite strains and transverse isotropy. Axial stress-stretch data and stress relaxation data at different axial stretches are collected on rat tail tendon fascicles in order to compute the model parameters. Toward this end, the rat tail tendon fascicles are assumed to be incompressible and undergo an isochoric axisymmetric deformation. A comparison with the experimental data proves that, unlike the quasi-linear viscoelastic model (Fung, Biomechanics: Mechanics of Living Tissues. Springer, New York, 1993) the constitutive law can capture the observed nonlinearities in the stress relaxation response of rat tail tendon fascicles.

  14. A Comparative Study of T1 and T2 Relaxation in Shale

    NASA Astrophysics Data System (ADS)

    Keating, K.; Obasi, C. C.; Pashin, J. C.

    2015-12-01

    Nuclear magnetic resonance (NMR) relaxation measurement have been used extensively in petroleum and, more recently, in groundwater resource evaluation to estimate the porosity, pore-size distributions, permeability, fluid saturation, and fluid mobility. In shale, the transverse decay rate of NMR signal is sensitive to the microporosity, but is also affected by the paramagnetic contributions of clay and other iron-bearing minerals. Furthermore, contrasts in the magnetic susceptibility of the mineral matrix and pore fluids that result in an inhomogeneous magnetic field within the pore space results in an extra term in transverse relaxation. These issues can cause errors in NMR-based estimates of pore-size distribution and permeability. In this study we compare T1 and T2 relaxation time distributions in order to study the molecular mechanism of relaxation in brine-saturated mixtures of clay and other common minerals. We collected measurements on a range of mixtures of clay minerals common in shale (illite, glauconite, celadonite, chamosite, montmorillonite and kaolinite) and pyrite. To constrain the interpretation of the NMR data, we measured the magnetic susceptibility and surface area of all samples. We are confident that by accounting for the presence and variations of clay and pyrite in shale, we can substantially improve both the NMR estimate of pore-size distribution and permeability.

  15. Capturing fast relaxing spins with SWIFT adiabatic rotating frame spin-lattice relaxation (T1ρ) mapping.

    PubMed

    Zhang, J; Nissi, M J; Idiyatullin, D; Michaeli, S; Garwood, M; Ellermann, J

    2016-04-01

    Rotating frame spin-lattice relaxation, with the characteristic time constant T1ρ, provides a means to access motion-restricted (slow) spin dynamics in MRI. As a result of their restricted motion, these spins are sometimes characterized by a short transverse relaxation time constant T2 and thus can be difficult to detect directly with conventional image acquisition techniques. Here, we introduce an approach for three-dimensional adiabatic T1ρ mapping based on a magnetization-prepared sweep imaging with Fourier transformation (MP-SWIFT) sequence, which captures signal from almost all water spin populations, including the extremely fast relaxing pool. A semi-analytical procedure for T1ρ mapping is described. Experiments on phantoms and musculoskeletal tissue specimens (tendon, articular and epiphyseal cartilages) were performed at 9.4 T for both the MP-SWIFT and fast spin echo (FSE) read outs. In the phantom with liquids having fast molecular tumbling and a single-valued T1ρ time constant, the measured T1ρ values obtained with MP-SWIFT and FSE were similar. Conversely, in normal musculoskeletal tissues, T1ρ values measured with MP-SWIFT were much shorter than the values obtained with FSE. Studies of biological tissue specimens demonstrated that T1ρ-weighted SWIFT provides higher contrast between normal and diseased tissues relative to conventional acquisitions. Adiabatic T1ρ mapping with SWIFT readout captures contributions from the otherwise undetected fast relaxing spins, allowing more informative T1ρ measurements of normal and diseased states.

  16. A nonlinear relaxation/quasi-Newton algorithm for the compressible Navier-Stokes equations

    NASA Technical Reports Server (NTRS)

    Edwards, Jack R.; Mcrae, D. S.

    1992-01-01

    A highly efficient implicit method for the computation of steady, two-dimensional compressible Navier-Stokes flowfields is presented. The discretization of the governing equations is hybrid in nature, with flux-vector splitting utilized in the streamwise direction and central differences with flux-limited artificial dissipation used for the transverse fluxes. Line Jacobi relaxation is used to provide a suitable initial guess for a new nonlinear iteration strategy based on line Gauss-Seidel sweeps. The applicability of quasi-Newton methods as convergence accelerators for this and other line relaxation algorithms is discussed, and efficient implementations of such techniques are presented. Convergence histories and comparisons with experimental data are presented for supersonic flow over a flat plate and for several high-speed compression corner interactions. Results indicate a marked improvement in computational efficiency over more conventional upwind relaxation strategies, particularly for flowfields containing large pockets of streamwise subsonic flow.

  17. Plasmon-mediated energy relaxation in graphene

    SciTech Connect

    Ferry, D. K.; Somphonsane, R.; Ramamoorthy, H.; Bird, J. P.

    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.

  18. Resonant relaxation in electroweak baryogenesis

    NASA Astrophysics Data System (ADS)

    Lee, Christopher; Cirigliano, Vincenzo; Ramsey-Musolf, Michael J.

    2005-04-01

    We compute the leading, chiral charge-changing relaxation term in the quantum transport equations that govern electroweak baryogenesis using the closed time path formulation of nonequilibrium quantum field theory. We show that the relaxation transport coefficients may be resonantly enhanced under appropriate conditions on electroweak model parameters and that such enhancements can mitigate the impact of similar enhancements in the CP-violating source terms. We also develop a power counting in the time and energy scales entering electroweak baryogenesis and include effects through second order in ratios ɛ of the small and large scales. We illustrate the implications of the resonantly enhanced O(ɛ2) terms using the Minimal Supersymmetric Standard Model, focusing on the interplay between the requirements of baryogenesis and constraints obtained from collider studies, precision electroweak data, and electric dipole moment searches.

  19. Kinetic activation-relaxation technique.

    PubMed

    Béland, Laurent Karim; Brommer, Peter; El-Mellouhi, Fedwa; Joly, Jean-François; Mousseau, Normand

    2011-10-01

    We present a detailed description of the kinetic activation-relaxation technique (k-ART), an off-lattice, self-learning kinetic Monte Carlo (KMC) algorithm with on-the-fly event search. Combining a topological classification for local environments and event generation with ART nouveau, an efficient unbiased sampling method for finding transition states, k-ART can be applied to complex materials with atoms in off-lattice positions or with elastic deformations that cannot be handled with standard KMC approaches. In addition to presenting the various elements of the algorithm, we demonstrate the general character of k-ART by applying the algorithm to three challenging systems: self-defect annihilation in c-Si (crystalline silicon), self-interstitial diffusion in Fe, and structural relaxation in a-Si (amorphous silicon).

  20. Kinetic activation-relaxation technique

    NASA Astrophysics Data System (ADS)

    Béland, Laurent Karim; Brommer, Peter; El-Mellouhi, Fedwa; Joly, Jean-François; Mousseau, Normand

    2011-10-01

    We present a detailed description of the kinetic activation-relaxation technique (k-ART), an off-lattice, self-learning kinetic Monte Carlo (KMC) algorithm with on-the-fly event search. Combining a topological classification for local environments and event generation with ART nouveau, an efficient unbiased sampling method for finding transition states, k-ART can be applied to complex materials with atoms in off-lattice positions or with elastic deformations that cannot be handled with standard KMC approaches. In addition to presenting the various elements of the algorithm, we demonstrate the general character of k-ART by applying the algorithm to three challenging systems: self-defect annihilation in c-Si (crystalline silicon), self-interstitial diffusion in Fe, and structural relaxation in a-Si (amorphous silicon).

  1. Fractional relaxations in photonic crystals

    NASA Astrophysics Data System (ADS)

    Giraldi, Filippo; Petruccione, Francesco

    2014-10-01

    A quantum dot interacting with the radiation field of a photonic crystal is considered. An analytical description of the dynamics and the coherence between the two states of the quantum dot is provided. Besides the well-known trapping, a fractional nature of the dynamics appears via relaxations of the Mittag-Leffler type. Furthermore, coherence exhibits a transition from the decay {{t}-3/2} to {{t}-1/2} if the transition frequency of the quantum dot is exactly in the middle of the band gap. Similarly, the population of the excited level undergoes a transition from the relaxation 1/{{t}3} to 1/t. These resonances and transitions belong also to the context of matter-wave emissions in optical lattices.

  2. Slow relaxation in granular compaction

    NASA Astrophysics Data System (ADS)

    Ben-Naim, E.; Knight, J. B.; Nowak, E. R.; Jaeger, H. M.; Nagel, S. R.

    1998-11-01

    Experimental studies show that the density of a vibrated granular material evolves from a low density initial state into a higher density final steady state. The relaxation towards the final density follows an inverse logarithmic law. As the system approaches its final state, a growing number of beads have to be rearranged to enable a local density increase. A free volume argument shows that this number grows as N = {ϱ}/{(1-ϱ)}. The time scale associated with such events increases exponentially ∼ e N, and as a result a logarithmically slow approach to the final state is found ϱ ∞ - ϱ(t) ∼ {1}/{lnt }. Furthermore, a one-dimensional toy model that captures this relaxation dynamics as well as the observed density fluctuations is discussed.

  3. Models of violently relaxed galaxies

    NASA Astrophysics Data System (ADS)

    Merritt, David; Tremaine, Scott; Johnstone, Doug

    1989-02-01

    The properties of spherical self-gravitating models derived from two distribution functions that incorporate, in a crude way, the physics of violent relaxation are investigated. The first distribution function is identical to the one discussed by Stiavelli and Bertin (1985) except for a change in the sign of the 'temperature', i.e., e exp(-aE) to e exp(+aE). It is shown that these 'negative temperature' models provide a much better description of the end-state of violent relaxation than 'positive temperature' models. The second distribution function is similar to the first except for a different dependence on angular momentum. Both distribution functions yield single-parameter families of models with surface density profiles very similar to the R exp 1/4 law. Furthermore, the central concentration of models in both families increases monotonically with the velocity anisotropy, as expected in systems that formed through cold collapse.

  4. Relaxation: A Fourth "R" for Education.

    ERIC Educational Resources Information Center

    Frederick, A. B.

    Relaxation training helps the individual handle tension through concentrating upon efficient use of muscles. A program of progressive relaxation can be easily incorporated into elementary and secondary schools. Objectives of such a program include the following: (a) to learn to relax technically for purposes of complete rest (deep muscle…

  5. Brief relaxation training program for hospital employees.

    PubMed

    Balk, Judith L; Chung, Sheng-Chia; Beigi, Richard; Brooks, Maria

    2009-01-01

    Employee stress leads to attrition, burnout, and increased medical costs. We aimed to assess if relaxation training leads to decreased stress levels based on questionnaire and thermal biofeedback. Thirty-minute relaxation training sessions were conducted for hospital employees and for cancer patients. Perceived Stress levels and skin temperature were analyzed before and after relaxation training.

  6. Domain relaxation in Langmuir films

    NASA Astrophysics Data System (ADS)

    Alexander, James C.; Bernoff, Andrew J.; Mann, Elizabeth K.; Mann, J. Adin; Wintersmith, Jacob R.; Zou, Lu

    We report on theoretical studies of molecularly thin Langmuir films on the surface of a quiescent subfluid and qualitatively compare the results to both new and previous experiments. The film covers the entire fluid surface, but domains of different phases are observed. In the absence of external forcing, the compact domains tend to relax to circles, driven by a line tension at the phase boundaries. When stretched (by a transient applied stagnation-point flow or by stirring), a compact domain elongates, creating a bola consisting of two roughly circular reservoirs connected by a thin tether. This shape will then relax slowly to the minimum-energy configuration of a circular domain. The tether is never observed to rupture, even when it is more than a hundred times as long as it is wide. We model these experiments by taking previous descriptions of the full hydrodynamics, identifying the dominant effects via dimensional analysis, and reducing the system to a more tractable form. The result is a free boundary problem for an inviscid Langmuir film whose motion is driven by the line tension of the domain and damped by the viscosity of the subfluid. Using this model we derive relaxation rates for perturbations of a uniform strip and a circular patch. We also derive a boundary integral formulation which allows an efficient numerical solution of the problem. Numerically this model replicates the formation of a bola and the subsequent relaxation observed in the experiments. Finally, we suggest physical properties of the system (such as line tension) that can be deduced by comparison of the theory and numerical simulations to the experiment. Two movies are available with the online version of the paper.

  7. Impact of electron-impurity scattering on the spin relaxation time in graphene: a first-principles study.

    PubMed

    Fedorov, Dmitry V; Gradhand, Martin; Ostanin, Sergey; Maznichenko, Igor V; Ernst, Arthur; Fabian, Jaroslav; Mertig, Ingrid

    2013-04-12

    The effect of electron-impurity scattering on momentum and spin relaxation times in graphene is studied by means of relativistic ab initio calculations. Assuming carbon and silicon adatoms as natural impurities in graphene, we are able to simulate fast spin relaxation observed experimentally. We investigate the dependence of the relaxation times on the impurity position and demonstrate that C or Si adatoms act as real-space spin hot spots inducing spin-flip rates about 5 orders of magnitude larger than those of in-plane impurities. This fact confirms the hypothesis that the adatom-induced spin-orbit coupling leads to fast spin relaxation in graphene.

  8. Arresting relaxation in Pickering Emulsions

    NASA Astrophysics Data System (ADS)

    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.

