双金属镍-锰／γ-Al2O3催化剂对甲烷二氧化碳重整反应的影响

用浸渍法制备γ-Al2O3负载的Ni-Mn双金属催化剂．在500-700。C按照17：17：2的C02／CHa／N2比例,以36mL／min的载气流速进行甲烷二氧化碳重整反应,利用甲烷二氧化碳的转化率、生成的合成气H2／CO比例以及长期稳定性等指标评价了催化剂的催化性能．实验表明,添加Mn提高催化性能并使双金属催化剂的稳定性更高,比单金属催化剂更好地抑制焦炭生成,Mn最合适的添加量为0．5wt％．通过BET、C02-TPD、TGA、XRD、SEM、EDX和FTIR各种技术对催化剂进行了表征．     

Analytical and semi-analytical solutions to flows of two immiscible Maxwell fluids between moving plates

Unsteady flows of two immiscible Maxwell fluids in a rectangular channel bounded by two moving parallel plates are studied. The fluid motion is generated by a time-dependent pressure gradient and by the translational motions of the channel walls in their planes. Analytical solutions for velocity and shear stress fields have been obtained by using the Laplace transform coupled with the finite sine-Fourier transform. These analytical solutions are new in the literature and the method developed in this paper can be generalized to unsteady flows of n-layers of immiscible fluids. By using the Laplace transform and classical method for ordinary differential equations, the second form of the Laplace transforms of velocity and shear stress are determined. For the numerical Laplace inversion, two accuracy numerical algorithms, namely the Talbot algorithm and the improved Talbot algorithm are used.     

The effect of replacing pnictogen elements on the physical properties of SrMg_2X_2(X=N,P,As,Sb,Bi) Zintl compounds

The effect of replacing the anion from N to Bi down the group in the periodic table is investigated on SrMg_2X_2(X = N,P,As,Sb,Bi).A full potential linearized augmented plane wave plus local orbitals method is used along with different exchange–correlation potentials to obtain the lattice constants,phonons,electronic,and optical properties of the Sr Mg_2X_2(X = N,P,As,Sb,Bi) Zintl compounds.A good agreement is achieved and our calculations are validated by previous experimental and theoretical data.All compounds have shown stable dynamical behavior with gamma centered longitudinal response having no imaginary frequencies.Electronic band structures reveal the semiconducting nature of the compounds.The Pnictogen(X)-p state contributed mainly in the valence band and the Sr-d state forms the conduction of the compounds.Relative charge transfer and low overlapping of the atomic densities indicates the preferable ionic bonding character of these materials.In the optical properties,real and imaginary parts of dielectric function,complex refractive index,birefringence,reflectivity,and optical conductivity are calculated.These compounds can be utilized in the optical and optoelectronic devices.     

Three-dimensional flow of Powell–Eyring nanofluid with heat and mass flux boundary conditions

This article investigates the three-dimensional flow of Powell–Eyring nanofluid with thermophoresis and Brownian motion effects. The energy equation is considered in the presence of thermal radiation. The heat and mass flux conditions are taken into account. Mathematical formulation is carried out through the boundary layer approach. The governing partial differential equations are transformed into the nonlinear ordinary differential equations through suitable variables. The resulting nonlinear ordinary differential equations have been solved for the series solutions. Effects of emerging physical parameters on the temperature and nanoparticles concentration are plotted and discussed. Numerical values of local Nusselt and Sherwood numbers are computed and examined.     

Four-dimensional parameter estimation of plane waves using swarming intelligence

This paper proposes an efficient approach for four-dimensional(4D) parameter estimation of plane waves impinging on a 2-L shape array. The 4D parameters include amplitude, frequency and the two-dimensional(2D) direction of arrival,namely, azimuth and elevation angles. The proposed approach is based on memetic computation, in which the global optimizer, particle swarm optimization is hybridized with a rapid local search technique, pattern search. For this purpose,a new multi-objective fitness function is used. This fitness function is the combination of mean square error and the correlation between the normalized desired and estimated vectors. The proposed hybrid scheme is not only compared with individual performances of particle swarm optimization and pattern search, but also with the performance of the hybrid genetic algorithm and that of the traditional approach. A large number of Monte–Carlo simulations are carried out to validate the performance of the proposed scheme. It gives promising results in terms of estimation accuracy, convergence rate, proximity effect and robustness against noise.     

Origin of Electric Field Dependence of the Charge Mobility and Spatial Energy Correlations in C60-Based Field Effect Transistors

We report on the influence of the lateral electric field on the charge mobility in organic field-effect transistors (OFET) based on C₆₀ films with multigrain morphology. The experimental data were quantitatively described using a recent analytical model by accounting for the strong local electric fields in a multigrain transistor channel and for the energy correlation effects. To rationalize the presence of a correlated disorder in a non-polar C₆₀ material, we show that randomly oriented permanent dipoles in organic gate dielectric layers can generate a significant dipolar disorder in an adjacent nonpolar semiconductor layer.     

