924 resultados para ASA PRETREATMENT


Relevância:

10.00% 10.00%

Publicador:

Resumo:

超纯水系统中的反渗透膜无法长时间在原水水质硬度过大的条件下正常运转,本文就原水水质硬度大对反渗透膜的不良影响,及软水剂、防垢剂除盐法和阳树脂交换除盐法这两种软化水方法的实际效果进行了探讨和比较.经过长期实践,采用膜前树脂交换除盐法为主,各类添加剂为辅的前处理方法成功解决了这一问题.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

With advancing age, monkeys develop deficits in spatial working memory resembling those induced by lesions of the prefrontal cortex (PFC). Aged monkeys also exhibit marked loss of dopamine from the PFC, a transmitter known to be important for proper PFC cognitive function. Previous results suggest that D1 agonist treatment can improve spatial working memory abilities in aged monkeys. However, this research was limited by the use of drugs with either partial agonist actions or significant D2 receptor actions. In our study, the selective dopamine D1 receptor full agonists A77636 and SKF81297 were examined in aged monkeys for effects on the working memory functions of the PFC. Both compounds produced a significant, dose-related effect on delayed response performance without evidence of side effects: low doses improved performance although higher doses impaired or had no effect on performance. Both the improvement and impairment in performance were reversed by pretreatment with the D1 receptor antagonist, SCH23390. These findings are consistent with previous results demonstrating that there is a narrow range of D1 receptor stimulation for optimal PFC cognitive function, and suggest that very low doses of D1 receptor agonists may have cognitive-enhancing actions in the elderly.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Ammonia (NH 3) plasma pretreatment is used to form and temporarily reduce the mobility of Ni, Co, or Fe nanoparticles on boron-doped mono- and poly-crystalline silicon. X-ray photoemission spectroscopy proves that NH 3 plasma nitrides the Si supports during nanoparticle formation which prevents excessive nanoparticle sintering/diffusion into the bulk of Si during carbon nanotube growth by chemical vapour deposition. The nitridation of Si thus leads to nanotube vertical alignment and the growth of nanotube forests by root growth mechanism. © 2012 American Institute of Physics.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

用不同浓度的外源抗坏血酸(ASA)对BY-2烟草悬浮细胞进行处理,测定了细胞中可溶性蛋白质含量、脂质过氧化产物丙二醛(MDA)含量、相对电解质渗透率、超氧化物歧化酶(SOD)活性、抗坏血酸(ASA)含量和还原型谷胱甘肽(GSH)含量等生理生化指标,从细胞脂质过氧化及抗氧化功能的角度探讨了不同浓度抗坏血酸对BY-2烟草悬浮细胞生长及衰老的影响。结果表明,当用2mmol.L-1 ASA处理时,能促进细胞分裂生长,增加可溶性蛋白产量,减少膜透性和MDA含量,维持SOD活性和ASA与GSH含量在较高水平,说明AS

Relevância:

10.00% 10.00%

Publicador:

Resumo:

When tobacco BY-2 cells were treated with 60 mu g/mL MC-RR for 5 d, time-dependent effects of MC-RR on the cells were observed. Morphological changes such as abnormal elongation, evident chromatin condensation and margination, fragmentation of nucleus and formation of apoptotic-like bodies suggest that 60 mu g/mL MC-RR induced rapid apoptosis in tobacco BY-2 cells. Moreover, there was a significant and rapid increase of ROS level before the loss of mitochondrial membrane potential (Delta Psi(m)) and the onset of cell apoptosis. Ascorbic acid (AsA), a major primary antioxidant, prevented the increase of ROS generation, blocked the decrease in Delta Psi(m) and subsequent cell apoptosis, indicating a critical role of ROS in serving as an important signaling molecule by causing a reduction of Delta Psi(m) and MC-RR-induced tobacco BY-2 cell apoptosis. In addition, a specific mitochondrial permeability transition pores (PTP) inhibitor, cyclosporin A (CsA), significantly blocked the MC-RR-induced ROS formation, loss of Delta Psi(m), as well as cell apoptosis when the cells were MC-RR stressed for 3 d, suggesting that PTP is involved in 60 mu g/mL MC-RR-induced tobacco cell apoptosis signalling process. Thus, we concluded that the mechanism of MC-RR-induced apoptosis signalling pathways in tobacco BY-2 cells involves not only the excess generation of ROS and oxidative stress, but also the opening of PTP inducing loss of mitochondrial membrane potential. (C) 2007 Published by Elsevier Ltd.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The growth direction of ZnO thin films grown by metal-organic chemical vapor deposition (MOCVD) is modulated by pretreatment of (001) SMO3 (STO) substrates. ZnO films show a-oriented smooth surface with epitaxial relationship of < 001 > ZnO//< 110 > STO on as-received SfO, and c-axis columnar growth with < 010 > ZnO//< 110 > STO on etched STO, respectively. The orientation alteration of ZnO films is supposed to be caused by the change of STO surface polarity. In addition, the c-ZnO films exhibit an enhanced photoluminescence (PL) intensity due to the improved crystal quality, while the blueshift of PL peak is attributed to the smaller tensile strain. These results show that high quality c-ZnO, which is essential for electronic and optoelectronic device applications, can be grown on (001) SfO by MOCVD. (C) 2008 Elsevier B.V. All rights reserved.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

