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921.
Steffen Dachwitz Dario H. Duwe Yating Hong Wang Dr. Hendrik Gruß Dr. Yvonne Hannappel Prof. Dr. Thomas Hellweg Prof. Norbert Sewald 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(69):16357-16364
Mild reaction conditions are highly desirable for bio-orthogonal side chain derivatizations of amino acids, peptides or proteins due to the sensitivity of these substrates. Transition metal catalysed cross-couplings such as Suzuki–Miyaura reactions are highly versatile, but usually require unfavourable reaction conditions, in particular, when applied with aryl bromides. Ligand-free solvent-stabilised Pd-nanoparticles represent an efficient and sustainable alternative to conventional phosphine-based catalysts, because the cross-coupling can be performed at considerably lower temperature. We report on the application of such a highly reactive heterogeneous catalyst for the Suzuki–Miyaura cross-coupling of brominated tryptophan derivatives. The solvent-stabilised Pd-nanoparticles are even more efficient than the literature-known ADHP-Pd precatalyst. Interestingly, the latter also leads to the formation of quasi-homogeneous Pd-nanoparticles as the catalytic species. One advantage of our approach is the compatibility with aqueous and aerobic conditions at near-ambient temperatures and short reaction times of only 2 h. The influence of different Nα-protecting groups, boronic acids as well as the impact of different amino acid side chains in bromotryptophan-containing peptides has been studied. Notably, a surprising acceleration of the catalysis was observed when palladium-coordinating side chains were present in proximal positions. 相似文献
922.
Capretto L Carugo D Cheng W Hill M Zhang X 《Journal of colloid and interface science》2011,355(1):243-251
The dynamics and stability of a thin, viscous film of volatile liquid flowing under the influence of gravity over a non-uniformly heated substrate are investigated using lubrication theory. Attention is focused on the regime in which evaporation balances the flow due to gravity. The film terminates above the heater at an apparent contact line, with a microscopically thin precursor film adsorbed due to the disjoining pressure. The film develops a weak thermocapillary ridge due to the Marangoni stress at the upstream edge of the heated region. As for spreading films, a more significant ridge is formed near the apparent contact line. For weak Marangoni effects, the film evolves to a steady profile. For stronger Marangoni effects, the film evolves to a time-periodic state. Results of a linear stability analysis reveal that the steady film is unstable to transverse perturbations above a critical value of the Marangoni parameter, leading to finger formation at the contact line. The streamwise extent of the fingers is limited by evaporation. The time-periodic profiles are always unstable, leading to the formation of periodically-oscillating fingers. For rectangular heaters, the film profiles after instability onset are consistent with images from published experimental studies. 相似文献
923.
Taccola S Desii A Pensabene V Fujie T Saito A Takeoka S Dario P Menciassi A Mattoli V 《Langmuir : the ACS journal of surfaces and colloids》2011,27(9):5589-5595
Freely suspended nanocomposite thin films based on soft polymers and functional nanostructures have been widely investigated for their potential application as active elements in microdevices. However, most studies are focused on the preparation of nanofilms composed of polyelectrolytes and charged colloidal particles. Here, a new technique for the preparation of poly(l-lactic acid) free-standing nanofilms embeddidng superparamagnetic iron oxide nanoparticles is presented. The fabrication process, based on a spin-coating deposition approach, is described, and the influence of each production parameter on the morphology and magnetic properties of the final structure is investigated. Superparamagnetic free-standing nanofilms were obtained, as evidenced by a magnetization hysteresis measurement performed with a superconducting quantum interference device (SQUID). Nanofilm surface morphology and thickness were evaluated by atomic force microscopy (AFM), and the nanoparticle dispersion inside the composites was investigated by transmission electron microscopy (TEM). These nanofilms, composed of a biodegradable polyester and remotely controllable by external magnetic fields, are promising candidates for many potential applications in the biomedical field. 相似文献
924.
