bluuebunny/crossref_metadata_2025 huggingface dataset:
Recycled‐wool‐based nonwoven material as a sorbent for lead cations
Authors: Radetić M. , Jocić D. , Jovančić P. , Rajaković L. , Thomas H. , Petrović Z. L.
Published: August 2003

The aim of this study was to investigate the sorption properties of a recycled‐wool‐based nonwoven material for lead cations. To improve sorption properties, the material was treated with low‐temperature air plasma and/or the biopolymer chitosan. The rate and extent of the uptake of lead cations by wool, the kinetics of adsorption, and the influence of concentration, pH, temperature, and mechanical agitation on the sorption process were determined. Changes in the electrokinetic properties of the sorbent were also investigated. Wool, even as a recycled material, efficiently bound lead cations in all of the investigated cases. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 379–386, 2003
Novolac resin–poly(ethyl methacrylate) interpenetrating polymer networks: Morphology and mechanical and thermal properties
Authors: Goswami S. , Bandyopadhyay D. , Mandal P. K. , Chakrabarty D.
Published: August 2003

Full interpenetrating networks (IPNs) and semi‐IPNs of Novolac (phenolic) resin and poly(ethyl methacrylate) (PEMA) were prepared by the sequential mode of synthesis. These were characterized with respect to their mechanical properties, that is, ultimate tensile strength (UTS), percentage elongation at break, modulus, and toughness. Thermal properties were studied by DSC and thermogravimetric analysis (TGA). The morphological features were studied through polarizing light microscopy (PLM). The effects of variation of the blend ratios on the above‐mentioned properties were examined. There was a gradual decrease of modulus and UTS with consequent increases in elongation at break and toughness for both types of IPNs with increasing proportions of PEMA. An inward shift and lowering (with respect to pure phenolic resin) of the glass‐transition temperatures of the IPNs with increasing proportions of PEMA were observed, thus indicating a plasticizing influence of PEMA on the rigid and brittle matrix of crosslinked phenolic resin. The TGA thermograms exhibit two‐step degradation patterns. Although there was an apparent increase in thermal stability at the initial stages, particularly at lower temperatures, a substantial decrease in thermal stability was observed in the regions of higher temperatures. The surface morphology as revealed by PLM clearly indicates two‐phase structures in all the full and semi‐IPNs, irrespective of PEMA content. The matrix–PEMA domain interfaces are quite sharp at higher concentrations of PEMA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 412–420, 2003
Effect of silica and rice husk ash fillers on the modulus of polysiloxane networks
Authors: Sereda Luciane , Visconte Leila L. Y. , Nunes Regina C. R. , Furtado Cristina R. G. , Riande Evaristo
Published: August 2003

The preparation of polymethylvinylsiloxane rubbers with silica (SC) and black rice husk ash (BRHA) as fillers is reported. We conducted stress–strain experiments on these vulcanized rubbers to study the reinforcement properties of the fillers. Curves showing the dependence of the stress on the reciprocal of the elongation ratio displayed, in most cases, a slow upturn starting at rather low values of the elongation ratio attributed to a rather wide distribution of chain lengths between crosslinking points. Physical crosslinks between the hydroxyl groups of SC fillers and the polymer matrix seemed to enhance the modulus. BRHA–polymer interactions were rather weak in comparison with those occurring between SC and the polymer, presumably as a consequence of the carbon coating of the surface of the former fillers. These interactions were even less important for calcined BRHA. The absence of voids in the polymer–filler interfaces was proven by the analysis of gas diffusion across the rubbers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 421–429, 2003
UV curable pressure‐sensitive adhesives for fabricating semiconductors. I. Development of easily peelable dicing tapes
Authors: Ebe Kazuyoshi , Seno Hideo , Horigome Katsuhiko
Published: August 2003

In order to develop easily peelable dicing tapes from diced wafers, UV curing of various pressure‐sensitive adhesives (PSAs) was studied. After UV irradiation, the adhesive strength of a PSA composition including a diacrylourethane oligomer (UDA) decreased drastically compared with other compositions. Because of network formation via UV irradiation, this composition had a greater volume contraction that might yield microvoids at the interface between the adhesive and the wafer, resulting in the loose adhesion. Its storage modulus increased up to about 1000 times that before UV curing, which was due to the crosslinking of the UDA component. It was suggested that the increased crosslinking density and the high internal coagulant energy of the UDA backbone structure caused a remarkable decrease of the adhesive strength. Furthermore, it was ascertained that the UV‐irradiated UDA adhesives left few residual deposits on the wafer released from the tape. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 436–441, 2003
Release kinetics and diffusion coefficients of solid and liquid pesticides through interpenetrating polymer network beads of polyacrylamide‐g‐guar gum with sodium alginate
Authors: Kumbar Sangamesh G. , Dave Ashok M. , Aminabhavi Tejraj M.
Published: August 2003

