bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on the Electrochemical Behavior of Melatonin with an Activated Electrode
Authors: Xiao‐Ping Wu , Lan Zhang , Wen‐Rong Liao , Jian‐Ping Duan , Hong‐Qing Chen , Guo‐Nan Chen 
Published: December 2002

AbstractIt was found that melatonin could be incorporated and accumulated on the surface of the glassy carbon electrode which was activated electrochemically by pretreatment in sodium hydroxide solution by means of cycling the potential well into the positive limit of the solvent. In Britton‐Robinson buffer solution (pH 6.7), melatonin gave a sensitive oxidation wave at a potential of +0.65 V (vs.Ag/AgCl) by using Osteryoung square‐wave stripping voltammetry (OSWSV). The oxidation process has been shown to be irreversible and adsorption‐controlled at this electrode by means of cyclic voltammetry and linear sweep voltammetry. A chronocoulometric characterization of the adsorption characteristics of melatonin at this electrode is also presented. The factors affecting the peak current were optimized, and the dependence of peak currents on the concentration of melatonin was found to be linear in the range 8.0×10−7−1.0×10−5 mol L−1. A detection limit of 5.0×10−8 mol L−1 was obtained (signal‐to‐noise ratio of 3). This method was applied to the assay of melatonin in tablets and capsules with good recoveries (98–100%).
Rapid Detection of Vanillin in Alcoholic Beverages Using Stabilized Polymerized Lipid Film Based Biosensors
Authors: Nikolelis Dimitrios P. , Theoharis George 
Published: December 2002

AbstractThis work reports a technique for the rapid detection of vanillin in alcoholic beverages using stabilized lipid membrane based biosensors. Microporous filters composed of glass fibers (nominal pore sizes 0.7 and 1.0 μm) were used as supports for the polymerization of the lipid film and stabilization of these devices. The lipid film is formed on the filter by polymerization prior its use. Methacrylic acid was the functional monomer, ethylene glycol dimethacrylate was the crosslinker and 2,2′‐azobis‐(2‐methylpropionitrile) was the initiator. The response towards vanillin of the present stabilized lipid membrane biosensors composed of phosphatidylcholine was investigated. The stabilized lipid membranes provided artificial ion gating events in the form of transient signals and can be used again after storage in air. This has allowed the practical use of the technique for chemical sensing based on lipid film for the rapid detection of vanillin in wines and alcoholic beverages.
Cyclodextrin Modified Carbon Paste Based Electrodes as Sensors for the Determination of Carcinogenic Polycyclic Aromatic Amines
Authors: Ferancová Adriana , Korgová Elena , Labuda Ján , Zima Jiří , Barek Jiří 
Published: December 2002

AbstractVoltammetric properties and possibility of the determination of carcinogenic aminoderivatives of polycyclic aromatic hydrocarbons, namely 1‐ and 2‐aminonaphthalene and 2‐aminobiphenyl, have been investigated. Carbon paste electrodes (CPE) modified with monomeric α‐, β‐ or γ‐cyclodextrin and carbon‐based screen‐printed electrodes (SPE) surface‐modified with a thin film of β‐cyclodextrin (β‐CDP) or carboxymethylated β‐cyclodextrin (β‐CDPA) condensation polymer were used for that purpose as simple electrochemical biosensors. Analytical procedure for the DPV determination of tested amines using these biosensors was proposed. Linear calibration plots within the concentration range of 2×10−8 – 2×10−7 mol dm−3 and 2×10−7–1×10−6 mol dm−3 with limits of quantification of the order of 10−9 mol dm−3 were obtained for the modified CPE and modified SPE.
Catalysis‐Electrochemical Detection of Horseradish Peroxidase at Zeptomole Level in Capillary Zone Electrophoresis
Authors: He Zhihui , Wang Haiyan , Sun Xuemei , Jin Wenrui 
Published: December 2002

