715 research outputs found
University of Palermo: Exploiting the Optical Quadratic Nonlinearity of Zinc-Blende Semiconductors for Guided-Wave Terahertz Generation: A Material Comparison
No full textContent synopsis of the following paper: Matteo Cherchi, Alberto Taormina, Alessandro C. Busacca, Roberto L. Oliveri, Saverio Bivona, Alfonso C. Cino, Salvatore Stivala, Stefano Riva Sanseverino, and Claudio Leone, "Exploiting the Optical Quadratic Nonlinearity of Zinc-Blende Semiconductors for Guided-Wave Terahertz Generation: A Material Comparison", IEEE Journal of Quantum Electronics, Vol. 46, N. 3, March 201
Low energy transfer to Mercury by using ballistic capture and electric propulsion
No full textPaper No. IAF-00-A.6.0
Resveratrol, a natural antioxidant phytoalexin, and 4 synthetic derivatives can promote expression of gamma-globin gene in vitro
No full textResveratrol (3,4′5-trihydroxystilbene) is a naturally occurring phenolic compound. It is found in the skin of red grapes and in a variety of medicinal plants. Resveratrol presents many biological activities that have been applied against cardiovascular disease and cancer. One of Resveratrol properties is inhibition of the enzyme Ribonucleotide reductase. It has been found that some other Ribonucleotide reductase inhibitors like Hydroxyurea, Didox and Trimidox are also inducers of gammaglobin gene expression. In this study we investigated whether Resveratrol and 10 newly synthesized derivatives can act as inducers of gamma-globin gene and increase HbF levels. These derivatives were synthesized by the group of Dr. L.A Stivala (Department of Chemistry, University of Modena) by modifications of the polar groups of Resveratrol structure in an effort to increase its antioxidant activity. We examined the effect of Resveratrol and 10 of its derivatives on gamma- and beta-globin gene promoter activity in a dual luciferase assay in GM979 cells. Hydroxyurea, a known Ribonucleotide reductase inhibitor and HbF inducer and propionic acid, an HbF inducer, were used as positive control substances. The results showed that Resveratrol and 4 of its derivatives increased the gamma-globin gene promoter activity more than 3 fold. The compounds which exhibited an effect were subsequently tested in human erythroid liquid cultures derived from normal individuals and thalassemic patients. HbF content was measured by HPLC. Despite their promising effects on gamma-globin gene promoter activity in MEL cells, Resveratrol and its 4 active derivative compounds did not cause significant increase in HbF production in erythroid progenitor cells (BFUe)
Inhibition of mammalian DNA polymerases by resveratrol: mechanism and structural determinants.
No full textResveratrol, a natural compound found in many dietary plants and in red wine, plays an important role in the prevention of many human pathological processes, including inflammation, atherosclerosis and carcinogenesis. We have shown that the antiproliferative activity of resveratrol correlated with its ability to inhibit the replicative pols (DNA polymerases) alpha and delta in vitro [Stivala, Savio, Carafoli, Perucca, Bianchi, Maga, Forti, Pagnoni, Albini, Prosperi and Vannini (2001) J. Biol. Chem. 276, 22586-22594]. In this paper, we present the first detailed biochemical investigation on the mechanism of action of resveratrol towards mammalian pols. Our results suggest that specific structural determinants of the resveratrol molecule are responsible for selective inhibition of different mammalian pols, such as the family B pol alpha and the family X pol lambda. Moreover, the resveratrol derivative trans-3,5-dimethoxy-4-hydroxystilbene, which is endowed with a strong antiproliferative activity (Stivala et al., 2001), can inhibit pols alpha and lambda and also suppress the in vitro SV40 DNA replication. The potency of inhibition is similar to that of aphidicolin, an inhibitor of the three replicative pols alpha, delta and epsilon. Our findings establish the necessary background for the synthesis of resveratrol derivatives having more selective and potent antiproliferative activity
Discursos en torno a las familias no heteronormativas : Un recorrido por el diario argentino La Nación (2002-2005)
