bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of modified open lung concept ventilation on the cardiovascular and pulmonary function of horses during total intravenous anaesthesia
Authors: Bringewatt T. , Hopster K. , Kästner S. B. R. , Rohn K. , Ohnesorge B.
Published: December 2010

The influence of a modified open lung concept (mOLC) on pulmonary and cardiovascular function during total intravenous anaesthesia (TIVA) in horses was evaluated. Forty‐two warmblood horses (American Society of Anesthesiologists class 1 to 2), scheduled for elective surgery (mean [sd] weight 526 [65] kg, age 6.4 [5.4] years) were randomly divided into three groups: ventilation with mOLC, intermittent positive‐pressure ventilation (IPPV), and spontaneous breathing. Premedication (0.8 mg/kg xylazine), induction (2.2 mg/kg ketamine and 0.05 mg/kg diazepam) and maintenance of anaesthesia with TIVA (1.4 mg/kg/hour xylazine, 5.6 mg/kg/hour ketamine and 131.1 mg/kg/hour guaifenesin), with inhalation of 35 per cent oxygen in air, were identical in all horses. Heart rate, respiratory rate, mean arterial blood pressure (MAP), pH, and arterial partial pressure of oxygen (paO2) and carbon dioxide (paCO2) were evaluated. Data were collected every 10 minutes from 20 to 90 minutes anaesthesia time. Factorial analysis of variance and Tukey's post hoc test were used for statistical analysis (a=5 per cent). Horses in the mOLC‐ventilated group had an overall significantly higher paO2(16.9 [1.0] v 11.7 [1.34] v 10.5 [0.57] kPa) and lower MAP (93.1 [5.47] v 107.1 [6.99] v 101.2 [5.45] mmHg) than the IPPV and spontaneously breathing groups, respectively.
Selection on size and secondary sexual characters of the damselfly Calopteryx splendens when sympatric with the congener Calopteryx virgo
Authors: Kuitunen Katja , Kotiaho Janne S. , Luojumäki Mari , Suhonen Jukka
Published: December 2010

Male mating success is often determined by body size or secondary sexual characters because of female mate choice or competition for females. In addition to intraspecific interactions, interspecific interactions may interfere with intraspecific selection. In this study, we investigated sexual selection on size and sexual characters of male banded demoiselle ( Calopteryx splendens (Harris, 1780)) in wild populations sympatric with the beautiful demoiselle ( Calopteryx virgo (L., 1758)). As secondary sexual characters, male C. splendens have pigmented wing spots whose size appears to be under positive selection. Male C. virgo resemble male C. splendens that have the largest wing spots, leading to interspecific male–male aggression and possibly also to heterospecific matings via mistaken species recognition. If interspecific interactions interfere with intraspecific sexual selection on wing-spot size of C. splendens, their effects should increase with the increasing relative abundance of C. virgo. Our results did not show the expected positive selection on wing-spot size in C. splendens, suggesting that interspecific interactions might interfere with sexual selection. Also, we observed no relationship between the strength of interspecific sexual selection and the relative abundance of C. virgo. However, there was a positive intraspecific density-dependent sexual selection for larger size. Although the present results are tentative, we suggest that interspecific interactions should be considered along with intraspecific selection when studies of sexual selection are performed in the wild.
Reproductive phase dependent variation in lung-associated immune system (LAIS) and expression of melatonin receptors (Mel1a and Mel1b) in the lung of the Jungle-Bush Quail (Perdicula asiatica)
Authors: Kharwar R. K. , Haldar C.
Published: December 2010

The present study was performed to assess the variation of the lung-associated immune system (LAIS) in the Jungle-Bush Quail ( Perdicula asiatica (Latham, 1790)) during two different reproductive phases when differences in the circulatory level of hormones (melatonin and gonadal steroid) and environmental conditions were maximum. We noted high significant variation in size and number of bronchus-associated lymphoid tissue (BALT) nodules, as well as in the size and number of non-BALT nodules, during the reproductively inactive phase (RIP; December) compared with the active phase (RAP; June). We also noted high significant variation in the percent stimulation ratio of lung lymphocyte, as well as in the concentrations of plasma melatonin and melatonin receptors, during RIP compared with RAP. Testosterone level and number of macrophages in lungs were high during RAP. Thus, we suggest that the LAIS had reproductive phase dependent variation, which could be due to (i) variation in environmental factors (photoperiod, temperature, and humidity) and (ii) circulatory level of hormones (melatonin and testosterone). Because of the importance of melatonin in avian immune regulation, we assess and document the expression of melatonin receptor types Mel1a and Mel1b in the avian lung, which suggest that the lung is a target organ for melatonin and that melatonin is an immunomodulator for lung-associated immunity in birds.
The role of Spadefoot Toad tadpoles in wetland trophic structure as influenced by environmental and morphological factors
Authors: Ghioca-Robrecht D. M. , Smith L. M.
Published: December 2010

