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971.
Dmitry S. Ryabukhin Anna D. Lisakova Anna S. Zalivatskaya Irina A. Boyarskaya Galina L. Starova Rostislav E. Trifonov Vladimir A. Ostrovskii Aleksander V. Vasilyev 《Tetrahedron》2018,74(15):1838-1849
Reaction of 5-arylethynyl-2-methyl-2H-tetrazoles (acetylene tetrazoles) with arenes under the action of Brønsted superacid CF3SO3H or acidic zeolite HUSY CBV-720 gives rise to E-/Z-5-(2,2-diarylethenyl)-2-methyl-2H-tetrazoles, as products of hydroarylation of acetylene bond, in yields up to 98% with predominant formation of E-isomers. Cationic intermediates of these reactions have been studied theoretically by DFT calculations. Addition of CF3SO3H to the triple bond of acetylene tetrazoles leads to the corresponding E-/Z-vinyl triflates in high yields. Hydration of triple bond in these tetrazoles in H2SO4 results in the formation of 5-(2-aryl-2-oxoethyl)-2-methyl-2H-tetrazoles. Tandem hydroarylation-ionic hydrogenation of acetylene tetrazoles in the systems acid(CF3SO3H or AlCl3)-arene-cyclohexane affords 5-(2,2-diarylethyl)-2-methyl-2H-tetrazoles. 相似文献
972.
Supramolecular Nested Microbeads as Building Blocks for Macroscopic Self‐Healing Scaffolds
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Dr. Ziyi Yu Dr. Ji Liu Dr. Cindy Soo Yun Tan Prof. Oren A. Scherman Prof. Chris Abell 《Angewandte Chemie (International ed. in English)》2018,57(12):3079-3083
The ability to construct self‐healing scaffolds that are injectable and capable of forming a designed morphology offers the possibility to engineer sustainable materials. Herein, we introduce supramolecular nested microbeads that can be used as building blocks to construct macroscopic self‐healing scaffolds. The core–shell microbeads remain in an “inert” state owing to the isolation of a pair of complementary polymers in a form that can be stored as an aqueous suspension. An annealing process after injection effectively induces the re‐construction of the microbead units, leading to supramolecular gelation in a preconfigured shape. The resulting macroscopic scaffold is dynamically stable, displaying self‐recovery in a self‐healing electronic conductor. This strategy of using the supramolecular assembled nested microbeads as building blocks represents an alternative to injectable hydrogel systems, and shows promise in the field of structural biomaterials and flexible electronics. 相似文献
973.
With the help of some new results about weight enumerators of self-dual codes over
we investigate a class of double circulant codes over
, one of which leads to an extremal even unimodular 40–dimensional lattice. It is conjectured that there should be Nine more constructions of the Leech lattice 相似文献
974.
TAOYOUSHAN GAOGUOZHU 《高校应用数学学报(英文版)》1998,13(3):271-280
In this paper the forced neutral difterential equation with positive and negative coefficients d/dt [x(t)-R(t)x(t-r)] P(t)x(t-x)-Q(t)x(t-σ)=f(t),t≥t0,is considered,where f∈L^1(t0,∞)交集C([t0,∞],R^ )and r,x,σ∈(0,∞),The sufficient conditions to oscillate for all solutions of this equation are studied. 相似文献
975.
Zhu Ning 《高校应用数学学报(英文版)》1998,13(3):241-250
ANOTEONTHEBEHAVIOROFBLOW┐UPSOLUTIONSFORONE┐PHASESTEFANPROBLEMSZHUNINGAbstract.Inthispaper,thefolowingone-phaseStefanproblemis... 相似文献
976.
Alicja Kowalska Krystian Pluta Andrzej Masślankiewicz Roman Luboradzki 《Journal of chemical crystallography》1999,29(1):103-106
The title compound (C8H10N4O2) is monoclinic, with a = 7.740(2), b = 17.044(7), c = 6.992(3) Å, = 100.60(1)°, and space group P21/c. Two O-methyl groups are coplanar with the pyrimidine ring. Whereas, the O(6)-methyl group is directed away from the imidazole ring toward the N(1) atom, the O(2)-methyl is pointed away from the N(1) atom toward the N(3) atom. Two intermolecular hydrogen bonds H(8)···N(1) and H(711)···O(2) of 2.48(2) and 2.58(3) Å make a linear arrangement of the molecules. The conformation of the O-methyl groups explains some results of thermal rearrangement of 2,6-dialkoxy-7-methylpurines and differences in alkylations of 2,4-dialkoxypyrimidines and 2,6-dialkoxy-7-methylpurines. 相似文献
977.
