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Sample records for precession cardiovascular magnetic

  1. Spin Precession in Oblique Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Li, Jing; Huang, Biqin; Appelbaum, Ian

    2009-03-01

    Spin precession and dephasing (``Hanle effect'') provide an unambiguous means to establish the presence of spin transport in semiconductors. We compare theoretical modeling with experimental data from drift-dominated silicon spin-transport devices, illustrating the non-trivial consequences of employing oblique magnetic fields (due to misalignment or intentional, fixed in-plane field components) to measure the effects of spin precession. Model results are also calculated for Hanle measurements under conditions of diffusion-dominated transport, revealing an expected Hanle peak-widening effect induced by the presence of fixed in-plane magnetic bias fields.

  2. Magnetic environment of hydrogen in Fe from muon precession measurements

    NASA Technical Reports Server (NTRS)

    Heiman, N.; Foy, M. L. G.; Kossler, W. J.; Stronach, C. E.

    1974-01-01

    Polarized positive muon radiation was stopped in an ellipsoidal iron target and its precession was observed in a transverse magnetic field. Results indicate that the conduction electron polarization in the 77 K-Fe Curie point region is less than expected, and that the relaxation time of the muon polarization is dominated by the static inhomogeneity to 900 K, at which point magnetization fluctuations become important.

  3. Thermally driven magnetic precession in spin valves

    NASA Astrophysics Data System (ADS)

    Luc, David; Waintal, Xavier

    2014-10-01

    We investigate the angular dependence of the spin torque generated when applying a temperature difference across a spin valve. Our study shows the presence of a nontrivial fixed point in this angular dependence. This fixed point opens the possibility for a temperature gradient to stabilize radio frequency oscillations without the need for an external magnetic field. This so-called "wavy" behavior can already be found upon applying a voltage difference across a spin valve but we find that this effect is much more pronounced with a temperature difference. We find that a spin asymmetry of the Seebeck coefficient of the order of 20 μ VK -1 should be large enough for a temperature gradient of a few degrees to trigger the radio-frequency oscillations. Our semiclassical theory is fully parametrized with experimentally measured(able) parameters and allows one to quantitatively predict the amplitude of the torque.

  4. Electromagnetic torques, precession and evolution of magnetic inclination of pulsars

    NASA Astrophysics Data System (ADS)

    Zanazzi, J. J.; Lai, Dong

    2015-07-01

    We present analytic calculations of the electromagnetic torques acting on a magnetic neutron star rotating in vacuum, including near-zone torques associated with the inertia of dipole and quadrupole magnetic fields. We incorporate these torques into the rotational dynamics of a rigid-body neutron star, and show that the effects of the inertial torque can be understood as a modification of the moment of inertia tensor of the star. We apply our rotational dynamics equation to the Crab pulsar, including intrinsic distortions of the star and various electromagnetic torques, to investigate the possibility that the counter-alignment of the magnetic inclination angle, as suggested by recent observations, could be explained by pulsar precession. We find that if the effective principal axis of the pulsar is nearly aligned with either the magnetic dipole axis or the rotation axis, then precession may account for the observed counter-alignment over decade time-scales. Over the spindown time-scale of the pulsar, the magnetic inclination angle always decreases.

  5. Regular and chaotic precession of magnetization in magnetic films with a stripe domain structure

    NASA Astrophysics Data System (ADS)

    Shutyĭ, A. M.

    2008-12-01

    Based on a numerical solution of the equations of motion found over a wide range of frequencies of an alternating magnetic field, the nonlinear precession dynamics of magnetization are studied in thin-film structures of the (100) type with a stripe domain structure in a perpendicular bias field. The conditions are determined under which high-amplitude regular and chaotic dynamic regimes occur. Bifurcational variations in the precession of coupled magnetic moments and dynamic-bistability states are detected. The specific features of the spectrum of Lyapunov exponents and of time analogs of Poincaré cross sections of trajectories in chaotic regimes are considered.

  6. Regular and chaotic dynamics of magnetization precession in ferrite-garnet films

    NASA Astrophysics Data System (ADS)

    Shutyĭ, Anatoliy M.; Sementsov, Dmitriy I.

    2009-03-01

    By numerically solving equations of motion and constructing the spectrum of Lyapunov exponents, nonlinear dynamics of uniformly precessing magnetization in (110) thin film structures with perpendicular magnetic bias is investigated over a wide frequency range of the alternating field. Bifurcational changes in magnetization precession and the states of dynamical bistability are discovered. Conditions for the realization of high-amplitude regular and chaotic dynamic regimes are revealed. The possibility of controlling those precession regimes by using external magnetic fields is shown. The features of time analogs of the Poincaré section of trajectories in the chaotic regimes are studied.

  7. Magnetization precession of magnetic thin films studied by all optical pump-probe technique

    NASA Astrophysics Data System (ADS)

    Michalski, Steven A.

    The study of magnetization dynamics such as magnetization precession and precessional damping provides insights into the behavior of complex magnetic systems, and indeed may lead to a better understanding of the fundamental limits of magnetic reversal process. In this work, a time-resolved magneto-optic Kerr effect system (TRMOKE) was developed to study magnetization dynamics: Precession and damping. The system uses a femtosecond laser in a pump-probe experiment with direct optical excitation, very similar to the method introduced by Ganping Ju and coworkers. Also, a model based on the Landau-Lifshitz-Gilbert equation (LLG) was developed and used to interpret and analyze the experimental magnetization precession data of a single magnetic layer. The model can be used to predict the precession frequencies with and without damping, the eigenvectors of the magnetization and allows the Gilbert damping parameter (alpha) to be determined. The model is extended to a system of two magnetic layers coupled through a nonmagnetic spacer layer. The capabilities of the TRMOKE system and the LLG models, were demonstrated by studying the magnetization dynamics of Ni/Pt bilayers. Static and dynamic magnetic properties of exchange-coupled magnetic layers have been investigated by magneto-optical measurements. The samples are [Pt/Co] multilayers with perpendicular magnetic anisotropy (PMA) exchange-coupled to a Co layer with in-plane magnetic anisotropy. The exchange is indirect, realized and tuned by an intervening Pt layer of varying thickness. Both the strength and the angle of an external applied magnetic field were varied and for many samples, two modes with two distinct precession frequencies were observed in the precession measurements. The frequencies of both modes depend on the strength and the angle of the applied magnetic field. The LLG model predicts two precessional modes ("acoustic" and "optic") whose behaviors depend on the strength and sign of the exchange coupling

  8. High frequency magnetic properties of ferromagnetic thin films and magnetization dynamics of coherent precession

    NASA Astrophysics Data System (ADS)

    Jiang, Chang-Jun; Fan, Xiao-Long; Xue, De-Sheng

    2015-05-01

    We focus on the ferromagnetic thin films and review progress in understanding the magnetization dynamic of coherent precession, its application in seeking better high frequency magnetic properties for magnetic materials at GHz frequency, as well as new approaches to these materials’ characterization. High frequency magnetic properties of magnetic materials determined by the magnetization dynamics of coherent precession are described by the Landau-Lifshitz-Gilbert equation. However, the complexity of the equation results in a lack of analytically universal information between the high frequency magnetic properties and the magnetization dynamics of coherent precession. Consequently, searching for magnetic materials with higher permeability at higher working frequency is still done case by case. Project supported by the National Basic Research Program of China (Grant No. 2012CB933101), the National Natural Science Foundation of China (Grant Nos. 11034004 and 51371093), the Program for Changjiang Scholars and Innovative Research Team in University, China (Grant No. IRT1251), and the Specialized Research Fund for the Doctoral Program of Higher Education, China (Grant No. 20130211130003).

  9. Modeling of magnetization precession in spin-torque nano-oscillators with a tilted polarizer

    SciTech Connect

    Lv, Gang; Zhang, Hong E-mail: yaowen@tongji.edu.cn; Cao, Xuecheng; Qin, Yufeng; Li, Guihua; Wang, Linhui; Liu, Yaowen E-mail: yaowen@tongji.edu.cn; Hou, Zhiwei

    2015-07-15

    The spin-torque induced magnetization precession dynamics are studied in a spin-valve with a tilted spin polarizer. Macrospin simulations demonstrate that the frequency of precession state depends both on the external DC current and the intrinsic parameters of devices such as the tilted angle of spin polarizer, the damping factor and saturation magnetization of the free layer. The dependence role of those parameters is characterized by phase diagrams. An analytical model is presented, which can successfully interpret the features of precession frequency.

  10. Magnetization switching by microwaves initially rotating in opposite direction to precession

    NASA Astrophysics Data System (ADS)

    Taniguchi, Tomohiro

    2015-12-01

    A common understanding of magnetization switching in microwave-assisted magnetization reversal is that the rotation direction of the microwaves should be the same as the precession direction of the magnetization. In this letter, however, we show that microwaves initially rotating opposite to the magnetization precession destabilize the magnetization at an equilibrium and induce switching more efficiently when the microwave frequency depends on time. This argument is analytically deduced from an energy balance equation. We also establish a model satisfying this condition and confirm magnetization switching solely by microwaves by using numerical simulation.

  11. Coherent control of magnetization precession in electrically detected time domain ferromagnetic resonance

    SciTech Connect

    Wid, O.; Wahler, M.; Homonnay, N.; Richter, T.; Schmidt, G.

    2015-11-15

    We demonstrate coherent control of time domain ferromagnetic resonance by all electrical excitation and detection. Using two ultrashort magnetic field steps with variable time delay we control the induction decay in yttrium iron garnet (YIG). By setting suitable delay times between the two steps the precession of the magnetization can either be enhanced or completely stopped. The method allows for a determination of the precession frequency within a few precession periods and with an accuracy much higher than can be achieved using fast fourier transformation. Moreover it holds the promise to massively increase precession amplitudes in pulsed inductive microwave magnetometry (PIMM) using low amplitude finite pulse trains. Our experiments are supported by micromagnetic simulations which nicely confirm the experimental results.

  12. Rotational properties of ferromagnetic nanoparticles driven by a precessing magnetic field in a viscous fluid.

    PubMed

    Lyutyy, T V; Denisov, S I; Reva, V V; Bystrik, Yu S

    2015-10-01

    We study the deterministic and stochastic rotational dynamics of ferromagnetic nanoparticles in a precessing magnetic field. Our approach is based on the system of effective Langevin equations and on the corresponding Fokker-Planck equation. Two key characteristics of the rotational dynamics, namely the average angular frequency of precession of nanoparticles and their average magnetization, are of interest. Using the Langevin and Fokker-Planck equations, we calculate both analytically and numerically these characteristics in the deterministic and stochastic cases, determine their dependence on the model parameters, and analyze in detail the role of thermal fluctuations. PMID:26565245

  13. Rotational properties of ferromagnetic nanoparticles driven by a precessing magnetic field in a viscous fluid

    NASA Astrophysics Data System (ADS)

    Lyutyy, T. V.; Denisov, S. I.; Reva, V. V.; Bystrik, Yu. S.

    2015-10-01

    We study the deterministic and stochastic rotational dynamics of ferromagnetic nanoparticles in a precessing magnetic field. Our approach is based on the system of effective Langevin equations and on the corresponding Fokker-Planck equation. Two key characteristics of the rotational dynamics, namely the average angular frequency of precession of nanoparticles and their average magnetization, are of interest. Using the Langevin and Fokker-Planck equations, we calculate both analytically and numerically these characteristics in the deterministic and stochastic cases, determine their dependence on the model parameters, and analyze in detail the role of thermal fluctuations.

  14. Origin of light-induced precession of magnetization in ferromagnetic (Ga,Mn)As

    NASA Astrophysics Data System (ADS)

    Rozkotova, Eva; Nemec, Petr; Sprinzl, Daniel; Tesarova, Nada; Maly, Petr; Novak, Vit; Olejnik, Kamil; Zemen, Jan; Cukr, Miroslav; Jungwirth, Tomas; Wunderlich, Joerg

    2009-03-01

    The impact of femtosecond laser pulse leads to the precession of magnetization in (Ga,Mn)As, which can be detected by the time- resolved Kerr rotation (KR) technique. Even though this phenomenon is known for several years [1], the exact physical mechanism inducing the precession is still not clear [2,3]. We show, by a detailed comparison of the KR experimental results and the microscopic calculations of the magnetic anisotropy, that the precession is a consequence of the anisotropy field modification due to the laser pulse-induced change of hole concentration and lattice temperature. [1] A. Oiwa, H. Takechi, H. Munekata, J. Supercond. 18, 9 (2005).[2] Y. Hashimoto, S. Kobayashi, H. Munekata, PRL 100, 067202 (2008).[3] E. Rozkotova, P. Nemec, P. Horodyska, D. Sprinzl, F. Trojanek, P. Maly, V. Novak, K. Olejnik, M. Cukr, T. Jungwirth, Appl. Phys. Lett 92, 122507 (2008).

  15. Magnetic field angle dependence of out-of-plane precession in spin torque oscillators having an in-plane magnetized free layer and a perpendicularly magnetized reference layer

    NASA Astrophysics Data System (ADS)

    Hiramatsu, Ryo; Kubota, Hitoshi; Tsunegi, Sumito; Tamaru, Shingo; Yakushiji, Kay; Fukushima, Akio; Matsumoto, Rie; Imamura, Hiroshi; Yuasa, Shinji

    2016-05-01

    Out-of-plane (OP) precession in spin torque oscillators having an in-plane (IP) magnetized free layer and a perpendicularly magnetized reference layer was studied. The bias voltage (V B) and magnetic field angle (θ) dependence of the OP precession were investigated. The absolute values of the critical magnetic fields (H\\text{B}\\text{c - } and H\\text{B}\\text{c + }) between which OP precession is excited increased as V B increased and as θ changed from the IP to the OP direction. The IP components of H\\text{B}\\text{c +/- } converged to a constant value regardless of θ. This result indicates that excitation of OP precession is suppressed entirely by the IP component of the magnetic field, and the contribution of the OP component can be ignored. The experimentally observed precession behavior was successfully modeled by macrospin simulations.

  16. Cardiovascular magnetic resonance artefacts

    PubMed Central

    2013-01-01

    The multitude of applications offered by CMR make it an increasing popular modality to study the heart and the surrounding vessels. Nevertheless the anatomical complexity of the chest, together with cardiac and respiratory motion, and the fast flowing blood, present many challenges which can possibly translate into imaging artefacts. The literature is wide in terms of papers describing specific MR artefacts in great technical detail. In this review we attempt to summarise, in a language accessible to a clinical readership, some of the most common artefacts found in CMR applications. It begins with an introduction of the most common pulse sequences, and imaging techniques, followed by a brief section on typical cardiovascular applications. This leads to the main section on common CMR artefacts with examples, a short description of the mechanisms behind them, and possible solutions. PMID:23697969

  17. Electromagnetic fields of a nonprecessing and precessing, spinning, permanent magnet, conducting sphere

    NASA Astrophysics Data System (ADS)

    Mueller, R. S.

    1991-02-01

    The electromagnetic fields inside and outside a steadily rotating, magnetized, conducting sphere are determined for the cases of nonprecession and precession. In both cases the spin rotational axis is aligned with the magnetic axis of the sphere. The field expressions are those measured in the laboratory reference frame. For a nonprecessing sphere the magnetic fields are identical to the fields of a stationary sphere, but in addition there is an induced induction of order v-squared/c-squared whose lines of force radiate in loops above and below the equator. The electric and magnetic induction field expressions were derived into static and dynamic parts. The amplitudes of these parts were plotted as functions of the angle of inclination of the polar axis. The dynamic parts are circularly and elliptically polarized. The pivot point of the precessing sphere was chosen off center. The only two stable positions are at theta = 0 deg and 180 deg for a center pivot.

  18. Resonantly exited precession motion of three-dimensional vortex core in magnetic nanospheres

    PubMed Central

    Kim, Sang-Koog; Yoo, Myoung-Woo; Lee, Jehyun; Lee, Ha-Youn; Lee, Jae-Hyeok; Gaididei, Yuri; Kravchuk, Volodymyr P.; Sheka, Denis D.

    2015-01-01

    We found resonantly excited precession motions of a three-dimensional vortex core in soft magnetic nanospheres and controllable precession frequency with the sphere diameter 2R, as studied by micromagnetic numerical and analytical calculations. The precession angular frequency for an applied static field HDC is given as ωMV = γeffHDC, where γeff = γ〈mΓ〉 is the effective gyromagnetic ratio in collective vortex dynamics, with the gyromagnetic ratio γ and the average magnetization component 〈mΓ〉 of the ground-state vortex in the core direction. Fitting to the micromagnetic simulation data for 〈mΓ〉 yields a simple explicit form of 〈mΓ〉 ≈ (73.6 ± 3.4)(lex/2R)2.20±0.14, where lex is the exchange length of a given material. This dynamic behavior might serve as a foundation for potential bio-applications of size-specific resonant excitation of magnetic vortex-state nanoparticles, for example, magnetic particle resonance imaging. PMID:26079895

  19. Resonantly excited precession motion of three-dimensional vortex core in magnetic nanospheres [corrected].

    PubMed

    Kim, Sang-Koog; Yoo, Myoung-Woo; Lee, Jehyun; Lee, Ha-Youn; Lee, Jae-Hyeok; Gaididei, Yuri; Kravchuk, Volodymyr P; Sheka, Denis D

    2015-01-01

    We found resonantly excited precession motions of a three-dimensional vortex core in soft magnetic nanospheres and controllable precession frequency with the sphere diameter 2R, as studied by micromagnetic numerical and analytical calculations. The precession angular frequency for an applied static field HDC is given as ωMV = γeffHDC, where γeff = γ〈mΓ〉 is the effective gyromagnetic ratio in collective vortex dynamics, with the gyromagnetic ratio γ and the average magnetization component 〈mΓ〉 of the ground-state vortex in the core direction. Fitting to the micromagnetic simulation data for 〈mΓ〉 yields a simple explicit form of 〈mΓ〉 ≈ (73.6 ± 3.4)(lex/2R)(2.20±0.14), where lex is the exchange length of a given material. This dynamic behavior might serve as a foundation for potential bio-applications of size-specific resonant excitation of magnetic vortex-state nanoparticles, for example, magnetic particle resonance imaging. PMID:26079895

  20. Resonantly exited precession motion of three-dimensional vortex core in magnetic nanospheres

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Koog; Yoo, Myoung-Woo; Lee, Jehyun; Lee, Ha-Youn; Lee, Jae-Hyeok; Gaididei, Yuri; Kravchuk, Volodymyr P.; Sheka, Denis D.

    2015-06-01

    We found resonantly excited precession motions of a three-dimensional vortex core in soft magnetic nanospheres and controllable precession frequency with the sphere diameter 2R, as studied by micromagnetic numerical and analytical calculations. The precession angular frequency for an applied static field HDC is given as ωMV = γeffHDC, where γeff = γ is the effective gyromagnetic ratio in collective vortex dynamics, with the gyromagnetic ratio γ and the average magnetization component of the ground-state vortex in the core direction. Fitting to the micromagnetic simulation data for yields a simple explicit form of  ≈ (73.6 ± 3.4)(lex/2R)2.20±0.14, where lex is the exchange length of a given material. This dynamic behavior might serve as a foundation for potential bio-applications of size-specific resonant excitation of magnetic vortex-state nanoparticles, for example, magnetic particle resonance imaging.

  1. Precession of Uranus and Neptune and their magnetic field

    NASA Technical Reports Server (NTRS)

    Dolginov, Sh. SH.

    1993-01-01

    The strength of the dipole magnetic field of a planet, H(sub p), can be estimated relative to that of the Earth at the epoch of the observation. The generation of magnetic fields in Uranus and Neptune occurs at very different depths for different values of sigma. This assertion is confirmed by the estimation of the Reynolds number (R(sub m)) and agrees with the difference of the contributions of the Joule heat losses into the observed heat fluxes of Uranus and Neptune.

  2. Practical applications of cardiovascular magnetic resonance

    PubMed Central

    Alpendurada, F; Wong, J; Pennell, D J

    2009-01-01

    Recent developments in magnetic resonance imaging have focused attention on evaluation of patients with cardiac disease. These improvements have been substantiated by a large and expanding body of clinical evidence, making cardiovascular magnetic resonance the imaging modality of choice in a wide variety of cardiovascular disorders. A brief review on the current applications of cardiovascular magnetic resonance is provided, with reference to some of the most relevant studies, statements and reviews published in this field.

  3. Parametric Harmonic Generation as a Probe of Unconstrained Spin Magnetization Precession in the Shallow Barrier Limit.

    PubMed

    Capua, Amir; Rettner, Charles; Parkin, Stuart S P

    2016-01-29

    We study the parametric excitation of high orders of magnetization precession in ultrathin films having perpendicular magnetic anisotropy. We observe that for a given driving field amplitude the harmonic generation can be increased by lowering the barrier with the application of an in-plane magnetic field in the manner of the Smit-Beljers effect. In this effect, the magnetic stiffness is reduced not by lowering the magnitude of the magnetic field upon which the spins precess, but rather by effectively releasing the field's "anchoring" point. This results in a shallow energy barrier where the electrons' spin is locally unconstrained. While the observation is unveiled in the form of nonlinear high harmonic generation, we believe that the physics whereby the barrier is suppressed by an external magnetic field may apply to other phenomena associated with ultrathin films. In these cases, such unconstrained motion may serve as a sensitive probe of the torques associated with proximate spin currents. Moreover, our approach may be used as a model system for the study of phase transitions in the field of nonlinear dynamics. PMID:26871356

  4. X-Ray Detected Magnetic Resonance: A Unique Probe of the Precession Dynamics of Orbital Magnetization Components

    PubMed Central

    Goulon, Jośe; Rogalev, Andrei; Goujon, Gérard; Wilhelm, Fabrice; Ben Youssef, Jamal; Gros, Claude; Barbe, Jean-Michel; Guilard, Roger

    2011-01-01

    X-ray Detected Magnetic Resonance (XDMR) is a novel spectroscopy in which X-ray Magnetic Circular Dichroism (XMCD) is used to probe the resonant precession of local magnetization components in a strong microwave pump field. We review the conceptual bases of XDMR and recast them in the general framework of the linear and nonlinear theories of ferromagnetic resonance (FMR). Emphasis is laid on the information content of XDMR spectra which offer a unique opportunity to disentangle the precession dynamics of spin and orbital magnetization components at given absorbing sites. For the sake of illustration, we focus on selected examples in which marked differences were found between FMR and XDMR spectra simultaneously recorded on ferrimagnetically ordered iron garnets. With pumping capabilities extended up to sub-THz frequencies, high-field XDMR should allow us to probe the precession of orbital magnetization components in paramagnetic organometallic complexes with large zero-field splitting. Even more challenging, we suggest that XDMR spectra might be recorded on selected antiferromagnetic crystals for which orbital magnetism is most often ignored in the absence of any supporting experimental evidence. PMID:22272105

  5. Topological currents in neutron stars: kicks, precession, toroidal fields, and magnetic helicity

    SciTech Connect

    Charbonneau, James; Zhitnitsky, Ariel E-mail: arz@phas.ubc.ca

    2010-08-01

    The effects of anomalies in high density QCD are striking. We consider a direct application of one of these effects, namely topological currents, on the physics of neutron stars. All the elements required for topological currents are present in neutron stars: degenerate matter, large magnetic fields, and parity violating processes. These conditions lead to the creation of vector currents capable of carrying momentum and inducing magnetic fields. We estimate the size of these currents for many representative states of dense matter in the neutron star and argue that they could be responsible for the large proper motion of neutron stars (kicks), the toroidal magnetic field and finite magnetic helicity needed for stability of the poloidal field, and the resolution of the conflict between type-II superconductivity and precession. Though these observational effects appear unrelated, they likely originate from the same physics — they are all P-odd phenomena that stem from a topological current generated by parity violation.

  6. Cardiovascular magnetic resonance in systemic hypertension

    PubMed Central

    2012-01-01

    Systemic hypertension is a highly prevalent potentially modifiable cardiovascular risk factor. Imaging plays an important role in the diagnosis of underlying causes for hypertension, in assessing cardiovascular complications of hypertension, and in understanding the pathophysiology of the disease process. Cardiovascular magnetic resonance (CMR) provides accurate and reproducible measures of ventricular volumes, mass, function and haemodynamics as well as uniquely allowing tissue characterization of diffuse and focal fibrosis. In addition, CMR is well suited for exclusion of common secondary causes for hypertension. We review the current and emerging clinical and research applications of CMR in hypertension. PMID:22559053

  7. Precession Control on Precipitation in the Western Pacific Warm Pool Inferred from Environmental Magnetism

    NASA Astrophysics Data System (ADS)

    Yamazaki, T.

    2014-12-01

    The Western Pacific Warm Pool (WPWP) has highest water temperature in the global ocean, and its spatiotemporal variations have significant impacts on large-scale atmospheric circulation and global hydrology. An environmental magnetic study was conducted on sediment cores of late Pleistocene age taken from the West Caroline Basin (WCB) offshore northern New Guinea in order to constrain hydrological variability over the WPWP on orbital timescales. Magnetite dominates magnetic mineral assemblages of the sediments. This is evidenced by that IRM acquisition curves are mostly explained by a low-coercivity component, and that the Verwey transition was obvious in low-temperature measurements. Existence of the sharp central ridges on FORC diagrams and TEM images indicate the occurrence of biogenic magnetite. Compared with pelagic sediments from other regions, however, FORC diagrams show a larger contribution of an interacting PSD and MD component, and the ratios of ARM susceptibility to SIRM (kARM/SIRM) are lower, which suggests a larger proportion of the terrigenous component. This is probably due to a large terrigenous sediment input from nearby land, New Guinea, induced by high precipitation in the intertropical convergence zone. Magnetic susceptibility (k) and kARM/SIRM well correlate with northern-hemisphere summer insolation. Maxima in k and minima in kARM/SIRM correspond to insolation minima, which suggests a larger terrigenous input caused by higher precipitation at these times. Interestingly, in the western part of WCB, k variations are dominated by the eccentricity periodicity and mimic δ18O curves, but the precession periodicity prevails in kARM/SIRM. These cores were taken at depths close to the CCD, and thus the k variations cannot be explained by dilution with carbonates. Sedimentation influenced by global sea-level changes may control the k variations; this part of the basin is adjacent to a wider continental shelf compared with the eastern part of WCB.

  8. Spin precession of slow neutrons in Einstein-Cartan gravity with torsion, chameleon, and magnetic field

    NASA Astrophysics Data System (ADS)

    Ivanov, A. N.; Wellenzohn, M.

    2016-02-01

    We analyze a spin precession of slow neutrons in the Einstein-Cartan gravity with torsion, chameleon and magnetic field. For the derivation of the Heisenberg equation of motion of the neutron spin we use the effective low-energy potential, derived by Ivanov and Wellenzohn [Phys. Rev. D 92, 125004 (2015)] for slow neutrons, coupled to gravitational, chameleon, and torsion fields to order 1 /m , where m is the neutron mass. In addition to these low-energy interactions we switch on the interaction of slow neutrons with a magnetic field. We show that to linear order approximation with respect to gravitational, chameleon, and torsion fields the Dirac Hamilton operator for fermions (neutrons), moving in spacetimes created by rotating coordinate systems, contains the anti-Hermitian operators of torsion-fermion (neutron) interactions, caused by torsion scalar and tensor space-space-time and time-space-space degrees of freedom. Such anti-Hermitian operators violate C P and T invariance. In the low-energy approximation the C P and T violating torsion-fermion (neutron) interactions appear only to order O (1 /m ). One may assume that in the rotating Universe and galaxies the obtained anti-Hermitian torsion-fermion interactions might be an origin of (i) violation of C P and T invariance in the Universe and (ii) of baryon asymmetry. We show that anti-Hermitian torsion-fermion interactions of relativistic fermions, violating C P and T invariance, (i) cannot be removed by nonunitary transformations of the Dirac fermion wave functions and (ii) are conformal invariant. According to general requirements of conformal invariance of massive particle theories in gravitational fields [see R. H. Dicke, Phys. Rev. 125, 2163 (1962) and A. J. Silenko, Phys. Rev. D 91, 065012 (2015)], conformal invariance of anti-Hermitian torsion-fermion interactions is valid only if the fermion mass is changed by a conformal factor.

  9. Precessing Ferromagnetic Needle Magnetometer

    NASA Astrophysics Data System (ADS)

    Jackson Kimball, Derek F.; Sushkov, Alexander O.; Budker, Dmitry

    2016-05-01

    A ferromagnetic needle is predicted to precess about the magnetic field axis at a Larmor frequency Ω under conditions where its intrinsic spin dominates over its rotational angular momentum, N ℏ≫I Ω (I is the moment of inertia of the needle about the precession axis and N is the number of polarized spins in the needle). In this regime the needle behaves as a gyroscope with spin N ℏ maintained along the easy axis of the needle by the crystalline and shape anisotropy. A precessing ferromagnetic needle is a correlated system of N spins which can be used to measure magnetic fields for long times. In principle, by taking advantage of rapid averaging of quantum uncertainty, the sensitivity of a precessing needle magnetometer can far surpass that of magnetometers based on spin precession of atoms in the gas phase. Under conditions where noise from coupling to the environment is subdominant, the scaling with measurement time t of the quantum- and detection-limited magnetometric sensitivity is t-3 /2. The phenomenon of ferromagnetic needle precession may be of particular interest for precision measurements testing fundamental physics.

  10. Precessing Ferromagnetic Needle Magnetometer.

    PubMed

    Jackson Kimball, Derek F; Sushkov, Alexander O; Budker, Dmitry

    2016-05-13

    A ferromagnetic needle is predicted to precess about the magnetic field axis at a Larmor frequency Ω under conditions where its intrinsic spin dominates over its rotational angular momentum, Nℏ≫IΩ (I is the moment of inertia of the needle about the precession axis and N is the number of polarized spins in the needle). In this regime the needle behaves as a gyroscope with spin Nℏ maintained along the easy axis of the needle by the crystalline and shape anisotropy. A precessing ferromagnetic needle is a correlated system of N spins which can be used to measure magnetic fields for long times. In principle, by taking advantage of rapid averaging of quantum uncertainty, the sensitivity of a precessing needle magnetometer can far surpass that of magnetometers based on spin precession of atoms in the gas phase. Under conditions where noise from coupling to the environment is subdominant, the scaling with measurement time t of the quantum- and detection-limited magnetometric sensitivity is t^{-3/2}. The phenomenon of ferromagnetic needle precession may be of particular interest for precision measurements testing fundamental physics. PMID:27232012

  11. Possible evidence for free precession of a strongly magnetized neutron star in the magnetar 4U 0142+61.

    PubMed

    Makishima, K; Enoto, T; Hiraga, J S; Nakano, T; Nakazawa, K; Sakurai, S; Sasano, M; Murakami, H

    2014-05-01

    Magnetars are a special type of neutron stars, considered to have extreme dipole magnetic fields reaching ∼ 10(11) T. The magnetar 4 U 0142+61, one of the prototypes of this class, was studied in broadband x rays (0.5-70 keV) with the Suzaku observatory. In hard x rays (15-40 keV), its 8.69 sec pulsations suffered slow phase modulations by ± 0.7 sec, with a period of ∼ 15 h. When this effect is interpreted as free precession of the neutron star, the object is inferred to deviate from spherical symmetry by ∼ 1.6 × 10(-4) in its moments of inertia. This deformation, when ascribed to magnetic pressure, suggests a strong toroidal magnetic field, ∼ 10(12) T, residing inside the object. This provides one of the first observational approaches towards toroidal magnetic fields of magnetars. PMID:24836230

  12. Tools for cardiovascular magnetic resonance imaging

    PubMed Central

    Krishnamurthy, Ramkumar; Cheong, Benjamin

    2014-01-01

    In less than fifteen years, as a non-invasive imaging option, cardiovascular MR has grown from a being a mere curiosity to becoming a widely used clinical tool for evaluating cardiovascular disease. Cardiovascular magnetic resonance imaging (CMRI) is now routinely used to study myocardial structure, cardiac function, macro vascular blood flow, myocardial perfusion, and myocardial viability. For someone entering the field of cardiac MR, this rapid pace of development in the field of CMRI might make it difficult to identify a cohesive starting point. In this brief review, we have attempted to summarize the key cardiovascular imaging techniques that have found widespread clinical acceptance. In particular, we describe the essential cardiac and respiratory gating techniques that form the backbone of all cardiovascular imaging methods. It is followed by four sections that discuss: (I) the gradient echo techniques that are used to assess ventricular function; (II) black-blood turbo spin echo (SE) methods used for morphologic assessment of the heart; (III) phase-contrast based techniques for the assessment of blood flow; and (IV) CMR methods for the assessment of myocardial ischemia and viability. In each section, we briefly summarize technical considerations relevant to the clinical use of these techniques, followed by practical information for its clinical implementation. In each of those four areas, CMRI is considered either as the benchmark imaging modality against which the diagnostic performance of other imaging modalities are compared against, or provides a complementary capability to existing imaging techniques. We have deliberately avoided including cutting-edge CMR imaging techniques practiced at few academic centers, and restricted our discussion to methods that are widely used and are likely to be available in a clinical setting. Our hope is that this review would propel an interested reader toward more comprehensive reviews in the literature. PMID:24834409

  13. Spin-to-charge conversion in lateral and vertical topological-insulator/ferromagnet heterostructures with microwave-driven precessing magnetization

    NASA Astrophysics Data System (ADS)

    Mahfouzi, Farzad; Nagaosa, Naoto; Nikolić, Branislav K.

    2014-09-01

    Using the charge-conserving Floquet-Green function approach to open quantum systems driven by an external time-periodic potential, we analyze how spin current pumped by the precessing magnetization of a ferromagnetic (F) layer is injected laterally into the interface with strong spin-orbit coupling (SOC) and converted into charge current flowing in the same direction. In the case of a metallic interface with the Rashba SOC used in recent experiments [J. C. R. Sánchez, L. Vila, G. Desfonds, S. Gambarelli, J. P. Attané, J. M. De Teresa, C. Magén, and A. Fert, Nat. Commun. 4, 2944 (2013), 10.1038/ncomms3944], both spin ISα and charge I current flow within the interface where I /ISα≃ 2-8% (depending on the precession cone angle), while for a F/topological-insulator (F/TI) interface employed in related experiments [Y. Shiomi, K. Nomura, Y. Kajiwara, K. Eto, M. Novak, K. Segawa, Y. Ando, and E. Saitoh, arXiv:1312.7091] the conversion efficiency is greatly enhanced (I /ISα≃ 40-60%) due to perfect spin-momentum locking on the surface of a TI. The spin-to-charge conversion occurs also when spin current is pumped vertically through the F/TI interface with smaller efficiency (I /ISα˜0.001%), but with the charge current signal being sensitive to whether the Dirac fermions at the interface are massive or massless.

  14. Cardiovascular magnetic resonance physics for clinicians: part I.

    PubMed

    Ridgway, John P

    2010-01-01

    There are many excellent specialised texts and articles that describe the physical principles of cardiovascular magnetic resonance (CMR) techniques. There are also many texts written with the clinician in mind that provide an understandable, more general introduction to the basic physical principles of magnetic resonance (MR) techniques and applications. There are however very few texts or articles that attempt to provide a basic MR physics introduction that is tailored for clinicians using CMR in their daily practice. This is the first of two reviews that are intended to cover the essential aspects of CMR physics in a way that is understandable and relevant to this group. It begins by explaining the basic physical principles of MR, including a description of the main components of an MR imaging system and the three types of magnetic field that they generate. The origin and method of production of the MR signal in biological systems are explained, focusing in particular on the two tissue magnetisation relaxation properties (T1 and T2) that give rise to signal differences from tissues, showing how they can be exploited to generate image contrast for tissue characterisation. The method most commonly used to localise and encode MR signal echoes to form a cross sectional image is described, introducing the concept of k-space and showing how the MR signal data stored within it relates to properties within the reconstructed image. Before describing the CMR acquisition methods in detail, the basic spin echo and gradient pulse sequences are introduced, identifying the key parameters that influence image contrast, including appearances in the presence of flowing blood, resolution and image acquisition time. The main derivatives of these two pulse sequences used for cardiac imaging are then described in more detail. Two of the key requirements for CMR are the need for data acquisition first to be to be synchronised with the subject's ECG and to be fast enough for the subject

  15. Cardiovascular magnetic resonance physics for clinicians: part I

    PubMed Central

    2010-01-01

    There are many excellent specialised texts and articles that describe the physical principles of cardiovascular magnetic resonance (CMR) techniques. There are also many texts written with the clinician in mind that provide an understandable, more general introduction to the basic physical principles of magnetic resonance (MR) techniques and applications. There are however very few texts or articles that attempt to provide a basic MR physics introduction that is tailored for clinicians using CMR in their daily practice. This is the first of two reviews that are intended to cover the essential aspects of CMR physics in a way that is understandable and relevant to this group. It begins by explaining the basic physical principles of MR, including a description of the main components of an MR imaging system and the three types of magnetic field that they generate. The origin and method of production of the MR signal in biological systems are explained, focusing in particular on the two tissue magnetisation relaxation properties (T1 and T2) that give rise to signal differences from tissues, showing how they can be exploited to generate image contrast for tissue characterisation. The method most commonly used to localise and encode MR signal echoes to form a cross sectional image is described, introducing the concept of k-space and showing how the MR signal data stored within it relates to properties within the reconstructed image. Before describing the CMR acquisition methods in detail, the basic spin echo and gradient pulse sequences are introduced, identifying the key parameters that influence image contrast, including appearances in the presence of flowing blood, resolution and image acquisition time. The main derivatives of these two pulse sequences used for cardiac imaging are then described in more detail. Two of the key requirements for CMR are the need for data acquisition first to be to be synchronised with the subject's ECG and to be fast enough for the subject

  16. Simplifying cardiovascular magnetic resonance pulse sequence terminology.

    PubMed

    Friedrich, Matthias G; Bucciarelli-Ducci, Chiara; White, James A; Plein, Sven; Moon, James C; Almeida, Ana G; Kramer, Christopher M; Neubauer, Stefan; Pennell, Dudley J; Petersen, Steffen E; Kwong, Raymond Y; Ferrari, Victor A; Schulz-Menger, Jeanette; Sakuma, Hajime; Schelbert, Erik B; Larose, Éric; Eitel, Ingo; Carbone, Iacopo; Taylor, Andrew J; Young, Alistair; de Roos, Albert; Nagel, Eike

    2014-01-01

    We propose a set of simplified terms to describe applied Cardiovascular Magnetic Resonance (CMR) pulse sequence techniques in clinical reports, scientific articles and societal guidelines or recommendations. Rather than using various technical details in clinical reports, the description of the technical approach should be based on the purpose of the pulse sequence. In scientific papers or other technical work, this should be followed by a more detailed description of the pulse sequence and settings. The use of a unified set of widely understood terms would facilitate the communication between referring physicians and CMR readers by increasing the clarity of CMR reports and thus improve overall patient care. Applied in research articles, its use would facilitate non-expert readers' understanding of the methodology used and its clinical meaning. PMID:25551695

  17. Effect of zero magnetic field on cardiovascular system and microcirculation

    NASA Astrophysics Data System (ADS)

    Gurfinkel, Yu. I.; At'kov, O. Yu.; Vasin, A. L.; Breus, T. K.; Sasonko, M. L.; Pishchalnikov, R. Yu.

    2016-02-01

    The effects of zero magnetic field conditions on cardiovascular system of healthy adults have been studied. In order to generate zero magnetic field, the facility for magnetic fields modeling "ARFA" has been used. Parameters of the capillary blood flow, blood pressure, and the electrocardiogram (ECG) monitoring were measured during the study. All subjects were tested twice: in zero magnetic field and, for comparison, in sham condition. The obtained results during 60 minutes of zero magnetic field exposure demonstrate a clear effect on cardiovascular system and microcirculation. The results of our experiments can be used in studies of long-term stay in hypo-magnetic conditions during interplanetary missions.

  18. Effect of zero magnetic field on cardiovascular system and microcirculation.

    PubMed

    Gurfinkel, Yu I; At'kov, O Yu; Vasin, A L; Breus, T K; Sasonko, M L; Pishchalnikov, R Yu

    2016-02-01

    The effects of zero magnetic field conditions on cardiovascular system of healthy adults have been studied. In order to generate zero magnetic field, the facility for magnetic fields modeling "ARFA" has been used. Parameters of the capillary blood flow, blood pressure, and the electrocardiogram (ECG) monitoring were measured during the study. All subjects were tested twice: in zero magnetic field and, for comparison, in sham condition. The obtained results during 60 minutes of zero magnetic field exposure demonstrate a clear effect on cardiovascular system and microcirculation. The results of our experiments can be used in studies of long-term stay in hypo-magnetic conditions during interplanetary missions. PMID:26948007

  19. Realizations of magnetic-monopole gauge fields - Diatoms and spin precession

    NASA Technical Reports Server (NTRS)

    Moody, J.; Shapere, A.; Wilczek, F.

    1986-01-01

    It is found that the effective Hamiltonian for nuclear rotation in a diatom is equivalent to that of a charged particle in a background magnetic-monopole field. In certain cases, half-integer orbital angular momentum or non-Abelian fields occur. Furthermore, the effects of magnetic-monopole-like gauge fields can be experimentally observed in spin-resonance experiments with variable magnetic fields.

  20. Cardiovascular Magnetic Resonance Myocardial Feature Tracking: Concepts and Clinical Applications.

    PubMed

    Schuster, Andreas; Hor, Kan N; Kowallick, Johannes T; Beerbaum, Philipp; Kutty, Shelby

    2016-04-01

    Heart failure-induced cardiovascular morbidity and mortality constitute a major health problem worldwide and result from diverse pathogeneses, including coronary artery disease, nonischemic cardiomyopathies, and arrhythmias. Assessment of cardiovascular performance is important for early diagnosis and accurate management of patients at risk of heart failure. During the past decade, cardiovascular magnetic resonance myocardial feature tracking has emerged as a useful tool for the quantitative evaluation of cardiovascular function. The method allows quantification of biatrial and biventricular mechanics from measures of deformation: strain, torsion, and dyssynchrony. The purpose of this article is to review the basic principles, clinical applications, accuracy, and reproducibility of cardiovascular magnetic resonance myocardial feature tracking, highlighting the prognostic implications. It will also provide an outlook on how this field might evolve in the future. PMID:27009468

  1. Mechanism of photoexcited precession of magnetization in (Ga,Mn)As on the basis of time-resolved spectroscopy

    NASA Astrophysics Data System (ADS)

    Matsuda, T.; Munekata, H.

    2016-02-01

    In order to investigate the mechanism of photoexcited precession of magnetization in ferromagnetic G a1 -xM nxAs , magneto-optical (MO) and differential reflectivity (Δ R /R ; DR) temporal profiles are studied at relatively long (picosecond to nanosecond) and ultrashort (1 ps or less) time scales for samples with different Mn content (x =0.01 -0.11 ) . As to the oscillatory MO profiles observed in the long time scale, simulation based on the Landau-Lifshitz-Gilbert equation combined with two different MO effects confirms photoinducement of the perpendicular anisotropy component Δ Heff ,⊥ . As for the profiles observed in the ultrashort time scale, they are consistently explained in terms of the dynamics of photogenerated carriers, but not by the sudden reduction in magnetization (the ultrafast demagnetization). In light of these experimental results and analyses, a mechanism that accounts for the photoinduced Δ Heff ,⊥ is addressed: namely, photoionizationlike excitation of M n2 + , M n2 ++h ν →M n2 +,*=M n3++e- . That such excitation tips magnetic anisotropy toward the out-of-plane direction through the inducement of orbital angular momentum and the gradient ∂ (M n2 +,* )/∂ z is discussed. The validity of the proposed mechanism is examined by estimating the efficiency of excitation on the basis of the Lambert-Beer law and the experimental Δ Heff ,⊥ values, through which an efficiency of 1-10 ppm with a nominal optical cross section of around 5 ×10-12m2 is obtained.

  2. Interventional cardiovascular magnetic resonance: still tantalizing

    PubMed Central

    Ratnayaka, Kanishka; Faranesh, Anthony Z; Guttman, Michael A; Kocaturk, Ozgur; Saikus, Christina E; Lederman, Robert J

    2008-01-01

    The often touted advantages of MR guidance remain largely unrealized for cardiovascular interventional procedures in patients. Many procedures have been simulated in animal models. We argue these opportunities for clinical interventional MR will be met in the near future. This paper reviews technical and clinical considerations and offers advice on how to implement a clinical-grade interventional cardiovascular MR (iCMR) laboratory. We caution that this reflects our personal view of the "state of the art." PMID:19114017

  3. Molecular Cardiovascular Magnetic Resonance: Current Status and Future Prospects.

    PubMed

    Bender, Yvonne Y; Pfeifer, Andreas; Ebersberger, Hans U; Diederichs, Gerd; Hoppe, Peter; Hamm, Bernd; Botnar, René M; Makowski, Marcus R

    2016-05-01

    In the Western world and developing countries, the number one causes of mortality and morbidity result from cardiovascular diseases. Cardiovascular diseases represent a wide range of pathologies, including myocardial infarction, peripheral vascular disease, and cerebrovascular disease, which are all linked by a common cause - atherosclerosis. Currently, the diagnosis of atherosclerosis is in most cases established at the end stage of the disease, when patients are administered to the emergency room due to a myocardial infarction or stroke. Even though cardiovascular diseases have an enormous impact on society, there are still limitations in the early diagnosis and the prevention of the disease. Current imaging methods mainly focus on morphological changes that occur at an advanced disease stage, e.g., degree of stenosis. Cardiovascular magnetic resonance imaging and specifically molecular cardiovascular magnetic resonance imaging are capable to reveal pathophysiological changes already occurring during early atherosclerotic plaque formation. This allows for the assessment of cardiovascular disease on a level, which goes beyond morphological or anatomical criteria. In this review, we will introduce promising MR-based molecular imaging strategies for the non-invasive assessment of cardiovascular disease. PMID:27038612

  4. The Conformal Steady-State Free Precession:. a Kepplerian Approach to Automorphic Scattering Theory of Orbiton/spinon Dynamics

    NASA Astrophysics Data System (ADS)

    Schempp, Walter J.

    2013-09-01

    Based on projective geometry, a quantum holographic approach to the orbiton / spinon dynamics of quantum blackholography and clinical magnetic resonance tomography is mathematically described. Crucial applications of the conformal steady-state free-precession modality and automorphic scattering theory are the evidence for a supermassive central black hole in the Milky Way galaxy and the modalities of clinical cardiovascular magnetic resonance tomography and diffusion weighted magnetic resonance tomography of non-invasive radiological diagnostics.

  5. Cardiovascular outcome associations among cardiovascular magnetic resonance measures of arterial stiffness: the Dallas heart study

    PubMed Central

    2014-01-01

    Background Cardiovascular magnetic resonance (CMR) has been validated for the noninvasive assessment of total arterial compliance and aortic stiffness, but their associations with cardiovascular outcomes is unknown. The purpose of this study was to evaluate associations of CMR measures of total arterial compliance and two CMR measures of aortic stiffness with respect to future cardiovascular events. Methods The study consisted of 2122 Dallas Heart Study participants without cardiovascular disease who underwent CMR at 1.5 Tesla. Aortic stiffness was measured by CMR-derived ascending aortic distensibility and aortic arch pulse wave velocity. Total arterial compliance was calculated by dividing left ventricular stroke volume by pulse pressure. Participants were monitored for cardiovascular death, non-fatal cardiac events, and non-fatal extra-cardiac vascular events over 7.8 ± 1.5 years. Cox proportional hazards regression was used to assess for associations between CMR measures and cardiovascular events. Results Age, systolic blood pressure, and resting heart rate were independently associated with changes in ascending aortic distensibility, arch pulse wave velocity, and total arterial compliance (all p < .0001). A total of 153 participants (6.9%) experienced a cardiovascular event. After adjusting for traditional risk factors, total arterial compliance was modestly associated with increased risk for composite events (HR 1.07 per 1SD, p = 0.03) while the association between ascending aortic distensibility and composite events trended towards significance (HR 1.18 per 1SD, p = 0.08). Total arterial compliance and aortic distensibility were independently associated with nonfatal cardiac events (HR 1.11 per 1SD, p = 0.001 and HR 1.45 per 1SD, p = 0.0005, respectively), but not with cardiovascular death or nonfatal extra-cardiac vascular events. Arch pulse wave velocity was independently associated with nonfatal extra-cardiac vascular events (HR

  6. Harnessing spin precession with dissipation

    NASA Astrophysics Data System (ADS)

    Crisan, A. D.; Datta, S.; Viennot, J. J.; Delbecq, M. R.; Cottet, A.; Kontos, T.

    2016-01-01

    Non-collinear spin transport is at the heart of spin or magnetization control in spintronics devices. The use of nanoscale conductors exhibiting quantum effects in transport could provide new paths for that purpose. Here we study non-collinear spin transport in a quantum dot. We use a device made out of a single-wall carbon nanotube connected to orthogonal ferromagnetic electrodes. In the spin transport signals, we observe signatures of out of equilibrium spin precession that are electrically tunable through dissipation. This could provide a new path to harness spin precession in nanoscale conductors.

  7. Harnessing spin precession with dissipation

    PubMed Central

    Crisan, A. D.; Datta, S.; Viennot, J. J.; Delbecq, M. R.; Cottet, A.; Kontos, T.

    2016-01-01

    Non-collinear spin transport is at the heart of spin or magnetization control in spintronics devices. The use of nanoscale conductors exhibiting quantum effects in transport could provide new paths for that purpose. Here we study non-collinear spin transport in a quantum dot. We use a device made out of a single-wall carbon nanotube connected to orthogonal ferromagnetic electrodes. In the spin transport signals, we observe signatures of out of equilibrium spin precession that are electrically tunable through dissipation. This could provide a new path to harness spin precession in nanoscale conductors. PMID:26816050

  8. High field magnetic resonance imaging of rodents in cardiovascular research.

    PubMed

    Vanhoutte, Laetitia; Gerber, Bernhard L; Gallez, Bernard; Po, Chrystelle; Magat, Julie; Jean-Luc, Balligand; Feron, Olivier; Moniotte, Stéphane

    2016-07-01

    Transgenic and gene knockout rodent models are primordial to study pathophysiological processes in cardiovascular research. Over time, cardiac MRI has become a gold standard for in vivo evaluation of such models. Technical advances have led to the development of magnets with increasingly high field strength, allowing specific investigation of cardiac anatomy, global and regional function, viability, perfusion or vascular parameters. The aim of this report is to provide a review of the various sequences and techniques available to image mice on 7-11.7 T magnets and relevant to the clinical setting in humans. Specific technical aspects due to the rise of the magnetic field are also discussed. PMID:27287250

  9. Contrast media in cardiovascular magnetic resonance.

    PubMed

    Lombardi, Massimo; Aquaro, Giovanni; Favilli, Brunella

    2005-01-01

    Among the available imaging techniques, Magnetic Resonance Imaging (MRI) is gaining an increasing role in the cardiologic setting because its specific properties such as the use of non ionising energies, the natural strong contrast between different tissues, the absence of spatial limitations, the good spatial and temporal resolution, the reduced operator dependency. To further improve the images quality and the histopathologic characterisation of tissues the use of contrast media (molecules containing gadolinium, manganese, iron, dysprosium ions) has been proposed both in the experimental and in the clinical settings. Among these ions gadolinium, which having 7 odd electrons in the external orbit has a strong magnetic momentum, is the most used. Gadolinium by itself is extremely toxic but once it is linked with a chelanting agent such as DTPA (Dietilen-Triamin-Penta-Acetic acid) the resulting complex shows a very low toxicity. The number of Gadolinium based compound is growing together with the use of contrast agents in MRI. These contrast agents are routinely used to perform Magnetic Resonance Angiography (MRA) and to a better definition of several cardiac diseases such as the presence of a intra- or paracardiac mass, the evaluation of myocardial perfusion and the evaluation of viability. Both the latter applications have relevant clinical implications. In fact the assessment of myocardial perfusion is one of the most used approach for detecting inducible myocardial ischemia due to major coronary artery disease or to assess the presence of a microvascular disease. The presence and the extent of viable myocardium is deeply modifying the clinical decision making as this viable tissue can recruit a normal function spontaneously or after revascularisation. Furthermore, the extent of viable myocardium has a strong correlation with negative prognosis. Clinical events are also time related to the detection of viable tissue. These evidences imply that the diagnostic

  10. Introduction to Cardiovascular Magnetic Resonance: Technical Principles and Clinical Applications

    PubMed Central

    Tseng, Wen-Yih Isaac; Su, Mao-Yuan Marine; Tseng, Yao-Hui Elton

    2016-01-01

    Cardiovascular magnetic resonance (CMR) is a set of magnetic resonance imaging (MRI) techniques designed to assess cardiovascular morphology, ventricular function, myocardial perfusion, tissue characterization, flow quantification and coronary artery disease. Since MRI is a non-invasive tool and free of radiation, it is suitable for longitudinal monitoring of treatment effect and follow-up of disease progress. Compared to MRI of other body parts, CMR faces specific challenges from cardiac and respiratory motion. Therefore, CMR requires synchronous cardiac and respiratory gating or breath-holding techniques to overcome motion artifacts. This article will review the basic principles of MRI and introduce the CMR techniques that can be optimized for enhanced clinical assessment. PMID:27122944

  11. Advances in clinical applications of cardiovascular magnetic resonance imaging

    PubMed Central

    Bandettini, W P; Arai, A E

    2008-01-01

    Cardiovascular magnetic resonance (CMR) is an evolving technology with growing indications within the clinical cardiology setting. This review article summarises the current clinical applications of CMR. The focus is on the use of CMR in the diagnosis of coronary artery disease with summaries of validation literature in CMR viability, myocardial perfusion, and dobutamine CMR. Practical uses of CMR in non-coronary diseases are also discussed. PMID:18208827

  12. 'Magic Angle Precession'

    SciTech Connect

    Binder, Bernd

    2008-01-21

    An advanced and exact geometric description of nonlinear precession dynamics modeling very accurately natural and artificial couplings showing Lorentz symmetry is derived. In the linear description it is usually ignored that the geometric phase of relativistic motion couples back to the orbital motion providing for a non-linear recursive precession dynamics. The high coupling strength in the nonlinear case is found to be a gravitomagnetic charge proportional to the precession angle and angular velocity generated by geometric phases, which are induced by high-speed relativistic rotations and are relevant to propulsion technologies but also to basic interactions. In the quantum range some magic precession angles indicating strong coupling in a phase-locked chaotic system are identified, emerging from a discrete time dynamical system known as the cosine map showing bifurcations at special precession angles relevant to heavy nuclei stability. The 'Magic Angle Precession' (MAP) dynamics can be simulated and visualized by cones rolling in or on each other, where the apex and precession angles are indexed by spin, charge or precession quantum numbers, and corresponding magic angles. The most extreme relativistic warping and twisting effect is given by the Dirac spinor half spin constellation with 'Hyperdiamond' MAP, which resembles quark confinement.

  13. Assessment of Myocardial Ischemia with Cardiovascular Magnetic Resonance

    PubMed Central

    Heydari, Bobak; Jerosch-Herold, Michael; Kwong, Raymond Y.

    2014-01-01

    Assessment of myocardial ischemia in symptomatic patients remains a common and challenging clinical situation faced by physicians. Risk stratification by presence of ischemia provides important utility for both prognostic assessment and management. Unfortunately, current noninvasive modalities possess numerous limitations and have limited prognostic capacity. More recently, ischemia assessment by cardiovascular magnetic resonance (CMR) has been shown to be a safe, available, and potentially cost-effective alternative with both high diagnostic and prognostic accuracy. Cardiovascular magnetic resonance has numerous advantages over other noninvasive methods, including high temporal and spatial resolution, relatively few contraindications, and absence of ionizing radiation. Furthermore, studies assessing the clinical utility and cost effectiveness of CMR in the short-term setting for patients without evidence of an acute myocardial infarction have also demonstrated favorable results. This review will cover techniques of ischemia assessment with CMR by both stress-induced wall motion abnormalities as well as myocardial perfusion imaging. The diagnostic and prognostic performance studies will also be reviewed, and the use of CMR for ischemia assessment will be compared with other commonly used noninvasive modalities. PMID:22014487

  14. Review of journal of cardiovascular magnetic resonance 2010.

    PubMed

    Pennell, Dudley J; Firmin, David N; Kilner, Philip J; Manning, Warren J; Mohiaddin, Raad H; Prasad, Sanjay K

    2011-01-01

    There were 75 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2010, which is a 34% increase in the number of articles since 2009. The quality of the submissions continues to increase, and the editors were delighted with the recent announcement of the JCMR Impact Factor of 4.33 which showed a 90% increase since last year. Our acceptance rate is approximately 30%, but has been falling as the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. Last year for the first time, the Editors summarized the papers for the readership into broad areas of interest or theme, which we felt would be useful to practitioners of cardiovascular magnetic resonance (CMR) so that you could review areas of interest from the previous year in a single article in relation to each other and other recent JCMR articles 1. This experiment proved very popular with a very high rate of downloading, and therefore we intend to continue this review annually. The papers are presented in themes and comparison is drawn with previously published JCMR papers to identify the continuity of thought and publication in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:21914185

  15. Review of journal of cardiovascular magnetic resonance 2010

    PubMed Central

    2011-01-01

    There were 75 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2010, which is a 34% increase in the number of articles since 2009. The quality of the submissions continues to increase, and the editors were delighted with the recent announcement of the JCMR Impact Factor of 4.33 which showed a 90% increase since last year. Our acceptance rate is approximately 30%, but has been falling as the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. Last year for the first time, the Editors summarized the papers for the readership into broad areas of interest or theme, which we felt would be useful to practitioners of cardiovascular magnetic resonance (CMR) so that you could review areas of interest from the previous year in a single article in relation to each other and other recent JCMR articles [1]. This experiment proved very popular with a very high rate of downloading, and therefore we intend to continue this review annually. The papers are presented in themes and comparison is drawn with previously published JCMR papers to identify the continuity of thought and publication in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:21914185

  16. Review of Journal of Cardiovascular Magnetic Resonance 2009.

    PubMed

    Pennell, D J; Firmin, D N; Kilner, P J; Manning, W J; Mohiaddin, R H; Neubauer, S; Prasad, S K

    2010-01-01

    There were 56 articles published in the Journal of Cardiovascular Magnetic Resonance in 2009. The editors were impressed with the high quality of the submissions, of which our acceptance rate was about 40%. In accordance with open-access publishing, the articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. We have therefore chosen to briefly summarise the papers in this article for quick reference for our readers in broad areas of interest, which we feel will be useful to practitioners of cardiovascular magnetic resonance (CMR). In some cases where it is considered useful, the articles are also put into the wider context with a short narrative and recent CMR references. It has been a privilege to serve as the Editor of the JCMR this past year. I hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:20302618

  17. Review of Journal of Cardiovascular Magnetic Resonance 2009

    PubMed Central

    2010-01-01

    There were 56 articles published in the Journal of Cardiovascular Magnetic Resonance in 2009. The editors were impressed with the high quality of the submissions, of which our acceptance rate was about 40%. In accordance with open-access publishing, the articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. We have therefore chosen to briefly summarise the papers in this article for quick reference for our readers in broad areas of interest, which we feel will be useful to practitioners of cardiovascular magnetic resonance (CMR). In some cases where it is considered useful, the articles are also put into the wider context with a short narrative and recent CMR references. It has been a privilege to serve as the Editor of the JCMR this past year. I hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:20302618

  18. Technology Preview: X-Ray Fused With Magnetic Resonance During Invasive Cardiovascular Procedures

    PubMed Central

    Gutiérrez, Luis F.; de Silva, Ranil; Ozturk, Cengizhan; Sonmez, Merdim; Stine, Annette M.; Raval, Amish N.; Raman, Venkatesh K.; Sachdev, Vandana; Aviles, Ronnier J.; Waclawiw, Myron A.; McVeigh, Elliot R.; Lederman, Robert J.

    2009-01-01

    Background We have developed and validated a system for real-time X-ray fused with magnetic resonance imaging, MRI (XFM), to guide catheter procedures with high spatial precision. Our implementation overlays roadmaps—MRI-derived soft-tissue features of interest—onto conventional X-ray fluoroscopy. We report our initial clinical experience applying XFM, using external fiducial markers, electrocardiogram (ECG)-gating, and automated real-time correction for gantry and table movement. Methods This prospective case series for technical development was approved by the NHLBI Institutional Review Board and included 19 subjects. Multimodality external fiducial markers were affixed to patients’ skin before MRI, which included contrast-enhanced, 3D T1-weighted, or breath-held and ECG-gated 2D steady state free precession imaging at 1.5T. MRI-derived roadmaps were manually segmented while patients were transferred to a calibrated X-ray fluoroscopy system. Image spaces were registered using the fiducial markers and thereafter permitted unrestricted gantry rotation, table panning, and magnification changes. Static and ECG-gated MRI data were transformed from 3D to 2D to correspond with gantry and table position and combined with live X-ray images. Results Clinical procedures included graft coronary arteriography, right ventricular free-wall biopsy, and iliac and femoral artery recanalization and stenting. MRI roadmaps improved operator confidence, and in the biopsy cases, outperformed the best available alternative imaging modality. Registration errors were increased when external fiducial markers were affixed to more mobile skin positions, such as over the abdomen. Conclusion XFM using external fiducial markers is feasible during X-ray guided catheter treatments. Multimodality image fusion may prove a useful adjunct to invasive cardiovascular procedures. PMID:18022851

  19. Free nuclear precession gradiometer system

    SciTech Connect

    Hinton, G. F.

    1985-10-08

    A free nuclear precession gradiometer uses a fluid sample surrounded by a coil the fluid sample containing one or more nuclear species which display a magnetic moment. Current in the coil polarizes the nucleii, which when the current is abruptly terminated precess coherently about the earth's magnetic field. The exact frequency generated is a precise measure of the absolute value of the earth's magnetic field. The signal is in the form of a damped sinusoid with the rate of decay being a function of gradients in the ambient magnetic field. Two vector magnetometers are mounted rigidly on the sensor at the right angles to each other and to the earth's magnetic field. A servo system continuously orients the sensor in a two-axis gimbal system to reduce the output of the vector magnetometers to zero. The instrument is polarized, a counter is triggered to make the frequency measurement, and the signal is analyzed by determining the average amplitude of the signal over a precise interval of time. The result is simultaneous measurement of total intensity and total gradient.

  20. Precession as a driving mechanism for the geodynamo

    NASA Astrophysics Data System (ADS)

    Tilgner, A.

    Precession of the earth's rotation axis has long ago been proposed as a possible driving mechanism for the geodynamo. Past research has focused on convectively driven dynamos and relatively little is known about the hydrodynamics of precession, even in the absence of a magnetic field. Some properties of precession driven flows will be presented and the possiblity of these flows acting as dynamos will be discussed.

  1. Low rate of cardiovascular events in patients with acute myocarditis diagnosed by cardiovascular magnetic resonance

    PubMed Central

    De Stefano, Luciano; Yeyati, Ezequiel Levy; Pietrani, Marcelo; Kohan, Andres; Falconi, Mariano; Benger, Juan; Dragonetti, Laura; Garcia-Monaco, Ricardo; Cagide, Arturo

    2014-01-01

    Background Myocarditis is a relatively common inflammatory disease that affects the myocardium. Infectious disease accounts for most of the cases either because of a direct viral infection or post-viral immune-mediated reaction. Cardiovascular magnetic resonance (CMR) has become an established non-invasive diagnosis tool for acute myocarditis. A recent large single centre study with patients with biopsy-proven viral myocarditis undergoing CMR scans found a high rate of mortality. The aim of this study was to assess the rate of clinical events in our population of patients with diagnosed myocarditis by CMR scan. Methods Patients who consulted to the emergency department with diagnosis of myocarditis by CMR were retrospectively included in the study from January 2008 to May 2012. A CMR protocol was used in all patients, and were followed up to assess the rate of the composite endpoint of all-cause death, congestive heart failure, sudden cardiac death, hospitalization for cardiac cause, recurrent myocarditis or need of radiofrequency ablation or implantable cardiac defibrillator (ICD). A descriptive statistical analysis was performed. Results Thirty-two patients with myocarditis were included in the study. The mean age was 42.6±21.2 years and 81.2% were male. In a mean follow up of 30.4±17.8 months, the rate of the composite endpoint of all-cause death, congestive heart failure, sudden cardiac death, hospitalization for cardiac cause, recurrent myocarditis or need of radiofrequency ablation or ICD was 15.6% (n=5). Two patients had heart failure (one of them underwent heart transplant), one patient needed ICD because of ventricular tachycardia and two other patients were re-hospitalized, for recurrent chest pain and for recurrent myocarditis respectively. Conclusions In our series of acute myocarditis diagnosed by CMR we found a low rate of cardiovascular events without mortality. These findings might oppose data from recently published myocarditis trials. PMID

  2. Multi-color magnetic particle imaging for cardiovascular interventions

    NASA Astrophysics Data System (ADS)

    Haegele, Julian; Vaalma, Sarah; Panagiotopoulos, Nikolaos; Barkhausen, Jörg; Vogt, Florian M.; Borgert, Jörn; Rahmer, Jürgen

    2016-08-01

    Magnetic particle imaging (MPI) uses magnetic fields to visualize the spatial distribution of superparamagnetic iron oxide nanoparticles (SPIOs). Guidance of cardiovascular interventions is seen as one possible application of MPI. To safely guide interventions, the vessel lumen as well as all required interventional devices have to be visualized and be discernible from each other. Until now, different tracer concentrations were used for discerning devices from blood in MPI, because only one type of SPIO could be imaged at a time. Recently, it was shown for 3D MPI that it is possible to separate different signal sources in one volume of interest, i.e. to visualize and discern different SPIOs or different binding states of the same SPIO. The approach was termed multi-color MPI. In this work, the use of multi-color MPI for differentiation of a SPIO coated guide wire (Terumo Radifocus 0.035″) from the lumen of a vessel phantom filled with diluted Resovist is demonstrated. This is achieved by recording dedicated system functions of the coating material containing solid Resovist and of liquid Resovist, which allows separation of their respective signal in the image reconstruction process. Assigning a color to the different signal sources results in a differentiation of guide wire and vessel phantom lumen into colored images.

  3. Quantification of regional myocardial wall motion by cardiovascular magnetic resonance

    PubMed Central

    Jiang, Kai

    2014-01-01

    Cardiovascular magnetic resonance (CMR) is a versatile tool that also allows comprehensive and accurate measurement of both global and regional myocardial contraction. Quantification of regional wall motion parameters, such as strain, strain rate, twist and torsion, has been shown to be more sensitive to early-stage functional alterations. Since the invention of CMR tagging by magnetization saturation in 1988, several CMR techniques have been developed to enable the measurement of regional myocardial wall motion, including myocardial tissue tagging, phase contrast mapping, displacement encoding with stimulated echoes (DENSE), and strain encoded (SENC) imaging. These techniques have been developed with their own advantages and limitations. In this review, two widely used and closely related CMR techniques, i.e., tissue tagging and DENSE, will be discussed from the perspective of pulse sequence development and image-processing techniques. The clinical and preclinical applications of tissue tagging and DENSE in assessing wall motion mechanics in both normal and diseased hearts, including coronary artery diseases, hypertrophic cardiomyopathy, aortic stenosis, and Duchenne muscular dystrophies, will be discussed. PMID:25392821

  4. Multi-color magnetic particle imaging for cardiovascular interventions.

    PubMed

    Haegele, Julian; Vaalma, Sarah; Panagiotopoulos, Nikolaos; Barkhausen, Jörg; Vogt, Florian M; Borgert, Jörn; Rahmer, Jürgen

    2016-08-21

    Magnetic particle imaging (MPI) uses magnetic fields to visualize the spatial distribution of superparamagnetic iron oxide nanoparticles (SPIOs). Guidance of cardiovascular interventions is seen as one possible application of MPI. To safely guide interventions, the vessel lumen as well as all required interventional devices have to be visualized and be discernible from each other. Until now, different tracer concentrations were used for discerning devices from blood in MPI, because only one type of SPIO could be imaged at a time. Recently, it was shown for 3D MPI that it is possible to separate different signal sources in one volume of interest, i.e. to visualize and discern different SPIOs or different binding states of the same SPIO. The approach was termed multi-color MPI. In this work, the use of multi-color MPI for differentiation of a SPIO coated guide wire (Terumo Radifocus 0.035″) from the lumen of a vessel phantom filled with diluted Resovist is demonstrated. This is achieved by recording dedicated system functions of the coating material containing solid Resovist and of liquid Resovist, which allows separation of their respective signal in the image reconstruction process. Assigning a color to the different signal sources results in a differentiation of guide wire and vessel phantom lumen into colored images. PMID:27476675

  5. Prognostic value of normal regadenoson stress perfusion cardiovascular magnetic resonance

    PubMed Central

    2013-01-01

    Background Regadenoson is a vasodilator stress agent that selectively activates the A2A receptor. Compared to adenosine, regadenoson is easier to administer and results in fewer side effects. Although extensively studied in patients undergoing nuclear perfusion imaging (MPI), its use for perfusion cardiovascular magnetic resonance (CMR) is not well described. The aim of this study was to determine the prognostic value of a normal regadenoson perfusion CMR in patients with known or suspected coronary artery disease. Methods Patients with known or suspected coronary artery disease were prospectively enrolled to receive perfusion CMR (Philips 1.5 T) with regadenoson. Three short-axis slices of the left ventricle (LV) were obtained during first pass of contrast using a hybrid GRE-EPI pulse sequence (0.075 mmol/kg Gadolinium-DTPA-BMA at 4 ml/sec). Imaging was performed 1 minute after injection of regadenoson (0.4 mg) and repeated 15 minutes after reversal of hyperemia with aminophylline (125 mg). Perfusion defects were documented if they persisted for ≥2 frames after peak enhancement of the LV cavity. CMR was considered abnormal if there was a resting wall motion abnormality, decreased LVEF (<40%), presence of LGE, or the presence of a perfusion defect during hyperemia. All patients were followed for a minimum of 1 year for major adverse cardiovascular event (MACE) defined as coronary revascularization, non-fatal myocardial infarction, and cardiovascular death. Results 149 patients were included in the final analysis. Perfusion defects were noted in 43/149 (29%) patients; 59/149 (40%) had any abnormality on CMR. During the mean follow-up period of 24 ± 9 months, 17/149 (11.4%) patients experienced MACE. The separation in the survival distributions for those with perfusion defects and those without perfusion defects was highly significant (log-rank p = 0.0001). When the absence of perfusion defects was added to the absence of other resting CMR

  6. Cardiovascular imaging in the diagnosis and monitoring of cardiotoxicity: cardiovascular magnetic resonance and nuclear cardiology.