Larval amphibians reach high densities in playa wetlands in the Southern Great Plains (SGP), USA, and thus may influence the entire structure and function of these ecosystems. We investigated whether both carnivorous and omnivorous morphotypes of Spadefoot Toad tadpoles (New Mexico Spadefoot, Spea multiplicata (Cope, 1863), and Plains Spadefoot, Spea bombifrons (Cope, 1863)) would exhibit a macrophagous feeding behavior that would allow them to occupy several trophic levels in playas. We also compared tadpole diets and foregut widths as influenced by the land use surrounding playas (cultivated versus grassland watersheds), year (dry versus wet year), and body size (snout-to-vent length). Tadpole diets were dominated by detritus and diatoms and tadpole foreguts increased with body size. Generally, more arthropods and less cyanobacteria were found in Spea tadpole diets as tadpoles grew larger, suggesting they influence different trophic levels with age. Foreguts were wider in carnivores than omnivores, suggesting carnivores had increased ability to ingest larger prey. Also, omnivores had wider foreguts in cropland than grassland playas, suggesting they ingest larger food items in cropland playas. From estimates of the amounts of invertebrates, detritus, and algae consumed by Spea tadpoles, we demonstrate that these larvae influence the entire trophic structure of wetland ecosystems.
Thermal ecology of Massasauga Rattlesnakes (Sistrurus catenatus) near their northern range limit
Authors: Harvey Daniel S. , Weatherhead Patrick J.
Published: December 2010

Using populations at their northern range limits, we compared the thermoregulatory behaviour of Massasauga Rattlesnakes ( Sistrurus catenatus (Rafinesque, 1818)) to published results for Ratsnakes ( Elaphe obsoleta (Say in James, 1823)) and Northern Watersnakes ( Nerodia sipedon (L., 1758)) to test the hypothesis that given similar benefits of thermoregulation, costs associated with foraging ecology should shape thermoregulatory behaviour. More than 32 000 body temperature measurements from 34 individual snakes over 4 years were used to quantify thermoregulation by Massasauga Rattlesnakes using standard indices and a new index (%MaxE) that describes how much of the thermoregulatory potential available to a snake is realized. On average, Massasaugas were much cooler (db = 6.9 °C) than their preferred body temperature range (30–33.6 °C) but warmer (de – db = 3.3 °C) than were they not thermoregulating. Massasaugas realized more than half of their environmental potential for effective thermoregulation (%MaxE = 64%). Consistent with there being less conflict between foraging and thermoregulation for ambush predators than active foragers, Massasaugas were more effective thermoregulators than Ratsnakes or Watersnakes during the day. All three species were effective thermoregulators at night, supporting the assumption that species in a cool environment will thermoregulate when there are few competing interests.
THE EFFECT OF A HISTORY-FITNESS-BASED UPDATING RULE ON EVOLUTIONARY GAMES
Authors: DU WEN-BO , CAO XIAN-BIN , LIU RUN-RAN , JIA CHUN-XIAO
Published: December 2010

In this paper, we introduce a history-fitness-based updating rule into the evolutionary prisoner's dilemma game (PDG) on square lattices, and study how it works on the evolution of cooperation level. Under this updating rule, the player i will firstly select player j from its direct neighbors at random and then compare their fitness which is determined by the current payoff and history fitness. If player i's fitness is larger than that of j, player i will be more likely to keep its own strategy. Numerical results show that the cooperation level is remarkably promoted by the history-fitness-based updating rule. Moreover, there exists a moderate mixing proportion of current payoff and history fitness that can induce the optimal fitness, where the highest cooperation level is obtained. Our work may shed some new light on the ubiquitous cooperative behaviors in nature and society induced by the history factor.
STRUCTURES, ELECTRONIC AND MAGNETIC PROPERTIES OF C20 FULLERENES DOPED TRANSITION METAL ATOMS M@C20 (M = Fe, Co, Ti, V)
Authors: SAMAH M. , BOUGHIDEN B.
Published: December 2010

Structures, binding energies, magnetic and electronic properties endohedrally doped C 20 fullerenes by metallic atoms ( Fe , Co , Ti and V ) have been obtained by pseudopotential density functional theory. All M @ C 20, except Co @ C 20, are more stable than the undoped C 20 cage. The magnetic moment values are 1 and 2μB. These values and semiconductor behavior give to these compounds interesting feature in several technological applications. Titanium doped C 20 has a same magnetic moment than the isolated Ti atom. Hybridization process in the Co doped C 20 fullerene is most strong than in other doped cages. Electrical and magnetic dipoles calculated in the iron doped C 20 are very strong compared with other clusters.
THE EFFECT OF VISCOSITY ON THE PHASE SEPARATION DYNAMICS OF BINARY IMMISCIBLE MIXTURE COUPLED WITH REVERSIBLE REACTION
Authors: LI HUI , LIU HONG , LU ZHONG-YUAN , WANG QIN , SUN CHIA-CHUNG
Published: December 2010

The phase-separating system coupled with a simple reversible reaction A ⇌ B in a binary immiscible mixture due to critical quench is investigated with Lowe-Andersen temperature controlling method in two dimensions. The system viscosity strongly influences the asymptotic relationship between the excess energy (characterizing the domain growth) and the reaction rate. The competition between different dynamic factors results in the steady states with characteristic domain sizes. For low viscosities, the domain growth exponent approximates to 0.4 in the cases of low reaction rates and to 0.25 in the cases of high reaction rates, which shows the suppressing effects of high reversible reaction rates on the phase separation. However, in the cases of high viscosities, we find a 0.25 scaling with low reaction rates but a 0.5 scaling with high reaction rates. In these cases, high viscosities prevent mass transport in the binary mixture, consequently result in much smaller steady state domain sizes. Therefore the domain sizes with high viscosities and low reaction rates are very similar to those with low viscosities and high reaction rates, and the dependence of domain sizes on the reaction rates are similar. For the high-viscosity systems with high reaction rates, the domain sizes are predominantly controlled by the reaction rates, therefore we can observe stronger dependence of domain size on the reaction rate.
A MODEL FOR BRAND COMPETITION WITHIN A SOCIAL NETWORK
Authors: HUERTA-QUINTANILLA R. , CANTO-LUGO E. , RODRÍGUEZ-ACHACH M.
Published: December 2010

