bluuebunny/crossref_metadata_2025 huggingface dataset:
Leukemic Cells Create Bone Marrow Niches That Disrupt the Behavior of Normal Hematopoietic Progenitor Cells
Authors: Colmone Angela , Amorim Maria , Pontier Andrea L. , Wang Sheng , Jablonski Elizabeth , Sipkins Dorothy A.
Published: December 2008

The host tissue microenvironment influences malignant cell proliferation and metastasis, but little is known about how tumor-induced changes in the microenvironment affect benign cellular ecosystems. Applying dynamic in vivo imaging to a mouse model, we show that leukemic cell growth disrupts normal hematopoietic progenitor cell (HPC) bone marrow niches and creates abnormal microenvironments that sequester transplanted human CD34
+
(HPC-enriched) cells. CD34
+
cells in leukemic mice declined in number over time and failed to mobilize into the peripheral circulation in response to cytokine stimulation. Neutralization of stem cell factor (SCF) secreted by leukemic cells inhibited CD34
+
cell migration into malignant niches, normalized CD34
+
cell numbers, and restored CD34
+
cell mobilization in leukemic mice. These data suggest that the tumor microenvironment causes HPC dysfunction by usurping normal HPC niches and that therapeutic inhibition of HPC interaction with tumor niches may help maintain normal progenitor cell function in the setting of malignancy.
Competitive Inhibition Flow Analysis Assay for the Non-Culture-Based Detection and Serotyping of Pneumococcal Capsular Polysaccharide
Authors: Findlow H. , Laher G. , Balmer P. , Broughton C. , Carrol E. D. , Borrow R.
Published: December 2008

Traditional confirmation procedures for the identification of a pneumococcal serotype require an isolate. Non-culture-based confirmation protocols are available. Some of these confirm only the presence of pneumococci, and others are capable of identifying a limited number of serotypes. The increased use of pneumococcal polysaccharide and conjugate vaccines, especially in high-risk patient groups, and the likely increase in the number of serotypes included in future versions of the conjugate vaccines have necessitated the need for improved enhanced surveillance in order to assess their impact on public health. Since 2006, a multiplexed assay has been used at the Health Protection Agency of the United Kingdom for the detection of 14 pneumococcal serotypes which requires pneumococcal serotype-specific monoclonal antibodies (MAbs). We have developed a microsphere competitive inhibition method capable of detecting 23 pneumococcal capsular polysaccharide serotypes in cerebrospinal fluid (CSF) and urine and serotyping pneumococcal suspensions, utilizing an international reference serum, 89-SF. The assay was shown to be reproducible and specific for homologous polysaccharide. Validation of the assay was performed with a selection of MAbs specific for pneumococcal capsular polysaccharide serotypes, which confirmed the specificity of the assay. Analysis of pneumolysin PCR-positive CSF samples in the competitive inhibition assay determined a serotype for 89% of the samples. The assay developed here is well suited to large-scale epidemiologic studies because the assay is simple, robust, and rapid and utilizes readily available resources.
In Vivo and In Vitro Alterations in Influenza A/H3N2 Virus M2 and Hemagglutinin Genes: Effect of Passage in MDCK-SIAT1 Cells and Conventional MDCK Cells
Authors: Li Danjuan , Saito Reiko , Suzuki Yasushi , Sato Isamu , Zaraket Hassan , Dapat Clyde , Caperig-Dapat Isolde Ma , Suzuki Hiroshi
Published: December 2008

No mutations were detected in the hemagglutinin gene of influenza A/H3N2 virus isolates from patients undergoing short-term amantadine treatment. However, genetic changes occurred after serial passage in either MDCK or MDCK-SIAT1 cells. Our results showed that only a few mutations were observed in MDCK-SIAT1-passaged isolates in the presence of amantadine.
Evaluation and Implementation of a Chromogenic Agar Medium for
Salmonella
Detection in Stool in Routine Laboratory Diagnostics
Authors: van Dijk Saskia , Bruins Marjan J. , Ruijs Gijs J. H. M.
Published: December 2008

We evaluated which chromogenic agar medium for
Salmonella
detection in stool would be most sensitive and specific in our culture protocol. The use of BBL CHROMagar
Salmonella
chromogenic medium combined with xylose-lysine-deoxycholate agar yielded a sensitivity of 100% and also reduced workload and costs.
Molecular Diagnostic Identification of
Staphylococcus pseudintermedius
Authors: Bannoehr Jeanette , Franco Alessia , Iurescia Manuela , Battisti Antonio , Fitzgerald J. Ross
Published: December 2008

We report the first diagnostic test for the identification of
Staphylococcus pseudintermedius
involving a simple PCR-restriction fragment length polymorphism approach. The method allows discrimination of
S. pseudintermedius
from the closely related members of the
Staphylococcus intermedius
group and other important staphylococcal pathogens of humans and dogs.
Interaction of Human Cytomegalovirus pUL84 with Casein Kinase 2 Is Required for oriLyt-Dependent DNA Replication
Authors: Gao Yang , Pari Gregory S.
Published: December 2008

Human cytomegalovirus pUL84 is a phosphorylated protein that is required for lytic DNA replication and participates in regulation of virus gene expression. We previously used a proteomics assay to show that human cytomegalovirus pUL84 interacts with casein kinase 2 (CK2). We now have demonstrated that pUL84 is a substrate for CK2 in vitro, and we have determined that two putative CK2 phosphorylation sites within pUL84 mediate binding to CK2. Mutation of a threonine residue at amino acid (aa) 148 and a serine residue at aa 157 within the pUL84 protein resulted in the inability of the protein to interact with the CK2α subunit in transfected cells. Interaction of pUL84 with CK2 was essential for complementation of oriLyt-dependent DNA replication, suggesting that phosphorylation is an essential modification.
Cricket ball injury: a cause of symptomatic muscle hernia of the leg: Figure 1
Authors: Gupta R K , Singh D , Kansay R , Singh H
Published: December 2008

A case of symptomatic muscle hernia of the leg in a provincial cricketer caused by a cricket ball injury is presented. It was diagnosed clinically and treated with a limited fasciotomy. However, delay in the diagnosis and treatment ended the professional career of the player. An awareness of the condition and a high index of suspicion are required to treat this condition in time.
A re-evaluation of Parasaurus geinitzi, the first named pareiasaur (Amniota, Parareptilia)
Authors: Tsuji Linda A. , Müller Johannes
Published: December 2008

The historically first named pareiasaur Parasaurus geinitzi from the Upper Permian Kupferschiefer deposits of Germany is re-described in detail, including information from recently discovered specimens, as well as material that was for a long time assumed to be lost. The re-study provides new information on both the cranial and the postcranial anatomy of the taxon, the most notable features being the presence of small spikes in the postero-temporal region of the skull and the apparent lack of osteoderms in the axial skeleton, which is unique among pareiasaurs but requires further investigation and new material. A phylogenetic analysis indicates that Parasaurus groups within the more derived pareiasaurs; however, the overall resolution of the analysis is very poor, most likely because many characters traditionally used in studies on pareiasaurian phylogeny were originally defined only for investigating turtle relationships, but not for deciphering the ingroup relationships of pareiasaurs. A careful revision of the phylogeny of the clade is necessary and should also include a detailed assessment of pareiasaurian anatomy, which is still poorly known.
Isolation and characterization of silicate mineral-solubilizing Bacillus globisporus Q12 from the surfaces of weathered feldspar
Authors: Sheng Xia Fang , Zhao Fei , He Lin Yan , Qiu Gang , Chen Liang
Published: December 2008

A silicate mineral-solubilizing bacterial strain Q12 was isolated from the surfaces of weathered feldspar and identified as Bacillus globisporus Q12 based on the 16S rDNA gene sequence analysis. Three silicate minerals (feldspar, muscovite, and biotite) were used to investigate potassium and silicon mobilization by strain Q12. In liquid cultures, the strain showed better growth on the biotite than on feldspar and muscovite. The biotite was the best potassium source for growth of the strain. Solubilization of potassium and silicon from the silicate minerals by the strain resulted mostly from the action of organic acids. Gluconic acid seemed to be the most active agent for the solubilization of the 3 silicate minerals. Gluconic and acetic acids were likely involved in the solubilization of feldspar. The strain could be acid or alkali and salt tolerant and temperature resistant.
Spatial distribution of bacterial communities in sediment of a eutrophic lake revealed by denaturing gradient gel electrophoresis and multivariate analysis
Authors: Zeng Jin , Yang Liu-Yan , Liang Yi , Li Jia-Yun , Xiao Lin , Jiang Li-Juan , Zhao Da-Yong
Published: December 2008

Bacterial community structure and the effects of several environmental factors on the microbial community distribution were investigated in the sediment of the eutrophic Lake Xuanwu. Profiles of bacterial communities were generated using denaturing gradient gel electrophoresis (DGGE), and the results were interpreted with multivariate statistical analysis. Five major variables in sediment were examined in a principal component analysis, which indicates notable differences of physicochemical parameters among different sites of the lake. To assess changes in the genetic diversity of bacterial communities of different sampling sites, DGGE band patterns were analyzed by multidimensional scaling analysis, which indicated that sampling sites having similar environmental characteristics also have the similar microbial communities. Canonical correspondence analysis demonstrated that pH and redox potential had significant effects on the bacterial community composition in the sediments. Analysis of DNA sequences revealed that the dominant bacterial groups in Lake Xuanwu belonged to Proteobacteria , Actinobacteria , Verrucomicrobia , and Nitrospirae , which are commonly isolated from freshwater ecosystems.
Innate immunity prevents tissue invasion byEntamoeba histolytica
Authors: Shibayama Mineko , Rivera-Aguilar Víctor , Barbosa-Cabrera Elizabeth , Rojas-Hernández Saúl , Jarillo-Luna Adriana , Tsutsumi Víctor , Pacheco-Yepez Judith , Campos-Rodríguez Rafael
Published: December 2008

Although innate and adaptive immunity both play a role in amoebiasis, the mechanisms involved in the elimination of Entamoeba histolytica are poorly understood. To provide more information about the innate immune mechanisms that may confer protection against invasive amoebiasis, we administered inflammatory substances (bacillus Calmette-Guérin, lipopolysaccharide, complete Freund’s adjuvant, or mineral oil) into the peritoneum of hamsters. The animals were then challenged with pathogenic trophozoites of E. histolytica and, after 7 days, the protective host response was analysed. We found that the nonspecific inflammatory response induced in the peritoneum was sufficient to prevent liver invasion by E. histolytica. In vitro experiments showed that the killing of trophozoites was mediated by peritoneal macrophages and a protein of 68 kDa with peroxidase activity.
Moose–habitat relationships: integrating local Cree native knowledge and scientific findings in northern Quebec
Authors: Jacqmain Hugo , Dussault Christian , Courtois Réhaume , Bélanger Louis
Published: December 2008

