二维伊辛模型自旋状态图样的蒙特卡罗模拟   总被引：1，自引：0，他引：1  

刘策军  郑有因 《华南农业大学学报》1995,16(4):101-105

以Ｍｅｔｒｏｐｏｌｉｓ蒙特卡罗模拟方法考察了在２０×２０正方格子上的二维伊辛自旋模型，得到了该模型不同温度下自旋状态的图样，符合统计力学分析。  相似文献   

离子束辐射水合DNA的电子自旋共振波谱研究     

宋风忠  朱晓蕊  谷令彪 《安徽农业科学》2011,39(15):8831+8839-8831,8839

从作用机制、化学径迹结构模型、低能离子、多重损伤位点等方面,阐述离子束辐射水合DNA的电子自旋共振波谱研究。  相似文献   

不同辐照剂量和氛围下 60 Co-γ射线辐照蚕丝的电子自旋共振分析     

林海涛  周小柳  唐忠锋  陈有双  黄武军  唐芳 《蚕业科学》2009,35(3)

在不同辐照剂量、不同辐照氛围下用60Co-γ射线辐照蚕丝纤维,通过电子自旋共振波谱(ESR)检测蚕丝纤维产生的自由基浓度,分析不同辐照条件对蚕丝纤维性能的影响。结果表明:在0~250 kGy剂量范围内,随辐照剂量的增加,60Co-γ射线辐照蚕丝产生的自由基浓度增加,但辐照剂量过大会使蚕丝纤维发生裂解而影响其性能,故辐照剂量应不超过50 kGy;与同剂量空气下辐照蚕丝纤维产生的自由基相比,在真空下辐照蚕丝纤维产生的自由基浓度增加,且主要为氨基己酸自由基,但随着辐照剂量的增加,真空和空气下辐照蚕丝纤维产生的自由基浓度差异变小。  相似文献   

Magnetic resonance spectroscopy of wheat proteins: a magic-angle-spinning ¹³C nuclear magnetic resonance and an electron spin resonance spin label study     

Johannes H.E. Moonen  Marcus A. Hemminga  Aris Graveland 《Journal of Cereal Science》1985,3(4):319-327

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Contrast-enhanced fluid-attenuated inversion recovery vs. contrast-enhanced spin echo T1-weighted brain imaging     

Cristian Falzone  Federica Rossi  Maurizio Calistri  Massimo Tranquillo  Massimo Baroni 《Veterinary radiology & ultrasound》2008,49(4):333-338

In humans, contrast-enhanced fluid-attenuated inversion recovery (FLAIR) imaging plays an important role in detecting brain disease. The aim of this study was to define the clinical utility of contrast-enhanced FLAIR imaging by comparing the results with those with contrast-enhanced spin echo T1-weighted images (SE T1WI) in animals with different brain disorders. Forty-one dogs and five cats with a clinical suspicion of brain disease and 30 normal animals (25 dogs and five cats) were evaluated using a 0.2 T permanent magnet. Before contrast medium injection, spin echo T1-weighted, SE T1WI, and FLAIR sequences were acquired in three planes. SE T1WI and FLAIR images were also acquired after gadolinium injection. Sensitivity in detecting the number, location, margin, and enhancement pattern and rate were evaluated. No lesions were found in a normal animal. In affected animals, 48 lesions in 34 patients were detected in contrast-enhanced SE T1WI whereas 81 lesions in 44 patients were detected in contrast-enhanced FLAIR images. There was no difference in the characteristics of the margins or enhancement pattern of the detected lesions. The objective enhancement rate, the mean value between lesion-to-white matter ratio and lesion-to-gray matter ratio, although representing an overlap of T1 and T2 effects and not pure contrast medium shortening of T1 relaxation, was better in contrast-enhanced FLAIR images. These results suggest a superiority of contrast-enhanced FLAIR images as compared with contrast-enhanced SE T1WI in detecting enhancing brain lesions.  相似文献   