An agent-based model was built representing an economic environment in which m brands are competing for a product market. These agents represent companies that interact within a social network in which a certain agent persuades others to update or shift their brands; the brands of the products they are using. Decision rules were established that caused each agent to react according to the economic benefits it would receive; they updated/shifted only if it was beneficial. Each agent can have only one of the m possible brands, and she can interact with its two nearest neighbors and another set of agents which are chosen according to a particular set of rules in the network topology. An absorbing state was always reached in which a single brand monopolized the network (known as condensation). The condensation time varied as a function of model parameters is studied including an analysis of brand competition using different networks.
SIMILARITY IN TRANSITIONS OF TWO DISTINCT NUMBER NETWORKS
Authors: CHANDRA ANJAN KUMAR , INOUE JUN-ICHI
Published: December 2010

The main objective of our study is to disclose if any network structure is hidden among the pairs of numbers obtained by splitting the consecutive integers. By adopting some preferred rule in placing the links among the pairs obtained, we have a transition from a regular to a random one through a small world one. This type of transition is also similar to the network of primes obtained by splitting the consecutive integers which indicates some general feature in both kinds of networks. We also obtained both with some numerical and analytical explanations that support the transition and also the point of transition.
Localized Impedance Measurements in Different Redox Potential Metals and their Galvanic Coupling by using AC-SECM
Authors: Estrada-Vargas Arturo , Casillas Norberto , Hernández-Gaitán Georgina , Bárcena-Soto Maximimiliano , Gómez-Salazar Sergio
Published: December 2010

In recent years, the use of Scanning Electrochemical Microscopy in its Alternating Current mode (AC-SECM) has increased due to its capability for detecting and interpreting local variations of electrochemical properties in surfaces with high spatial resolution. In this paper, we intend to extend the applications of AC-SECM for identifying local impedance variations in surfaces of materials with different redox potential, immersed in resistive media such as tequila in presence of supporting electrolyte. Preliminary results are promising since it is possible to visualize boundaries of materials with different redox potential by means of localized impedance measurements, which opens a new perspective for studying composite materials such as minerals.
Electrochemical Method to Evaluate Rapid Degradation of Multi-Layer Coatings on High Strength Galvanized
Authors: Ramirez-Reyes José Luis , Uruchurtu Chavarín Jorge , Malo-Tamayo José M. , Juárez-Rivera Victorino , Quintero-Portillo Cristian Alberto
Published: December 2010

Throughout history attempts have been made to protect galvanized steel using resin-based paints. Actually polyurethane compounds and polysiloxanes have been applied quite successfully to solve the problem of incompatibility with systems of galvanized coating systems generating highly resistive barriers to the passage of aggressive agents to and from the metal-polymer interface. The polymeric systems studied here provide excellent corrosion protection under conditions of extreme aggressiveness, such as NaCl and damage condition. Electrochemical techniques for the quality evaluation of coating performance were used, in particular the rapid electrochemical test applied on paints (REAP). The REAP test is an effective method to assess industrial coating systems usually having excellent corrosion resistance in NaCl solutions and good compatibility with galvanized steel. Also it is proposed the determination of a degradation index throughout the linear polarization resistance method LPR produced by the REAP test on multi-layer coatings.
Novel SVET Approach and its Application for Rapid Pitting Corrosion Studies of Chromatized Aerospatiale Aluminum Alloy
Authors: Ramos Rogelio , Zlatev Roumen , Stoytcheva Margarita , Valdez Benjamin , Kiyota Sayuri
Published: December 2010

The controversial statements reported till now about the local conductivity of the solution at its interface with the corroded specimen affecting the SVET results were verified by the simultaneous application of a combination of two measuring techniques: SVET and conductometry. Bare and chromated AA 6061-T6 aerospatial aluminum alloy samples in 5% NaCl solutions were employed in the experiments. It was confirmed that the local conductivity variations are negligible above the chromated specimens obviously because of the pit sealing while about 4% changes were observed 5 minutes after the immersion of the bare samples. An approach for fast automatic detection of pit sites on the entire specimen surface, based on high resolution digital optical scanning coupled with image recognition software was developed and applied in the SVET/Conductivity experiments.
Pitting Corrosion Characterization by SVET Applying a Synchronized Noise Suppression Technique
Authors: Ramos Rogelio , Zlatev Roumen , Stoytcheva Margarita , Valdez Benjamin , Flores Salvador F. , Herrera Abelardo M.
Published: December 2010

A noise suppression approach was developed and applied for pitting corrosion studies of chromatized 6061-T6 airspace aluminum alloy by Scanning Vibrating Electrode Technique (SVET). The proposed approach is based on the power line frequency application as a SVET probe driving frequency combined with a synchronized double integration of the SVET probe signal yielding a free of noise signal product. Noise suppression up to -58 dB was achieved allowing precise measurement of the ionic current above the corroded metal surface proving the opportunity to replace the high cost lock-in amplifier.
Electrochemical Behavior of Ni-Co-Ag- Alloy Applied as Biomaterial
Authors: Bahena Daniel , Uruchurtu Chavarín Jorge , Rosales Isai , Ruiz Juan Antonio
Published: December 2010