    PubMed

    Pepe, Alessia; Pizzino, Fausto; Gargiulo, Paola; Perrone-Filardi, Pasquale; Cadeddu, Christian; Mele, Donato; Monte, Ines; Novo, Giuseppina; Zito, Concetta; Di Bella, Gianluca

    2016-05-01

    Chemotherapy-induced cardiotoxicity (CTX) is a determining factor for the quality of life and mortality of patients administered potentially cardiotoxic drugs and in long-term cancer survivors. Therefore, prevention and early detection of CTX are highly desirable, as is the exploration of alternative therapeutic strategies and/or the proposal of potentially cardioprotective treatments. In recent years, cardiovascular imaging has acquired a pivotal role in this setting. Although echocardiography remains the diagnostic method most used to monitor cancer patients, the need for more reliable, reproducible and accurate detection of early chemotherapy-induced CTX has encouraged the introduction of second-line advanced imaging modalities, such as cardiac magnetic resonance (CMR) and nuclear techniques, into the clinical setting. This review of the Working Group on Drug Cardiotoxicity and Cardioprotection of the Italian Society of Cardiology aims to afford an overview of the most important findings from the literature about the role of CMR and nuclear techniques in the management of chemotherapy-treated patients, describe conventional and new parameters for detecting CTX from both diagnostic and prognostic perspectives and provide integrated insight into the role of CMR and nuclear techniques compared with other imaging tools and versus the positions of the most important international societies. PMID:27183525

  7. Fractal frontiers in cardiovascular magnetic resonance: towards clinical implementation.

    PubMed

    Captur, Gabriella; Karperien, Audrey L; Li, Chunming; Zemrak, Filip; Tobon-Gomez, Catalina; Gao, Xuexin; Bluemke, David A; Elliott, Perry M; Petersen, Steffen E; Moon, James C

    2015-01-01

    Many of the structures and parameters that are detected, measured and reported in cardiovascular magnetic resonance (CMR) have at least some properties that are fractal, meaning complex and self-similar at different scales. To date however, there has been little use of fractal geometry in CMR; by comparison, many more applications of fractal analysis have been published in MR imaging of the brain.This review explains the fundamental principles of fractal geometry, places the fractal dimension into a meaningful context within the realms of Euclidean and topological space, and defines its role in digital image processing. It summarises the basic mathematics, highlights strengths and potential limitations of its application to biomedical imaging, shows key current examples and suggests a simple route for its successful clinical implementation by the CMR community.By simplifying some of the more abstract concepts of deterministic fractals, this review invites CMR scientists (clinicians, technologists, physicists) to experiment with fractal analysis as a means of developing the next generation of intelligent quantitative cardiac imaging tools. PMID:26346700

  8. MRXCAT: Realistic numerical phantoms for cardiovascular magnetic resonance

    PubMed Central

    2014-01-01

    Background Computer simulations are important for validating novel image acquisition and reconstruction strategies. In cardiovascular magnetic resonance (CMR), numerical simulations need to combine anatomical information and the effects of cardiac and/or respiratory motion. To this end, a framework for realistic CMR simulations is proposed and its use for image reconstruction from undersampled data is demonstrated. Methods The extended Cardiac-Torso (XCAT) anatomical phantom framework with various motion options was used as a basis for the numerical phantoms. Different tissue, dynamic contrast and signal models, multiple receiver coils and noise are simulated. Arbitrary trajectories and undersampled acquisition can be selected. The utility of the framework is demonstrated for accelerated cine and first-pass myocardial perfusion imaging using k-t PCA and k-t SPARSE. Results MRXCAT phantoms allow for realistic simulation of CMR including optional cardiac and respiratory motion. Example reconstructions from simulated undersampled k-t parallel imaging demonstrate the feasibility of simulated acquisition and reconstruction using the presented framework. Myocardial blood flow assessment from simulated myocardial perfusion images highlights the suitability of MRXCAT for quantitative post-processing simulation. Conclusion The proposed MRXCAT phantom framework enables versatile and realistic simulations of CMR including breathhold and free-breathing acquisitions. PMID:25204441

  9. Visualization of coronary venous anatomy by cardiovascular magnetic resonance

    PubMed Central

    Younger, John F; Plein, Sven; Crean, Andrew; Ball, Stephen G; Greenwood, John P

    2009-01-01

    Background Coronary venous imaging with whole-heart cardiovascular magnetic resonance (CMR) angiography has recently been described using developmental pulse sequences and intravascular contrast agents. However, the practical utility of coronary venous imaging will be for patients with heart failure in whom cardiac resynchronisation therapy (CRT) is being considered. As such complementary information on ventricular function and myocardial viability will be required. The aim of this study was to determine if the coronary venous anatomy could be depicted as part of a comprehensive CMR protocol and using a standard extracellular contrast agent. Methods and Results Thirty-one 3D whole heart CMR studies, performed after intravenous administration of 0.05 mmol/kg gadolinium DTPA, were reviewed. The cardiac venous system was visualized in all patients. The lateral vein of the left ventricle was present in 74%, the anterior interventricular vein in 65%, and the posterior interventricular vein in 74% of patients. The mean maximum distance of demonstrable cardiac vein on the 3D images was 81.5 mm and was dependent on the quality of the 3D data set. Five patients showed evidence of myocardial infarction on late gadolinium enhancement (LGE) images. Conclusion Coronary venous anatomy can be reliably demonstrated using a comprehensive CMR protocol and a standard extracellular contrast agent. The combination of coronary venous imaging, assessment of ventricular function and LGE may be useful in the management of patients with LV dysfunction being considered for CRT. PMID:19671132

  10. The emerging clinical role of cardiovascular magnetic resonance imaging

    PubMed Central

    Kumar, Andreas; Patton, David J; Friedrich, Matthias G

    2010-01-01

    Starting as a research method little more than a decade ago, cardiovascular magnetic resonance (CMR) imaging has rapidly evolved to become a powerful diagnostic tool used in routine clinical cardiology. The contrast in CMR images is generated from protons in different chemical environments and, therefore, enables high-resolution imaging and specific tissue characterization in vivo, without the use of potentially harmful ionizing radiation. CMR imaging is used for the assessment of regional and global ventricular function, and to answer questions regarding anatomy. State-of-the-art CMR sequences allow for a wide range of tissue characterization approaches, including the identification and quantification of nonviable, edematous, inflamed, infiltrated or hypoperfused myocardium. These tissue changes are not only used to help identify the etiology of cardiomyopathies, but also allow for a better understanding of tissue pathology in vivo. CMR tissue characterization may also be used to stage a disease process; for example, elevated T2 signal is consistent with edema and helps differentiate acute from chronic myocardial injury, and the extent of myocardial fibrosis as imaged by contrast-enhanced CMR correlates with adverse patient outcome in ischemic and nonischemic cardiomyopathies. The current role of CMR imaging in clinical cardiology is reviewed, including coronary artery disease, congenital heart disease, nonischemic cardiomyopathies and valvular disease. PMID:20548977

  11. Assessment of the right ventricle with cardiovascular magnetic resonance at 7 Tesla

    PubMed Central

    2013-01-01

    Background Functional and morphologic assessment of the right ventricle (RV) is of clinical importance. Cardiovascular magnetic resonance (CMR) at 1.5T has become gold standard for RV chamber quantification and assessment of even small wall motion abnormalities, but tissue analysis is still hampered by limited spatial resolution. CMR at 7T promises increased resolution, but is technically challenging. We examined the feasibility of cine imaging at 7T to assess the RV. Methods Nine healthy volunteers underwent CMR at 7T using a 16-element TX/RX coil and acoustic cardiac gating. 1.5T served as gold standard. At 1.5T, steady-state free-precession (SSFP) cine imaging with voxel size (1.2x1.2x6) mm3 was used; at 7T, fast gradient echo (FGRE) with voxel size (1.2x1.2x6) mm3 and (1.3x1.3x4) mm3 were applied. RV dimensions (RVEDV, RVESV), RV mass (RVM) and RV function (RVEF) were quantified in transverse slices. Overall image quality, image contrast and image homogeneity were assessed in transverse and sagittal views. Results All scans provided diagnostic image quality. Overall image quality and image contrast of transverse RV views were rated equally for SSFP at 1.5T and FGRE at 7T with voxel size (1.3x1.3x4)mm3. FGRE at 7T provided significantly lower image homogeneity compared to SSFP at 1.5T. RVEDV, RVESV, RVEF and RVM did not differ significantly and agreed close between SSFP at 1.5T and FGRE at 7T (p=0.5850; p=0.5462; p=0.2789; p=0.0743). FGRE at 7T with voxel size (1.3x1.3x4) mm3 tended to overestimate RV volumes compared to SSFP at 1.5T (mean difference of RVEDV 8.2±9.3ml) and to FGRE at 7T with voxel size (1.2x1.2x6) mm3 (mean difference of RVEDV 9.3±8.6ml). Conclusions FGRE cine imaging of the RV at 7T was feasible and provided good image quality. RV dimensions and function were comparable to SSFP at 1.5T as gold standard. PMID:23497030

  12. Disk Precession in Pleione

    NASA Astrophysics Data System (ADS)

    Hirata, R.

    2007-03-01

    From the polarimetric observation of Pleione, we found that the intrinsic polarization angle varied from 60° to 130° in 1974-2003. The Hα profile also changed dramatically from the edge-on type (shell-line profile) to the surface-on type (wine-bottle profile). These facts clearly indicate the spatial motion of the disk axis. We interpret these variations in terms of the disk precession, caused by the secondary of this spectroscopic binary with a period of 218d. We performed the χ^2 minimization for the polarization angle, assuming uniform precession with an imposed condition that the shell maximum occurred at edge-on view. The resulting precession angle is 59° with a period of 81 years. Then, we can describe chronologically the spatial motion of disk axis. We also derived the Hα disk radius from the peak separation, assuming the Keplerian disk. The precession of the disk gives natural explanation of the mysterious long-term spectroscopic behaviors of this star.

  13. Dynamical Torque in CoxFe3–xO4 Nanocube Thin Films Characterized by Femtosecond Magneto-Optics: A π-Shift Control of the Magnetization Precession

    PubMed Central

    2016-01-01

    For spintronic devices excited by a sudden magnetic or optical perturbation, the torque acting on the magnetization plays a key role in its precession and damping. However, the torque itself can be a dynamical quantity via the time-dependent anisotropies of the system. A challenging problem for applications is then to disentangle the relative importance of various sources of anisotropies in the dynamical torque, such as the dipolar field, the crystal structure or the shape of the particular interacting magnetic nanostructures. Here, we take advantage of a range of colloidal cobalt ferrite nanocubes assembled in 2D thin films under controlled magnetic fields to demonstrate that the phase, ϕPrec, of the precession carries a strong signature of the dynamical anisotropies. Performing femtosecond magneto-optics, we show that ϕPrec displays a π-shift for a particular angle θH of an external static magnetic field, H. θH is controlled with the cobalt concentration, the laser intensity, as well as the interparticle interactions. Importantly, it is shown that the shape anisotropy, which strongly departs from those of equivalent bulk thin films or individual noninteracting nanoparticles, reveals the essential role played by the interparticle collective effects. This work shows the reliability of a noninvasive optical approach to characterize the dynamical torque in high density magnetic recording media made of organized and interacting nanoparticles. PMID:27398653

  14. Dynamical Torque in CoxFe3-xO4 Nanocube Thin Films Characterized by Femtosecond Magneto-Optics: A π-Shift Control of the Magnetization Precession.

    PubMed

    Vomir, Mircea; Turnbull, Robin; Birced, Ipek; Parreira, Pedro; MacLaren, Donald A; Lee, Stephen L; André, Pascal; Bigot, Jean-Yves

    2016-08-10

    For spintronic devices excited by a sudden magnetic or optical perturbation, the torque acting on the magnetization plays a key role in its precession and damping. However, the torque itself can be a dynamical quantity via the time-dependent anisotropies of the system. A challenging problem for applications is then to disentangle the relative importance of various sources of anisotropies in the dynamical torque, such as the dipolar field, the crystal structure or the shape of the particular interacting magnetic nanostructures. Here, we take advantage of a range of colloidal cobalt ferrite nanocubes assembled in 2D thin films under controlled magnetic fields to demonstrate that the phase, ϕPrec, of the precession carries a strong signature of the dynamical anisotropies. Performing femtosecond magneto-optics, we show that ϕPrec displays a π-shift for a particular angle θH of an external static magnetic field, H. θH is controlled with the cobalt concentration, the laser intensity, as well as the interparticle interactions. Importantly, it is shown that the shape anisotropy, which strongly departs from those of equivalent bulk thin films or individual noninteracting nanoparticles, reveals the essential role played by the interparticle collective effects. This work shows the reliability of a noninvasive optical approach to characterize the dynamical torque in high density magnetic recording media made of organized and interacting nanoparticles. PMID:27398653

  15. Highlights of the 16th annual scientific sessions of the Society for Cardiovascular Magnetic Resonance

    PubMed Central

    2013-01-01

    The 16th Annual Scientific Sessions of the Society for Cardiovascular Magnetic Resonance (SCMR) took place in San Francisco, USA at the end of January 2013. With a faculty of experts from across the world, this congress provided a wealth of insight into cutting-edge research and technological development. This review article intends to provide a highlight of what represented the most significant advances in the field of cardiovascular magnetic resonance (CMR) during this year’s meeting. PMID:23870663

  16. General spin precession and betatron oscillation in storage rings

    NASA Astrophysics Data System (ADS)

    Fukuyama, Takeshi

    2016-07-01

    Spin precession of particles having both anomalous magnetic and electric dipole moments (EDMs) is considered. We give the generalized expression of spin precession of these particles injected with transversal extent in magnetic storage rings. This is the generalization of the Farley’s pitch correction [F. J. N. Farley, Phys. Lett. B 42, 66 (1972)], including radial oscillation as well as vertical one. The transversal betatron oscillation formulae of these particles are also reproduced.

  17. Cardiovascular magnetic resonance: Diagnostic utility and specific considerations in the pediatric population

    PubMed Central

    Mitchell, Frances M; Prasad, Sanjay K; Greil, Gerald F; Drivas, Peter; Vassiliou, Vassilios S; Raphael, Claire E

    2016-01-01

    Cardiovascular magnetic resonance is a non-invasive imaging modality which is emerging as important tool for the investigation and management of pediatric cardiovascular disease. In this review we describe the key technical and practical differences between scanning children and adults, and highlight some important considerations that must be taken into account for this patient population. Using case examples commonly seen in clinical practice, we discuss the important clinical applications of cardiovascular magnetic resonance, and briefly highlight key future developments in this field. PMID:26862497

  18. Review of Journal of Cardiovascular Magnetic Resonance 2014.

    PubMed

    Pennell, D J; Baksi, A J; Prasad, S K; Raphael, C E; Kilner, P J; Mohiaddin, R H; Alpendurada, F; Babu-Narayan, S V; Schneider, J; Firmin, D N

    2015-01-01

    There were 102 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2014, which is a 6% decrease on the 109 articles published in 2013. The quality of the submissions continues to increase. The 2013 JCMR Impact Factor (which is published in June 2014) fell to 4.72 from 5.11 for 2012 (as published in June 2013). The 2013 impact factor means that the JCMR papers that were published in 2011 and 2012 were cited on average 4.72 times in 2013. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, the progress of the journal's impact over the last 5 years has been impressive. Our acceptance rate is <25% and has been falling because the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors have felt that it is useful once per calendar year to summarize the papers for the readership into broad areas of interest or theme, so that areas of interest can be reviewed in a single article in relation to each other and other recent JCMR articles. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality papers to JCMR for publication. PMID:26589839

  19. Review of Journal of Cardiovascular Magnetic Resonance 2011.

    PubMed

    Pennell, Dudley J; Carpenter, John Paul; Firmin, David N; Kilner, Philip J; Mohiaddin, Raad H; Prasad, Sanjay K

    2012-01-01

    There were 83 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2011, which is an 11% increase in the number of articles since 2010. The quality of the submissions continues to increase. The editors had been delighted with the 2010 JCMR Impact Factor of 4.33, although this fell modestly to 3.72 for 2011. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, we remain very pleased with the progress of the journal's impact over the last 5 years. Our acceptance rate is approximately 25%, and has been falling as the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors feel it is useful to summarize the papers for the readership into broad areas of interest or theme, which we feel would be useful, so that areas of interest from the previous year can be reviewed in a single article in relation to each other and other recent JCMR articles. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:23158097

  20. Review of Journal of Cardiovascular Magnetic Resonance 2011

    PubMed Central

    2012-01-01

    There were 83 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2011, which is an 11% increase in the number of articles since 2010. The quality of the submissions continues to increase. The editors had been delighted with the 2010 JCMR Impact Factor of 4.33, although this fell modestly to 3.72 for 2011. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, we remain very pleased with the progress of the journal's impact over the last 5 years. Our acceptance rate is approximately 25%, and has been falling as the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors feel it is useful to summarize the papers for the readership into broad areas of interest or theme, which we feel would be useful, so that areas of interest from the previous year can be reviewed in a single article in relation to each other and other recent JCMR articles [1]. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:23158097

  1. Review of Journal of Cardiovascular Magnetic Resonance 2012.

    PubMed

    Pennell, Dudley J; Baksi, A John; Carpenter, John Paul; Firmin, David N; Kilner, Philip J; Mohiaddin, Raad H; Prasad, Sanjay K

    2013-01-01

    There were 90 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2012, which is an 8% increase in the number of articles since 2011. The quality of the submissions continues to increase. The editors are delighted to report that the 2011 JCMR Impact Factor (which is published in June 2012) has risen to 4.44, up from 3.72 for 2010 (as published in June 2011), a 20% increase. The 2011 impact factor means that the JCMR papers that were published in 2009 and 2010 were cited on average 4.44 times in 2011. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, the progress of the journal's impact over the last 5 years has been impressive. Our acceptance rate is approximately 25%, and has been falling as the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors have felt that it is useful once per calendar year to summarize the papers for the readership into broad areas of interest or theme, so that areas of interest can be reviewed in a single article in relation to each other and other recent JCMR articles. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:24006874

  2. Review of Journal of Cardiovascular Magnetic Resonance 2013.

    PubMed

    Pennell, Dudley John; Baksi, Arun John; Kilner, Philip John; Mohiaddin, Raad Hashem; Prasad, Sanjay Kumar; Alpendurada, Francisco; Babu-Narayan, Sonya Vidya; Neubauer, Stefan; Firmin, David Nigel

    2014-01-01

    There were 109 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2013, which is a 21% increase on the 90 articles published in 2012. The quality of the submissions continues to increase. The editors are delighted to report that the 2012 JCMR Impact Factor (which is published in June 2013) has risen to 5.11, up from 4.44 for 2011 (as published in June 2012), a 15% increase and taking us through the 5 threshold for the first time. The 2012 impact factor means that the JCMR papers that were published in 2010 and 2011 were cited on average 5.11 times in 2012. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, the progress of the journal's impact over the last 5 years has been impressive. Our acceptance rate is <25% and has been falling because the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors have felt that it is useful once per calendar year to summarize the papers for the readership into broad areas of interest or theme, so that areas of interest can be reviewed in a single article in relation to each other and other recent JCMR articles. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:25475898

  3. Arrhythmogenic right ventricular cardiomyopathy mimics: role of cardiovascular magnetic resonance

    PubMed Central

    2013-01-01

    Background Cardiovascular magnetic resonance (CMR) is commonly used in patients with suspected arrhythmogenic right ventricular cardiomyopathy (ARVC) based on ECG, echocardiogram and Holter. However, various diseases may present with clinical characteristics resembling ARVC causing diagnostic dilemmas. The aim of this study was to explore the role of CMR in the differential diagnosis of patients with suspected ARVC. Methods 657 CMR referrals suspicious for ARVC in a single tertiary referral centre were analysed. Standardized CMR imaging protocols for ARVC were performed. Potential ARVC mimics were grouped into: 1) displacement of the heart, 2) right ventricular overload, and 3) non ARVC-like cardiac scarring. For each, a judgment of clinical impact was made. Results Twenty patients (3.0%) fulfilled imaging ARVC criteria. Thirty (4.6%) had a potential ARVC mimic, of which 25 (3.8%) were considered clinically important: cardiac displacement (n=17), RV overload (n=7) and non-ARVC like myocardial scarring (n=4). One patient had two mimics; one patient had dual pathology with important mimic and ARVC. RV overload and scarring conditions were always thought clinically important whilst the importance of cardiac displacement depended on the degree of displacement from severe (partial absence of pericardium) to epiphenomenon (minor kyphoscoliosis). Conclusions Some patients referred for CMR with suspected ARVC fulfil ARVC imaging criteria (3%) but more have otherwise unrecognised diseases (4.6%) mimicking potentially ARVC. Clinical assessment should reflect this, emphasising the assessment and/or exclusion of potential mimics in parallel with the detection of ARVC major and minor criteria. PMID:23398958

  4. Review of Journal of Cardiovascular Magnetic Resonance 2012

    PubMed Central

    2013-01-01

    There were 90 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2012, which is an 8% increase in the number of articles since 2011. The quality of the submissions continues to increase. The editors are delighted to report that the 2011 JCMR Impact Factor (which is published in June 2012) has risen to 4.44, up from 3.72 for 2010 (as published in June 2011), a 20% increase. The 2011 impact factor means that the JCMR papers that were published in 2009 and 2010 were cited on average 4.44 times in 2011. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, the progress of the journal's impact over the last 5 years has been impressive. Our acceptance rate is approximately 25%, and has been falling as the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors have felt that it is useful once per calendar year to summarize the papers for the readership into broad areas of interest or theme, so that areas of interest can be reviewed in a single article in relation to each other and other recent JCMR articles. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:24006874

  5. Cardiovascular magnetic resonance physics for clinicians: Part II.

    PubMed

    Biglands, John D; Radjenovic, Aleksandra; Ridgway, John P

    2012-01-01

    This is the second of two reviews that is intended to cover the essential aspects of cardiovascular magnetic resonance (CMR) physics in a way that is understandable and relevant to clinicians using CMR in their daily practice. Starting with the basic pulse sequences and contrast mechanisms described in part I, it briefly discusses further approaches to accelerate image acquisition. It then continues by showing in detail how the contrast behaviour of black blood fast spin echo and bright blood cine gradient echo techniques can be modified by adding rf preparation pulses to derive a number of more specialised pulse sequences. The simplest examples described include T2-weighted oedema imaging, fat suppression and myocardial tagging cine pulse sequences. Two further important derivatives of the gradient echo pulse sequence, obtained by adding preparation pulses, are used in combination with the administration of a gadolinium-based contrast agent for myocardial perfusion imaging and the assessment of myocardial tissue viability using a late gadolinium enhancement (LGE) technique. These two imaging techniques are discussed in more detail, outlining the basic principles of each pulse sequence, the practical steps required to achieve the best results in a clinical setting and, in the case of perfusion, explaining some of the factors that influence current approaches to perfusion image analysis. The key principles of contrast-enhanced magnetic resonance angiography (CE-MRA) are also explained in detail, especially focusing on timing of the acquisition following contrast agent bolus administration, and current approaches to achieving time resolved MRA. Alternative MRA techniques that do not require the use of an endogenous contrast agent are summarised, and the specialised pulse sequence used to image the coronary arteries, using respiratory navigator gating, is described in detail. The article concludes by explaining the principle behind phase contrast imaging techniques

  6. Cardiovascular magnetic resonance physics for clinicians: part II

    PubMed Central

    2012-01-01

    This is the second of two reviews that is intended to cover the essential aspects of cardiovascular magnetic resonance (CMR) physics in a way that is understandable and relevant to clinicians using CMR in their daily practice. Starting with the basic pulse sequences and contrast mechanisms described in part I, it briefly discusses further approaches to accelerate image acquisition. It then continues by showing in detail how the contrast behaviour of black blood fast spin echo and bright blood cine gradient echo techniques can be modified by adding rf preparation pulses to derive a number of more specialised pulse sequences. The simplest examples described include T2-weighted oedema imaging, fat suppression and myocardial tagging cine pulse sequences. Two further important derivatives of the gradient echo pulse sequence, obtained by adding preparation pulses, are used in combination with the administration of a gadolinium-based contrast agent for myocardial perfusion imaging and the assessment of myocardial tissue viability using a late gadolinium enhancement (LGE) technique. These two imaging techniques are discussed in more detail, outlining the basic principles of each pulse sequence, the practical steps required to achieve the best results in a clinical setting and, in the case of perfusion, explaining some of the factors that influence current approaches to perfusion image analysis. The key principles of contrast-enhanced magnetic resonance angiography (CE-MRA) are also explained in detail, especially focusing on timing of the acquisition following contrast agent bolus administration, and current approaches to achieving time resolved MRA. Alternative MRA techniques that do not require the use of an endogenous contrast agent are summarised, and the specialised pulse sequence used to image the coronary arteries, using respiratory navigator gating, is described in detail. The article concludes by explaining the principle behind phase contrast imaging techniques

  7. Sr{sub 4}Ru{sub 6}ClO{sub 18}, a new Ru{sup 4+/5+} oxy-chloride, solved by precession electron diffraction: Electric and magnetic behavior

    SciTech Connect

    Roussel, Pascal; Palatinus, Lukas; Belva, Frédéric; Daviero-Minaud, Sylvie; Mentre, Olivier; Huve, Marielle

    2014-04-01

    The crystal structure of Sr{sub 4}Ru{sub 6}ClO{sub 18}, a new Ru{sup 4+/5+} oxo-chloride, has been determined from Precession Electron Diffraction (PED) data acquired on a nanocrystal in a transmission electron microscope using the technique of electron diffraction tomography. This approach is described in details following a pedagogic route and a systematic comparison is made of this rather new method with other experimental methods of electron diffraction, and with the standard single crystal X-ray diffraction technique. Both transport and magnetic measurements, showed a transition at low temperature that may be correlated to Ru{sup 4+}/Ru{sup 5+} charge ordering. - Graphical abstract: Structure of Sr{sub 4}Ru{sub 6}ClO{sub 18}, determined using Precession Electron Diffraction data. - Highlights: • Structure of Sr{sub 4}Ru{sub 6}ClO{sub 18} was solved ab initio using precession electron diffraction. • This was done both on a nanometric sample and on a micrometric one. • Different type of experimental methods of electron diffraction are compared. • Single crystal X-ray diffraction was used to confirm the results. • Transport properties were characterized and show “exotic” behavior.

  8. Does the Atmosphere Precess?

    NASA Astrophysics Data System (ADS)

    Hester, R. E., Jr.

    2015-12-01

    The study considers a north-south pair of mid-latitude rings of atmospheric mass, symmetric with respect to the equator, and rotating with respect to the distant stars. The mass and angular velocity are assigned similar to the annual and zonal mean upper level westerlies. Their relatively rapid rotation is assumed to allow a rigid body approximation on long time and space scales. The rings are constrained to move as if rigidly connected to a common axis of rotation. The pair thus constitutes a symmetric top with a fixed pivot point at the center of mass. Analysis of the dynamics follows the classical mechanics approach used for precession of the equinoxes. The theoretical rate of precession for this highly idealized system yields a period on the order of decades. The predicted dynamics appears consistent with three prior studies of observational data: latitudinal movements of atmospheric circulation above far Southern Australia, latitudinal movements of ocean circulation in the Kuroshio Extension, and changes in global Atmospheric Angular Momentum before and after 1976. Each of these observational records indicates correlation with the Pacific Decadal Oscillation. The theoretical dynamics in combination with the observations suggests the axis of rotation of the atmospheric westerlies is offset from the Earth axis by a few degrees, and further, that this axis precesses around a mean axis on a time scale of a few decades.

  9. Clinical Utility of Cardiovascular Magnetic Resonance in Hypertrophic Cardiomyopathy

    PubMed Central

    2012-01-01

    Hypertrophic cardiomyopathy (HCM) is characterized by substantial genetic and phenotypic heterogeneity, leading to considerable diversity in clinical course including the most common cause of sudden death in young people and a determinant of heart failure symptoms in patients of any age. Traditionally, two-dimensional echocardiography has been the most reliable method for establishing a clinical diagnosis of HCM. However, cardiovascular magnetic resonance (CMR), with its high spatial resolution and tomographic imaging capability, has emerged as a technique particularly well suited to characterize the diverse phenotypic expression of this complex disease. For example, CMR is often superior to echocardiography for HCM diagnosis, by identifying areas of segmental hypertrophy (ie., anterolateral wall or apex) not reliably visualized by echocardiography (or underestimated in terms of extent). High-risk HCM patient subgroups identified with CMR include those with thin-walled scarred LV apical aneurysms (which prior to CMR imaging in HCM remained largely undetected), end-stage systolic dysfunction, and massive LV hypertrophy. CMR observations also suggest that the cardiomyopathic process in HCM is more diffuse than previously regarded, extending beyond the LV myocardium to include thickening of the right ventricular wall as well as substantial morphologic diversity with regard to papillary muscles and mitral valve. These findings have implications for management strategies in patients undergoing invasive septal reduction therapy. Among HCM family members, CMR has identified unique phenotypic markers of affected genetic status in the absence of LV hypertrophy including: myocardial crypts, elongated mitral valve leaflets and late gadolinium enhancement. The unique capability of contrast-enhanced CMR with late gadolinium enhancement to identify myocardial fibrosis has raised the expectation that this may represent a novel marker, which may enhance risk stratification. At

  10. [Utility of cardiovascular magnetic resonance in hypertrophic cardiomyopathy: when is it superior to echocardiography?].

    PubMed

    Kammoun, I; Marrakchi, S; Zidi, A; Ibn ElHaj, Z; Naccache, S; Ben Amara, W; Jebri, F; Bennour, E; Kachboura, S

    2015-02-01

    The diagnosis of hypertrophic cardiomyopathy is usually established by echocardiography. Recently, there has been greatly increased use of cardiac magnetic resonance (CMR) because of its precise determination of myocardial anatomy and the depiction of myocardial fibrosis. In this review, we describe the role of echocardiography and magnetic resonance in the assessment of this complex disease. In conclusion, there is a complementarity between cardiovascular magnetic resonance imaging and echocardiography for the diagnosis and the management of HCM. PMID:24834991

  11. Evaluation of aortic stenosis by cardiovascular magnetic resonance imaging: comparison with established routine clinical techniques

    PubMed Central

    Kupfahl, C; Honold, M; Meinhardt, G; Vogelsberg, H; Wagner, A; Mahrholdt, H; Sechtem, U

    2004-01-01

    Objective: To evaluate whether direct planimetry of aortic valve area (AVA) by cardiac magnetic resonance (CMR) imaging is a reliable tool for determining the severity of aortic stenosis compared with transthoracic echocardiography (TTE), transoesophageal echocardiography (TOE), and cardiac catheterisation. Methods: 44 symptomatic patients with severe aortic stenosis were studied. By cardiac catheterisation AVA was calculated by the Gorlin equation. AVA was measured with CMR from steady state free precession (true fast imaging with steady state precession) by planimetry. AVA was also determined from TOE images by planimetry and from TTE images by the continuity equation. Results: Bland-Altman analysis evaluating intraobserver and interobserver variability showed a very small bias for both (−0.016 and 0.019, respectively; n  =  20). Bias and limits of agreement between CMR and TTE were 0.05 (−0.35, 0.44) cm2 (n  =  37), between CMR and TOE 0.02 (−0.39, 0.42) cm2 (n  =  32), and between CMR and cardiac catheterisation 0.09 (−0.30, 0.47) cm2 (n  =  36). The sensitivity and specificity of CMR to detect AVA ⩽ 0.80 cm2 measured by cardiac catheterisation was 78% and 89%, of TOE 70% and 70%, and of TTE 74% and 67%, respectively. Conclusion: CMR planimetry is highly reliable and reproducible. Further, CMR planimetry had the best sensitivity and specificity of all non-invasive methods for detecting severe aortic stenosis in comparison with cardiac catheterisation. Therefore, CMR planimetry of AVA with steady state free precession is a new powerful diagnostic tool, particularly for patients with uncertain or discrepant findings by other modalities. PMID:15253962

  12. Cardiovascular Magnetic Resonance in Cardiology Practice: A Concise Guide to Image Acquisition and Clinical Interpretation.

    PubMed

    Valbuena-López, Silvia; Hinojar, Rocío; Puntmann, Valentina O

    2016-02-01

    Cardiovascular magnetic resonance plays an increasingly important role in routine cardiology clinical practice. It is a versatile imaging modality that allows highly accurate, broad and in-depth assessment of cardiac function and structure and provides information on pertinent clinical questions in diseases such as ischemic heart disease, nonischemic cardiomyopathies, and heart failure, as well as allowing unique indications, such as the assessment and quantification of myocardial iron overload or infiltration. Increasing evidence for the role of cardiovascular magnetic resonance, together with the spread of knowledge and skill outside expert centers, has afforded greater access for patients and wider clinical experience. This review provides a snapshot of cardiovascular magnetic resonance in modern clinical practice by linking image acquisition and postprocessing with effective delivery of the clinical meaning. PMID:26778592

  13. The precession dynamo experiment at HZDR

    NASA Astrophysics Data System (ADS)

    Giesecke, A.; Gundrum, T.; Herault, J.; Stefani, F.; Gerbeth, G.

    2015-12-01

    In a next generation dynamo experiment currently under development atthe Helmholtz-Zentrum Dresden-Rossendorf (HZDR) a fluid flow of liquidsodium, solely driven by precession, will be considered as a possiblesource for magnetic field generation. The experiment is mainlymotivated by alternative concepts for astrophysical dynamos that arebased on mechanical flow driving. For example, it has long beendiscussed whether precession may be a complementary power source forthe geodynamo (Malkus, Science 1968) or for the ancient lunar dynamodue to the Earth-driven precession of the lunar spin axis (Dwyer, Nature 2011).We will present the current state of development of the dynamoexperiment together with results from non-linear hydrodynamicsimulations with moderate precessional forcing. Our simulations reveala non-axisymmetric forced mode with an amplitude of up to one fourthof the rotation velocity of the cylindrical container confirming thatprecession provides a rather efficient flow driving mechanism even atmoderate precession rates.More relevant for dynamo action might be free Kelvin modes (thenatural flow eigenmodes in a rotating cylinder) with higher azimuthalwave number. These modes may become relevant when constituting atriadic resonance with the fundamental forced mode, i.e., when theheight of the container matches their axial wave lengths. We findtriadic resonances at aspect ratios close to those predicted by thelinear theory except around the primary resonance of the forcedmode. In that regime we still identify free Kelvin modes propagatingin retrograde direction but none of them can be assigned to a triade.Our results will enter into the development of flow models that willbe used in kinematic simulations of the electromagnetic inductionequation in order to determine whether a precession driven flow willbe capable to drive a dynamo at all and to limit the parameter spacewithin which the occurrence of dynamo action is most promising.

  14. Understanding cardiovascular injury after treatment for cancer: an overview of current uses and future directions of cardiovascular magnetic resonance

    PubMed Central

    2013-01-01

    While cancer-free survival has improved over the past 20 years for many individuals with prostate, renal, breast, and hematologic malignancies, the increasingly recognized prevalence of cardiovascular (CV) events in cancer survivors has been an unintended consequence of many of the therapies that have improved these survival rates. The increase in CV events threatens to offset the improvement in cancer related survival. As a result, there is an emerging need to develop methods to identify those individuals treated for cancer at increased risk of cardiovascular events. With its inherent ability to characterize myocardial tissue and identify both cardiac and vascular dysfunction, cardiovascular magnetic resonance (CMR) has the potential to identify both subclinical and early clinical CV injury before the development of an overt catastrophic event such as a myocardial infarction, stroke, or premature cardiac death. Early identification provides an opportunity for the implementation of primary prevention strategies to prevent such events, thereby improving overall cancer survivorship and quality of life. This article reviews the etiology of CV events associated with cancer therapy and the unique potential of CMR to provide early diagnosis of subclinical CV injury related to the administration of these therapies. PMID:23902649

  15. Laser-Induced Fast Magnetization Precession and Gilbert Damping for CoCrPt Alloy Thin Films with Perpendicular Magnetic Anisotropy

    NASA Astrophysics Data System (ADS)

    Mizukami, Shigemi; Watanabe, Daisuke; Kubota, Takahide; Zhang, Xianmin; Naganuma, Hiroshi; Oogane, Mikihiko; Ando, Yasuo; Miyazaki, Terunobu

    2010-12-01

    We have investigated magnetic field strength (up to 10 kOe) and angle dependences of spin dynamics in 4-nm-thick films of CoCrPt alloys with perpendicular magnetic anisotropy using the all-optical time-resolved magneto-optical Kerr effect (TRMOKE). The comprehensive TRMOKE measurements have indicated the Gilbert damping constant α of 0.05 for the alloy film with low coercivity. The experiments also indicated that α values for the alloy films deposited at higher temperatures with higher coercivities were also no greater than 0.06.

  16. Heating of cardiovascular stents in intense radiofrequency magnetic fields.

    PubMed

    Foster, K R; Goldberg, R; Bonsignore, C

    1999-01-01

    We consider the heating of a metal stent in an alternating magnetic field from an induction heating furnace. An approximate theoretical analysis is conducted to estimate the magnetic field strength needed to produce substantial temperature increases. Experiments of stent heating in industrial furnaces are reported, which confirm the model. The results show that magnetic fields inside inductance furnaces are capable of significantly heating stents. However, the fields fall off very quickly with distance and in most locations outside the heating coil, field levels are far too small to produce significant heating. The ANSI/IEEE C95.1-1992 limits for human exposure to alternating magnetic fields provide adequate protection against potential excessive heating of the stents. PMID:10029137

  17. Spin precession in anisotropic cosmologies

    NASA Astrophysics Data System (ADS)

    Kamenshchik, A. Yu.; Teryaev, O. V.

    2016-05-01

    We consider the precession of a Dirac particle spin in some anisotropic Bianchi universes. This effect is present already in the Bianchi-I universe. We discuss in some detail the geodesics and the spin precession for both the Kasner and the Heckmann-Schucking solutions. In the Bianchi-IX universe the spin precession acquires the chaotic character due to the stochasticity of the oscillatory approach to the cosmological singularity. The related helicity flip of fermions in the very early universe may produce the sterile particles contributing to dark matter.

  18. The Combined Effect of Precession and Convection on the Dynamo Action

    NASA Astrophysics Data System (ADS)

    Wei, Xing

    2016-08-01

    To understand the generation of the Earth’s magnetic field and those of other planets, we numerically investigate the combined effect of precession and convection on dynamo action in a spherical shell. Convection alone, precession alone, and the combined effect of convection and precession are studied at the low Ekman number at which the precessing flow is already unstable. The key result is that although precession or convection alone are not strong enough to support the dynamo action, the combined effect of precession and convection can support the dynamo action because of the resonance of precessional and convective instabilities. This result may explain why the geodynamo has been maintained for such a long time compared to the Martian dynamo.

  19. Cardiovascular magnetic resonance in rheumatology: Current status and recommendations for use.

    PubMed

    Mavrogeni, Sophie I; Kitas, George D; Dimitroulas, Theodoros; Sfikakis, Petros P; Seo, Philip; Gabriel, Sherine; Patel, Amit R; Gargani, Luna; Bombardieri, Stefano; Matucci-Cerinic, Marco; Lombardi, Massimo; Pepe, Alessia; Aletras, Anthony H; Kolovou, Genovefa; Miszalski, Tomasz; van Riel, Piet; Semb, AnneGrete; Gonzalez-Gay, Miguel Angel; Dessein, Patrick; Karpouzas, George; Puntmann, Valentina; Nagel, Eike; Bratis, Konstantinos; Karabela, Georgia; Stavropoulos, Efthymios; Katsifis, Gikas; Koutsogeorgopoulou, Loukia; van Rossum, Albert; Rademakers, Frank; Pohost, Gerald; Lima, Joao A C

    2016-08-15

    Targeted therapies in connective tissue diseases (CTDs) have led to improvements of disease-associated outcomes, but life expectancy remains lower compared to general population due to emerging co-morbidities, particularly due to excess cardiovascular risk. Cardiovascular magnetic resonance (CMR) is a noninvasive imaging technique which can provide detailed information about multiple cardiovascular pathologies without using ionizing radiation. CMR is considered the reference standard for quantitative evaluation of left and right ventricular volumes, mass and function, cardiac tissue characterization and assessment of thoracic vessels; it may also be used for the quantitative assessment of myocardial blood flow with high spatial resolution and for the evaluation of the proximal coronary arteries. These applications are of particular interest in CTDs, because of the potential of serious and variable involvement of the cardiovascular system during their course. The International Consensus Group on CMR in Rheumatology was formed in January 2012 aiming to achieve consensus among CMR and rheumatology experts in developing initial recommendations on the current state-of-the-art use of CMR in CTDs. The present report outlines the recommendations of the participating CMR and rheumatology experts with regards to: (a) indications for use of CMR in rheumatoid arthritis, the spondyloarthropathies, systemic lupus erythematosus, vasculitis of small, medium and large vessels, myositis, sarcoidosis (SRC), and scleroderma (SSc); (b) CMR protocols, terminology for reporting CMR and diagnostic CMR criteria for assessment and quantification of cardiovascular involvement in CTDs; and (c) a research agenda for the further development of this evolving field. PMID:27179903

  20. Probing for compositeness, discrete time effects and Markov enviromental influences using spin polarization precession.

    NASA Astrophysics Data System (ADS)

    Wolf, Carl

    By considering a spin-one particle precession in a magnetic field, we demonstrate that if very refined measurements were made of both the precession frequency and the amplitude of spin polarization, these measurements could be used to probe for compositeness of gauge bosons, discrete time effects and possible Markov environmental effects.

  1. Minimizing Risk of Nephrogenic systemic fibrosis in Cardiovascular Magnetic Resonance

    PubMed Central

    2012-01-01

    Nephrogenic Systemic Fibrosis is a rare condition appearing only in patients with severe renal impairment or failure and presents with dermal lesions and involvement of internal organs. Although many cases are mild, an estimated 5 % have a progressive debilitating course. To date, there is no known effective treatment thus stressing the necessity of ample prevention measures. An association with the use of Gadolinium based contrast agents (GBCA) makes Nephrogenic Systemic Fibrosis a potential side effect of contrast enhanced magnetic resonance imaging and offers the opportunity for prevention by limiting use of gadolinium based contrast agents in renal failure patients. In itself toxic, Gadolinium is embedded into chelates that allow its safe use as a contrast agent. One NSF theory is that Gadolinium chelates distribute into the extracellular fluid compartment and set Gadolinium ions free, depending on multiple factors among which the duration of chelates exposure is directly related to the renal function. Major medical societies both in Europe and in North America have developed guidelines for the usage of GBCA. Since the establishment of these guidelines and the increased general awareness of this condition, the occurrence of NSF has been nearly eliminated. Giving an overview over the current knowledge of NSF pathobiochemistry, pathogenesis and treatment options this review focuses on the guidelines of the European Medicines Agency, the European Society of Urogenital Radiology, the FDA and the American College of Radiology from 2008 up to 2011 and the transfer of this knowledge into every day practice. PMID:22607376

  2. Precession-driven dynamos in a full sphere and the role of large scale cyclonic vortices

    NASA Astrophysics Data System (ADS)

    Lin, Yufeng; Marti, Philippe; Noir, Jerome; Jackson, Andrew

    2016-06-01

    Precession has been proposed as an alternative power source for planetary dynamos. Previous hydrodynamic simulations suggested that precession can generate very complex flows in planetary liquid cores [Y. Lin, P. Marti, and J. Noir, "Shear-driven parametric instability in a precessing sphere," Phys. Fluids 27, 046601 (2015)]. In the present study, we numerically investigate the magnetohydrodynamics of a precessing sphere. We demonstrate precession driven dynamos in different flow regimes, from laminar to turbulent flows. In particular, we highlight the magnetic field generation by large scale cyclonic vortices, which has not been explored previously. In this regime, dynamos can be sustained at relatively low Ekman numbers and magnetic Prandtl numbers, which paves the way for planetary applications.

  3. Unmasking Silent Endothelial Activation in the Cardiovascular System Using Molecular Magnetic Resonance Imaging

    PubMed Central

    Belliere, Julie; Martinez de Lizarrondo, Sara; Choudhury, Robin P.; Quenault, Aurélien; Le Béhot, Audrey; Delage, Christine; Chauveau, Dominique; Schanstra, Joost P.; Bascands, Jean-Loup; Vivien, Denis; Gauberti, Maxime

    2015-01-01

    Endothelial activation is a hallmark of cardiovascular diseases, acting either as a cause or a consequence of organ injury. To date, we lack suitable methods to measure endothelial activation in vivo. In the present study, we developed a magnetic resonance imaging (MRI) method allowing non-invasive endothelial activation mapping in the vasculature of the main organs affected during cardiovascular diseases. In clinically relevant contexts in mice (including systemic inflammation, acute and chronic kidney diseases, diabetes mellitus and normal aging), we provided evidence that this method allows detecting endothelial activation before any clinical manifestation of organ failure in the brain, kidney and heart with an exceptional sensitivity. In particular, we demonstrated that diabetes mellitus induces chronic endothelial cells activation in the kidney and heart. Moreover, aged mice presented activated endothelial cells in the kidneys and the cerebrovasculature. Interestingly, depending on the underlying condition, the temporospatial patterns of endothelial activation in the vascular beds of the cardiovascular system were different. These results demonstrate the feasibility of detecting silent endothelial activation occurring in conditions associated with high cardiovascular risk using molecular MRI. PMID:26379785

  4. LVM Assessed by Echocardiography and Cardiac Magnetic Resonance, Cardiovascular Outcomes, and Medical Practice

    PubMed Central

    Armstrong, Anderson C.; Gidding, Samuel; Gjesdal, Ola; Wu, Colin; Bluemke, David A; Lima, João A.

    2012-01-01

    We investigate three important areas related to the clinical use of LVM (LVM): accuracy of assessments by echocardiography and cardiac magnetic resonance (CMR), the ability to predict cardiovascular outcomes, and the comparative value of different indexing methods. The recommended formula for echocardiographic estimation of LVM uses linear measurements and is based on the assumption of the left ventricle as a prolate ellipsoid of revolution. CMR permits a modeling of the left ventricle free of cardiac geometric assumptions or acoustic window dependency, showing better accuracy and reproducibility. However, echocardiography has lower cost, easier availability, and better tolerability. From the Medline database, 26 longitudinal echocardiographic studies and 5 CMR studies, investigating LVM or LV hypertrophy as predictors of death or major cardiovascular outcomes, were identified. LVM and LV hypertrophy were reliable cardiovascular risk predictors using both modalities. However, no study directly compared the methods for the ability to predict events, agreement in hypertrophy classification, or performance in cardiovascular risk reclassification. Indexing LVM to BSA was the earliest normalization process used, but it seems to underestimate the prevalence of hypertrophy in obese and overweight subjects. Dividing LVM by height to 1.7 or 2.7 as allometric powers are the most promising normalization methods in terms of practicality and usefulness from a clinical ans scientific standpoints for scaling myocardial mass to body size. The measurement of LVM, calculation of LVMi, and classification for LVH should be standardized by scientific societies across measurement techniques and adopted by clinicians in risk stratification and therapeutic decision. PMID:22897998

  5. Unmasking Silent Endothelial Activation in the Cardiovascular System Using Molecular Magnetic Resonance Imaging.

    PubMed

    Belliere, Julie; Martinez de Lizarrondo, Sara; Choudhury, Robin P; Quenault, Aurélien; Le Béhot, Audrey; Delage, Christine; Chauveau, Dominique; Schanstra, Joost P; Bascands, Jean-Loup; Vivien, Denis; Gauberti, Maxime

    2015-01-01

    Endothelial activation is a hallmark of cardiovascular diseases, acting either as a cause or a consequence of organ injury. To date, we lack suitable methods to measure endothelial activation in vivo. In the present study, we developed a magnetic resonance imaging (MRI) method allowing non-invasive endothelial activation mapping in the vasculature of the main organs affected during cardiovascular diseases. In clinically relevant contexts in mice (including systemic inflammation, acute and chronic kidney diseases, diabetes mellitus and normal aging), we provided evidence that this method allows detecting endothelial activation before any clinical manifestation of organ failure in the brain, kidney and heart with an exceptional sensitivity. In particular, we demonstrated that diabetes mellitus induces chronic endothelial cells activation in the kidney and heart. Moreover, aged mice presented activated endothelial cells in the kidneys and the cerebrovasculature. Interestingly, depending on the underlying condition, the temporospatial patterns of endothelial activation in the vascular beds of the cardiovascular system were different. These results demonstrate the feasibility of detecting silent endothelial activation occurring in conditions associated with high cardiovascular risk using molecular MRI. PMID:26379785

  6. Standardized cardiovascular magnetic resonance imaging (CMR) protocols, society for cardiovascular magnetic resonance: board of trustees task force on standardized protocols

    PubMed Central

    Kramer, Christopher M; Barkhausen, Jorg; Flamm, Scott D; Kim, Raymond J; Nagel, Eike

    2008-01-01

    Index 1. General techniques 1.1. Stress and safety equipment 1.2. Left ventricular (LV) structure and function module 1.3. Right ventricular (RV) structure and function module 1.4. Gadolinium dosing module. 1.5. First pass perfusion 1.6. Late gadolinium enhancement (LGE) 2. Disease specific protocols 2.1. Ischemic heart disease 2.1.1. Acute myocardial infarction (MI) 2.1.2. Chronic ischemic heart disease and viability 2.1.3. Dobutamine stress 2.1.4. Adenosine stress perfusion 2.2. Angiography: 2.2.1. Peripheral magnetic resonance angiography (MRA) 2.2.2. Thoracic MRA 2.2.3. Anomalous coronary arteries 2.2.4. Pulmonary vein evaluation 2.3. Other 2.3.1. Non-ischemic cardiomyopathy 2.3.2. Arrhythmogenic right ventricular cardiomyopathy (ARVC) 2.3.3. Congenital heart disease 2.3.4. Valvular heart disease 2.3.5. Pericardial disease 2.3.6. Masses PMID:18605997

  7. Hyperpolarized Magnetic Resonance: A Novel Technique for the In Vivo Assessment of Cardiovascular Disease

    PubMed Central

    Schroeder, Marie A.; Clarke, Kieran; Neubauer, Stefan; Tyler, Damian J.

    2011-01-01

    Non-invasive imaging plays a central role in cardiovascular disease for determining diagnosis, prognosis, and optimizing patient management. Recent experimental studies have demonstrated that monitoring hyperpolarized 13C-labelled tracers with magnetic resonance imaging and spectroscopy (MRI and MRS) offers a new way to investigate the normal and diseased heart, and that the technology may be useful in patients with heart disease. In this review, we show how hyperpolarized 13C-labelled tracers are generated and have been applied experimentally, and outline the methodological advances currently underway to enable translation of hyperpolarized 13C MRI and MRS into the clinic. Using hyperpolarized 13C-labelled metabolites and metabolic MRI and MRS could help assessment of many human cardiovascular diseases, including coronary artery disease, heart failure and metabolic cardiomyopathies. We discuss the clinical areas in which the technology may, in the future, aid in the diagnosis and management of patients with cardiovascular diseases, including dynamic investigations of in vivo metabolism, coronary angiography and quantitative perfusion imaging. It is possible that, in the future, hyperpolarized magnetic resonance will play a major role in clinical cardiology. PMID:21969318

  8. Cardiovascular alterations in Macaca monkeys exposed to stationary magnetic fields: experimental observations and theoretical analysis

    SciTech Connect

    Tenforde, T.S.; Gaffey, C.T.; Moyer, B.R.; Budinger, T.F.

    1983-01-01

    Simultaneous measurements were made of the electrocardiogram (ECG) and the intraarterial blood pressure of adult male Macaca monkeys during acute exposure to homogeneous stationary magnetic fields ranging in strength up to 1.5 tesla. An instantaneous, field strength-dependent increase in the ECG signal amplitude at the locus of the T wave was observed in fields greater than 0.1 tesla. The temporal sequence of this signal in the ECG record and its reversibility following termination of the magnetic field exposure are consistent with an earlier suggestion that it arises from a magnetically induced aortic blood flow potential superimposed on the native T-wave signal. No measurable alterations in blood pressure resulted from exposure to fields up to 1.5 tesla. This experimental finding is in agreement with theoretical calculations of the magnetohydrodynamic effect on blood flow in the major arteries of the cardiovascular system. 27 references, 1 figure, 1 table.

  9. Cardiovascular magnetic resonance at 3.0T: Current state of the art

    PubMed Central

    2010-01-01

    There are advantages to conducting cardiovascular magnetic resonance (CMR) studies at a field strength of 3.0 Telsa, including the increase in bulk magnetization, the increase in frequency separation of off-resonance spins, and the increase in T1 of many tissues. However, there are significant challenges to routinely performing CMR at 3.0T, including the reduction in main magnetic field homogeneity, the increase in RF power deposition, and the increase in susceptibility-based artifacts. In this review, we outline the underlying physical effects that occur when imaging at higher fields, examine the practical results these effects have on the CMR applications, and examine methods used to compensate for these effects. Specifically, we will review cine imaging, MR coronary angiography, myocardial perfusion imaging, late gadolinium enhancement, and vascular wall imaging. PMID:20929538

  10. Two spinning ways for precession dynamo

    NASA Astrophysics Data System (ADS)

    Cappanera, L.; Guermond, J.-L.; Léorat, J.; Nore, C.

    2016-04-01

    It is numerically demonstrated by means of a magnetohydrodynamic code that precession can trigger dynamo action in a cylindrical container. Fixing the angle between the spin and the precession axis to be 1/2 π , two limit configurations of the spinning axis are explored: either the symmetry axis of the cylinder is parallel to the spin axis (this configuration is henceforth referred to as the axial spin case), or it is perpendicular to the spin axis (this configuration is referred to as the equatorial spin case). In both cases, the centro-symmetry of the flow breaks when the kinetic Reynolds number increases. Equatorial spinning is found to be more efficient in breaking the centro-symmetry of the flow. In both cases, the average flow in the reference frame of the mantle converges to a counter-rotation with respect to the spin axis as the Reynolds number grows. We find a scaling law for the average kinetic energy in term of the Reynolds number in the axial spin case. In the equatorial spin case, the unsteady asymmetric flow is shown to be capable of sustaining dynamo action in the linear and nonlinear regimes. The magnetic field is mainly dipolar in the equatorial spin case, while it is is mainly quadrupolar in the axial spin case.

  11. A Precession-Driven Lunar Dynamo

    NASA Astrophysics Data System (ADS)

    Tian, B. Y.; Stanley, S.; Tikoo, S. M.; Weiss, B. P.

    2014-12-01

    Paleomagnetic studies of Apollo samples suggest that the Moon generated a magnetic field with surface field intensities of several tens of microteslas until at least 3.56 billion years ago (Ga). The field then declined by an order of magnitude from 3.56 - 3.19 Ga. Because of difficulties in reproducing such a long-lived and intense field with convection-driven dynamos, a dynamo driven by precession of the mantle relative to the core was proposed as an alternative. However, there have not been any detailed numerical models demonstrating the feasibility, lifetime, and intensity of such a lunar dynamo. Using fully 3D magnetohydrodynamic simulations, we determined the strength and duration of a mechanically-driven dynamo powered by mantle precession. We found that this mechanism was capable of not only generating the 10-100μT paleomagnetic intensities observed in Apollo samples aged between 4.25 and 3.56 Ga, but also reproducing the precipitous decline in paleointensity beyond 3.56 Ga as the obliquity of the Moon decreased below 15°.

  12. Toroidal Precession as a Geometric Phase

    SciTech Connect

    J.W. Burby and H. Qin

    2012-09-26

    Toroidal precession is commonly understood as the orbit-averaged toroidal drift of guiding centers in axisymmetric and quasisymmetric configurations. We give a new, more natural description of precession as a geometric phase effect. In particular, we show that the precession angle arises as the holonomy of a guiding center's poloidal trajectory relative to a principal connection. The fact that this description is physically appropriate is borne out with new, manifestly coordinate-independent expressions for the precession angle that apply to all types of orbits in tokamaks and quasisymmetric stellarators alike. We then describe how these expressions may be fruitfully employed in numerical calculations of precession.

  13. The Precession of Asteroid 1620 Geographos

    NASA Astrophysics Data System (ADS)

    Prokof'eva, V. V.; Tarashchuk, V. P.; Karachkina, L. G.

    The frequency analysis of the fine photometric effects in the photometric observation obtained during asteroid 1620 Geographos approaching to Earth in 1994 allowed to derive the precession of asteroid spin axis. The periods of 0({rm) d!.8 and 2({rm) d!.8 or multiple to them were revealed. The magnitude of precession angle was estimated to be near 3({circ) . The nature of the precession discussed. The emergence of the free precession may be supported at time of the formation of the asteroid or by the collision with another body. The forced precession does not contradict to the Geographos connection with meteor streams and the assumption that Geographos may have small satellites.

  14. Identification of Left Ventricular Myocardial Ischemia and Cardiac Prognosis with Cardiovascular Magnetic Resonance: Updates from 2008 to 2010

    PubMed Central

    Chotenimitkhun, Runyawan

    2013-01-01

    Noninvasive imaging modalities are often used to manage patients with cardiovascular disease. Cardiovascular magnetic resonance (CMR) is increasingly used for diagnosing and evaluating myocardial ischemia and viability; moreover, stress CMR study results can be used to determine cardiac prognosis. In this article, we review recently published material regarding the performance of stress testing with CMR including a brief update regarding techniques, stress agents, diagnostic accuracy, prognosis, economic implications, and ongoing trials and future developments. PMID:21125353

  15. Extra-cardiac findings in cardiovascular magnetic resonance: what the imaging cardiologist needs to know.

    PubMed

    Rodrigues, Jonathan C L; Lyen, Stephen M; Loughborough, William; Amadu, Antonio Matteo; Baritussio, Anna; Dastidar, Amardeep Ghosh; Manghat, Nathan E; Bucciarelli-Ducci, Chiara

    2016-01-01

    Cardiovascular magnetic resonance (CMR) is an established non-invasive technique to comprehensively assess cardiovascular structure and function in a variety of acquired and inherited cardiac conditions. A significant amount of the neck, thorax and upper abdomen are imaged at the time of routine clinical CMR, particularly in the initial multi-slice axial and coronal images. The discovery of unsuspected disease at the time of imaging has ethical, financial and medico-legal implications. Extra-cardiac findings at the time of CMR are common, can be important and can change clinical management. Certain patient groups undergoing CMR are at particular risk of important extra-cardiac findings as several of the cardiovascular risk factors for atherosclerosis are also risk factors for malignancy. Furthermore, the presence of certain extra-cardiac findings may contribute to the interpretation of the primary cardiac pathology as some cardiac conditions have multi-systemic extra-cardiac involvement. The aim of this review is to give an overview of the type of extra-cardiac findings that may become apparent on CMR, subdivided by anatomical location. We focus on normal variant anatomy that may mimic disease, common incidental extra-cardiac findings and important imaging signs that help distinguish sinister pathology from benign disease. We also aim to provide a framework to the approach and potential further diagnostic work-up of incidental extra-cardiac findings discovered at the time of CMR. However, it is beyond the scope of this review to discuss and determine the clinical significance of extracardiac findings at CMR. PMID:27156861

  16. Consistency of aortic distensibility and pulse wave velocity estimates with respect to the Bramwell-Hill theoretical model: a cardiovascular magnetic resonance study

    PubMed Central

    2011-01-01

    Background Arterial stiffness is considered as an independent predictor of cardiovascular mortality, and is increasingly used in clinical practice. This study aimed at evaluating the consistency of the automated estimation of regional and local aortic stiffness indices from cardiovascular magnetic resonance (CMR) data. Results Forty-six healthy subjects underwent carotid-femoral pulse wave velocity measurements (CF_PWV) by applanation tonometry and CMR with steady-state free-precession and phase contrast acquisitions at the level of the aortic arch. These data were used for the automated evaluation of the aortic arch pulse wave velocity (Arch_PWV), and the ascending aorta distensibility (AA_Distc, AA_Distb), which were estimated from ascending aorta strain (AA_Strain) combined with either carotid or brachial pulse pressure. The local ascending aorta pulse wave velocity AA_PWVc and AA_PWVb were estimated respectively from these carotid and brachial derived distensibility indices according to the Bramwell-Hill theoretical model, and were compared with the Arch_PWV. In addition, a reproducibility analysis of AA_PWV measurement and its comparison with the standard CF_PWV was performed. Characterization according to the Bramwell-Hill equation resulted in good correlations between Arch_PWV and both local distensibility indices AA_Distc (r = 0.71, p < 0.001) and AA_Distb (r = 0.60, p < 0.001); and between Arch_PWV and both theoretical local indices AA_PWVc (r = 0.78, p < 0.001) and AA_PWVb (r = 0.78, p < 0.001). Furthermore, the Arch_PWV was well related to CF_PWV (r = 0.69, p < 0.001) and its estimation was highly reproducible (inter-operator variability: 7.1%). Conclusions The present work confirmed the consistency and robustness of the regional index Arch_PWV and the local indices AA_Distc and AA_Distb according to the theoretical model, as well as to the well established measurement of CF_PWV, demonstrating the relevance of the regional and local CMR indices. PMID

  17. Alterations in vascular function in primary aldosteronism: a cardiovascular magnetic resonance imaging study.

    PubMed

    Mark, P B; Boyle, S; Zimmerli, L U; McQuarrie, E P; Delles, C; Freel, E M

    2014-02-01

    Excess aldosterone is associated with increased cardiovascular risk. Aldosterone has a permissive effect on vascular fibrosis. Cardiovascular magnetic resonance imaging (CMR) allows study of vascular function by measuring aortic distensibility. We compared aortic distensibility in primary aldosteronism (PA), essential hypertension (EH) and normal controls and explored the relationship between aortic distensibility and pulse wave velocity (PWV). We studied PA (n=14) and EH (n=33) subjects and age-matched healthy controls (n=17) with CMR, including measurement of aortic distensibility, and measured PWV using applanation tonometry. At recruitment, PA and EH patients had similar blood pressure and left ventricular mass. Subjects with PA had significantly lower aortic distensibility and higher PWV compared with EH and healthy controls. These changes were independent of other factors associated with reduced aortic distensibility, including ageing. There was a significant relationship between increasing aortic stiffness and age in keeping with physical and vascular ageing. As expected, aortic distensibility and PWV were closely correlated. These results demonstrate that PA patients display increased arterial stiffness compared with EH, independent of vascular ageing. The implication is that aldosterone invokes functional impairment of arterial function. The long-term implications of arterial stiffening in aldosterone excess require further study. PMID:23884211

  18. Role of cardiovascular magnetic resonance in assessment of acute coronary syndrome

    PubMed Central

    Azarisman, Shah M; Teo, Karen S; Worthley, Matthew I; Worthley, Stephen G

    2014-01-01

    Cardiovascular disease (CVD) is the leading cause of death in the western world and is becoming more important in the developing world. Recently, advances in monitoring, revascularisation and pharmacotherapy have resulted in a reduction in mortality. However, although mortality rates have declined, the burden of disease remains large resulting in high direct and indirect healthcare costs related to CVDs. In Australia, acute coronary syndrome (ACS) accounts for more than 300000 years of life lost due to premature death and a total cost exceeding eight billion dollars annually. It is also the main contributor towards the discrepancy in life expectancy between indigenous and non-indigenous Australians. The high prevalence of CVD along with its associated cost urgently requires a reliable but non-invasive and cost-effective imaging modality. The imaging modality of choice should be able to accelerate the diagnosis of ACS, aid in the risk stratification of de novo coronary artery disease and avail incremental information of prognostic value such as viability which cardiovascular magnetic resonance (CMR) allows. Despite its manifold benefits, there are limitations to its wider use in routine clinical assessment and more studies are required into assessing its cost-effectiveness. It is hoped that with greater development in the technology and imaging protocols, CMR could be made less cumbersome, its imaging protocols less lengthy, the technology more inexpensive and easily applied in routine clinical practice. PMID:24976912

  19. Long term effects of cocaine on the heart assessed by cardiovascular magnetic resonance at 3T

    PubMed Central

    2014-01-01

    Background Cocaine is an addictive, sympathomimetic drug with potentially lethal effects. The prevalence and features of cocaine cardiotoxicity are not well known. We aimed to assess these effects using a comprehensive cardiovascular magnetic resonance (CMR) protocol in a large group of asymptomatic cocaine users. Methods Consecutive (n = 94, 81 males, 36.6 ±7 years), non-selected, cocaine abusers were recruited and had a medical history, examination, ECG, blood test and CMR. The CMR study included measurement of left and right ventricular (LV, RV) dimensions and ejection fraction (EF), sequences for detection of myocardial oedema and late gadolinium enhancement (LGE). Images were compared to a cohort of healthy controls. Results Years of regular cocaine use were 13.9 ± 9. When compared to the age-matched healthy cohort, the cocaine abusers had increased LV end-systolic volume, LV mass index and RV end-systolic volume, with decreased LVEF and RVEF. No subject had myocardial oedema, but 30% had myocardial LGE indicating myocardial damage. Conclusions CMR detected cardiovascular disease in 71% of this cohort of consecutive asymptomatic cocaine abusers and mean duration of abuse was related to probability of LV systolic dysfunction. PMID:24758161

  20. Quantification of cardiovascular disease biomarkers via functionalized magnetic beads and on-demand detachable quantum dots.

    PubMed

    Park, Hoyoung; Lee, Jong-Wook; Hwang, Mintai P; Lee, Kwan Hyi

    2013-09-21

    Cardiovascular disease (CVD) is a potent cause of mortality in both advanced and developing countries. While soluble CD40L (sCD40L) has been implicated as a correlative factor among CVD patients, methods to quantify sCD40L are not yet well-established. In this paper, we present an ability to separate and quantify sCD40L via a simple immunomagnetic assay. Composed of functionalized magnetic beads conferred with directionality and on-demand detachable quantum dots for subsequent optical analysis, our system utilizes the competitive nature of imidazole and nickel ions for histidine. In essence, we demonstrate the capacity to effectively separate and detect sCD40L within a clinically relevant range that contains the cut-off value for acute coronary disease. While sCD40L was used to conduct this study, we envision the use of our system for the separation and quantification of other biomarkers. PMID:23893124

  1. Diagnostic and prognostic value of cardiovascular magnetic resonance in non-ischaemic cardiomyopathies

    PubMed Central

    2012-01-01

    Cardiovascular Magnetic Resonance (CMR) is recognised as a valuable clinical tool which in a single scan setting can assess ventricular volumes and function, myocardial fibrosis, iron loading, flow quantification, tissue characterisation and myocardial perfusion imaging. The advent of CMR using extrinsic and intrinsic contrast-enhanced protocols for tissue characterisation have dramatically changed the non-invasive work-up of patients with suspected or known cardiomyopathy. Although the technique initially focused on the in vivo identification of myocardial necrosis through the late gadolinium enhancement (LGE) technique, recent work highlighted the ability of CMR to provide more detailed in vivo tissue characterisation to help establish a differential diagnosis of the underlying aetiology, to exclude an ischaemic substrate and to provide important prognostic markers. The potential application of CMR in the clinical approach of a patient with suspected non-ischaemic cardiomyopathy is discussed in this review. PMID:22857649

  2. Quantification of cardiovascular disease biomarkers via functionalized magnetic beads and on-demand detachable quantum dots

    NASA Astrophysics Data System (ADS)

    Park, Hoyoung; Lee, Jong-Wook; Hwang, Mintai P.; Lee, Kwan Hyi

    2013-08-01

    Cardiovascular disease (CVD) is a potent cause of mortality in both advanced and developing countries. While soluble CD40L (sCD40L) has been implicated as a correlative factor among CVD patients, methods to quantify sCD40L are not yet well-established. In this paper, we present an ability to separate and quantify sCD40L via a simple immunomagnetic assay. Composed of functionalized magnetic beads conferred with directionality and on-demand detachable quantum dots for subsequent optical analysis, our system utilizes the competitive nature of imidazole and nickel ions for histidine. In essence, we demonstrate the capacity to effectively separate and detect sCD40L within a clinically relevant range that contains the cut-off value for acute coronary disease. While sCD40L was used to conduct this study, we envision the use of our system for the separation and quantification of other biomarkers.

  3. Remote magnetic targeting of iron oxide nanoparticles for cardiovascular diagnosis and therapeutic drug delivery: where are we now?

    PubMed Central

    Bietenbeck, Michael; Florian, Anca; Faber, Cornelius; Sechtem, Udo; Yilmaz, Ali

    2016-01-01

    Magnetic resonance imaging (MRI) allows for an accurate assessment of both functional and structural cardiac parameters, and thereby appropriate diagnosis and validation of cardiovascular diseases. The diagnostic yield of cardiovascular MRI examinations is often increased by the use of contrast agents that are almost exclusively based on gadolinium compounds. Another clinically approved contrast medium is composed of superparamagnetic iron oxide nanoparticles (IONs). These particles may expand the field of contrast-enhanced cardiovascular MRI as recently shown in clinical studies focusing on acute myocardial infarction (AMI) and atherosclerosis. Furthermore, IONs open up new research opportunities such as remote magnetic drug targeting (MDT). The approach of MDT relies on the coupling of bioactive molecules and magnetic nanoparticles to form an injectable complex. This complex, in turn, can be attracted to and retained at a desired target inside the body with the help of applied magnetic fields. In comparison to common systemic drug applications, MDT techniques promise both higher concentrations at the target site and lower concentrations elsewhere in the body. Moreover, concurrent or subsequent MRI can be used for noninvasive monitoring of drug distribution and successful delivery to the desired organ in vivo. This review does not only illustrate the basic conceptual and biophysical principles of IONs, but also focuses on new research activities and achievements in the cardiovascular field, mainly in the management of AMI. Based on the presentation of successful MDT applications in preclinical models of AMI, novel approaches and the translational potential of MDT are discussed. PMID:27486321

  4. Determining phase relations of proxy data using the eccentricity-precession pattern

    NASA Astrophysics Data System (ADS)

    Zeeden, C.; Rivera, T. A.

    2012-04-01

    The phase relation between proxy data and orbital forcing is not always obvious; a link to both precession/insolation maxima or -minima can often be reasoned for. We present a novel approach to extract the phase relation using solely eccentricity-precession pattern from high quality proxy data. We determine the position of consecutive eccentricity maxima as precisely as possible from a stratigraphic record using both eccentricity filters and the amplitude modulation of precession. This way we obtain both the position of these eccentricity maxima as well as the sedimentation rate between successive maxima with error margins. Combining these results with the precession pattern in the geological record, we can determine whether precession-related patterns relate to precession (or insolation) minima or maxima. This approach relies on high quality geological data, the assumption of a direct eccentricity and precession response to orbital forcing, and a well defined orbital solution, but avoids the assumption of an instantaneous response to obliquity. For data with filtered components showing a good fit with the proxy data, this approach yields good results. Using high quality proxy data (color, magnetic susceptibility), we are able to determine the phase relation for equatorial Atlantic Miocene successions of ODP Leg 154. The research leading to these results has received funding from the [European Community's] Seventh Framework Programme ([FP7/2007-2013] under grant agreement n° [215458]. This research used data provided by IODP. Funding for this research was provided by NWO.

  5. Non-Mathematical Explanation of Precession

    ERIC Educational Resources Information Center

    Cordell, John

    2011-01-01

    The phenomenon of precession is necessary to explain the motion of footballs, gyroscopes, tops, the Earth, and many other interesting physical systems, but it was very hard for me to understand as a student and is very difficult to teach to students now. Many explanations of precession in physics textbooks are highly mathematical and hard to…

  6. Myocardial edema imaging by cardiovascular magnetic resonance: current status and future potential.

    PubMed

    Carbone, Iacopo; Friedrich, Matthias G

    2012-02-01

    Cardiovascular magnetic resonance (CMR) imaging is widely established, free of radioactive material or ionizing radiation, and the accepted noninvasive gold standard for numerous noninvasive cardiac markers. Using a technique called T2-weighted imaging, CMR can be used to assess myocardial edema as a reliable marker for acute, potentially reversible myocardial injury. Contrast agents are not required as the myocardial free water content affects the magnetic properties of the tissue, thus providing inherent image contrast. In this review, we illustrate the utility of T2-weighted techniques in the assessment of myocardial edema in a range of clinical scenarios. The detection of myocardial edema is clinically relevant in many acute settings and may be further helpful to better understand the pathophysiology of many non-acute clinical diseases. Currently, T2-weighted CMR represents the only imaging modality that can accurately depict and quantify the presence of myocardial edema in a noninvasive fashion. Thus, T2-weighted imaging should be included in a comprehensive CMR imaging protocol, especially if an acute injury is suspected. PMID:22139527

  7. Cardiovascular magnetic resonance imaging of isolated perfused pig hearts in a 3T clinical MR scanner

    PubMed Central

    Chiribiri, Amedeo; Ishida, Masaki; Morton, Geraint; Paul, Matthias; Hussain, Shazia T.; Bigalke, Boris; Perera, Divaka; Schaeffter, Tobias; Nagel, Eike

    2012-01-01

    Purpose An isolated perfused pig heart model has recently been proposed for the development of novel methods in standard clinical magnetic resonance (MR) scanners. The original set-up required the electrical system to be within the safe part of the MR-room, which introduced significant background noise. The purpose of the current work was to refine the system to overcome this limitation so that all electrical parts are completely outside the scanner room. Methods Four pig hearts were explanted under terminal anaesthesia from large white cross landrace pigs. All hearts underwent cardiovascular magnetic resonance (CMR) scanning in the MR part of a novel combined 3T MR and x-ray fluoroscopy (XMR) suite. CMR scanning included real-time k-t SENSE functional imaging, k-t SENSE accelerated perfusion imaging and late gadolinium enhancement imaging. Interference with image quality was assessed by spurious echo imaging and compared to noise levels acquired while operating the electrical parts within the scanner room. Results Imaging was performed successfully in all hearts. The system proved suitable for isolated heart perfusion in a novel 3T XMR suite. No significant additional noise was introduced into the scanner room by our set-up. Conclusions We have substantially improved a previous version of an isolated perfused pig heart model and made it applicable for MR imaging in a state of the art clinical 3T XMR imaging suite. The use of this system should aid novel CMR sequence development and translation into clinical practice. PMID:24265875

  8. Early diagnosis and follow-up of chronic active Epstein–Barr-virus-associated cardiovascular complications with cardiovascular magnetic resonance imaging

    PubMed Central

    Jiang, Shu; Li, Xiao; Cao, Jian; Wu, Di; Kong, Lingyan; Lin, Lu; Jin, Zhengyu; An, Jing; Wang, Yining

    2016-01-01

    Abstract Introduction: Chronic active Epstein–Barr virus (EBV) infection (CAEBV) is characterized as chronic or recurrent mononucleosis-like symptoms and elevated EBV deoxyribonucleic acid (EBV-DNA) copies. Cardiovascular complications have high morbidity and mortality. The treatment regimen for CAEBV has not been established yet, resulting in poor prognoses. Herein, we present a case of cardiovascular magnetic resonance imaging (CMRI) evaluation with a series of sequences for CAEBV-associated cardiovascular involvement, which has never been reported. Case presentation: A 16-year-old female (body weight, 55 kg) developed a persistent fever and a positive EBV-DNA level of 28,000 copies/mL. Computed tomography angiography (CTA) showed aneurysms involving the aorta and its major branches, as well as multiple aneurysms and stenoses of the coronary arteries. CMRI of the coronary arteries depicted the dilution and stenosis of the arterial lumen as well as the thickening of the arterial wall. Late gadolinium enhancement (LGE) showed subendocardial and transmural delayed enhancement of the left ventricle, suggesting myocardial infarction. CAEBV and associated cardiovascular complications were diagnosed. After treatment with Medrol and Leflunomide, the clinical manifestation and serological parameters reversed to normal. However, the EBV-DNA level increased again to 13,900 copies/mL 2 months later. A follow-up with aorta CTA showed that the arterial walls of the bilateral common iliac artery aneurysms were thicker with new-onset mural thrombi. The aorta CTA also showed new-onset occlusion of the right coronary artery, but a follow-up of CMRI at the same day did not find new-onset delayed enhancement lesion. Conclusion: This case reminds clinicians of the vital importance of early diagnosis and close follow-up of CAEBV-associated cardiovascular complications. With cine imaging, coronary artery imaging, LGE imaging, and other novel techniques, CMRI can effectively and

  9. Nonlinear dynamo action in a precessing cylindrical container.

    PubMed

    Nore, C; Léorat, J; Guermond, J-L; Luddens, F

    2011-07-01

    It is numerically demonstrated by means of a magnetohydrodynamics code that precession can trigger the dynamo effect in a cylindrical container. When the Reynolds number, based on the radius of the cylinder and its angular velocity, increases, the flow, which is initially centrosymmetric, loses its stability and bifurcates to a quasiperiodic motion. This unsteady and asymmetric flow is shown to be capable of sustaining dynamo action in the linear and nonlinear regimes. The magnetic field thus generated is unsteady and quadrupolar. These numerical evidences of dynamo action in a precessing cylindrical container may be useful for an experiment now planned at the Dresden sodium facility for dynamo and thermohydraulic studies in Germany. PMID:21867314

  10. Insolation and the Precession Index

    NASA Technical Reports Server (NTRS)

    Rubincam, David Parry

    2000-01-01

    Simple nonlinear climate models yield a precession index-like term in the temperature. Despite its importance in the geologic record, the precession index e sin omega, where e is the Earth's orbital eccentricity and omega is the Sun's perigee in the geocentric frame, is not present in the insolation at the top of the atmosphere. Hence there is no one-for-one mapping of 23,000 and 19,000 year periodicities from the insolation to the paleoclimate record; a nonlinear climate model is needed to produce these periods. Two such models, a grey body and an energy balance climate model with an added quadratic term, produce e sin omega terms in temperature. These terms, which without feedback mechanisms achieve extreme values of about plus or minus 0.48 K for the grey body and plus or minus 0.64 K for the energy balance model, simultaneously cool one hemisphere while they warm the other. Moreover, they produce long-term cooling in the northern hemisphere when the Sun's perigee is near northern solstice and long-term warming in the northern hemisphere when the perigee is near southern solstice. Thus this seemingly paradoxical mechanism works against the standard model which requires cool northern summers (Sun far from Earth in northern summer) to build up northern ice sheets, so that if the standard model is correct it may be more efficient than previously thought. Alternatively, the new mechanism could possibly be dominant and indicate southern hemisphere control of the northern ice sheets, wherein the southern oceans undergo a long-term cooling when the Sun is close to the Earth during southern summer. The cold water eventually flows north, cooling the northern hemisphere. This might explain why the northern oceans lag the southern ones when it comes to orbital forcing.

