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Comodoro Rivadavia, Argentina

Vitorino G.P.,National University of la Patagonia | Sperandeo N.R.,National University of Cordoba | Caira M.R.,University of Cape Town | Mazzieri M.R.,National University of Cordoba | Mazzieri M.R.,University of Cape Town
Crystal Growth and Design | Year: 2013

The interaction in the solid state between ciprofloxacin (CIP) and norfloxacin (NOR) was investigated and a new multicomponent molecular complex (COP) was obtained and characterized. It is composed of equimolar quantities of both compounds, according to TLC and 1H NMR data. As single-crystal X-ray analysis showed, COP crystallizes in the triclinic system, space group P(1̄). The asymmetric unit comprises three independent zwitterions (A, B, and C) with contributions of both CIP and NOR, as well as 14.6 water molecules. At the zwitterion A site, the occurrence is about 37% (CIP), 63% (NOR); at the B site, there is predominantly CIP (70%); and at the C site the occurrence is about 43% (CIP) and 57% (NOR), yielding an overall 1:1 CIP-NOR ratio in the crystal. TG data evidenced a one-step loss of solvent (about 18% per COP zwitterion) below 110 °C, confirming the presence of water molecules. The propensity for heteroassociation between CIP and NOR, under the conditions described herein, originated a co-crystal reported for the first time between FQs, and became one of the most interesting aspects of this research. © 2013 American Chemical Society. Source

This study was intended to evaluate the quality chemical parameters of 62 Apis mellifera L. honey samples, from the Province of Chubut, Argentina. Samples were obtained from the three melliferous areas of this province: Andean region, lower Chubut River valley and plains of Senguerr River. The average values obtained for electrical conductivity (0.33 mS cm-1) and pH (4.17) indicate that the analyzed honeys came mainly from nectar. Electrical conductivity was higher in honeys from the Andean region than in honeys from the other two regions. Moisture (water content) was low, with an average value of 14.67%. The hydroxymethylfurfural (HMF) content was very low and ranged between 0.0 and 14.70 mg kg-1. Moisture, HMF and free acidity values show good maturity and absence of undesirable fermentation in all the samples. Diastase activity had a mean value of 13.50 units on the Gothe scale. Color parameter presented variations between honeys from different areas. The analytical values for the samples from the Andean region, the lower Chubut River valley and the plains of the Senguerr River respectively were: 67.73, 40.33 and 23.26 mm Pfund. Results obtained in this study, indicate that honeys produced in Chubut present excellent quality properties according to international standards. Source

Hechem V.,National University of la Patagonia | Calvino C.I.,CONICET | Ezcurra C.,CONICET
Taxon | Year: 2011

Diplolepis, a genus from southern South America traditionally considered monotypic, has recently been shown from molecular data to include a few species that form a monophyletic group at the base of the MOG clade of Asclepiadoideae (Apocynaceae). The species transferred to Diplolepis include plants from temperate South America mostly described under the generic name "Cynanchum". Phylogenetic analyses of cpDNA trnT-trnF and rps16 sequences of 51 accessions of Asclepiadaceae using maximum parsimony and Bayesian inference methods show that all "Cynanchum" from southern Argentina and Chile (except C. atacamense), Tweedia australis and Diplolepis form a well-supported monophyletic group. Within this group, three clades are recognized: two morphologically homogeneous groups from South Andean forests and high elevation areas, and a more diverse group in flower and leaf morphology from southern South American desert and semidesert areas. The phylogenetic position of C. atacamense is equivocal but the species is transferred to Diplolepis based on morphological and biogeographical coherence. The morphological, geographical and environmental characteristics of the three recognized clades of Diplolepis are discussed and eight nomenclatural changes are proposed. Source

Moreno L.,CONICET | Bertiller M.B.,CONICET | Bertiller M.B.,National University of la Patagonia
Acta Oecologica | Year: 2012

We asked whether morphological and chemical traits of perennial grasses in semiarid-arid ecosystems are influenced by the abundance of coexisting shrubs, in northern-central Patagonia, Chubut Province, Argentina. We selected populations of two perennial grass species, highly preferred by herbivores (4 for Festuca pallescens and 8 for Poa ligularis) at 10 sites distributed across a wide range of aridity. We assessed the relative shrub cover (shrub cover as percent of total cover) of each site and randomly collected 5 to 10 bunches of each grass species per site in December 2007 (late vegetative-early reproductive growth period). We measured the height of vegetative tillers, and morphological (length, width, area, dry mass, and specific area) and chemical (N, C, soluble phenolics and lignin concentration) attributes of full expanded green blades in the collected bunches. Further, we computed the aridity index of each site using temperature and precipitation data. The aridity index ranged from 1.07 to 3.9 at F. pallescens sites and from 3.6 to 7.3 at P. ligularis sites. The relative shrub cover increased significantly with aridity varying from 0.01 to 99%. Tiller height, blade length, and blade area of P. ligularis increased significantly with increasing relative shrub cover and aridity. Concentration of soluble phenolics in blades of both species decreased with increasing relative shrub cover and aridity. N concentration in blades of P. ligularis and specific blade area in F. pallescens decreased with increasing relative shrub cover and aridity. We conclude that some traits of perennial grasses (phenolics concentration in green blades in both species, and tiller height and some blade attributes in P. ligularis) were influenced by shrub cover itself. The variation in these traits was opposite to that expected by the effect of aridity and could be associated with escape from herbivores and/or drought, enhanced mesophytism, and reduced chemical defenses. © 2012 Elsevier Masson SAS. Source

Valenciaga F.,National University of La Plata | Fernandez R.D.,National University of la Patagonia
IET Renewable Power Generation | Year: 2015

This study presents a control design for a grid connected wind energy conversion system based on a gearless PMSG. The generation system structure comprises a three blade turbine, a 2 MW multi-pole PMSG and a full-scale backto-back frequency converter linked to the utility grid. The proposed control scheme allows following dynamical specifications taking into account operational requirements and ancillary services imposed by the recent grid connection codes, that is, reactive power regulation and fault ride-through (FRT) capabilities. The control actions to be applied during normal grid operation are designed through second-order sliding mode techniques using a two-stage cascade structure. The multi-variable controller designed attains to regulate the active and reactive powers delivered to the grid, minimising the resistive losses into the generator and maintaining important internal variables into the desired range. This controller presents attractive advantages such as robustness against unmodelled dynamics and external perturbations, finite time convergence to the sliding surfaces and chattering mitigation. To endorse the controlled system with FRT capabilities, a switching control scheme based on voltage grid measurements is also proposed. The performance of the whole control approach is analysed through representative simulations which include parameter variations, external perturbations and three-phase voltage dips. © The Institution of Engineering and Technology 2015. Source

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