The Changes of Intrinsic Excitability of Pyramidal Neurons in Anterior Cingulate Cortex in Neuropathic Pain

To find satisfactory treatment strategies for neuropathic pain syndromes, the cellular mechanisms should be illuminated. Central sensitization is a generator of pain hypersensitivity, and is mainly reflected in neuronal hyperexcitability in pain pathway. Neuronal excitability depends on two components, the synaptic inputs and the intrinsic excitability. Previous studies have focused on the synaptic plasticity in different forms of pain. But little is known about the changes of neuronal intrinsic excitability in neuropathic pain. To address this question, whole-cell patch clamp recordings were performed to study the synaptic transmission and neuronal intrinsic excitability 1 week after spared nerve injury (SNI) or sham operation in male C57BL/6J mice. We found increased spontaneous excitatory postsynaptic currents (sEPSC) frequency in layer II/III pyramidal neurons of anterior cingulate cortex (ACC) from mice with neuropathic pain. Elevated intrinsic excitability of these neurons after nerve injury was also picked up, which was reflected in gain of input-output curve, inter-spike interval (ISI), spike threshold and Refractory period (RP). Besides firing rate related to neuronal intrinsic excitability, spike timing also plays an important role in neural information processing. The precision of spike timing measured by standard deviation of spike timing (SDST) was decreased in neuropathic pain state. The electrophysiological studies revealed the elevated intrinsic excitation in layer II/III pyramidal neurons of ACC in mice with neuropathic pain, which might contribute to central excitation

White emission by self-regulated growth of InGaN/GaN quantum wells on in situ self-organized faceted n-GaN islands

National Natural Science Foundation of China [60876008, 61076091]The in situ self-organization of three-dimensional n-GaN islands of distinct sidewall faceting was realized by initial low V/III ratio growth under high reactor pressure followed by variations of the V/III ratio and reactor pressure. The naturally formed faceted islands with top and sidewall facets of various specific polar angles may serve as an ideal template for self-regulated growth of the InGaN/GaN multiple quantum wells (MQWs), i.e. the growth behavior is specific polar angle dependent. Further, the growth behavior and luminescence properties of the InGaN/GaN MQWs on various facets of different specific polar angles are directly compared and discussed. Tetrachromatic white emissions (blue, cyan, green, and red) from single-chip phosphor-free InGaN/GaN MQWs are realized by color tuning through island shaping, shape variations, and self-regulated growth of the InGaN/GaN MQWs

Characterization of MOCVD-grown non-stoichiometric SiNx

The surface morphologies and X-ray photoelectron spectra of MOCVD-grown SiNx were investigated. Highly Si-rich SiNx nanoislands not fully covering the sapphire surface were observed for SiNx deposition at low temperature (545 degrees C) with NH3/SiH4 flow rate of 2500/40 sccm. The surface roughness decreased from 0.91 nm to 0.23 nm with the reduction of SiH4 flow rate from 40 sccm to 3 sccm. The reduction of the SiH4 flow rate did not cause a linear decrease of SiN ratio, which indicated that the SiH4 Supply Was saturated when the NH3 supply was 2500 sccm and deposition temperature was fixed at 545 degrees C. Relatively "thick" SiNx layers with stoichiometry close to 1 were formed for SiNx deposition at high temperature due to high decomposition rate of ammonia and high reaction rate between silane and ammonia. The SiNx layers almost fully covered the sapphire surface and showed surface structures of both nanoislands and nanoholes. By employing the same NH3/SiH4 flow rate of 2500/40 sccm the surface roughness of SiNx layers decreased from 0.91 nm to 0.17 nm with the increase of deposition temperature from 545 degrees C to 1035 degrees C. Saturated pre-nitridation would likely cause surface roughening. (C) 2008 Elsevier B.V. All rights reserved

Significant increase of light emission efficiency by in situ site-selective etching of InGaN quantum wells

Natural Science Foundation of China [60876008]An indium post-treatment of the InGaN epilayers was employed for InGaN-to-GaN interface modification. We find that the treatment could lead to selective etching of the InGaN epilayers around threading dislocations (TDs) due to preferential etching of the chemically active step-correlated TDs and formation of indium-rich InGaN nanostructures on the smooth InGaN surface. The intentionally formed V-shaped pits by site-selective etching of the InGaN epilayers resulted in an increased surface potential barrier at the pit sidewalls due to the relatively thin InGaN single quantum well. The increased energy bandgap of the InGaN active layers around the TDs cores caused the lateral carrier confinement away from nonradiative recombination at the defects and thus significantly enhanced the light emission efficiency. (c) 2009 American Institute of Physics. [DOI: 10.1063/1.3176931

