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1.
Widespread use of nanoscale zinc oxide (nZnO) in various fields causes subsurface environment contamination. Even though the
transport of dissolved zinc ions in subsurface environments such as soils and sediments has been widely studied, the transport
mechanism of nZnO in such environments is poorly understood. In addition, nZnO is often combined with stabilizers or dispersing
agents to prevent its aggregation in products. The purpose of this study is to determine the influence of pH on the transport
properties of pristine nZnO and carboxymethyl cellulose (CMC) stabilized nZnO (CMC–nZnO) suspensions in silica sand packed
column under saturated flow conditions. Transport data were collected at different pHs (pHs: 3, 7, 9, and 11) under 1 mL/min
flow rate conditions in a 1.1 cm diameter column. It is found that the transport trends of pristine nZnO and CMC–nZnO were
different. For pristine nZnO, mobility of total Zn reached a minimum around its point of zero charge (pH 8.9). Whereas in
the case of CMC–nZnO, the mobility of total Zn decreased as the pH of the solution pH increased from 3 to 11. ZnO and Zn ion
mixture were separated using diafiltration membrane. It showed that most of the nZnO and CMC–nZnO exists as Zn ion at pH 3
before and after eluting from the sand packed column whereas at pH 11, they exist as particles. This study shows the strong
influence of pH and stabilizing agents on nZnO transport. These factors should be considered during subsurface transport of
nZnO. 相似文献
2.
Souhail Tebib Jean-Jacques Bourguignon Camille-Georges Wermuth 《Journal of computer-aided molecular design》1987,1(2):153-170
Summary Applied to seven potent benzodiazepine-receptor ligands belonging to chemically different classes, the active analog approach allowed the stepwise identification of the pharmacophoric pattern associated with the recognition by the benzodiazepine receptor.A unique pharmacophore model was derived which involves six critical zones: (a) a -electron rich aromatic (PAR) zone; (b) two electron-rich zones 1 and 2 placed at 5.0 and 4.5 Å respectively from the reference centroid in the PAR zone; (c) a freely rotating aromatic ring (FRA) region; (d) an out-of-plane region (OPR), strongly associated with agonist properties; and (e) an additional hydrophobic region (AHR).The model accommodates all presently known ligands of the benzodiazepine receptor, identifies sensitivity to steric hindrance close to the 1 zone, accounts forR andS differential affinities and distinguishes requirements for agonist versus non-agonist activity profiles.Abbreviations Pyrazoloquinolines
CGS (2-phenyl-2,5-dihydro pyrazolo [4,3-c] quinoline-3 (3H)-one)
- Cinnolinones
CIN (2-(4-methoxyphenyl)-benzo [h] 3-cinnolinone
- Triazolophthalazines
TZPH (3-(4-methoxyphenyl)-6 pyrrolidinotriazolo [4,3-a] phthalazine
- Cyclopyrrolones
RP 27267, CLO ([6-(5-chloro-2-pyridyl)-6,7-dihydro-7 oxo-5H-pyrrolo [3,4-b]pyrazin-5-yl] 4-methyl-l-piperazine carboxylate)
- Phenylquinolines
PK (phenyl-2 (morpholinocarbonyl methyl oxy)-4 quinoline
- -Carbolines
BCC (3-carboethoxy--carboline)
- Benzodiazepines: Diazepam
DZ (7-chloro-1,3-dihydro-1-methyl-5 phenyl-2H-1,4-benzodiazepin-2-one) 相似文献
3.
Turbidimetric method (TM), ion chromatography (IC) and inductively coupled plasma atomic emission spectrometry (ICP-AES) with and without acid digestion have been compared and validated for the determination of sulfate in mining wastewater. Analytical methods were chosen to compare the performance of a portable field turbidimetric instrument and to validate the underlying assumption utilized in conversion of total sulfur to sulfate during ICP-AES analysis. Accuracy and precision of analytical techniques were compared to one another using control and field samples collected from a mine site using the Bonferroni multiple comparison test. Effects of sample dilution, filter pore size and acidification on sulfate quantification were also studied. The results showed that IC and ICP-AES with and without acid digestion provided excellent recoveries in the case of control samples (within 90-110%). These analytical methods also showed lower relative standard deviation for both control and field samples. On the other hand, performance of the turbidimetric method was severely affected by sample dilution and acidification, and also revealed poor sulfate recoveries for control samples ranging from 0 to 83.5%. Analysis of variance (ANOVA) was used to evaluate the response (sulfate concentration) obtained from factorial design. Analytical method had significant effect (P < 0.0001) on the sulfate quantification. The interaction between determination method and sample dilution was more significant than other two-way interactions. 相似文献
4.
