bluuebunny/crossref_metadata_2025 huggingface dataset:
A cellular automata model can quickly approximate UDP and TCP network traffic
Authors: Brooks Richard R. , Griffin Christopher , Payne T. Alan
Published: March 2004

Brooks and Orr [R.R. Brooks and N. Orr, A model for mobile code using interacting automata. IEEE Trans Mobile Computing 2002, 1(4)] present a model for analysis and simulation of mobile code systems based on cellular automata (CA) abstractions. One flaw with that article was a lack of experimental support showing that CA can model IP networks. This article presents CA models, consistent with those in the work of Brooks and Orr, that model the transport layer of IP networks. We show how these models may be generalized for more complicated network topologies. We provide quantitative results comparing the quality of our CA implementation versus the standard network modeling tool ns‐2. The results from the CA model are qualitatively similar to ns‐2, but the CA simulation runs significantly faster and scales better. © 2004 Wiley Periodicals, Inc. Complexity 9:32–40, 2004
A novel method for detection of virus‐infected cells through moving optical gradient fields using adenovirus as a model system
Authors: Soo Hoo William , Wang Mark , Kohrumel Joshua R. , Hall Jeff
Published: March 2004

Background

Most methods for cellular analysis require labeling with specific antibodies or dyes and are often destructive. We have developed a technology called Optophoresis™, which measures cell physiology based on the cell's motion in a near‐infrared optical gradient. This technique does not require labels, is nondestructive, and involves minimal sample processing.

Methods

We have used Optophoresis to interrogate nonproductive and productive adenovirus‐infected cell lines. Using an adenoviral vector containing green fluorescent protein (GFP) as a secondary assay, we show that viral infection can be monitored with Optophoresis.

Results

In HeLa cells, adenovirus infection after 24 h caused a 12% to 17% increase in optophoretic motility of the cells. In 293 cells, adenovirus infection resulted in a 40% increase in the optophoretic motility. The P values obtained were 4.5 × 10−11 between noninfected and infected HeLa cells, and 2.1 × 10−13 between noninfected and infected 293 cells. Cells infected with adenovirus lacking the GFP reporter gene gave similar shifts. In a time course, we observed an optophoretic shift after 4 h of infection, well before GFP expression.

Conclusions

Optophoresis provides nondestructive, label‐free analysis of viral infection. Detection is independent of reporter gene expression and can be observed early in the infection process. © 2004 Wiley‐Liss, Inc.
Histone H1 and chromatin interactions in human fibroblast nuclei after H1 depletion and reconstitution with H1 subfractions
Authors: Kostova Nora N. , Srebreva Ljuba , Markov Dimiter V. , Rundquist Ingemar
Published: March 2004

Background

Linker histones constitute a family of lysine‐rich proteins associated with nucleosome core particles and linker DNA in eukaryotic chromatin. In permeabilized cells, they can be extracted from nuclei by using salt concentration in the range of 0.3 to 0.7 M. Although other nuclear proteins are also extracted at 0.7 M salt, the remaining nucleus represents a template that is relatively intact.

Methods

A cytochemical method was used to study the affinity of reconstituted linker histones for chromatin in situ in cultured human fibroblasts. We also investigated their ability to condense chromatin by using DNA‐specific osmium ammine staining for electron microscopy.

Results

Permeabilized and H1‐depleted fibroblast nuclei were suitable for the study of linker histone–chromatin interactions after reconstitution with purified linker histone subfractions. Our results showed that exogenous linker histones bind to chromatin with lower affinity than the native ones. We detected no significant differences between the main H1 and H1° histone fractions with respect to their affinity for chromatin or in their ability to condense chromatin.

Conclusions

Linker histone interactions with chromatin are controlled also by mechanisms independent of linker histone subtype composition. © 2004 Wiley‐Liss, Inc.
Telomere length assessment in tissue sections by quantitative FISH: Image analysis algorithms
Authors: O'Sullivan Jacintha N. , Finley Jennifer C. , Risques Rosa‐ana , Shen Wen‐Tang. , Gollahon Katherine A. , Moskovitz Alexander H. , Gryaznov Sergei , Harley Calvin B. , Rabinovitch Peter S.
Published: March 2004

Background

Telomeres are tandem repeated DNA sequences at the ends of every chromosome, which cap, stabilize, and prevent chromosome fusions and instability. Telomere regulation is an important mechanism in cellular proliferation and senescence in normal diploid and neoplastic cells. Quantitative methods to assess telomere lengths are essential to understanding how telomere dynamics play a role in these processes.

Methods

Telomere lengths have been conventionally measured using terminal restriction fragment (TRF), quantitative fluorescence in situ hybridization (QFISH), and flow FISH. In this study, we have applied QFISH to measure average telomere lengths in cultured cells and human tissues of the GI tract. Importantly, this method can be used to analyze telomere lengths in sections using confocal microscopy. We describe and compare three image analysis algorithms: a simple pixel histogram calculation of background corrected fluorescence, a telomere spot‐finding method, and a background curve subtraction algorithm.

Results

Using normal human diploid fibroblasts (NHDF) either dropped on slides or sectioned after agar embedding, similar telomere length shortening is evident with increasing population doubling levels (PDLs), using peptide nucleic acid (PNA) and an N3′‐P5′‐phosphoamidate (PA) oligonucleotide probe for all three methods. Validation of these in situ telomere quantification methods showed excellent agreement with the commonly used telomere repeat fragment‐Southern blot method. Telomere length reductions can also be demonstrated in tissue sections from histologically normal mucosa from patients with chronic ulcerative colitis (with dysplasia or cancer elsewhere in the colon), in colon adenomas, and in mucosal biopsies from patients with Barrett's esophagus. Both on slides and in tissue sections, the telomere spot‐finding method has the greatest variability, while intra‐ and inter‐biopsy variability in telomere length assessment using the other methods is relatively low.

