Preparation of nanoparticulate metal catalysts in porous supports using an ionic liquid route; hydrogenation and C-C coupling

Aerogels containing palladium metal nanoparticles were prepared using an ionic liquid route and tested for activity towards hydrogenation and Heck C-C coupling reactions. (C) 2003 Elsevier B.V. All rights reserved.

Clean preparation of nanoparticulate metals in porous supports: a supercritical route

Here we present the synthesis of nanometre sized silver particles which have been trapped within porous substrates; poly( styrene-divinylbenzene) beads and silica aerogels. This is the first time that supercritical carbon dioxide has been used to impregnate such porous materials with silver coordination complexes. In this paper we demonstrate that control over the resultant nanoparticles with respect to size, loading and distribution in the support material has been achieved by simple choice of the precursor complex. The solubility of the precursor complexes in the supercritical solvent is shown to be one of the key parameters in determining the size of the nanoparticles, their distribution and their homogeneity within the support matrix. Moreover, we demonstrate that the same methodology can be applied to two very different substrate materials. In the particular case of aerogels, conventional organic solvents could not be used to prepare nanoparticles because the surface tension of the solvent would lead to fracturing of the aerogel structure.

Capillary microreactors wall-coated with mesoporous titania thin film catalyst supports

A new method for catalyst deposition on the inner walls of capillary microreactors is proposed which allows exact control of the coating thickness, pore size of the support, metal particle size, and metal loading. The wall-coated microreactors have been tested in a selective hydrogenation reaction. Activity and selectivity reach values close to those obtained with a homogeneous Pd catalyst. The catalyst activity was stable for a period of 1000 h time-on-stream.

Beyond the Sign. Henri Meschonnic's Poetics of Rhythm and Continuum. Towards an Anthropological Theory of Language

Basing the conception of language on the sign represents also an obstacle to the awareness of certain elements of human life, especially to a full understanding of what language or art do, Henri Meschonnic’s poetics of the continuum and of rhythm criticizes the sign based on Benveniste’s terms of rhythm and discourse, developing an anthropology of language. Rhythm, for Meschonnic, is no formal metrical but a semantic principle, each time unique and unforeseeable. As for Humboldt, his starting point is not the word but the ensemble of speech; language is not ergon but energeia. The poem then is not a literary form but a process of transformation that Meschonnic defines as the invention of a form of life by a form of language and vice versa. Thus a poem is a way of thinking and rhythm is form in movement. The particular subject of art and literature is consequently not the author but a process of subjectivation – this is the contrary of the conception of the sign. By demonstrating the limits of the sign, Meschonnic’s poetics attempts to thematize the intelligibility of presence. Art and literature raise our awareness of this element of human life we cannot grasp conceptually. This poetical thinking is a necessary counterforce against all institutionalization.

Vortex-induced vibrations of a rigid cylinder on elastic supports with endstops. Part 1: Experimental Results

This paper describes an experimental investigation into the effect of restricting the vortex-induced vibrations of a spring-mounted rigid cylinder by means of stiff mechanical endstops. Cases of both asymmetric and symmetric restraint are investigated. Results show that limiting the amplitude of the vibrations strongly affects the dynamics of the cylinder, particularly when the offset is small. Fluid-structure interaction is profoundly affected, and the well-known modes of vortex shedding observed with a linear elastic system are modified or absent. There is no evidence of lock-in, and the dominant impact frequency corresponds to a constant Strouhal number of 0.18. The presence of an endstop on one side of the motion can lead to large increases in displacements in the opposite direction. Attention is also given to the nature of the developing chaotic motion, and to impact velocities, which in single-sided impacts approach the maximum velocity of a cylinder with linear compliance undergoing VIV at lock-in. With symmetrical endstops, impact velocities were about one-half of this. Lift coefficients are computed from an analysis of the cylinder’s motion between impacts.

HIF-2alpha Associated Familial Erythrocytosis Supports the PHD2-HIF2-alpha-VHL Axis as the Major Regulator of Erythropoietin Production

Transcriptionally erythropoietin (Epo) synthesis is tightly regulated by the hypoxia inducible factor (HIF), which is composed of one alpha and one beta subunit that are constitutively expressed. The beta subunit is non-variable, but three different alpha subunits give rise to three isoforms of HIF. The alpha subunit is proteasomally regulated in the presence of oxygen by hydroxylation of the proline in the LXXLAP motif of the oxygen dependent degradation (ODD) domain of HIFalpha, catalysed by members of the prolyl hydroxylase domain (PHD) family of enzymes. This allows the von Hippel Lindau (VHL) protein to associate with the alpha subunit, which is subsequently tagged with ubiquitin and degraded by the proteasome. Any defect in the oxygen sensing pathway that allows the alpha subunit to escape proteasomal regulation leads to elevated expression of HIF target genes.