In this work the synthesis of a Ni60-Co35-Ag5 wt% alloy was performed and evaluation of corrosion behavior of the ternary alloy in Hank solution was obtained. The ternary alloys were synthesized by induction heating under vacuum atmosphere. Heat treatments were performed at 500 {degree sign}C and 800 {degree sign}C for 1 hour. The electrochemical corrosion properties were evaluated by open circuit potential technique, polarization curves and electrochemical impedance (EIS) for 30 days. After 10 days, results show that for the three alloys tested, the free potential stabilized. All alloys present corrosion products in agreement with polarization curves, for alloys with a 500 {degree sign}C HT it is observed the lowest corrosion rate. An impedance measurement corroborates the other electrochemical results. The 500 {degree sign}C heat treated alloy shows the best corrosion behavior under the test condition.
Electrochemical Behavior Alloy Ni-Al-Cu, in Hanks Solution Simulating the Human Body
Authors: Castañeda Robles Iván E. , Martínez Villafañe Alberto , Neri Fores Miguel , Gonzalez-Rodriguez Gonzalo , Uruchurtu Chavarín Jorge
Published: December 2010

This paper presents an investigation about the corrosion resistence of intermetallic alloys Ni-Cu-Al, in Hank's solution which has been carried out using electrochemical techniques. The alloys tested were 50 (wt%) Ni- (25 and 30) Al-(25 and 20) Cu using Hank's solution, due to its high corrosion resistance provided by the formation of an external protective layer (Al2O3 and NiO oxides). For comparison, AISI 316L type stainless steel has also been used. Electrochemical techniques included linear polarization resistance (LPR), potentiodynamic polarization curves, and electrochemical impedance spectroscopy measurements. The different techniques have shown that these alloys show similar or higher corrosion resistance than conventional AISI 316L stainless steel. The corrosion resistance decreases when the Al content increases in the alloys. These alloys are susceptible to pitting corrosion attack in the rich in Ni interdendritic phases.
Electrochemical Impedance Spectroscopy (EIS) Applied to Study to Aluminum Alloys Degradation in Saline Solution
Authors: Orozco-Cruz Ricardo , Galvan-Martinez Ricardo , Martínez Enrique A. , Fernandez-Gómez Imelda
Published: December 2010

The electrochemical impedance spectroscopy (EIS) has been used to evaluate the behavior of alloys immersed in marine environment. This work presents the versatility of EIS technique to identify the formation of corrosion products and the different electrode processes than can be carried out on the interface metal-electrolyte when the aluminium alloys are in contact with a saline media (NaCl 0.5 M). After the time exposition, the samples were analyzed by X-Ray Diffraction (XRD), Scanning Electronic Microscopy (SEM) and EIS simulation with equivalent circuits (EEC) to propose a corrosion mechanism, and the results of these observations was the possible formation of an oxide film and a diffusion process across this film. The equivalent circuit selected from the simulation of experimental results takes in consideration a process with activation and mass transport control.
Aspects that Modify the Dissolution of Aluminum Electrodes in an Effluent from the Tissue Paper Industry
Authors: Vázquez Armando I. , Gerónimo Carlos , González Ignacio , Cruz Roel , Lázaro María I. , Rodríguez Israel
Published: December 2010

The electrocoagulation technology has emerged as a suitable option for the treatment of different types of wastewater. However, one of the aspects that have limited its application is the passivation phenomena involved in aluminum dissolution. Hence, this paper analyzes the oxidation behavior of aluminum in an effluent from tissue paper industry, and synthetic solution. The effluent contains high concentrations of organic matter, chloride and sulfate ions. Through micro-electrolysis experiments, the energy necessary for oxidation of aluminum electrodes, and the zone of potential for the electrodes passivation were studied. Experiments using industrial solution showed no passivation of the aluminum electrodes and also that the anodic current involved is much higher than the observed in experiments where synthetic solutions were used.
Electrochemical and Microscopy Study of Localized Corrosion on a Sensitized Stainless Steel AISI 304
Authors: Garfias-Garcia Elizabeth , Colin-Paniagua F. A. , Herrera-Hernández Héctor , Juarez-Garcia Jose M. , Palomar-Pardavé Manuel E. , Romero-Romo Mario R.
Published: December 2010

Corrosion has been frequently recognized as failure's root cause for diverse engineering components like those associated to production lines, like in boiling water reactor piping systems (1). It is important that several electrochemical techniques help conjointly to elucidate some of the corrosion specificities, like localized corrosion of traditional materials. Pitting corrosion has been usually reported to affect stainless steels because it engages more frequent than not, second phase particles that precipitate out at the matrix and the grain boundary network, thereby consuming alloying elements that, for example, participate on sustaining passivity. Thermally-dependent fabrication operations such as welding bring about sensitization, particularly within the 450 to 700 ºC range. Exposure propitiates nucleation and growth of chromium carbide networks: this makes the boundaries and neighboring areas sensitive to depletion. Thus the precipitates are directly suspect of significant decrements in protective potential as the chromium has been chemically bound to carbon, thereby decreasing the surface passivating abilities. Therefore, the present work reports the electrochemical and microscopy results obtained after immersing the heat treated SS304 samples for diverse periods in a suitable electrolyte to studying their potentiodynamic polarization and EIS behaviors.
Fractal Analysis of 316l Stainless Steel in a LiBr-Ethylene Glycol+H2O Solution
Authors: Sarmiento Estela , Uruchurtu Chavarín Jorge , González Gonzalo , Menchaca Carmina , Sarmiento Oscar
Published: December 2010

