Speckle reduction by selective spatial-domain mask in digital holography

An improved method of using a selective spatial-domain mask to reduce speckle noise in digital holography is proposed.The sub-holograms are obtained from the original hologram filtered by the binary masks including a shifting aperture for being reconstructed. Normally, the speckle patterns of these sub-reconstructed images are different. The speckle intensity of the final reconstructed image is suppressed by averaging the favorable sub-reconstructed images which are selected based on the most optimal pixel intensity sub-range in the sub-holograms. Compared with the conventional spatial-domain mask method, the proposed method not only reduces the speckle noise more effectively with fewer sub-reconstructed images,but also reduces the redundant information used in the reconstruction process.     

薄壁铸造和退火工艺对LPCN3.55Co0.75Mn0.4Al0.3贮氢合金电化学性能的影响

研究了不同铸锭厚度(1～10mm)对薄壁铸造的铸态和退火态LPCN3.55Co0.75Mn0.4Al0.3-一种新型贮氢合金电化学性能的影响。结果发现：铸态LPCNi3．55Co0.75Mn0.4Al0.3合金的0．2C放电容量随着合金锭厚度的增加有增大的趋势。10mm厚铸态合金的活化性能优于其它厚度的合金，且在1C的放电容量和循环稳定性比在其它厚度高。主要原因应归结为该厚度合金具有更大的晶胞体积和更小的晶格应力。退火态3mm LPCNi3.55Co0.75Mn0.4Al0.3合金的综合电化学性能比铸态更优异，6mm合金的循环稳定性和3～6mm合金的活化性能得到改善。主要原因应归结为晶格应力的极大释放以及Mn等元素偏析的改善。     

退火处理对快淬贮氢合金显微组织及电化学性能的影响

研究了退火处理对快淬贮氢合金电化学性能的影响。分析并讨论了退火处理的影响机制。快淬贮氢合金经退火处理后，P-C-T平台更为平坦，活化性能得到改善，最大放电容量和循环稳定性提高。通过XRD，SEM，DTA分析发现，退火处理后合金单胞体积有所增大，内应力降低，合金成分趋于均匀，从而使合金的电化学性能得到改善。加热过程中，合金在温度高于696℃发生再结晶。     

薄壁铸造和退火工艺对LPCNi3.55Co0.75Mn0.4Al0.3贮氢合金电化学性能的影响

研究了不同铸锭厚度(1～10mm)对薄壁铸造的铸态和退火态LPCNi3．55Co0.75Mn0.4Al0.3贮氢合金电化学性能的影响。结果发现：铸态LPCNi3．55Co0.75Mn0.4Al0.3合金的0．2C放电容量随着合金锭厚度的增加有增大的趋势。10mm厚铸态合金的活化性能优于其它厚度的合金，且在1C的放电容量和循环稳定性比在其它厚度的高。主要原因应归结为该厚度合金具有更大的晶胞体积和更小的晶格应力。退火态3mm LPCNi3．55Co0.75Mn0.4Al0.3合金的综合电化学性能比铸态更优异，6mm合金的循环稳定性和3～6mm合金的活化性能得到改善。主要原因应归结为晶格应力的极大释放以及Mn等元素偏析的改善。     

洋葱核仁的超微结构与rDNA复制位置

本文通过常规电子显微镜观察看到洋葱核仁是由纤维中心(FC)、纤维部分(F)和颗粒区(G)构成。FC是电子透明区,其内部有集缩或松散的染色质。F是围绕FC的环状结构部分,由密集的纤维构成,电子密度很高。用~3H-尿嘧啶核苷标记的电子显微镜放射自显影观察表明,它是rRNA合成的部位。颗粒区位于F外侧,由直径约25—30nm的颗粒组成。用~3H-胸腺嘧啶脱氧核苷标记的电子显微镜放射自显影观察表明,银粒大多分布在核仁边缘的颗粒区和核仁伴随染色质,在FC和F以及核仁内部颗粒区也有银粒出现,但频率很低。根据银粒分布频率和银粒范围的大小,推测rDNA复制的位置主要在核仁周边颗粒区和核仁伴随染色质,但在FC也有一些DNA区段开始复制,然后向核仁周边转移。     

一种金属有机框架纳米材料的制备及其染料吸附性能研究——推荐一个研究型综合化学实验

介绍一个从合成、表征到性能研究的完整研究型综合实验。合成路线巧妙,制备出了文献报道的尺寸最小的纳米金属有机框架。引入纳米材料研究基本表征手段和吸附动力学研究,通过实验教学展示材料研究方法,拓展学生知识面。通过对实验条件的设计,激发学生探索精神、培养学生创新意识、训练学生化学思维。     

ULTRASTRUCTURE OF THE NUCLEOLUS AND REPLICATION SITES OF RIBOSOMAL DNA IN Allium cepa

Our conventional EM observations indicate that the nucleolus of Allium cepa is composedof the fibrillar centre (FC), fibrillar component (F) and granular region (G). FC is an elec-tron-lucid zone which contains condensed or loosened chromatin. F is a circular, highly elec-tron-dense component which surrounds FC and consists of compact fibrils. EM autoradiographic(EM ARG) studies with ~3H- UdR reveal that the synthesis of ribosomal RNA (rRNA) takesplace in F. G is situated around F and composed of granules about 25 to 30 nm in diameter.EM ARG studies with ~3H- TdR demonstrate that silver grains are predominantly located in Gof the nucleolar periphery and the region of the nucleolus-associated chromatin. In addition,~3H- TdR labels are also present, but with a much lower frequency, in FC. F and G of the nu-cleolar interior. According to the distribution and sphere of silver grains in different compo-nents of the nucleolus, we suggest that the replication sites of ribosomal DNA (rDNA) aremainly located in     

LaFeO3电极材料的制备和电化学性能

利用硬脂酸燃烧法制备了具有正交结构的LaFeO3粉末, 研究了作为Ni/MH电池的负极材料的电化学性能. 研究结果表明: LaFeO3具有充放电可逆电化学容量, 其放电容量随实验温度升高而增大, 随放电电流增大而减小; 在充放电温度为298, 313, 333和353 K条件下, 经20次循环后, XRD显示LaFeO3仍然保持钙钛矿结构, 容量分别保持在49, 110, 310和490 mAh•g－1左右, 显示了良好的循环稳定性. 计算所得的交换电流密度和离子扩散系数随温度升高而增大, 与放电容量的变化规律一致.