The Kondo effect in an artificial quantum dot molecule

Double quantum dots provide an ideal model system for studying interactions between localized impurity spins. We report on the transport properties of a series-coupled double quantum dot as electrons are added one by one onto the dots. When the many-body molecular states are formed, we observe a splitting of the Kondo resonance peak in the differential conductance. This splitting reflects the energy difference between the bonding and antibonding states formed by the coherent superposition of the Kondo states of each dot. The occurrence of the Kondo resonance and its magnetic field dependence agree with a simple interpretation of the spin status of a double quantum dot.     

The Kondo effect in the presence of ferromagnetism

We measured Kondo-assisted tunneling via C60 molecules in contact with ferromagnetic nickel electrodes. Kondo correlations persisted despite the presence of ferromagnetism, but the Kondo peak in the differential conductance was split by an amount that decreased (even to zero) as the moments in the two electrodes were turned from parallel to antiparallel alignment. The splitting is too large to be explained by a local magnetic field. However, the voltage, temperature, and magnetic field dependence of the signals agree with predictions for an exchange splitting of the Kondo resonance. The Kondo effect leads to negative values of magnetoresistance, with magnitudes much larger than the Julliere estimate.     

离子束的生物效应及应用

概述了离子束的产生,作用于生物组织的原初过程以及在诱变育种和一物工程上的应用等,并对离子束生物效应研究中存在的问题发展方向进行了分析。     

Quantitative measurement of short-range chemical bonding forces

We report direct force measurements of the formation of a chemical bond. The experiments were performed using a low-temperature atomic force microscope, a silicon tip, and a silicon (111) 7x7 surface. The measured site-dependent attractive short-range force, which attains a maximum value of 2.1 nanonewtons, is in good agreement with first-principles calculations of an incipient covalent bond in an analogous model system. The resolution was sufficient to distinguish differences in the interaction potential between inequivalent adatoms, demonstrating the ability of atomic force microscopy to provide quantitative, atomic-scale information on surface chemical reactivity.     

Potassium ion: is the bulk of intracellular K+ adsorbed?

When a major portion of the intracellular K(+) in frog muscle is reversibly replaced by Na(+), the extra Na(+) gained by the cells does not show the nuclear magnetic resonance signal that free Na(+) does. The data contradict the membrane theory but are in accord with the concept that the bulk of intracellular K(+) is adsorbed.     

Atmospheric sulfur: its effect on the chemical weathering of New England

The present acidity and sulfur content of the upland streams of New England can be accounted for on the basis of the rainout and washout of sulfuric acid from the atmosphere. In spite of this excess acid flux over the New England landscape, the rate of cationic denudation of upland watersheds is relatively low.     

Atomic-scale chemical imaging of composition and bonding by aberration-corrected microscopy

Using a fifth-order aberration-corrected scanning transmission electron microscope, which provides a factor of 100 increase in signal over an uncorrected instrument, we demonstrated two-dimensional elemental and valence-sensitive imaging at atomic resolution by means of electron energy-loss spectroscopy, with acquisition times of well under a minute (for a 4096-pixel image). Applying this method to the study of a La(0.7)Sr(0.3)MnO3/SrTiO3 multilayer, we found an asymmetry between the chemical intermixing on the manganese-titanium and lanthanum-strontium sublattices. The measured changes in the titanium bonding as the local environment changed allowed us to distinguish chemical interdiffusion from imaging artifacts.     

