Assessement of sensory firmness and crunchiness of table grapes by acoustic and mechanical properties.

Background and Aims The instrumental measurement of crunchiness in tablegrapes has been the subject of little research in spite of the great relevance of this sensory texture trait to consumer preference. Therefore, our aim was to evaluate the potential of several mechanical and acoustic properties to assess the perceived firmness and crunchiness of tablegrape cultivars. Methods and Results The ripening effect was minimised by densimetric sorting of the berries before testing. The textural quality of seven tablegrape cultivars was evaluated by sensory analysis. Furthermore, three mechanical tests (texture profile analysis, cutting and denture) were performed on the berry flesh or on whole berries, and the acoustic emission produced was recorded simultaneously. Correlation studies showed strong and significant relationships between sensory texture attributes and instrumental parameters, particularly for the denture test. Nevertheless, satisfactory predictive accuracy for the perceived crunchiness required multivariate linear regression involving both mechanical and acoustic properties resulting from the denture test performed on whole berries. In this case, residual predictive interquartile amplitude was higher than 2. Most of the reliable models developed for perceived firmness are fairly recommended not for quantitative purposes but for fast screening (1.6 < residual predictive interquartile amplitude < 2). Conclusions The standardised protocol proposed permits more objective and quantitative sensory data to be obtained for firmness and crunchiness of tablegrapes. Significance of the Study A combined mechanical–acoustic strategy has not previously been used in tablegrapes and represents a powerful tool for a more complete and exhaustive texture characterisation, particularly firmness and crunchiness, by means of a more objective and standardised protocol

High quality epitaxial FeSe0.5Te0.5 thin films grown on SrTiO3 substrates by pulsed laser deposition

Superconducting epitaxial FeSe0.5Te0.5 thin films were prepared on SrTiO3 (001) substrates by pulsed laser deposition. The high purity of the phase, the quality of the growth and the epitaxy were studied with different experimental techniques: X-rays diffraction, reflection high energy electron diffraction, scanning tunnelling microscopy and atomic force microscopy. The substrate temperature during the deposition was found to be the main parameter governing sample morphology and superconducting critical temperature. Films obtained in the optimal conditions show an epitaxial growth with c axis perpendicular to the film surface and the a and b axis parallel to the substrates one, without the evidence of any other orientation. Moreover, such films show a metallic behavior over the whole measured temperature range and critical temperature above 17K, which is higher than the target one.Comment: 10 pages including 4 figure

Identification of a novel type of spacer element required for imprinting in fission yeast

Asymmetrical segregation of differentiated sister chromatids is thought to be important for cellular differentiation in higher eukaryotes. Similarly, in fission yeast, cellular differentiation involves the asymmetrical segregation of a chromosomal imprint. This imprint has been shown to consist of two ribonucleotides that are incorporated into the DNA during laggingstrand synthesis in response to a replication pause, but the underlying mechanism remains unknown. Here we present key novel discoveries important for unravelling this process. Our data show that cis-acting sequences within the mat1 cassette mediate pausing of replication forks at the proximity of the imprinting site, and the results suggest that this pause dictates specific priming at the position of imprinting in a sequence-independent manner. Also, we identify a novel type of cis-acting spacer region important for the imprinting process that affects where subsequent primers are put down after the replication fork is released from the pause. Thus, our data suggest that the imprint is formed by ligation of a not-fullyprocessed Okazaki fragment to the subsequent fragment. The presented work addresses how differentiated sister chromatids are established during DNA replication through the involvement of replication barriers

An evolutionary intra-molecular shift in the preferred U3 snoRNA binding site on pre-ribosomal RNA

Correct docking of U3 small nucleolar RNA (snoRNA) on pre-ribosomal RNA (pre-rRNA) is essential for rRNA processing to produce 18S rRNA. In this report, we have used Xenopus oocytes to characterize the structural requirements of the U3 snoRNA 3′-hinge interaction with region E1 of the external transcribed spacer (ETS) of pre-rRNA. This interaction is crucial for docking to initiate rRNA processing. 18S rRNA production was inhibited when fewer than 6 of the 8 bp of the U3 3′–hinge complex with the ETS could form; moreover, base pairing involving the right side of the 3′-hinge was more important than the left. Increasing the length of the U3 hinge–ETS interaction by 9 bp impaired rRNA processing. Formation of 18S rRNA was also inhibited by swapping the U3 5′- and 3′-hinge interactions with the ETS or by shifting the base pairing of the U3 3′-hinge to the sequence directly adjacent to ETS region E1. However, 18S rRNA production was partially restored by a compensatory shift that allowed the sequence adjacent to the U3 3′-hinge to pair with the eight bases directly adjacent to ETS region E1. The results suggest that the geometry of the U3 snoRNA interaction with the ETS is critical for rRNA processing

