The effects of turbulent aberration such as z-tilt aberration, and astigmatism on the intensity distribution of double ring shaped LG11 beam have been investigated using the Fresnel–Kirchhoff diffraction integral and the quadratic approximation. The effect of turbulent aberration on the intensity distributions at the focal plane with different turbulent strength, and propagation distance is analyzed numerically. It is observed that the effect of tilt aberration gives major effect on the intensity distribution of the LG(1,1) beam in the turbulent atmosphere. 相似文献
Three‐dimensional (3D) CeO2 micropillows were synthesized by using solvothermal method. The pH of the precursor solution was adjusted to 10 by adding ammonium hydroxide. The structural, morphology and compositional characteristics of CeO2 micropillows were investigated by XRD, SEM, TEM and EDAX. XRD analysis showed the formation of CeO2 micropillows. BET analysis showed high specific surface area for the synthesized CeO2 micropillows (191 m2 g–1). Optical absorption of CeO2 micropillows showed enhanced photoabsorption ability with the estimated band gap energy of 2.8 eV. The photodegradation rate of the CeO2micropillows was found to be 87% and obeys pseudo‐first‐order equation. The photocatalytic results indicated that the CeO2 micropillows exhibit enhanced photocatalytic property towards azo dye acid orange 7 (AO7) under UV–Vis light illumination.
In this study, we report on the influence of solvent on the two-photon absorption (2PA) spectra of Reichardt’s dye (RD). The measurement of 2PA cross-sections is performed for three solvents (chloroform, dimethyl formamide, and dimethyl sulfoxide) using the Z-scan technique. The key finding of this study is the observation that the cross-section, corresponding to the 2PA of the intramolecular charge-transfer state, diminishes substantially upon increasing the solvent polarity. To unravel the solvent dependence of the 2PA cross-section, the electronic structure of RD is determined using a hybrid quantum mechanics/molecular mechanics (QM/MM) approach, in which polarization between the solute and solvent is taken into account by using a self-consistent scheme in the solvent polarization. The two-state approximation proves to be adequate for the studied system, and allowed the observed solvent-polarity-induced decrease of the 2PA cross-section to be related to the decrease of the transition moment and the increase in the excitation energy. 相似文献
A new organic solvent-tolerant strain Bacillus megaterium AU02 which secretes an organic solvent-tolerant protease was isolated from milk industry waste. Statistical methods were employed to achieve optimum protease production of 43.6 U/ml in shake flask cultures. The productivity of the protease was increased to 53 U/ml when cultivated under controlled conditions in a 7-L fermentor. The protease was purified to homogeneity by a three-step process with 24 % yield and specific activity of 5,375 U/mg. The molecular mass of the protease was found to be 59 kDa. The enzyme was active over a wide range of pH (6.0–9.0), with an optimum activity at pH 7.0 and temperature from 40 to 70 °C having an optimum activity at 50 °C. The thermal stability of the enzyme increased significantly in the presence of CaCl2, and it retained 90 % activity at 50 °C for 3 h. The Km and Vmax values were determined as 0.722 mg/ml and 0.018 U/mg respectively. The metalloprotease exhibited significant stability in the presence of organic solvents with log P values more than 2.5, nonionic detergents and oxidising agent. An attempt was made to test the synthesis of aspartame precursor (Cbz-Asp-Phe-NH2) which was catalysed by AU02 protease in the presence of 50 % DMSO. These properties of AU02 protease make it an ideal choice for enzymatic peptide synthesis in organic media. 相似文献
Treatment of ketoaziridine with aqueous formaldehyde gives the unusual bridged indenobenzazepine derivative whose reduction uith sodium cyanoborohydride produces trans ketol . In the presence of hydrochloric acid, undergoes irreversible conversion to the more stable cis ketol . Periodate oxidation of supplies γ-laotone . NaBH4 reduction of followed by acid treatment affords δ-lactone which upon reduction and O-methylation furnishes cis rhoeadine analog . 相似文献