Optoelectronic Properties,Elastic Moduli and Thermoelectricity of SrAlGa： An Ab Initio Study

Half-Heusler compounds are an impressive class of materials with a huge potential for different applications such as in future energy, especially in the fields of thermoelectrics and solar cells. We present ab fnitio total energy calculations within the modified Becke-Johnson generalized gradient approximation （mBJ-GGA） to obtain the physical properties of SrAlGa compounds. The structural, elastic, acoustic, electronic, chemical bonding, optical, and thermoelectric properties are calculated and compared with the available calculation data. The SrAlGa is found to be a small-band-gap （0.125-0.175 eV） material, suitable for thermoelectric applications with a relatively high Seebeck coefficient. Also, SrAIGa has the potential in the optoelectronic applications due to high optical conductivity and reflectivity in the infrared and visible region of electromagnetic spectra.     

Antitussive and toxicological evaluation of Vitex negundo

Vitex negundo Linn. (Verbenaceae) is used in traditional medical system for respiratory disorders. This study was carried out to investigate its cough-relieving potential. The antitussive effect of the butanolic extract of V. negundo (Vn) on sulphur dioxide (SO(2))-induced cough was examined in mice. Safety profile of Vn was carried out by observing acute neurotoxicity, median lethal dose (LD(50)) and behavioural signs. Vn dose-dependently (250-1000?mg?kg(-1)) inhibited the cough provoked by SO(2) gas in mice and exhibited maximum protection after 60?min of administration. At 1000?mg?kg(-1), Vn caused maximum cough-suppressive effects i.e. cough inhibition at 60?min was 67.4%, as compared to codeine (10?mg?kg(-1)), dextromethorphan (10?mg?kg(-1)) and saline having cough-inhibitory potential 75.7%, 74.7% and 0%, respectively. LD(50) value of V. negundo was found to be greater than 5000?mg?kg(-1). In toxicity tests, no signs of neural impairment and acute behavioural toxicity were observed at antitussive doses and extract has been well tolerated at higher doses. These results indicate that V. negundo exhibits antitussive effect and it was found devoid of toxicity.     

Determination of perfluoroalkyl carboxylic, sulfonic, and phosphonic acids in food

A sensitive and accurate method was developed and validated for simultaneous analysis of perfluoroalkyl carboxylic acids, sulfonic acids, and phosphonic acids (PFPAs) at low picograms per gram concentrations in a variety of food matrices. The method employed extraction with acetonitrile/water and cleanup on a mixed-mode co-polymeric sorbent (C8?+?quaternary amine) using solid-phase extraction. High-performance liquid chromatographic separation was achieved on a C18 column using a mobile phase gradient containing 5?mM 1-methyl piperidine for optimal chromatographic resolution of PFPAs. A quadrupole time-of-flight high-resolution mass spectrometer operating in negative ion mode was used as detector. Method detection limits were in the range of 0.002 to 0.02?ng?g^?1 for all analytes. Sample preparation (extraction and cleanup) recoveries at a spiking level of 0.1?ng?g^?1 to a baby food composite were in the range of 59 to 98?%. A strong matrix effect was observed in the analysis of PFPAs in food extracts, which was tentatively assigned to sorption of PFPAs to the injection vial in the solvent-based calibration standard. The method was successfully applied to a range of different food matrices including duplicate diet samples, vegetables, meat, and fish samples.

Stability indicating HPLC method for the simultaneous determination of moxifloxacin and prednisolone in pharmaceutical formulations

ABSTRACT: BACKGROUND: A simple, specific, and fast stability indicating reverse phase liquid chromatographic method was established for instantaneous determination of moxifloxacin and prednisolone in bulk drugs and pharmaceutical formulations. RESULTS: Optimum chromatographic separations among the moxifloxacin, prednisolone and stressinduced degradation products were achieved within 10 minutes by use of BDS Hypersil C8 column (250 X 4.6 mm, 5 mum) as stationary phase with mobile phase consisted of a mixture of phosphate buffer (18 mM) containing 0.1% (v/v) triethylamine, at pH 2.8 (adjusted with dilute phosphoric acid) and methanol (38:62 v/v) at a flow rate of 1.5 mL min-1. Detection was performed at 254 nm using diode array detector. The method was validated in accordance with ICH guidelines. Response was a linear function of concentrations over the range of 20-80 mug mL-1 for moxifloxacin (r2 [greater than or equal to] 0.998) and 40-160 mug mL-1 for prednisolone (r2 [greater than or equal to] 0.998). The method was resulted in good separation of both the analytes and degradation products with acceptable tailing and resolution. The peak purity index for both the analytes after all types of stress conditions was [greater than or equal to] 0.9999 indicated a complete separation of both the analyte peaks from degradation products. The method can therefore, be regarded as stabilityindicating. CONCLUSIONS: The developed method can be applied successfully for simultaneous determination of moxifloxacin and prednisolone in pharmaceutical formulations and their stability studies.