Ballast water treatment techniques: review and suggestions regarding use in the Arctic and Great Lakes

The retreating ice cover opens up the opportunity for new shipping routes, and consequently shipping traffic in the Arctic region is increasing and with this the risk of introducing non-indigenous species (NIS) via ballast water. Ballast water must therefore be treated to prevent the transport of NIS in an environmentally friendly way to minimise the environmental impact of the treatment. There is, however, limited information on the suitability of different ballast water treatment methods for use specifically in Arctic conditions. A literature study was conducted to identify and summarise different ballast water treatment methods, evaluate their potential for use in the Arctic, and to identify gaps in the current knowledge on Arctic ballast water treatment for further investigation. As winter conditions on the Great Lakes present a useful analogue for Arctic operation, these conditions were also included in the scope of work. Three basic methods for ballast water treatment were addressed: mechanical systems, physical disinfection, and chemical treatments. In ballast water treatment systems often a combinations of these techniques is applied. From the literature, each technique was described and evaluated regarding key environmental conditions present in the Arctic and Great Lakes regions, such as salinity, temperature and turbidity

Aversive Counterconditioning Attenuates Reward Signaling in the Ventral Striatum

Appetitive conditioning refers to the process of learning cue-reward associations and is mediated by the mesocorticolimbic system. Appetitive conditioned responses are difficult to extinguish, especially for highly salient reward such as food and drugs. We investigate whether aversive counterconditioning can alter reward reinstatement in the ventral striatum in healthy volunteers using functional magnetic resonance imaging (fMRI). In the initial conditioning phase, two different stimuli were reinforced with a monetary reward. In the subsequent counterconditioning phase, one of these stimuli was paired with an aversive shock to the wrist. In the following extinction phase, none of the stimuli were reinforced. In the final reinstatement phase, reward was reinstated by informing the participants that the monetary gain could be doubled. Our fMRI data revealed that reward signaling in the ventral striatum and ventral tegmental area following reinstatement was smaller for the stimulus that was counterconditioned with an electrical shock, compared to the non-counterconditioned stimulus. A functional connectivity analysis showed that aversive counterconditioning strengthened striatal connectivity with the hippocampus and insula. These results suggest that reward signaling in the ventral striatum can be attenuated through aversive counterconditioning, possibly by concurrent retrieval of the aversive association through enhanced connectivity with hippocampus and insula

Are cocaine users too sensitive? Functional and structural brain imaging studies in regular cocaine users

While previous research primarily focused on the involvement of the frontostriatal network in the etiology of substance use disorder, it has recently been suggested that the amygdala, and its interaction with the frontostriatal circuitry, may play a key role in habitual drug seeking, and therefore in the etiology of substance use disorder The studies described in this dissertation demonstrate that cocaine use disorder is associated with hyper-activity of the amygdala in response to negative emotional facial expression, cocaine-related stimuli and fear-conditioned stimuli. Furthermore, we demonstrated that childhood adversity disrupts amygdala-ventral striatal coupling during cocaine cue-exposure, whereas state anxiety disrupts amygdala-prefrontal cortex coupling during cocaine cue-exposure. In addition, we demonstrated that trait impulsivity and the degree of polysubstance use selectively alters prefrontal cortex structure. Finally, in healthy, non-drug using individuals we demonstrated that anticipation of a negative outcome reduces reward reinstatement in the ventral striatum. Based on these findings I propose a model of the involvement of the amygdala-ventral striatal-prefrontal cortex circuitry in cocaine use disorder: In this model, impaired amygdala-ventral striatal coupling in cocaine users is suggested to be related to childhood adversities and to predispose to compulsive behavior. In addition, impaired amygdala-prefrontal cortex coupling is suggested to be related to impulsivity and polysubstance use and to predispose to impaired emotion regulation. Using this model we hope to increase to knowledge on the role of the amygdala and its interaction with the frontostriatal system in substance use disorder, which may contribute to improve treatment outcome in those that are currently treatment-resistant