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181.
182.
Alexandra Muñoz‐Bonilla Gema Marcelo Cintia Casado Francisco J. Teran Marta Fernández‐García 《Journal of polymer science. Part A, Polymer chemistry》2012,50(24):5087-5096
In this article, magnetite nanoparticles (MNPs) coated with glycopolymer bearing glucose moieties were designed with optimal structural, colloidal, and magnetic properties for biomedical applications. MNPs with an average size of 17 ± 2 nm were synthesized by thermal decomposition process and then their surfaces were modified with active vinyl groups. Two different monomers were immobilized onto the surfaces: dopamine methacrylamide, a monomer with properties inspired on mussels adhesive capacity, or unprotected glycomonomer, 2‐{[(D ‐glucosamin‐2N‐yl)carbonyl]‐oxy}ethyl methacrylate. Afterward, the glycomonomer were polymerized at the interface of both vinyl functionalized MNPs by conventional radical polymerization. The resultant hybrid NPs were water dispersible presenting good stability in aqueous solution for long time periods. Moreover, the high density of carbohydrates at the surface of the magnetic NPs could confer targeting properties to the system as demonstrated by studies of their binding interactions with lectins, where the binding activity is higher as the glycopolymer content augments. The magnetic and magneto‐thermal properties of the synthesized hybrid NPs were evaluated. The magnetization curves reveal superparamagnetic features at 300 K, with high values of saturation magnetization. Furthermore, the hybrid glycoparticles show suitable heat dissipation power when exposed to alternating magnetic field conditions. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
183.
Alexandra C. Stenson 《Rapid communications in mass spectrometry : RCM》2009,23(4):465-476
The interaction between metals and naturally occurring humic substances and the thereby induced issues of bioavailability and hydrogeochemical turnover of metal ions in natural waters have been the subject of intense study for decades. Traditional bulk techniques to investigate metal‐humic binding (e.g. potentiometry and inductively coupled plasma mass spectrometry (ICP‐MS)) can provide quantitative results for the relative abundance and distribution of metal species in humic samples and/or overall binding constants. The shortcoming of these bulk techniques is the absence of structural detail. Ultra‐high‐resolution mass spectrometry, currently the only technique demonstrated to resolve individual humic ions, is not generally employed to provide the missing qualitative information primarily because the identification of metal complexes within the already complex mixtures of humic substances is non‐trivial and time‐consuming to the extent of eliminating any possibility for real‐time manipulation of chelated analytes. Here, it is demonstrated that with tailored selection of the metal ion, it is possible to visually identify large numbers of metal‐humic complexes (~500 for Be2+, ~1100 for Mn2+, and ~1500 for Cr3+) in real‐time as the spectra are being acquired. Metal ions are chosen so that they form primarily even‐m/z complexes with humic ions. These even‐m/z complexes stand out in the spectrum and can readily be characterized based on molecular formulae, which here revealed for example that Suwannee River fulvic acid (SRFA) complexes encompassed primarily highly oxygenated fulvic acids of relatively low double‐bond equivalence. Facile, real‐time identification of even‐m/z metal‐humic complexes additionally allows for the specific selection of metal‐humic complexes for MSn analysis and in‐trap ion‐neutral reactions enabling investigation of metal‐humic complex structure. MS/MS data were collected to demonstrate the potential of the technique as well as highlight some of the remaining challenges. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
184.
Alexandra Zamboulis Nicolas J. Rahier Matthias Gehringer Xavier Cattoën Gilles Niel Catherine Bied Joël J.E. Moreau Michel Wong Chi Man 《Tetrahedron: Asymmetry》2009,20(24):2880-2885
New heterogenised silica-based organocatalysts have been prepared via the sol–gel process from two silylated derivatives of l-proline, featuring either a carbamate or an ether linker. Co-gelification with variable amounts of TEOS was performed with and without porogen to yield high surface area solids. These materials were evaluated as heterogeneous phase organocatalysts for the asymmetric aldol reaction of p-nitrobenzaldehyde with acetone. 相似文献
185.
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188.
Gabriel Chuchani Ignacio Martín Alexandra Rotinov Rosa M. Domínguez 《国际化学动力学杂志》1990,22(12):1249-1255
Elimination kinetics of 2-bromohexane and 2-bromo-4-methylpentane in the gas phase were examined over the temperature range of 310–360°C and pressure range of 46–213 torr. The reactionsin seasoned, static reaction vessels, and in the presence of the free radical inhibitor cyclohexene, are homogeneous, unimolecular, and follow first order rate laws. The overall rate coefficients are described by the following Arrhenius equations: For 2-bromohexane, log??1(s?1) = (13.08 ± 0.70) ? (185.7 ± 8.2) kJ mol?1 (2.303RT)?1; for 2-bromo-4-methylpentane, log??1(s?1) = (13.08 ± 0.33) ? (183.4 ± 3.8) kJ mol?1 (2.303RT)?1. The electron releasing effect of alkyl groups influences the overall elimination rates. The olefin products isomerize in the presence of HBr gas until an equilibrium mixture is reached. 相似文献
189.
Alexandra Rotinov Gabriel Chuchani Ruben A. Machado Carlos Rivas Jairo Quijano Maria Del Socorro Yepes Iliana Restrepo 《国际化学动力学杂志》1992,24(10):909-915
The pyrolysis kinetics of primary, secondary, and tertiary β-hydroxy ketones have been studied in static seasoned vessels over the pressure range of 21–152 torr and the temperature range of 190°–260°C. These eliminations are homogeneous, unimolecular, and follow a first-order rate law. The rate coefficients are expressed by the following equations: for 1-hydroxy-3-butanone, log k1(s?1) = (12.18 ± 0.39) ? (150.0 ± 3.9) kJ mol?1 (2.303RT)?1; for 4-hydroxy-2-pentanone, log k1(s?1) = (11.64 ± 0.28) ? (142.1 ± 2.7) kJ mol?1 (2.303RT)?1; and for 4-hydroxy-4-methyl-2-pentanone, log k1(s?1) = (11.36 ± 0.52) ? (133.4 ± 4.9) kJ mol?1 (2.303RT)?1. The acid nature of the hydroxyl hydrogen is not determinant in rate enhancement, but important in assistance during elimination. However, methyl substitution at the hydroxyl carbon causes a small but significant increase in rates and, thus, appears to be the limiting factor in a retroaldol type of mechanism in these decompositions. © John Wiley & Sons, Inc. 相似文献
190.
Nicholas P. Calta Dr. Jino Im Alexandra P. Rodriguez Dr. Lei Fang Dr. Daniel E. Bugaris Dr. Thomas C. Chasapis Prof. Arthur J. Freeman Prof. Mercouri G. Kanatzidis 《Angewandte Chemie (International ed. in English)》2015,54(32):9186-9191
EuIr4In2Ge4 is a new intermetallic semiconductor that adopts a non‐centrosymmetric structure in the tetragonal ${I\bar 42m}$ space group with unit cell parameters a=6.9016(5) Å and c=8.7153(9) Å. The compound features an indirect optical band gap Eg=0.26(2) eV, and electronic‐structure calculations show that the energy gap originates primarily from hybridization of the Ir 5d orbitals, with small contributions from the Ge 4p and In 5p orbitals. The strong spin–orbit coupling arising from the Ir atoms, and the lack of inversion symmetry leads to significant spin splitting, which is described by the Dresselhaus term, at both the conduction‐ and valence‐band edges. The magnetic Eu2+ ions present in the structure, which do not play a role in gap formation, order antiferromagnetically at 2.5 K. 相似文献