2,110 research outputs found
Coulomb corrections to low energy antiproton annihilation cross sections on protons and nuclei
We calculate, in a systematic way, the enhancement effect on
antiproton-proton and antiproton-nucleus annihilation cross sections at low
energy due to the initial state electrostatic interaction between the
projectile and the target nucleus. This calculation is aimed at future
comparisons between antineutron and antiproton annihilation rates on different
targets, for the extraction of pure isospin channels.Comment: 18 pages, 4 figures (latex format
Regeneration of plants from embryogenic callus-derived protoplasts of Garganega and Sangiovese grapevine (Vitis vinifera L.) cultivars
Protoplasts are useful research tools for basic and applied plant science, but the regeneration of whole plants from protoplasts is challenging in most of agronomically important crops, including grapevine (Vitis vinifera L.). Here we describe an efficient protocol for the induction of embryogenic callus, the isolation of protoplasts, and the regeneration of whole grapevine plants in two Italian grapevine cultivars. Embryogenic callus was induced successfully from stamens collected from immature flowers. Isolated protoplasts were tested to confirm their viability and then cultivated using the disc-culture method, at a density of 1\u2009
7\u2009105 protoplasts/mL in solid Nitsch\u2019s medium supplemented with 2 mg/L 1-naphthaleneacetic acid and 0.5 mg/L 6-benzylaminopurine. After 3\u20134 months, the protoplasts of both cultivars regenerated with similar efficiency into cotyledonal-stage somatic embryos. The somatic embryos were transferred to solid Nitsch\u2019s medium supplemented with 30 g/L sucrose and 2 g/L gellan gum, and were maintained in the dark for 4 weeks. This step was necessary for the embryo to complete germination, allowing subsequent shoot elongation in response to light on a medium with 4 \ub5M 6-benzylaminopurine. Then root elongation occurred after transferring on a medium with 0.5 \ub5M 1-naphthaleneacetic. After\u2009~\u20096 months from the isolation of protoplasts, normal plants were regenerated, which were moved to the greenhouse. The protoplasts could also be transfected using the polyethylene glycol method, as confirmed using a plasmid carrying the yellow florescent protein marker gene. The new method is therefore compatible with biotechnological applications such as gene transfer and genome editing
TRANSCRIPTOMIC ANALYSIS OF WHOLE PISTILS AND OVULE CELLS TO IDENTIFY GENES RELATED TO APOSPORY IN HYPERICUM PERFORATUM L.
St. John\u2019s wort (Hypericum perforatum L.) is a medicinal plant that produces important
metabolites with antidepressant and anticancer activities. Beside the pharmaceutical interest,
recently gained information has shown that H. perforatum is also an attractive model system for the
study of aposporous apomixis, that is a reproductive strategy, which, unlike sexual reproduction,
permits the inheritance of the maternal genome over generations without genetic recombination
events. This asexual mode of seed formation is believed to be a trait with enormous economic and
social potential in agriculture. Its innovative use in this area relies upon the idea that indefinitely
fixing highly complex genotypes, including hybrid cultivars, through apomixis would have
tremendous advantages in plant breeding, biomass and seed production. During the last decades, the
understanding of the molecular basis of apomixis in this species has been complicated by the lack of
biological data, e.g. genomic or even transcriptomic sequences. The aim of our research project was
the sequencing, annotation and comparative investigation of the H. perforatum flower
transcriptome, as critical steps toward a better understanding of the genetic control of aposporic and
sexual reproduction in the facultative apomict H. perforatum. To this end, next generation
sequencing technologies have been used to sequence the flower transcriptomes of obligate sexual
and unrelated apomictic H. perforatum genotypes. This approach has enabled the assembly and
annotation of large cDNA repositories and their exploitation to design a custom array to be used in
flower expression studies. Global gene expression analysis of H. perforatum was initially
performed on ovaries collected from sexual and aposporic plant accessions for the purpose of
identifying genes and processes potentially associated with apomixis in this model species. Overall,
across two selected developmental stages, 224 and 973 unigenes were found to be significantly upand down-regulated. Ontological annotation of differentially expressed genes indicated that terms
related to cell cycle, single-organism cellular process DNA (cytosine-5-)-methyltransferase activity,
among others, were significantly enriched. In a following step, a laser-capture microdissection
approach was adopted in combination the RNA-seq technology with the aim of identifying genes
differentially expressed in the ovule cell types primarily involved in the differentiation of the
megaspore mother cells and aposporous initials. On the whole, our data suggest that phenotypic
expression of apospory is concomitant with the modulation of key genes involved in the sexual
reproductive pathway and the responsive to hormonal stimuli. Annotation of all identified flower
transcripts as well as their qualitative and quantitative expression data will be presented and
critically discussed as they prove a far better understanding of molecular bases of pistil
development, embyo sac and egg cell formation in sexual and apomictic H. perforatum
Limits on the low energy antinucleon-nucleus annihilations from the Heisenberg principle
We show that the quantum uncertainty principle puts some limits on the
effectiveness of the antinucleon-nucleus annihilation at very low energies.