Participation of aboriginal people in Canadian forestry is a requirement of sustainable management. We proposed a culturally adapted process to integrate Cree and scientific knowledge in Eeyou Istchee (northern Quebec) that could contribute to a better mutual understanding between Cree and non-Cree, and eventually favour the social acceptability of forest management strategies. We studied moose ( Alces alces L.), the Cree featured species and the main forestry issue for the past 40 years. Cree and non-Cree have culturally differing visions for the management of moose habitat. In a previous article, we documented Cree knowledge about moose–habitat relationships. Here, we evaluated some hypotheses built from Cree knowledge by studying the behaviour of moose equipped with GPS collars. In general, results from our habitat use and selection analyses agreed with Cree observations and improved our understanding of moose–habitat relationships in northern Quebec. We jointly demonstrated the importance of mature mixedwoods, balsam fir ( Abies balsamea (L.) Mill.) stands, and riparian areas for moose in the northern black spruce ( Picea mariana (Mill.) BSP) forest. In these specific areas, management approaches other than clear-cutting should be developed to preserve moose habitat quality. Such an alternative would potentially be more acceptable for the Cree people.
Predicting the age of ancient Thuja occidentalis on cliffs
Authors: Matthes Uta , Kelly Peter E. , Larson Douglas W.
Published: December 2008

In rocky, heterogeneous environments that support old-growth forests, the relationship between tree size and age is weaker than it is for trees growing in productive and homogeneous habitats. To assist in the management and conservation of ancient forests on rocky land of low productivity, it would be useful if the relationships among age, environmental heterogeneity, and morphological variability could be understood and used to develop predictive models of longevity so that extensive core sampling of trees would not be required. Here we sampled 296 mature Thuja occidentalis L. growing on limestone cliffs along the Niagara Escarpment, southern Ontario, Canada. We measured a variety of site conditions and morphological traits, including age, which varied from 51 to 1316 years. We then used redundancy analysis and multiple regression to model the relationships among age, morphology, growth rate, and environment, resulting in quantitative models predicting tree age from four subsets of variables. We subsequently tested the models on 60 additional trees not used to build the models and found that they predicted up to 78% of the variation in actual tree age. This approach could be adopted for use in other forest types to predict the age of trees without using tree-ring analysis.
QCD CORRECTIONS TO THE RADIATIVE DECAY $\bar{B}\to X_s\gamma$
Authors: FERROGLIA ANDREA
Published: December 2008

In this short review, the calculation of the next-to-next-to-leading order QCD corrections to the inclusive radiative decay [Formula: see text] is described. We summarize the salient features of the calculational framework adopted, discuss the results obtained in the last few years, and indicate the technical tools that made the NNLO calculations possible. We conclude by comparing the current NNLO theoretical estimate for the branching ratio with the experimental measurement and by briefly discussing the size and origin of the residual theoretical uncertainty.
FIRST PRINCIPLE CALCULATIONS OF A FAMILY OF NOBLE METAL NITRIDES AND CARBIDES
Authors: LI LINYAN
Published: December 2008

The structural and electronic properties of selected noble metal nitrides and carbides are studied using the local density approximation and the generalized gradient approximation. The zinc-blende and rock-salt structures are employed. The nitride and carbide of palladium have high bulk modulus. From the DOS, the MX ( M = Pd , Ag , Au ; X = N , C ) compound display metallic nature.
SPIN PUMPING IN FERROMAGNETIC MULTILAYERS
Authors: TANIGUCHI TOMOHIRO , IMAMURA HIROSHI
Published: December 2008

We present a brief review of our recent study on spin pumping in ferromagnetic multilayers. First, we present theoretical models describing spin pumping induced by ferromagnetic resonance (FMR). Then we apply the spin-pumping theory to FMR in ferromagnetic multilayers and show that the line width of the FMR spectrum depends on the thickness of the ferromagnetic metal layer which is not in resonance. We also show that the penetration depths of transverse spin current in ferromagnetic metals can be determined by analyzing the line width of the FMR spectrum. The obtained penetration depths of the transverse spin current were 3.7 nm for Py , 2.5 nm for CoFe , 12.0 nm for CoFeB , and 1.7 nm for Co , respectively.
STRUCTURAL AND DIELECTRIC PROPERTIES OF Ba2Sr3SmTi3V7O30
Authors: SAHOO P. S. , PATRI S. K. , CHOUDHARY R. N. P. , PANIGRAHI A.
Published: December 2008

The polycrystalline sample of Ba 2 Sr 3 SmTi 3 V 7 O 30, a member of the tungsten bronze structural family, was prepared by a high-temperature solid-state reaction technique. Preliminary X-ray diffraction analysis suggests the formation of a single-phase compound with orthorhombic structure. Detailed studies of the dielectric constant and tangent loss as a function of frequency (100 Hz to 1 MHz) and temperature (32°–500°C) show that this compound has a diffused-type of ferroelectric phase transition at 230°C. Study of the surface morphology by SEM showed uniform grain distribution on the surface of the sample with less porosity. The activation energy, calculated from the plot of temperature dependence of AC conductivity, of the compound was found to be 0.11 eV and 0.14 eV at 500 kHz and 1 MHz respectively. The nature of the variation of conductivity and value of activation energy suggest that the conduction process is of a mixed-type.
A CORRESPONDING RELATION BETWEEN ELECTROLUMINESCENT INTENSITY AND THE ENERGY AND CHARGE TRANSFER IN DOPED ORGANIC ELECTROLUMINESCENT DEVICES
Authors: LI HONG-JIAN , WANG ZHI-JUN , WANG JUN-XI , LI XUE-YONG , XIA HUI , PENG JING-CUI
Published: December 2008

