Search results for "Allium"
showing 10 items of 385 documents
Allium paniculatum L., una specie critica ed erroneamente interpretata della flora europea
2010
Dalle indagini morfologiche e cariologiche condotte è emerso che Allium paniculatum è una specie ben differenziata dagli altri taxa della sez. Codonoprasum, con corredo cromosomico poliploide, esaploide o triploide, probabilmente originatosi in seguito all’adattamento ad ambienti sinantropici in territori con bioclima marcatamente mesico, come si desume dalle esigenze ecologiche, dal periodo di fioritura estivo e dalla distribuzione geografica.
Experimental and numerical study of anomalous thermocapillary convection in liquid gallium
1999
Thermocapillary Marangoni convection of liquid gallium was studied experimentally and numerically. A specially designed experimental setup ensured an oxide-free surface of the liquid gallium for a very long time. The convective flow at the free surface was found to be directed opposite to both buoyancy-driven and ordinary thermocapillary convection. The anomalous direction of the thermocapillary flow was explained by the presence of a small amount of a surface-active contaminant—lead adsorbed at the free surface. Two different approaches were used to describe the observed phenomenon. First, the flow was treated as a pure thermocapillary convection with a modified dependence of the surface t…
New antiasthmatic drugs from traditional medicine?
1991
Several plants are used in traditional medicine for the treatment of bronchial asthma. We are trying to identify the active compound(s) and their mode of action. For the isolation and identification of the active principles, different chromatographic methods, HPLC, MPLC, elementary analysis, UV, mass, <sup>1</sup>H- and <sup>13</sup>C-NMR spectroscopy are used. Whole plant extracts, fractionated extracts and pure compounds are tested in the following pharmacological systems: cyclooxygenase and lipoxygenase pathway of arachidonic acid metabolism, bronchial obstruction of guinea pigs after inhalation of allergens, platelet-activating factor (PAF), histamine or acetylch…
Internal photoemission in solar blind AlGaN Schottky barrier photodiodes
2005
We have analyzed the photoresponse of solar blind AlGaN Schottky barrier photodiodes below the alloy band gap energy, in the 3.5-4.5 eV range, and we show that it is dominated by internal photoemission. The n-type Schottky barrier height is shown to increase linearly with the band gap energy of the AlGaN alloy. The amplitude of the internal photoemission signal is about 20 times smaller than the value given by the Fowler theory based on a free electron model. We explain this result by taking into account the interband transitions and the ballistic transport of photoexcited electrons in the metal. This low value of internal photoemission allows us to achieve a spectral rejection ratio betwee…
Comparison of the chemopreventive efficacies of garlic powders with different alliin contents against aflatoxin B1 carcinogenicity in rats
2004
Garlic (Allium sativum) is well known for its beneficial effects on health and particularly for its chemopreventive potential against cancer. The present study was designed to compare the chemopreventive efficacies of several garlic powders with various levels of alliin, a precursor of active sulfur compounds. For this purpose we used the medium-term hepatocarcinogenesis protocol (resistant hepatocyte model), which allows the detection of preneoplasic foci expressing the placental form of glutathione S-transferase (GST-P) as an end-point. Rats were fed diets containing three garlic powders (5% of the diet) with various alliin contents for 3 weeks. Garlic powders were obtained from bulbs gro…
Synthesis of Silver Gallium Selenide (AgGaSe2) Nanotubes and Nanowires by Template-Based Electrodeposition
2020
In this work, a systematic investigation of the different parameters that control the electrodeposition processes was carried out at the aim to synthetizing AgGaSe₂ nanostructures. We found that pH is a key parameter to control both the morphology and composition of the nanostructures. Low pH favours mainly the formation of Ag2Se nanotubes with a scarce mechanical stability, while multi-phase nanowires well anchored to the substrate were obtained at higher pH. We also found that it was necessary to increase dramatically the concentration of the gallium precursor into the deposition bath in order to obtain AgGaSe₂ owing to lower redox potential of the Ga3+/Ga couple than Ag2+/Ag and Se4+/Se.…
Multiexciton complex from extrinsic centers in AlGaAs epilayers on Ge and Si substrates
2013
The multiexciton properties of extrinsic centers from AlGaAs layers on Ge and Si substrates are addressed. The two photon cascade is found both in steady state and in time resolved experiments. Polarization analysis of the photoluminescence provides clearcut attribution to neutral biexciton complexes. Our findings demonstrate the prospect of exploiting extrinsic centers for generating entangled photon pairs on a Si based device. © 2013 AIP Publishing LLC.
Indium surfactant effect on AlN/GaN heterostructures grown by metal-organic vapor-phase epitaxy: Applications to intersubband transitions
2006
We report on a dramatic improvement of the optical and structural properties of AlN/GaN multiple quantum wells (MQWs) grown by metal-organic vapor-phase epitaxy using indium as a surfactant. This improvement is observed using photoluminescence as well as x-ray diffraction. Atomic force microscopy shows different surface morphologies between samples grown with and without In. This is ascribed to a modified relaxation mechanism induced by different surface kinetics. These improved MQWs exhibit intersubband absorption at short wavelength (2 mu m). The absorption linewidth is as low as 65 meV and the absorption coefficient is increased by 85%.
Mid-infrared intersubband absorption in lattice-matched AlInN/GaN multiple-quantum wells
2005
We report the observation of midinfrared intersubband (ISB) absorption in nearly lattice-matched AlInNGaN multiple-quantum-wells. A clear absorption peak is observed around 3 μm involving transitions from the conduction band ground state to the first excited state. In addition to ISB absorption, photoluminescence experiments were carried out on lattice- matched AlInNGaN single quantum wells in order to determine the spontaneous polarization discontinuity between GaN and Al0.82 In0.18 N compounds. The experimental value is in good agreement with theoretical predictions. Our results demonstrate that the AlInNGaN system is very promising to achieve crack-free and low dislocation density struct…
68Ge/68Ga Generators: Past, Present, and Future
2012
In 1964, first (68)Ge/(68)Ga radionuclide generators were described. Although the generator design was by far not adequate to our today's level of chemical, radiopharmaceutical and medical expectations, it perfectly met the needs of molecular imaging of this period. (68)Ga-EDTA as directly eluted from the generators entered the field of functional diagnosis, in particular for brain imaging. A new type of generators became commercially available in the first years of the 21st century. Generator eluates based on hydrochloric acid provided "cationic" (68)Ga instead of "inert" (68)Ga-complexes and opened new pathways of Me(III) based radiopharmaceutical chemistry. The impressive success of util…