In-Situ Nuclear Magnetic Resonance Investigation of Strain, Temperature, and Strain-Rate Variations of Deformation-Induced Vacancy Concentration in Aluminum

Critical strain to serrated flow in solid solution alloys exhibiting dynamic strain aging (DSA) or Portevin–LeChatelier effect is due to the strain-induced vacancy production. Nuclear magnetic resonance (NMR) techniques can be used to monitor in situ the dynamical behavior of point and line defects in materials during deformation, and these techniques are nondestructive and noninvasive. The new CUT-sequence pulse method allowed an accurate evaluation of the strain-enhanced vacancy diffusion and, thus, the excess vacancy concentration during deformation as a function of strain, strain rate, and temperature. Due to skin effect problems in metals at high frequencies, thin foils of Al were used and experimental results correlated with models based on vacancy production through mechanical work (vs thermal jogs), while in situ annealing of excess vacancies is noted at high temperatures. These correlations made it feasible to obtain explicit dependencies of the strain-induced vacancy concentration on test variables such as the strain, strain rate, and temperature. These studies clearly reveal the power and utility of these NMR techniques in the determination of deformation-induced vacancies in situ in a noninvasive fashion.

Organization-Level Mentoring and Organizational Performance Within Substance Abuse Centers

Individual benefits to those who have been mentored are well documented. The present study demonstrates that organization-level mentoring relates to overall organizational performance. In a study of 589 employees of 39 substance abuse treatment agencies, the authors found that agencies with a greater proportion of mentored employees also reported greater overall agency performance. Organization-level mentoring also related to organization-level job satisfaction, organization-level organizational citizenship behavior, and organization-level learning. Results provide justification for organizational investment of time and resources into efforts designed to facilitate mentoring, as well as support the notion that mentoring may provide a competitive advantage to organization