The alterations of tonus and movements through the interplay between the cerebral hemispheres and the cerebellum

This paper deals with the experimental production of involuntary movenients and abnormal tonus in macaques ( Macacu mulatta ) and their alterations in these animals and in children with cerebral palsy and other cerebral lesions. The first major subdivision of the paper has three parts. The first part describes the effects of lesions in the macaque cerebral hemispheres, ranging from a small destructive lesion in area 4 to an essentially complete bicortectomy. The case histories of a few patients document some of the results. The second part reports the effects of lesions in the macaque cerebellum ranging from small vermal injuries to complete cerebellectomies. The third part is concerned with successive lesions in the cerebellum and cerebral hemispheres of macaques and with planned cerebellar lesions in a few children with grave hypertonicity and marked involuntary movements. This subdivision is illustrated with photographs of the monkeys and the children at various stages of the procedures, photographs of many monkey brains at postmortem, and some photomicrographs showing lesions. The second major subdivision has a discussion of the anatomic and the physiologic bases for the experimental results obtained and for the operations on the children. It correlates the material presented with data from the literature and is illustrated with photomicrographs of degenerated tracts and with diagrams. The paper stresses the balancing of cerebral hemisphere and cerebellar discharges in the regulation of tonus and in the stabilizing of movements. It discusses the possibility of producing more effective tonus by making carefully planned lesions in cerebellar areas of animals or of children with highly handicapping hypertonicity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49991/1/901270502_ftp.pd

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM