Differences of temporal dynamics and signal complexity of gamma band oscillations in first-episode psychosis during a working memory task

Gamma band oscillations participate in the temporal binding needed to synchronize cortical networks, involved in early sensory and short term memory processes. In earlier studies, alterations of these neurophysiological parameters have been found in psychotic disorders. To date no study has explored the temporal dynamics and signal complexity of gamma band oscillations in first episode psychosis (FEP). To address this issue, gamma band analysis was performed in 15 FEP patients and 18 healthy controls who successfully performed an adapted 2-back working memory task. Multiple linear and logistic regression models were computed to explore the relationship between the cognitive status and gamma oscillation changes over time. Based on regression model results, phase diagrams were constructed and their complexity was estimated using fractal dimension, a mathematical tool that describes shapes as numeric values. When adjusted for gamma values at time lags −3 to −4 ms and −15 to −16 ms, FEP patients displayed significantly higher time-dependent changes than controls, independently of the nature of the task. The present results are consistent with a discoordination of the activity of cortical generators engaged by the stimulus apparition in FEP patients, leading to a global binding deficit. In addition, fractal analysis showing higher complexity of gamma signal, confirmed this deficit. Our results provide evidence for recruitment of supplementary cortical generators as compensating mechanisms and yield further understanding for the pathophysiology cognitive impairments in FEP

Examining the Psychosocial and Behavioral Factors Associated with Adolescent Engagement in Multiple Types of Cyberdeviance: Results from an Australian Study

OnlinePublResearch has shown that psychosocial and behavioral factors are associated with engagement in a range of deviant behaviors across offline settings. To date, however, very little research has explored the impact of these factors in online contexts. This article addresses this gap by examining the psychosocial and behavioral factors associated with common types of adolescent cyberdeviance. This is accomplished through an empirical study of 327 adolescents enrolled in a high school located in a large Australian city. The study assesses various aspects of psychosocial and behavioral functioning using the Strengths and Difficulties Questionnaire (total difficulties, internalizing problems, externalizing problems, prosocial behavior), as well as numerous types of cyberdeviance relevant to young people, including cyberfraud, cyberhate, cyberviolence, sexting, digital piracy, hacking, and cyberbullying. A series of multivariate logistic regression analyses were conducted to demonstrate the association between psychosocial and behavioral difficulties and various types of cyberdeviance, independent of gender, school grade, socioeconomic status, and engagement in offline delinquency. Results indicate that total difficulties, internalizing problems, and externalizing problems were significantly associated with greater likelihood of engagement in most types of cyberdeviance examined in this study, whereas prosocial behavior was associated with a lower likelihood of engagement in digital piracy only. A discussion of the findings highlights the importance of understanding these factors in a digital context, as well as demonstrating the need to account for them when designing targeted interventions.Russell Brewer, Tyson Whitten, Katie Logos, Morgan Sayer, Colette Langos, Thomas J. Holt, Jesse Cale, Andrew Goldsmit

Effect of particle size on the flow properties of a South Australian coal-water slurry

The rheological behaviour of a low-rank coal-water slurry from Lochiel, South Australia, has been studied as a function of solids concentration, particle size and size distribution. Coal slurries consisting of particles finer than 45 μm suspended in water were found to exhibit a wide spectrum of flow behaviour ranging from Newtonian as low solids concentrations to shear-thinning and viscoplastic with a yield stress at higher concentrations. By adding a narrow-sized coarse coal fraction (208–279 μm) to the fine coal slurry, the flow characteristic of the slurry, at a fixed total solids concentrations, could be changed significantly with a substantial reduction in the slurry viscosity. An optimum coarse-to-fine particle ratio of 40:60 exists at which the slurry is Newtonian with a minimum viscosity of a about 5 times lower than the viscosity of a slurry containing only fine particles at the same solids concentration. A further reduction in the slurry viscosity of 50% was achieved by adding a second coarse coal particle (279–325 μm) to the bimodal slurry. The significant improvement in the rheological behaviour with changing the particle size distribution may be explained in terms of spatial rearrangement of the particles, and an apparent dilution effect. The results obtained in this study indicate that, with a careful control of the particle size distribution, it is possible to prepare an optimum coal-water slurry which has a low viscosity but with high solids loadings.C. Logos, Q.D. Nguye

Rheological properties of South Australian coal-water slurries

Q.D. Nguyen, C. Logos & T. Semmle