bluuebunny/crossref_metadata_2025_split huggingface dataset:
An analysis of superconducting fault current limiter for stabilization of synchronous generators in multimachine system: A two‐machine infinite bus system
Authors: Yagami Masaki , Shibata Shinsuke , Murata Toshiaki , Tamura Junji 
Published: June 2004

AbstractThis paper presents the results of analyses of the effectiveness of a superconducting fault current limiter (SFCL) to stabilize the synchronous generators, suppress turbine shaft torque oscillations, and limit the fault current in a two‐machine infinite bus system. In this study, the system model with two SFCLs having shunt resistance installed at each generator terminal was used taking 3LG (three lines to ground) fault at 12 fault points into account. These analyses were performed using EMTP/ATP. It is found that the use of SFCL with a shunt resistance value of 1.1 pu is most effective for all fault points for the stabilization of synchronous generators, the suppression of turbine shaft torque oscillations, and the limitation of fault current. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(3): 44–53, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10272
Impulse partial discharge and breakdown characteristics of rod–plane gaps in air and N2 gases
Authors: Saitoh Hitoshi , Morita Keiichi , Kikkawa Takashi , Hayakawa Naoki , Okubo Hitoshi 
Published: June 2004

AbstractIn response to growing environmental concerns, we attempted to develop switchgear without using SF6 gas. In our research, we used compressed air and pure N2 as an electrical insulation gas, because of their low global warming potential. In this paper, we examined the impulse breakdown and impulse partial discharge characteristics under various conditions related to nonuniformity of the electric field. The experimental results show that the breakdown voltage (BDV) of air is higher than that of pure N2 gas under highly nonuniform field conditions in the rod–plane gap. On the other hand, the discharge inception voltage of air and N2 were almost the same. Furthermore, first partial discharge (PD), leader discharge, and its transition to the breakdown were successfully observed through the measurement of discharge current and light emissions under impulse voltage application. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(3): 36–43, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10277
Relative permittivity and conductivity of water‐treed region in XLPE estimated by an equivalent circuit
Authors: Ozaki Tamon , Ito Noriyuki , Kawai Jiro , Nakamura Shuhei 
Published: June 2004

AbstractBy dividing a water‐treed XLPE sheet sample of 1 mm thickness into a nondegraded region and a water‐treed one, relative permittivity $\varepsilon'_{\rm T2}$ and AC conductivity σAC2 of the water‐treed region have been estimated using an equivalent circuit. The variation of $\varepsilon'_{\rm T2}$ and σAC2 with the length r of the water‐treed region has been discussed based on the Sillars model. It was concluded that the volume fraction of water in the water‐treed layer is in the range from 0.5% to 1.5% for the most‐degraded XLPE sheet, which depends on the ratio of axes of spheroids to which water‐filled voids and channels are compared. It was also concluded that the AC conductivity of water in the water‐treed region ranges from 3 × 10−3 S/m to 2 × 10−2 S/m. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(3): 7–14, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10332
Novel Phosphovanadate Layered Structure Assembled from a Tetrametallic Cubane‐Like VV Cluster
Authors: Shi Fa‐Nian , Paz Filipe A. Almeida , Rocha João , Klinowski Jacek , Trindade Tito 
Published: June 2004

AbstractA novel phosphovanadate layered structure intercalated by 4,4′‐bipyridinium cations, (C10H10N2)[(VO2)4(PO4)2], was synthesised under hydrothermal conditions and its crystal structure determined using single‐crystal X‐ray diffraction. The anionic [(VO2)4(PO4)2]n2n− perforated layers are strongly hydrogen bonded to the interlayer 4,4′‐bipyridinium cations and are assembled by an unprecedented secondary tetrametallic VV building unit constructed from a distorted cubane‐like {V4O4} cluster. The compound was further characterised by IR, Raman, 1H, 1H‐13C, 31P and 51V MAS NMR spectroscopy, and by thermal and elemental analysis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Characterization of Self‐Assembling of Glucose Dehydrogenase in Mono‐ and Multilayers on Gold Electrodes
Authors: Loew Noya , Scheller Frieder W. , Wollenberger Ulla 
Published: June 2004

AbstractGlucose dehydrogenase (GDH) was assembled electrostatically onto QCM‐gold electrodes by their sequential deposition with anionic polyelectrolytes such as PSS and PASA. For the layer‐by‐layer arrangements both the microgravimetric and the electrochemical sensor signal were followed. Increasing amounts of GDH were deposited by stepwise formation of alternating layers of GDH and PSS or PASA. The mass increase was about 1.88 μg/cm2 for one GDH/PASA bilayer and 2.4 μg/cm2 for a GDH/PSS bilayer. The addition of phenolic compounds resulted in an oxidation current, which could be catalytically increased by the GDH catalysed reaction in the presence of glucose. The system functions as glucose sensor when quinones are present in nonlimiting amount. The amperometric response was already diffusion limited when a single layer of GDH was adsorbed. The sensor sensitivity increased by a factor of 10 when MSA was used instead of MUA as initial electrode modifier.
Phospholipid‐lysozyme coating for chiral separation in capillary electrophoresis
Authors: Bo Tao , Wiedmer Susanne K. , Riekkola Marja‐Liisa 
Published: June 2004

AbstractA phospholipid coating with lysozyme as chiral recognition reagent permeated into the phospholipid membrane was developed for the chiral capillary electrophoretic (CE) separation of D‐ and L‐tryptophan. As a kind of carriers, coated as phospholipid membranes onto the inner wall of a fused‐silica capillary, liposomes are able to interact with basic proteins such as lysozyme, which may reside on the surface of the phospholipid membrane or permeate into the middle of the membrane. The interaction results in strong immobilization of lysozyme in the capillary. Coatings prepared with liposomes alone did not allow stable immobilization of lysozyme into the phospholipid membranes, as seen from the poor repeatability of the chiral separation. When 1‐(4‐iodobutyl)‐1,4‐dimethylpiperazin‐1‐ium iodide (M1C4) was applied as a first coating layer in the capillary, the electroosmotic flow (EOF) was effectively suppressed, the phospholipid coating was stabilized, and the lysozyme immobilization was much improved. The liposome composition, the running buffer, and the capillary inner diameter all affected the chiral separation of D‐ and L‐tryptophan. Coating with 4 mM M1C4 and then 1 mM phosphatidylcholine (PC)/phosphatidylserine (PS) (80:20 mol%), with 20 mM (ionic strength) Tris at pH 7.4 as the running buffer, resulted in optimal chiral separation with good separation efficiency and resolution. Since lysozyme was strongly permeated into the membrane of the phospholipids on the capillary surface, the chiral separation of D‐ and L‐tryptophan was achieved without lysozyme in the running buffer. The effects of different coating procedures and separation conditions on separation were evaluated, and the M1C4–liposome and liposome–lysozyme interactions were elucidated. The usefulness of protein immobilized into phospholipid membranes as a chiral selector in CE is demonstrated for the first time.
Influence of branch length asymmetry on the electrophoretic mobility of rigid rod‐like DNA
Authors: Heuer Daniel M. , Saha Sourav , Kusumo Andy T. , Archer Lynden A. 
Published: June 2004

AbstractThe electrophoretic mobility of three‐arm asymmetric star DNA molecules, produced by incorporating a short DNA branch at the midpoint of rigid‐rod linear DNA fragments, is investigated in polyacrylamide gels. We determine how long the added branch must be to separate asymmetric star DNA from linear DNA with the same total molecular weight. This work focuses on two different geometric progressions of small DNA molecules. First, branches of increasing length were introduced at the center of a linear DNA fragment of constant length. At a given gel concentration, we find that relatively small branch lengths are enough to cause a detectable reduction in electrophoretic mobility. The second geometric progression starts with a small branch on a linear DNA fragment. As the length of this branch is increased, the DNA backbone length is decreased such that the total molar mass of the molecule remains constant. The branch length was then increased until the asymmetric branched molecule becomes a symmetric three‐arm star polymer, allowing the effect of molecular topology on mobility to be studied independent of size effects. DNA molecules with very short branches have a mobility smaller than linear DNA of identical molar mass. The reason for this change in mobility when branching is introduced is not known, however, we explore two possible explanations in this article. (i) The branched DNA could have a greater interaction with the gel than linear DNA, causing it to move slower; (ii) the linear DNA could have modes of motion or access to pores that are unavailable to the branched DNA.
Injection by hydrostatic pressure in conjunction with electrokinetic force on a microfluidic chip
Authors: Gai Hongwei , Yu Linfen , Dai Zhongpeng , Ma Yinfa , Lin Bingcheng 
Published: June 2004

