An Experimental Facility for the Visual Study of Turbulent Flows

An experimental technique which allows visual observations of the wall area in turbulent pipe flow is described in detail. It requires neither the introduction of any injection or measuring device into the flow nor the presence of a two-phase flow or of a non-Newtonian fluid. The technique involves suspending solid MgO particles of colloidal size in trichloroethylene and photographing their motions near the wall with a high speed movie camera moving with the flow. Trichloroethylene was chosen in order to eliminate the index of refraction problem in a curved wall. Evaluation of the technique including a discussion of limitations is included. Also the technique is compared with previous methods of visual observations of turbulent flow

Stereoscopic Photography of Shear Flow Turbulence

The last several years have seen numerous advances in the understanding of the coherent motions that exist in turbulent shear flows. These studies have provided the underlying basis of most of the experimental investigations of coherent motions using conditional sampling, quadrant splitting, pattern recognition, etc. Lacking, however, in the visual work is a true three- dimensional view of the processes, which are known to be three-dimensional in nature. Possible means of providing information about the third dimension are reviewed. Details of an evaluation of a stereoscopic-photographic, high-speed motion picture system are given. The system utilizes the boundary layer flow channel previously developed in our work by Nychas, Hershey and Brodkey (J. Fluid Mech. (1973) 6l, 513)

Cognitive Function in Children With Type 1 Diabetes: A meta-analysis

OBJECTIVE—To quantify the magnitude and pattern of cognitive difficulties in pediatric type 1 diabetes as well as the effects associated with earlier disease onset and severe hypoglycemia

Unilateral vs. bilateral STN DBS effects on working memory and motor function in Parkinson disease

Bilateral subthalamic nucleus deep brain stimulation (STN DBS) can reduce working memory while improving motor function in Parkinson disease (PD), but findings are variable. One possible explanation for this variability is that the effects of bilateral STN DBS on working memory function depend in part on functional or disease asymmetry. The goal of this study was to determine the relative contributions of unilateral DBS to the effects seen with bilateral DBS. Motor (Unified Parkinson Disease Rating Scale Part III, UPDRS) and working memory function (Spatial Delayed Response, SDR) were measured in 49 PD patients with bilateral STN DBS while stimulators were Both-off, Left-on, Right-on and Both-on in a randomized, double-blind manner. Patients were off PD medications overnight. Effects of unilateral DBS were compared to effects of bilateral STN DBS. Mean UPDRS and SDR responses to Left-on vs. Right-on conditions did not differ (p>.20). However, improvement in contralateral UPDRS was greater and SDR performance was more impaired by unilateral DBS in the more affected side of the brain than in the less affected side of the brain (p=.008). The effect of unilateral DBS on the more affected side on contralateral UPDRS and SDR responses was equivalent to that of bilateral DBS. These results suggest that motor and working memory function respond to unilateral STN DBS differentially depending on the asymmetry of motor symptoms

Overcoming status quo bias in the human brain

Humans often accept the status quo when faced with conflicting choice alternatives. However, it is unknown how neural pathways connecting cognition with action modulate this status quo acceptance. Here we developed a visual detection task in which subjects tended to favor the default when making difficult, but not easy, decisions. This bias was suboptimal in that more errors were made when the default was accepted. A selective increase in subthalamic nucleus (STN) activity was found when the status quo was rejected in the face of heightened decision difficulty. Analysis of effective connectivity showed that inferior frontal cortex, a region more active for difficult decisions, exerted an enhanced modulatory influence on the STN during switches away from the status quo. These data suggest that the neural circuits required to initiate controlled, nondefault actions are similar to those previously shown to mediate outright response suppression. We conclude that specific prefrontal-basal ganglia dynamics are involved in rejecting the default, a mechanism that may be important in a range of difficult choice scenarios

Acute changes in mood induced by subthalamic deep brain stimulation in Parkinson disease are modulated by psychiatric diagnosis

BACKGROUND: Deep brain stimulation of the subthalamic nucleus (STN DBS) reduces Parkinson disease (PD) motor symptoms but has unexplained, variable effects on mood. OBJECTIVE: The study tested the hypothesis that pre-existing mood and/or anxiety disorders or increased symptom severity negatively affects mood response to STN DBS. METHODS: Thirty-eight PD participants with bilateral STN DBS and on PD medications were interviewed with Structured Clinical Interview for DSM-IV-TR Axis I Disorders (SCID) and completed Beck Depression Inventory (BDI) and Spielberger State Anxiety Inventory (SSAI) self-reports. Subsequently, during OFF and optimal ON (clinical settings) STN DBS conditions and while off PD medications, motor function was assessed with the United Parkinson Disease Rating Scale (UPDRS, part III), and participants rated their mood with Visual Analogue Scales (VAS), and again completed SSAI. VAS mood variables included anxiety, apathy, valence and emotional arousal. RESULTS: STN DBS improved UPDRS scores and mood. Unexpectedly, PD participants diagnosed with current anxiety or mood disorders experienced greater STN DBS-induced improvement in mood than those diagnosed with remitted disorders or who were deemed as having never met threshold criteria for diagnosis. BDI and SSAI scores did not modulate mood response to STN DBS, indicating that clinical categorical diagnosis better differentiates mood response to STN DBS than self-rated symptom severity. SCID diagnosis, BDI and SSAI scores did not modulate motor response to STN DBS. CONCLUSIONS: PD participants diagnosed with current mood or anxiety disorders are more sensitive to STN DBS-induced effects on mood, possibly indicating altered basal ganglia circuitry in this group