In doped organic electroluminescent devices (OLEDs), the changes of the fluorescence spectra occurred due to the energy and charge transfer from guest to host. A quantitative relation between the energy and charge transfer for doping OLEDs was studied by means of a Hamiltonian model. It was found that there is a corresponding relation between the EL intensity of doped PVK and the amount of the transferred charge and the change of the energy derived from charge transfer with dopant concentration, and the more the amount of the transferred charge and the decreasing of the energy from charge transfer, the higher the EL intensity in doped OLEDs. We can deduce that the efficient energy transfer results from the transferred charge between PVK and perylene. Based on the transport mechanism of carriers in conjugated polymer, an expression of conductivity was presented. Calculated results indicated that there is also a corresponding relation between the EL intensity of doped PVK and conductivities with dopant concentration. The larger the conductivities, the higher the EL intensity in doped OLEDs.
THERMAL DIFFUSIVITY OF Bi2Sr2CaCu2O8 CERAMICS WITH NANO Ag ADDITION MEASURED USING OPEN-CELL PHOTOACOUSTIC TECHNIQUE
Authors: NARRETO M. A. B. , WEI K. , ABD-SHUKOR R. , ALWI H. A.
Published: December 2008

This paper reports the results of thermal diffusivity measurement on nano Ag added Bi 2 Sr 2 CaCu 2 O 8- Ag x (with x = 0–1.0) ceramics using an open-cell photoacoustic instrument. The thermal diffusivities were obtained by analyzing the phase of the photo-acoustic signal of thermally thick samples using Calderon's method as well as the analysis of the phase in thermally thick region. We found that the thermal diffusivity increases with the amounts of nano Ag . The values of thermal diffusivity obtained were between 0.01250 ± 0.00128 to 0.01606 ± 0.00230 cm 2/ s for Ag 0 to Ag 1.0. The electrical resistance versus temperature measurements showed a metal-like behavior for all samples. However, a metal-like transition was observed between x = 0.5 and 0.7 when results of thermal diffusivity and electrical resistance measurements were analyzed together with samples x ≥ 0.7 showing the metallic behavior.
STIMULATED EMISSION ON SILICON AFTER OXIDATION BY IRRADIATION AND ANNEALING
Authors: ZHANG RONG-TAO , WANG HAI-XU , JIN FENG , XU LI , WU KE-YUE , QIN SHUI-JIE , LIU SHI-RONG , QIN CAO-JIAN
Published: December 2008

Stimulated emission has been observed from oxide structure of silicon when optically excited by 514 nm laser. The twin peaks in the region from 690 nm to 700 nm are dominated by stimulated emission which can be demonstrated by its threshold behavior and transition in linear evolution. The oxide structure was fabricated by laser irradiation and annealing treatment on silicon. A model for explaining the stimulated emission has been proposed in which the trap states of the interface between oxide of silicon and porous nanocrystal play an important role.
DARBOUX TRANSFORMATION AND VARIOUS SOLUTIONS FOR A NONLINEAR EVOLUTION EQUATION IN (3 + 1)-DIMENSIONS
Authors: ZHAQILAO  , LI ZHI-BIN
Published: December 2008

A new (3 + 1)-dimensional nonlinear evolution equation can be decomposed into three (1 + 1)-dimensional nonlinear evolution equations. In this paper, N-soliton solution, resonant solution and complexiton solution of the (3 + 1)-dimensional nonlinear evolution equation are obtained via an N-fold Darboux transformation of the Ablowitz–Kaup–Newell–Segur spectral problems.
MEASUREMENT OF AVERAGE ETCHED PORE RADIUS IN ION TRACK MEMBRANES THROUGH CONDUCTOMETRIC TECHNIQUE
Authors: KUMAR SANJEEV , CHAKARVARTI S. K.
Published: December 2008

In the present work, average pore radius in etched PC and PET membranes, exposed to various heavy ions, has been determined using the conductometric technique. The average pore radius, measured directly through optical microscope, has been found to be higher (15%) than the values determined using the conductometric method.
THE SIGNATURE OF PARTIALLY DEFINED LOCAL COEFFICIENT SYSTEMS
Authors: BANAGL MARKUS
Published: December 2008

Intersection homology enables the definition of a twisted signature of a stratified pseudomanifold with coefficients in a local system that is typically only given on the top stratum. If the local system extends to the entire space, then the twisted signature can be computed by a version of a characteristic class formula first observed by Atiyah for smooth fiber bundles. In the first part of this paper, we construct examples of singular spaces, equipped with local systems that do not extend, such that the above characteristic class formula fails. In the second part, we consider smooth codimension two embeddings of manifolds. We view the target as a stratified space with bottom stratum the image of the embedding and top stratum the complement. When the embedded manifold is a sphere, we establish various formulae that compute the twisted signature even when the local system does not extend from the top stratum to the entire space.
Microstructure Role in Passivation and Local Activation Processes of Carbon Steels
Authors: Muratova Natalia , Kaluzhina Svetlana
Published: December 2008

The regularity of carbon steels passivation and local activation in borate-sulphate solutiones at room temperature were analyzed. Pits on iron are initiating on ferrite/cementite interface. On carbon steel surface was observed the spots representing the uniformly dissoluble pearlite grain. So necessary to note that high carbon content in alloys decrease their corrosion stability under local destruction conditions.
Transmission Line Modeling of EIS Data for a Mg-Rich Primer on AA 2024-T3
Authors: Allahar Kerry N. , Battocchi Dante , Bierwagen Gordon , Tallman Dennis
Published: December 2008

