124 research outputs found
A quasi-stability result for dictatorships in Sn
No full textThe final publication is available at Springer via http://dx.doi.org/10.1007/s00493-014-3027-1Filmus - Supported by the Canadian Friends of the Hebrew University/University of Toronto
Permanent Endowment.
Friedgut - Supported in part by I.S.F. grant 0398246, and BSF grant 2010247
A Katona-type proof of an Erdős–Ko–Rado-type theorem
No full textAbstractLet p⩽1/2 and let μp be the product measure on {0,1}n, where μp(x)=p∑xi(1-p)n-∑xi. Let A⊂{0,1}n be an intersecting family, i.e. for every x,y∈A there exists 1⩽i⩽n such that xi=yi=1. Then μp(A)⩽p. Our proof uses a probabilistic trick first applied by Katona to prove the Erdős–Ko–Rado theorem
An RNA interference knock-down of nitrate reductase enhances lipid biosynthesis in the diatom Phaeodactylum tricornutum
No full textWhen diatoms are stressed for inorganic nitrogen they remodel their intermediate metabolism and redirect carbon towards lipid biosynthesis. However, this response comes at a significant cost reflected in decreased photosynthetic energy conversion efficiency and growth. Here we explore a molecular genetics approach to restrict the assimilation of inorganic nitrogen by knocking down nitrate reductase (NR). The transformant strain, NR21, exhibited about 50% lower expression and activity of the enzyme but simultaneously accumulated over 40% more fatty acids. However, in contrast to nitrogen-stressed wild-type (WT) cells, which grow at about 20% of the rate of nitrogen-replete cells, growth of NR21 was only reduced by about 30%. Biophysical analyses revealed that the photosynthetic energy conversion efficiency of photosystem II was unaffected in NR21; nevertheless, the plastoquinone pool was reduced by 50% at the optimal growth irradiance while in the WT it was over 90% oxidized. Further analyses reveal a 12-fold increase in the glutamate/glutamine ratio and an increase NADPH and malonyl-CoA pool size. Transcriptomic analyses indicate that the knock down resulted in changes in the expression of genes for lipid biosynthesis, as well as the expression of specific transcription factors. Based on these observations, we hypothesize that the allocation of carbon and reductants in diatoms is controlled by a feedback mechanism between intermediate metabolites, the redox state of the plastid and the expression and binding of transcription factors related to stress responses.Peer reviewe
Intersecting families of permutations
No full textResearch of the second author was supported in part by the Israel Science Foundation, grant no. 0397684, and NSERC grant 341527.
Research of the third author was supported in part by the Giora Yoel Yashinsky Memorial Grant
Stable juntas in the symmetric group I
No full textNon UBCUnreviewedAuthor affiliation: Hebrew UniversityFacult
An information-theoretic proof of a hypercontractive inequality
No full textIn this note I give an information-theoretic proof of the Bonami-Beckner-Gross hypercontractive inequality
Boolean Functions With Low Average Sensitivity Depend On Few Coordinates
No full text... f0; 1g. The sensitivity of a point v 2 f0; 1g ) = 1gj, i.e. the number of neighbors of the point in the discrete cube on which the value of f differs. The average sensitivity of f is the average of the sensitivity of all points in f0; 1g . (This can also be interpreted as the sum of the influences of the n variables on f , or as a measure of the edge boundary of the set which f is the characteristic function of.) We show here that if the average sensitivity of f is k then f can be approximated by a function depending on c coordinates where c is a constant depending only on the accuracy of the approximation but not on n. We also present a more general version of this theorem, where the sensitivity is measured with respect to a product measure which is not the uniform measure on the cube
Hypergraphs, Entropy and Inequalities
No full textreasonable to assume that most mathematicians would be puzzled to find these three terms as, say, key words for the same mathematical paper. (Just in case this puzzlement is a result of being unfamiliar with the term “hypergraph”: a hypergraph is nothing other than a family of sets, and will be defined formally later.) To further pique th
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