OBJECTIVE. The aim of our study was to evaluate prospectively the grades and patterns of gadopentetate-enhanced MR imaging in the radiocarpal joints of healthy subjects after IV contrast administration.SUBJECTS AND METHODS. The study included 18 healthy subjects (nine men, nine women; age range, 24-34 years; mean age, 30.8 years). We obtained coronal T1-weighted spin-echo images with fat suppression before and after IV administration of gadopentetate dimeglumine and additional axial T1-weighted spin-echo images after contrast administration. Patterns of signal-intensity enhancement in and around the radiocarpal joints were evaluated qualitatively and quantitatively.RESULTS. In eight (44.4%) of 18 healthy subjects, enhancement of the radiocarpal joints was seen and exclusively located in the region of the prestyloid recess. Enhancement patterns were bandlike in three (16.7%) of 18 healthy subjects, homogeneous in another three (16.7%) of 18, and nodular in two (11.1%) of 18.CONCLUSION. After IV administrat...

Patterns of gadopentetate-enhanced MR imaging of radiocarpal joints of healthy subjects.

The evolution of an anelastic relaxation process occurring around 80 K in La 2 - x Sr x CuO 4 at a measuring frequency of ∼1 kHz has been followed from x=0.0075 to the overdoped region x=0.2, where it disappears. The dependence of the peak intensity on doping is consistent with a polaronic mechanism, identified with the disordered charge stripes overcoming pinning centers. A marked decrease of the peak amplitude and of the effective energy barrier for relaxation occurs at x>0.045, the same doping range where a change of the stripe order from parallel to diagonal with respect to the Cu-O bonds has been observed by neutron diffraction. Both the energy barrier and peak amplitude also exhibit a rise near x=1/8.

Anelastic relaxation process of polaronic origin inLa2−xSrxCuO4: Interaction between charge stripes and pinning centers

We have used x-ray absorption spectroscopy as a tool to study instantaneous local lattice distortions of the CuO2 plane in high Tc superconductors and we have investigated the inhomogeneous charge states of these materials. The temperature-dependent Cu K-edge extended x-ray absorption fine structure (EXAFS) has been used to determine the correlated Debye–Waller factor of the Cu–O bonds, measuring local lattice fluctuations. The Debye–Waller factor of the Cu–O bonds shows an order-parameter-like behaviour across the charge stripe ordering temperature. The EXAFS results are supported by a temperature-dependent Cu K-edge x-ray absorption near edge structure (XANES) revealing a particular change in the local lattice displacements at the charge stripe ordering. The experimental Cu K-edge XANES results are well reproduced by full multiple scattering calculations including different distortions of the CuO2 plane showing particular lattice displacements which are consistent with the EXAFS results. The particular distortion mode as a response function to the charge stripe ordering has been discussed with several examples. The results are consistent with an inhomogeneous charge distribution in the high Tc cuprates suggesting an intimate relationship between the charge stripe ordering, local lattice fluctuations and high Tc superconductivity in the cuprates.

https://www.roma1.infn.it/stripes/Menu/002Papers/ArticoliStr/latticesuperconductors02.pdf

Lattice fluctuations and inhomogeneous charge states of high-Tc superconductors

A recall of the phase diagram for two-dimensional quantum Heisenberg antiferromagnets (2DQHAF) and of the main issues involving phase transitions and spin dynamics in these systems is first given. After a pedagogical description of the basic aspects for the NMR-NQR relaxation rates in terms of amplitudes and decay rates of spin fluctuations, the problem of the temperature dependence of the correlation length in prototype, pure 2DQHAF (CFTD and La 2 CuO 4 ) is addressed. Then spin- and charge-doped systems (Zn/Mg for Cu and Sr for La substitutions in La 2 CuO 4 ) are considered and the effects on the spin stiffness, on the correlation length and on the staggered Cu 2+ magnetic moment are reported, in particular near the percolation threshold. A critical outline of the properties of the cluster spin glass phase in Sr- doped La 2 CuO 4 is given. Finally the results of a 63 Cu NQR-NMR relaxation study around the quantum critical point (in CeCu 6-x Au x ) are presented. It is pointed out how the 2D response function with anomalous exponent and energy/temperature scaling indicated by neutron scattering is basically confirmed, while the 63 Cu relaxation measurements reveal novel effects involving low-energy spin excitations and the role of an external magnetic field.

Correlated Spin Dynamics and Phase Transitions in Pure and in Disordered 2D S = 1/2 Antiferromagnets: Insights from NMR-NQR

Entzundlich-rheumatische Erkrankungen mit Erstmanifestation im hoheren Lebensalter weisen einige Besonderheiten auf. Die rheumatoide Arthritis und die Polymyalgia rheumatica bzw. Riesenzellarteriitis sind die haufigsten Formen entzundlicher rheumatologischer Erkrankungen des Alteren. Sie sind durch einen akuten Beginn, starke schmerzbedingte Funktionseinschrankungen und eine breite Differenzialdiagnose gekennzeichnet. In der Akuttherapie sind Glukokortikoide in mittleren Dosierungen oft ausreichend. Fur die langerfristige Therapie stehen auch beim alteren Patienten verschiedene Immunsuppressiva und Biologika zur Verfugung.

Entzündlich-rheumatische Erkrankungen im höheren Lebensalter

Anelastic relaxation and 139LaNQR relaxation rates in La2–xSrxCuO4 for Sr content around 2 and 3 percent are discussed in terms of spin and lattice excitations and of the related ordering processes. It is argued how the phase diagram of La2–xSrxCuO4 at the boundary between the antiferromagnetic (AF) and the spin-glass phase (x
= 0.02) could be more complicate than previously thought, with a transition to a quasi-long range ordered state at K, as indicated by neutron scattering data. On the other hand, the 139LaNQR spectra are compatible with a transition to an AF phase around K, in agreement with the phase diagram commonly accepted in literature. In this case the peaks in NQR and anelastic relaxation rates around 150 K and 80 K respectively in La1.98Sr0.02CuO4, yield the first evidence of freezing process involving simultaneously lattice and spin excitations, possibly corresponding to motion of charged stripes.

Anelastic relaxation and around the critical Sr content x = 0.02

The vibrational dynamics in nearly stoichiometric La2CuO4+δ is studied by means of anelastic and 139La NQR relaxation. After lowering δ to values of the order of 0.001, a relaxational peak remains in both the anelastic and NQR spectra with a mean relaxation time τ=1.7×10−12 exp[(2800 K)/T]s. Such a process is attributed to the motion of CuO6 octahedra in doublewell potentials whose cooperative character increases the effective energy barrier to the observed value. It is speculated that the freezing of the motion of the octahedra may correspond to the locking of the stripes.

F. Cordero

Papers

Anelastic relaxation and around the critical Sr content x = 0.02

Vibrational Pseudo-Diffusive Motion of the Oxygen Octahedra in La2CuO4 from Anelastic and 139La Quadrupolar Relaxation