  9. Structural relaxation of acetaminophen glass.

    PubMed

    Gunawan, Lina; Johari, G P; Shanker, Ravi M

    2006-05-01

    The aim is to determine the structural stability of acetaminophen glass with time and temperature change, and to examine the merits of adapting the structural relaxation models of the glassy state for pharmaceuticals. Differential scanning calorimetry technique has been used to study the acetaminophen glass after keeping the samples for various periods at fixed temperatures and after keeping at various temperatures for fixed periods. A general formalism for thermodynamic changes during storage in a temperature fluctuating environment is given and the kinetics of the enthalpy and entropy decrease determined. At a fixed temperature, the decrease occurs according to a non-exponential kinetics. For the same storage time, but at different temperatures, the enthalpy and entropy decrease rises to a maximum value at a certain temperature and then declines. The peak appears at the temperature at which the internally equilibrated state of the sample is reached for a fixed storage time. The change in the normalized heat capacity during the heating of acetaminophen has been analysed in terms of a non-exponential, non-linear enthalpy relaxation model. A single set of parameters that fit the data for unannealed acetaminophen glass does not fit the calorimetric data for annealed glass. Since acetaminophen molecules form intermolecular hydrogen-bonds in the crystal state and likely to form such bonds more easily in the disordered state, effect of such bonds on structural relaxation is likely to be significant.

  10. Spin relaxation in metallic ferromagnets

    NASA Astrophysics Data System (ADS)

    Berger, L.

    2011-02-01

    The Elliott theory of spin relaxation in metals and semiconductors is extended to metallic ferromagnets. Our treatment is based on the two-current model of Fert, Campbell, and Jaoul. The d→s electron-scattering process involved in spin relaxation is the inverse of the s→d process responsible for the anisotropic magnetoresistance (AMR). As a result, spin-relaxation rate 1/τsr and AMR Δρ are given by similar formulas, and are in a constant ratio if scattering is by solute atoms. Our treatment applies to nickel- and cobalt-based alloys which do not have spin-up 3d states at the Fermi level. This category includes many of the technologically important magnetic materials. And we show how to modify the theory to apply it to bcc iron-based alloys. We also treat the case of Permalloy Ni80Fe20 at finite temperature or in thin-film form, where several kinds of scatterers exist. Predicted values of 1/τsr and Δρ are plotted versus resistivity of the sample. These predictions are compared to values of 1/τsr and Δρ derived from ferromagnetic-resonance and AMR experiments in Permalloy.

  11. Relaxation response in femoral angiography.

    PubMed

    Mandle, C L; Domar, A D; Harrington, D P; Leserman, J; Bozadjian, E M; Friedman, R; Benson, H

    1990-03-01

    Immediately before they underwent femoral angiography, 45 patients were given one of three types of audiotapes: a relaxation response tape recorded for this study, a tape of contemporary instrumental music, or a blank tape. All patients were instructed to listen to their audiotape during the entire angiographic procedure. Each audiotape was played through earphones. Radiologists were not told the group assignment or tape contents. The patients given the audiotape with instructions to elicit the relaxation response (n = 15) experienced significantly less anxiety (P less than .05) and pain (P less than .001) during the procedure, were observed by radiology nurses to exhibit significantly less pain (P less than .001) and anxiety (P less than .001), and requested significantly less fentanyl citrate (P less than .01) and diazepam (P less than .01) than patients given either the music (n = 14) or the blank (n = 16) control audiotapes. Elicitation of the relaxation response is a simple, inexpensive, efficacious, and practical method to reduce pain, anxiety, and medication during femoral angiography and may be useful in other invasive procedures.

  12. Effects of Various Forms of Relaxation Training on Physiological and Self-Report Measures of Relaxation

    ERIC Educational Resources Information Center

    Reinking, Richard H.; Kohl, Marilyn L.

    1975-01-01

    Examines relative effectiveness of four types of relaxation training including Jacobson-Wolpe and electromyograph (EMG) feedback. Dependent measures are EMG recordings and self-report measures of relaxation. All groups reported increased relaxation, but EMG groups were superior in EMG measures of speed of learning and depth of relaxation.…

  13. Relation between Direct Observation of Relaxation and Self-Reported Mindfulness and Relaxation States

    ERIC Educational Resources Information Center

    Hites, Lacey S.; Lundervold, Duane A.

    2013-01-01

    Forty-four individuals, 18-47 (MN 21.8, SD 5.63) years of age, took part in a study examining the magnitude and direction of the relationship between self-report and direct observation measures of relaxation and mindfulness. The Behavioral Relaxation Scale (BRS), a valid direct observation measure of relaxation, was used to assess relaxed behavior…

  14. Effects of Various Forms of Relaxation Training on Physiological and Self-Report Measures of Relaxation

    ERIC Educational Resources Information Center

    Reinking, Richard H.; Kohl, Marilyn L.

    1975-01-01

    Examines relative effectiveness of four types of relaxation training including Jacobson-Wolpe and electromyograph (EMG) feedback. Dependent measures are EMG recordings and self-report measures of relaxation. All groups reported increased relaxation, but EMG groups were superior in EMG measures of speed of learning and depth of relaxation.…

  15. Effects of Progressive Relaxation versus Biofeedback-Assisted Relaxation with College Students.

    ERIC Educational Resources Information Center

    See, John D.; Czerlinsky, Thomas

    1990-01-01

    Examined use of biofeedback, relaxation training, or both in a college relaxation class with an enrollment of 33 students. Results indicated students receiving relaxation training plus biofeedback improved significantly more on psychological variables than did students receiving only relaxation training. (Author/ABL)

  16. Effects of Progressive Relaxation versus Biofeedback-Assisted Relaxation with College Students.

    ERIC Educational Resources Information Center

    See, John D.; Czerlinsky, Thomas

    1990-01-01

    Examined use of biofeedback, relaxation training, or both in a college relaxation class with an enrollment of 33 students. Results indicated students receiving relaxation training plus biofeedback improved significantly more on psychological variables than did students receiving only relaxation training. (Author/ABL)

  17. Generalized dynamic scaling for quantum critical relaxation in imaginary time.

    PubMed

    Zhang, Shuyi; Yin, Shuai; Zhong, Fan

    2014-10-01

    We study the imaginary-time relaxation critical dynamics of a quantum system with a vanishing initial correlation length and an arbitrary initial order parameter M0. We find that in quantum critical dynamics, the behavior of M0 under scale transformations deviates from a simple power law, which was proposed for very small M0 previously. A universal characteristic function is then suggested to describe the rescaled initial magnetization, similar to classical critical dynamics. This characteristic function is shown to be able to describe the quantum critical dynamics in both short- and long-time stages of the evolution. The one-dimensional transverse-field Ising model is employed to numerically determine the specific form of the characteristic function. We demonstrate that it is applicable as long as the system is in the vicinity of the quantum critical point. The universality of the characteristic function is confirmed by numerical simulations of models belonging to the same universality class.

  18. Superfluid Density and Phase Relaxation in Superconductors with Strong Disorder

    NASA Astrophysics Data System (ADS)

    Seibold, G.; Benfatto, L.; Castellani, C.; Lorenzana, J.

    2012-05-01

    We consider the attractive Hubbard model with on-site disorder as a prototype of a disordered superconductor. We solve the Bogoliubov-de Gennes equations on two-dimensional finite clusters at zero temperature and evaluate the electromagnetic response to a vector potential. We find that the standard decoupling between transverse and longitudinal response does not apply in the presence of disorder. Moreover, the superfluid density is strongly reduced by the relaxation of the phase of the order parameter already at mean-field level when disorder is large. We also find that the anharmonicity of the phase fluctuations is strongly enhanced by disorder. Beyond mean field, this provides an enhancement of quantum fluctuations inducing a zero-temperature transition to a nonsuperconducting phase of disordered preformed pairs. Finally, the connection of our findings with the glassy physics for extreme dirty superconductors is discussed.

  19. Capturing molecular multimode relaxation processes in excitable gases based on decomposition of acoustic relaxation spectra

    NASA Astrophysics Data System (ADS)

    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.

  20. Analysis of reliable sub-ns spin-torque switching under transverse bias magnetic fields

    SciTech Connect

    D'Aquino, M.; Perna, S.; Serpico, C.; Bertotti, G.; Mayergoyz, I. D.

    2015-05-07

    The switching process of a magnetic spin-valve nanosystem subject to spin-polarized current pulses is considered. The dependence of the switching probability on the current pulse duration is investigated. The further application of a transverse field along the intermediate anisotropy axis of the particle is used to control the quasi-random relaxation of magnetization to the reversed magnetization state. The critical current amplitudes to realize the switching are determined by studying the phase portrait of the Landau-Lifshtz-Slonczewski dynamics. Macrospin numerical simulations are in good agreement with the theoretical prediction and demonstrate reliable switching even for very short (below 100 ps) current pulses.

  1. Water proton spin saturation affects measured protein backbone 15 N spin relaxation rates

    NASA Astrophysics Data System (ADS)

    Chen, Kang; Tjandra, Nico

    2011-12-01

    Protein backbone 15N NMR spin relaxation rates are useful in characterizing the protein dynamics and structures. To observe the protein nuclear-spin resonances a pulse sequence has to include a water suppression scheme. There are two commonly employed methods, saturating or dephasing the water spins with pulse field gradients and keeping them unperturbed with flip-back pulses. Here different water suppression methods were incorporated into pulse sequences to measure 15N longitudinal T1 and transversal rotating-frame T1ρ spin relaxation. Unexpectedly the 15N T1 relaxation time constants varied significantly with the choice of water suppression method. For a 25-kDa Escherichiacoli. glutamine binding protein (GlnBP) the T1 values acquired with the pulse sequence containing a water dephasing gradient are on average 20% longer than the ones obtained using a pulse sequence containing the water flip-back pulse. In contrast the two T1ρ data sets are correlated without an apparent offset. The average T1 difference was reduced to 12% when the experimental recycle delay was doubled, while the average T1 values from the flip-back measurements were nearly unchanged. Analysis of spectral signal to noise ratios ( s/ n) showed the apparent slower 15N relaxation obtained with the water dephasing experiment originated from the differences in 1H N recovery for each relaxation time point. This in turn offset signal reduction from 15N relaxation decay. The artifact becomes noticeable when the measured 15N relaxation time constant is comparable to recycle delay, e.g., the 15N T1 of medium to large proteins. The 15N relaxation rates measured with either water suppression schemes yield reasonable fits to the structure. However, data from the saturated scheme results in significantly lower Model-Free order parameters (< S2> = 0.81) than the non-saturated ones (< S2> = 0.88), indicating such order parameters may be previously underestimated.

  2. Dynamics of Glass Relaxation at Room Temperature

    NASA Astrophysics Data System (ADS)

    Welch, Roger C.; Smith, John R.; Potuzak, Marcel; Guo, Xiaoju; Bowden, Bradley F.; Kiczenski, T. J.; Allan, Douglas C.; King, Ellyn A.; Ellison, Adam J.; Mauro, John C.

    2013-06-01

    The problem of glass relaxation under ambient conditions has intrigued scientists and the general public for centuries, most notably in the legend of flowing cathedral glass windows. Here we report quantitative measurement of glass relaxation at room temperature. We find that Corning® Gorilla® Glass shows measurable and reproducible relaxation at room temperature. Remarkably, this relaxation follows a stretched exponential decay rather than simple exponential relaxation, and the value of the stretching exponent (β=3/7) follows a theoretical prediction made by Phillips for homogeneous glasses.

  3. Relaxing consistency in recoverable distributed shared memory

    NASA Technical Reports Server (NTRS)

    Janssens, Bob; Fuchs, W. K.

    1993-01-01

    Relaxed memory consistency models have recently been proposed to tolerate memory access latency in both hardware and software distributed shared memory systems. In recoverable shared memory multiprocessors, relaxing consistency has the added benefit of reducing the number of checkpoints needed to avoid rollback propagation. In this paper, we introduce new checkpointing algorithms that take advantage of relaxed consistency to reduce the performance overhead of checkpointing. We also introduce a scheme based on lazy relaxed consistency, that reduces both checkpointing overhead and the overhead of avoiding error propagation in systems with error latency. Multiprocessor address traces are used to evaluate the relaxed consistency approach to checkpointing with distributed shared memory.

  4. Relaxing consistency in recoverable distributed shared memory

    NASA Technical Reports Server (NTRS)

    Janssens, Bob; Fuchs, W. K.

    1993-01-01

    Relaxed memory consistency models tolerate increased memory access latency in both hardware and software distributed shared memory systems. In recoverable systems, relaxing consistency has the added benefit of reducing the number of checkpoints needed to avoid rollback propagation. In this paper, we introduce new checkpointing algorithms that take advantage of relaxed consistency to reduce the performance overhead of checkpointing. We also introduce a scheme based on lazy relaxed consistency, that reduces both checkpointing overhead and the overhead of avoiding error propagation in systems with error latency. We use multiprocessor address traces to evaluate the relaxed consistency approach to checkpointing with distributed shared memory.

  5. Time of relaxation in dusty plasma model

    NASA Astrophysics Data System (ADS)

    Timofeev, A. V.

    2015-11-01

    Dust particles in plasma may have different values of average kinetic energy for vertical and horizontal motion. The partial equilibrium of the subsystems and the relaxation processes leading to this asymmetry are under consideration. A method for the relaxation time estimation in nonideal dusty plasma is suggested. The characteristic relaxation times of vertical and horizontal motion of dust particles in gas discharge are estimated by analytical approach and by analysis of simulation results. These relaxation times for vertical and horizontal subsystems appear to be different. A single hierarchy of relaxation times is proposed.

