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971.
Nano–silica functionalized with thiol–based dendrimer as a host for gold nanoparticles: An efficient and reusable catalyst for chemoselective oxidation of alcohols
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Sara Haghshenas Kashani Amir Landarani‐Isfahani Majid Moghadam Shahram Tangestaninejad Valiollah Mirkhani Iraj Mohammadpoor‐Baltork 《应用有机金属化学》2018,32(9)
In this paper, we present the synthesis of Au nanoparticles supported on nanosilica thiol based dendrimer, nSTDP. The catalyst was prepared by reduction of HAuCl4 with NaBH4 in the presence of nSTDP. The resulting Aunp–nSTDP materials were characterized by FT–IR and UV–vis spectroscopic methods, SEM, TEM, TGA, XPS and ICP analyses. The characterization of the catalyst showed that Au nanoparticles with the size of 2–6 nm are homogeneously distributed on the nSTDP dendrimer with a catalyst loading of about 0.19 mmol/g of catalyst. The Aunp–nSTDP catalyst was used in the oxidation of alcohols with tert–butyl hydroperoxide (TBHP) as oxidant. The influence of vital reaction parameters such as solvent, oxidant and amount of catalyst on the oxidation of alcohols was investigated. These reactions were best performed in an acetonitrile/water mixture (3:2) in the presence of 0.76 mol% of the catalyst on the basis of the Au content at 80 °C under atmospheric pressure of air to afford the desired products in high yields (80–93% for benzyl alcohols). The Aunp–nSTDP catalyst exhibited a high selectivity toward the corresponding aldehyde and ketone (up to 100%). Reusabiliy and stability tests demonstrated that the Aunp–nSTDP catalyst can be recycled with a negligible loss of its activity. Also this catalytic exhibited a good chemoselectivity in the oxidation of alcohols. 相似文献
972.
Sara Hesham Abdelghaffar Maha Abdelmonem Hegazy Basma Mohamed Eltanany 《Biomedical chromatography : BMC》2022,36(2):e5258
Ramucirumab (RAMU) is a recently US Food and Drug Administration-approved monoclonal antibody that is included in various anticancer protocols. It has a structural complexity and high degradation risk that have a significant effect on its safety and effectiveness. The major aim of this work was to assess the degradation pattern of RAMU based on physicochemical characterization. Mechanical agitation, repeated freeze–thaw cycles, pH and temperature were the selected stress conditions to which RAMU samples were subjected. The SE-HPLC method was applied and validated to monitor the RAMU monomer along with its aggregates and/or fragments. The purity of the separated peaks together with system suitability parameters were determined through the calculation of percentage purity and percentage drop in RAMU concentration. The results were interpreted by correlating them with those of dynamic light scattering and reducing and non-reducing sodium dodecyl sulfate–polyacrylamide gel electrophoresis. Samples incubated at pH 2.0–10.0 and 37°C for up to 4 weeks were analysed, recording detection of reversed phase (RP) aggregates and low molecular weight peptide fragments. Similarly, samples under short-term storage conditions of 4 weeks at different temperatures (−20, 2–8, 25, 37 and 50°C) showed low molecular weight peptide fragments but to a lesser extent. These results highlight the alarming effect on RAMU multidose vial efficacy and safety. 相似文献
973.
Annals of Operations Research - We analyze a dual-channel supply chain comprising two suppliers that offer vertically-differentiated agricultural products; specifically, one offers an organic... 相似文献
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Paola Stagnaro Giorgio Mancini Achille Piccinini Simona Losio Maria Carmela Sacchi Caterina Viglianisi Stefano Menichetti Alessandro Adobati Sara Limbo 《Journal of Polymer Science.Polymer Physics》2013,51(13):1007-1016
An efficient procedure for the copolymerization of ethylene (E) with a novel norbornenic comonomer (NArOH) bearing a stabilizing moiety analogous to commercial antioxidant 2,6‐di‐tert‐butyl‐4‐methylphenol (BHT) is successfully developed. This study is aimed at: i) tuning the concentration of the stabilizing function along the polymer chain, and ii) preparing “nonreleasing” polymeric additives specifically destined to protect commercial low‐density polyethylene (LDPE). Films obtained from blends of the novel E/NArOH copolymers with an antioxidant‐free LDPE matrix are characterized by superior thermal, thermo‐oxidative, and photostability when compared not only with neat LDPE films but also with films stabilized by the commercial BHT additive. Specific migration tests conducted in order to investigate the nonreleasing character of the novel macromolecular additives confirm the reduced risk of migration, from the films into food simulants, of unreacted comonomer or degradation products bearing the antioxidant moiety. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013 , 51, 1007–1016 相似文献
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979.
Frederick L. Theiss Sara J. Palmer Godwin A. Ayoko Ray L. Frost 《Journal of Thermal Analysis and Calorimetry》2012,107(3):1123-1128
The removal of the sulfate anion from water using synthetic hydrotalcite (Mg/Al LDH) was investigated using powder X-ray diffraction
(XRD) and thermogravimetric analysis (TG). Synthetic hydrotalcite Mg6Al2(OH)16(CO3)·4H2O was prepared by the co-precipitation method from aluminum and magnesium chloride salts. The synthetic hydrotalcite was thermally
activated to a maximum temperature of 380 °C. Samples of thermally activated hydrotalcite where then treated with aliquots
of 1000 ppm sulfate solution. The resulting products where dried and characterized by XRD and TG. Powder XRD revealed that
hydrotalcite had been successfully prepared and that the product obtained after treatment with sulfate solution also conformed
well to the reference pattern of hydrotalcite. The d(003) spacing of all samples was found to be within the acceptable region for a LDH structure. TG revealed all products underwent
a similar decomposition to that of hydrotalcite. It was possible to propose a reasonable mechanism for the thermal decomposition
of a sulfate containing Mg/Al LDH. The similarities in the results may indicate that the reformed hydrotalcite may contain
carbonate anion as well as sulfate. Further investigation is required to confirm this. 相似文献
980.
Dr. Sara Morales-Reina Dr. Chandan Giri Maxime Leclercq Dr. Sonia Vela-Gallego Isabel de la Torre Dr. José R. Castón Dr. Mathieu Surin Dr. Andrés de la Escosura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(5):1082-1090
One of the major goals in systems chemistry is to create molecular assemblies with emergent properties that are characteristic of life. An interesting approach toward this goal is based on merging different biological building blocks into synthetic systems with properties arising from the combination of their molecular components. The covalent linkage of nucleic acids (or their constituents: nucleotides, nucleosides and nucleobases) with lipids in the same hybrid molecule leads, for example, to the so-called nucleolipids. Herein, we describe nucleolipids with a very short sequence of two nucleobases per lipid, which, in combination with hydrophobic effects promoted by the lipophilic chain, allow control of the self-assembly of lipidic amphiphiles to be achieved. The present work describes a spectroscopic and microscopy study of the structural features and dynamic self-assembly of dinucleolipids that contain adenine or thymine moieties, either pure or in mixtures. This approach leads to different self-assembled nanostructures, which include spherical, rectangular and fibrillar assemblies, as a function of the sequence of nucleobases and chiral effects of the nucleolipids involved. We also show evidence that the resulting architectures can encapsulate hydrophobic molecules, revealing their potential as drug delivery vehicles or as compartments to host interesting chemistries in their interior. 相似文献