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Published By Springer Nature

1745-2481, 1745-2473

2022 ◽  
Author(s):  
James Gallagher
Keyword(s):  

2022 ◽  
Author(s):  
Bart Verberck

2022 ◽  
Author(s):  
Mingu Kang ◽  
Shiang Fang ◽  
Jeong-Kyu Kim ◽  
Brenden R. Ortiz ◽  
Sae Hee Ryu ◽  
...  

2022 ◽  
Author(s):  
F. Nespoli ◽  
S. Masuzaki ◽  
K. Tanaka ◽  
N. Ashikawa ◽  
M. Shoji ◽  
...  

AbstractIn state-of-the-art stellarators, turbulence is a major cause of the degradation of plasma confinement. To maximize confinement, which eventually determines the amount of nuclear fusion reactions, turbulent transport needs to be reduced. Here we report the observation of a confinement regime in a stellarator plasma that is characterized by increased confinement and reduced turbulent fluctuations. The transition to this regime is driven by the injection of submillimetric boron powder grains into the plasma. With the line-averaged electron density being kept constant, we observe a substantial increase of stored energy and electron and ion temperatures. At the same time, the amplitude of the plasma turbulent fluctuations is halved. While lower frequency fluctuations are damped, higher frequency modes in the range between 100 and 200 kHz are excited. We have observed this regime for different heating schemes, namely with both electron and ion cyclotron resonant radio frequencies and neutral beams, for both directions of the magnetic field and both hydrogen and deuterium plasmas.


2022 ◽  
Author(s):  
Veikko F. Geyer ◽  
Jonathon Howard ◽  
Pablo Sartori

AbstractBiological systems are robust to perturbations at both the genetic and environmental levels, although these same perturbations can elicit variation in behaviour. The interplay between functional robustness and behavioural variability is exemplified at the organellar level by the beating of cilia and flagella. Cilia are motile despite wide genetic diversity between and within species, differences in intracellular concentrations of ATP and calcium, and considerable environment fluctuations in temperature and viscosity. At the same time, these perturbations result in a variety of spatio-temporal patterns that span a rich behavioural space. To investigate this behavioural space we analysed the dynamics of isolated cilia from the unicellular algae Chlamydomonas reinhardtii under many different environmental and genetic conditions. We found that, despite large changes in beat frequency and amplitude, the space of waveform shapes is low-dimensional in the sense that two features account for 80% of the observed variation. The geometry of this behavioural space accords with the predictions of a simple mechanochemical model in the low-viscosity regime. This allowed us to associate waveform shape variability with changes in only the curvature response coefficients of the dynein motors.


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