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71.
This paper introduces an improved formula for the bed‐shear stress by applying the vorticity effect and its application in a 3D flow and sediment model to estimate scouring around bridge piers. Up to now, the sediment transport formulae used for computing pier scour were developed based on the general scouring in unobstructed flow. The capability for numerical models to predict local scour around bridge piers was severely restricted by the sediment transport formulae. The new formula introduced in this paper can take into account vortices that affect the local scour process by adding some terms into the classic bed‐shear stress equation. The 3D numerical model system used in this study consists of three modules: (a) an unsteady hydrodynamic module; (b) a sediment transport module; and (c) a Fation module. The hydrodynamic module is based on the 3D RANS equations. The sediment transport module is comprised of semi empirical models of suspended load and non‐equilibrium bed load. The bed‐deformation module is based on the mass balance for sediment. The model was used to simulate pier scour in tree different test cases: (1) a circular pier; (2) a square pier; and (3) a rectangular pier, by applying the ordinary sediment equation and the newly introduced sediment equation. Results of both numerical simulations were compared against laboratory measured data and also in case 1 with result of Olsen and Melaaen (J. Hydraul. Eng. 1993; 119 (9):1048–1054). Comparisons show that the new sediment formula could predict the scour more accurately than the ordinary one. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
72.
Hassan Saadat S. N. Mousavi M. Saadat N. Saadat A. M. Saadat 《International Journal of Theoretical Physics》2010,49(10):2506-2511
This paper visualizes effect of dark matter on solar system and especially perihelion precession of Earth planet. The relation between the rate of perihelion shift of Earth planet and dark matter are obtained. 相似文献
73.
Surfactant‐assisted electromembrane extraction combined with capillary electrophoresis as a novel technique for the determination of acidic drugs in biological fluids 下载免费PDF全文
Ali Reza Fakhari Kobra Sadat Hasheminasab Zolfaghar Aladaghlo Mohammad Hosein Koruni 《Electrophoresis》2015,36(24):3034-3041
In this paper, for the first time, surfactant‐assisted electromembrane extraction coupled with capillary electrophoresis with UV detector was introduced for the extraction of acidic drugs from biological fluids. In this technique, in the presence of the nonionic surfactant in the donor phase, tendency of analyte ions into the supported liquid membrane (SLM) was increased. Naproxen and diclofenac were selected as model acidic drugs. In order to obtain the best extraction efficiency, several factors influencing the extraction efficiency were investigated. Optimal extractions were accomplished with 1‐octanol as the SLM, 15 Volt dc potential as the driving force, pH 12 in acceptor solution, and 0.2 mmol/L Triton X‐100 with pH 7.4 in donor solution. Equilibrium extraction conditions were obtained after 15 min of operation where the whole assembly agitated at 1000 rpm. Under the optimized conditions, preconcentration factors in the range of 176–184 and recoveries in the range of 88–92% were obtained. The applied method offers acceptable linearity with correlation coefficients higher than 0.9992. Limits of detection of 1.51 ng/mL and 2.42 ng/mL were obtained for naproxen and diclofenac, respectively. Finally, the developed method was successfully applied for the determination of naproxen and diclofenac in different matrices including plasma and urine samples. 相似文献
74.
Hosein Vahedi Mehdi M. Baradarani Ahmad Rashidi John A. Joule 《Journal of heterocyclic chemistry》2015,52(4):1208-1211
Three‐component reactions of 5,6‐dihydro‐4H‐pyrrolo[3,2,1‐ij]quinoline‐1,2‐dione with malononitrile, or ethyl cyanoacetate, and cyclic six‐membered or a five‐membered 1,3‐diketone, produce spiro[4H‐pyran‐3,3′‐oxindoles]. 相似文献
75.
Zhang X Picariello W Hosein N Towle M Goetzinger W 《Journal of chromatography. A》2006,1119(1-2):147-155
In this paper we report a systematic recovery study based on reversed phase high performance liquid chromatography (RP-HPLC) separation and mass spectrometric (MS) based fractionation. Factors including a compound's physicochemical properties, column mass loading and presence of impurities were investigated through commercially available compounds. Results suggest that the delay time between MS peak detection and fraction collection, fraction detector's signal-to-noise ratio and compound's base peak width in the chromatogram have the biggest impacts on purification recovery. In an effort to assess sample recovery within our high throughput purification process, re-purification was performed on four compound libraries that were synthesized in-house. Reproducible recoveries (>80%) were achieved in all tests. 相似文献
76.
An effective electrochemical sensor for the rapid and simultaneous determination of tramadol and acetaminophen based on carbon paste electrode (CPE) modified with NiFe2O4/graphene nanoparticles was developed. The structures of the synthesized NiFe2O4/graphene nanocomposite and the electrode composition were confirmed by X-ray diffraction (XRD) spectrometry, Fourier transform infrared (FT-IR) spectrometry and scanning electron microscopy (SEM). The peak currents of square wave voltammetry of tramadol and acetaminophen increased linearly with their concentration in the range of 0.01–9 μmol L−1. The detection limit for their determination was found to be 0.0036 and 0.0030 μmol L−1, respectively. The results show that the combination of graphene and NiFe2O4 nanoparticles causes a dramatic enhancement in the sensitivity of the sensor. The fabricated sensor exhibited high sensitivity and good stability, and would be valuable for the clinical assay of tramadol and acetaminophen. 相似文献
77.
