The mechanisms underlying long-term potentiation of C-fiber evoked field potentials in spinal dorsal horn

Long-term potentiation(LTP) of C-fiber evoked field potentials in spinal dorsal horn is first reported in 1995.Since then,the mechanisms underlying the long-lasting enhancement in synaptic transmission between primary afferent C-fibers and neurons in spinal dorsal horn have been investigated by different laboratories.In this article,the related data were summarized and discussed.

Conversion of polyaluminocarbosilane(PACS) to Si-Al-C-(O) fibers:evolutions and effect of oxygen

The evolvement of oxygen from polyaluminocarbosilane(PACS) to Si-Al-C-(O) fibers and its effect on properties were investigated by element analysis, solid-state 27Al nuclear magnetic resonance(NMR), Fourier transform infrared spectroscopy(FT-IR), thermo-gravimetric analyses(TGA), scanning electron microscope(SEM) and X-ray diffraction(XRD). Element analysis of PACS precursor polymer gives an empirical formula of SiC2.1H11.1O0.12Al0.024. 27Al NMR spectra mass gain shows that the oxygen of cured PACS fibers comes from aluminum aletylacetanate (Al(AcAc)3) and the curing process. Oxygen content can be regarded as a constant mass during the pyrolysis process. During the sintering process of Si-Al-C-O fibers into Si-Al-C fibers, oxygen and carbon decreases with the release of a small amount of CO and/or SiO. Oxygen has a positive effect on the ceramic yield while has a negative effect on the crystallization of Si-Al-C-O fibers. It has great influence on mechanical properties of Si-Al-C-O and excellent tensile strength is usually obtained at the oxygen content of 8%-10%. The Si-Al-C-(O) fibers have excellent thermal stability and creep resistance.

Axonotmesis-evoked plantar vasodilatation as a novel assessment of C-fiber afferent function after sciatic nerve injury in rats

Quantitative assessment of the recovery of nerve function, especially sensory and autonomic nerve function, remains a challenge in the field of nerve regeneration research. We previously found that neural control of vasomotor activity could be potentially harnessed to evaluate nerve function. In the present study, five different models of left sciatic nerve injury in rats were established: nerve crush injury, nerve transection/ suturing, nerve defect/autografting, nerve defect/conduit repair, and nerve defect/non-regeneration. Laser Doppler perfusion imaging was used to analyze blood perfusion of the hind feet. The toe pinch test and walking track analysis were used to assess sensory and motor functions of the rat hind limb, respectively. Transmission electron microscopy was used to observe the density of unmyelinated axons in the injured sciatic nerve. Our results showed that axonotmesis-evoked vasodilatation in the foot 6 months after nerve injury/repair recovered to normal levels in the nerve crush injury group and partially in the other three repair groups;whereas the nerve defect/non-regeneration group exhibited no recovery in vasodilatation. Furthermore, the recovery index of axonotmesis-evoked vasodilatation was positively correlated with toe pinch reflex scores and the density of unmyelinated nerve fibers in the regenerated nerve. As C-fiber afferents are predominantly responsible for dilatation of the superficial vasculature in the glabrous skin in rats, the present findings indicate that axonotmesis-evoked vasodilatation can be used as a novel way to assess C-afferent function recovery after peripheral nerve injury. This study was approved by the Ethics Committee for Laboratory Animals of Nantong University of China (approval No. 20130410-006) on April 10, 2013.

Preparation of continuous Si-Fe-C-O functional ceramic fibers

A new polymer named polyferrocarbosilane(PFCS) was prepared from polydimethylsilane and ferrocene. The spinnability of this polymer can be tailored by controlling the content of ferrocene in the polymer. The prepared polymer was spun into a continuous polymer fiber that was subsequently cured in air and heat-treated finally in N2 up to 1 350 ℃ for conversion into Si-Fe-C-O fibers. The resulted Si-Fe-C-O fibers display low specific resistance and magnetic property due to the existence of Fe, which also reduces the specific resistance significantly to 10-2Ω·cm at room temperature when the amount of ferrocene in feed is as low as 3.0% (mass fraction). The resulted Si-Fe-C-O fibers, with C/Si molar ratio of about 1.3 and the maximum Fe content of about 2.0% (mole fraction), are composed of β-SiC and small amount of Fe3Si-like crystalline and have an average tensile strength of about 2.0 GPa.

