Energy dispersion in turbulent jets. Part 2. A robust model for unsteady jets

In this paper we develop an integral model for an unsteady turbulent jet that incorporates longitudinal dispersion of two distinct types. The model accounts for the difference in the rate at which momentum and energy are advected (type I dispersion) and for the local deformation of velocity profiles that occurs in the vicinity of a sudden change in the momentum flux (type II dispersion). We adapt the description of dispersion in pipe flow by Taylor (Proc. R. Soc. Lond. A, vol. 219, 1953, pp. 186–203) to develop a dispersion closure for the longitudinal transportation of energy in unsteady jets. We compare our model’s predictions to results from direct numerical simulation and find a good agreement. The model described in this paper is robust and can be solved numerically using a simple central differencing scheme. Using the assumption that the longitudinal velocity profile in a jet has an approximately Gaussian form, we show that unsteady jets remain approximately straight-sided when their source area is fixed. Straight-sidedness provides an algebraic means of reducing the order of the governing equations and leads to a simple advection–dispersion relation. The physical process responsible for straight-sidedness is type I dispersion, which, in addition to determining the local response of the area of the jet, determines the growth rate of source perturbations. In this regard the Gaussian profile has the special feature of ensuring straight-sidedness and being insensitive to source perturbations. Profiles that are more peaked than the Gaussian profile attenuate perturbations and, following an increase (decrease) in the source momentum flux, lead to a local decrease (increase) in the area of the jet. Conversely, profiles that are flatter than the Gaussian amplify perturbations and lead to a local increase (decrease) in the area of the jet

The entrainment and energetics of turbulent plumes in a confined space

We analyse the entrainment and energetics of equal and opposite axisymmetric tur-bulent air plumes in a vertically confined space at a Rayleigh number of1.24×107using theory and direct numerical simulation. On domains of sufficiently large aspectratio, the steady-state consists of turbulent plumes penetrating an interface betweentwo layers of approximately uniform buoyancy. As described by Baines & Turner (J.Fluid Mech.vol. 37, 1969, pp. 51-80), upon penetrating the interface the flow in eachplume becomes forced and behaves like a constant-momentum jet, due to a reduction inits mean buoyancy relative to the local environment. To observe the behaviour of theplumes we partition the domain into sub-domains corresponding to each plume. Domainsof relatively small aspect ratio produce a single primary mean-flow circulation betweenthe sub-domains that is maintained by entrainment into the plumes. At larger aspectratios the mean flow between the sub-domains bifurcates, indicating the existence of asecondary circulation within each layer associated with entrainment into the jets. Thelargest aspect ratios studied here exhibit an additional, tertiary, circulation in the vicinityof the interface. Consistency between independent calculations of an effective entrainmentcoefficient allows us to identify aspect ratios for which the flow can be modelled usingplume theory, under the assumption of a two-layer stratification.To study the flow’s energetics we use a local definition of available potential energy(APE). For plumes with Gaussian velocity and buoyancy profiles, the theory we developsuggests that the kinetic energy dissipation is split equally between the jets and theplumes and, collectively, accounts for almost half of the input of APE at the boundaries.In contrast,1/4of the APE dissipation and background potential energy (BPE) pro-duction occurs in the jets, with the remaining3/4occurring in the plumes. These bulktheoretical predictions agree with observations of BPE production from simulations towithin1%and form the basis of a similarity solution that models the vertical dependenceof APE dissipation and BPE production. Unlike results concerning the dissipation ofbuoyancy variance and the strength of the circulations described above, the model forthe flow’s energetics does not involve an entrainment coefficient

Turbulent transport and entrainment in jets and plumes: A DNS study

We present a new DNS data set for a statistically axisymmetric turbulent jet, plume and forced plume in a domain of size 40r$_{0}$ x 40r$_{0}$ x 60r$_{0}$, where r$_{0}$ is the source diameter. The data set supports the validity of the Priestley and Ball entrainment model in unstratified environments (excluding the region near the source), which is corroborated further by the Wang and Law and Ezzamel et al. experimental data sets, the latter being corrected for a small but influential co-flow that affected the statistics. We show that the second-order turbulence statistics in the core region of the jet and the plume are practically indistinguishable, although there are significant differences near the plume edge. The DNS data indicates that the turbulent Prandtl number is about 0.7 for both jets and plumes. For plumes, this value is a result of the difference in the ratio of the radial turbulent transport of radial momentum and buoyancy. For jets however, the value originates from a different spread of the buoyancy and velocity profiles, in spite of the fact that the ratio of radial turbulent transport terms is approximately unity. The DNS data does not show any evidence of similarity drift associated with gradual variations in the ratio of buoyancy profile to velocity profile widths

Verbal instructions targeting valence alter negative conditional stimulus evaluations (but do not affect reinstatement rates)

