92 research outputs found
Flavonoids of Aerial Parts of an Endemic Species of the Apiaceae of Algeria, Ammoides atlantica
Optimization of a ClââHâ inductively coupled plasma etching process adapted to nonthermalized InP wafers for the realization of deep ridge heterostructures
Inductively coupled plasmaetching using ClââHâ chemistry with no additive gas (CHâ, Ar, or Nâ) is studied to realize deep (>5ÎŒm) ridges with smooth and vertical sidewalls. The process is optimized for nonthermalized InP wafers to avoid the use of thermal grease. Cleaning of the rear side of the wafer after etching is avoided, which is suitable for an industrial process or for critical subsequent steps such as epitaxial regrowth. The influence of the ClââHâ ratio on the etching mechanism is investigated for both InP bulk layers and InGaAsâInP or InGaAlAsâInPheterostructures. The authors show that this ratio is the main parameter controlling the ridge profile, in a similar way for both bulk InP and InGa(Al)AsâInP samples. Smooth and vertical sidewalls with neither undercuts nor notches can be obtained in the 0.5â1mTpressure range for a hydrogen percentage of 35%â45% in the gas mixture. Etching rates from 900to1300nmâmin together with a selectivity over SiNx dielectric mask as high as 24:1â29:1 are measured for the InP bulk layers under these conditions. Etching does not affect the optical quality of the heterostructures as evidenced from micro-photoluminescence measurements performed on 1.6âto0.85âÎŒm-wide deep etched ridge waveguides. The process is well adapted to the realization of low loss deep ridge waveguides or buried heterostructures
Identification of coumarins in DCM bark, leaf and fruit extracts from Mammea neurophylla (Calophyllaceae) by LC-PDA-MSn
4-phenyl and 4-propylcoumarins display a wide variety of biological activities including anti-oxidant and anti-inflammatory effects, antiparasitical activities against Leishmania or Plasmodium as well as antibacterial, antiviral (HIV) and cytotoxic activities. Using LC-PDA-MSn we have developed a specific protocol allowing the simultaneous and qualitative detection of 4-phenyl and 4-propylcoumarins in DCM bark, fruit and leaf extracts obtained from Mammea neurophylla. By comparison of their retention times, MS and UV data with that of authentic samples, nine, seven and five 4-phenylcoumarins could be directly identified in bark, leaf and fruit extracts respectively. On the other hand, interlocking UV spectra and ESI-MSn data analysis allowed us to deduce plausible structures of five, eight and four other coumarins in bark, leaf and fruit respectively by comparison with their reported spectral data. During this study new Mammea A/AA 9-hydroxy-cyclo F and Mammea A/AB 9-hydroxy-cyclo F were identified. We believe that this protocol will be useful in case of dereplicative studies of Mammea and related species
High contrast reflection modulation near 1.55 mu m in InP 2D photonic crystals on silicon wafer
Explosion Mechanisms of Core-Collapse Supernovae
Supernova theory, numerical and analytic, has made remarkable progress in the
past decade. This progress was made possible by more sophisticated simulation
tools, especially for neutrino transport, improved microphysics, and deeper
insights into the role of hydrodynamic instabilities. Violent, large-scale
nonradial mass motions are generic in supernova cores. The neutrino-heating
mechanism, aided by nonradial flows, drives explosions, albeit low-energy ones,
of ONeMg-core and some Fe-core progenitors. The characteristics of the neutrino
emission from new-born neutron stars were revised, new features of the
gravitational-wave signals were discovered, our notion of supernova
nucleosynthesis was shattered, and our understanding of pulsar kicks and
explosion asymmetries was significantly improved. But simulations also suggest
that neutrino-powered explosions might not explain the most energetic
supernovae and hypernovae, which seem to demand magnetorotational driving. Now
that modeling is being advanced from two to three dimensions, more realism, new
perspectives, and hopefully answers to long-standing questions are coming into
reach.Comment: 35 pages, 11 figures (29 eps files; high-quality versions can be
obtained upon request); accepted by Annual Review of Nuclear and Particle
Scienc
Preliminary study of Lead (Pb) immobilization by meat and bone meal combustion residues (MBMCR) in soil: Assessment of Pb toxicity (phytotoxicity and genotoxicity) using the tobacco model (Nicotiana tabacum var. xanthi Dulieu).