紫外光下木荷的ESR和XPS分析     

张文辉  陈琼 《福建林学院学报》2012,32(3):274-279

分析紫外光照射下木荷产生自由基的规律和表面化学组成及结构的变化。利用电子自旋共振波谱(ESR)和X射线光电子能谱(XPS)技术分别测量紫外光辐照后木荷颗粒的自由基波谱和X射线光电子能谱。结果表明,木荷自由基的光谱分裂因子g=2.003 3,自由基的强度随着辐照时间按Y=1-e-biPt规律增加,紫外光辐照60 min后,木荷表面氧、碳原子比稍有增加,C—C、C—H和C—O含量增加,C=O含量减少,—O—C=O含量增加为原来的2倍左右,说明木荷表面生成了一些含氧官能团或碳的氧化态增高。  相似文献   

茶叶中自由基的研究   总被引：8，自引：0，他引：8  

刘国根  罗泽民  邱冠周  李娟 《湖南农业大学学报(自然科学版)》1999,25(4):290-292

利用ＥＳＲ波谱技术对不同茶类成茶和苦丁茶,七叶参茶的自由基进行了较系统的研究,结果表明：茶叶中含有大量的稳定的自由基,不同成茶自由基含量因茶类不同而有较大差异,各茶类自由基含量高低依次为黑茶、青茶、红茶、黄茶,绿茶、白茶。  相似文献   

VALUE OF A SINGLE-SHOT TURBO SPIN-ECHO PULSE SEQUENCE FOR ASSESSING THE ARCHITECTURE OF THE SUBARACHNOID SPACE AND THE CONSTITUTIVE NATURE OF CEREBROSPINAL FLUID     

ANTHONY PEASE  STACEY SULLIVAN  NATASHA OLBY  HEATHER GALANO  SOPHIA CERDA-GONZALEZ  IAN D. ROBERTSON  PATRICK GAVIN  DONALD THRALL 《Veterinary radiology & ultrasound》2006,47(3):254-259

Three case history reports are presented to illustrate the value of the single-shot turbo spin-echo pulse sequence for assessment of the subarachnoid space. The use of the single-shot turbo spin-echo pulse sequence, which is a heavily T2-weighted sequence, allows for a rapid, noninvasive evaluation of the subarachnoid space by using the high signal from cerebrospinal fluid. This sequence can be completed in seconds rather than the several minutes required for a T2-fast spin-echo sequence. Unlike the standard T2-fast spin-echo sequence, a single-shot turbo spin-echo pulse sequence also provides qualitative information about the protein and the cellular content of the cerebrospinal fluid, such as in patients with inflammatory debris or hemorrhage in the cerebrospinal fluid. Although the resolution of the single-shot turbo spin-echo pulse sequence images is relatively poor compared with more conventional sequences, the qualitative information about the subarachnoid space and cerebrospinal fluid and the rapid acquisition time, make it a useful sequence to include in standard protocols of spinal magnetic resonance imaging.  相似文献   

拖拉机与旋耕机连接保护器的设计     

王维忠  陈长海  刘恩宏 《农机化研究》2007,(5):131-132

为了保证在农业生产中拖拉机与其挂接机具的正常工作,减少养机户因机具、机车损坏造成的经济损失,在春、秋两季短暂的农业生产中取得更大的效益,设计了安全离合器.为此,主要介绍了其工作原理、主要参数的确定及其试验情况,为保护器的设计生产提供了理论依据.  相似文献   

Effects of Metal Ions and EDTA on Free Radical Reaction Intermediates of Laccase-catalyzed Oxidation of Wood Powder from Szemao Pine     

ZHOUGuanwu  DUANXinfang** CAOYongjian CHENYongsheng CAO Yuanlin** .Division of Wood Protection  Research Institute of Wood Industry Chinese Academy ofForestry  Beijing  P.R.China .Centerfor Brain  CognitiveSciences  Institute of Biophysics Chinese AcademyofSciences  Beijing  P.R. China 《中国林业科技(英文版)》2006,5(2):28-32

INTRODUCTIONLaccase (EC 1.10.3.2) is multicopper oxidase catalyzing oxidation of various phenolic compounds, aromatic amines, and even certain inorganic compounds by a one-electron transfer mechanism. The electron withdrawn from the substrates is transferred via four copper atoms to molecular oxygen (Messerschmidt 1997). Laccase is very common in nature, especially in plants and fungi (Gianfreda et al. 1999). Fungal laccases participate in plant pathogenesis, pigment production and ligni…  相似文献