Electrochemiluminescence Detection of TNT by Resonance Energy Transfer through the Formation of a TNT–Amine Complex 下载免费PDF全文
Wenjing Qi Min Xu Lei Pang Zhongyuan Liu Wei Zhang Saadat Majeed Prof. Dr. Guobao Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(16):4829-4835
2,4,6‐Trinitrotoluene (TNT) is a widely used nitroaromatic explosive with significant detrimental effects on the environment and human health. Its detection is of great importance. In this study, both electrochemiluminescence (ECL)‐based detection of TNT through the formation of a TNT–amine complex and the detection of TNT through electrochemiluminescence resonance energy transfer (ECRET) are developed for the first time. 3‐Aminopropyltriethoxysilane (APTES)‐modified [Ru(phen)3]2+ (phen=1,10‐phenanthroline)‐doped silica nanoparticles (RuSiNPs) with uniform sizes of (73±3) nm were synthesized. TNT can interact with APTES‐modified RuSiNPs through charge transfer from electron‐rich amines in the RuSiNPs to the electron‐deficient aromatic ring of TNT to form a red TNT–amine complex. The absorption spectrum of this complex overlaps with the ECL spectrum of the APTES‐modified RuSiNPs/triethylamine system. As a result, ECL signals of the APTES‐modified RuSiNPs/triethylamine system are turned off in the presence of TNT owing to resonance energy transfer from electrochemically excited RuSiNPs to the TNT–amine complex. This ECRET method has been successfully applied for the sensitive determination of TNT with a linear range from 1×10?9 to 1×10?6 M with a fast response time within 1 min. The limit of detection is 0.3 nM . The method exhibits good selectivity towards 2,4‐dinitrotoluene, p‐nitrotoluene, nitrobenzene, phenol, p‐quinone, 8‐hydroxyquinoline, p‐phenylenediamine, K3[Fe(CN)6], Fe3+, NO3?, NO2?, Cr3+, Fe2+, Pb2+, SO32?, formaldehyde, oxalate, proline, and glycine. 相似文献
78.
Characterization and surface reactivity of ferrihydrite nanoparticles assembled in ferritin 总被引:1,自引:0,他引:1
Liu G Debnath S Paul KW Han W Hausner DB Hosein HA Michel FM Parise JB Sparks DL Strongin DR 《Langmuir : the ACS journal of surfaces and colloids》2006,22(22):9313-9321
Ferrihydrite nanoparticles with nominal sizes of 3 and 6 nm were assembled within ferritin, an iron storage protein. The crystallinity and structure of the nanoparticles (after removal of the protein shell) were evaluated by high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), and scanning tunneling microscopy (STM). HRTEM showed that amorphous and crystalline nanoparticles were copresent, and the degree of crystallinity improved with increasing size of the particles. The dominant phase of the crystalline nanoparticles was ferrihydrite. Morphology and electronic structure of the nanoparticles were characterized by AFM and STM. Scanning tunneling spectroscopy (STS) measurements suggested that the band gap associated with the 6 nm particles was larger than the band gap associated with the 3 nm particles. Interaction of SO2(g) with the nanoparticles was investigated by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and results were interpreted with the aid of molecular orbital/density functional theory (MO/DFT) frequency calculations. Reaction of SO2(g) with the nanoparticles resulted primarily in SO(3)2- surface species. The concentration of SO3(2-) appeared to be dependent on the ferrihydrite particle size (or differences in structural properties). 相似文献
79.
Min Xu Wenjing Qi Ling Zhang Jianping Lai Aziz-ur-Rehman Saadat Majeed Guobao Xu 《Mikrochimica acta》2014,181(7-8):737-742
The reaction of hydrogen tetracholoroaurate, sodium borohydride and the diazonium compound prepared from 4-aminobenzoic acid results in the formation of gold nanocorals (Au-NCs) for the first time. Scanning electron microscopy images and transmission electron microscopy images show that the Au-NCs are composed of nanowires with a diameter of 5.3 nm. A glassy carbon electrode modified with Au-NCs is found to trigger intense electrochemiluminescence of the luminol/H2O2 system at a potential of ?0.13 V. The effect was exploited to determine H2O2 in the 0.1 to 100 μM concentration range with a 30 nM detection limit. Figure
Gold nanocoral has been synthesized using diazonium salt chemistry for the first time. The Gold nanocoral-modified electrode show intense electrochemiluminescence at a low potential of ?0.13 V. 相似文献
80.
Abbas Afkhami Hosein Khoshsafar Tayyebeh Madrakian Ali Shirzadmehr 《Journal of the Iranian Chemical Society》2014,11(5):1373-1380
A macrocyclic ligand “7,10,13-triaza-1-thia-4,16-dioxa-20,24-dimethyl-2,3;17,18-dibenzo-cyclooctadecane-6,14-dione” as an efficient ionophore was used into a new Cu2+ nano-composite potentiometric carbon paste sensor containing multi-walled carbon nanotubes (MWCNTs), nanosilica particles, and room temperature ionic liquid (1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [BMP]Tf2N). This potentiometric sensor responds to copper ions in a wide linear dynamic range of 4.50 × 10?8 to 1.00 × 10?2 mol L?1 with Nernstian slope of 29.64 ± 0.10 mV per decade. The detection limit of 2.34 × 10?8 mol L?1 was obtained at the pH range 3.5–6.0. It has a fast response with response time of about 10 s, and can be used for at least 16 weeks without any considerable divergence in the potentials. The suggested sensor thus allows sensitive, selective, simple, low cost, and stable electrochemical sensing of Cu2+ ions in the presence of a large number of alkali, alkaline earth, transition and heavy metal ions. This sensor was successfully applied in the determination of copper ions in water and waste water samples. 相似文献