6,665 research outputs found
Clustering of nicotinic acetylcholine receptors: from the neuromuscular junction to interneuronal synapses
Fast and accurate synaptic transmission requires high-density accumulation of neurotransmitter receptors in the postsynaptic membrane. During development of the neuromuscular junction, clustering of acetylcholine receptors (AChR) is one of the first signs of postsynaptic specialization and is induced by nerve-released agrin. Recent studies have revealed that different mechanisms regulate assembly vs stabilization of AChR clusters and of the postsynaptic apparatus. MuSK, a receptor tyrosine kinase and component of the agrin receptor, and rapsyn, an AChR-associated anchoring protein, play crucial roles in the postsynaptic assembly. Once formed, AChR clusters and the postsynaptic membrane are stabilized by components of the dystrophin/utrophin glycoprotein complex, some of which also direct aspects of synaptic maturation such as formation of postjunctional folds. Nicotinic receptors are also expressed across the peripheral and central nervous system (PNS/CNS). These receptors are localized not only at the pre- but also at the postsynaptic sites where they carry out major synaptic transmission. In neurons, they are found as clusters at synaptic or extrasynaptic sites, suggesting that different mechanisms might underlie this specific localization of nicotinic receptors. This review summarizes the current knowledge about formation and stabilization of the postsynaptic apparatus at the neuromuscular junction and extends this to explore the synaptic structures of interneuronal cholinergic synapse
Strain-rate effect on the dynamic behaviours of a rectangular conducting plate
This paper is concerned with thermo-elasto-plastic dynamic response of a conductive
plate in a magnetic pulse field. The influence of the strain rate effect and the temperature
effect are taken into account for the electromagnetic elasto-plastic dynamic transient
response and deformation of the conductive plate which made of strain-rate sensitive
materials. The Johnson-Cook model is employed to study the strain rate effect and the
temperature effect on the deformation of the plate. Basic governing equations are derived
for electro-magnetic field considering the eddy current. The analysis includes the elastoplastic
transient dynamic response and the heat transfer of a conductive rectangular plate,
and then an appropriate numerical code based on the finite element method to
quantitatively simulate the electro-magneto-elasto-plastic mechanical behaviors of the
conductive rectangular plate. The numerical results indicate that the strain rate effect has
to be considered for the conductive plates, especially for those with high strain rate
sensitivity. Comparison of the influence of the temperature effect on the deformation of the
plate with that of the strain rate effect shows that the influence of the temperature effect
on the deformation of a plate is not significant
Photoinduced Magnetization in a Thin Fe-CN-Co Film
The magnetization of a thin Fe-Co cyanide film has been investigated from 5 K
to 300 K and in fields up to 500 G. Upon illumination with visible light, the
magnetization of the film rapidly increases. The original cluster glass
behavior is further developed in the photoinduced state and shows substantial
changes in critical temperature and freezing temperature.Comment: 2 pages, 2 figures, 1 table, International Conference on Magnetism
200
Modulated structures in electroconvection in nematic liquid crystals
Motivated by experiments in electroconvection in nematic liquid crystals with
homeotropic alignment we study the coupled amplitude equations describing the
formation of a stationary roll pattern in the presence of a weakly-damped mode
that breaks isotropy. The equations can be generalized to describe the planarly
aligned case if the orienting effect of the boundaries is small, which can be
achieved by a destabilizing magnetic field. The slow mode represents the
in-plane director at the center of the cell. The simplest uniform states are
normal rolls which may undergo a pitchfork bifurcation to abnormal rolls with a
misaligned in-plane director.We present a new class of defect-free solutions
with spatial modulations perpendicular to the rolls. In a parameter range where
the zig-zag instability is not relevant these solutions are stable attractors,
as observed in experiments. We also present two-dimensionally modulated states
with and without defects which result from the destabilization of the
one-dimensionally modulated structures. Finally, for no (or very small)
damping, and away from the rotationally symmetric case, we find static chevrons
made up of a periodic arrangement of defect chains (or bands of defects)
separating homogeneous regions of oblique rolls with very small amplitude.
These states may provide a model for a class of poorly understood stationary
structures observed in various highly-conducting materials ("prechevrons" or
"broad domains").Comment: 13 pages, 13 figure
Practice of lingual orthodontics and practitioners' opinion and experience with lingual braces in the United States
A survey was done on practicing Orthodontists in the United States on their experience with lingual orthodontics. The objectives of this survey study were to assess 1) the satisfaction level with cases treated with lingual orthodontics, 2) factors that i
Endogenous circatidal rhythm in the Manila clam Ruditapes philippinarum (Bivalvia: Veneridae)
Manila clams, Ruditapes philippinarum, removed from their natural environment and maintained for 9 weeks in continuously immersed conditions exhibited a clear endogenous circatidal rhythm in oxygen consumption. The clams exhibited a semidiurnal rhythmicity in oxygen consumption after showing a diurnal pattern in the first few days (5 to 7 d) of the experiment. The results of the present study indicate that activity rhythms of clams are controlled not only by exogenous factors, but also by an endogenous circatidal periodicity
- …