National University of Santa
Chimbote, Peru

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Giovanini L.,National University of Santa
IET Control Theory and Applications | Year: 2011

This study introduces a framework for distributed model predictive control (MPC) based on dynamic games, where centralised and decentralised control algorithms can be viewed as dynamical games with coupled control sets. The original optimisation problem is decomposed into smaller coupled optimisation problems in a distributed structure, which is solved iteratively. Then, the resulting dynamic game is analysed using the theory of potential games to derive the properties of the resulting algorithms. This sheds new light on the properties of existing MPC algorithms and allows us to establish a unified framework to analyse them. The control problem of a heat-exchanger network (HEN) is used to illustrate the effectiveness, practicality and limitations of the proposed framework. © 2011 The Institution of Engineering and Technology.

Fabbro D.,National University of Santa
Revista do Instituto de Medicina Tropical de São Paulo | Year: 2013

This work compared the time at which negative seroconversion was detected by conventional serology (CS) and by the ELISA-F29 test on a cohort of chronic chagasic patients treated with nifurtimox or benznidazole. A retrospective study was performed using preserved serum from 66 asymptomatic chagasic adults under clinical supervision, and bi-annual serological examinations over a mean follow-up of 23 years. Twenty nine patients received trypanocide treatment and 37 remained untreated. The ELISA-F29 test used a recombinant antigen which was obtained by expressing the Trypanosoma cruzi flagellar calcium-binding protein gene in Escherichia coli. Among the untreated patients, 36 maintained CS titers. One patient showed a doubtful serology in some check-ups. ELISA-F29 showed constant reactivity in 35 out of 37 patients and was negative for the patient with fluctuating CS. The treated patients were divided into three groups according to the CS titers: in 13 they became negative; in 12 they decreased and in four they remained unchanged. ELISA-F29 was negative for the first two groups. The time at which negativization was detected was significantly lower for the ELISA-F29 test than for CS, 14.5 ± 5.7 and 22 ± 4.9 years respectively. Negative seroconversion was observed in treated patients only. The results obtained confirm that the ELISA-F29 test is useful as an early indicator of negative seroconversion in treated chronic patients.

Zeballos L.J.,National University of Santa
Robotics and Computer-Integrated Manufacturing | Year: 2010

This paper presents a constraint programming (CP) methodology to deal with the scheduling of flexible manufacturing systems (FMSs). The proposed approach, which consists of both a model and a search strategy, handles several features found in industrial environments, such as limitations on number of tools in the system, lifetime of tools, as well as tool magazine capacity of machines. In addition, it tackles the problem in a integrated way by considering tool planning and allocation, machine assignment, part routing, and task timing decisions altogether in the approach. The formulation, which is able to take into account a variety of objective functions, has been successfully applied to the solution of test problems of various sizes and degrees of difficulty. © 2010 Elsevier Ltd.

Luque G.C.,National University of Santa | Fernandez J.L.,National University of Santa
Journal of Power Sources | Year: 2012

This work reports an electrode material containing molybdenum phosphate that shows a very interesting behavior as an electrocatalyst for the reduction of oxygen to water (ORR) in acid medium. The material is electrodeposited on a glassy carbon electrode from a solution of Mo(VI) and Co(II) in phosphate buffer at pH = 7. Cobalt is required to obtain a compact and uniform film. It is a non-crystalline solid conformed by metal oxide and phosphate groups that, according to XPS analysis, contains mostly Mo(VI) and a small fraction of Mo(V). Even though most of the Co-containing phase dissolves in acid, the film keeps its integrity and shows stable ORR activity in acid at very low overpotentials (from -0.3 V). The observed current density reaches a very small limiting value (∼2 μA cm -2) that is independent of the mass-transport conditions and could be associated to the small fraction of Mo(V) centers that function as ORR active sites. Although the film is thermally stable up to temperatures of 400 °C, by heating the material at temperatures above 100 °C it looses its unusual ORR activity due to the complete oxidation of Mo(V) to Mo(VI). © 2011 Elsevier B.V. All rights reserved.

Viola I.L.,National University of Santa | Guttlein L.N.,National University of Santa | Gonzalez D.H.,National University of Santa
Plant Physiology | Year: 2013

TEOSINTE BRANCHED1-CYCLOIDEA-PROLIFERATING CELL FACTOR1 (TCP) transcription factors participate in plant developmental processes associated with cell proliferation and growth. Most members of class I, one of the two classes that compose the family, have a conserved cysteine at position 20 (Cys-20) of the TCP DNA-binding and dimerization domain. We show that Arabidopsis (Arabidopsis thaliana) class I proteins with Cys-20 are sensitive to redox conditions, since their DNAbinding activity is inhibited after incubation with the oxidants diamide, oxidized glutathione, or hydrogen peroxide or with nitric oxide-producing agents. Inhibition can be reversed by treatment with the reductants dithiothreitol or reduced glutathione or by incubation with the thioredoxin/thioredoxin reductase system. Mutation of Cys-20 in the class I protein TCP15 abolished its redox sensitivity. Under oxidizing conditions, covalently linked dimers were formed, suggesting that inactivation is associated with the formation of intermolecular disulfide bonds. Inhibition of class I TCP protein activity was also observed in vivo, in yeast (Saccharomyces cerevisiae) cells expressing TCP proteins and in plants after treatment with redox agents. This inhibition was correlated with modifications in the expression of the downstream CUC1 gene in plants. Modeling studies indicated that Cys-20 is located at the dimer interface near the DNA-binding surface. This places this residue in the correct orientation for intermolecular disulfide bond formation and explains the sensitivity of DNA binding to the oxidation of Cys-20. The redox properties of Cys-20 and the observed effects of cellular redox agents both in vitro and in vivo suggest that class I TCP protein action is under redox control in plants. © 2013 American Society of Plant Biologists. All Rights Reserved.

