Immersion Deposition of Pt Nanoparticles on Porous Silicon for Methanol Oxidation

Porous silicon (PS) was chosen as the substrate for supporting the Pt particles because of great surface area, good conductivity and stability. Pt nanoparticles have been successfully prepared on the substrate by immersion deposition, which is convenient. The component and morphological properties of the films have been investigated by means of X‐ray diffraction (XRD), energy dispersive X‐ray spectroscopy (EDX) and scanning electron microscopy (SEM), which shows that the Pt particles have small size and big specific surface. Cyclic voltammetry (CV) research showed that the Pt nanoparticles had novel catalytic activity for methanol when the immersion deposition time was past 24 min.     

Abietane Diterpenoids from the Hairy Roots of Salvia corrugata

Salvia corrugata Vahl. is an interesting source of abietane and abeo-abietane compounds that showed antibacterial, antitumor, and cytotoxic activities. The aim of the study was to obtain transformed roots of S. corrugata and to evaluate the production of terpenoids in comparison with in vivo root production. Hairy roots were initiated from leaf explants by infection with ATCC 15834 Agrobacterium rhizogenes onto hormone-free Murashige and Skoog (MS) solid medium. Transformation was confirmed by polymerase chain reaction analysis of rolC and virC1 genes. The biomass production was obtained in hormone-free liquid MS medium using Temporary Immersion System bioreactor RITA^®. The chromatographic separation of the methanolic extract of the untransformed roots afforded horminone, ferruginol, 7-O-acetylhorminone and 7-O-methylhorminone. Agastol and ferruginol were isolated and quantified from the hairy roots. The amount of these metabolites indicated that the hairy roots of S. corrugata can be considered a source of these compounds.     

FDTD方法对固体浸没透镜的光场分析

采用二维时域有限差分(2D-FDTD)方法研究了高斯光束通过固体浸没透镜(SIL)的光场分布特性.模拟结果表明,SIL的折射率越大,底面出射的光斑越小,但随离底面距离的增大光束很快展宽;当只有入射角大于全反射临界角、具有高空间频率的部分高斯光束聚焦到SIL底面金属膜中心的微孔时,针对不同直径的微孔,模拟了出射光场的分布,发现微孔直径在某一特定值时,出射光斑半径在距SIL底面近半个波长范围内无明显改变,该结果为增大SIL和存储介质间距的方案提供了理论依据.     

不同冻结对大黄鱼冻藏期间品质的影响

为研究冻结速率对大黄鱼冻藏期间品质的影响, 采用冰箱慢速冻结、酒精浸渍速冻、液氮浸渍速冻方法处理新鲜大黄鱼, 以pH值、汁液损失率、TVB-N值、盐溶性蛋白提取率、质构等指标研究鱼肉冻藏过程中的理化特性变化, 并通过扫描电镜研究其组织微结构的变化. 结果显示, 随着冻藏时间的延长, 慢冻组和酒精速冻组样品pH值先下降后上升, 液氮速冻组样品的pH值趋于平缓; 3组样品TVB-N值均逐渐上升, 但液氮速冻组的TVB-N值较小, 且上升速率最缓慢, 冻藏210d时, 慢冻组、酒精速冻组、液氮速冻组的TVB-N值分别达到27.79, 25.024, 21.57 mg?dg-1; 盐溶性蛋白提取率和硬度、弹性、胶黏性、凝聚性、回复性降低, 液氮速冻组的值下降程度较小; 扫描电镜观察发现贮藏过程中大黄鱼的肌肉纤维损伤程度逐渐增大, 而液氮浸渍速冻对大黄鱼肌肉纤维的损伤最小. 与慢速冻结样品相比, 虽然速冻组样品(液氮速冻组、酒精速冻组)有较大的汁液损失率, 但其更有利于延缓大黄鱼蛋白质变性和降解, 保持样品质构特性, 且液氮浸渍速冻优于酒精浸渍速冻. 本研究可为进一步改进水产品的速冻技术提供参考依据.     

关于极小曲面度量特征的一个证明

通过构造某个乘积流形中的一个子流形Q及Q上外微分式环中某个理想的一组生成元,利用[4]的主要工作,在这里证明了理想是d-封闭的。从而确定了一个3维积分子流形S.并由此给出了空间形式中一类极小曲面的度量特征的一个独特的构造性的证明。其中关于丛映射的证明对一般情形也适用,     

用两区π-相位滤波器改善超半球形固体浸没透镜显微系统的成像特性

利用矢量衍射理论分析了π-相位滤波器在超半球形固体浸没透镜显微系统中的超分辨特性.结果显示,光斑的增益、Strehl率和边瓣强度随相位区域边界呈现出同步的、只一个周期的振荡性变化.从辐射场和速逝场的角度解释了这种变化的原因.对于近场显微,速逝场起决定性作用.π-相位滤波器的相位区域边界角大于临界角时,才能产生较大的超分辨作用.滤波器边界参量等于0.743（对应的角度大于临界角）的π-相位滤波器,可以使系统分辨率提高16%.     

用于原子力与光子扫描隧道组合显微镜的浸油显微物镜

双功能原子力与光子扫描隧道显微镜（AF／PSTM）用π对称双光束照明方法来消除假象。为改进现有的AF／PSTM系统,提出新的照明系统方案,并设计了新方案中需要的高数值孔径的浸油显微物镜。根据具体的物镜系统参数要求,选择合适的初始结构,用ZEMAX光学设计软件对物镜进行设计、优化和像质评价,设计结果显示浸油物镜的数值孔径大约1.54,可以很好地满足照明系统的需要。     

On the Haefliger-Hirsch-Wu invariants for embeddings and immersions

We prove beyond the metastable dimension the PL cases of the classical theorems due to Haefliger, Harris, Hirsch and Weber on the deleted product criteria for embeddings and immersions. The isotopy and regular homotopy versions of the above theorems are also improved. We show by examples that they cannot be improved further. These results have many interesting corollaries, e.g.? 1) Any closed homologically 2-connected smooth 7-manifold smoothly embeds in .? 2) If and then the set of PL embeddings up to PL isotopy is in 1-1 correspondence with?. Received: July 6, 2000     

Relation between immersion enthalpy and the acidity of clay pillared minerals

Total acidity for a series of modified clays obtained from a natural vermiculite is determined through temperature programmed desorption (TPD) using ammonia as probe molecule. Results obtained for the acidity range from 15.1 to 68.5 meq/100 g. Immersion enthalpies of the clays in benzene, water and aqueous solutions of NH₃ 0.058 M and NaHCO₃ 0.053 M are determined. The results obtained show that immersion enthalpies in benzene and water are between −6.26 and −25.6 J g⁻¹ and −2.10 and 5.55 J g⁻¹, respectively and are smaller than the values obtained for the immersion enthalpies in the solutions. Immersion enthalpy values in NH₃ solution are greater than the obtained using NaHCO₃. Linear relations between the total acidity of the clays and the immersion enthalpies in the basic solutions are determined. An interaction factor using ammonia is calculated since the relation between the immersion enthalpy in ammonia solution and in water and it may be deduced that the relation with the total acidity is of second order tendency between them.     

Isometric immersions from the hyperbolic space

In this paper, we transform the problem of determining isometric immersions from into into that of solving a degenerate Monge-Ampère equation on the unit disc. By presenting one family of special solutions to the equation, we obtain a great many noncongruent examples of such isometric immersions with or without umbilic set.