Financial and Psychological Risk Attitudes Associated with Two Single Nucleotide Polymorphisms in the Nicotine Receptor (CHRNA4) Gene

With recent advances in understanding of the neuroscience of risk taking, attention is now turning to genetic factors that may contribute to individual heterogeneity in risk attitudes. In this paper we test for genetic associations with risk attitude measures derived from both the psychology and economics literature. To develop a long-term prospective study, we first evaluate both types of risk attitudes and find that the economic and psychological measures are poorly correlated, suggesting that different genetic factors may underlie human response to risk faced in different behavioral domains. We then examine polymorphisms in a spectrum of candidate genes that affect neurotransmitter systems influencing dopamine regulation or are thought to be associated with risk attitudes or impulsive disorders. Analysis of the genotyping data identified two single nucleotide polymorphisms (SNPs) in the gene encoding the alpha 4 nicotine receptor (CHRNA4, rs4603829 and rs4522666) that are significantly associated with harm avoidance, a risk attitude measurement drawn from the psychology literature. Novelty seeking, another risk attitude measure from the psychology literature, is associated with several COMT (catechol-O-methyl transferase) SNPs while economic risk attitude measures are associated with several VMAT2 (vesicular monoamine transporter) SNPs, but the significance of these associations did not withstand statistical adjustment for multiple testing and requires larger cohorts. These exploratory results provide a starting point for understanding the genetic basis of risk attitudes by considering the range of methods available for measuring risk attitudes and by searching beyond the traditional direct focus on dopamine and serotonin receptor and transporter genes

Pseudo-Villari Experimental Characterization of Magneto-Rheological Elastomers

Magneto-rheological elastomers (MRE) are composite materials with magnetically polarized particles dispersed in an elastomeric soft matrix. These materials are an important branch of the smart material family being the mechanical and rheological properties can be reversibly changed upon exposure to a magnetic field. Conversely, this multi-physics coupling shows also an inverse effect associating a dependence of magnetic induction field of a material on mechanical stress/strain and taking the name of pseudo-Villari effect. This paper describes an experimental characterization conducted on MRE with the aim of adopting these materials to make smart mounts to be used as vibration isolators and able at the same time to give useful information to monitor the component to be isolated. In the first part of the paper, the experimental procedures for making samples are described as well as the test bench. The samples are subjected to shear periodic loads, varying both the amplitude and the frequency of the excitation. The testing machine is equipped with an excitation coil, with which it is possible to vary the intensity of the magnetic field crossing the sample during testing and a search coil able to evaluate the pseudo-Villari effec