Synthesis and Anti‐proliferative Activity of N,N′‐bis‐substituted 1,2,4‐Triazolium Salts against Breast Cancer and Prostate Cancer Cell Lines

A series of 1,4‐N,N′‐bis‐substituted 1,2,4‐triazolium bromide salts were synthesized and tested for anti‐proliferative activity. 1,4‐Bis(naphthalen‐2‐ylmethyl)‐1,2,4‐triazolium bromide ( 2 ) showed activity against MDA‐MB‐468 breast cancer and PC‐3 prostate cancer cell lines.     

Superconductivity and relative phase stability in 1:2:2 ternary transition metal silicides and germanides

Twenty-seven ternary intermetallic compounds belonging to either the ThCr₂Si₂-type or the CaBe₂Ge₂-type structures are investigated for their superconducting properties. The primitive tetragonal CaBe₂Ge₂-type structure consistently favors superconductivity over the ThCr₂Si₂-type structure for which we find no superconductivity above 1.1 K.     

Vortex pinning in polycrystalline Eu1.5Ce0.5Sr2Cu2NbO10 from rotational magnetic measurements

Rotational magnetization-vector measurements were carried out on a superconducting polycrystalline disk of EuCSCNO. The results at 4.2 K and low fields resemble recent results for YBa₂Cu₃O_7−δ (YBCO) and Ba_0.57K_0.43BiO₃ (BKBO) in revealing a broad distribution in the strength of the vortex pinning torques. This resemblance extends to higher fields, where it was found that the average pinning torque per vortex (τ_p), which is directly related to the critical current density, decreases steadily with increasing field in a manner consistent with vortex bundling. Quantitatively, however, the values of τ_p for EuCSCNO are smaller by an order of magnitude than those for YBCO but are only moderately smaller than those for BKBO. This comparison supports the notion that the vortex pinning may derive in part from deviations from oxygen stoichiometry, which are normally present in YBCO but are essentially absent in EuCSCNO and BKBO. Moreover, as in YBCO and BKBO, the τ_p in EuCSCNO at fixed field is found to diminish rapidly as the temperature rises towards T_c.     

Dependence of the excitation wavelength on the Raman-active phonons of YBa2Cu3O7 Search for Landau damping in single-domain crystals

In single-domain crystals of YBa₂Cu₃O₇, we examine the dependence of phonon linewidth on wavevector by varying the wavelength of the exciting laser. In three crystals, we find the linewidths of the Raman-active phonons at 120 and 150 cm⁻¹ to be nearly invariant for excitation wavelengths between 647 and 413 nm. That is, we find no broadening of the phonon linewidths with increasing phonon wavevector (decreasing excitation wavelength), and thus no evidence of Landau damping in our crystals. In addition, the correlation between the intensity of the chain-related Raman feature at ≈232 cm⁻¹ and the temperature dependence of the B_1g-like phonon at 340 cm⁻¹ has been investigated. In all three crystals, we find a net sharpening of the 340 cm⁻¹ phonon below T_c and essentially no intensity for the ≈232 cm⁻¹ mode under resonance conditions.     

A possible replacement of single crystal by melt-textured material in the study of YBa2Cu3O7−y

Improved superconducting properties were observed in melt-textured YBa₂Cu₃O_7-y ceramic material. The inductive current density has a small field dependence up to 5.5 T over a wide temperature range. The field and temperature dependences of the magnetic properties are similar to the behavior found in single crystals. Values of the intragrain critical current density in melt-texture samples have the same order of magnitude as in single crystals. The reduced porosity and improved grain alignment help to probe intrinsic physical properties that depend on crystallographic orientation. Thus experiments similar to those involving single crystals are possible. The modified Bean critical state model applied to single crystals can also be used in these melt-textured samples. Thus, it is possible to use melt-textured samples in some basic research which originally required the use of single crystals.     

The Global Dimension of Rings of Differential Operators on Projective Spaces

We compute the global dimension of the twisted rings of globaldifferential operators D on complex projective n-space. As varies through the complex numbers, this global dimension takeson the values n, 2n and infinity. We also study the embeddingof D in the Weyl algebra A_n in the cases when the global dimensionis infinite. In these cases, we see that the flat dimensionof A_n as a D-module is infinite as well.