This work presents electrochemical noise results obtained for 316L stainless steel immersed in LiBr+ethylene glycol+H2O solution for different temperatures. The evaluation was obtained from fractal dimension analysis of the electrochemical noise-time series using the so called the Rescale Range Analysis (R/S) proposed by Hurst. The fractal dimensions were calculated from the time series obtained for the different condition signals. This dimension is obtained from the empirical law R/S = (/2)H where R represents the difference between the maximum and minimum values of the variable, S the standard deviation of the time series, is the period of time measured and H the Hurst exponent between 0 < H < 1. For comparison polarization curves and electrochemical impedance spectroscopy was also performed. The fractal analysis of electrochemical noise helps to evaluate the surface condition and electrochemical performance under the corrosion conditions tested.
Dielectric and Electrochemical Properties of Sustainable Concrete
Authors: Corral-Higuera Ramon , Arredondo-Rea Susana P. , Neri Flores Miguel A. , Orozco-Carmona Victor , Gómez-Soberón Jose M. , Almeraya Calderon Facundo , Almaral-Sánchez Jorge L.
Published: December 2010

It is planned to improve the durability of reinforced concrete structures and the total or partial replacement of their components by the use of recyclable materials; as strategies to contribute to the concrete industry sustainability. The electrical resistivity and its relationship with the microstructure and electrochemical corrosion resistance in reinforced concrete manufactured with sustainable characteristics, that is, with recycled aggregates and supplementary cementitious materials; was evaluated in this study. The electrical resistivity in reinforced concretes is closely related to the microstructure of the cementitious matrix, and with the pore structure and distribution. As a consequence of the their components nature, it is assumed that the proposed sustainable concretes present different microstructure and porosity than the conventional concretes; because of this, the electrical and electrochemical response of those systems was analyzed with the help of the electrochemical impedance spectroscopy technique.
Electrochemical Realkalisation of Reinforced Concrete Using a Conductive Mortar Anode
Authors: Baldenebro Lopez Francisco J. , Barrios Durstewitz Carlos P. , Fajardo San Miguel Gerardo , Nuñez Jaquez Rosa E. , Almeraya Calderon Facundo , Almaral-Sánchez Jorge L. , Castorena Gonzalez Jose H.
Published: December 2010

Carbonation causes concrete acidification that brings in the loss of the steel rebar's passive layer, which in turn will allow initiation of an active corrosion process. A nondestructive technique to revert this condition is the electrochemical realkalisation (ER) that consists in applying a direct current between the steel bars and an external auxiliary electrode placed on concrete surface with the aim of restoring the alkalinity loss. In the present work is studied the use of a conductive mortar as anode in the electrochemical realkalisation of concrete. Carbonated reinforced concrete specimens with a water/cement ratio of 0.65 were evaluated. ER was applied by 5 days period with a current density of 2 A/m2 and using as anode a layer of modified mortar (add 25% graphite powder by cement weight) saturated with a 1M Na2CO3 solution. The pH in the concrete was determined by the phenolphthalein test and potentiometric titration. After the ER treatment the pH value of the carbonated concrete samples had increased from 8 to 11.95.
Voltammetric Modeling of the Kinetics Involved in the Nickel Deposition onto Nickel
Authors: Vazquez-Arenas Jorge G. , Altamirano-Garcia Liliana , Luna-Sanchez Rosa M. , Cabrera-Sierra Roman
Published: December 2010

A comprehensive physicochemical model is used to account for the nickel electrodeposition in sulfate media employing a rotating disk electrode. The model accounts for the nickel deposition, H+ and water reduction. These reactions involve the reduction of Ni(II) by two consecutive 1-electron transfer steps and the H+ and water reduction via the two-step Volmer-Tafel mechanism. Diffusion and convection are considered in the mass-transport balances. Reasonable fits of the model to the experimental data were obtained at different NiSO4 concentrations. Further insights of this system show that the reduction process starting from the open circuit potential to more negative potentials occurs in the following order: H+ reduction, nickel deposition and water reduction. The computation of other variables involved in the model such as the surface pH and concentrations provide additional support to those finds elucidated with the model.
Influence of the Crystallinity of the Substrate on Kinetic Parameters of Zinc Electrodeposition Process
Authors: Granados Neri Madai , Mendoza-Huizar Luis H.
Published: December 2010

The influence of the crystallinity of the carbon substrate on kinetic parameters was investigated by mean electrochemical techniques such as cyclic voltammetry and chronoamperometry from an electrolytic bath 0.01M ZnSO4 + 1M (NH4)2SO4 onto GCE and HOPG work electrodes. It was found that the predominant redox couple was [ZnSO4(H2O)5]/Zn{degree sign} in our experimental conditions. Furthermore, the electrochemical study indicated the existence of a progressive nucleation mechanism and 3D growth of the zinc electrodeposition. The parameters kinetic, such as nucleation rate and active sites number, showed that the zinc electrodeposition was more favored onto GCE than onto HOPG.
Study of the Copper Electrodeposition on Titanium Electrodes
Authors: De la Rosa Fernando , Ramos Aurora
Published: December 2010

The electrodeposition of copper on titanium electrodes was investigated using cyclic voltammetry and a potential step technique in 5x10-3 M CuSO4, 1M (NH4)2SO4 and pH values of 8, 9 and 10.3. Voltammetric analysis showed that the reaction is carried in two steps. The first corresponds to the reduction of Cu(NH3)2+ to Cu(NH3)2
+, possibly controlled by electronic transfer. The second corresponds to the reduction of Cu(NH3)2
+ to Cu(0). The electrocrystallization mechanism and the coupled reactions are pH function. The overcrossing potential, Ec, remains constant, and may be related to the thermodynamic potential. The current transients confirmed nucleation and growth process. There is a possible kinetically controlled reaction occurring on the first Cu layer of the deposit or the Ti substrate and it will be confirmed on a later work by applying the appropriate model.
Role of the Solvent Employed for the Cathodic Electrophoretic Deposition (EPD) of ITO/TiO2 Films, over its Morphology, Electronic Properties and Photoelectrochemical Behavior
Authors: Acevedo-Peña Próspero , Manríquez Juan , González Ignacio
Published: December 2010

