نتایج جستجو برای: n derivation
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In order to delineate the origin of soil fatty acids, crop soil samples have been incubated for 21 days in vitro either with unlabelled or 13C-labelled glucose. Analyses of C14-C32 n-alkanoic acids from monocarboxylic acid fractions, as methyl esters, by gas chromatography-combustion-isotope ratio monitoring mass spectrometry (GC-C-IRMS) show that C14, C16 and C18 n-alkanoic acids are 13C-label...
Let k be a field of characteristic zero, n any positive integer and let δn be the derivation ∑n i=1Xi ∂ ∂Yi of the polynomial ring k[X1, . . . , Xn, Y1, . . . , Yn] in 2n variables over k. A Conjecture of Nowicki (Conjecture 6.9.10 in (8)) states the following ker δn = k[X1, . . . , Xn, XiYj −XjYi; 1 ≤ i < j ≤ n] in which case we say that δn is standard. In this paper, we use the elimination th...
X iv :0 80 1. 22 07 v1 [ m at h. R A ] 1 5 Ja n 20 08 The derivation algebra and automorphism group of the twisted Schrödinger-Virasoro algebra Junbo Li, Yucai Su ∗)Department of Mathematics, Shanghai Jiao Tong University, Shanghai 200240, China †)Department of Mathematics, Changshu Institute of Technology, Changshu 215500, China ‡)Department of Mathematics, University of Science and Technology...
When an algebra is graded by a group, any additive character of the group induces a diagonalizable derivation of the ring. This construction is studied in detail for the case of a path algebra modulo relations and its fundamental group. We describe an injection of the character group into the first cohomology group following Assem-de la Peña. Rather general conditions are determined, in this co...
BACKGROUND Human embryonic stem cells (hESCs) have opened up a new area of research in biomedicine. The efficiency of hESC derivation from frozen poor-quality embryos is low and normally achieved by plating embryos on mouse or human foreskin feeders (HFFs). We attempted to optimize embryo survival and hESC derivation. METHODS Three conditions were tested on frozen poor-quality embryos: (i) em...
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