1,213 research outputs found
Pump-and-probe optical transmission phase shift as a quantitative probe of the Bogoliubov dispersion relation in a nonlinear channel waveguide
We theoretically investigate the dispersion relation of small-amplitude
optical waves superimposing upon a beam of polarized monochromatic light
propagating along a single-mode channel waveguide characterized by an
instantaneous and spatially local Kerr nonlinearity. These small luminous
fluctuations propagate along the waveguide as Bogoliubov elementary excitations
on top of a one-dimensional dilute Bose quantum fluid evolve in time. They
consequently display a strongly renormalized dispersion law, of Bogoliubov
type. Analytical and numerical results are found in both the absence and the
presence of one- and two-photon losses. Silicon and silicon-nitride waveguides
are used as examples. We finally propose an experiment to measure this
Bogoliubov dispersion relation, based on a stimulated four-wave mixing and
interference spectroscopy techniques.Comment: 17 pages, 7 figure
The role of mediterranean fruit tree orchards and vineyards in maintaining the traditional agricultural landscape
The Mediterranean area represents one of the most suitable and diversified
environments for horticultural crops, being this propriety well expressed in the
commonly accepted definition of “Mediterranean cultivated garden”. In Italy, fruit
crops have been in the past introduced and expanded in different environments
depending on the species and adaptability to the physiographic characteristics of the
regions. The climate and the diversity of environmental contexts, the specificity of
soils, the plasticity of the cultivated genotypes, have allowed a tight and typical
relationship among land and farmers. Since the past centuries olive and fruit
orchards, vineyards and Citrus plantations have represented the typicity of the Italian
rural landscape. The physiognomy of tree cropping systems has been changed rapidly
starting from half of the past century owing to the introduction of new genetic
resources, the change in the concepts of quality, the modernization and intensification
of the agronomical techniques, resulting in loss of environmental and biological
diversity. Nonetheless, some historic fruit orchards and vineyards have survived. The
research is focused: a) on the recognition and mapping of the traditional landscapes of
fruit crops in two representative Mediterranean regions; b) on the identification of
their typological traits; c) on the definition of their environmental and technical
sustainability based on an interdisciplinary methodology. Through a multi-criterial
analysis it was possible to recognize and measure the sustainability of these cropping
models and their ecological function, turning into preservation of environmental
resources, environmental quality and quality of life. The study also underlined the
crucial role of the traditional agricultural landscapes in the maintenance of local
identity, history and economy. By representing a cultural heritage, traditional agricultural
landscapes and traditional farming might justify preservation and valorisation
actions
Tomato ionomic approach for food fortification and safety.
Food fortification is an issue of paramount of importance for people living both in developed
and in developing countries. Among substances listed as "nutriceuticals", essential minerals have
been recognised for their involvement in several healthy issues, involving all ages. In this frame,
food plants are playing a pivotal role since their capability to compartmentalise ions and proteinmetal
complexes in edible organs. Conversely, the accumulation of high metal levels in those
organs may lead to safety problems. In the recent years, thanks to the availability of new and
improved analytical apparatus in both ionic and genomic/transcrittomics areas, it is became feasible
to couple data coming from plant physiology and genetics. Ionomics is the discipline that studies
the cross-analysis of both data sets. Our group, in the frame of GenoPom project granted by MiUR,
is interested to study the ionomics of tomatoes cultivars derived by breeding programmes in which
wild relatives have been used to transfer several useful traits, such as resistance to biotic or abiotic
stresses, fruit composition and textiture, etc. The introgression of the wild genome into the
cultivated one produces new gene combinations. They might lead to the expression of some traits,
such as increased or reduced adsorption of some metals and their exclusion or loading into edible
organs, thus strongly involving the nutritional food value. Our final goal is to put together data
coming from ions homeostasis and gene expression analyses, thus obtaining an ionomic tomato
map related to ions absorption, translocation and accumulation in various plant organs, fruits
included. To follow our hypothesis, we are studying the ionome of Solanum lycopersicum cv. M82
along with 76 Introgression Lines (ILs) produced by interspecific crosses between this cultivar and
the wild species S. pennellii. These ILs are homozygous for small portions of the wild species
genome introgressed into the domesticated M82 one. They are used as a useful tool for mapping
QTL associated with many traits of interest. It is worthy to note that, until now, little information is
available on QTL for ions accumulation in tomato. Moreover, as our knowledge, effects of new
gene combinations in introgressed lines on ions uptake related to food safety have not been
extensively studied. In this presentation we show results coming from the ionome analysis, carried
out on S . lycopersicum M82 and several ILs. Plants were grown in pots in a greenhouse and
watered with deionised water Thirty day-old plants were left to grow for 15 days in the presence of
non-toxic concentration of Cd, Pb, As, Cr and Zn given combined. Leaves of all plants were then
harvested and stored at -80°C for ionome and gene expression analyses. Preliminary results of
ionome analysis of S. lycopersicum M82 and several ILs, carried out using an ICP-MS, showed that
traits correlated to toxic metals and micronutrients accumulation in apical leaves were significantly
modified in response to specific genetic backgrounds. Those results are perhaps due to the
introgression of traits linked to uptake, translocation and accumulation of useful and/or toxic metal
into plant apical leaves and to interactions of the wild type introgressed genomic regions with the
cultivated genome. Also, data are shown on the identification and isolation of Solanum gene
sequences related to ions uptake, translocation and accumulation, useful for further real-time gene
expression evaluation in both cultivated and ILs during the treatments with the above-mentioned
metals
In vitro evidence for CCl4 metabolites covalently bound to lipoprotein micelles
AbstractCCl4-induced impairment of the lipoprotein secretion pathway of intact rat hepatocytes was carried out using 14CCl4 to check the possibility of binding to lipoproteins by CCl4 metabolites. After separation of different cell suspension fractions by means of ultracentrifugation and chemical precipitation procedures, a significant amount of the radioisotope was found covalently bound to the lipid and protein components of low density lipoproteins. Suitable experiments demonstrated that the bound radioisotope was represented by CCl4 metabolites and not by unactivated CCl4
Dynamic origin of chirality transfer between chiral surface and achiral ligand in Au38 clusters
The transfer of chirality between nanomolecules is at the core of several applications in chiral technology such as sensing and catalysis. However, the origin of this phenomenon and how exactly nanoscale objects transfer chirality to molecules in their vicinity remain largely obscure. Here, we show that the transfer of chirality for the intrinsically chiral gold cluster Au38(SR)24 is site dependent; that is, it differs depending on the ligand-binding sites. This is closely related to the dynamic nature of the ligands on the cluster surface. Using a combination of NMR techniques and molecular dynamics simulations, we could assign the four symmetry- unique ligands on the cluster. The study reveals largely different conformational dynamics of the bound ligands, explaining the diverse diastereotopicities observed for the CH2 protons of the ligands. Although chirality is a structural property, our study reveals the importance of dynamics for the transfer of chirality
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