T. Aziz J. L. Bailly S. Banerjee W. Bartl F. Bruyant B. Buschbeck C. Caso H. Dibon F. J. Diez-Hedo B. Epp A. Ferrando F. Fontanelli S. N. Ganguli I. V. Gorelov A. Gurtu P. Herquet J. Hrubec V. Khalatyan E. Kistenev S. Kitamura J. M. Kohli D. Kuhn J. MacNaughton P. K. Malhotra J. C. Marin S. Matsumoto I. S. Mittra L. Montanet G. Neuhofer P. Porth T. Rodrigo J. M. Salicio J. B. Singh S. Squarcia V. Stopchenko K. Takahashi U. Trevisan T. Tsurugai T. Yamagata G. Zholobov S. A. Zotkin EHS-RCBC Collaboration 《Zeitschrift fur Physik C Particles and Fields》1986,30(3):381-389
We have studied the inclusive production of strange meson and baryon resonances in 360 GeV/cpp interactions. Cross sections forK *+(892) andK *?(892) are estimated to be 4.42±0.62 mb and 2.54±0.47 mb respectively and those for∑ +(1385) and∑ ?(1385) are 0.67±0.11 mb and 0.26±0.07 mb respectively. Longitudinal and transverse momentum distributions forK *(892) and Σ(1385) are presented, as well as for their decay productsK 0 and Λ. An estimation is given on theK *(1430) and∑ *(1915) productions. 相似文献
925.
Giacomo Bondietti Gianfranco Suardi Renzo Ros Raymond Roulet Fabrizia Grepioni Dario Braga 《Helvetica chimica acta》1993,76(8):2913-2925
The synthesis of [Ir2Rh2(CO)12] ( 1 ) by the literature method gives a mixture 1 /[IrRh3(CO)12] which cannot be separated using chromatography. The reaction of [Ir(CO)4]? with 1 mol-equiv. of [Rh(CO)2(THF)2]+ in THF gives pure 1 in 61% yield. Crystals of 1 are highly disordered, unlike those of its derivative [Ir2Rh2(CO)5(μ2-CO)3(norbornadiene)2] which were analysed using X-ray diffraction. The ground-state geometry of 1 in solution has three edge-bridging CO's on the basal IrRh2 face of the metal tetrahedron. Time averaging of CO's takes place above 230 K. The CO site exchange of lowest activation energy is due to one synchronous change of basal face, as shown by 2D- and VT-13C-NMR. Substitution of CO by X? in 1 takes place at a Rh-atom giving [Ir2Rh2(CO)8(μ2-CO)3X]? (X = Br, I). Substitution by bidentate ligands gives [Ir2Rh2(CO)7(μ2-CO)3(η4-L)] (L = norbornadiene, cycloocta-1,5-diene) where the ligand L is chelating a Rh-atom of the basal IrRh2 face. Carbonyl substitution by tridentate ligands gives [Ir2Rh2(CO)6(μ2-CO)3(μ3-L)] (L = 1,3,5-trithiane, tripod) with L capping the triangular basal face of the metal tetrahedron. Carbonyl scrambling is also observed in these substituted derivatives of 1 and is mainly due to the rotation of three terminal CO's about a local C3 axis on the apical Ir-atom. 相似文献
926.
927.
928.
Giovanni Polacco Dario Biondi Jiri Stastna Zora Vlachovicova Ludovit Zanzotto 《Macromolecular Symposia》2004,218(1):333-342
In this note rheological properties of two different polymer modified asphalts (PMA) are compared. PMAs were prepared from two different base asphalts, a soft one (200/300 Pen grade) and a hard one (70/100 Pen grade), by addition of 4% by weight of radial SBS as modifier. Dynamic mechanical properties were determined in a wide temperature range for bases and modified asphalts both before and after artificial aging. As expected, the moduli of the soft base are more sensitive to polymer addition and the two PMAs attain similar maximum values after aging. However a significant difference in the frequency at which the maxima of the loss modulus are reached is maintained within the two materials irrespectively of aging or polymer addition. 相似文献
929.
María Inés Gareis Federico Dario Kovac Fabián Eduardo Levis 《Mathematische Nachrichten》2023,296(8):3328-3343
In this paper, we consider the best polynomial approximation operator defined on an Orlicz–Lorentz space , and its extension to , where w is a non-negative continuous weight function and is the derivative of ϕ, which is not required to be an Orlicz function. Our work generalizes a recent result in this field on an Orlicz–Lorentz space generated by an Orlicz function. In addition, we establish some properties and estimates for any extended best polynomial approximation. 相似文献
930.
We prove that the kth Gaussian map is surjective on a polarized unnodal Enriques surface with . In particular, as a consequence, when , we obtain the surjectivity of the kth Gauss-Prym map , with , on smooth hyperplane sections . In case , it is sufficient to ask . 相似文献