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We study the global polarizations of Λ, Ξ−, and Ω− hyperons in noncentral Au + Au collisions at √SNN = 7.7-200 GeV$\sqrt {{S_{{\rm{NN}}}}} = 7.7 - 200\,{\rm{GeV}}$SNN=7.7−200 GeV. We highlight the importance of effect of decay feeddown to the measured global polarization. With the decay contributions taken into account, the global polarization ordering PΩ− > PΞ− > PΛ${P_{{\Omega ^ - }}} > {P_{{\Xi ^ - }}} > {P_\Lambda }$PΩ−>PΞ−>PΛ can be naturally explained, which is consistent with the observation recently reported from the STAR experiment from Au+Au collisions at 200 GeV. We also extend our calculations to predict expectations from the RHIC-BES II data.

Abstract: SmDy1−x Gd x Zr2O7 (0 ≤ x ≤ 1.0) ceramics are prepared by solid state reaction method at 1973 K for 10 h in air. The crystal structure and microstructure of SmDy1−x Gd x Zr2O7 ceramics are investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). All the SmDy1−x Gd x Zr2O7 ceramics (x = 0.2, 0.4, 0.6, 0.8, 1.0) exhibit a pyrochlore structure except for SmDyZr2O7 ceramic. SmDyZr2O7 ceramic has a defective fluorite structure. The incorporation of Gd3+ facilitates a structural evolution from a defective fluorite into an ordered pyrochlore-type structure. Electrical conductivity of SmDy1−x Gd x Zr2O7 ceramics has been investigated by impedance spectroscopy over a frequency range of 1 Hz to 8 MHz from 673 to 1173 K. The grain conductivity of SmDy1−x Gd x Zr2O7 ceramics follows the Arrhenius behavior. The grain conductivity of SmDy1−x Gd x Zr2O7 ceramics increases obviously with increasing Gd3+ content in the temperature range of 673–1073 K, and the optimal grain conductivity value is 1.90 × 10−2 S cm−1 in the composition of SmGdZr2O7 ceramic at 1173 K. All the SmDy1−x Gd x Zr2O7 ceramics are purely oxide ionic conductors in the test temperature range. [Copyright &y& Elsevier]

Abstract: (Sm1−x Dy x )2Zr2O7 (0≤ x ≤1) ceramics are prepared by a solid state reaction process at 1973K for 10h in air. (Sm1−x Dy x )2Zr2O7 (0≤ x ≤0.3) ceramics exhibit a single phase of pyrochlore-type structure, while (Sm1−x Dy x )2Zr2O7 (0.5≤ x ≤1.0) possess a defective fluorite-type structure. The full width at half-maxima in the Raman spectra increases with increasing Dy content, which indicates that the degree of structural disorder increases as the Dy content increases. The ionic conductivity of (Sm1−x Dy x )2Zr2O7 ceramics is investigated by impedance spectroscopy over a frequency range of 0.2Hz to 8MHz in the temperature range of 873–1173K in air and hydrogen atmospheres, respectively. The ionic conductivity has a maximum near the phase boundary between the pyrochlore- and the defective fluorite-type phases under identical temperature levels. The ionic conductivity is determined by the degree of structural disorder or unit cell free volume, which is depending on the Dy content. As the ionic conductivity in the hydrogen atmosphere is almost the same as that obtained in air, the conduction of (Sm1−x Dy x )2Zr2O7 is purely ionic with negligible electronic conduction. [ABSTRACT FROM AUTHOR]

Abstract: Gd2(Zr1−x Nb x )2O7+x (0≤ x ≤0.2) ceramics are prepared via the solid state reaction process at 1973K for 10h in air. Gd2(Zr1−x Nb x )2O7+x (x =0.1, 0.2) ceramics exhibit an ordered pyrochlore-type structure, whereas Gd2Zr2O7 has a defective fluorite-type structure. The electrical property of Gd2(Zr1−x Nb x )2O7+x ceramics is investigated by electrochemical impedance spectroscopy over a frequency range of 10Hz to 8MHz from 623 to 923K. The electrical conductivity obeys the Arrhenius equation. The grain conductivity of Gd2(Zr1−x Nb x )2O7+x ceramics varies with doping different Nb contents, and exhibits a maximum at the Nb content of x =0.1 in the temperature range of 623–923K. The conductivity in hydrogen atmosphere is a little bit higher than in air in the temperature range of 723–923K, which indicates that the doping of Zr4+ by Nb5+ can increase the proton-type conduction and reduce the oxide-ionic conduction. The conduction of Gd2(Zr1−x Nb x )2O7+x is not a pure oxide-ionic conductor. [Copyright &y& Elsevier]