  6. Cryogenic oxygen jet response to transverse acoustic excitation with the first transverse and the first combined longitudinal-transverse modes

    NASA Astrophysics Data System (ADS)

    Hardi, J. S.; Oschwald, M.

    2016-07-01

    The intact length of the dense oxygen core from an oxygen-hydrogen shear coaxial rocket injector was measured. The measurements were made in a rectangular rocket combustor with optical access and acoustic forcing. The combustor was operated at chamber pressures of 40 and 60 bar, with either ambient temperature or cryogenic hydrogen. The multielement injection spray is subjected to forced transverse gas oscillations of two different acoustic resonance modes; the first transverse (1T) mode at 4200 Hz and the first combined longitudinal-transverse (1L1T) at 5500 Hz. Intact core length is measured from high-speed shadowgraph imaging. The dependence of intact core length with increasing acoustic amplitude is compared for the two modes of excitation.

  7. Microscale simulations of NMR relaxation in porous media

    NASA Astrophysics Data System (ADS)

    Mohnke, Oliver; Klitzsch, Norbert

    2010-05-01

    In petrophysical applications of nuclear magnetic resonance (NMR), the measured relaxation signals originate from the fluid filled pore space. Hence, in rocks or sediments the water content directly corresponds to the initial amplitude of the recorded NMR relaxation signals. The relaxation rate (longitudinal/transversal decay time T1, T2) is sensitive to pore sizes and physiochemical properties of rock-fluid interfaces (surface relaxivity), as well as the concentration of paramagnetic ions in the fluid phases (bulk relaxivity). In the subproject A2 of the TR32 we aim at improving the basic understanding of these processes at the pore scale and thereby advancing the interpretation of NMR data by reducing the application of restrictive approximated interpretation schemes, e.g. for deriving pore size distributions, connectivity or permeability. In this respect we numerically simulate NMR relaxation data at the micro sale to study the impact of physical and hydrological parameters such as internal field gradients or pore connectivities on NMR signals. Joint numerical simulations of the NMR relaxation behavior (Bloch equations) in the presence of internal gradients (Ampere's law) and fluid flow (Navier-Stokes) on a pore scale dimension have been implemented in a finite element (FE) model using Comsol Multiphysics. Processes governing the time and spatial behavior of the nuclear magnetization density in a porous medium are diffusion and surface interactions at the rock-fluid interface. Based on Fick's law of diffusive motion Brownstein and Tarr (1979) introduced differential equations that describe the relaxation behavior of the Spin magnetization in single isolated pores and derived analytical solutions for simple geometries, i.e. spherical, cylindrical and planar. However, by numerically solving these equations in a general way using a FE algorithm this approach can be applied to study and simulate coupled complex pore systems, e.g. derived from computer tomography (CT

  8. Microscale simulations of NMR relaxation in porous media

    NASA Astrophysics Data System (ADS)

    Mohnke, O.; Klitzsch, N.; Clauser, C.

    2009-12-01

    In petrophysical applications of nuclear magnetic resonance (NMR), the measured relaxation signals originate from the fluid filled pore space. Hence, in rocks or sediments the water content directly corresponds to the initial amplitude of the recorded NMR relaxation signals. The relaxation rate (longitudinal/transversal decay time T1, T2) is sensitive to pore sizes and physiochemical properties of rock-fluid interfaces (surface relaxivity), as well as the concentration of paramagnetic ions in the fluid phases (bulk relaxivity). We aim at improving the basic understanding of these processes at the pore scale and thereby advancing the interpretation of NMR data by reducing the application of restrictive approximated interpretation schemes, e.g. for deriving pore size distributions, connectivity or permeability. In this respect we numerically simulate NMR relaxation data at the micro sale to study the impact of physical and hydrological parameters such as internal field gradients or pore connectivities on NMR signals. Joint numerical simulations of the NMR relaxation behavior (Bloch equations) in the presence of internal gradients (Ampere’s law) and fluid flow (Navier-Stokes) on a pore scale dimension have been implemented in a finite element (FE) model using Comsol Multiphysics. Processes governing the time and spatial behavior of the nuclear magnetization density in a porous medium are diffusion and surface interactions at the rock-fluid interface. Based on Fick's law of diffusive motion Brownstein and Tarr (1979) introduced differential equations that describe the relaxation behavior of the Spin magnetization in single isolated pores and derived analytical solutions for simple geometries, i.e. spherical, cylindrical and planar. However, by numerically solving these equations in a general way using a FE algorithm this approach can be applied to study and simulate coupled complex pore systems, e.g. derived from computer tomography (CT). In this respect substantial

  9. Search for supersymmetry in events with opposite-sign dileptons and missing transverse energy using an artificial neural network

    NASA Astrophysics Data System (ADS)

    Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Aguilo, E.; Bergauer, T.; Dragicevic, M.; Erö, J.; Fabjan, C.; Friedl, M.; Frühwirth, R.; Ghete, V. M.; Hörmann, N.; Hrubec, J.; Jeitler, M.; Kiesenhofer, W.; Knünz, V.; Krammer, M.; Krätschmer, I.; Liko, D.; Mikulec, I.; Pernicka, M.; Rabady, D.; Rahbaran, B.; Rohringer, C.; Rohringer, H.; Schöfbeck, R.; Strauss, J.; Taurok, A.; Waltenberger, W.; Wulz, C.-E.; Mossolov, V.; Shumeiko, N.; Suarez Gonzalez, J.; Bansal, M.; Bansal, S.; Cornelis, T.; De Wolf, E. A.; Janssen, X.; Luyckx, S.; Mucibello, L.; Ochesanu, S.; Roland, B.; Rougny, R.; Selvaggi, M.; Van Haevermaet, H.; Van Mechelen, P.; Van Remortel, N.; Van Spilbeeck, A.; Blekman, F.; Blyweert, S.; D'Hondt, J.; Gonzalez Suarez, R.; Kalogeropoulos, A.; Maes, M.; Olbrechts, A.; Van Doninck, W.; Van Mulders, P.; Van Onsem, G. P.; Villella, I.; Clerbaux, B.; De Lentdecker, G.; Dero, V.; Gay, A. P. R.; Hreus, T.; Léonard, A.; Marage, P. E.; Mohammadi, A.; Reis, T.; Thomas, L.; Vander Velde, C.; Vanlaer, P.; Wang, J.; Adler, V.; Beernaert, K.; Cimmino, A.; Costantini, S.; Garcia, G.; Grunewald, M.; Klein, B.; Lellouch, J.; Marinov, A.; Mccartin, J.; Ocampo Rios, A. A.; Ryckbosch, D.; Strobbe, N.; Thyssen, F.; Tytgat, M.; Walsh, S.; Yazgan, E.; Zaganidis, N.; Basegmez, S.; Bruno, G.; Castello, R.; Ceard, L.; Delaere, C.; du Pree, T.; Favart, D.; Forthomme, L.; Giammanco, A.; Hollar, J.; Lemaitre, V.; Liao, J.; Militaru, O.; Nuttens, C.; Pagano, D.; Pin, A.; Piotrzkowski, K.; Vizan Garcia, J. M.; Beliy, N.; Caebergs, T.; Daubie, E.; Hammad, G. H.; Alves, G. A.; Correa Martins Junior, M.; Martins, T.; Pol, M. E.; Souza, M. H. G.; Aldá Júnior, W. L.; Carvalho, W.; Custódio, A.; Da Costa, E. M.; De Jesus Damiao, D.; De Oliveira Martins, C.; Fonseca De Souza, S.; Malbouisson, H.; Malek, M.; Matos Figueiredo, D.; Mundim, L.; Nogima, H.; Prado Da Silva, W. L.; Santoro, A.; Soares Jorge, L.; Sznajder, A.; Vilela Pereira, A.; Anjos, T. S.; Bernardes, C. A.; Dias, F. A.; Fernandez Perez Tomei, T. R.; Gregores, E. M.; Lagana, C.; Marinho, F.; Mercadante, P. G.; Novaes, S. F.; Padula, Sandra S.; Genchev, V.; Iaydjiev, P.; Piperov, S.; Rodozov, M.; Stoykova, S.; Sultanov, G.; Tcholakov, V.; Trayanov, R.; Vutova, M.; Dimitrov, A.; Hadjiiska, R.; Kozhuharov, V.; Litov, L.; Pavlov, B.; Petkov, P.; Bian, J. G.; Chen, G. M.; Chen, H. S.; Jiang, C. H.; Liang, D.; Liang, S.; Meng, X.; Tao, J.; Wang, J.; Wang, X.; Wang, Z.; Xiao, H.; Xu, M.; Zang, J.; Zhang, Z.; Asawatangtrakuldee, C.; Ban, Y.; Guo, Y.; Li, W.; Liu, S.; Mao, Y.; Qian, S. J.; Teng, H.; Wang, D.; Zhang, L.; Zou, W.; Avila, C.; Gomez, J. P.; Gomez Moreno, B.; Osorio Oliveros, A. F.; Sanabria, J. C.; Godinovic, N.; Lelas, D.; Plestina, R.; Polic, D.; Puljak, I.; Antunovic, Z.; Kovac, M.; Brigljevic, V.; Duric, S.; Kadija, K.; Luetic, J.; Mekterovic, D.; Morovic, S.; Attikis, A.; Galanti, M.; Mavromanolakis, G.; Mousa, J.; Nicolaou, C.; Ptochos, F.; Razis, P. A.; Finger, M.; Finger, M., Jr.; Assran, Y.; Elgammal, S.; Ellithi Kamel, A.; Mahmoud, M. A.; Mahrous, A.; Radi, A.; Kadastik, M.; Müntel, M.; Murumaa, M.; Raidal, M.; Rebane, L.; Tiko, A.; Eerola, P.; Fedi, G.; Voutilainen, M.; Härkönen, J.; Heikkinen, A.; Karimäki, V.; Kinnunen, R.; Kortelainen, M. J.; Lampén, T.; Lassila-Perini, K.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Peltola, T.; Tuominen, E.; Tuominiemi, J.; Tuovinen, E.; Ungaro, D.; Wendland, L.; Banzuzi, K.; Karjalainen, A.; Korpela, A.; Tuuva, T.; Besancon, M.; Choudhury, S.; Dejardin, M.; Denegri, D.; Fabbro, B.; Faure, J. L.; Ferri, F.; Ganjour, S.; Givernaud, A.; Gras, P.; Hamel de Monchenault, G.; Jarry, P.; Locci, E.; Malcles, J.; Millischer, L.; Nayak, A.; Rander, J.; Rosowsky, A.; Titov, M.; Baffioni, S.; Beaudette, F.; Benhabib, L.; Bianchini, L.; Bluj, M.; Busson, P.; Charlot, C.; Daci, N.; Dahms, T.; Dalchenko, M.; Dobrzynski, L.; Florent, A.; Granier de Cassagnac, R.; Haguenauer, M.; Miné, P.; Mironov, C.; Naranjo, I. N.; Nguyen, M.; Ochando, C.; Paganini, P.; Sabes, D.; Salerno, R.; Sirois, Y.; Veelken, C.; Zabi, A.; Agram, J.-L.; Andrea, J.; Bloch, D.; Bodin, D.; Brom, J.-M.; Cardaci, M.; Chabert, E. C.; Collard, C.; Conte, E.; Drouhin, F.; Fontaine, J.-C.; Gelé, D.; Goerlach, U.; Juillot, P.; Le Bihan, A.-C.; Van Hove, P.; Fassi, F.; Mercier, D.; Beauceron, S.; Beaupere, N.; Bondu, O.; Boudoul, G.; Brochet, S.; Chasserat, J.; Chierici, R.; Contardo, D.; Depasse, P.; El Mamouni, H.; Fay, J.; Gascon, S.; Gouzevitch, M.; Ille, B.; Kurca, T.; Lethuillier, M.; Mirabito, L.; Perries, S.; Sgandurra, L.; Sordini, V.; Tschudi, Y.; Verdier, P.; Viret, S.; Tsamalaidze, Z.; Autermann, C.; Beranek, S.; Calpas, B.; Edelhoff, M.; Feld, L.; Heracleous, N.; Hindrichs, O.; Jussen, R.; Klein, K.

    2013-04-01

    In this paper, a search for supersymmetry (SUSY) is presented in events with two opposite-sign isolated leptons in the final state, accompanied by hadronic jets and missing transverse energy. An artificial neural network is employed to discriminate possible SUSY signals from a standard model background. The analysis uses a data sample collected with the CMS detector during the 2011 LHC run, corresponding to an integrated luminosity of 4.98fb-1 of proton-proton collisions at the center-of-mass energy of 7 TeV. Compared to other CMS analyses, this one uses relaxed criteria on missing transverse energy (E̸T>40GeV) and total hadronic transverse energy (HT>120GeV), thus probing different regions of parameter space. Agreement is found between standard model expectation and observations, yielding limits in the context of the constrained minimal supersymmetric standard model and on a set of simplified models.

  10. Unusual fast secondary relaxation in metallic glass

    PubMed Central

    Wang, Q.; Zhang, S.T.; Yang, Y.; Dong, Y.D.; Liu, C.T.; Lu, J.