Mg-rich primers (MRPs) have been shown to provide cathodic and barrier-type protection to aluminum substrates similar to that provided by zinc-rich primers (ZRPs) for steel. The former protection is driven by the more active Mg particles compared to the Al substrate and the latter by the insulation of the substrate from the environment by Mg containing products. A transmission line model was used to interpret ZRP EIS data that accounts for the contact impedance between zinc particles, the impedance associated with zinc dissolution, and the electrolyte resistance. Experiments were conducted for the evolution of the electrochemical behavior of a MRP on AA 2024-T3 under immersion in diluted Harrison's solution. The transmission line model was applicable to the MRP data. Comparison between the parameters of a ZRP and those for the MRP indicated that the loss of cathodic protection for a MRP was related to the interfacial resistance of the particles.
ElectroData: a FORTRAN Program to Evaluate Rotating Disc Electrode Data
Authors: Ramos-Velasco César A. , Galván-Valencia Marisol , Durón-Torres Sergio M.
Published: December 2008

The Rotating Disk Electrode (RDE) hydrodynamic technique is well known as an important tool for obtaining the kinetic parameters of catalytic electrochemical reactions. Using RDE, a significant amount of data can be obtained and mathematical treatment is necessary for the elucidation of the catalytic behavior of materials. This mathematical procedure is normally performed using a spreadsheet through several repetitive steps applied to some hundred current-potential data pairs. To eliminate errors in these tedious calculations, it is convenient to have a computer program that makes calculations feasible and efficient. In this work we selected the FORTRAN language to build the required program. The most important characteristics of ElectroData are the automatic mixed control zone delimitation of RDE curves using a Stavitzky-Golay numerical derivation and smoothing, and the feasibility of obtaining Tafel curves through a Koutecký-Levich procedure to calculate the kinetic parameters of a certain reaction.
Evaluation and Characterization of Palladium Oxides used for Increasing the Rate of the Hydrogen Oxidation Reaction
Authors: Mendoza M. H. , Antaño René L. , Meas Yunny V.
Published: December 2008

The catalytic effect in hydrogen oxidation experiments was evaluated using oxides of palladium that were formed electrochemically and their behavior was compared to oxides thermally formed in air. I-t curves measured at 0.6V(NHE) showed average current densities of 30 mA cm-2 obtained with the electrochemical oxide compared to 40 mA cm-2 obtained with the thermally formed oxide. Though the oxide formed electrochemically had 25% less current density than the oxide formed thermally, its synthesis conditions are more energy efficient than those for the thermal oxide. This leads to envisioning its use as a catalyzer in low temperature fuel cells. XRD characterization confirms that the electrochemical method generates palladium monoxide at the working potential used in these experiments.
Electrochemical Characterization of MnO2 Anodically Formed During the Zinc Electrowinning Process
Authors: Recéndiz Alejandro , Nava José L. , González Ignacio
Published: December 2008

This work describes the different species formed over a lead-silver substrate after being applied an oxidation potential pulse in an electrolyte similar to that employed in the electro-recovery of zinc. At the beginning, a layer of PbSO4 is developed, followed by the formation of PbO2, which is catalyzed by the presence of Mn(II) in the electrolyte; after 5 minutes occurring this process, a layer of MnO2 is electrochemically formed over the PbO2. The manganese oxide catalyzes in major proportion the oxidation of other species of manganese to MnO4- than the oxygen evolution reaction. Furthermore, this manganese film shows resistive properties increasing the overpotential oxidation process.
Preparation and Characterization of Modified Electrodes Based on Carbon Nanotubes /Pyrrole/Cobalt Phthalocyanine for the Development of Hybrid Materials for the Electrochemical Activation of 2-mercaptoethanol
Authors: Porras Guiterrez Anita , Gutierrez Granados Silvia , Alatorre Ordaz Alejandro , Griveau Sophie , Richard Cyrille , Zagal José , Bedioui Fethi
Published: December 2008

In this paper the preparation and characterization of modified electrodes based on carbon nanotubes / pyrrole / cobalt phthalocyanine was done to obtain hybrid materials for the electrochemical oxidation of 2-mercaptoethanol. To prepare these new electrodes, two steps were followed. First, single-walled CNT (SWNT) deposits were made in aqueous solution on glassy carbon (GC) to obtain GC/CNT electrodes. Subsequently, pyrrole (Py) was incorporated on the CNTs to produce GC/CNT/PPy electrodes by electropolymerization. Pyrrole electropolymerization was a useful method to control the film characteristics. Both deposits were studied using a redox model reaction with ferrocenemethanol (FeMeOH), enabling the determination of the stability and charge transfer characteristics of the obtained electrodes. Finally, CoPc was incorporated into the hybrid electrodes, and their response for the oxidation of 2-mercaptoethanol was investigated.
The Effect of the Anion on Copper Electrocrystallization. Impedance Analysis
Authors: Vázquez Gerardo , Roldán-Fernández C. M. , González Ignacio
Published: December 2008

The effect of the anion employed in the supporting electrolyte (SO42-, ClO4- or NO3-) during the copper electrocrystallization onto glassy carbon (GC) was investigated using the electrochemical impedance spectroscopy. The influence of the anion is observed as a variation of Zre and Zim. The Nyquist diagrams of GC in the supporting electrolytes show one time constant in all cases. Unlike this, the Nyquist diagrams of GC in the electrolytes containing Cu2+ present two times constants associated to the electroreduction of Cu2+. By means of an electric circuit the parameters associated to the electrodeposition process were obtained. It was found that the values of R2 (associated to Cu2+/Cu+ process) are much greater than the values of R1 (Cu+/Cu0 process) in all cases, this indicates that the rate-limiting step is R2. The values calculated for R2 at n=0mV, in sulfate, perchlorate and nitrate solutions are 731 Ohmscm2, 523 Ohmscm2 and 535 Ohmscm2 respectively.
Copper Electrodeposition on Carbon Film Electrodes
Authors: Figueroa Ramirez Sandra J. , Miranda-Hernadez Margarita
Published: December 2008

