Polymerization reactions can benefit from continuous‐flow microprocess in terms of kinetics control, reactants mixing or simply efficiency when high‐throughput screening experiments are carried out. In this work, we perform for the first time the synthesis of branched macromolecular architecture through a controlled/‘living' polymerization technique, in tubular microreactor. Just by tuning process parameters, such as flow rates of the reactants, we manage to generate a library of polymers with various macromolecular characteristics. Compared to conventional batch process, polymerization kinetics shows a faster initiation step and more interestingly an improved branching efficiency. Due to reduced diffusion pathway, a characteristic of microsystems, it is thus possible to reach branched polymers exhibiting a denser architecture, and potentially a higher functionality for later applications. 相似文献
New asymmetric trans-platinum(II) complexes, composed of an isopropylamine, an azole and two carboxylate leaving groups, are presented. The crystal and molecular structures of one of the complexes has been determined and the cytotoxicity and reactivity with 5'-guanosine monophosphate is reported. The complexes show a reduced reactivity, but no decrease in cytotoxic activity compared to their chloro-counterparts. Furthermore the complexes largely overcome cisplatin resistance, they therefore present an interesting class of antitumour active trans-platinum complexes. 相似文献
Bachus et al. [1] recently described a new derivatisation method using 2-furoyl chloride for the characterisation of mixtures of polyethoxylated
alcohols and their corresponding sulfates. This paper deals with the control of the derivatisation steps; hydrolysis and extraction
conditions were optimised. The method is extended to the characterisation of alkyl sulfosuccinates, alkyl sulfoacetates and
alkyl phosphates and to the analysis of residual polyethoxylated alcohols in surfactants. Extraction of non-ionic compounds
using solid-phase extraction cartridges was performed before derivatisation. Residual amounts of alcohol were determined in
five commercial anionic surfactants. Moreover, direct derivatisation without preliminary SPE in the same anionic surfactants
proved to be efficient for dry samples. 相似文献
Caenorhabditis elegans actively crawls down thermal gradients until it reaches the temperature of its prior cultivation, exhibiting what is called cryophilic movement. Implicit in the worm's performance of cryophilic movement is the ability to detect thermal gradients, and implicit in regulating the performance of cryophilic movement is the ability to compare the current temperature of its surroundings with a stored memory of its cultivation temperature. Several lines of evidence link the AFD sensory neuron to thermotactic behavior, but its precise role is unclear. A current model contends that AFD is part of a thermophilic mechanism for biasing the worm's movement up gradients that counterbalances the cryophilic mechanism for biasing its movement down gradients.
Results
We used tightly-focused femtosecond laser pulses to dissect the AFD neuronal cell bodies and the AFD sensory dendrites in C. elegans to investigate their contribution to cryophilic movement. We establish that femtosecond laser ablation can exhibit submicrometer precision, severing individual sensory dendrites without causing collateral damage. We show that severing the dendrites of sensory neurons in young adult worms permanently abolishes their sensory contribution without functional regeneration. We show that the AFD neuron regulates a mechanism for generating cryophilic bias, but we find no evidence that AFD laser surgery reduces a putative ability to generate thermophilic bias. In addition, although disruption of the AIY interneuron causes worms to exhibit cryophilic bias at all temperatures, we find no evidence that laser killing the AIZ interneuron causes thermophilic bias at any temperature.
Conclusion
We conclude that laser surgical analysis of the neural circuit for thermotaxis does not support a model in which AFD opposes cryophilic bias by generating thermophilic bias. Our data supports a model in which the AFD neuron gates a mechanism for generating cryophilic bias. 相似文献
Sufficient conditions are given to assert that two C1-mappings share only one value in a connected compact Banach manifold modelled over ?n. The proof of the result, which is based upon continuation methods, is constructive. 相似文献
Let G be a split simple group of type over a field k, and let be its Lie algebra. Answering a question of J.-L. Colliot-Thélène, B. Kunyavski?, V.L. Popov, and Z. Reichstein, we show that the function field is generated by algebraically independent elements over the field of adjoint invariants . 相似文献
We consider the almost sure asymptotic behavior of the periodogram of stationary and ergodic sequences. Under mild conditions we establish that the limsup of the periodogram properly normalized identifies almost surely the spectral density function associated with the stationary process. Results for a specified frequency are also given. Our results also lead to the law of the iterated logarithm for the real and imaginary parts of the discrete Fourier transform. The proofs rely on martingale approximations combined with results from harmonic analysis and techniques from ergodic theory. Several applications to linear processes and their functionals, iterated random functions, mixing structures and Markov chains are also presented. 相似文献
Below its ordering temperature (TN = 90 K), bulk bcc Eu has a helical magnetic state with propagation vectors along the three equivalent 〈100〉 directions. In
contrast, epitaxial (110)Eu films exhibit a unique magnetic ordering: the domain with a magnetic helix propagating along the
in-plane [001] direction vanishes on cooling, at the expense of other domains with helices propagating along [100] and [010].
This paper is devoted to the study of the stability of the magnetic domains in an external magnetic field using neutron scattering
experiments and macroscopic magnetization measurements. The helix propagating along the [001] direction can be restored by
the application of an external field along this direction. On the contrary, when a magnetic field is applied along an intermediate
direction, specifically [10], the domain with a helix propagating along [001] is suppressed. Both effects depend on the film thickness. They are explained
if one considers that, because of the low magnetic anisotropy of Eu, a helix with a propagation vector parallel to (or close
to) the applied magnetic field is energetically more favourable than cycloidal structures with unchanged propagation vectors.
Finally, the amplitudes of the propagation vectors and their directions (that are modified in films compared to bulk) do not
vary under magnetic field. 相似文献
In this communication, γ‐phenyl‐γ‐butyrodithiolactone (DTL1) is presented as the first example of a new type of control agent. The styrene polymerization carried out at 60 °C in the presence of DTL1 exhibits living characteristics, without consuming DTL1 during the process. This unprecedented behavior was explained by a mechanism based on the reversible formation of a persistent radical adduct between the DTL1 and the polystyrene macroradicals.