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1.
Successive action of α-bromoesters and organometallics on hydroximates constitute a good way to obtain - 5,6 dihydro-1,4,2 dioxazines. 相似文献
2.
Mariem Nafti Radhouane Chakroun Chiraz Hannachi Bechir Hamrouni Habib Nouaïgui 《Analytical letters》2017,50(12):2012-2022
Hexavalent chromium Cr(VI) is a well-established carcinogen associated with lung, nasal, and sinus cancer. Cr(VI) threshold limit values in workroom air have been recently lowered. Consequently, the currently available analytical methods are insufficiently sensitive or high cost. In this paper, a simple, cost-effective, sensitive, and reproducible method using solid-phase extraction with electrothermal atomic absorption spectrometry for determination of hexavalent chromium in airborne samples is reported. The method validation included selectivity, linearity, accuracy, and precision. Interferences from other ions likely to be present in airborne samples, including trivalent chromium, were tested and selectivity was demonstrated. The detection and quantification limits were, respectively, as low as 0.1 and 0.4?µg?L?1. The linearity ranged from 0.5 to 50.0?µg?L?1, with a regression coefficients exceeding 0.998. The extraction recovery exceeded 98%. The developed method was successfully compared with a reference spectrophotometric method. The performances achieved were similar to ion chromatography and high-performance liquid chromatography approaches. The novel method was tested on airborne samples collected from the workplace. The method’s performance suggests that it may be an alternative to high-cost techniques for monitoring occupational exposure to hexavalent chromium. 相似文献
3.
Jean-Michel Ghidagli Ahmed Amine Mrabet 《Journal of Applied Analysis & Computation》2018,8(3):675-689
An alternative to the stiffened-gas equation of state is proposed that corrects for unphysical behavior, namely the returning of negative pressure values for densities lower than the reference density. The question of generalizing a given isentropic equation of state is first addressed. Then, a regularized stiffened-gas equation of state is derived, which is the main goal of this work. Finally, the use of the new equation of state is briefly illustrated for a classical computational fluid dynamics benchmark concerning the evaluation of liquid impact on a wall. 相似文献
4.
The main purpose of this article is to study the L
p
-boundedness of linear and bilinear multiplier operators for the Dunkl transform in the one dimensional case. 相似文献
5.
S. Bednarczyk R. Bechir P. Baclet 《Applied Physics A: Materials Science & Processing》1999,69(7):S495-S500
Targets for high-energy laser experiments are polymer or metal objects of small dimensions. These objects need high-precision processes (typical sizes of a few hundred micrometers with micrometer accuracy). In this paper, some targets for high-energy laser experiments obtained by picosecond Q-switched Nd:YAG laser and KrF excimer laser micro-machining are presented. All of the targets use an original process. Activities include cutting, drilling, and marking elements. A summary of targets made using laser processes will be presented. 相似文献
6.
Mrabet KE Poitevin M Vial J Pichon V Amarouche S Hervouet G Lalere B 《Journal of chromatography. A》2006,1134(1-2):151-161
Matrix reference materials (MRM) are essential tools for the validation of analytical protocols. Nowadays, there are no such materials for the determination of herbicides in water. Pesticides stored in acetonitrile and stored on solid phase extraction (SPE) cartridges previously percolated with a water sample spiked with triazines and phenylureas have proven to be good candidates for reference materials because of their satisfactory stability under appropriate temperature conditions. To evaluate the behaviors of these materials containing pesticides and to be analyzed by liquid chromatography, a collaborative study including 15 laboratories has been organized. Observed reproducibility on candidate materials after the removal of extreme results was 16.1% for the vials with pesticides in acetonitrile (at around 0.125 mg/L) directly analyzed, 29.2% for a water sample spiked with the pesticides (at around 0.5 microg/L) analyzed after preconcentration on a cartridge and 26.7% for the cartridges previously percolated with a water containing the pesticides (250 mL at around 0.5 microg/L for each pesticide) analyzed after elution. Such dispersion values are quite compatible with the requirement of a further certification for such materials. 相似文献
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8.
Hatem ElloumiMongi Stambouli Jean Jacques DamelincourtBrahim Mrabet 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,74(6):731-744
In this paper, we present the detail calculations of the indirect spectral irradiance E(λ) as a function of the spectral radiant flux Φt(λ) of a radiating source. This relation is used to predict the integrating cylinder irradiance for a given input radiant flux as a function of the geometrical parameters and reflectivity called “multiplier constant”. The radiation transfer within a cylindrical enclosure composed of three different surfaces, the inside circular surface and the two bases in the ends, has been examined. The configuration factor is introduced. Then all the configuration factors needed for our calculation have been given in analytical form. 相似文献
9.
Marwa Moumni Mohamed Bechir Allagui Kaies Mezrioui Hajer Ben Amara Gianfranco Romanazzi 《Molecules (Basel, Switzerland)》2021,26(8)
Essential oils are gaining interest as environmentally friendly alternatives to synthetic fungicides for management of seedborne pathogens. Here, seven essential oils were initially tested in vivo for disinfection of squash seeds (Cucurbita maxima) naturally contaminated by Stagonosporopsis cucurbitacearum, Alternaria alternata, Fusarium fujikuro, Fusarium solani, Paramyrothecium roridum, Albifimbria verrucaria, Curvularia spicifera, and Rhizopus stolonifer. The seeds were treated with essential oils from Cymbopogon citratus, Lavandula dentata, Lavandula hybrida, Melaleuca alternifolia, Laurus nobilis, and Origanum majorana (#1 and #2). Incidence of S. cucurbitacearum was reduced, representing a range between 67.0% in L. nobilis to 84.4% in O. majorana #2. Treatments at 0.5 mg/mL essential oils did not affect seed germination, although radicles were shorter than controls, except with C. citratus and O. majorana #1 essential oils. Four days after seeding, seedling emergence was 20%, 30%, and 10% for control seeds and seeds treated with C. citratus essential oil (0.5 mg/mL) and fungicides (25 g/L difenoconazole plus 25 g/L fludioxonil). S. cucurbitacearum incidence was reduced by ~40% for plantlets from seeds treated with C. citratus essential oil. These data show the effectiveness of this essential oil to control the transmission of S. cucurbitacearum from seeds to plantlets, and thus define their potential use for seed decontamination in integrated pest management and organic agriculture. 相似文献
10.
K. Karoui M. Ben Bechir A. Ben Rhaiem A. Bulou F. Calvayrac K. Guidara 《Phase Transitions》2013,86(6):613-628
The infrared and Raman spectra of [N(CH3)4]2ZnCl4?yBry, where y = 0, 2 and 4, have been analyzed with ab initio calculations of the vibrational characteristics of constitutive polyhedra, tetramethylammonium [N(CH3)4]+ and [ZnCl4?xBrx]2? (x = 0, 1, 2, 3 and 4) tetrahedra. The optimized geometries, calculated vibrational frequencies, infrared intensities and Raman activities are calculated using Hartree–Fock and density functional theory B3LYP methods with 3-21G, 6-31G(d) and 6-311G+(d,p) basis sets. Calculation of the root mean square difference δrms between the observed and calculated frequencies allows to give scaling factors and to deduce that the best agreements are obtained by B3LYP/6-311G+(d,p) for [N(CH3)4]+ and B3LYP/3-21G for [ZnCl4?xBrx]2?. The present study establishes a strongly reliable assignment of the vibrational modes of [ZnCl4?xBrx]2? tetrahedra based on comparison between experimental and ab initio calculations, both of the frequencies and the intensities of the Raman signals. 相似文献