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991.
An examination of partition data for trace metals (Cd, Cr, Cu, Hg, Ni, Pb, Zn) from a number of independent studies conducted in a highly contaminated, organic-rich estuary (Mersey, UK) indicates an increase in the sediment-water distribution coefficient, KD, with increasing salinity for all metals with the excepton of Cd. This behavior is not consistent with inorganic speciation calculations or empirical modeling studies in other estuaries, which predict an inverse relationship between KD and salinity due to competitive adsorption and complexation with seawater ions. The data are, however, well-defined by an empirical model based on the salting out of neutral organic chemicals and yield salting constants in the range 0.7-2.0 L mol(-1). It is suggested that trace metals are complexed by and, subsequently, neutralize organic ligands, and that the resulting neutral assemblages are salted out, possibly via electrostriction. Examination of sorption date from other environments suggests that the effect may be more general in highly contaminated or organic-rich estuaries, and that a specific pool of relatively large, but undefined ligands, is mainly responsible. 相似文献
992.
Measurements of soot properties by means of laser-induced incandescence (LII) and combined scattering-extinction were performed in well-characterized premixed ethylene-air flames. In particular, the possibility of using LII as a tool for quantitative particle sizing was investigated. Particle sizes were evaluated from the temporal decay of the LII signal combined with heat balance modeling of laser-heated particles, and these sizes were compared with the particle sizes deduced from scattering-extinction measurements based on isotropic sphere theory. The correspondence was good early in the soot-formation process but less good at later stages, possibly because aggregation to clusters began to occur. A critical analysis has been made of how uncertainties in different parameters, both experimental and in the model, affect the evaluated particle sizes for LII. A sensitivity analysis of the LII model identified the ambient-flame temperature as a major source of uncertainty in the evaluated particle size, a conclusion that was supported by an analysis based on temporal LII profiles. 相似文献
993.
Beno?t Geneviève; Fortin Lucy; Lemelin Sophie; Laplante Louis; Thomas Jacques; Everett James 《Canadian Metallurgical Quarterly》1992,46(1):41
Studied the relationship between clinical psychomotor retardation and selective attention among patients with depression. Human Ss: 21 male and female Canadian adults (mean age 38 yrs) (major depressive disorders). 35 normal male and female Canadian adults (mean age 32 yrs) (comparison group). Ss completed a depression rating scale to assess degree of psychomotor retardation and a computerized version of the Stroop Color and Word Test to assess selective attention. Interactions between the 2 measures were analyzed, and intergroup differences were determined. Tests used: The Hamilton Rating Scale for Depression. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
994.
J. K. Richard Weber Dennis R. Merkley Collin D. Anderson Paul C. Nordine Chandra S. Ray Delbert E. Day 《Journal of the American Ceramic Society》1993,76(8):2139-2141
Glass formation from melts of 44 CaO 56Ga2 O3 (mol%) was investigated under containerless conditions obtained by acoustically stabilized aerodynamic levitation in combination with laser beam heating. The critical cooling rate for glass formation was Rc <100°C/s, much less than values reported in the literature ( Rc =550o ±120o C/s and ca 350o C/s) for pendant drops of this composition attached to Pt-Rh thermocouples. High values of Rc in pendant drop experiments were confirmed for the specimens used in this work. 相似文献
995.
A second form of compounds CuxVS2 is described here. As in Cu0.75VS2 (1) the structure of Cu0.65VS2 is related to the CdI2-type. In Cu0.75VS2, Cu atoms are ordered in tetrahedral sites between the CdI2-type subunits, whereas in the Cu0.65VS2, Cu atoms are partially disordered and occupy 4 different sites. Both structures differ from one another in vanadium atoms arrangements: In Cu0.75VS2, V-atoms form triangular clusters while in Cu0.65VS2 they form zigzag chains perpendicular to the hexagonal axis. The physical properties show a metallic type behaviour. Resistivity decreases with temperature with low 300 K/4.2 K ratio according to a disordered nature of the compound. Magnetic susceptibility shows a Pauli paramagnetism with an additionnal Curie-Weiss term due to a relatively large amount of paramagnetic impureties (0,9 % V3+ atoms). The observed low temperature localisation of the 3d electrons in Cu0.75VS2 disappears in the case of Cu0.65VS2. 相似文献
996.
Groebbens Adelbert Colle Didier Maesschalck Sophie De Lievens Ilse Pickavet Mario Demeester Piet Tran Lan Steenhaut Kris Nowé Ann 《Photonic Network Communications》2003,6(3):191-206
Multi-protocol lambda switching (MPS) has recently been applied in the optical network control plane to provide fast lightpath provisioning. As an increasing amount of traffic is carried in optical transport networks (OTNs), single network failures can affect a vast amount of traffic, making lightpath protection crucial. Therefore, shared backup tree (BT) lightpath protection is a promising paradigm in MPS networks due to its ability of fast recovery and its efficiency in consumed resources. A shared BT is used to protect a group of working lightpaths towards the same destination. From the working lightpaths in such a group, only one affected lightpath at a time can be recovered using the BT. The main problem is how to group and route the working paths (WPs) and how to route the BTs, in such a way that the capacity resources used by the WPs and the BTs are minimized. In Part One of this study (presented in this paper), we propose three approaches to cope with this problem. The first approach is a purely integer linear programming (ILP) based method. The second one is a combination of ILP and a heuristic technique. The last one is a purely heuristic approach. In this paper, these approaches are theoretically compared. In Part Two [1] of this study, several simulations are carried out in order to compare these approaches in terms of performance and computing effort. The experimental results are in line with the theoretical expectations. 相似文献
997.
