bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ca for Er substitution in tetragonal ErPO4 · H2O crystallised from phosphoric acid solution
Authors: Kijkowska R. 
Published: February 2004

AbstractErbium phosphate monohydrate with limited Ca for Er substitution, obtained through crystallisation from boiling phosphoric acid solution has been characterised by X‐ray diffraction, Ir‐spectroscopy and thermal analysis (TGA‐DTA) methods. The difference in the electric charge between di‐valent calcium and tri‐valent erbium in the solid crystallised was compensated by simultaneous substitution of HPO42‐ for PO43‐. Ca incorporation in erbium phosphate made expansion of tetragonal ErPO4 · H2O unit cell. After ignition at 900 °C the tetragonal crystal modification was maintained but the unit cell parameters of all the investigated phosphates, whether Ca‐substituted or Ca‐free, contracted to the same level. The unique contraction of the unit cell was resulted from recrystallisation of Ca‐substituted into Ca‐free erbium phosphate, while Ca was transferred into Ca(PO3)2 formed as a separate phase. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fluctuation of crystallization at center part of floating molten zone under reduced gravity condition
Authors: Kimura H. , Miyazaki A. , Maiwa K. , Nakamura H. 
Published: February 2004

AbstractFluctuation of crystallization was observed at floating molten zone under reduced gravity condition on airplane. The zone material was Ba(B0.9Al0.1)2O4. A pair of Pt tubes was used at the upper and the lower positions, and the molten zone was formed between two Pt tubes. Double peak temperature profile could be performed using two Pt tubes. Crystallization of the molten Ba(B0.9Al0.1)2O4 was started at center part of side surface of floating molten zone under reduced gravity condition. The formed crystal was melted again during the crystallization by the gravity fluctuation at the center part of the floating molten zone. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystallization of phosphogypsum in continuous phosphoric acid industrial plant
Authors: Abdel‐Aal E. A. 
Published: February 2004

AbstractUnderstanding crystallization of phosphogypsum is generally of basic importance for industrial wet‐process phosphoric acid production. In this paper, measuring the phosphogypsum crystal size distribution during primary and secondary nucleation is reported. The results show that, secondary nucleation was occurred at 5 hr run time (12.5% solid content). Crystal growth rates were about 18.4 μm/hr at 2.5% solid content and about 4.5 μm at 30% solid content. At steady state (16 hr run time and 30% solid content), the mean diameter of the crystals and the average specific surface area are about 25 μm and 0.69 m2/g, respectively. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Studies on a new Rb3H9(PO4)4 crystal
Authors: Fukami T. , Chen R. H. 
Published: February 2004

AbstractA new type of trirubidium nonahydrogen tetraphosphate, Rb3H9(PO4)4, crystal has been crystallized. Differential scanning calorimetry (DSC) and X‐ray diffraction measurements have been performed on the title compound. The crystal does not undergo any structural phase transition in the temperature range from 120 to 440 K except a melting transition at 399 K. The compound belongs to a monoclinic system with space group C2/c at room temperature. The structure is built on a framework of PO4 tetrahedra linked by five types of OH‐O hydrogen bonds in the length range from 2.472(4) to 2.679(4) Å. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of density of states on optical properties of GaSe thin film
Authors: Thamilselvan M. , Premnazeer K. , Mangalaraj D. , Narayandass Sa. K. , Yi Junsin 
Published: February 2004

AbstractA systematic investigation on the effect of substrate temperature on the structure, optical absorption and density of states of vacuum evaporated gallium monoselenide (GaSe) thin films is reported. The X‐ray diffraction analysis shows an occurrence of amorphous to polycrystalline transformation in the films deposited at higher‐temperature substrates (573K). The compositional analysis is made with Auger Electron Spectroscopy (AES). The thickness of the film (175nm) is measured by a multiple beam interferometery. Optical characteristics of the GaSe sample have been analyzed using spectrophotometer in the photon energy range of 1.0 ‐ 4 eV. The absorption mechanism has been recognized and the allowed indirect as well as forbidden direct transitions have been found. As‐deposited films show two indirect and allowed transitions due to spin‐orbit splitting of the valence band, as reported here for the first time. Low field conduction have enabled us to determine the density of states in amorphous and poly‐GaSe films. The amorphous and polycrystalline GaSe thin films have localized states density values of N (EF) = 1.686 × 1017 cm‐3 eV‐1 and 1.257 × 1015 cm‐3 eV‐1 respectively. The experimental results are interpreted in terms of variations in the density of localized states due to progressive decrease of the unsaturated bonds during deposition. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Measurements of optical anisotropy of a calamitic lyotropic liquid crystal
Authors: Beica T. , Moldovan R. , Tintaru M. , Enache I. , Frunza S. 
Published: February 2004

