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排序方式: 共有1330条查询结果,搜索用时 15 毫秒
1.
Rishikesh Yadav Ramakanta Meher Vishnu Narayan Mishra 《Mathematical Methods in the Applied Sciences》2019,42(18):7172-7191
In this paper, we study the approximation properties of bivariate summation‐integral–type operators with two parameters . The present work deals within the polynomial weight space. The rate of convergence is obtained while the function belonging to the set of all continuous and bounded function defined on ([0],∞)(×[0],∞) and function belonging to the polynomial weight space with two parameters, also convergence properties, are studied. To know the asymptotic behavior of the proposed bivariate operators, we prove the Voronovskaya type theorem and show the graphical representation for the convergence of the bivariate operators, which is illustrated by graphics using Mathematica. Also with the help of Mathematica, we discuss the comparison by means of the convergence of the proposed bivariate summation‐integral–type operators and Szász‐Mirakjan‐Kantorovich operators for function of two variables with two parameters to the function. In the same direction, we compute the absolute numerical error for the bivariate operators by using Mathematica and is illustrated by tables and also the comparison takes place of the proposed bivariate operators with the bivariate Szász‐Mirakjan operators in the sense of absolute error, which is represented by table. At last, we study the simultaneous approximation for the first‐order partial derivative of the function. 相似文献
2.
Seema Yadav Sriparna Ray Ajeet Singh Shaikh M. Mobin Tapta Kanchan Roy Chandrakanta Dash 《应用有机金属化学》2020,34(11):e5942
Dinuclear gold(I)-N-heterocyclic carbene complexes were developed for the hydrohydrazidation of terminal alkynes. The gold(I)-N-heterocyclic carbene complexes 2a-2b were synthesized in good yields from silver complexes synthesized in situ, which in turn were obtained from the corresponding imidazolium salts with Ag2O in dichloromethane as a solvent. The new air-stable gold(I)-NHC complexes, 2a - 2b, were characterized using NMR spectroscopy, elemental analysis, infrared, and mass spectroscopy studies. The gold(I) complex 2a was characterized using X-ray crystallography. Bis-N-heterocyclic carbene–based gold(I) complexes 2a - 2b exhibited excellent catalytic activities for hydrohydrazidation of terminal alkynes yielding acylhydrazone derivatives. The working catalytic system can be used in gram-scale synthesis. In addition, the catalytic reaction mechanism of the hydrohydrazidation of terminal alkynes by gold(I)-NHC complex was studied in detail using density functional theory. 相似文献
3.
Kenchappa R. Bodke Yadav D. Telkar Sandeep Sindhe M. Aruna Giridhar M. 《Russian Journal of General Chemistry》2016,86(12):2827-2836
Russian Journal of General Chemistry - A novel series of (5-substituted-1-benzofuran-2-yl)(2,4-substituted phenyl)methanones (4a–4i) have been prepared by the Knoevenagel condensation of... 相似文献
4.
M. Sharma K. Chaudhary M. Kumari P. Yadav K. Sachdev V. Chandra Janu R. Gupta 《Materials Today Chemistry》2020
A green and environment-friendly magnetically separable nanocomposite, glutathione@magnetite was fabricated sonochemically through the functionalization of Fe3O4 by glutathione which was well characterized using Fourier-transform infrared spectroscopy, ultravoilet-visible spectroscopy, scanning electron microscope, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, thermogravimetric analysis, vibrating sample magnetometer, Brunauer-Emmett-Teller, and high-resolution transmission electron microscope. The parameters affecting adsorption including pH, temperature, contact time, initial adsorbate concentration, and adsorbent amount were optimized by batch experiments. The magnetic glutathione@magnetite was applied for the removal of uranium(VI) in water with maximum adsorption capacity found to be 333.33 mg/g in 120 min at a neutral pH at 25 °C showing high efficiency for U(VI) ions. Furthermore, adsorption results obtained from UV-vis spectroscopy were validated by inductively coupled plasma optical emission spectroscopy. The thermodynamic parameters, viz Gibbs free energy (ΔGº), standard enthalpy change (ΔHº), and standard entropy change (ΔSº) of the process were calculated using the Langmuir constants. The pseudo-second-order kinetics model is seen to be applicable for describing the uptake process using a kinetics test. Moreover, desorption studies reveals that glutathione@magnetite can be used repeatedly, and removal efficiency shows only a small decrease after six cycles. Thus, glutathione@magnetite acts as a potential adsorbent for the removal of U(VI) from the water with great adsorption performance. 相似文献
5.
6.
Dr. Ashok Yadav Meghamala Sarkar Dr. Sappati Subrahmanyam Atul Chaudhary Prof. Dr. Evamarie Hey-Hawkins Prof. Dr. Ramamoorthy Boomishankar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(19):4209-4213
The design of porous materials for the recognition of multiple hydrocarbons is highly desirable for the energy-efficient separation and recognition of chemical feedstock. Herein, three new iso-structural porous discrete metal–organic cages of formula {[Pd3(NiPr)3PO]4(R-AN)6} (R-AN=anilate linkers) for the selective recognition of substituted aromatic hydrocarbons are reported. The tetrahedral cages 1 , 2 , and 3 containing anilate, chloranilate, and bromanilate linkers exhibited selective encapsulation of mesitylene, o-xylene, and p-xylene, respectively, over other analogous aromatic hydrocarbons. These selective encapsulations were driven by the variations in the portal diameters present at each of these cages and their interactions with the hydrocarbon guests. These observations are supported by mass spectrometry, NMR studies, and theoretical binding-energy calculations. 相似文献
7.