    2015-01-01

    The relaxation spectrum of glassy solids has long been used to probe their dynamic structural features and the fundamental deformation mechanisms. Structurally complicated glasses, such as molecular glasses, often exhibit multiple relaxation processes. By comparison, metallic glasses have a simple atomic structure with dense atomic packing, and their relaxation spectra were commonly found to be simpler than those of molecular glasses. Here we show the compelling evidence obtained across a wide range of temperatures and frequencies from a La-based metallic glass, which clearly shows two peaks of secondary relaxations (fast versus slow) in addition to the primary relaxation peak. The discovery of the unusual fast secondary relaxation unveils the complicated relaxation dynamics in metallic glasses and, more importantly, provides us the clues which help decode the structural features serving as the ‘trigger' of inelasticity on mechanical agitations. PMID:26204999

  11. Nucleon Spin Structure: Longitudinal and Transverse

    SciTech Connect

    Jian-Ping Chen

    2011-02-01

    Inclusive Deep-Inelastic Scattering (DIS) experiments have provided us with the most extensive information on the unpolarized and longitudinal polarized parton (quark and gluon) distributions in the nucleon. It has becoming clear that transverse spin and transverse momentum dependent distributions (TMDs) study are crucial for a more complete understanding of the nucleon structure and the dynamics of the strong interaction. The transverse spin structure and the TMDs are the subject of increasingly intense theoretical and experimental study recently. With a high luminosity electron beam facility, JLab has played a major role in the worldwide effort to study both the longitudinal and transverse spin structure. Highlights of recent results will be presented. With 12-GeV energy upgrade, JLab will provide the most precise measurements in the valence quark region to close a chapter in longitudinal spin study. JLab will also perform a multi-dimensional mapping of the transverse spin structure and TMDs in the valence quark region through Semi-Inclusive DIS (SIDIS) experiments, providing a 3-d partonic picture of the nucleon in momentum space and extracting the u and d quark tensor charges of the nucleon. The precision mapping of TMDs will also allow a detailed study of the quark orbital motion and its dynamics.

  12. Rapid communication: Transverse spin with coupled plasmons

    NASA Astrophysics Data System (ADS)

    Mukherjee, Samyobrata; Gopal, A. V.; Gupta, S. Dutta

    2017-08-01

    We study theoretically the transverse spin associated with the eigenmodes of a thin metal film embedded in a dielectric. We show that the transverse spin has a direct dependence on the nature and strength of the coupling leading to two distinct branches for the long- and short-range modes. We show that the short-range mode exhibits larger extraordinary spin because of its more `structured' nature due to higher decay in propagation. In contrast to some of the earlier studies, calculations are performed retaining the full lossy character of the metal. In the limit of vanishing losses, we present analytical results for the extraordinary spin for both the coupled modes. The results can have direct implications for enhancing the elusive transverse spin exploiting the coupled plasmon structures.

  13. High-power, fundamental transverse mode laser

    SciTech Connect

    Dental, A.G.; Eisenstein, G.; Marcatili, E.A.J.; Tucker, R.S.

    1988-11-22

    This patent describes an optical source comprising: first and second reflectors separated from and opposite to each other for forming a single resonant optical cavity, a semiconductor gain medium having a major surface including a stripe contact extending longitudinally and transversely along the major surface for defining a large optical cavity in a volume of the gain medium thereunder, the semiconductor gain medium for generating a high-power optical signal by spontaneous emission, a single-mode optical fiber coupled to the semiconductor gain medium responsive to the high-power optical signal for causing a fundamental transverse mode optical signal to be amplified by the gain medium, the semiconductor gain medium and the single-mode optical fiber being disposed within the single resonant optical cavity formed by the reflectors, the optical source for producing stimulated coherent radiation in a fundamental transverse mode.

  14. Transverse gradient in Apple-type undulators

    PubMed Central

    Calvi, M.; Camenzuli, C.; Prat, E.; Schmidt, Th.

    2017-01-01

    Apple-type undulators are globally recognized as the most flexible devices for the production of variable polarized light in the soft X-ray regime, both at synchrotron and free-electron laser facilities. Recently, the implementation of transverse gradient undulators has been proposed to enhance the performance of new generation light sources. In this paper it is demonstrated that Apple undulators do not only generate linear and elliptical polarized light but also variable transverse gradient under certain conditions. A general theoretical framework is introduced to evaluate the K-value and its transverse gradient for an Apple undulator, and formulas for all regular operational modes and different Apple types (including the most recent Delta type and Apple X) are calculated and critically discussed. PMID:28452751

  15. Efficient modeling in transversely isotropic inhomogeneous media

    SciTech Connect

    Alkhalifah, T.

    1993-11-01

    An efficient modeling technique for transversely isotropic, inhomogeneous media, is developed using a mix of analytical equations and numerical calculations. The analytic equation for the raypath in a factorized transversely isotropic (FTI) media with linear velocity variation, derived by Shearer and Chapman, is used to trace between two points. In addition, I derive an analytical equation for geometrical spreading in FTI media that aids in preserving program efficiency; however, the traveltime is calculated numerically. I then generalize the method to treat general transversely isotropic (TI) media that are not factorized anisotropic inhomogeneous by perturbing the FTI traveltimes, following the perturbation ideas of Cerveny and Filho. A Kirchhoff-summation-based program relying on Trorey`s (1970) diffraction method is used to generate synthetic seismograms for such a medium. For the type of velocity models treated, the program is much more efficient than finite-difference and general ray-trace modeling techniques.

  16. Transverse Bursts in Inclined Layer Convection: Experiment

    NASA Astrophysics Data System (ADS)

    Daniels, Karen; Wiener, Richard; Bodenschatz, Eberhard

    2002-03-01

    We report experimental results on inclined layer convection in a fluid of Prandtl number σ ≈ 1. A codimension-two point divides regions of buoyancy-driven convection (longitudinal rolls) at lower angles from shear-driven convection (transverse rolls) at higher angles (Daniels et al. PRL 84: 5320, 2000). In the region of buoyancy-driven convection, near the codimension-two point, we observe longitudinal rolls with intermittent, localized, subharmonic transverse bursts. The patterns are spatiotemporally chaotic. With increasing temperature difference the bursts increase in duration and number. We examine the details of the bursting process (e.g. the energy of longitudinal, transverse, and mixed modes) and compare our results to bursting processes in other systems. This work is supported by the National Science Foundation under grant DMR-0072077 and the IGERT program in nonlinear systems, grant DGE-9870631.

  17. Differentiation of Transverse Sinus Thrombosis from Congenitally Atretic Cerebral Transverse Sinus with Computed Tomography

    PubMed Central

    Chik, Yolanda; Gottesman, Rebecca F.; Zeiler, Steven; Rosenberg, Jason; Llinas, Rafael H.

    2015-01-01

    Background Transverse sinus thrombosis can have nonspecific clinical and radiographic signs. We hypothesized that the novel “sigmoid notch sign” (on head CT) can help differentiate transverse sinus thrombosis from a congenitally atretic sinus among individuals with absent signal in one transverse sinus by magnetic resonance venography (MRV). Methods We retrospectively evaluated 53 subjects with a unilaterally absent transverse sinus signal on MRV. 11 had true transverse sinus thrombosis and 42 had an atretic transverse sinus. Reviewers were trained in the sigmoid notch sign: “positive” if one of the sigmoid notches was asymmetrically smaller than the other, consistent with a congenitally absent transverse sinus on that side. This sign was scored on CT scans by, two blinded reviewers to determine if signal dropout was clot or atretic sinus. A consensus rating was reached when the reviewers disagreed. Characteristics of the sigmoid notch sign as a diagnostic test were compared to a gold standard of full chart review by an independent reviewer. Results Each reviewer had a sensitivity of 91% (detecting 10/11 clots based on a negative sigmoid notch sign) and specificity of 71-81%; consensus specificity increased to 86% (36 of 42 individuals with an atretic sinus had a positive notch sign, detecting atretic sinuses based on presence of the sign). Conclusion Asymmetries of the sigmoid notches on non-contrast brain CT is a very sensitive and specific measure of differentiating transverse sinus thrombosis from an atretic transverse sinus when absence of transverse sinus flow is visualized on MRV. PMID:22588265

  18. Evolution of transverse modes in FELIX macropulses

    SciTech Connect

    Weits, H.H.; Lin, L.; Werkhoven, G.H.C. van

    1995-12-31

    We present ringdown measurements of both the intracavity beam, using a low reflection beamsplitter, as well as the hole-outcoupled beam of FELIX, the intracavity measurements being taken at various sets of transverse coordinates. Recent measurements show a significant difference in the decay of the signals at different radial positions, suggesting the presence of higher order transverse modes. The formation of transverse modes depends on the properties of the cold cavity and its losses (i.e. resonator parameters, diffraction and outcoupling at the hole, absorption and edge losses on the mirrors, waveguide clipping), as well as on the gain mechanism. Both simulations with the axisymmetric ELIXER code and previous hole-outcoupled measurements indicated a substantial energy content of the 2nd or 4th Gauss-Laguerre (GL) mode for the 20-30 {mu}m regime of FELIX. Moreover, as FELIX has a phase degenerate cavity, the fundamental and higher order transverse modes can interplay to create a reduced outcoupling efficiency at the hole. For example, in contrast to the decay rate of 13% per roundtrip that we would expect for a pure gaussian beam when we include a loss of 6% for the reflection at the intracavity beamsplitter, recent simulations indicate a decay rate as high as 23% of the hole-outcoupled signal. In this case the 2nd order GL mode contains 30% of the total intracavity power. The effect of transverse modes on subpulses in the limit cycle regime is an interesting aspect. As soon as a subpulse is losing contact with the electrons, its transverse pattern will exhibit an on-axis hole after a few roundtrips, according to the simulations. This process could mean that the subpulses are less pronounced in the hole-outcoupled signal of FELIX 1.

  19. NMR Relaxation and Diffusion Study of Ultrasound Recycling of Polyurethanes

    NASA Astrophysics Data System (ADS)

    von Meerwall, E.; Ghose, S.; Isayev, A. I.

    2004-04-01

    We have examined the effect of intense ultrasound on unfilled polyurethane foam and rubber using proton NMR transverse relaxation and pulsed-gradient diffusion studies, sol extraction, GPC characterization, and glass transition measurements. Results correlate well with ultrasound amplitude. The proton T2 relaxation at 70.5 deg. C exhibits three discrete components, due to heavily entangled sol and crosslinked network; unentangled polymeric sol plus dangling network chain ends; and oligomer remnants. Devulcanizing produces heavy sol, increases segmental mobility of all species, and generates more dangling chain ends. In foams, but not in rubber, additional light sol is generated at the expense of network. All mobilities are significantly lower than in the other rubbers we have studied, an effect unrelated to the glass transition, nearly constant at -60 deg. C. Diffusion measurements, possible only in foams, show a bimodal spectrum whose fast component slows markedly with ultrasound amplitude, attesting to the production of fragments heavier than the original oligomers, as confirmed by GPC analysis. This work is the first to study ultrasound devulcanization in industrial rubbery foams.

  20. Effective rotational correlation times of proteins from NMR relaxation interference

    NASA Astrophysics Data System (ADS)

    Lee, Donghan; Hilty, Christian; Wider, Gerhard; Wüthrich, Kurt

    2006-01-01

    Knowledge of the effective rotational correlation times, τc, for the modulation of anisotropic spin-spin interactions in macromolecules subject to Brownian motion in solution is of key interest for the practice of NMR spectroscopy in structural biology. The value of τc enables an estimate of the NMR spin relaxation rates, and indicates possible aggregation of the macromolecular species. This paper reports a novel NMR pulse scheme, [ 15N, 1H]-TRACT, which is based on transverse relaxation-optimized spectroscopy and permits to determine τc for 15N- 1H bonds without interference from dipole-dipole coupling of the amide proton with remote protons. [ 15N, 1H]-TRACT is highly efficient since only a series of one-dimensional NMR spectra need to be recorded. Its use is suggested for a quick estimate of the rotational correlation time, to monitor sample quality and to determine optimal parameters for complex multidimensional NMR experiments. Practical applications are illustrated with the 110 kDa 7,8-dihydroneopterin aldolase from Staphylococcus aureus, the uniformly 15N-labeled Escherichia coli outer membrane protein X (OmpX) in 60 kDa mixed OmpX/DHPC micelles with approximately 90 molecules of unlabeled 1,2-dihexanoyl- sn-glycero-3-phosphocholine (DHPC), and the 16 kDa pheromone-binding protein from Bombyx mori, which cover a wide range of correlation times.

  1. End-tidal PCO2 as an index of psychophysiological activity during VDT data-entry work and relaxation.

    PubMed

    Schleifer, L M; Ley, R

    1994-02-01

    The present study was designed to assess the utility of end-tidal PCO2 (peak concentration of carbon dioxide in a single breath of exhaled air) as an index of psychophysiological activity during performance of a computer-based task and during relaxation. Eleven data-entry operators were monitored continuously for three consecutive, 6 hour work days under the following conditions: (a) during a self-relaxation baseline period; (b) during an abbreviated progressive muscle relaxation period; and (c) during a period of computer-based data-entry work. End-tidal PCO2, respiration frequency, and cardiac inter-beat interval (a measure of heart rate and its variability) were monitored continuously during the three conditions of the study. Self-ratings of relaxation and tension were also monitored at periodic intervals. Consistent with a decrease in psychophysiological arousal, end-tidal PCO2 and self-ratings of relaxation were significantly higher during progressive muscle relaxation than during baseline relaxation. Consistent with an increase in psychophysiological arousal, end-tidal PCO2, cardiac inter-beat interval, and relaxation ratings during data-entry work were significantly lower than during either baseline relaxation or progressive muscle relaxation, while respiration frequency and tension ratings were higher. The findings indicate that end-tidal PCO2 discriminates among different psychophysiological states, and that end-tidal PCO2 may be useful in indexing the stress-health effects of human-computer interactions.