Negative conditional stimulus (CS) valence acquired during fear conditioning may enhance fear relapse and is difficult to remove as it extinguishes slowly and does not respond to the instruction that unconditional stimulus (US) presentations will cease. We examined whether instructions targeting CS valence would be more effective. In Experiment 1, an image of one person (CS+) was paired with an aversive US, while another (CS-) was presented alone. After acquisition, participants were given positive information about the CS+ poser and negative information about the CS- poser. Instructions reversed the pattern of differential CS valence present during acquisition and eliminated differential electrodermal responding. In Experiment 2, we compared positive and negative CS revaluation by providing positive/negative information about the CS+ and neutral information about CS-. After positive revaluation, differential valence was removed and differential electrodermal responding remained intact. After negative revaluation, differential valence was strengthened and differential electrodermal responding was eliminated. Unexpectedly, the instructions did not affect the reinstatement of differential electrodermal responding

Preliminary Evidence That CD38 Moderates the Association of Neuroticism on Amygdala-Subgenual Cingulate Connectivity.

CD38 genetic variation has been associated with autism spectrum disorders and social anxiety disorder, which may result from CD38's regulation of oxytocin secretion. Converging evidence has found that the rs3796863 A-allele contributes to increased social sensitivity compared to the CC genotype. The current study examined the moderating role of CD38 genetic variants (rs3796863 and rs6449182) that have been associated with enhanced (or reduced) social sensitivity on neural activation related to neuroticism, which is commonly elevated in individuals with social anxiety and depression. Adults (n = 72) with varying levels of social anxiety and depression provided biological samples for DNA extraction, completed a measure of neuroticism, and participated in a standardized emotion processing task (affect matching) while undergoing fMRI. A significant interaction effect was found for rs3796863 x neuroticism that predicted right amygdala-subgenual anterior cingulate cortex (sgACC) functional connectivity. Simple slopes analyses showed a positive association between neuroticism and right amygdala-sgACC connectivity among rs3796863 A-allele carriers. Findings suggest that the more socially sensitive rs3796863 A-allele may partially explain the relationship between a known risk factor (i.e. neuroticism) and promising biomarker (i.e. amygdala-sgACC connectivity) in the development and maintenance of social anxiety and depression

Association of persistent and severe postnatal depression with child outcomes

IMPORTANCE Maternal postnatal depression (PND) is common and associated with adverse child outcomes. These effects are not inevitable, and it is critical to identify those most at risk. Previous work suggests that the risks of adverse outcomes are increased when PND is severe and persistent, but this has not been systematically studied. OBJECTIVE To examine the association between differing levels of persistence and severity of PND and long-term child outcomes. DESIGN, SETTING, AND PARTICIPANTS The sample for this observational study comprised participants in the Avon Longitudinal Study of Parents and Children in the United Kingdom. Three thresholds of PND severity—moderate, marked, and severe—were defined using the self-rated Edinburgh Postnatal Depression Scale (EPDS). Depression was defined as persistent when the EPDS score was above the threshold level at both 2 and 8 months after childbirth. For each of these severity and persistence categories, the following were examined: (1) the trajectories of later EPDS scores (6 time points between 21 months and 11 years after childbirth) and (2) child outcomes—behavioral problems at 3.5 years of age, school-leaving mathematics grades at 16 years of age, and depression at 18 years of age. Data analysis was conducted from July 12, 2016, to February 8, 2017. MAIN OUTCOMES AND MEASURES Child behavioral problems at 3.5 years of age using the Rutter total problems scale, school-leaving mathematics grades at 16 years of age extracted from records of external national public examinations, and offspring depression at 18 years of age using the Clinical Interview Schedule–Revised. RESULTS For the 9848 mothers in the sample, the mean (SD) age at delivery was 28.5 (4.7) years. Of the 8287 children, 4227 (51%) were boys and 4060 (49%) were girls. Compared with women with PND that was not persistent and women who did not score above the EPDS threshold, for all 3 severity levels, women with persistent PND showed elevated depressive symptoms up to 11 years after childbirth. Whether persistent or not, PND doubled the risk of child behavior disturbance. The odds ratio (OR) for child behavioral disturbance for mothers with moderate PND was 2.22 (95% CI, 1.74-2.83), for mothers with marked PND was 1.91 (95% CI, 1.36-2.68), and for mothers with severe PND was 2.39 (95% CI, 1.78-3.22). Persistence of severe PND was particularly important to child development, substantially increasing the risk for behavioral problems at 3.5 years of age (OR, 4.84; 95% CI, 2.94-7.98), lower mathematics grades at 16 years of age (OR, 2.65; 95% CI, 1.26-5.57), and higher prevalence of depression at 18 years of age (OR, 7.44; 95% CI, 2.89-19.11). CONCLUSIONS AND RELEVANCE Persistent and severe PND substantially raises the risk for adverse outcome on all child measures. Meeting criteria for depression both early and late in the postnatal year, especially when the mood disturbance is severe, should alert health care professionals to a depression that is likely to be persistent and to be associated with an especially elevated risk of multiple adverse child outcomes. Treatment for this group should be prioritized

Protocol for a randomized controlled trial examining multilevel prediction of response to behavioral activation and exposure-based therapy for generalized anxiety disorder.

