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991.
992.
André Loupy Noelle Philippon Philippe Pigeon Jean Sansoulet Hervé Galons 《合成通讯》2013,43(18):2855-2864
Solid-liquid PTC without added solvent efficiently promotes SNAr reactions of a variety of anionic nucleophiles generated in situ. This methodology is applied with success to some examples concerning non-activated aromatic systems. TDA-1 is the most effective catalyst. 相似文献
993.
Neville Boden Richard J. Bushby Kevin Donovan Quanying Liu Zhibao Lu Theo Kreouzis 《Liquid crystals》2013,40(12):1739-1748
A synthesis has been developed for 2,3,7,8,12,13-hexakis[2-(2-methoxyethoxy)ethoxy]-tricycloquinazoline (TCQ6EO2M) in which the ethylenoxy side chains are introduced before elaboration of the heterocylic core. This discogen gives a hexagonal columnar phase (Colh) between 77 and 233°C. n-Doping using potassium metal is facilitated firstly by the electron poor/π-deficient nature of the core and secondly by the polyethylenoxy side chains which complex the potassium K+ counter-ions. The conductivity of the Colh phase of TCQ6EO2M doped with 10 mol % potassium (σ ∥ = 1.1 x 10-3 S m-1) is substantially higher than that previously reported for 2,3,7,8,12,13-hexa(hexylthio)tricycloquinazoline doped with 6 mol % potassium (σ ∥ = 2.9 x 10-5 S m-1). Photoconductivity studies of TCQ6EO2M using a time of flight sample configuration show transient photocurrents for both holes and electrons. From these an upper limit on the mobility for the electrons is estimated as ~10-4 cm2 V-1 s-1 at 150°C which is of the same magnitude as that for hole mobilities in other columnar discotic liquid crystals. 相似文献
994.
Baptiste Schindler Agathe Depraz Depland Gina Renois-Predelus Gabriel Karras Bruno Concina Gulabi Celep Jacques Maurelli Vincent Loriot Eric Constant Richard Bredy Christian Bordas Franck Lépine Isabelle Compagnon 《International Journal for Ion Mobility Spectrometry》2017,20(3-4):119-124
An original workflow allowing inline FAIMS separation, electrospray ionization, mass analysis and ion spectroscopy (IRMPD: InfraRed Multiple Photon Dissociation) is presented for multidimensional molecular analysis. This new instrument consists of an ultraFAIMS (Owlstone) device interfaced to a linear ion trap (LTQ XL Thermo Scientific) which was modified for IRMPD spectroscopy. Two modes of operation are demonstrated on an isomeric mixture of paracetamol and 2-phenylglycine. In the first mode a FAIMS (high-Field Asymmetric waveform Ion Mobility Spectrometry) separation of the isomers is performed with a static compensation field for mass- and isomer- selective ion spectroscopy. In the second mode, the compensation field is scanned while the ions are irradiated at a fixed wavenumber. The advantages of this workflow as compared to traditional FAIMS-MS and IRMPD spectroscopy are described. The potential of the two modes for molecular spectroscopy and analytical applications, in particular the new “omics” are discussed. 相似文献
995.
996.
Fouad Laoutid Marion Lorgouilloux Didier Lesueur Leila Bonnaud Philippe Dubois 《Polymer Degradation and Stability》2013
In this study, we evaluated the potential flame retardant effect of calcium-based hydrated minerals, such as hydrated lime, partially and completely hydrated dolomitic limes in polyethylene (MDPE) and ethylene vinyl acetate copolymers (EVA) and compared to that obtained with magnesium di-hydroxide (MDH). The most significant flame retardant effects, observed using the mass loss calorimeter test, indicated that Ca-based MDPE composites showed similar peak Heat Release Rate (pHRR) level to that obtained with MDH composite while the pHRR was lower for Ca-based fillers in EVA compositions. X-ray Diffraction (XRD) data, combined with thermal analysis results, indicated that the calcium di-hydroxide plays a role in the formation of an intumescent cohesive residue during the combustion. Indeed, Ca(OH)2 reacts with CO2 formed during the thermal degradation of the polymer to generate CaCO3 (calcium carbonate) that contributes to the enhancement of the mechanical resistance of the residue. 相似文献
997.
