Atomic-resolution electrochemistry with the atomic force microscope: copper deposition on gold

The atomic force microscope (AFM) was used to image an electrode surface at atomic resolution while the electrode was under potential control in a fluid electrolyte. A new level of subtlety was observed for each step of a complete electrochemical cycle that started with an Au(111) surface onto which bulk Cu was electrodeposited. The Cu was stripped down to an underpotential-deposited monolayer and finally returned to a bare Au(111) surface. The images revealed that the underpotential-deposited monolayer has different structures in different electrolytes. Specifically, for a perchloric acid electrolyte the Cu atoms are in a close-packed lattice with a spacing of 0.29 +/- 0.02 nanometer (nm). For a sulfate electrolyte they are in a more open lattice with a spacing of 0.49 +/- 0.02 nm. As the deposited Cu layer grew thicker, the Cu atoms converged to a (111)-oriented layer with a lattice spacing of 0.26 +/- 0.02 nm for both electrolytes. A terrace pattern was observed during dissolution of bulk Cu. Images were obtained of an atomically resolved Cu monolayer in one region and an atomically resolved Au substrate in another in which a 30 degrees rotation of the Cu monolayer lattice from the Au lattice is clearly visible.     

Diploid-Triploid Mosaicism: An Unusual Phenomenon in Side-Necked Turtles (Platemys platycephala)

Diploid and diploid-triploid mosaic individuals of Platemys platycephala were found in natural populations. In mosaic specimens, the blood, spleen, liver, and testis contained both diploid and triploid cells. The ratio of triploid to diploid cells was more variable among individuals than among somatic tissues within an individual. Only diploid cells underwent meiosis in males; haploid gametes were produced. There appears to be geographic variation for mosaicism in that only diploids were found in Bolivia, whereas diploids and diploid-triploid mosaics occured in Surinam.     

烤烟钾素和氯素含量及其比值与物理性状的关系分析

以我国烤烟南方烟区122份烟叶中部叶样品为基础,系统地分析了烟叶钾含量、氯含量、钾氯比与物理性状之间的关系。结果表明:各性状在供试材料间存在着广泛的变异。烟叶钾含量与叶长、叶面密度分别呈极显著正相关、负相关;烟叶氯含量与叶面密度呈显著正相关;烟叶钾氯比与叶长、叶厚分别呈极显著正相关、显著负相关。南方烟区烤烟中部叶烟叶钾含量与叶长、叶面密度的关系可分别用逆函数■=7.803-343.262/x、复合函数■=4.612×0.991x进行描述;烟叶氯含量与叶面密度的关系可用二次函数■=1.268-0.034x 0.000 3x2描述;烟叶钾氯比与叶长、叶厚的关系可分别用复合函数■=0.023×1.105x、二次函数■=94.408-1 355.208x 5 897.907x2进行描述;且均达到5%显著水平,表明曲线回归一般较简单线性回归分析更有效。烤烟中部叶钾含量、钾氯比随单叶重的增加而降低,随叶长的增长而增加明显;氯含量随单叶重的增加而升高,随叶长的增加而迅速下降,随叶厚的增加而增加;南方烟区烤烟叶宽为23.5 cm、叶面密度为85.31 g/m2是两个敏感阈值。     

探讨有机烟叶的生产和管理

概述了国内外有机烟叶的发展状况,并从品种筛选、基地选择、施肥、除草、病虫害防治、打顶、抹杈、调制、收购、包装、贮存和不适用烟叶处理方面探讨了有机烟叶的生产技术体系,从生产管理和质量管理2个方面探讨了有机烟叶的生产管理,并对有机烟叶的发展进行了展望。     

恩施与国外白肋烟中性致香成分含量的差异比较

为明确恩施白肋烟中性致香成分组分和含量及与国外白肋烟的异同,以恩施不同产区及美国、马拉维白肋烟样品为材料,采用气质联用仪对样品的中性致香成分含量进行分析测定,结果表明:恩施白肋烟中性致香成分总量及各组分含量在产地之间存在一定差异,其中香叶基丙酮、苯甲醛、糠醇等单一致香成分含量的变异较大。以巨豆三烯酮为代表的类胡萝卜素类降解产物含量以美国烟叶最高,恩施次之,马拉维最低;恩施白肋烟苯丙氨酸类、棕色化反应产物含量均高于美国和马拉维,而西柏三烯的主要降解产物茄酮则低于国外烟叶。聚类分析将供试样品分为3类,80%的恩施样点与美国同属一类,表明恩施白肋烟中性致香成分含量与美国具有较高的相似性。