Grafting of acrylamide onto guar gum is achieved by Ce(IV) induced free‐radical polymerization to prepare interpenetrating polymer network (IPN) beads of polyacrylamide‐g‐guar gum with sodium alginate by crosslinking with glutaraldehyde. Two widely used pesticides, solid chlorpyrifos and liquid fenvelarate, are loaded up to 60–70% efficiency in the IPN beads. The polymer and beads are characterized by Fourier transform IR spectroscopy to confirm grafting and to understand the possible interactions between the pesticides and the polymer matrix. Scanning electron microscopy is used to study the morphology of the beads. Equilibrium swelling experiments indicate that the swelling of the beads decreases with an increase in crosslinking, as well as an increase in pesticide loading. The in vitro release studies are performed under static conditions, and the release data are fitted to an empirical relationship to evaluate the transport parameters. Diffusion coefficients are calculated for the transport of pesticides through the polymeric beads using the initial and later time approximation methods. These values show a decrease with increasing crosslinking and increasing pesticide loading. Long‐term diffusion coefficients as computed by Fick's equations are found to be smaller in magnitude when compared to the initial time diffusion coefficients. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 451–457, 2003
Preparation and electrorheological characterization of suspensions of poly(urethane acrylate)/clay nanocomposite particles
Authors: Jun Jung‐Bae , Suh Kyung‐Do
Published: August 2003

Micron‐sized poly(urethane acrylate) (PUA)/clay nanocomposite particles were synthesized by suspension polymerization. UA containing a poly(ethylene oxide) group in the main chain was first inserted into the silicate layers of montmorillonite clay through mixing the UA with the clay. Then, ethylene glycol dimethacrylate and an oil‐soluble initiator were added into this UA/clay mixture, followed by the emulsification of the monomer mixture in an aqueous solution of polymeric stabilizer. Suspension polymerization was carried out at 60°C for 12 h to obtain the PUA/clay composite particles. The incorporation of clay into the polymer phase was verified by FTIR spectroscopy, and the intercalation structure of the clay composite was confirmed by X‐ray diffraction analysis. Other characterizations including thermal analysis, morphological observation, and dielectric analysis were also performed. After suspensions of bare PUA and PUA/clay nanocomposite particles in silicone oil were prepared, their electrorheological properties were measured under various electric fields and compared. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 458–464, 2003
Adsorption of chromium (VI) on a novel quaternized chitosan resin
Authors: Qin Caiqin , Du Yumin , Zhang Zuqun , Liu Yi , Xiao Ling , Shi Xiaowen
Published: August 2003

An inverse emulsion method was used to prepare the chitosan microspheres, which were crosslinked with epichlorohydrin between the hydroxyl groups under protection of amino groups to obtain crosslinked chitosan resin. Further chemical modification with glycidyl trimethylammonium chloride was used to form the quaternary ammonium ion resin. The resin had different adsorption ability for the chromium (VI) in anionic forms from that of the crosslinked chitosan beads. The crosslinked chitosan resin exhibited maximum adsorption for chromium (VI) at pH 3.0 and the adsorption capacity decreased sharply above pH 6, whereas the adsorption capacities of quaternized chitosan resin were significant over pH 3 to 11. The quaternized resin was more efficient than the crosslinked chitosan resin in media of pH above 5. The complete removal of chromium from the solution of K2Cr2O7was achieved with a column method using the quaternized chitosan resin, which was hard, and the decrease in pressure in the column was small. The breakthrough point of 10.0 mg L−1chromium in quaternized resin column was 3200 mL g−1resin greater than 600 mL g−1resin in the crosslinked chitosan resin column. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 505–510, 2003
Preparation and characterization of poly(hydroxybutyrate‐co‐hydroxyvalerate)–organoclay nanocomposites
Authors: Mook Choi Won , Wan Kim Tae , Ok Park O , Keun Chang Yong , Woo Lee Jin
Published: August 2003

