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551.
A class of generalized polynomials is considered consisting of the null spaces of certain differential operators with constant
coefficients. This class strictly contains ordinary polynomials and appropriately scaled trigonometric polynomials. An analog
of the classical Bernstein operator is introduced and it is shown that generalized Bernstein polynomials of a continuous function
converge to this function. A convergence result is also proved for degree elevation of the generalized polynomials. Moreover,
the geometric nature of these functions is discussed and a connection with certain rational parametric curves is established.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
552.
Fabiana Tescione Olimpia Tammaro Aurelio Bifulco Giovanni Del Monaco Serena Esposito Michele Pansini Brigida Silvestri Aniello Costantini 《Molecules (Basel, Switzerland)》2022,27(6)
Hybrid tannic acid-silica-based porous nanoparticles, TA-SiO2 NPs, have been synthesized under mild conditions in the presence of green and renewable tannic acid biopolymer, a glycoside polymer of gallic acid present in a large part of plants. Tannic acid (TA) was exploited as both a structuring directing agent and green chelating site for heavy metal ions recovery from aqueous solutions. Particles morphologies and porosity were easily tuned by varying the TA initial amount. The sample produced with the largest TA amount showed a specific surface area an order of magnitude larger than silica nanoparticles. The adsorption performance was investigated by using TA-SiO2 NPs as adsorbents for copper (II) ions from an aqueous solution. The effects of the initial Cu2+ ions concentration and the pH values on the adsorption capability were also investigated. The resulting TA-SiO2 NPs exhibited a different adsorption behaviour towards Cu2+, which was demonstrated through different tests. The largest adsorption (i.e., ~50 wt% of the initial Cu2+ amount) was obtained with the more porous nanoplatforms bearing a higher final TA content. The TA-nanoplatforms, stable in pH value around neutral conditions, can be easily produced and their use would well comply with a green strategy to reduce wastewater pollution. 相似文献
553.
Casey Van Stappen Emilio Jimnez-Vicente Ana Prez-Gonzlez Zhi-Yong Yang Lance C. Seefeldt Serena DeBeer Dennis R. Dean Laure Decamps 《Chemical science》2022,13(12):3489
Reduction of dinitrogen by molybdenum nitrogenase relies on complex metalloclusters: the [8Fe:7S] P-cluster and the [7Fe:9S:Mo:C:homocitrate] FeMo-cofactor. Although both clusters bear topological similarities and require the reductive fusion of [4Fe:4S] sub-clusters to achieve their respective assemblies, P-clusters are assembled directly on the NifD2K2 polypeptide prior to the insertion of FeMo-co, which is fully assembled separately from NifD2K2. P-cluster maturation involves the iron protein NifH2 as well as several accessory proteins, whose role has not been elucidated. In the present work, two NifD2K2 species bearing immature P-clusters were isolated from an Azotobacter vinelandii strain in which the genes encoding NifH and the accessory protein NifZ were deleted, and characterized by X-ray absorption spectroscopy and EPR. These analyses showed that both NifD2K2 complexes harbor clusters that are electronically and structurally similar, with each NifDK unit containing two [4Fe:4S]2+/+ clusters. Binding of the accessory protein NifW parallels a decrease in the distance between these clusters, as well as a subtle change in their coordination. These results support a conformational role for NifW in P-cluster biosynthesis, bringing the two [4Fe:4S] precursors closer prior to their fusion, which may be crucial in challenging cellular contexts.Upon binding of NifW, a subtle conformation change occurs in NifD2K2, decreasing the distance between the two [4Fe:4S] clusters precursors of the P-cluster in nitrogenase. 相似文献
554.
Serena Fantasia Björn Bartels Fritz Bliss Fritz Koch Michelangelo Scalone Daniel Spiess Markus Steiner Shaoning Wang Kurt Püntener 《Helvetica chimica acta》2023,106(10):e202300116
The research efforts to attain a suitable process for the timely delivery of Gemlapodect for initial toxicological and phase 1/2 clinical studies are described. The original discovery chemistry route was hampered by considerable safety issues and low overall yield. The safety issues were solved by the introduction of a copper-catalyzed oxidative cyclization while a novel process for the synthesis of the pyrazole building block as well as the implementation of a palladium-catalyzed coupling between the pyrazole amide and the bromo-triazolopyridine scaffolds contributed to improve the route efficiency. Overall, a safe and sustainable process was attained that allowed the production of up to 19.2 kg of drug substance with a reduced number of steps and an increased overall yield. 相似文献
555.
Serena Margadonna Efstathios Aslanis Wen Zhi Li Kosmas Prassides Andrew N. Fitch Thomas C. Hansen 《ChemInform》2001,32(1):no-no
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
556.
557.
Dr. Francesco Messa Dr. Andrea Nicola Paparella Dr. Dominik Veselý Prof. Jozef Krajčovič Dr. Paride Papadia Dr. Serena Perrone Prof. Antonio Salomone 《European journal of organic chemistry》2023,26(24):e202300309
The Pd-catalyzed amino- and alkoxycarbonylation of aryl iodides has been exploited, for the first time, in a bioinspired Deep Eutectic Solvent and under gas-free conditions, by using Mo(CO)6 as the CO source. The method allows for the preparation of carboxylic amides and esters in high yields (up to 99 %), short reaction time (2 h) and under mild reaction conditions (80 °C), with a low catalyst loading (2.5 mol %). Noteworthy, in the case of N-hexylbenzamide, it has been demonstrated that both the catalyst and DES can be used for four consecutive runs, with a moderate decrease of catalytic efficiency. The methodology has been also applied to the preparation of an Active Pharmaceutical Ingredient used for the treatment of human scabies and lice. 相似文献
558.
Elisa Passaglia Serena Coiai Mauro Aglietto Giacomo Ruggeri Marco Rubertà Francesco Ciardelli 《Macromolecular Symposia》2003,198(1):147-160
Previous studies carried out in our laboratory on the functionalization of ethylene polymers (homo and copolymers) through free radical processes, using mechanical mixers and/or extruders with diethylmaleate (DEM) and dicumyl peroxide (DCP), have shown that the presence of branched α-olefin blocks favours degradation versus functionalization and crosslinking whereas these last are more effective with linear ethylene blocks. In this contest the present paper reports about attempts to extend the same processes to propylene polymers by benefitting of the indications of previous results. In particular the one step functionalization of EPM with two or more different groups was carried through the use of different monomers. Moreover the procedure was extended to polypropylene thus obtaining a significant functionalization degree flanked by a remarkable decrease of molecular weight. 相似文献