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Perrin, Charles L.,Lau, Jonathan S.,Kim, Yeong-Joon,Karri, Phaneendrasai,Moore, Curtis,Rheingold, Arnold L. American Chemical Society 2009 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.131 No.37
<P>The large pK(a) difference between first and second deprotonations of (+/-)-alpha,alpha'-di-tert-butylsuccinic acid has been interpreted as evidence for a short, strong intramolecular hydrogen bond in the monoanion. Incorporation of (18)O into one carboxyl group allows investigation of the symmetry of the H-bond in solution by the method of isotopic perturbation. Relative to the intrinsic (18)O-induced isotope shift at the carboxyl carbon, as measured in the diacid, an additional isotope shift of 8 ppb in methanol, 14 ppb in acetone, and 5 ppb in THF is observed for potassium hydrogen (+/-)-alpha,alpha'-di-tert-butylsuccinate-(18)O. This increase indicates that the ion exists as an equilibrating pair of interconverting tautomers and not as a single symmetric resonance hybrid. The X-ray crystal structures of the tetrapropylammonium, tetrabutylammonium, tetrabutylphosphonium, magnesium, and calcium hydrogen (+/-)-alpha,alpha'-di-tert-butylsuccinate salts show a remarkably short O-O distance of 2.41 A, consistent with a strong hydrogen bond. However, the dicesium salt of the (+/-)-alpha,alpha'-di-tert-butylsuccinate dianion also shows the short O-O distance of 2.41 A, so this cannot be taken as evidence for a strong hydrogen bond in the monoanion. Moreover, the two O-H distances in the monoanions are unequal, and the hydrogen bond is asymmetric in these crystals. It is concluded that there is no evidence for any special stabilization associated with symmetric H-bonds. The large Delta pK(a) difference is therefore not due to any feature of the H-bond itself but is attributed to the electrostatic repulsion between the carboxylates in the dianion, which is relieved in the monoanion by inserting a proton between the carboxylates.</P>
Munoz, Victor,Perrin, Marianne,Pastor, Marie-Laetitia,Welemane, Helene,Cantarel, Arthur,Karama, Moussa Techno-Press 2015 Advances in aircraft and spacecraft science Vol.2 No.3
The mechanical characterization of composite materials is nowadays a major interest due to their increasing use in the aeronautic industry. The design of most of these materials is based on their stiffness, which is mainly obtained by means of tensile tests with strain gauge measurement. For thin laminated composites, this classical method requires adequate samples with specific orientation and does not provide all the independent elastic constants. Regarding ultrasonic characterization, especially immersion technique, only one specimen is needed and the entire determination of the stiffness tensor is possible. This paper presents a study of different methods to determine the mechanical properties of transversely isotropic carbon fibre composite materials (gauge and correlation strain measurement during tensile tests, ultrasonic immersion technique). Results are compared to ISO standards and manufacturer data to evaluate the accuracy of these techniques.
A Computer-based Training Intervention for Work Supervisors to Respond to Intimate Partner Violence
Glass, Nancy,Bloom, Tina,Perrin, Nancy,Anger, W. Kent Occupational Safety and Health Research Institute 2010 Safety and health at work Vol.1 No.2
Objectives: Intimate partner violence (IPV), commonly known as domestic violence is a problem throughout the world. An estimated 36% to 75% of employed abused woman are monitored, harassed and physically assaulted by their partners or ex-partners while trying to get to work and while at work. The objective of this research is to evaluate the effectiveness of interactive training to increase knowledge, change perceptions and develop an intention to address domestic violence that spills over into the workplace. Methods: Community-based participatory research approaches were employed to develop and evaluate an interactive computer-based training (CBT) intervention, aimed to teach supervisors how to create supportive and safe workplaces for victims of IPV. Results: The CBT intervention was administered to 53 supervisors. All participants reacted positively to the training, and there was a significant improvement in knowledge between pre- and post-training test performance (72% versus 96% correct), effect size (d) = 3.56. Feedback from focus groups was more productive than written feedback solicited from the same participants at the end of the training. Conclusion: Effective training on the impacts of IPV can improve knowledge, achieving a large effect size, and produce changes in perspective about domestic violence and motivation to address domestic violence in the workplace, based on questionnaire responses.