The role played by solvent during cathodic EPD of TiO2 film was investigated. The differences in film morphology are attributed to the dissimilar surface excess charge of the TiO2 agglomerates in each solvent and to the secondary reactions occurring during the EPD. For the films obtained in aqueous medium an augmentation of donor density and a change toward less negative values of the flat band potential were measured. Furthermore, a decrease in photocurrents and photovoltages was provoked by increasing the electric field used to form the film. Meanwhile, for the films formed in organic medium, the semiconductive properties did not change with the electric field employed to grow the films, and the photoelectrochemical behavior of these films showed completely different trends. The dissimilarities found were attributed to the ability of the solvent to be reduced earlier than TiO2, avoiding the generation of species Ti3+ that acts like trap states.
Fluid Dynamics Study to Compare Two Different Flow-Field Geometries
Authors: Rivas Sandra V. , Hidalgo Pablo E. , Chapman Thomas W. , Orozco German
Published: December 2010

The effect of gas-channel geometry on a proton exchange membrane fuel-cell oxygen cathode was investigated by comparing numerical simulations for two alternative channel geometries. Calculations were done by use of Multiphysics COMSOL® software. One geometry consists of parallel channels, and the other is a criss-cross design called "re-direct pattern" (rdp). The parallel-channel design does not provide uniform distribution of the flow over the electrode so oxygen is depleted and water accumulates in some regions.
Mass Transfer Modeling and Simulation under Turbulent Flow in Filter-Press-Type FM01-LC Electrochemical Reactor
Authors: Rivero Eligio P. , Mayen Elvia , Rivera Fernando F. , Cruz-Diaz Martín , González Ignacio
Published: December 2010

This work presents the mass transfer simulation results of potassium ferri/ferrocyanide system using sodium sulfate as supporting electrolyte in a filter-press-type FM01-LC electrochemical reactor under mass-transfer controlled conditions. The following working conditions were investigated: 5/25 and 15/25 mM ferri/ferrocyanide ratio, and Reynolds numbers between 187 and 1407. The model employed herein consists of mass transfer equations coupled to hydrodynamic solution obtained from Reynolds-averaged Navier-Stokes equations by using standard k-ε turbulence model. The results show flow patterns and their effect on the local mass transfer rate. The integration of mass transfer flux on the electrode surface is closely consistent with experimental values of limiting current.
Characterization of a Multiple-Channel Electrochemical Cell by Computational Fluid Dynamics (CFD) and Residence Time Distribution (RTD)
Authors: Vázquez Armando I. , Almazán Francisco J. , Cruz-Diaz Martín , Delgadillo José A. , Lázaro María I. , Ojeda Carmen , Rodríguez Israel
Published: December 2010

Multiple-channel electrochemical cells are used for the electrocoagulation treatment of pollutants, but sometimes their use can be limited because of lack of knowledge of both hydrodynamic and current distribution performance. Most of the research devoted to electrocoagulation processes, do not present a preliminary hydrodynamic study of the selected cell. Thus, in this paper the importance of having a hydrodynamic characterization and current distribution analysis of a multi-channel electrochemical cell is highlighted. Studies of primary current distribution and, hydrodynamics were supported on applications of the COMSOL Multhiphysics{trade mark, serif} and FLUENT{trade mark, serif} software, respectively. The flow path was described by the residence time distribution (RTD) method. The current distribution analysis showed that a better distribution is obtained when an interelectrode gap of 3 cm is chosen. The RTD charts and the flow distribution described accurately channeling sections and stagnant zones that must be taken into account, since channeling reduce the entrapment of mud and stagnant zones promote the formation of clots.
Removal of Non-Biodegradable Compounds in a Complex Industrial Wastewater by Electrocoagulation - Activated Sludge Processes
Authors: Linares-Hernández Ivonne , Barrera-Díaz Carlos E. , Roa-Morales Gabriela , Martínez-Miranda Verónica , Bernal-Martínez Lina A. , Lugo-Lugo Violeta
Published: December 2010

The aim of this paper is to investigate the effectiveness of a coupled system electrocoagulation - activated sludge processes, in the removal of contaminant from industrial wastewater. An electrochemical treatment provides the elimination of recalcitrant compounds from wastewater, and an activated sludge removes the dissolved pollutants. The electrochemical process reduced 69% of chemical oxygen demand (COD) and the biological removed 55% COD, the global efficiencies were 86% COD, 85% color and 82% turbidity.
Evaluation of a Blue Indigo Dye Degradation with Electrochemical Peroxidation by UV-Vis Spectrophotometry
Authors: Olvera Vargas Hugo , Roa-Morales Gabriela , Marín Rosalinda , Ramírez M. Teresa , Balderas Patricia , Barrera-Díaz Carlos E.
Published: December 2010

