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481.
482.
We derive the asymptotics of the OLS estimator for a purely autoregressive spatial model. Only low-level conditions are used. As the sample size increases, the spatial matrix is assumed to approach a square-integrable function on the square (0,1)2. The asymptotic distribution is a ratio of two infinite linear combinations of χ2 variables. The formula involves eigenvalues of an integral operator associated with the function approached by the spatial matrices. Under the conditions imposed identification conditions for the maximum likelihood method and method of moments fail. A corrective two-step procedure using the OLS estimator is proposed. 相似文献
483.
Ramandeep Kaur Ripneel Kaur Aman Grover Susheela Rani Ashok Kumar Malik Abuzar Kabir Kenneth G. Furton 《Journal of separation science》2019,42(14):2407-2417
A rapid extraction and cleanup method using selective fabric phase sorptive extraction combined with gas chromatography and mass spectrometry has been developed and validated for the determination of broad polarity spectrum emerging pollutants, ethyl paraben, butyl paraben, diethyl phthalate, dibutyl phthalate, lidocaine, prilocaine, triclosan, and bisphenol A in various aqueous samples. Some important parameters of fabric phase sorptive extraction such as extraction time, matrix pH, stirring speed, type and volume of desorption solvent were investigated and optimized. Calibration curves were obtained in the concentration range 0.05–500 ng/mL. Under the optimum conditions, the limits of detection were in the range 0.009 –0.021 ng/mL. This method was validated by analyzing the compounds in spiked aqueous samples at different levels with recoveries of 93 to 99% and relative standard deviations of <6%. The developed method was applied for the determination of the emerging contaminants in tap water, municipal water, ground water, sewage water, and sludge water samples. The results demonstrate that fabric phase sorptive extraction has great potential in the preconcentration of trace analytes in complex matrix. 相似文献
484.
Preety Saini S.S. Bari Subash C. Sahoo Sadhika Khullar Sanjay K. Mandal Aman Bhalla 《Tetrahedron》2019,75(33):4591-4601
A stereoselective synthesis and C–3 functionalization of a long series of novel hybrid 4-(thiophenyl)pyrazolyl-β-lactams have been carried out. The divergent substrate scope and mechanistic insights were examined to delineate the generality of reaction that favored trans-β-lactams 4a-q almost exclusively in all cases. The C–3 functionalization was achieved by Lewis acid assisted nucleophilic substitution reaction of cis-3-chloro-β-lactams 6a-e to afford cis-3-monosubstituted-β-lactams 7a-e. The cis stereochemistry of β-lactams 7a-e was further established by stereospecific desulfurization with Raney-nickel, in representative cases (7a,b), leading to the formation of cis-β-lactams 8a,b. The structures and stereochemical assignments for synthesized β-lactams have been unambiguously confirmed using FT-IR, 1D NMR (1H and 13C), 2D NMR (1H–1H COSY, 1H–13C HSQC and 13C DEPT–135), elemental analysis (CHN), mass spectrometry (ESI-MS) and single crystal X-ray crystallography, in representative cases (4b,e). The cis and trans configuration of the hydrogen/chloro/nucleophile substituent at C–3 was assigned with respect C4–H of the β-lactam ring. 相似文献
485.
Rashmi Mahajan Mona Rouhi Sudhirkumar Shinde Thomas Bedwell Anil Incel Liliia Mavliutova Sergey Piletsky Ian A. Nicholls Brje Sellergren 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(3):737-740
We report an approach integrating the synthesis of protein‐imprinted nanogels (“plastic antibodies”) with a highly sensitive assay employing templates attached to magnetic carriers. The enzymes trypsin and pepsin were immobilized on amino‐functionalized solgel‐coated magnetic nanoparticles (magNPs). Lightly crosslinked fluorescently doped polyacrylamide nanogels were subsequently produced by high‐dilution polymerization of monomers in the presence of the magNPs. The nanogels were characterised by a novel competitive fluorescence assay employing identical protein‐conjugated nanoparticles as ligands to reversibly immobilize the corresponding nanogels. Both nanogels exhibited Kd<10 pM for their respective target protein and low cross‐reactivity with five reference proteins. This agrees with affinities reported for solid‐phase‐synthesized nanogels prepared using low‐surface‐area glass‐bead supports. This approach simplifies the development and production of plastic antibodies and offers direct access to a practical bioassay. 相似文献
486.
