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941.
Lower Activation Energy for Catalytic Reactions through Host–Guest Cooperation within Metal–Organic Frameworks 下载免费PDF全文
Briana Aguila Dr. Qi Sun Xiaoliang Wang Erica O'Rourke Prof. Abdullah M. Al‐Enizi Prof. Ayman Nafady Prof. Shengqian Ma 《Angewandte Chemie (International ed. in English)》2018,57(32):10107-10111
Industrial synthesis is driven by a delicate balance of the value of the product against the cost of production. Catalysts are often employed to ensure product turnover is economically favorable by ensuring energy use is minimized. One method, which is gaining attention, involves cooperative catalytic systems. By inserting a flexible polymer into a metal–organic framework (MOF) host, the advantages of both components work synergistically to create a composite that efficiently fixes carbon dioxide to transform various epoxides into cyclic carbonates. The resulting material retains high yields under mild conditions with full reusability. By quantitatively studying the kinetic rates, the activation energy was calculated, for a physical mixture of the catalyst components to be about 50 % higher than that of the composite. Through the unification of two catalytically active components, a new opportunity opens up for the development of synergistic systems in multiple applications. 相似文献
942.
Oussama Dehbi Esam A. Ishak Mohammed A. Bakht Mohammed H. Geesi Mohammed B. Alshammari Vincent Chagnault 《Green Chemistry Letters and Reviews》2018,11(2):62-66
An efficient and ecofriendly method for the synthesis of disubstituted 5-aminopyrimidines from vinyl azides and urea or thiourea was developed. This reaction proceeds under microwave irradiation conditions in the presence of water as a solvent. The remarkable features of this new protocol are high conversion, short reaction times, cleaner reaction profiles and straightforward procedure. 相似文献
943.
Sahar?Alhogail Ghadeer?A.?R.?Y.?Suaifan Sergio?Bizzarro Wendy?E.?Kaman Floris?J.?Bikker Karina?Weber Dana?Cialla-May Jürgen?Popp Mohammed?ZourobEmail author 《Mikrochimica acta》2018,185(2):149
Porphyromonas gingivalis (P. gingivalis) is a pathogen causing periodontitis. A rapid assay is described for the diagnosis of periodontal infections related to P. gingivalis. The method is making use of gingipains, a group of P. gingivalis specific proteases as a detection biomarker. Magnetic-nanobeads were labeled with gingipain-specific peptide substrates and immobilized on a gold biosensing platform via gold-thiol linkage. As a result of this, the color of the gold layer turns black. Upon cleavage of the immobilized substrates by gingipains, the magnetic-nanobeads-peptide fragments were attracted by a magnet so that the golden surface color becomes visible again. This assay is highly sensitive and specific. It is capable of detecting as little as 49 CFU·mL?1 of P. gingivalis within 30 s. Examination of periodontitis patients and healthy control saliva samples showed the potential of the assay. The simplicity and rapidity of the assay makes it an effective point-of-care device. 相似文献
944.
Adib Ghaleb Aouidate Adnane Lakhlifi Tahar Bouachrine Mohammed Maghat Hamid Sbai Abdelouahid 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2018,92(12):2464-2471
Russian Journal of Physical Chemistry A - Copper-catalyzed azide–alkyne cycloaddition (CuAAC) is a straightforward way for making covalent connections between building blocks containing... 相似文献
945.
946.
947.
On the effect of a magnetic field on the yield point and kinetics of macroplasticity in LiF crystals
A strong effect of a static magnetic field B on active deformation kinetics (
=const) in LiF crystals is observed. This is a threshold effect with respect to B and
; it is observed only for B> B
c
(B≃0.4 T) and
. Magnetic sensitivity is exhibited by the yield stress τ
y
, which decreases by approximately a factor of 1.5 for B=0.48 T, and by the stage-II and stage-III hardening coefficients θII and θ III, the former decreasing and the latter increasing in a magnetic field. A physical interpretation is proposed for the observed
behavior.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 6, 470–474 (25 March 1997) 相似文献
948.
The thermally irreversible photochromic compound dithia-dithienylethenophane was synthesized, which is the first example of a dithienylethene bridged with benzene ring and due to the fixation to the photoactive anti-conformation the quantum yield for the photocyclization reaction became higher than that of the corresponding nonbridged type dithienylethene. 相似文献
949.
Laurent CalculArlette Longeon Ali Al MourabitMichèle Guyot Marie-Lise Bourguet-Kondracki 《Tetrahedron》2003,59(34):6539-6544
Four novel alkaloids of the aaptamine class have been isolated in addition to the known aaptamine, isoaaptamine, demethyl(oxy)aaptamine and its dimethylketal from an unidentified species of Indonesian marine sponge of the genus Xestospongia. Their structures were elucidated on the basis of detailed 1D and 2D NMR spectroscopic data. Their antimicrobial activity was tested towards Gram (+) (S. aureus), Gram (−) (E. coli, V. anguillarum) bacterial strains, a fungus (C. tropicalis); their cytotoxic activity was evaluated against KB cells. 相似文献
950.
Summary In this work the potential of porous graphitic carbon (PGC) as a new stationary phase in, capillary electrochromatography
has been explored. Its behavior under the action of an applied potential is described for the separation of phenylureas. First,
it was shown that porous graphitic carbon enables high efficiency in capillary electrochromatography over a wide range of
mobile phase velocities. It was then demonstrated that this material might be responsible for degradation of the solutes at
frit-PGC interfaces. Although electrolytic degradation reactions are suspected to occur on this type of conductive material,
voltamperometric measurements furnished no clear evidence. A specific injection procedure is proposed for avoiding degradation
of the solutes at the inlet interface before their chromatographic separation. Comparison of the retention behavior of phenylureas
on PGC in liquid chromatography and in capillary electrochromatography show that the retention propertiets of PGC are altered
by application of an electrical field, because this modifies the donor-acceptor interactions between the solutes and the stationary
phase. 相似文献