AbstractOptical birefringence measurements for a calamitic lyotropic liquid crystal containing sodium lauryl sulphate/decanol/water are presented. A value of the order of 10‐3 was obtained, much smaller than that of thermotropic liquid crystals. The order parameter temperature dependence is evaluated using an extrapolating method and taking into accounts the influence of the micelle shape. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dielectric characteristics of Ce3+ doped Sr0.61Ba0.39Nb2O6 with Cole‐Cole plots technique
Authors: Şentürk E. 
Published: February 2004

AbstractIn this paper, we have investigated two‐relaxator mechanism and dielectric characteristics of Ce3+ doped Sr0.61Ba0.39Nb2O6 with dielectric spectroscopy measurements. The crystal undergoes a ferroelectric phase transition at 340 K. The temperature dependence of the real and imaginer part of the complex dielectric susceptibility in vicinity of ferroelectric‐paraelectric phase transition has been studied in the frequency region 0.1 kHz–10 MHz. The measurements of the dielectric constant of the real and imaginer parts show strongly frequency dependence. The investigations of the dielectric constant revealed a non‐Debye type dielectric relaxation for Ce+3 doped SBN61 by using Cole‐Cole plots. It reveals the coexistence of the two dielectric relaxators in vicinity of the phase transition. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystal structure analysis of 5‐amino‐7‐(pyrrolidin‐1‐yl)‐2,4,4‐trimethyl‐1,4‐dihydro‐1,6‐naphthyridine‐8‐carbonitrile
Authors: Selvanayagam S. , Rajakannan V. , Narasinga Rao S. , Shanmuga Sundara Raj S. , Fun H. K. , Raghukumar V. , Velmurugan D. 
Published: February 2004

AbstractThe title compound [CCDC 199359], C16H20N5 crystallized in Monoclinic system with the space group C2/c. The unit cell parameters are: a = 16.554(6), b = 12.145(4), c = 16.221(5)Å and β = 102.67(1)°. The molecular structure is stabilized by an intramolecular C‐H…N type hydrogen bond and the molecular packing by the intermolecular C‐H…N and N‐H…N type hydrogen bonds. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrocatalytic Oxidation of Methanol on a Nickel‐Porphyrin IX Complex Modified Glassy Carbon Electrode in Alkaline Medium
Authors: Golabi S. M. , Nozad A. 
Published: February 2004

AbstractElectrocatalytic oxidation of methanol on a glassy carbon disc electrode modified with Ni(II)‐hematoporphyrin IX, complex and conditioned by potential recycling in a limited range (between 100 and 600 mV vs. SCE) in 0.10 M NaOH solution, abbreviated as NiOHPME(A), was studied by cyclic voltammetry in alkaline medium. The results were compared with those obtained for a NiO modified glassy carbon electrode, NiOME, prepared in similar conditions. The findings show that the NiOHP film at NiOHPME(A) behaves as an efficient electrocatalyst for the oxidation of methanol in alkaline medium via Ni(III) species with the cross‐exchange reaction occurring throughout the layer at a low concentration of methanol and for a thin film of modifier. A plausible mechanism was proposed for catalytic oxidation of methanol at NiOHP modified electrode. Moreover, the effects of various parameters such as the scan rate, methanol concentration, thickness of NiOHP film and the real surface area of modified electrode on the oxidation of methanol were investigated. Finally, it has been shown that the NiOHPME(A) has a long‐term stability toward the oxidation of methanol.
Self‐Assembling of Hybrid Prussian Blue Units in Cinder Matrix: Characterization and Electrocatalysis
Authors: Kumar Annamalai Senthil , Chen Pei‐Yan , Zen Jyh‐Myng 
Published: February 2004