AbstractCapillary zone electrophoresis with catalysis‐electrochemical detection has been developed and applied to determining horseradish peroxidase (HRP) at zeptomole levels. In this method, an on‐line enzyme catalysis reactor with a reaction capillary was designed. Isoenzymes of HRP were separated by capillary zone electrophoresis, and then they catalyzed the enzyme substrate 3,3′,5,5′‐tetramethylbenzide (TMB(Red)) and H2O2 in the reaction capillary. The reaction product, TMB(Ox), could be determined using amperometric detection on a carbon fiber microdisk bundle electrode at the outlet of the reaction capillary. Because of enzyme amplification, a significant amount of TMB(Ox) could be produced for detection. Therefore, the limit of detection (LOD) of HRP is very low. The optimum conditions of the method are 1.5×10−2 mol/L borate (pH 7.4) for the run buffer, 2×10−3 mol/L for the concentration of H2O2, 2×10−4 mol/L TMB(Red)+2.0×10−2 mol/L citrate‐phosphate (pH 5.0) for the substrate solution, 40 cm for the liquid pressure height, 20 kV for the separation voltage, 100 mV for the detection potential. HRP could be measured with a detection limit of 4.8×10−12 mol/L or 47.5 zmol (S/N=3). The linear range is from 2.40×10−11 to 2.40×10−8 mol/L. Using this method, commercial HRP was measured at zeptomole within ten minutes.
Label‐Free and Label Based Electrochemical Detection of Hybridization by Using Methylene Blue and Peptide Nucleic Acid Probes at Chitosan Modified Carbon Paste Electrodes
Authors: Kara Pinar , Kerman Kagan , Ozkan Dilsat , Meric Burcu , Erdem Arzum , Nielsen Peter E. , Ozsoz Mehmet 
Published: December 2002

AbstractA chitosan modified carbon paste electrode (ChiCPE) based DNA biosensor for the recognition of calf thymus double stranded DNA (dsDNA), single stranded DNA (ssDNA) and hybridization detection between complementary DNA oligonucleotides is presented. DNA and oligonucleotides were electrostatically attached by using chitosan onto CPE. The amino groups of chitosan formed a strong complex with the phosphate backbone of DNA. The immobilized probe could selectively hybridize with the target DNA to form hybrid on the CPE surface. The detection of hybridization was observed by using the label‐free and label based protocols. The oxidation signals of guanine and adenine greatly decreased when a hybrid was formed on the ChiCPE surface. The changes in the peak currents of methylene blue (MB), an electroactive label, were observed upon hybridization of probe with target. The signals of MB were investigated at dsDNA modified ChiCPE and ssDNA modified ChiCPE and the increased peak currents were observed, in respect to the order of electrodes. The hybridization of peptide nucleic acid (PNA) probes with the DNA target sequences at ChiCPE was also investigated. Performance characteristics of the sensor were described, along with future prospects.
Differential Pulse Voltammetric Simultaneous Determination of Four Anti‐Inflammatory Drugs by Using Soft Modelling
Authors: Reguera Celia , Ortiz M. Cruz , Arcos M. Julia 
Published: December 2002

AbstractAn application of a partial least squares calibration method for the simultaneous voltammetric determination of indomethacin, acemethacin, piroxicam and tenoxicam is suggested. It was shown that it is possible to resolve complex mixtures of analytes even when they have strongly overlapped signals. In order to check the proposed method, statistical analysis of the results was performed by mean of hypothesis tests. The method developed was applied to the electrochemical reduction region of four anti‐inflammatory drugs and allowed the drugs to be quantified at concentrations between 0.52 and 4.09 μg mL−1 for acemethacin, 0.44 and 3.50 μg mL−1 for indomethacin, 0.43 and 3.40 μg mL−1 for piroxicam, and 0.42 and 3.30 μg mL−1 for tenoxicam with good results. The average absolute value of relative errors was 2.25%, 4.31%, 1.68% and 2.49%, respectively.
A Study on Operational Parameters for Advanced Use of Bismuth Film Electrode in Anodic Stripping Voltammetry
Authors: Hočevar Samo B. , Ogorevc Božidar , Wang Joseph , Pihlar Boris 
Published: December 2002

AbstractA study is presented on the characterization, evaluation and optimization of several key operational parameters for a reliable and effective use of a bismuth film electrode (BiFE) as an advanced replacement of the mercury film electrode in anodic stripping voltammetric measurements of trace heavy metals. Applying in situ preparation of the BiFE and employing lead(II) and cadmium(II) as model analyte ions, key parameters including bismuth precursor salt and substrate surface (platinum, gold, glassy carbon, carbon paste, carbon fiber) for bismuth plating, concentration as well as cationic and anionic composition of the measurement solution, solution pH and temperature, potential interferents, and stripping modes were carefully examined for their effects in the preconcentration and stripping steps. Parameters such as substrate surface (except platinum), precursor salt, solution matrix and temperature showed no or little impact on the BiFE performance in stripping analysis. On the other hand, the BiFE performance was found to be dependent on the solution pH (with maximum efficiency in the range of 4 to 5), on the stripping mode (with square‐wave voltammetry as the best choice) and to a certain degree on the presence of surface active substances. The results revealed that the non‐toxic solid‐state BiFE is applicable under a wide variety of conditions which proves it highly suitable for practical work in environmental trace heavy metal analysis.
Copper Complexation with Soluble and Surface Freshwaters Ligands
Authors: Botelho Cidália M. S. , Boaventura Rui A. R. , de L. S. Simões Gonçalves Maria 
Published: December 2002