No full textFil: Libson, Micaela. Grupo de Estudios sobre Sexualidades (IIGG/UBA-CONICET).Fil: Stivala, Gabriela. Grupo de Estudios sobre Sexualidades (IIGG/UBA)
Light self-confinement via second harmonic generation in a 2D nonlinear photonic crystal waveguide
No full textSpatial solitary waves induced by quadratic nonlinearities have been the subject of many theoretical and experimental investigations in the last decade, with extensive studies being devoted to soliton formation in 1D Nonlinear Photonic Crystals (NPC) such as PPLN (Periodically Poled LiNbO). Here we present results on a new class of (1+1)D spatial solitary waves, the first examples of quadratic self-confinement in a 2D NPC
Resveratrol is a peroxidase-mediated inactivator of COX-1 but not COX-2 - A mechanistic approach to the design of COX-1 selective agents
No full textResveratrol (3,4', 5- trihydroxy- trans- stilbene) is a phytoalexin found in grapes that has anti- inflammatory, cardiovascular protective, and cancer chemopreventive properties. It has been shown to target prostaglandin H-2 synthase (COX)-1 and COX-2, which catalyze the first committed step in the synthesis of prostaglandins via sequential cyclooxygenase and peroxidase reactions. Resveratrol discriminates between both COX isoforms. It is a potent inhibitor of both catalytic activities of COX-1, the desired drug target for the prevention of cardiovascular disease, but only a weak inhibitor of the peroxidase activity of COX-2, the isoform target for nonsteroidal anti- inflammatory drugs. We have investigated the unique inhibitory properties of resveratrol. We find that it is a potent peroxidase- mediated mechanism-based inactivator of COX-1 only (k(inact) = 0.069 +/- 0.004 s(-1), K-i( inact) = 1.52 +/- 0.15 muM), with a calculated partition ratio of 22. Inactivation of COX-1 was time- and concentration- dependent, it had an absolute requirement for a peroxide substrate, and it was accompanied by a concomitant oxidation of resveratrol. Resveratrol-inactivated COX-1 was devoid of both the cyclooxygenase and peroxidase activities, neither of which could be restored upon gel- filtration chromatography. Inactivation of COX-1 by [H-3] resveratrol was not accompanied by stable covalent modification as evident by both SDS-PAGE and reverse phase- high performance liquid chromatography analysis. Structure activity relationships on methoxy- resveratrol analogs showed that the m-hydroquinone moiety was essential for irreversible inactivation of COX-1. We propose that resveratrol inactivates COX-1 by a hit- and- run mechanism, and offers a basis for the design of selective COX-1 inactivators that work through a mechanism- based event at the peroxidase active site
Parametric solitons in nonlinear photonic crystals
No full textWe present theoretical and experimental investigations on the soliton dynamics associated to multiple second harmonic generation resonances in two-dimensional nonlinear photonic crystals, highlighting a wealth of new possibilities for soliton management in such structures
Novel Configuration for a C-Band Axial Vircator With High Output Power
No full textWe present a novel configuration for an axial virtual cathode oscillator (Vircator) operating in the C-band and designed for high output power applications. In order to enhance the efficiency, we have employed a geometry with up to seven reflectors along the drift space. While in previous research works this optimization process has been
performed only varying the reflectors radii while using a fixed distance between reflectors,in our work we propose an optimization in terms of both reflectors radii and distances. Our optimized structure for the axial Vircator is able to provide an efficiency up to 15.6% and an output power of 1.6 GW in the C-band, with a working voltage of 510 kV and a cathodic current of 24 kA
Effetti trasversi nella propagazione di fasci ottici in vetri ad alto indice
No full textWe investigate beam propagation in a novel Heavy Metal Oxide glass, reporting near infrared beam self-confinement and solitons, filamentation, interactions and conical emission at picoseconds and discussing them with the aid of a model
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