AbstractIndustrial waste cinder (CFe*) has been utilized as a stable anchoring matrix for self‐assembling of Fe(CN)63− as hybrid Prussian blue units (PB, *Fe3+FeII(CN)6) on a screen‐printed carbon electrode (SPE) for efficient catalytic applications. The waste cinder was found to be a composite of calcium and iron silicates similar to glass matrix by X‐ray photoelectron spectroscopic (XPS) study. The hybrid PB formations were confirmed by both FT‐IR and electrochemical methods. Most importantly, the free iron (Fe*) ion bound to the non‐bridging oxygen terminals of the silicates was found to play a key role in the PB formation. The self‐assembled PB hybrid on the cinder‐modified screen‐printed electrodes (designated as PBCFe*‐SPE) improved linear detection range and sensitivity for H2O2 mediated oxidation than those obtained at a classical PB‐SPE in 0.1 M, pH 2 KCl/HCl base electrolyte at 0.0 V (vs. Ag/AgCl) by amperometric batch analysis.
Determination of Azidothymidine – an Antiproliferative and Virostatic Drug by Square‐Wave Voltammetry
Authors: Vacek Jan , Andrysík Zdeněk , Trnková Libuše , Kizek René 
Published: February 2004

AbstractThe 3′‐azido‐3′‐deoxythymidine (AZT, Zidovudine) is an antiproliferative and virostatic drug widely used in human immunodeficiency virus type 1 (HIV‐1) infection treatment. With respect to side effects of high doses and a short half‐life of AZT, a fast and simple detection method for this agent could be helpful. The aim of our study was to determine AZT levels in natural samples (urine, serum, whole blood, and cell cultures, such as the HaCaT line of keratinocytes) without their mineralization and/or purification, by means of electrochemical methods using hanging mercury drop electrode (HMDE). On this electrode, AZT undergoes irreversible reduction at the peak potential near Ep−1.1 V (vs. Ag/AgCl/3 M KCl). Reduction AZT signals were measured by cyclic voltammetry (CV), differential pulse voltammetry (DPV), square‐wave voltammetry (SWV), and constant current chronopotentiometric stripping analysis (CPSA). In phosphate buffer (pH 8) the SWV yielded the best AZT signal with the detection limit of 1 nM. The determination of AZT concentration in biological materials is affected by electroactive components, such as proteins and DNA. For monitoring the influence of these compounds, AZT reduction was performed in the presence of 10 μg/mL calf thymus ssDNA and/or 100 μg/mL bovine serum albumin. In these cases, the detection limit increased to 0.25 μM. Also studied was the AZT concentration in keratinocyte cells (HaCaT line) during cell cultivation. It has been shown that the SWV may be considered as a useful tool for the determination of AZT concentration in cell cultures, and for monitoring AZT pharmacokinetics.
Reference Electrodes Based on Solid Amalgams
Authors: Yosypchuk Bogdan , Novotný Ladislav 
Published: February 2004

AbstractA reference saturated calomel electrode based on the non‐toxic silver solid amalgam (SCE‐AgSA) as a substitute for liquid mercury is described. Long‐term as well as short‐term tests made during a period of one year confirmed the SCE‐AgSA potential to be equal to that of SCE within the limits of ±1 mV (the difference ΔESCE‐AgSA=+1.08±0.24 mV (vs. SCE); SD=0.87; N=51). The voltammograms of four selected metal ions registered vs. SCE‐AgSA and vs. SCE could practically overlap each other. None of the mentioned electrodes were polarized to a significant degree even if the electric current applied reached 2 mA. On the basis of the obtained results the SCE‐AgSA could be considered as equivalent substitute for SCE. Owing to practically identical electrode potential of both types of the mentioned electrodes the results obtained using SCE‐AgSA are completely comparable to those measured vs. SCE, without any correction of peak potentials.
Electrochemical Detection of Trace Concentrations of Cadmium and Lead with a Boron‐Doped Diamond Electrode: Effect of KCl and KNO3 Electrolytes, Interferences and Measurement in River Water
Authors: Babyak Carol , Smart Ronald B. 
Published: February 2004