  11. Prognostic Value of Late Gadolinium Enhancement Cardiovascular Magnetic Resonance in Cardiac Amyloidosis

    PubMed Central

    Fontana, Marianna; Pica, Silvia; Reant, Patricia; Abdel-Gadir, Amna; Treibel, Thomas A.; Banypersad, Sanjay M.; Maestrini, Viviana; Barcella, William; Rosmini, Stefania; Bulluck, Heerajnarain; Sayed, Rabya H.; Patel, Ketna; Mamhood, Shameem; Bucciarelli-Ducci, Chiara; Whelan, Carol J.; Herrey, Anna S.; Lachmann, Helen J.; Wechalekar, Ashutosh D.; Manisty, Charlotte H.; Schelbert, Eric B.; Kellman, Peter; Gillmore, Julian D.; Hawkins, Philip N.

    2015-01-01

    Background— The prognosis and treatment of the 2 main types of cardiac amyloidosis, immunoglobulin light chain (AL) and transthyretin (ATTR) amyloidosis, are substantially influenced by cardiac involvement. Cardiovascular magnetic resonance with late gadolinium enhancement (LGE) is a reference standard for the diagnosis of cardiac amyloidosis, but its potential for stratifying risk is unknown. Methods and Results— Two hundred fifty prospectively recruited subjects, 122 patients with ATTR amyloid, 9 asymptomatic mutation carriers, and 119 patients with AL amyloidosis, underwent LGE cardiovascular magnetic resonance. Subjects were followed up for a mean of 24±13 months. LGE was performed with phase-sensitive inversion recovery (PSIR) and without (magnitude only). These were compared with extracellular volume measured with T1 mapping. PSIR was superior to magnitude-only inversion recovery LGE because PSIR always nulled the tissue (blood or myocardium) with the longest T1 (least gadolinium). LGE was classified into 3 patterns: none, subendocardial, and transmural, which were associated with increasing amyloid burden as defined by extracellular volume (P<0.0001), with transitions from none to subendocardial LGE at an extracellular volume of 0.40 to 0.43 (AL) and 0.39 to 0.40 (ATTR) and to transmural at 0.48 to 0.55 (AL) and 0.47 to 0.59 (ATTR). Sixty-seven patients (27%) died. Transmural LGE predicted death (hazard ratio, 5.4; 95% confidence interval, 2.1–13.7; P<0.0001) and remained independent after adjustment for N-terminal pro-brain natriuretic peptide, ejection fraction, stroke volume index, E/E′, and left ventricular mass index (hazard ratio, 4.1; 95% confidence interval, 1.3–13.1; P<0.05). Conclusions— There is a continuum of cardiac involvement in systemic AL and ATTR amyloidosis. Transmural LGE is determined reliably by PSIR and represents advanced cardiac amyloidosis. The PSIR technique provides incremental information on outcome even after

  12. Disease-specific cardiovascular positron emission tomography/magnetic resonance imaging: a brief review of the current literature

    PubMed Central

    Zheng, Jie

    2016-01-01

    The hybrid positron emission tomography/magnetic resonance (PET/MR) is a new imaging tool that has garnered immense research interest for its potentials to assist clinical investigations. PET/MR combines the quantitative measurement of PET with dynamic functional and anatomic assessment of MR and can deliver a robust clinical examination. Currently, simultaneous cardiovascular PET/MR imaging remains in the pre-clinical research stage, and most institutions have not adopted a clinical PET/MR clinical imaging service. Nevertheless, PET/MR examination has unique promises in several areas of cardiovascular medicine, and in recent years more and more research publications have become available to lend us insight into its utility in cardiovascular imaging. Here we review the existing literature on simultaneous cardiovascular PET/MR imaging, with an emphasis on organizing the current literature into disease-specific discussions. These areas include coronary artery disease (CAD), carotid atherosclerosis, various infiltrative, inflammatory and hereditary heart diseases, myocarditis, vasculitis, and cardiac mass assessment. The purpose of this review is to provide an overview of the current understanding of cardiovascular PET/MR clinical imaging, in a disease-specific manner, from a clinician’s perspective. Potential limitations of simultaneous PET/MR, such as cost effectiveness, artifacts, contraindications, and radiation exposure, are briefly discussed. PMID:27429913

  13. Torque-induced precession of bacterial flagella.

    PubMed

    Shimogonya, Yuji; Sawano, Yoichiro; Wakebe, Hiromichi; Inoue, Yuichi; Ishijima, Akihiko; Ishikawa, Takuji

    2015-01-01

    The bacterial flagellar motor is an ion-driven rotary machine in the cell envelope of bacteria. Using a gold nanoparticle as a probe, we observed the precession of flagella during rotation. Since the mechanism of flagella precession was unknown, we investigated it using a combination of full simulations, theory, and experiments. The results show that the mechanism can be well explained by fluid mechanics. The validity of our theory was confirmed by our full simulation, which was utilized to predict both the filament tilt angle and motor torque from experimental flagellar precession data. The knowledge obtained is important in understanding mechanical properties of the bacterial motor and hook. PMID:26691402

  14. Contribution of cardiovascular magnetic resonance in the evaluation of coronary arteries

    PubMed Central

    Mavrogeni, Sophie; Markousis-Mavrogenis, George; Kolovou, Genovefa

    2014-01-01

    Cardiovascular magnetic resonance (CMR) allows the nonradiating assessment of coronary arteries; to achieve better image quality cardiorespiratory artefacts should be corrected. Coronary MRA (CMRA) at the moment is indicated only for the detection of abnormal coronary origin, coronary artery ectasia and/or aneurysms (class I indication) and coronary bypass grafts (class II indication). CMRA utilisation for coronary artery disease is not yet part of clinical routine. However, the lack of radiation is of special value for the coronary artery evaluation in children and women. CMRA can assess the proximal part of coronary arteries in almost all cases. The best results have been observed in the evaluation of the left anterior descending and the right coronary artery, while the left circumflex, which is located far away from the coil elements, is frequently imaged with reduced quality, compared to the other two. Different studies detected an increase in wall thickness of the coronaries in patients with type I diabetes and abnormal renal function. Additionally, the non-contrast enhanced T1-weighed images detected the presence of thrombus in acute myocardial infarction. New techniques using delayed gadolinium enhanced imaging promise the direct visualization of inflamed plaques in the coronary arteries. The major advantage of CMR is the potential of an integrated protocol offering assessment of coronary artery anatomy, cardiac function, inflammation and stress perfusion-fibrosis in the same study, providing an individualized clinical profile of patients with heart disease. PMID:25349650

  15. Assessment of Left Ventricular Structural Remodelling in Patients with Diabetic Cardiomyopathy by Cardiovascular Magnetic Resonance.

    PubMed

    Shang, Yongning; Zhang, Xiaochun; Chen, Liu; Leng, Weiling; Lei, Xiaotian; Yang, Qi; Liang, Ziwen; Wang, Jian

    2016-01-01

    Background. Diabetic cardiomyopathy (DCM) is always accompanied with alteration of left ventricular structure and function. The aims of this study were to assess the structural remodelling in patients with DCM by cardiovascular magnetic resonance (CMR) and correlation of structural remodelling with severity of DCM. Methods. Twenty-five patients (53.8 ± 8.8 years, 52.0% males) with DCM and thirty-one normal healthy controls (51.9 ± 13.6 years, 45.2% males) were scanned by CMR cine to assess function and structure of left ventricular. Length of diabetic history and results of cardiac echocardiography (E', A', and E'/A') were also measured. Results. Compared with normal controls group, DCM group was associated with significantly increased ratio of left ventricular mass at end diastole to end-diastolic volume (MVR) (P < 0.05) and no significant difference was in mass at end diastole (P > 0.05). The ratio correlated with both length of diabetic history and echocardiographic Doppler tissue imaging E' (all P < 0.05). Conclusions. CMR can be a powerful technique to assess LV remodelling, and MVR may be considered as an imaging marker to evaluate the severity of LV remodelling in patients with DCM. PMID:27419144

  16. Assessment of Left Ventricular Structural Remodelling in Patients with Diabetic Cardiomyopathy by Cardiovascular Magnetic Resonance

    PubMed Central

    Zhang, Xiaochun; Leng, Weiling

    2016-01-01

    Background. Diabetic cardiomyopathy (DCM) is always accompanied with alteration of left ventricular structure and function. The aims of this study were to assess the structural remodelling in patients with DCM by cardiovascular magnetic resonance (CMR) and correlation of structural remodelling with severity of DCM. Methods. Twenty-five patients (53.8 ± 8.8 years, 52.0% males) with DCM and thirty-one normal healthy controls (51.9 ± 13.6 years, 45.2% males) were scanned by CMR cine to assess function and structure of left ventricular. Length of diabetic history and results of cardiac echocardiography (E′, A′, and E′/A′) were also measured. Results. Compared with normal controls group, DCM group was associated with significantly increased ratio of left ventricular mass at end diastole to end-diastolic volume (MVR) (P < 0.05) and no significant difference was in mass at end diastole (P > 0.05). The ratio correlated with both length of diabetic history and echocardiographic Doppler tissue imaging E′ (all P < 0.05). Conclusions. CMR can be a powerful technique to assess LV remodelling, and MVR may be considered as an imaging marker to evaluate the severity of LV remodelling in patients with DCM. PMID:27419144

  17. Diagnosis and management of ischemic cardiomyopathy: Role of cardiovascular magnetic resonance imaging.

    PubMed

    Doesch, Christina; Papavassiliu, Theano

    2014-11-26

    Coronary artery disease (CAD) represents an important cause of mortality. Cardiovascular magnetic resonance (CMR) imaging evolved as an imaging modality that allows the assessment of myocardial function, perfusion, contractile reserve and extent of fibrosis in a single comprehensive exam. This review highlights the role of CMR in the differential diagnosis of acute chest pain by detecting the location of obstructive CAD or necrosis and identifying other conditions like stress cardiomyopathy or myocarditis that can present with acute chest pain. Besides, it underlines the prognostic implication of perfusion abnormalities in the setting of acute chest pain. Furthermore, the review addresses the role of CMR to detect significant CAD in patients with stable CAD. It elucidates the accuracy and clinical utility of CMR with respect to other imaging modalities like single-photon emission computed tomography and positron emission tomography. Besides, the prognostic value of CMR stress testing is discussed. Additionally, it summarizes the available CMR techniques to assess myocardial viability and describes algorithm to identify those patient who might profit from revascularization those who should be treated medically. Finally, future promising imaging techniques that will provide further insights into the fundamental disease processes in ischemic cardiomyopathy are discussed. PMID:25429329

  18. The Emerging Role of Cardiovascular Magnetic Resonance Imaging in the Evaluation of Metabolic Cardiomyopathies.

    PubMed

    Mavrogeni, S; Markousis-Mavrogenis, G; Markussis, V; Kolovou, G

    2015-08-01

    The aim of this review is to discuss the role of Cardiovascular Magnetic Resonance (CMR) in the diagnosis, risk stratification, and follow-up of metabolic cardiomyopathies. The classification of myocardial diseases, proposed by WHO/ISFC task force, distinguished specific cardiomyopathies, caused by metabolic disorders, into 4 types: 1) endocrine disorders, 2) storage or infiltration disorders (amyloidosis, hemochromatosis and familial storage disorders), 3) nutritional disorders (Kwashiorkor, beri-beri, obesity, and alcohol), and 4) diabetic heart. Thyroid disease, pheochromocytoma, and growth hormone excess or deficiency may contribute to usually reversible dilated cardiomyopathy. Glucogen storage diseases can be presented with myopathy, liver, and heart failure. Lysosomal storage diseases can provoke cardiac hypertrophy, mimicking hypertrophic cardiomyopathy and arrhythmias. Hereditary hemochromatosis, an inherited disorder of iron metabolism, leads to tissue iron overload in different organs, including the heart. Cardiac amyloidosis is the result of amyloid deposition in the heart, formed from breakdown of normal or abnormal proteins that leads to increased heart stiffness, restrictive cardiomyopathy, and heart failure. Finally, nutritional disturbances and metabolic diseases, such as Kwashiorkor, beri-beri, obesity, alcohol consumption, and diabetes mellitus may also lead to severe cardiac dysfunction. CMR, through its capability to reliably assess anatomy, function, inflammation, rest-stress myocardial perfusion, myocardial fibrosis, aortic distensibility, iron and/or fat deposition can serve as an excellent tool for early diagnosis of heart involvement, risk stratification, treatment evaluation, and long term follow-up of patients with metabolic cardiomyopathies. PMID:26197853

  19. Late gadolinium enhanced cardiovascular magnetic resonance of lamin A/C gene mutation related dilated cardiomyopathy

    PubMed Central

    2011-01-01

    Background The purpose of this study was to identify early features of lamin A/C gene mutation related dilated cardiomyopathy (DCM) with cardiovascular magnetic resonance (CMR). We characterise myocardial and functional findings in carriers of lamin A/C mutation to facilitate the recognition of these patients using this method. We also investigated the connection between myocardial fibrosis and conduction abnormalities. Methods Seventeen lamin A/C mutation carriers underwent CMR. Late gadolinium enhancement (LGE) and cine images were performed to evaluate myocardial fibrosis, regional wall motion, longitudinal myocardial function, global function and volumetry of both ventricles. The location, pattern and extent of enhancement in the left ventricle (LV) myocardium were visually estimated. Results Patients had LV myocardial fibrosis in 88% of cases. Segmental wall motion abnormalities correlated strongly with the degree of enhancement. Myocardial enhancement was associated with conduction abnormalities. Sixty-nine percent of our asymptomatic or mildly symptomatic patients showed mild ventricular dilatation, systolic failure or both in global ventricular analysis. Decreased longitudinal systolic LV function was observed in 53% of patients. Conclusions Cardiac conduction abnormalities, mildly dilated LV and depressed systolic dysfunction are common in DCM caused by a lamin A/C gene mutation. However, other cardiac diseases may produce similar symptoms. CMR is an accurate tool to determine the typical cardiac involvement in lamin A/C cardiomyopathy and may help to initiate early treatment in this malignant familiar form of DCM. PMID:21689390

  20. Advancing Cardiovascular, Neurovascular, and Renal Magnetic Resonance Imaging in Small Rodents Using Cryogenic Radiofrequency Coil Technology

    PubMed Central

    Niendorf, Thoralf; Pohlmann, Andreas; Reimann, Henning M.; Waiczies, Helmar; Peper, Eva; Huelnhagen, Till; Seeliger, Erdmann; Schreiber, Adrian; Kettritz, Ralph; Strobel, Klaus; Ku, Min-Chi; Waiczies, Sonia

    2015-01-01

    Research in pathologies of the brain, heart and kidney have gained immensely from the plethora of studies that have helped shape new methods in magnetic resonance (MR) for characterizing preclinical disease models. Methodical probing into preclinical animal models by MR is invaluable since it allows a careful interpretation and extrapolation of data derived from these models to human disease. In this review we will focus on the applications of cryogenic radiofrequency (RF) coils in small animal MR as a means of boosting image quality (e.g., by supporting MR microscopy) and making data acquisition more efficient (e.g., by reducing measuring time); both being important constituents for thorough investigational studies on animal models of disease. This review attempts to make the (bio)medical imaging, molecular medicine, and pharmaceutical communities aware of this productive ferment and its outstanding significance for anatomical and functional MR in small rodents. The goal is to inspire a more intense interdisciplinary collaboration across the fields to further advance and progress non-invasive MR methods that ultimately support thorough (patho)physiological characterization of animal disease models. In this review, current and potential future applications for the RF coil technology in cardiovascular, neurovascular, and renal disease will be discussed. PMID:26617515

  1. About detection of precessing circumpulsar discs

    NASA Astrophysics Data System (ADS)

    Grimani, Catia

    2016-08-01

    Detections of circumpulsar discs and planetary systems through electromagnetic observations appear quite rare. In the case of PSR 1931+24 and B0656+14, the hypothesis of a precessing disc penetrating the pulsar light cylinder is found consistent with radio and gamma observations from these stars. Disc self-occultation and precession may affect electromagnetic measurements. We investigate here under which conditions gravitational waves generated by circumpulsar disc precession may be detected by the proposed second-generation space interferometers DECI-hertz Interferometer Gravitational Wave Observatory and Big Bang Observer. The characteristics of circumpulsar detectable precessing discs are estimated as a function of distance from the Solar system. Speculations on detection rates are presented.

  2. Consistent Numerical Expressions for Precession Formulae.

    NASA Astrophysics Data System (ADS)

    Soma, M.

    The precession formulae by Lieske et al. (1977) have been used since 1984 for calculating apparent positions and reducing astrometric observations of celestial objects. These formulae are based on the IAU (1976) Astronomical Constants, some of which deviate from their recently determined values. They are also derived using the secular variations of the ecliptic pole from Newcomb's theory, which is not consistent with the recent planetary theories. Accordingly Simon et al. (1994) developed new precession formulae using the recently determined astronomical constants and also being based on the new planetary theory VSOP87. There are two differing definitions of the ecliptic: ecliptic in the inertial sense and ecliptic in the rotating sense (Standish 1981). The ecliptic given by the VSOP87 theory is that in the inertial sense, but the value for obliquity Simon et al. used is the obliquity in the rotating sense. Therefore their precession formulae has inconsistency. This paper gives corrections for consistent precession formulae.

  3. About detection of precessing circumpulsar disks

    NASA Astrophysics Data System (ADS)

    Grimani, Catia

    2016-05-01

    Detections of circumpulsar disks and planetary systems through electromagnetic observations appear quite rare. In the case of PSR 1931+24 and B0656+14, the hypothesis of a precessing disk penetrating the pulsar light cylinder is found consistent with radio and gamma observations from these stars. Disk self-occultation and precession may affect electromagnetic measurements. We investigate here under which conditions gravitational waves generated by circumpulsar disk precession may be detected by the proposed second generation space interferometers DECIGO (DECI-hertz Interferometer Gravitational Wave Observatory) and BBO (Big Bang Observer). The characteristics of circumpulsar detectable precessing disks are estimated as a function of distance from the Solar System. Speculations on detection rates are presented.

  4. Trapped Electron Precession Shear Induced Fluctuation Decorrelation

    SciTech Connect

    T.S. Hahm; P.H. Diamond; E.-J. Kim

    2002-07-29

    We consider the effects of trapped electron precession shear on the microturbulence. In a similar way the strong E x B shear reduces the radial correlation length of ambient fluctuations, the radial variation of the trapped electron precession frequency can reduce the radial correlation length of fluctuations associated with trapped electrons. In reversed shear plasmas, with the explicit dependence of the trapped electron precession shearing rate on B(subscript)theta, the sharp radial gradient of T(subscript)e due to local electron heating inside qmin can make the precession shearing mechanism more effective, and reduce the electron thermal transport constructing a positive feedback loop for the T(subscript)e barrier formation.

  5. On the Subjective Acceptance during Cardiovascular Magnetic Resonance Imaging at 7.0 Tesla

    PubMed Central

    Klix, Sabrina; Els, Antje; Paul, Katharina; Graessl, Andreas; Oezerdem, Celal; Weinberger, Oliver; Winter, Lukas; Thalhammer, Christof; Huelnhagen, Till; Rieger, Jan; Mehling, Heidrun; Schulz-Menger, Jeanette; Niendorf, Thoralf

    2015-01-01

    Purpose This study examines the subjective acceptance during UHF-CMR in a cohort of healthy volunteers who underwent a cardiac MR examination at 7.0T. Methods Within a period of two-and-a-half years (January 2012 to June 2014) a total of 165 healthy volunteers (41 female, 124 male) without any known history of cardiac disease underwent UHF-CMR. For the assessment of the subjective acceptance a questionnaire was used to examine the participants experience prior, during and after the UHF-CMR examination. For this purpose, subjects were asked to respond to the questionnaire in an exit interview held immediately after the completion of the UHF-CMR examination under supervision of a study nurse to ensure accurate understanding of the questions. All questions were answered with “yes” or “no” including space for additional comments. Results Transient muscular contraction was documented in 12.7% of the questionnaires. Muscular contraction was reported to occur only during periods of scanning with the magnetic field gradients being rapidly switched. Dizziness during the study was reported by 12.7% of the subjects. Taste of metal was reported by 10.1% of the study population. Light flashes were reported by 3.6% of the entire cohort. 13% of the subjects reported side effects/observations which were not explicitly listed in the questionnaire but covered by the question about other side effects. No severe side effects as vomiting or syncope after scanning occurred. No increase in heart rate was observed during the UHF-CMR exam versus the baseline clinical examination. Conclusions This study adds to the literature by detailing the subjective acceptance of cardiovascular magnetic resonance imaging examinations at a magnetic field strength of 7.0T. Cardiac MR examinations at 7.0T are well tolerated by healthy subjects. Broader observational and multi-center studies including patient cohorts with cardiac diseases are required to gain further insights into the subjective

  6. Myocardial tagging by Cardiovascular Magnetic Resonance: evolution of techniques--pulse sequences, analysis algorithms, and applications

    PubMed Central

    2011-01-01

    Cardiovascular magnetic resonance (CMR) tagging has been established as an essential technique for measuring regional myocardial function. It allows quantification of local intramyocardial motion measures, e.g. strain and strain rate. The invention of CMR tagging came in the late eighties, where the technique allowed for the first time for visualizing transmural myocardial movement without having to implant physical markers. This new idea opened the door for a series of developments and improvements that continue up to the present time. Different tagging techniques are currently available that are more extensive, improved, and sophisticated than they were twenty years ago. Each of these techniques has different versions for improved resolution, signal-to-noise ratio (SNR), scan time, anatomical coverage, three-dimensional capability, and image quality. The tagging techniques covered in this article can be broadly divided into two main categories: 1) Basic techniques, which include magnetization saturation, spatial modulation of magnetization (SPAMM), delay alternating with nutations for tailored excitation (DANTE), and complementary SPAMM (CSPAMM); and 2) Advanced techniques, which include harmonic phase (HARP), displacement encoding with stimulated echoes (DENSE), and strain encoding (SENC). Although most of these techniques were developed by separate groups and evolved from different backgrounds, they are in fact closely related to each other, and they can be interpreted from more than one perspective. Some of these techniques even followed parallel paths of developments, as illustrated in the article. As each technique has its own advantages, some efforts have been made to combine different techniques together for improved image quality or composite information acquisition. In this review, different developments in pulse sequences and related image processing techniques are described along with the necessities that led to their invention, which makes this

  7. Improvement of the IAU 2000 precession model

    NASA Astrophysics Data System (ADS)

    Capitaine, N.; Wallace, P. T.; Chapront, J.

    2005-03-01

    The IAU 2000 precession consists of the IAU 1976 ecliptic precession (Lieske et al. [CITE], A&A, 58, 1) and the precession part of the IAU 2000A equator adopted by IAU 2000 Resolution B1.6 (Mathews et al. [CITE], J. Geophys. Res., 107, B4, 10.1029/2001JB000390). In this paper we provide a range of new expressions as possible replacements for the IAU 2000 precession. The new expressions are based upon the so-called P03 solution of Capitaine et al. ([CITE], A&A, 412, 567) for the equator and the ecliptic. In addition an improved model for the precession of the equator is discussed. This improved solution was obtained in exactly the same way as P03 but using a refined model for the contributions of the non-rigid Earth (Mathews [CITE], private communication) and revised integration constants for the precession rates resulting from fits to the most recent VLBI data. The paper reports on the procedure that was used for improving the P03 solution and on the comparisons of this solution with the MHB 2000, IAU 2000 and P03 solutions. It also discusses the choices for the solution to be put forward as a replacement for IAU 2000. We concluded that the existing VLBI data were insufficient to provide convincing evidence that the improved solutions would deliver better accuracy than the existing P03 solution, and we recommend retaining P03 as the replacement for IAU 2000. P03, which unlike the IAU 2000 precession is dynamically consistent, has the advantage of already having been used experimentally by a number of groups; the model is recalled in Tables [see full text]- [see full text]. Due to the strong dependence of the precession expressions on the precession rates and of the precession in longitude (or equivalently the celestial CIP X coordinate) on the J2 rate model, we also provide a parameterized P04 solution for these quantities as functions of those parameters. The expressions include the quantities to be used in both the equinox-based and CIO-based (i.e. referred to

  8. Three-axis atomic magnetometer based on spin precession modulation

    SciTech Connect

    Huang, H. C.; Dong, H. F. Hu, X. Y.; Chen, L.; Gao, Y.

    2015-11-02

    We demonstrate a three-axis atomic magnetometer with one intensity-modulated pump beam and one orthogonal probe beam. The main field component is measured using the resonance of the pumping light, while the transverse field components are measured simultaneously using the optical rotation of the probe beam modulated by the spin precession. It is an all-optical magnetometer without using any modulation field or radio frequency field. Magnetic field sensitivity of 0.8 pT/Hz{sup 1∕2} is achieved under a bias field of 2 μT.

  9. Parametric pumping of precession modes in ferromagnetic nanodisks

    NASA Astrophysics Data System (ADS)

    Guo, Feng; Belova, L. M.; McMichael, R. D.

    2014-03-01

    We report on the parametric excitation of magnetic precession modes in nanodisks using a parallel pumping configuration. The excitations are detected using a ferromagnetic resonance force microscopy method, and the parallel-pumped spectra reveal nonlinear characteristics including instability thresholds and multiple, narrow, sawtooth-shaped resonances. These characteristics are in accord with analytical theory and micromagnetic modeling results. Modeled mode profiles of the excitations show that higher-order standing spin-wave modes with both even and odd symmetries are excited under parallel pumping.

  10. Using 4D Cardiovascular Magnetic Resonance Imaging to Validate Computational Fluid Dynamics: A Case Study

    PubMed Central

    Biglino, Giovanni; Cosentino, Daria; Steeden, Jennifer A.; De Nova, Lorenzo; Castelli, Matteo; Ntsinjana, Hopewell; Pennati, Giancarlo; Taylor, Andrew M.; Schievano, Silvia

    2015-01-01

    Computational fluid dynamics (CFD) can have a complementary predictive role alongside the exquisite visualization capabilities of 4D cardiovascular magnetic resonance (CMR) imaging. In order to exploit these capabilities (e.g., for decision-making), it is necessary to validate computational models against real world data. In this study, we sought to acquire 4D CMR flow data in a controllable, experimental setup and use these data to validate a corresponding computational model. We applied this paradigm to a case of congenital heart disease, namely, transposition of the great arteries (TGA) repaired with arterial switch operation. For this purpose, a mock circulatory loop compatible with the CMR environment was constructed and two detailed aortic 3D models (i.e., one TGA case and one normal aortic anatomy) were tested under realistic hemodynamic conditions, acquiring 4D CMR flow. The same 3D domains were used for multi-scale CFD simulations, whereby the remainder of the mock circulatory system was appropriately summarized with a lumped parameter network. Boundary conditions of the simulations mirrored those measured in vitro. Results showed a very good quantitative agreement between experimental and computational models in terms of pressure (overall maximum % error = 4.4% aortic pressure in the control anatomy) and flow distribution data (overall maximum % error = 3.6% at the subclavian artery outlet of the TGA model). Very good qualitative agreement could also be appreciated in terms of streamlines, throughout the cardiac cycle. Additionally, velocity vectors in the ascending aorta revealed less symmetrical flow in the TGA model, which also exhibited higher wall shear stress in the anterior ascending aorta. PMID:26697416

  11. Left ventricular reverse remodeling after transcatheter aortic valve implantation: a cardiovascular magnetic resonance study

    PubMed Central

    2013-01-01

    Background In patients with severe aortic stenosis, left ventricular hypertrophy is associated with increased myocardial stiffness and dysfunction linked to cardiac morbidity and mortality. We aimed at systematically investigating the degree of left ventricular mass regression and changes in left ventricular function six months after transcatheter aortic valve implantation (TAVI) by cardiovascular magnetic resonance (CMR). Methods Left ventricular mass indexed to body surface area (LVMi), end diastolic volume indexed to body surface area (LVEDVi), left ventricular ejection fraction (LVEF) and stroke volume (SV) were investigated by CMR before and six months after TAVI in patients with severe aortic stenosis and contraindications for surgical aortic valve replacement. Results Twenty-sevent patients had paired CMR at baseline and at 6-month follow-up (N=27), with a mean age of 80.7±5.2 years. LVMi decreased from 84.5±25.2 g/m2 at baseline to 69.4±18.4 g/m2 at six months follow-up (P<0.001). LVEDVi (87.2±30.1 ml /m2vs 86.4±22.3 ml/m2; P=0.84), LVEF (61.5±14.5% vs 65.1±7.2%, P=0.08) and SV (89.2±22 ml vs 94.7±26.5 ml; P=0.25) did not change significantly. Conclusions Based on CMR, significant left ventricular reverse remodeling occurs six months after TAVI. PMID:23692630

  12. Cardiovascular magnetic resonance for the assessment of patients undergoing transcatheter aortic valve implantation: a pilot study

    PubMed Central

    2011-01-01

    Background Before trans-catheter aortic valve implantation (TAVI), assessment of cardiac function and accurate measurement of the aortic root are key to determine the correct size and type of the prosthesis. The aim of this study was to compare cardiovascular magnetic resonance (CMR) and trans-thoracic echocardiography (TTE) for the assessment of aortic valve measurements and left ventricular function in high-risk elderly patients submitted to TAVI. Methods Consecutive patients with severe aortic stenosis and contraindications for surgical aortic valve replacement were screened from April 2009 to January 2011 and imaged with TTE and CMR. Results Patients who underwent both TTE and CMR (n = 49) had a mean age of 80.8 ± 4.8 years and a mean logistic EuroSCORE of 14.9 ± 9.3%. There was a good correlation between TTE and CMR in terms of annulus size (R2 = 0.48, p < 0.001), left ventricular outflow tract (LVOT) diameter (R2 = 0.62, p < 0.001) and left ventricular ejection fraction (LVEF) (R2 = 0.47, p < 0.001) and a moderate correlation in terms of aortic valve area (AVA) (R2 = 0.24, p < 0.001). CMR generally tended to report larger values than TTE for all measurements. The Bland-Altman test indicated that the 95% limits of agreement between TTE and CMR ranged from -5.6 mm to + 1.0 mm for annulus size, from -0.45 mm to + 0.25 mm for LVOT, from -0.45 mm2 to + 0.25 mm2 for AVA and from -29.2% to 13.2% for LVEF. Conclusions In elderly patients candidates to TAVI, CMR represents a viable complement to transthoracic echocardiography. PMID:22202669

  13. Cardiovascular magnetic resonance feature-tracking assessment of myocardial mechanics: Intervendor agreement and considerations regarding reproducibility

    PubMed Central

    Schuster, A.; Stahnke, V.-C.; Unterberg-Buchwald, C.; Kowallick, J.T.; Lamata, P.; Steinmetz, M.; Kutty, S.; Fasshauer, M.; Staab, W.; Sohns, J.M.; Bigalke, B.; Ritter, C.; Hasenfuß, G.; Beerbaum, P.; Lotz, J.

    2015-01-01

    Aim To assess intervendor agreement of cardiovascular magnetic resonance feature tracking (CMR-FT) and to study the impact of repeated measures on reproducibility. Materials and methods Ten healthy volunteers underwent cine imaging in short-axis orientation at rest and with dobutamine stimulation (10 and 20 μg/kg/min). All images were analysed three times using two types of software (TomTec, Unterschleissheim, Germany and Circle, cvi42, Calgary, Canada) to assess global left ventricular circumferential (Ecc) and radial (Err) strains and torsion. Differences in intra- and interobserver variability within and between software types were assessed based on single and averaged measurements (two and three repetitions with subsequent averaging of results, respectively) as determined by Bland–Altman analysis, intraclass correlation coefficients (ICC), and coefficient of variation (CoV). Results Myocardial strains and torsion significantly increased on dobutamine stimulation with both types of software (p<0.05). Resting Ecc and torsion as well as Ecc values during dobutamine stimulation were lower measured with Circle (p<0.05). Intra- and interobserver variability between software types was lowest for Ecc (ICC 0.81 [0.63–0.91], 0.87 [0.72–0.94] and CoV 12.47% and 14.3%, respectively) irrespective of the number of analysis repetitions. Err and torsion showed higher variability that markedly improved for torsion with repeated analyses and to a lesser extent for Err. On an intravendor level TomTec showed better reproducibility for Ecc and torsion and Circle for Err. Conclusions CMR-FT strain and torsion measurements are subject to considerable intervendor variability, which can be reduced using three analysis repetitions. For both vendors, Ecc qualifies as the most robust parameter with the best agreement, albeit lower Ecc values obtained using Circle, and warrants further investigation of incremental clinical merit. PMID:26139384

  14. Using 4D Cardiovascular Magnetic Resonance Imaging to Validate Computational Fluid Dynamics: A Case Study.

    PubMed

    Biglino, Giovanni; Cosentino, Daria; Steeden, Jennifer A; De Nova, Lorenzo; Castelli, Matteo; Ntsinjana, Hopewell; Pennati, Giancarlo; Taylor, Andrew M; Schievano, Silvia

    2015-01-01

    Computational fluid dynamics (CFD) can have a complementary predictive role alongside the exquisite visualization capabilities of 4D cardiovascular magnetic resonance (CMR) imaging. In order to exploit these capabilities (e.g., for decision-making), it is necessary to validate computational models against real world data. In this study, we sought to acquire 4D CMR flow data in a controllable, experimental setup and use these data to validate a corresponding computational model. We applied this paradigm to a case of congenital heart disease, namely, transposition of the great arteries (TGA) repaired with arterial switch operation. For this purpose, a mock circulatory loop compatible with the CMR environment was constructed and two detailed aortic 3D models (i.e., one TGA case and one normal aortic anatomy) were tested under realistic hemodynamic conditions, acquiring 4D CMR flow. The same 3D domains were used for multi-scale CFD simulations, whereby the remainder of the mock circulatory system was appropriately summarized with a lumped parameter network. Boundary conditions of the simulations mirrored those measured in vitro. Results showed a very good quantitative agreement between experimental and computational models in terms of pressure (overall maximum % error = 4.4% aortic pressure in the control anatomy) and flow distribution data (overall maximum % error = 3.6% at the subclavian artery outlet of the TGA model). Very good qualitative agreement could also be appreciated in terms of streamlines, throughout the cardiac cycle. Additionally, velocity vectors in the ascending aorta revealed less symmetrical flow in the TGA model, which also exhibited higher wall shear stress in the anterior ascending aorta. PMID:26697416

  15. Assessment of atrial septal defects in adults comparing cardiovascular magnetic resonance with transoesophageal echocardiography

    PubMed Central

    2010-01-01

    Background Many adult patients with secundum-type atrial septal defects (ASDs) are able to have these defects fixed percutaneously. Traditionally, this has involved an assessment of ASD size, geometry and atrial septal margins by transoesophageal echocardiography (TOE) prior to percutaneous closure. This is a semi-invasive technique, and all of the information obtained could potentially be obtained by non-invasive cardiovascular magnetic resonance (CMR). We compared the assessment of ASDs in consecutive patients being considered for percutaneous ASD closure using CMR and TOE. Methods Consecutive patients with ASDs diagnosed on transthoracic echocardiography (TTE) were invited to undergo both CMR and TOE. Assessment of atrial septal margins, maximal and minimal defect dimensions was performed with both techniques. Analyses between CMR and TOE were made using simple linear regression and Bland Altman Analyses. Results Total CMR scan time was 20 minutes, and comparable to the TOE examination time. A total of 20 patients (M:F = 5:15, mean age 42.8 years ± 15.7) were included in the analyses. There was an excellent agreement between CMR and TOE for estimation of maximum defect size (R = 0.87). The anterior inferior, anterior superior and posterior inferior margins could be assessed in all patients with CMR. The posterior superior margin could not be assessed in only one patient. Furthermore, in 1 patient in whom TOE was unable to be performed, CMR was used to successfully direct percutaneous ASD closure. Conclusions CMR agrees with TOE assessment of ASDs in the work-up for percutaneous closure. Potentially CMR could be used instead of TOE for this purpose. PMID:20663157

  16. Cardiovascular magnetic resonance T2 mapping can detect myocardial edema in idiopathic dilated cardiomyopathy.

    PubMed

    Nishii, Tatsuya; Kono, Atsushi K; Shigeru, Mayumi; Takamine, Sachiko; Fujiwara, Sei; Kyotani, Katsusuke; Aoyama, Nobukazu; Sugimura, Kazuro

    2014-06-01

    Myocardial edema and inflammation play an important role in dilated cardiomyopathy (DCM). This pathologic condition can be identified noninvasively using cardiovascular magnetic resonance imaging (CMR). The purpose of this study was to determine the effectiveness of T2 values obtained with T2 mapping in the detection of edema in DCM patients, compared with that of conventional T2-weighted imaging (T2WI). CMR was used for 15 normal controls (NML) and 26 DCM patients. The DCM patients were classified as having either mild dysfunction with a left ventricular ejection fraction (EF) >35% or severe dysfunction with an EF ≤35%. Myocardial edema was assessed by both T2 mapping and T2WI. The differences between the T2 values determined from T2 mapping and the T2 ratios that were calculated from the T2WI were compared among the NML, mild DCM, and severe DCM patients. The T2 values for the NML, mild DCM, and severe DCM patients were 51.2 ± 1.6, 61.2 ± 0.37, and 67.4 ± 6.8, respectively (P < 0.05 for each pair), and the corresponding T2 ratios were 1.88 ± 0.09, 2.12 ± 0.37, and 2.04 ± 0.34, respectively (P > 0.05). T2 mapping clearly showed that the myocardial water content was larger in DCM patients than in NML controls and that the myocardial water content increased as the disease progressed. Thus, T2 mapping is a useful technique for the diagnosis and quantitation of diffuse myocardial edema. PMID:24715436

  17. Automated quantitative assessment of cardiovascular magnetic resonance-derived atrioventricular junction velocities.

    PubMed

    Leng, Shuang; Zhao, Xiao-Dan; Huang, Fei-Qiong; Wong, Jia-Ing; Su, Bo-Yang; Allen, John Carson; Kassab, Ghassan S; Tan, Ru-San; Zhong, Liang

    2015-12-01

    The assessment of atrioventricular junction (AVJ) deformation plays an important role in evaluating left ventricular systolic and diastolic function in clinical practice. This study aims to demonstrate the effectiveness and consistency of cardiovascular magnetic resonance (CMR) for quantitative assessment of AVJ velocity compared with tissue Doppler echocardiography (TDE). A group of 145 human subjects comprising 21 healthy volunteers, 8 patients with heart failure, 17 patients with hypertrophic cardiomyopathy, 52 patients with myocardial infarction, and 47 patients with repaired Tetralogy of Fallot were prospectively enrolled and underwent TDE and CMR scan. Six AVJ points were tracked with three CMR views. The peak systolic velocity (Sm1), diastolic velocity during early diastolic filling (Em), and late diastolic velocity during atrial contraction (Am) were extracted and analyzed. All CMR-derived septal and lateral AVJ velocities correlated well with TDE measurements (Sm1: r = 0.736; Em: r = 0.835; Am: r = 0.701; Em/Am: r = 0.691; all p < 0.001) and demonstrated excellent reproducibility [intrastudy: r = 0.921-0.991, intraclass correlation coefficient (ICC): 0.918-0.991; interstudy: r = 0.900-0.970, ICC: 0.887-0.957; all p < 0.001]. The evaluation of three-dimensional AVJ motion incorporating measurements from all views better differentiated normal and diseased states [area under the curve (AUC) = 0.918] and provided further insights into mechanical dyssynchrony diagnosis in HF patients (AUC = 0.987). These findings suggest that the CMR-based method is feasible, accurate, and consistent in quantifying the AVJ deformation, and subsequently in diagnosing systolic and diastolic cardiac dysfunction. PMID:26408537

  18. Static magnetic field effect on the arterial baroreflex-mediated control of microcirculation: implications for cardiovascular effects due to environmental magnetic fields.

    PubMed

    Gmitrov, Juraj

    2007-08-01

    Increasing evidence suggests that time-varying and static magnetic fields in the environment might affect the cardiovascular system. To explore the underlying physiology, the effect of static magnetic fields (SMFs) on the carotid baroreflex control of microcirculation was studied. Twenty-four hemodynamic monitorings were performed in rabbits sedated by pentobarbital infusion (5 mg/kg/h) during experiments that lasted 120 min. Mean femoral artery blood pressure, heart rate, and ear lobe skin microcirculatory blood flow, measured by microphotoelectric plethysmogram (MPPG), were simultaneously recorded before and after a 40 min exposure of the sinocarotid baroreceptors to Nd(2)-Fe(14)-B alloy magnets (n = 14) or sham magnets (n = 10, control series). The local SMF field was 350 mT, at the baroreceptors' site. Arterial baroreflex sensitivity (BRS) was estimated from heart rate/blood pressure response to intravenous bolus injections of nitroprusside and phenylephrine. A significant positive correlation was found between the SMF-induced increase in BRS (DeltaBRS = BRS(afterSMF) - BRS(priorSMF)) and the increment in microvascular blood flow (DeltaMPPG = MPPG(afterSMF) - MPPG(priorSMF)) (r = 0.66, p < 0.009). The SMF probably modulated the arterial baroreflex-mediated microcirculatory control. This could represent one possible mechanism how environmental magnetic fields act on the cardiovascular system, and a method how to complexly adjust macro- and microcirculation with potential clinical implementation. PMID:17530271

  19. Current-Controlled Spin Precession of Quasistationary Electrons in a Cubic Spin-Orbit Field.

    PubMed

    Altmann, P; Hernandez, F G G; Ferreira, G J; Kohda, M; Reichl, C; Wegscheider, W; Salis, G

    2016-05-13

    Space- and time-resolved measurements of spin drift and diffusion are performed on a GaAs-hosted two-dimensional electron gas. For spins where forward drift is compensated by backward diffusion, we find a precession frequency in the absence of an external magnetic field. The frequency depends linearly on the drift velocity and is explained by the cubic Dresselhaus spin-orbit interaction, for which drift leads to a spin precession angle twice that of spins that diffuse the same distance. PMID:27232032

  20. Current-Controlled Spin Precession of Quasistationary Electrons in a Cubic Spin-Orbit Field

    NASA Astrophysics Data System (ADS)

    Altmann, P.; Hernandez, F. G. G.; Ferreira, G. J.; Kohda, M.; Reichl, C.; Wegscheider, W.; Salis, G.

    2016-05-01

    Space- and time-resolved measurements of spin drift and diffusion are performed on a GaAs-hosted two-dimensional electron gas. For spins where forward drift is compensated by backward diffusion, we find a precession frequency in the absence of an external magnetic field. The frequency depends linearly on the drift velocity and is explained by the cubic Dresselhaus spin-orbit interaction, for which drift leads to a spin precession angle twice that of spins that diffuse the same distance.

  1. Highly stable atomic vector magnetometer based on free spin precession.

    PubMed

    Afach, S; Ban, G; Bison, G; Bodek, K; Chowdhuri, Z; Grujić, Z D; Hayen, L; Hélaine, V; Kasprzak, M; Kirch, K; Knowles, P; Koch, H-C; Komposch, S; Kozela, A; Krempel, J; Lauss, B; Lefort, T; Lemière, Y; Mtchedlishvili, A; Naviliat-Cuncic, O; Piegsa, F M; Prashanth, P N; Quéméner, G; Rawlik, M; Ries, D; Roccia, S; Rozpedzik, D; Schmidt-Wellenburg, P; Severjins, N; Weis, A; Wursten, E; Wyszynski, G; Zejma, J; Zsigmond, G

    2015-08-24

    We present a magnetometer based on optically pumped Cs atoms that measures the magnitude and direction of a 1 μT magnetic field. Multiple circularly polarized laser beams were used to probe the free spin precession of the Cs atoms. The design was optimized for long-time stability and achieves a scalar resolution better than 300 fT for integration times ranging from 80 ms to 1000 s. The best scalar resolution of less than 80 fT was reached with integration times of 1.6 to 6 s. We were able to measure the magnetic field direction with a resolution better than 10 μrad for integration times from 10 s up to 2000 s. PMID:26368184

  2. Real-time cine and myocardial perfusion with treadmill exercise stress cardiovascular magnetic resonance in patients referred for stress SPECT

    PubMed Central

    2010-01-01

    Background To date, stress cardiovascular magnetic resonance (CMR) has relied on pharmacologic agents, and therefore lacked the physiologic information available only with exercise stress. Methods 43 patients age 25 to 81 years underwent a treadmill stress test incorporating both Tc99m SPECT and CMR. After rest Tc99m SPECT imaging, patients underwent resting cine CMR. Patients then underwent in-room exercise stress using a partially modified treadmill. 12-lead ECG monitoring was performed throughout. At peak stress, Tc99m was injected and patients rapidly returned to their prior position in the magnet for post-exercise cine and perfusion imaging. The patient table was pulled out of the magnet for recovery monitoring. The patient was sent back into the magnet for recovery cine and resting perfusion followed by delayed post-gadolinium imaging. Post-CMR, patients went to the adjacent SPECT lab to complete stress nuclear imaging. Each modality's images were reviewed blinded to the other's results. Results Patients completed on average 9.3 ± 2.4 min of the Bruce protocol. Stress cine CMR was completed in 68 ± 14 sec following termination of exercise, and stress perfusion CMR was completed in 88 ± 8 sec. Agreement between SPECT and CMR was moderate (κ = 0.58). Accuracy in eight patients who underwent coronary angiography was 7/8 for CMR and 5/8 for SPECT (p = 0.625). Follow-up at 6 months indicated freedom from cardiovascular events in 29/29 CMR-negative and 33/34 SPECT-negative patients. Conclusions Exercise stress CMR including wall motion and perfusion is feasible in patients with suspected ischemic heart disease. Larger clinical trials are warranted based on the promising results of this pilot study to allow comparative effectiveness studies of this stress imaging system vs. other stress imaging modalities. PMID:20624294

  3. Thomas precession and squeezed states of light

    NASA Technical Reports Server (NTRS)

    Han, D.; Hardekopf, E. E.; Kim, Y. S.

    1989-01-01

    The Lorentz group, which is the language of special relativity, is a useful theoretical toll in modern optics. Optics experiments can therefore serve as analog computers for special relativity. Possible optics experiments involving squeezed states are discussed in connection with the Thomas precession and the Wigner rotation.

  4. Nonrelativistic Contribution to Mercury's Perihelion Precession.

    ERIC Educational Resources Information Center

    Price, Michael P.; Rush, William F.

    1979-01-01

    Presents a calculation of the precession of the perihelion of Mercury due to the perturbations from the outer planets. The time-average effect of each planet is calculated by replacing that planet with a ring of linear mass density equal to the mass of the planet divided by the circumference of its orbit. (Author/GA)

  5. Precession of the Earth-Moon System

    ERIC Educational Resources Information Center

    Urbassek, Herbert M.

    2009-01-01

    The precession rate of the Earth-Moon system by the gravitational influence of the Sun is derived. Attention is focussed on a physically transparent but complete presentation accessible to first- or second-year physics students. Both a shortcut and a full analysis are given, which allows the inclusion of this material as an example of the physics…

  6. Spinor approach to gravitational motion and precession

    SciTech Connect

    Hestenes, D.

    1986-06-01

    The translational and rotational equations of motion for a small rigid body in a gravitational field are combined in a single spinor equation. Besides its computational advantages, this unifies the description of gravitational interaction in classical and quantum theory. Explicit expressions for gravitational precession rates are derived.

  7. Feature tracking compared with tissue tagging measurements of segmental strain by cardiovascular magnetic resonance

    PubMed Central

    2014-01-01

    Background Left ventricular segmental wall motion analysis is important for clinical decision making in cardiac diseases. Strain analysis with myocardial tissue tagging is the non-invasive gold standard for quantitative assessment, however, it is time-consuming. Cardiovascular magnetic resonance myocardial feature-tracking (CMR-FT) can rapidly perform strain analysis, because it can be employed with standard CMR cine-imaging. The aim is to validate segmental peak systolic circumferential strain (peak SCS) and time to peak systolic circumferential strain (T2P-SCS) analysed by CMR-FT against tissue tagging, and determine its intra and inter-observer variability. Methods Patients in whom both cine CMR and tissue tagging has been performed were selected. CMR-FT analysis was done using endocardial (CMR-FTendo) and mid-wall contours (CMR-FTmid). The Intra Class Correlation Coefficient (ICC) and Pearson correlation were calculated. Results 10 healthy volunteers, 10 left bundle branch block (LBBB) and 10 hypertrophic cardiomyopathy patients were selected. With CMR-FT all 480 segments were analyzable and with tissue tagging 464 segments. Significant differences in mean peak SCS values of the total study group were present between CMR-FTendo and tissue tagging (-23.8 ± 9.9% vs -13.4 ± 3.3%, p < 0.001). Differences were smaller between CMR-FTmid and tissue tagging (-16.4 ± 6.1% vs -13.4 ± 3.3%, p = 0.001). The ICC of the mean peak SCS of the total study group between CMR-FTendo and tissue tagging was low (0.19 (95%-CI-0.10-0.49), p = 0.02). Comparable results were seen between CMR-FTmid and tissue tagging. In LBBB patients, mean T2P-SCS values measured with CMR-FTendo and CMR-FTmid were 418 ± 66 ms, 454 ± 60 ms, which were longer than with tissue tagging, 376 ± 55 ms, both p < 0.05. ICC of the mean T2P-SCS between CMR-FTendo and tissue tagging was 0.64 (95%-CI-0.36-0.81), p < 0.001, this was better in the healthy

  8. Cardiovascular magnetic resonance in pregnancy: Insights from the cardiac hemodynamic imaging and remodeling in pregnancy (CHIRP) study

    PubMed Central

    2014-01-01

    Background Cardiovascular disease in pregnancy is the leading cause of maternal mortality in North America. Although transthoracic echocardiography (TTE) is the most widely used imaging modality for the assessment of cardiovascular function during pregnancy, little is known on the role of cardiovascular magnetic resonance (CMR). The objective of the Cardiac Hemodynamic Imaging and Remodeling in Pregnancy (CHIRP) study was to compare TTE and CMR in the non-invasive assessment of maternal cardiac remodeling during the peripartum period. Methods Between 2010–2012, healthy pregnant women aged 18 to 35 years were prospectively enrolled. All women underwent TTE and CMR during the third trimester and at least 3 months postpartum (surrogate for non-pregnant state). Results The study population included a total of 34 women (mean age 29 ± 3 years). During the third trimester, TTE and CMR demonstrated an increase in left ventricular end-diastolic volume from 95 ± 11 mL to 115 ± 14 mL and 98 ± 6 mL to 125 ± 5 mL, respectively (p < 0.05). By TTE and CMR, there was also an increase in left ventricular (LV) mass during pregnancy from 111 ± 10 g to 163 ± 11 g and 121 ± 5 g to 179 ± 5 g, respectively (p < 0.05). Although there was good correlation between both imaging modalities for LV mass, stroke volume, and cardiac output, the values were consistently underestimated by TTE. Conclusion This CMR study provides reference values for cardiac indices during normal pregnancy and the postpartum state. PMID:24387349

  9. Relativistic spin precession in the double pulsar.

    PubMed

    Breton, Rene P; Kaspi, Victoria M; Kramer, Michael; McLaughlin, Maura A; Lyutikov, Maxim; Ransom, Scott M; Stairs, Ingrid H; Ferdman, Robert D; Camilo, Fernando; Possenti, Andrea

    2008-07-01

    The double pulsar PSR J0737-3039A/B consists of two neutron stars in a highly relativistic orbit that displays a roughly 30-second eclipse when pulsar A passes behind pulsar B. Describing this eclipse of pulsar A as due to absorption occurring in the magnetosphere of pulsar B, we successfully used a simple geometric model to characterize the observed changing eclipse morphology and to measure the relativistic precession of pulsar B's spin axis around the total orbital angular momentum. This provides a test of general relativity and alternative theories of gravity in the strong-field regime. Our measured relativistic spin precession rate of 4.77 degrees (-0 degrees .65)(+0 degrees .66) per year (68% confidence level) is consistent with that predicted by general relativity within an uncertainty of 13%. PMID:18599782

  10. Prospects for aberration corrected electron precession.

    PubMed

    Own, C S; Sinkler, W; Marks, L D

    2007-01-01

    Recent developments in aberration control in the TEM have yielded a tremendous enhancement of direct imaging capabilities for studying atomic structures. However, aberration correction also has substantial benefits for achieving ultra-resolution in the TEM through reciprocal space techniques. Several tools are available that allow very accurate detection of the electron distribution in surfaces allowing precise atomic-scale characterization through statistical inversion techniques from diffraction data. The precession technique now appears to extend this capability to the bulk. This article covers some of the progress in this area and details requirements for a next-generation analytical diffraction instrument. An analysis of the contributions offered by aberration correction for precision electron precession is included. PMID:17207934

  11. Using the P03 Precession Model

    NASA Astrophysics Data System (ADS)

    Wallace, P. T.; Capitaine, N.

    2006-08-01

    The precession model adopted by the IAU in 2000 comprised the existing Lieske et al. (1977) model plus rate corrections of about 300 mas/cy in longitude and 25 mas/cy in obliquity. Though accurate with respect to existing VLBI observations, the IAU 2000 model is not consistent with dynamical theory, and consequently the IAU Working Group on precession and the ecliptic has recommended (Hilton et al. 2006) that it be replaced by the "P03" model of Capitaine et al. (2003). P03 provides improved models for both the equator and the ecliptic, and also includes parameterized provision for future adjustment to match new determinations of properties of the non-rigid Earth such as the precession rates and J2 rate. Practical use of the new model involves choices of algorithm and computational procedure, and a number of ways have been studied (Capitaine & Wallace 2006) of generating the directions of the celestial intermediate pole and origin (CIP, CIO), from which the usual rotation matrices can be obtained. From a wide range of possible procedures we have selected two that target different classes of application, typified by the SOFA software and the IERS Conventions respectively. These procedures achieve a high standard of consistency, both internal and mutual, as well as being efficient and versatile. One is based on the Fukushima-Williams precession-nutation angles, the other on series for the CIP coordinates. Both use the CIO locator s, and both deliver the full range of products, supporting classical equinox/GST methods in addition to the CIO/ERA "new paradigm".

  12. Turbulent mixing in a precessing sphere

    SciTech Connect

    Goto, Susumu Shimizu, Masaki; Kawahara, Genta

    2014-11-15

    By numerically simulating turbulent flows at high Reynolds numbers in a precessing sphere, we propose a method to enhance the mixing of a fluid confined within a smooth cavity by its rotational motion alone. To precisely evaluate the mixing efficiency, we extend the quantification method proposed by Danckwerts [“The definition and measurement of some characteristics of mixtures,” Appl. Sci. Res. A 3, 279–296 (1952)] to the case in which only a finite number of fluid particle trajectories can be known. Our accurate numerical tracking of fluid particles in the flow, which is controlled by the Reynolds number (an indicator of the spin rate) and the Poincaré number (the precession rate), shows the following results. First, the mixing process on the time scale normalized by the spin period is independent of the Reynolds number as long as it is high enough for the flow to be developed turbulence. Second, fastest mixing is achieved under weak precession (Poincaré number ≈0.1); in such cases, perfect mixing requires only 10–15 spins of the container. Third, the power to sustain turbulence is a weakly increasing function of the Poincaré number, and the energy efficiency of the mixing is also maximized when the Poincaré number is about 0.1. Fourth, efficient mixing driven by the weak precession arises from the effective cooperation of complex large-scale flow and small-scale turbulence, which itself is sustained by the large-scale flow.

  13. Uncertainty relations and precession of perihelion

    NASA Astrophysics Data System (ADS)

    Scardigli, Fabio; Casadio, Roberto

    2016-03-01

    We compute the corrections to the Schwarzschild metric necessary to reproduce the Hawking temperature derived from a Generalized Uncertainty Principle (GUP), so that the GUP deformation parameter is directly linked to the deformation of the metric. Using this modified Schwarzschild metric, we compute corrections to the standard General Relativistic predictions for the perihelion precession for planets in the solar system, and for binary pulsars. This analysis allows us to set bounds for the GUP deformation parameter from well-known astronomical measurements.

  14. Geodetic precession or dragging of inertial frames

    NASA Technical Reports Server (NTRS)

    Ashby, Neil; Shahid-Saless, Bahman

    1989-01-01

    In General Relativity, the Principle of General Covariance allows one to describe phenomena by means of any convenient choice of coordinate system. Here, it is shown that the geodetic precession of a gyroscope orbiting a spherically symmetric, nonrotating mass can be recast as a Lense-Thirring frame-dragging effect, in an appropriately chosen coordinate frame whose origin falls freely along with the gyroscope and whose spatial coordinate axes point in fixed directions.

  15. Method of propulsion of a ferromagnetic core in the cardiovascular system through magnetic gradients generated by an MRI system.

    PubMed

    Mathieu, Jean-Baptiste; Beaudoin, Gilles; Martel, Sylvain

    2006-02-01

    This paper reports the use of a magnetic resonance imaging (MRI) system to propel a ferromagnetic core. The concept was studied for future development of microdevices designed to perform minimally invasive interventions in remote sites accessible through the human cardiovascular system. A mathematical model is described taking into account various parameters such as the size of blood vessels, the velocities and viscous properties of blood, the magnetic properties of the materials, the characteristics of MRI gradient coils, as well as the ratio between the diameter of a spherical core and the diameter of the blood vessels. The concept of magnetic propulsion by MRI is validated experimentally by measuring the flow velocities that magnetized spheres (carbon steel 1010/1020) can withstand inside cylindrical tubes under the different magnetic forces created with a Siemens Magnetom Vision 1.5 T MRI system. The differences between the velocities predicted by the theoretical model and the experiments are approximately 10%. The results indicate that with the technology available today for gradient coils used in clinical MRI systems, it is possible to generate sufficient gradients to propel a ferromagnetic sphere in the larger sections of the arterial system. In other words, the results show that in the larger blood vessels where the diameter of the microdevices could be as large as a couple a millimeters, the few tens of mT/m of gradients required for displacement against the relatively high blood flow rate is well within the limits of clinical MRI systems. On the other hand, although propulsion of a ferromagnetic core with diameter of approximately 600 microm may be possible with existing clinical MRI systems, gradient amplitudes of several T/m would be required to propel a much smaller ferromagnetic core in small vessels such as capillaries and additional gradient coils would be required to upgrade existing MRI systems for operations at such a scale. PMID:16485758

  16. Warp evidence in precessing galactic bar models

    NASA Astrophysics Data System (ADS)

    Sánchez-Martín, P.; Romero-Gómez, M.; Masdemont, J. J.

    2016-04-01

    Most galaxies have a warped shape when they are seen edge-on. The reason for this curious form is not completely known so far, so in this work we apply dynamical system tools to contribute to its explanation. Starting from a simple, but realistic model formed by a bar and a disc, we study the effect of a small misalignment between the angular momentum of the system and its angular velocity. To this end, a precession model was developed and considered, assuming that the bar behaves like a rigid body. After checking that the periodic orbits inside the bar continue to be the skeleton of the inner system even after inflicting a precession to the potential, we computed the invariant manifolds of the unstable periodic orbits departing from the equilibrium points at the ends of the bar to find evidence of their warped shapes. As is well known, the invariant manifolds associated with these periodic orbits drive the arms and rings of barred galaxies and constitute the skeleton of these building blocks. Looking at them from a side-on viewpoint, we find that these manifolds present warped shapes like those recognised in observations. Lastly, test particle simulations have been performed to determine how the stars are affected by the applied precession, this way confirming the theoretical results.

  17. Structure refinement from precession electron diffraction data.

    PubMed

    Palatinus, Lukáš; Jacob, Damien; Cuvillier, Priscille; Klementová, Mariana; Sinkler, Wharton; Marks, Laurence D

    2013-03-01

    Electron diffraction is a unique tool for analysing the crystal structures of very small crystals. In particular, precession electron diffraction has been shown to be a useful method for ab initio structure solution. In this work it is demonstrated that precession electron diffraction data can also be successfully used for structure refinement, if the dynamical theory of diffraction is used for the calculation of diffracted intensities. The method is demonstrated on data from three materials - silicon, orthopyroxene (Mg,Fe)(2)Si(2)O(6) and gallium-indium tin oxide (Ga,In)(4)Sn(2)O(10). In particular, it is shown that atomic occupancies of mixed crystallographic sites can be refined to an accuracy approaching X-ray or neutron diffraction methods. In comparison with conventional electron diffraction data, the refinement against precession diffraction data yields significantly lower figures of merit, higher accuracy of refined parameters, much broader radii of convergence, especially for the thickness and orientation of the sample, and significantly reduced correlations between the structure parameters. The full dynamical refinement is compared with refinement using kinematical and two-beam approximations, and is shown to be superior to the latter two. PMID:23403968

  18. Longitudinal and transverse right ventricular function in pulmonary hypertension: cardiovascular magnetic resonance imaging study from the ASPIRE registry

    PubMed Central

    Rajaram, Smitha; Capener, Dave; Elliot, Charlie; Condliffe, Robin; Wild, Jim M.; Kiely, David G.

    2015-01-01

    Abstract Right ventricular (RV) function is a strong predictor of outcome in cardiovascular diseases. Two components of RV function, longitudinal and transverse motion, have been investigated in pulmonary hypertension (PH). However, their individual clinical significance remains uncertain. The aim of this study was to determine the factors associated with transverse and longitudinal RV motion in patients with PH. In 149 treatment-naive patients with PH and 16 patients with suspected PH found to have mean pulmonary arterial pressure of <20 mmHg, cardiovascular magnetic resonance imaging was performed within 24 hours of right heart catheterization. In patients with PH, fractional longitudinal motion (fractional tricuspid annulus to apex distance [f-TAAD]) was significantly greater than fractional transverse motion (fractional septum to free wall distance [f-SFD]; P = 0.002). In patients without PH, no significant difference between f-SFD and f-TAAD was identified (P = 0.442). Longitudinal RV motion was singularly associated with RV ejection fraction independent of age, invasive hemodynamics, and cardiac magnetic resonance measurements (P = 0.024). In contrast, transverse RV motion was independently associated with left ventricular eccentricity (P = 0.036) in addition to RV ejection fraction (P = 0.014). In conclusion, RV motion is significantly greater in the longitudinal direction in patients with PH, whereas patients without PH have equal contributions of transverse and longitudinal motion. Longitudinal RV motion is primarily associated with global RV pump function in PH. Transverse RV motion not only reflects global pump function but is independently influenced by ventricular interaction in patients with PH. PMID:26401257

  19. Cardiovascular magnetic resonance and computed tomography in the evaluation of aneurysmal coronary-cameral fistula

    PubMed Central

    Detorakis, Efstathios E; Foukarakis, Emmanouil; Karavolias, George; Dermitzakis, Alkiviades

    2015-01-01

    Coronary artery fistulas represent abnormal communications between a coronary artery and a major vessel like venae cavae, pulmonary arteries or veins, the coronary sinus, or a cardiac chamber. The latter is called coronary cameral fistula is a rare condition and is most of the times congenital but can be also post traumatic or post surgical, especially after cardiovascular interventional procedures. Most patients are asymptomatic and coronary-cameral fistulae are discovered incidentally during angiographic evaluation for coronary vascular disorders, while other patients have a clinical presentation ranging from angina pectoris to heart failure. In this article, we report a rare case of an aneurysmal right coronary cameral fistula draining into the left ventricle. Echocardiography usually represents the first diagnostic imaging approach, but often due to a poor acoustic window may not show the entire course of the fistula which is crucial for the final diagnosis. ECG-gated cardiovascular CT may play an important role in the evaluation of the origin, course, termination and morphology of the fistula, its relation to the adjacent anatomical structures as well as the morphology and contractility of the heart. Cardiac MRI instead plays an additional crucial role regarding not only the above mentioned factors but also in estimating the blood flow within the fistula, providing more detailed information about the cardiac function but also about myocardial wall viability. PMID:26629294

  20. Quipus and System of Coordinated Precession

    NASA Astrophysics Data System (ADS)

    Campos, T. C.

    2004-05-01

    The Incas of ancient Peru possessed no writing. Instead, they developed a unique system expressed on spatial arrays of colored knotted cords called Quipus to record and transmit information throughout their vast empire. In their thorough description of quipus, Ascher & Ascher observed that in two cases the numbers registered in their strings have a very special relationship to each other. For this to occur the numbers must have been obtained through the multiplication of whole numbers by fractions or decimals, operations apparently beyond the arithmetic knowledge of the Incas. The quipus AS120 and AS143, coming from Ica (Peru) and conserved in the Museum of Berlin has the suitable characteristics previously. In the AS143 there is a the relationship with the systems of coordinated precession (tilt of Earth's spin axis (40036); eccentricity of Earth's orbit (97357); and precession of equinoxes (between 18504 and 23098)). For the history of the Earth are necessary an chronometer natural to coordinate and to classify the observations and this chronometer comes to be the vernal point, defining the vernal point as" a sensitive axis of maximum conductivity" as itdemonstrates it the stability of the geomagnetic equator (inclination of the field is zero grades), in the year 1939 calculated with the IGRF from the year 1900 up to the 2004 and that it is confirmed with tabulated data of the Geophysical Institute of Huancayo (Peru),from that date until this year (2004) and this fluctuating between the 12-14 South.,on the other hand in the area of Brazil it has advanced very quickly toward the north, and above to 108 km. approximately it is located the equatorial electrojet that is but intense in the equinoxes in South America. And this stability from the point of view of the precession of the equinoxes this coinciding with the entrance of the apparent sun for the constellation of Aquarius, being this mechanism the base to establish a system of coordinated precession where it is

  1. Laser induced spin precession in highly anisotropic granular L1{sub 0} FePt

    SciTech Connect

    Becker, J.; Mosendz, O.; Weller, D.; Kirilyuk, A.; Rasing, Th.; Kimel, A.; Maan, J. C.; Christianen, P. C. M.

    2014-04-14

    The dynamic magnetic properties of a highly anisotropic, granular L1{sub 0} FePt thin film in magnetic fields up to 7 T are investigated using time-resolved magneto-optical Kerr effect measurements. We find that ultrashort laser pulses induce coherent spin precession in the granular FePt sample. Frequencies of spin precession up to over 400 GHz are observed, which are strongly field and temperature dependent. The high frequencies can be ascribed to the high value of the magnetocrystalline anisotropy constant K{sub u} leading to large anisotropy fields H{sub a} of up to 10.7 T at 170 K. A Gilbert damping parameter of α ∼ 0.1 was derived from the lifetimes of the oscillations.

  2. Research program in nuclear and solid state physics. [including pion absorption spectra and muon spin precession

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The survey of negative pion absorption reactions on light and medium nuclei was continued. Muon spin precession was studied using an iron target. An impulse approximation model of the pion absorption process implied that the ion will absorb almost exclusively on nucleon pairs, single nucleon absorption being suppressed by energy and momentum conservation requirements. For measurements on both paramagnetic and ferromagnetic iron, the external magnetic field was supplied by a large C-type electromagnet carrying a current of about 100 amperes.

  3. Electrocardiographic diagnosis of left ventricular hypertrophy in aortic valve disease: evaluation of ECG criteria by cardiovascular magnetic resonance

    PubMed Central

    Buchner, Stefan; Debl, Kurt; Haimerl, Josef; Djavidani, Behrus; Poschenrieder, Florian; Feuerbach, Stefan; Riegger, Guenter AJ; Luchner, Andreas

    2009-01-01

    Background Left ventricular hypertrophy (LVH) is a hallmark of chronic pressure or volume overload of the left ventricle and is associated with risk of cardiovascular morbidity and mortality. The purpose was to evaluate different electrocardiographic criteria for LVH as determined by cardiovascular magnetic resonance (CMR). Additionally, the effects of concentric and eccentric LVH on depolarization and repolarization were assessed. Methods 120 patients with aortic valve disease and 30 healthy volunteers were analysed. As ECG criteria for LVH, we assessed the Sokolow-Lyon voltage/product, Gubner-Ungerleider voltage, Cornell voltage/product, Perugia-score and Romhilt-Estes score. Results All ECG criteria demonstrated a significant correlation with LV mass and chamber size. The highest predictive values were achieved by the Romhilt-Estes score 4 points with a sensitivity of 86% and specificity of 81%. There was no difference in all ECG criteria between concentric and eccentric LVH. However, the intrinsicoid deflection (V6 37 ± 1.0 ms vs. 43 ± 1.6 ms, p < 0.05) was shorter in concentric LVH than in eccentric LVH and amplitudes of ST-segment (V5 -0.06 ± 0.01 vs. -0.02 ± 0.01) and T-wave (V5 -0.03 ± 0.04 vs. 0.18 ± 0.05) in the anterolateral leads (p < 0.05) were deeper. Conclusion By calibration with CMR, a wide range of predictive values was found for the various ECG criteria for LVH with the most favourable results for the Romhilt-Estes score. As electrocardiographic correlate for concentric LVH as compared with eccentric LVH, a shorter intrinsicoid deflection and a significant ST-segment and T-wave depression in the anterolateral leads was noted. PMID:19486532

  4. Role of cardiovascular magnetic resonance imaging in arrhythmogenic right ventricular dysplasia

    PubMed Central

    Jain, Aditya; Tandri, Harikrishna; Calkins, Hugh; Bluemke, David A

    2008-01-01

    Arrhythmogenic right ventricular dysplasia (ARVD) is a genetic cardiomyopathy characterized clinically by ventricular arrhythmias and progressive right ventricular (RV) dysfunction. The histopathologic hallmark is fibro-fatty replacement of RV myocardium. It is inherited in an autosomal pattern with variable penetrance. ARVD is unique in that it most commonly presents in young, otherwise healthy and highly athletic individuals. The cause of ARVD is not well-known but recent evidence suggests strongly that it is a disease of desmosomal dysfunction. The disease involvement is not limited only to the RV as left ventricle (LV) has also been reportedly affected. Diagnosis of ARVD is challenging and is currently based upon a multi-disciplinary work-up of the patient as defined by the Task Force. Currently, implanted cardioverter defibrillators (ICD) are routinely used to prevent sudden death in patients with ARVD. Cardiovascular MR is an important non-invasive diagnostic modality that allows both qualitative and quantitative evaluation of RV. This article reviews the genetics of ARVD, current status and role of CMR in the diagnosis of ARVD and LV involvement in ARVD. PMID:18570661

  5. Photon-assisted electronic and spin transport in a junction containing precessing molecular spin

    NASA Astrophysics Data System (ADS)

    Filipović, Milena; Belzig, Wolfgang

    2016-02-01

    We study the ac charge and -spin transport through an orbital of a magnetic molecule with spin precessing in a constant magnetic field. We assume that the source and drain contacts have time-dependent chemical potentials. We employ the Keldysh nonequilibrium Green's functions method to calculate the spin and charge currents to linear order in the time-dependent potentials. The molecular and electronic spins are coupled via exchange interaction. The time-dependent molecular spin drives inelastic transitions between the molecular quasienergy levels, resulting in a rich structure in the transport characteristics. The time-dependent voltages allow us to reveal the internal precession time scale (the Larmor frequency) by a dc conductance measurement if the ac frequency matches the Larmor frequency. In the low-ac-frequency limit the junction resembles a classical electric circuit. Furthermore, we show that the setup can be used to generate dc-spin currents, which are controlled by the molecular magnetization direction and the relative phases between the Larmor precession and the ac voltage.

  6. Ultra-Wideband Sensors for Improved Magnetic Resonance Imaging, Cardiovascular Monitoring and Tumour Diagnostics

    PubMed Central

    Thiel, Florian; Kosch, Olaf; Seifert, Frank

    2010-01-01

    The specific advantages of ultra-wideband electromagnetic remote sensing (UWB radar) make it a particularly attractive technique for biomedical applications. We partially review our activities in utilizing this novel approach for the benefit of high and ultra-high field magnetic resonance imaging (MRI) and other applications, e.g., for intensive care medicine and biomedical research. We could show that our approach is beneficial for applications like motion tracking for high resolution brain imaging due to the non-contact acquisition of involuntary head motions with high spatial resolution, navigation for cardiac MRI due to our interpretation of the detected physiological mechanical contraction of the heart muscle and for MR safety, since we have investigated the influence of high static magnetic fields on myocardial mechanics. From our findings we could conclude, that UWB radar can serve as a navigator technique for high and ultra-high field magnetic resonance imaging and can be beneficial preserving the high resolution capability of this imaging modality. Furthermore it can potentially be used to support standard ECG analysis by complementary information where sole ECG analysis fails. Further analytical investigations have proven the feasibility of this method for intracranial displacements detection and the rendition of a tumour’s contrast agent based perfusion dynamic. Beside these analytical approaches we have carried out FDTD simulations of a complex arrangement mimicking the illumination of a human torso model incorporating the geometry of the antennas applied. PMID:22163498

  7. Review Of The Working Group On Precession And The Ecliptic

    NASA Astrophysics Data System (ADS)

    Hilton, J. L.

