Structural features of highly stable reproducible C₆₀ fullerene aqueous colloid solution probed by various techniques

The method of preparation of highly stable reproducible C₆₀ fullerene aqueous colloid solution is described. The structural organization of C₆₀ fullerenes in aqueous solution was studied and analyzed in detail using various techniques such as chemical analysis, UV/VIS spectroscopy, atomic force and scanning tunneling microscopy, dynamic light scattering, and zeta potential method

Resonance Chiral Lagrangian analysis of τ−→η(′)π−π0ντ\tau^- \to \eta^{(\prime)} \pi^- \pi^0 \nu_\tau decays

The hadronization structure of $\tau^- \to \eta \pi^- \pi^0 \nu_\tau$ decays is analyzed using Chiral Perturbation Theory with resonances, considering only the contribution of the lightest meson resonances at leading order in the $1/N_C$ expansion. After imposing the asymptotic behavior of vector spectral functions ruled by QCD, unknown effective couplings are determined by fitting the $\tau^- \to \eta \pi^- \pi^0 \nu_\tau$ branching ratio and decay spectrum to recent data. Predictions for the partner decay $\tau^- \to \eta^\prime \pi^- \pi^0 \nu_\tau$ and the low-energy behavior of the cross section $\sigma (e^+e^-\to \eta\pi^+\pi^-)$ are also discussed.Comment: 21 pages, 5 figures, v2: Title changed, references added and rewriting of some sentences. It matches the published version in PR

Phase equilibria, crystal structure and oxygen nonstoichiometry of the complex oxides in Sm – (Sr, Ba) – (Co, Fe) – O systems

Received: 18.01.2018. Accepted: 14.02.2018. Published: 10.05.2018.Present paper contains available information on the phase equilibria in the Sm – (Sr, Ba) – (Co, Fe) – O systems, including the synthesis routes used, crystal structure, which is often depended on oxygen nonstoichiometry, the data on thermodynamic stability of complex oxides, the obtained results on the homogeneity ranges of solid solutions, formed in the systems, and graphical presentation of phase relations in a form of phase diagrams

The Kagome Antiferromagnet with Defects: Satisfaction, Frustration, and Spin Folding in a Random Spin System

It is shown that site disorder induces noncoplanar states, competing with the thermal selection of coplanar states, in the nearest neighbor, classical kagome Heisenberg antiferromagnet (AFM). For weak disorder, it is found that the ground state energy is the sum of energies of separately satisfied triangles of spins. This implies that disorder does not induce conventional spin glass behavior. A transformation is presented, mapping ground state spin configurations onto a folded triangular sheet (a new kind of ``spin origami'') which has conformations similar to those of tethered membranes.Comment: REVTEX, 11 pages + 3 pictures upon reques

Parametric generation of second sound in superfluid helium: linear stability and nonlinear dynamics

We report the experimental studies of a parametric excitation of a second sound (SS) by a first sound (FS) in a superfluid helium in a resonance cavity. The results on several topics in this system are presented: (i) The linear properties of the instability, namely, the threshold, its temperature and geometrical dependencies, and the spectra of SS just above the onset were measured. They were found to be in a good quantitative agreement with the theory. (ii) It was shown that the mechanism of SS amplitude saturation is due to the nonlinear attenuation of SS via three wave interactions between the SS waves. Strong low frequency amplitude fluctuations of SS above the threshold were observed. The spectra of these fluctuations had a universal shape with exponentially decaying tails. Furthermore, the spectral width grew continuously with the FS amplitude. The role of three and four wave interactions are discussed with respect to the nonlinear SS behavior. The first evidence of Gaussian statistics of the wave amplitudes for the parametrically generated wave ensemble was obtained. (iii) The experiments on simultaneous pumping of the FS and independent SS waves revealed new effects. Below the instability threshold, the SS phase conjugation as a result of three-wave interactions between the FS and SS waves was observed. Above the threshold two new effects were found: a giant amplification of the SS wave intensity and strong resonance oscillations of the SS wave amplitude as a function of the FS amplitude. Qualitative explanations of these effects are suggested.Comment: 73 pages, 23 figures. to appear in Phys. Rev. B, July 1 st (2001

Critical temperature for the nuclear liquid-gas phase transition (from multifragmentation and fission)

Critical temperature Tc for the nuclear liquid-gas phase transition is stimated both from the multifragmentation and fission data. In the first case,the critical temperature is obtained by analysis of the IMF yields in p(8.1 GeV)+Au collisions within the statistical model of multifragmentation (SMM). In the second case, the experimental fission probability for excited 188Os is compared with the calculated one with Tc as a free parameter. It is concluded for both cases that the critical temperature is higher than 16 MeV.Comment: 15 pages, 8 figure

Synthesis and characterization of the oxygen-deficient perovskite BaFe0.9-xY0.1CoxO3-δ (0 ≤ x ≤ 0.15)

BaFe0.9-xY0.1CoxO3-δ (0 ≤ x ≤ 0.15) is shown to adopt the cubic perovskite structure at temperatures up to 1400 K in air. The oxygen vacancy concentration increases with both cobalt content and temperature, with BaFe0.75Y0.1Co0.15O2.35 being the most oxygen-deficient composition observed. At 700 K the conductivity is ∼2 S cm−1 across the whole composition range. Measurements of the Seebeck coefficient show that holes are the dominant carrier. The coefficient of thermal expansion is essentially constant above 800 K, but not at lower temperatures. Chemical reactivity tests, along with the coefficient of expansion, show that these perovskites would not be suitable electrodes for fuel cells with fluorite electrolytes but they might serve as permeable membranes in catalytic reactors. © 2016 Elsevier Lt