To heteroepitaxally grow the crystalline cubic-GaN (c-GaN) film on the substrates with large lattice mismatch is basically important for fabricating the blue or ultraviolet laser diodes based on cubic group III nitride materials. We have obtained the crystalline c-GaN film and the heteroepitaxial interface between c-Gan and GaAs (001) substrate by the ECR Plasma-Assisted Metal Organic Chemical Vapor Deposition (PA-MOCVD) under low-pressure and low-temperature (similar to600degreesC) on a homemade ECR-plasma Semiconductor Processing Device (ESPD). In order to decrease the growth temperature, the ECR plasma source was adopted as the activated nitrogen source, therefore the working pressure of MOCVD was decreased down to the region less than 1 Pa. To eliminate the damages from energetic ions of current plasma source, a Multi-cusp cavity,coupling ECR Plasma source (MEP) was selected to use in our experiment. To decrease the strain and dislocations induced from the large lattice mismatch between c-GaN and GaAs substrate, the plasma pretreatment procedure i.e., the initial growth technique was investigated The experiment arrangements, the characteristics of plasma and the growth procedure, the characteristics on-GaN film and interface between c-GaN and GaAs(001), and the roles of ECR plasma are described in this contribution.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The electronic state of a two-dimensional electron system (2DES) in the presence of a perpendicular uniform magnetic field and a lateral superlattice (LS) is investigated theoretically. A comparative study is made between a LS induced by a spatial electrostatic potential modulation (referred to as a PMLS) and that induced by a spatial magnetic-field modulation (referred ro asa MMLS). By utilizing a finite-temperature self-consistent Hartree-Fock approximation scheme; the dependence of the electronic state on different system parameters (e.g., the modulation period, the modulation strength, the effective electron-electron interaction strength, the averaged electron density, and the system temperature) is studied in detail. The inclusion of exchange effect is found to bring qualitative changes to the electronic state of a PMLS, leading generally to a nonuniform spin splitting, and consequently the behavior of the electronic state becomes similar to that of a MMLS. The Landau-level coupling is taken into account, and is found to introduce some interesting features not observed before. It is also found that, even in the regime of intermediate modulation strength, the density dependence of the spin splitting of energy levels, either for a PMLS or a MMLS, can be qualitatively understood within the picture of a 2DES in a perpendicular magnetic field with the modulation viewed as a perturbation. [S0163-1829(97)02248-0].

Relevância:

10.00% 10.00%

Publicador:

Resumo:

An automatic step adjustment (ASA) method for average power analysis (APA) technique used in fiber amplifiers is proposed in this paper for the first time. In comparison with the traditional APA technique, the proposed method has suggested two unique merits such as a higher order accuracy and an ASA mechanism, so that it can significantly shorten the computing time and improve the solution accuracy. A test example demonstrates that, by comparing to the APA technique, the proposed method increases the computing speed by more than a hundredfold under the same errors. By computing the model equations of erbium-doped fiber amplifiers, the numerical results show that our method can improve the solution accuracy by over two orders of magnitude at the same amplifying section number. The proposed method has the capacity to rapidly and effectively compute the model equations of fiber Raman amplifiers and semiconductor lasers. (c) 2006 Optical Society of America

Relevância:

10.00% 10.00%

Publicador:

Resumo:

在植物生长箱通过种子萌发试验,从种子发芽进程、发芽率和吸水量等方面研究了水分和低温胁迫对红豆草种子萌发的影响。用10%,15%,20%,25%,30%的聚乙二醇(PEG)溶液和5℃左右低温预处理红豆草种子,结果表明,不同浓度的聚乙二醇和5℃左右低温预处理可以缩短种子的平均发芽时间,提高发芽率;比较发现,聚乙二醇浓度30%和低温处理时间4 d时可促进红豆草种子的萌发。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

HF etching followed by relatively low temperature (almost-equal-to 600-degrees-C) pretreatment is shown to provide a suitable substrate for the heteroepitaxial growth of GaAs on Si(100) by CBE using TEGa and AsH3 as sources. Rutherford backscattering (RBS), photoluminescence (PL), transmission electron microscopy (TEM), and Raman measurements show the low-defect nature of the GaAs epilayer.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

