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91.
iPP/sPP, iPP/rPP, iPP/PVDF and iPP/PA-6 blends, and their β-nucleated forms were prepared in the present study. The components of iPP/sPP and iPP/rPP blends are compatible in the molten state. The phase structure of the melt of iPP/PVDF and iPP/PA-6 blends is heterogeneous. The melting and crystallisation characteristics as well as the structure and polymorphic composition of these blends were studied by polarised light microscopy (PLM) and differential scanning calorimetry (DSC). When semicrystalline polymers are added to iPP, the most important factor of the formation a blend with β-crystalline phase is the α-nucleation effect of the second polymer. In the case of polymers with an α-nucleating effect, the temperature range of their crystallisation should be lower than that of β-iPP. β-nucleated iPP/PVDF and iPP/PA-6 blends are extreme examples showing that completely β-iPP matrix can not form even in the presence of a highly effective β-nucleant, because of the strong α-nucleating ability and higher crystallisation temperature range of PVDF and PA-6. We found that the β-crystallisation tendency of random propylene copolymers can be enhanced by adding an iPP homopolymer. 相似文献
92.
《Tetrahedron letters》2005,46(16):2771-2774
Treatment of 3β-acetoxy-5-bromo-6β,19-epoxy-5α-androstan-17-one with Ac2O and BF3·OEt2, produced the cleavage of the epoxy moiety and migration of the bromine atom to afford 3β,19-diacetoxy-6α-bromo-5-hydroxy-5β-androst-17-one in high yield. 相似文献
93.
Yuan-Yuan Zhou Shuang Guo Ying Wang Hong-Juan Song Hui-Rui Gao Xiao-Juan Zhang 《Natural product research》2020,34(13):1805-1813
AbstractFive new α-tetralone glycosides, juglanbiosides A-E (1–5), together with an α-tetralone derivative (15) and nine known 1,4-naphthoquinones (6–14) were isolated from the 95% EtOH extract of green walnut husks of Juglans mandshurica Maxim. Their structures were elucidated by comprehensive spectroscopic methods (1H, 13C NMR, DEPT, HSQC, HMBC, CD, HR-ESI-MS). In vitro cytotoxicities of all the isolated compounds were evaluated against BGC-823, HCT-15 and K562 cancer cell lines. 相似文献
94.
Four 2-(α-hydroxyalkyl)-2-oxazolines and a 2-(α-hydroxy-α,α-diphenyl)-2-benzooxazole were synthesized from β-amimoalcohols and α-hydroxy carboxylic acids under microwave irradiation in the absence of a solvent. 相似文献
95.
J. A. Fridy 《Aequationes Mathematicae》1976,14(3):405-412
Letf be a real-valued function sequence {f
k
} that converges to on a deleted neighborhoodD of . If there is a subsequence {f
k(j)
} and a number sequencex such that lim
j
x
j
= and either lim
j
f
k(j)
(x
j
)>lim sup
x
(x) or lim
j
f
k(j)
(x
j
)
x
(x), thenf is said to display theGibbs phenomenon at . IfA is a (real) summability matrix, thenAf is a function sequence given by(Af)
n
(x)=
k=0
a
n,k
f
k
(x). IfAf displays the Gibbs phenomenon wheneverf does, thenA is said to beGP-preserving. By replacingf
k
(x) withf
k
(x
j
)F
k,j
, the Gibbs phenomenon is viewed as a property of the matrixF, andGP-preserving matrices are determined by properties of the matrix productAF.
The general results give explicit conditions on the entries {a
n,k
} that are necessary and/or sufficient forA to beGP-preserving. For example: if(x)0 thenF displaysGP iff lim
k,j
F
k,j
0, and ifA isGP-preserving then lim
n,k
A
n,k
0. IfA is a triangular matrix that is stronger than convergence, thenA is notGP-preserving. The general results are used to study the preservation of the Gibbs phenomenon by matrix methods of Nörlund, Hausdorff, and others. 相似文献
96.
S. Munavalli D. K. Rohrbaugh H. D. Durst 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1657-1671
Trifluoromethylthiocopper has been found to catalyze the opening of the epoxide ring and to furnish not-so-easily accessible novel trifluoromethylthiolated α-hydroxy compounds. This communication presents the mechanism of the formation of the various compounds and their mass spectral data. 相似文献
97.
V. Padmavathi T. V. Ramana Reddy A. Balaiah K. Audisesha Reddy D. Bhaskar Reddy 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5):1223-1235
Some new heterocyclic compounds containing selenadiazole, thiadiazole and diazaphosphole fused to cyclohexanones have been prepared and characterized by spectral data. 相似文献
98.
《合成通讯》2013,43(20):3575-3581
Abstract The nucleophilic substitution of the benzotriazolyl group in the N-(α-benzotriazol-1-ylalkyl)amides and N-(α-benzotriazol-1-ylalkyl) sulfonamides with allylsamarium bromide was investigated, and the corresponding homoallylamides or homoallylsulfonamides were obtained in good to excellent yields. 相似文献
99.
We consider the algebraic Riccati equation for which the four coefficient matrices form an M-matrix K. When K is a nonsingular M-matrix or an irreducible singular M-matrix, the Riccati equation is known to have a minimal nonnegative solution and several efficient methods are available to find this solution. In this paper we are mainly interested in the case where K is a reducible singular M-matrix. Under a regularity assumption on the M-matrix K, we show that the Riccati equation still has a minimal nonnegative solution. We also study the properties of this particular solution and explain how the solution can be found by existing methods. 相似文献
100.
The synthesis of the first series of 5-alkoxy-1,3-thiazole-based liquid crystals is reported. The aforementioned liquid crystals were synthesised through a Lawesson's reagent-mediated cyclisation of appropriate α-benzamido esters. This methodology was found to be highly efficient, even on a large scale, and the resulting 5-alkoxy-1,3-thiazoles could be purified without the use of column chromatography. The synthesis and mesomorphic properties of a family of 5-alkoxy-2-(4-cyanophenyl)-1,3-thiazole liquid crystals prepared via this approach are discussed and compared with their thiophene and phenyl analogues. 相似文献