改良everStick C&B纤维树脂粘接桥在老年切牙缺失修复中的疗效观察

目的:评价改良everStick C&B纤维树脂粘接桥在老年切牙缺失修复中的临床疗效。方法:纳入年龄65岁以上切牙缺失患者32例。其中上颌切牙缺失13例、下颌切牙缺失19例;缺牙1颗13例、缺牙2颗11例、缺牙3颗5例、缺牙4颗3例;基牙松动24例、基牙无松动8例。对所有患者均采取改良everStick C&B纤维树脂粘接桥修复治疗。分别于修复完成后6、 12、 18个月复查,复查内容包括修复体脱粘接、折断、颜色变化、缺损以及基牙松动、牙周组织炎症等6项指标。修复完成后6个月对患者进行满意度调查,调查内容包括治疗过程是否舒适、美观效果是否满意、修复后发音、咀嚼是否舒适等3项指标。结果:32位老年患者修复完成后6个月,6项指标均为A级。12个月,出现1例修复体缺损B级,2例基牙牙周组织炎症B级,其余均为A级。18个月,出现1例修复体缺损B级,3例基牙牙周组织炎症B级,其余均为A级。2例修复体缺损B级经过树脂充填后均达到A级。5例基牙牙周组织炎症B级经过牙周洁治后5~7 d均达到A级。患者满意度调查3项指标均为A级。结论:改良everStick C&B纤维树脂粘接桥在老年切牙缺失修复中临床疗效良好。

三维四向C/C预制体压实规律与高精度控制策略研究

为实现预制体层间密实度均匀可调控,保证预制体产品质量一致性,基于胡克定律建立压实理论模型对不同截面尺寸预制体压实规律进行研究,揭示了压实载荷与压实次数的关系:在压实次数小于疲劳次数阶段,预制体受到的压实载荷随压实次数呈线性变化;在压实次数大于等于疲劳次数阶段,预制体受到的压实载荷不再随压实次数增加而发生变化;同时在编织不同截面尺寸预制体时,xoy截面积呈倍数增加,预制体受到的压实载荷近似呈倍数增长。基于三维四向C/C复合材料预制体成型工艺,建立预制体编织层数、压实厚度与纤维体积含量映射关系,并通过该映射关系进行不同截面尺寸预制体编织实验,得到压实载荷与厚度的变化曲线,其实验值与拟合值的最大偏差率小于3%,验证了理论模型的可行性。根据压实规律理论模型设计出压实装置双闭环控制系统,在该系统中预先设定映射关系所对应的厚度与压力值,在压实过程中借助传感器将采集到的厚度与压力值反馈至控制器,控制器根据偏差值控制压实装置输出值。最后通过观察其所编预制体截面,发现该预制体孔隙小而均匀,验证了该控制系统可输出最优压力值,能够保证预制体层间密实度均匀及产品质量的一致性。

Defects of Polymer-derived Si-C-O Fibers and Their Originations

Defects of polymer-derived Si-C-O fibers were intensively studied by the SEM and TEM techniques and their originations were also discussed on the basis of factors experiments.The defects were found mainly in the form of strumaes,pits and splits on surfaces as well as microflaw networks,porosity clusters and inclusions in the bulk.Factors experiments reveal that a nonuniform or an insufficient curing would result in larger-sized strumaes or interior microflaws.Gas evolution rates due to different firing rates have a great influence on the formation of internal microflaws or porosity clusters and some oxidation-induced pits or splits may be formed on surfaces because of a trace of oxygen or water vapor accumulated from the flowing inert atmosphere during pyrolysis.

