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排序方式: 共有109条查询结果,搜索用时 15 毫秒
81.
82.
Dr. Tom Wirtanen Santeri Aikonen Dr. Mikko Muuronen Dr. Michele Melchionna Dr. Marianna Kemell Fatemeh Davodi Prof. Tanja Kallio Dr. Tao Hu Dr. Juho Helaja 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(53):12288-12293
HNO3-oxidized carbon nanotubes catalyze oxidative dehydrogenative (ODH) carbon–carbon bond formation between electron-rich (hetero)aryls with O2 as a terminal oxidant. The recyclable carbocatalytic method provides a convenient and an operationally easy synthetic protocol for accessing various benzofused homodimers, biaryls, triphenylenes, and related benzofused heteroaryls that are highly useful frameworks for material chemistry applications. Carbonyls/quinones are the catalytically active site of the carbocatalyst as indicated by model compounds and titration experiments. Further investigations of the reaction mechanism with a combination of experimental and DFT methods support the competing nature of acid-catalyzed and radical cationic ODHs, and indicate that both mechanisms operate with the current material. 相似文献
83.
Ossi Laitinen Jonna Ojala Juho Antti Sirviö Henrikki Liimatainen 《Cellulose (London, England)》2017,24(4):1679-1689
There is an urgent global need to develop novel types of environmentally safe dispersing chemicals from renewable resources in order to reduce the environmental impact of oil spills. For this goal, cellulose, the most abundant natural polymeric source, is a promising green, nontoxic alternative that could replace the current synthetic surfactants. In this study, cellulose nanocrystals (CNC) synthesized using a deep eutectic solvent (DES) and two commercially available cellulose nanocrystals were used as marine diesel oil–water Pickering emulsion stabilizers. In particular, oil in water (o/w) emulsion formation and stability of emulsified oil during storing were addressed using a laser diffraction particle size analyzer, image analysis, and oil emulsion volume examination. The particle size of the o/w reference without CNCs after dispersing was over 50 µm and coalescence occurred only a few minutes after the emulsifying mixing procedure. All three investigated CNCs were effective stabilizers for the o/w system (oil droplets size under 10 µm) by preventing the oil droplet coalescence over time (6 weeks) and resulting in a stable creaming layer. The CNCs prepared using green DES systems boasted performance comparable to that of commercial CNCs, and they showed effectiveness at 0.1% dispersant dosage. 相似文献
84.
Synthesis,Aromaticity and Photophysical Behaviour of Ferrocene‐ and Ruthenocene‐Appended Semisynthetic Chlorin Derivatives 下载免费PDF全文
Taru Nikkonen Dr. María Moreno Oliva Dr. Stefan Taubert Dr. Michele Melchionna Dr. Axel Kahnt Dr. Juho Helaja 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(36):12755-12768
Two novel synthetic strategies to covalently link a metallocene electron‐donor unit to a chlorin ring are presented. In one approach, pyropheophorbide a is readily converted into its 131‐ferrocenyl dehydro derivative by nucleophilic addition of the ferrocenyl anion to the 131‐carbonyl group. In another approach, the corresponding 131‐pentamethylruthenocenyl derivative is synthesised from 131‐fulvenylchlorin by a facile ligand exchange/deprotonation reaction with the [RuCp*(cod)Cl] (Cp*=pentamethylcyclopentadienyl; cod=1,5‐cyclooctadiene) complex. The resulting metallocene–chlorins exhibit reduced aromaticity, which was unequivocally supported by ring‐current calculations based on the gauge‐including magnetically induced current (GIMIC) method and by calculated nucleus‐independent chemical shift (NICS) values. The negative ring current in the isocyclic E ring suggests the antiaromatic character of this moiety and also clarifies the spontaneous reactivity of the complexes with oxygen. The oxidation products were isolated and their electrochemical and photophysical properties were studied. The ruthenocene derivatives turned out to be stable under light irradiation and showed photoinduced charge transfer with charge‐separation lifetimes of 152–1029 ps. 相似文献
85.
Highly monodispersed polystyrene (PS) nanoparticles were prepared via reversible addition fragmentation transfer (RAFT) living radical emulsion polymerization technique. Two types of novel sur-iniferters with different hydrophilic lipophilic balance (HLB) values, 4-diethythiocarbonylsulfanylmethyl-benzoic acid and 4-(2-hydroxyethyl)piperazine-1-carbodithioicacid benylether, were synthesized for the PS RAFT reaction and their chemical synthesis was identified using nuclear magnetic resonance spectroscopy. Scanning electron microscope and dynamic light scattering experiments showed that the size distribution of the particles prepared was highly monodispersed. The average particle size was affected by the type and concentration of sur-iniferters. It increased with decreasing sur-iniferter concentrations, and the use of sur-iniferters with higher HLB values led to increases of particle sizes, as the particles were growing from, initially, much larger monomer droplets. The surfaces of the nano particles prepared were ionically charged. The surface charge measured was −50 mV, which enabled particles to be stably dispersed in aqueous medium. 相似文献
86.
Heli Tuominen 《Arkiv f?r Matematik》2007,45(1):123-139
We give a new characterization of the Orlicz–Sobolev space W
1,Ψ(R
n
) in terms of a pointwise inequality connected to the Young function Ψ. We also study different Poincaré inequalities in the
metric measure space. 相似文献
87.
We provide a complete extension of Minimal Walking Technicolor able to account for the Standard Model fermion masses. The model is supersymmetric at energies greater or equal to the technicolor compositeness scale. We integrate out, at the supersymmetry breaking scale, the elementary Higgses. We use the resulting four-fermion operators to derive the low energy effective theory. We then determine the associated tree-level vacuum and low energy spectrum properties. Furthermore we investigate the phenomenological viability of the model by comparing its predictions with electroweak precision tests and experimental bounds on the mass spectrum. We then turn to the composite Higgs phenomenology at the LHC and show that current data are already constraining the parameter space of the model. 相似文献
88.
Inside Back Cover: Photoinduced Charge Transfer in a Conformational Switching Chlorin Dimer–Azafulleroid in Polar and Nonpolar Media (Chem. Eur. J. 2/2015) 下载免费PDF全文
89.
Frankamp BL Boal AK Tuominen MT Rotello VM 《Journal of the American Chemical Society》2005,127(27):9731-9735
Cationic superparamagnetic iron oxide nanoparticles were assembled using a series of anionic polyamidoamine dendrimers. The resulting assemblies featured systematically increasing average interparticle spacing over a 2.4 nm range with increasing dendrimer generation. This increase in spacing modulated the collective magnetic behavior by effective lowering of the dipolar coupling between particles. The results obtained in these studies deviate from the predicted dependence of collective behavior on interparticle spacing, suggesting that a dense assembly of magnetically "free" particles can exist with a surprisingly small space between particles. 相似文献
90.
We derive sufficient conditions for ∝ λ (dx)6Pn(x, ·) - π6 to be of order o(ψ(n)-1), where Pn (x, A) are the transition probabilities of an aperiodic Harris recurrent Markov chain, π is the invariant probability measure, λ an initial distribution and ψ belongs to a suitable class of non-decreasing sequences. The basic condition involved is the ergodicity of order ψ, which in a countable state space is equivalent to for some i, where τi is the hitting time of the tate i. We also show that for a general Markov chain to be ergodic of order ψ it suffices that a corresponding condition is satisfied by a small set.We apply these results to non-singular renewal measures on providing a probabilisite method to estimate the right tail of the renewal measure when the increment distribution F satisfies ∝ tF(dt) 0; > 0 and ∝ ψ(t)(1- F(t))dt< ∞. 相似文献