AbstractSpeciation of copper has been done using samples collected at different times of the year (December 92 and October 93) and in three sites of a polluted river (Este River, Northern Portugal). Filtered samples and the suspended particulate matter were titrated with metal ion and the labile metal concentrations measured by anodic stripping voltammetry (DPASV). An extra peak in the Cu voltammograms has been noticed when titrating filtered samples and its origin was investigated. Results have suggested that the extra peak is due to copper(I) stabilized by ligands adsorbed on the mercury electrode and a model for the electrochemical mechanism is proposed. From titrations of the same samples with zinc, cadmium and lead it has been concluded that there are two types of organics in the river water: macromolecules and small molecules with DML≈DM with higher affinity for soft cations such as Cd(II) and Cu(I), that can be adsorbed on mercury electrode as anions.
Electrochemical Determination of Some Organic Pollutants Using Wall‐Jet Electrode
Authors: Manisankar P. , Selvanathan G. , Viswanathan S. , Gurumallesh Prabu H. 
Published: December 2002

AbstractDetermination of organic pollutants in trace level in a flow stream was developed using a wall‐jet electrode system and square‐wave stripping principles. Pesticides such as endosulfan, isoproturon and carbendazim, o‐chlorophenol and a benzidine bisazo dye, direct orange 8 were chosen for this study. The optimum conditions for adsorptive square‐wave stripping voltammetry were arrived at and the peak current responses of analyte were correlated over flow rate. Calibration plots were obtained by correlating the peak currents with concentration under optimum conditions. The best determination range, 1×10−4 to 4.0 mg/mL for endosulfan and 1×10−4 to 1.5 mg/mL for the remaining pollutants in a flowing stream was obtained with adsorptive square‐wave stripping technique.
Combined Voltammetric‐Potentiometric Sensor with Silver Solid Amalgam Link for Electroanalytical Measurements
Authors: Yosypchuk Bogdan , Novotný Ladislav 
Published: December 2002

AbstractAn arrangement of a combined voltammetric‐potentiometric sensor (CVPS) with a silver solid amalgam link (AgSAL) was designed, comprising a working electrode inserted into an internal solution of a proper depolarizer (e.g., 10 ppm Cu(II) in 0.2 M acetate buffer, 2% tartaric acid), which is separated from the analyzed solution by the AgSAL or other amalgam links. The preparation procedure of the AgSAL was described. The sensor has been successfully tested using solutions at various concentrations of Ag(I) and Hg(II) in various types of base electrolytes, exhibiting good selectivity with respect to Ag(I) or Hg(II) ions. The proportional voltammetric current concentration dependences ip−ln c were obtained and interpreted.
The Palaeogene flora of Hochstetten‐Dhaun (Nahe‐area, Rhineland‐Palatinate, SW‐Germany)
Authors: Uhl D. , Walther H. , Krings M. 
Published: December 2002

AbstractA flora from the Palaeogene of Hochstetten‐Dhaun (Nahe‐area, Rhineland‐Palatinate, SW‐Germany) is described. Leaf remains of the intermediate Fagaceae species Eotrigonobalanus furcinervis (Rossmaessler) Walther & Kvaček represent the dominant element. Moreover, Equisetum sp., Tetraclinis salicornioides (Unger) Kvaček, Daphnogene cinnamomifolia (Brongniart) Unger forma lanceolata sensu Kvaček & Walther, Daphnogene cinnamomifolia (Brongniart) Unger forma cinnamomifolia sensu Kvaček & Walther, Daphnogene sp., cf. Quercus sp. vel Castaneophyllum sp., Eotrigonobalanus furcinervis (Rossmaessler) Walther & Kvaček, cf. subsp. haselbachensis Kvaček & Walther, cf. Trigonobalanopsis rhamnoides (Rossmaessler) Kvaček & Walther, and Populus cf. germanica (Menzel) Walther occur in this flora. In addition, three leaf‐morphotypes are characterized and several undeterminable leaf remains are listed. We interpret the source vegetation as a mixed mesophytic forest. Based on the composition and overall morphological and physiognomical character, we conclude that the flora is of lowermost Oligocene age.
Hieracia balcanica II. Taxonomic and nomenclatural notes on Hieracium calophyllum and its relatives (Asteraceae)
Authors: Szeląg Z. 
Published: December 2002

AbstractOn the basis of morphological features the taxonomic position of three taxa hitherto referred to the collective species Hieracium calophyllum R.Uechtr. is discussed. A new combination is introduced, considering H. hercegovinicum (Freyn & Vandas) Szeląg stat. nov. as a separate species. H. calophylloides Rohlena & Zahn is removed from the H. calophyllum group. Lectotypes for all names concerned are selected and illustrated.
Taxonomic significance of pollen morphology in some taxa of Resedaceae
Authors: El Naggar S.M. 
Published: December 2002

AbstractPollen morphology of 13 species and two subspecies belonging to five genera: Caylusea St.‐Hil., Ochradenus Delile, Randonia Coss., Oligomeris Cambess., and Reseda L. of Resedaceae in Egypt were investigated by light and scanning microscopy. The pollen grains were examined and separated into three pollen types and six subtypes representing the different taxonomic categories on the basis of pollen morphological characters, principally pollen shape, size and exine sculpture. The palynological results are discussed with respect to current systematic treatments of Resedaceae. According to the present palynological results, Resedaceae is a eurypalynous and not a stenopalynous family. In addition, this work came to the conclusions that further studies on the pollen of Resedaceae will be useful in establishing a phylogenetic relationship.
The delimitation, infrageneric subdivision, ecology and distribution of BomareaMirbel (Alstroemeriaceae)
Authors: Hofreiter A. , Tillich H.‐J. 
Published: December 2002

AbstractThe genus Bomarea (Alstroemeriaceae) was revised for the last time by Baker (1888). Since then the number of validly published names has increased from 75 to recently 280. A revision is urgently needed. Extended field studies in Peru (A. H.) revealed the experience to start this project. In the present paper the taxonomic history of the genus is described and the delimitation of Bomarea to the closely related genus Alstroemeria is analysed. Among the most important differences between the two genera are the fruit structure and the basic chromosome numbers, in Alstroemeria x = 8 and in Bomarea x = 9. The three known subgenera of Bomarea are redefined, mainly on ovary and fruit characters, and a fourth subgenus is added. The members of subgen. Bomarea s.str. (c. 100 species) have an inferior ovary and a dehiscent capsule, in subgen. Sphaerine (c. 15) the plants are always not twining, they have an inferior ovary and indehiscent and strikingly coloured fruits. In subgen. Wichuraea (c. 15) the ovary is semi‐inferior, and the fruit is a dehiscent capsule. In Baccata Hofreiter subgen. nov. (3) the plants are twining, the ovary is inferior and develops into an indehiscent fruit with a thick fleshy pericarp. A key to determine the subgenera is given in English and Spanish. For each subgenus the typical growth forms and their variability, habitat preferences and general distribution are discussed. Field studies in Peru revealed a high variability within the populations of Bomarea. Based on these experiences the systematic value of different characters is discussed. In general, the vegetative characters were found to be most variable, while selected generative characters are appropriate to characterise systematic groups. The greatest amount of character variability was found in subgen. Wichuraea, the most constant characters are found in subgen. Sphaerine.
How important are economic factors in choice of medical specialty?
Authors: Thornton James , Esposto Fred 
Published: December 2002

AbstractAn ongoing debate exists among health care researchers about the mechanism that allocates physicians across medical specialties, and appropriate policy measures to correct imbalances that may arise from time to time. Most researchers believe that choice of residency program by medical school graduates is key to understanding how physicians are distributed across specialties, but there is much disagreement about whether economic or non‐economic factors are most influential in determining this choice. We undertake an empirical investigation of two potentially important economic factors: income and leisure. To do so, we specify a two way error component regression model to estimate the effects of expected earnings and available leisure time, and uncertainty of earnings and leisure, on specialty choices of medical residents. Our findings indicate that economic factors are an important influence in the specialty choice process; in particular, medical residents are attracted to specialties that offer the prospect of longer and more certain annual vacations, higher earnings, shorter residency programs, and more certain work schedules. Our results suggest that employment contracts that provide generous annual vacation time and promise regular weekly work schedules may be more effective than increased earnings in correcting the current perceived shortage of primary care physicians. Copyright © 2002 John Wiley & Sons, Ltd.
A utility‐theoretic model for QALYs and willingness to pay
Authors: Klose Thomas 
Published: December 2002

AbstractDespite the widespread use of quality‐adjusted life years (QALY) in economic evaluation studies, their utility‐theoretic foundation remains unclear. A model for preferences over health, money, and time is presented in this paper. Under the usual assumptions of the original QALY‐model, an additive separable presentation of the utilities in different periods exists. In contrast to the usual assumption that QALY‐weights do solely depend on aspects of health‐related quality of life, wealth‐standardized QALY‐weights might vary with the wealth level in the presented extension of the original QALY‐model resulting in an inconsistent measurement of QALYs. Further assumptions are presented to make the measurement of QALYs consistent with lifetime preferences over health and money. Even under these strict assumptions, QALYs and WTP (which also can be defined in this utility‐theoretic model) are not equivalent preference‐based measures of the effects of health technologies on an individual level. The results suggest that the individual WTP per QALY can depend on the magnitude of the QALY‐gain as well as on the disease burden, when health influences the marginal utility of wealth. Further research seems to be indicated on this structural aspect of preferences over health and wealth and to quantify its impact. Copyright © 2002 John Wiley & Sons, Ltd.
Assessing and comparing costs: how robust are the bootstrap and methods based on asymptotic normality?
Authors: O'Hagan Anthony , Stevens John W. 
Published: December 2002

AbstractThis article addresses and challenges some common perceptions in the statistical assessment of costs and cost‐effectiveness in health economics. Cost data typically exhibit highly skew distributions. Two techniques whose validity does not depend on any specific form of underlying distribution are the bootstrap and methods based on asymptotic normality of sample means. These methods are generally thought to be appropriate for the analysis of cost data.We argue that, even when these methods are technically valid, they may often lead to inefficient and even misleading inferences. It is important to apply methods that recognise the skewness in cost data.We further demonstrate that it may also be important to incorporate relevant prior information in a Bayesian analysis. Copyright © 2002 John Wiley & Sons, Ltd.
Eliciting several willingness to pay in a single contingent valuation survey: application to health care
Authors: Luchini Stéphane , Protière Christel , Moatti Jean‐Paul 
Published: December 2002

AbstractThe usual implementation of contingent valuation (CV), in the context of priorities setting for allocation of public funds in health care, is to develop as many surveys as there are programmes, i.e. to perform separate evaluations (SE). In the EuroWill project, three health programmes (for heart disease, breast cancer and a service of helicopter ambulance) were however simultaneously evaluated, i.e. a joint evaluation (JE) was performed. The paper examines the issue of the econometric techniques that should be used to estimate WTP values obtained in the context of JE by comparing the application of independent OLS regressions for each programme versus simultaneous estimations using seemingly unrelated regressions (SUR) on data of the French EuroWill survey. It shows that separate estimations may lead to misspecifications because they cannot take into account that JE exogenously provides a reference structure to the respondent which affects the estimates of WTP for each programme. Therefore, the potential advantage of JE versus SE as an elicitation technique in CV studies applied to health care (to better control the referents used by respondents for evaluating different programmes) only holds if simultaneous rather than independent techniques are used in the estimation of WTPs. Copyright © 2002 John Wiley & Sons, Ltd.
Estimating the monetary value of health care: lessons from environmental economics
Authors: Hanley Nick , Ryan Mandy , Wright Robert 
Published: December 2002

AbstractIn the recent past, considerable effort in health economics has been made on applying stated preference methods such as contingent valuation and choice experiments. Despite this increased use, there is still considerable scepticism concerning the value of these approaches. The application of contingent valuation in environmental economics has a long history and has been widely accepted. Whilst choice experiments were introduced to the environmental and health economics literature at a similar time, the wider acceptance of monetary measures of benefit in environmental economics has meant that they have also been more widely applied. The purpose of this paper is to identify some of the key issues and debates that have taken place in the environmental economics literature, summarise the state of the art with respect to these issues, and consider how health economists have addressed these issues. Important areas for future research in health economics are identified. Copyright © 2002 John Wiley & Sons, Ltd.