Correlations between ground and excited state spectra of a quantum Dot

The ground and excited state spectra of a semiconductor quantum dot with successive electron occupancy were studied with linear and nonlinear magnetoconductance measurements. A direct correlation was observed between the mth excited state of the N-electron system and the ground state of the (N + m)-electron system for m up to 4. The results are consistent with a single-particle picture in which a fixed spectrum of energy levels is successively filled, except for a notable absence of spin degeneracy. Further departures from the single-particle picture due to electron-electron interaction were also observed. Magnetoconductance fluctuations of ground states show anticrossings where wave function characteristics are exchanged between adjacent levels.     

The role of pisigma* excited states in the photodissociation of heteroaromatic molecules

High-resolution measurements of the kinetic energies of hydrogen atom fragments formed during ultraviolet photolysis of imidazole, pyrrole, and phenol in the gas phase confirm that N(O)-H bond fission is an important nonradiative decay process from their respective 1pisigma* excited states. The measurements also reveal that the respective cofragments (imidazolyl, pyrrolyl, and phenoxyl) are formed in very limited subsets of their available vibrational states. Identification of these product states yields uniquely detailed insights into the vibronic couplings involved in the photoinduced evolution from parent molecule to ultimate fragments.     

Quantum criticality: competing ground states in low dimensions

Small changes in an external parameter can often lead to dramatic qualitative changes in the lowest energy quantum mechanical ground state of a correlated electron system. In anisotropic crystals, such as the high-temperature superconductors where electron motion occurs primarily on a two-dimensional square lattice, the quantum critical point between two such lowest energy states has nontrivial emergent excitations that control the physics over a significant portion of the phase diagram. Nonzero temperature dynamic properties near quantum critical points are described, using simple theoretical models. Possible quantum phases and transitions in the two-dimensional electron gas on a square lattice are discussed.     

保护地莴苣霜霉病的发生与防治

描述了棚栽莴苣霜霉病的发病症状和特点，提出了防治方法。     

Dynamics of the pacific-north american plate boundary in the western united states

The vertically averaged deviatoric stress tensor field within the western United States was determined with topographic data, geoid data, recent global positioning system observations, and strain rate magnitudes and styles from Quaternary faults. Gravitational potential energy differences control the large fault-normal compression on the California coast. Deformation in the Basin and Range is driven, in part, by gravitational potential energy differences, but extension directions there are modified by plate interaction stresses. The California shear zone has relatively low vertically averaged viscosity of about 10(21) pascal.seconds, whereas the Basin and Range has a higher vertically averaged viscosity of 10(22) pascal.seconds.     

Interception of excited vibrational quantum states by O2 in atmospheric association reactions

Bimolecular reactions in Earth's atmosphere are generally assumed to proceed between reactants whose internal quantum states are fully thermally relaxed. Here, we highlight a dramatic role for vibrationally excited bimolecular reactants in the oxidation of acetylene. The reaction proceeds by preliminary adduct formation between the alkyne and OH radical, with subsequent O(2) addition. Using a detailed theoretical model, we show that the product-branching ratio is determined by the excited vibrational quantum-state distribution of the adduct at the moment it reacts with O(2). Experimentally, we found that under the simulated atmospheric conditions O(2) intercepts ~25% of the excited adducts before their vibrational quantum states have fully relaxed. Analogous interception of excited-state radicals by O(2) is likely common to a range of atmospheric reactions that proceed through peroxy complexes.     

Photochemical formation of hydrogen peroxide in surface and ground waters exposed to sunlight

A rapid increase in the concentration of hydrogen peroxide was observed when samples of natural surface and ground water from various locations in the United States were exposed to sunlight. The hydrogen peroxide is photochemically generated from organic constituents present in the water; humic materials are believed to be the primary agent producing the peroxide. Studies with superoxide dismutase suggest that the superoxide anion is the precursor of the peroxide.     

Strengite dissolution in flooded soils and sediments

Strengite (FePO(4) . 2H(2)O) undergoes partial dissolution under the reducing conditions existing in a flooded soil. The greatest release of phosphate and iron occurs under conditions of low oxidation-reduction potential in combination with low pH.     