In this work an aqueous solution containing a concentration of the dye 5,5',7-indigo trisulfonic acid of 100 mg L-1 have been degraded by an environmentally friendly electrochemical method. Two different supporting electrolytic media, phosphoric acid and sodium sulfate, were used to investigate their contribution in the efficiency of the degradation process. The electrochemical process used is electrochemical peroxidation (ECP), which uses an undivided cell with iron sheets as cathodes and requires the addition of hydrogen peroxide. As a result, the system promotes the production of hydroxyl radicals (.OH) from the Fenton's reaction that takes place between electro generated Fe (II) and the added H2O2. Under optimal conditions a complete color removal is achieved whereas the COD removal is 97%. The sludge generated from the treatment carried out in phosphate media is a fine white powder composed by oxihydroxi Fe-phosphate species. ECP is a highly efficient method for the degradation of the synthetic indigoid dye.
Reactive Black 5 Treatment and Hydrogen Production by PEM Electrolysis
Authors: Navarro Haydeana I. , Alvarez Alberto , Uruchurtu Chavarín Jorge , León Ismael
Published: December 2010

This paper proposes a new approach to PEM electrolysis, by replacing the conventional anodic reaction, by a reaction of lower energy requirements and technological application. Hydrogen is generated in the catholyte, through the reduction of protons on a cathode of stainless steel in acidic medium (H2SO4 1M), with a difference potential of 1V with a solar panel. While the anolyte is produced, a mixture of ions Fe2+/Fe3+ from the oxidation of a sacrificial electrode, made of carbon steel mesh, was used as anolyte Na2SO4 0.05M (pH≈2.5). The generation of iron ions in the anolyte is harnessed for the development of a Fenton type process in the presence of H2O2. Ions Fe2+/Fe3+ to interact with the H2O2 generated strong oxidants which are responsible for oxidizing organic matter. The main results show that it is possible to oxidize almost completely, different concentrations of Reactive Black 5 (0.00012M and 0.00024M) in 40 minutes.
Copper Removal in Tequila and Ethyl Alcohol by Cementation
Authors: Carreon Alvarez María A. , Avalos-Martínez Jorge , Castañeda-Valderrama Rocio , Bárcena-Soto Maximimiliano , Casillas Norberto
Published: December 2010

In this paper results of copper removal in ordinario and ethyl alcohol by cementation using an iron rod as a sacrifice anode are presented. Experiments were performed in ordinario containing copper without controlling pH and in an acetate buffer. Concentration before and after cementation were determined by atomic absorption spectroscopy. The highest removal efficiency of Cu (II) in ethyl alcohol and ordinario without buffer occurs at pHs of 4.8 and 3.3 respectively, with 49% removal in both cases. On the other hand, the highest removal percentage of Cu(II) in ethyl alcohol and ordinario at buffered conditions and pHs of 4.9 and 3.0 are 52.1 and 61.1% respectively, the major removal efficiency appears at more acidic pHs because iron has a major facility to oxidize in acidic pH.
Hexavalent Chromium Reduction by Iron: Electro-Generated and Galvanic Production
Authors: Lugo-Lugo Violeta , Barrera-Díaz Carlos E. , Roa-Morales Gabriela , Ureña-Núñez Fernando , Linares-Hernández Ivonne
Published: December 2010

Electrochemical methods are a novel approach for Cr(VI) reduction due their high capability, ease and inexpensive use. It was found that Cr(VI) reduction can be done using iron (Fe2+): electro-generated and galvanic production. The behavior of copper was examined as cathode material for optimized continuous reactors, determining copper-iron ratio surface areas (3.5:1) in batch studies of corrosion tests. Results of Cr(VI) reduction capacity showed that copper-iron galvanic systems offers advantages over traditional and even iron electro-generative copper-iron systems and moreover include no energy or chemical input into the system and no sludge generation. On the other hand electro-generative reactor showed a strong correlation between current density and Cr(VI) reduction capacity.
Hexavalent Chromium Recovery by Electrochemical Reactor of Ceramic Spacers Compartments Separated by Potentiostat Operating Mode
Authors: Reyes Pineda Henry , Jiménez Francy N. , Pérez Herranz Valentín
Published: December 2010

The key parameters in the control of an electrochemical reactor in operation are the potential of working electrode and the current distribution, which depend on many factors, among which include: the transfer, the hydrodynamic conditions and the total voltage of the cell, Uc. However, it is often impossible to monitor these parameters and we must resort to measure other parameters such as total intensity, (the electrode potential) and the total voltage of the cell. Thus in the control of an electrochemical reactor (or the operation of an electrochemical reactor) can be carried out by controlling one of three variables: the electrode potential, voltage or current total. In this paper works in potenctiostat mode determined the main parameters or figures of merit that characterize this type of reactor, which is designed first and then at laboratory pilot scale
Heuristic Correlation of Rheological Measurements and Electrochemical Impedance Spectroscopy (EIS) of the DNA/Water System
Authors: Topete Antonio , Carvajal Francisco , Fuentes-Vázquez Veronica , Pérez-Lopez Juan H. , González Omar I. , Macías-Balleza Emma R. , Álvarez Juan G. , Casillas Norberto , Rodríguez Julio R. , Varela Luis M. , Soltero José F.
Published: December 2010

In this work, it is reported viscosity, density, sound velocity and electrochemical impedance spectroscopy (EIS) measurements of calf thymus DNA in aqueous solutions, in order to investigate the overlapping C* and entanglement concentrations Ce. These critical concentrations demark the conditions at which start appearing interactions and entanglements between DNA molecules in solution. EIS has been proposed as new alternative analytical techniques to obtain C* and Ce in polyelectrolyte solutions. A new parameter the characteristic time (τc) was defined, and it is obtained from a new type of log-log Bode plot using the crossover frequency (τc=1/ωc) of the real (Z') and imaginary (Z") components when they are plotted as a function of the frequency. Preliminary results show similar values C* and Ce by EIS to those obtained from rheological, densimetry and sound velocity measurements.
Increased Selectivity Towards Oxygen Reduction Reaction in the Presence of Methanol by Incorporation of Tungsten Oxides and Platinum
Authors: Meza Calderón Doralice , Salgado Leonardo , Morales Ulises , Montiel Manuel , Fatás Enrique , Ocón Pilar
Published: December 2010

