Mechanisms of Photochemical Air Pollution

Selected aspects of the chemistry of photochemical air pollution is discussed and some important, unresolved problems dilineated. The reactive species considered include NO₂, O₃, O(³P), O(¹D), O₂(¹Δ_g), OH and HO₂. Both the kinetics and mechanicsms of the reactions constituting the major tropospheric sources and sinks of these species are treated where available. The application of this information in both computer and smog chamber simulations of photochemical smog is discussed.     

Recent results from the TCV tokamak

During the first two years of operation, the TCV tokamak has produced a large variety of plasma shapes and magnetic configurations, with 1.0B _tor1.46T,I _p800kA,k2.05, –0.71. A new shape control algorithm, based on a finite element reconstruction of the plasma current in real time, has been implemented. Vertical growth rates up to 1000s^–1 have been stabilized using the external coil system. Ohmic H-modes with Troyon factors ( _tor aB/I _p) up to two and densities up to 2.25×10²⁰m^–3, corresponding to the Greenwald limit, have been obtained in diverted discharges. Limiter H-modes with line averaged electron densities up to 1.7×10²⁰m^–3 have been obtained in elongated D-shaped plasmas with 360 kAI _P600 kA.Presented at 17^th Symposium Plasma Physics and Technology, Prague, June 13–16, 1995.This work was partly supported by the Fonds National Suisse de la Recherche Scientifique.     

Wavelength dependence of the I(52P12,32) branching ratio from ICN Ã state photolysis

Quantum yields for the production of I(5²P$\text{1}\text{2}$) atoms from the photolysis of ICN in the à state continuum are presented as a function of wavelength. Evidence is presented for the existence of at least three electronic states giving rise to the absorption spectra. Primary photophysical processes involved in the dissociation of ICN are discussed.     

膜流动电位测试中Ag-AgCl电极的制备及稳定性研究

膜的动电特性研究中,往往采用流动电位方法。该方法中,Ag-Ag Cl测试电极的质量是影响测试准确性的关键要素。本文采用正交试验设计和方差分析,着重考察电解法制备Ag-Ag Cl电极过程中,电流强度(I)、氯化时间(t)、电解质溶液浓度(CHCl)、电极来源(n)、烘烤温度(T)、活化电极溶液浓度(CKCl)等因素对Ag-Ag Cl电极稳定性的影响。得到Ag-Ag Cl电极的最优制备参数为:电流密度3.0m A/cm2,氯化时间50min,盐酸浓度0.1mol·L-1,烘烤温度120℃,活化电极溶液(KCl)浓度0.001mol·L-1;最显著影响因素为电极来源,显著影响因素为氯化时间和烘烤温度。对最优条件组合下制备的AgAg Cl电极,进行了稳定性实验,结果表明:制备的电极具有较好的稳定性,24h内电极电位漂移量小于0.10mv,7天内电极电位漂移量小于0.2mv;在聚偏氟乙烯中空纤维超滤膜流动电位测试中,流动电位与流动压差具有良好的线性和可重复性,回归曲线R20.99,变化规律符合Helmholtz-Smoluehowski公式,可以较好满足膜的流动电位测试要求。     

Evaluation of a simple plasma catecholamine extraction procedure prior to high-performance liquid chromatography and electrochemical detection

The modified extraction method for catecholamines described in this study is reproducible, simple, rapid, economical and relatively hazard-free. This method is based on the principle that plasma catecholamines are selectively adsorbed on acid-washed alumina at pH 8.6 and then eluted at a pH between 1.0 and 2.0. No statistically significant differences were obtained by using either 0.5 or 1.0 ml of plasma with 0.5 or 1.0 ml of Tris buffer. A 15-min mixing time during the adsorption and desorption steps was found to be practical, but any standardized time up to 1 h can be used. If the washing step was omitted, the catecholamines could not be eluted from the acid-washed alumina. To prevent dilution, the alumina had to be centrifuged and not aspirated to dryness after the washing step. An amount of 50 mg of WA-4 alumina was found to be the most practical in this study. Extracted or unextracted plasma as well as catecholamine standards were stable for four months at -20 degrees C.     

镁掺杂氧化铈整体式催化剂催化CO2和CH3OH直接合成碳酸二甲酯

采用共沉淀法成功地合成了不同Mg掺杂量的Ce_1-xMg_xO₂(x=0.05、0.10、0.15、0.20)固溶体催化材料,并运用透射电子显微镜(TEM)、X射线衍射(XRD)、氮气吸附-脱附测试、拉曼光谱、X射线光电子能谱(XPS)、CO₂程序升温脱附(CO₂-TPD)等技术对这些材料进行了表征。结果发现,通过调控CeO₂晶格中Mg的含量,可以调控所制备的Ce_1-xMg_xO₂催化材料的粒径、比表面积、表面缺陷等。其中Ce_0.90Mg_0.10O₂展现了最佳的表面性质,具有最小的平均粒径(约5.8 nm),最大的比表面积(约136 m2·g^-1)以及最高的表面氧含量(31.98%)。将Ce_1-xMg_xO₂催化材料涂覆在堇青石蜂窝陶瓷上制成整体催化剂,考察其对CO₂和CH₃OH直接合成碳酸二甲酯的催化性能。在140℃、2.4 MPa、反应2 h的条件下,Ce_0.90Mg_0.10O₂整体催化剂上碳酸二甲酯的收率高达20.21%,催化效果明显优于CeO₂和其余的Ce_1-xMg_xO₂(x=0.05、0.15、0.20)催化材料。     

Gauge-invariant localization of infinitely many gravitational energies from all possible auxiliary structures

The problem of finding a covariant expression for the distribution and conservation of gravitational energy–momentum dates to the 1910s. A suitably covariant infinite-component localization is displayed, reflecting Bergmann’s realization that there are infinitely many conserved gravitational energy–momenta. Initially use is made of a flat background metric (or rather, all of them) or connection, because the desired gauge invariance properties are obvious. Partial gauge-fixing then yields an appropriate covariant quantity without any background metric or connection; one version is the collection of pseudotensors of a given type, such as the Einstein pseudotensor, in every coordinate system. This solution to the gauge covariance problem is easily adapted to any pseudotensorial expression (Landau–Lifshitz, Goldberg, Papapetrou or the like) or to any tensorial expression built with a background metric or connection. Thus the specific functional form can be chosen on technical grounds such as relating to Noether’s theorem and yielding expected values of conserved quantities in certain contexts and then rendered covariant using the procedure described here. The application to angular momentum localization is straightforward. Traditional objections to pseudotensors are based largely on the false assumption that there is only one gravitational energy rather than infinitely many.     

Non-parametric Estimation for the M/G/∞ Queue

Given an M/G/ queue with input rate and service-time distribution G, we consider the problem of estimating and G from data on the queue-length process Q = (Q_t). Our motivation is to study departures of G from exponentiality, following recent work of Bingham and Dunham (1997, Ann. Inst. Statist. Math., 49, 667–679).