Effect of fiber characteristics on fracture behavior of C_f/SiC composites

C f/SiC composites were prepared by precursor pyrolysis hot pressing, and the effect of fiber characteristics on the fracture behavior of the composites was investigated. Because the heat treatment temperature of fiber T300 (below 1?500?℃) was much lower than that of fiber M40JB (over 2?000?℃), fiber T300 had lower degree of graphitization and consisted of more impurities compared with fiber M40JB, suggesting that T300 exhibits higher chemical activity. As a result, the composite with T300 showed a brittle fracture behavior, which is mainly ascribed to a strongly bonded fiber/matrix interface as well as the degradation of fibers during the preparation of the composite. However, the composite with M40JB exhibits a tough fracture behavior, which is primarily attributed to a weakly bonded fiber/matrix interface and higher strength retention of the fibers.

Fabrication and formation mechanism of NbC_x-C three-dimensional netted fibers

Micrometer NbC_x-C three-dimensional netted fibers were synthesized by thecarbothermal method under 0.1 MPa of N_2 ambient atmosphere at a relatively low temperature. Rawmaterials were commercial powders of Nb_2O_5 (99.95 percent), reactive carbon (99.99 percent), NaCl(99.95 percent) and sucrose (99.94 percent). The relationship of the fabrication processing with thecomposition, crystal structure and morphology of fibers was investigated. The formation mechanismwas also proposed and discussed.

Fiber Residues from <i>Canavalia ensiformis</i>L. Seeds with Potential Use in Food Industry

The objective of this research was to determine the physicochemical characteristics of fiber residues from Jack bean (Canavalia ensiformis L.) obtained by two technological processes. The proximal composition of the fiber residues from Canavalia ensiformis registered values of moisture, ash, protein, fat, fiber and nitrogen-free extract (NFE) of 7.14%, 3.17%, 9.14%, 1.34%, ?23.84% and 62.51% for residue A and 4.74%, 2.68%, 7.73%, 1.39%, 23.76% and 64.44% for residue B. Total dietary fiber (TDF) contents in the fiber residues were 47.06 (Residue A) and 54.96 (Residue B) g/100g sample, with most of this content represented by insoluble dietary fiber (IDF) 45.46 g/100g sample in Residue A and 52.75 g/100g of sample in Residue B. The remainder was constituted by soluble dietary fiber (SDF). The neutral detergent fiber (NDF) content was slightly higher in residue B (41.8 g/100g sample). Acid detergent fiber (ADF) that includes principally cellulose, lignin and cutin, and acid detergent lignin (ADL) that include lignin and cutin were higher in residue B (32.5 g/100g sample) and similar for both residues (1.0 (A) and 1.2 (B) g/100g sample), respectively. Resistant starch (RS) was higher in residue B (0.607%) than in residue A (0.358%). No statistical difference (p > 0.05) was registered in the tannins content of both residues. However, the phytates content was higher in the fiber residue obtained by the fists technological process (A residue). In vitro digestibility was higher in residue A (85.81%) than that in B residue (81.51%). The results of the present study suggest the potential use of C. ensiformis fiber residues as a functional ingredient in foods, especially in the development of reduced calorie food and dietary fiber enriched foods.

维生素C对聚合物/金属导电复合材料电磁屏蔽稳定性的影响

采用熔融共混法制备了动态硫化热塑性弹性体(TPV)/镀镍(Ni)玻璃纤维(NCGF)/维生素C(VC)导电复合材料TPV/NCGF_(VC),系统研究了VC对该复合材料老化前后的微观形貌、分子结构及力学性能的影响,探讨了VC对Ni金属网络的选择性保护作用机制。结果表明,在TPV/NCGF复合材料中添加VC能够有效抑制老化过程中Ni导电网络的氧化,从而使复合材料表现出稳定的导电性和电磁屏蔽性能,其中电磁屏蔽效能保持率超过90%;在纯TPV基体中引入VC后,VC能有效抑制老化后TPV分子链的断裂;在TPV/NCGF_(VC)复合材料的老化过程中,VC优先与Ni网络发生还原反应,将NCGF表面Ni层因氧化生成的Ni离子(Ni^(2+))还原为单质Ni(Ni^(0)),表明VC对Ni金属网络具有选择性保护作用。

EXPERIMENTAL STUDY ON PEK -C MODIFIED EPOXIES AND THE CARBON FIBER COMPOSITES FOR AEROSPACE APPLICATION

The morphological structure of various epoxies toughened with a special amorphous thermoplastic PEK-C and their carbon fiber composites were studied by using SEM. For both cases, phase separation and inversion took place to form fine epoxy-rich globules dispersing in the PEK-C matrix, in which the epoxy-rich phase had the absolutely higher volume fraction. The phase structure and the interfacial properties were also studied by means of FTIR, DSC, and DMTA as well. An accompanying mechanical determination revealed that an improved toughness was achieved both in the blend casts and in the carbon fiber composites. A composite structural model was hence suggested.