本文以开顶箱法分别控制CO2、O3浓度,在CO2、O3浓度升高及其二者相互作用条件下,分析沈阳城市森林主要树种油松、银杏活性氧水平,抗氧化系统活性以及膜脂过氧化程度动态变化,揭示城市油松、银杏抗氧化系统对全球气候变化的响应规律。 1. 在短期(60天)内CO2浓度倍增(700µmol mol-1)使油松、银杏超氧自由基(O2-.) 产生速率与过氧化氢(H2O2)含量减少,而抗坏血酸(ASA)含量与超氧化物歧化酶(SOD)、抗坏血酸过氧化物酶(APX)、单脱氢抗坏血酸还原酶(MDAR)、脱氢抗坏血酸还原酶(GR)活性升高,丙二醛(MDA)含量下降。与对照相比,大多数测定显示出显著差别。植株抗氧化能力增强,对活性氧清除能力提高。但长期(70天以上)CO2浓度倍增处理则使试验结果发生逆转。 2. 高浓度O3(80nmol mol-1)使O2-. 产生速率提高,H2O2 含量增加,MDA含量也随之增加。ASA含量与SOD、APX及GR活性在高浓度臭氧熏蒸的前期升高,但随着臭氧暴露时间的延长ASA含量与保护酶活性均变得低于对照。因此,在高浓度臭氧熏蒸的前期(30天以内),抗氧化酶能够在一定程度上调节自身的活性适应环境变化。但连续的高浓度臭氧胁迫导致活性氧含量升高,抗氧化酶活性下降。在试验后期, 虽然肉眼可见的伤害尚未观察到,但丙二醛含量显著升高,膜脂过氧化程度加深,油松、银杏的抗氧化系统已经不能抵抗长期臭氧胁迫所带来的氧化伤害。 3. 高浓度O3熏蒸初期,经倍增浓度CO2预处理的油松、银杏O2-.产生速率与H2O2含量,SOD、APX、MDAR、GR活性与自然O3浓度条件下植株无显著差异,表明高浓度CO2预处理银杏、油松对O3的抵抗能力增强。但随着高O3曝露时间的延长,O2-.产生速率与H2O2含量增加,SOD、APX、MDAR与GR活性低于对照,而且(经高CO2预处理后移入自然CO2、O3浓度中的植株)之差异逐渐增大,在试验末期达到差异显著水平,表明高CO2诱导油松、银杏产生的对O3胁迫的高抗性是不稳定的。 4.高浓度O3预处理(50天)使油松、银杏的抗氧化系统活性下降,已如前述。将经高浓度O3预处理的油松、银杏分别置入倍增浓度CO2与自然CO2环境中,随后的20天高CO2处理使活性氧水平低于自然CO2环境,而抗氧化酶活性高于自然CO2环境。这表明倍增CO2浓度能有效的恢复高浓度O3处理对油松、银杏的氧化胁迫。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

随着工农业的快速发展,土壤重金属污染问题日益严重,在我国东北,大面积的蔬菜种植地受到Cd、Pb的污染。大白菜在东北地区一直得到广泛种植,然而,Cd、Pb单一及复合污染对这一地区大白菜的胁迫效应仍然缺乏系统的研究。本研究以辽宁省普遍种植的四种大白菜(抗病金春KB、东洋春夏DY、青绿王QL、强势QS)为对象,用发芽实验、砂培实验和盆栽实验,研究了Cd、Pb单一及复合胁迫下大白菜的生理生化变化。 在发芽阶段,Cd、Pb单一及复合胁迫下,重金属浓度与根长、芽长和生物量抑制率间呈极显著线性相关,根伸长对Cd、Pb的毒害最敏感。KB对Cd毒害的抗性最强,DY对Pb单一和Cd、Pb复合胁迫的抗性最强,而QS对Cd、Pb单一及复合胁迫的抗性最弱。Cd、Pb复合胁迫时,对根伸长、芽伸长和生物量抑制的联合作用类型都为相加作用。 砂培实验中,在Cd、Pb浓度较低时,4种大白菜超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性及丙二醛(MDA)、可溶性蛋白(SP)、脯氨酸(PRO)含量都不同程度提高,但是随Cd、Pb浓度的提高,各生理过程受到抑制。KB和QS中PRO的含量约是DY和QL中的2-3倍,高PRO累积量很可能是Cd、Pb耐性大白菜品种所具有的特点。 盆栽实验中,在各生长时期,抗氧化酶活性、抗坏血酸(AsA)和还原型谷胱甘肽(GSH),及可溶性糖和SP的含量随Cd、Pb浓度的提高先升高后下降。硝态氮的含量基本随Cd、Pb浓度的提高而上升。在整个实验期间,KB和QS中MDA都保持较低的水平,KB对Cd、Pb的耐性主要是由于其体内PRO及AsA、GSH等抗氧化剂的累积;而GSH和可溶性糖对QS的Cd、Pb耐性起重要作用。QL和DY中MDA的含量要高于KB和QS,它们体内的抗氧化酶活性,及PRO、AsA和GSH含量在某个生长时期会达到较高的水平,但是与KB和QS相比,这些变化并不稳定,所以比KB和QS对Cd、Pb的耐性要弱。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

