An overview of dynamical methods for studying transitions between states in sheared plasma flows.

The self-organization of structures in a tokamak plasma as it undergoes an [Formula: see text]-mode transition shows properties similar to simpler shear flow configurations. We will describe recent dynamical studies of plasma shear flows, including the idea of tracking the edge of chaos that separates two bistable states, computing the nonlinear minimal seed that can lead to turbulence, finding the attractor solution on the edge and seeing how starting from this solution we can understand the stability of relative period orbits that permeate the turbulent basin of attraction. We present a modus operandi developed for these simple configurations that can be adapted to understand the [Formula: see text]-mode transition. This article is part of a discussion meeting issue 'H-mode transition and pedestal studies in fusion plasmas'.

Dual-energy KUB radiographic examination for the detection of renal calculus.

RATIONALE AND OBJECTIVES: The dual-energy radiographic technique has been proved to be clinically useful in the thorax. Herein, we attempt to apply this technique to the abdomen and pelvis in the context of renal colic. MATERIALS AND METHODS: The visibility of renal calculi were assessed using various dual energy peak kilovoltage combination radiographs applied to standard phantoms. RESULTS: This technique demonstrates a higher than acceptable radiation dosage required to optimize the image quality and the optimized diagnostic quality is inferior to that of the standard Kidneys, Ureters, and Bladder radiograph. CONCLUSIONS: The dual-energy radiographic technique could not better identify the radiopaque renal calculi. Limiting technical considerations include the increased subcutaneous and peritoneal adipose tissue and the limited contrast between the soft tissue and underlying calculi.

Growth kinetics of renal masses: analysis of a prospective cohort of patients undergoing active surveillance.

BACKGROUND: Active surveillance (AS) represents a treatment option for renal masses in patients who are not surgical candidates either because of existing comorbidities or patient choice. Among renal masses undergoing AS, some grow rapidly and require treatment or progress to metastatic disease. Patient and tumour characteristics related to this more aggressive behaviour have been poorly studied. OBJECTIVE: To report the analysis of a multi-institutional cohort of patients undergoing AS for small renal masses. DESIGN, SETTING, AND PARTICIPANTS: This prospective study included 82 patients with 84 renal masses who underwent AS in three Canadian institutions between July 2001 and June 2009. INTERVENTION: All patients underwent AS for renal masses presumed to be renal cell carcinoma (RCC) as based on diagnostic imaging. MEASUREMENTS: Age, sex, symptoms at presentation, maximum diameter at diagnosis (cm), tumour location (central/peripheral), degree of endophytic component (1-100%), and tumour consistency (solid/cystic) were used to develop a predictive model of the tumour growth rate using binary recursive partitioning analysis with a repeated measures outcome. RESULTS AND LIMITATIONS: With a median follow-up of 36 mo (range: 6-96), the mean annual renal mass growth rate for the entire cohort was 0.25 cm/yr (standard deviation [SD]: 0.49 cm/yr). Only one patient (1.2%) developed metastatic RCC. Amongst all variables, maximum diameter at diagnosis was the only predictor of tumour growth rate, and two distinct growth rates were identified. Masses that are ≥2.45 cm in largest diameter at diagnosis grow faster than smaller masses. This series was limited by its moderate sample size, although it is the largest published prospective series to date. CONCLUSIONS: We confirm that most renal masses grow slowly and carry a low metastatic potential. Tumour size is a predictor of tumour growth rate, with renal masses <2.45 cm growing more slowly than masses >2.45 cm.