1,483 research outputs found
Pressure-induced Superconductivity in CaLi2
A search for superconductivity has been carried out on the hexagonal
polymorph of Laves-phase CaLi2, a compound for which Feng, Ashcroft, and
Hoffmann predict highly anomalous behavior under pressure. No superconductivity
is observed above 1.10 K at ambient pressure. However, high-pressure ac
susceptibility and electrical resistivity studies to 81 GPa reveal bulk
superconductivity in CaLi2 at temperatures as high as 13 K. The normal-state
resistivity shows a dramatic increase with pressure.Comment: bulk superconductivity in CaLi2 now confirme
Probing the strength of infants' preference for helpers over hinderers:Â two replication attempts of Hamlin and Wynn (2011)
Several studies indicate that infants prefer individuals who act prosocially over those
who act antisocially toward unrelated third parties. In the present study, we focused on a
paradigm published by Kiley Hamlin and Karen Wynn in 2011. In this study, infants were
habituated to a live puppet show in which a protagonist tried to open a box to retrieve a toy
placed inside. The protagonist was either helped by a second puppet (the “Helper”), or hindered by a third puppet (the “Hinderer”). At test, infants were presented with the Helper and the Hinderer, and encouraged to reach for one of them. In the original study, 75% of 9-month-olds selected the Helper, arguably demonstrating a preference for prosocial over antisocial individuals. We conducted two studies with the aim of replicating this result. Each
attempt was performed by a different group of experimenters. Study 1 followed the methods
of the published study as faithfully as possible. Study 2 introduced slight modifications to the
stimuli and the procedure following the guidelines generously provided by Kiley Hamlin and
her collaborators. Yet, in our replication attempts, 9-month-olds’ preference for helpers over hinderers did not differ significantly from chance (62.5% and 50%, respectively, in Studies 1 and 2). Two types of factors could explain why our results differed from those of Hamlin and Wynn: minor methodological dissimilarities (in procedure, materials, or the population
tested), or the effect size being smaller than originally assumed. We conclude that fine
methodological details that are crucial to infants’
success in this task need to be identified to
ensure the replicability of the original result
Studies of superconductivity and structure for CaC6 to pressures above 15 GPa
The dependence of the superconducting transition temperature Tc of CaC6 has
been determined as a function of hydrostatic pressure in both helium-loaded gas
and diamond-anvil cells to 0.6 and 32 GPa, respectively. Following an initial
increase at the rate +0.39(1) K/GPa, Tc drops abruptly from 15 K to 4 K at 10
GPa. Synchrotron x-ray measurements to 15 GPa point to a structural transition
near 10 GPa from a rhombohedral to a higher symmetry phase
Superconductivity at 17 K in Yttrium Metal under Nearly Hydrostatic Pressures to 89 GPa
In an experiment in a diamond anvil cell utilizing helium pressure medium,
yttrium metal displays a superconducting transition temperature which increases
monotonically from Tc ? 3.5 K at 30 GPa to 17 K at 89.3 GPa, one of the highest
transition temperatures for any elemental superconductor. The pressure
dependence of Tc differs substantially from that observed in previous studies
under quasihydrostatic pressure to 30 GPa. Remarkably, the dependence of Tc on
relative volume V/Vo is linear over the entire pressure range above 33 GPa,
implying that higher values of Tc are likely at higher pressures. For the
trivalent metals Sc, Y, La, Lu there appears to be some correlation between Tc
and the ratio of the Wigner-Seitz radius to the ion core radius.Comment: submitted for publicatio
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