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141.
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143.
Hans Schoutens 《代数通讯》2017,45(1):262-274
We prove Hochster’s small maximal Cohen–Macaulay conjecture for three-dimensional complete F-pure rings. We deduce this from a more general criterion, and show that only a weakening of the notion of F-purity is needed, to wit, being weakly F-split. We conjecture that any complete ring is weakly F-split. 相似文献
144.
Jairo Z. Goncalves 《代数通讯》2017,45(12):5193-5201
Let k(t) be the field of rational functions over the field k, let σ be a k-automorphism of K = k(t), let D = K(X;σ) be the ring of fractions of the skew polynomial ring K[X;σ], and let D? be the multiplicative group of D. We show that if N is a noncentral normal subgroup of D?, then N contains a free subgroup. We also prove that when k is algebraically closed and σ has infinite order, there exists a specialization from D to a quaternion algebra. This allows us to explicitly present free subgroups in D?. 相似文献
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146.
In [1], Bannai presents a fusion condition and uses this to consider central Schur rings (S-rings) over the simple groups PSL(2,q) where q is a prime power. In this paper, we concretely describe all such S-rings in terms of symmetric S-rings over cyclic groups. The final section discusses counting these. 相似文献
147.
Sina Hedayat 《代数通讯》2017,45(4):1711-1718
A proper ideal of a commutative ring is called pseudo-irreducible if it cannot be written as a product of two comaximal proper ideals. In this paper, we give a necessary and su?cient condition for every proper ideal of a commutative ring to be a product of pairwise comaximal pseudo-irreducible ideals. Examples of such rings include Laskerian rings, or more generally J-Noetherian rings and ZD-rings. We study when certain classes of rings satisfy this condition. 相似文献
148.
Unsaturated acyloxy sulfones 3 undergo intramolecular cyclization upon deprotonation with LHMDS in THF. Dehydration and double bond isomerization of the products upon exposure to acid, gave the fused ring furans, 4, in good yields. This strategy could be readily adapted to prepare substituted benzofurans 12 from the cyclization reactions of acyloxy sulfones 11 prepared from phenols. Finally, this approach could be successfully modified to access dihydropyrans and benzopyrans. 相似文献
149.
Hong‐Jian Wang Paul v. R. Schleyer Judy I. Wu Yan Wang Hai‐Jun Wang 《International journal of quantum chemistry》2011,111(5):1031-1038
The resonance energies (REs) of neutral three membered ring analogs of the cyclopropenyl cation, computed using block localized wave function (BLW) methods, reveal considerable variations. The RE's of cyclopropenes substituted with exocyclic double bonded groups C?X, (X = O, NH, CH2, S, PH, SiH2) increase with the electronegativity of X in the same row (SiH2 < PH < S and CH2 < NH < O). The extra cyclic resonance energies (ECREs) (an energetic measure of aromaticity based on comparisons with the RE's of acyclic models) of these derivatives range from +10.5 kcal/mol for cyclopropenone (X = O) (somewhat aromatic; the benzene ECRE is 29.3 kcal/mol) to ?2.4 kcal/mol (slightly antiaromatic) for X = SiH2. Additional disubstitution of the C?C double bond by X′ groups (X′ = CH3, NH2, OH, SiH3, PH2, SH) increases the REs considerably, but has only small effects on the ECREs. Even the ECRE of deltic acid (X = O, X′ = OH) is only increased to +13.3 kcal/mol. The conclusion based on ECRE's, that all 12 of the three membered rings are only marginally aromatic/antiaromatic, is supported by the satisfactorily plot (R2 = 0.92) of ECRE against values of NICS(0)πzz (a superior nucleus chemical independent shift magnetic index of aromaticity), which range only from ?6.1 ppm (diatropic) for deltic acid (cf., ?35.5 ppm for benzene and ?14.2 ppm for the parent cyclopropenium ion) to +8.9 ppm (paratropic) for the silicon derivative, X = SiH2, X′ = SiH3. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
150.
Leon Kaganovskiy 《International Journal of Non》2011,46(1):9-13
In this article, we use a hierarchical panel method for representing vortex sheet surface motion in 3D flow to investigate the oblique collision of two vortex rings. The particles representing the sheet are advected by a regularized Biot-Savart integral with smoothed Rosenhead-Moore kernel. The particle velocities are evaluated by an adaptive treecode algorithm based on Taylor expansions in Cartesian coordinates. The method allowed us to consider late stages of a vortex rings collision, producing a funnel region. Vorticity iso-surfaces evolution is also investigated. 相似文献