The spectroscopic and X-ray investigation of the N-(2-phenylethyl) amide of -(1,1-ethylenedioxy)-ethyl--hydroxybutyric acid are reported. The1H NMR spectra for the title structure and for the N-(p-methoxybenzyl) amide of -(1,1-ethylenedioxy)-ethyl--hydroxybutyric acid are given. The N-(2-phenylethyl)amide of -(1,1-ethylenedioxy)-ethyl--hydroxybutyric acid, C16H23O4N, crustallizes in the monoclinic space groupP2
1/c witha=21.547(5),b=6.333(2),c=11.822(3) Å and =101.01(2)°. The dioxolane ring has a half-chair conformation with C2(O3)=2.4° and ||av=18.2°. The inconsiderable deviations from planarity of the six atoms of the amide group are caused mainly by twist around the C4–N1 bond and out-of-plane bending at the N1 atom ((C4–N1)=4°, XN =7°, Xc =0.4° ). The amide group plane is nearly coplanar with the phenyl ring. The molecules are connected by two intermolecular hydrogen bonds. 相似文献
978.
A new method for the highly sensitive and selective determination of boron at nanograms per cubic decimeter levels has been
developed based on the derivatization reaction of boron using salicylaldehyde and 1-amino-8-naphtol-3,6-disulfonate with reversed-phase
partition high-performance liquid chromatography. A detection limit as low as 2.0 nmol/dm3 (22 ng/dm3) was achieved without any preconcentration. No significant interference was observed in the determination of 16 μmol/dm3 of boron with the addition of nine metal ions (AlIII, CuII, CoII, FeII, FeIII, NiII, MnII, VV, ZnII) at concentrations 100 times greater than that of boron without any masking procedure. The proposed method was successfully
applied to the determination of boron in river water, tap water, doubly distilled water, and highly purified water.
Figure Scheme of formation of boron-azomethine-H complex with salicylaldehyde and 1-amino-8-naphthol-3, 6-disulfonate 相似文献
979.
Mehrorang Ghaedi Ardeshir Shokrollahi Raziyeh Mehrnoosh Omid Hossaini Mustafa Soylak 《Central European Journal of Chemistry》2008,6(3):488-496
In the presented work, the conditions for cloud point extraction of iron from aqueous solutions using 7-iodo-8-hydroxyquinolin-5-sulphonic
acid (Ferron) was investigated and optimized. The procedure is based on the separation of its ferron complex into the micellar
media by adding the surfactant Triton X-114. After phase separation, the surfactant-rich phase was dissolved with 1.0 M HNO3
in methanol. Iron was determined by flame atomic absorption spectrometry. Optimization of the pH, ligand and surfactant quantities,
incubation time, temperature, viscosity, sample volume, and interfering ions were investigated. The effects of the matrix
ions were also examined. The detection limits for three times the standard deviations of the blank for iron was 0.4 ng m L-1,
enrichment factor of 19.6 and preconcentration factor of 30 could be achieved. The validity of cloud point extraction was
checked by employing real samples including soil, blood, spinach, milk, meat, liver and orange juice samples using the standard
addition method, which gave satisfactory results.In the presented work, the conditions for cloud point extraction of iron
from aqueous solutions using 7-iodo-8-hydroxyquinolin-5-sulphonic acid (Ferron) was investigated and optimized. The procedure
is based on the separation of its ferron complex into the micellar media by adding the surfactant Triton X-114. After phase
separation, the surfactant-rich phase was dissolved with 1.0 M HNO3 in methanol. Iron was determined by flame atomic absorption spectrometry. Optimization of the pH, ligand and surfactant quantities,
incubation time, temperature, viscosity, sample volume, and interfering ions were investigated. The effects of the matrix
ions were also examined. The detection limits for three times the standard deviations of the blank for iron was 0.4 ng m L−1, enrichment factor of 19.6 and preconcentration factor of 30 could be achieved. The validity of cloud point extraction was
checked by employing real samples including soil, blood, spinach, milk, meat, liver and orange juice samples using the standard
addition method, which gave satisfactory results.
相似文献
980.
Brualdi et al. [Codes with a poset metric, Discrete Math. 147 (1995) 57-72] introduced the concept of poset codes, and gave an example of poset structure which admits the extended binary Golay code to be a 4-error-correcting perfect P-code. In this paper we classify all of the poset structures which admit the extended binary Golay code to be a 4-error-correcting perfect P-code, and show that there are no posets which admit the extended binary Golay code to be a 5-error-correcting perfect P-code. 相似文献