On the two-reactant one-step activation-energy asymptotics for steady,adiabatic, planar flames with Lewis numbers of unity

Aspects of predictions of activation-energy asymptotics concerning the dependence of the burning velocity on the equivalence ratio are examined here through both asymptotic analyses and numerical computation. In typical hydrocarbon–air flames, the burning velocity achieves its maximum value for fuel-rich mixture, the cause being generally attributed to the effects of detailed chemical kinetics and unequal diffusivities of the reactants. The present results demonstrate the possibility of this attribute of the burning velocity occurring even when these two effects are absent. This is accomplished by parametrically studying the burning-velocity formula valid for all equivalence ratios under the conditions specified in the title of this article, with special attention paid to implications for hydrocarbon–air flames.     

Inhibitive action of <Emphasis Type="Italic">Clematis gouriana</Emphasis> extract on the corrosion of mild steel in acidic medium

The inhibitive action of Clematis gouriana (CG) on mild steel (MS) corrosion in 1.0 M HCl solution was studied. Inhibition efficiency of CG was carried out by using various weight loss methods, potentiodynamic polarisation, and electrochemical impedance spectroscopy. Inhibition efficiencies of up to 95.70% for CG can be obtained. Adsorption of CG on the MS surface was found to obey the Langmuir adsorption isotherm. Free energy of adsorption calculated from the temperature studies revealed the possibility of both chemisorptions and physisorption. The adsorbed film on the MS surface containing the CG inhibitor was also characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope and energy-dispersive spectrum. The possible active ingredient responsible for the anticorrosion effect is identified as aporphine alkaloid which is isolated and screened for the anticorrosion effect using electrochemical studies. The possible mode of corrosion inhibition of aporphine alkaloid is also derived using FTIR studies.     

Facile synthesis of 3-aryl-1-((4-aryl-1,2,3-selenadiazol-5-yl)sulfanyl)isoquinolines

A new series of 1,2,3-selenadiazoles containing an aryl or a 3-arylisoquinoline sulfanyl moiety at carbons 4 and 5, respectively, was prepared by cyclization of the respective semicarbazones in the presence of selenium(II) oxide and tetrahydrofuran at 70–75°C. Semicarbazones required for the reaction were obtained from 2-((3-arylisoquinolin-1-yl)sulfanyl)-1-phenylethanones, I, by a reaction with semicarbazide hydrochloride in ethanol/water mixture and potassium acetate base.     

A Highly Conjugated Benzimidazole Carbene‐Based Ruthenium Sensitizer for Dye‐Sensitized Solar Cells

A new type of carbene‐based ruthenium sensitizer, CB104, with a highly conjugated ancillary ligand, diphenylvinylthiophene‐substituted benzimidazolepyridine, was designed and developed for dye‐sensitized solar cell applications. The influence of the thiophene antenna on the performance of the cell anchored with CB104 was investigated. Compared with the dye CBTR, the conjugated thiophene in the ancillary ligand of CB104 enhanced the molar extinction coefficient of the intraligand π–π* transition and the intensity of the lower energy metal‐to‐ligand charge‐transfer band. However, the incident photon‐to‐current conversion efficiency spectrum of the cell anchored with CB104 (0.15 mM ) showed a maximum of 63 % at 420 nm. The cell sensitized with the dye CB104 attained a power conversion efficiency of 7.30 %, which was lower than that of the cell with nonconjugated sensitizer CBTR (8.92 %) under the same fabrication conditions. The variation in the performance of these two dyes demonstrated that elongating the conjugated light‐harvesting antenna resulted in the reduction of short‐circuit photocurrent density, which might have been due to the aggregation of dye molecules. In the presence of a coabsorbate, chenodeoxycholic acid, the CB104‐sensitized cell exhibited an enhanced photocurrent density and achieved a photovoltaic efficiency of 8.36 %.     

Effect of spherical aberrations in tight focusing of higher order radially polarized beam

The effect of spherical aberration, in higher order radially polarized beam, is investigated theoretically by vector diffraction theory. It is observed that an increase in aberration results in the spreading of the intensity distribution, positional shift and the size of the generated focal pattern.     

Amorphization of Si (100) under O implantation studied by spectroscopic ellipsometry

The amorphization of crystalline Si (100) under 125 keV O⁺ ion implantation is investigated in the fluence range 1×10¹⁴ ions/cm² to 1×10¹⁶ ions/cm². The microstructure of the O⁺ implanted Si is modeled from ellipsometric data using a two phase, multilayer model within Bruggeman effective medium approximation (BEMA). The transition from the crystalline to the amorphous phase is found to be smooth and progressive. From a detailed analysis of the moments of the dielectric spectra and laser Raman spectroscopy, we infer that the amorphization occurs through a progressive disruption of long-range order caused by the overlap of amorphous nanozones. The dielectric spectrum of the fully amorphous phase is characterized using the Forouhi-Bloomer interband model.     

Convenient Approaches towards the Synthesis of Novel Pyrano[2,3‐a]carbazoles

Previously not easily accessible pyrano[2,3‐a]carbazoles were synthesized in highly convergent syntheses avoiding multistep procedures from readily available 1‐hydroxycarbazoles. Substituted pyrano[2,3‐a]carbazoles were produced by three different methods by treatment of the 1‐hydroxycarbazoles with dimethyl acetylene dicarboxylate (DMAD) and triphenylphoshine, by reaction with ethyl 2‐methylacetoacetate in the presence of ZnCl₂/POCl₃, and by reaction with trifluoroacetic acid followed by Wittig reaction with (carbethoxymethylene) triphenylphosphorane. The article also highlights the optimization of reaction conditions and strategies to avoid formation of byproducts for all three types of reactions.     

Generation of multiple sub wavelength focal spot segments using radially polarized Bessel Gaussian beam with complex phase filter

We propose a new approach for generating multiple focal spot segment of sub wavelength size, by tight focusing of phase modulated radially polarized Bessel Gaussian beam. The focusing properties are investigated theoretically by vector diffraction theory. We observed that focal segment with multiple focal spots structure separated with different axial distance can be generated by properly tuning the phase of the incident radially polarized Bessel Gaussian (BG) beam. Potential applications of this focal shaping technique are also discussed.     

Tight focusing properties of radially polarized Lorentz–Gaussian beam

Focusing properties of radially polarized Lorentz–Gauss beam with one on-axis optical vortex was investigated by vector diffraction theory. Results show that intensity distribution in the focal region can be altered considerably by charge number of the optical vortex and the beam parameters. Many novel focal patterns may occur, Such as Peak-centered, donut focal shapes which is potentially useful in optical tweezers, material processing and laser printing.