AbstractA simple method was developed for injecting a sample on a cross‐form microfluidic chip by means of hydrostatic pressure combined with electrokinetic forces. The hydrostatic pressure was generated simply by adjusting the liquid level in different reservoirs without any additional driven equipment such as a pump. Two dispensing strategies using a floating injection and a gated injection, coupled with hydrostatic pressure loading, were tested. The fluorescence observation verified the feasibility of hydrostatic pressure loading in the separation of a mixture of fluorescein sodium salt and fluorescein isothiocyanate. This method was proved to be effective in leading cells to a separation channel for single cell analysis.
Chamber with modifiable inner width for performing transversal alternating field electrophoresis in variable numbers of minigels
Authors: Riverón Ana María , Herrera José Alfredo , López‐Cánovas Lilia 
Published: June 2004

AbstractWe present a transversal alternating field electrophoresis chamber that allows modifiable inner widths to accommodate low‐ or high‐throughput formats, with 7.8 cm opposite electrode separation and 30.4 cm electrode length. Removable slotted sheets divide the chamber into four smaller compartments, each one supporting a minigel of 3.85 cm in length and 7.1 cm in width. Replacements of slotted sheets with solid dielectric blocks with the sizes and shapes of compartments permit to occlude chamber compartments, changing from 4 to 1 the numbers of minigels per run, from 88 to 13 the maximum numbers of samples, and from 1688 to 422 mL the volume of buffer poured into the chamber. Saccharomyces cerevisiae chromosomes gave its characteristic DNA band pattern in all compartments, whereas migrations of DNA molecules are not affected by the occlusion of compartments.
Direct multicomponent analysis of beer samples constituents using micellar electrokinetic capillary chromatography
Authors: Cortacero‐Ramírez Sonia , Segura‐Carretero Antonio , Cruces‐Blanco Carmen , Hernáinz‐Bermúdez de Castro Miguel , Fernández‐Gutiérrez Alberto 
Published: June 2004

AbstractA capillary electrophoretic method was developed using micellar electrokinetic capillary chromatography (MEKC) with diode‐array detection to analyze simultaneously 26 beer constituents in a single procedure, including alcohols, iso‐α‐acids, amino acids, flavonoids, isoflavonoids, a vitamin, purine and pyrimidine bases. After filtration, sample components were separated with an uncoated capillary and a 25 mM sodium borate and 110 mM SDS buffer at pH 10.5. Analyses were run at 14 kV and 8 s of hydrodynamic injection with UV detection at 210 nm and 270 nm. The proposed method was successfully applied to the direct determination of beer constituents without any sample cleanup procedures.
Separation of fluorescein isothiocyanate‐labeled amines by microchip electrophoresis in uncoated and polyvinyl alcohol‐coated glass chips using water and dimethyl sulfoxide as solvents of background electrolyte
Authors: Varjo Sami J. O. , Ludwig Martin , Belder Detlev , Riekkola Marja‐Liisa 
Published: June 2004

AbstractOn‐chip capillary electrophoresis with uncoated and polyvinyl alcohol‐coated glass channels in aqueous and nonaqueous dimethyl sulfoxide (DMSO) background electrolyte (BGE) solutions was applied in the separation of five amines derivatized with fluorescein‐5‐isothiocyanate. In aqueous BGE at pH 9.2, baseline separation of the analytes was not achieved on uncoated glass chips, but the separation was clearly improved when the chip channels were coated with polyvinyl alcohol (PVA). Separation was successful in nonaqueous DMSO electrolyte solution containing ammonium acetate and sodium methoxide, on both uncoated and PVA‐coated glass microchips. The differences in the pKa values of analytes were probably amplified in DMSO, and all five analytes were at least partly dissociated and were separated. Because the viscosity of DMSO is higher than that of water, the migration times were longer in DMSO.
Determination of protein‐ligand affinity constants from direct migration time in capillary electrophoresis
Authors: Nilsson Mikael , Harang Valerie , Bergström Maria , Ohlson Sten , Isaksson Roland , Johansson Gunnar 
Published: June 2004

AbstractA simple method to calculate dissociation constants for protein‐ligand interactions by partial‐filling capillary electrophoresis is demonstrated. The method uses raw migration time data for the ligand and needs only additional information about capillary inner radius and the absolute amount of protein loaded. A theoretical study supported by experimental data also demonstrates that the retention of analyte in affinity capillary electrophoresis (ACE) using the partial‐filling technique depends linearly on the absolute amount of selector added but is independent of both selector zone length and selector mobility. Factors such as field strength and electroosmotic flow are also cancelled out if they are kept constant. The theory is confirmed and the usefulness of the method is demonstrated by enantioseparations using α‐acid glycoprotein (AGP) and cellulase (Cel 7A) as chiral selectors.
Separation of flavonoids and phenolic acids from propolis by capillary zone electrophoresis
Authors: Volpi Nicola 
Published: June 2004

