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We present data of multiharmonic magneto-dynamic experiments. In particular, we performed ac magnetic susceptibility experiments on layered pnictide-oxide quaternary compound NdOFeAs doped with fluorine. The experiments allow one to measure the critical temperature and probe the flux dynamic behavior using the third harmonic component of the ac susceptibility of an NdF0.16FeAsO0.84 bulk sample as a function of temperature and frequency of the applied ac magnetic fields. Measured signals are connected with the nonlinear superconducting flux dynamic behavior and are characterized by a “flux critical states” sustaining a superconducting critical current. In this framework the irreversibility line that describes the stable superconducting state has been extracted from the onset of the third harmonic signal vs. frequency. Finally we present also the analysis of the flux dynamic dimensionality in the investigated sample. [ABSTRACT FROM AUTHOR]

We have studied the variation of superconducting critical temperature T c as a function of electron doping in the Mg10B2 system using Sc for Mg substitution. The critical temperature in the10B isotope substituted system Mg1− x Sc x 10B2 increases by increasing the scandium content x in the range 0< x<0.012 up to 41.4 K, while the T c of the natural boron system Mg1− x Sc x B2 is nearly constant. The overall difference of T c in Mg1− x Sc x B2 as function of x between the natural B and 10B isotope system seems to indicate that the isotope effect shows large variations with electron doping as expected for the T c enhancement driven by a shape resonance. [ABSTRACT FROM AUTHOR]

The thermal lattice expansion in the superconducting Mg1− x Al x B2 system ( x = 0, 0.13, and 0.59) has been measured using high-resolution X-ray powder diffraction. An unusual large negative thermal expansion (NTE) appears for temperatures below T * = 60 K in the MgB2. The NTE effect increases in Mg0.87Al0.13B2 and disappears at high Al content in the Mg0.59Al0.41B2 where the temperature dependence of volume follows a standard Einstein model in the whole temperature range. The anomalous behavior of the thermal expansion provides a direct evidence in the physics of diborides for the relevance of the proximity to the 2.5 Lifshitz electronic topological transition where the Fermi surface of the σband changes from a two-dimensional (2D) to a three-dimensional (3D) topology. [ABSTRACT FROM AUTHOR]

The interstitial oxygen ordering in a La2CuO4+ y ( y = 0.08) single crystal with a T c = 38 K has been investigated. We have studied the growth dynamics of the three dimensional (3D) ordered phase, called Q2, at different temperatures under X-ray illumination. The critical temperature T 0∼334 K of the order-disorder transition for the Q2 phase has been determined. We have found that the illumination of the sample with a continuous polarized synchrotron radiation X-ray flux stimulates the oxygen ordering kinetics. The photoinduced ordering process shows a threshold characteristic of cooperative phenomena and its kinetics shows a temperature dependence that is controlled by the activation energy E A = 100 meV. [ABSTRACT FROM AUTHOR]

One possible application of Nb3Sn, whose superconducting properties far exceed those of NbTi, is the fabrication of short and powerful quadrupole magnets for the Interaction Regions (IR) of large particle accelerators. In some cases, as in the future linear collider TESLA, the quadrupole magnets are inside the detector solenoid and must operate in its background field. This situation gives singular Lorentz force distribution in the ends of the magnet. To learn about Nb3Sn technology, evaluate fabrication techniques and test the interaction with a solenoidal field, DAPNIA/SACM at CEA/Saclay has started the manufacturing of a 1-m-long, 56-mm-single-aperture quadrupole magnet model. The model relies on the same coil geometry as the Lilt arc quadrupole magnets, but has no iron yoke. It will produce a nominal field gradient of 211 T/m at 11,870 A. The coils are wound from Rutherford-type cables insulated with glass fiber tape, before being heattreated and vacuum-impregnated with epoxy resin. Laminated collars, locked around the coil assembly by means of keys, restrain the Lorentz forces. After a recall of the conceptual design, the paper re- views the progress in the manufacturing and test of the main com- ponents as well as in the design and delivery of the main tooling. The first coil is expected to be wound and heat treated during the last quarter of 2003. [ABSTRACT FROM AUTHOR]

Choroid plexus, pineal gland, and habenula tend to accumulate physiologic calcifications (concrements) over a lifetime. However, until now the composition and causes of the intracranial calcifications remain unclear. The detailed analysis of concrements has been done by us using X-ray diffraction analysis (XRD), X-ray diffraction topography (XRDT), micro-CT, X-ray phase-contrast tomography (XPCT), as well as histology and immunohistochemistry (IHC). By combining physical (XRD) and biochemical (IHC) methods, we identified inorganic (hydroxyapatite) and organic (vimentin) components of the concrements. Via XPCT, XRDT, histological, and IHC methods, we assessed the structure of concrements within their appropriate tissue environment in both two and three dimensions. The study found that hydroxyapatite was a major component of all calcified depositions. It should be noted, however, that the concrements displayed distinctive characteristics corresponding to each specific structure of the brain. As a result, our study provides a basis for assessing the pathological and physiological changes that occur in brain structure containing calcifications. [ABSTRACT FROM AUTHOR]