    2006-08-01

    The IAU Working Group on Precession and the Ecliptic was charged with providing a precession model that was both dynamically consistent and compatible with the IAU 2000A nutation model, along with an updated definition and model for the ecliptic. The report of the working group has been accepted for publication in Celestial Mechanics (Hilton et al. 2006, in press) and has resulted in a recommendation to be considered at this General Assembly of the IAU. Specifically, the working group recommends: 1. That the terms lunisolar precession and planetary precession be replaced by precession of the equator and precession of the ecliptic, respectively. 2. That, beginning on 1 January 2009, the precession component of the IAU 2000A precession-nutation model be replaced by the P03 precession theory, of Capitaine et al. (2003, A&A, 412, 567-586) for the precession of the equator (Eqs. 37) and the precession of the ecliptic (Eqs. 38); the same paper provides the polynomial developments for the P03 primary angles and a number of derived quantities for use in both the equinox based and Celestial Intermediate Origin based paradigms. 3. That the choice of precession parameters be left to the user. 4. That the ecliptic pole should be explicitly defined by the mean orbital angular momentum vector of the Earth-Moon barycenter in an inertial reference frame, and this definition should be explicitly stated to avoid confusion with other, older definitions. consistent and compatible with the IAU 2000A nutation model, along consistent and compatible with the IAU 2000A nutation model, along with an updated definition and model for the ecliptic. The report of the working group has been accepted for publication in Celestial Mechanics (Hilton et al. 2006, in press) and has resulted in a recommendation to be considered at this General Assembly of the IAU. Specifically, the working group recommends, * that the terms lunisolar precession and planetary precession be replaced by precession of the

  8. Relativistic 3D precessing jet simulations for the X-ray binary SS433

    NASA Astrophysics Data System (ADS)

    Monceau-Baroux, Rémi; Porth, Oliver; Meliani, Zakaria; Keppens, Rony

    2014-01-01

    Context. Modern high-resolution radio observations allow us a closer look into the objects that power relativistic jets. This is especially the case for SS433, an X-ray binary that emits a precessing jet that is observed down to the subparsec scale. Aims: We aim to study full 3D dynamics of relativistic jets associated with active galactic nuclei or X-ray binaries (XRB). In particular, we incorporate the precessing motion of a jet into a model for the jet associated with the XRB SS433. Our study of the jet dynamics in this system focuses on the subparsec scales. We investigate the impact of jet precession and the variation of the Lorentz factor of the injected matter on the general 3D jet dynamics and its energy transfer to the surrounding medium. After visualizing and quantifying jet dynamics, we aim to realize synthetic radio mapping of the data, to compare our results with observations. Methods: For our study we used a block-tree adaptive mesh refinement scheme and an inner time-dependent boundary prescription to inject precessing bipolar supersonic jets. Parameters extracted from observations were used. Different 3D jet realizations that match the kinetic flux of the SS433 jet were intercompared, which vary in density contrast and jet beam velocity. We tracked the energy content deposited in different regions of the domain affected by the jet. Our code allows us to follow the adiabatic cooling of a population of relativistic particles injected by the jet. This evolving energy spectrum of accelerated electrons, using a pressure-based proxy for the magnetic field, allowed us to obtain the radio emission from our simulation. Results: We find a higher energy transfer for a precessing jet than for standing jets with otherwise identical parameters as a result of the effectively increased interaction area. We obtain synthetic radio maps for all jets, from which one can see that dynamical flow features are clearly linked with enhanced emission sites. Conclusions: The

  9. SU-E-T-145: Effects of Temporary Tachytherapy Inhibition Magnet On MOSFET Dose Measurements of Cardiovascular Implantable Electronic Devices (CIED) in Radiation Therapy Patients

    SciTech Connect

    P, Joshi; Salomons, G; Kerr, A; Peters, C; Lalonde, M

    2014-06-01

    Purpose: To determine the effects of temporary tachytherapy inhibition magnet on MOSFET dose measurements of cardiovascular implantable electronic devices (CIED) in radiation therapy patients. Methods: Infield and peripheral MOSFET dose measurements with 6MV photon beams were performed to evaluate dose to a CIED in the presence of a doughnut shaped temporary tachytherapy inhibition magnet. Infield measurements were done to quantify the effects of the magnetic field alone and shielding by the magnet. MOSFETs were placed inside a 20×20cm{sup 2} field at a depth of 3cm in the isocentre plane in the presence and absence of the magnet. Peripheral dose measurements were done to determine the impact of the magnet on dose to the CIED in a clinical setting. These measurements were performed at the centre, under the rim and half way between a 10×10cm{sup 2} field edge and the magnet with MOSFETS placed at the surface, 0.5cm and 1cm depths in the presence and absence of the magnet. Results: Infield measurements showed that effects of magnetic field on the MOSFET readings were within the 2% MOSFET dose measurement uncertainty; a 20% attenuation of dose under the magnet rim was observed. Peripheral dose measurements at the centre of the magnet show an 8% increase in surface dose and a 6% decrease in dose at 1cm depth. Dose under the magnet rim was reduced by approximately 68%, 45% and 25% for MOSFET placed at 0.0, 0.5 and 1.0cm bolus depths, respectively. Conclusions: The magnetic field has an insignificant effect on MOSFET dose measurements. Dose to the central region of CIED represented by centre of the magnet doughnut increases at the surface, and decreases at depths due to low energy scattering contributions from the magnet. Dose under the magnet rim, representing CIED edges, decreased significantly due to shielding.

  10. Geodetic precession in squashed Kaluza-Klein black hole spacetimes

    SciTech Connect

    Matsuno, Ken; Ishihara, Hideki

    2009-11-15

    We investigate the geodetic precession effect of a parallelly transported spin vector along a circular geodesic in five-dimensional squashed Kaluza-Klein black hole spacetime. Then we derive the higher-dimensional correction of the precession angle to general relativity. We find that the correction is proportional to the square of (size of extra dimension)/(gravitational radius of central object)

  11. precession: Dynamics of spinning black-hole binaries with python

    NASA Astrophysics Data System (ADS)

    Gerosa, Davide; Kesden, Michael

    2016-06-01

    We present the numerical code precession, a new open-source python module to study the dynamics of precessing black-hole binaries in the post-Newtonian regime. The code provides a comprehensive toolbox to (i) study the evolution of the black-hole spins along their precession cycles, (ii) perform gravitational-wave-driven binary inspirals using both orbit-averaged and precession-averaged integrations, and (iii) predict the properties of the merger remnant through fitting formulas obtained from numerical-relativity simulations. precession is a ready-to-use tool to add the black-hole spin dynamics to larger-scale numerical studies such as gravitational-wave parameter estimation codes, population synthesis models to predict gravitational-wave event rates, galaxy merger trees and cosmological simulations of structure formation. precession provides fast and reliable integration methods to propagate statistical samples of black-hole binaries from/to large separations where they form to/from small separations where they become detectable, thus linking gravitational-wave observations of spinning black-hole binaries to their astrophysical formation history. The code is also a useful tool to compute initial parameters for numerical-relativity simulations targeting specific precessing systems. precession can be installed from the python Package Index, and it is freely distributed under version control on github, where further documentation is provided.

  12. Established and emerging cardiovascular magnetic resonance techniques for the assessment of stable coronary heart disease and acute coronary syndromes

    PubMed Central

    Ripley, David P.; Motwani, Manish; Plein, Sven

    2014-01-01

    Coronary heart disease (CHD) is a leading cause of death and disability worldwide. International guidelines recommend cardiovascular magnetic resonance (CMR) as an investigative option in those presenting with chest pain to inform diagnosis, risk stratify and determine the need for revascularization. CMR offers a unique method to assess global and regional cardiac function, myocardial perfusion, myocardial viability, tissue characterisation and proximal coronary anatomy all within a single study. This results in high diagnostic accuracy for the detection of significant coronary stenoses and an established role in the management of both stable CHD and acute coronary syndromes (ACS). The growing evidence base for the prognostic value of CMR, emerging advances in acquisition techniques, improvements in hardware and the completion of current major multi-centre clinical CMR trials will further raise its prominence in international guidelines and routine cardiological practice. This article will focus on the rapidly evolving role of the multi-parametric CMR examination in the assessment of patients with stable and unstable CHD. PMID:25392820

  13. Is there a place for cardiovascular magnetic resonance conditional devices in systemic inflammatory diseases?

    PubMed

    Mavrogeni, Sophie I; Poulos, George; Sfikakis, Petros P; Kitas, George D; Kolovou, Genovefa; Theodorakis, George

    2016-06-01

    Rhythm disturbances and sudden cardiac death (SCD) are important manifestations of cardiac involvement in systemic inflammatory diseases (SID). The commonest events demanding the implantation of a device include ventricular tachycardia and atrioventricular block, mainly diagnosed in sarcoidosis, systemic lupus erythematosus and scleroderma. In SCD, cardiac magnetic resonance (CMR) identified areas of late gadolinium enhancement (LGE) in 71% and provided an arrhythmic substrate in 76%, while during the follow-up, the extent of LGE identified a subgroup at increased risk for future adverse events. CMR has been successfully used for detection of cardiac disease in SID, including myocarditis, coronary, microvascular and valvular disease. Additionally, SIDs have a higher probability to need MRI scanning of other organs, due to their systemic disease. These reasons support the necessity of an MRI conditional device in SIDs. A broad selection of devices, approved for the MRI environment under defined conditions allows the safe and accurate scanning of SID patients. PMID:26878099

  14. Aortic Relative Pressure Components Derived from Four-Dimensional Flow Cardiovascular Magnetic Resonance

    PubMed Central

    Lamata, Pablo; Pitcher, Alex; Krittian, Sebastian; Nordsletten, David; Bissell, Malenka M; Cassar, Thomas; Barker, Alex J; Markl, Michael; Neubauer, Stefan; Smith, Nicolas P

    2014-01-01

    Purpose To describe the assessment of the spatiotemporal distribution of relative aortic pressure quantifying the magnitude of its three major components. Methods Nine healthy volunteers and three patients with aortic disease (bicuspid aortic valve, dissection, and Marfan syndrome) underwent 4D-flow CMR. Spatiotemporal pressure maps were computed from the CMR flow fields solving the pressure Poisson equation. The individual components of pressure were separated into time-varying inertial (“transient”), spatially varying inertial (“convective”), and viscous components. Results Relative aortic pressure is primarily caused by transient effects followed by the convective and small viscous contributions (64.5, 13.6, and 0.3 mmHg/m, respectively, in healthy subjects), although regional analysis revealed prevalent convective effects in specific contexts, e.g., Sinus of Valsalva and aortic arch at instants of peak velocity. Patients showed differences in peak transient values and duration, and localized abrupt convective changes explained by abnormalities in aortic geometry, including the presence of an aneurysm, a pseudo-coarctation, the inlet of a dissection, or by complex flow patterns. Conclusion The evaluation of the three components of relative pressure enables the quantification of mechanistic information for understanding and stratifying aortic disease, with potential future implications for guiding therapy. Magn Reson Med 72:1162–1169, 2014. © 2013 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. 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. PMID:24243444

  15. In vitro study on the feasibility of magnetic stent hyperthermia for the treatment of cardiovascular restenosis.

    PubMed

    Li, Li; Wang, Rui; Shi, Huan-Huan; Xie, LE; Li, Jing-Ding-Sha; Kong, Wei-Chao; Tang, Jin-Tian; Ke, DA-Nian; Zhao, Ling-Yun

    2013-08-01

    Thermal treatment or hyperthermia has received considerable attention in recent years due to its high efficiency, safety and relatively few side-effects. In this study, we investigated whether it was possible to utilize targeted thermal or instent thermal treatments for the treatment of restenosis following percutaneous transluminal coronary angioplasty (PTCA) through magnetic stent hyperthermia (MSH). A 316L stainless steel stent and rabbit vascular smooth muscle cells (VSMCs) were used in the present study, in which the inductive heating characteristics of the stent under alternative magnetic field (AMF) exposure, as well as the effect of MSH on the proliferation, apoptosis, cell cycle and proliferating cell nuclear antigen (PCNA) expression of the rabbit VSMCs, were evaluated. The results demonstrated that 316L stainless steel coronary stents possess ideal inductive heating characteristics under 300 kHz AMF exposure. The heating properties were shown to be affected by the field intensity of the AMF, as well as the orientation the stent axis. MSH had a significant effect on the proliferation and apoptosis of VSMCs, and the effect was temperature-dependent. While a mild temperature of 43°C demonstrated negligible effects on the growth of VSMCs, MSH treatment above 47°C effectively inhibited the VSMC proliferation and induced apoptosis. Furthermore, a 47°C treatment exhibited a significant and long-term inhibitory effect on VSMC migration. The results strongly suggested that MSH may be potentially applied in the clinic as an alternative approach for the prevention and treatment of restenosis. PMID:24137187

  16. Effect of equinoctial precession on geosynchronous earth satellites

    NASA Astrophysics Data System (ADS)

    Gurfil, P.

    The long-periodic effects of the equinoctial precession on geosynchronous Earth orbit satellites are investigated. The equations of motion in a reference frame that coprecesses with the Earth are developed, and the resulting variational equations are derived using mean classical orbital elements. The Earth gravitational model includes the J_2 and J_3 zonal harmonics, which induce the equinoctial precession due to the lunisolar gravitational torque. It is shown that the ever-growing lifetime and mass of geosynchronous Earth orbit satellites render the equinoctial precession a significant factor, which should be taken into account during mission design, as it affects north-south stationkeeping maneuvers. The equilibria of the variational equations including the zonal harmonics and the equinoctial precession are investigated and a class of stable frozen orbits which are equinoctial precession invariant is derived.

  17. Rectification and precession signals in the climate system

    NASA Astrophysics Data System (ADS)

    Huybers, P.; Wunsch, C.

    2003-10-01

    Precession of the equinoxes has no effect on the mean annual insolation, but does modulate the amplitude of the seasonal cycle. In a linear climate system, there would be no energy near the 21,000 year precession period. It is only when a non-linear mechanism rectifies the seasonal modulation that precession-period variability appears. Such rectification can arise from physical processes within the climate system, for example a dependence of ice cover only on summer maximum insolation. The possibility exists, however, that the seasonality inherent in many climate proxies will produce precession-period variability in the records independent of any precession-period variability in the climate. One must distinguish this instrumental effect from true climate responses. Careful examination of regions without seasonal cycles, for example the abyssal ocean, and the use of proxies with different seasonal responses, might permit separation of physical from instrumental effects.

  18. Meeting Highlights of the 11th Annual Scientific Sessions of the Society for Cardiovascular Magnetic Resonance, Los Angeles, February 1–3, 2008

    PubMed Central

    2008-01-01

    This paper features the most interesting presentations and discussions of the 2008 Annual Sessions of the Society for Cardiovascular Magnetic Resonance, which were held in Los Angeles from February 1 to 3, 2008. With more than 1100 attendees, this was the largest of the SCMR meetings ever. Among this year's highlights were scientific reports on CMR-based risk assessment, non-contrast tissue characterization, 3 T data, and interventional CMR. PMID:19128420

  19. Division I Working Group on `Precession and the Ecliptic'

    NASA Astrophysics Data System (ADS)

    Hilton, James L.; Capitaine, N.; Chapront, J.; Ferrandiz, J. M.; Fienga, A.; Fukushima, T.; Getino, J.; Mathews, P.; Simon, J.-L.; Soffel, M.; Vondrak, J.; Wallace, P.; Williams, J.

    2007-03-01

    The WG has conferred via email on the topics of providing a precession theory dynamically consistent with the IAU 2000A nutation theory and updating the expressions defining the ecliptic. The consensus of the WG is to recommend:(a) The terms lunisolar precession and planetary precession be replaced by precession of the equator and precession of the ecliptic, respectively.(b) The IAU adopt the P03 precession theory, of Capitaine et al (2003a, A& A 412, 567-586) for the precession of the equator (Eqs. 37) and the precession of the ecliptic (Eqs. 38); the same paper provides the polynomial developments for the P03 primary angles and a number of derived quantities for use in both the equinox based and celestial intermediate origin based paradigms.(c) The choice of precession parameters be left to the user.(d) The recommended polynomial coefficients for a number of precession angles are given in Table 1 of the WG report, including the P03 expressions set out in Tables 3-5 of Capitaine et al (2005, A& A 432, 355-367), and those of the alternative Fukushima (2003, AJ 126, 494-534) parameterization; the corresponding matrix representations are given in equations 1, 6, 11, and 22 of the WG report.(e) The ecliptic pole should be explicitly defined by the mean orbital angular momentum vector of the Earth-Moon barycenter in an inertial reference frame, and this definition should be explicitly stated to avoid confusion with older definitions. The formal WG report will be submitted, shortly to Celest. Mech. for publication and their recommendations will be submitted at the next General Assembly for adoption by the IAU.

  20. Scanning precession electron tomography for three-dimensional nanoscale orientation imaging and crystallographic analysis.

    PubMed

    Eggeman, Alexander S; Krakow, Robert; Midgley, Paul A

    2015-01-01

    Three-dimensional (3D) reconstructions from electron tomography provide important morphological, compositional, optical and electro-magnetic information across a wide range of materials and devices. Precession electron diffraction, in combination with scanning transmission electron microscopy, can be used to elucidate the local orientation of crystalline materials. Here we show, using the example of a Ni-base superalloy, that combining these techniques and extending them to three dimensions, to produce scanning precession electron tomography, enables the 3D orientation of nanoscale sub-volumes to be determined and provides a one-to-one correspondence between 3D real space and 3D reciprocal space for almost any polycrystalline or multi-phase material. PMID:26028514

  1. Scanning precession electron tomography for three-dimensional nanoscale orientation imaging and crystallographic analysis

    PubMed Central

    Eggeman, Alexander S.; Krakow, Robert; Midgley, Paul A.

    2015-01-01

    Three-dimensional (3D) reconstructions from electron tomography provide important morphological, compositional, optical and electro-magnetic information across a wide range of materials and devices. Precession electron diffraction, in combination with scanning transmission electron microscopy, can be used to elucidate the local orientation of crystalline materials. Here we show, using the example of a Ni-base superalloy, that combining these techniques and extending them to three dimensions, to produce scanning precession electron tomography, enables the 3D orientation of nanoscale sub-volumes to be determined and provides a one-to-one correspondence between 3D real space and 3D reciprocal space for almost any polycrystalline or multi-phase material. PMID:26028514

  2. Precession, Nutation and Wobble of the Earth

    NASA Astrophysics Data System (ADS)

    Dehant, V.; Mathews, P. M.

    2015-04-01

    Covering both astronomical and geophysical perspectives, this book describes changes in the Earth's orientation, specifically precession and nutation, and how they are observed and computed in terms of tidal forcing and models of the Earth's interior. Following an introduction to key concepts and elementary geodetic theory, the book describes how precise measurements of the Earth's orientation are made using observations of extra-galactic radio-sources by Very Long Baseline Interferometry techniques. It demonstrates how models are used to accurately pinpoint the location and orientation of the Earth with reference to the stars and how to determine variations in its rotation speed. A theoretical framework is also presented that describes the role played by the structure and properties of the Earth's deep interior. Incorporating suggestions for future developments in nutation theory for the next generation models, this book is ideal for advanced-level students and researche! rs in solid Earth geophysics, planetary science and astronomy.

  3. Precession electron diffraction – a topical review

    PubMed Central

    Midgley, Paul A.; Eggeman, Alexander S.

    2015-01-01

    In the 20 years since precession electron diffraction (PED) was introduced, it has grown from a little-known niche technique to one that is seen as a cornerstone of electron crystallography. It is now used primarily in two ways. The first is to determine crystal structures, to identify lattice parameters and symmetry, and ultimately to solve the atomic structure ab initio. The second is, through connection with the microscope scanning system, to map the local orientation of the specimen to investigate crystal texture, rotation and strain at the nanometre scale. This topical review brings the reader up to date, highlighting recent successes using PED and providing some pointers to the future in terms of method development and how the technique can meet some of the needs of the X-ray crystallography community. Complementary electron techniques are also discussed, together with how a synergy of methods may provide the best approach to electron-based structure analysis. PMID:25610633

  4. Solutions to the relativistic precession model

    NASA Astrophysics Data System (ADS)

    Ingram, Adam; Motta, Sara

    2014-11-01

    The relativistic precession model (RPM) can be used to obtain a precise measurement of the mass and spin of a black hole when the appropriate set of quasi-periodic oscillations is detected in the power-density spectrum of an accreting black hole. However, in previous studies, the solution of the RPM equations could be obtained only through numerical methods at a price of an intensive computational effort. Here, we demonstrate that the RPM system of equations can be solved analytically, drastically reducing the computational load, now limited to the Monte Carlo simulation necessary to estimate the uncertainties. The analytical method not only provides an easy solution to the RPM system when three oscillations are detected, but in all the cases where the detection of two simultaneous oscillations is coupled with an independent mass measurement. We also present a computationally inexpensive method to place limits on the black hole mass and spin when only two oscillations are observed.

  5. Precession electron diffraction - a topical review.

    PubMed

    Midgley, Paul A; Eggeman, Alexander S

    2015-01-01

    In the 20 years since precession electron diffraction (PED) was introduced, it has grown from a little-known niche technique to one that is seen as a cornerstone of electron crystallography. It is now used primarily in two ways. The first is to determine crystal structures, to identify lattice parameters and symmetry, and ultimately to solve the atomic structure ab initio. The second is, through connection with the microscope scanning system, to map the local orientation of the specimen to investigate crystal texture, rotation and strain at the nanometre scale. This topical review brings the reader up to date, highlighting recent successes using PED and providing some pointers to the future in terms of method development and how the technique can meet some of the needs of the X-ray crystallography community. Complementary electron techniques are also discussed, together with how a synergy of methods may provide the best approach to electron-based structure analysis. PMID:25610633

  6. Relationship between coronary flow reserve evaluated by phase-contrast cine cardiovascular magnetic resonance and serum eicosapentaenoic acid

    PubMed Central

    2013-01-01

    Background Long-term intake of long-chain n-3 polyunsaturated fatty acids (n-3 PUFAs), especially eicosapentaenoic acid (EPA) is associated with a low risk for cardiovascular disease. Phase-contrast cine cardiovascular magnetic resonance (PC cine CMR) can assess coronary flow reserve (CFR). The present study investigates the relationship between CFR evaluated by PC cine CMR and the serum EPA. Methods We studied 127 patients (male, 116 (91%); mean age, 72.2 ± 7.4 years) with known or suspected coronary artery disease (CAD). X-ray coronary angiography revealed no significant coronary arterial stenoses (defined as luminal diameter reduction ≥50% on quantitative coronary angiogram (QCA) analysis) in all study participants. Breath-hold PC cine CMR images of the coronary sinus (CS) were acquired to assess blood flow of the CS both at rest and during adenosine triphosphate (ATP) infusion. We calculated CFR as CS blood flow during ATP infusion divided by that at rest. Patients were allocated to groups according to whether they had high (n = 64, EPA ≥ 75.8 μg/mL) or low (n = 63, EPA < 75.8 μg/mL) median serum EPA. Results CFR was significantly lower in the low, than in the high EPA group (2.54 ± 1.00 vs. 2.91 ± 0.98, p = 0.038). Serum EPA positively correlated with CFR (R = 0.35, p < 0.001). We defined preserved CFR as > 2.5, which is the previously reported lower limit of normal flow reserve without obstructive CAD. Multivariate analysis revealed that EPA is an independent predictor of CFR > 2.5 (odds ratio, 1.01; 95% confidence interval, 1.00 – 1.02, p = 0.008). Conclusions The serum EPA is significantly correlated with CFR in CAD patients without significant coronary artery stenosis. PMID:24359564

  7. Quantitative myocardial perfusion imaging by cardiovascular magnetic resonance and positron emission tomography.

    PubMed

    Bratis, K; Mahmoud, I; Chiribiri, A; Nagel, E

    2013-10-01

    Recent studies have demonstrated that a detailed knowledge of the extent of angiographic coronary artery disease (CAD) is not a prerequisite for clinical decision making, and the clinical management of patients with CAD is more and more focused towards the identification of myocardial ischemia and the quantification of ischemic burden. In this view, non-invasive assessment of ischemia and in particular stress imaging techniques are emerging as preferred and non-invasive options. A quantitative assessment of regional myocardial perfusion can provide an objective estimate of the severity of myocardial injury and may help clinicians to discriminate regions of the heart that are at increased risk for myocardial infarction. Positron emission tomography (PET) has established itself as the reference standard for myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) quantification. Cardiac magnetic resonance (CMR) is increasingly used to measure MBF and MPR by means of first-pass signals, with a well-defined diagnostic performance and prognostic value. The aim of this article is to review the currently available evidence on the use of both PET and CMR for quantification of MPR, with particular attention to the studies that directly compared these two diagnostic methods. PMID:23868071

  8. ECG-based gating in ultra high field cardiovascular magnetic resonance using an independent component analysis approach

    PubMed Central

    2013-01-01

    Background In Cardiovascular Magnetic Resonance (CMR), the synchronization of image acquisition with heart motion is performed in clinical practice by processing the electrocardiogram (ECG). The ECG-based synchronization is well established for MR scanners with magnetic fields up to 3 T. However, this technique is prone to errors in ultra high field environments, e.g. in 7 T MR scanners as used in research applications. The high magnetic fields cause severe magnetohydrodynamic (MHD) effects which disturb the ECG signal. Image synchronization is thus less reliable and yields artefacts in CMR images. Methods A strategy based on Independent Component Analysis (ICA) was pursued in this work to enhance the ECG contribution and attenuate the MHD effect. ICA was applied to 12-lead ECG signals recorded inside a 7 T MR scanner. An automatic source identification procedure was proposed to identify an independent component (IC) dominated by the ECG signal. The identified IC was then used for detecting the R-peaks. The presented ICA-based method was compared to other R-peak detection methods using 1) the raw ECG signal, 2) the raw vectorcardiogram (VCG), 3) the state-of-the-art gating technique based on the VCG, 4) an updated version of the VCG-based approach and 5) the ICA of the VCG. Results ECG signals from eight volunteers were recorded inside the MR scanner. Recordings with an overall length of 87 min accounting for 5457 QRS complexes were available for the analysis. The records were divided into a training and a test dataset. In terms of R-peak detection within the test dataset, the proposed ICA-based algorithm achieved a detection performance with an average sensitivity (Se) of 99.2%, a positive predictive value (+P) of 99.1%, with an average trigger delay and jitter of 5.8 ms and 5.0 ms, respectively. Long term stability of the demixing matrix was shown based on two measurements of the same subject, each being separated by one year, whereas an averaged detection

  9. P03-based precession-nutation matrices

    NASA Astrophysics Data System (ADS)

    Wallace, P.; Capitaine, N.

    2006-10-01

    The IAU WG on precession and the ecliptic has recommended the adoption of the P03 models of Capitaine et al. (2003). We discuss methods for generating the rotation matrices that transform celestial to terrestrial coordinates, taking into account frame bias (B), P03 precession (P), P03-adjusted IAU 2000A nutation (N) and Earth rotation. The NPB portion can refer either to the equinox or the celestial intermediate origin (CIO), requiring either the Greenwich sidereal time (GST) or the Earth rotation angle (ERA) as the measure of Earth rotation. The equinox based NPB transformation can be formed using various sequences of rotations, while the CIO based transformation can be formed using series for the X, Y coordinates of the celestial intermediate pole (CIP) and for the CIO locator s; also, either matrix can be computing using series for the x, y, z components of the "rotation vector". Common to both methods is the CIP, which forms the bottom row of the transformation matrix. In the case of the CIO based transformation, the CIO is the top row of the NPB matrix, whereas in the equinox based case it enters via the GST formulation in the form of the equation of the origins (EO). The EO is the difference between ERA and GST and equivalently the distance between the CIO and equinox. The choice of method is dictated by considerations of internal consistency, flexibility and ease of use; the different ways agree at the level of a few microarcseconds over several centuries, and consume similar computing resources.

  10. Precession of the isolated neutron star PSR B1828-11

    NASA Astrophysics Data System (ADS)

    Akgün, Taner; Link, Bennett; Wasserman, Ira

    2006-01-01

    Stairs, Lyne & Shemar have found that the arrival-time residuals from PSR B1828-11 vary periodically with a period ~500 d. This behaviour can be accounted for by precession of the radio pulsar, an interpretation that is reinforced by the detection of variations in its pulse profile on the same time-scale. Here, we model the period residuals from PSR B1828-11 in terms of precession of a triaxial rigid body. We include two contributions to the residuals: (i) the geometric effect, which arises because the times at which the pulsar emission beam points towards the observer varies with precession phase; and (ii) the spin-down contribution, which arises from any dependence of the spin-down torque acting on the pulsar on the angle between its spin and magnetic axes. We use the data to probe numerous properties of the pulsar, most notably its shape, and the dependence of its spin-down torque on , for which we assume the sum of a spin-aligned component (with a weight 1 -a) and a dipolar component perpendicular to the magnetic beam axis (weight a), rather than the vacuum dipole torque (a= 1). We find that a variety of shapes are consistent with the residuals, with a slight statistical preference for a prolate star. Moreover, a range of torque possibilities fit the data equally well, with no strong preference for the vacuum model. In the case of a prolate star, we find evidence for an angle-dependent spin-down torque. Our results show that the combination of geometrical and spin-down effects associated with precession can account for the principal features of the timing behaviour of PSR B1828-11, without fine tuning of the parameters.

  11. Three-Directional Evaluation of Mitral Flow in the Rat Heart by Phase-Contrast Cardiovascular Magnetic Resonance

    PubMed Central

    Skårdal, Kristine; Espe, Emil KS; Zhang, Lili; Aronsen, Jan Magnus; Sjaastad, Ivar

    2016-01-01

    Purpose Determination of mitral flow is an important aspect in assessment of cardiac function. Traditionally, mitral flow is measured by Doppler echocardiography which suffers from several challenges, particularly related to the direction and the spatial inhomogeneity of flow. These challenges are especially prominent in rodents. The purpose of this study was to establish a cardiovascular magnetic resonance (CMR) protocol for evaluation of three-directional mitral flow in a rodent model of cardiac disease. Materials and Methods Three-directional mitral flow were evaluated by phase contrast CMR (PC-CMR) in rats with aortic banding (AB) (N = 7) and sham-operated controls (N = 7). Peak mitral flow and deceleration rate from PC-CMR was compared to conventional Doppler echocardiography. The accuracy of PC-CMR was investigated by comparison of spatiotemporally integrated mitral flow with left ventricular stroke volume assessed by cine CMR. Results PC-CMR portrayed the spatial distribution of mitral flow and flow direction in the atrioventricular plane throughout diastole. Both PC-CMR and echocardiography demonstrated increased peak mitral flow velocity and higher deceleration rate in AB compared to sham. Comparison with cine CMR revealed that PC-CMR measured mitral flow with excellent accuracy. Echocardiography presented significantly lower values of flow compared to PC-CMR. Conclusions For the first time, we show that PC-CMR offers accurate evaluation of three-directional mitral blood flow in rodents. The method successfully detects alterations in the mitral flow pattern in response to cardiac disease and provides novel insight into the characteristics of mitral flow. PMID:26930073

  12. Potential clinical impact of cardiovascular magnetic resonance assessment of ejection fraction on eligibility for cardioverter defibrillator implantation

    PubMed Central

    2012-01-01

    Background For the primary prevention of sudden cardiac death, guidelines provide left ventricular ejection fraction (EF) criteria for implantable cardioverter defibrillator (ICD) placement without specifying the technique by which it should be measured. We sought to investigate the potential impact of performing cardiovascular magnetic resonance (CMR) for EF on ICD eligibility. Methods The study population consisted of patients being considered for ICD implantation who were referred for EF assessment by CMR. Patients who underwent CMR within 30 days of echocardiography were included. Echocardiographic EF was determined by Simpson’s biplane method and CMR EF was measured by Simpson’s summation of discs method. Results Fifty-two patients (age 62±15 years, 81% male) had a mean EF of 38 ± 14% by echocardiography and 35 ± 14% by CMR. CMR had greater reproducibility than echocardiography for both intra-observer (ICC, 0.98 vs 0.94) and inter-observer comparisons (ICC 0.99 vs 0.93). The limits of agreement comparing CMR and echocardiographic EF were – 16 to +10 percentage points. CMR resulted in 11 of 52 (21%) and 5 of 52 (10%) of patients being reclassified regarding ICD eligibility at the EF thresholds of 35 and 30% respectively. Among patients with an echocardiographic EF of between 25 and 40%, 9 of 22 (41%) were reclassified by CMR at either the 35 or 30% threshold. Echocardiography identified only 1 of the 6 patients with left ventricular thrombus noted incidentally on CMR. Conclusions CMR resulted in 21% of patients being reclassified regarding ICD eligibility when strict EF criteria were used. In addition, CMR detected unexpected left ventricular thrombus in almost 10% of patients. Our findings suggest that the use of CMR for EF assessment may have a substantial impact on management in patients being considered for ICD implantation. PMID:23043729

  13. A Novel Approach to Early Detection of Doxorubicin Cardiotoxicity using Gadolinium Enhanced Cardiovascular Magnetic Resonance Imaging in an Experimental Model

    PubMed Central

    Lightfoot, James C.; D'Agostino, Ralph B.; Hamilton, Craig A; Jordan, Jennifer; Torti, Frank M.; Kock, Nancy D.; Jordan, James; Workman, Susan; Hundley, W Gregory

    2011-01-01

    Background To determine if cardiovascular magnetic resonance (CMR) measures of gadolinium (Gd) signal intensity (SI) within the left ventricular (LV) myocardium are associated with future changes in LV ejection fraction (LVEF) after receipt of doxorubicin (DOX). Methods and Results Forty Sprague-Dawley rats were divided into 3 groups scheduled to receive weekly intravenous doses of: normal saline (NS) (n=7), 1.5 mg/kg DOX (n=19), or 2.5 mg/kg DOX (n=14). MR determinations of LVEF and myocardial Gd-SI were performed before and then at 2, 4, 7, and 10 weeks after DOX initiation. During treatment, animals were sacrificed at different time points so that histopathological assessments of the LV myocardium could be obtained. Within group analyses were performed to examine time-dependent relationships between Gd-SI and primary events (a deterioration in LVEF or an unanticipated death). Six of 19 animals receiving 1.5 mg/kg of DOX and 10/14 animals receiving 2.5 mg/kg of DOX experienced a primary event; no NS animals experienced a primary event. In animals with a primary event, histopathological evidence of myocellular vacuolization occurred (p=0.04), and the Gd-SI was elevated relative to baseline at the time of the event (p<0.0001) and during the measurement period prior to the event (p=0.0001). In all animals (including NS) without an event, measures of Gd-SI did not differ from baseline. Conclusions After DOX, low serial measures of Gd-SI predict an absence of a LVEF drop or unanticipated death. An increase in Gd-SI after DOX forecasts a subsequent drop in LVEF as well as histopathologic evidence of intracellular vacuolization consistent with DOX cardiotoxicity. PMID:20622140

  14. Cine and tagged cardiovascular magnetic resonance imaging in normal rat at 1.5 T: a rest and stress study

    PubMed Central

    Daire, Jean-Luc; Jacob, Jean-Pascal; Hyacinthe, Jean-Noel; Croisille, Pierre; Montet-Abou, Karin; Richter, Sophie; Botsikas, Diomidis; Lepetit-Coiffé, Matthieu; Morel, Denis; Vallée, Jean-Paul

    2008-01-01

    Background The purpose of this study was to measure regional contractile function in the normal rat using cardiac cine and tagged cardiovascular magnetic resonance (CMR) during incremental low doses of dobutamine and at rest. Methods Five rats were investigated for invasive left ventricle pressure measurements and five additional rats were imaged on a clinical 1.5 T MR system using a cine sequence (11–20 phases per cycle, 0.28/0.28/2 mm) and a C-SPAMM tag sequence (18–25 phases per cycle, 0.63/1.79/3 mm, tag spacing 1.25 mm). For each slice, wall thickening (WT) and circumferential strains (CS) were calculated at rest and at stress (2.5, 5 and 10 μg/min/kg of dobutamine). Results Good cine and tagged images were obtained in all the rats even at higher heart rate (300–440 bpm). Ejection fraction and left ventricular (LV) end-systolic volume showed significant changes after each dobutamine perfusion dose (p < 0.001). Tagged CMR had the capacity to resolve the CS transmural gradient and showed a significant increase of both WT and CS at stress compared to rest. Intra and interobserver study showed less variability for the tagged technique. In rats in which a LV catheter was placed, dobutamine produced a significant increase of heart rate, LV dP/dtmax and LV pressure significantly already at the lowest infusion dose. Conclusion Robust cardiac cine and tagging CMR measurements can be obtained in the rat under incremental dobutamine stress using a clinical 1.5 T MR scanner. PMID:18980685

  15. Forward and Backward Precession of a Vertical Anisotropically Supported Rotor

    NASA Astrophysics Data System (ADS)

    Muszynska, A.

    1996-04-01

    This paper presents the analytical and experimental study of a vertical, overhung imbalanced rotor supported by flexible, anisotropic bearings. The results show that existence of imbalance and shaft bow causes the synchronous forced precession of the rotor to be forward (below the first value of split balance resonance and above the second value of the split balance resonance) or backward (between the two values of the split resonance). This phenomenon is classical. The new result consists of exploring the existence of forward precession of the inboard and midspan rotor sections while the outboard disk is precessing backward. The sensitivity analysis shows which system parameters are mainly responsible for this apparently bizarre phenomenon.

  16. Refinements on precession, nutation, and wobble of the Earth

    NASA Astrophysics Data System (ADS)

    Dehant, V. Folgueira M.; Puica, M.; Van Hoolst, T.

    2015-08-01

    Most of the essential elements of the theory of nutation of the nonrigid Earth have been presented in the IAU adopted model MHB2000 (Mathews et al., 2002) considering an ellipsoidal rotating Earth, with a solid inner core, a liquid outer core, and an ellipsoidal inelastic mantle, and with a magnetic field. However in the meantime, the observed nutation amplitudes have been redetermined with a better precision. A number of relatively small significant effects have to be taken into account before one can expect to have a theoretical framework that can yield numerical results matching the precession and nutation observations. The adopted model already accounts for the existence of a geomagnetic field passing through the mantle and the fluid core regions and beyond. The model MHB2000 considers an electromagnetic torque generated by this field when the core and the mantle are moving relative to each other, which can in turn affect some nutation amplitudes (both in phase and out-of-phase) to the extent of a few hundreds of microarcsecond (μas), playing thus a significant role. The paper revisits the last adopted model in order to incorporate potential additional coupling effects at the core-mantle boundary, that can be at an observable level, such as the existence of a non-hydrostatic core-mantle boundary topography, the viscosity of the liquid core, the existence of stratification in the core, the existence of boundary layers at both sides of the core-mantle boundary.

  17. Suppression of vortex core precession in a swirling reacting flow

    NASA Astrophysics Data System (ADS)

    Litvinov, I. V.; Nazarov, A. V.; Shtork, S. I.

    2016-03-01

    The influence of combustion effect on unsteady vortex structure in the form of precessing vortex core was studied using the non-intrusive method of laser Doppler anemometry and special procedure of extracting the non-axisymmetric mode of flow fluctuations. The studies show that combustion has a significant effect on the parameters of such a core, reducing the amplitude (vortex deviation from the burner center) and increasing precession frequency. At the same time, the acoustic sensors detect almost an order reduction in the level of pressure pulsations generated by the precessing vortex core. Moreover, distributions of tangential velocity fluctuations and cross-correlation analysis show that vortex precession is quite pronounced even under the combustion conditions, bringing a significant coherent component to distributions of velocity fluctuations.

  18. GRAVITATIONAL WAVES OF JET PRECESSION IN GAMMA-RAY BURSTS

    SciTech Connect

    Sun Mouyuan; Liu Tong; Gu Weimin; Lu Jufu

    2012-06-10

    The physical nature of gamma-ray bursts (GRBs) is believed to involve an ultra-relativistic jet. The observed complex structure of light curves motivates the idea of jet precession. In this work, we study the gravitational waves of jet precession based on neutrino-dominated accretion disks around black holes, which may account for the central engine of GRBs. In our model, the jet and the inner part of the disk may precess along with the black hole, which is driven by the outer part of the disk. Gravitational waves are therefore expected to be significant from this black-hole-inner-disk precession system. By comparing our numerical results with the sensitivity of some detectors, we find that it is possible for DECIGO and BBO to detect such gravitational waves, particularly for GRBs in the Local Group.

  19. The Equivalence of Precession Phenomena in Metric Theories of Gravity

    NASA Technical Reports Server (NTRS)

    Krisher, Timothy P.

    1996-01-01

    A simple argument is presented that demonstrates clearly, without the need for detailed calculation, how geodetic precession of a gyroscope and the effect of fram-draggin are fundamentally equivalent.

  20. Determination of the spin-lifetime anisotropy in graphene using oblique spin precession

    PubMed Central

    Raes, Bart; Scheerder, Jeroen E.; Costache, Marius V.; Bonell, Frédéric; Sierra, Juan F.; Cuppens, Jo; Van de Vondel, Joris; Valenzuela, Sergio O.

    2016-01-01

    We determine the spin-lifetime anisotropy of spin-polarized carriers in graphene. In contrast to prior approaches, our method does not require large out-of-plane magnetic fields and thus it is reliable for both low- and high-carrier densities. We first determine the in-plane spin lifetime by conventional spin precession measurements with magnetic fields perpendicular to the graphene plane. Then, to evaluate the out-of-plane spin lifetime, we implement spin precession measurements under oblique magnetic fields that generate an out-of-plane spin population. We find that the spin-lifetime anisotropy of graphene on silicon oxide is independent of carrier density and temperature down to 150 K, and much weaker than previously reported. Indeed, within the experimental uncertainty, the spin relaxation is isotropic. Altogether with the gate dependence of the spin lifetime, this indicates that the spin relaxation is driven by magnetic impurities or random spin-orbit or gauge fields. PMID:27157318

  1. Determination of the spin-lifetime anisotropy in graphene using oblique spin precession.

    PubMed

    Raes, Bart; Scheerder, Jeroen E; Costache, Marius V; Bonell, Frédéric; Sierra, Juan F; Cuppens, Jo; Van de Vondel, Joris; Valenzuela, Sergio O

    2016-01-01

    We determine the spin-lifetime anisotropy of spin-polarized carriers in graphene. In contrast to prior approaches, our method does not require large out-of-plane magnetic fields and thus it is reliable for both low- and high-carrier densities. We first determine the in-plane spin lifetime by conventional spin precession measurements with magnetic fields perpendicular to the graphene plane. Then, to evaluate the out-of-plane spin lifetime, we implement spin precession measurements under oblique magnetic fields that generate an out-of-plane spin population. We find that the spin-lifetime anisotropy of graphene on silicon oxide is independent of carrier density and temperature down to 150 K, and much weaker than previously reported. Indeed, within the experimental uncertainty, the spin relaxation is isotropic. Altogether with the gate dependence of the spin lifetime, this indicates that the spin relaxation is driven by magnetic impurities or random spin-orbit or gauge fields. PMID:27157318

  2. Magnetohydrodynamic instabilities in rotating and precessing sheared flows: An asymptotic analysis

    NASA Astrophysics Data System (ADS)

    Salhi, A.; Lehner, T.; Cambon, C.

    2010-07-01

    Linear magnetohydrodynamic instabilities are studied analytically in the case of unbounded inviscid and electrically conducting flows that are submitted to both rotation and precession with shear in an external magnetic field. For given rotation and precession the possible configurations of the shear and of the magnetic field and their interplay are imposed by the “admissibility” condition (i.e., the base flow must be a solution of the magnetohydrodynamic Euler equations): we show that an “admissible” basic magnetic field must align with the basic absolute vorticity. For these flows with elliptical streamlines due to precession we undertake an analytical stability analysis for the corresponding Floquet system, by using an asymptotic expansion into the small parameter ɛ (ratio of precession to rotation frequencies) by a method first developed in the magnetoelliptical instabilities study by Lebovitz and Zweibel [Astrophys. J. 609, 301 (2004)]10.1086/420972. The present stability analysis is performed into a suitable frame that is obtained by a systematic change of variables guided by symmetry and the existence of invariants of motion. The obtained Floquet system depends on three parameters: ɛ , η (ratio of the cyclotron frequency to the rotation frequency) and χ=cosα , with α being a characteristic angle which, for circular streamlines, ɛ=0 , identifies with the angle between the wave vector and the axis of the solid body rotation. We look at the various (centrifugal or precessional) resonant couplings between the three present modes: hydrodynamical (inertial), magnetic (Alfvén), and mixed (magnetoinertial) modes by computing analytically to leading order in ɛ the instabilities by estimating their threshold, growth rate, and maximum growth rate and their bandwidths as functions of ɛ , η , and χ . We show that the subharmonic “magnetic” mode appears only for η>5/2 and at large η (≫1) the maximal growth rate of both the

  3. Pulsar state switching, timing noise and free precession

    NASA Astrophysics Data System (ADS)

    Jones, D. I.

    2012-03-01

    Recent radio pulsar observations have shown that a number of pulsars display interesting long-term periodicities in their spin-down rates. At least some of these pulsars also undergo sharp changes in pulse profile. This has been convincingly attributed to the stars abruptly switching between two different magnetospheric states. The sharpness of these transitions has been taken as evidence against free precession as the mechanism behind the long-term variations. We argue that such a conclusion is premature. By performing a simple best-fitting analysis to the data, we show that the relationship between the observed spin and modulation periods is of approximately the correct form to be accounted for by the free precession of a population of neutron stars with strained crusts, the level of strain being similar in all of the stars, and consistent with the star retaining a memory of a former faster rotation rate. We also provide an argument as to why abrupt magnetospheric changes can occur in precessing stars, and how such changes would serve to magnify the effect of precession in the timing data, making the observation of the precession more likely in those stars where such switching occurs. We describe how future observations could further test the precession hypothesis advanced here.

  4. Single-spin precessing gravitational waveform in closed form

    NASA Astrophysics Data System (ADS)

    Lundgren, Andrew; O'Shaughnessy, R.

    2014-02-01

    In coming years, gravitational-wave detectors should find black hole-neutron star (BH-NS) binaries, potentially coincident with astronomical phenomena like short gamma ray bursts. These binaries are expected to precess. Gravitational-wave science requires a tractable model for precessing binaries, to disentangle precession physics from other phenomena like modified strong field gravity, tidal deformability, or Hubble flow; and to measure compact object masses, spins, and alignments. Moreover, current searches for gravitational waves from compact binaries use templates where the binary does not precess and are ill-suited for detection of generic precessing sources. In this paper we provide a closed-form representation of the single-spin precessing waveform in the frequency domain by reorganizing the signal as a sum over harmonics, each of which resembles a nonprecessing waveform. This form enables simple analytic calculations of the Fisher matrix for use in template bank generation and coincidence metrics, and jump proposals to improve the efficiency of Markov chain Monte Carlo sampling. We have verified that for generic BH-NS binaries, our model agrees with the time-domain waveform to 2%. Straightforward extensions of the derivations outlined here (and provided in full online) allow higher accuracy and error estimates.

  5. Experimental study of fluid flows in a precessing cylindrical annulus

    NASA Astrophysics Data System (ADS)

    Lin, Yufeng; Noir, Jerome; Jackson, Andrew

    2014-04-01

    The flow inside a precessing fluid cavity has been given particular attention since the end of the 19th century in geophysical and industrial contexts. The present study aims at shedding light on the underlying mechanism by which the flow inside a precessing cylindrical annulus transitions from laminar to multiple scale complex structures. We address this problem experimentally using ultrasonic Doppler velocimetry to diagnose the fluid velocity in a rotating and precessing cylindrical annulus. When precession is weak, the flow can be described as a superposition of forced inertial modes. Above a critical value of the precession rate, the forced flow couples with two free inertial modes satisfying triadic resonance conditions, leading to the classical growth and collapse. Using a Bayesian approach, we extract the wavenumber, frequency, growth rate, and amplitude of each mode involved in the instability. In some cases, we observe for the first time ever experimentally two pairs of free modes coexisting with the forced flow. At larger precession rates, we do not observe triadic resonance any more, instead we observe several harmonics whose frequencies are integer multiples of the rotation frequency.

  6. Assessment of global myocardial perfusion reserve using cardiovascular magnetic resonance of coronary sinus flow at 3 Tesla

    PubMed Central

    2014-01-01

    Background Despite increasing clinical use, there is limited data regarding regadenoson in stress perfusion cardiovascular magnetic resonance (CMR). In particular, given its long half-life the optimal stress protocol remains unclear. Although Myocardial Perfusion Reserve (MPR) may provide additive prognostic information, current techniques for its measurement are cumbersome and challenging for routine clinical practice. The aims of this study were: 1) To determine the feasibility of MPR quantification during regadenoson stress CMR by measurement of Coronary Sinus (CS) flow; and 2) to investigate the role of aminophylline reversal during regadenoson stress-CMR. Methods 117 consecutive patients with possible myocardial ischemia were prospectively enrolled. Perfusion imaging was performed at 1 minute and 15 minutes after administration of 0.4 mg regadenoson. A subgroup of 41 patients was given aminophylline (100 mg) after stress images were acquired. CS flow was measured using phase-contrast imaging at baseline (pre CS flow), and immediately after the stress (peak CS flow) and rest (post CS flow) perfusion images. Results CS flow measurements were obtained in 92% of patients with no adverse events. MPR was significantly underestimated when calculated as peak CS flow/post CS flow as compared to peak CS flow/pre CS flow (2.43 ± 0.20 vs. 3.28 ± 0.32, p = 0.03). This difference was abolished when aminophylline was administered (3.35 ± 0.44 vs. 3.30 ± 0.52, p = 0.95). Impaired MPR (peak CS flow/pre CS flow <2) was associated with advanced age, diabetes, current smoking and higher Framingham risk score. Conclusions Regadenoson stress CMR with MPR measurement from CS flow can be successfully performed in most patients. This measurement of MPR appears practical to perform in the clinical setting. Residual hyperemia is still present even 15 minutes after regadenoson administration, at the time of resting-perfusion acquisition, and is completely

  7. Comparison of different electrocardiographic scoring systems for detection of any previous myocardial infarction as assessed with cardiovascular magnetic resonance imaging.

    PubMed

    Jaarsma, Caroline; Bekkers, Sebastiaan C; Haidari, Zaki; Smulders, Martijn W; Nelemans, Patricia J; Gorgels, Anton P; Crijns, Harry J; Wildberger, Joachim E; Schalla, Simon

    2013-10-15

    Although electrocardiography is frequently used as an initial test to detect or rule out previous myocardial infarction (MI), the diagnostic performance of commonly used electrocardiographic scoring systems is not well described. We aimed to determine the diagnostic accuracy of (1) the Universal Definition, (2) Minnesota ECG Code (MC), (3) Selvester QRS Score, and (4) assessment by cardiologists using late gadolinium enhancement cardiovascular magnetic resonance imaging as the reference standard. Additionally, the effect of electrocardiographic patterns and infarct characteristics on detecting previous MI was evaluated. The 3-month follow-up electrocardiograms of 78 patients with first-time reperfused ST elevation MI were pooled with electrocardiograms of 36 healthy controls. All 114 electrocardiograms were randomly analyzed, blinded to clinical and LGE-CMR data. The sensitivity of the Universal Definition, MC, Selvester QRS Score, and cardiologists to detect previous MI was 33%, 79%, 90%, and 67%, respectively; specificity 97%, 72%, 31%, and 89%, respectively; diagnostic accuracy 54%, 77%, 71%, and 74%, respectively. Probability of detecting MI by cardiologists increased with an increasing number (odds ratio [OR] 2.00, 95% confidence interval [CI] 1.30 to 3.09), width (OR 1.02, 95% CI 1.01 to 1.03), and depth (OR 1.16, 95% CI 1.07 to 1.27) of Q waves as well as increasing infarct size (OR 1.15, 95% CI 1.06 to 1.25) and transmurality (OR 1.05, 95% CI 1.01 to 1.08; p <0.05 for all). The time-consuming MC and rapid visual assessment by cardiologists achieved the best and similar diagnostic accuracies to detect previous MI. The diagnostic performance of all 4 electrocardiographic scoring systems was modest and related to the number, depth, and width of Q waves as well as increasing infarct size and transmurality. In conclusion, the exclusion of a previous MI based solely on electrocardiographic findings should be done with caution. Future studies are needed to define

  8. Cardiovascular magnetic resonance by non contrast T1-mapping allows assessment of severity of injury in acute myocardial infarction

    PubMed Central

    2012-01-01

    Background Current cardiovascular magnetic resonance (CMR) methods, such as late gadolinium enhancement (LGE) and oedema imaging (T2W) used to depict myocardial ischemia, have limitations. Novel quantitative T1-mapping techniques have the potential to further characterize the components of ischemic injury. In patients with myocardial infarction (MI) we sought to investigate whether state-of the art pre-contrast T1-mapping (1) detects acute myocardial injury, (2) allows for quantification of the severity of damage when compared to standard techniques such as LGE and T2W, and (3) has the ability to predict long term functional recovery. Methods 3T CMR including T2W, T1-mapping and LGE was performed in 41 patients [of these, 78% were ST elevation MI (STEMI)] with acute MI at 12-48 hour after chest pain onset and at 6 months (6M). Patients with STEMI underwent primary PCI prior to CMR. Assessment of acute regional wall motion abnormalities, acute segmental damaged fraction by T2W and LGE and mean segmental T1 values was performed on matching short axis slices. LGE and improvement in regional wall motion at 6M were also obtained. Results We found that the variability of T1 measurements was significantly lower compared to T2W and that, while the diagnostic performance of acute T1-mapping for detecting myocardial injury was at least as good as that of T2W-CMR in STEMI patients, it was superior to T2W imaging in NSTEMI. There was a significant relationship between the segmental damaged fraction assessed by either by LGE or T2W, and mean segmental T1 values (P < 0.01). The index of salvaged myocardium derived by acute T1-mapping and 6M LGE was not different to the one derived from T2W (P = 0.88). Furthermore, the likelihood of improvement of segmental function at 6M decreased progressively as acute T1 values increased (P < 0.0004). Conclusions In acute MI, pre-contrast T1-mapping allows assessment of the extent of myocardial damage. T1-mapping might become an important

  9. Role of Perfusion at Rest in the Diagnosis of Myocardial Infarction Using Vasodilator Stress Cardiovascular Magnetic Resonance.

    PubMed

    Patel, Mita B; Mor-Avi, Victor; Kawaji, Keigo; Nathan, Sandeep; Kramer, Christopher M; Lang, Roberto M; Patel, Amit R

    2016-04-01

    In clinical practice, perfusion at rest in vasodilator stress single-photon emission computed tomography is commonly used to confirm myocardial infarction (MI) and ischemia and to rule out artifacts. It is unclear whether perfusion at rest carries similar information in cardiovascular magnetic resonance (CMR). We sought to determine whether chronic MI is associated with abnormal perfusion at rest on CMR. We compared areas of infarct and remote myocardium in 31 patients who underwent vasodilator stress CMR (1.5 T), had MI confirmed by late gadolinium enhancement (LGE scar), and coronary angiography within 6 months. Stress perfusion imaging during gadolinium first pass was followed by reversal with aminophylline (75 to 125 mg), rest perfusion, and LGE imaging. Resting and peak-stress time-intensity curves were used to obtain maximal upslopes (normalized by blood pool upslopes), which were compared between infarcted and remote myocardial regions of interest. At rest, there was no significant difference between the slopes in the regions of interest supplied by arteries with and without stenosis >70% (0.31 ± 0.16 vs 0.26 ± 0.15 1/s), irrespective of LGE scar. However, at peak stress, we found significant differences (0.20 ± 0.11 vs 0.30 ± 0.22 1/s; p <0.05), reflecting the expected stress-induced ischemia. Similarly, at rest, there was no difference between infarcted and remote myocardium (0.27 ± 0.14 vs 0.30 ± 0.17 1/s), irrespective of stenosis, but significant differences were seen during stress (0.21 ± 0.16 vs 0.28 ± 0.18 1/s; p <0.001), reflecting inducible ischemia. In conclusion, abnormalities in myocardial perfusion at rest associated with chronic MI are not reliably detectable on CMR images. Accordingly, unlike single-photon emission computed tomography, normal CMR perfusion at rest should not be used to rule out chronic MI. PMID:26830261

  10. Guidelines and protocols for cardiovascular magnetic resonance in children and adults with congenital heart disease: SCMR expert consensus group on congenital heart disease

    PubMed Central

    2013-01-01

    Cardiovascular magnetic resonance (CMR) has taken on an increasingly important role in the diagnostic evaluation and pre-procedural planning for patients with congenital heart disease. This article provides guidelines for the performance of CMR in children and adults with congenital heart disease. The first portion addresses preparation for the examination and safety issues, the second describes the primary techniques used in an examination, and the third provides disease-specific protocols. Variations in practice are highlighted and expert consensus recommendations are provided. Indications and appropriate use criteria for CMR examination are not specifically addressed. PMID:23763839

  11. Balanced steady state-free precession (b-SSFP) imaging for MRCP: techniques and applications.

    PubMed

    Glockner, James F; Lee, Christine U

    2014-12-01

    Balanced steady state-free precession (b-SSFP) pulse sequences have a number of properties which can be useful in magnetic resonance cholangiopancreatography (MRCP), including short acquisition times, high signal-to-noise ratios, and T2/T1 contrast weighting. The utility and versatility of b-SSFP sequences for MRCP imaging are probably underappreciated, and this pictorial essay briefly discusses benefits and limitations of 2D and 3D b-SSFP techniques used in place of or in addition to conventional single-shot fast spin echo or 3D fast spin echo acquisitions and illustrates their appearance in several clinical cases. PMID:24811765

  12. Perihelion precession, polar ice and global warming

    NASA Astrophysics Data System (ADS)

    Steel, Duncan

    2013-03-01

    The increase in mean global temperature over the past 150 years is generally ascribed to human activities, in particular the rises in the atmospheric mixing ratios of carbon dioxide and other greenhouse gases since the Industrial Revolution began. Whilst it is thought that ice ages and interglacial periods are mainly initiated by multi-millennial variations in Earth's heliocentric orbit and obliquity, shorter-term orbital variations and consequent observable climatic effects over decadal/centurial timescales have not been considered significant causes of contemporary climate change compared to anthropogenic influences. Here it is shown that the precession of perihelion occurring over a century substantially affects the intra-annual variation of solar radiation influx at different locations, especially higher latitudes, with northern and southern hemispheres being subject to contrasting insolation changes. This north/south asymmetry has grown since perihelion was aligned with the winter solstice seven to eight centuries ago, and must cause enhanced year-on-year springtime melting of Arctic (but not Antarctic) ice and therefore feedback warming because increasing amounts of land and open sea are denuded of high-albedo ice and snow across boreal summer and into autumn. The accelerating sequence of insolation change now occurring as perihelion moves further into boreal winter has not occurred previously during the Holocene and so would not have been observed before by past or present civilisations. Reasons are given for the significance of this process having been overlooked until now. This mechanism represents a supplementary - natural - contribution to climate change in the present epoch and may even be the dominant fundamental cause of global warming, although anthropogenic effects surely play a role too.

  13. Report of the International Astronomical Union Division I Working Group on Precession and the Ecliptic

    NASA Astrophysics Data System (ADS)

    Hilton, J. L.; Capitaine, N.; Chapront, J.; Ferrandiz, J. M.; Fienga, A.; Fukushima, T.; Getino, J.; Mathews, P.; Simon, J.-L.; Soffel, M.; Vondrak, J.; Wallace, P.; Williams, J.

    2006-03-01

    The IAU Working Group on Precession and the Equinox looked at several solutions for replacing the precession part of the IAU 2000A precession nutation model, which is not consistent with dynamical theory. These comparisons show that the (Capitaine et al., Astron. Astrophys., 412, 2003a) precession theory, P03, is both consistent with dynamical theory and the solution most compatible with the IAU 2000A nutation model. Thus, the working group recommends the adoption of the P03 precession theory for use with the IAU 2000A nutation. The two greatest sources of uncertainty in the precession theory are the rate of change of the Earth’s dynamical flattening, ΔJ 2, and the precession rates (i.e. the constants of integration used in deriving the precession). The combined uncertainties limit the accuracy in the precession theory to approximately 2 mas cent-2.

  14. Coherent spin-transfer precession switching in orthogonal spin-torque devices

    NASA Astrophysics Data System (ADS)

    Ryan, Colm; Rowlands, Graham; Pinna, Daniele; Ye, Li; Rehm, Laura; Sluka, Volker; Kent, Andy; Ohki, Thomas

    We present experimental results in concert with macrospin simulations of the switching characteristics of orthogonal spin-transfer devices incorporating an out-of-plane magnetized polarizing layer and an in-plane magnetized spin valve device at cryogenic temperatures. Switching at 3.4K between parallel and anti-parallel spin-valve states is investigated for current pulses with varying durations from 0.1 to 1.4ns to observe the averaged response of the time dependent dynamics of the spin-transfer induced precession of the magnetization. We demonstrate high speed switching at short pulse lengths, down to 100ps, and also observe ensemble decoherence effects with longer pulses. The results show that even at cryogenic temperatures finite temperature noise is still important in the dynamics of precessional switching.

  15. High spatial and temporal resolution retrospective cine cardiovascular magnetic resonance from shortened free breathing real-time acquisitions

    PubMed Central

    2013-01-01

    Background Cine cardiovascular magnetic resonance (CMR) is challenging in patients who cannot perform repeated breath holds. Real-time, free-breathing acquisition is an alternative, but image quality is typically inferior. There is a clinical need for techniques that achieve similar image quality to the segmented cine using a free breathing acquisition. Previously, high quality retrospectively gated cine images have been reconstructed from real-time acquisitions using parallel imaging and motion correction. These methods had limited clinical applicability due to lengthy acquisitions and volumetric measurements obtained with such methods have not previously been evaluated systematically. Methods This study introduces a new retrospective reconstruction scheme for real-time cine imaging which aims to shorten the required acquisition. A real-time acquisition of 16-20s per acquired slice was inputted into a retrospective cine reconstruction algorithm, which employed non-rigid registration to remove respiratory motion and SPIRiT non-linear reconstruction with temporal regularization to fill in missing data. The algorithm was used to reconstruct cine loops with high spatial (1.3-1.8 × 1.8-2.1 mm2) and temporal resolution (retrospectively gated, 30 cardiac phases, temporal resolution 34.3 ± 9.1 ms). Validation was performed in 15 healthy volunteers using two different acquisition resolutions (256 × 144/192 × 128 matrix sizes). For each subject, 9 to 12 short axis and 3 long axis slices were imaged with both segmented and real-time acquisitions. The retrospectively reconstructed real-time cine images were compared to a traditional segmented breath-held acquisition in terms of image quality scores. Image quality scoring was performed by two experts using a scale between 1 and 5 (poor to good). For every subject, LAX and three SAX slices were selected and reviewed in the random order. The reviewers were blinded to the reconstruction approach and

  16. Rotation of rigid Venus: a complete precession-nutation model

    NASA Astrophysics Data System (ADS)

    Cottereau, L.; Souchay, J.

    2009-12-01

    Context: With the increasing knowledge of the terrestrial planets due to recent space probes it is possible to model their rotation with increasing accuracy. Despite that fact, an accurate determination of Venus precession and nutation is lacking Aims: Although Venus rotation has been studied in several aspects, a full and precise analytical model of its precession-nutation motion remains to be constructed. We propose to determine this motion with up-to-date physical parameters of the planet Methods: We adopt a theoritical framework already used for a precise precession-nutation model of the Earth, based on a Hamiltonian formulation, canonical equations and an accurate development of the perturbing function due to the Sun. Results: After integrating the disturbing function and applying the canonical equations, we can evaluate the precession constant dot{Psi} and the coefficients of nutation, both in longitude and in obliquity. We get dot{Psi} = 4474farcs35/Jcy ± 66.5 , corresponding to a precession period of 28 965.10±437 years. This result, based on recent estimations of the Venus moment of inertia is significantly different from previous estimations. The largest nutation coefficient in longitude with an argument 2 LS (where LS is the longitude of the Sun) has a 2''19 amplitude and a 112.35 d period. We show that the coefficients of nutation of Venus due to its triaxiality are of the same order of amplitude as these values due to its dynamical flattening, unlike of the Earth, for which they are negligible. Conclusions: We have constucted a complete theory of the rotation of a rigid body applied to Venus, with up-to-date determinations of its physical and rotational parameters. This allowed us to set up a new and better constrained value of the Venus precession constant and to calculate its nutation coefficients for the first time.

  17. Precessive sand ripples in intense steady shear flows.

    PubMed

    Restrepo, Juan M; Moulton, Derek E; Uys, Hermann

    2011-03-01

    We describe experimental observations of fully developed, large-amplitude bars under the action of a shearing fluid. The experiments were performed in an annular tank filled with water and sheared above by a steady motor source. The same steady shearing flow can produce a variety of different erodible bed manifestations: advective or precessive bars, which refer to bar structures with global regularity and a near-steady precession velocity; interactive bars, the structure of which depends on local rearrangements, which are in turn a response to complex background topography; and dispersive bars, which are created when an initially isolated mound of sand evolves into a train of sand ripples. Of these, the most amenable to analysis are the precessive bars. For precession bars, we find that the skin depth, which is the nondimensionalized mean-field transport rate, grows exponentially as a function of the shear velocity. From this, we arrive at an analytical expression that approximates the precession speed of the bars as a function of shear velocity. We use this to obtain a formula for sediment transport rate. However, in intense flows, the bars can get large engendering boundary layer separation, leading to a different dynamic for bar formation and evolution. Numerical flow calculations over an experimentally obtained set of precessive bars are presented and show that classical parametrizations of mass flux in terms of bottom gradients have shortcomings. Within the range of shear rates considered, a quantity that does not change appreciably in time is the aspect ratio, which is defined as the ratio of the average bar amplitude, with respect to a mean depth, to the average bar length. PMID:21517492

  18. Precessive sand ripples in intense steady shear flows

    NASA Astrophysics Data System (ADS)

    Restrepo, Juan M.; Moulton, Derek E.; Uys, Hermann

    2011-03-01

    We describe experimental observations of fully developed, large-amplitude bars under the action of a shearing fluid. The experiments were performed in an annular tank filled with water and sheared above by a steady motor source. The same steady shearing flow can produce a variety of different erodible bed manifestations: advective or precessive bars, which refer to bar structures with global regularity and a near-steady precession velocity; interactive bars, the structure of which depends on local rearrangements, which are in turn a response to complex background topography; and dispersive bars, which are created when an initially isolated mound of sand evolves into a train of sand ripples. Of these, the most amenable to analysis are the precessive bars. For precession bars, we find that the skin depth, which is the nondimensionalized mean-field transport rate, grows exponentially as a function of the shear velocity. From this, we arrive at an analytical expression that approximates the precession speed of the bars as a function of shear velocity. We use this to obtain a formula for sediment transport rate. However, in intense flows, the bars can get large engendering boundary layer separation, leading to a different dynamic for bar formation and evolution. Numerical flow calculations over an experimentally obtained set of precessive bars are presented and show that classical parametrizations of mass flux in terms of bottom gradients have shortcomings. Within the range of shear rates considered, a quantity that does not change appreciably in time is the aspect ratio, which is defined as the ratio of the average bar amplitude, with respect to a mean depth, to the average bar length.

  19. A precessing relativistic jet model for 3C 449

    NASA Technical Reports Server (NTRS)

    Gower, A. C.; Hutchings, J. B.

    1982-01-01

    It is shown that the radio structure of 3C 449 can be matched with a model in which the jets are precessing and have relativistic (beta greater-than or equal to 0.4) velocities. The best-fit model implies a precession period of about 100,000 yr and a cone angle which increases with time. A similar model may be relevant for the radio structure of 3C 31. A brief discussion of the implications for 3C 449 is given.

  20. Bounce Precession Fishbones in the National Spherical Tokamak Experiment

    SciTech Connect

    Eric Fredrickson; Liu Chen; Roscoe White Eric Fredrickson; Roscoe White

    2003-06-27

    Bursting modes are observed on the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 40 (2000) 557], which are identified as bounce-precession-frequency fishbone modes. They are predicted to be important in high-current, low-shear discharges with a significant population of trapped particles with a large mean-bounce angle, such as produced by near-tangential beam injection into a large aspect-ratio device. Such a distribution is often stable to the usual precession-resonance fishbone mode. These modes could be important in ignited plasmas, driven by the trapped-alpha-particle population.

  1. Why currently used diagnostic techniques for heart failure in rheumatoid arthritis are not enough: the challenge of cardiovascular magnetic resonance imaging.

    PubMed

    Mavrogeni, Sophie; Dimitroulas, Theodoros; Gabriel, Sherine; Sfikakis, Petros P; Pohost, Gerald M; Kitas, George D

    2014-01-01

    Rheumatoid arthritis (RA) is a multiorgan inflammatory disorder affecting approximately 1% of the population that leads to progressive joint destruction and disability. Patients with RA exhibit a high risk of cardiovascular disease, which results in premature morbidity and mortality and reduced life expectancy, when compared with the general population. Among various guises of myocardial involvement, heart failure (HF) has been recently recognized as an important contributory factor to the excess cardiovascular mortality associated with RA. HF in RA typically presents with occult clinical symptomatology and is mainly associated with structural and functional left ventricular abnormalities leading to diastolic dysfunction, while systolic myocardial performance remains well preserved. As isolated diastolic dysfunction is a predictor of high mortality, the evaluation of patients in early asymptomatic stages, when treatment targeting the heart is more likely to be effective, is of great importance. Although patient history and physical examination remain the cornerstones of HF evaluation, noninvasive imaging of cardiac chambers, coronary arteries, and great vessels may be necessary. Echocardiography, nuclear techniques, and invasive coronary angiography are already established in the routine assessment of HF; however, many aspects of HF pathophysiology in RA remain obscure, due to the limitations of currently used techniques. The capability of cardiovascular magnetic resonance (CMR) to capture early tissue changes allows timely detection of pathophysiologic phenomena of HF in RA, such as myocardial inflammation and myocardial perfusion defects, due to either macrovascular (coronary artery disease) or microvascular (vasculitis) disease. Therefore, CMR may be a useful tool for early, accurate diagnosis and research in patients with RA. PMID:25662926

  2. Triadic resonances in nonlinear simulations of a fluid flow in a precessing cylinder

    NASA Astrophysics Data System (ADS)

    Giesecke, André; Albrecht, Thomas; Gundrum, Thomas; Herault, Johann; Stefani, Frank

    2015-11-01

    We present results from three-dimensional nonlinear hydrodynamic simulations of a precession driven flow in cylindrical geometry. The simulations are motivated by a dynamo experiment currently under development at Helmholtz-Zentrum Dresden-Rossendorf in which the possibility of generating a magnetohydrodynamic dynamo will be investigated in a cylinder filled with liquid sodium and simultaneously rotating around two axes. In this study, we focus on the emergence of non-axisymmetric time-dependent flow structures in terms of inertial waves which—in cylindrical geometry—form so-called Kelvin modes. For a precession ratio (Poincaré number) {{Po}}={{{Ω }}}{{p}}/{{{Ω }}}{{c}}=0.014 considered by us, the amplitude of the forced Kelvin mode reaches up to one fourth of the rotation velocity of the cylindrical container confirming that precession provides a rather efficient flow driving mechanism even at moderate values of Po. More relevant for dynamo action might be free Kelvin modes with higher azimuthal wave number. These free Kelvin modes are triggered by nonlinear interactions and may constitute a triadic resonance with the fundamental forced mode when the height of the container matches their axial wave lengths. Our simulations reveal triadic resonances at aspect ratios close to those predicted by the linear theory except around the primary resonance of the forced mode. In that regime we still identify various free Kelvin modes, however, all of them exhibit a retrograde drift around the symmetry axis of the cylinder and none of them can be assigned to a triadic resonance. The amplitudes of the free Kelvin modes always remain below the forced mode but may reach up to 6% of the of the container’s angular velocity. The properties of the free Kelvin modes, namely their amplitude and their frequency, will be used in future simulations of the magnetic induction equation to investigate their ability to provide for dynamo action.

  3. Cardiovascular Deconditioning

    NASA Technical Reports Server (NTRS)

    Charles, John B.; Fritsch-Yelle, Janice M.; Whitson, Peggy A.; Wood, Margie L.; Brown, Troy E.; Fortner, G. William

    1999-01-01

    Spaceflight causes adaptive changes in cardiovascular function that may deleteriously affect crew health and safety. Over the last three decades, symptoms of cardiovascular changes have ranged from postflight orthostatic tachycardia and decreased exercise capacity to serious cardiac rhythm disturbances during extravehicular activities (EVA). The most documented symptom of cardiovascular dysfunction, postflight orthostatic intolerance, has affected a significant percentage of U.S. Space Shuttle astronauts. Problems of cardiovascular dysfunction associated with spaceflight are a concern to NASA. This has been particularly true during Shuttle flights where the primary concern is the crew's physical health, including the pilot's ability to land the Orbiter, and the crew's ability to quickly egress and move to safety should a dangerous condition arise. The study of astronauts during Shuttle activities is inherently more difficult than most human research. Consequently, sample sizes have been small and results have lacked consistency. Before the Extended Duration Orbiter Medical Project (EDOMP), there was a lack of normative data on changes in cardiovascular parameters during and after spaceflight. The EDOMP for the first time allowed studies on a large enough number of subjects to overcome some of these problems. There were three primary goals of the Cardiovascular EDOMP studies. The first was to establish, through descriptive studies, a normative data base of cardiovascular changes attributable to spaceflight. The second goal was to determine mechanisms of cardiovascular changes resulting from spaceflight (particularly orthostatic hypotension and cardiac rhythm disturbances). The third was to evaluate possible countermeasures. The Cardiovascular EDOMP studies involved parallel descriptive, mechanistic, and countermeasure evaluations.

