Energy surface model and magnetization switching for exchange coupled magnetic particles

2006 ◽  
Vol 99 (8) ◽  
pp. 08K503 ◽  
Author(s):  
Kai-Zhong Gao ◽  
Juan Fernandez-de-Castro
Keyword(s):  
Magnetic Particles ◽  
Energy Surface ◽  
Surface Model ◽  
Magnetization Switching

scholarly journals Pathways for nicotinic receptor desensitization

2020 ◽  
Vol 152 (10) ◽  
Author(s):  
Anthony Auerbach
Keyword(s):  
Transition State ◽  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Open Channel ◽  
Energy Surface ◽  
Surface Model ◽  
Closed Channel ◽  
Discrete State ◽  
State Region ◽  
Selection Of

Nicotinic acetylcholine receptors (AChRs) are ligand-gated ion channels that generate transient currents by binding agonists and switching rapidly between closed- and open-channel conformations. Upon sustained exposure to ACh, the cell response diminishes slowly because of desensitization, a process that shuts the channel even with agonists still bound. In liganded receptors, the main desensitization pathway is from the open-channel conformation, but after agonists dissociate the main recovery pathway is to the closed-channel conformation. In this Viewpoint, I discuss two mechanisms that can explain the selection of different pathways, a question that has puzzled the community for 60 yr. The first is based on a discrete-state model (the “prism”), in which closed, open, and desensitized conformational states interconnect directly. This model predicts that 5% of unliganded AChRs are desensitized. Different pathways are taken with versus without agonists because ligands have different energy properties (φ values) at the transition states of the desensitization and recovery reactions. The second is a potential energy surface model (the “monkey saddle”), in which the states connect indirectly at a shared transition state region. Different pathways are taken because agonists shift the position of the gating transition state relative to the point where gating and desensitization conformational trajectories intersect. Understanding desensitization pathways appears to be a problem of kinetics rather than of thermodynamics. Other aspects of the two mechanisms are considered, as are experiments that may someday distinguish them.

Computer simulations of magnetization switching of elongated magnetic particles with shape defects

2003 ◽  
Vol 93 (12) ◽  
pp. 9865-9868 ◽  
Author(s):  
Hiraku Endo ◽  
Yasutaro Uesaka ◽  
Yoshinobu Nakatani ◽  
Nobuo Hayashi ◽  
Hiroshi Fukushima
Keyword(s):  
Computer Simulations ◽  
Magnetic Particles ◽  
Magnetization Switching

scholarly journals Dynamics of magnetic particles near a surface: Model and experiments on field-induced disaggregation

2014 ◽  
Vol 89 (4) ◽  
Author(s):  
A. van Reenen ◽  
Y. Gao ◽  
A. M. de Jong ◽  
M. A. Hulsen ◽  
J. M. J. den Toonder ◽  
...  
Keyword(s):  
Magnetic Particles ◽  
Surface Model
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