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Fast beta (20–28 Hz) electroencephalogram (EEG) oscillatory activity may be a useful endophenotype for studying the genetics of disorders characterized by neural hyperexcitability, including substance use disorders (SUDs). However, the genetic underpinnings of fast beta EEG have not previously been studied in a population of African-American ancestry (AA). In a sample of 2382 AA individuals from 482 families drawn from the Collaborative Study on the Genetics of Alcoholism (COGA), we performed a genome-wide association study (GWAS) on resting-state fast beta EEG power. To further characterize our genetic findings, we examined the functional and clinical/behavioral significance of GWAS variants. Ten correlated single-nucleotide polymorphisms (SNPs) (r2>0.9) located in an intergenic region on chromosome 3q26 were associated with fast beta EEG power at P<5 × 10−8. The most significantly associated SNP, rs11720469 (β: −0.124; P<4.5 × 10−9), is also an expression quantitative trait locus for BCHE(butyrylcholinesterase), expressed in thalamus tissue. Four of the genome-wide SNPs were also associated with Diagnostic and Statistical Manual of Mental Disorders Alcohol Dependence in COGA AA families, and two (rs13093097, rs7428372) were replicated in an independent AA sample (Gelernter et al.). Analyses in the AA adolescent/young adult (offspring from COGA families) subsample indicated association of rs11720469 with heavy episodic drinking (frequency of consuming 5+ drinks within 24 h). Converging findings presented in this study provide support for the role of genetic variants within 3q26 in neural and behavioral disinhibition. These novel genetic findings highlight the importance of including AA populations in genetics research on SUDs and the utility of the endophenotype approach in enhancing our understanding of mechanisms underlying addiction susceptibility.

Heavy episodic drinking is developmentally normative among adolescents and young adults, but is linked to adverse consequences in later life, such as drug and alcohol dependence. Genetic and peer influences are robust predictors of heavy episodic drinking in youth, but little is known about the interplay between polygenic risk and peer influences as they impact developmental patterns of heavy episodic drinking. Data were from a multisite prospective study of alcohol use among adolescents and young adults with genome‐wide association data (n =412). Generalized linear mixed models were used to characterize the initial status and slopes of heavy episodic drinking between age 15 and 28. Polygenic risk scores (PRS) were derived from a separate genome‐wide association study for alcohol dependence and examined for their interaction with substance use among the adolescents’ closest friends in predicting the initial status and slopes of heavy episodic drinking. Close friend substance use was a robust predictor of adolescent heavy episodic drinking, even after controlling for parental knowledge and peer substance use in the school. PRS were predictive of the initial status and early patterns of heavy episodic drinking in males, but not in females. No interaction was detected between PRS and close friend substance use for heavy episodic drinking trajectories in either males or females. Although substance use among close friends and genetic influences play an important role in predicting heavy episodic drinking trajectories, particularly during the late adolescent to early adult years, we found no evidence of interaction between these influences after controlling for other social processes, such as parental knowledge and broader substance use among other peers outside of close friends. The use of longitudinal models and accounting for multiple social influences may be crucial for future studies focused on uncovering gene–environment interplay. Clinical implications are also discussed. Heavy drinking behaviors are influenced by polygenic risk, but few studies have examined the extent to which polygenic risk interacts with environmental factors on developmental trajectories of these behaviors. Indeed, close peer substance use and polygenic influences significantly predicted heavy episodic drinking trajectories from adolescence and young adulthood, but there was no evidence of interaction between these influences. The use of longitudinal models and accounting for multiple social influences may be crucial for future studies focused on uncovering gene–environment interplay.

We report the formation of stable bound wave packets in a modified Belousov−Zhabotinsky reaction. These densely stacked structures arise from an attractive interaction between oxidation pulses that is not known from the classical Belousov−Zhabotinsky system. The characteristic stacking period increases with the initial concentration of bromate but decreases with cyclohexanedione. Wave stacking can also induce cascades of bunching events in which internally dense but mutually well segregated wave clusters are formed. For different initial concentrations, we observed the apparent merging of waves in front-to-back collisions. All three modes of wave dynamics are analyzed in terms of their dispersion behavior. The dispersion relations proved to be anomalous in each case and revealed the existence of an attractor which induces the formation of stable wave packets. The underlying mechanism has a pure reaction−diffusion character since wave propagation is not affected by fluid convection. At high initial concentrations of ferroin, we detected complex relaxation kinetics which indicate the presence of at least two independent species that control the recovery and hence the dispersion behavior of the medium.

We present experimental results that demonstrate anomalous dispersion in a Belousov−Zhabotinsky system. The reaction is carried out at high concentrations of sulfuric acid and involves 1,4-cyclohexanedione as its organic substrate. The unusual dispersion behavior of this excitable medium induces an attractive interaction between pulses that results in fusion or closed stacking of waves. Experimental results from quasi-one-dimensional as well as two-dimensional media are presented. In two-dimensional reaction systems, a complex dependence of the propagation velocity on the relative direction between fronts is found and the formation of spiral defects is observed.