Fernandez J.L.,National University of Santa
Journal of Electroanalytical Chemistry | Year: 2010

This work develops the equations that relate the kinetic parameters of the hydrogen electrode reaction (HER) with the current density (j) vs. potential (E) dependences of a thin-layer cell (TLC). Two operation modes of the TLC are analyzed. The first one proposes to examine the j(E) dependence of the hydrogen evolution reaction (her) on one electrode while the paired electrode oxidized the dissolved H 2 back to H + under diffusion control. The second mode proposes to analyze the j(E) dependence of the hydrogen oxidation reaction (hor) on one electrode while the other generates dissolved H 2 from H + under diffusion control. In both cases, as very high mass-transport rates are reached for distances in the micrometer range, the j(E) curves are sensitive to the complete set of kinetic parameters even for very large reaction rates. Possible ways to incorporate these equations in the theoretical formalisms of well-established TLC-based techniques such as scanning electrochemical microscopy are discussed. © 2010 Published by Elsevier B.V.

Cabello J.V.,National University of Santa | Arce A.L.,National University of Santa | Chan R.L.,National University of Santa
Plant Journal | Year: 2012

Plants deal with cold temperatures via different signal transduction pathways. The HD-Zip I homologous transcription factors HaHB1 from sunflower and AtHB13 from Arabidopsis were identified as playing a key role in such cold response. The expression patterns of both genes were analyzed indicating an up-regulation by low temperatures. When these genes were constitutively expressed in Arabidopsis, the transgenic plants showed similar phenotypes including cell membrane stabilization under freezing treatments and cold tolerance. An exploratory transcriptomic analysis of HaHB1 transgenic plants indicated that several transcripts encoding glucanases and chitinases were induced. Moreover, under freezing conditions some proteins accumulated in HaHB1 plants apoplasts and these extracts exerted antifreeze activity in vitro. Three genes encoding two glucanases and a chitinase were overexpressed in Arabidopsis and these plants were able to tolerate freezing temperatures. All the obtained transgenic plants exhibited cell membrane stabilization after a short freezing treatment. Finally, HaHB1 and AtHB13 were used to transiently transform sunflower and soybean leading to the up-regulation of HaHB1/AtHB13-target homologues thus indicating the conservation of cold response pathways. We propose that HaHB1 and AtHB13 are involved in plant cold tolerance via the induction of proteins able to stabilize cell membranes and inhibit ice growth. © 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd.

Giovanini L.,National University of Santa
IET Control Theory and Applications | Year: 2011

The supervisory control problem is analysed as an online robust design problem using switching to select the relevant models for designing the control law. The proposed supervisory control algorithm is based on the integration of concepts used in supervisory adaptive control, robust control and receding horizon control. It involves a two-stage adaptive control algorithm: (i) the identification of a time-varying set of models PL(k), from the set of admissible models PL, that explains the input-output behaviour of the system, followed by (ii) the design of the control law using a parametric linear optimisation problem. The authors show that under the proposed supervisory control algorithm, the system output remains bounded for any bounded disturbance. The use of superstability concepts, together with certain assumptions on PL, allows us to establish overall performance and robust stability guarantees for the supervisory scheme and to include constrains in the closed-loop variables as well as in the controller structure. The relevant features of the proposed control algorithm are demonstrated in a numerical simulation. © 2011 The Institution of Engineering and Technology.

Beldomenico P.M.,National University of Santa | Begon M.,University of Liverpool
Trends in Ecology and Evolution | Year: 2010

Epidemiological models and studies of disease ecology typically ignore the role of host condition and immunocompetence when trying to explain the distribution and dynamics of infections and their impact on host dynamics. Recent research, however, indicates that host susceptibility should be considered carefully if we are to understand the mechanism by which parasite dynamics influence host dynamics and vice versa. Studies in insects, fish, amphibians and rodents show that infection occurrence and intensity are more probable and more severe in individuals with an underlying poor condition. Moreover, infection itself results in further deterioration of the host and a 'vicious circle' is created. We argue that this potential synergy between host susceptibility and infection should be more widely acknowledged in disease ecology research. © 2009 Elsevier Ltd.

Colli A.N.,National University of Santa | Bisang J.M.,National University of Santa
Electrochimica Acta | Year: 2011

The hydrodynamic behaviour of electrochemical reactors with parallel plate electrodes is experimentally studied using the stimulus-response method either with an empty reactor or with different turbulence promoters. Theoretical results which are in accordance with the analytical and numerical resolution of the dispersion model for a closed system are compared with the classical relationships of the normalized outlet concentration for open systems and the validity range of the equations is discussed. The experimental results were well correlated with the dispersion model using glass beads or expanded plastic meshes as turbulence promoters, which have shown the most advantageous performance. The Peclet number was higher than 63. The dispersion coefficient was found to increase linearly with flow velocity in these cases. © 2011 Elsevier Ltd. All rights reserved.

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