Dislocation dynamics (DD) simulations are used to investigate the emerging metal-fatigue detection technique of nonlinear ultrasonics. The acoustic nonlinearity parameter, β, is quantitatively predicted for a single dislocation bowing in its glide plane between pinning points under a quasi-static loading assumption using DD simulations. The existing model using a constant line energy assumption fails to capture the correct behavior of β for edge dislocations in materials with a nonzero Poisson's ratio. A strong dependence of β on the orientation of Burgers vector relative to the line direction of the dislocation is shown by the DD simulations. A new model using an orientation-dependent line energy is derived for the cases of initially-pure edge and screw dislocations. The model is shown to agree with the DD simulations over a range of Poisson's ratio and static stresses.
Investigation of tricyclic heterocycles related to the 2-arylpyrazolo[4,3-c]quinolin-3(5H)-ones, structures with high affinity for the benzodiazepine (BZ) receptor, led to the synthesis of 2-phenyl-[1,2,4]triazolo[1,5-c]quinazolin-5(6H)-one, a compound with 4 nM binding affinity to the BZ receptor. Analogues were prepared to assess the importance of the 2-substituent and ring substitution in modifying activity. Several novel synthetic routes were designed to prepare the target compounds, including a two-step synthesis beginning with an anthranilonitrile and a hydrazide. Of the 34 compounds screened in this series, three compounds were found to be potent BZ antagonists in rat models. The leading compound, 9-chloro-2-(2-fluorophenyl) [1,2,4]triazolo[1,5- c]quinazolin-5(6H)-one (CGS 16228), showed activity comparable to that of CGS 8216 from the pyrazolo[4,3-c]quinoline series.
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