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Search Results: 1 - 10 of 13015 matches for " RENE TORRES "
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LA DIVISION DE QUIMICA DE PRODUCTOS NATURALES DE LA SOCIEDAD CHILENA DE QUíMICA
MIGUEL RENE TORRES GAONA
Boletín de la Sociedad Chilena de Química , 2001,
Abstract:
IDENTIFICATION OF A NEW AROMATIC GERANYL DERIVATIVE IN THE RESINOUS EXUDATE OF HELIOTROPIUM FILIFOLIUM (BORAGINACEAE)
URZúA,ALEJANDRO; MODAK,BRENDA; TORRES,RENE;
Boletín de la Sociedad Chilena de Química , 2001, DOI: 10.4067/S0366-16442001000200011
Abstract: a new aromatic geranyl derivative was isolated from the resinous exudate of heliotropium filifolium. the structure was elucidated by high-resolution spectroscopic methods as filifolinyl senecionate. the compound has shown antibacterial activity against escherichia coli k-12. after irradiation of a solution of filifolinyl senecionate with uv at 366 nm, the antibacterial activity was enhanced by 100%
IDENTIFICATION OF A NEW AROMATIC GERANYL DERIVATIVE IN THE RESINOUS EXUDATE OF HELIOTROPIUM FILIFOLIUM (BORAGINACEAE)
ALEJANDRO URZúA,BRENDA MODAK,RENE TORRES
Boletín de la Sociedad Chilena de Química , 2001,
Abstract: A new aromatic geranyl derivative was isolated from the resinous exudate of Heliotropium filifolium. The structure was elucidated by high-resolution spectroscopic methods as filifolinyl senecionate. The compound has shown antibacterial activity against Escherichia coli K-12. After irradiation of a solution of filifolinyl senecionate with UV at 366 nm, the antibacterial activity was enhanced by 100% Del exudado resinoso de Heliotropium filifolium, se aisló un nuevo derivado aromático geranilado. Este compuesto se identificó por métodos espectrópicos de alta resolución como filifolinil senecionato. El compuesto mostró actividad antibacteriana contra Escherichia coli K-12. Esta actividad se vio incrementada en un 100% después de irradiar una solución de filifolinil senecionato con UV a 366 nm
The polydisperse cell model: Non-linear screening and charge renormalization in colloidal mixtures
Aldemar Torres,Gabriel Tellez,Rene van Roij
Physics , 2008, DOI: 10.1063/1.2907719
Abstract: We propose a model for the calculation of renormalized charges and osmotic properties of mixtures of highly charged colloidal particles. The model is a generalization of the cell model and the notion of charge renormalization as introduced by Alexander and his collaborators (J. Chem. Phys. 80, 5776 (1984)). The total solution is partitioned into as many different cells as components in the mixture. The radii of these cells are determined self-consistently for a given set of parameters from the solution of the non-linear Poisson-Boltzmann equation with appropriate boundary conditions. This generalizes Alexanders's model where the (unique) Wigner-Seitz cell radius is fixed solely by the colloids packing fraction. We illustrate the technique by considering a binary mixture of colloids with the same sign of charge. The present model can be used to calculate thermodynamic properties of highly charged colloidal mixtures at the level of linear theories, while taking the effect of non-linear screening into account.
Finite-Thickness and Charge Relaxation in Double-Layer Interactions
Aldemar Torres,Rene van Roij,Gabriel Tellez
Physics , 2006, DOI: 10.1016/j.jcis.2006.04.058
Abstract: We extend the classical Gouy-Chapman model of two planar parallel interacting double-layers, which is used as a first approximation to describe the force between colloidal particles, by considering the finite-thickness of the colloids. The formation of two additional double layers due to this finite thickness, modifies the interaction force compared to the Gouy-Chapman case, in which the colloids are semi-infinite objects. In this paper we calculate this interaction force and some other size-dependent properties using a mean field level of description, based on the Poisson-Boltzmann (PB) equation. We show that in the case of finite-size colloids, this equation can be set in a closed form depending on the geometrical parameters and on their surface charge. The corresponding linear (Debye-Huckel) theory and the well-known results for semi-infinite colloids are recovered from this formal solution after taking appropriate limits. We use a density functional corresponding to the PB level of description to show how in the case when the total colloidal charge is fixed, it redistribute itself on their surfaces to minimize the energy of the system depending on the afore mentioned parameters. We study how this charge relaxation affects the colloidal interactions.