草莓根系自毒物质降解菌的筛选及降解效果研究

对羟基苯甲酸是导致草莓连作障碍的自毒物质,快速降解连作土壤中积累的对羟基苯甲酸,有利于有效控制连作草莓根部病害的发生。本研究筛选出对羟基苯甲酸降解菌菌株B3512,利用盆栽试验研究了其对对羟基苯甲酸的降解效果。结果表明菌株B3512在48 h内的对羟基苯甲酸降解率达95.7%。在含有对羟基苯甲酸的基质中接种B3512,能通过降解对羟基苯甲酸,增强根系活力、降低根系细胞膜渗透性,明显提高组培苗根长、单株叶面积、株高和植株干重等生长指标,说明菌株B3512能有效缓解对羟基苯甲酸的自毒作用。     

Magnetic clusters on single-walled carbon nanotubes: the Kondo effect in a one-dimensional host

Single-walled carbon nanotubes are ideal systems for investigating fundamental properties and applications of one-dimensional electronic systems. The interaction of magnetic impurities with electrons confined in one dimension has been studied by spatially resolving the local electronic density of states of small cobalt clusters on metallic single-walled nanotubes with a low-temperature scanning tunneling microscope. Spectroscopic measurements performed on and near these clusters exhibit a narrow peak near the Fermi level that has been identified as a Kondo resonance. Using the scanning tunneling microscope to fabricate ultrasmall magnetic nanostructures consisting of small cobalt clusters on short nanotube pieces, spectroscopic studies of this quantum box structure exhibited features characteristic of the bulk Kondo resonance, but also new features due to finite size.     

Lizard reflectivity change and its effect on light transmission through body wall

Light transmission through the body wall of living, color-labile desert iguanas (Dipsosaurus dorsalis) was measured by spectrophotometry. In the dark phase, the body wall's absorption of ultraviolet light and visible light was approximately twice that of the body wall in the light phase. The shorter wavelengths of ultraviolet could penetrate the body wall in the light phase but not in the dark phase. The intensity and wavelengths of light which could penetrate the body wall without pigments are potentially mutagenic when judged by bacterial standards.     

中华微刺盲蝽对棉蚜的控制作用

探讨了中华微刺盲蝽Campylomma chinensis对不同密度的棉蚜Aphis gassypii的捕食功能反应,经拟合表明功能反应均呈Holling Ⅱ型．对弃置地上小型灌木水茄Salanum torvum上中华微刺盲蝽和棉蚜的种群动态的调查表明,当水茄上其他小型节肢动物的数量稀少时,中华微刺盲蝽自然种群的大小、迁入、迁出与水茄上棉蚜的数量有密切的关系,在自然状态下此盲蝽可以有效地控制棉蚜的种群数量．     

蛇床子素防治南瓜病毒病的效果

蛇床子素水乳剂对南瓜病毒病预防效果甚微。1％蛇床子素水乳剂50μg/m1可有效防治南瓜病毒病,防效为70．79％,显著高于对照药剂6％病毒克星51．69％的防效。     

利益机制下种子生产风险及防范措施

围绕市场化条件下形成的生产企业与农户之间的利益关系,讨论了在该利益机制下的生产风险及防范措施。     

烟草和茶叶上炭疽病的发生规律及其防治

介绍了烟草、茶叶两种叶用植物炭疽病的症状和发生规律,总结了烟草和茶叶发生该病害的防治技术。     

Ozone destruction by chlorine: the impracticality of mitigation through ion chemistry

The feasibility of using negative ion chemistry to mitigate stratospheric ozone depletion by chlorine-containing radicals, as proposed recently, is addressed here. Previous in situ measurements of the negative ion composition of the stratosphere show that chlorine-containing ions represent only a small fraction of total ions. New measurements of the negative ion temporal evolution in the stratosphere show that the fractional abundance of chlorine-containing ions is never greater than 1 percent at any time in the ion evolution. On the basis of these and other arguments, using negative ion chemistry to mitigate ozone depletion by chlorine-containing compounds is not feasible.     

10％烯啶虫胺水剂防治棉花蚜虫田间药效试验

10%烯啶虫胺水剂是一种有效防治刺吸式害虫的新型杀虫剂.近几年在中国南方应用较多,北方特别是棉花生产区还未见使用的报道.试验通过田间施药的方式证明,在中国北方棉区10%烯啶虫胺水剂10～30g/hm2用量范围内,对棉花蚜虫7天的防治效果在92.96%～96.91%之间,对靶标作物棉花安全.可在生产上大面积推广使用.