A mathematical model for unsteady mixed flows in closed water pipes

We present the formal derivation of a new unidirectional model for unsteady mixed flows in non uniform closed water pipe. In the case of free surface incompressible flows, the \FS-model is formally obtained, using formal asymptotic analysis, which is an extension to more classical shallow water models. In the same way, when the pipe is full, we propose the \Pres-model, which describes the evolution of a compressible inviscid flow, close to gas dynamics equations in a nozzle. In order to cope the transition between a free surface state and a pressured (i.e. compressible) state, we propose a mixed model, the \PFS-model, taking into account changes of section and slope variation

The HIV Tat protein affects processing of ribosomal RNA precursor

<p>Abstract</p> <p>Background</p> <p>Inside the cell, the HIV Tat protein is mainly found in the nucleus and nucleolus. The nucleolus, the site of ribosome biogenesis, is a highly organized, non-membrane-bound sub-compartment where proteins with a high affinity for nucleolar components are found. While it is well known that Tat accumulates in the nucleolus via a specific nucleolar targeting sequence, its function in this compartment it still unknown.</p> <p>Results</p> <p>To clarify the significance of the Tat nucleolar localization, we induced the expression of the protein during oogenesis in <it>Drosophila melanogaster </it>strain transgenic for HIV-<it>tat </it>gene. Here we show that Tat localizes in the nucleoli of <it>Drosophila </it>oocyte nurse cells, where it specifically co-localizes with fibrillarin. Tat expression is accompanied by a significant decrease of cytoplasmic ribosomes, which is apparently related to an impairment of ribosomal rRNA precursor processing. Such an event is accounted for by the interaction of Tat with fibrillarin and U3 snoRNA, which are both required for pre-rRNA maturation.</p> <p>Conclusion</p> <p>Our data contribute to understanding the function of Tat in the nucleolus, where ribosomal RNA synthesis and cell cycle control take place. The impairment of nucleolar pre-rRNA maturation through the interaction of Tat with fibrillarin-U3snoRNA complex suggests a process by which the virus modulates host response, thus contributing to apoptosis and protein shut-off in HIV-uninfected cells.</p

Locus-Specific Ribosomal RNA Gene Silencing in Nucleolar Dominance

The silencing of one parental set of rRNA genes in a genetic hybrid is an epigenetic phenomenon known as nucleolar dominance. We showed previously that silencing is restricted to the nucleolus organizer regions (NORs), the loci where rRNA genes are tandemly arrayed, and does not spread to or from neighboring protein-coding genes. One hypothesis is that nucleolar dominance is the net result of hundreds of silencing events acting one rRNA gene at a time. A prediction of this hypothesis is that rRNA gene silencing should occur independent of chromosomal location. An alternative hypothesis is that the regulatory unit in nucleolar dominance is the NOR, rather than each individual rRNA gene, in which case NOR localization may be essential for rRNA gene silencing. To test these alternative hypotheses, we examined the fates of rRNA transgenes integrated at ectopic locations. The transgenes were accurately transcribed in all independent transgenic Arabidopsis thaliana lines tested, indicating that NOR localization is not required for rRNA gene expression. Upon crossing the transgenic A. thaliana lines as ovule parents with A. lyrata to form F1 hybrids, a new system for the study of nucleolar dominance, the endogenous rRNA genes located within the A. thaliana NORs are silenced. However, rRNA transgenes escaped silencing in multiple independent hybrids. Collectively, our data suggest that rRNA gene activation can occur in a gene-autonomous fashion, independent of chromosomal location, whereas rRNA gene silencing in nucleolar dominance is locus-dependent

Preferential Localization of Human Origins of DNA Replication at the 5′-Ends of Expressed Genes and at Evolutionarily Conserved DNA Sequences

Replication of mammalian genomes requires the activation of thousands of origins which are both spatially and temporally regulated by as yet unknown mechanisms. At the most fundamental level, our knowledge about the distribution pattern of origins in each of the chromosomes, among different cell types, and whether the physiological state of the cells alters this distribution is at present very limited.We have used standard λ-exonuclease resistant nascent DNA preparations in the size range of 0.7–1.5 kb obtained from the breast cancer cell line MCF–7 hybridized to a custom tiling array containing 50–60 nt probes evenly distributed among genic and non-genic regions covering about 1% of the human genome. A similar DNA preparation was used for high-throughput DNA sequencing. Array experiments were also performed with DNA obtained from BT-474 and H520 cell lines. By determining the sites showing nascent DNA enrichment, we have localized several thousand origins of DNA replication. Our major findings are: (a) both array and DNA sequencing assay methods produced essentially the same origin distribution profile; (b) origin distribution is largely conserved (>70%) in all cell lines tested; (c) origins are enriched at the 5′ends of expressed genes and at evolutionarily conserved intergenic sequences; and (d) ChIP on chip experiments in MCF-7 showed an enrichment of H3K4Me3 and RNA Polymerase II chromatin binding sites at origins of DNA replication.Our results suggest that the program for origin activation is largely conserved among different cell types. Also, our work supports recent studies connecting transcription initiation with replication, and in addition suggests that evolutionarily conserved intergenic sequences have the potential to participate in origin selection. Overall, our observations suggest that replication origin selection is a stochastic process significantly dependent upon local accessibility to replication factors