AbstractThe simultaneous determination of twelve different flavonoids, pinocembrin, acacetin, chrysin, rutin, catechin, naringenin, galangin, luteolin, kaempferol, apigenin, myricetin, and quercetin, two phenolic acids, cinnamic acid and caffeic acid, and one stilbene derivative, resveratrol, in propolis extracts used in medicine has been investigated by capillary zone electrophoresis (CZE). With a buffer constituted by sodium tetraborate 30 mM, pH 9.0, and 15 kV applied voltage, the 15 polyphenols were separated on an uncoated fused‐silica capillary within 40 min using normal polarity. Under the experimental conditions used, a linear relationship was calculated between the CZE migration times and the molecular weight of polyphenols' expression of the increasing amount of their hydroxyl groups and polarity. Regression equations revealed a linear relationship (correlation coefficients > 0.97) between the peak area of each polyphenol species and their concentration, from 6 to 120 ng. The levels of analytes in three different propolis extracts, ethanolic, aqueous‐ethanolic and aqueous‐glycolic, used to prepare various commercial medicinal products, were determined. The aqueous‐ethanolic propolis extract showed a great percentage of caffeic acid, galangin, quercetin, and chrysin, whilst the ethanolic preparation was composed of a great amount of resveratrol, chrysin, and caffeic acid. On the contrary, the aqueous‐glycolic propolis preparation was composed of approx. 11% of caffeic acid and a low amount of the other identified flavonoids due to the presence of approx. 85% of nonidentified compounds. CZE represents a valuable method for the qualitative and quantitative assay of the most relevant polyphenol components of propolis, representing an alternative to obtain typical fingerprints of propolis and a reliable identification of a large number of propolis polyphenolic species.
Three‐dimensional flow modelling and sediment transport in the River Klarälven
Authors: Dargahi Bijan 
Published: June 2004

AbstractA three‐dimensional ﬂow model that uses the RNG k‐ε turbulence model and a non‐equilibrium wall function was applied to the River Klarälven in the southwest part of Sweden. The objectives were to study the nature of the ﬂow in the river bifurcation and to investigate the short‐term sediment transport patterns in the river. The effectiveness of three‐dimensional ﬂow models depends upon: (1) how well the river geometry and it surface roughness are modelled; and (2) the choice of the closure model. Improvements were obtained by modelling the river in two parts: the entire river reach, and a selected part. Composite Manning coefﬁcients were used to account for roughness properties. The method requires a calibration process that ensures the water surface proﬁles match the ﬁeld data. The k‐ε model under‐predicted both the extent of ﬂow separation zones and the number of secondary ﬂow regions having a spiral motion, in comparison with the RNG k‐ε model. The 3‐D model could predict with good accuracy both the general and secondary ﬂow ﬁelds in the river. The results agreed well with the 3‐D velocity measurements using an acoustic Doppler current proﬁler. A conceptual model was developed that accounts for the development of secondary ﬂows in a river bifurcation having two bends. The main ﬂow feature in the river cross‐sections was the existence of multiple counter‐rotating spiral motions. The number of spiral motions increased as the river bends were approached. The river bends also caused vorticity intensiﬁcation and increased the vertical velocities. The application of the 3‐D ﬂow model was extended by solving the sediment continuity equation. The sediment transport patterns were related to the secondary ﬂow ﬁelds in the river. The sediment transport patterns at the river bifurcations are characterized by the growth of a sandbank. Copyright © 2004 John Wiley & Sons, Ltd.
Electrochemical detection of ascorbic acid (vitamin C) using a glassy carbon electrode
Authors: Ly Suw Young , Chae Jung Ik , Jung Young Sam , Jung Woon Won , Lee Hye Jeong , Lee Seong Ho 
Published: June 2004

