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José de San Martín, Argentina

Cacace V.I.,University of Buenos Aires | Cacace V.I.,CONICET | Montalbetti N.,University of Buenos Aires | Montalbetti N.,CONICET | And 5 more authors.
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

The corneal endothelium is a fluid-transporting epithelium. As other similar tissues, it displays an electrical potential of ∼1 mV (aqueous side negative) across the entire layer [transendothelial potential difference (TEPD)]. It appears that this electrical potential is mainly the result of the transport of anions across the cell layer (from stroma to aqueous). There is substantial evidence that the TEPD is related linearly to fluid transport; hence, under proper conditions, its measure could serve as a measure of fluid transport. Furthermore, the TEPD is not steady; instead, it displays a spectrum of frequency components (0-15 Hz) recognized recently using Fourier transforms. Such frequency components appear due to charge-separating (electrogenic) processes mediated by epithelial plasma membrane proteins (both ionic channels and ionic cotransporters). In particular, the endothelial TEPD oscillations of the highest amplitude (1-2 Hz) were linked to the operation of so-called sodium bicarbonate cotransporters. However, no time localization of that activity could be obtained with the Fourier methodology utilized. For that reason we now characterize the TEPD using wavelet analysis with the aim to localize in time the variations in TEPD. We find that the mentioned high-amplitude oscillatory components of the TEPD appear cyclically during the several hours that an endothelial preparation survives in vitro. They have a period of 4.6 ± 0.4 s on average (n=4). The wavelet power value at the peak of such oscillations is 1.5 ± 0.1 mV2 Hz on average (n = 4), and is remarkably narrow in its distribution. © 2011 American Physical Society. Source


Gutierrez Z.N.,Trujillo National University | Luppo M.I.,National Commission of Atomic Energy | Danon C.A.,National Commission of Atomic Energy | Toda-Caraballo I.,CSIC - National Center for Metallurgical Research | And 3 more authors.
Materials Science and Technology (United Kingdom) | Year: 2013

The coupled influence of the initial metallurgical state and the heating rate to austenite on the occurrence of heterogeneous grain growth during austenitisation of an ASTM A213-T91 steel has been studied. To that aim, two-step thermal cycles were designed. In the first step, different starting metallurgical conditions were obtained by treating the as received material at 780 C for increasing times up to 6 h. In the second step, in situ austenitisation was performed by heating to austenite at rates of 1, 30 and 50 C s-1 and then holding at 1050 C for 30'. Two types of austenite grain structures were obtained after austenitisation, namely, homogeneous and heterogeneous. The homogeneous structure was characterised by a smooth size distribution of approximately equiaxed, normally grown grains. The heterogeneous structure, instead, exhibited the exaggerated growth of a few austenite grains embedded in a small to medium sized matrix. For the 1 C s-1 heating rate and all of the initial metallurgical states, only homogeneous grain growth was observed, whereas for the 50 C s-1 heating rate only heterogeneous grain growth was observed regardless the starting metallurgical condition. Instead, the occurrence of homogeneous or heterogeneous grain growth after heating at 30 C s-1 was observed to be a function of the time of previous tempering. Some explanations of the phenomenon are advanced taking into account the precipitation state of second phases. © 2013 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute. Source


Espinosa M.S.,National Commission of Atomic Energy | Folguera L.,National Commission of Atomic Energy | Magallanes J.F.,National Commission of Atomic Energy | Magallanes J.F.,National University of General San Martin | And 2 more authors.
Chemometrics and Intelligent Laboratory Systems | Year: 2015

Analyte response in mass spectrometry with electrospray ionization was studied for a typical single quadrupole LC-MS instrument, as a function of eight instrumental variables and nine physicochemical properties for a variety of small molecules. Due to the high number of factors, three different experimental designs have been applied in order to balance the amount of gathered information and the number of experimental runs. The analyses were made by nonlinear modeling through artificial neural networks. One of the experimental designs (a Plackett-Burman design) involved 20 compounds of different chemical nature, with 12 runs per compound. It allowed finding general instrumental conditions capable of giving enough sensitivity for all the compounds; some relationships among instrumental parameters and physicochemical properties have also been identified. The other two experimental designs (a 73 runs Doehlert design, and a 19 runs fractional factorial design) were aimed at obtaining optimum instrumental sensitivity for one specific compound; they both allowed identifying the RF component of the Q-array and the desolvation line temperature as the most influential instrumental factors and let us detect several associations among instrumental variables. In order to select the most efficient optimization strategy, these two methods were compared. The fractional factorial design, which requires a much smaller number of runs, was found suitable to identify the optimum working zone, with a fair economy of experiments. © 2015 Elsevier B.V. Source


Espinosa M.S.,National Commission of Atomic Energy | Servant R.,National Commission of Atomic Energy | Babay P.A.,National Commission of Atomic Energy
Microchemical Journal | Year: 2016

Electrospray ionization-mass spectrometry (ESI-MS) has been used to investigate the speciation of La, Nd and Th in the presence of the complexing agent EDTA. Two methods of sample introduction were optimized and compared: direct infusion and flow injection, without chromatographic column. The species found were independent of the sample introduction method applied. The dependence of the species response with ESI parameters and focusing of ions was studied, and a significant change in relative intensities was observed while no differences in the species found were detected. The predominant species were always the same. System behavior was evaluated by varying the pH and the metal/ligand ratio. The results are consistent with literature data. Although the linear range is rather small (10-4-10-5 M), this technique could be useful to identify the species in equilibrium in different chemical environments. System behavior for mixtures of metals and for a mineral water sample was studied. The characterization of formed complexes will contribute to understand their environmental mobility. © 2016 Elsevier B.V. Source

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