In-situ Formation of Spinel Fibers in MgO-C Refractory Matrixes

In-situ magnesia-rich spinel fiber was formed resulting from the addition of ferrocene into MgO-C refractory matrixes. The formation of in-situ spinel fiber was detected to start at 1300 ℃. The amount, diameter and length of the fibers increased with rising temperature. Ferrocene may have catalytic effects on the growth of the fibers in two aspects. First, the reaction between MgO and C and the decomposition of Al4C3 may be catalyzed at high temperature. Suitable concentration gaseous phase is then created for vapor-vapor reaction which could result in the in-situ formation of fibers. Second, Fe nanoparticle produced from ferrocene can act as catalytic droplets and catalyze the growth of the fibers. The fibers are formed via the vapor-liquid-solid and vapor-solid mechanisms. In terms of chemical thermodynamics, the partial pressure of CO and Mg（g） are found to play an important role in the in-situ fibers formation. Different concentration of vapors affects the size, amount and composition of the fibers at different temperatures. The mechanical properties of MgO-C brick was found to be improved by ferrocene addition.

Microstructure Characterization of Long W Core SiC Fiber

Microstructure of SiC fiber manufactured by chemical vapor deposition （CVD） onto tungsten （W） wire core was investigated by analytical electron microscopy （AEM）. The results reveal that the fiber consists of W core, SiC sheath and C-coating. SiC sheath could be subdivided into two parts according to whether containing C rich stripe, or not. An emphasis was put on W/SiC interfacial reaction products and the transition zone between sub-layers in SiC sheath. The W/SiC interface consists of three layers of reaction production, namely, W2C, W5Si3 and WC. And there are amounts of facet faults existing in （100） face of WC crystalline and two classes of stack faults in WC have been revealed. The formation essence of different sublayers in SiC sheath was also discussed.

PIP结合CVI制备氧化铝-莫来石陶瓷基复合材料

通过PIP结合CVI法制备了C纤维增初三维氧化铝-莫来石陶瓷基复合材料,采用CVD法制备了防氧化涂层,研究了复合材料致密化过程、复合材料的物相、微观结构、力学性能和抗氧化性能。结果表明,CVI能够将氧化硅引入到多孔氧化铝基体内部,1400℃处理后氧化硅与氧化铝完全反应生成莫来石,显著提高了仅以PIP法制备的多孔氧化铝基复合材料的力学性能,CVD制备的氧化硅涂层有效阻止了氧气的侵入,复合材料在1200℃大气环境下保温50h后,试样三点弯曲强度保持率为70％。

急性神经损伤引起脊髓背角C-纤维诱发电位长时程增强(英文)

神经损伤引起神经病性疼痛,表现为持续性痛超敏和痛觉过敏.目前对神经病性疼痛的机制尚缺乏了解.我们以往的工作表明强直电刺激坐骨神经可引起脊髓背角C-纤维诱发电位的长时程增强(long-term potentiation,LTP),该LTP被认为是病理性疼痛的突触模型.本研究的目的在于探讨急性神经损伤是否能在完整动物的脊髓背角诱发出C-纤维诱发电位LTP.在以测试刺激(10～20 V,0.5 ms)电刺激坐骨神经的同时在脊髓背角用微电极记录C-纤维诱发电位.分别用强直刺激、剪断或夹捏坐骨神经诱导LTP.结果发现:(1)剪断或夹捏坐骨神经都可以诱导脊髓背角C-纤维诱发电位的LTP,该LTP可持续到实验结束(3～9h),在剪断神经前10 min用利多卡因局部阻滞坐骨神经则可完全阻断LTP的产生;(2)神经损伤诱导的LTP可被NMDA受体阻断剂AP5所阻断;(3)用单次强直刺激引起LTP后,切断坐骨神经可使LTP的幅度进一步增大,而用多次强直电刺激使LTP饱和后,损伤神经则不能使LTP进一步增大.切断神经引起LTP后,强直电刺激也不能使LTP进一步增大.这些结果表明,急性神经损伤可以诱导脊髓背角C纤维诱发电位LTP,且切断神经能更有效地诱导LTP.该试验进一步支持我们的设想,即脊髓背角C-纤维诱发电位LTP可能在病理性疼痛的形成中起重要作用.