We develop a fully calibrated positive mathematical programming model for Hawaii's local food systems—which captures the production and the consumer sides of the market. Then we use the model to assess two proposed policies—a general excise tax (GET) exemption on locally produced foods, and an investment in agricultural infrastructure. For the GET exemption case, our results indicate an economic gain of $118 per $100 cost. On the other hand, an investment in 1,200 acres of land injected to support local production may generate an economic gain of up to $357 per $100 annual cost of the investment. However, these estimates should be considered preliminary, and thus viewed with caution. Although the model is used to capture Hawaii's local food systems, we believe that our model is generalizable and can be adopted by other economies to assess their respective food localization policies. Recommendations for Resource Managers
- Local food policies need to be based on quantitative terms instead of mere armchair speculation because often their potential outcomes may vary significantly.
- The current modeling framework demonstrates the potential of using positive mathematical programming (PMP) in capturing the intricacies of local food systems. However, this exploratory exercise should be viewed as preliminary in nature and the ensuing results were taken with caution because many important factors such as labor availability may have been left out.
- Thus, further model refinements are necessary to better capture the complexities of local food systems such as farm heterogeneity, availability of farm labor, water availability, and interisland transportation of farm products in the case of Hawaii.
998.
Farah Naz Bibimaryam Mousavi Zhixiong Luo Christia Jabbour Philippe M. Heynderickx Somboon Chaemchuen Francis Verpoort 《应用有机金属化学》2019,33(5)
A series of spray dried zeolitic imidazolate frameworks (ZIFs = ZIF‐8, ZIF‐67, and Zn/Co‐ZIF) are used as a catalyst for the bulk ring‐opening polymerization of δ‐valerolactone without any co‐catalyst to generate polyvalerolactone. Interestingly, using the same catalyst under the same reaction conditions could manipulate the structure of the product polymer, and thus its physical properties. Thus, using a dried substrate leads to the formation of the cyclic polymer while a linear polymer was formed on using the commercially available substrate. An activated monomer mechanism has been suggested where the propagating zinc alkoxide undergoes an intramolecular transesterification to release cyclic or linear polyvalerolactone. The ROP of δ‐VL without drying shows that the polymeric zwitterions have little tendency to cyclize in the presence of moisture. At 140 °C, ZIF‐8 shows a superior catalytic activity resulting in the production of cyclic polyvalerolactone having a high molecular weight as compared to ZIF‐67 or Zn/Co‐ZIF due to the presence of highly active sites. The catalyst could be recycled and reused without any significant loss of catalytic activity. 相似文献
999.
Dr. Christoph Ludwig Teske Dr. Anna-Lena Hansen Prof. Dr. Richard Weihrich Prof. Dr. Lorenz Kienle Marius Kamp Kasper Pieter van der Zwan Prof. Dr. Jürgen Senker Dr. Carsten Dosche Prof. Dr. Gunther Wittstock Prof. Dr. Wolfgang Bensch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(27):6763-6772
A new preparation route is developed for the synthesis of needle-like crystals of [Au(S2CNH2)2]SCN, which avoids disproportionation of the AuI salt used as a starting material. In the crystal structure, the two crystallographically independent AuIII centers are in a square-planar environment of two S2CNH2 ligands. The Hirshfeld surface analysis reveals the presence of noncovalent intermolecular S⋅⋅⋅S interactions, which are essential for the spatial arrangement of the molecules. Density functional theory (DFT) calculations including dispersion and damping corrections result in a unit cell volume very close to the value determined experimentally. Thermal decomposition in an inert atmosphere generates black needles with lengths of up to 500 μm. X-ray powder diffraction and pair distribution function analyses demonstrate that the needles are composed of nanosized crystals with a volume-weighted average domain size of 20(1) nm. According to results of X-ray photoemission experiments, the black needles are covered by a nitrogen-rich carbon nitride with composition near (CN)2N. 13C solid-state NMR investigations indicate that two different carbon species are present, with signals corresponding well to heptazine units as in melon and triazine units as in poly(triazin imide) type compounds. Scanning transmission electron microscopy tomography evidences that the needles are composed of slightly elongated nanoparticles. 相似文献
1000.
Dr. Antoine Nitelet Dr. Damien Thevenet Dr. Bruno Schiavi Dr. Christophe Hardouin Dr. Jean Fournier Dr. Rodolphe Tamion Prof. Dr. Xavier Pannecoucke Prof. Dr. Philippe Jubault Prof. Dr. Thomas Poisson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(13):3262-3266
The copper-photocatalyzed borylation of aryl, heteroaryl, vinyl and alkyl halides (I and Br) was reported. The reaction proceeded using a new heteroleptic Cu complex under irradiation with blue LEDs, giving the corresponding boronic-acid esters in good to excellent yields. The reaction was extended to continuous-flow conditions to allow an easy scale-up. The mechanism of the reaction was studied and a mechanism based on a reductive quenching (CuI/CuI*/Cu0) was suggested. 相似文献