An improved polymer electrolyte membrane fuel cell-based amperometric hydrogen sensor has been developed. The sensor operates
at room temperature, and the electrolyte used in the sensor is Nafion which is a proton-conducting solid polymer electrolyte. Platinum black is used as both anode and cathode. The sensor
functions as a fuel cell, H2/Pt//Nafion//Pt/O2, and a mechanical barrier limits the supply of hydrogen to the sensing side electrode. The limiting current is found to be
linearly related to the hydrogen concentration. The sensor can be used to measure hydrogen in argon in parts per million and
percentage levels. The basic principle, details of assembly, and response behavior of the sensor are discussed. 相似文献
The synthesis and reactivity of a CoI pincer complex [Co(ϰ3P,CH,P‐P(CH)PNMe‐iPr)(CO)2]+ featuring an η2‐ Caryl−H agostic bond is described. This complex was obtained by protonation of the CoI complex [Co(PCPNMe‐iPr)(CO)2]. The CoIII hydride complex [Co(PCPNMe‐iPr)(CNtBu)2(H)]+ was obtained upon protonation of [Co(PCPNMe‐iPr)(CNtBu)2]. Three ways to cleave the agostic C−H bond are presented. First, owing to the acidity of the agostic proton, treatment with pyridine results in facile deprotonation (C−H bond cleavage) and reformation of [Co(PCPNMe‐iPr)(CO)2]. Second, C−H bond cleavage is achieved upon exposure of [Co(ϰ3P,CH,P‐P(CH)PNMe‐iPr)(CO)2]+ to oxygen or TEMPO to yield the paramagnetic CoII PCP complex [Co(PCPNMe‐iPr)(CO)2]+. Finally, replacement of one CO ligand in [Co(ϰ3P,CH,P‐P(CH)PNMe‐iPr)(CO)2]+ by CNtBu promotes the rapid oxidative addition of the agostic η2‐Caryl−H bond to give two isomeric hydride complexes of the type [Co(PCPNMe‐iPr)(CNtBu)(CO)(H)]+. 相似文献
The widely applied reversed phase high-performance liquid chromatography (RP-HPLC) is an indispensable purification technique in drug discovery. During drug discovery, recovery was usually calculated based on the weight of the purified product after drying over the weight of the crude material multiplied by the assumed purity from HPLC/UV area percent of the product. Such a purity assumption can be off significantly when the crude material contains water, solvents, other UV-inactive impurities and inorganic salts. In this paper, we report a simple and efficient way to estimate recovery of preparative HPLC purification process. It is based on the ratio of the HPLC/UV peak area measured for the product in the crude solution and that in the final collected fraction with both accounted for their volumes. This approach eliminates not only the need for drying of the collected fraction to calculate recovery but also the inaccuracy associated with the true content in the crude sample using the traditional method. A systematic study was conducted to verify this method using caffeine mixed with various UV-active and -inactive impurities. The calculated recoveries using this approach were found to be consistent within 4% with the true recoveries based on dry weight estimation. The approach has been successfully applied for our in-house purifications. Furthermore, the approach was extended to library purifications, where in many cases heart-cutting the desired peaks is used to meet the purity requirements.
Platinum (Pt) and iridium (Ir) catalysts are well known to strongly enhance the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics, respectively. Pt–Ir-based bimetallic compounds along with carbon-supported titanium oxides (C–TiO2) have been synthesized for the application as electrocatalysts in lithium oxygen batteries. Transition metal oxide-based bimetallic nanocomposites (Pt–Ir/C–TiO2) were prepared by an incipient wetness impregnation technique. The as-prepared electrocatalysts were composed of a well-dispersed homogenous alloy of nanoparticles as confirmed by X-ray diffraction patterns and Fourier transform scanning electron microscopy analyses. The electrochemical characterizations reveal that the Pt–Ir/C–TiO2 electrocatalysts were bifunctional with high activity for both ORR and OER. When applied as an air cathode catalyst in lithium-air batteries, the electrocatalyst improved the battery performance in terms of capacity, reversibility, and cycle life compared to that of cathodes without any catalysts. 相似文献