Laberge-Nadeau C Maag U Bellavance F Lapierre SD Desjardins D Messier S Saïdi A 《Accident; analysis and prevention》2003,35(5):649-660
In light of the rapidly increasing development of the cell phone market, the use of such equipment while driving raises the question of whether it is associated with an increased accident risk; and if so, what is its magnitude. This research is an epidemiological study on two large cohorts, namely users and non-users of cell phones, with the objective of verifying whether an association exists between cell phone use and road crashes, separating those with injuries.The Société de l'Assurance Automobile du Québec (SAAQ) mailed a questionnaire and letter of consent to 175000 licence holders for passenger vehicles. The questionnaire asked about exposure to risk, driving habits, opinions about activities likely to be detrimental to driving and accidents within the last 24 months. For cell phone users, questions pertaining to the use of the telephone were added. We received 36078 completed questionnaires, with a signed letter of consent. Four wireless phone companies provided the files on cell phone activity, and the SAAQ the files for 4 years of drivers' records and police reports. The three data sources were merged using an anonymized identification number. The statistical methods include logistic-normal regression models to estimate the strength of the links between the explanatory variables and crashes.The relative risk of all accidents and of accidents with injuries is higher for users of cell phones than for non-users. The relative risks (RR) for injury collisions and also for all collisions is 38% higher for men and women cell phone users. These risks diminish to 1.1 for men and 1.2 for women if other variables, such as the kilometres driven and driving habits are incorporated into the models. Similar results hold for several sub-groups. The most significant finding is a dose-response relationship between the frequency of cell phone use, and crash risks. The adjusted relative risks for heavy users are at least two compared to those making minimal use of cell phones; the latter show similar collision rates as do the non-users. 相似文献
998.
Goldner LS Fasolka MJ Nougier S Nguyen HP Bryant GW Hwang J Weston KD Beers KL Urbas A Thomas EL 《Applied optics》2003,42(19):3864-3881
We present measurements of the local diattenuation and retardance of thin-film specimens by using techniques that combine near-field scanning optical microscopy (NSOM) and a novel polarization-modulation (PM) polarimetry utilizing Fourier analysis of the detected intensity signal. Generally, quantitative near-field polarimetry is hampered by the optical anisotropy of NSOM probes. For example, widely used aluminum-coated pulled-fiber aperture probes typically exhibit a diattenuation near 10%. Our analysis of aperture diattenuation demonstrates that the usual techniques for nulling a PM polarimeter result in a nonzero residual probe retardance in the presence of a diattenuating tip. However, we show that both diattenuation and retardance of the sample can be determined if the corresponding tip properties are explicitly measured and accounted for in the data. In addition, in thin films (<100 nm thick), where the sample retardance and diattenuation are often small, we show how to determine these polarimetric quantities without requiring alignment of the fast and diattenuating axes, which is a more general case than has been previously discussed. We demonstrate our techniques by using two types of polymer-film specimens: ultrahigh molecular weight block copolymers (recently noted for their photonic activity) and isotactic polystyrene spherulites. Finally, we discuss how changes in the tip diattenuation during data collection can limit the accuracy of near-field polarimetry and what steps can be taken to improve these techniques. 相似文献
999.
Cieplik MK Carbonell JP Muñoz C Baker S Krüger S Liljelind P Marklund S Louw R 《Environmental science & technology》2003,37(15):3323-3331
Iron ore sintering is an important source of "dioxins", polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). This paper reports on attempts to identify materials, conditions, and mechanisms responsible for PCDD/F formation (i) by investigating salient properties of ores (viz., with respect to oxidation, condensation, and chlorination of model organics) and (ii) by mimicking the industrial process on a microscale with real-life materials. Principles of Design of Experiments (DOE) are employed. The reactivities of iron ores differ greatly. Limonite/goethite "soft" ore is a very active oxidation catalyst (e.g., for benzene and phenol), a property that may be useful in cleaning up crude sintering process offgases, whereas hematite/magnetite "hard" ore is not. The latter, however strongly promotes condensation of phenol to dibenzofuran. A newly built lab-microscale sintering facility could satisfactorily imitate the large-scale process, in part or as a whole. Results obtained with realistic feed mixtures point at dioxin formation in the sinter bed at levels significant enough to explain a major part of the outputs observed in the real-life process. With approximately 8 ppm (wt) of chloride added as NaCl, the PCDD/F output doubled, but with the same proportion of chlorine administered as C2Cl4, the dioxin output was over 2 orders of magnitude larger. The use of process reverts, etc. containing chlorinated organics should therefore be avoided. PCDD/F congener patterns are also reported and compared with those observed in practice. 相似文献
1000.
Sophie Monge Andr Mas Amina Hamzaoui Camille M. Kassis Joseph M. Desimone Franois Schu 《应用聚合物科学杂志》2003,87(11):1794-1802
Plasma polymerization of allylamine, acrylic acid, and an allylamine/acrylic acid mixture on Silastic® silicone rubber led to a strong increase in the silicone rubber's hydrophilicity and surface energy. Analysis of the deposited layer by X‐ray photoelectron spectroscopy with 20° and 70° takeoff angles showed segregation of the atoms according to the depth and the incorporation of amino groups, oxygenated groups, and both. The endothelialization of untreated and treated samples was evaluated by the seeding and growth of aorta epithelial cells from pigs in cellular adherence (%), doubling time (in hours), and confluent density (104 cells/cm2). The best results were obtained with the allylamine/acrylic acid mixture treatment, which brought a biocompatibility to Silastic® similar to classic tissue culture on polystyrene plates. The interpretation was based on the presence of NH/CO2? microareas in the deposited layer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1794–1802, 2003 相似文献