  2. Simulations of a Detonation Wave in Transverse Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Cole, Lord; Karagozian, Ann; Cambier, Jean-Luc

    2010-11-01

    Numerical simulations of magneto-hydrodynamic (MHD) effects on detonation wave structures are performed, with applications to flow control and MHD power extraction in Pulse Detonation Engines (PDE) and their design variations. In contrast to prior studies of MHD interactions in PDEs,ootnotetextCambier, et al., AIAA-2008-4688 the effects of the finite relaxation length scale for ionization on the stability of the detonation wave are examined. Depending on the coupling parameters, the magnetic field can quench the detonation and effectively act as a barrier to its propagation. Conversely, an applied transient magnetic field can exert a force on a pre-ionized gas and accelerate it. The dynamics are subject to non-linear effects; a propagating transverse magnetic field will initially exert a small force if the gas has a low conductivity and the magnetic Reynolds number (Rem) is low. Nevertheless, the gas accelerated by the "piston" action of the field can pre-heat the ambient gas and increase its conductivity. As the wave progresses, Rem increases and the magnetic field becomes increasingly effective. The dynamics of this process are examined in detail with a high-order shock-capturing method and full kinetics of combustion and ionization. The complex chemical kinetics calculations are ported onto a GPU using the CUDA language, and computational performance is compared with standard CPU-based computations.

  3. Encapsulated gadolinium and dysprosium ions within ultra-short carbon nanotubes for MR microscopy at 11.75 and 21.1 T.

    PubMed

    Rosenberg, Jens T; Cisneros, Brandon T; Matson, Michael; Sokoll, Michelle; Sachi-Kocher, Afi; Bejarano, Fabian Calixto; Wilson, Lon J; Grant, Samuel C

    2014-01-01

    Single-walled carbon nanotubes (SWNTs) have gained interest for their biocompatibility and multifunctional properties. Ultra-short SWNTs (US-tubes) have demonstrated high proton relaxivity when encapsulating gadolinium ions (Gd(3+)) at clinical field strengths. At higher field strengths, however, Gd(3+) ions demonstrate decreased proton relaxation properties while chemically similar dysprosium ions (Dy(3+)) improve relaxation properties. This report investigates the first use of Gd(3+) and Dy(3+) ions within US-tubes (GNTs and DNTs, respectively) at ultra-high magnetic field (21.1 T). Both agents are compared in solution and as an intracellular contrast agent labeling a murine microglia cell line (Bv2) immobilized in a tissue-mimicking agarose phantom using two high magnetic fields: 21.1 and 11.75 T. In solution at 21.1 T, results show excellent transverse relaxation; DNTs outperformed GNTs as a T(2) agent with measured r(2)/r(1) ratios of 247 and 47, respectively. Additionally, intracellular DNTs were shown to be a better T(2) agent than GNTs with higher contrast percentages and contrast-to-noise ratios. As such, this study demonstrates the potential of DNTs at high magnetic fields for cellular labeling and future in vivo, MRI-based cell tracking.

  4. Transverse dune trailing ridges and vegetation succession

    NASA Astrophysics Data System (ADS)

    Hesp, Patrick A.; ‘Marisa' Martinez, M. L.

    2008-07-01

    We describe the evolution of, and vegetation succession on, a previously undescribed landform: transverse dune trailing ridges at El Farallón transgressive dunefield in the state of Veracruz, Mexico. Three-dimensional clinometer/compass and tape topographic surveys were conducted in conjunction with 1 m 2 contiguous percent cover and presence/absence vegetation survey transects at eight locations across two adjacent trailing ridges. At the study site, and elsewhere, the transverse dune trailing ridges are formed by vegetation colonization of the lateral margins of active transverse, barchanoidal transverse, and aklé or network dunes. For simplicity, all trailing ridges formed from these dune types are referred to as transverse dune trailing ridges. Because there are several transverse dunes in the dunefield, multiple trailing ridges can be formed at one time. Two adjacent trailing ridges were examined. The shortest length ridge was 70 m long, and evolving from a 2.5 m-high transverse dune, while the longer ridge was 140 m long, and evolving from an 8 m-high dune. Trailing ridge length is a proxy measure of ridge age, since the longer the ridge, the greater the length of time since initial formation. With increasing age or distance upwind, species diversity increased, as well as species horizontal extent and percent cover. In turn, the degree of bare sand decreased. Overall, the data indicate a successional trend in the vegetation presence and cover with increasing age upwind. Those species most tolerant to burial ( Croton and Palafoxia) begin the process of trailing ridge formation. Ipomoea and Canavalia are less tolerant to burial and also are typically the next colonizing species. Trachypogon does not tolerate sand burial or deposition very well and only appears after significant stabilization has taken place. The ridges display a moderately defined successional sequence in plant colonization and percentage cover with time (and upwind distance). They are

  5. [The transversality and health promotion schools].

    PubMed

    Gavidia Catalán, V

    2001-01-01

    The following article shows the evolution of the schools contribution to the Health Education of children and young people. Moving on from the traditional concept of health, today, Health Education has a general and global meaning, which encompasses all of the physical, psychological and social aspects of health. These aspects define the characteristics of the "Healthy School". The need to broach the "transversal subject" offers schools the possibility of developing "transversality" in the Health Education. Finally, the concept of promoting health defines, together with the other subjects, that which we understand by "the heath promotion schools", which attempts to progress the full integration of schools in the society in which they are located.

  6. Transverse dimension and long-term stability.

    PubMed

    Vanarsdall, R L

    1999-09-01

    This article emphasizes the critical importance of the skeletal differential between the width of the maxilla and the width of the mandible. Undiagnosed transverse discrepancy leads to adverse periodontal response, unstable dental camouflage, and less than optimal dentofacial esthetics. Hundreds of adult retreatment patients corrected for significant maxillary transverse deficiency using surgically assisted maxillary expansion (similar to osseous distraction) has produced excellent stability. Eliciting tooth movement for children (orthopedics, lip bumper, Cetlin plate) in all three planes of space by muscles, eruption, and growth, develops the broader arch form (without the mechanical forces of fixed or removable appliances) and has also demonstrated impressive long term stability.

  7. Transversely stable soliton trains in photonic lattices

    SciTech Connect

    Yang Jianke

    2011-09-15

    We report the existence of transversely stable soliton trains in optics. These stable soliton trains are found in two-dimensional square photonic lattices when they bifurcate from X-symmetry points with saddle-shaped diffraction inside the first Bloch band and their amplitudes are above a certain threshold. We also show that soliton trains with low amplitudes or bifurcated from edges of the first Bloch band ({Gamma} and M points) still suffer transverse instability. These results are obtained in the continuous lattice model and are further corroborated by the discrete model.

  8. Chatter in a transverse grinding process

    NASA Astrophysics Data System (ADS)

    Yan, Yao; Xu, Jian; Wiercigroch, Marian

    2014-02-01

    In transverse grinding, the wheel moves along the workpiece, which induces unique grinding dynamics. To understand these dynamic phenomena, specifically the grinding chatter, a new dynamical model of the process is proposed, in which the wheel position is assumed to be quasi-static since the transverse wheel velocity is small. From the stability and bifurcation analyses of the chatter vibration, it appears that the dynamics of the process is governed by the quasi-static interactions. Moreover, the obtained results also show that the wheel and workpiece chatters are quite different, having continuous and intermittent characters respectively.

  9. Transverse color tolerances for visual optical systems

    SciTech Connect

    Mouroulis, P.; Kim, T.G.; Zhao, G. )

    1993-12-01

    We performed psychophysical experiments to determine the effects of transverse chromatic aberration on observer performance through a specially designed telescopic system that presents negligible monochromatic aberration. Our results provide the basis for assessing the performance of visually coupled lenses in detail. The effect of transverse color on contrast sensitivity is more severe than on resolution. Color effects are compared with those of astigmatism: It is shown how one may make detailed predictions of system performance in order to decide on the necessary balance of aberrations at the design stage.

  10. Estimation of the transition/transversion ratio.

    PubMed

    Ina, Y

    1998-05-01

    A simple method for estimating the transition/transversion ratio was developed. This method can be applied to not only two sequences but also more than two sequences. The statistical properties of the method and some other methods were examined by numerical computation and computer simulation. The results obtained showed that, in terms of bias and variance, the new method gives a better estimate of the transition/transversion ratio than do the other examined methods. The new method was applied to human and chimpanzee mitochondrial control region sequences.

  11. Fractional variational calculus and the transversality conditions

    NASA Astrophysics Data System (ADS)

    Agrawal, O. P.

    2006-08-01

    This paper presents the Euler-Lagrange equations and the transversality conditions for fractional variational problems. The fractional derivatives are defined in the sense of Riemann-Liouville and Caputo. The connection between the transversality conditions and the natural boundary conditions necessary to solve a fractional differential equation is examined. It is demonstrated that fractional boundary conditions may be necessary even when the problem is defined in terms of the Caputo derivative. Furthermore, both fractional derivatives (the Riemann-Liouville and the Caputo) arise in the formulations, even when the fractional variational problem is defined in terms of one fractional derivative only. Examples are presented to demonstrate the applications of the formulations.

  12. Program Computes Universal Transverse Mercator Projection

    NASA Technical Reports Server (NTRS)

    Wallis, David E.

    1991-01-01

    Computer program produces Gauss-Kruger (constant meridional scale) transverse Mercator projection, used to construct U.S. Army's universal transverse Mercator (UTM) grid system. Capable of mapping entire Northern Hemisphere of Earth (and, by symmetry of projection, entire Earth) accurately with respect to single principal meridian. Mathematically insensitive to proximity to pole or equator and insensitive to departure of meridian from central meridian. Useful to any mapmaking agency. FORTRAN 77 program developed on IBM PC-series computer equipped with Intel Math Coprocessor.

  13. Transverse beam emittance measurement using quadrupole variation at KIRAMS-430

    NASA Astrophysics Data System (ADS)

    An, Dong Hyun; Hahn, Garam; Park, Chawon

    2015-02-01

    In order to produce a 430 MeV/u carbon ion (12 C 6+) beam for medical therapy, the Korea Institute of Radiological & Medical Sciences (KIRAMS) has carried out the development of a superconducting isochronous cyclotron, the KIRAMS-430. At the extraction of the cyclotron, an Energy Selection System (ESS) is located to modulate the fixed beam energy and to drive the ion beam through High Energy Beam Transport (HEBT) into the treatment room. The beam emittance at the ion beamline is to be measured to provide information on designing a beam with high quality. The well-known quadrupole variation method was used to determine the feasibility of measuring the transverse beam emittance. The beam size measured at the beam profile monitor (BPM) is to be utilized and the transformation of beam by transfer matrix is to be applied being taken under various transport condition of varying quadrupole magnetic strength. Two different methods where beam optics are based on the linear matrix formalism and particle tracking with a 3-D magnetic field distribution obtained by using OPERA3D TOSCA, are applied to transport the beam. The fittings for the transformation parameters are used to estimate the transverse emittance and the twiss parameters at the entrance of the quadrupole in the ESS. Including several systematic studies, we conclude that within the uncertainty the estimated emittances are consistent with the ones calculated by using Monte Carlo simulations.

  14. Crimp morphology in relaxed and stretched rat Achilles tendon.

    PubMed

    Franchi, Marco; Fini, Milena; Quaranta, Marilisa; De Pasquale, Viviana; Raspanti, Mario; Giavaresi, Gianluca; Ottani, Vittoria; Ruggeri, Alessandro

    2007-01-01

    Fibrous extracellular matrix of tendon is considered to be an inextensible anatomical structure consisting of type I collagen fibrils arranged in parallel bundles. Under polarized light microscopy the collagen fibre bundles appear crimped with alternating dark and light transverse bands. This study describes the ultrastructure of the collagen fibrils in crimps of both relaxed and in vivo stretched rat Achilles tendon. Under polarized light microscopy crimps of relaxed Achilles tendons appear as isosceles or scalene triangles of different size. Tendon crimps observed via SEM and TEM show the single collagen fibrils that suddenly change their direction containing knots. The fibrils appear partially squeezed in the knots, bent on the same plane like bayonets, or twisted and bent. Moreover some of them lose their D-period, revealing their microfibrillar component. These particular aspects of collagen fibrils inside each tendon crimp have been termed 'fibrillar crimps' and may fulfil the same functional role. When tendon is physiologically stretched in vivo the tendon crimps decrease in number (46.7%) (P<0.01) and appear more flattened with an increase in the crimp top angle (165 degrees in stretched tendons vs. 148 degrees in relaxed tendons, P<0.005). Under SEM and TEM, the 'fibrillar crimps' are still present, never losing their structural identity in straightened collagen fibril bundles of stretched tendons even where tendon crimps are not detectable. These data suggest that the 'fibrillar crimp' may be the true structural component of the tendon crimp acting as a shock absorber during physiological stretching of Achilles tendon.

