128,305 research outputs found
Connectivity of Direct Products of Graphs
Let be the connectivity of and the direct product
of and . We prove that for any graphs and with ,
, which was conjectured
by Guji and Vumar.Comment: 5 pages, accepted by Ars Com
Anisotropic thermal expansion of AEFe2As2 (AE = Ba, Sr, Ca) single crystals
We report anisotropic thermal expansion of the parent, AEFe2As2 (AE = Ba, Sr,
and Ca), compounds. Above the structural/antiferromagnetic phase transition
anisotropy of the thermal expansion coefficients is observed, with the
coefficient along the a-axis being significantly smaller than the coefficient
for the c-axis. The high temperature (200 K < T < 300 K) coefficients
themselves have similar values for the compounds studied. The sharp anomalies
associated with the structural/antiferromagnetic phase transitions are clearly
seen in the thermal expansion measurements. For all three pure compounds the
"average" a-value increases and the c-lattice parameter decreases on warming
through the transition with the smallest change in the lattice parameters
observed for SrFe2As2. The data are in general agreement with the literature
data from X-ray and neutron diffraction experiments
Specific heat jump at the superconducting transition temperature in Ba(Fe(1-x)Cox)2As2 and Ba(Fe(1-x)Nix)2As2 single crystals
We present detailed heat capacity measurements for Ba(Fe(1-x)Cox)2As2 and
Ba(Fe(1-x)Nix)2As2 single crystals in the vicinity of the superconducting
transitions. The specific heat jump at the superconducting transition
temperature (Tc), Delta Cp/Tc, changes by a factor ~ 10 across these series.
The Delta Cp/T$ vs. Tc data of this work (together with the literature data for
Ba(Fe0.939Co0.061)2As2, (Ba0.55K0.45)Fe2As2, and (Ba0.6K0.4)Fe2As2) scale well
to a single log-log plot over two orders of magnitude in Delta Cp/Tc and over
about an order of magnitude in Tc, giving Delta Cp/Tc ~ Tc^2
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