采用开顶箱法模拟大气O3和CO2浓度升高(80 nmol•mol-1,700 μmol•mol-1),对银杏(Ginkgo biloba)和油松(Pinus tabulaeformis)幼树进行了连续两个生长季的熏蒸试验,研究了银杏叶片和油松针叶活性氧产生清除系统的生理变化过程,从活性氧代谢生理机制上揭示其抗性变化规律,为研究城市森林对全球变化的响应与反馈机制提供重要的理论基础。 得出如下结论: 1. 高浓度O3显著增加了银杏叶片ASA含量和抗氧化酶(SOD、APX)活性,增强了活性氧清除能力;但这种抗氧化能力的提高不足以消除高O3带来的氧化逆境,H2O2和MDA含量显著高于对照处理。与银杏相比,高浓度O3在试验初期诱导油松针叶SOD和APX酶活性升高,增强了活性氧清除能力;随着处理时间的延长ASA被耗竭,H2O2过量积累显著地抑制了抗氧化酶活性,加剧了氧化伤害。银杏和油松结果的差异表明,银杏对80 nmol•mol-1浓度的O3具有更高的抗性,而油松针叶活性氧代谢等生理过程受其影响更大。 2. 高浓度CO2对银杏叶片活性氧代谢无显著性影响。然而,高浓度CO2减缓了油松针叶活性氧的产生,抗氧化酶活性呈降低的趋势;但针叶内ASA含量显著高于对照处理,这说明高浓度CO2促进了油松针叶ASA合成,或者是减少了ASA的消耗。在试验处理后期,针叶内H2O2含量和MDA含量显著低于对照处理。 3. 高浓度O3和高浓度CO2复合处理中,高浓度CO2缓解了高浓度O3对银杏叶片和油松针叶造成的氧化胁迫,但其生理机制不同:银杏叶片ASA含量以及抗氧化酶活性普遍低于高浓度O3单因素处理而高于对照处理,并且叶片H2O2含量和膜质过氧化产物MDA含量显著低于高浓度O3单因素处理,这说明高浓度CO2通过减少活性氧的产生来缓解高浓度O3所致的活性氧积累以及膜质过氧化伤害。与银杏不同的是,高浓度CO2使油松针叶内ASA含量显著高于高浓度O3处理,增强了活性氧清除能力,减轻了活性氧对抗氧化酶活性的抑制作用,有效的控制了ROS的产生与清除之间的平衡,缓解了高O3带来的氧化伤害。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

为了探讨远紫外辐射对植物的损伤机理和紫杉的濒杉机制,本文就远紫外辐射对紫杉幼苗针叶膜脂过氧化及内源保护物质的影响进行了模拟研究,初步得到如下结果:UV-C 辐射紫杉针叶离体叶绿体可使膜脂过氧化产物丙二醛(MDA)含量增加,类胡萝卜素含量和光系统II(PS II)电子传递少性下降。UV-BC 辐射紫杉幼苗针叶可使叶绿体超氧离子自由基(O~-_2),单线态氧(~O_2),针叶有机自由基产额和H_2O_2含量有不同程度增加。针叶MDA,组织自动氧化速率及质膜相对透性也随辐射时间进程面增加。UV-BC处理初期超氧化物歧化酶(SOD),过氧化氢酶(CAT)活性及谷胱甘肽(GSH)含量均被诱导增高,21d后SOD活性开始下降,而GSH 含量和CAT活性始终高于对照。维生素C(ASA),类胡萝卜素(Car),叶绿素(chl),PS II 电子传递活性在处理期间始终呈下降趋势,其中ASA下降最明显。可溶性蛋白21d前变化不大,之后开始下降。外源活性氧清除剂苯甲酸钠和抗坏血酸对针叶膜脂过氧化有抑制作用;甲基紫精和DDC 对针叶膜脂过氧化有促进效果。根据上述结果推测,紫杉的UV-BC伤害可能是由于活性氧产生过剩和清除系统水平下降,而引起的膜脂过氧化损伤。