Methodology and Computing in Applied Probability - This paper investigate the approximation of invariant distributions for countable space Markov chains using truncations of the transition matrix.... 相似文献
5.
We study the classical optimal investment and consumption problem of Merton in a discrete time model with frictions. Market friction causes the investor to lose wealth due to trading. This loss is modeled through a nonlinear penalty function of the portfolio adjustment. The classical transaction cost and the liquidity models are included in this abstract formulation. The investor maximizes her utility derived from consumption and the final portfolio position. The utility is modeled as the expected value of the discounted sum of the utilities from each step. At the final time, the stock positions are liquidated and a utility is obtained from the resulting cash value. The controls are the investment and the consumption decisions at each time. The utility function is maximized over all controls that keep the after liquidation value of the portfolio non-negative. A dynamic programming principle is proved and the value function is characterized as its unique solution with appropriate initial data. Optimal investment and consumption strategies are constructed as well. 相似文献
6.
Nanosized TiO2 particles (nTiO2) are usually coated with an Al(OH)3 layer when used in sunscreen to shield against the harmful effects of free radicals that are generated when these particles
are exposed to UV radiation. Therefore, it is vital to insure the structural stability of these particles in the environment
where the protective layer may be damaged and adverse health and environmental effects can occur. This study utilized X-ray
analysis (SEM–EDS) to provide a qualitative and semi-quantitative assessment of the chemical and physical characteristics
of Al(OH)3-coated original and damaged nTiO2 particles (used in sunscreen lotion formulations) in the presence of both swimming pool and seawater. Also, by utilizing
statistical tools, a distribution of Al/Ti (%) on the particle surface was determined and evaluated. It was found that 45 min
of treatment with swimming pool and seawater significantly induced the redistribution of Al/Ti (%), which changed the surface
characteristics of particles and, therefore, may have induced undesired photo-activity and the consequent formation of free
radicals. 相似文献
7.
Badredine?IssaadiEmail author Karim?Abbas Djamil?A?ssani 《Methodology and Computing in Applied Probability》2017,19(3):819-841
This paper investigates the M/M/s queueing model to predict an estimate for the proximity of the performance measures of queues with arrival processes that are slightly different from the Poisson process. Specifically, we use the strong stability method to obtain perturbation bounds on the effect of perturbing the arrival process in the M/M/s queue. Therefore, we build some algorithms based on strong stability method to predict stationary performance measures of the GI/M/s queue. Some numerical examples are sketched out to illustrate the accuracy of the proposed method. 相似文献
8.
Transport in Porous Media - Foam is to be used as a blocking agent for confining a pollutant source zone and avoid spreading in an aquifer. To this end, it is necessary to determine where injected... 相似文献
9.
Zakariae Amghouz Santiago García-Granda Badredine Souhail Fa-nian Shi 《Journal of solid state chemistry》2009,182(12):3365-3373
New polymeric yttrium-succinates, Y2(C4H4O4)3(H2O)4·6H2O and Y2(C4H4O4)3(H2O)2, have been synthesized, and their structures (solved by single crystal XRD) are compared with that of Y2(C4H4O4)3(H2O)2·H2O. Three compounds were obtained as single phases, and their thermal behaviour is described. 相似文献
10.
Souhail Dahmen Hassiba Ketata Mohamed Hédi Ben Ghozlen Bernard Hosten 《Ultrasonics》2010,50(4-5):502-507
A hybrid elastic wave method is applied to determine the anisotropic constants of Olive wood specimen considered as an orthotropic solid. The method is based on the measurements of the Lamb wave velocities as well as the bulk ultrasonic wave velocities. Electrostatic, air-coupled, ultrasonic transducers are used to generate and receive Lamb waves which are sensitive to material properties. The variation of phase velocity with frequency is measured for several modes propagating parallel and normal to the fiber direction along a thin Olivier wood plates. A numerical model based mainly on an optimization method is developed; it permits to recover seven out of nine elastic constants with an uncertainty of about 15%. The remaining two elastic constants are then obtained from bulk wave measurements. The experimental Lamb phase velocities are in good agreement with the calculated dispersion curves. The evaluation of Olive wood elastic properties has been performed in the low frequency range where the Lamb length wave is large in comparison with the heterogeneity extent. Within the interval errors, the obtained elastic tensor doesn’t reveal a large deviation from a uniaxial symmetry. 相似文献