Self-organization of 3D triangular GaN nanoislands and the shape variation to hexagonal

We report on the self-organization of large-scale uniform aligned three-dimensional (3D) GaN islands with distinct triangular (0001) and smooth side facets and the shape variations of the (0001) facets from triangular to hexagonal during metalorganic vapor-phase epitaxy (MOVPE) growth of GaN films on Si-rich SiNx patterned sapphire substrates. The triangular island shaping during the recrystallization processes of GaN nucleation layers (NLs) can be attributed to the enhanced diffusion and regrowth anisotropy. The island shape transition from triangular to hexagonal in the early stages of high-temperature growth of GaN epilayers is due to the gas-phase transport dominating growth mechanism and the limited diffusion length of edge adatoms compared with the increased island size

Significant increase of crystalline quality and green emission by an interface modification of InGaN/GaN quantum wells

National Natural Science Foundation of China [60876008, 61076091]A GaN-to-InGaN interface modification by predeposition of an ultrathin In-rich InGaN incomplete layer followed by a thin triangular InGaN well layer was employed to overcome the negative effects of polarization field on light emission efficiency of InGaN/GaN quantum wells as well as to improve the crystalline quality by avoidance of a significant strain generation and enhanced surfactant effect. Further, the interface modification induced energy band structure engineering reduces the spatial separation of electrons and holes, and thus increases the carrier recombination rate. The improvement in crystalline quality, localized potential fluctuation, and energy band engineering contribute to the significant increase of green emission of the InGaN/GaN quantum wells

MOCVD growth of GaN films on Si-rich SiNx nanoislands patterned sapphire - art no 69842V

We intentionally patterned Si-rich SiNX nanoislands on sapphire substrates and found the SiNx significantly influenced the subsequent growth of GaN films. Distinct GaN islands of triangular base were formed caused by the enhanced diffusion and regrowth anisotropy during the annealing processes of GaN nucleation layers. Subsequent growth of GaN epilayers at high temperature with initial low V/III ratios on the nucleated triangular islands resulted in island coarsening and shape variations from triangular to hexagonal due to the dominating gas phase transport growth mechanism and limited diffusion length. Further growth with high V/III ratios eventually resulted in layer-growth with surface roughness of similar to 2.6 A. Both AFM and XRD results showed a significant improvement of the crystalline qualities with estimated threading dislocation (TD) density of about 1 x 10(8) cm(-2) when Si-rich SiNx nanoislands patterning was performed. Photoluminescence measurements showed that the yellow and blue emissions were substantially suppressed

MOCVD growth of GaN films on Si-rich SiNx nanoislands patterned sapphire - art no 69842V

We intentionally patterned Si-rich SiNX nanoislands on sapphire substrates and found the SiNx significantly influenced the subsequent growth of GaN films. Distinct GaN islands of triangular base were formed caused by the enhanced diffusion and regrowth anisotropy during the annealing processes of GaN nucleation layers. Subsequent growth of GaN epilayers at high temperature with initial low V/III ratios on the nucleated triangular islands resulted in island coarsening and shape variations from triangular to hexagonal due to the dominating gas phase transport growth mechanism and limited diffusion length. Further growth with high V/III ratios eventually resulted in layer-growth with surface roughness of similar to 2.6 A. Both AFM and XRD results showed a significant improvement of the crystalline qualities with estimated threading dislocation (TD) density of about 1 x 10(8) cm(-2) when Si-rich SiNx nanoislands patterning was performed. Photoluminescence measurements showed that the yellow and blue emissions were substantially suppressed

MOCVD growth of GaN films on Si-rich SiNx nanoislands patterned sapphire - art no 69842V

Conference Name:6th International Conference on Thin Film Physics and Applications. Conference Address: Shanghai, PEOPLES R CHINA. Time:SEP 25-28, 2007.We intentionally patterned Si-rich SiNX nanoislands on sapphire substrates and found the SiNx significantly influenced the subsequent growth of GaN films. Distinct GaN islands of triangular base were formed caused by the enhanced diffusion and regrowth anisotropy during the annealing processes of GaN nucleation layers. Subsequent growth of GaN epilayers at high temperature with initial low V/III ratios on the nucleated triangular islands resulted in island coarsening and shape variations from triangular to hexagonal due to the dominating gas phase transport growth mechanism and limited diffusion length. Further growth with high V/III ratios eventually resulted in layer-growth with surface roughness of similar to 2.6 A. Both AFM and XRD results showed a significant improvement of the crystalline qualities with estimated threading dislocation (TD) density of about 1 x 10(8) cm(-2) when Si-rich SiNx nanoislands patterning was performed. Photoluminescence measurements showed that the yellow and blue emissions were substantially suppressed