bluuebunny/crossref_metadata_2025 huggingface dataset:
Immunogenicity of a Reduced Schedule of Meningococcal Group C Conjugate Vaccine Given Concomitantly with the Prevenar and Pediacel Vaccines in Healthy Infants in the United Kingdom
Authors: Southern Jo , Borrow Ray , Andrews Nick , Morris Rhonwen , Waight Pauline , Hudson Michael , Balmer Paul , Findlow Helen , Findlow Jamie , Miller Elizabeth
Published: December 2008

This study investigated the use of two doses of three different meningococcal group C conjugate (MCC) vaccines when given for primary immunization with a seven-valent pneumococcal conjugate vaccine (PCV7) and Pediacel, a combination product containing five acellular pertussis components, diphtheria and tetanus toxoids,
Haemophilus influenzae
type b (Hib) conjugate, and inactivated-poliovirus vaccine. The immune response after a single dose of MCC is also presented. Infants were randomized to receive two doses of one of the MCC vaccines and PCV7 at 2 and 3 months or at 2 and 4 months of age. Meningococcal group C serum bactericidal antibody (SBA) geometric mean titers, Hib-polyribosylribitol phosphate (PRP) immunoglobulin G (IgG) geometric mean concentrations (GMCs), and diphtheria and tetanus antitoxin GMCs, together with the proportions of infants achieving putative protective levels, were determined. A total of 393 infants were recruited. Following the first dose of NeisVac-C (MCC conjugated to tetanus toxoid), 97% of infants achieved protective levels (SBA titer of ≥8), compared with 80% and 53%, respectively, for Menjugate and Meningitec (both of which are conjugated to CRM
197
). SBA responses to MCC vaccines were not significantly different when administered at 2 and 3 or 2 and 4 months of age. Following two doses of each MCC, 98 to 100% of infants achieved protective levels. Both PRP IgG and tetanus responses were significantly enhanced when Pediacel was coadministered with NeisVac-C. This study demonstrates that NeisVac-C and Menjugate generate good immunogenicity after the first dose at 2 months of age when coadministered with PCV7 and Pediacel and merit further investigation in single-dose priming strategies.
Cocirculation of Antigenic Variants and the Vaccine-Type Virus during the 2004-2005 Influenza B Virus Epidemics in Japan
Authors: Nakagawa Naoko , Higashi Natsumi , Nakagawa Toshimasa
Published: December 2008

In the 2004-2005 season, there was a large epidemic of the influenza B virus Yamagata group in Kobe, Japan. In hemagglutination inhibition tests, most of the clinical isolates from Kobe showed antigenicities similar to those of previous isolates (the vaccine-type virus). Only a few antigenic variants were isolated around the peak of the epidemic; however, Kobe residents developed antibodies against the variants during the season. The antigenic variants showed a one-point mutation of a nucleotide in the HA1 gene (C440A or G421A), which resulted in the substitution of one amino acid in the 150 loop of the HA molecule (T147N or G141R). The 150 loop is one of four epitopes of the hemagglutinin molecule of the influenza B virus. We established a system to detect one-point differences in the nucleotides of the 150 loop by means of high-resolution melting curve analysis with LCGreen. With this system, the isolates were determined to be the vaccine-type virus, antigenic variants, or a mixture of both. Some isolates were shown to be mixtures although they had been recognized as the vaccine-type virus with the hemagglutination inhibition tests. Thus, the antigenic variants appeared in the early period of the epidemic and were cocirculating with the vaccine-type virus during the epidemic.
Abbott RealTime Hepatitis C Virus (HCV) and Roche Cobas AmpliPrep/Cobas TaqMan HCV Assays for Prediction of Sustained Virological Response to Pegylated Interferon and Ribavirin in Chronic Hepatitis C Patients
Authors: Matsuura Kentaro , Tanaka Yasuhito , Hasegawa Izumi , Ohno Tomoyoshi , Tokuda Hiroshi , Kurbanov Fuat , Sugauchi Fuminaka , Nojiri Shunsuke , Joh Takashi , Mizokami Masashi
Published: December 2008

Two commercial real-time PCR assays are currently available for sensitive hepatitis C virus (HCV) RNA quantification: the Abbott RealTime HCV assay (ART) and Roche Cobas AmpliPrep/Cobas TaqMan HCV assay (CAP/CTM). We assessed whether the two real-time PCR assays were more effective than Roche Cobas Amplicor HCV Monitor test, v.2.0 (CAM) for prediction of the sustained virological response (SVR) to pegylated interferon (PEG-IFN) plus ribavirin (RBV) in chronic hepatitis C. Sixty patients chronically infected with HCV genotype 1b (37 males and 23 females, 53 ± 12 years of age) were treated with PEG-IFNα2b plus RBV for 48 weeks. Stored specimens at nine time points for each patient (at baseline, on treatment, and 24 weeks after treatment) were tested by the two real-time PCR assays and CAM. Twenty-six (43.3%) patients reached SVR. The positive predictive values (PPVs) for SVR of undetectable HCV RNA at week 12 by CAM, ART, and CAP/CTM were 74.3%, 88.0%, and 95.2%, respectively. An undetectable HCV RNA level by CAM, ART, and CAP/CTM correctly predicted SVR at week 4 in 100%, 100%, and 100% of patients, at weeks 5 to 8 in 91.7%, 100%, and 100% of patients, at weeks 9 to 12 in 55.6%, 75%, and 87.5% of patients, and at weeks 13 to 24 in 0%, 26.7%, and 40% of patients, respectively. Of 16 patients who relapsed after treatment, HCV RNA was detectable in 2 patients at the end of treatment by CAP/CTM but undetectable by ART and CAM. HCV RNA tests using ART and CAP/CTM are considered to be more effective at predicting SVR than CAM, and the PPV for SVR was slightly higher in CAP/CTM than in ART.
Proteasomal Turnover of Hepatitis C Virus Core Protein Is Regulated by Two Distinct Mechanisms: a Ubiquitin-Dependent Mechanism and a Ubiquitin-Independent but PA28γ-Dependent Mechanism
Authors: Suzuki Ryosuke , Moriishi Kohji , Fukuda Kouichirou , Shirakura Masayuki , Ishii Koji , Shoji Ikuo , Wakita Takaji , Miyamura Tatsuo , Matsuura Yoshiharu , Suzuki Tetsuro
Published: December 2008