The reaction and nucleation mechanisms of the electrodeposition of copper from ammoniacal solutions were investigated by cyclic voltammetric and chronoamperometric techniques on carbon film electrodes in an ammoniacal bath. The process of copper formation is carried out in two steps. The first is associated to reduction of complex couple Cu(NH3)42+ to Cu(NH3)2+ this processes is controlled by diffusion, whereas in second correspond to the reduction of Cu(NH3)2+ to Cu(0) in wide potential range. Theoretical models of electrocrystallization reported in literature were used to analyze the experimental current transients. The analysis of the experimental current transients shows a three-dimensional growth (3D) for the metallic copper with a great number of monolayer; this indicated that in these experimental conditions of work massive copper deposits was obtained.
Reinforcement Corrosion Measurement in Reinforced Concrete Structures from the Crack's width in the Cover
Authors: Castorena-González José H. , Calderón-Guillén Joel A. , Núñez-Jáquez Rosa E. , Almeraya Calderon Facundo , Díaz-Vásquez Felipe , Barrios-Durstewitz Carlos , Almaral-Sanchez Jorge L.
Published: December 2008

Two experiments of accelerated corrosion are carried out in a reinforced concrete block and a cylinder to calibrate a finite three-dimensional element model where the corrosion cracking is simulated due to the expansion of oxides. The model obtained is used then to find a theoretical relationship between the consumed steel (corrosion penetration) and the crack's width. It is found that this relationship is a function of the corroded length, free coating, reinforcement diameter and concrete type. The results obtained are validated with three experiments found in literature: a beam subjected to accelerated corrosion, and two beams subjected to natural corrosion conditions. These beams are also subjected to the simultaneous action of flexion and corrosion, as they are expected to be found in use. It is shown that there is a good correlation between the model and experimental results.
Ion Transfer at the Interface between Two Immiscible Electrolytes Formed by the Biphasic System Water-Propanol-Sucrose-PEG
Authors: Videa Marcelo V. , Martínez Juan Andrés &.
Published: December 2008

The study of ionic transference at the interface between two immiscible electrolytes (ITIES) has grown in interest in the last years, extending the type of interfaces formed by non-traditional immiscible electrolytes, like the ionic liquids, for example. In this work we present the development of a biphasic system which can be adopted for the development of novel interfaces for the ionic transfer. The composition of the two-phase system is based on water, sucrose, propanol and polyethylenglycol (PEG). The partition coefficients of lithium chloride, potassium thiocyanate, bis-(triphenylenphosphoran-ylidene) ammonium chloride and thiocyanate in the biphasic system were determined. From these measurements, lithium chloride and bis-(triphenylenphosphoran-ylidene) ammonium thiocyanate were selected as supporting electrolytes. An electrochemical window of 1000 mV was determined form cyclic voltammetry experiments.
Electrochemical Characterization of Nitrate Reduction on Recently Deposited Cooper Nuclei
Authors: Aguilar-Sanchez Miriam , Palomar-Pardavé Manuel E. , Scharifker Benjamin R. , Mostany Jorge , Ramírez-Silva Maria T. , Romero-Romo Mario A.
Published: December 2008

This work shows that nitrate ion reduction occurs on electrochemically deposited copper nuclei over a glassy carbon electrode in aqueous acid media. It was found that plots of J vs v1/2 at constant [NO3-] and J vs [NO3-], with constant sweep speed (v) the Randles-Sevick equation gives a congruent diffusion limiting rate that involves NO(g) formation, through transfer of 3 electrons. Under hydrodynamic conditions imposed on the electrode, it was possible to observe the simultaneous reduction of protons and nitrates with a deviation of the Levich equation at high rotation speeds
Electro-reduction of Nitrate and Nitrite Ions on Carbon-Supported Pt Nanoparticles
Authors: Estudillo Wong Luis A. , Alonso Vante Nicolas , Manzo Robledo Arturo
Published: December 2008

Synthesized carbon-supported Pt nanoparticles (10 wt% Pt/C) and their commercial counterpart (40 wt% Pt-Etek/C) have been used to study the electrochemical reduction of NOx- ions at different concentrations in alkaline and acid pH. A comparative study between nanostructured and massif platinum was evaluated. Cycling Voltammetry (CV), Rotating Disc Electrode (RDE) and Differential Mass Spectrometry (DEMS) were used for this purpose. Stationary current-potential curves indicate that the adsorption-desorption phenomena take place in two different regions of potential: the electrochemical reduction of NOx- ions for potentials ranging from -0.60 to -0.95 V/SCE, and the hydrogen evolution reaction (HER) at potential lower than -0.95 V/SCE. These results confirmed that the reduction of NOx- ions follows the order Pt/C > Pt-Etek/C > Pt-massif. DEMS demonstrated the formation of nitrogen species such as N2, NO, N2O and NO2.
Electrochemical Incineration of Indigo Textile Dye in Filter-Press-Type FM01-LC Electrochemical Cell Using Mesh-DSA Anode
Authors: López Oscar , González Ignacio , Nava José L.
Published: December 2008

This work shows results obtained in the incineration of 1 mM indigo textile dye (536 ppm COD) in 0.05 M NaCl aqueous media (which resembles a denim laundry industrial wastewater). Electrolyses studies indicated that oxidation of indigo dye was carried out via hydroxyl radicals (OH•) formed by water oxidation on the mesh-DSA (Ti/IrO2-SnO2-Sb2O5) electrode. Electrolyses in a FM01-LC reactor were performed at Reynolds between 50 < Re < 300, and a fixed current density of 7 mA cm-2. The experimental set-up achieved 100% in color removal, indigo mineralization, and 80% in current efficiency. The rate of degradation of indigo was not a function of the hydrodynamics, proving that this process is not controlled by mass transport. The FM01-LC equipped with mesh-DSA improves space-time yield, allowing better interaction between DSA(OH•) and organics, a phenomenon that increases organic mineralization efficiency.
Potassium Ferrate and/or Sodium Ferrate Generation Using a Prototype of Electrochemical Reactor without Membrane
Authors: López Juan R. , Peñuelas Fong Dora C. , Méndez Herrera Perla F. , Pérez Sicairos Sergio , Calderón Ayala Ignacio , Ortíz del Castillo Jesús R.
Published: December 2008