Lead (Pb) is a major chemical pollutant in the environment. The present investigation evaluates the possible use of Meat and Bone Meal Combustion Residues (MBMCR), to sequester Pb from the soil compartment using the heterozygous tobacco model (Nicotiana tabacum var. xanthi Dulieu) characterized by the a1+/a1 a2+/a2 system. The toxic potential of Pbcontaminations(50, 100, 1,000, 2,000 and 10,000 mg Pb kg-1) as Pb(NO3) in standard soil was investigated in lab conditions according to three endpoints: (i) acute toxicity of plants (mortality, height and surface area parameters), (ii) Pb-accumulation in roots, stems and leaves, and (iii) genetic effects as the expression of reversion in the leaf of plants. Moreover, chemical investigations of Pb interactions with soil were realized to complete the toxicity evaluation. The results demonstrated that: (i) MBMCR were not acutely toxic or genotoxic to tobacco plants, (ii) Pb is acutely toxic to tobacco plants at 10,000 mg Pb kg-1 of soil, (ii) but is not genotoxic, and (iii) Pbbioaccumulation is significant in leaves, stems and roots (from 1,000, 2,000, and 50 mg Pb kg-1 of soil, respectively). In contrast, in the presence of MBMCR, the toxic impacts of Pb were inhibited and Pb-accumulation in tobacco plants was reduced. In complement, chemical analyses highlighted the high capacity of the standard soil to immobilize Pb. The results suggest that even if Pb is bioavailable from soils to plants, complex mechanisms could occur in plants protecting them from the toxic impact of Pb
Etude de lâextrait hexanique de lâespĂšce Ferula vesceritensis par les techniques couplĂ©es LC-UV-DAD, LC-MS et GC-MS
Dihydrochalcones: Implication in resistance to oxidative stress and bioactivities against advanced glycation end-products and vasoconstriction
Flavonoids are a group of polyphenol compounds with known antioxidant activities. Among them, dihydrochalcones are mainly found in apple leaves (Malus domestica). Glycosylated dihydrochalcones were previously found in large amounts in leaves of two genotypes of Malus with contrasting resistance to fire blight, a bacterial disease caused by Erwinia amylovora. In the present study we demonstrate that soluble polyphenol patterns comprised phloridzin alone or in combination with two additional dihydrochalcones, identified as sieboldin and trilobatin. Presence of sieboldin in young leaves correlated well with a high 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity. Moreover, these leaves displayed enhanced tolerance to paraquat, a photooxidative-stress generating herbicide. Interestingly, phloridzin had a high activity in the oxygen radical absorbance capacity (ORAC) assay, but its presence alone in leaves did not correlate with tolerance to paraquat. In order to further characterise the activity of these compounds, we tested their ability to prevent oxidative-dependent formation of advanced glycation end-products (AGEs) and phenylephrine-induced contraction of isolated rat mesenteric arteries. The antioxidant capacity of sieboldin was clearly demonstrated by showing that this compound (i) prevented vasoconstriction and (ii) inhibited AGEs formation. Both assays provided interesting information concerning a potential use of sieboldin as a therapeutic. Hence, our results strongly argue for a bioactivity of dihydrochalcones as functional antioxidants in the resistance of Malus leaves to oxidative stress. In addition, we demonstrate for the first time that sieboldin is a powerful multipotent antioxidant, effective in preventing physiopathological processes. Further work should aim at demonstrating the potential use of this compound as a therapeutic in treating free radical-involving diseases
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