L^2-Betti numbers of rigid C*-tensor categories and discrete quantum groups

We compute the $L^2$-Betti numbers of the free $C^*$-tensor categories, which are the representation categories of the universal unitary quantum groups $A_u(F)$. We show that the $L^2$-Betti numbers of the dual of a compact quantum group $G$ are equal to the $L^2$-Betti numbers of the representation category $Rep(G)$ and thus, in particular, invariant under monoidal equivalence. As an application, we obtain several new computations of $L^2$-Betti numbers for discrete quantum groups, including the quantum permutation groups and the free wreath product groups. Finally, we obtain upper bounds for the first $L^2$-Betti number in terms of a generating set of a $C^*$-tensor category.Comment: v4: Minor changes, final version, to appear in Analysis and PDE. v3: We corrected a mistake in Section 3.2 without impact on the main results of the paper. v2: No major changes, but several remarks and a few references were adde

Modulating active sites in MOFs for improved Lewis acid or base catalysis

International audienc

Arabidopsis RecQl4A suppresses homologous recombination and modulates DNA damage responses

The DNA damage response and DNA recombination are two interrelated mechanisms involved in maintaining the integrity of the genome, but in plants they are poorly understood. RecQ is a family of genes with conserved roles in the regulation of DNA recombination in eukaryotes; there are seven members in Arabidopsis. Here we report on the functional analysis of the Arabidopsis RecQl4A gene. Ectopic expression of Arabidopsis RecQl4A in yeast RecQ-deficient cells suppressed their hypersensitivity to the DNA-damaging drug methyl methanesulfonate (MMS) and enhanced their rate of homologous recombination (HR). Analysis of three recQl4A mutant alleles revealed no obvious developmental defects or telomere deregulation in plants grown under standard growth conditions. Compared with wild-type Arabidopsis, the recQl4A mutant seedlings were found to be hypersensitive to UV light and MMS, and more resistant to mitomycin C. The average frequency of intrachromosomal HR in recQl4A mutant plants was increased 7.5-fold over that observed in wild-type plants. The data reveal roles for Arabidopsis RecQl4A in maintenance of genome stability by modulation of the DNA damage response and suppression of HR.

One-step synthesis of 2,5-bis(chloromethyl)-1,4-dioxane from epichlorohydrin using ZIF-8, taking advantage of structural defects

We demonstrate herein the ZIF-8-only-mediated catalysis of the cyclodimerization of epichlorohydrin to 2,5-bis(chloromethyl)-1,4-dioxane in the absence of co-catalyst and solvent. The easy handling and economic aspects of ZIF-8, in addition to the one-step reaction to produce the cyclodimer, make this catalyst attractive even for industry. It has been clearly illustrated that the nature of the method used to synthesize ZIF-8 affected the yields of the cyclodimers. Specifically, the method employed to produce ZIF-8 directly influences the amount of crystal structural defects, which in turn impacts their performance as catalysts. To emphasize the role of defects, other physical properties, such as surface area and particle size, were controlled during the synthesis of the ZIF-8 catalysts. Remarkably, the amount of structural defects was quantified by temperature program desorption analysis

Evolutionary conservation and regulation of particular alternative splicing events in plant SR proteins

Alternative splicing is an important mechanism for fine tuning of gene expression at the post-transcriptional level. SR proteins govern splice site selection and spliceosome assembly. The Arabidopsis genome encodes 19 SR proteins, several of which have no orthologues in metazoan. Three of the plant specific subfamilies are characterized by the presence of a relatively long alternatively spliced intron located in their first RNA recognition motif, which potentially results in an extremely truncated protein. In atRSZ33, a member of the RS2Z subfamily, this alternative splicing event was shown to be autoregulated. Here we show that atRSp31, a member of the RS subfamily, does not autoregulate alternative splicing of its similarily positioned intron. Interestingly, this alternative splicing event is regulated by atRSZ33. We demonstrate that the positions of these long introns and their capability for alternative splicing are conserved from green algae to flowering plants. Moreover, in particular alternative splicing events the splicing signals are embedded into highly conserved sequences. In different taxa, these conserved sequences occur in at least one gene within a subfamily. The evolutionary preservation of alternative splice forms together with highly conserved intron features argues for additional functions hidden in the genes of these plant-specific SR proteins

Versatile Barium and Calcium Imidazolium-Dicarboxylate Heterogeneous Catalysts in Quinoline Synthesis

This article details the development of heterogeneous catalysts based on calcium and barium in combination with the organic linker 1,3-bis(carboxymethyl)imidazolium (bcmim). The linker and the materials from alkaline earth metals are easily prepared under very smooth conditions. The use of linkers with different counterions (Cl or Br) provided different materials. Calcium- and barium-based catalysts were successfully employed in the preparation of quinoline derivatives from ketones and 2-aminoarylaldehydes or 2-aminoarylketones. In general, barium-based catalysts provided better results than calcium, although the latter are an excellent complement for certain substrates. Thus, a notable feature of such catalysts is the possibility of accessing a variety of complementary heterogeneous catalytic systems, rendering the catalysis adaptive to the reactant.The Ministerio de Economía y Competitividad, CTQ2015-66624-P) and the University of Alicante (VIGROB-285) are gratefully acknowledged for financial support. M. A. S. thanks the Ministerio de Educación, Cultura y Deporte, FPU15/06040) for a predoctoral fellowship