IN VITRO SENSITIVITY OF BOTRYTIS CINéREA TO RESINOUS EXUDATES OF HELIOTROPIUM FILIFOLIUMAND GERANYL DERIVATIVES COMPOUNDS
MENDOZA,LEONORA; MODAK,BRENDA; TORRES,RENE; COTORAS,MILENA;
Journal of the Chilean Chemical Society , 2008, DOI: 10.4067/S0717-97072008000100024
Abstract: the activity of the extract ofheliotropium filifolium, of the natural compounds obtained from its resinous exudates, filifolinol and fihfohnyl senecionate, and of the synthetic derivative of filifolinol, filifolinoic acid, on the mycehal growth of the phytopathogenic fungus botrytis cinérea was analyzed in liquid and solid media. the extract of h'. filifolium, filifolinol, and filifolinoic acid reduced mycehal growth of this fungus. the effect of these compounds was dose-dependant. the compound fihfohnyl senecionate was inactive in all the tested conditions. the extract of h'. filifolium and filifolinol retarded the germination of conidia of the fungus
ACTIVIDAD ANTIBACTERIANA DE FLAVONOIDES AISLADOS DEL EXUDADO RESINOSO DE HELIOTROPIUM SINUATUM: EFECTO DEL TIPO DE ESTRUCTURA
MODAK,BRENDA; ARRIETA,ABEL; TORRES,RENE; URZUA,ALEJANDRO;
Boletín de la Sociedad Chilena de Química , 2002, DOI: 10.4067/S0366-16442002000100005
Abstract: from the resinous exudates of heliotropium sinuatum have been isolated and characterized eight flavonoids. in this paper we show the bacteride activity of resin and previously isolated flavonoids. kinetics of bacterial growth gave the generation time of bacterial population. this method let it knew a quantitative approach of the antibacterial capacity of resins and flavonoids. a discussion of the effect of flavonoids class and type of substituents is developed
Pre- and post-infection activity of new fungicides against Botrytis cinérea and other fungi causing decay of table grapes
Serey,Ricardo A; Torres,Rene; Latorre,Bernardo A;
Ciencia e investigación agraria , 2007, DOI: 10.4067/S0718-16202007000300005
Abstract: pre- and post-harvest diseases restrict table grape production and exports (vitis vinifera l.) in chile, with the most important disease being grey mold (botrytis cinérea). in addition, rot due to aspergillus niger, cladosporium herbarum, penicillium expansum, and rhizopus stolonifer frequently occurs. the pre- and post-infection activity of fungicides against these pathogens was studied on thompson seedless table grapes. detached, mature, berries were used, and inoculations were performed with 20 μl of a 106 spores?ml-1 suspension placed on three punctures aseptically made at the calyx end of each berry. fungicides used (per liter) were boscalid (600 mg), boscalid (200 mg) + pyraclostrobin (100 mg), boscalid (200 mg) + kresoxim methyl (100 mg), cyprodinil (60 mg) + fludioxonil (40 mg), bas 600 kbf (100 mg) + metrafenone (150 mg), bas 600 kbf (200 mg) + boscalid (300 mg), bas 600 kbf (100 mg) + pyraclostrobin (100 mg), and captan (400 mg). each fungicide was applied either by drop (12 μl?-berry-1) placed on three punctures made with a sterile hypodermic needle or by 60 s immersion. berries were then incubated in humid chambers at 20°c the pre-infection (protection) activity of the fungicides varied considerably among the pathogens tested and was found to be significant (p < 0.001) and, with one exception (a. niger), it was significantly (p < 0.002) affected by the application method. the interaction between fungicide and application method was only significant (p < 0.001) for r. stolonifer at 48 h post treatment. in general, pre-infection activity gave 0 to 4 days protection after drop applications and 0 to 21 days after immersion treatments. the post-infection (curative) activity varied among pathogens and fungicide treatments. however, it was always below 24