Global spin polarization of hyperons is an important observable to probe the vorticity of the quark-gluon plasma produced in heavy-ion collisions. We calculate the global polarizations of Λ, Ξ − , and Ω − in Au+Au collisions at energies s NN = 7.7–200 GeV based on a multiphase transport model. Our calculations suggest that their primary global polarizations fulfill P Ω − ≃ 5 / 3 P Ξ − ≃ 5 / 3 P Λ. We also estimate the feed-down effect of particle decay on the global polarization. With the feed-down effect taken into account, the global polarizations of Λ and Ξ − are clearly separated, and the final global polarizations are in the ordering: P Ω − > P Ξ − > P Λ. Such a relation can be tested in experiments, which will provide us more information about the global polarization mechanism. [ABSTRACT FROM AUTHOR]

Abstract: (Sm1−x Ca x )2Zr2O7−x (0≤ x ≤0.100) ceramics were prepared by a solid state reaction process at 1973K for 10h in air, and were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). (Sm1−x Ca x )2Zr2O7−x (0≤ x ≤0.025) ceramics have a single phase of pyrochlore-type structure; however (Sm1−x Ca x )2Zr2O7−x (0.050≤ x ≤0.100) consist of pyrochlore phase and a small amount of perovskite-like CaZrO3. The electrical conductivity of (Sm1−x Ca x )2Zr2O7−x ceramics was investigated by complex impedance spectroscopy over a frequency range of 0.1Hz to 20MHz in the temperature range of 573–873K. The measured electrical conductivity obeys the Arrhenius relation. Both the activation energy and pre-exponential factor for grain conductivity increase with increasing the CaO content; however, electrical conductivity of (Sm1−x Ca x )2Zr2O7−x decreases with increasing the CaO content, which is due to the increase in structural disordering at 0≤ x ≤0.025 and the presence of the poorly conducting CaZrO3 phase at 0.050≤ x ≤0.100, respectively. [Copyright &y& Elsevier]

We investigate the spin alignment of vector mesons arising from locally polarized quarks and anti-quarks (local spin alignment) in heavy-ion collisions. We find that ρ 00 ≠ 1 / 3 does not necessarily signal the global polarization of quarks and anti-quarks along the orbital angular momentum of the system, but may also originate from their local spin polarization. Such local spin polarization could be induced by local vorticity arising from the anisotropic expansion of the fireball. We further propose experimental observables that can distinguish between the local and the global spin alignments. Measurements of these observables in heavy-ion collisions can probe the vorticity pattern and shed light on the puzzles of ϕ and K ⁎ 0 spin alignments. [ABSTRACT FROM AUTHOR]

We compute the fermion spin distribution in the vortical fluid created in off-central high energy heavy-ion collisions. We employ the event-by-event (3+1)D viscous hydrodynamic model. The spin polarization density is proportional to the local fluid vorticity in quantum kinetic theory. As a result of strong collectivity, the spatial distribution of the local vorticity on the freeze-out hyper-surface strongly correlates to the rapidity and azimuthal angle distribution of fermion spins. We investigate the sensitivity of the local polarization to the initial fluid velocity in the hydrodynamic model and compute the global polarization of Λ hyperons by the AMPT model. The energy dependence of the global polarization agrees with the STAR data. [ABSTRACT FROM AUTHOR]