愈风宁心分散片的制备及体外溶出度的研究

分散片(Dispersible tablets)又称水分散片(Water dispersible tablets),系指遇水可迅速崩解形成均匀黏性混悬液的片剂[1].分散片是近年来研究较多的一种新型口服制剂,该剂型最显著特点是不需用水送服,其服用方便,在口腔内遇到唾液便能够迅速溶解,给一些吞服功能不好、婴幼儿及儿童、取水不便的患者提供方便[2].     

Calcium and bromide contents of natural waters

The linear relation observed in a log Ca++ versus log Brplot for subsurface Cl- waters is attributed to ultrafiltration by shale of sea water and fresh water that have passed through sedimentary rocks since their formation. Reactions between these solutions and sedimentary minerals, particularly dolomitization, must have contributed additional Ca++ to solution.     

Carbonate dissolution and sedimentation on the mid-atlantic continental margin

The calcium carbonate content was determined for core tops from two transects on the upper slope to lower rise on the mid-Atlantic continental margin. Carbonate content in the sediment increases from approximately 5 percent (by weight) on the upper slope to more than 30 percent on the upper rise. A zone of low-carbonate content extends from 3000 to 4400 meters. Below 4400 meters, the percent carbonate increases. An examination of dissolution indices in these core tops indicates that the low-carbonate zone is associated with intense dissolution. Below 4400 meters, dissolution decreases and carbonate is well preserved. The decrease in dissolution occurs where the high-velocity core of the Western Boundary Undercurrent is first encountered.     

微波消解法测定水中的总磷含量探析

微波消解技术以其耗时短、样品用量少、消解完全等特点而受到化学界人士的高度重视。利用微波消解法测定水中的总磷含量效果良好。对GB11893— 89《钼酸铵光度法》中规定的消解方法与微波消解法的对比实验证明 ,后者比前者操作简便、省时、省力、省料、快捷 ,测定结果准确可靠。     

布地奈德混悬液联合沙丁胺醇、溴化异丙托品雾化吸入治疗儿童哮喘

目的：观察布地奈德混悬液联合沙丁胺醇、溴化异丙托品雾化吸入治疗哮喘的效果。方法：急诊哮喘患儿88例随机分为2组，布地奈德混悬液联合沙丁胺醇、溴化异丙托品雾化吸入组(A组)46例，沙丁胺醇、溴化异丙托品联合吸入组(B组)42例。2组均用单剂量空气压缩泵雾化吸入。记录吸药前后喘息、哮鸣音记分和呼气峰流速(PEF)的变化。结果：A组患儿喘息及哮鸣音记分别于吸药后90min开始低于B组，而PEF在吸药后90min开始高于B组。结论：布地奈德混悬液联合沙丁胺醇、溴化异丙托品雾化吸入治疗急性哮喘的效果优于沙丁胺醇联合溴化异丙托品吸入治疗。     

地面观测数据的维护及管理

2012年4月中国气象局对地面观测报文及传输方式进行了调整,调整后,基层台站地面气象观测业务也随之进行了大幅度的调整,其中变动最大的是增加了正点地面观测数据维护。文章以当前的业务调整及未来发展方向为着眼点,从地面管理角度出发,对基层台站在地面观测业务中观测数据的维护、录入规定、传输方式、重要天气报发报内容的变化等方面进行了归纳总结,并提出合理建议,以便更好地指导台站的测报业务。     

人工湿地外加碳源碳溶出及反硝化效果研究

为了解人工湿地中固体外加碳源的碳溶出规律及添加量对反硝化效果的影响,本研究选择竹子、木块和木本泥炭作为外加C源材料,在厌氧下测定3种材料的碳溶出量,同时应用于人工湿地中试试验,为人工湿地外加碳源的应用提供依据。结果表明:单位质量的试验材料C的溶出量是竹子木块木本泥炭,竹子、木块和木本泥炭的C溶出量均值分别达577、266和59mg/(kg·d);材料C溶出量随时间变化的回归曲线拟合度较高,溶出稳定。人工湿地中试试验中,添加62kg木块为外加碳源时的湿地系统对总氮和铵氮的去除率明显高于添加31kg木块的湿地系统。溶出试验中木块作为人工湿地反硝化脱氮的外加碳源材料促进了人工湿地对氮的去除。