This study describes the microstructure and thermal and mechanical properties of poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHB/HV)–organoclay nanocomposites prepared by melt intercalation using Cloisite 30B, a monotallow bis‐hydroxyethyl ammonium‐modified montmorillonite clay. X‐ray diffractometry and transmission electron microscopy analyses clearly confirm that an intercalated microstructure is formed and finely distributed in the PHB/HV copolymer matrix because PHB/HV has a strong hydrogen bond interaction with the hydroxyl group in the organic modifier of Cloisite 30B. The nanodispersed organoclay also acts a nucleating agent, increasing the temperature and rate of crystallization of PHB/HV; therefore, the thermal stability and tensile properties of the organoclay‐based nanocomposites are enhanced. These results confirm that the organoclay nanocomposite greatly improves the material properties of PHB/HV. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 525–529, 2003
Environmental degradation of biodegradable polyesters. IV. The effects of pores and surface hydrophilicity on the biodegradation of poly(ϵ‐caprolactone) and poly[(R)‐3‐hydroxybutyrate] films in controlled seawater
Authors: Tsuji Hideto , Suzuyoshi Kaori
Published: August 2003

Poly(ϵ‐caprolactone) (PCL) and poly[(R)‐3‐hydroxybutyrate] (R‐PHB) films with pores and hydrophilic surfaces were prepared by the water extraction of poly(ethylene oxide) from as‐cast blend films (1:1) and by the alkali treatment of as‐cast nonporous films, respectively. These films, as well as as‐cast nonporous PCL and R‐PHB films, were biodegraded in static seawater kept at 25°C, and their biodegradation was monitored with gravimetry, gel permeation chromatography (GPC), and scanning electron microscopy. The pores or highly hydrophilic surfaces of the PCL and R‐PHB films enhanced their biodegradation in seawater. Moreover, GPC measurements could be used to trace the biodegradation in seawater when the biodegradation proceeded to a great extent. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 587–593, 2003
A comparison of youngsters' use of CD‐ROM and the Internet as information resources
Authors: Shenton Andrew K. , Dixon Pat
Published: August 2003

Little research has compared youngsters' use of CD‐ROM and the Internet for information‐seeking purposes. Nevertheless, the area has recently been addressed within a largely qualitative project more generally devoted to young people's information universes. Home access to the Internet was seen to be more limited than that to CD‐ROM, although the former was consulted to tackle needs of a greater number of types. The strategies employed to exploit each form of information resource were essentially similar. No attempts were reported to check the credibility of any information retrieved from electronic sources. The Internet was, however, used more frequently beyond the informants' own homes than was CD‐ROM. There was also greater employment of the Internet by adults acting on the youngsters' behalf. As Internet use for school purposes rose in accordance with age, that of CD‐ROM declined. When youngsters themselves compared the two resources as information‐seeking tools, CD‐ROM software was criticized for its lack of detailed material and the Internet for the problems in locating what was desired. Project findings have implications in a range of areas, including the marketing of CD‐ROM packages, research and development and practices within schools.
Relevance data for language models using maximum likelihood
Authors: Bodoff David , Wu Bin , Wong K. Y. Michael
Published: August 2003

We present a preliminary empirical test of a maximum likelihood approach to using relevance data for training information retrieval (IR) parameters. Similar to language models, our method uses explicitly hypothesized distributions for documents and queries, but we add to this an explicitly hypothesized distribution for relevance judgments. The method unifies document‐oriented and query‐oriented views. Performance is better than the Rocchio heuristic for document and/or query modification. The maximum likelihood methodology also motivates a heuristic estimate of the MLE optimization. The method can be used to test competing hypotheses regarding the processes of authors' term selection, searchers' term selection, and assessors' relevancy judgments.
An IP‐level analysis of usage statistics for electronic journals in chemistry: Making inferences about user behavior
Authors: Davis Philip M. , Solla Leah R.
Published: August 2003

This study reports an analysis of American Chemical Society electronic journal downloads at Cornell University by individual IP addresses. While the majority of users (IPs) limited themselves to a small number of both journals and article downloads, a small minority of heavy users had a large effect on total journal downloads. There was a very strong relationship between the number of article downloads and the number of users, implying that a user‐population can be estimated by just knowing the total use of a journal. Aggregate users (i.e. Library Proxy Server and public library computers) can be regarded as a sub‐sample of the entire user population. Analysis of article downloads by format (PDF versus HTML) suggests that individuals are using the system like a networked photocopier, for the purposes of creating print‐on‐demand copies of articles.
Peripheral social awareness information in collaborative work
Authors: Spring Michael B. , Vathanophas Vichita
Published: August 2003