In this work, electrochemical generation of ferrate ion (FeO4-2) using a prototype of batch electrochemical reactor with agitation was studied. The anode used was a piece of steel tube (ASTM-A53) of 2 inches of nominal diameter and the cathode used was a steel bar of 0.5 inches. In the electrochemical reactor we did not use membranes, in order to diminish production costs and to make it a much more competitive and attractive process. Two different electrolytes were tested as reactant medium in the system: NaOH (10 M) and KOH (10 M). A current density of 53.62 mA/cm2 was applied with respect to the anode during a period of time of two hours. Afterwards the concentration of ferrate was determined in function of time using a spectroscopy method. It was found that the concentration of ferrate is higher in NaOH as reactant medium than KOH.
Electrochemical Evaluation of the Properties of the Immobilized Enzyme Glucose Oxidase
Authors: Stoytcheva Margarita S. , Zlatev Roumen K. , Velkova Zdravka , Salas Benjamin V. , Ovalle Marcela M.
Published: December 2008

The enzyme glucose oxidase was evaluated as a recognition element in electrochemical biosensors. Immobilization techniques as physical adsorption, entrapment in electrogenerated polymer film, affinity and covalent binding are discussed based in the involved physicochemical and kinetic phenomena. This includes the determination of the main kinetic parameters: apparent Michaelis-Menten constant Kmapp and maximal rate Imax of the heterogeneous enzyme reactions of glucose oxidation in the absence and in the presence of inhibitors. Parameters as pH, optimal temperature and stability of the biocatalyst were established analyzing the transfer function of the developed amperometric glucose oxidase sensors of first and second generation I=Imax [S] / (Kmapp + [S]).
Electrochemical Response of Flavonoids in Model and Real Samples at Screen-Printed Carbon Electrodes and Modified with Nanotubes
Authors: Davila Martin M. , Flores María S. , De la Paz Elizalde María
Published: December 2008

Five phenolic compounds, (+)-catechin, (-)-epicatechin, (-)-epigallocatechin, (-)-epigallocatechin gallate and quercetin prepared in methanol solution were investigated with respect to their electrochemical response after long time storage at screen-printed carbon and at modified with carbon nanotube electrodes. The differential pulse voltammograms for these compounds showed a shift of their potential peaks and a change in the current intensity with the storage time. The differential pulse voltammograms showed that for (+)-catechin, (-)-epicatechin and (-)-epigallocatechin the current intensity decreased slowly with the storage time. From these results it was concluded that by differential pulse voltammetry the stability and the level of the antioxidant capacity of phenolic standard solutions can be monitored. The interaction of phenolic compounds in binary solutions is also discussed.
Pencil Electrodes for Determination of Dopamine, Serotonin and Ascorbic Acid
Authors: Galván-Valencia Marisol , Albino-Navarro Gregorio , Flores-Morales Virginia , Durón-Torres Sergio M.
Published: December 2008

In this work a graphite pencil electrode is used to determine ascorbic acid, dopamine and serotonin. The electrochemical technique employed was cyclic voltammetry. These low cost electrodes were able to detect the biomolecules in the order of mM concentration. The oxidation peak potentials for the analytes are similar to those already reported, although a better peak definition was obtained. Also, this report includes the effect of the pH over the oxidation potential of these three species.
Electrochemistry and Spectrophotometric Study for Boron-Azomethine-H Complex Detection
Authors: Ramírez Ortega David , Ramírez-Silva Maria T. , Alvarez-Diduk Ruslán , Alarcón Ángeles Georgina , Rojas-Hernándéz Alberto
Published: December 2008

Boron is an essential element for plants and fruits: its deficiency is known to be the cause of growth damages, like in form and color, whereas its excess can be toxic. The fundamental importance of boron to animals and humans has not been identified, although excess boron can seriously affect human health. Thus, boron determination is important, so numerous research works have determined the element through spectrophotometric methods, based on the formation of the boron-azomethine-H complex. However, the methods based on this principle that are proposed exhibit inconsistencies, because at pH 4 - 8, the wavelengths 400 - 420 nm and analysis time, vary significantly, namely from 10 to 45min, thus making the methodology unreliable. This work focused on the formation of the boron-azomethine-H complex using UV-Vis; also, an electrochemical method was designed to determine boron, which resulted fast, simple and efficient, due to construction of a working electrode that indicates boron, based on its surface modification with B-Cyclodextrin, B-CD, and azomethine-H, where the former acts as recognition agent for boron, thus enabling potentiometric detection.
Electrochemical and Spectrophotometric Evaluation of the Formation Constants of the AA-βCD and DA-βCD Inclusion Complexes
Authors: Alarcón Ángeles Georgina , Corona- Avendaño Silvia , Palomar-Pardavé Manuel E. , Romero-Romo Mario A. , Rojas-Hernándéz Alberto , Ramírez-Silva Maria T.
Published: December 2008