  15. Engineered magnetic hybrid nanoparticles with enhanced relaxivity for tumor imaging.

    PubMed

    Aryal, Santosh; Key, Jaehong; Stigliano, Cinzia; Ananta, Jeyarama S; Zhong, Meng; Decuzzi, Paolo

    2013-10-01

    Clinically used contrast agents for magnetic resonance imaging (MRI) suffer by the lack of specificity; short circulation time; and insufficient relaxivity. Here, a one-step combinatorial approach is described for the synthesis of magnetic lipid-polymer (hybrid) nanoparticles (MHNPs) encapsulating 5 nm ultra-small super-paramagnetic iron oxide particles (USPIOs) and decorated with Gd(3+) ions. The MHNPs comprise a hydrophobic poly(lactic acid-co-glycolic acid) (PLGA) core, containing up to ~5% USPIOs (w/w), stabilized by lipid and polyethylene glycol (PEG). Gd(3+) ions are directly chelated to the external lipid monolayer. Three different nanoparticle configurations are presented including Gd(3+) chelates only (Gd-MHNPs); USPIOs only (Fe-MHNPs); and the combination thereof (MHNPs). All three MHNPs exhibit a hydrodynamic diameter of about 150 nm. The Gd-MHNPs present a longitudinal relaxivity (r1 = 12.95 ± 0.53 (mM s)(-1)) about four times larger than conventional Gd-based contrast agents (r1 = 3.4 (mM s)(-1)); MHNPs have a transversal relaxivity of r2 = 164.07 ± 7.0 (mM s)(-1), which is three to four times larger than most conventional systems (r2 ~ 50 (mM s)(-1)). In melanoma bearing mice, elemental analysis for Gd shows about 3% of the injected MHNPs accumulating in the tumor and 2% still circulating in the blood, at 24 h post-injection. In a clinical 3T MRI scanner, MHNPs provide significant contrast confirming the observed tumor deposition. This approach can also accommodate the co-loading of hydrophobic therapeutic compounds in the MHNP core, paving the way for theranostic systems.

  16. Perturbative calculations of quantum spin tunneling in effective spin systems with a transversal magnetic field and transversal anisotropy

    NASA Astrophysics Data System (ADS)

    Krizanac, M.; Vedmedenko, E. Y.; Wiesendanger, R.

    2017-01-01

    We present a perturbative approach for the resonant tunnel splittings of an arbitrary effective single spin system. The Hamiltonian of such a system contains a uniaxial anisotropy, a transversal magnetic field and a second-order transversal anisotropy. Further, we investigate the influence of the transversal magnetic field on the energy splittings for higher integer quantum spins and we introduce an exact formula, which defines values of the transversal magnetic field, the transversal anisotropy and the uniaxial anisotropy where the contribution of the transversal magnetic field to the energy splitting is at least equal to the contribution of the transversal anisotropy.

  17. Relaxation damping in oscillating contacts

    PubMed Central

    Popov, M.; Popov, V.L.; Pohrt, R.

    2015-01-01

    If a contact of two purely elastic bodies with no sliding (infinite coefficient of friction) is subjected to superimposed oscillations in the normal and tangential directions, then a specific damping appears, that is not dependent on friction or dissipation in the material. We call this effect “relaxation damping”. The rate of energy dissipation due to relaxation damping is calculated in a closed analytic form for arbitrary axially-symmetric contacts. In the case of equal frequency of normal and tangential oscillations, the dissipated energy per cycle is proportional to the square of the amplitude of tangential oscillation and to the absolute value of the amplitude of normal oscillation, and is dependent on the phase shift between both oscillations. In the case of low frequency tangential oscillations with superimposed high frequency normal oscillations, the dissipation is proportional to the ratio of the frequencies. Generalization of the results for macroscopically planar, randomly rough surfaces as well as for the case of finite friction is discussed. PMID:26549011

  18. Domain Relaxation in Polymer Monolayers

    NASA Astrophysics Data System (ADS)

    Bernoff, Andrew J.; Alexander, James C.; Mann, J. R.; Mann, Elizabeth K.

    2004-11-01

    We report on an experimental and theoretical study of a polymer monolayer on the surface of a subfluid. When stretched (by a transient applied flow), the monolayer takes the form of a bola consisting of two roughly circular reservoirs connected by a thin tether. This shape relaxes to the minimum energy configuration of a circular domain. The tether is never observed to rupture, even when it is more than a hundred times as long as it is thin. We model these experiments by taking previous descriptions of the hydrodynamics (primarily those of Stone & McConnell and Lubensky & Goldstein ), identifying the dominant effects, and reducing the system to a more tractable form. The result is a free boundary problem where motion is driven by the line tension of the domain and damped by the viscosity of the subfluid. Using this model we derive relaxation rates for perturbations of a uniform strip and a circular patch. Lubrication theory for the tether evolution yields the thin film equation HT = -(H^2H_XXX)_X. This evolution equation appears not to manifest rupture, in agreement with the experiments. Finally, we speculate on which physical properties of the system (such as line tension) can be deduced by comparison of theory to experiment.

  19. Violent relaxation of ellipsoidal clouds

    NASA Astrophysics Data System (ADS)

    Benhaiem, David; Sylos Labini, Francesco

    2015-04-01

    An isolated, initially cold and ellipsoidal cloud of self-gravitating particles represents a relatively simple system in which to study the effects of deviations from spherical symmetry in the mechanism of violent relaxation. Initial deviations from spherical symmetry are shown to play a dynamical role that is equivalent to that of density fluctuations in the case of an initially spherical cloud. Indeed, these deviations control the amount of particle-energy change and thus determine the properties of the final energy distribution, particularly the appearance of two species of particles: bound and free. Ejection of mass and energy from the system, together with the formation of a density profile decaying as ρ(r) ˜ r-4 and a Keplerian radial velocity dispersion profile, are prominent features similar to those observed after the violent relaxation of spherical clouds. In addition, we find that ejected particles are characterized by highly non-spherical shapes, the features of which can be traced in the initial deviations from spherical symmetry that are amplified during the dynamical evolution: particles can indeed form anisotropic configurations, like bars and/or discs, even though the initial cloud was very close to spherical.

  20. Nuclear magnetic relaxation by the dipolar EMOR mechanism: General theory with applications to two-spin systems

    NASA Astrophysics Data System (ADS)

    Chang, Zhiwei; Halle, Bertil

    2016-02-01

    In aqueous systems with immobilized macromolecules, including biological tissue, the longitudinal spin relaxation of water protons is primarily induced by exchange-mediated orientational randomization (EMOR) of intra- and intermolecular magnetic dipole-dipole couplings. We have embarked on a systematic program to develop, from the stochastic Liouville equation, a general and rigorous theory that can describe relaxation by the dipolar EMOR mechanism over the full range of exchange rates, dipole coupling strengths, and Larmor frequencies. Here, we present a general theoretical framework applicable to spin systems of arbitrary size with symmetric or asymmetric exchange. So far, the dipolar EMOR theory is only available for a two-spin system with symmetric exchange. Asymmetric exchange, when the spin system is fragmented by the exchange, introduces new and unexpected phenomena. Notably, the anisotropic dipole couplings of non-exchanging spins break the axial symmetry in spin Liouville space, thereby opening up new relaxation channels in the locally anisotropic sites, including longitudinal-transverse cross relaxation. Such cross-mode relaxation operates only at low fields; at higher fields it becomes nonsecular, leading to an unusual inverted relaxation dispersion that splits the extreme-narrowing regime into two sub-regimes. The general dipolar EMOR theory is illustrated here by a detailed analysis of the asymmetric two-spin case, for which we present relaxation dispersion profiles over a wide range of conditions as well as analytical results for integral relaxation rates and time-dependent spin modes in the zero-field and motional-narrowing regimes. The general theoretical framework presented here will enable a quantitative analysis of frequency-dependent water-proton longitudinal relaxation in model systems with immobilized macromolecules and, ultimately, will provide a rigorous link between relaxation-based magnetic resonance image contrast and molecular parameters.

  1. Relaxation of liquid bridge after droplets coalescence

    NASA Astrophysics Data System (ADS)

    Zheng, Jiangen; Shi, Haiyang; Chen, Guo; Huang, Yingzhou; Wei, Hua; Wang, Shuxia; Wen, Weijia

    2016-11-01

    We investigate the relaxation of liquid bridge after the coalescence of two sessile droplets resting on an organic glass substrate both experimentally and theoretically. The liquid bridge is found to relax to its equilibrium shape via two distinct approaches: damped oscillation relaxation and underdamped relaxation. When the viscosity is low, damped oscillation shows up, in this approach, the liquid bridge undergoes a damped oscillation process until it reaches its stable shape. However, if the viscous effects become significant, underdamped relaxation occurs. In this case, the liquid bridge relaxes to its equilibrium state in a non-periodic decay mode. In depth analysis indicates that the damping rate and oscillation period of damped oscillation are related to an inertial-capillary time scale τc. These experimental results are also testified by our numerical simulations with COMSOL Multiphysics.

  2. Cross relaxation in nitroxide spin labels

    NASA Astrophysics Data System (ADS)

    Marsh, Derek

    2016-11-01

    Cross relaxation, and mI -dependence of the intrinsic electron spin-lattice relaxation rate We , are incorporated explicitly into the rate equations for the electron-spin population differences that govern the saturation behaviour of 14N- and 15N-nitroxide spin labels. Both prove important in spin-label EPR and ELDOR, particularly for saturation recovery studies. Neither for saturation recovery, nor for CW-saturation EPR and CW-ELDOR, can cross relaxation be described simply by increasing the value of We , the intrinsic spin-lattice relaxation rate. Independence of the saturation recovery rates from the hyperfine line pumped or observed follows directly from solution of the rate equations including cross relaxation, even when the intrinsic spin-lattice relaxation rate We is mI -dependent.

  3. Barnett relaxation in non-symmetric grains

    NASA Astrophysics Data System (ADS)

    Kolasi, Erald; Weingartner, Joseph C.

    2017-10-01

    Barnett relaxation, first described by Purcell in 1979, appears to play a major role in the alignment of grains with the interstellar magnetic field. In 1999, Lazarian and Draine proposed that Barnett relaxation and its relative, nuclear relaxation, can induce grains to flip. If this thermal flipping is rapid then the dynamical effect of torques that are fixed relative to the grain body can be greatly reduced. To date, detailed studies of Barnett relaxation have been confined to grains exhibiting dynamic symmetry. In 2009, Weingartner argued that internal relaxation cannot induce flips in any grains, whether they exhibit dynamic symmetry or not. In this work, we develop approximate expressions for the dissipation rate and diffusion coefficient for Barnett relaxation. We revisit the issue of internally induced thermal flipping, finding that it cannot occur for grains with dynamic symmetry, but does occur for grains lacking dynamic symmetry.

  4. Measuring transverse shape with virtual photons

    SciTech Connect

    Hoyer, Paul; Kurki, Samu

    2011-06-01

    A two-dimensional Fourier transform of hadron form factors allows to determine their charge density in transverse space. We show that this method can be applied to any virtual photon induced transition, such as {gamma}{sup *}(q)+N{yields}{pi}N. Only Fock states that are common to the initial and final states contribute to the amplitudes, which are determined by the overlap of the corresponding light-front wave functions. Their transverse extent may be studied as a function of the final state configuration, allowing qualitatively new insight into strong interaction dynamics. Fourier transforming the cross section (rather than the amplitude) gives the distribution of the transverse distance between the virtual photon interaction vertices in the scattering amplitude and its complex conjugate. While the measurement of parton distributions in longitudinal momentum depends on the leading twist approximation (-q{sup 2}{yields}{infinity} limit), all q{sup 2}<0 values contribute to the Fourier transform, with the transverse resolution increasing with the available range in q{sup 2}. We illustrate the method using QED amplitudes.

  5. Transversal filter for parabolic phase equalization

    NASA Technical Reports Server (NTRS)

    Kelly, Larry R. (Inventor); Waugh, Geoffrey S. (Inventor)

    1993-01-01

    An equalizer (10) for removing parabolic phase distortion from an analog signal (3), utilizing a pair of series connected transversal filters. The parabolic phase distortion is cancelled by generating an inverse parabolic approximation using a sinusoidal phase control filter (18). The signal (3) is then passed through an amplitude control filter (21) to remove magnitude ripple components.

  6. Transverse instability of a rectangular bunch

    SciTech Connect

    Balbekov, V.; /Fermilab

    2005-12-01

    Transverse instability of a rectangular bunch is investigated. Known theory of bunched beam instability is modified to take into account 100% spread of synchrotron frequency. Series of equations adequately describing the instability is derived and solved analytically and numerically. The theory is applied to the Fermilab Recycler Ring.

  7. Sex Education as a Transversal Subject

    ERIC Educational Resources Information Center

    Rabelo, Amanda Oliveira; Pereira, Graziela Raupp; Reis, Maria Amélia; Ferreira, António G.