不同频率脉冲射频对大鼠脊髓背角C-纤维诱发电位长时程增强的影响

目的:观察不同频率脉冲射频(DRF)对大鼠脊髓背角C-纤维诱发电位长时程增强的影响,探讨脉冲射频镇痛效应的机制。方法:SD大鼠21只随机分为3组,分别采用不同频率脉冲射频:I组(2 Hz),II组(4 Hz),III组(8 Hz),细胞外记录脊髓背角C-纤维诱发电位。强直刺激坐骨神经诱导出C-纤维诱发电位LTP 1小时后,按分组在坐骨神经干分别给予2、4、8 Hz(30 V,20 ms)脉冲射频刺激120 s。结果:I组LTP抑制了22.2±3.5%(n=7,P<0.01);II组LTP抑制率为2.57±0.6%(P>0.05);III组脉冲射频刺激对LTP无抑制作用,相反LTP由272.6±64.0%升至347.4±71.9%。结论:2 Hz脉冲射频对LTP有一定程度的抑制,这可能是PRF镇痛效应的生物学机制之一;脉冲射频的镇痛效应具有频率响应低频优于高频;脉冲射频频率大于8 Hz可能产生非治疗效应。

碘对豌豆苗生长及其可食部分游离氨基酸和维生素C及纤维素含量的影响(英文)

为探索碘元素的生理效应 ,以豌豆苗为材料 ,研究了加碘溶液培养对其生长及品质的影响 .结果表明 ,低浓度碘可促进豌豆苗生长 ,增加根系和菜苗长度、可食部分游离氨基酸总量和维生素 C含量 ,并大幅度提高菜苗可食部分含碘量 ,而对纤维素含量无明显影响 ,碘质量浓度以 1.0～ 1.5 mg/ L 时效果最好 ,当质量浓度超过 1.5 mg/ L时出现高碘毒害 .

传入 C 纤维的兴奋在电针“足三里” 激活中缝大核中的作用

为了分析电针“足三里”是否以其伤害性刺激性质引起镇痛作用,我们试探了电刺激“足三里”穴区所引起的传人(顺行)冲动是否可以减小刺激腓总神经引起的逆行 C 波。碰撞实验表明刺激“足三里”确可兴奋了腓神经的一些 C 纤维。此外我们还观察到刺激“足三里”的强度达到或超过 C 纤维阈值时。可明显激活中缝大核神经元,当刺激强度达到可引起最大 c 波时,激活 NRM 的效应也达到最大。上述结果提示电针“足三里”除可以其非伤害性刺激性质引起镇痛作用外,可能主要是以其伤害性刺激,经 C 类纤维激活 NRM,再经过痛负反馈调制引起镇痛。

自由碳的脱除对SiC纤维微观结构和性能的影响

采用加氢烧成法脱碳,制备了不同自由碳含量的连续SiC纤维。通过元素分析、红外、X射线衍射和拉伸试验等手段对纤维的脱碳过程、元素组成、微观结构和性能进行了分析。结果表明:加氢烧成通过抑制脱H_2反应、促进脱CH_4反应而实现有效脱碳,且氢气浓度越高,纤维中的碳含量越低。纤维芯部元素分布均匀,表明该方法可以实现均匀脱碳,但表面出现很薄的富碳层,这是纤维经氢气处理后表面吸附氧形成的富氧层在高温烧成时分解所致。自由碳的脱除引起纤维晶粒长大,密度增加,孔隙率降低,电阻率升高,拉伸强度与拉伸模量提高。近化学计量SiC纤维具有优异的综合性能。