  4. Cardiovascular response to physical exercise in adult patients after atrial correction for transposition of the great arteries assessed with magnetic resonance imaging

    PubMed Central

    Roest, A A W; Lamb, H J; van der Wall, E E; Vliegen, H W; van den Aardweg, J G; Kunz, P; de Roos, A; Helbing, W A

    2004-01-01

    Objective: To assess with magnetic resonance imaging (MRI) cardiovascular function in response to exercise in patients after atrial correction of transposition of the great arteries (TGA). Methods: Cardiac function at rest and during submaximal exercise was assessed with MRI in 27 patients with TGA (mean (SD) age 26 (5) years) late (23 (2) years) after atrial correction and in 14 control participants (25 (5) years old). Results: At rest, only right ventricular ejection fraction was significantly lower in patients than in controls (56 (7)% v 65 (7)%, p < 0.05). In response to exercise, increases in right ventricular end diastolic (155 (55) ml to 163 (57) ml, p < 0.05) and right ventricular end systolic volumes (70 (34) ml to 75 (36) ml, p < 0.05) were observed in patients. Furthermore, right and left ventricular stroke volumes and ejection fraction did not increase significantly in patients. Changes in right ventricular ejection fraction with exercise correlated with diminished exercise capacity (r  =  0.43, p < 0.05). Conclusions: In patients with atrially corrected TGA, MRI showed an abnormal response to exercise of both systemic right and left ventricles. Exercise MRI provides a tool for close monitoring of cardiovascular function in these patients, who are at risk for late death. PMID:15145879

  5. Precession of the Earth as the Cause of Geomagnetism: Experiments lend support to the proposal that precessional torques drive the earth's dynamo.

    PubMed

    Malkus, W V

    1968-04-19

    I have proposed that the precessional torques acting on the earth can sustain a turbulent hydromagnetic flow in the molten core. A gross balance of the Coriolis force, the Lorentz force, and the precessional force in the core fluid provided estimates of the fluid velocity and the interior magnetic field characteristic of such flow. Then these numbers and a balance of the processes responsible for the decay and regeneration of the magnetic field provided an estimate of the magnetic field external to the core. This external field is in keeping with the observations, but its value is dependent upon the speculative value for the electrical conductivity of core material. The proposal that turbulent flow due to precession can occur in the core was tested in a study of nonmagnetic laboratory flows induced by the steady precession of fluid-filled rotating spheroids. It was found that these flows exhibit both small wavelike instabilities and violent finite-amplitude instability to turbulent motion above critical values of the precession rate. The observed critical parameters indicate that a laminar flow in the core, due to the earth's precession, would have weak hydrodynamic instabilities at most, but that finite-amplitude hydromagnetic instability could lead to fully turbulent flow. PMID:17788230

  6. Existence of Exotic Torus Isomer States and Their Precession Motions

    NASA Astrophysics Data System (ADS)

    Ichikawa, Takatoshi; Matsuyanagi, Kenichi; Maruhn, Joachim A.; Itagaki, Naoyuki

    We systematically investigate the existence of exotic high-spin torus isomers and their precession motions for a series of N = Z even-even nuclei from 28Si to 56Ni. For this purpose, we use the cranked three-dimensional Hatree-Fock (HF) method in a systematic search for high-spin torus isomers and the three-dimensional time-dependent Hatree-Fock (TDHF) method for describing the precession motion of the torus isomer. We obtain high-spin torus isomers in 36Ar, 40Ca, 44Ti, 48Cr, and 52Fe. The emergence of the torus isomers is associated with the alignments of single-particle angular momenta, which is the same mechanism as found in 40Ca. We find that all the obtained torus isomers execute the precession motion at least two rotational periods. The moment of inertia about a perpendicular axis, which characterizes the precession motion, is found to be close to the classical rigid-body value.

  7. Variations of a Constant -- On the History of Precession

    NASA Astrophysics Data System (ADS)

    Kokott, W.

    The precession of the equinoxes, the phenomenon which defines one of the fundamental constants of astronomy, has been with us for more than two millennia. Discovered by Hipparchos who did notice a systematic difference of his star positions as compared with older observations, subsequently adopted by Ptolemaios, its correct value became the object of prolonged controversy. The apparent variability of the precession led to the superimposition of a so-called ''trepidation``, an oscillation of typically +/- 9 deg amplitude and 7000 years period, over a linear precession of only 26 arcsec per annum. This construction, finalized in the Alfonsine Tables (ca. 1280), did work for less than two centuries. The motion of the vernal equinox, at 39 arcsec p.a. too small from the outset, decreases according to this theory to 34 arcsec in the year 1475, the first year covered by the printed version of Johannes Regiomontanus' Ephemerides. Regiomontanus had to re-adjust his longitudes to the real situation, but the difficulties caused by the apparent nonlinearity did persist, leading to a prolonged debate which was finally put to rest by Tycho Brahe. Subsequent to Edmond Halley's successful derivation of a modern value of the precessional constant, again by comparing contemporary star positions with the Almagest catalogue, and Bradley's discovery of the nutation, the last long-term comparison of modern with Ptolemaic coordinates was published by Bode (1795). Shortly after, the analytical theory of precession was established by Bessel in his Fundamenta Astronomiae (1818).

  8. Do Jets Precess... or Even Move at All?

    NASA Astrophysics Data System (ADS)

    Nixon, Chris; King, Andrew

    2013-03-01

    Observations of accreting black holes often provoke suggestions that their jets precess. The precession is usually supposed to result from a combination of the Lense-Thirring effect and accretion disk viscosity. We show that this is unlikely for any type of black hole system, as the disk generally has too little angular momentum compared with a spinning hole to cause any significant movement of the jet direction across the sky on short timescales. Uncorrelated accretion events, as in the chaotic accretion picture of active galactic nuclei (AGNs), change AGN jet directions only on timescales >~ 107 yr. In this picture AGN jet directions are stable on shorter timescales, but uncorrelated with any structure of the host galaxy, as observed. We argue that observations of black hole jets precessing on timescales short compared to the accretion time would be a strong indication that the accretion disk, and not the standard Blandford-Znajek mechanism, is responsible for driving the jet. This would be particularly convincing in a tidal disruption event. We suggest that additional disk physics is needed to explain any jet precession on timescales short compared with the accretion time. Possibilities include the radiation warping instability, or disk tearing.

  9. Sparse representations of gravitational waves from precessing compact binaries.

    PubMed

    Blackman, Jonathan; Szilagyi, Bela; Galley, Chad R; Tiglio, Manuel

    2014-07-11

    Many relevant applications in gravitational wave physics share a significant common problem: the seven-dimensional parameter space of gravitational waveforms from precessing compact binary inspirals and coalescences is large enough to prohibit covering the space of waveforms with sufficient density. We find that by using the reduced basis method together with a parametrization of waveforms based on their phase and precession, we can construct ultracompact yet high-accuracy representations of this large space. As a demonstration, we show that less than 100 judiciously chosen precessing inspiral waveforms are needed for 200 cycles, mass ratios from 1 to 10, and spin magnitudes ≤0.9. In fact, using only the first 10 reduced basis waveforms yields a maximum mismatch of 0.016 over the whole range of considered parameters. We test whether the parameters selected from the inspiral regime result in an accurate reduced basis when including merger and ringdown; we find that this is indeed the case in the context of a nonprecessing effective-one-body model. This evidence suggests that as few as ∼100 numerical simulations of binary black hole coalescences may accurately represent the seven-dimensional parameter space of precession waveforms for the considered ranges. PMID:25062160

  10. Comparing post-Newtonian and numerical relativity precession dynamics

    NASA Astrophysics Data System (ADS)

    Ossokine, Serguei; Boyle, Michael; Kidder, Lawrence E.; Pfeiffer, Harald P.; Scheel, Mark A.; Szilágyi, Béla

    2015-11-01

    Binary black-hole systems are expected to be important sources of gravitational waves for upcoming gravitational-wave detectors. If the spins are not colinear with each other or with the orbital angular momentum, these systems exhibit complicated precession dynamics that are imprinted on the gravitational waveform. We develop a new procedure to match the precession dynamics computed by post-Newtonian (PN) theory to those of numerical binary black-hole simulations in full general relativity. For numerical relativity (NR) simulations lasting approximately two precession cycles, we find that the PN and NR predictions for the directions of the orbital angular momentum and the spins agree to better than ˜1 ° with NR during the inspiral, increasing to 5° near merger. Nutation of the orbital plane on the orbital time scale agrees well between NR and PN, whereas nutation of the spin direction shows qualitatively different behavior in PN and NR. We also examine how the PN equations for precession and orbital-phase evolution converge with PN order, and we quantify the impact of various choices for handling partially known PN terms.

  11. Wigner-Thomas spin precession in polarized coincidence electronuclear scattering

    SciTech Connect

    Dmitrasinovic, V. )

    1993-05-01

    The role of the Wigner-Thomas precession in nucleon recoil polarization measurements in coincidence electron scattering processes is examined. The necessary formalism is developed within the framework of the Jacob-Wick method, and then applied to two processes: the pseudoscalar electroproduction off a nucleon and the deuteron two-body electrodisintegration.

  12. Comparing Post-Newtonian and Numerical-Relativity Precession Dynamics

    NASA Astrophysics Data System (ADS)

    Kidder, Lawrence; Ossokine, Sergei; Boyle, Michael; Pfeiffer, Harald; Scheel, Mark; Szilagyi, Bela

    2015-04-01

    Binary black-hole systems are expected to be important sources of gravitational waves for upcoming gravitational-wave detectors. If the spins are not colinear with each other or with the orbital angular momentum, these systems exhibit complicated precession dynamics that are imprinted on the gravitational waveform. We develop a new procedure to match the precession dynamics computed by post-Newtonian (PN) theory to those of numerical binary black-hole simulations in full general relativity. For numerical relativity (NR) simulations lasting approximately two precession cycles, we find that the PN and NR predictions for the directions of the orbital angular momentum and the spins agree to better than ~1° with NR during the inspiral, increasing to 5° near merger. Nutation of the orbital plane on the orbital time-scale agrees well between NR and PN, whereas nutation of the spin direction shows qualitatively different behavior in PN and NR. We also examine how the PN equations for precession and orbital-phase evolution converge with PN order, and we quantify the impact of various choices for handling partially known PN terms.

  13. Predicting Mercury's precession using simple relativistic Newtonian dynamics

    NASA Astrophysics Data System (ADS)

    Friedman, Y.; Steiner, J. M.

    2016-03-01

    We present a new simple relativistic model for planetary motion describing accurately the anomalous precession of the perihelion of Mercury and its origin. The model is based on transforming Newton's classical equation for planetary motion from absolute to real spacetime influenced by the gravitational potential and introducing the concept of influenced direction.

  14. Magnetism of outdoor and indoor settled dust and its utilization as a tool for revealing the effect of elevated particulate air pollution on cardiovascular mortality

    NASA Astrophysics Data System (ADS)

    Jordanova, Diana; Jordanova, Neli; Lanos, Philippe; Petrov, Petar; Tsacheva, Tsenka

    2012-08-01

    Settled indoor and outdoor dusts in urban environment represent an important source of secondary pollution. Magnetic characteristics of the settled dust from six cities in Bulgaria are explored, allowing comparison on a national (country) scale. Monthly variations of the mass-specific magnetic susceptibilities (χindoor) and (χoutdoor) and calculated dust loading rates for a period of 17 months do not show seasonal variability, probably due to the dominant role of traffic-related emissions and soil-derived particles in the settled dust. The main magnetic mineral is magnetite, present as spherules and irregular particles of pseudo-single-domain grain sizes. Systematically lower remanence coercivities are obtained for outdoor dusts when compared with the corresponding indoor samples, implying that penetration of smaller particles of ambient origin indoors is the main source of the indoor dust. Mean yearly values of the ratio (χindoor/χoutdoor) for each city show statistically significant correlation with mortality due to cardiovascular diseases. This ratio reveals the source- and site-specific importance of the anthropogenically derived toxicogenic fraction. Heavy metal content of the settled dust is related to the contribution from several pollution sources (soil-derived, combustion and industrial), discriminated through analysis of principal components. SEM/EDX analyses reveal abundant presence of anthopogenic Fe-containing spherules, irregular particles and diesel exhaust conglomerates. High molecular weight polyaromatic hydrocarbons (PAH) dominate the total PAH content of the outdoor dust samples. The observed linear correlation between total PAH content, coercivity of remanence and the ratio Mrs/χ suggest either adsorption of PAHs on iron oxide particles and especially magnetite, or emission related increase in total PAH concentration along with a decrease of effective magnetic grain size of the accompanying magnetic fraction.

  15. Lense-Thirring precession around neutron stars with known spin

    NASA Astrophysics Data System (ADS)

    Van Doesburgh, Marieke; van der Klis, Michiel

    2016-07-01

    Quasi periodic oscillations (QPOs) between 300 and 1200 Hz in the X-ray emission from low mass X-ray binaries have been linked to Keplerian orbital motion at the inner edge of accretion disks. Lense-Thirring precession is precession of the line of nodes of inclined orbits with respect to the equatorial plane of a rotating object due to the general relativistic effect of frame dragging. The Lense-Thirring model of Stella and Vietri (1998) explains QPOs observed in neutron star low mass X-ray binaries at frequencies of a few tens of Hz by the nodal precession of the orbits at the inner disk edge at a precession frequency, ν_{LT} , identical to the Lense-Thirring precession of a test particle orbit. A quadratic relation between ν_{LT} and the Keplerian orbital frequency, and a linear dependence on spin frequency are predicted. In early work (van Straaten et al., 2003) this quadratic relation was confirmed to remarkable precision in three objects of uncertain spin. Since the initial work, many neutron star spin frequencies have been measured in X-ray sources that show QPOs at both low and high frequency. Using archival data from the Rossi X-ray Timing Explorer, we compare the Lense-Thirring prediction to the properties of quasi periodic oscillations measured in a sample of 14 low mass X-ray binaries of which the neutron star spin frequencies can be inferred from their bursting behaviour. We find that in the range predicted for the precession frequency, we can distinguish two different oscillations that often occur simultaneously. In previous works, these two oscillations have often been confused. For both frequencies, we find correlations with inferred Keplerian frequency characterized by power laws with indices that differ significantly from the prediction of 2.0 and therefore inconsistent with the Lense-Thirring model. Also, the specific moment of inertia of the neutron star required by the observed frequencies exceeds values predicted for realistic equations of

  16. 2014 Korean Guidelines for Appropriate Utilization of Cardiovascular Magnetic Resonance Imaging: A Joint Report of the Korean Society of Cardiology and the Korean Society of Radiology

    PubMed Central

    Yoon, Yeonyee E.; Hong, Yoo Jin; Kim, Hyung-Kwan; Kim, Jeong A; Na, Jin Oh; Yang, Dong Hyun

    2014-01-01

    Cardiac magnetic resonance (CMR) imaging is now widely used in several fields of cardiovascular disease assessment due to recent technical developments. CMR can give physicians information that cannot be found with other imaging modalities. However, there is no guideline which is suitable for Korean people for the use of CMR. Therefore, we have prepared a Korean guideline for the appropriate utilization of CMR to guide Korean physicians, imaging specialists, medical associates and patients to improve the overall medical system performances. By addressing CMR usage and creating these guidelines we hope to contribute towards the promotion of public health. This guideline is a joint report of the Korean Society of Cardiology and the Korean Society of Radiology. PMID:25469078

  17. 2014 Korean Guidelines for Appropriate Utilization of Cardiovascular Magnetic Resonance Imaging: A Joint Report of the Korean Society of Cardiology and the Korean Society of Radiology

    PubMed Central

    Yoon, Yeonyee E.; Hong, Yoo Jin; Kim, Hyung-Kwan; Kim, Jeong A; Na, Jin Oh; Yang, Dong Hyun

    2014-01-01

    Cardiac magnetic resonance (CMR) imaging is now widely used in several fields of cardiovascular disease assessment due to recent technical developments. CMR can give physicians information that cannot be found with other imaging modalities. However, there is no guideline which is suitable for Korean people for the use of CMR. Therefore, we have prepared a Korean guideline for the appropriate utilization of CMR to guide Korean physicians, imaging specialists, medical associates and patients to improve the overall medical system performances. By addressing CMR usage and creating these guidelines we hope to contribute towards the promotion of public health. This guideline is a joint report of the Korean Society of Cardiology and the Korean Society of Radiology. PMID:25469139

  18. Precessing Gamma Jets in the extended and evaporating galactic halo as the sources of GRBs

    NASA Astrophysics Data System (ADS)

    Fargion, Daniele; Salis, Andrea

    1996-08-01

    Precessing Gamma Jets (GJ) in binary systems located in extended or evaporating galactic halos should be the sources of GRBs. The GJ are born by Inverse Compton Scattering (ICS) of thermal photons (optical, infrared,...) onto (power law) electron jets (from GeV energies and above) produced by spinning pulsars or black holes. The thermal photons are emitted by the binary companion (or by their nearby accreting disk). The collimated GJ beam is trembling with the characteristic pulsar millisecond period and it is bent by the companion magnetic field interactions, as a lighthouse, in a nearly conical shape within the characteristic Keplerian period; an additional nutation due to the asymmetric inertial momentum may lead, in general, to aperiodic behaviour of GRB signals. SGRs are GRBs seen at the periphery of the hard energy GJ beam core. The original birth locations of GJ (SNRs, planetary nebulae, globular clusters,...) are smeared out by the high escape velocity of the system; the Neutron Star (NS) high velocity is possibly due to the asymmetric jet precession, and consequent ``rowing'' acceleration, related to the eccentricity of the binary system. The GJ power is, for realistic parameters, comparable to that needed for GRBs in an extended or evaporating galactic halo. Their detailed spectra and time evolution fit the observed data. The expected GRB source number (within present BATSE sensitivity) is tens of thousands, compatible with the allowed presence of 10-20% GRB repeaters.

  19. Electrical detection of coherent spin precession using the ballistic intrinsic spin Hall effect.

    PubMed

    Choi, Won Young; Kim, Hyung-jun; Chang, Joonyeon; Han, Suk Hee; Koo, Hyun Cheol; Johnson, Mark

    2015-08-01

    The spin-orbit interaction in two-dimensional electron systems provides an exceptionally rich area of research. Coherent spin precession in a Rashba effective magnetic field in the channel of a spin field-effect transistor and the spin Hall effect are the two most compelling topics in this area. Here, we combine these effects to provide a direct demonstration of the ballistic intrinsic spin Hall effect and to demonstrate a technique for an all-electric measurement of the Datta-Das conductance oscillation, that is, the oscillation in the source-drain conductance due to spin precession. Our hybrid device has a ferromagnet electrode as a spin injector and a spin Hall detector. Results from multiple devices with different channel lengths map out two full wavelengths of the Datta-Das oscillation. We also use the original Datta-Das technique with a single device of fixed length and measure the channel conductance as the gate voltage is varied. Our experiments show that the ballistic spin Hall effect can be used for efficient injection or detection of spin polarized electrons, thereby enabling the development of an integrated spin transistor. PMID:26005997

  20. Ballistic missile precession frequency extraction based on the Viterbi & Kalman algorithm

    NASA Astrophysics Data System (ADS)

    Wu, Longlong; Xie, Yongjie; Xu, Daping; Ren, Li

    2015-12-01

    Radar Micro-Doppler signatures are of great potential for target detection, classification and recognition. In the mid-course phase, warheads flying outside the atmosphere are usually accompanied by precession. Precession may induce additional frequency modulations on the returned radar signal, which can be regarded as a unique signature and provide additional information that is complementary to existing target recognition methods. The main purpose of this paper is to establish a more actual precession model of conical ballistic missile warhead and extract the precession parameters by utilizing Viterbi & Kalman algorithm, which improving the precession frequency estimation accuracy evidently , especially in low SNR.

  1. High-spin torus isomers and their precession motions

    NASA Astrophysics Data System (ADS)

    Ichikawa, T.; Matsuyanagi, K.; Maruhn, J. A.; Itagaki, N.

    2014-09-01

    Background: In our previous study, we found that an exotic isomer with a torus shape may exist in the high-spin, highly excited states of Ca40. The z component of the total angular momentum, Jz=60ℏ, of this torus isomer is constructed by totally aligning 12 single-particle angular momenta in the direction of the symmetry axis of the density distribution. The torus isomer executes precession motion with the rigid-body moments of inertia about an axis perpendicular to the symmetry axis. The investigation, however, has been focused only on Ca40. Purpose: We systematically investigate the existence of exotic torus isomers and their precession motions for a series of N =Z even-even nuclei from Si28 to Ni56. We analyze the microscopic shell structure of the torus isomer and discuss why the torus shape is generated beyond the limit of large oblate deformation. Method: We use the cranked three-dimensional Hartree-Fock method with various Skyrme interactions in a systematic search for high-spin torus isomers. We use the three-dimensional time-dependent Hartree-Fock method for describing the precession motion of the torus isomer. Results: We obtain high-spin torus isomers in Ar36,Ca40,Ti44,Cr48, and Fe52. The emergence of the torus isomers is associated with the alignments of single-particle angular momenta, which is the same mechanism as found in Ca40. It is found that all the obtained torus isomers execute the precession motion at least two rotational periods. The moment of inertia about a perpendicular axis, which characterizes the precession motion, is found to be close to the classical rigid-body value. Conclusions: The high-spin torus isomer of Ca40 is not an exceptional case. Similar torus isomers exist widely in nuclei from Ar36 to Fe52 and they execute the precession motion. The torus shape is generated beyond the limit of large oblate deformation by eliminating the 0s components from all the deformed single-particle wave functions to maximize their mutual

  2. Precessing rotating flows with additional shear: Stability analysis

    NASA Astrophysics Data System (ADS)

    Salhi, A.; Cambon, C.

    2009-03-01

    We consider unbounded precessing rotating flows in which vertical or horizontal shear is induced by the interaction between the solid-body rotation (with angular velocity Ω0 ) and the additional “precessing” Coriolis force (with angular velocity -ɛΩ0 ), normal to it. A “weak” shear flow, with rate 2ɛ of the same order of the Poincaré “small” ratio ɛ , is needed for balancing the gyroscopic torque, so that the whole flow satisfies Euler’s equations in the precessing frame (the so-called admissibility conditions). The base flow case with vertical shear (its cross-gradient direction is aligned with the main angular velocity) corresponds to Mahalov’s [Phys. Fluids A 5, 891 (1993)] precessing infinite cylinder base flow (ignoring boundary conditions), while the base flow case with horizontal shear (its cross-gradient direction is normal to both main and precessing angular velocities) corresponds to the unbounded precessing rotating shear flow considered by Kerswell [Geophys. Astrophys. Fluid Dyn. 72, 107 (1993)]. We show that both these base flows satisfy the admissibility conditions and can support disturbances in terms of advected Fourier modes. Because the admissibility conditions cannot select one case with respect to the other, a more physical derivation is sought: Both flows are deduced from Poincaré’s [Bull. Astron. 27, 321 (1910)] basic state of a precessing spheroidal container, in the limit of small ɛ . A Rapid distortion theory (RDT) type of stability analysis is then performed for the previously mentioned disturbances, for both base flows. The stability analysis of the Kerswell base flow, using Floquet’s theory, is recovered, and its counterpart for the Mahalov base flow is presented. Typical growth rates are found to be the same for both flows at very small ɛ , but significant differences are obtained regarding growth rates and widths of instability bands, if larger ɛ values, up to 0.2, are considered. Finally, both flow cases

  3. Precession of cylindrical dust particles in the plasma sheath

    SciTech Connect

    Banu, N.; Ticoş, C. M.

    2015-10-15

    The vertical precession of cylindrical dust particles levitated in the sheath of an rf plasma is experimentally investigated. Typically, the dust particles have two equilibrium positions depending on the orientation of their longitudinal axis: horizontal and vertical. A transition between these two states is induced by rapidly increasing the neutral gas pressure in the plasma chamber. During this transition, the cylindrical dust particles make an angle with the horizontal and rotate about their center of mass. The rotation speed increases as the dust rods aligned with the vertical axis. All dust particles will eventually end up in the vertical state while spinning fast about their longitudinal axis. Dust-dust interaction and the attracting ion wakes are possible mechanisms for inducing the observed dust precession.

  4. Spike phase precession persists after transient intrahippocampal perturbation

    PubMed Central

    Zugaro, Michaël B; Monconduit, Lénaïc; Buzsáki, György

    2007-01-01

    Oscillatory spike timing in the hippocampus is regarded as a temporal coding mechanism for space, but the underlying mechanisms are poorly understood. To contrast the predictions of the different models of phase precession, we transiently turned off neuronal discharges for up to 250 ms and reset the phase of theta oscillations by stimulating the commissural pathway in rats. After recovery from silence, phase precession continued. The phase of spikes for the first theta cycle after the perturbation was more advanced than the phase of spikes for the last theta cycle just before the perturbation. These findings indicate that phase advancement that emerges within hippocampal circuitry may be updated at the beginning of each theta cycle by extrahippocampal inputs. PMID:15592464

  5. Triadic instability of a non-resonant precessing fluid cylinder

    NASA Astrophysics Data System (ADS)

    Lagrange, Romain; Meunier, Patrice; Eloy, Christophe

    2016-06-01

    Flows forced by a precessional motion can exhibit instabilities of crucial importance, whether they concern the fuel of a flying object or the liquid core of a telluric planet. So far, stability analyses of these flows have focused on the special case of a resonant forcing. Here, we address the instability of the flow inside a precessing cylinder in the general case. We first show that the base flow forced by the cylinder precession is a superposition of a vertical or horizontal shear flow and of an infinite sum of forced modes. We then perform a linear stability analysis of this base flow by considering its triadic resonance with two free Kelvin modes. Finally, we derive the amplitude equations of the free Kelvin modes and obtain an expression of the instability threshold and growth rate. xml:lang="fr"

  6. Precession and circularization of elliptical space-tether motion

    NASA Technical Reports Server (NTRS)

    Chapel, Jim D.; Grosserode, Patrick

    1993-01-01

    In this paper, we present a simplified analytic model for predicting motion of long space tethers. The perturbation model developed here addresses skip rope motion, where each end of the tether is held in place and the middle of the tether swings with a motion similar to that of a child's skip rope. If the motion of the tether midpoint is elliptical rather than circular, precession of the ellipse complicates the procedures required to damp this motion. The simplified analytic model developed in this paper parametrically predicts the precession of elliptical skip rope motion. Furthermore, the model shows that elliptic skip rope motion will circularize when damping is present in the longitudinal direction. Compared with high-fidelity simulation results, this simplified model provides excellent predictions of these phenomena.

  7. Chaotic spin precession in anisotropic universes and fermionic dark matter

    NASA Astrophysics Data System (ADS)

    Kamenshchik, A. Yu.; Teryaev, O. V.

    2016-05-01

    We consider the precession of a Dirac particle spin in some anisotropic Bianchi universes. This effect is present already in the Bianchi-I universe. In the Bianchi-IX universe it acquires the chaotic character due to the stochasticity of the oscillatory approach to the cosmological singularity. The related helicity flip of fermions in the veryearly Universe may produce the sterile particles contributing to dark matter.

  8. Contribution of HIPPARCOS to the Determination of Precession

    NASA Astrophysics Data System (ADS)

    Vityazev, V. V.

    2002-01-01

    The IAU (1976) luni-solar precession constant was derived by Fricke from intensive study of the catalog of 512 FK4-FK4/Sup distant stars. At present, when the data from the catalog HIPPARCOS is available, it is helpful to reconsider Fricke's analysis. This paper presents a redetermination of precession based on the following new factors: (a) the accurate parallaxes of stars have been taken into account; (b) galactic rotation and other kinematics have been eliminated from the proper motions of 512 stars; (c) the systems of the FK5 and improved GC catalog were used in combination with the HIPPARCOS catalog; (d) a new method (the MOTOR) of studying stellar kinematics was used. This method is based on the decomposition of proper motions on a set of orthogonal functions. The MOTOR, in contrast to the commonly used Least Squares Procedure, provides a test for whether or not the model is compatible with the data. Derived corrections to the IAU (1976) luni-solar precession constant are consistent with the results from VLBI observations and kinematic study of modern catalogues of proper motions.

  9. Shear secondary instability in a precessing cylinder flow

    NASA Astrophysics Data System (ADS)

    Mouhali, Waleed; Lehner, Thierry; Ater Collaboration

    2015-11-01

    For a certain value of the forcing parameter, cyclones regime has been observed in our experiment involving water in a precessing cylinder. They result from an instability. We propose here to study the nature of this so-called instability. We consider first the mode coupling of two inertial waves with azimuthal wavenumber m =0 and m =1 (mode forced by the precession) in the inviscid regime (at high Re number limit) creates a differential rotation regime which has been observed in the same experiment at small enough Poincaré number ɛ (ratio of the precession to the rotation frequencies). Secondly, the radial profile of the corresponding axial mean flow vorticity shows an inflexion point leading to a localized inflectional secondary instability. We show that when ɛ is increased from low values the forced mode m =0 becomes the most instable in this induced differential rotation, which can be responsible for the observed eruptions of jets from the lateral walls of the cylinder leading to the cyclones formation within the volume from the development of an inviscid secondary shear instability.

  10. Wobbling and Precessing Jets from Warped Disks in Binary Systems

    NASA Astrophysics Data System (ADS)

    Sheikhnezami, Somayeh; Fendt, Christian

    2015-12-01

    We present results of the first ever three-dimensional (3D) magnetohydrodynamic (MHD) simulations of the accretion-ejection structure. We investigate the 3D evolution of jets launched symmetrically from single stars but also jets from warped disks in binary systems. We have applied various model setups and tested them by simulating a stable and bipolar symmetric 3D structure from a single star-disk-jet system. Our reference simulation maintains a good axial symmetry and also a bipolar symmetry for more than 500 rotations of the inner disk, confirming the quality of our model setup. We have then implemented a 3D gravitational potential (Roche potential) due by a companion star and run a variety of simulations with different binary separations and mass ratios. These simulations show typical 3D deviations from axial symmetry, such as jet bending outside the Roche lobe or spiral arms forming in the accretion disk. In order to find indications of precession effects, we have also run an exemplary parameter setup, essentially governed by a small binary separation of only ≃200 inner disk radii. This simulation shows a strong indication that we observe the onset of a jet precession caused by the wobbling of the jet-launching disk. We estimate the opening angle of the precession cone defined by the lateral motion of the jet axis to be about 4° after about 5000 dynamical time steps.

  11. S5FP: Spectrally Selective Suppression with Steady State Free Precession

    PubMed Central

    Derbyshire, J. A.; Herzka, D. A.; McVeigh, E. R.

    2007-01-01

    A method is presented that employs the inherent spectral selectivity of the Steady-State Free Precession (SSFP) pulse sequence to provide a spectral band of suppression. At TE = TR/2, SSFP partitions the magnetization into two phase-opposed spectral components. Z-storing one of these components simultaneously further excites the other, which is then suppressed by gradient crushing and RF spoiling. The Spectrally Selective Suppression with SSFP (S5FP) method is shown to provide significant attenuation of fat signals, while the water signals are essentially unaffected and provide the normal SSFP contrast. Fat suppression is achieved with relatively little temporal overhead (less than 10% reduction in temporal resolution). S5FP was validated using simulations, phantoms, and human studies. Published 2005 Wiley-Liss, Inc.† PMID:16155880

  12. Conductance dips and spin precession in a nonuniform waveguide with spin–orbit coupling

    SciTech Connect

    Malyshev, A. I. Kozulin, A. S.

    2015-07-15

    An infinite waveguide with a nonuniformity, a segment of finite length with spin–orbit coupling, is considered in the case when the Rashba and Dresselhaus parameters are identical. Analytical expressions have been derived in the single-mode approximation for the conductance of the system for an arbitrary initial spin state. Based on numerical calculations with several size quantization modes, we have detected and described the conductance dips arising when the waves are localized in the nonuniformity due to the formation of an effective potential well in it. We show that allowance for the evanescent modes under carrier spin precession in an effective magnetic field does not lead to a change in the direction of the average spin vector at the output of the system.

  13. Experiments and models of low Reynolds number flows generated by a precessing rod over a plane

    NASA Astrophysics Data System (ADS)

    Martindale, James; Camassa, Roberto; McLaughlin, Richard M.; Vicci, Leandra; Zhao, Longhua; UNC NSF RTG Fluids Team Collaboration

    2012-11-01

    Slender body asymptotics and experiments are developed to emulate dynamics biological interest such as primary cilia in developing embryos. Experiments are performed using high viscosity silicon oil with magnetically actuated precessing rod in a table-top setup. Stereoscopic Lagrangian tracking show quantified long-time agreement with an appropriately imaged slender body theory to enforce the no-slip boundary condition of the floor. In contrast, breaking symmetry by a bent rod creates additional flow components which destroy quantitative short time agreement with the theory while maintaining its qualitative features including the creation of large scale Lagrangian tori. Higher order asymptotic corrections are implemented and compared in an attempt to restore quantitative predictability. Direct comparison with 3D stereoscopic PIV measurements will be presented. NSF RTG DMS-0502266, NSF RTG DMS-0943851, and NSF DMS-1009750.

  14. Nutation and precession control of the High Energy Solar Physics (HESP) satellite

    NASA Technical Reports Server (NTRS)

    Jayaraman, C. P.; Robertson, B. P.

    1993-01-01

    The High Energy Solar Physics (HESP) spacecraft is an intermediate class satellite proposed by NASA to study solar high-energy phenomena during the next cycle of high solar activity in the 1998 to 2005 time frame. The HESP spacecraft is a spinning satellite which points to the sun with stringent pointing requirements. The natural dynamics of a spinning satellite includes an undesirable effect: nutation, which is due to the presence of disturbances and offsets of the spin axis from the angular momentum vector. The proposed Attitude Control System (ACS) attenuates nutation with reaction wheels. Precessing the spacecraft to track the sun in the north-south and east-west directions is accomplished with the use of torques from magnetic torquer bars. In this paper, the basic dynamics of a spinning spacecraft are derived, control algorithms to meet HESP science requirements are discussed and simulation results to demonstrate feasibility of the ACS concept are presented.

  15. Variable neutron star free precession in Hercules X-1 from evolution of RXTE X-ray pulse profiles with phase of the 35-d cycle

    NASA Astrophysics Data System (ADS)

    Postnov, K.; Shakura, N.; Staubert, R.; Kochetkova, A.; Klochkov, D.; Wilms, J.

    2013-10-01

    Accretion of matter on to the surface of a freely precessing neutron star (NS) with a complex non-dipole magnetic field can explain the change of X-ray pulse profiles of Her X-1 observed by RXTE with the phase of the 35-d cycle. We demonstrate this using all available measurements of X-ray pulse profiles in the 9-13 keV energy range obtained with the RXTE/Proportional Counter Array (PCA). The measured profiles guided the elaboration of a geometrical model and the definition of locations of emitting poles, arcs and spots on the NS surface which satisfactorily reproduce the observed pulse profiles and their dependence on free precession phase. We have found that the observed trend of the times of the 35-d turn-ons on the O-C diagram, which can be approximated by a collection of consecutive linear segments around the mean value, can be described by our model by assuming a variable free precession period, with a fractional period change of about a few per cent. Under this assumption and using our model, we have found that the times of phase zero of the NS free precession (which we identify with the maximum separation of the brightest spot on the NS surface with the NS spin axis) occur about 1.6 d after the mean turn-on times inside each `stable' epoch, producing a linear trend on the O-C diagram with the same slope as the observed times of turn-ons. We propose that the 2.5 per cent changes in the free precession period that occur on time scales of several to tens of 35-d cycles can be related to wandering of the principal inertia axis of the NS body due to variations in the patterns of accretion on to the NS surface. The closeness of periods of the disc precession and the NS free precession can be explained by the presence of a synchronization mechanism in the system, which modulates the dynamical interaction of the gas streams and the accretion disc with the NS free precession period.

  16. The precessing jets of 1E 1740.7-2942

    NASA Astrophysics Data System (ADS)

    Luque-Escamilla, Pedro L.; Martí, Josep; Martínez-Aroza, José

    2015-12-01

    Context. The source 1E 1740.7-2942 is believed to be one of the two prototypical microquasars towards the Galactic center region whose X-ray states strongly resemble those of Cygnus X-1. Yet, the bipolar radio jets of 1E 1740.7-2942 are very reminiscent of a radio galaxy. The true nature of the object has thus remained an open question for nearly a quarter of a century. Aims: Our main goal here is to confirm the Galactic membership of 1E 1740.7-2942 by searching for morphological changes of its extended radio jets in human timescales. This work was triggered as a result of recent positive detection of fast structural changes in the large-scale jets of the very similar source GRS 1758-258. Methods: We carried out an in-depth exploration of the Very Large Array public archives and fully recalibrated all 1E 1740.7-2942 extended data sets in the C configuration of the array. We obtained and analyzed matching beam radio maps for five epochs, covering years 1992, 1993, 1994, 1997 and 2000, with an angular resolution of a few arcseconds. Results: We clearly detected structural changes in the arc-minute jets of 1E 1740.7-2942 on timescales of roughly a year, which set a firm distance upper limit of 12 kpc. Moreover, a simple precessing twin-jet model was simultaneously fitted to the five observing epochs available. The observed changes in the jet flow are strongly suggestive of a precession period of ~1.3 yr. Conclusions: The fitting of the precession model to the data yields a distance of ~5 kpc. This value, and the observed changes, rule out any remaining doubts about the 1E 1740.7-2942 Galactic nature. To our knowledge, this microquasar is the second whose jet precession ephemeris become available after SS433. This kind of information is relevant to the physics of compact objects, since the genesis of the precession phenomenon occurs very close to the interplay region between the accretion disk and the compact object in the system. Appendix A and a movie associated to

  17. Long-term evolution of orbits about a precessing oblate planet. 2. The case of variable precession

    NASA Astrophysics Data System (ADS)

    Efroimsky, Michael

    2006-11-01

    We continue the study undertaken in Efroimsky [Celest. Mech. Dyn. Astron. 91, 75 108 (2005a)] where we explored the influence of spin-axis variations of an oblate planet on satellite orbits. Near-equatorial satellites had long been believed to keep up with the oblate primary’s equator in the cause of its spin-axis variations. As demonstrated by Efroimsky and Goldreich [Astron. Astrophys. 415, 1187 1199 (2004)], this opinion had stemmed from an inexact interpretation of a correct result by Goldreich [Astron. J. 70, 5 9 (1965)]. Although Goldreich [Astron. J. 70, 5 9 (1965)] mentioned that his result (preservation of the initial inclination, up to small oscillations about the moving equatorial plane) was obtained for non-osculating inclination, his admonition had been persistently ignored for forty years. It was explained in Efroimsky and Goldreich [Astron. Astrophys. 415, 1187 1199 (2004)] that the equator precession influences the osculating inclination of a satellite orbit already in the first order over the perturbation caused by a transition from an inertial to an equatorial coordinate system. It was later shown in Efroimsky [Celest. Mech. Dyn. Astron. 91, 75 108 (2005a)] that the secular part of the inclination is affected only in the second order. This fact, anticipated by Goldreich [Astron. J. 70, 5 9 (1965)], remains valid for a constant rate of the precession. It turns out that non-uniform variations of the planetary spin state generate changes in the osculating elements, that are linear in | \\varvec{dot{μ}} |, where \\varvec{μ} is the planetary equator’s total precession rate that includes the equinoctial precession, nutation, the Chandler wobble, and the polar wander. We work out a formalism which will help us to determine if these factors cause a drift of a satellite orbit away from the evolving planetary equator.

  18. CARDIOVASCULAR MAGNETIC RESONANCE IMAGING IN DELIVERING AND EVALUATING THE EFFICACY OF HEPATOCYTE GROWTH FACTOR GENE IN CHRONIC INFARCT SCAR

    PubMed Central

    Saeed, Maythem; Saloner, David; Do, Loi; Wilson, Mark; Martin, Alastair

    2012-01-01

    Background In open-chest model of acute infarct, epicardial delivery of hepatocyte growth factor (HGF) gene improved LV function. This study was designed to test 1) the efficacy of HGF gene in infarct scar delivered under MR guidance and 2) the potential of multiple MR sequences in assessing the effects of pCK-HGF (treatment) and pCK-LacZ (control) genes on myocardial structure and function. Methods and Materials Swine (6 per group) were subjected to myocardial infarct, under X-ray fluoroscopy, developed LV remodelling at 5weeks. Multiple clinical MR imaging sequences were performed before delivery of gene (at 5 weeks after infarction) and 5 weeks after delivery of gene. Under MR-guidance, the active endovascular catheter was introduced into LV to transendocardially deliver 3.96×1011 viral copies of pCK-HGF or pCK-LacZ in the border and core of the infarct scar. Histological evaluation of the infarct scar was performed 5 weeks after delivery of gene. Results At 5weeks after infarction, there was no significant difference in measured cardiovascular MR parameters between the groups. PCK-HGF gene caused significant improvement in the following parameters (P<0.05 for these parameters): 3D strain (radial, circumferential, and longitudinal) , perfusion (maximum upslope, peak signal intensity, and time to peak) compared with control pCK-LacZ at 5 weeks after delivery of the genes. The ejection fraction was higher in pCK-HGF treated (43±1%) than pCK-LacZ control (37±1%, P<0.05). These changes are associated with a decrease in infarct scar size (11.3±2.0% in pCK-LacZ control and 6.7±1.3%, in pCK-HGF treated, P<0.01) and transmurality in 4 out of 5 infarct scar segments (P<0.05) on DE-MR imaging. Microscopic study confirmed the increase in capillary (P<0.05), and arteriole (P<0.05) density of infarct scar in pCK-HGF treated compared with pCK-LacZ control animals. Conclusions HGF gene delivered under MR-guidance into infarct scar ameliorated global function, 3D strain

  19. Myocardial Regional Interstitial Fibrosis is Associated With Left Intra-Ventricular Dyssynchrony in Patients With Heart Failure: A Cardiovascular Magnetic Resonance Study

    PubMed Central

    Lin, Lian-Yu; Wu, Cho-Kai; Juang, Jyh-Ming Jimmy; Wang, Yi-Chih; Su, Mao-Yuan Marine; Lai, Ling-Ping; Hwang, Juey-Jen; Chiang, Fu-Tien; Tseng, Wen-Yih Issac; Lin, Jiunn-Lee

    2016-01-01

    Left ventricular (LV) dyssynchrony is associated with poor prognosis in patients with heart failure (HF). The mechanisms leading to LV dyssynchrony are not fully elucidated. This study evaluates whether myocardium regional variation in interstitial fibrosis is associated with LV dyssynchrony. Forty-two patients with systolic heart failure (SHF), 76 patients with heart failure with preserved ejection fraction (HFpEF) and 20 patients without HF received cardiovascular magnetic resonance imaging (MRI) study. LV was divided into 18 segments by short-axis view. In each segment, regional extracellular volume fraction (ECV) and the time taken to reach minimum regional volume (Tmv) were derived. Intra-LV dyssynchrony were represented by maximum difference (Dysyn_max) and standard deviation (Dysyn_sd) of all Tmv. The results showed that among the covariates, only age (1.87, 95% CI: 0.61–3.13, p = 0.004) and ECV (3.77, 95% CI: 2.72–4.81, p < 0.001) were positively associated with Tmv. The results remained robust in certain subgroups. In conclusion, we demonstrated that LV myocardium regional variation in interstitial fibrosis is closely related to LV intra-ventricular dyssynchrony irrespective of the LV global function. These data might help explain the pathophysiology of LV dyssynchrony and it’s underlying mechanisms leading to poor prognosis. PMID:26846306

  20. Molecular and Integrative Physiological Effects of Isoflurane Anesthesia: The Paradigm of Cardiovascular Studies in Rodents using Magnetic Resonance Imaging

    PubMed Central

    Constantinides, Christakis; Murphy, Kathy

    2016-01-01

    To-this-date, the exact molecular, cellular, and integrative physiological mechanisms of anesthesia remain largely unknown. Published evidence indicates that anesthetic effects are multifocal and occur in a time-dependent and coordinated manner, mediated via central, local, and peripheral pathways. Their effects can be modulated by a range of variables, and their elicited end-effect on the integrative physiological response is highly variable. This review summarizes the major cellular and molecular sites of anesthetic action with a focus on the paradigm of isoflurane (ISO) – the most commonly used anesthetic nowadays – and its use in prolonged in vivo rodent studies using imaging modalities, such as magnetic resonance imaging (MRI). It also presents established evidence for normal ranges of global and regional physiological cardiac function under ISO, proposes optimal, practical methodologies relevant to the use of anesthetic protocols for MRI and outlines the beneficial effects of nitrous oxide supplementation. PMID:27525256

  1. Evolution and precession of accretion disk in tidal disruption events

    NASA Astrophysics Data System (ADS)

    Shen, R.-F.; Matzner, C. D.

    2012-12-01

    In a supermassive black hole (BH) tidal disruption event (TDE), the tidally disrupted star feeds the BH via an accretion disk. Most often it is assumed that the accretion rate history, hence the emission light curve, tracks the rate at which new debris mass falls back onto the disk, notably the t-5/3 power law. But this is not the case when the disk evolution due to viscous spreading - the driving force for accretion - is carefully considered. We construct a simple analytical model that comprehensively describes the accretion rate history across 4 different phases of the disk evolution, in the presence of mass fallback and disk wind loss. Accretion rate evolves differently in those phases which are governed by how the disk heat energy is carried away, early on by advection and later by radiation. The accretion rate can decline as steeply as t-5/3 only if copious disk wind loss is present during the early advection-cooled phase. Later, the accretion rate history is t-8/7 or shallower. These have great implications on the TDE flare light curve. A TDE accretion disk is most likely misaligned with the equatorial plane of the spinning BH. Moreover, in the TDE the accretion rate is super- or near-Eddington thus the disk is geometrically thick, for which case the BH's frame dragging effect may cause the disk precess as a solid body, which may manifest itself as quasi-periodic signal in the TDE light curve. Our disk evolution model predicts the disk precession period increases with time, typically as ∝ t. The results are applied to the recently jetted TDE flare Swift transient J1644 + 57 which shows numerous, quasi-periodic dips in its long-term X-ray light curve. As the current TDE sample increases, the identification of the disk precession signature provides a unique way of measuring BH spin and studying BH accretion physics.

  2. Pluto and Charon: A Case of Precession-Orbit Resonance?

    NASA Technical Reports Server (NTRS)

    Rubincam, David Parry; Smith, David E. (Technical Monitor)

    2000-01-01

    Pluto may be the only known case of precession-orbit resonance in the solar system. The Pluto-Charon system orbits the Sun with a period of 1 Plutonian year, which is 250.8 Earth years. The observed parameters of the system are such that Charon may cause Pluto to precess with a period near 250.8 Earth years. This gives rise to two possible resonances, heretofore unrecognized. The first is due to Pluto's orbit being highly eccentric, giving solar torques on Charon with a period of 1 Plutonian year. Charon in turn drives Pluto near its precession period. Volatiles, which are expected to shuttle across Pluto's surface between equator and pole as Pluto's obliquity oscillates, might change the planet's dynamical flattening enough so that Pluto crosses the nearby resonance, forcing the planet's equatorial plane to depart from Charon's orbital plane. The mutual tilt can reach as much as 2 deg after integrating over 5.6 x 10(exp 6) years, depending upon how close Pluto is to the resonance and the supply of volatiles. The second resonance is due to the Sun's traveling above and below Charon's orbital plane; it has a period half that of the eccentricity resonance. Reaching this half-Plutonian year resonance requires a much larger but still theoretically possible amount of volatiles. In this case the departure of Charon from an equatorial orbit is about 1 deg after integrating for 5.6 x 10(exp 6) years. The calculations ignore libration and tidal friction. It is not presently known how large the mutual tilt can grow over the age of the solar system, but if it remains only a few degrees, then observing such small angles from a Pluto flyby mission would be difficult. It is not clear why the parameters of the Pluto-Charon system are so close to the eccentricity resonance.

  3. The forced precession of the Moon's inner core

    NASA Astrophysics Data System (ADS)

    Dumberry, Mathieu; Wieczorek, Mark A.

    2016-07-01

    The tilt angle of the 18.6 year precession of the Moon's solid inner core is unknown, but it is set by a balance between gravitational and pressure torques acting on its elliptical figure. We show here that to first order, the angle of precession of the inner core of a planetary body is determined by the frequency of the free inner core nutation, ωficn, relative to the precession frequency, Ωp. If |ωficn|≪|Ωp|, the inner core is blind to the gravitational influence of the mantle. If |ωficn|≫|Ωp|, the inner core is gravitationally locked to the mantle and is nearly aligned with it. If ωficn≈Ωp, large inner core tilt angles can result from resonant excitation. Viscous inner core relaxation and electromagnetic coupling can attenuate large tilt angles. For the specific case of the Moon, we show that ωficn is to within a factor of 2 of Ωp = 2π/18.6 yr-1. For a rigid inner core, this implies a tilt of 2 to 5° with respect to the mantle, and larger if ωficn is very close to Ωp. More modest tilt angles between 0 and 0.5° result if viscous relaxation within the inner core occurs on a timescale of one lunar day. Predictions from our model may be used in an attempt to detect the gravity signal resulting from a tilted inner core, to determine the past history of the inner core tilt angle, and to assess models of dynamo generation powered by differential rotation at the core-mantle and inner core boundaries.

  4. Cardiovascular Disease

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cardiovascular disease (CVD), particularly CHD (coronary heart disease) and stroke, remain the leading causes of death of women in America and most developed countries. In recent years the rate of CVD has declined in men but not in women. This is contributed to by an under-recognition of women’s C...

  5. Cardiovascular system

    MedlinePlus Videos and Cool Tools

    The cardiovascular system is composed of the heart and the network of arteries, veins, and capillaries that transport blood throughout the body. The ... which they are eliminated. Most of the blood is made up of a watery, protein-laden fluid ...

  6. Gravitational waves from rotating and precessing rigid bodies. 2: General solutions and computationally useful formulae

    NASA Technical Reports Server (NTRS)

    Zimmerman, M.

    1979-01-01

    The classical mechanics results for free precession which are needed in order to calculate the weak field, slow-motion, quadrupole-moment gravitational waves are reviewed. Within that formalism, algorithms are given for computing the exact gravitational power radiated and waveforms produced by arbitrary rigid-body freely-precessing sources. The dominant terms are presented in series expansions of the waveforms for the case of an almost spherical object precessing with a small wobble angle. These series expansions, which retain the precise frequency dependence of the waves, may be useful for gravitational astronomers when freely-precessing sources begin to be observed.

  7. Precession-nutation procedures consistent with IAU 2006 resolutions

    NASA Astrophysics Data System (ADS)

    Wallace, P. T.; Capitaine, N.

    2006-12-01

    Context: .The 2006 IAU General Assembly has adopted the P03 model of Capitaine et al. (2003a) recommended by the WG on precession and the ecliptic (Hilton et al. 2006) to replace the IAU 2000 model, which comprised the Lieske et al. (1977) model with adjusted rates. Practical implementations of this new "IAU 2006" model are therefore required, involving choices of procedures and algorithms. Aims: .The purpose of this paper is to recommend IAU 2006 based precession-nutation computing procedures, suitable for different classes of application and achieving high standards of consistency. Methods: .We discuss IAU 2006 based procedures and algorithms for generating the rotation matrices that transform celestial to terrestrial coordinates, taking into account frame bias (B), P03 precession (P), P03-adjusted IAU 2000A nutation (N) and Earth rotation. The NPB portion can refer either to the equinox or to the celestial intermediate origin (CIO), requiring either the Greenwich sidereal time (GST) or the Earth rotation angle (ERA) as the measure of Earth rotation. Where GST is used, it is derived from ERA and the equation of the origins (EO) rather than through an explicit formula as in the past, and the EO itself is derived from the CIO locator. Results: .We provide precession-nutation procedures for two different classes of full-accuracy application, namely (i) the construction of algorithm collections such as the Standards Of Fundamental Astronomy (SOFA) library and (ii) IERS Conventions, and in addition some concise procedures for applications where the highest accuracy is not a requirement. The appendix contains a fully worked numerical example, to aid implementors and to illustrate the consistency of the two full-accuracy procedures which, for the test date, agree to better than 1 μas. Conclusions: .The paper recommends, for case (i), procedures based on angles to represent the PB and N components and, for case (ii), procedures based on series for the CIP X,Y. The two

  8. Geometric phase and gravitational precession of D-branes

    NASA Astrophysics Data System (ADS)

    Pedder, Chris; Sonner, Julian; Tong, David

    2007-12-01

    We study Berry’s phase in the D0-D4-brane system. When a D0-brane moves in the background of D4-branes, the first excited states undergo a holonomy described by a non-Abelian Berry connection. At weak coupling this is an SU(2) connection over R5, known as the Yang monopole. At strong coupling, the holonomy is recast as the classical gravitational precession of a spinning particle. The Berry connection is the spin connection of the near-horizon limit of the D4-branes, which is a continuous deformation of the Yang and anti-Yang monopole.

  9. Accretion-disc precession in UX Ursae Majoris

    NASA Astrophysics Data System (ADS)

    de Miguel, E.; Patterson, J.; Cejudo, D.; Ulowetz, J.; Jones, J. L.; Boardman, J.; Barret, D.; Koff, R.; Stein, W.; Campbell, T.; Vanmunster, T.; Menzies, K.; Slauson, D.; Goff, W.; Roberts, G.; Morelle, E.; Dvorak, S.; Hambsch, F.-J.; Starkey, D.; Collins, D.; Costello, M.; Cook, M. J.; Oksanen, A.; Lemay, D.; Cook, L. M.; Ogmen, Y.; Richmond, M.; Kemp, J.

    2016-04-01

    We report the results of a long campaign of time series photometry on the nova-like variable UX Ursae Majoris during 2015. It spanned 150 nights, with ˜ 1800 h of coverage on 121 separate nights. The star was in its normal `high state' near magnitude V = 13, with slow waves in the light curve and eclipses every 4.72 h. Remarkably, the star also showed a nearly sinusoidal signal with a full amplitude of 0.44 mag and a period of 3.680 ± 0.007 d. We interpret this as the signature of a retrograde precession (wobble) of the accretion disc. The same period is manifest as a ±33 s wobble in the timings of mid-eclipse, indicating that the disc's centre of light moves with this period. The star also showed strong `negative superhumps' at frequencies ωorb + N and 2ωorb + N, where ωorb and N are, respectively, the orbital and precession frequencies. It is possible that these powerful signals have been present, unsuspected, throughout the more than 60 yr of previous photometric studies.

  10. Searching for gravitational waves from compact binaries with precessing spins

    NASA Astrophysics Data System (ADS)

    Harry, Ian; Privitera, Stephen; Bohé, Alejandro; Buonanno, Alessandra

    2016-07-01

    Current searches for gravitational waves from compact-object binaries with the LIGO and Virgo observatories employ waveform models with spins aligned (or antialigned) with the orbital angular momentum. Here, we derive a new statistic to search for compact objects carrying generic (precessing) spins. Applying this statistic, we construct banks of both aligned- and generic-spin templates for binary black holes and neutron star-black hole binaries, and compare the effectualness of these banks towards simulated populations of generic-spin systems. We then use these banks in a pipeline analysis of Gaussian noise to measure the increase in background incurred by using generic- instead of aligned-spin banks. Although the generic-spin banks have roughly a factor of ten more templates than the aligned-spin banks, we find an overall improvement in signal recovery at a fixed false-alarm rate for systems with high-mass ratio and highly precessing spins. This gain in sensitivity comes at a small loss of sensitivity (≲4 %) for systems that are already well covered by aligned-spin templates. Since the observation of even a single binary merger with misaligned spins could provide unique astrophysical insights into the formation of these sources, we recommend that the method described here be developed further to mount a viable search for generic-spin binary mergers in LIGO/Virgo data.

  11. THE RECENTLY DETERMINED ANOMALOUS PERIHELION PRECESSION OF SATURN

    SciTech Connect

    Iorio, Lorenzo

    2009-03-15

    The astronomer E. V. Pitjeva, by analyzing with the EPM2008 ephemerides a large number of planetary observations including also two years (2004-2006) of normal points from the Cassini spacecraft, phenomenologically estimated a statistically significant nonzero correction to the usual Newtonian/Einsteinian secular precession of the longitude of the perihelion of Saturn, i.e., {delta}{omega}-bar-dot{sub Sat} = -0.006{+-}0''.002 cy{sup -1}; the formal, statistical error is 0.''0007. It can be explained neither by any of the standard classical and general relativistic dynamical effects mismodeled/unmodeled in the force models of the EPM2008 ephemerides nor by several exotic modifications of gravity recently put forth to accommodate certain cosmological/astrophysical observations without resorting to dark energy/dark matter. Both independent analyses by other teams of astronomers and further processing of larger data sets from Cassini will be helpful in clarifying the nature and the true existence of the anomalous precession of the perihelion of Saturn.

  12. Shear-induced molecular precession in a hexatic Langmuir monolayer.

    PubMed

    Ignés-Mullol, J; Schwartz, D K

    2001-03-15

    Liquid crystalline behaviour is generally limited to a select group of specially designed bulk substances. By contrast, it is a common feature of simple molecular monolayers and other quasi-two-dimensional systems, which often possess a type of in-plane ordering that results from unbinding of dislocations-a 'hexatic' liquid crystalline phase. The flow of monolayers is closely related to molecular transport in biological membranes, affects foam and emulsion stability and is relevant to microfluidics research. For liquid crystalline phases, it is important to understand the coupling of the molecular orientation to the flow. Orientationally ordered (nematic) phases in bulk liquid crystals exhibit 'shear aligning' or 'tumbling' behaviour under shear, and are described quantitatively by Leslie-Ericksen theory. For hexatic monolayers, the effects of flow have been inferred from textures of Langmuir-Blodgett films and directly observed at the macroscopic level. However, there is no accepted model of hexatic flow at the molecular level. Here we report observations of a hexatic Langmuir monolayer that reveal continuous, shear-induced molecular precession, interrupted by occasional jump discontinuities. Although superficially similar to tumbling in a bulk nematic phase, the kinematic details are quite different and provide a possible mechanism for domain coarsening and eventual molecular alignment in monolayers. We explain the precession and jumps within a quantitative framework that involves coupling of molecular orientation to the local molecular hexatic 'lattice', which is continuously deformed by shear. PMID:11268206

  13. Impact of Heart Rate on Myocardial Salvage in Timely Reperfused Patients with ST-Segment Elevation Myocardial Infarction: New Insights from Cardiovascular Magnetic Resonance

    PubMed Central

    Arcari, Luca; Cimino, Sara; De Luca, Laura; Francone, Marco; Galea, Nicola; Reali, Manuela; Carbone, Iacopo; Iacoboni, Carlo; Agati, Luciano

    2015-01-01

    Background Previous studies evaluating the progression of the necrotic wave in relation to heart rate were carried out only in animal models of ST-elevated myocardial infarction (STEMI). Aim of the study was to investigate changes of myocardial salvage in relation to different heart rates at hospital admission in timely reperfused patients with STEMI by using cardiovascular magnetic resonance (CMR). Methods One hundred-eighty-seven patients with STEMI successfully and timely treated with primary coronary angioplasty underwent CMR five days after hospital admission. According to the heart rate at presentation, patients were subcategorized into 5 quintiles: <55 bpm (group I, n = 44), 55–64 bpm (group II, n = 35), 65–74 bpm (group III, n = 35), 75–84 bpm (group IV, n = 37), ≥85 bpm (group V, n = 36). Area at risk, infarct size, microvascular obstruction (MVO) and myocardium salvaged index (MSI) were assessed by CMR using standard sequences. Results Lower heart rates at presentation were associated with a bigger amount of myocardial salvage after reperfusion. MSI progressively decreased as the heart rates increased (0.54 group I, 0.46 group II, 0.38 group III, 0.34 group IV, 0.32 group V, p<0.001). Stepwise multivariable analysis showed heart rate, peak troponin and the presence of MVO were independent predictor of myocardial salvage. No changes related to heart rate were observed in relation to area at risk and infarct size. Conclusions High heart rates registered before performing coronary angioplasty in timely reperfused patients with STEMI are associated with a reduction in salvaged myocardium. In particular, salvaged myocardium significantly reduced when heart rate at presentation is ≥85 bpm. PMID:26716452

  14. Radial dyssynchrony assessed by cardiovascular magnetic resonance in relation to left ventricular function, myocardial scarring and QRS duration in patients with heart failure

    PubMed Central

    2009-01-01

    Background Intuitively, cardiac dyssynchrony is the inevitable result of myocardial injury. We hypothezised that radial dyssynchrony reflects left ventricular remodeling, myocardial scarring, QRS duration and impaired LV function and that, accordingly, it is detectable in all patients with heart failure. Methods 225 patients with heart failure, grouped according to QRS duration of <120 ms (A, n = 75), between 120-149 ms (B, n = 75) or ≥150 ms (C, n = 75), and 50 healthy controls underwent assessment of radial dyssynchrony using the cardiovascular magnetic resonance tissue synchronization index (CMR-TSI = SD of time to peak inward endocardial motion in up to 60 myocardial segments). Results Compared to 50 healthy controls (21.8 ± 6.3 ms [mean ± SD]), CMR-TSI was higher in A (74.8 ± 34.6 ms), B (92.4 ± 39.5 ms) and C (104.6 ± 45.6 ms) (all p < 0.0001). Adopting a cut-off CMR-TSI of 34.4 ms (21.8 plus 2xSD for controls) for the definition of dyssynchrony, it was present in 91% in A, 95% in B and 99% in C. Amongst patients in NYHA class III or IV, with a LVEF<35% and a QRS>120 ms, 99% had dyssynchrony. Amongst those with a QRS<120 ms, 91% had dyssynchrony. Across the study sample, CMR-TSI was related positively to left ventricular volumes (p < 0.0001) and inversely to LVEF (CMR-TSI = 178.3 e (-0.033 LVEF) ms, p < 0.0001). Conclusion Radial dyssynchrony is almost universal in patients with heart failure. This vies against the notion that a lack of response to CRT is related to a lack of dyssynchrony. PMID:19930713

  15. Discrepancies between cardiovascular magnetic resonance and Doppler echocardiography in the measurement of transvalvular gradient in aortic stenosis: the effect of flow vorticity

    PubMed Central

    2013-01-01

    Background Valve effective orifice area EOA and transvalvular mean pressure gradient (MPG) are the most frequently used parameters to assess aortic stenosis (AS) severity. However, MPG measured by cardiovascular magnetic resonance (CMR) may differ from the one measured by transthoracic Doppler-echocardiography (TTE). The objectives of this study were: 1) to identify the factors responsible for the MPG measurement discrepancies by CMR versus TTE in AS patients; 2) to investigate the effect of flow vorticity on AS severity assessment by CMR; and 3) to evaluate two models reconciling MPG discrepancies between CMR/TTE measurements. Methods Eight healthy subjects and 60 patients with AS underwent TTE and CMR. Strouhal number (St), energy loss (EL), and vorticity were computed from CMR. Two correction models were evaluated: 1) based on the Gorlin equation (MPGCMR-Gorlin); 2) based on a multivariate regression model (MPGCMR-Predicted). Results MPGCMR underestimated MPGTTE (bias = −6.5 mmHg, limits of agreement from −18.3 to 5.2 mmHg). On multivariate regression analysis, St (p = 0.002), EL (p = 0.001), and mean systolic vorticity (p < 0.001) were independently associated with larger MPG discrepancies between CMR and TTE. MPGCMR-Gorlin and MPGTTE correlation and agreement were r = 0.7; bias = −2.8 mmHg, limits of agreement from −18.4 to 12.9 mmHg. MPGCMR-Predicted model showed better correlation and agreement with MPGTTE (r = 0.82; bias = 0.5 mmHg, limits of agreement from −9.1 to 10.2 mmHg) than measured MPGCMR and MPGCMR-Gorlin. Conclusion Flow vorticity is one of the main factors responsible for MPG discrepancies between CMR and TTE. PMID:24053194

  16. Towards real-time cardiovascular magnetic resonance-guided transarterial aortic valve implantation: In vitro evaluation and modification of existing devices

    PubMed Central

    2010-01-01

    Background Cardiovascular magnetic resonance (CMR) is considered an attractive alternative for guiding transarterial aortic valve implantation (TAVI) featuring unlimited scan plane orientation and unsurpassed soft-tissue contrast with simultaneous device visualization. We sought to evaluate the CMR characteristics of both currently commercially available transcatheter heart valves (Edwards SAPIEN™, Medtronic CoreValve®) including their dedicated delivery devices and of a custom-built, CMR-compatible delivery device for the Medtronic CoreValve® prosthesis as an initial step towards real-time CMR-guided TAVI. Methods The devices were systematically examined in phantom models on a 1.5-Tesla scanner using high-resolution T1-weighted 3D FLASH, real-time TrueFISP and flow-sensitive phase-contrast sequences. Images were analyzed for device visualization quality, device-related susceptibility artifacts, and radiofrequency signal shielding. Results CMR revealed major susceptibility artifacts for the two commercial delivery devices caused by considerable metal braiding and precluding in vivo application. The stainless steel-based Edwards SAPIEN™ prosthesis was also regarded not suitable for CMR-guided TAVI due to susceptibility artifacts exceeding the valve's dimensions and hindering an exact placement. In contrast, the nitinol-based Medtronic CoreValve® prosthesis was excellently visualized with delineation even of small details and, thus, regarded suitable for CMR-guided TAVI, particularly since reengineering of its delivery device toward CMR-compatibility resulted in artifact elimination and excellent visualization during catheter movement and valve deployment on real-time TrueFISP imaging. Reliable flow measurements could be performed for both stent-valves after deployment using phase-contrast sequences. Conclusions The present study shows that the Medtronic CoreValve® prosthesis is potentially suited for real-time CMR-guided placement in vivo after suggested

  17. Multimodal cardiovascular magnetic resonance quantifies regional variation in vascular structure and function in patients with coronary artery disease: Relationships with coronary disease severity

    PubMed Central

    2011-01-01

    Background Cardiovascular magnetic resonance (CMR) of the vessel wall is highly reproducible and can evaluate both changes in plaque burden and composition. It can also measure aortic compliance and endothelial function in a single integrated examination. Previous studies have focused on patients with pre-identified carotid atheroma. We define these vascular parameters in patients presenting with coronary artery disease and test their relations to its extent and severity. Methods and Results 100 patients with CAD [single-vessel (16%); two-vessel (39%); and three-vessel (42%) non-obstructed coronary arteries (3%)] were studied. CAD severity and extent was expressed as modified Gensini score (mean modified score 12.38 ± 5.3). A majority of carotid plaque was located in the carotid bulb (CB). Atherosclerosis in this most diseased segment correlated modestly with the severity and extent of CAD, as expressed by the modified Gensini score (R = 0.251, P < 0.05). Using the AHA plaque classification, atheroma class also associated with CAD severity (rho = 0.26, P < 0.05). The distal descending aorta contained the greatest plaque, which correlated with the degree of CAD (R = 0.222; P < 0.05), but with no correlation with the proximal descending aorta, which was relatively spared (R = 0.106; P = n. s.). Aortic distensibility varied along its length with the ascending aorta the least distensible segment. Brachial artery FMD was inversely correlated with modified Gensini score (R = -0.278; P < 0.05). In multivariate analysis, distal descending aorta atheroma burden, distensibility of the ascending aorta, carotid atheroma class and FMD were independent predictors of modified Gensini score. Conclusions Multimodal vascular CMR shows regional abnormalities of vascular structure and function that correlate modestly with the degree and extent of CAD. PMID:22017860

  18. Effect of earth's precession on geosynchronous satellites under lunisolar perturbations and tesseral resonance

    NASA Astrophysics Data System (ADS)

    Belyanin, S.; Gurfil, P.

    2008-06-01

    In this study, we investigate the effect of Earth's precession on the orbital dynamics of geostationary satellites. Our astrodynamical model includes second-order zonal and tesseral harmonics, and lunisolar gravitation. We show that the equinoctial precession induces secular inclination growth and thus bares a non-negligible effect on north-south stationkeeping for long mission lifetimes.

  19. Effect of earth's precession on geosynchronous satellites under lunisolar perturbations and tesseral resonance

    NASA Astrophysics Data System (ADS)

    Belyanin, S.; Gurfil, P.

    2008-02-01

    In this study, we investigate the effect of Earth's precession on the orbital dynamics of geostationary satellites. Our astrodynamical model includes second-order zonal and tesseral harmonics, and lunisolar gravitation. We show that the equinoctial precession induces secular inclination growth and thus bares a non-negligible effect on north-south stationkeeping for long mission lifetimes.

  20. Parameter estimation of gravitational waves from precessing black hole-neutron star inspirals with higher harmonics

    NASA Astrophysics Data System (ADS)

    O'Shaughnessy, Richard; Farr, Benjamin; Ochsner, Evan; Cho, Hee-Suk; Raymond, V.; Kim, Chunglee; Lee, Chang-Hwan

    2014-05-01

    Precessing black hole-neutron star (BH-NS) binaries produce a rich gravitational wave signal, encoding the binary's nature and inspiral kinematics. Using the lalinference_mcmc Markov chain Monte Carlo parameter estimation code, we use two fiducial examples to illustrate how the geometry and kinematics are encoded into the modulated gravitational wave signal, using coordinates well adapted to precession. Extending previous work, we demonstrate that the performance of detailed parameter estimation studies can often be estimated by "effective" studies: comparisons of a prototype signal with its nearest neighbors, adopting a fixed sky location and idealized two-detector network. Using a concrete example, we show that higher harmonics provide nonzero but small local improvement when estimating the parameters of precessing BH-NS binaries. We also show that higher harmonics can improve parameter estimation accuracy for precessing binaries by breaking leading-order discrete symmetries and thus ruling out approximately degenerate source orientations. Our work illustrates quantities gravitational wave measurements can provide, such as the orientation of a precessing short gamma ray burst progenitor relative to the line of sight. More broadly, "effective" estimates may provide a simple way to estimate trends in the performance of parameter estimation for generic precessing BH-NS binaries in next-generation detectors. For example, our results suggest that the orbital chirp rate, precession rate, and precession geometry are roughly independent observables, defining natural variables to organize correlations in the high-dimensional BH-NS binary parameter space.

  1. The precession constant of the Earth: Variations through the ice-age

    SciTech Connect

    Peltier, W.R.; Jiang, X.

    1994-10-01

    We directly calculate the history of variations in Earth`s precession constant H that are forced by variations in surface mass associated with late Pleistocene ice-age glaciation and deglaciation events. Our analyses show that the magnitude of Delta H/H(sub zero) is lower than that required to cause the recently hypothesized resonant reduction of the precession period.

  2. The Pole Orientation, Pole Precession, and Moment of Inertia Factor of Saturn

    NASA Technical Reports Server (NTRS)

    Jacobson, R. A.; French, R. G.; Nicholson, P. D.; Hedman, M.; Colwell, J. E.; Marouf, E.; Rappaport, N.; McGhee, C.; Sepersky, T.; Lonergan, K.

    2011-01-01

    This paper discusses our determination of the Saturn's pole orientation and precession using a combination of Earthbased and spacecraft based observational data. From our model of the polar motion and the observed precession rate we obtain a value for Saturn's polar moment of inertia

  3. Dephasing in photoinduced large-angle spin precession of confined ferromagnetic structures

    NASA Astrophysics Data System (ADS)

    Lee, Kyeong-Dong; Ryu, Kwang-Su; Kim, Ji-Wan; Song, Hyon-Seok; Jeong, Jae-Woo; Shin, Sung-Chul

    2010-10-01

    Spin precessions in the stripes of α-MnAs films prepared on GaAs(001) are investigated using an all-optical pump-probe method. We find that a large-angle spin precession appears while the stripe width decreases. In addition, the large-angle precession considerably changes the resonance frequency, resulting in a significant decrease in the relaxation time. These changes in the precessional motion are mainly ascribed to the dephasing of the nonuniform spin waves existing at the large-angle precession, as experimentally confirmed by varying the precession angle via tuning pump fluence. Micromagnetic simulations using a single Gilbert damping constant well predict the experimental observations, which verifies the interpretation of the change in the precessional motion.

  4. Jet-intracluster medium interaction in Hydra A - II. The effect of jet precession

    NASA Astrophysics Data System (ADS)

    Nawaz, M. A.; Bicknell, G. V.; Wagner, A. Y.; Sutherland, R. S.; McNamara, B. R.

    2016-05-01

    We present three-dimensional relativistic hydrodynamical simulations of a precessing jet interacting with the intracluster medium and compare the simulated jet structure with the observed structure of the Hydra A northern jet. For the simulations, we use jet parameters obtained in the parameter space study of the first paper in this series and probe different values for the precession period and precession angle. We find that for a precession period P ≈ 1 Myr and a precession angle ψ ≈ 20°, the model reproduces (i) the curvature of the jet, (ii) the correct number of bright knots within 20 kpc at approximately correct locations and (iii) the turbulent transition of the jet to a plume. The Mach number of the advancing bow shock ≈1.85 is indicative of gentle cluster atmosphere heating during the early stages of the AGN's activity.

  5. The Precession Index, A Nonlinear Energy Balance Model, And Seversmith Psychroterms

    NASA Technical Reports Server (NTRS)

    Rubincam, David Parry

    2004-01-01

    An important component of Milankovitch's astronomical theory of climate change is the precession index. The precession index, along with the Earth's tilt and orbital eccentricity, are believed to be the major controlling factors of climate change in the last few million years. The precession index is e sin omega(sub s) where e is the Earth's orbital eccentricity and omega(sub s) measures how close the Sun is to the Earth at midsummer. When omega(sub s) = 90deg the Sun is close to the Earth during northern summer, and at 270deg it is far from the Earth during northern summer. The precession index varies with time, because both the eccentricity e and the parameter omega(sub s) are constantly changing due to disturbances in the Earth's orbit by other planets, and due to the precession of the Earth, The change is largely periodic, with a period of about 23,000 years.

  6. Cardiac magnetic resonance imaging findings and the risk of cardiovascular events in patients with recent myocardial infarction or suspected or known coronary artery disease: a systematic review of prognostic studies.