AbstractParts‐per‐billion levels of cadmium and lead were detected using square‐wave anodic stripping voltammetry with a boron‐doped diamond electrode. Calibration plots (10‐minute deposition time) in KCl and KNO3 were non‐linear at low concentrations (1–5 ppb) due to the deposition mechanism of these metals. The preferred electrolyte for cadmium was KCl, while lead could be measured in either electrolyte. The lowest concentrations included in the linear portion of the calibration plot (5 minute deposition time) for cadmium were 10 ppb and 50 ppb in KCl and KNO3, respectively, and 10 ppb for lead in KNO3. The presence of either lead or copper suppressed the cadmium stripping peak, but the lead stripping peak was unaffected by cadmium, and enhanced by the addition of copper. A river water sample was analyzed for cadmium and lead, and the cadmium results were confirmed using ICP‐AES spectrometry. It was determined electrochemically that a fraction of lead in the river sample was bound by complexing material in the sample.
Determination of Reserpine in Urine by Capillary Electrophoresis with Electrochemiluminescence Detection
Authors: Cao Weidong , Yang Xiurong , Wang Erkang 
Published: February 2004

AbstractA fast and sensitive approach to detect reserpine in urine using micellar electrokinetic capillary chromatography with electrochemiluminescence (ECL) of Ru(bpy)32+ detection is described. Using a 25 μm i.d. capillary as separation column, the ECL detector was coupled to the capillary in the absence of an electric field decoupler. Field‐amplified injection was used to minimize the effect of ionic strength in the sample and to achieve high sensitivity. In this way, the sample was analyzed directly without any pretreatment. The method was validated for reserpine in the urine over the range of 1×10−6−1×10−4 mol/L with a correlation coefficient of 0.996. The RSD for reserpine at a level of 5 μmol/L was 4.3%. The LOD (S/N=3) was estimated to be 7.0×10−8 mol/L. The average recoveries for 10 μmol/L reserpine spiked in human urine were 94%.
Flow Injection Amperometric Detection at Enzyme‐Modified Gold Nanoelectrodes
Authors: Delvaux Marc , Demoustier‐Champagne Sophie , Walcarius Alain 
Published: February 2004

AbstractGold nanotubular electrode ensembles were prepared by using electroless deposition of the metal within the pores of polycarbonate particle track‐etched membranes. Glucose oxidase (Gox), used as a model enzyme, has been immobilized onto preformed self‐assembled monolayers (mercaptoethylamine or mercaptopropionic acid) on electroless gold via cross‐linking with glutaraldehyde or covalent attachment by carbodiimide coupling. Flow‐injection analysis systems in flow‐through or wall‐jet configurations using these Gox‐modified nanoelectrodes are described. The influence of different experimental parameters (i.e., applied potential, flow rate, interferents…︁) on the analytical response of the sensor to glucose has been evaluated. Under optimized conditions, very reproducible results (standard deviations <4%, n=38) were obtained, linear calibration was achieved in the 2×10−4 M to 3×10−2 M concentration range and the detection limit was 2×10−4 M. Moreover, no significant interferences from species like ascorbic and uric acids were observed at a potential of +0.9 V.
Electroanalytical Characteristics of Amisulpride and Voltammetric Determination of the Drug in Pharmaceuticals and Biological Media
Authors: Özkan Sibel A. , Uslu Bengi , Sentürk Zühre 
Published: February 2004

AbstractThe electrochemical oxidation of antipsychotic drug amisulpride (AMS) has been studied in pH range 1.8–11.0 at a stationary glassy carbon electrode by cyclic, differential pulse and square‐wave voltammetry. Two oxidation processes were produced in different supporting electrolyte media. Both of the oxidation processes were irreversible and exhibited diffusion controlled. For analytical purposes, very resolved voltammetric peaks were obtained using differential pulse and square‐wave modes. The linear response was obtained in the range of 4×10−6 to 6×10−4 M for the first and second oxidation steps in Britton‐Robinson buffer at pH 7.0 and pH 3.0 (20% methanol v/v), respectively, using both techniques. These methods were used for the determination of AMS in tablets. The first oxidation process was chosen as indicative of the analysis of AMS in biological media. The methods were successfully applied to spiked human serum, urine and simulated gastric fluid samples.
Effect of Carbon Dioxide and Ammonia on Polymer Electrolyte Membrane Fuel Cell Stack Performance
Authors: Rajalakshmi N. , Jayanth T.T. , Dhathathreyan K.S. 
Published: February 2004

