Statistical Analysis of Plasma Dynamics in Gyrokinetic Simulations of Stellarator Turbulence.

A geometrical method for assessing stochastic processes in plasma turbulence is investigated in this study. The thermodynamic length methodology allows using a Riemannian metric on the phase space; thus, distances between thermodynamic states can be computed. It constitutes a geometric methodology to understand stochastic processes involved in, e.g., order-disorder transitions, where a sudden increase in distance is expected. We consider gyrokinetic simulations of ion-temperature-gradient (ITG)-mode-driven turbulence in the core region of the stellarator W7-X with realistic quasi-isodynamic topologies. In gyrokinetic plasma turbulence simulations, avalanches, e.g., of heat and particles, are often found, and in this work, a novel method for detection is investigated. This new method combines the singular spectrum analysis algorithm with a hierarchical clustering method such that the time series is decomposed into two parts: useful physical information and noise. The informative component of the time series is used for the calculation of the Hurst exponent, the information length, and the dynamic time. Based on these measures, the physical properties of the time series are revealed.

Anti-CV2 associated cerebellar degeneration after complete response to chemoradiation of head and neck carcinoma.

Paraneoplastic cerebellar degeneration is a rare neurological disorder that frequently precedes the detection of malignancy. Here, we report the case of a 60 year-old woman with locally advanced squamous cell carcinoma of the tongue who developed a subacute cerebellar syndrome associated with the presence of anti-CV2/CRMP5 antibodies in the cerebrospinal fluid, after achieving complete remission of the primary tumor and the involved cervical lymph nodes by chemoradiation. The patient's symptoms on presentation were dizziness and gait unsteadiness. On examination she showed dysarthria, nystagmus and limb and gait ataxia. The diagnosis of paraneoplastic cerebellar syndrome was made on the basis of the clinical findings and immunological testing that revealed the presence of anti-CV2/CRMP5 antibodies in the patient's cerebrospinal fluid. This syndrome, which is very rare in association with head and neck cancer, commonly precedes the detection of malignancy by a year or more and has been documented in only a few cases after completion of anticancer treatment.