    2015-01-01

    Currently, sex education is in many countries a transversal subject, in which the school becomes a privileged place for the implementation of policies that aim at promoting "public health." Its design as a cross-cutting subject envisages fostering the dissemination of these subjects in all pedagogical and curricular fields; however, we…

  8. Transverse stability in a Stark decelerator

    SciTech Connect

    Meerakker, Sebastiaan Y. T. van de; Bethlem, Hendrick L.; Vanhaecke, Nicolas; Meijer, Gerard

    2006-02-15

    The concept of phase stability in a Stark decelerator ensures that polar molecules can be accelerated, guided, or decelerated without loss; molecules within a certain position and velocity interval are kept together throughout the deceleration process. In this paper the influence of the transverse motion on phase stability in a Stark decelerator is investigated. For typical deceleration experiments--i.e., for high values of the phase angle {phi}{sub 0}--the transverse motion considerably enhances the region in phase space for which phase stable deceleration occurs. For low values of {phi}{sub 0}, however, the transverse motion reduces the acceptance of a Stark decelerator and unstable regions in phase space appear. These effects are quantitatively explained in terms of a coupling between the longitudinal and transverse motion. The predicted longitudinal acceptance of a Stark decelerator is verified by measurements on a beam of OH (X {sup 2}{pi}{sub 3/2},J=3/2) radicals passing through a Stark decelerator.

  9. Semi-Inclusive DIS and Transversity

    SciTech Connect

    Ratcliffe, Philip G.

    2005-02-10

    A review is presented of some aspects of semi-inclusive deeply inelastic scattering and transversity. In particular, the role of kT-dependent and higher-twist (or multi-parton) distributions in generating single-spin asymmetries is discussed.

  10. Bending of Beams Subjected to Transverse Impacts,

    DTIC Science & Technology

    1983-04-01

    and rotary inertia effects have been considered by Karunes and Onat [6] Symonds [7] and Jones and Gomes de Oliveira (8]. The main aspects of the...Phys. Sol., Vol. 2, 1954, pp. 92-102. 6. Karunes , B. and Onat, E.T., "On the Effect of Shear on Plastic Deformation of Beams Under Transverse Impact

  11. Sex Education as a Transversal Subject

    ERIC Educational Resources Information Center

    Rabelo, Amanda Oliveira; Pereira, Graziela Raupp; Reis, Maria Amélia; Ferreira, António G.

    2015-01-01

    Currently, sex education is in many countries a transversal subject, in which the school becomes a privileged place for the implementation of policies that aim at promoting "public health." Its design as a cross-cutting subject envisages fostering the dissemination of these subjects in all pedagogical and curricular fields; however, we…

  12. Transverse Flow Effects In Dilepton Emission

    SciTech Connect

    Kajantie, K.; Kataja., M.; McLerran, L.; Ruuskanen, P. V.

    1986-08-01

    Dilepton emission from expanding QCD matter formed in ultrarelativistic nuclear collisions is computed. The energy density and the velocity field of the expanding matter are computed numerically with a 1+3 dimensional numerical code which assumes cylindrical invariance in the transverse and boost invariance in the longitudinal direction.

  13. Transverse vibration techniques : logs to structural systems

    Treesearch

    Robert J. Ross

    2008-01-01

    Transverse vibration as a nondestructive testing and evaluation technique was first examined in the early 1960s. Initial research and development efforts focused on clear wood, lumber, and laminated products. Out of those efforts, tools were developed that are used today to assess lumber properties. Recently, use of this technique has been investigated for evaluating a...

  14. Barium granuloma of the transverse colon.

    PubMed Central

    McKee, P. H.; Cameron, C. H.

    1978-01-01

    A case of barium sulphate granuloma of the transverse colon following gunshot wounds to the abdomen has been described. Scanning electron microscopy with electron probe microanalysis was used to confirm the presence of barium sulphate and the absence of lead or other elements related to the gunshot wounds. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 PMID:740599

  15. Formulas for Precise Transverse Mercator Projection

    NASA Technical Reports Server (NTRS)

    Wallis, D. E.

    1983-01-01

    Transverse mercator projection, surface of Earth or other spheroid is mapped onto cylinder tangent at meridian of longitude. New method performs mapping by means of mathematical series in which higher order terms correct for deviation from exact sphericity. New method yields precise geodetic maps.

  16. Stabilization of electrical sensing properties of carbon fiber sensors using pre-tensioning approach

    NASA Astrophysics Data System (ADS)

    Saifeldeen, M. A.; Fouad, N.; Huang, H.; Wu, Z. S.

    2017-01-01

    Owing to fabrication defects in carbon fiber (CF) tows, the unevenness of fiber roves, such as local bends, misalignments, and skewness, results in irregular distribution of the electrical resistance in the transverse direction along the gauge length of a sensor, which affects its performance. In this study, a pre-tension approach was developed according to the creep mechanism of composites to straighten the CFs. In addition, the resin relaxation was controlled by tensioning the fibers during and after hardening of the epoxy resin using a double-tension method to enhance the electrical sensing properties of long gauge carbon fiber line (CFL) strain sensors. Different levels of sustained tensile stresses were studied to obtain the optimal tensile stress level both during and after hardening to be applied in the double-tension method. The results of static and dynamic tests showed that the double-tension technique could significantly straighten the fibers, and stabilize the transverse connections of CFL sensors in the case of tensioning the fibers during and after hardening under a sustained stress of 60% of the ultimate tensile stress of the CFs. The proposed double-tension method was utilized to improve the response of the CFL sensors with short gauge lengths.

  17. Conservation of magnetic helicity during plasma relaxation

    SciTech Connect

    Ji, H.; Prager, S.C.; Sarff, J.S.

    1994-07-01

    Decay of the total magnetic helicity during the sawtooth relaxation in the MST Reversed-Field Pinch is much larger than the MHD prediction. However, the helicity decay (3--4%) is smaller than the magnetic energy decay (7--9%), modestly supportive of the helicity conservation hypothesis in Taylor`s relaxation theory. Enhanced fluctuation-induced helicity transport during the relaxation is observed.

  18. Relaxation dynamics of a single DNA molecule

    NASA Astrophysics Data System (ADS)

    Goshen, E.; Zhao, W. Z.; Carmon, G.; Rosen, S.; Granek, R.; Feingold, M.

    2005-06-01

    The relaxation of a single DNA molecule is studied. The experimental system consists of optical tweezers and a micron-sized bead that is tethered to the bottom of the sample by a single double-stranded DNA molecule. The bead slows down the DNA relaxation from a strongly stretched configuration such that it is passing through stretched equilibrium states. This allows for a theoretical description of the relaxation trajectory, which is in good agreement with experiment.

  19. Dielectric relaxation in a protein matrix

    SciTech Connect

    Pierce, D.W.; Boxer, S.G.

    1992-06-25

    The dielectric relaxation of a sperm whale ApoMb-DANCA complex is measured by the fluorescence dynamic Stokes shift method. Emission energy increases with decreasing temperature, suggesting that the relaxation activation energies of the rate-limiting motions either depend on the conformational substrate or different types of protein motions with different frequencies participate in the reaction. Experimental data suggest that there may be relaxations on a scale of <100 ps. 61 refs., 7 figs., 2 tabs.

  20. The logarithmic relaxation process and the critical temperature of liquids in nano-confined states

    PubMed Central

    Chen, Changjiu; Wong, Kaikin; Mole, Richard A.; Yu, Dehong; Chathoth, Suresh M.

    2016-01-01

    The logarithmic relaxation process is the slowest of all relaxation processes and is exhibited by only a few molecular liquids and proteins. Bulk salol, which is a glass-forming liquid, is known to exhibit logarithmic decay of intermediate scattering function for the β-relaxation process. In this article, we report the influence of nanoscale confinements on the logarithmic relaxation process and changes in the microscopic glass-transition temperature of salol in the carbon and silica nanopores. The generalized vibrational density-of-states of the confined salol indicates that the interaction of salol with ordered nanoporous carbon is hydrophilic in nature whereas the interaction with silica surfaces is more hydrophobic. The mode-coupling theory critical temperature derived from the QENS data shows that the dynamic transition occurs at much lower temperature in the carbon pores than in silica pores. The results of this study indicate that, under nano-confinements, liquids that display logarithmic β-relaxation phenomenon undergo a unique glass transition process. PMID:27671486

  1. The logarithmic relaxation process and the critical temperature of liquids in nano-confined states

    NASA Astrophysics Data System (ADS)

    Chen, Changjiu; Wong, Kaikin; Mole, Richard A.; Yu, Dehong; Chathoth, Suresh M.

    2016-09-01

    The logarithmic relaxation process is the slowest of all relaxation processes and is exhibited by only a few molecular liquids and proteins. Bulk salol, which is a glass-forming liquid, is known to exhibit logarithmic decay of intermediate scattering function for the β-relaxation process. In this article, we report the influence of nanoscale confinements on the logarithmic relaxation process and changes in the microscopic glass-transition temperature of salol in the carbon and silica nanopores. The generalized vibrational density-of-states of the confined salol indicates that the interaction of salol with ordered nanoporous carbon is hydrophilic in nature whereas the interaction with silica surfaces is more hydrophobic. The mode-coupling theory critical temperature derived from the QENS data shows that the dynamic transition occurs at much lower temperature in the carbon pores than in silica pores. The results of this study indicate that, under nano-confinements, liquids that display logarithmic β-relaxation phenomenon undergo a unique glass transition process.

  2. Anomalous transport and phonon renormalization in a chain with transverse and longitudinal vibrations.

    PubMed

    G, Santhosh; Kumar, Deepak

    2010-07-01

    We study thermal transport in a chain of coupled atoms, which can vibrate in longitudinal as well as transverse directions. The particles interact through anharmonic potentials upto cubic order. The problem is treated quantum mechanically. We first calculate the phonon frequencies self-consistently taking into account the anharmonic interactions. We show that for all the modes, frequencies must have linear dispersion with wave vector q for small q irrespective of their bare dispersions. We then calculate the phonon relaxation rates Γi(q), where i is the polarization index of the mode, in a self-consistent approximation based on second-order perturbation diagrams. We find that the relaxation rate for the longitudinal phonon, Γx(q)∝q(3/2), while that for the transverse phonon Γy(q)∝q2. The consequence of these results on the thermal conductivity κ(N) of a chain of N particles is that κ(N)∝N(1/2).

  3. Use of cross-correlated NMR relaxation for the study of motional anisotropy of liquid crystals

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Rangeet; Kumar, Anil

    2003-04-01

    A method to measure the rotational diffusion coefficients of a liquid crystal based on the measurements of auto and cross-correlated relaxation is presented here. We report the measurements of cross-correlations between the relaxation processes originating from the chemical shift anisotropy (CSA) of 13C and its dipolar coupling with the attached proton, for various carbons in a liquid crystal. The spectral densities are expressed as a function of motional parameters, using extended Lipari-Szabo model-free approach. These motional parameters were extracted from the measured self-relaxation, cross-relaxation and the cross-correlation rates. The potential of this method is demonstrated by the determination of the rotational diffusion coefficients of N-4-methoxybenzylidene-4-butylaniline (MBBA) at 297 K undergoing magic angle sample spinning.

  4. Paley-Wiener criterion for relaxation functions

    NASA Astrophysics Data System (ADS)

    Ngai, K. L.; Rajagopal, A. K.; Rendell, R. W.; Teitler, S.

    1983-11-01

    It is shown how the Paley-Wiener theorem in Fourier-transform theory can provide the bound for physically acceptable relaxation functions for long times. In principle the linear exponential decay function, and hence also a superposition of linear exponential decay functions, does not provide an acceptable description of relaxation phenomenon although the Paley-Wiener bound can be made to approach arbitrarily close to linear exponential. A class of relaxation functions proposed recently obeys the Paley-Wiener bound. The general necessity for time-dependent relaxation rates is emphasized and discussed.

  5. [Desmin content and transversal stiffness of the left ventricle mouse cardiomyocytes and skeletal muscle fibers after a 30-day space flight on board "BION-M1" biosatellite].

    PubMed

    Ogneva, I V; Maximova, M V; Larina, I M

    2014-01-01

    The aim of this study was to determine the transversal stiffness of the cortical cytoskeleton and the cytoskeletal protein desmin content in the left ventricle cardiomyocytes, fibers of the mouse soleus and tibialis anterior muscle after a 30-day space flight on board the "BION-M1" biosatellite (Russia, 2013). The dissection was made after 13-16.5 h after landing. The transversal stiffness was measured in relaxed and calcium activated state by, atomic force microscopy. The desmin content was estimated by western blotting, and the expression level of desmin-coding gene was detected using real-time PCR. The results indicate that, the transversal stiffness of the left ventricle cardiomyocytes and fibers of the soleus muscle in relaxed and activated states did not differ from the control. The transversal stiffness of the tibialis muscle fibers in relaxed and activated state was increased in the mice group after space flight. At the same time, in all types of studied tissues the desmin content and the expression level of desmin-coding gene did not differ from the control level.

  6. Stress relaxation behavior of tessellated cartilage from the jaws of blue sharks.

    PubMed

    Liu, Xiaoxi; Dean, Mason N; Youssefpour, Hamed; Summers, Adam P; Earthman, James C

    2014-01-01

    Much of the skeleton of sharks, skate and rays (Elasmobranchii) is characterized by a tessellated structure, composed of a shell of small, mineralized plates (tesserae) joined by intertesseral ligaments overlaying a soft cartilage core. Although tessellated cartilage is a defining feature of this group of fishes, the significance of this skeletal tissue type - particularly from a mechanical perspective - is unknown. The aim of the present work was to perform stress relaxation experiments with tessellated cartilage samples from the jaws of blue sharks to better understand the time dependent behavior of this skeletal type. In order to facilitate this aim, the resulting relaxation behavior for different loading directions were simulated using the transversely isotropic biphasic model and this model combined with generalized Maxwell elements to represent the tessellated layer. Analysis of the ability of the models to simulate the observed experimental behavior indicates that the transversely isotropic biphasic model can provide good predictions of the relaxation behavior of the hyaline cartilage. However, the incorporation of Maxwell elements into this model can achieve a more accurate simulation of the dynamic behavior of calcified cartilage when the loading is parallel to the tessellated layer. Correlation of experimental data with present combined composite models showed that the equilibrium modulus of the tessellated layer for this loading direction is about 45 times greater than that for uncalcified cartilage. Moreover, tessellation has relatively little effect on the viscoelasticity of shark cartilage under loading that is normal to the tessellated layer.