Relative susceptibility of peach rootstocks to crown gall and Phytophthora root and crown rot in Chile
Guzman,Gonzalo; Latorre,Bernardo A; Torres,Rene; Wilcox,Wayne F;
Ciencia e investigación agraria , 2007, DOI: 10.4067/S0718-16202007000100004
Abstract: crown gall (agrobacterium tumefaciens) and phytophthora root and crown rot (prcr), caused by p. cryptogea, are two major limiting factors affecting peach (prunus pérsica) production in chile. at present, nemaguard is the most important rootstock used in peach orchards, and although several clonal rootstocks are under development worldwide, there is little information regarding their susceptibility to crown gall and prcr. therefore this investigation was undertaken to study the susceptibility to a. tumefaciens and p. cryptogea of the clonally propagated rootstocks cadman?-avimag (p. pérsica x p. davidiana), mr.s 2/5 (p. cerasifera x p. spinosa), viking ([p. pérsica x p. davidiana] x [p. dulcís 'jordanolo'x p. blireiana]), and nemaguard (p. pérsica x p. davidiana), a seedling rootstock, which was included as a reference standard. based on our results, mr.s 2/5 was highly resistant to a. tumefaciens. differences among nemaguard, viking and cadman grown for 20 months in artifically-infested soil were not statistically significant, but only cadman developed crown gall in soil with natural levels of inoculum. the extent of the canker lesions produced by p. cryptogea on excised twigs of each rootstock was greater on actively growing twigs than on dormant twigs. however, differences among rootstocks determined with the dormant twig assay correlated better with the results following trunk inoculations of 2-yr-old plants budded with 'ruby diamond' peach. for all rootstocks, prcr severity increased considerably after repeated soil saturation episodes, and the loss of root mass increased in a linear manner as the saturation periods increased from 0 to 144 h. our results showed that mr.s 2/5 is relatively resistant to root rot caused by p. cryptogea, which is the most common phytophthora species presently found on peach trees in chile
PROPIEDADES ANTIVIRALES DE COMPUESTOS NATURALES Y SEMI-SINTETICOS DE LA RESINA DE HELIOTROPIUM FILIFOLIUM
RENE TORRES,BRENDA MODAK,ALEJANDRO URZúA,FRANCO DELLE MONACHE
Boletín de la Sociedad Chilena de Química , 2002,
Abstract: Del producto mayoritario del exudado resinoso de Heliotropium filifolium ( Fam. Boraginacea), el inusual alcohol espiránico filifolinol 1, se sintetizó el compuesto, no previamente descrito, filifolinona 3. Estos dos, junto al también aislado previamente de H. filifolium , senecionato de filifolinol 2, fueron ensayados en sus antividades antivirales frente a cepas de cinco virus, productores de enfermedades en seres humanos. El filifolinol resultó ser el más activo frente al virus de la poliomelitis, pero con una estrecha relación entre la dosis antiviral y la citotóxica A new compound called filifolinone 3 was synthesized from the unusual spiranic alcohol filifolinol 1, the principal compound isolated from the resinous exudate of Heliotropium filifolium. (fam.Boraginaceae) Both compounds and the ester derivative of 1, filifolinyl senecionate 2 were tested as antiviral agents against five virus species of importance in human diseases. The most active compound resulted 1, specially against polio virus, but with a tight relationship between antiviral dosis/cytotoxic dosis
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