Lakhera Shradha Rana Meenakshi Devlal Kamal Celik Ismail Yadav Rohitash 《Structural chemistry》2022,33(3):703-719
Structural Chemistry - Tridax procumbens is a flowering plant of the Asteraceae family with a wide range of medicinal uses like anti-inflammatory, anti-diabetic, anti-microbial, immunomodulatory,... 相似文献
8.
Geetika Wadhwa Kowthavarapu Venkata Krishna Rajeev Taliyan Neeraj Tandon Satyapal Singh Yadav Dipankar Banerjee Avinash Narwaria Chandrakant Katiyar Sunil Kumar Dubey 《Biomedical chromatography : BMC》2022,36(2):e5275
Trigonelline (TR), 4-hydroxyisoleucine (4-HI), and diosgenin (DG) are the main bioactives of the purified standardized extract of the popular plant Trigonella foenum-graecum L. (TFG), and it has been proven effective for the treatment of various diseases. However, to the best of our knowledge, no study has investigated the pharmacokinetic parameters of purified standardized T. foenum-graecum extract in normal and diabetic Wistar rats. The present study has developed and validated a rapid, reliable, and sensitive simultaneous ultra-performance liquid chromatography MS method to estimate these bioactives. The chromatographic separation was achieved using methanol, acetonitrile, and 0.1% formic acid with the ideal gradient flow system on a BEH Shield RP 18 column. A positive electrospray ionization mode was selected to estimate m/z values of TR (138.14 > 94.63), 4-HI (148.19 > 74.08), and DG (415.54 > 271.33). The method was robust and reproducible over the linearity range of 60–5000, 6–5000, and 15–5000 ng/mL for TR, 4-HI, and DG, respectively. Using this novel validated method, we investigated the pharmacokinetic parameters of bioactives using Phoenix WinNonlin version 8.0 (Certera) in normal and diabetic rats. The assay was successfully applied for the estimation of pharmacokinetic parameters using noncompartmental analysis. This investigation shows that the absorption rate increased, whereas distribution and elimination processes slowed down in diabetic rats compared with normal rats. 相似文献
9.
Dr. Mamta Yadav Dr. Devesh Kumar Singh Dr. Dharmendra Kumar Yadav Dr. Piyush Kumar Sonkar Dr. Rupali Gupta Prof. Dr. Vellaichamy Ganesan 《Chemphyschem》2023,24(19):e202300117
In the present work, the oxygen reduction reaction (ORR) is explored in an acidic medium with two different catalytic supports (multi-walled carbon nanotubes (MWCNTs) and nitrogen-doped multi-walled carbon nanotubes (NMWCNTs)) and two different catalysts (copper phthalocyanine (CuPc) and sulfonic acid functionalized CuPc (CuPc-SO3−)). The composite, NMWCNTs-CuPc-SO3− exhibits high ORR activity (assessed based on the onset potential (0.57 V vs. reversible hydrogen electrode) and Tafel slope) in comparison to the other composites. Rotating ring disc electrode (RRDE) studies demonstrate a highly selective four-electron ORR (less than 2.5 % H2O2 formation) at the NMWCNTs-CuPc-SO3−. The synergistic effect of the catalyst support (NMWCNTs) and sulfonic acid functionalization of the catalyst (in CuPc-SO3−) increase the efficiency and selectivity of the ORR at the NMWCNTs-CuPc-SO3−. The catalyst activity of NMWCNTs-CuPc-SO3− has been compared with many reported materials and found to be better than several catalysts. NMWCNTs-CuPc-SO3− shows high tolerance for methanol and very small deviation in the onset potential (10 mV) between the linear sweep voltammetry responses recorded before and after 3000 cyclic voltammetry cycles, demonstrating exceptional durability. The high durability is attributed to the stabilization of CuPc-SO3− by the additional coordination with nitrogen (Cu-Nx) present on the surface of NMWCNTs. 相似文献
10.
Dhananjay Yadav Prof. Dr. Maya Shankar Singh 《European journal of organic chemistry》2023,26(10):e202201335
An operationally simple and efficient cascade approach to access a series of 1,3-thiazinanes has been developed through intermolecular [3+3] heteroannulative coupling employing β-ketothioamide as a C1 N1S1 unit and epichlorohydrin as a C3 unit at room temperature for the first time. The reaction proceeds by nucleophilic attack of thiocarbonyl sulfur to less hindered primary carbon of oxirane followed by sequential intramolecular N-cyclization and dehydrochlorination enabling the coupling by cleavage of C−O bond and formation of two new C−S and C−N bonds in one stretch. This protocol not only avoids potential toxicity and tedious work up procedures, but also features open atmosphere, good to high yields, gram-scalability, and easy performance from inexpensive, readily available starting materials under transition-metal-free conditions. A probable mechanism for the formation of 1,3-thiazinanes has been suggested. 相似文献