Abstract: SmYb1−x Gd x Zr2O7 (0≤ x ≤1.0) ceramics were pressureless-sintered at 1973K for 10h in air. The relative density, structure and electrical conductivity of SmYb1−x Gd x Zr2O7 ceramics were investigated by the Archimedes method, X-ray diffraction, scanning electron microscopy and impedance spectroscopy measurements. SmYb1−x Gd x Zr2O7 (0≤ x ≤0.5) ceramics exhibit a defect fluorite-type structure, while SmYb1−x Gd x Zr2O7 (0.7≤ x ≤1.0) ceramics have a pyrochlore-type structure. The measured values of the electrical conductivities obey the Arrhenius relation. The grain conductivity of each composition in SmYb1−x Gd x Zr2O7 ceramics increases with increasing temperature from 723 to 1173K. The grain conductivity of SmYb1−x Gd x Zr2O7 ceramics gradually increases with increasing gadolinium content at identical temperature levels. An increase of about one order of magnitude in grain conductivity is found at all temperature levels when the gadolinium content increases from 0.5 to 0.7. SmYb1−x Gd x Zr2O7 ceramics are oxide-ion conductors in the oxygen partial pressure range of 1.0×10−4 to 1.0atm at all test temperature levels. The highest grain conductivity value obtained in this work is 2.69×10−2 Scm−1 at 1173K for SmGdZr2O7 ceramic. [Copyright &y& Elsevier]

Abstract: (Nd1−x Yb x )2Zr2O7 (0≤ x ≤1) ceramics were prepared by pressureless-sintering to obtain dense bulk materials. The electrical conductivity of (Nd1−x Yb x )2Zr2O7 was investigated by complex impedance spectroscopy over a frequency range of 20Hz to 2MHz from 723 to 1173K in air. A high-temperature dilatometer was used to analyze thermal expansion coefficient of (Nd1−x Yb x )2Zr2O7 in the temperature range of 373–1523K. The measured electrical conductivity obeys the Arrhenius relation. The grain conductivity of each composition in (Nd1−x Yb x )2Zr2O7 gradually increases with increasing temperature. A decrease of about one order of magnitude in grain conductivity is found at all temperature levels when the Yb content increases from x =0.3 to x =0.5. The highest electrical conductivity value obtained in this work is 9.32×10−3 Scm−1 at 1173K for (Nd0.7Yb0.3)2Zr2O7 ceramic. (Nd1−x Yb x )2Zr2O7 ceramics are oxide-ion conductors in the oxygen partial pressure range from 1.0×10−4 to 1.0atm at all test temperature levels. Thermal expansion coefficients of (Nd1−x Yb x )2Zr2O7 gradually decrease with increasing ytterbium content at identical temperature levels. [Copyright &y& Elsevier]

Abstract: The phase stability and thermal expansion property of ZrO2–NdO1.5–AlO1.5 ceramics from 50 to 1550°C were investigated for potential high-temperature structural and functional applications. All ZrO2–NdO1.5–AlO1.5 ceramics consist mainly of perovskite-like NdAlO3 and pyrochlore or fluorite (F–ZrO2) structures, and have relatively stable thermal expansion coefficients from 200 to 1400°C. However, ZrO2–NdO1.5 (Nd2Zr2O7) ceramics have a single pyrochlore-type lattice, and exhibit a distinct decreasing tendency of thermal expansion coefficients from 400 to 1550°C. The thermal expansion coefficients of ZrO2–NdO1.5–AlO1.5 ceramics are within the range of 10.3–11.5×10−6 K−1 at 1400°C, which are of the same order of magnitude as 7wt.% yttria stabilized zirconia. [Copyright &y& Elsevier]

Abstract: Gd2−x Sm x Zr2O7 (x =0, 0.2, 0.6, 1.0, 1.4, 1.8, 2.0) ceramic powders synthesized with the chemical-coprecipitation and calcination method were pressureless-sintered at 1873K for 10h in air. The electrical conductivity of Gd2−x Sm x Zr2O7 ceramics was investigated by complex impedance spectroscopy over a frequency range of 0.01Hz to 15MHz. Gd2−x Sm x Zr2O7 is an oxide-ion conductor in the oxygen partial pressure range from 1.0×10−15 to 1.0atm and in the temperature range of 623–873K. The measured electrical conductivity obeys the Arrhenius relation. The activation energy and pre-exponential factor for grain-interior conductivity gradually decrease with increasing Sm content. The grain-interior conductivity varies with the Sm substitution for Gd, and reaches the maximum at the equal molar of Sm3+ and Gd3+ in Gd2−x Sm x Zr2O7 ceramics. A significant increase in the grain-interior conductivity is obtained by isovalent rare-earth element like Sm substitution for Gd in the temperature range of 623–873K. [Copyright &y& Elsevier]