This work shows the interaction of dopamine (DA) and ascorbic acid (AA) with β-cyclodextrin (βCD), by means of UV-VIS spectrophotomety and cyclic voltammetry, to demonstrate the formation of inclusion complexes of the species and to determine the values of the formation constants in aqueous media at pH 3.0, also through both methods. For the ascorbic acid-βCD complex (H2AA-βCD) a value of 3.5082 {plus minus} 0.0445 was found, while for the dopamine complex DA-βCD (H3DA+βCD) it was 3.772 {plus minus} 01631. With such values theoretical absorption spectra were generated which fitted quite well to the experimental ones, thus indicating clearly that the constants are reliable.
Voltammetric Study of Dental Solid Amalgams in HCl and their Application for Detecting Cu(II) Ions in Solution
Authors: Gonzalez-Lopez Julia L. , Carreon-Alvarez A. M. , Gomez-Salazar Sergio , Ibañez Jorge G. , Barcena Soto Maximiliano , Casillas Norberto
Published: December 2008

A voltammetric characterization of a dental amalgam and simple solid metal amalgams and their applications for detecting low concentrations of Cu(II) ions in solution is presented. Dental amalgams display a series of oxidation peaks characteristic of the different metal phases present. A reaction between deposited copper and γ2-Sn7-8Hg phase which transforms into a η'-Cu6Sn5 phase has been proposed to explain the well defined oxidation peaks in the potential range of-0.2 to 0.1 V vs. SCE. Dental amalgams were not found suitable for detecting Cu(II) ions in solution, due to the interference between the γ2-Sn7-8Hg oxidation peak and the copper stripping peak. Instead of a dental amalgam a silver amalgam, i.e, Ag-Hg, is recommended as a better option for detecting Cu(II) ions in solution at low concentrations. It yields a well defined oxidation peaks for copper stripping without having interfering oxidation peaks for the amalgam phase oxidation.
Electrochemical Methodology Based on Carbon Paste Electroactive Electrodes for Determination of Cyanide-Leachable Silver-Bearing Minerals in Flotation Heads
Authors: Gerónimo Carlos , Meléndez Angel M. , Lara Carlos , González Ignacio
Published: December 2008

Silver metallurgy is one of the more complex of all elements because of the large number of existing silver minerals that have different cyanide leaching properties. Voltammetric measurements have been applied on carbon paste electroactive electrodes (CPEEs), in order to asses if silver-bearing minerals in flotation heads are cyanide leachable. Electrochemical methodology has been applied to seven samples, each one from different Mexican mine sites. This methodology is based in a preliminar oxidation of samples (embedded in carbon paste electrodes) immersed in aqueous medium 0.3 M NaCN, both quiescent and disturbed. Reduction of previously oxidated silver-bearing minerals were identified in voltammogram. Results shown that signal intensity is not proportional to total silver content in each sample. Therefore, observed electrochemical response is associated only to cyanide-leachable silver, which is function of both the silver-bearing minerals and the formation of galvanic interactions between the phases present in flotation heads
Effects of Substrate Cooling on the Ionic Conductivity of Ta2O5 Solid-Electrolyte Thin Films Prepared by Reactive Sputtering Using H2O Gas
Authors: Abe Yoshio , Peng Fei , Takiguchi Yasuhiro , Kawamura Midori , Sasaki Katsutaka , Itoh Hidenobu , Suzuki Tsutomu
Published: December 2008

Hydrogen-containing tantalum oxide (Ta2O5:H) thin films, which are considered to be candidates for proton-conducting solid electrolytes, were prepared by reactive sputtering in H2O atmosphere. The substrate temperature during sputtering was changed from -20 to 70{degree sign}C. The H/Ta atomic ratio was found to increase with decreasing substrate temperature. The ion conductivity measured at room temperature also increased with decreasing substrate temperature, and a maximum conductivity of 4 × 10-8 S/cm was obtained at -20{degree sign}C. It is considered that the desorption rate of H2O molecules from the growing film surface was decreased by the substrate cooling, which resulted in the increase in the hydrogen content and the improvement of the ion conductivity.
Characteristics of Oxygen Reduction on Nanocrystalline YSZ
Authors: Huang Hong , Shim Joon-hyun , Chao Cheng-chieh , Pornprasertsuk Rojana , Sugawara Masayuki , Gür Turgut M. , Prinz Fritz
Published: December 2008

In this paper we present a series of experimental results indicating improved oxygen reduction characteristics on nanocrystalline YSZ surfaces. We compare 1) cathodic interface impedances on nanocrystalline and microcrystalline YSZ; 2) oxygen exchange rate on and bulk diffusivity in nano-YSZ and single crystal YSZ; and 3) bulk and surface conductivities of nano-YSZ. The results collectively indicate that oxygen reduction/exchange rate is faster on nanocrystalline YSZ than on micro- and single crystal YSZ, which likely is related to fast oxygen transport on the surface.
Effect of Temperature and Applied Potential on Oxygen Transport Paths around Gold / Ion Conducting Oxides Hetero Interfaces
Authors: Kishimoto Haruo , Sakai Natsuko , Yamaji Katsuhiko , Horita Teruhisa , Brito Manuel E. , Yokokawa H.
Published: December 2008

The effect of applied potential on the oxygen transport around gold / gadolinium doped ceria (GDC) or yttria stabilized zirconia (YSZ) was investigated by using oxygen isotope exchange and secondary ion mass spectrometry (SIMS). The active area of oxygen exchange was clearly observed along Au / YSZ / O2 triple phase boundary (TPB) treated under an applied potential (cathodic polarization) of E = -0.3 V at T = 773 K in dry O2, whereas no obvious activation was observed at E = 0 V. On the other hand, the activation of oxygen exchange was broadly observed on GDC surface around Au/GDC boundary, and it was remarkably enhanced by applying the electric potential of E = -0.3 V. The difference of oxygen transport path between Au/YSZ system and Au/GDC system was discussed in relation to the difference in chemical properties of electrolyte materials.