Platinum-tungsten oxides supported on Vulcan carbon were incorporated by means of an impregnation method. XRD and TEM-EDX results indicated that the material is formed by a mixture of tungsten trioxide and platinum particles supported on carbon. XPS analysis showed the presence of tungsten trioxide, metallic platinum and platinum oxides (PtO and PtO2) on the surface of the material. The catalytic performance of PtWOx/C and Pt/C for the oxygen reduction reaction (ORR) was analyzed in the absence and presence of methanol throughout cyclic voltammetry and rotating disk electrode. The results indicated that the addition of tungsten trioxide increases both the catalytic performance of the ORR and catalyst's methanol tolerance.
Electrochemical Study of Flavonoids in Acetonitrile: Structure-Activity Relationships
Authors: Arroyo-Currás Netzahualcoyotl , Videa Marcelo F.
Published: December 2010

Relations between structure, antioxidant capacity and formal redox potentials (E{degree sign}') of six flavonoids dissolved in acetonitrile were studied by cyclic voltammetry and square wave voltammetry using a glassy carbon electrode. This work shows correlation between the electrochemical parameter E{degree sign}' and the number of hydroxyl groups present in the B ring of flavonoids. Besides, it has been observed that E{degree sign}' measured as a function of B ring oxidation depends considerably on the functional groups present in the ring C of these molecules. Since antioxidant activity of flavonoids is attributed to their proton-donating, the results of this work were compared to previous reports regarding the antioxidant capacity of these compounds. Even though the antioxidant activity of flavonoids depends on several factors, the conclusions of this investigation suggest that the E{degree sign}' value should be considered as a key parameter for the evaluation of antioxidant activity.
Effect of Membrane Composition and Thickness on the Behavior of Solid Contact Ion Selective Electrodes for Pb2+ using a Diazadibenzo-18-Crown-6 Ether as Ionophore
Authors: Cuervo-Ochoa Germán , Aguilar-Cordero Julio C.
Published: December 2010

Several solid contact ion selective electrodes (SC-ISE) for Pb2+ based on a diazadibenzo-18-crown-6 ether as the ionophore were constructed with varying membrane composition and thicknesses in order to study the effect of those given variables on the potentiometric behavior of the sensor. Thus, the potentiometric response of the electrodes was investigated with changing content of ionophore, plasticizer, ion-exchanger as well as changing the pH of the sample solutions. The corresponding analytical figures of merit, i.e. slope, detection limit, linear range and potentiometric selectivity coefficient (kpot), were determined.
Influence of Dispersing Agent on the Electroanalytical Quantification of 8-Hydroxy 2'-Deoxyguanosine or Uric Acid on a Glassy Carbon Electrode Modified with Carbon Nanotubes
Authors: Gutiérrez Alejandro , Gutiérrez Silvia , García Guadalupe , Galicia Laura , Rivas Gustavo A.
Published: December 2010

In this paper we report the highly sensitive quantification of 8-hydroxy 2'-deoxyguanosine (8-OHdG) or uric acid (UA) in the presence of ascorbic acid (AA) using glassy carbon electrodes (GCE) modified with multiple-wall carbon nanotubes (CNT), dispersed in various polymers such as nafion (GCE/CNT Pnaf),polyacrylic acid (GCE/CNT-Paa), percoll (GCE/CNT-Prl) and polyvinyl alcohol (GCE/CNT-Pva). The electrocatalytic activity of CNT deposited on GCE shows a significant diminish on the AA overpotential oxidation value (257 mV); making possible the AA oxidation process separation from 8-OHdG and UA ones. Using differential pulse anodic stripping voltammetry (DPASV), the analytes were quantified. The optimum sensitivity obtained in the quantification of 8-OHdG was (3.3 {plus minus} 0.1) x 106 μAM-1 (r = 0.994),and for UA, (3.2 {plus minus} 0.2) x 106 μAM-1 (r = 0.991) on GCE/CNTPnaf, both in the presence of 1.0 mM of AA. The detection limits for 8-OHdG and UA on GCE/CNT-Pnaf are around 13x10-9 M.
Evaluation of the Analytical Capabilities of Some Bacterial and Hybrid Sensors for Environmental Pollutants Determination
Authors: Stoytcheva Margarita , Zlatev Roumen , Velkova Zdravka , Valdez Benjamin , Ovalle Marcela
Published: December 2010

Some bacterial and hybrid (bacterial/enzymatic) electrochemical sensors were evaluated for potential in situ metal ions and organophosphorus pesticides determinations. The analytical performances of the Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans based sensors for ferrous iron and of the Arthrobacter globiformis/acetylcholinesterase based one for chlorofos quantification were estimated throughout comparative studies. It was found that the two Fe2+ sensors provide better LOD (0.9 μmol L-1 and 2.4 μmol L-1 respectively) than that developed by Mandl et al. (60 μmol L-1) earlier. The hybrid (bacterial/enzymatic) sensor for chlorofos provides the same LOD but much longer lifetime at ambient temperature than the enzymatic ones. Reproducibility and high detection sensitivity of the determinations were achieved applying an original bacteria immobilization strategy, improved transducer design, and noise suppression technique.