    PubMed

    El Aidi, Hamza; Adams, Arthur; Moons, Karel G M; Den Ruijter, Hester M; Mali, Willem P Th M; Doevendans, Pieter A; Nagel, Eike; Schalla, Simon; Bots, Michiel L; Leiner, Tim

    2014-03-25

    The goal of this study was to review the prognostic value of cardiac magnetic resonance (CMR) imaging findings for future cardiovascular events in patients with a recent myocardial infarction (MI) and patients with suspected or known coronary artery disease (CAD). Although the diagnostic value of CMR findings is established, the independent prognostic association with future cardiovascular events remains largely unclear. Studies published by February 2013, identified by systematic MEDLINE and EMBASE searches, were reviewed for associations between CMR findings (left ventricular ejection fraction [LVEF], wall motion abnormalities [WMA], abnormal myocardial perfusion, microvascular obstruction, late gadolinium enhancement, edema, and intramyocardial hemorrhage) and hard events (all-cause mortality, cardiac death, cardiac transplantation, and MI) or major adverse cardiovascular events (MACE) (hard events and other cardiovascular events defined by the authors of the evaluated papers). Fifty-six studies (n = 25,497) were evaluated. For patients with recent MI, too few patients were evaluated to establish associations between CMR findings and hard events. LVEF (range of adjusted hazard ratios [HRs]: 1.03 to 1.05 per % decrease) was independently associated with MACE. In patients with suspected or known CAD, WMA (adjusted HRs: 1.87 to 2.99), inducible perfusion defects (adjusted HRs: 3.02 to 7.77), LVEF (adjusted HRs: 0.72 to 0.82 per 10% increase), and infarction (adjusted HRs: 2.82 to 9.43) were independently associated with hard events, and the presence of inducible perfusion defects was associated with MACE (adjusted HRs: 1.76 to 3.21). The independent predictor of future cardiovascular events for patients with a recent MI was LVEF, and the predictors for patients with suspected or known CAD were WMA, inducible perfusion defects, LVEF, and presence of infarction. PMID:24486280

  7. Test of Lorentz Invariance with Spin Precession of Ultracold Neutrons

    SciTech Connect

    Altarev, I.; Gutsmiedl, E.; Baker, C. A.; Iaydjiev, P.; Ivanov, S. N.; Ban, G.; Lefort, T.; Naviliat-Cuncic, O.; Quemener, G.; Bodek, K.; Kistryn, S.; Zejma, J.; Daum, M.; Henneck, R.; Kirch, K.; Knecht, A.; Lauss, B.; Mtchedlishvili, A.; Petzoldt, G.

    2009-08-21

    A clock comparison experiment, analyzing the ratio of spin precession frequencies of stored ultracold neutrons and {sup 199}Hg atoms, is reported. No daily variation of this ratio could be found, from which is set an upper limit on the Lorentz invariance violating cosmic anisotropy field b{sub perpendicular}<2x10{sup -20} eV (95% C.L.). This is the first limit for the free neutron. This result is also interpreted as a direct limit on the gravitational dipole moment of the neutron |g{sub n}|<0.3 eV/c{sup 2} m from a spin-dependent interaction with the Sun. Analyzing the gravitational interaction with the Earth, based on previous data, yields a more stringent limit |g{sub n}|<3x10{sup -4} eV/c{sup 2} m.

  8. System design and verification of the precession electron diffraction technique

    NASA Astrophysics Data System (ADS)

    Own, Christopher Su-Yan

    2005-07-01

    Bulk structural crystallography is generally a two-part process wherein a rough starting structure model is first derived, then later refined to give an accurate model of the structure. The critical step is the determination of the initial model. As materials problems decrease in length scale, the electron microscope has proven to be a versatile and effective tool for studying many problems. However, study of complex bulk structures by electron diffraction has been hindered by the problem of dynamical diffraction. This phenomenon makes bulk electron diffraction very sensitive to specimen thickness, and expensive equipment such as aberration-corrected scanning transmission microscopes or elaborate methodology such as high resolution imaging combined with diffraction and simulation are often required to generate good starting structures. The precession electron diffraction technique (PED), which has the ability to significantly reduce dynamical effects in diffraction patterns, has shown promise as being a "philosopher's stone" for bulk electron diffraction. However, a comprehensive understanding of its abilities and limitations is necessary before it can be put into widespread use as a standalone technique. This thesis aims to bridge the gaps in understanding and utilizing precession so that practical application might be realized. Two new PED systems have been built, and optimal operating parameters have been elucidated. The role of lens aberrations is described in detail, and an alignment procedure is given that shows how to circumvent aberration in order to obtain high-quality patterns. Multislice simulation is used for investigating the errors inherent in precession, and is also used as a reference for comparison to simple models and to experimental PED data. General trends over a large sampling of parameter space are determined. In particular, we show that the primary reflection intensity errors occur near the transmitted beam and decay with increasing angle and

  9. Superhumps and Accretion Disk Precession in TT ARIETIS

    NASA Astrophysics Data System (ADS)

    Skillman, David R.; Harvey, David A.; Patterson, Joseph; Kemp, Jonathan; Jensen, Lasse; Fried, Robert E.; Garradd, Gordon; Gunn, Jerry; van Zyl, Liza; Kiyota, Seiichiro; Retter, Alon; Vanmunster, Tonny; Warhurst, Paul

    1998-08-01

    We have been conducting a long-term (1988-1998) photometric study of the nova-like variable TT Arietis. The main periodic signal in the star's light curve normally occurs at a period that varies but averages ~0.1329 days, which is about 3.5% shorter than the orbital period of the binary. In 1997, this signal disappeared and was replaced by a stronger signal 8.5% longer than the orbital period. This new wave strongly resembles the``superhumps'' commonly seen in SU UMa-type dwarf novae during superoutburst. In superhump parlance, we could say that a negative superhump was replaced by a positive superhump (P>Porb). This could signify the development of an eccentric instability in the accretion disk. The two superhumps probably signify two types of disk precession: apsidal advance and nodal regression. TT Ari is an excellent candidate for observational studies that probe the origin of superhumps.

  10. A decadal precession of atmospheric pressures over the North Pacific

    NASA Astrophysics Data System (ADS)

    Anderson, Bruce T.; Gianotti, Daniel J. S.; Furtado, Jason C.; Di Lorenzo, Emanuele

    2016-04-01

    Sustained droughts over the Northwestern U.S. can alter water availability to the region's agricultural, hydroelectric, and ecosystem service sectors. Here we analyze decadal variations in precipitation across this region and reveal their relation to the slow (~10 year) progression of an atmospheric pressure pattern around the North Pacific, which we term the Pacific Decadal Precession (PDP). Observations corroborate that leading patterns of atmospheric pressure variability over the North Pacific evolve in a manner consistent with the PDP and manifest as different phases in its evolution. Further analysis of the data indicates that low-frequency fluctuations of the tropical Pacific Ocean state energize one phase of the PDP and possibly the other through coupling with the polar stratosphere. Evidence that many recent climate variations influencing the North Pacific/North American sector over the last few years are consistent with the current phase of the PDP confirms the need to enhance our predictive understanding of its behavior.

  11. A PRECESSING JET IN THE CH Cyg SYMBIOTIC SYSTEM

    SciTech Connect

    Karovska, Margarita; Gaetz, Terrance J.; Raymond, John C.; Lee, Nicholas P.; Carilli, Christopher L.; Hack, Warren

    2010-02-20

    Jets have been detected in only a few symbiotic binaries to date, and CH Cyg is one of them. In 2001, a non-relativistic jet was detected in CH Cyg for the first time in X-rays. We carried out coordinated Chandra, Hubble Space Telescope (HST), and VLA observations in 2008 to study the propagation of this jet and its interaction with the circumbinary medium. We detected the jet with Chandra and HST and determined that the apex has expanded to the south from {approx}300 AU to {approx}1400 AU, with the shock front propagating with velocity <100 km s{sup -1}. The shock front has significantly slowed down since 2001. Unexpectedly, we also discovered a powerful jet in the NE-SW direction, in the X-ray, optical and radio. This jet has a multi-component structure, including an inner jet and a counterjet at {approx}170 AU, and a SW component ending in several clumps extending out to {approx}750 AU. The structure of the jet and the curvature of the outer portion of the SW jet suggest an episodically powered precessing jet or a continuous precessing jet with occasional mass ejections or pulses. We carried out detailed spatial mapping of the X-ray emission and correlation with the optical and radio emission. X-ray spectra were extracted from the central source, inner NE counterjet, and the brightest clump at a distance of {approx}500 AU from the central source. We discuss the initial results of our analyses, including the multi-component spectral fitting of the jet components and of the central source.

  12. The Orientation and Precession of the Pole of Saturn - Revised

    NASA Astrophysics Data System (ADS)

    Jacobson, Robert A.; French, R. G.

    2011-04-01

    The effort to determine the orientation and precession of Saturn's pole is currently motivated by three needs: to orient the Saturn gravity field for ephemeris development and spacecraft navigation, to orient the Saturn ring plane for studies of ring structure and dynamics, and to determine Saturn's polar moment of inertia for studies of Saturn's interior. Boué, G. and Laskar, J. (2006 Icarus 185, 312) published an informative theoretical discussion of polar motion applicable to Saturn. However, their model cannot be easily used in practice. Jacobson (2007 BAAS 39, 317) presented a pole model in the standard IAU trigometric series representation based on the rigid body rotational equations of motion with couples exerted by the Sun, Titan, and Iapetus. He determined the orientation and precession by fitting Saturn ring occultation measurements, in particular: the radio occultation of Voyager 1, the occultation of the star δSco seen with the Voyager 2 Ultraviolet Spectrometer, the 1989 occultation of the star 28 Sgr seen from the Earth, the 1991 occultation of the star GSC 6323-01396 seen from HST, and ring plane crossing times (Nicholson and French, 1997 BAAS 29, 1097). We have since acquired measurements from the 1995 occultation of the star GSC 5249-01240 seen from HST and the re-reduced meansurements of the 1991 occultation (French et al. 2010 AJ 139, 1649). In this paper we present our current results using the occultation data together with satellite astrometry and tracking of the Voyager and Cassini spacecraft. We also discuss future plans for the incorporation of Cassini ring occultation observations.

  13. Impact of diastolic dysfunction severity on global left ventricular volumetric filling - assessment by automated segmentation of routine cine cardiovascular magnetic resonance

    PubMed Central

    2010-01-01

    Objectives To examine relationships between severity of echocardiography (echo) -evidenced diastolic dysfunction (DD) and volumetric filling by automated processing of routine cine cardiovascular magnetic resonance (CMR). Background Cine-CMR provides high-resolution assessment of left ventricular (LV) chamber volumes. Automated segmentation (LV-METRIC) yields LV filling curves by segmenting all short-axis images across all temporal phases. This study used cine-CMR to assess filling changes that occur with progressive DD. Methods 115 post-MI patients underwent CMR and echo within 1 day. LV-METRIC yielded multiple diastolic indices - E:A ratio, peak filling rate (PFR), time to peak filling rate (TPFR), and diastolic volume recovery (DVR80 - proportion of diastole required to recover 80% stroke volume). Echo was the reference for DD. Results LV-METRIC successfully generated LV filling curves in all patients. CMR indices were reproducible (≤ 1% inter-reader differences) and required minimal processing time (175 ± 34 images/exam, 2:09 ± 0:51 minutes). CMR E:A ratio decreased with grade 1 and increased with grades 2-3 DD. Diastolic filling intervals, measured by DVR80 or TPFR, prolonged with grade 1 and shortened with grade 3 DD, paralleling echo deceleration time (p < 0.001). PFR by CMR increased with DD grade, similar to E/e' (p < 0.001). Prolonged DVR80 identified 71% of patients with echo-evidenced grade 1 but no patients with grade 3 DD, and stroke-volume adjusted PFR identified 67% with grade 3 but none with grade 1 DD (matched specificity = 83%). The combination of DVR80 and PFR identified 53% of patients with grade 2 DD. Prolonged DVR80 was associated with grade 1 (OR 2.79, CI 1.65-4.05, p = 0.001) with a similar trend for grade 2 (OR 1.35, CI 0.98-1.74, p = 0.06), whereas high PFR was associated with grade 3 (OR 1.14, CI 1.02-1.25, p = 0.02) DD. Conclusions Automated cine-CMR segmentation can discern LV filling changes that occur with increasing severity of

  14. High Spatial Resolution Cardiovascular Magnetic Resonance at 7.0 Tesla in Patients with Hypertrophic Cardiomyopathy – First Experiences: Lesson Learned from 7.0 Tesla

    PubMed Central

    Prothmann, Marcel; von Knobelsdorff-Brenkenhoff, Florian; Töpper, Agnieszka; Dieringer, Matthias A.; Shahid, Etham; Graessl, Andreas; Rieger, Jan; Lysiak, Darius; Thalhammer, C.; Huelnhagen, Till; Kellman, Peter; Niendorf, Thoralf; Schulz-Menger, Jeanette

    2016-01-01

    Background Cardiovascular Magnetic Resonance (CMR) provides valuable information in patients with hypertrophic cardiomyopathy (HCM) based on myocardial tissue differentiation and the detection of small morphological details. CMR at 7.0T improves spatial resolution versus today’s clinical protocols. This capability is as yet untapped in HCM patients. We aimed to examine the feasibility of CMR at 7.0T in HCM patients and to demonstrate its capability for the visualization of subtle morphological details. Methods We screened 131 patients with HCM. 13 patients (9 males, 56 ±31 years) and 13 healthy age- and gender-matched subjects (9 males, 55 ±31years) underwent CMR at 7.0T and 3.0T (Siemens, Erlangen, Germany). For the assessment of cardiac function and morphology, 2D CINE imaging was performed (voxel size at 7.0T: (1.4x1.4x2.5) mm3 and (1.4x1.4x4.0) mm3; at 3.0T: (1.8x1.8x6.0) mm3). Late gadolinium enhancement (LGE) was performed at 3.0T for detection of fibrosis. Results All scans were successful and evaluable. At 3.0T, quantification of the left ventricle (LV) showed similar results in short axis view vs. the biplane approach (LVEDV, LVESV, LVMASS, LVEF) (p = 0.286; p = 0.534; p = 0.155; p = 0.131). The LV-parameters obtained at 7.0T where in accordance with the 3.0T data (pLVEDV = 0.110; pLVESV = 0.091; pLVMASS = 0.131; pLVEF = 0.182). LGE was detectable in 12/13 (92%) of the HCM patients. High spatial resolution CINE imaging at 7.0T revealed hyperintense regions, identifying myocardial crypts in 7/13 (54%) of the HCM patients. All crypts were located in the LGE-positive regions. The crypts were not detectable at 3.0T using a clinical protocol. Conclusions CMR at 7.0T is feasible in patients with HCM. High spatial resolution gradient echo 2D CINE imaging at 7.0T allowed the detection of subtle morphological details in regions of extended hypertrophy and LGE. PMID:26863618

  15. Cardiovascular magnetic resonance of myocardial edema using a short inversion time inversion recovery (STIR) black-blood technique: Diagnostic accuracy of visual and semi-quantitative assessment

    PubMed Central

    2012-01-01

    Background The short inversion time inversion recovery (STIR) black-blood technique has been used to visualize myocardial edema, and thus to differentiate acute from chronic myocardial lesions. However, some cardiovascular magnetic resonance (CMR) groups have reported variable image quality, and hence the diagnostic value of STIR in routine clinical practice has been put into question. The aim of our study was to analyze image quality and diagnostic performance of STIR using a set of pulse sequence parameters dedicated to edema detection, and to discuss possible factors that influence image quality. We hypothesized that STIR imaging is an accurate and robust way of detecting myocardial edema in non-selected patients with acute myocardial infarction. Methods Forty-six consecutive patients with acute myocardial infarction underwent CMR (day 4.5, +/- 1.6) including STIR for the assessment of myocardial edema and late gadolinium enhancement (LGE) for quantification of myocardial necrosis. Thirty of these patients underwent a follow-up CMR at approximately six months (195 +/- 39 days). Both STIR and LGE images were evaluated separately on a segmental basis for image quality as well as for presence and extent of myocardial hyper-intensity, with both visual and semi-quantitative (threshold-based) analysis. LGE was used as a reference standard for localization and extent of myocardial necrosis (acute) or scar (chronic). Results Image quality of STIR images was rated as diagnostic in 99.5% of cases. At the acute stage, the sensitivity and specificity of STIR to detect infarcted segments on visual assessment was 95% and 78% respectively, and on semi-quantitative assessment was 99% and 83%, respectively. STIR differentiated acutely from chronically infarcted segments with a sensitivity of 95% by both methods and with a specificity of 99% by visual assessment and 97% by semi-quantitative assessment. The extent of hyper-intense areas on acute STIR images was 85% larger than

  16. Importance of tides for periastron precession in eccentric neutron star-white dwarf binaries

    SciTech Connect

    Sravan, N.; Valsecchi, F.; Kalogera, V.; Althaus, L. G.

    2014-09-10

    Although not nearly as numerous as binaries with two white dwarfs, eccentric neutron star-white dwarf (NS-WD) binaries are important gravitational-wave (GW) sources for the next generation of space-based detectors sensitive to low frequency waves. Here we investigate periastron precession in these sources as a result of general relativistic, tidal, and rotational effects; such precession is expected to be detectable for at least some of the detected binaries of this type. Currently, two eccentric NS-WD binaries are known in the galactic field, PSR J1141–6545 and PSR B2303+46, both of which have orbits too wide to be relevant in their current state to GW observations. However, population synthesis studies predict the existence of a significant Galactic population of such systems. Though small in most of these systems, we find that tidally induced periastron precession becomes important when tides contribute to more than 3% of the total precession rate. For these systems, accounting for tides when analyzing periastron precession rate measurements can improve estimates of the inferred WD component mass and, in some cases, will prevent us from misclassifying the object. However, such systems are rare, due to rapid orbital decay. To aid the inclusion of tidal effects when using periastron precession as a mass measurement tool, we derive a function that relates the WD radius and periastron precession constant to the WD mass.

  17. Inspiral waveforms for spinning compact binaries in a new precessing convention

    NASA Astrophysics Data System (ADS)

    Gupta, Anuradha; Gopakumar, Achamveedu

    2016-05-01

    It is customary to use a precessing convention, based on Newtonian orbital angular momentum L N, to model inspiral gravitational waves from generic spinning compact binaries. A key feature of such a precessing convention is its ability to remove all spin precession induced modulations from the orbital phase evolution. However, this convention usually employs a postNewtonian (PN) accurate precessional equation, appropriate for the PN accurate orbital angular momentum L, to evolve the L N-based precessing source frame. This motivated us to develop inspiral waveforms for spinning compact binaries in a precessing convention that explicitly use L to describe the binary orbits. Our approach introduces certain additional 3PN order terms in the orbital phase and frequency evolution equations with respect to the usual L N-based implementation of the precessing convention. The implications of these additional terms are explored by computing the match between inspiral waveforms that employ L and L N-based precessing conventions. We found that the match estimates are smaller than the optimal value, namely 0.97, for a non-negligible fraction of unequal mass spinning compact binaries.

  18. Cardiovascular group

    NASA Technical Reports Server (NTRS)

    Blomqvist, Gunnar

    1989-01-01

    As a starting point, the group defined a primary goal of maintaining in flight a level of systemic oxygen transport capacity comparable to each individual's preflight upright baseline. The goal of maintaining capacity at preflight levels would seem to be a reasonable objective for several different reasons, including the maintenance of good health in general and the preservation of sufficient cardiovascular reserve capacity to meet operational demands. It is also important not to introduce confounding variables in whatever other physiological studies are being performed. A change in the level of fitness is likely to be a significant confounding variable in the study of many organ systems. The principal component of the in-flight cardiovascular exercise program should be large-muscle activity such as treadmill exercise. It is desirable that at least one session per week be monitored to assure maintenance of proper functional levels and to provide guidance for any adjustments of the exercise prescription. Appropriate measurements include evaluation of the heart-rate/workload or the heart-rate/oxygen-uptake relationship. Respiratory gas analysis is helpful by providing better opportunities to document relative workload levels from analysis of the interrelationships among VO2, VCO2, and ventilation. The committee felt that there is no clear evidence that any particular in-flight exercise regimen is protective against orthostatic hypotension during the early readaptation phase. Some group members suggested that maintenance of the lower body muscle mass and muscle tone may be helpful. There is also evidence that late in-flight interventions to reexpand blood volume to preflight levels are helpful in preventing or minimizing postflight orthostatic hypotension.

  19. Precessed electron beam electron energy loss spectroscopy of graphene: Beyond channelling effects

    SciTech Connect

    Yedra, Ll.; Estradé, S.; Torruella, P.; Eljarrat, A.; Peiró, F.; Darbal, A. D.; Weiss, J. K.

    2014-08-04

    The effects of beam precession on the Electron Energy Loss Spectroscopy (EELS) signal of the carbon K edge in a 2 monolayer graphene sheet are studied. In a previous work, we demonstrated the use of precession to compensate for the channeling-induced reduction of EELS signal when in zone axis. In the case of graphene, no enhancement of EELS signal is found in the usual experimental conditions, as graphene is not thick enough to present channeling effects. Interestingly, though it is found that precession makes it possible to increase the collection angle, and, thus, the overall signal, without a loss of signal-to-background ratio.

  20. Geodesic and Lense-Thirring precessions effects on the near earth artificial satellites

    NASA Astrophysics Data System (ADS)

    Radwan, M.; El-Salam, F. A. A.; El-Bar, S. E. A.

    2013-02-01

    The present work deals with the effect of the geodesic and Lense-Thirring precessions in a near Earth artificial satellite orbit. The effects of the geodesic and Lense-Thirring precessions on the orbit evolution are surveyed. The Picard method of successive approximation is described. The canonical equations of motion including forces non-derivable from a potential are presented. The acceleration components coming from the geodesic and Lense-Thirring precessions are first obtained, then, the images of these accelerations are evaluated. The integrations are effected using the method of Picard successive iteration.

  1. The Precession Index and a Nonlinear Energy Balance Climate Model

    NASA Technical Reports Server (NTRS)

    Rubincam, David

    2004-01-01

    A simple nonlinear energy balance climate model yields a precession index-like term in the temperature. Despite its importance in the geologic record, the precession index e sin (Omega)S, where e is the Earth's orbital eccentricity and (Omega)S is the Sun's perigee in the geocentric frame, is not present in the insolation at the top of the atmosphere. Hence there is no one-for-one mapping of 23,000 and 19,000 year periodicities from the insolation to the paleoclimate record; a nonlinear climate model is needed to produce these long periods. A nonlinear energy balance climate model with radiative terms of form T n, where T is surface temperature and n less than 1, does produce e sin (omega)S terms in temperature; the e sin (omega)S terms are called Seversmith psychroterms. Without feedback mechanisms, the model achieves extreme values of 0.64 K at the maximum orbital eccentricity of 0.06, cooling one hemisphere while simultaneously warming the other; the hemisphere over which perihelion occurs is the cooler. In other words, the nonlinear energy balance model produces long-term cooling in the northern hemisphere when the Sun's perihelion is near northern summer solstice and long-term warming in the northern hemisphere when the aphelion is near northern summer solstice. (This behavior is similar to the inertialess gray body which radiates like T 4, but the amplitude is much lower for the energy balance model because of its thermal inertia.) This seemingly paradoxical behavior works against the standard Milankovitch model, which requires cool northern summers (Sun far from Earth in northern summer) to build up northern ice sheets, so that if the standard model is correct it must be more efficient than previously thought. Alternatively, the new mechanism could possibly be dominant and indicate southern hemisphere control of the northern ice sheets, wherein the southern oceans undergo a long-term cooling when the Sun is far from the Earth during northern summer. The cold

  2. SR calculation of the geodetic precession of gpb.

    NASA Astrophysics Data System (ADS)

    Collins, Russell

    2003-03-01

    The gpb satellite, see http://www.nas.edu/ssb/gpb.html, should enter a low circular polar orbit about earth July 2003. Its near-perfect gyroscopes will probe the metric of space near the earth. An in-plane precession is expected, termed the geodetic effect, because measured distance is not Euclidean in the presence of gravity. The circumference of a circle tangent to the outside of the gyroscope is, by SR, shortened slightly more than a circle tangent to the inside. The gyroscope axis is slowly tilted backward (counter to the orbital direction) by this geodetic effect, ΔΘ = -3π GM/r c^2 = -3π v^2/c^2 rad/rev = -6.55467 arcsec/year. This is identical to the GR result, arXiv:gr-qc/9909054 v2 21 Sep 1999, except for the sign. After including small perturbations due to the sun and the earth's oblateness, GR expects +6.58048 and SR expects - 6.56124 arcsec/yr. The predicted precision of the experiment is 0.00045 arcsec/yr. Let the experiment decide.

  3. Tidal-Force-Induced Precessions of Accretion Disks

    NASA Astrophysics Data System (ADS)

    Inoue, Hajime

    2012-04-01

    The preccession of an accretion disk around a compact star in a close binary has been studied. When the accretion disk tilts, the tidal force from the companion star induces a torque on it, which causes a preccession of the disk. We firstly consider the properties of a preccessing motion of a ring, which is circularly rotating around a compact star, and is preccessing with a slightly tilting angle under the influence of a tidal force from a companion star. We next compare the predicted behaviors of the preccessing ring with observations, and find that several observational facts from Her X-1, SS 433, and some other X-ray binaries can be explained by a tidal-force-induced precession scheme quite reasonably. We further examine the energetics of the preccessing ring as a function of the tilting angle. It is shown that the kinetic and potential energies of the orbiting motions of the ring matter around the compact star increases as the tilting angle increases, while the thermal and effective potential energies for hydro-static balance in the meridian cross section of the ring decreases through adiabatic expansion. Quantitative estimations have shown that when the ring has sufficient thermal energy, the decrease of the energy for the hydro-static balance can be larger than the increase of the energy for circular motion around the compact star until the tilting angle reaches a certain value. It is strongly suggested that preccessions of accretion disks are often realized in close binaries.

  4. Exact solution for spin precession in the radiationless relativistic Kepler problem

    NASA Astrophysics Data System (ADS)

    Mane, S. R.

    2014-11-01

    There is interest in circulating beams of polarized particles in all-electric storage rings to search for nonzero permanent electric dipole moments of subatomic particles. To this end, it is helpful to derive exact analytical solutions of the spin precession in idealized models, both for pedagogical reasons and to serve as benchmark tests for analysis and design of experiments. This paper derives exact solutions for the spin precession in the relativistic Kepler problem. Some counterintuitive properties of the solutions are pointed out.

  5. Movement dependence and layer specificity of entorhinal phase precession in two-dimensional environments.

    PubMed

    Reifenstein, Eric; Stemmler, Martin; Herz, Andreas V M; Kempter, Richard; Schreiber, Susanne

    2014-01-01

    As a rat moves, grid cells in its entorhinal cortex (EC) discharge at multiple locations of the external world, and the firing fields of each grid cell span a hexagonal lattice. For movements on linear tracks, spikes tend to occur at successively earlier phases of the theta-band filtered local field potential during the traversal of a firing field - a phenomenon termed phase precession. The complex movement patterns observed in two-dimensional (2D) open-field environments may fundamentally alter phase precession. To study this question at the behaviorally relevant single-run level, we analyzed EC spike patterns as a function of the distance traveled by the rat along each trajectory. This analysis revealed that cells across all EC layers fire spikes that phase-precess; indeed, the rate and extent of phase precession were the same, only the correlation between spike phase and path length was weaker in EC layer III. Both slope and correlation of phase precession were surprisingly similar on linear tracks and in 2D open-field environments despite strong differences in the movement statistics, including running speed. While the phase-precession slope did not correlate with the average running speed, it did depend on specific properties of the animal's path. The longer a curving path through a grid-field in a 2D environment, the shallower was the rate of phase precession, while runs that grazed a grid field tangentially led to a steeper phase-precession slope than runs through the field center. Oscillatory interference models for grid cells do not reproduce the observed phenomena. PMID:24959748

  6. Movement Dependence and Layer Specificity of Entorhinal Phase Precession in Two-Dimensional Environments

    PubMed Central

    Reifenstein, Eric; Stemmler, Martin; Herz, Andreas V. M.; Kempter, Richard; Schreiber, Susanne

    2014-01-01

    As a rat moves, grid cells in its entorhinal cortex (EC) discharge at multiple locations of the external world, and the firing fields of each grid cell span a hexagonal lattice. For movements on linear tracks, spikes tend to occur at successively earlier phases of the theta-band filtered local field potential during the traversal of a firing field – a phenomenon termed phase precession. The complex movement patterns observed in two-dimensional (2D) open-field environments may fundamentally alter phase precession. To study this question at the behaviorally relevant single-run level, we analyzed EC spike patterns as a function of the distance traveled by the rat along each trajectory. This analysis revealed that cells across all EC layers fire spikes that phase-precess; indeed, the rate and extent of phase precession were the same, only the correlation between spike phase and path length was weaker in EC layer III. Both slope and correlation of phase precession were surprisingly similar on linear tracks and in 2D open-field environments despite strong differences in the movement statistics, including running speed. While the phase-precession slope did not correlate with the average running speed, it did depend on specific properties of the animal's path. The longer a curving path through a grid-field in a 2D environment, the shallower was the rate of phase precession, while runs that grazed a grid field tangentially led to a steeper phase-precession slope than runs through the field center. Oscillatory interference models for grid cells do not reproduce the observed phenomena. PMID:24959748

  7. Doppler effect in a solid medium: Spin wave emission by a precessing domain wall drifting in spin current

    NASA Astrophysics Data System (ADS)

    Xia, Hong; Chen, Jie; Zeng, Xiaoyan; Yan, Ming

    2016-04-01

    The Doppler effect is a fundamental physical phenomenon observed for waves propagating in vacuum or various media, commonly gaseous or liquid. Here, we report on the occurrence of a Doppler effect in a solid medium. Instead of a real object, a topological soliton, i.e., a magnetic domain wall (DW) traveling in a current-carrying ferromagnetic nanowire, plays the role of the moving wave source. The Larmor precession of the DW in an external field stimulates emission of monochromatic spin waves (SWs) during its motion, which show a significant Doppler effect, comparable to the acoustic one of a train whistle. This process involves two prominent spin-transfer-torque effects simultaneously, the current-driven DW motion and the current-induced SW Doppler shift. The latter gives rise to an interesting feature, i.e., the observed SW Doppler effect appears resulting from a stationary source and a moving observer, contrary to the laboratory frame.

  8. Regadenoson and adenosine are equivalent vasodilators and are superior than dipyridamole- a study of first pass quantitative perfusion cardiovascular magnetic resonance

    PubMed Central

    2013-01-01

    Background Regadenoson, dipyridamole and adenosine are commonly used vasodilators in myocardial perfusion imaging for the detection of obstructive coronary artery disease. There are few comparative studies of the vasodilator properties of regadenoson, adenosine and dipyridamole in humans. The specific aim of this study was to determine the relative potency of these three vasodilators by quantifying stress and rest myocardial perfusion in humans using cardiovascular magnetic resonance (CMR). Methods Fifteen healthy normal volunteers, with Framingham score less than 1% underwent vasodilator stress testing with regadenoson (400 μg bolus), dipyridamole (0.56 mg/kg) and adenosine (140 μg /kg/min) on separate days. Rest perfusion imaging was performed initially. Twenty minutes later, stress imaging was performed at peak vasodilation, i.e. 70 seconds after regadenoson, 4 minutes after dipyridamole infusion and between 3–4 minutes of the adenosine infusion. Myocardial blood flow (MBF) in ml/min/g and myocardial perfusion reserve (MPR) were quantified using a fully quantitative model constrained deconvolution. Results Regadenoson produced higher stress MBF than dipyridamole and adenosine (3.58 ± 0.58 vs. 2.81 ± 0.67 vs. 2.78 ± 0.61 ml/min/g, p = 0.0009 and p = 0.0008 respectively). Regadenoson had a much higher heart rate response than adenosine and dipyridamole respectively (95 ± 11 vs. 76 ± 13 vs. 86 ± 12 beats/ minute) When stress MBF was adjusted for heart rate, there were no differences between regadenoson and adenosine (37.8 ± 6 vs. 36.6 ± 4 μl/sec/g, p = NS), but differences between regadenoson and dipyridamole persisted (37.8 ± 6 vs. 32.6 ± 5 μl/sec/g, p = 0.03). The unadjusted MPR was higher with regadenoson (3.11 ± 0.63) when compared with adenosine (2.7 ± 0.61, p = 0.02) and when compared with dipyridamole (2.61 ± 0.57, p = 0.04). Similar to stress MBF, these differences in MPR between regadenoson and adenosine were abolished when adjusted

  9. Periastron precession measurements in transiting extrasolar planetary systems at the level of general relativity

    NASA Astrophysics Data System (ADS)

    Pál, András; Kocsis, Bence

    2008-09-01

    Transiting exoplanetary systems are surpassingly important among the planetary systems since they provide the widest spectrum of information for both the planet and the host star. If a transiting planet is on an eccentric orbit, the duration of transits TD is sensitive to the orientation of the orbital ellipse relative to the line of sight. The precession of the orbit results in a systematic variation in both the duration of individual transit events and the observed period between successive transits, Pobs. The periastron of the ellipse slowly precesses due to general relativity and possibly the presence of other planets in the system. This secular precession can be detected through the long-term change in Pobs (transit timing variations, TTV) or in TD (transit duration variations, TDV). We estimate the corresponding precession measurement precision for repeated future observations of the known eccentric transiting exoplanetary systems (XO-3b, HD 147506b, GJ 436b and HD 17156b) using existing or planned space-borne instruments. The TDV measurement improves the precession detection sensitivity by orders of magnitude over the TTV measurement. We find that TDV measurements over a approximately 4yr period can typically detect the precession rate to a precision well exceeding the level predicted by general relativity.

  10. Fuel Distribution Estimate via Spin Period to Precession Period Ratio for the Advanced Composition Explorer

    NASA Technical Reports Server (NTRS)

    DeHart, Russell; Smith, Eric; Lakin, John

    2015-01-01

    The spin period to precession period ratio of a non-axisymmetric spin-stabilized spacecraft, the Advanced Composition Explorer (ACE), was used to estimate the remaining mass and distribution of fuel within its propulsion system. This analysis was undertaken once telemetry suggested that two of the four fuel tanks had no propellant remaining, contrary to pre-launch expectations of the propulsion system performance. Numerical integration of possible fuel distributions was used to calculate moments of inertia for the spinning spacecraft. A Fast Fourier Transform (FFT) of output from a dynamics simulation was employed to relate calculated moments of inertia to spin and precession periods. The resulting modeled ratios were compared to the actual spin period to precession period ratio derived from the effect of post-maneuver nutation angle on sun sensor measurements. A Monte Carlo search was performed to tune free parameters using the observed spin period to precession period ratio over the life of the mission. This novel analysis of spin and precession periods indicates that at the time of launch, propellant was distributed unevenly between the two pairs of fuel tanks, with one pair having approximately 20% more propellant than the other pair. Furthermore, it indicates the pair of the tanks with less fuel expelled all of its propellant by 2014 and that approximately 46 kg of propellant remains in the other two tanks, an amount that closely matches the operational fuel accounting estimate. Keywords: Fuel Distribution, Moments of Inertia, Precession, Spin, Nutation

  11. Millennial scale climatic responses through a Late Miocene precession cycle

    NASA Astrophysics Data System (ADS)

    Marzocchi, Alice; Lunt, Dan; Flecker, Rachel; Bradshaw, Catherine

    2014-05-01

    Late Miocene (11.61-5.33 Ma) climate is thought to have been warmer and wetter than the present, with nearly ice-free conditions over the Northern Hemisphere, and significant differences in vegetation distribution. There still is considerable uncertainty in the reconstructed CO2 levels for this time period, fostered by the temporally and spatially biased distribution of the available proxy record. Previous model-data comparison studies (i.e. Bradshaw et al., 2012; Pound et al., 2011) highlighted the mismatch between model results and proxy data for this time period. Here, we investigate how taking into account the variability due to changes in orbital forcing can account for some of these differences. We also explore the orbital control on the monsoonal systems at millennial scale resolution, as well as the impact of background CO2 on orbital sensitivity. Long-term changes in seasonal and latitudinal solar insolation are generated by periodic oscillations in the Earth's orbit and tilt relative to the Sun. These cycles have a modulating effect on climate and ocean circulation patterns. A record of this signal can be found in a number of terrestrial and marine sedimentary sequences. A series of 22 fully coupled atmosphere-ocean-vegetation simulations has been run through an entire precession cycle during the Late Miocene (~6.5 Ma). These experiments were performed using HadCM3L (Hadley Centre Coupled Model, Version 3 - Low resolution ocean) with TRIFFID (Top-down Representation of Interactive Foliage and Flora Including Dynamics) to test the climatic response to changes in orbital forcing. The Mediterranean Sea provides a remarkable geological record for this time slice. Several sequences around the basin margins have been astronomically tuned so that high resolution geological data can be directly compared with our model results. However, this is not the case for the rest of the world, where the distribution of climate proxy data for the Late Miocene is sparse

  12. Low-temperature instability of uniform spin precession in the B phase of pure {sup 3}He and {sup 3}He in an aerogel

    SciTech Connect

    Surovtsev, E. V. Fomin, I. A.

    2010-08-15

    The magnetic-field dependences of the threshold temperature of the low-temperature instability of uniform spin precession in pure {sup 3}He-B and {sup 3}He-B in an aerogel have been determined for the bulk mechanism. These dependences appear to be different. The theoretical dependence of the threshold temperature for the pure case has been compared with the experimental dependence. The threshold temperature of the instability for {sup 3}He in the aerogel has been estimated for typical experimental conditions.

  13. Global temperatures, precession, and CO{sub 2}

    SciTech Connect

    Thomson, D.J.

    1995-12-31

    Despite much work, the effects of the increasing quantities of carbon dioxide and other so-called {open_quotes}greenhouse gases{close_quotes} on the earth`s climate remain controversial. I show that previous statistical analyses of the climate time series are flawed due to inappropriate assumptions about the timing of the seasons and that the seasonal cycle appears to be changing at an unprecedented rate as a result of greenhouse forcing. Writing the dominant component of the annual seasonal temperature cycle as A(t) cos(2{pi}t + {theta}(t)) where t time in years, and the phase, {theta}(t), describes the timing of the seasons, I show that: From the start of the instrumental series in 1659, up to about 1940, the phase of the Northern Hemisphere temperature {theta}(t) has a decreasing linear trend of about 50 arc-seconds per year. Since about 1940 the phase of the annual cycle has increased rapidly at an average rate of 300 arc-seconds per year with even more rapid changes at many individual stations. From these observations I conclude: (1) From 1669 to 1940 the temperature cycle usually follows perihelion rather the equinoxes. (2) The change after 1940 may be accounted for as a result in the increase in the direct radiation component of temperature by CO{sub 2} relative to transport. (3) The apparent seasonal dependence of the slope of the hemispheric temperature records over the last century noted by several researchers is an artifact of ignoring precession. (4) Changes in CO{sub 2} resulting from human activities are causing large, and readily observable, changes both in the average temperature and in the seasonal cycle.

  14. Magnetization dynamics using ultrashort magnetic field pulses

    NASA Astrophysics Data System (ADS)

    Tudosa, Ioan

    Very short and well shaped magnetic field pulses can be generated using ultra-relativistic electron bunches at Stanford Linear Accelerator. These fields of several Tesla with duration of several picoseconds are used to study the response of magnetic materials to a very short excitation. Precession of a magnetic moment by 90 degrees in a field of 1 Tesla takes about 10 picoseconds, so we explore the range of fast switching of the magnetization by precession. Our experiments are in a region of magnetic excitation that is not yet accessible by other methods. The current table top experiments can generate fields longer than 100 ps and with strength of 0.1 Tesla only. Two types of magnetic were used, magnetic recording media and model magnetic thin films. Information about the magnetization dynamics is extracted from the magnetic patterns generated by the magnetic field. The shape and size of these patterns are influenced by the dissipation of angular momentum involved in the switching process. The high-density recording media, both in-plane and perpendicular type, shows a pattern which indicates a high spin momentum dissipation. The perpendicular magnetic recording media was exposed to multiple magnetic field pulses. We observed an extended transition region between switched and non-switched areas indicating a stochastic switching behavior that cannot be explained by thermal fluctuations. The model films consist of very thin crystalline Fe films on GaAs. Even with these model films we see an enhanced dissipation compared to ferromagnetic resonance studies. The magnetic patterns show that damping increases with time and it is not a constant as usually assumed in the equation describing the magnetization dynamics. The simulation using the theory of spin-wave scattering explains only half of the observed damping. An important feature of this theory is that the spin dissipation is time dependent and depends on the large angle between the magnetization and the magnetic

  15. Influence of orbital precession on the polar methane accumulation on Titan

    NASA Astrophysics Data System (ADS)

    Liu, J.; Schneider, T.

    2014-12-01

    Data collected by Cassini Spacecraft indicate that lakes on Titan are primarily found in the polar regions, preferentially in the north. It has been suggested that the hemispherical asymmetry in lake distribution is related to Saturn's orbital precession, which changes the seasonal distribution of solar radiation on Titan, but not the annual mean (Aharonson et al., 2009; Schneider et al., 2012). Saturn's current longitude of perihelion is near northern winter solstice. Hence, the northern summer on Titan is longer and less intense than the southern summer. The longer northern summer leads to greater net precipitation in the annual mean and the methane accumulation over the northern polar region (Schneider et al. 2012). Saturn's perihelion precesses over an approximately 45-kyr period, so the solar radiation at the top of Titan's atmosphere varies on this time scale. Here we investigate how the orbital precession influences the polar methane accumulation with a three-dimensional atmospheric model coupled to a dynamic surface reservoir of methane (Schneider et al. 2012). We find that methane accumulation is closely tied to Saturn's orbital precession. At the time when Saturn's longitude of perihelion is 180 degree away from the present day value, methane is mainly accumulated in the southern polar region due to the stronger annual-mean precipitation there induced by the longer southern summer. The annual-mean evaporation is largely unchanged with orbital precession, since it scales with the annual-mean insolation, which does not change under orbital precession. When Saturn's longitude of perihelion is close to equinox, methane is approximately evenly distributed in the northern and southern polar regions, and the lake dichotomy disappears. The timescale of methane redistribution from one pole to the other is short compared with the timescale of orbital precession, so the surface methane distribution can be viewed as being approximately in equilibrium with the solar

  16. Precession and accretion in circumbinary discs: the case of HD 104237

    NASA Astrophysics Data System (ADS)

    Dunhill, A. C.; Cuadra, J.; Dougados, C.

    2015-04-01

    We present the results of smoothed particle hydrodynamics (SPH) simulations of the disc around the young, eccentric stellar binary HD 104237. We find that the binary clears out a large cavity in the disc, driving a significant eccentricity at the cavity edge. This then precesses around the binary at a rate of dot{\\varpi } = 0.48°Tb^{-1}, which for HD 104237 corresponds to a precession period of 40 years. We find that the accretion pattern into the cavity and on to the binary changes with this precession, resulting in a periodic accretion variability driven purely by the physical parameters of the binary and its orbit. For each star we find that this results in order of magnitude changes in the accretion rate. We also find that the accretion variability allows the primary to accrete gas at a higher rate than the secondary for approximately half of each precession period. Using a large number of three-body integrations of test particles orbiting different binaries, we find good agreement between the precession rate of a test particle and our SPH disc precession. These rates also agree very well with the precession rates predicted by the analytic theory of Leung & Lee, showing that their prescription can be accurately used to predict long-term accretion variability time-scales for eccentric binaries accreting from a disc. We discuss the implications of our result, and suggest that this process provides a viable way of preserving unequal-mass ratios in accreting eccentric binaries in both the stellar and supermassive black hole regimes.

  17. Spectral element simulation of precession driven flows in the outer cores of spheroidal planets

    NASA Astrophysics Data System (ADS)

    Vormann, Jan; Hansen, Ulrich

    2015-04-01

    A common feature of the planets in the solar system is the precession of the rotation axes, driven by the gravitational influence of another body (e.g. the Earth's moon). In a precessing body, the rotation axis itself is rotating around another axis, describing a cone during one precession period. Similar to the coriolis and centrifugal force appearing from the transformation to a rotating system, the addition of precession adds another term to the Navier-Stokes equation, the so called Poincaré force. The main geophysical motivation in studying precession driven flows comes from their ability to act as magnetohydrodynamic dynamos in planets and moons. Precession may either act as the only driving force or operate together with other forces such as thermochemical convection. One of the challenges in direct numerical simulations of such flows lies in the spheroidal shape of the fluid volume, which should not be neglected since it contributes an additional forcing trough pressure torques. Codes developed for the simulation of flows in spheres mostly use efficient global spectral algorithms that converge fast, but lack geometric flexibility, while local methods are usable in more complex shapes, but often lack high accuracy. We therefore adapted the spectral element code Nek5000, developed at Argonne National Laboratory, to the problem. The spectral element method is capable of solving for the flow in arbitrary geometries while still offering spectral convergence. We present first results for the simulation of a purely hydrodynamic, precession-driven flow in a spheroid with no-slip boundaries and an inner core. The driving by the Poincaré force is in a range where theoretical work predicts multiple solutions for a laminar flow. Our simulations indicate a transition to turbulent flows for Ekman numbers of 10-6 and lower.

  18. Electronic spin transport and spin precession in single graphene layers at room temperature.

    PubMed

    Tombros, Nikolaos; Jozsa, Csaba; Popinciuc, Mihaita; Jonkman, Harry T; van Wees, Bart J

    2007-08-01

    Electronic transport in single or a few layers of graphene is the subject of intense interest at present. The specific band structure of graphene, with its unique valley structure and Dirac neutrality point separating hole states from electron states, has led to the observation of new electronic transport phenomena such as anomalously quantized Hall effects, absence of weak localization and the existence of a minimum conductivity. In addition to dissipative transport, supercurrent transport has also been observed. Graphene might also be a promising material for spintronics and related applications, such as the realization of spin qubits, owing to the low intrinsic spin orbit interaction, as well as the low hyperfine interaction of the electron spins with the carbon nuclei. Here we report the observation of spin transport, as well as Larmor spin precession, over micrometre-scale distances in single graphene layers. The 'non-local' spin valve geometry was used in these experiments, employing four-terminal contact geometries with ferromagnetic cobalt electrodes making contact with the graphene sheet through a thin oxide layer. We observe clear bipolar (changing from positive to negative sign) spin signals that reflect the magnetization direction of all four electrodes, indicating that spin coherence extends underneath all of the contacts. No significant changes in the spin signals occur between 4.2 K, 77 K and room temperature. We extract a spin relaxation length between 1.5 and 2 mum at room temperature, only weakly dependent on charge density. The spin polarization of the ferromagnetic contacts is calculated from the measurements to be around ten per cent. PMID:17632544

  19. Electronic spin transport and spin precession in single graphene layers at room temperature

    NASA Astrophysics Data System (ADS)

    Tombros, Nikolaos; Jozsa, Csaba; Popinciuc, Mihaita; Jonkman, Harry T.; van Wees, Bart J.

    2007-08-01

    Electronic transport in single or a few layers of graphene is the subject of intense interest at present. The specific band structure of graphene, with its unique valley structure and Dirac neutrality point separating hole states from electron states, has led to the observation of new electronic transport phenomena such as anomalously quantized Hall effects, absence of weak localization and the existence of a minimum conductivity. In addition to dissipative transport, supercurrent transport has also been observed. Graphene might also be a promising material for spintronics and related applications, such as the realization of spin qubits, owing to the low intrinsic spin orbit interaction, as well as the low hyperfine interaction of the electron spins with the carbon nuclei. Here we report the observation of spin transport, as well as Larmor spin precession, over micrometre-scale distances in single graphene layers. The `non-local' spin valve geometry was used in these experiments, employing four-terminal contact geometries with ferromagnetic cobalt electrodes making contact with the graphene sheet through a thin oxide layer. We observe clear bipolar (changing from positive to negative sign) spin signals that reflect the magnetization direction of all four electrodes, indicating that spin coherence extends underneath all of the contacts. No significant changes in the spin signals occur between 4.2K, 77K and room temperature. We extract a spin relaxation length between 1.5 and 2μm at room temperature, only weakly dependent on charge density. The spin polarization of the ferromagnetic contacts is calculated from the measurements to be around ten per cent.

  20. On turbulence driven by axial precession and tidal evolution of the spin-orbit angle of close-in giant planets

    NASA Astrophysics Data System (ADS)

    Barker, Adrian J.

    2016-08-01

    The spin axis of a rotationally deformed planet is forced to precess about its orbital angular momentum vector, due to the tidal gravity of its host star, if these directions are misaligned. This induces internal fluid motions inside the planet that are subject to a hydrodynamic instability. We study the turbulent damping of precessional fluid motions, as a result of this instability, in the simplest local computational model of a giant planet (or star), with and without a weak internal magnetic field. Our aim is to determine the outcome of this instability, and its importance in driving tidal evolution of the spin-orbit angle in precessing planets (and stars). We find that this instability produces turbulent dissipation that is sufficiently strong that it could drive significant tidal evolution of the spin-orbit angle for hot Jupiters with orbital periods shorter than about 10-18 days. If this mechanism acts in isolation, this evolution would be towards alignment or anti-alignment, depending on the initial angle, but the ultimate evolution (if other tidal mechanisms also contribute) is expected to be towards alignment. The turbulent dissipation is proportional to the cube of the precession frequency, so it leads to much slower damping of stellar spin-orbit angles, implying that this instability is unlikely to drive evolution of the spin-orbit angle in stars (either in planetary or close binary systems). We also find that the instability-driven flow can act as a system-scale dynamo, which may play a role in producing magnetic fields in short-period planets.

  1. On turbulence driven by axial precession and tidal evolution of the spin-orbit angle of close-in giant planets

    NASA Astrophysics Data System (ADS)

    Barker, Adrian J.

    2016-08-01

    The spin axis of a rotationally deformed planet is forced to precess about its orbital angular momentum vector, due to the tidal gravity of its host star, if these directions are misaligned. This induces internal fluid motions inside the planet that are subject to a hydrodynamic instability. We study the turbulent damping of precessional fluid motions, as a result of this instability, in the simplest local computational model of a giant planet (or star), with and without a weak internal magnetic field. Our aim is to determine the outcome of this instability, and its importance in driving tidal evolution of the spin-orbit angle in precessing planets (and stars). We find that this instability produces turbulent dissipation that is sufficiently strong that it could drive significant tidal evolution of the spin-orbit angle for hot Jupiters with orbital periods shorter than about 10-18 d. If this mechanism acts in isolation, this evolution would be towards alignment or anti-alignment, depending on the initial angle, but the ultimate evolution (if other tidal mechanisms also contribute) is expected to be towards alignment. The turbulent dissipation is proportional to the cube of the precession frequency, so it leads to much slower damping of stellar spin-orbit angles, implying that this instability is unlikely to drive evolution of the spin-orbit angle in stars (either in planetary or close binary systems). We also find that the instability-driven flow can act as a system-scale dynamo, which may play a role in producing magnetic fields in short-period planets.

  2. Understanding the Effect of Precession on South American Climate

    NASA Astrophysics Data System (ADS)

    Liu, X.; Battisti, D. S.

    2014-12-01

    The oxygen isotope concentration in calcite (δ18Oc) in speleothems over South America shows a distinct spatial pattern of change for the past 250,000 years orchestrated by precessional forcing. Using an isotope-enabled model (ECHAM4.6) coupled to a slab ocean model, we study how and why precession changes the climate of South America. Two experiments, called the "low insolation" experiment and "high insolation" experiment, were performed with the same modern boundary conditions, but forced with the extreme minimum and maximum of Southern Hemisphere (SH) summer insolation, respectively. Differences between these two experiments ("low" minus "high") display as a dipole pattern: less precipitation and heavier precipitation-weighted δ18O (δ18Op) along the Andes, and more precipitation and lighter δ18Op in northeastern Brazil. The differences in δ18Op are consistent with δ18Oc of speleothems, in terms of both sign and magnitude. Further analysis of the δ18O of precipitation, the δ18O of water vapor and the probability distribution function (pdf) of precipitation intensity reveals that changes in both the seasonality of precipitation and the "amount effect" contribute to the heavier δ18Op along the Andes, while the "amount effect" almost exclusively contributes to the lighter δ18Op in northeastern Brazil. To identify the causes of precipitation response, three additional experiments are performed with localized albedo increase over South America and/or Africa. These show that the decrease in precipitation along the Andes is caused by cooling of South American continent, whereas the increase in precipitation over northeastern Brazil is associated with cooling of northern Africa. Reduction of SH summer insolation cools both South America and northern Africa. Cooling of South America weakens the South American summer monsoon (SASM) and changes the pdf of precipitation intensity over tropical South America and along the Andes; contrary to previous suggestions

  3. Effective potentials and morphological transitions for binary black hole spin precession.

    PubMed

    Kesden, Michael; Gerosa, Davide; O'Shaughnessy, Richard; Berti, Emanuele; Sperhake, Ulrich

    2015-02-27

    We derive an effective potential for binary black hole (BBH) spin precession at second post-Newtonian order. This effective potential allows us to solve the orbit-averaged spin-precession equations analytically for arbitrary mass ratios and spins. These solutions are quasiperiodic functions of time: after a fixed period, the BBH spins return to their initial relative orientations and jointly precess about the total angular momentum by a fixed angle. Using these solutions, we classify BBH spin precession into three distinct morphologies between which BBHs can transition during their inspiral. We also derive a precession-averaged evolution equation for the total angular momentum that can be integrated on the radiation-reaction time and identify a new class of spin-orbit resonances that can tilt the direction of the total angular momentum during the inspiral. Our new results will help efforts to model and interpret gravitational waves from generic BBH mergers and predict the distributions of final spins and gravitational recoils. PMID:25768748

  4. Theta Phase Precession in Rat Ventral Striatum Links Place and Reward Information

    PubMed Central

    Redish, A. David

    2011-01-01

    A functional interaction between the hippocampal formation and the ventral striatum is thought to contribute to the learning and expression of associations between places and rewards. However, the mechanism of how such associations may be learned and used is currently unknown. We recorded neural ensembles and local field potentials from the ventral striatum and CA1 simultaneously as rats ran a modified T-maze. Theta-modulated cells in ventral striatum almost invariably showed firing phase precession relative to the hippocampal theta rhythm. Across the population of ventral striatal cells, phase precession was preferentially associated with an anticipatory ramping of activity up to the reward sites. In contrast, CA1 population activity and phase precession were distributed more uniformly. Ventral striatal phase precession was stronger to hippocampal than ventral striatal theta and was accompanied by increased theta coherence with hippocampus, suggesting that this effect is hippocampally derived. These results suggest that the firing phase of ventral striatal neurons contains motivationally relevant information and that phase precession serves to bind hippocampal place representations to ventral striatal representations of reward. PMID:21414906

  5. Misaligned Spin and Orbital Axes Cause the Anomalous Precession of DI Herculis

    NASA Technical Reports Server (NTRS)

    Albrecht, Simon; Reffert, Sabine; Snellen, Ignas A. G.; Winn, Joshua N.

    2009-01-01

    In this case we applied our Rossiter-McLaughlin methodology to a binary star, rather than a star-planet system. The orbits of binary stars precess as a result of general relativistic effects, forces arising from the asphericity of the stars, and forces from any additional stars or planets in the system. For most binaries, the theoretical and observed precession rates are in agreement. However, one system known as DI Herculis has resisted explanation for 30 years. The observed precession rate is a factor of four slower than the theoretical rate, a disagreement that once was interpreted as evidence for a failure of general relativity. Among the contemporary explanations are the existence of a circumbinary planet and a large tilt of the stellar spin axes with respect to the orbit. In this paper we reported that both stars of DI Herculis rotate with their spin axes nearly perpendicular to the orbital axis (contrary to the usual assumption for close binary stars). The rotationally induced stellar oblateness causes precession in the direction opposite to that of relativistic precession, thereby reconciling the theoretical and observed rates.

  6. Reference values of myocardial structure, function, and tissue composition by cardiac magnetic resonance in healthy African-Americans at 3T and their relations to serologic and cardiovascular risk factors.

    PubMed

    Liu, Chia-Ying; Bluemke, David A; Gerstenblith, Gary; Zimmerman, Stefan L; Li, Ji; Zhu, Hong; Lai, Shenghan; Lai, Hong

    2014-09-01

    Cardiac magnetic resonance (CMR) is a standard of reference for cardiac structure and function. Recent advances in T1 mapping and spectroscopy also provide assessment of myocardial tissue composition. However, the reference ranges of left ventricular parameters have rarely been assessed in an African-American (AA) population without known cardiac disease. To estimate the reference values of myocardial structure, function, and tissue composition by CMR and to explore their relationships to serologic factors and cardiovascular risk factors in asymptomatic AAs with low Framingham risk, between November 2010 and June 2012, 92 healthy AAs aged ≥21 years, from Baltimore, MD, were enrolled in an observational study. CMR examination was performed on a 3T scanner. Proton magnetic resonance spectroscopy was performed to noninvasively quantify myocardial triglyceride content. Native T1 values were obtained from modified Look-Locker inversion recovery sequence. The median age was 37 (interquartile range IQR 27 to 44) years (41% men). The median native T1 time of the myocardium was 1,228 ms (IQR 1,200 to 1,263) with no gender difference. The median myocardial fat content was 0.6% (IQR 0.7% to 4.6%). Native T1 time was not influenced by age, sex, and body mass index. Among the factors investigated, myocardial fat and elevated C-reactive protein (>2.0 mg/dL) were independently associated with T1 relaxation time. Native T1 time was also independently associated with left ventricular end-diastolic volume indexed to body surface area. In conclusion, this study of asymptomatic AAs provides reference ranges for cardiovascular structure, function, and tissue composition. Alterations in myocardial fat are associated with native T1 time, a CMR measure of interstitial fibrosis. PMID:25037675

  7. Cardiovascular Disease and Diabetes

    MedlinePlus

    ... Blood Pressure Tools & Resources Stroke More Cardiovascular Disease & Diabetes Updated:Mar 23,2016 The following statistics speak ... disease. This content was last reviewed August 2015. Diabetes • Home • About Diabetes • Why Diabetes Matters Introduction Cardiovascular ...

  8. ASCI 2010 contrast media guideline for cardiac imaging: a report of the Asian Society of Cardiovascular Imaging cardiac computed tomography and cardiac magnetic resonance imaging guideline working group

    PubMed Central

    Kitagawa, Kakuya; Tsai, I-Chen; Chan, Carmen; Yu, Wei; Yong, Hwan Seok; Choi, Byoung Wook

    2010-01-01

    The use of contrast media for cardiac imaging becomes increasing as the widespread of cardiac CT and cardiac MR. A radiologist needs to carefully consider the indication and the injection protocol of contrast media to be used as well as the possibility of adverse effect. There are several guidelines for contrast media in western countries. However, these are focusing the adverse effect of contrast media. The Asian Society of Cardiovascular Imaging, the only society dedicated to cardiovascular imaging in Asia, formed a Working Group and created a guideline, which summarizes the integrated knowledge of contrast media for cardiac imaging. In cardiac imaging, coronary artery evaluation is feasible by non-contrast MR angiography, which can be an alternative examination in high risk patients for the use of iodine contrast media. Furthermore, the body habitus of Asian patients is usually smaller than that of their western counterparts. This necessitates modifications in the injection protocol and in the formula for calculation of estimated glomerular filtration rate. This guideline provided fundamental information for the use of contrast media for Asian patients in cardiac imaging. PMID:20931289

  9. Infection and Cardiovascular Disease

    ClinicalTrials.gov

    2016-02-17

    Cardiovascular Diseases; Coronary Disease; Cerebrovascular Accident; Heart Diseases; Myocardial Infarction; Infection; Chlamydia Infections; Cytomegalovirus Infections; Helicobacter Infections; Atherosclerosis

  10. Precession-tracking coordinates for simulations of compact-object binaries

    NASA Astrophysics Data System (ADS)

    Ossokine, Serguei; Kidder, Lawrence E.; Pfeiffer, Harald P.

    2013-10-01

    Binary black hole simulations with black hole excision using spectral methods require a coordinate transformation into a corotating coordinate system where the black holes are essentially at rest. This paper presents and discusses two coordinate transformations that are applicable to precessing binary systems, one based on Euler angles, the other on quaternions. Both approaches are found to work well for binaries with moderate precession, i.e., for cases where the orientation of the orbital plane changes by ≪90°. For strong precession, performance of the Euler-angle parametrization deteriorates, eventually failing for a 90° change in orientation because of singularities in the parametrization (“gimbal lock”). In contrast, the quaternion representation is invariant under an overall rotation and handles any orientation of the orbital plane as well as the Euler-angle technique handles nonprecessing binaries.

  11. Simulation of Statistical Fluctuations in the Spin Precession Measurements at RHIC

    SciTech Connect

    Poblaguev, A. A.

    2014-02-25

    Measurements of the driven spin coherent precession Sx(t)=Sx(0) - Sx(1) sin(ωt+φ0) were initiated in RHIC Run13. The expected value of the precession amplitude Sx(1) ~ 2 x 10-4 is about the statistical error in a single measurement and data fit gives a biased estimate of the Sx(1). For a proper statistical interpretation of the results of the several measurements, statistical fluctuations were studied using Monte-Carlo simulation. Preliminary results of the spin precession measurements in RHIC Run13 are presented.

  12. Nonsingular modeling of the equinoctial precession of planets using the Euler parameters

    NASA Astrophysics Data System (ADS)

    Gurfil, Pini; Klein, Itzik

    2007-01-01

    This paper develops a nonsingular model for the effect of equinoctial precession on natural and artificial satellite orbits based on the Euler parameters instead of the Euler angles. The use of Euler parameters removes the zero-inclination singularity in the variational equations, thus facilitating numerical integration of low-inclination orbits. Euler-parameter-based planetary and variational equations are developed. These equations are subsequently used for modeling the long-periodic effect of a uniformly precessing reference frame on a given orbit. The Euler parameter-based model is used for simulating the orbit of Deimos, taking into account the Martian oblateness and precession of the spin axis. It is shown that the new model yields an order-of-magnitude faster simulation than the classical element-based model.

  13. Rotational Kinematics and Torques for Triaxial Bodies: A Simple Derivation of Precession with Synchronous Locking

    NASA Astrophysics Data System (ADS)

    Newman, William I.

    2012-05-01

    Precession of the equinoxes and of satellite orbits for axisymmetric bodies is a celebrated part of the classical and orbital mechanics literature. The theory underlying the behavior of triaxial bodies, particularly when synchronous phase locking is present, has proven to be difficult to evaluate and controversial. We perform a first-principles derivation where we incorporate triaxial geometry into the analysis using a straightforward description of the configuration. We calculate the effect of triaxiality and phase locking upon precession rates by using multiple time scales techniques. This is required to make possible the direct numerical integration of the kinematic equations of motion over solar system time scales. In so doing, we provide a simple derivation of the time-averaged gravitational potential and the associated torque that drives precession, and resolve an outstanding controversy emerging from its calculation.

  14. CYCLIC TRANSIT PROBABILITIES OF LONG-PERIOD ECCENTRIC PLANETS DUE TO PERIASTRON PRECESSION

    SciTech Connect

    Kane, Stephen R.; Von Braun, Kaspar; Horner, Jonathan

    2012-09-20

    The observed properties of transiting exoplanets are an exceptionally rich source of information that allows us to understand and characterize their physical properties. Unfortunately, only a relatively small fraction of the known exoplanets discovered using the radial velocity technique are known to transit their host due to the stringent orbital geometry requirements. For each target, the transit probability and predicted transit time can be calculated to great accuracy with refinement of the orbital parameters. However, the transit probability of short period and eccentric orbits can have a reasonable time dependence due to the effects of apsidal and nodal precession, thus altering their transit potential and predicted transit time. Here we investigate the magnitude of these precession effects on transit probabilities and apply this to the known radial velocity exoplanets. We assess the refinement of orbital parameters as a path to measuring these precessions and cyclic transit probabilities.

  15. Crystalline Direction Dependence of Spin Precession Angle and Its Application to Complementary Spin Logic Devices.

    PubMed

    Park, Youn Ho; Kim, Hyung-Jun; Chang, Joonyeon; Choi, Heon-Jin; Koo, Hyun Cheol

    2015-10-01

    In a semiconductor channel, spin-orbit interaction is divided into two terms, Rashba and Dresselhaus effects, which are key phenomena for modulating spin precession angles. The direction of Rashba field is always perpendicular to the wavevector but that of Dresselhaus field depends on the crystal orientation. Based on the individual Rashba and Dresselhaus strengths, we calculate spin precession angles for various crystal orientations in an InAs quantum well structure. When the channel length is 1 μm, the precession angle is 550° for the [110] direction and 460° for the [1-10] direction, respectively. Using the two spin transistors with different crystal directions, which play roles of n- and p-type transistors in conventional charge transistors, we propose a complementary logic device. PMID:26726362

  16. The Origin of Warped, Precessing Accretion Disks in X-ray Binaries

    NASA Technical Reports Server (NTRS)

    Maloney, Philip R.; Begelman, Mitchell C.

    1997-01-01

    The radiation-driven warping instability discovered by Pringle holds considerable promise as the mechanism responsible for producing warped, precessing accretion disks in X-ray binaries. This instability is an inherently global mode of the disk, thereby avoiding the difficulties with earlier models for the precession. Here we follow up on earlier work to study the linear behavior of the instability in the specific context of a binary system. We treat the influence of the companion as an orbit-averaged quadrupole torque on the disk. The presence of this external torque allows the existence of solutions in which the direction of precession of the warp is retrograde with respect to disk rotation, in addition to the prograde solutions that exist in the absence of external torques.

  17. Gravitational waves from rotating and precessing rigid bodies - Simple models and applications to pulsars

    NASA Technical Reports Server (NTRS)

    Zimmermann, M.; Szedenits, E., Jr.

    1979-01-01

    An axially symmetric, torque-free rigid body, rotating and precessing, emits gravitational quadrupole radiation at two frequencies, omega and 2 omega, corresponding to the l = 2, m = 1,2 spherical harmonics. The paper presents explicitly the waveforms of the two polarizations at both frequencies. From observations of gravitational waves, one can derive information about the body's orientation and its precession amplitude. Electromagnetic radiation emitted by a spot fixed on the surface of the body arrives in pulses at a mean frequency Omega which is typically different from omega. If the body is not axially symmetric but the amplitude of the precession is small, the gravitational radiation at the lower frequency omega is split into two frequencies on either side of the electromagnetic pulse frequency. Explicit waveforms for the two polarizations in this case are also presented.

  18. Subcritical transition to turbulence of a precessing flow in a cylindrical vessel

    NASA Astrophysics Data System (ADS)

    Herault, Johann; Gundrum, Thomas; Giesecke, André; Stefani, Frank

    2015-12-01

    The transition to turbulence in a precessing cylindrical vessel is experimentally investigated. Our measurements are performed for a nearly resonant configuration with an initially laminar flow dominated by an inertial mode with azimuthal wave number m = 1 superimposed on a solid body rotation. By increasing the precession ratio, we observe a transition from the laminar to a non-linear regime, which then breakdowns to turbulence for larger precession ratio. Our measurements show that the transition to turbulence is subcritical, with a discontinuity of the wall-pressure and the power consumption at the threshold ɛLT. The turbulence is self-sustained below this threshold, describing a bifurcation diagram with a hysteresis. In this range of the control parameters, the turbulent flows can suddenly collapse after a finite duration, leading to a definitive relaminarization of the flow. The average lifetime <τ> of the turbulence increases rapidly when ɛ tends to ɛLT.

  19. On the three-dimensional precessing jet flow past a sudden expansion

    NASA Astrophysics Data System (ADS)

    Cafiero, Gioacchino; Ceglia, Giuseppe; Discetti, Stefano; Ianiro, Andrea; Astarita, Tommaso; Cardone, Gennaro

    2014-02-01

    A circular jet flow past an abrupt expansion under some conditions switches intermittently between two states: quasi-axisymmetric expansion and gyroscopic-like precessing motion. In this work, an experimental investigation into the self-excited precessing flow generated by a 5:1 expansion of a round jet in a coaxial cylindrical chamber is carried out by means of tomographic particle image velocimetry. The experiments are performed on a jet issued from a short pipe at a Reynolds number equal to 150,000. Proper orthogonal decomposition (POD) is applied to extract information on the organization of the large coherent structures of the precessing motion. The application of this technique highlights the dominance of three modes: the most energetic two are associated with the jet precession; the third one is representative of the axial motion. An estimate of the precession probability based on the modal energy obtained from the application of POD is proposed. The precession frequency is extracted using a low-order reconstruction (LOR) of a subset of the POD modes. The reconstructed flow field topology obtained by the LOR highlights an underlying mechanism of swirl generation in proximity of the inlet nozzle; the phenomenon is closely related to the interaction between the entrainment in the far field and the recirculation regions in the near field. The application of a stability criterion shows that the self-induced swirl flow results to be unstable. The instability is responsible for the generation of helical-shaped vortices in the near field, even though the dominant feature for the unconfined jet issued from the same nozzle is the axisymmetric ring-vortices generation.

  20. Jupiter spin-pole precession rate and moment of inertia from Juno radio-science observations

    NASA Astrophysics Data System (ADS)

    Le Maistre, S.; Folkner, W. M.; Jacobson, R. A.; Serra, D.

    2016-07-01

    Through detailed and realistic numerical simulations, the present paper assesses the precision with which the Juno spacecraft can measure the normalized polar moment of inertia (MOI) of Jupiter. Based on Ka-band Earth-based Doppler data, created with realistic 10 μm/s of white noise at 60 s of integration, this analysis shows that the determination of the precession rate of Jupiter is by far more efficient than the Lense-Thirring effect previously proposed to determine the moment of inertia and therefore to constrain the internal structure of the giant planet with Juno. We show that the Juno mission will allow the estimation of the precession rate of Jupiter's pole with an accuracy better than 0.1%. We provide an equation relating the pole precession rate and the normalized polar moment of inertia of Jupiter. Accounting for the uncertainty in the parameters affecting precession, we show that the accuracy of the MOI inferred from the precession rate is also better than 0.1%, and at least 50 times better than inferred from the Lense-Thirring acceleration undergone by Juno. This accuracy of the MOI determination should provide tight constraints on the interior structure of Jupiter, especially the core size and mass, helping to distinguish among competing scenarios of formation and evolution of the giant planet. In addition, though the Juno mission operations are already defined, the exact duration of the tracking and its occurrence with respect to the spacecraft pericenter pass are not definitely scheduled. The simulations performed here quantify the impact of this aspect of the mission on the Juno sensitivity to (in particular) the spin-pole precession rate of Jupiter. Finally, additional simulations have been performed to test the usefulness of combining Doppler data with VLBI data, showing the latter measurements to be 104-105 times less sensitive than the former to our parameters of interest and therefore, obviously, totally needless.

  1. Predicting Precession Rates from Secular Dynamics for Extra-solar Multi-planet Systems

    NASA Astrophysics Data System (ADS)

    Van Laerhoven, Christa

    2015-12-01

    Considering the secular dynamics of multi-planet systems provides substantial insight into the interactions between planets in those systems. Secular interactions are those that don't involve knowing where a planet is along its orbit, and they dominate when planets are not involved in mean motion resonances. These interactions exchange angular momentum among the planets, evolving their eccentricities and inclinations. To second order in the planets' eccentricities and inclinations, the eccentricity and inclination perturbations are decoupled. Given the right variable choice, the relevant differential equations are linear and thus the eccentricity and inclination behaviors can be described as a sum of eigenmodes. Since the underlying structure of the secular eigenmodes can be calculated using only the planets' masses and semi-major axes, one can elucidate the eccentricity and inclination behavior of planets in exoplanet systems even without knowing the planets' current eccentricities and inclinations. I have calculated both the eccentricity and inclination secular eigenmodes for the population of known multi-planet systems whose planets have well determined masses and periods and have used this to predict what range of pericenter precession (and nodal regression) rates the planets may have. One might have assumed that in any given system the planets with shorter periods would have faster precession rates, but I show that this is not necessarily the case. Planets that are 'loners' have narrow ranges of possible precession rates, while planets that are 'groupies' can have a wider range of possible precession rates. Several planets are expected to undergo significant precession on few-year timescales and many planets (though not the majority of planets) will undergo significant precession on decade timescales.

  2. Precession Constant Correction and Proper Motion Systems of FK5 and Hipparcos

    NASA Astrophysics Data System (ADS)

    Zhu, Zi

    2007-07-01

    Results of many researches have shown that the relation between the proper motion systems of FK5 and Hipparcos is not consistent with the precession constant corrections determined by VLBI and LLR. We analysed proper motion data of PPM and ACRS based on the FK5 system for many different sub-samples and found that consistent values of the precession correction and equinox motion correction can not be given by either PPM or ACRS proper motion data, thereby indicating that the internal systematic error of the FK5 proper motion is the main underlying factor of the inconsistency.

  3. New test of general relativity - Measurement of de Sitter geodetic precession rate for lunar perigee

    NASA Technical Reports Server (NTRS)

    Bertotti, Bruno; Ciufolini, Ignazio; Bender, Peter L.

    1987-01-01

    According to general relativity, the calculated rate of motion of lunar perigee should include a contribution of 19.2 msec/yr from geodetic precession. It is shown that existing analyses of lunar-laser-ranging data confirm the general-relativistic rate for geodetic precession with respect to the planetary dynamical frame. In addition, the comparison of earth-rotation results from lunar laser ranging and from VLBI shows that the relative drift of the planetary dynamical frame and the extragalactic VLBI reference frame is small. The estimated accuracy is about 10 percent.

  4. The evolution of adopted values for precession. [historical survey of reference systems

    NASA Technical Reports Server (NTRS)

    Lieske, J. H.

    1985-01-01

    The history of astronomical longitude precession determination is reviewed. Consideration is given to the work of Hipparchus and Ptolemy, the definition of rotation axes, the major 19th-century determinations, and 20th-century studies (using the data of Newcomb; based on PGC, GC, and McCormick/Cape catalogs; using FK3, FK4, and AGK3; involving galaxies; and using the dynamical method). Laser ranging and VLBI are seen as the most promising techniques for future precession measurements. Diagrams, graphs, and tables of numerical data are provided.