People working in physical proximity have access to information about one another. Much of this information is unavailable when people collaborate remotely using groupware. Being aware of other members of a team in a collaborative environment involves knowing both what people are doing and what is happening to the shared information space or artifact. Increasing the amount of information about the group in a computer‐mediated system may increase the group's ability to complete the task. This article reports on a study that examined group performance on a task that was computer mediated with and without awareness information. In particular, the study examined how an awareness tool impacts the quality of the work effort and the communications between group members in the completion of a collaborative authoring task. The study found that the use of an awareness tool decreased the quality of the work effort. The number of communications also decreased when the tool was used. Although the results contradict some of the theoretical predictions, an examination of the data suggests theoretical support for a more complex interaction. There was evidence that the awareness tool may have reduced the users' need to communicate and this reduction in communications may have caused the reduction in the quality of the work effort. There is also data to suggest that the existence of the awareness tool may have negatively influenced the effort of some participants, and it was that effort reduction that caused the reduction in the quality of the product.
Greeklish: An experimental interface for automatic transliteration
Authors: Karakos Alexandros
Published: August 2003

“Transliteration” in linguistics means the system of conveying as nearly as possible by means of one set of letters or characters the pronunciation of the words in languages written and printed in a totally different script. This term may be applied to a transcription in Latin letters of Greek, Hebrew, or the Slavonic languages written in the Cyrillic alphabet. We present in this article Greeklish, a Windows application that automatically produces English to Greek transliteration and back‐transliteration (retransliteration). This transliteration is based on an algorithm with a table of associations between the two character sets. This table can be modified by the user so that it can cover personal preferences or formal present and future rules. The novelty of this system is its speed of operation, its simplicity, and its ease of use. Our examples use a Greek to Latin (English) alphabet mapping, but the Greeklish application can easily use any X to Latin mapping, where X is any non‐Latin alphabet.
Clays as a Host Matrix in the Synthesis of Organic Macrocycles
Authors: Georgakilas Vasilios , Gournis Dimitrios , Bourlinos Athanasios B. , Karakassides Michael A. , Petridis Dimitrios
Published: August 2003

A new approach for the synthesis of amide macrocycles, based on the use of organo‐clay derivatives as controlling template, is proposed as an alternative to the rotaxane method. Dications of p‐xylylene diamine inserted in the clay interlayer space act as molding pillars around which neutral diamine molecules are erected via hydrogen bonding and π–π interactions to form supramolecular arrays. Condensation of diamines in the supramolecular arrays with diacetyl dichlorides yields various tetramide macrocycles in good yields. Shape, aromaticity and dimensions of the reactants are factors affecting the condensation reaction.
Study on the Phase Behaviors, Viscosities, and Thermodynamic Properties of CO2/[C4mim][PF6]/Methanol System at Elevated Pressures
Authors: Liu Zhimin , Wu Weize , Han Buxing , Dong Zexuan , Zhao Guoying , Wang Jiaqiu , Jiang Tao , Yang Guanying
Published: August 2003

An apparatus to determine the vapor–liquid equilibria of CO2/ionic liquid (IL)/organic solvent multisystems and the viscosity of the liquid phase at elevated pressures has been constructed. The solubility of CO2 in 3‐butyl‐1‐methyl‐imidazolium hexafluorophosphate ([C4mim][PF6]) and the viscosity of CO2‐saturated [C4mim][PF6] have been studied at 313.15, 323.15, and 333.15 K and at pressures up to 12.5 MPa. The phase behavior of CO2/[C4mim][PF6]/methanol ternary mixture and the viscosity of the liquid phases at equilibrium condition have also been determined at 313.15 K and at 7.15 and 10.00 MPa. The partition coefficients of the components in the ternary system are calculated. Peng–Robinson equation of state and some thermodynamic functions are combined to calculate the fugacity coefficients of the components in the system. It demonstrates that the viscosity of the IL‐rich phase decreases significantly with increasing pressure of CO2, and the effect of temperature on the viscosity of CO2/IL mixture is not noticeable at high pressure, although the viscosity of the CO2‐free IL decreases dramatically with increasing temperature. Compressed CO2 may become an attractive reagent for reducing the viscosity of ILs in many applications. The mole fraction of methanol in the CO2‐rich phase is much lower than that in the IL‐rich phase; this indicates that the interaction between the IL and methanol is stronger than that between CO2 and methanol. The fugacity coefficient of CO2 in IL‐rich phase is larger than unity, while that of methanol is much small than unity, which further suggests that methanol–IL interaction is much stronger than CO2–IL interaction. However, the CO2–IL interaction is stronger than the CO2–methanol interaction.
Electrostatic Complexation and Photoinduced Electron Transfer between Zn‐Cytochrome c and Polyanionic Fullerene Dendrimers
Authors: Braun Martin , Atalick Stefan , Guldi Dirk M. , Lanig Harald , Brettreich Michael , Burghardt Stephan , Hatzimarinaki Maria , Ravanelli Elena , Prato Maurizio , van Eldik Rudi , Hirsch Andreas
Published: August 2003