Conclusions

Accurate and reproducible telomere length measurements can be made in tissue sections using QFISH and confocal microscopy. The simplest methods proved the most reliable and make these methods readily accessible to many laboratories. The use of these methods will enhance the ability to measure telomere lengths in tissue samples and aid in the understanding of the role of telomere length in aging and disease. © 2004 Wiley‐Liss, Inc.
A single‐step, sensitive flow cytofluorometric assay for the simultaneous assessment of membrane‐bound and ingested Candida albicans in phagocytosing neutrophils
Authors: Busetto Sara , Trevisan Elisa , Patriarca Pierluigi , Menegazzi Renzo
Published: March 2004

Background

Distinguishing ingested particles from those attached to the cell surface is an essential requirement when performing quantitative studies of phagocytosis. In the present report, we describe a simple, sensitive and reliable flow cytofluorometric method that achieves this goal in a Candida albicans‐human neutrophils (PMN) system.

Methods

The assay is based on the observation that the vital dye trypan blue (TB), while quenching the green fluorescence of fluorescein‐labeled C. albicans, causes them to fluoresce red. PMN were incubated with fluorescein‐labeled yeast particles for the required time. Aliquots of the incubation mixtures were then promptly diluted with an equal volume of a TB solution at pH 4.0, and subsequently analyzed by flow cytometry for green and red fluorescence.

Results

Since TB does not penetrate into the cells, ingested yeasts retain their green fluorescence, while membrane‐bound particles display a red fluorescence.

Conclusions

Our fluorescence flow cytometric method enables to simultaneously distinguish, within the leukocyte population, cell subsets with attached and ingested yeast particles. Its major features are: (1) accuracy, sensitivity and reproducibility; (2) no further sample manipulations after completion of phagocytosis; (3) possibility of counting free, attached and internalized yeast particles; and (4) use of a nontoxic reagent (TB). © 2004 Wiley‐Liss, Inc.
Automated detection of immunofluorescently labeled cytomegalovirus‐infected cells in isolated peripheral blood leukocytes using decision tree analysis
Authors: Ladanyi Andras , Sher Andrew C. , Herlitz Anna , Bergsrud Danielle E. , Kraeft Stine‐Kathrein , Kepros Jane , McDaid Gizelda , Ferguson David , Landry Marie L. , Chen Lan Bo
Published: March 2004

Background

Cytomegalovirus (CMV) infection continues to be a major problem for immunocompromised patients. Detection of viral antigens in leukocytes (antigenemia assay) is widely used for the diagnosis of CMV infection and for guiding antiviral therapy. The antigenemia technique, contingent upon the manual microscopic analysis of rare cells, is a laborious task that is subject to human error. In this study, we combine automated microscopy with artificial intelligence for reliable detection of fluorescently labeled CMV‐infected cells.

Methods

Cytospin preparations of peripheral blood leukocytes were immunofluorescently labeled for the CMV lower matrix phosphoprotein (pp65) and scanned in the Rare Event Imaging System (REIS), a fully automated image cytometer. The REIS detected potential positive objects and digitally recorded 49 measured cellular features for each identified case. The measurement data of these objects were analyzed by the See5 decision tree (DT) algorithm to ascertain whether they were true‐positive detections.

Results

The DT was built from the measurement data of 2,047 true‐ and 2,028 false‐positive detections, collected from 32 patient samples. By designating misclassifications of false‐negatives three times more costly, the 10‐fold cross‐validation sensitivity, specificity, and misclassification error of the assay was 94.3%, 56.2%, and 25%, respectively. The method was also validated using an independent test set of 21 patient samples, in which similar results were obtained.

Conclusions

To our knowledge, this study represents the first attempt to improve the accuracy of rare event image cytometry through the implementation of artificial intelligence methodology. Results suggest that cost‐sensitive decision tree analysis of digitally measured cellular features vastly improves the performance of rare event image cytometry. © 2004 Wiley‐Liss, Inc.
Stress reactivity in 15‐month‐old infants: Links with infant temperament, cognitive competence, and attachment security
Authors: van Bakel Hedwig J. A. , Riksen‐Walraven J. Marianne
Published: March 2004

In a sample of eighty‐five 15‐month‐old infants, salivary cortisol was obtained prior to and following a potentially stressful episode in which the child was confronted with a stranger and with a frightening robot. Infant characteristics such as anger proneness, cognitive competence, and attachment security were expected to be related to cortisol reactivity during the stressful event. The results showed higher cortisol reactivity in more anger‐prone infants and in infants with higher levels of cognitive development as assessed with the Bayley Scales of Infant Development (N. Bayley, 1969). Attachment security, assessed with the Attachment Q‐Set (AQS; E. Waters, 1995), was found to moderate the relation between cognitive level and cortisol reactivity; the positive relation between cognitive development and cortisol response was found in only infants with low AQS security scores. The findings may have important implications for research in the development of self‐regulation in humans as well as in studies with animals. © 2004 Wiley Periodicals, Inc. Dev Psychobiol 44: 157–167, 2004.
Similar and functionally typical kinematic reaching parameters in 7‐ and 15‐month‐old in utero cocaine‐exposed and unexposed infants
Authors: Tronick E. Z. , Fetters Linda , Olson Karen L. , Chen Yuping
Published: March 2004

This study examined the effects of intrauterine cocaine exposure on the reaches of 19 exposed and 15 unexposed infants at 7 and 15 months using kinematic measures. Infants sat at a table and reached for a rattle, a toy doll, and a chair. Videotaped reaches were digitized using the Peak Performance system. Kinematic movement variables were extracted (e.g., reach duration, peak velocity, movement units, path length) and ratios computed (e.g., path length divided by number of movement units). Regardless of exposure status, reaches of older infants were faster, more direct, had fewer movement units, and covered more distance with the first movement unit. Exposed infants covered more distance per movement unit than unexposed infants, but there were no other significant differences. Reaches of exposed and unexposed infants were essentially similar. Importantly, reach parameters for these high‐risk infants were similar to reach parameters for infants at lower social and biological risk. © 2004 Wiley Periodicals, Inc. Dev Psychobiol 44: 168–175, 2004.
Separation as a natural cue to danger in the spotted hyena (Crocuta crocuta)
Authors: Rifkin Anne , Glickman Stephen E.
Published: March 2004

Spotted hyena biology suggests mothers and infants will exhibit one of two alternative responses to separation: (a) Due to prolonged dependency, infants will act similarly to Old World monkeys, displaying distress and proximity seeking behaviors; or (b) because mother–infant separations are frequent in the wild, infants will exhibit little distress or change in reunion behavior. Hence, reunion behavior following mother–infant separation was compared to control periods in captive hyena (Crocuta crocuta) mothers and infants at two developmental periods. Significant increases (p ≤ .05) in distress (i.e., agitated arousal and increased vocalization) and proximity maintenance (i.e., cub and maternal approaches, and maternal monitoring) as well as a trend towards increased sibling aggression following separation were observed. Responsibility for proximity maintenance, assessed by the Hinde Index, adhered to patterns common to primates—with cubs assuming increased responsibility later in development. Findings are discussed in light of hyena ecology and Attachment Theory. © 2004 Wiley Periodicals, Inc. Dev Psychobiol 44: 199–207, 2004.
The antidiabetic agent, gliclazide, reduces high insulin–enhanced neutrophil‐transendothelial migration through direct effects on the endothelium
Authors: Okouchi Masahiro , Okayama Naotsuka , Omi Hitoshi , Imaeda Kenro , Fukutomi Tatsuya , Nakamura Atsushi , Itoh Makoto
Published: March 2004

Background and aim

Many lines of evidence indicate that hyperinsulinemia might be associated with coronary athrosclerosis, and, currently, there are no effective strategies for preventing this. We previously reported that high insulin enhances neutrophil‐transendothelial migration, a process that involves increased surface presentation of platelet endothelial cell adhesion molecule‐1 (PECAM‐1) through a mitogen‐activated protein (MAP) kinase–dependent event. In this current study, we examined if antidiabetic agents, especially KATP channel blockers, might similarly protect against the leukocyte‐endothelial cell interactions enhanced by high insulin.

Methods

Neutrophils transmigration across umbilical vein endothelial cells (in high insulin medium) with or without KATP channel blockers was performed. Neutrophil migration was quantified by measuring myeloperoxidase, and surface expression of endothelial PECAM‐1 was examined using cell‐surface enzyme immunoassay.

Results

Neutrophil‐transendothelial migration and PECAM‐1 expression were enhanced by insulin (100 µU/mL, 24 h) and were attenuated by gliclazide (20 µM), but not by other KATP channel blockers (glibenclamide, nateglinide, and glimepiride). Neutrophil migration and PECAM‐1 expression were also increased by the mitogen‐activated protein (MAP) kinase activator, anisomycin (1 µM), and also attenuated by gliclazide. Nitric oxide (NO) synthase inhibitors did not modify either gliclazide effect.

Conclusions

Our results suggest that the KATP channel blocker, gliclazide, blocks high insulin–mediated neutrophil migration and PECAM‐1 expression. These gliclazide effects may be mediated through the inhibition of MAP kinase activation and are unrelated to NO production. Copyright © 2004 John Wiley & Sons, Ltd.
LDL oxidative modifications in well‐ or moderately controlled type 2 diabetes
Authors: Scheffer P. G. , Henry R. M. A. , Wever E. J. M. , van Rooij G. J. , Bos G. , Heine R. J. , Dekker J. M. , Diamant M. , Stehouwer C. D. A. , Nijpels G. , Blankenstein M. A. , Teerlink T.
Published: March 2004

Background

The aim of the study was to examine, by measurement of specific indicators of free radical‐mediated oxidation of LDL, whether there is evidence of increased in vivo oxidation of LDL in type 2 diabetic patients, and to investigate their associations with carotid intima media thickness (IMT).

Methods

In native LDL, we quantified five different products of LDL oxidation reflecting various stages of LDL oxidative modification in 38 individuals with well‐ or moderately controlled type 2 diabetes (HbA1c ≤ 8.5%) and 38 gender‐matched subjects with normal glucose metabolism. Baseline conjugated dienes (BCD), 7‐OH‐glycero‐phosphocholine (7‐OH‐GPC), lyso‐phosphatidylcholine (lyso‐PC), and ketocholesterol were determined in LDL, and circulating in vivo oxidized apolipoprotein B100 (Ox‐apoB) was measured in plasma. The IMT of the carotid artery was measured by ultrasound.

Results

Borderline higher carotid IMT values were observed in individuals with diabetes (0.88 ± 0.14 vs 0.83 ± 0.11 mm, p = 0.06). LDL‐ketocholesterol (45.5 ± 19.4 vs 37.1 ± 13.8 nmol/mmol LDL‐cholesterol, p < 0.05) and Ox‐apoB (25.3 ± 5.5 vs 22.2 ± 5.8 U/mmol LDL‐cholesterol, p < 0.05) were significantly increased in diabetic patients. The concentration of BCD, 7‐OH‐GPC and lyso‐PC in LDL did not differ between diabetic patients and control subjects. No significant correlations were demonstrated between the measured indicators of LDL oxidation and carotid IMT.

Conclusion

Levels of BCD, 7‐OH‐GPC and lyso‐PC, that is, intermediary products of LDL oxidation, were not significantly elevated, but ketocholesterol and Ox‐apoB, that is, stable end products of the oxidation process, were increased in diabetic patients. We conclude that in vivo oxidation of LDL is increased, even in subjects with well‐ or moderately controlled type 2 diabetes. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis and Monitoring of α‐Bi2Mo3O12 Catalyst Formation using Thermo‐Raman Spectroscopy
Authors: Ghule Anil , Tzing Shin‐Hwa , Chang Jia‐Yaw , Ghule Kalyani , Chang Hua , Ling Yong Chien
Published: March 2004

Thermo‐Raman spectroscopy was used to monitor the dehydration and phase transformations of Bi2Mo3O12·5H2O. The hydrated forms Bi2Mo3O12·5H2O, Bi2Mo3O12·4.75H2O, Bi2Mo3O12·3H2O, Bi2Mo3O12·2H2O, and anhydrous Bi2Mo3O12 were observed during dehydration in the wavelength range from 200 to 1400 cm−1. Representative Raman spectra of these compounds are reported for the first time. The thermo‐Raman intensity thermogram showed a systematic dehydration in four steps, and the differential thermo‐Raman intensity thermogram confirmed this. Thermogravimetry, differential thermogravimetry, and differential scanning calorimetry results were in harmony with the results of the thermo‐Raman spectroscopy. Additionally, the dehydration resulting in formation of anhydrous Bi2Mo3O12 (amorphous Bi2Mo3O12 phase) and the final transformation into the α‐Bi2Mo3O12 phase was observed to be a dynamic thermal process. The slow, controlled heating rate produced α‐Bi2Mo3O12 catalyst with a particle size averaging 200 nm. The catalyst formed was further characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, time of flight SIMS, transmission electron microscopy, and energy‐dispersive X‐ray analysis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Structural Study of Novel Graphite−Lithium−Calcium Intercalation Compounds
Authors: Pruvost Sébastien , Hérold Claire , Hérold Albert , Lagrange Philippe
Published: March 2004

Three new layered compounds were synthesised by immersing a pyrographite platelet in a molten Ca−Li alloy creating a new graphite intercalation compound family. The samples were studied by X‐ray and neutron diffraction, revealing that the intercalated sheets are polylayered. The study of the 00l reflections allowed us to establish the c‐axis stacking of these three phases. The α‐phase exhibits a five‐layered intercalated sheet which has something in common with a Li−Ca−Li−Ca−Li slice cut in the CaLi2 structure (ThMn2 Laves phase type). The β‐phase, which is richer in metallic elements and with a greater repeat distance, possesses seven‐layered intercalated sheets due to the splitting of the middle lithium plane in three. The third phase is a pseudo‐binary compound, containing monolayered sheets and with a formula close to CaC6. Electron microdiffraction allowed us to determine the 2D unit cell for each compound, all of which were commensurate with that of graphite. Charge transfer from the intercalate to the host lattice was evaluated for the three phases from hk0 data, leading to high values. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Reactivity of a Phosphanylalane Complex towards Lewis Bases
Authors: Vogel Ulf , Schwan Karl‐Christian , Scheer Manfred
Published: March 2004

The reactivity of the Lewis acid/base stabilized complex of phosphanylalane [(CO)5W(H2PAlH2·NMe3)] (1) towards the Lewis bases THF and NMe3 has been investigated. The reaction with THF leads to decomposition of the complex. One of the decomposition products was identified as containing the anion [{(CO)5W}2PH2]− (2). This anion could be synthesized independently by reaction of [(CO)5WPH3] with KH in the presence of [(CO)5W(THF)] and was isolated as the tetraphenylphosphonium salt [Ph4P][{(CO)5W}2PH2] (2a). The treatment of 1 with NMe3 leads to the formation of [(CO)5W(H2PAlH2·2 NMe3)] (3) containing a five‐coordinate aluminum atom. Compound 3 exhibits a fast exchange of the NMe3 ligands in solution containing an excess of NMe3. The products were characterized by spectroscopic methods and X‐ray crystallography. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Rotaxanes and Catenanes Built Around Octahedral Transition Metals
Authors: Chambron Jean‐Claude , Collin Jean‐Paul , Heitz Valérie , Jouvenot Damien , Kern Jean‐Marc , Mobian Pierre , Pomeranc Didier , Sauvage Jean‐Pierre
Published: March 2004

Transition metals are extremely useful tools for the preparation of rotaxanes and catenanes. Traditionally, copper(I) has played an important role in this field, but recently octahedrally coordinated metal centres such as ruthenium(II), have allowed the preparation of highly functional interlocking ring systems. The present review article will discuss this new approach, which gives access to novel rotaxanes and catenanes. Besides the purely synthetic work described, the potential of the prepared compounds to be used as light‐driven molecular machines will be mentioned. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Chemistry of Thiacalixarenes
Authors: Lhoták Pavel
Published: March 2004

Thiacalixarenes — new members of the calixarene family — are very promising molecules with many potential applications in supramolecular chemistry. The presence of four sulfur atoms in the place of methylene groups imparts many novel features and properties to these molecules. This review deals with the chemistry of thiacalixarenes, and by comparision with “classical” calixarenes, emphasizes their differences in reactivity, unusual conformational preferences and modified complexation abilities. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Non‐Rusty [2]Catenanes with Huge Rings and Their Polymers
Authors: Godt Adelheid
Published: March 2004

We describe the design and synthetic realisation of [2]catenanes characterised by having huge rings that can rotate freely and shift laterally within the constraints of concatenation. The synthetic strategy, which is based on using a carbonate group as a covalent template and oxidative dimerization of alkynes to achieve ring formation, is versatile with respect to ring size and the presence of functional groups. The monocyclic constitutional isomer of the catenane is available by a simple exchange of steps in the sequence. EPR spectroscopy revealed that in solution the catenanes adopt all possible co‐conformations in equal abundances. The thermotropic liquid crystallinity of the [2]catenanes and their corresponding non‐intertwined macrocycles proves intermolecular ordering in the bulk phase. The [2]catenanes were polymerized through ester formation and through acyclic diene metathesis. All of the poly[2]catenanes have rather low degrees of polymerisation ( ≈︁ 10), possibly because cyclisation occurs. For the preparation of [n]catenanes having n > 3, we propose fusing the rings of [2]catenanes so that the crucial steps of threading and cyclisation need only occur during the synthesis of the smallest catenane. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Transition Metal‐Catalyzed Carbon−Carbon Bond Formation with Grignard Reagents − Novel Reactions with a Classic Reagent
Authors: Shinokubo Hiroshi , Oshima Koichiro
Published: March 2004

Organomagnesium compounds are among the most useful organometallic reagents in organic synthesis. Besides their classical nucleophilic reactions to carbonyl compounds, Grignard reagents gain versatile reactivity when combined with various transition metal salts. In this article, we review mainly our own studies on manganese‐, iron‐, chromium‐, and cobalt‐catalyzed carbon−carbon bond formation reactions using Grignard reagents. Other closely related research in this field is also discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
A Study of the Determination of Cu(II) by Anodic Stripping Voltammetry on a Novel Nylon/Carbon Fiber Electrode
Authors: Mylonakis A. , Economou A. , Fielden P. R. , Goddard N. J. , Voulgaropoulos A.
Published: March 2004

In this work we report a new electrode material formed by injection‐moulding of a conducting polymer consisting of carbon fibers in a Nylon matrix. This material is highly conductive, inexpensive, easy to mould in different shapes and requires minimal pretreatment. The electrode was tested as a mercury‐free sensor for the trace determination of Cu(II) by anodic stripping voltammetry (ASV). The deposition and stripping behavior of copper on the conducting material was initially studied by cyclic voltammetry and the chemical and instrumental parameters of the determination were investigated. The electrode has been shown to be suitable for the determination of Cu(II) in the range 8 μg L−1 to 30 mg L−1 (with deposition times ranging from 30 s to 10 min) with a relative standard deviation of 2.2% (at the 0.5 mg L−1 level) and a limit of detection of 8 μg L−1 Cu(II) for 10 min of accumulation (at a S/N ratio of 5). The electrode was, finally, applied to the determination of copper in tap‐water, pharmaceutical tablets and bovine serum with recoveries of 97.4, 94.9 and 93.4%, respectively
Novel Ni(II) Mixed Ligand Complex Modified Electrode: Catalytic Effect on Anodic Oxidation of Phenol
Authors: Mohan Jegan , Joshi Seema , Prakash Rajiv , Srivastava R. C.
Published: March 2004

Cyclic voltammetry, using graphite paste electrode (GPE) and chemically modified GPE with Ni(II) mixed ligand complex (MGPE), is described for sensing and detoxification of phenol. A novel mixed ligand complex of nickel with 1,4,8,11‐tetraaza cyclotetradecane (cyclam) and thiocyanate in the molar ratio of 1 : 2 : 5 is synthesized and characterized by spectroscopic and electrochemical studies. The Ni(II)‐cyclam‐thiocyanate complex behaves as a fast electron‐transfer mediator, as nickel ions exist in higher oxidation state of Ni(III) on applying a potential of 1.25 V (vs. Ag/AgCl), which catalyses the oxidation of the target species. The mixed ligand complex, when incorporated in the graphite paste electrode, is sensitive to detect phenol as low as 10 μg/L in solution. The catalytic effect of the Ni(II)‐cyclam‐thiocyanate complex enhanced many folds the oxidation of phenol compared to GPE. The technique has potential for sensing/monitoring and detoxification of phenol released in the ecosystem from polluting industries.
A Simulation of an Anion‐Induced Adsorption of Metal Ions in Pseudopolarography Using a Thin Mercury Film Covered Rotating Disk Electrode
Authors: Omanović Dario , Lovrić Milivoj
Published: March 2004

A theory of the influence of anion‐induced adsorption of metal ions in pseudopolarography using the thin mercury film covered rotating disk electrode is developed. The model is developed assuming that the metal ion is forming several labile complexes with the ligand which is present in a great excess, and that only one complex species is adsorbed following a linear isotherm. The results obtained assuming steady‐state conditions are compared with the simulation of transient processes using Galerkin and finite difference methods. It is shown that the adsorption of metal complexes on the disk electrode surface does not prevent the determination of the stability constants.
Construction and Characterization of a New Flexible and Nonbreakable Nitric Oxide Microsensor
Authors: Dickson Alec , Lin Jie , Sun Jie , Broderick Mark , Fein Harry , Zhang Xueji
Published: March 2004

Nitric oxide (NO) is an important molecule in many different physiological phenomena. Investigation of nitric oxide production in vivo requires a specialized sensor capable of real‐time concentration measurement, with a high spatial resolution of NO gas production. In this study, a flexible microsensor is developed specifically for measurement of production of nitric oxide. The new sensor consists of a Pt/Ir working electrode coupled with an integrated Ag/AgCl reference electrode. The sensor is coated with a series of NO‐selective membrane polymers to prevent potential amperometric response due to interfering species. Presented experimental data demonstrates the ability for NO detection between 100 and 400 nM concentrations with a linear response (R2=0.9997). The detection limit of the sensor is 2.14 nM (S/N=3). Various selectivity experiments are indicative of a resistance to interfering species such as dopamine, norepinephrine, L‐arginine.
Heterogeneous ECE Processes at Channel Electrodes: Analytical Solution for all Reaction Rate Constants and Different Diffusion Coefficients
Authors: Zhang Jinsuo , Li Ning
Published: March 2004

An analytical solution is developed for heterogeneous ECE processes occurring at channel electrode surface for both laminar and turbulent flow. The solution explicitly links the behavior of ECE processes and the parameters. A simple expression of the effective number of electrons transferred, covering all the reaction rate constants and different diffusion coefficients of the reactant A and the intermediate product B, is obtained. Excellent agreement with previous numerical and analytical results is shown . Parametric studies illustrate the effects of diffusion coefficients, hydrodynamic factors and reaction rate constants on the effective number of electrons transferred and the currents.
Voltammetric Behavior of Mifepristone (RU‐486) Using Square‐Wave and Adsortive Stripping‐Wave Techniques. Determination in Urine Samples
Authors: Rodríguez J. , Berzas J. J. , Castañeda G. , Rodríguez N.
Published: March 2004

The behavior of Mifepristone (RU‐486) was studied by square‐wave technique, leading to two methods for its determination in aqueous samples and urine samples at pH 2. The application of the square‐wave (SW) without the adsorptive accumulation and stripping voltammetric (AdSV) show the maximum response at −0.896 V using an accumulation potential of −0.5 V. The effect of experimental parameters that affect this determination are discussed. For the stripping technique, Mifepristone proved to be more sensitive, yielding signals four times larger than those obtained by applying a square‐wave scan without the previous accumulation. The calibration plot to determine Mifepristone was linear in the range 2.4×10−8 and 5.4×10−7 M by stripping mode with an accumulation time tacc of 30 s. The relative standard deviation obtained for concentration levels of Mifepristone as low as 2.0×10−7 M with square‐wave was 1.17% (n=10) and with stripping square‐wave 2.02% (n=10) in the same day. The two proposed methods (SW and SWAdSV) were applied to the determination of Mifepristone in urine.
Carbon Paste Electrode Modified with Carbamoylphosphonic Acid Functionalized Mesoporous Silica: A New Mercury‐Free Sensor for Uranium Detection
Authors: Yantasee Wassana , Lin Yuehe , Fryxell Glen E. , Wang Zheming
Published: March 2004

This study reports a new approach for developing a uranium electrochemical sensor that is mercury‐free, solid‐state, and has less chance for ligand depletion than existing sensors. A carbon‐paste electrode modified with carbamoylphosphonic acid self‐assembled monolayer on mesoporous silica was developed for uranium detection based on an adsorptive square‐wave stripping votammetry technique. Voltammetric responses for uranium detection are reported as a function of pH, preconcentration time, and aqueous phase uranium concentration. The uranium detection limit is 25 ppb after 5 minutes preconcentration and improved to 1 ppb after 20 minutes preconcentration. The relative standard deviations are normally less than 5%.
Voltammetry as a Virtual Potentiometric Sensor in Modeling of a Metal‐Ligand System and Refinement of Stability Constants. Part 1. Polarographic and Glass Electrode Potentiometric Study of a Dynamic Cd‐Glycine System
Authors: Cukrowski Ignacy , Zhang Jian Min
Published: March 2004

A mathematical conversion of data coming from nonequilibrium and dynamic voltammetric techniques (a direct current sampled (DC) and differential pulse (DP) polarography) into potentiometric sensor type of data is described and tested on a dynamic metal‐ligand system. A combined experiment involving DCP, DPP and glass electrode potentiometry (GEP) was performed on a single solution sample containing a fixed [LT] : [MT] ratio (acid‐base titration). Dedicated potentiometric software ESTA was successfully employed in the refinement operations performed on virtual potentiometric (VP) data obtained from DC and DP polarography. It was possible to refine stability constants either separately, from VP‐DC or VP‐DP, or simultaneously from any combination of VP‐DC, VP‐DP and GEP. The concept of VP‐DC or VP‐DP is reported for the first time and numerous documented and possible advantages are discussed. The proposed procedure can be easily utilized also by nonelectrochemists who are interested in, e.g., the ligand design strategies.
Voltammetric and Differential Pulse Stripping Study of Adenine on a Sol‐gel Derived Carbon Composite Electrode
Authors: Teh Huey Fang , Yang Xinhao , Gong Haiqing , Tan Swee Ngin
Published: March 2004

This communication reports on the electrochemical investigation of adenine on a sol‐gel carbon composite electrode (CCE). Cyclic voltammetric (CV) technique is used to characterize the redox behavior of adenine at CCE. The peak current and peak potentials are dependent on the pH of the buffer solution. From the scan rate and peak current study, there is evidence of adsorption of adenine on the CCE. The parameters affecting the differential pulse stripping adsorption peak were systematically optimized. Under optimum conditions of Eacc=−0.10 and tacc=60 s, a linear calibration plot was obtained, 2×10−7–1×10−6 M. This CCE is useful for the simultaneous analysis of adenine and guanine from denatured DNA.
Characterization and Optimization of Interdigitated Ultramicroelectrode Arrays as Electrochemical Biosensor Transducers
Authors: Min Junhong , Baeumner Antje J.
Published: March 2004

Interdigitated ultramicroelectrode arrays (IDUAs) were fabricated on glass wafers and investigated to obtain optimal oxidation and reduction reactions of potassium ferro/ferrihexacyanide, Fe2+/3+(CN)6, when using a 2‐electrode set up. These electrodes will be used as transducers in portable microfluidic‐based biosensors in the future for the detection in an aqueous, biocompatible matrix. IDUAs were designed to maximize the signal‐to‐noise ratio (S/N) investigating electrode height, gap size, finger width, and material. Interesting differences in the electrode materials gold and platinum were found, which were due to the oxidization of platinum and gold during the IDUA fabrication process. It resulted in gold IDUAs being by far superior in respect to signal‐to‐noise ratio and overall signal magnitude to those made of platinum. The effects of gap size, electrode width and number of electrode fingers were as expected. Optimal electrode heights were in the range of 70 nm–140 nm, much larger and smaller electrodes had lower signal‐to‐noise ratios due to overall reduced signal or increased background. The optimized IDUA was made out of gold, had 400 fingers with a finger width of 2.7 μm, a finger height between 70 nm and 140 nm and a gap size of 0.9–1 μm. A detection limit of as low as 0.1 μM ferro/ferrihexacyanide measured in a simple 2‐electrode set up was obtained with a signal‐to‐noise ratio of 9.7.
Immobilization of Enzymes on the Nano‐Au Film Modified Glassy Carbon Electrode for the Determination of Hydrogen Peroxide and Glucose
Authors: Lei Cun‐Xi , Wang Hua , Shen Guo‐Li , Yu Ru‐Qin
Published: March 2004

A new enzyme‐based amperometric biosensor for hydrogen peroxide was developed relying on the efficient immobilization of horseradish peroxidase (HRP) to a nano‐scaled particulate gold (nano‐Au) film modified glassy carbon electrode (GC). The nano‐Au film was obtained by a chitosan film which was first formed on the surface of GC. The high affinity of chitosan for nano‐Au associated with its amino groups resulted in the formation of nano‐Au film on the surface of GC. The film formed served as an intermediator to retain high efficient and stable immobilization of the enzyme. H2O2 was detected using hydroquinone as an electron mediator to transfer electrons between the electrode and HRP. The HRP immobilized on nano‐Au film maintained excellent electrocatalytical activity to the reduction of H2O2. The experimental parameters such as the operating potential of the working electrode, mediator concentration and pH of background electrolyte were optimized for best analytical performance of amperometry. The linear range of detection for H2O2 is from 6.1×10−6 to 1.8×10−3 mol L−1 with a detection limit of 6.1 μmol L−1 based on signal/noise=3. The proposed HRP enzyme sensor has the features of high sensitivity (0.25 Almol−1cm−2), fast response time (t90%≤10 s) and a long‐term stability (>1 month). As an extension, glucose oxidase (GOD) was chemically bound to HRP‐modified electrode. A GOD/HRP bienzyme‐modified electrode formed in this way can be applied to the determination of glucose with satisfactory performance.
Batch Injection Analysis: An Almost Unexplored Powerful Tool
Authors: Quintino Maria S. M. , Angnes Lúcio
Published: March 2004

The main purpose of this review is to report the development and potentialities of batch injection analysis (BIA) and call the attention of researchers about the power of this (until now) almost unexplored tool. The text focuses on the concepts and potentialities of BIA combined with other techniques for analytical purposes. The association of BIA with amperometry, potentiometry, voltammetry, calorimetry, fluorescence and spectrophotometry is presented and important aspects related with each technique are discussed. Some aspects comparing the similarities and differences between BIA, FIA and wall‐jet are presented along the text.
Voltammetric Elucidation of Ion Transfer Through an Extremely Thin Membrane
Authors: Ichieda Nobuyuki , Shirai Osamu , Yoshida Yumi , Maeda Kohji , Torimura Masaki , Kihara Sorin
Published: March 2004

Digital simulation of the cyclic voltammogram for the ion transfer through a liquid membrane of thickness from 1 mm to 10 nm was performed. The magnitude of current and the shape of the voltammogram simulated for extremely thin membrane (10 nm thick) were similar to those observed experimentally with a bilayer lipid membrane, BLM, of about 10 nm in thick, when the diffusion coefficient of an ion in the BLM was assumed to be extraordinary small (10−13 to 10−14 cm2 s−1).
Immunosensors Based on Layer‐by‐Layer Self‐Assembled Au Colloidal Electrode for the Electrochemical Detection of Antigen
Authors: Wang Meijia , Wang Lianying , Yuan Hang , Ji Xiaohui , Sun Chunyan , Ma Lan , Bai Yubai , Li Tiejin , Li Jinghong
Published: March 2004

Colloidal Au particles have been deposited on the gold electrode through layer‐by‐layer self‐assembly using cysteamine as cross‐linkers. Self‐assembly of colloidal Au on the gold electrode resulted in an easier attachment of antibody, larger electrode surface and ideal electrode behavior. The redox reactions of [Fe(CN)6]4−/[Fe(CN)6]3− on the gold surface were blocked due to antibody immobilization, which were investigated by cyclic voltammetry and impedance spectroscopy. The interaction of antigen with grafted antibody recognition layers was carried out by soaking the modified electrode into a phosphate buffer at pH 7.0 with various concentrations of antigen at 37 °C for 30 min. Further, an amplification strategy to use biotin conjugated antibody was introduced for improving the sensitivity of impedance measurements. Thus, the sensor based on this immobilization method exhibits a large linear dynamic range, from 5–400 μg/L for detection of Human IgG. The detection limit is about 0.5 μg/L.
Determination of Cytochrome C with Cellulose – DNA Modified Carbon Paste Electrodes
Authors: Lee Tae‐Young , Kim Hwa‐Jeong , Moon Jeon‐Ok , Shim Yoon‐Bo
Published: March 2004

A sensor for cytochrome c (cyt c) was developed using a carbon paste electrode (CPE) modified with cellulose‐DNA. Cyt c was adsorbed on the cellulose‐DNA modified CPE through the electrostatic interaction between them. Owing to this process, a pair of well‐defined peaks appeared at +48 mV/85 mV (Epc/Epa vs. Ag/AgCl). This property of the cellulose‐DNA modified CPE was utilized for the analysis of cyt c in a biological sample. The optimum experimental conditions for analysis were investigated and a calibration plot was obtained between 1.0×10−4 M and 1.0×10−6 M (±5% at n=5) at the optimized condition. The detection limit for cyt c at the optimized experimental condition was 5.0×10−7 M (S/N=3) for 30 min of deposition time with differential pulse voltammetry (DPV). The real sample analysis was carried out with the standard addition method to evaluate the developed method. The content of cyt c in total proteins of 80.0 mg/mL in rat mitocondria fractions was determined to be 0.12 (±0.02) mg/mL.
Flow‐Injection Amperometric Detection with Solvent Polymeric Membrane Ion Sensors
Authors: Ortuño Joaquín A. , Hernández Jorge , Sánchez‐Pedreño Concepción
Published: March 2004

An amperometric detector for hydrophobic ions based on a plasticized poly(vinyl) chloride (PVC) membrane incorporated in a flow‐injection system was developed. A four‐electrode potentiostat with ohmic drop compensation was used, while a flow‐through cell incorporated the four electrodes and the membrane, which contained tetrabutylammonium tetraphenylborate. When the influence of the applied potential and of the flow‐injection variables on the determination of tetrabutylammonium was studied, a linear relationship was observed between current peak height and ion concentration over a range of 5×10−6–6×10−5 M tetrabutylammonium. Good repeatability and between‐day reproducibility and high sample frequency were obtained. The effect of other ions was studied. Two different amperometric methods, indirect and direct, were also developed for the determination of dodecylsulfate in the concentration range 3×10−5–9×10−4 M.
Selective Determination of Uric Acid in Presence of Ascorbic Acid and Dopamine at Neutral pH Using Exfoliated Graphite Electrodes
Authors: Ramesh P. , Sampath S.
Published: March 2004

Exfoliated graphite electrodes have been used to detect uric acid at neutral pHs, by following its oxidation. A linear range of 5–53 μM and a detection limit of 5 μM are observed at a pH of 7.0. Uric acid was found to be selectively adsorbed on exfoliated graphite surface in the presence of excess ascorbic acid. This leads to its selective determination in the presence of ascorbic acid. Simultaneous detection of uric acid, dopamine and ascorbic acid has also been demonstrated on exfoliated graphite electrodes in a pH 7 buffer.
Electrocatalytic Oxidation of NADH by Oxidized s‐Adenosyl‐L‐Methionine (SAMe): Application to NADH and SAMe Determinations
Authors: de‐los‐Santos‐Álvarez Noemí , Lobo‐Castañón María Jesús , Miranda‐Ordieres Arturo J. , Tuñón‐Blanco Paulino
Published: March 2004

s‐Adenosyl‐L‐methionine (SAMe) is an adenosine analogue with therapeutical activity against affective disorders and liver dysfunctions. It can be oxidized on graphite electrode yielding a strongly adsorbed electroactive oxidation product for which a quinone‐imine structure is proposed. This compound is capable of electrocatalyzing the NADH oxidation at low potentials, lowering the overvoltage by about 300 mV. An amperometric method for NADH determination at +0.1 V (Ag|AgCl|KClsat) is developed using an oxidized‐SAMe‐modified electrode in pH 9. Linear calibration plots were obtained with a detection limit of 2.4 nM. The electrode response time and the relative standard deviation of the slope of the calibration plot for 5 different modified electrodes were 12 s and 5.6% respectively. The catalytic scheme also provides the first method to determine SAMe itself by adsorptive differential pulse voltammetry. The linear range was found to be 42.4–424 nM with a reproducibility of 6.9%. The method was applied to SAMe determination in a pharmaceutical formulation.
Sonoelectroanalysis in Acoustically Emulsified Media: Zinc and Cadmium
Authors: Kruusma Jaanus , Tomčík Peter , Banks Craig E. , Compton Richard G.
Published: March 2004

Dithizone (diphenylthiocarbazone) dissolved in chloroform was employed as a ligand for the solvent extraction of either cadmium or zinc from aqueous media. Acoustic emulsification was shown to be effective both in extraction and recovery or ‘back extraction’ with a fresh clean aqueous solution. Quantitative analysis of cadmium or zinc removed via double sono‐extraction from aqueous media hostile to voltammetric analysis proceeded via sono‐square wave anodic stripping voltammetry (sono‐SWASV), resulting in high sensitivity in the relatively clean medium. This technique was shown to be viable for the quantification of cadmium from surfactant containing media where direct electroanalytical techniques fail. The method was also applied to the analysis of zinc in commercial shampoo and toothpaste, giving results in close agreement with those obtained from independent analysis. Biphasic sono‐extraction synergistically coupled with sono‐SWASV therefore presents an attractive technique for cadmium or zinc analysis in electrode passsivating media. The technique likely removes contaminants present in the test solution since these will ‘prefer’ to remain in the initial aqueous phase, or will transfer to the extracting organic phase, but are unlikely to be doubly transferred into the clean final aqueous phase.