We have previously reported on the ubiquitylation and degradation of hepatitis C virus core protein. Here we demonstrate that proteasomal degradation of the core protein is mediated by two distinct mechanisms. One leads to polyubiquitylation, in which lysine residues in the N-terminal region are preferential ubiquitylation sites. The other is independent of the presence of ubiquitin. Gain- and loss-of-function analyses using lysineless mutants substantiate the hypothesis that the proteasome activator PA28γ, a binding partner of the core, is involved in the ubiquitin-independent degradation of the core protein. Our results suggest that turnover of this multifunctional viral protein can be tightly controlled via dual ubiquitin-dependent and -independent proteasomal pathways.
Gene Regulation and Functional Alterations Induced by Kaposi's Sarcoma-Associated Herpesvirus-Encoded
ORFK13/vFLIP
in Endothelial Cells
Authors: Sakakibara Shuhei , Pise-Masison Cynthia A. , Brady John N. , Tosato Giovanna
Published: December 2008

Kaposi's sarcoma (KS) is an angioproliferative inflammatory disorder induced by endothelial cell infection with the KS-associated herpesvirus (KSHV).
ORFK13/vFLIP
, one of the KSHV genes expressed in KS, encodes a 188-amino-acid protein which binds to the Iκb kinase (IKK) complex to activate NF-κB. We examined
ORFK13/vFLIP
contribution to KS phenotype and potential for therapeutic targeting. Retroviral transduction of
ORFK13/vFLIP
into primary human endothelial cells induces the spindle morphology distinctive of KS cells and promotes the formation of abnormal vascular networks typical of KS vasculature; upregulates the expression of proinflammatory cytokines, chemokines, and interferon-responsive genes; and stimulates the adhesion of inflammatory cells characteristic of KS lesions. Thymidine phosphorylase, a cellular enzyme markedly induced by
ORFK13/vFLIP
, can metabolize the prodrug 5-fluoro-5-deoxyuridine (5-dFUrd) to 5-fluouridine (5-FU), a potent thymidine synthase inhibitor, which blocks DNA and RNA synthesis. When tested for cytotoxicity, 5-dFUrd (0.1 to 1 μM) selectively killed
ORFK13/vFLIP
-expressing endothelial cells while sparing control cells. These results demonstrate that
ORFK13/vFLIP
directly and indirectly contributes to the inflammatory and vascular phenotype of KS and identify 5-dFUrd as a potential new drug that targets KSHV latency for the treatment of KS and other KSHV-associated malignancies.
Comprehensive Profiling of Epstein-Barr Virus MicroRNAs in Nasopharyngeal Carcinoma
Authors: Cosmopoulos Katherine , Pegtel Michiel , Hawkins Jared , Moffett Howell , Novina Carl , Middeldorp Jaap , Thorley-Lawson David A.
Published: December 2008

Epstein-Barr Virus (EBV) establishes a long-term latent infection and is associated with a number of human malignancies that are thought to arise from deregulation of different stages of the viral life cycle. Recently, a large number of microRNAs (miRNAs) have been described for EBV, and it has been suggested that their expression may vary between the different latency states found in normal and malignant tissue. To date, however, no technique has been utilized to comprehensively and quantitatively test this idea by profiling expression of the EBV miRNAs in primary infected tissues. We describe here a multiplex reverse transcription-PCR assay that allows the profiling of 39 of the 40 known mature EBV miRNAs from as little as 250 ng of RNA. With this approach, we present a comprehensive profile of EBV miRNAs in primary nasopharyngeal carcinoma (NPC) tumors including estimates of miRNA copy number per tumor cell. This is the first comprehensive profiling of EBV miRNAs in any EBV-associated tumor. In contrast to previous suggestions, we show that the BART-derived miRNAs are present in a wide range of copy numbers from ≤10
3
per cell in both primary tumors and the widely used NPC-derived C666-1 cell line. However, we confirm the hypothesis that the BHRF1 miRNAs are not expressed in NPC. Lastly, we demonstrate that EBV miRNA expression in the widely used NPC line C666-1 is, with some caveats, broadly representative of primary NPC tumors.
Genome Comparison of a Nonpathogenic Myxoma Virus Field Strain with Its Ancestor, the Virulent Lausanne Strain
Authors: Morales Mónica , Ramírez Miguel A. , Cano María J. , Párraga Mario , Castilla Joaquín , Pérez-Ordoyo Luis I. , Torres Juan M. , Bárcena Juan
Published: December 2008

One of the best-studied examples of host-virus coevolution is the release of myxoma virus (MV) for biological control of European rabbits in Australia and Europe. To investigate the genetic basis of MV adaptation to its new host, we sequenced the genome of 6918, an attenuated Spanish field strain, and compared it with that of Lausanne, the strain originally released in Europe in 1952. Although isolated 43 years apart, the genomes were highly conserved (99.95% identical). Only 32 of the 159 MV predicted proteins revealed amino acid changes. Four genes (M009L, M036L, M135R, and M148R) in 6918 were disrupted by frameshift mutations.
Continuous, diurnally fluctuating turbidity currents in Kluane Lake, Yukon Territory
Authors: Crookshanks Sarah , Gilbert Robert
Published: December 2008

Modern sedimentary processes were studied in Kluane Lake, Yukon Territory, to determine the spatial and temporal patterns of sediment distribution in a large, dynamic, glacier-fed lake. Data from a river monitoring station, moored instruments, sediment traps, and water-column profiles in the lake were used to document lacustrine sedimentary processes in 2006 and 2007. During the peak melt season, the suspended sediment concentration of Slims River is weakly dependent on river discharge and can reach up to 5 g L–1, although a diurnal range between 1 and 2 g L–1 is more commonly observed. The high suspended sediment load in the river generates continuous, diurnally fluctuating turbidity currents in Kluane Lake with maximum velocities up to 0.6 m s–1. During times of peak flow, variations in velocity can be traced to beyond 4 km from the river mouth. The vertical concentration profiles, mass accumulation rates, and suspended sediment loads show distinctive longitudinal variations; the highest rate of accumulation occurs ∼1 km from the point of inflow, which is concurrent with a distinct change in flow structure. Diurnal laminations are apparent in sediment traps close to the point of inflow and can be directly linked to variations in current velocity; however, these laminations do not occur consistently over space or time. These results suggest that long-term measurement records of lacustrine turbidity currents provide valuable insights regarding the multiple scales of environmental variability and have important implications for paleoenvironmental reconstruction using lacustrine sediments.
Bacterial chemotaxis differences inEscherichia coliisolated from different hosts
Authors: Dzinic Sijana H. , Luercio Marcella , Ram Jeffrey L.
Published: December 2008

The mechanisms mediating the association between Escherichia coli and specific hosts are unknown. This study investigates the hypothesis that the host-specific associations of E. coli strains are mediated in part by differences in chemotaxis. To test this hypothesis, chemotactic responses of E. coli strains isolated from different host groups (carnivores, herbivores, and omnivores) were tested with various attractants. In low-density agar chemotaxis assays, the average motility of E. coli in response to aspartate, serine, and ribose among the different groups was not significantly different; however, strains from carnivores responded significantly more to aspartate, relative to their responses to serine, in comparison with strains from herbivores, which responded equally or better to serine than to aspartate. The relatively greater chemotactic response of strains from carnivores to aspartate than to serine was confirmed in a subset of strains by capillary chemotaxis assay. Differences in responses to serine and aspartate were not due to growth differences, as determined by comparison of 24 h growth curves with glycerol, aspartate, and serine carbon sources. The differences in chemotactic behavior of E. coli strains isolated from herbivores and carnivores support the hypothesis that host-specific associations of E. coli strains are mediated in part by differences in chemotactic behavior.
Measuring the competitiveness of Canadian pulp and paper in the US market reveals needs for more research
Authors: Tang Xiaoli , Kant Shashi , Laaksonen-Craig Susanna , Asinas Emmanuel R.
Published: December 2008

This paper studies substitution between main categories of imported pulp and paper products and between imported and domestic pulp and paper products in the US market. A restricted translog subcost function approach was employed to derive the elasticity of substitution. The results suggest that Canadian pulp and paper products are competitive and have maintained their competitiveness in the US market, and therefore, the challenges faced by the Canadian pulp and paper industry are not because of the loss of its product competitiveness but are due to other reasons such as declining demand for paper products in the United States. It seems that if the Canadian pulp and paper industry wants to retain its dominant position in the world market place, it will have to create global reach and develop new markets.
A spatiotemporal Ripley’sK-function to analyze interactions between spruce budworm and fire in British Columbia, Canada
Authors: Lynch Heather J. , Moorcroft Paul R.
Published: December 2008

In this paper, we extend traditional methods of spatial statistics to study spatiotemporal correlations between two different point processes. After introducing the methodology, we apply this analysis to a particular case study of interest in ecology, the interaction between damage by a particular forest pest (western spruce budworm ( Choristoneura occidentalis )) and forest fires. Our analysis, which covers parts of British Columbia in the 26-year period from 1970 to 1995, indicates that areas affected by budworm infestation have a significantly decreased risk of forest fire for the 7 years following the infestation. Conversely, forest fires decrease the risk of infestation for at least 6 years after the fire. These temporal correlations extend over a spatial range of at least 25 km. Our study rejects the common assumption that insect infestation necessarily results in increased fire risk. This case study illustrates the utility of point process modeling and spatial statistics to understanding ecosystem dynamics extending over both space and time.
Long-term recovery of vegetation communities after harvesting in the coastal temperate rainforests of northern British Columbia
Authors: Banner Allen , LePage Philip
Published: December 2008

We sampled second-growth forests ranging in age from 28 to 98 years and compared them with old-growth forests to quantify rates of terrestrial vegetation recovery following harvesting on the northcentral coast of British Columbia. Species richness approximately doubles, while Simpson’s index of diversity increases from 0.81 to 0.91 from young to old forests. Nonmetric multidimensional scaling ordinations showed differentiation, with some overlap, of old-growth and second-growth forests and a fairly strong correlation of stand age with plot scores, driven by plant species presence and cover. Vegetation succession following logging disturbance is driven primarily by predisturbance species composition; most species found in the young forests are present in old forests and the higher species richness typical of old growth is largely due to the establishment of additional cryptogam and herb species of low cover and constancy. Significantly higher cover of shrub, herb, and bryophyte species differentiates old forests from second-growth forests. Forests 41–100 years old average 63%–73% similarity (depending on site type) to old-growth forests based on species presence–absence and 53%–58% similarity based on species cover. The scarcity of western redcedar ( Thuja plicata Donn ex D. Don) in second-growth stands is of particular concern because of the high ecological, cultural, and economic importance of this tree species.
Do decomposing Scots pine, Norway spruce, and silver birch stems retain nitrogen?
Authors: Palviainen Marjo , Laiho Raija , Mäkinen Harri , Finér Leena
Published: December 2008

The contents of nitrogen (N) have generally been observed to increase in the early stages of decomposition in coarse woody debris and then to decrease slowly. This is potentially an important mechanism of nutrient retention in ecosystems after disturbances. We studied N dynamics in decomposing Scots pine ( Pinus sylvestris L.), Norway spruce ( Picea abies (L.) Karst.), and silver birch ( Betula pendula Roth.) stems in Finland. The oldest stems had decomposed for 34 (spruce and birch) or 45 (pine) years. Concentrations of N in both fallen logs and standing snags increased and C/N ratios decreased with time, and birch had significantly higher N concentrations and lower C/N ratios than pine and spruce. Even though increased N contents were observed in some cases, N was generally already released in the early stages of decomposition and more rapidly from birch than from conifers. Based on model analysis, from 40% (pine and spruce) to 50% (birch) of initial N was released within 30 years. The results suggest that decomposing stems of especially Scots pine and Norway spruce retain N rather effectively in boreal forest ecosystems and form a long-term, small but steady N pool with a slow release rate.
XANES AND ATOMIC FORCE MICROSCOPY STUDIES ON PRE- AND POST-IRRADIATED SAPPHIRE
Authors: BHARDWAJ D. M. , JAIN D. C. , KUMAR RAVI , GUPTA R. P. , GARG K. B.
Published: December 2008

XANES measurements at the Fe - K edge on natural South African sapphire single crystal (corundum) and an irradiated sample with fluence 1 × 1012 Ni 6+ ions/cm 2 are reported. Some decrease in intensity of pre-edge features (1s → 3d) and increase in intensity of 1s → 4p transition in Fe is observed with Ni fluence. Structural changes and modification on surface of irradiated sapphire with Ni 6+ ion have been observed by the atomic force microscopy technique and discussed in the term of defects.
CHIRALITY VS. HOMFLY AND KAUFFMAN POLYNOMIALS
Authors: GANZELL SANDY , KAPP AMY V.
Published: December 2008

We exhibit an infinite family of knots that are detected chiral by the Kauffman polynomial but not by the HOMFLY polynomial.
KNOT GROUPS AND SLICE CONDITIONS
Authors: HILLMAN J. A.
Published: December 2008

We introduce the notions of "k-connected-slice" and "π1-slice", interpolating between "homotopy ribbon" and "slice". Every high-dimensional knot group π is the group of an (n - 1)-connected-slice n-knot, for all n ≥ 3. However, if π is the group of an n-connected-slice n-knot, the augmentation ideal I(π) has deficiency 1 as a module, while (n + 1)-connected-slice n-knots are trivial. If π is the group of a π1-slice 2-knot and π' is finitely generated, then π' is free, and so def(π) = 1.
KHOVANOV–ROZANSKY GRAPH HOMOLOGY AND COMPOSITION PRODUCT
Authors: WAGNER E.
Published: December 2008

In analogy with a recursive formula for the HOMFLY-PT polynomial of links given by Jaeger, we give a recursive formula for the graph polynomial introduced by Kauffman and Vogel. We show how this formula extends to the Khovanov–Rozansky graph homology.
THE WRITHE OF ORIENTED POLYGONAL GRAPHS
Authors: LAING CHRISTIAN , SUMNERS DE WITT
Published: December 2008

Given an edge-oriented polygonal graph in ℝ3, we describe a method for computing the writhe as the average of weighted directional writhe numbers of the graph in a few directions. These directions are determined by the graph and the weights are determined by areas of path-connected open regions on the unit sphere. Within each open region, the directional writhe is constant. We obtain a closed formula which extends the formula for the writhe of a polygon in ℝ3, including the important special case of writhe of embedded open arcs.
Effect of Natural Rubber Electrolytes Modified with CdCl2, MgCl2, MoCl2, NiCl2 and Active Carbon
Authors: Borowski Tomasz
Published: December 2008

Natural rubber (NR), as a solvent and repository of electric charges, starts to gain these properties after adding to NR CdCl2 or MgCl2 or MoCl2 or NiCl2 in the form of methanol solution with addition of active carbon. Electrical conductivity of such a NR - active carbon system with added NR CdCl2 or MgCl2 or MoCl2 or NiCl2 equals to 106 to 105 S-cm1 at a room temperature of 293 K and a frequency of 10 kHz. The examined electrolytes were tested for the frequency range of 1 kHz to 25 kHz. These polymer electrolyte systems may find their application as materials for anticorrosive and antielectrostatic protection of fuel or hazardous material tanks.
Effect of Coating Layer Thickness on Corrosion Detection
Authors: Wheat Harovel G. , Liu Guangjuan
Published: December 2008

Corrosion in steel and aluminum alloys can be detected based on coatings that incorporate corrosion indicators. Coating systems typically consist of a primer and a topcoat and the indicator is in the primer. In this investigation, the corrosion indicator is positive for steel; it is initially non-fluorescent, but glows over areas of corrosion. The corrosion indicator is negative for aluminum alloys; it is normally fluorescent and that fluorescence is quenched in the presence of corrosion. Specimens were prepared with different layers; primer and/or topcoat and different layer thicknesses. The specimens were exposed to saltwater conditions and examined as a function of time using a UV lamp in combination with optical microscopy. The specimens were also examined using EIS as a function of exposure. The effect of the coating and coating layer thickness will be discussed.
Kinetics and Structure Aspects of the Dissolution of Metals in Acids
Authors: Schorr Michael , Valdez Benjamin S. , Stoytcheva Margarita S. , Zlatev Roumen K.
Published: December 2008

The dissolution of metals in acids is a heterogeneous electrochemical reaction, taking place at the interface between a solid and a liquid, described in terms of energy and configuration of the species involved. The energy of activation for two stainless steels in phosphoric acid was determined from their corrosion rates in the temperature range 50-120 oC, applying the Arrhenius equation. Energy of activation values for the overall process of anodic metal dissolution and cathodic liberation of hydrogen are in the 10-20 Kcal.gat-1 range. Metal corrosion is a structure sensitive process; its mechanism and rate are related to the density of surface defects, based on the Boltzman expression. A model for the activated complex is proposed based on considerations of energy and configuration. This work is an integration of a theoretical analysis and an experimental investigation of metal corrosion in acids.
Electrochemical Behavior of Ru-based Electrocatalysts for the ORR in the Presence of C2H5OH
Authors: González Ramírez S.E. , Rodríguez Varela F. J. , Dabek Klapco R.
Published: December 2008

We report on the electrochemical behavior of Ru/C electrocatalysts for the Oxygen Reduction Reaction (ORR) in an acid medium without and with ethanol. As a reference, a Pt/C electrocatalysts was also studied. The results show that Ru/C has a lower catalytic activity for the ORR related to Pt/C in a substance-free electrolyte. However, this study shows that Ru/C possess a high degree of tolerance to C2H5OH, i.e., the shift in onset potential for the ORR () is negligible on this electrocatalyst. In contrast, the catalytic capacity of Pt/C is considerably diminished when alcohol is added to the electrolyte. The shift in from its value in the absence to its value in the presence of C2H5OH on a 10% Ru/C electrocatalyst is 15 times smaller than the shift on 20% Pt/C. Based on these results, the specific application of Ru/C-based electrocatalysts may be in Direct Alcohol Fuel Cells.
Preparation and Evaluation of Electrocatalysts to Generate Oxygen Bubbles for the Electroflotation Process
Authors: Perez M. R. , Oropeza Mercedes T. , Nava José L. , González Ignacio , Gradilla Martinez Israel
Published: December 2008

Oxygen evolution electrocatalysts were prepared and evaluated by accelerated life tests under extremely oxidation conditions. Experiments were done using chronopotentiometry for each electrode in H2SO4 1 M applying 1Acm-2. The aim of this test was to compare the operating life of different electrodes related to the stability and predict electrocatalyst loss during electrolysis. Results showed that IrO2-SnO2-Sb2O3 was the more durable electrode. In addition, superficial characterization for catalytic electrodes with Scanning Electrón Microscope SEM and Energy Dispersive X-Ray Spectroscopy EDS o EDX, were performed before and after the accelerated test.
Comparative Study of Polypyrrole Electrochemical Deposition onto Different Substrates
Authors: Garfias-García Elizabeth , Romero-Romo Mario A. , Ramírez-Silva Maria T. , Morales Jesús , Paloma-Pardavé Manuel
Published: December 2008

The present research work studied the polypyrrole's electrochemical formation process onto glassy carbon and gold electrodes in the presence of nitrates. During the first cycle of its potentiodynamic growth, the oxidation potential was independent of the nature of the electrode used. However, once the polypyrrole had been deposited, for example onto gold, the subsequent oxidation process potential occurs at a slightly smaller value as compared to when deposition took place onto the glassy carbon electrode, which suggests that different oligomeric pyrrole species Pyn, are undergoing oxidation, implying a strong dependence on the substrate's nature. The study conducted under potentiostatic conditions showed that polypyrrole's electrochemical growth on the gold electrode is limited by diffusion, rather than by incorporation of diverse pyrrole's oligomeric species, as was the case for the glassy carbon electrode.
Quantum-Chemical Calculations of the Electronic Properties of Pyrrole Oligomers
Authors: Cuan Angeles , Ramírez-Silva Maria T. , Romero-Romo Mario A. , Palomar-Pardavé Manuel E.
Published: December 2008

The electrochemical pyrrole polymerization mechanism at initial stages is theoretically studied through sequential monomer units coupling to obtain 2 to 9 oligomer formation. The relevance of these oligomers lies on their solubility in water as well as on the influence in uniformity of the final polymer film. The dependence of the growing chain electronic properties has been studied by the Polarizable Continuum Method (PCM) taking into account the influence of water as solvent effect. It was observed that the |HOMO-LUMO| energy difference, defined as Eg, decreases as the delocalization (resonance) of the π-electrons increases within the 5-member rings, which occur while the length of the oligomer molecule increases in line with literature reported experimental observation. The improvement in electron conduction of the stepwise oligomer product as a function of its chemical structure is also discussed.
Characterization of Vapor Phase Copper Corrosion Products Using Electrochemical Methods
Authors: Bastidas David M. , Cano Emilio , La Iglesia Victoria M. , Bastidas Jose M.
Published: December 2008

The copper corrosion products originated by the action of formic, acetic and propionic acid vapors at a 100% relative humidity were studied for a period of 21 days. Five formic, acetic and propionic vapor concentrations (10, 50, 100, 200 and 300 ppm) were tested. The corrosion-product layers were characterized using electrochemical methods. Some of the compounds identified were: cuprite (Cu2O), for the three acids; cupric hydroxide monohydrate (Cu(OH)2•H2O) and copper formate tetrahydrate (Cu(HCOO)2•4H2O), for formic acid; copper acetate dihydrate (Cu(CH3COO)2•2H2O) and copper hydroxide acetate dihydrate (Cu4(OH)(CH3COO)7•2H2O), for acetic acid; and copper propionate (Cu4(OH)(CH3CH2COO)7•2H2O) for propionic acid.
Voltammetric Characterization of Liquid/Liquid Interfaces Modified with Cetyl-Trimethyl-Ammonium Bromide (CTAB)
Authors: Gallegos Covarrubias Belinda , Estrada-Vargas Arturo , Carreon Gutierrez Carlos A. , Barcena Soto Maximiliano , Casillas Norberto
Published: December 2008

In this paper a voltammetric study of a three-phase system modified with the surfactant CTAB in a liquid/liquid interface is presented. The three-phase system consists of a nitrobenzene microdroplet (1μL) with 0.1 M ferrocene, immobilized in a paraffin impregnated graphite electrode and immersed in a LiClO4 solution. Surfactant molecules present at the interface increase the ClO4¯ ion transfer resistance at low concentrations, and the ferrocenium ion transfer at high concentrations. A current mapping of the ClO4¯ ions around a nitrobenzene microdroplet using SECM is included. SECM results demonstrate that ionic transport takes place at the three-phase region, according to data published in the literature. Experimental data simulations using the finite element method qualitatively describe the system.
Electrochemical Study of Dopamine and Ascorbic Acid by Means of Supramolecular Systems
Authors: Ramirez-Silva Maria T. , Alarcón Ángeles Georgina , Corona- Avendaño Silvia , Palomar-Pardavé Manuel E. , Merkoçi Arben , Romero-Romo Mario A. , Rojas-Hernándéz Alberto
Published: December 2008

The present research work presents the results concerning the effect of the modifications done on a carbon paste electrode, CPE, through using supramolecular systems, such as: multiwalled carbon nanotubes, MWCNT, b-cyclodextrin, b-CD, and a new conducting polymer electrochemically formed on the CPE, via polymerization of the b-CD, polyb-CD. Such systems induced increases in the heterogeneous reaction constants k0 and on the ratio jap/jcp, and a decrease in the Ep difference, as compared to the unmodified CPE. Also, the determination of dopamine, DA, was carried out from a commercial pharmaceutical product in the presence of ascorbic acid, AA, with the CPE/poly-b-CD and the CPE/MWCNT/b-CD, because these gave the best analytical parameters for the quantification of DA, giving satisfactory results.
Electrochemical Study of Phenolic and Quinoid Derivatives with Putative Activity on Ion Channels
Authors: Rodríguez-Fernández Thalina , García-Valdés Jose de Jesus , Ugalde-Saldívar Victor , González Ignacio
Published: December 2008

Conduction across ion channels is fundamental for many physiological processes. BK channel is modulated by several stimuli as calcium, ATP, naphtoquinones and thymol; the last two develop opposite action: decreasing or increasing ion flow. These effects could be explained because both compounds have different redox properties: naphtoquinones as oxidants and thymol as reductant. Redox potential for these compounds could be modified by different substituent addition, thus, five naphtoquinone and four phenolic derivatives were selected to be studied by cyclic voltammetry. Compounds as 5-hydroxy-1,4-naphtoquinone versus 2-amine-1,4-naphtoquinone and 2-isopropyl-5-methyl-phenol (thymol) versus 2,4,6-trimethyl-phenol showed the largest difference in peak potential. Then, these compounds will be considered to assess their action by electrophysiological trials on BK channel. At this moment only the study with thymol was carried out and it was found, for the first time, an increase in BK channel currents expressed in Xenopus oocytes.
Application of MWCNT to Study Azometine-H by Cyclic Voltammetry
Authors: Alarcón Ángeles Georgina , Ramírez-Silva Maria T. , Corona- Avendaño Silvia , Romero-Romo Mario A. , Palomar-Pardavé Manuel E. , Rojas-Hernándéz Alberto
Published: December 2008

This work deals with the electrochemical study of Azometine-H by mean of cyclic voltammetry using a carbon paste electrode modified with multi-wall carbon nanotubes, MWCNT, and b-Cyclodextrin. The results obtained evidence that it possible to follow the electrochemical evolution of the azometin-H at pH 7.0 and that the use of an electrode modified with carbon nanotubes improved the electrochemical response, favoring the electron transfer and increasing the oxidation peak's current, as compared with a conventional carbon paste electrode. Further, it was found that the azometine-H displayed an adsorption process associated to the interaction between the compound under study and the b-ciclodextrin.
Development of a Polypyrrole Selective Membrane For The Potentiometric Quantification of Saccharinate Anion
Authors: Lozada Ascencio Sandy M. , Alvarez Romero Giaan A. , Rodríguez Ávila José A. , Galán Vidal Carlos A. , Páez Hernández María E.
Published: December 2008

A selective electrode for the quantification of saccharinate ion based on a polypyrrole-doped membrane is developed. The membrane is electrochemically prepared using stainless steel as working electrode. Potentiostatic variables for membrane growing such as pyrrole concentration, saccharinate concentration, applied potential and deposition time are optimized in order to maximize sensibility. The optimized membrane was analytically characterized by means of calibration curves, the detection limit was found to be 3.6 x 10-4 M and the quantification limits were found between 5 x 10-4 M and over 1 M. Selectivity of the membrane is evaluated for different inorganic anions, resulting in the following selectivity coefficients: pKSaccharinate,Citrate= 3.4, pKSaccharinate,H2PO4= 3.4, pKSaccharinate,HPO4-2= 3.4 y pKSaccharinate,SO4-2= 2.5. This results demonstrate an adecuate performance of the proposed selective polypyrrole membrane so it can be considered as an alternative to the tradicional analytical methods for the direct quantification of sacarine in diverse samples.
Electrochemical Determination of the Antioxidant Capacity of Organic Compounds
Authors: Alvarez-Diduk Ruslán , Ibarra-Escutia Pedro , Marty Jean-Louis , Galano Annia , Rojas-Hernándéz Alberto , Ramírez-Silva Maria T.
Published: December 2008

This work analyzes different proposals concerning the importance of organic compounds to determine their antioxidant capacity per equivalent, among which that of ({plus minus})-6-Hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid, trolox, is considered because it is based on a stable radical reaction 2,2-Diphenyl-1-picryl-hidrazyl, DPPH, with trolox; the decrease of the DPPH signal given by trolox is compared to that of trolox with the species of interest. The study was carried out electrochemically and spectrophotometrically, although it was also determined using biosensors with tyrosinase, which analyzes the response of the biosensor in the presence of catechol to determine thus the antioxidant capacity referred to catechol equivalents, monitoring the substrate's amperometric signal. The reaction was analyzed with the Folin-Ciocalteu reagent to determine total phenol compounds, comparing with the results from the methods used.
Effect of CTAB Interfacial Supramolecular Systems on the Voltammetry Signals of Adrenalin and Ascorbic Acid
Authors: Corona- Avendaño Silvia , Alarcón Ángeles Georgina , Romero-Romo Mario A. , Ramírez-Silva Maria T. , Palomar-Pardavé Manuel E.
Published: December 2008

A carbon paste electrode and the cationic surfactant cetyltrimethyl ammonium bromide, CTAB, were used to carry out an electrochemical study at pH 3 in 0.1 M NaCl by means of differential pulse voltammetry (DPV), to discern the effect of the surfactant on the electrochemical signals of the analytes. It was shown that the oxidation process of adrenaline was not favored, whereas the opposite is truth for the ascorbic acid, due to electrostatic interactions between the CTAB and the analytes. Further, the effects observed may be used advantageously to separate the respective signals in sample containing both analytes, to manufacture thus an electrode to determine both species.
Pb Detection in Soil Samples by Electroanalysis: Cyclic Voltammetry and Osteryoung Square Wave Stripping Voltammetry
Authors: Beristain-Ortiz Gabriela , Sumbarda Ramos Emgdia G. , Garcia M. G. , Oropeza Mercedes T.
Published: December 2008

Carbon Paste Electrodes (CPE) and Chemical Modified Electrodes (CMEs) are proposed as Pb sensors for soil samples treated with ammonium acetate. The extracted fraction were analyzed by electroanalytical techniques. The use of CPE and CMEs in conjunction with electroanalytical techniques as Cyclic Voltammetry (CV) and Anodic Stripping Voltammetry with Osteryoung Square Wave (OSWSV) showed to be very suitable to analyze the lead content in samples (under 10 ppm) of dangerous residues collected from a historically polluted site in Tijuana B.C., Mexico.
Electroanalytic Study of Nitrates Detection using Cooper and Glassy Carbon Electrodes Modified with Copper Nuclei
Authors: Aguilar-Sanchez Miriam , Corona- Avendaño Silvia , Ramírez-Silva Maria T. , Palomar-Pardavé Manuel E. , Scharifker Benjamin R. , Mostany Jorge , Romero-Romo Mario A.
Published: December 2008

The results obtained in the present work indicate that during electrochemical reduction of nitrate ions, the glassy carbon electrode modified with copper nuclei electrodeposited displayed the best analytic parameters, as follows: a sensitivity of 2.44 {plus minus} 0.04 / A cm-2 M-1, a detection limit of 2.20 {plus minus} 0.10 mM, a linearity range of 3.69 - 43 mM and a quantification limit of 7.33 {plus minus} 0.08 mM. However, the copper electrode also gave reliable analytic parameters although with a concentration range smaller than that of the glassy carbon.
PLD-deposited (BaxSr1-x)(CoyFe1-y)O3-δ Thin-Film Microelectrodes: Structure Aspects and Oxygen Incorporation Kinetics
Authors: Wang Lei , Merkle Rotraut , Cristiani Georg , Stuhlhofer Benjamin , Habermeier Hanns-Ulrich , Maier Joachim
Published: December 2008

Among the mixed conducting perovskites, (BaxSr1-x)(CoyFe1-y)O3-d (BSCF) attracts special attention due to its exceptionally high effective oxygen incorporation rate constant. The structure of the dense BSCF thin films prepared by pulsed laser deposition (PLD) was investigated. Long-term stability of the cubic perovskite phase for different cation compositions at intermediate temperatures was evaluated. The surface resistance Rs associated with the oxygen incorporation reaction for different cation compositions was determined from impedance spectroscopy measurements on dense thin-film microelectrodes without interference from electrode morphology. The correlation between some bulk properties and Rs was studied.
Impact of Electrochemical Reaction Mechanisms on Overpotentials in the Solid Oxide Fuel Cell Anode
Authors: Grew Kyle N. , Izzo John R. , Chiu Wilson
Published: December 2008

Further improvements of the solid oxide fuel cell (SOFC) performance, reliability, and durability are necessary for the SOFC to become an attractive option for wide spread use. If we are to meet these challenges, an advanced understanding of the materials and structures are necessary. To aid in development of this advanced understanding, this work will develop a methodology for the pore-scale modeling of coupled mass transfer, electronic and ionic charge transfer, and the associated interfacial electrochemical reactions within the detailed anode microstructure. The approach provides the capability for understanding the effects of the coupling between the transport and reaction processes. Just as importantly, by taking a pore-scale approach, a direct understanding of the impact of the microstructure on the transport and reaction processes can be gained on a non-empirical basis.
Effect of A-site Deficiency on Mixed Conducting Properties of (Ba,Sr)(Co,Fe)O3-δ Electrodes for Solid Oxide Fuel Cell
Authors: Kim Yu-Mi , Bae Joongmyeon
Published: December 2008

The effect of A-site deficiency on mixed conducting properties was investigated in (Ba,Sr)(Co,Fe)O3-d (BSCF) perovskite structure cathode material for solid oxide fuel cells (SOFC). For this purpose, BSCF powders with various Sr deficiencies were synthesized via a glycine nitrate process (GNP), followed by calcinations at 1273 K for 10 h. From the structural analyses, the lattice parameter increased with Sr deficiency increased, and the electrode had better sinterability with respect to Sr deficiency. Moreover, from the electrochemical analyses, the electrical conductivity decreased and area specific resistance (ASR) value increased as Sr deficiency increased.
Pd-promoted La0.75Sr0.25Cr0.5Mn0.5O3/YSZ Composite Anodes for Solid Oxide Fuel Cells
Authors: Jiang San Ping , Ye Yinmei
Published: December 2008

Palladium-impregnated La0.75Sr0.25Cr0.5Mn0.5O3-δ/yttria-stabilized zirconia (LSCM/YSZ) composite anode is investigated in detail for the direct utilization of methane in solid oxide fuel cells (SOFCs). Impregnation of Pd nanoparticles significantly promotes the electrocatalytic activity of LSCM/YSZ composite anodes for the methane oxidation reaction in wet CH4. At 800{degree sign}C, the electrode polarization resistance for the methane oxidation is reduced by a factor of 3 after impregnation of 0.10 - 0.66 mg cm-2 Pd. Pd impregnation primarily enhances the diffusion and dissociation associated with the electrode processes at low frequencies. No carbon deposition was observed for the reaction in wet CH4 on Pd-impregnated LSCM/YSZ composite anodes. In contrast, Pd impregnation has little effect on the hydrogen oxidation in wet H2. The results demonstrate that the Pd-impregnated LSCM/YSZ composite is a promising carbon-tolerant anode for natural gas fuel-based SOFCs.
Evaluation of LSF based SOFC Cathodes using Cone-shaped Electrodes
Authors: Kammer Hansen Kent , Mogensen Mogens
Published: December 2008

Seven La1-xSrxFeO3-δ (x = 0, 0.05, 0.15, 0.25, 0.35, 0.50, 0.70) based perovskites were synthesized using the glycine-nitrate method. The La1-xSrxFeO3-δ compounds were characterized with powder X-ray diffraction and electrochemical impedance spectroscopy on cone-shaped electrodes using a Ce1.9Gd0.1O1.95 electrolyte. The activity of the La1-xSrxFeO3-δ based perovskites towards the electrochemical reduction of oxygen was strongly dependent of the strontium content, the activity being highest for the composition La0.85Sr0.15FeO3-δ. The results indicates that Fe(III) is the catalytic active specie towards the electrochemical reduction of oxygen in a solid oxide fuel cell on La1-xSrxFeO3-δ compounds. The results also show that oxide ion vacancies in the perovskite structure are important for the electrochemical reduction of oxygen. However, the effect of ordering of oxide ion vacancies for the strontium rich compounds can not be excluded.
Electronic and Local Structures of La1-x SrxCoO3-δ Studied by In-Situ Micro XAS Measurements
Authors: Amezawa Koji , Orikasa Yuki , Ina Toshiaki , Unemoto Atsushi , Sase Maya , Watanabe Hirdetaka , Fukutsuka Tomokazu , Kawada Tatsuya , Terada Yasuko , Uchimoto Yoshiharu
Published: December 2008

Electronic and local structures of the perovskite-type La0.6Sr0.4CoO3-d, which is a promising cathode material for solid oxide fuel cells, were investigated by means of in-situ micro x-ray absorption spectroscopy measurements under working conditions of solid oxide fuel cells, 1073 K of temperature and 10-105 Pa of oxygen partial pressure. It was found that variations of electronic and local structures of La0.6Sr0.4CoO3-d depending on variations of ambient oxygen partial pressure were clearly detected and could be associated with formation/disappearance of oxygen vacancies in the oxide. It was shown that in-situ x-ray absorption spectroscopy measurements could be a useful tool to examine electronic and local structures of high temperature materials in use.
Performance and Electrochemical Characterisation of Thin Electrolyte SOFCs
Authors: Ramos Tânia G. , Hjelm Johan , Wandel Marie , Hagen Anke , Mogensen Mogens
Published: December 2008

The performance and electrochemical behavior of two anode-supported thin electrolyte cells, with different manufacturing parameters, is determined by polarization measurements and electrochemical impedance spectroscopy (EIS). In addition to characterization, a previously suggested equivalent circuit consisting of a series resistance (Rs) and five arcs to describe the polarization resistance of the cell is tested. The aim is to breakdown and assign the losses to each individual cell component around open circuit voltage at selected temperatures. As will be seen, the proposed in-depth electrochemical characterization can provide valuable guidelines for production/performance optimization.
Effect of Anode Active Layer on Performance of Single Step Co-fired Solid Oxide Fuel Cells (SOFCs)
Authors: Yoon Kyung Joong , Gopalan Srikanth , Pal Uday B.
Published: December 2008

Anode-supported planar solid oxide fuel cells (SOFCs) with and without the anode active layer were fabricated by a single step co-firing process. The cells were comprised of a porous Ni + yittria-stabilized zirconia (YSZ) anode support, a porous-fine-grained Ni + YSZ anode active layer for some experiments, a dense YSZ electrolyte, a porous-fine-grained Ca-doped LaMnO3 (LCM) + YSZ cathode active layer, and a porous LCM cathode current collector layer. Fabricated cells were electrochemically tested between 700~800oC with air as oxidant and various compositions of humidified hydrogen as fuel to simulate the effect of fuel utilization on cell performance. The electrochemical performances of the cells were analyzed using a polarization model, and it indicated that the anode active layer significantly improves the cell performance at high fuel utilization by lowering the anodic activation polarization.
First-Principles Modeling of LaMnO3 SOFC Cathode Material
Authors: Kotomin Eugene A. , Mastrikov Yuri , Heifets Eugene , Merkle Rotraut , Fleig Jurgen , Maier Joachim , Gordon Alexander , Felsteiner Joshua
Published: December 2008

We present and discuss the results of first principles DFT plane-wave supercell calculations for atomic and molecular oxygen adsorption and diffusion on the LaMnO3 (001) surface which serves as a model material for a solid oxide fuel cell cathode. The dissociative adsorption of O2 molecules from the gas phase is energetically favorable on surface Mn ions even on a defect-free surface. We discuss optimal adsorption sites for oxygen, binding energies, electronic density redistribution as well as charge transfer. We also compare the surface migration energies for adsorbed O atoms and vacancies in the bulk and on the cathode surface