BACKGROUND:Only 40-60% of patients with generalized anxiety disorder experience long-lasting improvement with gold standard psychosocial interventions. Identifying neurobehavioral factors that predict treatment success might provide specific targets for more individualized interventions, fostering more optimal outcomes and bringing us closer to the goal of "personalized medicine." Research suggests that reward and threat processing (approach/avoidance behavior) and cognitive control may be important for understanding anxiety and comorbid depressive disorders and may have relevance to treatment outcomes. This study was designed to determine whether approach-avoidance behaviors and associated neural responses moderate treatment response to exposure-based versus behavioral activation therapy for generalized anxiety disorder. METHODS/DESIGN:We are conducting a randomized controlled trial involving two 10-week group-based interventions: exposure-based therapy or behavioral activation therapy. These interventions focus on specific and unique aspects of threat and reward processing, respectively. Prior to and after treatment, participants are interviewed and undergo behavioral, biomarker, and neuroimaging assessments, with a focus on approach and avoidance processing and decision-making. Primary analyses will use mixed models to examine whether hypothesized approach, avoidance, and conflict arbitration behaviors and associated neural responses at baseline moderate symptom change with treatment, as assessed using the Generalized Anxiety Disorder-7 item scale. Exploratory analyses will examine additional potential treatment moderators and use data reduction and machine learning methods. DISCUSSION:This protocol provides a framework for how studies may be designed to move the field toward neuroscience-informed and personalized psychosocial treatments. The results of this trial will have implications for approach-avoidance processing in generalized anxiety disorder, relationships between levels of analysis (i.e., behavioral, neural), and predictors of behavioral therapy outcome. TRIAL REGISTRATION:The study was retrospectively registered within 21 days of first participant enrollment in accordance with FDAAA 801 with ClinicalTrials.gov, NCT02807480. Registered on June 21, 2016, before results

Self-Guided Multimedia Stress Management and Resilience Training for Flight Controllers

Stress and anxiety-related problems are among the most common and costly behavioral health problems in society, and for those working in operational environments (i.e. astronauts, flight controllers, military) this can seriously impact crew performance, safety, and wellbeing. Technology-based interventions are effective for treating behavioral health problems, and can significantly improve the delivery of evidence-based health care. This study is evaluating the effectiveness, usefulness, and usability of a self-guided multimedia stress management and resilience training program in a randomized controlled trial (RCT) with a sample of flight controllers at Johnson Space Center. The intervention, SMART-OP (Stress Management and Resilience Training for Optimal Performance), is a six-session, cognitive behavioral-based computer program that uses self-guided, interactive activities to teach skills that can help individuals build resilience and manage stress. In a prior RCT with a sample of stressed but otherwise healthy individuals, SMART-OP reduced perceived stress and increased perceived control over stress in comparison to an Attention Control (AC) group. SMART-OP was rated as "highly useful" and "excellent" in usability and acceptability. Based on -amylase data, individuals in SMART-OP recovered quicker and more completely from a social stress test as compared to the AC group [1]. In the current study, flight controllers are randomized either to receive SMART-OP training, or to a 6-week waitlist control period (WLC) before beginning SMART-OP. Eligible participants include JSC flight controllers and instructors without any medical or psychiatric disorder, but who are stressed based on self-report. Flight controllers provide a valid analog sample to astronauts in that they work in an operational setting, use similar terminology to astronauts, are mission-focused, and work under the same broader work culture. The study began in December 2014, and to date 79 flight controllers and instructors have expressed interest in the study, 49 of those were cleared for participation, we have screened 44 for eligibility, and 23 have met inclusion criteria. Recruitment is ongoing and the study will continue until December 2016. Outcome measures include perceived stress, perceived control over stress, resilience, mood, personality, emotion regulation, sleep, health behaviors, and psychophysiological data such as 24-hour heart rate, alpha amylase, and urinary and salivary cortisol. We are also collecting user feedback such as usability, working alliance, usefulness, and treatment credibility

Biased attention to threat and anxiety: on taking a developmental approach

Several researchers have proposed a causal relation between biased attention to threat and the development and maintenance of anxiety disorders in both children and adults. However, despite the widely-documented correlation between attention bias to threat and anxiety, developmental research in this domain is limited. In this review, we highlight the importance of taking a developmental approach to studying attention biases to threat and anxiety. First, we discuss how recent developmental work on attention to threat fits into existing theoretical frameworks for the development of anxiety, and how attention biases might interact with other risk factors across development. Then we review the developmental literature on attention bias to threat and anxiety, and describe how classic methodologies can be modified to study attention biases in even the youngest infants. Finally, we discuss limitations and future directions in this domain, emphasizing the need for future longitudinal research beginning in early infancy that tracks concurrent developments in both biased attention and anxiety. Altogether, we hope that by highlighting the importance of development in the study of attention bias to threat and anxiety, we can provide a roadmap for how researchers might implement developmental approaches to studying a potential core mechanism in anxiety