Recently mutations in both VHL and PHD2 have been identified in a cohort of patients with erythrocytosis, but no mutations were found in the ODD domain of HIF1alpha. Instead, investigation of the homologous region in HIF-2alpha revealed four different mutations, Pro534Leu, Met535Val, Gly537Arg and Gly537Trp in seven individuals/families. Affected individuals presented at a young age with elevated serum Epo. Several individuals have a clinical history of thrombosis, but no evidence of a von Hippel Lindau-like syndrome.

To define how the four mutations relate to the erythrocytosis phenotype functional assays were performed in vitro. Binding of PHD2 to the four HIF-2alpha mutants was impaired to varying degrees, with both the Gly537 mutants showing the greatest reduction. The association of VHL with the hydroxylated Met535Val mutant peptide was similar to wild type HIF- 2alpha, but was decreased in the other three HIF-2alpha mutants. Expression of three HIF- 2alpha target genes, adrenomedullin, NDRG1 and VEGF, was significantly up-regulated in cells stably transfected with the mutants under normoxia compared to wild type HIF-2alpha. Mutations in the ODD domain of HIF-2alpha disrupt proteasomal regulation by reducing the association with PHD2 and hence hydroxylation. Furthermore the binding of VHL is also impaired, even when HIF-2alpha is hydroxylated. Examination of the three-dimensional structure of hydroxylated HIF-1alpha bound to VHL confirms that amino acids close to site of hydroxylation (Pro-531 in isoform 2) are important for this association. These observations, together with recent studies utilising murine models of erythrocytosis, support the PHD2-HIF-2alpha-VHL axis as the major regulator of erythropoietin.

Species introduction promotes hybridization and introgression in Coregonus: is there sign of selection against hybrids?

Species introductions are considered one of the major drivers of biodiversity loss via ecological interactions and genetic admixture with local fauna. We examined two well-recognized fish species, native whitefish (Coregonus lavaretus) and introduced vendace (Coregonus albula), as well as their morphological hybrids in a single lake to test for selection against hybrids and backcrosses in the wild. A representative random subsample of 693 individuals (27.8%) was taken from the total catch of coregonids. This subsample was examined with the aim to select c. 50 individuals of pure whitefish (n = 52), pure vendace (n = 55) and putative hybrid (n = 19) for genetic analyses. The subsequent microsatellites and mitochondrial (mt) DNA analyses provided compelling evidence of hybridization and introgression. Of the 126 fish examined, four were found to be F-1, 14 backcrosses to whitefish and seven backcrosses to vendace. The estimates of historical gene flow suggested higher rates from introduced vendace into native whitefish than vice versa, whereas estimates of contemporary gene flow were equal. Mitochondrial introgression was skewed, with 18 backcrosses having vendace mtDNA and only three with whitefish mtDNA. Hybrids and backcrosses had intermediate morphology and niche utilization compared with parental species. No evidence of selection against hybrids or backcrosses was apparent, as both hybrid and backcross growth rates and fecundities were high. Hybrids (F-1) were only detected in 2 year-classes, suggesting temporal variability in mating between vendace and whitefish. However, our data show that hybrids reached sexual maturity and reproduced actively, with backcrosses recorded from six consecutive year-classes, whereas no F-2 individuals were found. The results indicate widespread introgression, as 10.8% of coregonids were estimated to be backcrosses.

The Sign of the Whale

A two-act stage play performed in Belfast's Opera House with a subsequent Irish tour. In a parable about how to remember the past, Dermy, a journalist in 1977 Belfast, is neurotically compelled to remember every victim of the Troubles. But when a whale sails into Belfast Lough, his life is changed. But is it a miracle or a mirage?

Mutational spectrum of the ZEB1 gene in corneal dystrophies supports a genotype-phenotype correlation

Mutations in ZEB1 have been reported in posterior polymorphous corneal dystrophy (PPCD3; MIM #609141) and Fuchs' endothelial corneal dystrophy (FECD6; MIM #613270). Although PPCD and keratoconus are clinically and pathologically distinct, PPCD has been associated with keratoconus, suggesting a common genetic basis. The purpose of our study was to perform mutational screening of the ZEB1 gene in patients affected with keratoconus or PPCD.

THE IMPROVED SIGN BIT ENCRYPTION OF MOTION VECTORS FOR H.264/AVC

In this paper, an improved video encryption method for encrypting the sign bit of motion vectors is proposed based on H.264/AVC, which belongs to selective encryption. This method improves upon previous work involving the sign bit encryption of motion vectors by ensuring the four candidates for the encrypted motion vectors are always located in two orthogonal lines. The improved method can provide a much more effective scrambling effect while keeping the encrypted stream format-compliant and the compression ratio unchanged. The combination of the proposed method with encryption of intra prediction modes can further enhance the scrambling effect, especially for the first few frames which are left clear when only the motion vectors are encrypted.