  7. Metabasin transitions are Johari-Goldstein relaxation events.

    PubMed

    Cicerone, Marcus T; Tyagi, Madhusudan

    2017-02-07

    We show that by representing quasi-elastic and inelastic neutron scattering from propylene carbonate (PC) with an explicitly heterogeneous model, we recover signatures of two distinct localized modes in addition to diffusive motion. The intermediate scattering function provides access to the time-dependence of these two localized dynamic processes, and they appear to correspond to transitions between inherent states and between metabasins on a potential energy landscape. By fitting the full q-dependence of inelastic scattering, we confirm that the Johari-Goldstein (βJG) relaxation in PC is indistinguishable from metabasin transitions.

  8. Metabasin transitions are Johari-Goldstein relaxation events

    NASA Astrophysics Data System (ADS)

    Cicerone, Marcus T.; Tyagi, Madhusudan

    2017-02-01

    We show that by representing quasi-elastic and inelastic neutron scattering from propylene carbonate (PC) with an explicitly heterogeneous model, we recover signatures of two distinct localized modes in addition to diffusive motion. The intermediate scattering function provides access to the time-dependence of these two localized dynamic processes, and they appear to correspond to transitions between inherent states and between metabasins on a potential energy landscape. By fitting the full q-dependence of inelastic scattering, we confirm that the Johari-Goldstein (βJ G) relaxation in PC is indistinguishable from metabasin transitions.

  9. An optimized transversely isotropic, hyper-poro-viscoelastic finite element model of the meniscus to evaluate mechanical degradation following traumatic loading.

    PubMed

    Wheatley, Benjamin B; Fischenich, Kristine M; Button, Keith D; Haut, Roger C; Haut Donahue, Tammy L

    2015-06-01

    Inverse finite element (FE) analysis is an effective method to predict material behavior, evaluate mechanical properties, and study differences in biological tissue function. The meniscus plays a key role in load distribution within the knee joint and meniscal degradation is commonly associated with the onset of osteoarthritis. In the current study, a novel transversely isotropic hyper-poro-viscoelastic constitutive formulation was incorporated in a FE model to evaluate changes in meniscal material properties following tibiofemoral joint impact. A non-linear optimization scheme was used to fit the model output to indentation relaxation experimental data. This study is the first to investigate rate of relaxation in healthy versus impacted menisci. Stiffness was found to be decreased (p=0.003), while the rate of tissue relaxation increased (p=0.010) at twelve weeks post impact. Total amount of relaxation, however, did not change in the impacted tissue (p=0.513). Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Cross-Correlated Relaxation of Dipolar Coupling and Chemical-Shift Anisotropy in Magic-Angle Spinning R1ρ NMR Measurements: Application to Protein Backbone Dynamics Measurements

    PubMed Central

    Kurauskas, Vilius; Weber, Emmanuelle; Hessel, Audrey; Ayala, Isabel; Marion, Dominique; Schanda, Paul

    2016-01-01

    Transverse relaxation rate measurements in MAS solid-state NMR provide information about molecular motions occurring on nanoseconds-to-milliseconds (ns-ms) time scales. The measurement of heteronuclear (13C, 15N) relaxation rate constants in the presence of a spin-lock radio-frequency field (R1ρ relaxation) provides access to such motions, and an increasing number of studies involving R1ρ relaxation in proteins has been reported. However, two factors that influence the observed relaxation rate constants have so far been neglected, namely (i) the role of CSA/dipolar cross-correlated relaxation (CCR), and (ii) the impact of fast proton spin flips (i.e. proton spin diffusion and relaxation). We show that CSA/D CCR in R1ρ experiments is measurable, and that this cross-correlated relaxation rate constant depends on ns-ms motions, and can thus itself provide insight into dynamics. We find that proton spin-diffusion attenuates this cross-correlated relaxation, due to its decoupling effect on the doublet components. For measurements of dynamics, the use of R1ρ rate constants has practical advantages over the use of CCR rates, and the present manuscript reveals factors that have so far been disregarded and which are important for accurate measurements and interpretation. PMID:27500976

  11. Zen meditation and ABC relaxation theory: an exploration of relaxation states, beliefs, dispositions, and motivations.

    PubMed

    Gillani, N B; Smith, J C

    2001-06-01

    This study is an attempt to rigorously map the psychological effects of Zen meditation among experienced practitioners. Fifty-nine Zen meditators with at least six years of experience practiced an hour of traditional Zazen seated meditation. A control group of 24 college students spent 60 min silently reading popular magazines. Before relaxation, all participants took the Smith Relaxation States Inventory (SRSI), the Smith Relaxation Dispositions/Motivations Inventory (SRD/MI), and the Smith Relaxation Beliefs Inventory (SRBI). After practice, participants again took the SRSI. Analyses revealed that meditators are less likely to believe in God, more likely to believe in Inner Wisdom, and more likely to display the relaxation dispositions Mental Quiet, Mental Relaxation, and Timeless/Boundless/Infinite. Pre- and postsession analyses revealed that meditators showed greater increments in the relaxation states Mental Quiet, Love and Thankfulness, and Prayerfulness, as well as reduced Worry. Results support Smith's ABC Relaxation Theory.

  12. Myocardial contraction-relaxation coupling

    PubMed Central

    2010-01-01

    Since the pioneering work of Henry Pickering Bowditch in the late 1800s to early 1900s, cardiac muscle contraction has remained an intensely studied topic for several reasons. The heart is located centrally in our body, and its pumping motion demands the attention of the observer. The contraction of the heart encompasses a complex interplay of mechanical, chemical, and electrical properties, and its function can thus be studied from any of these viewpoints. In addition, diseases of the heart are currently killing more people in the Westernized world than any other disease. When combined with the increasing emphasis of research to be clinically relevant, this contributes to the heart remaining a topic of continued basic and clinical investigation. Yet, there are significant aspects of cardiac muscle contraction that are still not well understood. A big complication of the study of cardiac muscle contraction is that there exists no equilibrium among many of the important governing parameters, which include pre- and afterload, intracellular ion concentrations, membrane potential, and velocity and direction of movement. Thus the classic approach of perturbing an equilibrium or a steady state to learn about the role of the perturbing factor in the system cannot be unambiguously interpreted, since each of the parameters that govern contraction are constantly changing, as well as constantly changing their interaction with each other. In this review, presented as the 54th Bowditch Lecture at Experimental Biology meeting in Anaheim in April 2010, I will revisit several governing factors of cardiac muscle relaxation by applying newly developed tools and protocols to isolated cardiac muscle tissue in which the dynamic interactions between the governing factors of contraction and relaxation can be studied. PMID:20852049

  13. Music assisted progressive muscle relaxation, progressive muscle relaxation, music listening, and silence: a comparison of relaxation techniques.

    PubMed

    Robb, S L

    2000-01-01

    The purpose of this study was to compare the effects of music assisted progressive muscle relaxation (M + PMR), progressive muscle relaxation (PMR), music listening, and silence/suggestion on measures of anxiety and perceived relaxation. The study also examined participant responses to a posttreatment questionnaire to identify relationships between musical and nonmusical elements in relaxation techniques. Sixty university students participated in the study. Fifteen participants were randomly assigned to each treatment condition. Subjects were tested individually using the same relaxation script for M + PMR and PMR conditions. One-way analyses of covariance were computed to compare pre and posttest differences among groups. Results of the ANCOVA revealed no differences among groups for the State Trait Anxiety Inventory (STAI) or the Visual Analog Scale (VAS). Analysis of variance, however, revealed each treatment condition to be equally effective in producing significant changes in anxiety and perceived relaxation from the pre to posttest period. Additionally, mean score differences revealed decreases for all conditions with M + PMR eliciting the greatest amount of change. A content analysis of posttreatment questionnaire items revealed detailed information about each participant's relaxation experience, state of mind, and use of self-generated relaxation techniques.

  14. The Effects of Progressive Relaxation and Music on Attention, Relaxation and Stress Responses: An Investigation of the Cognitive-Behavioral Model of Relaxation

    DTIC Science & Technology

    1999-01-28

    295’-6772 APPROVAL SHEET Title ofDissertation: "The Effects ofProgressive Relaxation and Music on Attention, Relaxation~ and Stress Responses: An...and Music on Attention, Relaxation, and Stress Responses: An Investigation of the Cognitive-Behavioral Model of Relaxation.n beyond brief excerpts is...Health Sciences ii ABSTRACT Title: The Effects of Progressive Relaxation and Music on Attention, Relaxation, and Stress Responses: An Investigation of

  15. Repetitive operation of switchless transverse flow transversely excited atmosphere CO2 lasers.

    PubMed

    Patil, Gautam C; Nilaya, J Padma; Biswas, D J

    2011-09-01

    The enhanced preionisation efficiency of a mutually coupled parallel spark preioniser has been exploited to achieve switchless operation of a transversely excited atmosphere (TEA) CO(2) laser in the conventional transverse gas flow configuration. This made the laser more compatible to repetitive operation and the satisfactory performance of a switchless TEA CO(2) laser of ~8 cc active volume is reported here up to a maximum repetition rate of 100 Hz at a gas replenishment factor of ~2.

  16. Dielectric relaxations in partly deuterated ammonium dichromate

    NASA Astrophysics Data System (ADS)

    Gilchrist, John le G.

    1987-12-01

    Two dielectric relaxations in partly deuterated ammonium dichromate are attributed to reorientations of mixed-isotope ammonium ions. Loss peaks were observed between 20 and 40 K and obey the Arrhenius law with activation energy 1.5 kcal/mol for the stronger relaxation. The dipole moment is of the order of 0.015 D.

  17. Analysis of sawtooth relaxation oscillations in tokamaks

    SciTech Connect

    Yamazaki, K.; McGuire, K.; Okabayashi, M.

    1982-07-01

    Sawtooth relaxation oscillations are analyzed using the Kadomtsev's disruption model and a thermal relaxation model. The sawtooth period is found to be very sensitive to the thermal conduction loss. Qualitative agreement between these calculations and the sawtooth period observed in several tokamaks is demonstrated.

  18. Mechanical spectroscopy of Snoek type relaxation

    NASA Astrophysics Data System (ADS)

    Golovin, S. A.; Golovin, I. S.

    2012-09-01

    A review is presented for work in the area of elasticity for metals and alloys with a body-centered cubic lattice caused by diffusion under stress of interstitial atoms, i.e., Snoek relaxation in metals and Snoek type relaxation in alloys. Practical possibilities in analyzing materials of this class by mechanical spectroscopy are demonstrated.

  19. Magnetization Transfer Induced Biexponential Longitudinal Relaxation

    PubMed Central

    Prantner, Andrew M.; Bretthorst, G. Larry; Neil, Jeffrey J.; Garbow, Joel R.; Ackerman, Joseph J.H.

    2009-01-01

    Longitudinal relaxation of brain water 1H magnetization in mammalian brain in vivo is typically analyzed on a per voxel basis using a monoexponential model, thereby assigning a single relaxation time constant to all 1H magnetization within a given voxel. This approach was tested by obtaining inversion recovery data from grey matter of rats at 64 exponentially-spaced recovery times. Using Bayesian probability for model selection, brain water data were best represented by a biexponential function characterized by fast and slow relaxation components. At 4.7 T, the amplitude fraction of the rapidly relaxing component is 3.4 ± 0.7 % with a rate constant of 44 ± 12 s-1 (mean ± SD; 174 voxels from 4 rats). The rate constant of the slow relaxing component is 0.66 ± 0.04 s-1. At 11.7 T, the corresponding values are 6.9 ± 0.9 %, 19 ± 5 s-1, and 0.48 ± 0.02 s-1 (151 voxels from 4 rats). Several putative mechanisms for biexponential relaxation behavior were evaluated, and magnetization transfer between bulk water protons and non-aqueous protons was determined to be the source of biexponential longitudinal relaxation. MR methods requiring accurate quantification of longitudinal relaxation may need to take this effect explicitly into account. PMID:18759367

  20. Damped transverse oscillations of interacting coronal loops

    NASA Astrophysics Data System (ADS)

    Soler, Roberto; Luna, Manuel

    2015-10-01

    Damped transverse oscillations of magnetic loops are routinely observed in the solar corona. This phenomenon is interpreted as standing kink magnetohydrodynamic waves, which are damped by resonant absorption owing to plasma inhomogeneity across the magnetic field. The periods and damping times of these oscillations can be used to probe the physical conditions of the coronal medium. Some observations suggest that interaction between neighboring oscillating loops in an active region may be important and can modify the properties of the oscillations. Here we theoretically investigate resonantly damped transverse oscillations of interacting nonuniform coronal loops. We provide a semi-analytic method, based on the T-matrix theory of scattering, to compute the frequencies and damping rates of collective oscillations of an arbitrary configuration of parallel cylindrical loops. The effect of resonant damping is included in the T-matrix scheme in the thin boundary approximation. Analytic and numerical results in the specific case of two interacting loops are given as an application.