AbstractProton exchange membrane fuel cell (PEMFC) performance degrades when impurities are present in the anode fuel gas, referred to as catalyst poisoning. This paper investigates the effect of carbon dioxide and ammonia as impurities in the anode gas of the PEMFC, and found that the presence of CO2decreases the performance of the fuel cell by up to 10%. The performance loss depends on the CO2concentration and the exposure time. The voltage loss is recoverable on passing pure hydrogen gas, indicating that a permanent poisoning of the catalyst layer has not taken place. Exposure of the fuel cell to ammonia beyond 20 ppm, even for a short duration, causes permanent PEMFC failure, probably due to the deterioration of the membrane.
Analysis of Optimal Heat Transfer in a PEM Fuel Cell Cooling Plate
Authors: Chen F.C. , Gao Z. , Loutfy R.O. , Hecht M. 
Published: February 2004

AbstractAn analysis of three‐dimensional computational fluid dynamics (CFD) is conducted to investigate the coupled cooling process involved in fluid flow and heat transfer between the solid plate and the coolant flow for optimization of the cooling design of a fuel cell stack. A conception of IUT (Index of Uniform Temperature) across the entire area is presented to evaluate the degree of uniform temperature profile across the cooling plates. Six cooling modes, including three serpentine‐type modes and another three parallel‐type modes, are presented and analyzed for optimization of the cooling mode of fuel cells. The prediction finds that the cooling effect of serpentine‐type cooling modes could be better than that of parallel‐type cooling modes.
First Steps Towards Fuel Cells Testing Harmonisation: Procedures and Parameters for Single Cell Performance Evaluation
Authors: Lunghi P. , Ubertini S. 
Published: February 2004

AbstractThe great interest in Fuel Cell Systems, combined with the innovation of the device itself, has led to a huge developmental effort to make the steps necessary for future FC plant commissioning.The clearest and most effective way to evaluate the performance of a fuel cell is to measure it directly and, since few fuel cell test rigs are available at the moment, standard experimental procedures have not been realized so far.Our research group is currently performing single cell testing at the University of Perugia fuel cell laboratory and particular emphasis has been put on the definition of procedures and the testing of parameterisation. The work team strongly believes that this is the key to effective system testing and reliable performance evaluation.In this work, the test parameterisation developed by the team, and the resulting advanced control procedure used for a single MCFC experimental characterization are presented. Efforts have been dedicated to obtain some relevant non‐dimensional parameters to allow an easy understanding of the results and quick comparisons with other tests under different operating conditions, or with results obtained on different cells eventually tested in different laboratories. The authors strongly emphasise this topic to avoid the data that developers and research institutions collect being of no practical use due to a lack of shared rules.
Design of a Tubular Ceramic Membrane for Gas Separation in a PEMFC System
Authors: Kamarudin S.K. , Daud W.R.W. , Mohammad A.W. , Som A.Md. , Takriff M.S. 
Published: February 2004

AbstractThe objective of this study is to introduce a shortcut in the method of design for a tubular ceramic membrane (TCM) for gas separation. Generally, it explains the permeation of the multi component gas using cross flow models in a porous membrane and the surface area of the membrane required. The novel aspect of this method is that the expression for the length of the membrane is simplified to a number unit (NTU) and a height of transfer unit (HTU). The HTU term for porous membranes is characterised by the physical properties of the membrane; the feed flow rate, nF, membrane thickness, lM, feed pressure, PF, K the permeability of gas and the diameter of the membrane, DM. The integral for NTU of a porous membrane is the solution for the local permeate along the length of the membrane. It is found that, NTU mainly depends on the rejection stream, xR,, along the membrane and it describes the relative degree of separation. The Proton Electrolyte Membrane Fuel Cell (PEMFC) system is taken as the case study. CO is the main culprit in reducing the performance of the PEMFC and will act as a catalyst poison for the fuel cell anode at a concentration as low as 100 ppm. Thus, the reformate, from primary reforming, contains a significant amount of CO and must be purified. The effect of some important parameters such as temperature, pressure and the thickness of membrane to the degree of separation are presented in this paper. From the results, it can be seen that the system could reduce the CO concentration from 2000 – 500 ppm. Basically the TCM will operate, in series, with a pressure swing adsorber in order to further reduce the concentration of CO to less than 10 ppm before entering the fuel cell stack. However, this paper only focuses on the design of the TCM. Besides this, it is observed that the purity of the hydrogen increased from 72.8 – 96% (at θ = 0.5) after the membrane.