  5. Probing white dwarf interiors with LISA: periastron precession in eccentric double white dwarfs.

    PubMed

    Willems, B; Vecchio, A; Kalogera, V

    2008-02-01

    In globular clusters, dynamical interactions give rise to a population of eccentric double white dwarfs detectable by the Laser Interferometer Space Antenna (LISA) up to the Large Magellanic Cloud. In this Letter, we explore the detectability of periastron precession in these systems with LISA. Unlike previous investigations, we consider contributions due to tidal and rotational distortions of the binary components in addition to general relativistic contributions to the periastron precession. At orbital frequencies above a few mHz, we find that tides and stellar rotation dominate, opening up a possibly unique window to the study of the interior and structure of white dwarfs. PMID:18352253

  6. Optimal three-dimensional reusable tug trajectories for planetary missions including correction for nodal precession

    NASA Technical Reports Server (NTRS)

    Borsody, J.

    1976-01-01

    Equations are derived by using the maximum principle to maximize the payload of a reusable tug for planetary missions. The analysis includes a correction for precession of the space shuttle orbit. The tug returns to this precessed orbit (within a specified time) and makes the required nodal correction. A sample case is analyzed that represents an inner planet mission as specified by a fixed declination and right ascension of the outgoing asymptote and the mission energy. The reusable stage performance corresponds to that of a typical cryogenic tug. Effects of space shuttle orbital inclination, several trajectory parameters, and tug thrust on payload are also investigated.

  7. [Cardiovascular safety of antidiabetics].

    PubMed

    Aline Roth, Pressl-Wenger; Jornayvaz, François R

    2016-06-01

    Type 2 diabetes is characterized by a high risk of micro- and macro-vascular complications. Cardiovascular diseases are the leading cause of death of diabetic patients. In this context, the search for molecules decreasing cardiovascular mortality makes sense. Until the EMPA-REG OUTCOME study published late 2015, showing a reduction of cardiovascular mortality of patients treated with empagliflozin, an SGLT2 inhibitor, there was no molecule known to decrease cardiovascular mortality. The purpose of this article is to review the various existing antidiabetic molecules and their impact (positive/neutral/negative) on cardiovascular mortality. PMID:27487675

  8. Dynamics of nuclear spin polarization induced and detected by coherently precessing electron spins in fluorine-doped ZnSe

    NASA Astrophysics Data System (ADS)

    Heisterkamp, F.; Kirstein, E.; Greilich, A.; Zhukov, E. A.; Kazimierczuk, T.; Yakovlev, D. R.; Pawlis, A.; Bayer, M.

    2016-02-01

    We study the dynamics of optically induced nuclear spin polarization in a fluorine-doped ZnSe epilayer via time-resolved Kerr rotation. The nuclear polarization in the vicinity of a fluorine donor is induced by interaction with coherently precessing electron spins in a magnetic field applied in the Voigt geometry. It is detected by nuclei-induced changes in the electron spin coherence signal. This all-optical technique allows us to measure the longitudinal spin relaxation time T1 of the 77Se isotope in a magnetic field range from 10 to 130 mT under illumination. We combine the optical technique with radio frequency methods to address the coherent spin dynamics of the nuclei and measure Rabi oscillations, Ramsey fringes, and the nuclear spin echo. The inhomogeneous spin dephasing time T2* and the spin coherence time T2 of the 77Se isotope are measured. While the T1 time is on the order of several milliseconds, the T2 time is several hundred microseconds. The experimentally determined condition T1≫T2 verifies the validity of the classical model of nuclear spin cooling for describing the optically induced nuclear spin polarization.

  9. Pure collective precession motion of a high-spin torus isomer

    NASA Astrophysics Data System (ADS)

    Ichikawa, T.; Matsuyanagi, K.; Maruhn, J. A.; Itagaki, N.

    2014-01-01

    We investigate the precession motion of the exotic torus configuration in high-spin excited states of 40Ca. For this aim, we use the three-dimensional time-dependent Hartree-Fock (TDHF) method. Although the high-spin torus isomer is a unique quantum object characterized by the alignment of angular momenta of independent single-particle motions, we find that the obtained moment of inertia for rotations about an axis perpendicular to the symmetry axis is close to the rigid-body value. We also analyze the microscopic structure of the precession motion using the random-phase approximation (RPA) method for high-spin states. In the RPA calculation, the precession motion of the torus isomer is generated by coherent superposition of many one-particle-one-hole excitations across the sloping Fermi surface that strongly violates the time-reversal symmetry. By comparing results of the TDHF and the RPA calculations, we find that the precession motion obtained by the TDHF calculation is a pure collective motion well decoupled from other collective modes.

  10. THE DETECTABILITY OF TRANSIT DEPTH VARIATIONS DUE TO EXOPLANETARY OBLATENESS AND SPIN PRECESSION

    SciTech Connect

    Carter, Joshua A.; Winn, Joshua N.

    2010-06-10

    Knowledge of an exoplanet's oblateness and obliquity would give clues about its formation and internal structure. In principle, a light curve of a transiting planet bears information about the planet's shape, but previous work has shown that the oblateness-induced signal will be extremely difficult to detect. Here, we investigate the potentially larger signals due to planetary spin precession. The most readily detectable effects are transit depth variations (T{delta}V's) in a sequence of light curves. For a planet as oblate as Jupiter or Saturn, the transit depth will undergo fractional variations of order 1%. The most promising systems are those with orbital periods of approximately 15-30 days, which are short enough for the precession period to be less than about 40 yr and long enough to avoid spin-down due to tidal friction. The detectability of the T{delta}V signal would be enhanced by moons (which would decrease the precession period) or planetary rings (which would increase the amplitude). The Kepler mission should find several planets for which precession-induced T{delta}V signals will be detectable. Due to modeling degeneracies, Kepler photometry would yield only a lower bound on oblateness. The degeneracy could be lifted by observing the oblateness-induced asymmetry in at least one transit light curve or by making assumptions about the planetary interior.

  11. Measurement of the Nodal Precession of WASP-33 b via Doppler Tomography

    NASA Astrophysics Data System (ADS)

    Johnson, Marshall C.; Cochran, William D.; Collier Cameron, Andrew; Bayliss, Daniel

    2015-09-01

    We have analyzed new and archival time series spectra taken six years apart during transits of the hot Jupiter WASP-33 b, and spectroscopically resolved the line profile perturbation caused by the Rossiter-McLaughlin effect. The motion of this line profile perturbation is determined by the path of the planet across the stellar disk, which we show to have changed between the two epochs due to nodal precession of the planetary orbit. We measured rates of change of the impact parameter and the sky-projected spin-orbit misalignment of {db}/{dt}={-0.0228}-0.0018+0.0050 {{yr}}-1 and dλ /{dt}={-0\\buildrel{\\circ}\\over{.} 487}-0.076+0.089 {{yr}}-1, respectively, corresponding to a rate of nodal precession of d{{Ω }}/{dt}=0\\buildrel{\\circ}\\over{.} {373}-0.083+0.031 {{yr}}-1. This is only the second measurement of nodal precession for a confirmed exoplanet transiting a single star. Finally, we used the rate of precession to set limits on the stellar gravitational quadrupole moment of 0.0054≤slant {J}2≤slant 0.035.

  12. Numerical expressions for precession formulae and mean elements for the Moon and the planets

    NASA Astrophysics Data System (ADS)

    Simon, J. L.; Bretagnon, P.; Chapront, J.; Chapront-Touze, M.; Francou, G.; Laskar, J.

    1994-02-01

    We present, in this paper, a coherent set of formula giving numerical expressions for precession quantities and mean elements of the Moon and the planets. First, using the notations of Lieske et al. (1977), we construct expressions for the precession quantities based upon the use of the secular variations of the ecliptic pole from the planetary theories built at the Bureau des Longitudes and taking into account recent determinations of the precession constant and of the obliquity in J2000. Also we give the derivatives of these expressions with respect to the masses of the planets, to the precession constant and to the obliquity. So, this set of formulas is applicable whenever the values of the planetary masses and of the constants are improved. Afterwards, we give the mean elements of the Moon and the planets connected to the fixed J2000 ecliptic and connected to the ecliptic of date. At last, we give formula which enable one to compute approximate ephemerides of the Moon and the planets from mean elements.

  13. Elementary Analysis of the Special Relativistic Combination of Velocities, Wigner Rotation and Thomas Precession

    ERIC Educational Resources Information Center

    O'Donnell, Kane; Visser, Matt

    2011-01-01

    The purpose of this paper is to provide an elementary introduction to the qualitative and quantitative results of velocity combination in special relativity, including the Wigner rotation and Thomas precession. We utilize only the most familiar tools of special relativity, in arguments presented at three differing levels: (1) utterly elementary,…

  14. Cardiovascular MRI with ferumoxytol.

    PubMed

    Finn, J P; Nguyen, K-L; Han, F; Zhou, Z; Salusky, I; Ayad, I; Hu, P

    2016-08-01

    The practice of contrast-enhanced magnetic resonance angiography (CEMRA) has changed significantly in the span of a decade. Concerns regarding gadolinium (Gd)-associated nephrogenic systemic fibrosis in those with severely impaired renal function spurred developments in low-dose CEMRA and non-contrast MRA as well as efforts to seek alternative MR contrast agents. Originally developed for MR imaging use, ferumoxytol (an ultra-small superparamagnetic iron oxide nanoparticle), is currently approved by the US Food and Drug Administration for the treatment of iron deficiency anaemia in adults with renal disease. Since its clinical availability in 2009, there has been rising interest in the scientific and clinical use of ferumoxytol as an MR contrast agent. The unique physicochemical and pharmacokinetic properties of ferumoxytol, including its long intravascular half-life and high r1 relaxivity, support a spectrum of MRI applications beyond the scope of Gd-based contrast agents. Moreover, whereas Gd is not found in biological systems, iron is essential for normal metabolism, and nutritional iron deficiency poses major public health challenges worldwide. Once the carbohydrate shell of ferumoxytol is degraded, the elemental iron at its core is incorporated into the reticuloendothelial system. These considerations position ferumoxytol as a potential game changer in the field of CEMRA and MRI. In this paper, we aim to summarise our experience with the cardiovascular applications of ferumoxytol and provide a brief synopsis of ongoing investigations on ferumoxytol-enhanced MR applications. PMID:27221526

  15. The impact of precession and obliquity on the Late-Devonian greenhouse climate

    NASA Astrophysics Data System (ADS)

    De Vleeschouwer, D.; Crucifix, M.; Bounceur, N.; Claeys, P. F.

    2012-12-01

    To date, only few general circulation model (GCM) have been used to simulate the extremely warm greenhouse climate of the Late-Devonian (~370 Ma). As a consequence, the current knowledge on Devonian climate dynamics comes almost exclusively from geological proxy data. Given the fragmentary nature of these data sources, the understanding of the Devonian climate is rather limited. Nonetheless, the Late-Devonian is a key-period in the evolution of life on Earth: the continents were no longer bare but were invaded by land plants, the first forests appeared, soils were formed, fish evolved to amphibians and 70-80% of all animal species were wiped out during the Late Devonian extinction (~376 Ma). In order to better understand the functioning of the climate system during this highly important period in Earth's history, we applied the HadSM3 climate model to the Devonian period under different astronomical configurations. This approach provides insight into the response of Late-Devonian climate to astronomical forcing due to precession and obliquity. Moreover, the assessment of the sensitivity of the Late-Devonian climate to astronomical forcing, presented here, will allow cyclostratigraphers to make better and more detailed interpretations of recurring patterns often observed in Late-Devonian sections. We simulated Late-Devonian climates by prescribing palaeogeography, vegetation distribution and pCO2 concentration (2180 ppm). Different experiments were carried out under 31 different astronomical configurations: three levels for obliquity (ɛ = 22°; 23.5° and 24.5°) and eccentricity (e = 0; 0.03 and 0.07) were chosen. For precession, 8 levels were considered (longitude of the perihelion= 0°; 45°; 90°; 135°; 180°; 235°; 270°). First results suggest that the intensity of precipitation on the tropical Euramerican continent (also known as Laurussia) is highly dependent on changes in precession: During precession maxima (= maximal insolation in SH during winter

  16. Spin precession by pulsed inductive magnetometry in thin amorphous plates

    SciTech Connect

    Magni, Alessandro; Bottauscio, Oriano; Caprile, Ambra Celegato, Federica; Ferrara, Enzo; Fiorillo, Fausto

    2014-05-07

    Broadband magnetic loss and damping behavior of Co-based amorphous ribbons and thin films have been investigated. The permeability and loss response of the transverse anisotropy ribbon samples in the frequency range DC to 1 GHz is interpreted in terms of combined and distinguishable contributions to the magnetization process by domain wall displacements and magnetization rotations. The latter alone are shown to survive at the highest frequencies, where the losses are calculated via coupled Maxwell and Landau–Lifshitz–Gilbert (LLG) equations. Remarkably high values of the LLG damping coefficient α = 0.1–0.2 are invoked in this theoretical prediction. Direct measurements of α by pulsed inductive microwave magnetometry are thus performed, both in these laminae and in amorphous films of identical composition, obtaining about one order of magnitude increase of the α value upon the 100 nm÷10 μm thickness range. This confirms that dissipation by eddy currents enters the LLG equation via large increase of the damping coefficient.

  17. Spin precession by pulsed inductive magnetometry in thin amorphous plates

    NASA Astrophysics Data System (ADS)

    Magni, Alessandro; Bottauscio, Oriano; Caprile, Ambra; Celegato, Federica; Ferrara, Enzo; Fiorillo, Fausto

    2014-05-01

    Broadband magnetic loss and damping behavior of Co-based amorphous ribbons and thin films have been investigated. The permeability and loss response of the transverse anisotropy ribbon samples in the frequency range DC to 1 GHz is interpreted in terms of combined and distinguishable contributions to the magnetization process by domain wall displacements and magnetization rotations. The latter alone are shown to survive at the highest frequencies, where the losses are calculated via coupled Maxwell and Landau-Lifshitz-Gilbert (LLG) equations. Remarkably high values of the LLG damping coefficient α = 0.1-0.2 are invoked in this theoretical prediction. Direct measurements of α by pulsed inductive microwave magnetometry are thus performed, both in these laminae and in amorphous films of identical composition, obtaining about one order of magnitude increase of the α value upon the 100 nm÷10 μm thickness range. This confirms that dissipation by eddy currents enters the LLG equation via large increase of the damping coefficient.

  18. Reducing Field Distortion in Magnetic Resonance Imaging

    NASA Technical Reports Server (NTRS)

    Eom, Byeong Ho; Penanen, Konstantin; Hahn, Inseob

    2010-01-01

    A concept for a magnetic resonance imaging (MRI) system that would utilize a relatively weak magnetic field provides for several design features that differ significantly from the corresponding features of conventional MRI systems. Notable among these features are a magnetic-field configuration that reduces (relative to the conventional configuration) distortion and blurring of the image, the use of a superconducting quantum interference device (SQUID) magnetometer as the detector, and an imaging procedure suited for the unconventional field configuration and sensor. In a typical application of MRI, a radio-frequency pulse is used to excite precession of the magnetic moments of protons in an applied magnetic field, and the decaying precession is detected for a short time following the pulse. The precession occurs at a resonance frequency proportional to the strengths of the magnetic field and the proton magnetic moment. The magnetic field is configured to vary with position in a known way; hence, by virtue of the aforesaid proportionality, the resonance frequency varies with position in a known way. In other words, position is encoded as resonance frequency. MRI using magnetic fields weaker than those of conventional MRI offers several advantages, including cheaper and smaller equipment, greater compatibility with metallic objects, and higher image quality because of low susceptibility distortion and enhanced spin-lattice-relaxation- time contrast. SQUID MRI is being developed into a practical MRI method for applied magnetic flux densities of the order of only 100 T

  19. Obesity and cardiovascular disease.

    PubMed

    Jokinen, E

    2015-02-01

    Cardiovascular disease is the most common cause of mortality in rich countries and today it has the same meaning for health care as the epidemics of past centuries had for medicine in earlier times: 50% of the population in these countries die of cardiovascular disease. The amount of cardiovascular disease is also increasing in the developing countries together with economic growth. By 2015 one in three deaths will globally be due to cardiovascular diseases. Coronary heart disease is a chronic disease that starts in childhood, even if the symptoms first occur in the middle age. The risks for coronary heart disease are well-known: lipid disorders, especially high serum LDL-cholesterol concentration, high blood pressure, tobacco smoking, obesity, diabetes, male gender and physical inactivity. Obesity is both an independent risk factor for cardiovascular disease but is also closely connected with several other risk factors. This review focuses on the connection between overweight or obesity and cardiovascular disease. PMID:25387321

  20. Synchronously pumped nuclear magnetic oscillator

    NASA Astrophysics Data System (ADS)

    Korver, Anna; Thrasher, Daniel; Bulatowicz, Michael; Walker, Thad

    2015-05-01

    We present progress towards a synchronously pumped nuclear magnetic oscillator. Alkali frequency shifts and quadrupole shifts are the dominant systematic effects in dual Xe isotope co-magnetometers. By synchronously pumping the Xe nuclei using spin-exchange with an oscillating Rb polarization, the Rb and Xe spins precess transverse to the longitudinal bias field. This configuration is predicted to be insensitive to first order quadrupole interactions and alkali spin-exchange frequency shifts. A key feature that allows co-precession of the Rb and Xe spins, despite a ~ 1000 fold ratio of their gyromagnetic ratios, is to apply the bias field in the form of a sequence of Rb 2 π pulses whose repetition frequency is equal to the Rb Larmor frequency. The 2 π pulses result in an effective Rb magnetic moment of zero, while the Xe precession depends only on the time average of the pulsed field amplitude. Polarization modulation of the pumping light at the Xe NMR frequency allows co-precession of the Rb and Xe spins. We will present our preliminary experimental studies of this new approach to NMR of spin-exchange pumped Xe. Support by the NSF and Northrop Grumman Co.

  1. Analysis of spin precession in binary black hole systems including quadrupole-monopole interaction

    NASA Astrophysics Data System (ADS)

    Racine, Étienne

    2008-08-01

    We analyze in detail the spin precession equations in binary black hole systems, when the tidal torque on a Kerr black hole due to quadrupole-monopole coupling is taken into account. We show that completing the precession equations with this term reveals the existence of a conserved quantity at 2PN order when averaging over orbital motion. This quantity allows one to solve the (orbit-averaged) precession equations exactly in the case of equal masses and arbitrary spins, neglecting radiation reaction. For unequal masses, an exact solution does not exist in closed form, but we are still able to derive accurate approximate analytic solutions. We also show how to incorporate radiation-reaction effects into our analytic solutions adiabatically, and compare the results to solutions obtained numerically. For various configurations of the binary, the relative difference in the accumulated orbital phase computed using our analytic solutions versus a full numerical solution varies from ˜0.3% to ˜1.8% over ˜80 140 orbital cycles accumulated while sweeping over the orbital frequency range ˜20 300Hz. This typically corresponds to a discrepancy of order ˜5 6 radians. While this may not be accurate enough for implementation in LIGO template banks, we still believe that our new solutions are potentially quite useful for comparing numerical relativity simulations of spinning binary black hole systems with post-Newtonian theory. They can also be used to gain more understanding of precession effects, with potential application to the gravitational recoil problem, and to provide semianalytical templates for spinning, precessing binaries.

  2. Effects of the observed J2 variations on the Earth's precession and nutation

    NASA Astrophysics Data System (ADS)

    Ferrándiz, José M.; Baenas, Tomás; Belda, Santiago

    2016-04-01

    The Earth's oblateness parameter J2 is closely related to the dynamical ellipticity H, which factorizes the main components of the precession and the different nutation terms. In most theoretical approaches to the Earth's rotation, with IAU2000 nutation theory among them, H is assumed to be constant. The precession model IAU2006 supposes H to have a conventional linear variation, based on the J2 time series derived mainly from satellite laser ranging (SLR) data for decades, which gives rise to an additional quadratic term of the precession in longitude and some corrections of the nutation terms. The time evolution of J2 is, however, too complex to be well approximated by a simple linear model. The effect of more general models including periodic terms and closer to the observed time series, although still unable to reproduce a significant part of the signal, has been seldom investigated. In this work we address the problem of deriving the effect of the observed J2 variations without resorting to such simplified models. The Hamiltonian approach to the Earth rotation is extended to allow the McCullagh's term of the potential to depend on a time-varying oblateness. An analytical solution is derived by means of a suitable perturbation method in the case of the time series provided by the Center for Space Research (CSR) of the University of Texas, which results in non-negligible contributions to the precession-nutation angles. The presentation focuses on the main effects on the longitude of the equator; a noticeable non-linear trend is superimposed to the linear main precession term, along with some periodic and decadal variations.

  3. High spatial resolution brain functional MRI using submillimeter balanced steady-state free precession acquisition

    SciTech Connect

    Wu, Pei-Hsin; Chung, Hsiao-Wen; Tsai, Ping-Huei; Wu, Ming-Long; Chuang, Tzu-Chao; Shih, Yi-Yu; Huang, Teng-Yi

    2013-12-15

    Purpose: One of the technical advantages of functional magnetic resonance imaging (fMRI) is its precise localization of changes from neuronal activities. While current practice of fMRI acquisition at voxel size around 3 × 3 × 3 mm{sup 3} achieves satisfactory results in studies of basic brain functions, higher spatial resolution is required in order to resolve finer cortical structures. This study investigated spatial resolution effects on brain fMRI experiments using balanced steady-state free precession (bSSFP) imaging with 0.37 mm{sup 3} voxel volume at 3.0 T. Methods: In fMRI experiments, full and unilateral visual field 5 Hz flashing checkerboard stimulations were given to healthy subjects. The bSSFP imaging experiments were performed at three different frequency offsets to widen the coverage, with functional activations in the primary visual cortex analyzed using the general linear model. Variations of the spatial resolution were achieved by removing outerk-space data components. Results: Results show that a reduction in voxel volume from 3.44 × 3.44 × 2 mm{sup 3} to 0.43 × 0.43 × 2 mm{sup 3} has resulted in an increase of the functional activation signals from (7.7 ± 1.7)% to (20.9 ± 2.0)% at 3.0 T, despite of the threefold SNR decreases in the original images, leading to nearly invariant functional contrast-to-noise ratios (fCNR) even at high spatial resolution. Activation signals aligning nicely with gray matter sulci at high spatial resolution would, on the other hand, have possibly been mistaken as noise at low spatial resolution. Conclusions: It is concluded that the bSSFP sequence is a plausible technique for fMRI investigations at submillimeter voxel widths without compromising fCNR. The reduction of partial volume averaging with nonactivated brain tissues to retain fCNR is uniquely suitable for high spatial resolution applications such as the resolving of columnar organization in the brain.

  4. ASCI 2010 appropriateness criteria for cardiac magnetic resonance imaging: a report of the Asian Society of Cardiovascular Imaging cardiac computed tomography and cardiac magnetic resonance imaging guideline working group

    PubMed Central

    Choi, Byoung Wook; Chan, Carmen; Jinzaki, Masahiro; Tsai, I-Chen; Yong, Hwan Seok; Yu, Wei

    2010-01-01

    There has been a growing need for standard Asian population guidelines for cardiac CT and cardiac MR due to differences in culture, healthcare system, ethnicity and disease prevalence. The Asian Society of Cardiovascular Imaging, as the only society dedicated to cardiovascular imaging in Asia, formed a cardiac CT and cardiac MR guideline working group in order to help Asian practitioners to establish cardiac CT and cardiac MR services. In this ASCI cardiac MR appropriateness criteria report, 23 Technical Panel members representing various Asian countries were invited to rate 50 indications that can frequently be encountered in clinical practice in Asia. Indications were rated on a scale of 1–9 to be categorized into ‘appropriate’ (7–9), ‘uncertain’ (4–6), or ‘inappropriate’ (1–3). According to median scores of the 23 members, the final ratings for indications were 24 appropriate, 18 uncertain and 8 inappropriate with 22 ‘highly-agreed’ (19 appropriate and 3 inappropriate) indications. This report is expected to have a significant impact on the cardiac MR practices in many Asian countries by promoting the appropriate use of cardiac MR. Electronic supplementary material The online version of this article (doi:10.1007/s10554-010-9687-z) contains supplementary material, which is available to authorized users. PMID:20734234

  5. Obesity reduces left ventricular strains, torsion, and synchrony in mouse models: a cine displacement encoding with stimulated echoes (DENSE) cardiovascular magnetic resonance study

    PubMed Central

    2013-01-01

    Background Obesity affects a third of adults in the US and results in an increased risk of cardiovascular mortality. While the mechanisms underlying this increased risk are not well understood, animal models of obesity have shown direct effects on the heart such as steatosis and fibrosis, which may affect cardiac function. However, the effect of obesity on cardiac function in animal models is not well-defined. We hypothesized that diet-induced obesity in mice reduces strain, torsion, and synchrony in the left ventricle (LV). Methods Ten 12-week-old C57BL/6 J mice were randomized to a high-fat or low-fat diet. After 5 months on the diet, mice were imaged with a 7 T ClinScan using a cine DENSE protocol. Three short-axis and two long-axis slices were acquired for quantification of strains, torsion and synchrony in the left ventricle. Results Left ventricular mass was increased by 15% (p = 0.032) with no change in volumes or ejection fraction. Subepicardial strain was lower in the obese mice with a 40% reduction in circumferential strain (p = 0.008) a 53% reduction in radial strain (p = 0.032) and a trend towards a 19% reduction in longitudinal strain (p = 0.056). By contrast, subendocardial strain was modestly reduced in the obese mice in the circumferential direction by 12% (p = 0.028), and no different in the radial (p = 0.690) or longitudinal (p = 0.602) directions. Peak torsion was reduced by 34% (p = 0.028). Synchrony of contraction was also reduced (p = 0.032) with a time delay in the septal-to-lateral direction. Conclusions Diet-induced obesity reduces left ventricular strains and torsion in mice. Reductions in cardiac strain are mostly limited to the subepicardium, with relative preservation of function in the subendocardium. Diet-induced obesity also leads to reduced synchrony of contraction and hypertrophy in mouse models. PMID:24380567

  6. Status and perspectives of neutrino magnetic moments

    NASA Astrophysics Data System (ADS)

    Alexander, Studenikin

    2016-05-01

    Basic theoretical and experimental aspects of neutrino magnetic moments are reviewed, including the present best upper bounds from reactor experiments and astrophysics. An interesting effect of neutrino spin precession induced by the background matter transversal current or polarization is also discussed.

  7. Experimental demonstration of scanned spin-precession microscopy.

    PubMed

    Bhallamudi, V P; Wolfe, C S; Amin, V P; Labanowski, D E; Berger, A J; Stroud, D; Sinova, J; Hammel, P C

    2013-09-13

    We present a new tool for imaging spin properties. We show that a spatially averaged spin signal, measured as a function of a scanned magnetic probe's position, contains information about the local spin properties. In this first demonstration we map the injected spin density in GaAs by measuring spin photoluminescence with a resolution of 1.2  μm. The ultimate limit of the technique is set by the gradient of the probe's field, allowing for a resolution beyond the optical diffraction limit. Such probes can also be integrated with other detection methods. This generality allows the technique to be extended to buried interfaces and optically inactive materials. PMID:24074116

  8. Flow measurement by cardiovascular magnetic resonance: a multi-centre multi-vendor study of background phase offset errors that can compromise the accuracy of derived regurgitant or shunt flow measurements

    PubMed Central

    2010-01-01

    Aims Cardiovascular magnetic resonance (CMR) allows non-invasive phase contrast measurements of flow through planes transecting large vessels. However, some clinically valuable applications are highly sensitive to errors caused by small offsets of measured velocities if these are not adequately corrected, for example by the use of static tissue or static phantom correction of the offset error. We studied the severity of uncorrected velocity offset errors across sites and CMR systems. Methods and Results In a multi-centre, multi-vendor study, breath-hold through-plane retrospectively ECG-gated phase contrast acquisitions, as are used clinically for aortic and pulmonary flow measurement, were applied to static gelatin phantoms in twelve 1.5 T CMR systems, using a velocity encoding range of 150 cm/s. No post-processing corrections of offsets were implemented. The greatest uncorrected velocity offset, taken as an average over a 'great vessel' region (30 mm diameter) located up to 70 mm in-plane distance from the magnet isocenter, ranged from 0.4 cm/s to 4.9 cm/s. It averaged 2.7 cm/s over all the planes and systems. By theoretical calculation, a velocity offset error of 0.6 cm/s (representing just 0.4% of a 150 cm/s velocity encoding range) is barely acceptable, potentially causing about 5% miscalculation of cardiac output and up to 10% error in shunt measurement. Conclusion In the absence of hardware or software upgrades able to reduce phase offset errors, all the systems tested appeared to require post-acquisition correction to achieve consistently reliable breath-hold measurements of flow. The effectiveness of offset correction software will still need testing with respect to clinical flow acquisitions. PMID:20074359

  9. Turbulence driven by precession in spherical and slightly elongated spheroidal cavities

    SciTech Connect

    Goto, Susumu; Matsunaga, Arihiro; Tsuda, Shinya; Fujiwara, Masahiro; Yamato, Masahiro; Nishioka, Michio; Kida, Shigeo

    2014-05-15

    Motivated by the fascinating fact that strong turbulence can be sustained in a weakly precessing container, we conducted a series of laboratory experiments on the flow in a precessing spherical cavity, and in a slightly elongated prolate spheroidal cavity with a minor-to-major axis ratio of 0.9. In order to determine the conditions required to sustain turbulence in these cavities, and to investigate the statistics of the sustained turbulence, we developed an experimental technique to conduct high-quality flow visualizations as well as measurements via particle image velocimetry on a turntable and by using an intense laser. In general, flows in a precessing cavity are controlled by two non-dimensional parameters: the Reynolds number Re (or its reciprocal, the Ekman number) which is defined by the cavity size, spin angular velocity, and the kinematic viscosity of the confined fluid, and the Poincaré number Po, which is defined by the ratio of the magnitude of the precession angular velocity to that of the spin angular velocity. However, our experiments show that the global flow statistics, such as the mean velocity field and the spatial distribution of the intensity of the turbulence, are almost independent of Re, and they are determined predominantly by Po, whereas the instability of these global flow structures is governed by Re. It is also shown that the turbulence statistics are most likely similar in the two cavities due to the slight difference between their shapes. However, the condition to sustain the unsteady flows, and therefore the turbulence, differs drastically depending on the cavity shape. Interestingly, the asymmetric cavity, i.e., the spheroid, requires a much stronger precession than a sphere to sustain such unsteady flows. The most developed turbulence for a given Re is generated in these cavities when 0.04 ≲ Po ≲ 0.1. In such cases, the sustained turbulence is always accompanied by vigorous large-scale vortical structures, and shearing

  10. The role of cardiovascular magnetic resonance in the assessment of severe aortic stenosis and in post-procedural evaluation following transcatheter aortic valve implantation and surgical aortic valve replacement.

    PubMed

    Musa, Tarique Al; Plein, Sven; Greenwood, John P

    2016-06-01

    Degenerative aortic stenosis (AS) is the most common valvular disease in the western world with a prevalence expected to double within the next 50 years. International guidelines advocate the use of cardiovascular magnetic resonance (CMR) as an investigative tool, both to guide diagnosis and to direct optimal treatment. CMR is the reference standard for quantifying both left and right ventricular volumes and mass, which is essential to assess the impact of AS upon global cardiac function. Given the ability to image any structure in any plane, CMR offers many other diagnostic strengths including full visualisation of valvular morphology, direct planimetry of orifice area, the quantification of stenotic jets and in particular, accurate quantification of valvular regurgitation. In addition, CMR permits reliable and accurate measurements of the aortic root and arch which can be fundamental to appropriate patient management. There is a growing evidence base to indicate tissue characterisation using CMR provides prognostic information, both in asymptomatic AS patients and those undergoing intervention. Furthermore, a number of current clinical trials will likely raise the importance of CMR in routine patient management. This article will focus on the incremental value of CMR in the assessment of severe AS and the insights it offers following valve replacement. PMID:27429910

  11. The role of cardiovascular magnetic resonance in the assessment of severe aortic stenosis and in post-procedural evaluation following transcatheter aortic valve implantation and surgical aortic valve replacement

    PubMed Central

    Musa, Tarique Al; Plein, Sven

    2016-01-01

    Degenerative aortic stenosis (AS) is the most common valvular disease in the western world with a prevalence expected to double within the next 50 years. International guidelines advocate the use of cardiovascular magnetic resonance (CMR) as an investigative tool, both to guide diagnosis and to direct optimal treatment. CMR is the reference standard for quantifying both left and right ventricular volumes and mass, which is essential to assess the impact of AS upon global cardiac function. Given the ability to image any structure in any plane, CMR offers many other diagnostic strengths including full visualisation of valvular morphology, direct planimetry of orifice area, the quantification of stenotic jets and in particular, accurate quantification of valvular regurgitation. In addition, CMR permits reliable and accurate measurements of the aortic root and arch which can be fundamental to appropriate patient management. There is a growing evidence base to indicate tissue characterisation using CMR provides prognostic information, both in asymptomatic AS patients and those undergoing intervention. Furthermore, a number of current clinical trials will likely raise the importance of CMR in routine patient management. This article will focus on the incremental value of CMR in the assessment of severe AS and the insights it offers following valve replacement. PMID:27429910

  12. Clinical Applications of Cine Balanced Steady-State Free Precession MRI for the Evaluation of the Subarachnoid Spaces.

    PubMed

    Li, A E; Wilkinson, M D; McGrillen, K M; Stoodley, M A; Magnussen, J S

    2015-12-01

    The purpose of this article is to review the physiology of normal brain and spinal cord motion in the subarachnoid space, principles of cine balanced steady-state free precession (bSSFP) magnetic resonance imaging (MRI), clinical applications, and the pitfalls encountered with this technique. The brain and spinal cord are dynamic structures that move with each heartbeat due to transmitted arterial pulse waves. Conventional MRI sequences do not allow anatomic evaluation of the pulsatile movement of the neural structures in the subarachnoid space due to limitations in temporal resolution. Cine bSSFP MRI uses cardiac gating to evaluate dynamically the brain and spinal cord with high contrast and temporal resolution.Cine bSSFP can be used in the evaluation of idiopathic syringomyelia to assess an underlying treatable cause, including arachnoid bands, which are usually not well visualized with conventional MR sequences due to motion artifact. This MRI technique is also useful in the evaluation of intraspinal and intracranial arachnoid cysts and the degree of mass effect on the cord. Other applications include preoperative and postoperative evaluation of Chiari I malformation and the evaluation of lateral ventricular asymmetry. The major limitation of cine bSSFP is the presence of banding artifacts, which can be reduced by shimming and modifying other scan parameters. PMID:25854921

  13. Steering trajectories in magnetically actuated colloidal propellers.

    PubMed

    Tierno, P; Sagués, F

    2012-08-01

    Microscale colloidal doublets composed of DNA-linked paramagnetic particles and floating close to a surface are able to propel in viscous fluids when subjected to external precessing magnetic fields. We show here that for certain values of the precession angle, the composite particles can be steered into tilted rather than linear trajectories characterized by a non-vanishing lateral velocity during motion. We extend the original model developed in Phys. Rev. Lett. 101, 218304 (2008) in order to explain this phenomenon, by including high-order corrections in the expansion of the director field and demonstrate the validity of this approach by comparing the analytical results with the experimental data. PMID:22872443

  14. Gravitomagnetism: a novel explanation of the precession of planets and binary pulsars

    NASA Astrophysics Data System (ADS)

    Arbab, Arbab I.

    2010-11-01

    We have studied the consequences of applying gravitomagnetism to gravitating objects. Gravitomagnetism was the missing part of the Newton’s law of gravitation. This phenomenon is manifest in the generalized Newton’s law of gravitation that is published in A.I. Arbab, Astrophys. Space Sci. 325:37, 2010a. Owing to gravitomagnetism, we have shown, the precession of planetary and pulsars orbits is due to the interaction of these objects with the gravitomagnetic field. We have calculated the gravitomagnetic fields arising from the orbital motion of the planets and binary pulsars and we have shown that they are double the Larmor-like frequency. This effect coincides with the prediction of general relativity and places the general theory of relativity on new affirmative grounds. Consequently, a modified Newton law of gravitation of Lorentz-type is proposed, which explains this precession.

  15. Measuring the Lense-Thirring precession using a second Lageos satellite

    NASA Technical Reports Server (NTRS)

    Tapley, B. D.; Ciufolini, I.

    1989-01-01

    A complete numerical simulation and error analysis was performed for the proposed experiment with the objective of establishing an accurate assessment of the feasibility and the potential accuracy of the measurement of the Lense-Thirring precession. Consideration was given to identifying the error sources which limit the accuracy of the experiment and proposing procedures for eliminating or reducing the effect of these errors. Analytic investigations were conducted to study the effects of major error sources with the objective of providing error bounds on the experiment. The analysis of realistic simulated data is used to demonstrate that satellite laser ranging of two Lageos satellites, orbiting with supplemental inclinations, collected for a period of 3 years or more, can be used to verify the Lense-Thirring precession. A comprehensive covariance analysis for the solution was also developed.

  16. Self-precession and frequency shift for electromagnetic waves in homogeneous plasmas

    NASA Technical Reports Server (NTRS)

    Arons, J.; Max, C. E.

    1974-01-01

    The nonlinear propagation of an arbitrarily polarized electromagnetic wave in a uniform plasma is studied. It is shown that nonlinear effects cause precession of the polarization ellipse as the wave propagates. The ellipticity remains constant, but the orientation of the principal axes is rotated relative to its initial value. A relativistic Vlasov model is used to study nonlinear frequency shifts as well as self-precession, in a plasma of arbitrary temperature. Even when the electron temperature is much greater than the product of the electron mass times the square of the velocity of light, the qualitative nature of these two processes remains unchanged, although their dependence on the plasma density is altered in significant ways. Implications of these effects for plasma instabilities driven by strong electromagnetic waves are briefly discussed.

  17. Non-ballistic motion and precessing helical trajectory in quasar NRAO 150

    NASA Astrophysics Data System (ADS)

    Qian, Shan-Jie

    2016-01-01

    NRAO 150 is a very special radio quasar in which prominent non-ballistic superluminal motion has been observed in its inner-jet region. We apply model-fittings to the kinematics of the superluminal knots (trajectory, distance from the core and apparent velocity) in terms of a helical precessing jet-nozzle model. Five cases are considered in which the angle between the jet axis and the line of sight is assumed to be 6°, 3°, 1°, 0.6° and 0.12°, respectively. It is shown that the superluminal components have intrinsic acceleration in the innermost regions (≲ 0.2 mas from the core). The phenomenon of precessing nozzle/trajectory can be understood on the basis of relativistic magnetohydrodynamic theories for relativistic jets.

  18. MAGNETS

    DOEpatents

    Hofacker, H.B.

    1958-09-23

    This patent relates to nmgnets used in a calutron and more particularly to means fur clamping an assembly of magnet coils and coil spacers into tightly assembled relation in a fluid-tight vessel. The magnet comprises windings made up of an assembly of alternate pan-cake type coils and spacers disposed in a fluid-tight vessel. At one end of the tank a plurality of clamping strips are held firmly against the assembly by adjustable bolts extending through the adjacent wall. The foregoing arrangement permits taking up any looseness which may develop in the assembly of coils and spacers.

  19. Forcing and feedbacks: the role of obliquity and precession in past climate change

    NASA Astrophysics Data System (ADS)

    Erb, M. P.; Broccoli, A. J.; Clement, A. C.

    2011-12-01

    Over long periods of time, changes in Earth's obliquity and precession alter the seasonal and latitudinal distribution of insolation. Milankovitch theory states that these changes, amplified by internal climate feedbacks, are responsible for the glacial-interglacial cycles of the Pleistocene and some features of the Holocene, though the exact interplay of how these forcing and feedbacks led to the changes observed in the proxy record is still not fully understood. To better understand the sensitivity of Earth's climate to orbital forcing, idealized runs have been conducted with the GFDL CM2.1 coupled atmosphere-ocean GCM. In one set of experiments, obliquity is set to the high and low values of the past 600 kyr, while in the other, the longitude of perihelion is set to four key times in the precession cycle. In these experiments, non-orbital values are set to preindustrial levels in order to isolate the climate effects of obliquity and precession alone. Because changes in precession and obliquity result in zero annual, global-mean change in insolation, feedbacks are expected to play a large role in determining the response to this forcing. Preliminary efforts to quantify and explore the effects of the lapse rate, water vapor, albedo, and cloud feedbacks confirm that they are important to explaining the magnitude and, in places, even the sign, of climate response to orbital forcing. Cloud feedbacks tend to oppose radiative forcing in northern high latitudes in summer, which can be regarded as a negative feedback relative to the forcing and would discourage large changes in snow and ice cover. Ongoing research will explore the sensitivity of cloud feedback processes to the state of the underlying surface, which may be important when considering feedbacks involving ice sheet growth and decay.

  20. Precession of orbits around the stellar-mass black hole in H 1743-322

    NASA Astrophysics Data System (ADS)

    Ingram, Adam

    2016-07-01

    Accreting stellar-mass black holes often show a quasi-periodic oscillation (QPO) in their X-ray flux with a period that slowly drifts from ~10s to ~0.05s, and an iron emission line in their X-ray spectrum. The iron line is generated by fluorescent re-emission, by the accretion disk, of X-ray photons originating in the innermost hot flow. The line shape is distorted by relativistic motion of the orbiting plasma and the gravitational pull of the black hole. The QPO arises from the immediate vicinity of the black hole, but its physical origin has long been debated. It has been suggested that the QPO originates via Lense-Thirring precession, a General Relativistic effect causing the inner flow to precess as the spinning black hole twists up the surrounding space-time. This predicts a characteristic rocking of the iron line between red and blue shift as the receding and approaching sides of the disk are respectively illuminated. I will talk about our observations of the black hole binary H 1743-322 in which the line energy varies in step with the ~4.5s QPO cycle, providing strong evidence that such QPOs originate via Lense-Thirring precession. This effect has previously been measured in our Solar System but our detection is in the strong field regime of General Relativity, at a precession rate 14 orders of magnitude faster than possible in the Earth's gravitational field. Our result enables the application of tomographic techniques to map the motion of matter in the strong gravity near black hole event horizons.

  1. Precessing cylinders at the second and third resonance: Turbulence controlled by geostrophic flow

    NASA Astrophysics Data System (ADS)

    Jiang, Jianfei; Kong, Dali; Zhu, Rixiang; Zhang, Keke

    2015-09-01

    We investigate, via both asymptotic analysis and direct numerical simulation, precessionally driven flow of a homogeneous fluid confined in fluid-filled circular cylinders that rotate rapidly about their symmetry axis and precess about a different axis and that are marked by radius-height aspect ratios Γ =1.045 945 and Γ =1.611 089 . At these radius-height aspect ratios, the Poincaré force resonates directly with the two special inertial modes that have the simplest vertical structure. An asymptotic analytical solution in closed form describing weakly precessing flow is derived in the mantle frame of reference for asymptotically small Ekman numbers, showing quantitative agreement with the result of direct nonlinear numerical simulation. Our numerical simulation makes use of a finite-element method with the three-dimensional tetrahedralization of a cylindrical cavity that allows the construction of dense nodes in the vicinity of the bounding surface of the cavity for resolving the thin viscous boundary layer. It is found that axisymmetric geostrophic flow in the alternating eastward and westward direction can be generated and maintained by nonlinear and viscous effects in the viscous boundary layer. It is also found that, when the precessing rate is moderate and, consequently, the geostrophic flow is weak, nonlinear interaction between the resonant inertial mode and the nonesonant inertial modes driven by the Poincaré force and the boundary-layer influx leads to strongly turbulent flow with irregular temporal-spatial fluctuation. When the cylinders are strongly precessing such that the geostrophic flow becomes predominant, however, the effect of the geostrophic flow controls/stabilizes its nonlinear dynamics, leading to weakly turbulent flow that can be largely described by a dominant quasisteady geostrophic component and a weak nonaxisymmetric component localized in the region where the geostrophic flow is weak.

  2. Relativistic precessing jets in quasars and radio galaxies - Models to fit high resolution data

    NASA Technical Reports Server (NTRS)

    Gower, A. C.; Gregory, P. C.; Unruh, W. G.; Hutchings, J. B.

    1982-01-01

    The formulation of generalized models tracing the geometry and intensity of the synchrotron emission from precessing, twin, relativistic jets as projected on the plane of the sky is presented. It is shown that neither the shape of the image nor its relative intensities are altered by including the effects of a cosmological redshift and a relative velocity between the source and observer. The models are fitted to the available data for several quasars and radio galaxies and demonstrate the plausibility of the phenomenon. Probable selection effects are considered and diagnostics given for recognizing objects showing this behavior. In the radio galaxies considered, velocities up to about 0.2c and precession periods of 1,000,000 yr are deduced. In the QSOs investigated, velocities of 0.7c and greater are found and periods of order 10,000 yr. In some cases precession cone angles increase with time. Consequences in terms of lifetimes of QSO behavior and binary supermassive objects are discussed.

  3. An Apparent Precessing Helical Outflow from a Massive Evolved Star: Evidence for Binary Interaction

    NASA Astrophysics Data System (ADS)

    Lau, R. M.; Hankins, M. J.; Herter, T. L.; Morris, M. R.; Mills, E. A. C.; Ressler, M. E.

    2016-02-01

    Massive, evolved stars play a crucial role in the metal enrichment, dust budget, and energetics of the interstellar medium; however, the details of their evolution are uncertain because of their rarity and short lifetimes before exploding as supernovae. Discrepancies between theoretical predictions from single-star evolutionary models and observations of massive stars have evoked a shifting paradigm that implicates the importance of binary interaction. We present mid- to far-infrared observations from the Stratospheric Observatory for Infrared Astronomy of a conical “helix” of warm dust (˜180 K) that appears to extend from the Wolf-Rayet star WR102c. Our interpretation of the helix is a precessing, collimated outflow that emerged from WR102c during a previous evolutionary phase as a rapidly rotating luminous blue variable. We attribute the precession of WR102c to gravitational interactions with an unseen compact binary companion whose orbital period can be constrained to 800 days < P < 1400 days from the inferred precession period, τp ˜ 1.4 × 104 yr, and limits imposed on the stellar and orbital parameters of the system. Our results concur with the range of orbital periods (P ≲ 1500 days) where spin-up via mass exchange is expected to occur for massive binary systems.

  4. Lense-Thirring precession around supermassive black holes during tidal disruption events

    NASA Astrophysics Data System (ADS)

    Franchini, Alessia; Lodato, Giuseppe; Facchini, Stefano

    2016-01-01

    A tidal disruption event occurs when a star wanders close enough to a black hole to be disrupted by its tidal force. The debris of a tidally disrupted star are expected to form an accretion disc around the supermassive black hole. The light curves of these events sometimes show a quasi-periodic modulation of the flux that can be associated with the precession of the accretion disc due to the Lense-Thirring (`frame-dragging') effect. Since the initial star orbit is in general inclined with respect to the black hole spin, this misalignment combined with the Lense-Thirring effect leads to a warp in the disc. In this paper, we provide a simple model of the system composed by a thick and narrow accretion disc surrounding a spinning supermassive black hole, with the aim to: (a) compute the expected precession period as a function of the system parameters, (b) discuss the conditions that have to be satisfied in order to have rigid precession, (c) investigate the alignment process, highlighting how different mechanisms play a role leading the disc and the black hole angular momenta into alignment.

  5. Shaping the Red Rectangle Proto-planetary Nebula by a Precessing Jet

    NASA Astrophysics Data System (ADS)

    Velázquez, Pablo F.; Steffen, Wolfgang; Raga, Alejandro C.; Haro-Corzo, Sinhué; Esquivel, Alejandro; Cantó, Jorge; Riera, Angels

    2011-06-01

    We carried out three-dimensional hydrodynamical simulations (employing the YGUAZÚ-A code) of a precessing jet launched by a star in a binary system. Synthetic scattered light intensity maps were generated in order to compare them with images of the Red Rectangle proto-planetary nebula (PPN), which contains the binary system HD 44179. Our results show that the angular size, the global biconical or hourglass morphology, and the existence of its "ladder rungs" features can be explained in terms of a jet precessing with a period 20 times the orbital period of the HD 44179 system, a semi-angle of 30° (of the precession cone), and a velocity of 300 km s-1. In addition, we calculated the flux predicted from the models, which is of the same order of magnitude as the observed flux in the outer regions of the nebula. Finally, the orbital motion was found to have a negligible influence on the large-scale morphology of the PPN.

  6. Testosterone and Cardiovascular Disease

    PubMed Central

    Tambo, Amos; Roshan, Mohsin H.K.; Pace, Nikolai P.

    2016-01-01

    Cardiovascular disease [CVD] is a leading cause of mortality accounting for a global incidence of over 31%. Atherosclerosis is the primary pathophysiology underpinning most types of CVD. Historically, modifiable and non-modifiable risk factors were suggested to precipitate CVD. Recently, epidemiological studies have identified emerging risk factors including hypotestosteronaemia, which have been associated with CVD. Previously considered in the realms of reproductive biology, testosterone is now believed to play a critical role in the cardiovascular system in health and disease. The actions of testosterone as they relate to the cardiac vasculature and its implication in cardiovascular pathology is reviewed. PMID:27014372

  7. Cardiovascular disease screening.

    PubMed

    Duffy, Jennifer Y; Hameed, Afshan B

    2015-06-01

    Cardiovascular disease is the leading cause of death amongst women worldwide. Cardiovascular risk assessment and primary prevention are important strategies to improve morbidity and mortality. In additional to the traditional risk factors, pregnancy complications such as pre-eclampsia and gestational diabetes increment future risk of developing cardiovascular complications. Additionally, several serum biomarkers are valuable measures for both risk assessment and predictors of clinical outcomes in women. The purpose of this review is to describe current risk stratification schemes as well as outline the role of obstetric history and serum biomarkers in adjusting risk stratification in women. PMID:26143091

  8. In vivo semi-automatic segmentation of multicontrast cardiovascular magnetic resonance for prospective cohort studies on plaque tissue composition: initial experience.

    PubMed

    Yoneyama, Taku; Sun, Jie; Hippe, Daniel S; Balu, Niranjan; Xu, Dongxiang; Kerwin, William S; Hatsukami, Thomas S; Yuan, Chun

    2016-01-01

    Automatic in vivo segmentation of multicontrast (multisequence) carotid magnetic resonance for plaque composition has been proposed as a substitute for manual review to save time and reduce inter-reader variability in large-scale or multicenter studies. Using serial images from a prospective longitudinal study, we sought to compare a semi-automatic approach versus expert human reading in analyzing carotid atherosclerosis progression. Baseline and 6-month follow-up multicontrast carotid images from 59 asymptomatic subjects with 16-79 % carotid stenosis were reviewed by both trained radiologists with 2-4 years of specialized experience in carotid plaque characterization with MRI and a previously reported automatic atherosclerotic plaque segmentation algorithm, referred to as morphology-enhanced probabilistic plaque segmentation (MEPPS). Agreement on measurements from individual time points, as well as on compositional changes, was assessed using the intraclass correlation coefficient (ICC). There was good agreement between manual and MEPPS reviews on individual time points for calcification (CA) (area: ICC; 0.85-0.91; volume: ICC; 0.92-0.95) and lipid-rich necrotic core (LRNC) (area: ICC; 0.78-0.82; volume: ICC; 0.84-0.86). For compositional changes, agreement was good for CA volume change (ICC; 0.78) and moderate for LRNC volume change (ICC; 0.49). Factors associated with LRNC progression as detected by MEPPS review included intraplaque hemorrhage (positive association) and reduction in low-density lipoprotein cholesterol (negative association), which were consistent with previous findings from manual review. Automatic classifier for plaque composition produced results similar to expert manual review in a prospective serial MRI study of carotid atherosclerosis progression. Such automatic classification tools may be beneficial in large-scale multicenter studies by reducing image analysis time and avoiding bias between human reviewers. PMID:26169389

  9. Cardiovascular magnetic resonance imaging-based computational fluid dynamics/fluid-structure interaction pilot study to detect early vascular changes in pediatric patients with type 1 diabetes.

    PubMed

    Samyn, Margaret M; Dholakia, Ronak; Wang, Hongfeng; Co-Vu, Jennifer; Yan, Ke; Widlansky, Michael E; LaDisa, John F; Simpson, Pippa; Alemzadeh, Ramin

    2015-04-01

    We hypothesized that pediatric patients with type 1 diabetes have cardiac magnetic resonance (CMR) detectable differences in thoracic aortic wall properties and hemodynamics leading to significant local differences in indices of wall shear stress, when compared with age-matched control subjects without diabetes. Pediatric patients with type 1 diabetes were recruited from Children's Hospital of Wisconsin and compared with controls. All underwent morning CMR scanning, 4-limb blood pressure, brachial artery reactivity testing, and venipuncture. Patient-specific computational fluid dynamics modeling with fluid-structure interaction, based on CMR data, determined regional time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI). Twenty type 1 diabetic subjects, median age 15.8 years (11.6-18.4) and 8 controls 15.4 years (10.3-18.2) were similar except for higher glucose, hemoglobin A1c, and triglycerides for type 1 diabetic subjects. Lower flow-mediated dilation was seen for those with type 1 diabetes (6.5) versus controls (7.8), p = 0.036. For type 1 diabetic subjects, the aorta had more regions with high TAWSS when compared to controls. OSI maps appeared similar. Flow-mediated dilation positively correlated with age at diabetes diagnosis (r = 0.468, p = 0.038) and hemoglobin A1c (r = 0.472, p = 0.036), but did not correlate with aortic distensibility, TAWSS, or OSI. TAWSS did not correlate with any clinical parameter for either group. CMR shows regional differences in aortic wall properties for young diabetic patients. Some local differences in wall shear stress indices were also observed, but a longitudinal study is now warranted. PMID:25577225

  10. The magnetic monopole and the separation between fast and slow magnetic degrees of freedom.

    PubMed

    Wegrowe, J-E; Olive, E

    2016-03-16

    The Landau-Lifshitz-Gilbert (LLG) equation that describes the dynamics of a macroscopic magnetic moment finds its limit of validity at very short times. The reason for this limit is well understood in terms of separation of the characteristic time scales between slow degrees of freedom (the magnetization) and fast degrees of freedom. The fast degrees of freedom are introduced as the variation of the angular momentum responsible for the inertia. In order to study the effect of the fast degrees of freedom on the precession, we calculate the geometric phase of the magnetization (i.e. the Hannay angle) and the corresponding magnetic monopole. In the case of the pure precession (the slow manifold), a simple expression of the magnetic monopole is given as a function of the slowness parameter, i.e. as a function of the ratio of the slow over the fast characteristic times. PMID:26871542

  11. The magnetic monopole and the separation between fast and slow magnetic degrees of freedom

    NASA Astrophysics Data System (ADS)

    Wegrowe, J.-E.; Olive, E.

    2016-03-01

    The Landau-Lifshitz-Gilbert (LLG) equation that describes the dynamics of a macroscopic magnetic moment finds its limit of validity at very short times. The reason for this limit is well understood in terms of separation of the characteristic time scales between slow degrees of freedom (the magnetization) and fast degrees of freedom. The fast degrees of freedom are introduced as the variation of the angular momentum responsible for the inertia. In order to study the effect of the fast degrees of freedom on the precession, we calculate the geometric phase of the magnetization (i.e. the Hannay angle) and the corresponding magnetic monopole. In the case of the pure precession (the slow manifold), a simple expression of the magnetic monopole is given as a function of the slowness parameter, i.e. as a function of the ratio of the slow over the fast characteristic times.

  12. Modeling North American Ice Sheet Response to Changes in Precession and Obliquity

    NASA Astrophysics Data System (ADS)

    Tabor, C.; Poulsen, C. J.; Pollard, D.

    2012-12-01

    precession on the Laurentide and Cordillera ice sheets of North America. Preliminary model results show that the ice sheet response to changes in obliquity are larger than for precession despite providing a smaller direct insolation variation in the Northern Hemisphere high latitudes. A combination of enhanced Northern Hemisphere mid-latitude temperature gradient and longer cycle duration allow for a larger ice sheet response to obliquity than would be expected from insolation forcing alone. Conversely, a shorter duration dampens the ice sheet response to precession. Nevertheless, the precession cycle does cause significant changes in ice volume, a feature not observed in the Early Pleistocene δ18O records (Raymo and Nisancioglu, 2003). Future work will examine the climate response to an idealized transient orbit that includes concurrent variations in obliquity, precession, and eccentricity.

  13. Autophagy in cardiovascular biology

    PubMed Central

    Lavandero, Sergio; Chiong, Mario; Rothermel, Beverly A.; Hill, Joseph A.

    2015-01-01

    Cardiovascular disease is the leading cause of death worldwide. As such, there is great interest in identifying novel mechanisms that govern the cardiovascular response to disease-related stress. First described in failing hearts, autophagy within the cardiovascular system has been widely characterized in cardiomyocytes, cardiac fibroblasts, endothelial cells, vascular smooth muscle cells, and macrophages. In all cases, a window of optimal autophagic activity appears to be critical to the maintenance of cardiovascular homeostasis and function; excessive or insufficient levels of autophagic flux can each contribute to heart disease pathogenesis. In this Review, we discuss the potential for targeting autophagy therapeutically and our vision for where this exciting biology may lead in the future. PMID:25654551

  14. Hypertriglyceridemia and Cardiovascular Outcomes.

    PubMed

    Malhotra, Gurveen; Sethi, Ankur; Arora, Rohit

    2016-01-01

    Cardiovascular disease, particularly ischemic heart disease, is one of the most common causes of morbidity and mortality in the United States. Atherosclerosis, the root cause of ischemic heart disease, is promoted by risk factors like elevated plasma low-density lipoprotein, low plasma high-density lipoprotein, smoking, hypertension, and diabetes mellitus. Even 66 years after a relation between triglycerides (TG) and cardiovascular disease was first suspected, TGs still continue to be a controversial risk factor and target for therapy. Some previous studies did not show any significant positive relationship between TG and cardiovascular mortality; however, recent meta-analyses found otherwise. The role of elevated TG in patients with low low-density lipoprotein and interventions to lower TG to reduce cardiovascular mortality and morbidity is an area of active research. PMID:25415545

  15. Cardiovascular modeling and diagnostics

    SciTech Connect

    Kangas, L.J.; Keller, P.E.; Hashem, S.; Kouzes, R.T.

    1995-12-31

    In this paper, a novel approach to modeling and diagnosing the cardiovascular system is introduced. A model exhibits a subset of the dynamics of the cardiovascular behavior of an individual by using a recurrent artificial neural network. Potentially, a model will be incorporated into a cardiovascular diagnostic system. This approach is unique in that each cardiovascular model is developed from physiological measurements of an individual. Any differences between the modeled variables and the variables of an individual at a given time are used for diagnosis. This approach also exploits sensor fusion to optimize the utilization of biomedical sensors. The advantage of sensor fusion has been demonstrated in applications including control and diagnostics of mechanical and chemical processes.

  16. Cardiovascular Effects of Weightlessness

    NASA Technical Reports Server (NTRS)

    Short, K.

    1985-01-01

    Physiological changes resulting from long term weightlessness are reviewed and activities conducted to study cardiovascular deconditioning at NASA Ames are discussed. Emphasis is on using monkeys in chair rest, water immersion, and tilt table studies to simulate space environment effects.

  17. [Cardiovascular syphilis: diagnosis, treatment].

    PubMed

    Carrada-Bravo, Teodoro

    2006-01-01

    Cardiovascular tertiary syphilis may lead to aortitis, aortic aneurism, coronary stenosis, aortic insufficiency and, rarely, to myocarditis. The physician must be familiar with the clinical presentations of this process, including the asymptomatic variety and must be able to have an organized plan for the diagnosis and evaluation to establish or exclude the presence of cardiovascular pathology and the differential diagnosis with other entities. Once the etiologic and topographic diagnosis is established, the patient should be treated with penicillin, doxicycline and other antibiotics, and the consequences of the disorder, both actual and potential, should be considered before deciding weather to recommend surgical intervention. Although late syphilis can be prevented by appropriate therapy of early syphilis, this is a cardiovascular disease that most likely will continue to be diagnosed lately. Understanding of the pathology and pathophysiology of the disease, is most important for its prompt recognition and subsequent management. This paper reviews the natural history, diagnosis and therapy of cardiovascular syphilis. PMID:17469346

  18. [Cardiovascular complications of obesity].

    PubMed

    Cascella, Teresa; Giallauria, Francesco; Tafuri, Domenico; Lombardi, Gaetano; Colao, Annamaria; Vigorito, Carlo; Orio, Francesco

    2006-12-01

    Obesity is one of the major coronary risk factor representing an increasingly important worldwide health problem. The increased prevalence of obesity among younger population is likely to have long-term implications for cardiovascular disease (CVD). Obesity plays a central role in the insulin resistance syndrome and contributes to increase the risk of atherosclerotic CVD. The present review will examine the relationships among cardiovascular risk factors during the childhood-adolescence-adulthood transition. In fact, the relationship between obesity (especially visceral obesity) and CVD appears to develop at a relatively young age. The foremost physical consequence of obesity is atherosclerotic cardiovascular disease and polycystic ovary syndrome represents an intriguing example of obesity-related cardiovascular complications affecting young women. PMID:17312846

  19. Cocaine and Cardiovascular Events.

    ERIC Educational Resources Information Center

    Cantwell, John D.; Rose, Fred D.

    1986-01-01

    The case of a 21-year-old man who suffered a myocardial infarction after using cocaine and amphetamines is reported. A brief literature review provides evidence of cocaine's potential cardiovascular effects. (Author/MT)

  20. Understanding cardiovascular disease

    MedlinePlus

    ... of plaque. Narrow arteries reduce or block blood flow. When blood and oxygen can't get to the legs, it can injure nerves and tissue. High blood pressure (hypertension) is a cardiovascular disease that ...

  1. Depression and cardiovascular disease.

    PubMed

    Bradley, Steven M; Rumsfeld, John S

    2015-10-01

    There is a wealth of evidence linking depression to increased risk for cardiovascular disease (CVD) and worse outcomes among patients with known CVD. In addition, there are safe and effective treatments for depression. Despite this, depression remains under-recognized and undertreated in patients at risk for or living with CVD. In this review, we first summarize the evidence linking depression to increased risk of CVD and worse patient outcomes. We then review the mechanisms by which depression may contribute to cardiovascular risk and poor cardiovascular outcomes. We then summarize prior studies of depression treatment on cardiovascular outcomes. Finally, we offer guidance in the identification and management of depression among CVD populations. Given that 1 in 4 CVD patients has concurrent depression, application of these best-practices will assist providers in achieving optimal outcomes for their CVD patients. PMID:25850976

  2. Testosterone and Cardiovascular Disease.

    PubMed

    Kloner, Robert A; Carson, Culley; Dobs, Adrian; Kopecky, Stephen; Mohler, Emile R

    2016-02-01

    Testosterone (T) is the principal male sex hormone. As men age, T levels typically fall. Symptoms of low T include decreased libido, vasomotor instability, and decreased bone mineral density. Other symptoms may include depression, fatigue, erectile dysfunction, and reduced muscle strength/mass. Epidemiology studies show that low levels of T are associated with more atherosclerosis, coronary artery disease, and cardiovascular events. However, treating hypogonadism in the aging male has resulted in discrepant results in regard to its effect on cardiovascular events. Emerging studies suggest that T may have a future role in treating heart failure, angina, and myocardial ischemia. A large, prospective, long-term study of T replacement, with a primary endpoint of a composite of adverse cardiovascular events including myocardial infarction, stroke, and/or cardiovascular death, is needed. The Food and Drug Administration recently put additional restrictions on T replacement therapy labeling and called for additional studies to determine its cardiac safety. PMID:26846952

  3. Detection of Hydroxyapatite in Calcified Cardiovascular Tissues

    PubMed Central

    Lee, Jae Sam; Morrisett, Joel D.; Tung, Ching-Hsuan

    2012-01-01

    Objective The objective of this study is to develop a method for selective detection of the calcific (hydroxyapatite) component in human aortic smooth muscle cells in vitro and in calcified cardiovascular tissues ex vivo. This method uses a novel optical molecular imaging contrast dye, Cy-HABP-19, to target calcified cells and tissues. Methods A peptide that mimics the binding affinity of osteocalcin was used to label hydroxyapatite in vitro and ex vivo. Morphological changes in vascular smooth muscle cells were evaluated at an early stage of the mineralization process induced by extrinsic stimuli, osteogenic factors and a magnetic suspension cell culture. Hydroxyapatite components were detected in monolayers of these cells in the presence of osteogenic factors and a magnetic suspension environment. Results Atherosclerotic plaque contains multiple components including lipidic, fibrotic, thrombotic, and calcific materials. Using optical imaging and the Cy-HABP-19 molecular imaging probe, we demonstrated that hydroxyapatite components could be selectively distinguished from various calcium salts in human aortic smooth muscle cells in vitro and in calcified cardiovascular tissues, carotid endarterectomy samples and aortic valves, ex vivo. Conclusion Hydroxyapatite deposits in cardiovascular tissues were selectively detected in the early stage of the calcification process using our Cy-HABP-19 probe. This new probe makes it possible to study the earliest events associated with vascular hydroxyapatite deposition at the cellular and molecular levels. This target-selective molecular imaging probe approach holds high potential for revealing early pathophysiological changes, leading to progression, regression, or stabilization of cardiovascular diseases. PMID:22877867

  4. Violence and Cardiovascular Health

    PubMed Central

    Suglia, Shakira F.; Sapra, Katherine J.; Koenen, Karestan C.

    2014-01-01

    Context Violence, experienced in either childhood or adulthood, has been associated with physical health outcomes including cardiovascular disease. However, the consistency of the existing literature has not been evaluated. Evidence acquisition In 2013, the authors conducted a PubMed and Web of Science review of peer reviewed articles published prior to August 2013 on the relation between violence exposure, experienced in either childhood or adulthood, and cardiovascular outcomes. To meet inclusion criteria, articles had to present estimates for the relation between violence exposure and cardiovascular outcomes (hypertension, blood pressure, stroke, coronary disease, or myocardial infarction) adjusted for demographic factors. Articles focusing on violence from TV, video games, natural disasters, terrorism, or war were excluded. Evidence synthesis The initial search yielded 2,273 articles; after removing duplicates and applying inclusion and exclusion criteria, 30 articles were selected for review. A consistent positive relation was noted on the association between violence experienced during childhood and cardiovascular outcomes in adulthood (i.e., hypertension, coronary heart disease, and myocardial infarction). Associations across genders with varying types of violence exposure were also noted. By contrast, findings were mixed on the relation between adult violence exposure and cardiovascular outcome. Conclusions Despite varying definitions of violence exposure and cardiovascular endpoints, a consistent relation exists between childhood violence exposure, largely assessed retrospectively, and cardiovascular endpoints. Findings are mixed for the adult violence–cardiovascular health relation. The cross-sectional nature of most adult studies and the reliance of self-reported outcomes can potentially be attributed to the lack of findings among adult violence exposure studies. PMID:25599905

  5. Computer analysis of cardiovascular parameters.

    PubMed

    Mass, H J; Gean, J T; Gwirtz, P A

    1987-01-01

    A computer program is described for the analysis of several cardiovascular parameters frequently measured or derived in the chronically instrumented dog model. Data are stored on magnetic tape and are subsequently analyzed with the Apple IIe microcomputer equipped with the ADALAB (Interactive Microware, Inc.) analog-to-digital convertor. Not limited to the chronically instrumented animal model, the program is capable of analyzing left ventricular pressure, three channels of regional myocardial segment length, coronary flow velocity as measured by the Doppler ultrasonic flow technique, and two channels of systemic arterial pressure. Derived data include: left ventricular dP/dtmax, left ventricular pressure-heart rate product, left ventricular ejection time, tension time index; percent segment length shortening and velocity of shortening, dL/dt(s)max, regional stroke work and power, duration of systole and diastole; mean coronary flow velocity, peak diastolic and systolic flow velocity, and true mean systemic arterial pressure. PMID:3581809

  6. Consistency Problems in the Improvement of the IAU Precession-Nutation Theories: Effects of the Dynamical Ellipticity Differences

    NASA Astrophysics Data System (ADS)

    Escapa, Alberto; Ferrándiz, José M.; Baenas, Tomás; Getino, Juan; Navarro, Juan F.; Belda-Palazón, Santiago

    2016-03-01

    The complexity of the modeling of the rotational motion of the Earth in space has produced that no single theory has been adopted to describe it in full. Hence, it is customary using at least a theory for precession and another one for nutation. The classic approach proceeds by deriving some of the fundamental parameters from the precession theory, like, e.g., the dynamical ellipticity Hd, and then using those values in the nutation theory. The former IAU 1976 precession and IAU 1980 nutation theories followed that scheme. Along with the improvement of the accuracy of the determination of Earth orientation parameters, IAU 1980 was superseded by IAU2000, based on the application of the MHB2000 transfer function to the previous rigid Earth analytical theory REN2000. The latter was derived while the precession model IAU 1976 was still in force, therefore it used the corresponding values for some of the fundamental parameters, as the precession rate, associated to the dynamical ellipticity. The new precession model P03 was adopted as IAU 2006. That change introduced some inconsistency since P03 used different values for some of the fundamental parameters that MHB2000 inherited from REN2000. Besides, the derivation of the basic Earth parameters of MHB2000 itself comprised a fitted variation of the dynamical ellipticity adopted in the background rigid theory. Due to the strict requirements of accuracy of the present and coming times, the magnitude of the inconsistencies originated by this twofold approach is no longer negligible as earlier, hence the need of discussing the effects of considering slightly different values for H_d in precession and nutation theories.

  7. Radiological features of uncommon aneurysms of the cardiovascular system

    PubMed Central

    Kalisz, Kevin; Rajiah, Prabhakar

    2016-01-01

    Although aortic aneurysms are the most common type encountered clinically, they do not span the entire spectrum of possible aneurysms of the cardiovascular system. As cross sectional imaging techniques with cardiac computed tomography and cardiac magnetic resonance imaging continue to improve and becomes more commonplace, once rare cardiovascular aneurysms are being encountered at higher rates. In this review, a series of uncommon, yet clinically important, cardiovascular aneurysms will be presented with review of epidemiology, clinical presentation and complications, imaging features and relevant differential diagnoses, and aneurysm management. PMID:27247710

  8. Marathon run: cardiovascular adaptation and cardiovascular risk.

    PubMed

    Predel, Hans-Georg

    2014-11-21

    The first marathon run as an athletic event took place in the context of the Olympic Games in 1896 in Athens, Greece. Today, participation in a 'marathon run' has become a global phenomenon attracting young professional athletes as well as millions of mainly middle-aged amateur athletes worldwide each year. One of the main motives for these amateur marathon runners is the expectation that endurance exercise (EE) delivers profound beneficial health effects. However, with respect to the cardiovascular system, a controversial debate has emerged whether the marathon run itself is healthy or potentially harmful to the cardiovascular system, especially in middle-aged non-elite male amateur runners. In this cohort, exercise-induced increases in cardiac biomarkers-troponin and brain natriuretic peptide-and acute functional cardiac alterations have been observed and interpreted as potential cardiac damage. Furthermore, in the cohort of 40- to 65-year-old males engaged in intensive EE, a significant risk for the development of atrial fibrillation has been identified. Fortunately, recent studies demonstrated a normalization of the cardiac biomarkers and the functional alterations within a short time frame. Therefore, these alterations may be perceived as physiological myocardial reactions to the strenuous exercise and the term 'cardiac fatigue' has been coined. This interpretation is supported by a recent analysis of 10.9 million marathon runners demonstrating that there was no significantly increased overall risk of cardiac arrest during long-distance running races. In conclusion, intensive and long-lasting EE, e.g. running a full-distance Marathon, results in high cardiovascular strain whose clinical relevance especially for middle-aged and older athletes is unclear and remains a matter of controversy. Furthermore, there is a need for evidence-based recommendations with respect to medical screening and training strategies especially in male amateur runners over the age of

  9. Chaotic magnetization dynamics in single-crystal thin-film structures

    SciTech Connect

    Shutyi, A. M. Sementsov, D. I.

    2009-01-15

    The nonlinear dynamics of homogeneously precessing magnetization in perpendicularly magnetized single-crystal films has been investigated in a wide range of ac field frequencies on the basis of a numerical solution to the Landau-Lifshitz equation and construction of the spectrum of Lyapunov exponents. The conditions for implementing and specific features of chaotic dynamic modes are revealed for films of three basic crystallographic orientations: (100), (110), and (111). It is shown that chaotic precession modes can be controlled using external magnetic fields. Time analogs of the Poincare section of chaotic mode trajectories are considered.

  10. Chaotic magnetization dynamics in single-crystal thin-film structures

    NASA Astrophysics Data System (ADS)

    Shutyi, A. M.; Sementsov, D. I.

    2009-01-01

    The nonlinear dynamics of homogeneously precessing magnetization in perpendicularly magnetized single-crystal films has been investigated in a wide range of ac field frequencies on the basis of a numerical solution to the Landau-Lifshitz equation and construction of the spectrum of Lyapunov exponents. The conditions for implementing and specific features of chaotic dynamic modes are revealed for films of three basic crystallographic orientations: (100), (110), and (111). It is shown that chaotic precession modes can be controlled using external magnetic fields. Time analogs of the Poincaré section of chaotic mode trajectories are considered.

  11. Cardiovascular Pharmacogenomics: The Future of Cardiovascular Therapeutics?

    PubMed Central

    Roden, Dan M.

    2012-01-01

    Responses to drug therapy vary from benefit to no effect to adverse effects which can be serious or occasionally fatal. Increasing evidence supports the idea that genetic variants can play a major role in this spectrum of responses. Well-studied examples in cardiovascular therapeutics include predictors of steady-state warfarin dosage, predictors of reduced efficacy among patients receiving clopidogrel for drug eluting stents, and predictors of some serious adverse drug effects. This review summarizes contemporary approaches to identifying and validating genetic predictors of variability in response to drug treatment. Approaches to incorporating this new knowledge into clinical care, and the barriers to this concept, are addressed. PMID:23200096

  12. Diabetes Drugs and Cardiovascular Safety

    PubMed Central

    2016-01-01

    Diabetes is a well-known risk factor of cardiovascular morbidity and mortality, and the beneficial effect of improved glycemic control on cardiovascular complications has been well established. However, the rosiglitazone experience aroused awareness of potential cardiovascular risk associated with diabetes drugs and prompted the U.S. Food and Drug Administration to issue new guidelines about cardiovascular risk. Through postmarketing cardiovascular safety trials, some drugs demonstrated cardiovascular benefits, while some antidiabetic drugs raised concern about a possible increased cardiovascular risk associated with drug use. With the development of new classes of drugs, treatment options became wider and the complexity of glycemic management in type 2 diabetes has increased. When choosing the appropriate treatment strategy for patients with type 2 diabetes at high cardiovascular risk, not only the glucose-lowering effects, but also overall benefits and risks for cardiovascular disease should be taken into consideration. PMID:27302713

  13. A Statistical Approach to Determine the Values of the Correction for the Precession

    NASA Astrophysics Data System (ADS)

    Marco, F. J.; Martinez, M. J.; Lopez, J. A.

