Influence of annealing on nanocrystal formation in Ni amorphous alloy

It is established that nanocrystals in the alloy samples increase in size with increasing annealing temperature. The rise of resistivity upon annealing at temperatures below 300°C and its significant decrease at higher temperatures is consistent with the change in the amorphous alloy microstructureyesBelgorod State Universit

Analisi scientifiche sulle tempere murali di Villa Pace

International audienceThe morphology, mineralogy, and solid-liquid phase separation of the Cu and Zn precipitates formed with sulfide produced in a sulfate-reducing bioreactor were studied at pH 3, 5, and 7. The precipitates formed at pH 7 display faster settling rates, better dewaterability, and higher concentrations of settleable solids as compared to the precipitates formed at pH 3 and 5. These differences were linked to the agglomeration of the sulfidic precipitates and coprecipitation of the phosphate added to the bioreactor influent. The Cu and Zn quenched the intensity of the dissolved organic matter peaks identified by fluorescence-excitation emission matrix spectroscopy, suggesting a binding mechanism that decreases supersaturation, especially at pH 5. X-ray absorption fine structure spectroscopy analyses confirmed the precipitation of Zn-S as sphalerite and Cu-S as covellite in all samples, but also revealed the presence of Zn sorbed on hydroxyapatite. These analyses further showed that CuS structures remained amorphous regardless of the pH, whereas the ZnS structure was more organized at pH 5 as compared to the ZnS formed at pH 3 and 7, in agreement with the cubic sphalerite-type structures observed through scanning electron microscopy at pH 5

Evidence for nonmonotonic magnetic field penetration in a type-I superconductor

Polarized neutron reflectometry (PNR) provides evidence that nonlocal electrodynamics governs the magnetic field penetration in an extreme low-k superconductor. The sample is an indium film with a large elastic mean free path (11 mkm) deposited on a silicon oxide wafer. It is shown that PNR can resolve the difference between the reflected neutron spin asymmetries predicted by the local and nonlocal theories of superconductivity. The experimental data support the nonlocal theory, which predicts a nonmonotonic decay of the magnetic field.Comment: 5 pages, 4 figures, LaTex, corrected typos and figure

Magnetic proximity effect in [Nb/Gd] superlattices seen by neutron scattering

We have used spin-polarized neutron reflectometry to investigate the magnetization profile of superlattices composed of ferromagnetic Gd and superconducting Nb layers. We have observed a partial suppression of ferromagnetic (F) order of Gd layers in [Gd($d_F$)/Nb(25nm)]$_{12}$ superlattices below the superconducting (S) transition of the Nb layers. The amplitude of the suppression decreases with increasing $d_F$. By analyzing the neutron spin asymmetry we conclude that the observed effect has an electromagnetic origin - the proximity-coupled S layers screen out the external magnetic field and thus suppress the F response of the Gd layers inside the structure. Our investigation demonstrates the considerable influence of electromagnetic effects on the magnetic properties of S/F systems

Photon Physics in Heavy Ion Collisions at the LHC

Various pion and photon production mechanisms in high-energy nuclear collisions at RHIC and LHC are discussed. Comparison with RHIC data is done whenever possible. The prospect of using electromagnetic probes to characterize quark-gluon plasma formation is assessed.Comment: Writeup of the working group "Photon Physics" for the CERN Yellow Report on "Hard Probes in Heavy Ion Collisions at the LHC", 134 pages. One figure added in chapter 5 (comparison with PHENIX data). Some figures and correponding text corrected in chapter 6 (off-chemical equilibrium thermal photon rates). Some figures modified in chapter 7 (off-chemical equilibrium photon rates) and comparison with PHENIX data adde

Atomic structure of dislocation kinks in silicon

We investigate the physics of the core reconstruction and associated structural excitations (reconstruction defects and kinks) of dislocations in silicon, using a linear-scaling density-matrix technique. The two predominant dislocations (the 90-degree and 30-degree partials) are examined, focusing for the 90-degree case on the single-period core reconstruction. In both cases, we observe strongly reconstructed bonds at the dislocation cores, as suggested in previous studies. As a consequence, relatively low formation energies and high migration barriers are generally associated with reconstructed (dangling-bond-free) kinks. Complexes formed of a kink plus a reconstruction defect are found to be strongly bound in the 30-degree partial, while the opposite is true in the case of 90-degree partial, where such complexes are found to be only marginally stable at zero temperature with very low dissociation barriers. For the 30-degree partial, our calculated formation energies and migration barriers of kinks are seen to compare favorably with experiment. Our results for the kink energies on the 90-degree partial are consistent with a recently proposed alternative double-period structure for the core of this dislocation.Comment: 12 pages, two-column style with 8 postscript figures embedded. Uses REVTEX and epsf macros. Also available at http://www.physics.rutgers.edu/~dhv/preprints/index.html#rn_di