Aman Razia Sadiq Saima Ali Muhammad Sadiq Muhammad Gul Jehan Saeed Khalid Khan Adnan Ali Shah Sagheer Hussain 《Research on Chemical Intermediates》2019,45(5):2947-2961
Research on Chemical Intermediates - Mn–Co-decorated reduced graphene oxide (Mn–Co–rGO) was prepared by modified condensation method and characterized through XRD, SEM, EDX, FTIR... 相似文献
487.
Kinetic theory has been applied to study the damping characteristics of dust ion acoustic waves (DIAWs) in a dusty plasma comprising q‐non‐extensive distributed electrons and ions, while the dust particles are considered extensive following the Maxwellian velocity distribution function. It is found that the results of the three‐dimensional velocity distribution function are more accurate compared to the results of the one‐dimensional velocity distribution function. The numerical solution of the dispersion relation is carried out to study the effect of the non‐extensivity parameter q on the dispersion, the damping rate, and the range of the values of the normalized wavenumber ( k λD) for which the DIAWs are weakly damped. It is found that the change in the value of the electron non‐extensivity parameter qe has a minor effect on the dispersion, the damping rate, and the range of the values of the normalized wavenumber ( k λD) for which the DIAWs are weakly damped, while on the other hand, ion non‐extensivity parameter qi has a strong effect on these arguments. The effect of other parameters, such as the ratio of electron to ion number density and ratio of electron to ion temperature, on the damping characteristics of DIAWs is also highlighted. 相似文献
488.
同相气泡耦合特性实验研究 总被引:3,自引:1,他引:2
设计实验, 利用电火花打火生成气泡来研究两个气泡之间以及两个气泡与自由面的相互作用, 在实验过程中, 精确控制打火电路, 使两个电火花气泡的生成时间间隔控制在67\mus以内, 实现了气泡的同相生成. 大量实验后发现, 两气泡相互作用过程中可能会出现融合、蘑菇状气泡、对射流、射流方向逆转、反向射流等现象, 自由面附近不同安置方式的两同相气泡会出现不同的脉动形式. 通过系列实验提出了气泡之间的无量纲距离、无量纲周期差等参数来描述气泡耦合特性, 为气泡群的相互作用提供实验依据.} 相似文献
489.
A Nonlinear Stability Analysis for Thermoconvective Magnetized Ferrofluid Saturating a Porous Medium
The generalized energy method is developed to study the nonlinear stability analysis for a magnetized ferrofluid layer heated
from below saturating a porous medium, in the stress-free boundary case. The mathematical emphasis is on how to control the
nonlinear terms caused by magnetic body force. By introducing a suitable generalized energy functional, we perform a nonlinear
energy stability (conditional) analysis. It is found that the nonlinear critical stability magnetic thermal Rayleigh number
does not coincide with that of linear instability analysis, and thus indicates that the subcritical instabilities are possible.
However, it is noted that, in case of non-ferrofluid, global nonlinear stability Rayleigh number is exactly the same as that
for linear instability. For lower values of magnetic parameters, this coincidence is immediately lost. The effect of magnetic
parameter, M
3, and medium permeability, Da, on subcritical instability region has also been analyzed. It is shown that with the increase of magnetic parameter (M
3) and Darcy number (Da), the subcritical instability region between the two theories decreases quickly. We also demonstrate coupling between the
buoyancy and magnetic forces in nonlinear energy stability analysis as well as in linear instability analysis. 相似文献
490.
Meenu Thakur B. R. Behera Ruchi Mahajan N. Saneesh Gurpreet Kaur Priya Sharma R. Dubey Kushal Kapoor A. Yadav Neeraj Kumar S. Kumar Kavita Rani P. Sugathan A. Jhingan A. Chatterjee M. B. Chatterjee S. Mandal A. Saxena Santanu Pal S. Kailas Avazbek Nasirov Bakhodir Kayumov 《The European Physical Journal A - Hadrons and Nuclei》2017,53(6):133