    2010-10-01

    The Hipparcos catalogue [1] provides a reference frame at optical wavelengths for the new ICRS. The adoption of this new reference system was decided following a resolution that was agreed at the 23rd IAU assembly held in Kyoto in 1997. Differences in the Hipparcos system of proper motions and the previous materialization of the reference frame, the FK5, are expected to be caused only by the combined effects of the motion of the equinox of the FK5 and the Luni-solar and planetary precession. Several authors have, however, pointed out an inconsistency in the differences in proper motion of the FK5-Hipparcos with the Δp of the Luni-solar precession as determined from VLBI and LLR, and most of them have claimed that these discrepancies are due to slightly biased proper motions in the FK5 catalogue [3], [5]. The different mathematical models employed to explain these errors have not completely accounted for the previous discrepancies in the precessional parameters. Our goal is to offer an explanation for this fact. To this end and according to [2] we propose the use of independent parametric and non-parametric methods. Thus, the introduction of a non-parametric method, combined with the inner product in L2 over S2, would give us values which do not depend on the possible interdependencies existing in the data-set. In addition, the evidence shows that zonal studies are needed. This would lead us to introduce a local non-parametric model [4]. All these models will provide independent precessional values which could be compared in order to study their reliability. Finally, we obtain values for the precession corrections that are very consistent with those that are currently adopted.

  14. Theta phase precession and phase selectivity: a cognitive device description of neural coding

    NASA Astrophysics Data System (ADS)

    Zalay, Osbert C.; Bardakjian, Berj L.

    2009-06-01

    Information in neural systems is carried by way of phase and rate codes. Neuronal signals are processed through transformative biophysical mechanisms at the cellular and network levels. Neural coding transformations can be represented mathematically in a device called the cognitive rhythm generator (CRG). Incoming signals to the CRG are parsed through a bank of neuronal modes that orchestrate proportional, integrative and derivative transformations associated with neural coding. Mode outputs are then mixed through static nonlinearities to encode (spatio) temporal phase relationships. The static nonlinear outputs feed and modulate a ring device (limit cycle) encoding output dynamics. Small coupled CRG networks were created to investigate coding functionality associated with neuronal phase preference and theta precession in the hippocampus. Phase selectivity was found to be dependent on mode shape and polarity, while phase precession was a product of modal mixing (i.e. changes in the relative contribution or amplitude of mode outputs resulted in shifting phase preference). Nonlinear system identification was implemented to help validate the model and explain response characteristics associated with modal mixing; in particular, principal dynamic modes experimentally derived from a hippocampal neuron were inserted into a CRG and the neuron's dynamic response was successfully cloned. From our results, small CRG networks possessing disynaptic feedforward inhibition in combination with feedforward excitation exhibited frequency-dependent inhibitory-to-excitatory and excitatory-to-inhibitory transitions that were similar to transitions seen in a single CRG with quadratic modal mixing. This suggests nonlinear modal mixing to be a coding manifestation of the effect of network connectivity in shaping system dynamic behavior. We hypothesize that circuits containing disynaptic feedforward inhibition in the nervous system may be candidates for interpreting upstream rate codes to

  15. Hysteresis and precession of a swirling jet normal to a wall.

    PubMed

    Shtern, V; Mi, J

    2004-01-01

    Interaction of a swirling jet with a no-slip surface has striking features of fundamental and practical interest. Different flow states and transitions among them occur at the same conditions in combustors, vortex tubes, and tornadoes. The jet axis can undergo precession and bending in combustors; this precession enhances large-scale mixing and reduces emissions of NOx. To explore the mechanisms of these phenomena, we address conically similar swirling jets normal to a wall. In addition to the Serrin model of tornadolike flows, a new model is developed where the flow is singularity free on the axis. New analytical and numerical solutions of the Navier-Stokes equations explain occurrence of multiple states and show that hysteresis is a common feature of wall-normal vortices or swirling jets no matter where sources of motion are located. Then we study the jet stability with the aid of a new approach accounting for deceleration and nonparallelism of the base flow. An appropriate transformation of variables reduces the stability problem for this strongly nonparallel flow to a set of ordinary differential equations. A particular flow whose stability is studied in detail is a half-line vortex normal to a rigid plane-a model of a tornado and of a swirling jet issuing from a nozzle in a combustor. Helical counter-rotating disturbances appear to be first growing as Reynolds number increases. Disturbance frequency changes its sign along the neutral curve while the wave number remains positive. Short disturbance waves propagate downstream and long waves propagate upstream. This helical instability causes bending of the vortex axis and its precession-the effects observed in technological flows and in tornadoes. PMID:14995717

  16. Multifaceted prospects of nanocomposites for cardiovascular grafts and stents

    PubMed Central

    Vellayappan, Muthu Vignesh; Balaji, Arunpandian; Subramanian, Aruna Priyadarshini; John, Agnes Aruna; Jaganathan, Saravana Kumar; Murugesan, Selvakumar; Supriyanto, Eko; Yusof, Mustafa

    2015-01-01

    Cardiovascular disease is the leading cause of death across the globe. The use of synthetic materials is indispensable in the treatment of cardiovascular disease. Major drawbacks related to the use of biomaterials are their mechanical properties and biocompatibility, and these have to be circumvented before promoting the material to the market or clinical setting. Revolutionary advancements in nanotechnology have introduced a novel class of materials called nanocomposites which have superior properties for biomedical applications. Recently, there has been a widespread recognition of the nanocomposites utilizing polyhedral oligomeric silsesquioxane, bacterial cellulose, silk fibroin, iron oxide magnetic nanoparticles, and carbon nanotubes in cardiovascular grafts and stents. The unique characteristics of these nanocomposites have led to the development of a wide range of nanostructured copolymers with appreciably enhanced properties, such as improved mechanical, chemical, and physical characteristics suitable for cardiovascular implants. The incorporation of advanced nanocomposite materials in cardiovascular grafts and stents improves hemocompatibility, enhances antithrombogenicity, improves mechanical and surface properties, and decreases the microbial response to the cardiovascular implants. A thorough attempt is made to summarize the various applications of nanocomposites for cardiovascular graft and stent applications. This review will highlight the recent advances in nanocomposites and also address the need of future research in promoting nanocomposites as plausible candidates in a campaign against cardiovascular disease. PMID:25897223

  17. [Cardiovascular disease in pregnancy].

    PubMed

    Hilfiker-Kleiner, Denise; Bauersachs, Johann

    2016-01-01

    Cardiovascular diseases are among the most frequent complications in pregnancies. Among them preexisting heart diseases including congenital heart disease, genetic cardiomyopathies, myocardial infarction and chemotherapy-induced cardiomyopathies display a special challenge for the mother and her physicians. Moreover, the incidence of cardiovascular disease induced by or associated with pregnancy, i.e. hypertensive disorders and peripartum cardiomyopathies, has increased over the past decades. In the present overview we explain why pregnancy is a stress model for the maternal heart and summarize the current knowledge on the influence of pregnancy on preexisting cardiomyopathies. We highlight recent advances in research with regard to hypertensive complications in pregnancy and peripartum cardiomyopathy (PPCM). Moreover, we summarize etiologies, risk factors, pathomechanisms, diagnosis, treatment, management and prognosis. Finally, interdisciplinarity between different clinical fields and basic science is a key requirement to avoid longterm damage to the cardiovascular system induced by pregnancy associated impacts and with this improve women's health in general. PMID:26800071

  18. Cardiovascular actions of berberine.

    PubMed

    Lau, C W; Yao, X Q; Chen, Z Y; Ko, W H; Huang, Y

    2001-01-01

    Berberine, is an alkaloid from Hydrastis canadensis L., Chinese herb Huanglian, and many other plants. It is widely used in traditional Chinese medicine as an antimicrobial in the treatment of dysentery and infectious diarrhea. This manuscript describes cardiovascular effects of berberine and its derivatives, tetrahydroberberine and 8-oxoberberine. Berberine has positive inotropic, negative chronotropic, antiarrhythmic, and vasodilator properties. Both derivatives of berberine have antiarrhythmic activity. Some cardiovascular effects of berberine and its derivatives are attributed to the blockade of K+ channels (delayed rectifier and K(ATP)) and stimulation of Na+ -Ca(2+) exchanger. Berberine has been shown to prolong the duration of ventricular action potential. Its vasodilator activity has been attributed to multiple cellular mechanisms. The cardiovascular effects of berberine suggest its possible clinical usefulness in the treatment of arrhythmias and/or heart failure. PMID:11607041

  19. Spin transport and precession in graphene measured by nonlocal and three-terminal methods

    SciTech Connect

    Dankert, André Kamalakar, Mutta Venkata; Bergsten, Johan; Dash, Saroj P.

    2014-05-12

    We investigate the spin transport and precession in graphene by using the Hanle effect in nonlocal and three-terminal measurement geometries. Identical spin lifetimes, spin diffusion lengths, and spin polarizations are observed in graphene devices for both techniques over a wide range of temperatures. The magnitude of the spin signals is well explained by spin transport models. These observations rules out any signal enhancements or additional scattering mechanisms at the interfaces for both geometries. This validates the applicability of both the measurement methods for graphene based spintronics devices and their reliable extractions of spin parameters.

  20. 4C 18.68 - A QSO with precessing radio jets

    NASA Technical Reports Server (NTRS)

    Gower, A. C.; Hutchings, J. B.

    1982-01-01

    High-resolution VLA radio maps at 20 cm and 6 cm wavelengths of the quasar 4C 18.68 reveal an extended halo of about 20 arcsec containing complex curved structures extending east and west from the central source. The central source has a flat spectrum, while the spectrum generally steepens with distance from the center of the structure. The details of the structure and polarization of the emission suggest relativistic ejection in opposing directions by a precessing or rotating double jet with a period of about 50,000 years, consistent with the presence of two interacting massive bodies in the central source.

  1. An Interacting Binary System Powers Precessing Outflows of an Evolved Star

    NASA Astrophysics Data System (ADS)

    Boffin, Henri M. J.; Miszalski, Brent; Rauch, Thomas; Jones, David; Corradi, Romano L. M.; Napiwotzki, Ralf; Day-Jones, Avril C.; Köppen, Joachim

    2012-11-01

    Stars are generally spherical, yet their gaseous envelopes often appear nonspherical when ejected near the end of their lives. This quirk is most notable during the planetary nebula phase, when these envelopes become ionized. Interactions among stars in a binary system are suspected to cause the asymmetry. In particular, a precessing accretion disk around a companion is believed to launch point-symmetric jets, as seen in the prototype Fleming 1. Our finding of a post-common-envelope binary nucleus in Fleming 1 confirms that this scenario is highly favorable. Similar binary interactions are therefore likely to explain these kinds of outflows in a large variety of systems.

  2. An interacting binary system powers precessing outflows of an evolved star.

    PubMed

    Boffin, Henri M J; Miszalski, Brent; Rauch, Thomas; Jones, David; Corradi, Romano L M; Napiwotzki, Ralf; Day-Jones, Avril C; Köppen, Joachim

    2012-11-01

    Stars are generally spherical, yet their gaseous envelopes often appear nonspherical when ejected near the end of their lives. This quirk is most notable during the planetary nebula phase, when these envelopes become ionized. Interactions among stars in a binary system are suspected to cause the asymmetry. In particular, a precessing accretion disk around a companion is believed to launch point-symmetric jets, as seen in the prototype Fleming 1. Our finding of a post-common-envelope binary nucleus in Fleming 1 confirms that this scenario is highly favorable. Similar binary interactions are therefore likely to explain these kinds of outflows in a large variety of systems. PMID:23139326

  3. What was the phase relationship between precession and sedimentation in the Mediterranean during the Late Miocene?

    NASA Astrophysics Data System (ADS)

    Marzocchi, Alice; Flecker, Rachel; Lunt, Dan; Gladstone, Rupert; Hilgen, Frits; Krijgsman, Wout; Sierro, Francisco; Ivanovic, Ruza

    2014-05-01

    The Messinian Salinity Crisis (MSC) drastically modified the environment of the Mediterranean Sea. The large signal-noise ratio preserved in the geological record for this extreme event makes it a perfect target for exploring the biogeochemical processes involved through palaeoclimate modelling. In addition, Late Miocene sequences in the Mediterranean have been astronomically tuned, providing a very high-resolution age model that resolves sediment data on a millennial timescale or shorter. Consequently it is possible to carry out robust model-data comparison where the precise orbital phasing is equivalent. Sequences of laminated sapropelitic beds interbedded within homogeneous marls are frequently found in Late Miocene sections in the Mediterranean and have been associated with orbitally-driven climate responses. In fact, the deposition of these sediments has been linked to freshwater input causing both stratification of the water column and increased surface productivity, at times of high summer insolation. Most of the hypotheses relating the phasing of the sedimentary record to the orbital forcing are, however, still untested. Insight can therefore be gained by investigating the impact of varying orbital parameters on the Mediterranean's hydrologic budget using global climate models. A series of 22 fully coupled atmosphere-ocean-vegetation snap-shot simulations have been run at evenly spaced intervals (1kyr) through an entire precession cycle during the pre-evaporite stage of the MSC (~6.5 Ma). In our simulations, the Mediterranean Sea's hydrologic budget exhibits high seasonal variability. Model results can be directly compared with high-resolution geological data that is available for our selected time slice; for instance, cyclic changes in microfaunal assemblages that have a strong seasonal bias can be compared with our model output. This allows us to test the biogeochemical phasing of Mediterranean successions in relation to orbital forcing. Our simulations

  4. [Cardiovascular complications of diabetes].

    PubMed

    Nishio, Yoshihiko

    2015-12-01

    Several lines of epidemical evidence have shown that type 2 diabetes is the most important risk factor for cardiovascular diseases (CVD). It has been shown that the risk of primary prevention of CVD in patients with diabetes is equal to that of the secondary prevention in general population. In this manuscript, recent reports on the cardiac tests to detect the cardiovascular lesions will be reviewed. The data suggest that MDCT is a promising test even in the patients with diabetes. Furthermore, recent evidence of the treatment of diabetes with insulin or the drugs available recently such as DPP-4 inhibitors and SGLT-2 inhibitors will be reviewed. PMID:26666152

  5. Advancing cardiovascular tissue engineering

    PubMed Central

    Truskey, George A.

    2016-01-01

    Cardiovascular tissue engineering offers the promise of biologically based repair of injured and damaged blood vessels, valves, and cardiac tissue. Major advances in cardiovascular tissue engineering over the past few years involve improved methods to promote the establishment and differentiation of induced pluripotent stem cells (iPSCs), scaffolds from decellularized tissue that may produce more highly differentiated tissues and advance clinical translation, improved methods to promote vascularization, and novel in vitro microphysiological systems to model normal and diseased tissue function. iPSC technology holds great promise, but robust methods are needed to further promote differentiation. Differentiation can be further enhanced with chemical, electrical, or mechanical stimuli. PMID:27303643

  6. Cardiovascular autonomic neuropathy

    PubMed Central

    McCarty, Niamh

    2016-01-01

    Cardiovascular autonomic neuropathy often goes unrecognized. We present a case of a 22-year-old man with multiple manifestations of this disease, including weakness, dizziness, fatigue, tachycardia, abnormal QTc, and orthostasis, which occurred 2 years after his type 1 diabetes diagnosis. He exhibited parasympathetic denervation with resting tachycardia and exercise intolerance but also had evidence of orthostatic hypotension, which suggests sympathetic denervation. He did not have complete cardiovascular autonomic reflex testing, which would have been helpful, but improved with aggressive diabetes treatment and the increase of beta-blockade. It is important to identify these patients to understand their signs and symptoms and consider appropriate therapies. PMID:27034552

  7. Cardiovascular autonomic neuropathy.

    PubMed

    McCarty, Niamh; Silverman, Barry

    2016-04-01

    Cardiovascular autonomic neuropathy often goes unrecognized. We present a case of a 22-year-old man with multiple manifestations of this disease, including weakness, dizziness, fatigue, tachycardia, abnormal QTc, and orthostasis, which occurred 2 years after his type 1 diabetes diagnosis. He exhibited parasympathetic denervation with resting tachycardia and exercise intolerance but also had evidence of orthostatic hypotension, which suggests sympathetic denervation. He did not have complete cardiovascular autonomic reflex testing, which would have been helpful, but improved with aggressive diabetes treatment and the increase of beta-blockade. It is important to identify these patients to understand their signs and symptoms and consider appropriate therapies. PMID:27034552

  8. Nanomedicine and Cardiovascular Disease

    PubMed Central

    McCarthy, Jason R.

    2010-01-01

    Nanomedicine has become an important tool in the imaging and therapy of numerous diseases. This is due, in large part, to the ability to generate multifunctional nanoagents bearing combinations of targeting, diagnostic, and therapeutic moieties, allowing for the tailoring of the properties of the synthesized nanomaterials. With respect to cardiovascular disease and its sequelae, nanomedicine has the potential to detect and treat some of the leading causes of death and disability in the developed world, including atherosclerosis, thrombosis, and myocardial infarction. As such, this review focuses on some of the most poignant examples of the utility of nanomedicine in the detection and treatment of cardiovascular disease that have been recently reported. PMID:20369034

  9. Photoinduced magnetization enhancement in two-dimensional weakly anisotropic Heisenberg magnets

    NASA Astrophysics Data System (ADS)

    Caretta, Antonio; Donker, Michiel C.; Polyakov, Alexey O.; Palstra, Thomas T. M.; van Loosdrecht, Paul H. M.

    2015-01-01

    By comparing the photoinduced magnetization dynamics in simple layered systems we show how light-induced modifications of the magnetic anisotropy directly enhance the magnetization. It is observed that the spin precession in (CH3NH3) 2CuCl4 , initiated by a light pulse, increases in amplitude at the critical temperature TC. The phenomenon is related to the dependence of the critical temperature on the axial magnetic anisotropy. The present results underline the possibility and the importance of the optical modifications of the anisotropy, opening different paths toward the control of the magnetization state for ultrafast memories.

  10. Cardiovascular magnetic resonance guided electrophysiology studies

    PubMed Central

    Kolandaivelu, Aravindan; Lardo, Albert C; Halperin, Henry R

    2009-01-01

    Catheter ablation is a first line treatment for many cardiac arrhythmias and is generally performed under x-ray fluoroscopy guidance. However, current techniques for ablating complex arrhythmias such as atrial fibrillation and ventricular tachycardia are associated with suboptimal success rates and prolonged radiation exposure. Pre-procedure 3D CMR has improved understanding of the anatomic basis of complex arrhythmias and is being used for planning and guidance of ablation procedures. A particular strength of CMR compared to other imaging modalities is the ability to visualize ablation lesions. Post-procedure CMR is now being applied to assess ablation lesion location and permanence with the goal of indentifying factors leading to procedure success and failure. In the future, intra-procedure real-time CMR, together with the ability to image complex 3-D arrhythmogenic anatomy and target additional ablation to regions of incomplete lesion formation, may allow for more successful treatment of even complex arrhythmias without exposure to ionizing radiation. Development of clinical grade CMR compatible electrophysiology devices is required to transition intra-procedure CMR from pre-clinical studies to more routine use in patients. PMID:19580654

  11. Society for Cardiovascular Magnetic Resonance President's page

    PubMed Central

    Kramer, Christopher M

    2009-01-01

    The year 2009 has been a busy one for the SCMR. With health care reform in the headlines, SCMR is committed to expanding the use of CMR in clinical practice and research. Progress is being made quickly as the U.S. moves towards approval of payment for flow and in Europe, publication of the CMR registry is nigh. The impact factor of JCMR jumped up and the program for the 2010 meeting in Phoenix looks outstanding. All in all, SCMR is making advancements in many fronts.

  12. Detecting interfacial defects at magnetic/non-magnetic junctions

    NASA Astrophysics Data System (ADS)

    Harmon, Nicholas; Flatté, Michael

    Recent three terminal (3T) measurements in Co/LaAlO3/SrTiO3 show that spin-dependent transport through an interfacial defect is occurring instead of Hanle dephasing. We propose extending 3T measurements into a coherent regime where single defects are detected by their local fields. The setup involves defects being situated between biased non-magnetic (NM) and ferromagnetic (FM) contacts. Spin torque on the FM drives an AC magnetization. Due to the large exchange interaction, the ability for charge to enter the FM depends on its spin and FM's relative orientation. As the FM precesses, the spin is dynamically filtered and a precessing spin accumulation remains at the defect. Local fields also precess the defect spin and interfere with the dynamic spin filtering. If the AC and local field are resonant, the spin accumulation is locked anti-parallel to the FM and leads to a dip in current. By adjusting the AC frequency, information on the local field is ascertained which, for hyperfine local fields, tells which nuclei are present at the defect and aids in identifying the defect. In the DC limit, defect spin accumulation leads to modifications in Hanle signals This material is based on work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award Number DE-SC0014336.

  13. Magnetic

    NASA Astrophysics Data System (ADS)

    Aboud, Essam; El-Masry, Nabil; Qaddah, Atef; Alqahtani, Faisal; Moufti, Mohammed R. H.

    2015-06-01

    The Rahat volcanic field represents one of the widely distributed Cenozoic volcanic fields across the western regions of the Arabian Peninsula. Its human significance stems from the fact that its northern fringes, where the historical eruption of 1256 A.D. took place, are very close to the holy city of Al-Madinah Al-Monawarah. In the present work, we analyzed aeromagnetic data from the northern part of Rahat volcanic field as well as carried out a ground gravity survey. A joint interpretation and inversion of gravity and magnetic data were used to estimate the thickness of the lava flows, delineate the subsurface structures of the study area, and estimate the depth to basement using various geophysical methods, such as Tilt Derivative, Euler Deconvolution and 2D modeling inversion. Results indicated that the thickness of the lava flows in the study area ranges between 100 m (above Sea Level) at the eastern and western boundaries of Rahat Volcanic field and getting deeper at the middle as 300-500 m. It also showed that, major structural trend is in the NW direction (Red Sea trend) with some minor trends in EW direction.

  14. Pulmonary blood volume indexed to lung volume is reduced in newly diagnosed systemic sclerosis compared to normals – a prospective clinical cardiovascular magnetic resonance study addressing pulmonary vascular changes

    PubMed Central

    2013-01-01

    Background Pulmonary involvement, manifested as pulmonary arterial hypertension or pulmonary fibrosis, is the most common cause of death in systemic sclerosis (SSc). We aimed to explore the feasibility of detecting early pulmonary involvement in SSc using recently developed non-invasive quantitative measures of pulmonary physiology using cardiovascular magnetic resonance (CMR). Methods Twenty-seven SSc patients (9 men, 57 ± 13 years) and 10 healthy controls (3 men, 54 ± 9 years) underwent CMR to determine the pulmonary blood volume (PBV) and the PBV variation (PBVV) throughout the cardiac cycle. Patients underwent Doppler echocardiography, high-resolution computed tomography (HRCT), and pulmonary function testing by spirometry. Comparisons were performed using the unpaired t-test and linear regression analysis was performed with Pearson’s correlation coefficient (r). Results Compared to healthy controls, the PBV indexed to lung volume (PBVI) was lower in patients (16 ± 4 vs 20 ± 5%, p < 0.05). There was no difference in PBV (466 ± 87 vs 471 ± 122 mL, p = 0.91) or PBVV/stroke volume (45 ± 10 vs 40 ± 6%, p = 0.09). There were no significant correlations between PBVI and pulmonary artery pressure estimated by Doppler (p = 0.08) the lung’s diffusion capacity for carbon monoxide (DLCO) (p = 0.09), vital capacity (p = 0.45), or pulmonary fibrosis by HRCT (p = 0.74). Conclusions This study is the first to measure the PBV in humans using CMR. Compared to healthy controls, newly diagnosed SSc patients have a reduced amount of blood in the pulmonary vasculature (PBVI) but unchanged pulmonary vascular distensibility (PBVV/stroke volume). PBVI is unrelated to DLCO, pulmonary artery pressure, vital capacity, and the presence of pulmonary fibrosis. PBVI may be a novel parameter reflecting vascular lung involvement in early-stage SSc, and these findings may be consistent with pathophysiological changes of

  15. ACCF/SCCT/ACR/AHA/ASE/ASNC/NASCI/SCAI/SCMR 2010 Appropriate Use Criteria for Cardiac Computed Tomography. A Report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, the Society of Cardiovascular Computed Tomography, the American College of Radiology, the American Heart Association, the American Society of Echocardiography, the American Society of Nuclear Cardiology, the North American Society for Cardiovascular Imaging, the Society for Cardiovascular Angiography and Interventions, and the Society for Cardiovascular Magnetic Resonance.

    PubMed

    Taylor, Allen J; Cerqueira, Manuel; Hodgson, John McB; Mark, Daniel; Min, James; O'Gara, Patrick; Rubin, Geoffrey D

    2010-11-23

    The American College of Cardiology Foundation, along with key specialty and subspecialty societies, conducted an appropriate use review of common clinical scenarios where cardiac computed tomography (CCT) is frequently considered. The present document is an update to the original CCT/cardiac magnetic resonance appropriateness criteria published in 2006, written to reflect changes in test utilization, to incorporate new clinical data, and to clarify CCT use where omissions or lack of clarity existed in the original criteria. The indications for this review were drawn from common applications or anticipated uses, as well as from current clinical practice guidelines. Ninety-three clinical scenarios were developed by a writing group and scored by a separate technical panel on a scale of 1 to 9 to designate appropriate use, inappropriate use, or uncertain use. In general, use of CCT angiography for diagnosis and risk assessment in patients with low or intermediate risk or pretest probability for coronary artery disease was viewed favorably, whereas testing in high-risk patients, routine repeat testing, and general screening in certain clinical scenarios were viewed less favorably. Use of noncontrast computed tomography for calcium scoring was rated as appropriate within intermediate- and selected low-risk patients. Appropriate applications of CCT are also within the category of cardiac structural and functional evaluation. It is anticipated that these results will have an impact on physician decision making, performance, and reimbursement policy, and that they will help guide future research. PMID:20975004

  16. ACCF/SCCT/ACR/AHA/ASE/ASNC/NASCI/SCAI/SCMR 2010 appropriate use criteria for cardiac computed tomography. A report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, the Society of Cardiovascular Computed Tomography, the American College of Radiology, the American Heart Association, the American Society of Echocardiography, the American Society of Nuclear Cardiology, the North American Society for Cardiovascular Imaging, the Society for Cardiovascular Angiography and Interventions, and the Society for Cardiovascular Magnetic Resonance.

    PubMed

    Taylor, Allen J; Cerqueira, Manuel; Hodgson, John McB; Mark, Daniel; Min, James; O'Gara, Patrick; Rubin, Geoffrey D; Kramer, Christopher M; Berman, Daniel; Brown, Alan; Chaudhry, Farooq A; Cury, Ricardo C; Desai, Milind Y; Einstein, Andrew J; Gomes, Antoinette S; Harrington, Robert; Hoffmann, Udo; Khare, Rahul; Lesser, John; McGann, Christopher; Rosenberg, Alan; Schwartz, Robert; Shelton, Marc; Smetana, Gerald W; Smith, Sidney C

    2010-11-23

    The American College of Cardiology Foundation (ACCF), along with key specialty and subspecialty societies, conducted an appropriate use review of common clinical scenarios where cardiac computed tomography (CCT) is frequently considered. The present document is an update to the original CCT/cardiac magnetic resonance (CMR) appropriateness criteria published in 2006, written to reflect changes in test utilization, to incorporate new clinical data, and to clarify CCT use where omissions or lack of clarity existed in the original criteria (1). The indications for this review were drawn from common applications or anticipated uses, as well as from current clinical practice guidelines. Ninety-three clinical scenarios were developed by a writing group and scored by a separate technical panel on a scale of 1 to 9 to designate appropriate use, inappropriate use, or uncertain use. In general, use of CCT angiography for diagnosis and risk assessment in patients with low or intermediate risk or pretest probability for coronary artery disease (CAD) was viewed favorably, whereas testing in high-risk patients, routine repeat testing, and general screening in certain clinical scenarios were viewed less favorably. Use of noncontrast computed tomography (CT) for calcium scoring was rated as appropriate within intermediate- and selected low-risk patients. Appropriate applications of CCT are also within the category of cardiac structural and functional evaluation. It is anticipated that these results will have an impact on physician decision making, performance, and reimbursement policy, and that they will help guide future research. PMID:21087721

  17. ACCF/SCCT/ACR/AHA/ASE/ASNC/NASCI/SCAI/SCMR 2010 Appropriate Use Criteria for Cardiac Computed Tomography. A Report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, the Society of Cardiovascular Computed Tomography, the American College of Radiology, the American Heart Association, the American Society of Echocardiography, the American Society of Nuclear Cardiology, the North American Society for Cardiovascular Imaging, the Society for Cardiovascular Angiography and Interventions, and the Society for Cardiovascular Magnetic Resonance.

    PubMed

    Taylor, Allen J; Cerqueira, Manuel; Hodgson, John McB; Mark, Daniel; Min, James; O'Gara, Patrick; Rubin, Geoffrey D

    2010-01-01

    The American College of Cardiology Foundation (ACCF), along with key specialty and subspecialty societies, conducted an appropriate use review of common clinical scenarios where cardiac computed tomography (CCT) is frequently considered. The present document is an update to the original CCT/cardiac magnetic resonance (CMR) appropriateness criteria published in 2006, written to reflect changes in test utilization, to incorporate new clinical data, and to clarify CCT use where omissions or lack of clarity existed in the original criteria (1). The indications for this review were drawn from common applications or anticipated uses, as well as from current clinical practice guidelines. Ninety-three clinical scenarios were developed by a writing group and scored by a separate technical panel on a scale of 1 to 9 to designate appropriate use, inappropriate use, or uncertain use. In general, use of CCT angiography for diagnosis and risk assessment in patients with low or intermediate risk or pretest probability for coronary artery disease (CAD) was viewed favorably, whereas testing in high-risk patients, routine repeat testing, and general screening in certain clinical scenarios were viewed less favorably. Use of noncontrast computed tomography (CT) for calcium scoring was rated as appropriate within intermediate- and selected low-risk patients. Appropriate applications of CCT are also within the category of cardiac structural and functional evaluation. It is anticipated that these results will have an impact on physician decision making, performance, and reimbursement policy, and that they will help guide future research. PMID:21232696

  18. Testosterone therapy and cardiovascular risk.

    PubMed

    Walsh, James P; Kitchens, Anne C

    2015-04-01

    Endogenous testosterone levels are inversely associated with cardiovascular risk in older men and men with cardiovascular disease. Current data on cardiovascular outcomes of testosterone therapy include only observational studies and adverse event monitoring in short-term trials that were not designed to measure cardiovascular outcomes. These studies have yielded conflicting results, and some have raised concerns that testosterone therapy may increase cardiovascular risk. A well-designed, adequately powered, prospective trial will ultimately be required to clarify whether testosterone therapy impacts cardiovascular outcomes. This review describes the findings and limitations of recent studies of cardiovascular risk in older men on testosterone therapy and discusses some of the mechanisms through which testosterone may modify cardiovascular risk. PMID:25467243

  19. Magnetic fields of the spinning bodies

    NASA Astrophysics Data System (ADS)

    Trenčevski, Kostadin

    2015-03-01

    In this paper we show that the Thomas precession of the spinning bodies, which is in general case constrained in all rigid bodies, induces magnetic field of the spinning bodies. This is one of the main reasons for the magnetic field of the spinning bodies. The general formula for this magnetic field is deduced and if it is applied to the Earth, its magnetic field changes between 0.295 G at the equator and 0.59 G at the poles, assuming that the density inside the Earth is uniform.

  20. Revealing giant internal magnetic fields due to spin fluctuations in magnetically doped colloidal nanocrystals.

    PubMed

    Rice, William D; Liu, Wenyong; Baker, Thomas A; Sinitsyn, Nikolai A; Klimov, Victor I; Crooker, Scott A

    2016-02-01

    Strong quantum confinement in semiconductors can compress the wavefunctions of band electrons and holes to nanometre-scale volumes, significantly enhancing interactions between themselves and individual dopants. In magnetically doped semiconductors, where paramagnetic dopants (such as Mn(2+), Co(2+) and so on) couple to band carriers via strong sp-d spin exchange, giant magneto-optical effects can therefore be realized in confined geometries using few or even single impurity spins. Importantly, however, thermodynamic spin fluctuations become increasingly relevant in this few-spin limit. In nanoscale volumes, the statistical fluctuations of N spins are expected to generate giant effective magnetic fields Beff, which should dramatically impact carrier spin dynamics, even in the absence of any applied field. Here we directly and unambiguously reveal the large Beff that exist in Mn(2+)-doped CdSe colloidal nanocrystals using ultrafast optical spectroscopy. At zero applied magnetic field, extremely rapid (300-600 GHz) spin precession of photoinjected electrons is observed, indicating Beff ∼ 15 -30 T for electrons. Precession frequencies exceed 2 THz in applied magnetic fields. These signals arise from electron precession about the random fields due to statistically incomplete cancellation of the embedded Mn(2+) moments, thereby revealing the initial coherent dynamics of magnetic polaron formation, and highlighting the importance of magnetization fluctuations on carrier spin dynamics in nanomaterials. PMID:26595331

  1. Epidemiology of Cardiovascular Diseases.

    ERIC Educational Resources Information Center

    Jenkins, C. David

    1988-01-01

    Reviews epidemiological studies of cardiovascular diseases especially coronary heart disease (CHD), to document their major public health importance, changes in mortality during this century, and international comparisons of trends. Finds major risk factors for CHD are determined in large part by psychosocial and behavioral mechanisms. Asserts…

  2. Cardiovascular Effects Of Weightlessness

    NASA Technical Reports Server (NTRS)

    Sandler, Harold

    1992-01-01

    NASA technical memorandum presents study of effects of weightlessness and simulations upon cardiovascular systems of humans and animals. Reviews research up to year 1987 in United States and Soviet space programs on such topics as physiological changes induced by weightlessness in outer space and by subsequent return to Earth gravity and also reviews deconditioning effects of prolonged bed rest on ground.

  3. Cardiovascular Health, Part 2

    PubMed Central

    Baman, Timir S.; Gupta, Sanjaya; Day, Sharlene M.

    2010-01-01

    Context: An athlete’s health may be endangered if he or she continues to compete after diagnosis of certain cardiovascular conditions. The most worrisome risk is sudden cardiac death; the annual rate in US athletes is 1 in 50 000 to 200 000. Evidence Acquisition: Part 2 of this review highlights the current guidelines and controversies surrounding compatibility of participation with a variety of cardiac conditions in competitive and recreational athletics. Data sources were limited to peer-reviewed publications from 1984 to the April 2009. Results: The guidelines published by the American College of Cardiology and the European Society of Cardiology provide a framework for safe competitive and recreational sports participation in athletes with a broad spectrum of inherited and acquired cardiovascular disorders. These guidelines are necessarily conservative because it is not currently possible to individualize risk prediction. Few data are available in many areas, particularly in the noncompetitive arena or in older athletes. Conclusions: Published national guidelines are currently the foundation governing return-to-play decisions in athletes with cardiovascular conditions. Further studies are needed to refine risk stratification algorithms to allow athletes with cardiovascular conditions to reap the health benefits of regular exercise and sports participation without undue risk. PMID:23015920

  4. Epigenetics and cardiovascular disease

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Despite advances in the prevention and management of cardiovascular disease (CVD), this group of multifactorial disorders remains a leading cause of mortality worldwide. CVD is associated with multiple genetic and modifiable risk factors; however, known environmental and genetic influences can only...

  5. Nuclear Magnetic Resonance Gyroscope

    NASA Astrophysics Data System (ADS)

    Larsen, Michael; Griffith, Robert; Bulatowicz, Michael

    2014-03-01

    The navigation grade micro Nuclear Magnetic Resonance Gyroscope (micro-NMRG) being developed by the Northrop Grumman Corporation (NGC) has concluded the fourth and final phase of the DARPA Navigation Grade Integrated Micro Gyro (NGIMG) program. Traditional MEMS gyros utilize springs as an inherent part of the sensing mechanism, leading to bias and scale factor sensitivity to acceleration and vibration. As a result, they have not met performance expectations in real world environments and to date have been limited to tactical grade applications. The Nuclear Magnetic Resonance Gyroscope (NMRG) utilizes the fixed precession rate of a nuclear spin in a constant magnetic field as an inertial reference for determining rotation. The nuclear spin precession rate sensitivity to acceleration and vibration is negligible for most applications. Therefore, the application of new micro and batch fabrication methods to NMRG technology holds great promise for navigation grade performance in a low cost and compact gyro. This presentation will describe the operational principles, design basics, and demonstrated performance of the NMRG including an overview of the NGC designs developed and demonstrated in the DARPA gyro development program.

  6. Nuclear Magnetic Resonance Gyroscope

    NASA Astrophysics Data System (ADS)

    Bulatowicz, Michael; Clark, Philip; Griffith, Robert; Larsen, Michael; Mirijanian, James

    2012-06-01

    The navigation grade micro Nuclear Magnetic Resonance Gyroscope (micro-NMRG) being developed by the Northrop Grumman Corporation is concluding the fourth and final phase of the DARPA Navigation Grade Integrated Micro Gyro (NGIMG) program. Traditional MEMS gyros utilize springs as an inherent part of the sensing mechanism, leading to bias and scale factor sensitivity to acceleration and vibration. As a result, they have not met performance expectations in real world environments and to date have been limited to tactical grade applications. The Nuclear Magnetic Resonance Gyroscope (NMRG) utilizes the fixed precession rate of a nuclear spin in a constant magnetic field as an inertial reference for determining rotation. The nuclear spin precession rate sensitivity to acceleration and vibration is negligible for most applications. Therefore, the application of new micro and batch fabrication methods to NMRG technology holds great promise for navigation grade performance in a low cost and compact gyro. This poster will describe the history, operational principles, and design basics of the NMRG including an overview of the NSD designs developed and demonstrated in the DARPA gyro development program. General performance results from phases 3 and 4 will also be presented.

  7. Nuclear Magnetic Resonance Gyroscope

    NASA Astrophysics Data System (ADS)

    Bulatowicz, Michael; Griffith, Robert; Larsen, Michael

    2014-03-01

    The navigation grade micro Nuclear Magnetic Resonance Gyroscope (micro-NMRG) being developed by the Northrop Grumman Corporation (NGC) has concluded the fourth and final phase of the DARPA Navigation Grade Integrated Micro Gyro (NGIMG) program. Traditional MEMS gyros utilize springs as an inherent part of the sensing mechanism, leading to bias and scale factor sensitivity to acceleration and vibration. As a result, they have not met performance expectations in real world environments and to date have been limited to tactical grade applications. The Nuclear Magnetic Resonance Gyroscope (NMRG) utilizes the fixed precession rate of a nuclear spin in a constant magnetic field as an inertial reference for determining rotation. The nuclear spin precession rate sensitivity to acceleration and vibration is negligible for most applications. Therefore, the application of new micro and batch fabrication methods to NMRG technology holds great promise for navigation grade performance in a low cost and compact gyro. This poster will describe the history, operational principles, design, and demonstrated performance of the NMRG including an overview of the NGC designs developed and demonstrated in the DARPA gyro development program.

  8. Exploring the use of numerical relativity waveforms in burst analysis of precessing black hole mergers

    SciTech Connect

    Fischetti, Sebastian; Cadonati, Laura; Mohapatra, Satyanarayan R. P.; Healy, James; London, Lionel; Shoemaker, Deirdre

    2011-02-15

    Recent years have witnessed tremendous progress in numerical relativity and an ever improving performance of ground-based interferometric gravitational wave detectors. In preparation for the Advanced Laser Interferometer Gravitational Wave Observatory (Advanced LIGO) and a new era in gravitational wave astronomy, the numerical relativity and gravitational wave data analysis communities are collaborating to ascertain the most useful role for numerical relativity waveforms in the detection and characterization of binary black hole coalescences. In this paper, we explore the detectability of equal mass, merging black hole binaries with precessing spins and total mass M{sub T}(set-membership sign)[80,350]M{sub {center_dot}}, using numerical relativity waveforms and templateless search algorithms designed for gravitational wave bursts. In particular, we present a systematic study using waveforms produced by the MayaKranc code that are added to colored, Gaussian noise and analyzed with the Omega burst search algorithm. Detection efficiency is weighed against the orientation of one of the black-hole's spin axes. We find a strong correlation between the detection efficiency and the radiated energy and angular momentum, and that the inclusion of the l=2, m={+-}1, 0 modes, at a minimum, is necessary to account for the full dynamics of precessing systems.

  9. Precession, nutation, and variation of UT1 due to the Sun's post-Newtonian torque

    NASA Astrophysics Data System (ADS)

    Fukushima, Toshio

    We derived the post-Newtonian transformation laws of the coordinate velocity and the coordinate acceleration between a global and a body-centric coordinate system, which is related to each other by a kinematically non-rotating coordinate transformation. Next, by using the latter transformation, we obtained an explicit expression of the post-Newtonian tidal acceleration. Then, by conducting a special volume integral of torque element on an equal body-centric coordinate time hypersurface, we computed the post-Newtonian form of the gravitational torque. Finally, by integrating the Poisson approximation of the post-Newtonian extension of the Eulerian equation of rotational motion of the Earth moving along an elliptic orbit around the Sun and suffering the Sun's torque only, we evaluated post-Newtonian corrections to the precession, the nutation, and the variation of UT1. Except the geodesic precession and the geodesic nutation (Fukushima 1991), the largest effects are those related to the rotation angle of the Earth, UT1, as much as ΔUT1 = 10.50 sin l' + 0.09 sin 2l' where the unit is millisecond and l' denotes the mean anomaly of the Sun. The associated variation of the angular velocity of the Earth rotation becomes ΔΩ = 2.4 cos l' in the unit of 10-14rad/s. These are comparable with the tidal effects due to the nonrigidity of the Earth.

  10. THE EVOLUTION OF PSR J0737-3039B AND A MODEL FOR RELATIVISTIC SPIN PRECESSION

    SciTech Connect

    Perera, B. B. P.; McLaughlin, M. A.; Kramer, M.; Lyne, A. G.; Stairs, I. H.; Ferdman, R. D.; Freire, P. C. C.; Possenti, A.; Burgay, M.; Breton, R. P.; Manchester, R. N.; Camilo, F.

    2010-10-01

    We present the evolution of the radio emission from the 2.8 s pulsar of the double pulsar system PSR J0737- 3039A/B. We provide an update on the Burgay et al. analysis by describing the changes in the pulse profile and flux density over five years of observations, culminating in the B pulsar's radio disappearance in 2008 March. Over this time, the flux density decreases by 0.177 mJy yr{sup -1} at the brightest orbital phases and the pulse profile evolves from a single to a double peak, with a separation rate of 2.{sup 0}6 yr{sup -1}. The pulse profile changes are most likely caused by relativistic spin precession but cannot be easily explained with a circular hollow-cone beam as in the model of Clifton and Weisberg. Relativistic spin precession, coupled with an elliptical beam, can model the pulse profile evolution well and the reappearance is expected to happen in {approx}2035 with the same part of the beam or in {approx}2014 if we assume a symmetric beam shape. This particular beam shape predicts geometrical parameters for the two bright orbital phases which are consistent with and similar to those derived by Breton et al. However, the observed decrease in flux over time and B's eventual disappearance cannot be easily explained by the model and may be due to the changing influence of A on B.

  11. The three-fold theoretical basis of the Gravity Probe B gyro precession calculation

    NASA Astrophysics Data System (ADS)

    Adler, Ronald J.

    2015-11-01

    The Gravity Probe B (GP-B) experiment is complete and the results are in agreement with the predictions of general relativity (GR) for both the geodetic precession, 6.6 arcsec yr-1 to about 0.3%, and the Lense-Thirring precession, 39 marcsec to about 19%. This note is concerned with the theoretical basis for the predictions. The predictions depend on three elements of gravity theory, firstly that macroscopic gravity is described by a metric theory such as GR, secondly that the Lense-Thirring metric provides an approximate description of the gravitational field of the spinning Earth, and thirdly that the spin axis of a gyroscope is parallel displaced in spacetime, which gives its equation of motion. We look at each of these three elements to show how each is solidly based on previous experiments and well-tested theory. The agreement of GP-B with theory strengthens our belief that all three elements are correct and increases our confidence in applying GR to astrophysical phenomena. Conversely, if GP-B had not verified the predictions a major theoretical quandary would have occurred.

  12. Metal Oxide Growth, Characterization and Spin Precession Measurements in CVD Graphene

    NASA Astrophysics Data System (ADS)

    Matsubayashi, Akitomo; Nolting, Westly; Sinha, Dhiraj Prasad; Jayanthinarasimham, Avyaya; Lee, Ji Ung; Labella, Vincent

    2014-03-01

    Thin metal oxide layers deposited on graphene can be utilized as dielectric barriers between metals and graphene to help isolate a metal contact from the graphene channel. This is important for graphene based spintronic devices as dielectric layers between the ferromagnetic electrode and graphene have been shown to increase the spin relaxation time measured utilizing non-local detection and spin precession measurements by avoiding the conductivity mismatch problem. However, simply depositing metal oxide layers such as aluminum oxide on graphene results in non-uniform film lowering the quality of the interface barrier. We will present a systematic study of aluminum oxide layers grown on CVD (chemical vapor deposition) graphene under ultra-high vacuum conditions with and without titanium seed layers. The aluminum oxide layers with the 0.2 nm titanium seed layers showed reduced surface roughness. The chemical and structural composition determined by XPS (X-ray photoelectron spectroscopy) will be also presented that shows full oxidation of the aluminum and partial oxidation of the titanium. The results on the I-V and spin precession measurements in CVD graphene will be also presented.

  13. A model for precessing helical vortex in the turbine discharge cone

    NASA Astrophysics Data System (ADS)

    Kuibin, P. A.; Susan-Resiga, R. F.; Muntean, S.

    2014-03-01

    The decelerated swirling flow in the discharge cone of hydraulic turbine develops various self-induced instabilities and associated low frequency phenomena when the turbine is operated far from the best efficiency regime. In particular, the precessing helical vortex ("vortex rope") developed at part-load regimes is notoriously difficult and expensive to be computed using full three-dimensional turbulent unsteady flow models. On the other hand, modern design and optimization techniques require robust, tractable and accurate a-priori assessment of the turbine flow unsteadiness level within a wide operating range before actually knowing the runner geometry details. This paper presents the development and validation of a quasi-analytical model of the vortex rope in the discharge cone. The first stage is the computing of the axisymmetrical swirling flow at runner outlet with input information related only to the operating point and to the blade outlet angle. Then, the swirling flow profile further downstream is computed in successive cross-sections through the discharge cone. The second stage is the reconstruction of the precessing vortex core parameters in successive cross-sections of the discharge cone. The final stage lies in assembling 3D unsteady flow field in the discharge cone. The end result is validated against both experimental and numerical data.

  14. High Velocity Precessing Jet from the Water Fountain IRAS 18286-0959 Revealed by VLBA Observations

    NASA Astrophysics Data System (ADS)

    Yung, Bosco; Nakashima, J.; Imai, H.; Deguchi, S.; Diamond, P. J.; Kwok, S.

    2011-05-01

    We report the multi-epoch VLBA observations of 22.2GHz water maser emission associated with the "water fountain" star IRAS 18286-0959. The detected maser emission are distributed in the velocity range from -50km/s to 150km/s. The spatial distribution of over 70% of the identified maser features is found to be highly collimated along a spiral jet (namely, jet 1) extended from southeast to northwest direction, and the rest of the features appear to trace another spiral jet (jet 2) with a different orientation. The two jets form a "double-helix" pattern which lies across 200 milliarcseconds (mas). The maser features are reasonably fit by a model consisting of two precessing jets. The velocities of jet 1 and jet 2 are derived to be 138km/s and 99km/s, respectively. The precession period of jet 1 is about 56 years, and for jet 2 it is about 73 years. We propose that the appearance of two jets observed are the result of a single driving source with a significant proper motion. This research was supported by grants from the Research Grants Council of the Hong Kong Special Administrative Region, China, the Seed Funding Programme for Basic Research of the University of Hong Kong, Grant-in-Aid for Young Scientists from the Ministry 9 of Education, Culture, Sports, Science, and Technology, and Grant-in-Aid for Scientific Research from Japan Society for Promotion Science.

  15. Sculpting a Pre-Planetary Nebula with a Precessing Jet: IRAS 16342-3814

    NASA Technical Reports Server (NTRS)

    Sahai, R.; Le Mignant, D.; Sanchez Contreras, C.; Campbell, R. D.; Chaffee, F. H.

    2005-01-01

    We have imaged the bipolar pre-planetary nebula IRAS 16342-3814 with the Keck adaptive optics (AO) system in four near-infrared bands in the 1.6-4.7 (micro)m range. The lobes, which showed smoothly varying brightness distributions in previous optical images taken with the Hubble Space Telescope, have a limb-brightened appearance in the AO images, with a remarkable corkscrew structure inscribed on the lobe walls. A well-collimated, precessing jet with a diameter less than or approximately equal to 100 AU and a precession period less than or approximately equal to 50 yr, interacting with ambient circumstellar material, is most likely responsible for the corkscrew structure and the lobes, as indicated by a detailed comparison of our observations with published numerical simulations. The very red colors of the lobes in the near-infrared, coupled with their visibility at optical wavelengths, require that at least half, but not all, of the light of the central star be trapped by a compact circumstellar dust cloud heated to approximately 600-700 K and reradiated in the infrared. The lobes are thus illuminated both by the infrared light from this dust cloud as well as by the optical light from the central star.

  16. Constraints on Galileon-induced precessions from solar system orbital motions

    SciTech Connect

    Iorio, L.

    2012-07-01

    We use latest data from solar system planetary orbital motions to put constraints on some Galileon-induced precessional effects. Due to the Vainshtein mechanism, the Galileon-type spherically symmetric field of a monopole induces a small, screened correction ∝(r){sup 1/2} to the r{sup −1} Newtonian potential which causes a secular precession of the pericenter of a test particle. In the case of our solar system, latest data from Mars allow to constrain the magnitude of such an interaction down to α ≤ 0.3 level, where α corresponds to the non minimal coupling of the Galileon to matter. Another Galileon-type effect which might impact solar system dynamics is due to an unscreened constant gradient induced by the peculiar motion of the Galaxy. The magnitude of such an effect, depending on the different gravitational binding energies of the Sun and the planets, taken into account by ξ, is ξ ≤ 0.004 from the latest bounds on the supplementary perihelion precession of Saturn.

  17. Constraints on Non-Standard Gravitomagnetism by the Anomalous Perihelion Precession of the Planets

    NASA Astrophysics Data System (ADS)

    Acedo, Luis

    2014-09-01

    A team of astronomers has recently reported an anomalous retrograde precession of the perihelion of Saturn amounting to Δω SATURN = -0.006(2) arcsec per century (arcsec cy-1). This unexplained precession was obtained after taking into account all classical and relativistic effects in the context of the highly refined EPM2008 ephemerides. More recent analyzes have not confirmed this effect, but they have found similar discrepancies in other planets. Our objective in this paper is to discuss a non-standard model involving transversal gravitomagnetism generated by the Sun as a possible source of these anomalies. In order to compute the Lense-Thirring perturbations induced by the suggested interaction, we should consider the orientation of the Sun's rotational axis in Carrington elements and the inclination of the planetary orbits with respect to the ecliptic plane. We find that an extra component of the gravitomagnetic field not predicted by General Relativity could explain the reported anomalies without conflicting with the Gravity Probe B experiment and the orbits of the geodynamics satellites.

  18. High-frequency and type-C QPOs from oscillating, precessing hot, thick flow

    NASA Astrophysics Data System (ADS)

    Fragile, P. Chris; Straub, Odele; Blaes, Omer

    2016-09-01

    Motivated by recent studies showing an apparent correlation between the high-frequency quasi-periodic oscillations (QPOs) and the low-frequency, type-C QPO in black hole low-mass X-ray binaries (LMXBs), we explore a model that explains all three QPOs in terms of an oscillating, precessing hot flow in the truncated-disc geometry. Our model favours attributing the two high-frequency QPOs, often occurring in a near 3:2 frequency ratio, to the breathing and vertical epicyclic frequency modes of the hot, thick flow, although we cannot rule out the Keplerian and m = -1 radial epicyclic modes. In either case, the type-C QPO is attributed to precession. The correlation of the QPOs comes from the fact that all three frequencies are associated with the same geometrical structure. While the exact QPO frequencies are sensitive to the black hole mass and spin, their evolution over the course of an outburst is mainly tied to the truncation radius between the geometrically thin, optically thick disc and the inner, hot flow. We show that, in the case of the LMXB GRO J1655-40, this model can explain the one simultaneous observation of all three QPOs and that an extrapolation of the model appears to match lower frequency observations where only two of the three components are seen. Thus, this model may be able to unify multiple QPO observations using the properties of a single, simple, geometrical model.

  19. [Preventing cardiovascular risk in miners].

    PubMed

    Lipatova, L V; Izmailova, O A

    2016-01-01

    The article presents results concerning usage of intravenous laser radiation of blood in miners with cardiovascular diseases. After cardiovascular state assessment, the miners at high cardiovascular risk were subjected to prophylactic procedures with traditional medical treatment added by intravenous laser therapy. Findings are anti-arrhythmic, antihypertensive, antiatherogenic and anti-aggregation effects of complex treatment with intravenous laser radiation of blood in miners at high cardiovascular risk and its subsequent decrease due to treatment. PMID:27265943

  20. Cardiovascular effects of thyroid disease.

    PubMed

    Sangster, Jodi K; Panciera, David L; Abbott, Jonathan A

    2013-07-01

    Thyroid hormones have many effects on cardiovascular function, and deficiency or excess of thyroid hormones can result in cardiac dysfunction. Abnormalities of the cardiovascular system are often identified during examination of hyperthyroid and hypothyroid patients. This article addresses the effects of thyroid hormones on the cardiovascular system and the clinical relevance of the cardiovascular response to thyroid dysfunction. In addition, treatment recommendations are presented. PMID:23677842

  1. Long-term evolution of orbits about a precessing oblate planet: 3. A semianalytical and a purely numerical approach

    NASA Astrophysics Data System (ADS)

    Gurfil, Pini; Lainey, Valéry; Efroimsky, Michael

    2007-12-01

    Construction of an accurate theory of orbits about a precessing and nutating oblate planet, in terms of osculating elements defined in a frame associated with the equator of date, was started in Efroimsky and Goldreich (2004) and Efroimsky (2004, 2005, 2006a, b). Here we continue this line of research by combining that analytical machinery with numerical tools. Our model includes three factors: the J 2 of the planet, its nonuniform equinoctial precession described by the Colombo formalism, and the gravitational pull of the Sun. This semianalytical and seminumerical theory, based on the Lagrange planetary equations for the Keplerian elements, is then applied to Deimos on very long time scales (up to 1 billion years). In parallel with the said semianalytical theory for the Keplerian elements defined in the co-precessing equatorial frame, we have also carried out a completely independent, purely numerical, integration in a quasi-inertial Cartesian frame. The results agree to within fractions of a percent, thus demonstrating the applicability of our semianalytical model over long timescales. Another goal of this work was to make an independent check of whether the equinoctial-precession variations predicted for a rigid Mars by the Colombo model could have been sufficient to repel its moons away from the equator. An answer to this question, in combination with our knowledge of the current position of Phobos and Deimos, will help us to understand whether the Martian obliquity could have undergone the large changes ensuing from the said model (Ward 1973; Touma and Wisdom 1993, 1994; Laskar and Robutel 1993), or whether the changes ought to have been less intensive (Bills 2006; Paige et al. 2007). It has turned out that, for low initial inclinations, the orbit inclination reckoned from the precessing equator of date is subject only to small variations. This is an extension, to non-uniform equinoctial precession given by the Colombo model, of an old result obtained by

  2. On the clock mechanism and the implausibility of the 35 day precessing disk in HZ Herculis/Hercules X-1

    NASA Technical Reports Server (NTRS)

    Kondo, Y.; Wolff, C. L.; Van Flandern, T. C.

    1983-01-01

    The concept of the precessing accretion disk in HZ Her/Her X-1 in its varied forms, to account for the 35 day periodicity in the X-ray flux, has met many objections from a number of workers on various grounds, but it is still being invoked in current publications. These objections are reviewed and additional arguments are presented against the precessing accretion disk model. The implausibility of the disk models is demonstrated. An alternate clock mechanism, based on nonlinear oscillations in the normal star, which provides the modulation of the mass flow is discussed.

  3. Newton's problems with rigid body dynamics in the light of his treatment of the precession of the equinoxes.

    NASA Astrophysics Data System (ADS)

    Dobson, G. J.

    1998-07-01

    Newton's treatment of the precession of the equinoxes in his Philosophiae Naturalis Principia Mathematica was recognised by d'Alembert in 1749 as being faulty, despite the very close agreement between Newton's calculated value for the rate of precesion and the observed value. Here, the author presents an analysis of Newton's geometrical methods applied in his treatment of precession and claims that it was basically flawed because Newton lacked knowledge of the principles of rigid body dynamics and, in particular, was unaware of the idea of angular momentum.

  4. Calculation of the Precession of the Perihelion of Mercury's Orbit Within the Framework of Newton's Law of Universal Gravitation

    NASA Astrophysics Data System (ADS)

    Kupryaev, N. V.

    2015-05-01

    The precession of the perihelion of Mercury's orbit in the gravitational field of the Sun and planets has been numerically modeled within the framework of Newton's law of universal gravitation. The calculations were performed with enhanced calculational accuracy and with an iteration step of 0.0005 s. It has been shown that the average precession of Mercury's orbit after 100 years within the framework of Newton's law of universal gravitation comprises +553''. This is 21'' greater than the generally accepted value of +532''.

  5. Electrical spin injection and detection of spin precession in room temperature bulk GaN lateral spin valves

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Aniruddha; Baten, Md Zunaid; Bhattacharya, Pallab

    2016-01-01

    We report the measurement of diffusive electronic spin transport characteristics in an epitaxial wurtzite GaN lateral spin valve at room temperature. Hanle spin precession and non-local spin accumulation measurements have been performed with the spin valves fabricated with FeCo/MgO spin contacts. Electron spin relaxation length and spin-flip lifetime of 176 nm and 37 ps, respectively, are derived from analysis of results obtained from four-terminal Hanle spin precession measurements at 300 K. The role of dislocations and defects in bulk GaN has also been examined in the context of electronic spin relaxation dynamics.

  6. Childhood obesity and cardiovascular disease

    PubMed Central

    Bridger, Tracey

    2009-01-01

    Childhood obesity has reached epidemic proportions. Many of these children have risk factors for later disease, including cardiovascular disease. For optimal cardiovascular health, health care professionals must be able to identify children and youth at risk and provide appropriate support as needed. The present article reviews the current medical literature on obesity and cardiovascular disease risk factors in the paediatric population, the long-term cardiovascular consequences of childhood obesity and the importance of early life. Recommendations promoting optimal cardiovascular health in all children and youth are discussed. PMID:20190900

  7. Slow breathing and cardiovascular disease.

    PubMed

    Chaddha, Ashish

    2015-01-01

    Cardiovascular disease is the leading cause of death for both men and women worldwide. Much emphasis has been placed on the primary and secondary prevention of cardiovascular disease. While depression and anxiety increase the risk of developing cardiovascular disease, cardiovascular disease also increases the risk of developing anxiety and depression. Thus, promoting optimal mental health may be important for both primary and secondary prevention of cardiovascular disease. Like lowering blood pressure, lipids, and body weight, lowering anger and hostility and improving depression and anxiety may also be an important intervention in preventive cardiology. As we strive to further improve cardiovascular outcomes, the next bridge to cross may be one of offering patients nonpharmacologic means for combating daily mental stress and promoting mental health, such as yoga and pranayama. Indeed, the best preventive cardiovascular medicine may be a blend of both Western and Eastern medicine. PMID:26170595

  8. Impact of Precession On Monsoon Characteristics From Coupled Ocean Atmosphere Experiments

    NASA Astrophysics Data System (ADS)

    Braconnot, Pascale; Marti, Olivier

    Precession cycle modulates the seasonal distribution of the incoming solar radiation at the top of the atmosphere with a periodicity of about 23 kyr. Summer insolation is the largest for periods during which the Earth is near the perihelion of its orbit dur- ing summer. The associated continental warming favours the deepening of the sum- mer thermal low over the Northern Hemisphere continents and the inland advection of moist air from the tropical oceans, strengthening the monsoon activity. Different orbital configurations (precession) can lead to large June-July-August (summer) inso- lation forcing. Amongst these, the maximum insolation can occur between the vernal equinox and the summer solstice or between the summer solstice and the autumnal equinox. Using a fully coupled ocean-atmosphere model we investigate the response of the Indian and southeast monsoons to changes in precession and we explore the differences between periods where the monsoon activity is strong compared to the period of reference but the seasonal timing of the insolation forcing is different. Our aim is to determine if extreme phases in the seasonal forcing can lead to different signatures in the monsoon response. We focus on the Asian monsoon and on the at- mospheric and oceanic circulation in the Indian Ocean. Our results show that, even though the changes in the land-sea contrast that drives the monsoon flow follows quite well the differences in the insolation forcing, the regional distribution over the con- tinental regions affected by the monsoon and the ocean substantially varies from one simulation to the other. Large differences are found in the simulated surface temper- ature and salinity in the Indian Ocean. They are related to various feedbacks, where the changes in the hydrological cycle over the basin through precipitation, evapora- tion and river runoff play and important role. Our results strongly emphasize that the timing of the seasonal cycle need to be considered in

  9. Cardiovascular adaptation to spaceflight

    NASA Technical Reports Server (NTRS)

    Charles, John B.; Lathers, Claire M.

    1991-01-01

    Data are presented on the rate of adaptation of the human cardiovascular system to conditions of spaceflight, with particular attention given to data obtained during spaceflight in the U.S. Space Shuttle Program. It is pointed out that many of the cardiovascular changes that occurred during spaceflights that lasted from 2 to 11 days can be traced directly to changes in the body fluid volume. The beneficial effects of a fluid loading countermeasure (oral rehydration) and of the supine body position on the heart rate during the spaceflight are demonstrated. It is noted that, after hours or a few days of spaceflight, a state of adaptation is reached, in which the subject is well adapted and appropriately hydrated for the weightless environment. However, the return to the normal gravity of the earth leaves the individual especially sensitive to orthostatic stress.

  10. Cardiovascular responses to spaceflight

    NASA Technical Reports Server (NTRS)

    Nicogossian, A.; Pool, S. L.; Rambaut, P. C.

    1983-01-01

    The cardiovascular system's adaptive changes during and after spaceflight are discussed. Cephalic fluid shifts are demonstrated by photographs along with calf girth and leg volume changes. Inflight measurements show an increase in average resting heart rate and systolic blood pressure, and a sympathetic-parasympathetic neural imbalance. Postflight findings include a small but reversible decrease in the left ventricular muscle mass. Since 1980, NASA's research has emphasized cardiovascular deconditioning and countermeasures: hemodynamic changes, endocrine and neurohumoral aspects, etiologic factors, and lower body negative pressure devices. Though human beings acclimate to the space environment, questions concerning the immediate and long-term aspects of spaceflight need to be answered for adequate planning of extended space missions.

  11. Ethiopian cardiovascular studies

    PubMed Central

    Parry, E. H. O.; Gordon, C. G. I.

    1968-01-01

    No large series of patients with cardiovascular disease has yet been reported from Ethiopia, where only limited means for investigation are at present available. The authors therefore studied the types of heart disease detected by mass miniature radiography in a largely self-selected population at the Addis Ababa Tuberculosis Centre, and examined the value of this method of cardiac case-finding. Rheumatic heart disease occurred in 34.8% of patients, but syphilitic aortitis, hypertension, “cardiomyopathy” and tuberculous pericarditis were also common. Endomyocardial fibrosis was not seen; this may be a further significant fact in the search for its cause. Mass miniature radiography is valuable for detecting symptomatic patients with the cardiovascular diseases mentioned above. The technique described in this paper could be used in other developing countries as it uses a single method of screening for 2 groups of diseases. ImagesFIG. 2 PMID:5306099

  12. Cardiovascular adaptation to spaceflight

    NASA Technical Reports Server (NTRS)

    Hargens, A. R.; Watenpaugh, D. E.

    1996-01-01

    This article reviews recent flight and ground-based studies of cardiovascular adaptation to spaceflight. Prominent features of microgravity exposure include loss of gravitational pressures, relatively low venous pressures, headward fluid shifts, plasma volume loss, and postflight orthostatic intolerance and reduced exercise capacity. Many of these short-term responses to microgravity extend themselves during long-duration microgravity exposure and may be explained by altered pressures (blood and tissue) and fluid balance in local tissues nourished by the cardiovascular system. In this regard, it is particularly noteworthy that tissues of the lower body (e.g., foot) are well adapted to local hypertension on Earth, whereas tissues of the upper body (e.g., head) are not as well adapted to increase in local blood pressure. For these and other reasons, countermeasures for long-duration flight should include reestablishment of higher, Earth-like blood pressures in the lower body.

  13. Cardiovascular Health Disparities

    PubMed Central

    Davis, Andrew M.; Vinci, Lisa M.; Okwuosa, Tochi M.; Chase, Ayana R.; Huang, Elbert S.

    2008-01-01

    Racial and ethnic disparities in cardiovascular health care are well documented. Promising approaches to disparity reduction are increasingly described in literature published since 1995, but reports are fragmented by risk, condition, population, and setting. The authors conducted a systematic review of clinically oriented studies in communities of color that addressed hypertension, hyperlipidemia, physical inactivity, tobacco, and two major cardiovascular conditions, coronary artery disease and heart failure. Virtually no literature specifically addressed disparity reduction. The greatest focus has been African American populations, with relatively little work in Hispanic, Asian, and Native American populations. The authors found 62 interventions, 27 addressing hypertension, 9 lipids, 18 tobacco use, 8 physical inactivity, and 7 heart failure. Only 1 study specifically addressed postmyocardial infarction care. Data supporting the value of registries, multidisciplinary teams, and community outreach were found across several conditions. Interventions addressing care transitions, using telephonic outreach, and promoting medication access and adherence merit further exploration. PMID:17881625

  14. Lycopene and cardiovascular disease.

    PubMed

    Arab, L; Steck, S

    2000-06-01

    Considerable evidence suggests that lycopene, a carotenoid without provitamin A activity found in high concentrations in a small set of plant foods, has significant antioxidant potential in vitro and may play a role in preventing prostate cancer and cardiovascular disease in humans. Tomato products, including ketchup, tomato juice, and pizza sauce, are the richest sources of lycopene in the US diet, accounting for >80% of the total lycopene intake of Americans. Unlike other carotenoids, lycopene is not consistently lower among smokers than among nonsmokers, suggesting that any possible preventive activity is not as an antioxidant. Instead, lycopene may have a cholesterol synthesis-inhibiting effect and may enhance LDL degradation. Available evidence suggests that intimal wall thickness and risk of myocardial infarction are reduced in persons with higher adipose tissue concentrations of lycopene. The question of whether lycopene helps to prevent cardiovascular disease can only be answered by a trial specifically evaluating its effectiveness in this area. PMID:10837319

  15. Winter Cardiovascular Diseases Phenomenon

    PubMed Central

    Fares, Auda

    2013-01-01

    This paper review seasonal patterns across twelve cardiovascular diseases: Deep venous thrombosis, pulmonary embolism, aortic dissection and rupture, stroke, intracerebral hemorrhage, hypertension, heart failure, angina pectoris, myocardial infarction, sudden cardiac death, venricular arrythmia and atrial fibrillation, and discuss a possible cause of the occurrence of these diseases. There is a clear seasonal trend of cardiovascular diseases, with the highest incidence occurring during the colder winter months, which have been described in many countries. This phenomenon likely contributes to the numbers of deaths occurring in winter. The implications of this finding are important for testing the relative importance of the proposed mechanisms. Understanding the influence of season and other factors is essential when seeking to implement effective public health measures. PMID:23724401

  16. Cardiovascular instrumentation for spaceflight

    NASA Technical Reports Server (NTRS)

    Schappell, R. T.; Polhemus, J. T.; Ganiaris, N. J.

    1976-01-01

    The observation mechanisms dealing with pressure, flow, morphology, temperature, etc. are discussed. The approach taken in the performance of this study was to (1) review ground and space-flight data on cardiovascular function, including earlier related ground-based and space-flight animal studies, Mercury, Gemini, Apollo, Skylab, and recent bed-rest studies, (2) review cardiovascular measurement parameters required to assess individual performance and physiological alternations during space flight, (3) perform an instrumentation survey including a literature search as well as personal contact with the applicable investigators, (4) assess instrumentation applicability with respect to the established criteria, and (5) recommend future research and development activity. It is concluded that, for the most part, the required instrumentation technology is available but that mission-peculiar criteria will require modifications to adapt the applicable instrumentation to a space-flight configuration.

  17. Current control of magnetic anisotropy via stress in a ferromagnetic metal waveguide

    NASA Astrophysics Data System (ADS)

    An, Kyongmo; Ma, Xin; Pai, Chi-Feng; Yang, Jusang; Olsson, Kevin S.; Erskine, James L.; Ralph, Daniel C.; Buhrman, Robert A.; Li, Xiaoqin

    2016-04-01

    We demonstrate that in-plane charge current can effectively control the spin precession resonance in an A l2O3/CoFeB /Ta heterostructure. Brillouin light scattering was used to detect the ferromagnetic resonance field under microwave excitation of spin waves at fixed frequencies. The current control of spin precession resonance originates from modification of the in-plane uniaxial magnetic anisotropy field Hk, which changes symmetrically with respect to the current direction. Numerical simulation suggests that the anisotropic stress introduced by joule heating plays an important role in controlling Hk. These results provide new insight into current manipulation of magnetic properties and have broad implications for spintronic devices.

  18. NMR techniques in the study of cardiovascular structure and functions

    SciTech Connect

    Osbakken, M.; Haselgrove, J.

    1987-01-01

    The chapter titles of this book are: Introduction to NMR Techniques;Theory of NMR Probe Design;Overview of Magnetic Resonance Imaging to Study the Cardiovascular System;Vascular Anatomy and Physiology Studied with NMR Techniques;Assessment of Myocardial Ischemia and Infarction by Nuclear Magnetic Resonance Imaging;The Use of MRI in Congenital Heart Disease;Cardiomyopathies and Myocarditis Studied with NMR Techniques;Determination of Myocardial Mechanical Function with Magnetic Resonance Imaging Techniques;Determination of Flow Using NMR Techniques;The Use of Contrast Agents in Cardiac MRI;Can Cardiovascular Disease Be Effectively Evaluated with NMR Spectroscopy. NMR Studies of ATP Synthesis Reactions in the Isolated Heart;Studies of Intermediary Metabolism in the Heart by 13C NMR Spectroscopy;23Na and 39K NMR Spectroscopic Studies of the Intact Beating Heart;and Evaluation of Skeletal Muscle Metabolism in Patients with Congestive Heart Failure Using Phosphorus Nuclear Magnetic Resonance.

  19. Emission of gravitational waves by precession of slim accretion disks dynamically driven by the Bardeen-Petterson effect

    NASA Astrophysics Data System (ADS)

    Alfonso, W. D.; Sánchez, L. A.; Mosquera, H. J.

    2015-11-01

    The electromagnetic radiation emitted from some astrophysical objects such as active galactic nuclei (AGN), micro-quasars (M-QSRs), and central engines of gamma-ray burst (GRBs), seems to have a similar physical origin: a powerful jet of plasma ejected from a localized system, presumably composed of an accretion disk encircling a compact object. This radiation is generally beamed in the polar directions and in some cases, it appears to have a spiral-like structure that could be explained if the central system itself precesses. In this work, we use the slim disk accretion model, presented by Popham et al. (1999), to studying the gravitational waves (GWs) emitted by the precession of the accretion disk around a solar-mass Kerr black hole (KBH). For practical purposes, this model describes the central engine of a class of GRBs when some astrophysical constrains are fulfilled. The induced precession considered here is driven by the Bardeen-Petterson effect, which results from the combination of viscous effects in such disks and the relativistic frame-dragging effect. We evaluate the feasibility of direct detection of the GWs computed for such a model and show that the precession of this kind of systems could be detected by gravitational wave observatories like DECIGO, ultimate-DECIGO, and BBO, with higher probability if such a class of sources are placed at distances less than 1 Mpc.

  20. The Periodicity Analysis of the Light Curve of 3C 279 and Implications for the Precession Jet

    NASA Astrophysics Data System (ADS)

    Li, H. Z.; Xie, G. Z.; Chen, L. E.; Dai, H.; Lei, B. Y.; Yi, T. F.; Ren, J. Y.

    2009-11-01

    We have analyzed the light curves of 3C 279 at 22 GHz, 37 GHz, optical R band, and X-ray (2-10 KeV), and found evidence of quasi-periodic outbusts. The light curves show that 3C 279 is an extremely active object. A period of P = 130.6 ± 1.3 days was consistently confirmed by three methods: the power-spectrum method, the discrete correlation function (DCF) method, and the Jurkevich method. Based on the relationship between observed period Pobs and the precession period Pp given by Rieger and our result, the precession period of jet in 3C 279 is Pp sime 29.6 yr, which is completely consistent with the precession period of jet of about 30 yr obtained by Carrara et al.. This suggests that there is a precession jet in 3C 279 and the variability period of about 130.6 days that we obtained is most likely caused by the helical motion of the jet.