This is caused by the fact that the realization a very effective short-distance
reaction process implies information on the relative distance of the reacting
particles. Some quantitative predictions are possible on this ground, including
the approximate A-independence of antinucleon-nucleus annihilation rates.Comment: 10 pages, no figure
A major QTL is associated with berry grape texture characteristics
Berry texture and berry skin mechanical properties are traits with high agronomic relevance because they are related to quality parameters and marketing requirements of wine, table, and raisin grapes. Searching for QTLs linked to berry texture, an F1 population of 152 individuals and their parents were used in this study. These F1 plants were obtained crossing Raboso Veronese, a seeded black wine grape cultivar, and Sultanina, a seedless white grape variety, especially used for raisins. Density flotation was applied for berry sorting improving the management of many and highly variable genotypes, irrespective of the quantification of specific molecule classes. Berries were evaluated for technological ripeness parameters and mechanical properties. Texture parameters were taken as raw data and as data normalised on berry dimensions, i.e., berry diameter or surface or volume. SSR molecular markers were used to produce a genetic map and a major QTL for berry texture was found on chromosome 18 with traits related to berry firmness showing a phenotypical explained variance higher than 60 %, and traits related to berry resilience, springiness and cohesiveness showing a variance higher than 50 %. Surprisingly, this QTL showed to be associated with SSR markers linked to VviAGL11, the main gene linked to seedlessness. VviAGL11 expression and co-expression profiling during grape ripening was evaluated using available information; this data suggested a role for this gene on the texture of a ripe berry
Noise reduction in muon tomography for detecting high density objects
The muon tomography technique, based on multiple Coulomb scattering of cosmic
ray muons, has been proposed as a tool to detect the presence of high density
objects inside closed volumes. In this paper a new and innovative method is
presented to handle the density fluctuations (noise) of reconstructed images, a
well known problem of this technique. The effectiveness of our method is
evaluated using experimental data obtained with a muon tomography prototype
located at the Legnaro National Laboratories (LNL) of the Istituto Nazionale di
Fisica Nucleare (INFN). The results reported in this paper, obtained with real
cosmic ray data, show that with appropriate image filtering and muon momentum
classification, the muon tomography technique can detect high density
materials, such as lead, albeit surrounded by light or medium density material,
in short times. A comparison with algorithms published in literature is also
presented
First determination of the one-proton induced Non-Mesonic Weak Decay width of p-shell {\Lambda}-Hypernuclei
Previous studies of proton and neutron spectra from Non-Mesonic Weak Decay of
eight Lambda-Hypernuclei (A = 5-16) have been revisited. New values of the
ratio of the two-nucleon and the one-proton induced decay widths,
Gamma_2N/Gamma_p, are obtained from single proton spectra, Gamma_2N/Gamma_p =
0.50 +/- 0.24, and from neutron and proton coincidence spectra,
Gamma_2N/Gamma_p = 0.36 +/- 0.14stat +0.05sys -0.04sys , in full agreement with
previously published ones. With these values, a method is developed to extract
the one-proton induced decay width in units of the free Lambda decay width,
Gamma_p/Gamma_Lambda, without resorting to Intra Nuclear Cascade models but by
exploiting only experimental data, under the assumption of a linear dependence
on A of the Final State Interaction contribution. This is the first systematic
determination ever done and it agrees within the errors with recent theoretical
calculations.Comment: 16 pages, 3 figures, 2 table
- …