Age of second language acquisition affects nonverbal conflict processing in children : an fMRI study

Background: In their daily communication, bilinguals switch between two languages, a process that involves the selection of a target language and minimization of interference from a nontarget language. Previous studies have uncovered the neural structure in bilinguals and the activation patterns associated with performing verbal conflict tasks. One question that remains, however is whether this extra verbal switching affects brain function during nonverbal conflict tasks. Methods: In this study, we have used fMRI to investigate the impact of bilingualism in children performing two nonverbal tasks involving stimulus-stimulus and stimulus-response conflicts. Three groups of 8-11-year-old children - bilinguals from birth (2L1), second language learners (L2L), and a control group of monolinguals (1L1) - were scanned while performing a color Simon and a numerical Stroop task. Reaction times and accuracy were logged. Results: Compared to monolingual controls, bilingual children showed higher behavioral congruency effect of these tasks, which is matched by the recruitment of brain regions that are generally used in general cognitive control, language processing or to solve language conflict situations in bilinguals (caudate nucleus, posterior cingulate gyrus, STG, precuneus). Further, the activation of these areas was found to be higher in 2L1 compared to L2L. Conclusion: The coupling of longer reaction times to the recruitment of extra language-related brain areas supports the hypothesis that when dealing with language conflicts the specialization of bilinguals hampers the way they can process with nonverbal conflicts, at least at early stages in life

Components of Behavioral Activation Therapy for Depression Engage Specific Reinforcement Learning Mechanisms in a Pilot Study

Background: Behavioral activation is an evidence-based treatment for depression. Theoretical considerations suggest that treatment response depends on reinforcement learning mechanisms. However, which reinforcement learning mechanisms are engaged by and mediate the therapeutic effect of behavioral activation remains only partially understood, and there are no procedures to measure such mechanisms. Objective: To perform a pilot study to examine whether reinforcement learning processes measured through tasks or self-report are related to treatment response to behavioral activation. Method: The pilot study enrolled 13 outpatients (12 completers) with major depressive disorder, from July of 2018 through February of 2019, into a nine-week trial with BA. Psychiatric evaluations, decision-making tests and self-reported reward experience and anticipations were acquired before, during and after the treatment. Task and self-report data were analysed by using reinforcement-learning models. Inferred parameters were related to measures of depression severity through linear mixed effects models. Results: Treatment effects during different phases of the therapy were captured by specific decision-making processes in the task. During the weeks focusing on the active pursuit of reward, treatment effects were more pronounced amongst those individuals who showed an increase in Pavlovian appetitive influence. During the weeks focusing on the avoidance of punishments, treatment responses were more pronounced in those individuals who showed an increase in Pavlovian avoidance. Self-reported anticipation of reinforcement changed according to formal RL rules. Individual differences in the extent to which learning followed RL rules related to changes in anhedonia. Conclusions: In this pilot study both task-and self-report-derived measures of reinforcement learning captured individual differences in treatment response to behavioral activation. Appetitive and aversive Pavlovian reflexive processes appeared to be modulated by separate psychotherapeutic interventions, and the modulation strength covaried with response to specific interventions. Self-reported changes in reinforcement expectations are also related to treatment response

Development of Casbar: a Two-phase Flow Code for the Interior Ballistics Problem

Accurate modelling of gun interior ballistic processes aids in the design and analysis of guns and their propelling charges. Presently, the most accurate modelling of the interior ballistics problem is provided by two-phase, multidimensional computational fluid dynamics (CFD) codes. We present our development of a CFD code, Casbar, which solves a two-phase (gas/particulate) flow problem in axisymmetric geometries. Our model is based on the governing equations for two-phase flow derived from separated flow theory. A finite-volume discretisation of the governing equations is used. The resulting set of equations is solved with a timestep-splitting approach based on the separation of various physical processes. We also present the modelling for the component physics such as propellant combustion and interphase drag. In addition, the solver includes the motion of the projectile and its influence on the flow dynamics. The capabilities of the code are demonstrated with some verification exercises

Simulation of CO2–N2 expansion tunnel flow for the study of radiating bluntbody shock layers

A 25MJ/kg CO2–N2 expansion tunnel condition has been developed for the X2 impulse facility at the University of Queensland. A hybrid Lagrangian and Navier–Stokes computational simulation technique is found to give good correlation with experimentally measured shock speeds and pressure traces. The use of an inertial diaphragm model for describing secondary diaphragm rupture is found to estimate between 4% and 25% more CO2 recombination over the test time than the widely accepted holding-time model. The obtained freestream conditions are assessed for application to proposed bluntbody spectroscopy and subscale aeroshell experiments. The chemically and vibrationally excited freestream test gas is found to prevent exact thermochemical similarity from being achieved, and the strong radiation–flowfield coupling characteristic of Mars aerocapture conditions cannot be reproduced experimentally

Superorbital expansion tube operation: estimates of flow conditions via numerical simulation

Two new operating conditions of the X3 superorbital expansion tube are studied experimentally and numerically. A two-stage numerical simulation is used to model the flow processes within the whole facility, from the compressed driver gas, through the initial shock-processing of the test gas and then through the unsteady expansion process to the final test flow state. Experimental measurements provide static pressure histories at particular points along the shock and acceleration tubes while the numerical simulations provide complementary information on gas density, temperature and composition. Operating condition properties such as shock speed are both observed in the experiment and produced as a result of the simulation are used to check the reliability of the numerical simulations

Origin of Variability in Northern Hemisphere Winter Blocking on Interannual to Decadal Time Scales

Variability of mid-latitude blocking in the boreal winter northern hemisphere is investigated for the period 1960/61 to 2001/02 by means of relaxation experiments with the model of the European Center for Medium-Range Weather Forecasts. It is shown that there is pronounced interannual and decadal variability in blocking, especially over the Eurasian continent, consistent with previous studies. The relaxation experiments show that realistic variability in the tropics can account for a significant part of observed interannual blocking variability, but also that about half of the observed variability can only be explained by extratropical tropospheric variability. On the quasi-decadal time scale, extratropical sea surface temperature and sea-ice, in addition to tropical variability, play a more important role. The stratosphere, which has been shown to influence interannual variability of the North Atlantic Oscillation in previous studies, has no significant influence on blocking according to our analysis