A new way to fabricate monodisperse polymer particles in a microfluidic device without UV‐light and without the need for high temperatures is described in this article. By applying an activator regeneration by electron transfer ‐ atom transfer radical polymerization (ARGET‐ATRP) initiator system in a co‐capillary microfluidic setup and by separating the monomer mixture in an initiator and a catalyst phase, a fast polymerization of the droplets at low temperature without premature curing and thus clogging of the capillaries can be achieved. The influence of the flow rates on the particle sizes and their polydispersity as well as the controlled character of the polymerization are investigated. The particle size is well adjustable, but the reaction is not controlled due to the high radical concentration needed for rapid polymerization. In addition, particles with incorporated UV‐dyes are produced as a proof of concept at low temperature.
Molecular simulations and NMR relaxometry experiments demonstrate that pure benzene or xylene confined in isoreticular metal–organic frameworks (IRMOFs) exhibit true vapor–liquid phase equilibria where the effective critical point may be reduced by tuning the structure of the MOF. Our results are consistent with vapor and liquid phases extending over many MOF unit cells. These results are counterintuitive since the MOF pore diameters are approximately the same length scale as the adsorbate molecules. As applications of these materials in catalysis, separations, and gas storage rely on the ability to tune the properties of adsorbed molecules, we anticipate that the ability to systematically control the critical point, thereby preparing spatially inhomogeneous local adsorbate densities, could add a new design tool for MOF applications. 相似文献
Methyl methacrylate, benzyl methacrylate, butyl methacrylate, and methacrylic acid can be polymerized by 1, 2, 2-tetraphenyl-1, 2-diphenoxyethane (TPPA), 1, 1, 2, 2-tetraphenyl-1, 2-bis-(trimethylsiloxy) ethane (TPSA), and 1, 1, 2, 2-tetraphenyl-1, 2-dicyanoethane (TPCA) (1–3). The polymerization with these initiators is characterized by three steps; in the first period oligomers from MMA and initiator radicals are formed by primary radical termination. 相似文献
Large-amplitude climate shifts, the so-called Dansgaard-Oeschger events, repeatedly occurred throughout the last ice age.
These events, which are apparently threshold-crossing events, show a reported tendency to recur preferably in near multiples
of about 1470 years. Several non-linear resonance mechanisms were proposed to explain this recurrence pattern in response
to noise and/or periodic forcing. Standard methods of linear time series analysis are not sufficient to distinguish between
these hypotheses, owing to the threshold-crossing dynamics of the events. Recently, new approaches were made by means of null-hypothesis
testing with Monte Carlo methods. A major hurdle in this approach is the need of efficient, but yet simple measures of regularity
that allow to distinguish between the proposed resonance mechanisms. By means of surrogate time series (i.e. by using a large
ensemble of Dansgaard-Oeschger events as simulated with a very simple two-state model) I here test the ability of three standard
measures of periodicity to distinguish between a scenario of solely noise-induced events and a ghost stochastic resonance
scenario. Only one measure is found to be applicable for that purpose. The choice of adequate measures, which is not trivial,
should be given more attention in future studies that focus on the question what triggered threshold-crossing events such
as Dansgaard-Oeschger events. 相似文献
The running coupling is introduced into the equation for the odderon via the bootstrap relation. It is shown that the previously
found odderon state with a maximal intercept, which is constructed from an antisymmetric pomeron wave function, continues
to exist in the running coupling case. Its intercept is found to remain equal to unity independent of the behaviour assumed
for the running coupling at low momenta. 相似文献
The intersection between dislocations and a Ag(111) surface has been studied using an interplay of scanning tunneling microscopy (STM) and molecular dynamics. Whereas the STM provides atomically resolved information about the surface structure and Burgers vectors of the dislocations, the simulations can be used to determine dislocation structure and orientation in the near-surface region. In a similar way, the subsurface structure of other extended defects can be studied. The simulations show dislocations to reorient the partials in the surface region leading to an increased splitting width at the surface, in agreement with the STM observations. Implications for surface-induced cross slip are discussed. 相似文献
The oxidative cyclization of a phenolic amide to a spirolactam has long been regarded as an "impossible" reaction, because exposure of the substrates to a variety of oxidants results in formation of spirolactones with consequent loss of the amine segment. We recently communicated that this heretofore unknown transformation may be achieved by oxidation of oxazoline analogues of phenolic and indolic amides. Herein, we provide full details of our work. 相似文献
Rapid and regioselective activation of the C-F bond of 2,4,6-trifluoropyrimidine occurs on reaction with [Ni(cod)(2)] (cod=1,5-cyclooctadiene) in the presence of PEt(3) to give 1, which can be converted into complex 2, containing a further N(3)-metalated pyrimidin-4-one unit. The novel pyrimidin-4-one 3 is released on protonation of 2. 相似文献