Si被注入Gd后的磁性及其整流特性的研究

采用离子束技术,在n型硅基片中注入稀土元素钆,制备了磁性-非磁性p-n结.磁性层Gd_xSi_(1-x)表现出优良的磁学性能,高居里温度,高原子磁矩(利用RKKY模型可以得到解释),低矫顽力,并保持着半导体的属性,磁性-非磁性p-n结具有整流特性,但没有观察到明显的磁电阻效应.

THEORETICAL AND EXPERIMENTAL STUDY OF POLARIZATION CHARACTERISTICS OF POLARIZATION MAINTAINING FIBER BASED ON WAVELENGTH-SWEEPING MODULATION

We analyze theoretically the polarization characteristics of polarization maintaining fiber and study the basic measurement principles of beat length and polarization extinction ratio of this kind of optical fiber. According, to the dependence of the phase difference between two orthogonally polarized modes (denoted Os HE(11)(x) and HE(11)(y)) transmitted in the polarization maintaining fiber on the light wavelength, we propose the wavelength-sweeping modulation method to measure the beat length and the model birefringence. Based on this technique, the hew length and polarization extinction ratio of the PANDA polarization maintaining fibers (PMFs) (provided by Yangtze Optical Fiber and Cable Company, Wuhan, China) were investigated in detail. Experimental results show good consistent with the theoretical ones. We find that this method shows high measurement precision with the advantages of clear measurement principle and easy to operate. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1466-1469, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25244

X-ray spectra induced by slow highly charged Arq+ ions in collision with Nb surface

The X-ray spectra of Nb surface induced by Arq+ (q = 16,17) ions with the energy range from 10 to 20 keV/q were studied by the optical spectrum technology. The experimental results indicate that the multi-electron excitation occurred as a highly charged Ar16+ ion was neutralized below the metal surface. The K shell electron of Ar16+ was excited and then de-excited cascadly to emit K X-ray. The intensity of the X-ray emitted from K shell of the hollow Ar atom decreased with the increase of projectile kinetic energy. The intensity of the X-ray emitted from L shell of the target atom Nb increased with the increase of projectile kinetic energy. The X-ray yield of Ar17+ is three magnitude orders larger than that of Ar16+.

长白山次生林演替过程中土壤动物群落的变化

通过对长白山白河局不同林龄的次生林土壤动物的组成进行比较 ,探讨了土壤动物群落随森林采伐更新演替的变化以及演替阶段 (增长期、过渡期和稳定期 ) .研究表明 ,不同类群土壤动物的演变趋势是腐食类群数量相对较多 ,其变化趋势接近植被的变化规律 ,均是经过上升、下降 ,最后达到稳定 ;植食类群演替前期在整个群落中所占比例较高 ,随着演替年代的增加 ,比例呈下降的趋势 ;捕食类群经过 10 0年左右的演替 ,数量明显增加 ;从昆虫类群组成来看 ,林龄较短者 ,未稳定的类群数较多 ,林龄较长者 ,未稳定的类群较少 .

大兴安岭呼中林区火烧迹地粗木质残体特征

对大兴安岭呼中林区不同年份火烧迹地的粗木质残体特征进行了研究.结果表明:呼中林区火烧迹地粗木质残体贮量在24.87～180.98m3.hm-2,其中倒木和枯立木分别为6.03～93.91m3.hm-2和15.29～138.37m3.hm-2,且不同年份火烧迹地之间差异显著;倒木、枯立木所占比例分别为24.26%～86.00%和14.01%～75.4%,且不同年份火烧迹地之间差异显著;倒木和枯立木的优势径级分别为2.50～20cm和1.50～15m,优势长度分别为2.50～15cm和5～20m;随着火烧迹地的恢复,粗木质残体贮量的动态变化不明显.粗木质残体特征与火前林分条件和火烧强度密切相关.

脱落酸对UV-C胁迫下小麦幼苗光合特性及抗氧化酶活性的影响

研究了UV-C辐射下短期和长期脱落酸(ABA)处理对小麦幼苗CO2同化作用、羧化效率、光合CO2响应以及抗氧化酶活性等的影响.结果表明,在无UV-C辐射情况下,短期和长期ABA处理能提高光合速率,比对照增加14·69%和20·46%,降低气孔导度,比对照降低14·74%和17·31%,但对胞间CO2浓度和羧化效率影响不大.当受到UV-C辐射时,光合速率、羧化效率、气孔导度和胞间CO2浓度逐渐降低.长期ABA处理变化最小,其次为ABA短期处理,对照降低最大.ABA处理能够提高小麦光合对CO2的响应,UV-C辐射抑制光合对CO2的响应.ABA处理能够提高小麦抗氧化酶(CAT、SOD、POD)活性而降低MDA含量.在UV-C辐射下,CAT活性先升高随后降低,在辐射处理1h时活性达最大值,ABA处理的SOD和POD活性先升高后降低,且ABA长期处理比短期处理增加明显,对照则逐渐降低.ABA处理可能通过提高小麦CO2同化作用和抗氧化酶活性增强对UV-C胁迫的抗性,且ABA长期处理比短期处理效果更明显.