Two dendritic fullerene (DF) monoadducts, 2 and 3, which can carry up to 9 and 18 negative charges, respectively, were examined with respect to electrostatic complexation with Cytochrome c (Cytc). To facilitate comprehensive photophysical investigations, the zinc analogue of Cytc (ZnCytc) was prepared according to a novel, modified procedure. The association of ZnCytc and DF, and consequential photoinduced electron transfer within ZnCytc‐DF from the photoexcited protein to the fullerene, was proven by fluorescence spectroscopy and transient absorption spectroscopy. These findings were also supported by circular dichroism as well as by extensive molecular dynamics (MD) simulations.
A Simplified and Convenient Laboratory‐Scale Preparation of 14N or 15N High Molecular Weight Poly(dichlorophosphazene) Directly from PCl5
Authors: Carriedo Gabino A. , García Alonso Francisco. J. , Gómez‐Elipe Paloma , Fidalgo J. Ignacio , García Álvarez J. L. , Presa‐Soto A.
Published: August 2003

A simple and convenient one‐pot synthesis of THF solutions of high molecular weight poly(dichlorophosphazene) [NPCl2]n, or the 15N isotopomer [15NPCl2]n, starting directly from PCl5 and NH4Cl or 15NH4Cl in a solution of 1,2,4‐trichlorobenzene in the presence of sulfamic acid and calcium sulfate dihydrate, is described. The solutions of [NPCl2]n in THF, which are obtained free of poly(tetrahydrofuran) by preparing them in the presence of K2CO3, can be reacted directly with phenols, biphenols, or even HO‐CH2CF3 in the presence of K2CO3 or Cs2CO3 to obtain, after a very simple workup, the corresponding polyphosphazene derivatives almost free of chlorine.
Syntheses, Structures, Photoluminescence, and Theoretical Studies of a Novel Class of d10 Metal Complexes of 1H‐[1,10]phenanthrolin‐2‐one
Authors: Zheng Shao‐Liang , Zhang Jie‐Peng , Chen Xiao‐Ming , Huang Zhen‐Li , Lin Zhen‐Yang , Wong Wing‐Tak
Published: August 2003

A novel asymmetric monosubstituted 1,10‐phenanthroline, Hophen⋅0.5 H2O (1, Hophen=1H‐[1,10]phenanthrolin‐2‐one), was generated by a facile route, and a novel class of crystalline, d10‐metal, monomeric or oligomeric complexes of this ligand, namely [Hg(ophen)2]⋅4 H2O⋅CH2Cl2 (2), [Cd3Cl(ophen)5]⋅1.5 H2O⋅2 CH2Cl2 (3), and [Zn4O(ophen)4(OAc)2]⋅4H2O⋅2 CH2Cl2 (4), were obtained by means of liquid diffusion, and were characterized by X‐ray crystallography and photoluminescence studies. Complex 1 exhibits a hydrogen‐bonded dimeric structure, 2 is a neutral monomeric complex, 3 has a trinuclear structure with the ophen ligand acting as a bridge through the ketone groups, and 4 features a tetranuclear Zn4O core that is consolidated further by bridging ophen and acetate ligands. All the complexes display photoluminescent properties in the blue/green region. The photoluminescent mechanisms were investigated by means of molecular orbital calculations, which showed that the photoluminescent properties are ligand‐based and can be tuned upon ligation to different metal ions.
Spectroelectrochemical Studies on Mixed‐Valence States in a Cyanide‐Bridged Molecular Square, [RuII2FeII2(μ‐CN)4(bpy)8](PF6)4⋅CHCl3⋅H2O
Authors: Oshio Hiroki , Onodera Hironori , Ito Tasuku
Published: August 2003

A cyanide‐bridged molecular square of [RuII2FeII2(μ‐CN)4(bpy)8](PF6)4⋅CHCl3⋅H2O, abbreviated as [RuII2FeII2](PF6)4, has been synthesised and electrochemically generated mixed‐valence states have been studied by spectroelectrochemical methods. The complex cation of [RuII2FeII2]4+ is nearly a square and is composed of alternate RuII and FeII ions bridged by four cyanide ions. The cyclic voltammogram (CV) of [RuII2FeII2](PF6)4 in acetonitrile showed four quasireversible waves at 0.69, 0.94, 1.42 and 1.70 V (vs. SSCE), which correspond to the four one‐electron redox processes of [RuII2FeII2]4+ ