激光对uv-B辐射大青叶和板蓝根品质的影响

IEECAS SKLLQG

低剂量微波辐射对增强uv-B辐射损伤菘蓝幼苗抗氧化酶活性的影响

IEECAS SKLLQG

UV-B辐射增强对长白山五种藓类植物生长的影响

对生长在中国长白山的5种藓类植物——垂枝藓、拟垂枝藓、塔藓、星塔藓和高山金发藓分别以辐射强度为0.2(自然光照,对照)、3.0(紫外线中等辐射强度)和6.0kJ.m-2.d-1(高剂量辐射强度)的UV-B照射40d后,测定其株高、生物量及叶绿素含量.结果表明:中等和高强度的UV-B辐射使拟垂枝藓和塔藓的株高、生物量和叶绿素含量分别下降了32.3%、62.4%、81.3%和21.4%、59.4%、62.8%,其相对生长速率均为负值;高剂量UV-B辐射处理下垂枝藓的生物量稍有上升,而高山金发藓地下部分的生物量增加1倍,但叶绿素含量变化不明显.高山金发藓和垂枝藓抵抗UV-B辐射的能力较强,拟垂枝藓和塔藓对UV-B辐射较敏感.

UV-B增强对番茄的伤害及H_2O_2的防护作用

UVB辐射使番茄叶片的叶绿素a,叶绿素b及总叶绿素含量先升高后降低,同样使叶片的抗氧化酶过氧化氢酶(CAT)和过氧化物酶(POD)活性先升高随后降低,而使超氧化物歧化酶(SOD)活性升高,膜脂过氧化产物MDA的含量增加;中等剂量(5mmol·l-1)的H2O2预处理能提高叶绿素b的含量,明显提高抗氧化酶的活性,并延缓CAT活性的降低,抑制膜质过氧化产物MDA的产生.中等浓度H2O2预处理能提高番茄对UVB增强的抗性.

不同UV-C辐射时间对豌豆幼苗光合特性及抗氧化酶活性的影响

研究了不同UV-C辐射时间对豌豆幼苗光合特性及抗氧化酶活性的影响。结果表明,UV-C辐射增强使叶片光合速率减弱,气孔导度、胞间CO2浓度、蒸腾速率和羧化效率明显降低,CO2补偿点升高。随着UV-C辐射时间的延长,POD和CAT活性先升高随后降低,SOD活性、叶绿素含量则逐渐降低,但丙二醛含量逐渐增加。这说明UV-C辐射增强引起抗氧化酶活性降低,使膜脂过氧化,导致光合作用减弱。

Identifying the isolated transition metal ions/oxides in molecular sieves and on oxide supports by UV resonance Raman spectroscopy

Isolated transition metal ions/oxides in molecular sieves and on surfaces are a class of active sites for selective oxidation of hydrocarbons. Identifying the active sites and their coordination structure is vital to understanding their essential role played in catalysis and designing and synthesizing more active and selective catalysts. The isolated transition metal ions in the framework of molecular sieves (e.g., TS-1, Fe-ZSM-5, and V-MCM-41) or on the surface of oxides (e.g., MoO3/Al2O3 and TiO2/SiO2) were successfully identified by UV resonance Raman spectroscopy. The charge transfer transitions between the transition metal ions and the oxygen anions are excited by a UV laser and consequently the UV resonance Raman effect greatly enhances the Raman signals of the isolated transition metal ions. The local coordination of these ions in the rigid framework of molecular sieves or in the relatively flexible structure on the surface can also be differentiated by the shifts of the resonance Raman bands. The relative concentration of the isolated transition metal ion/oxides could be estimated by the intensity ratio of Raman bands. This study demonstrates that the UV resonance Raman spectroscopy is a general technique that can be widely applied to the in-situ characterization of catalyst synthesis and catalytic reactions. (C) 2003 Elsevier Science (USA). All rights reserved.

Phase transformation in the surface region of zirconia and doped zirconia detected by UV Raman spectroscopy

The phase evolution of yttrium oxide and lanthanum oxide doped zirconia (Y2O3-ZrO2 and La2O3-ZrO2, respectively) from their tetragonal to monoclinic phase has been studied using UV Raman spectroscopy, visible Raman spectroscopy and XRD. UV Raman spectroscopy is found to be more sensitive at the surface region while visible Raman spectroscopy and XRD mainly give the bulk information. For Y2O3-ZrO2 and La2O3-ZrO2, the transformation of the bulk phase from the tetragonal to the monoclinic is significantly retarded by the presence of yttrium oxide and lanthanum oxide. However, the tetragonal phase in the surface region is difficult to stabilize, particularly when the stabilizer's content is low. The phase in the surface region can be more effectively stabilized by lanthanum oxide than yttrium oxide even though zirconia seemed to provide more enrichment in the surface region of the La2O3-ZrO2 sample than the Y2O3-ZrO2 sample, based on XPS analysis. The surface structural tension and the enrichment of the ZrO2, component in the surface region of ZrO2-Y2O3 and ZrO2-La2O3 might be the reasons for the striking difference between the phase change in the surface region and the bulk. Accordingly, the stabilized tetragonal surface region can significantly prevent the phase transition from developing into the bulk when the stabilizer's content is high.