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Mathematical Programming - We present a connection between two dynamical systems arising in entirely different contexts: the Iteratively Reweighted Least Squares (IRLS) algorithm used in compressed... 相似文献
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A simple and inexpensive method for immobilizing alpha-amylase from Bacillus circulans GRS 313 on coconut fiber was developed. The immobilization conditions for highest efficiency were optimized with respect to immobilization pH of 5.5, 30 degrees C, contact time of 4 h, and enzyme to support a ratio of 1:1 containing 0.12 mg/mL of protein. The catalytic properties of the immobilized enzyme were compared with that of the free enzyme. The activity of amylase adsorbed on coconut fiber was 38.7 U/g of fiber at its optimum pH of 5.7 and 48 degrees C, compared with the maximum activity of 40.2 U/mL of free enzyme at the optimum pH of 4.9 and 48 degrees C. The reutilization capacity of the immobilized enzyme was up to three cycles. 相似文献
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The importance of adsorption induced convection in the macropores of a bidisperse adsorbent particle is studied for a step change in mole fraction or total pressure at the surface of the particle. Material balance equations for a binary gas mixture are written for both the macropores and the macropores with allowance for convection in the macropores, which is described by Darcy's law. The coupled set o1' partial differential equations is solved by orthogonal collocation. The enhancement in mass transfer as a result of convection is assessed by comparing the fractional uptake curves obtained with and without allowance for convection. Both equilibrium-based and kinetic-based separation processes are considered. The effect of the presence of convection in determining the controlling diffusional resistance (macropore or micropore) is also examined. Due to inclusion of convection no single non-dimensional group alone can determine the relative importance of macropore and micropore resistances. Results show that convection can significantly affect the performance of an equilibrium-based macropore diffusion controlled process and that the enhancement in mass transfer is more for a particle with a high value of Darcy permeability. 相似文献
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The X-ray Absorption Near Edge Structure (XANES) of the AuLIII edge in gold metal and in its two compounds AuCN and AuCl3 have been recorded. The observed chemical shifts of the edge and the fine structure peaks in the compounds are discussed.
It is observed that the energy shifts ΔE of the AuLIII due to chemical effects in aurous cyanide (AuCN) and auric chloride (AuCl3) with respect to the pure Au edge is 2.9 eV in AuCN and 0.7eV in AuCl3. The edge widths in AuCN and AuCl3 are found to be almost the same for both the compounds, presumably because electronegativities of CN and Cl are not very
different. The observed fine structure peaks of the discontinuities of AuCN and AuCl3 are displaced progressively away from the main edge. 相似文献
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Chemical Fixation of CO2 and Other Heterogeneous Catalytic Studies by Employing a Layered Cu‐Porphyrin Prepared Through Single‐Crystal to Single‐Crystal Exchange of a Zn Analogue 下载免费PDF全文
A solvothermal reaction of Zn(NO3)2 ? 6 H2O, tetra‐(4‐pyridyl)porphyrin (H2TPyP), and 4,4′‐oxybis(benzoic acid) (H2OBA) resulted in a new two‐dimensional Zn‐ porphyrin metal–organic framework compound, [Zn2(C40H24N8)0.5(C14H8O5)(DMA)](DMA)(H2O)6 ( 1 ; DMA=N,N‐dimethylacetamide). The ZnII ions present in 1 could be exchanged by using a solution of Cu(NO3)2 ? 3 H2O in DMA at room temperature to give [Cu2(C40H24N8)0.5(C14H8O5)(DMA)](DMA)(H2O)3 ( Cu∈1 ). The extra‐framework solvent molecules have been shown to be reversibly removed or exchanged without collapse of the framework. Solvent‐free Cu∈1 was explored as an active heterogeneous catalyst towards three different organic reactions: 1) the chemical fixation of CO2 into cyclic carbonate at room temperature and 1 atm; 2) the nitroaldol reaction under solvent‐free conditions, and 3) the three‐component coupling of aminopyridine, benzaldehyde, and aryl alkynes followed by 5‐exo‐dig cyclization to produce the important pharmacophore imidazopyridine. 相似文献
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Dr. Greggory T. Kent Emily Morgan Kaitlin R. Albanese Dr. Anna Kallistova Dr. Alexandra Brumberg Linus Kautzsch Dr. Guang Wu Prof. Pratap Vishnoi Prof. Ram Seshadri Prof. Anthony K. Cheetham 《Angewandte Chemie (International ed. in English)》2023,62(32):e202306000
Halide double perovskites [A2MIMIIIX6] are an important class of materials that have garnered substantial interest as non-toxic alternatives to conventional lead iodide perovskites for optoelectronic applications. While numerous studies have examined chloride and bromide double perovskites, reports of iodide double perovskites are rare, and their definitive structural characterization has not been reported. Predictive models have aided us here in the synthesis and characterization of five iodide double perovskites of general formula Cs2NaLnI6 (Ln=Ce, Nd, Gd, Tb, Dy). The complete crystal structures, structural phase transitions, optical, photoluminescent, and magnetic properties of these compounds are reported. 相似文献
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Nanocrystalline thin films of Ni–Ti shape memory alloy are deposited on an Si substrate by the DC-magnetron co-sputtering technique and 120?keV Ag ions are implanted at different fluences. The thickness and composition of the pristine films are determined by Rutherford Backscattering Spectrometry (RBS). X-Ray diffraction (XRD), atomic force microscopy (AFM) and four-point probe resistivity methods have been used to study the structural, morphological and electrical transport properties. XRD analysis has revealed the existence of martensitic and austenite phases in the pristine film and also evidenced the structural changes in Ag-implanted Ni–Ti films at different fluences. AFM studies have revealed that surface roughness and grain size of Ni–Ti films have decreased with an increase in ion fluence. The modifications in the mechanical behaviour of implanted Ni–Ti films w.r.t pristine film is determined by using a Nano-indentation tester at room temperature. Higher hardness and the ratio of higher hardness (H) to elastic modulus (Er) are observed for the film implanted at an optimized fluence of 9?×?1015 ions/cm2. This improvement in mechanical behaviour could be understood in terms of grain refinement and dislocation induced by the Ag ion implantation in the Ni–Ti thin films. 相似文献