AbstractA method for the detection of ascorbic acid (AA) was developed using square wave anodic stripping voltammetric (SWASV) analysis with a glassy carbon electrode (GCE). The results indicated a sensitive oxidation peak current of AA on the GCE. A linear curve was obtained within a concentration range of 1–130.0 μg/L with a preconcentration time of 270 s. The relative standard deviation of 30.0 μg/L observed was 0.1016% (n = 12) under optimum conditions. The low detection limit (S/N) was pegged at 0.30 μg/L. Results showed that the method developed can be used to assay biological and pharmaceutical samples, and food samples, as well as other materials requiring AA analyses.
A study on the lipid fraction of Adriatic sardine filets (Sardina pilchardus)
Authors: De Leonardis Antonella , Macciola Vincenzo 
Published: June 2004

AbstractSardine (Sardina pilchardus Walb.) is an important Mediterranean commercial fish species. In this study, the lipids of sardine filets, fished in the Adriatic Sea at different times, were examined. In function of their total lipid (TL) content, sardine filet samples were grouped into lean (TL < 4%) and fat (TL > 4%). It was demonstrated that the differences of TL were exclusively due to a seasonal cyclical increase of neutral lipids. In fact, during moderate‐hot months, sardines accumulated reserve fat that was metabolised during the winter months. The fatty acid composition was similar in both sardine sample groups and the fatty acid profile was equally distributed among saturated fatty acids, on average 38.3%, 31.2% monounsaturated, and 30.4% polyunsaturated. The polyunsaturated fatty acid n3 (PUFA‐n3) represented on average 20.9%, always higher than PUFA‐n6. C20 : 5n3 eicosapentaenoic acid, (EPA) and C22 : 6n3 docosahexaenoic acid (DHA) were the must abundant PUFA‐n3. Under nutritional aspects, the lipids of 100 g of fat‐sardines provided PUFA‐n3 quantities, in particular EPA and DHA, significantly higher than human daily requirements. In lean‐sardines, the PUFA‐n3 input drastically decreased and was estimated that EPA and DHA inputs in 100 g of sardines covered around 17% and 50% of daily requirements, respectively. Finally, cholesterol was equal to 93 mg/100 g of sardines, ranging from 67 to 131 and it did not increase in relation to the total lipid content. In conclusion, this study has highlighted that, under nutritional aspects, regarding EPA and DHA inputs, it is preferable to consume sardines with at least 4% total lipids.
Chemical, technological, and nutritional characteristics of two lines of “farro” (Triticum turgidum ssp. dicoccum)
Authors: Acquistucci Rita , Aureli Gabriella , Codianni Pasquale , Colonna Michaela , Galterio Giovanni 
Published: June 2004

AbstractIn recent years, the renewed interest for foods with a natural image has increased the demand for dry pasta produced from “hulled” wheat such as the Triticum turgidum ssp. dicoccum, also known as “farro”. In order to contribute to the general knowledge, two lines of farro were considered in this study. To have a comparison, an old cultivar of Triticum turgidum ssp. durum (Senatore Cappelli) in addition to a commercial semolina were also examined. All semolina samples were used to produce pasta samples. Results showed some differences among pasta samples that seem to be due not to the presence of specific protein subunits but especially to the quantitative ratio between the different subunits. Results also reconfirmed the role played by the drying technology that is able to affect the sensory characteristics of pasta products.
Purification and physicochemical characterization of ovine β‐lactoglobulin and α‐lactalbumin
Authors: El‐Zahar Khaled , Sitohy Mahmoud , Dalgalarrondo Michèle , Choiset Yvan , Métro François , Haertlé Thomas , Chobert Jean‐Marc 
Published: June 2004

AbstractOvine whey proteins were fractionated and studied by using different analytical techniques. Anion‐exchange chromatography and reversed‐phase high‐performance liquid chromatography (HPLC) showed the presence of two fractions of β‐lactoglobulin but only one of α‐lactalbumin. Gel permeation and sodium dodecyl sulfate (SDS)‐polyacrylamide gel electrophoresis allowed the calculation of the apparent molecular mass of each component, while HPLC coupled to electrospray ionisation‐mass spectrometry (ESI‐MS) technique, giving the exact molecular masses, demonstrated the presence of two variants A and B of ovine β‐lactoglobulin. Amino acid compositions of the two variants of β‐lactoglobulin differed only in their His and Tyr contents. Circular dichroism spectroscopy profiles showed pH conformation changes of each component. The thermograms of the different whey protein components showed a higher heat resistance of β‐lactoglobulin A compared to β‐lactoglobulin B at pH 2, and indicated high instability of ovine α‐lactalbumin at this pH.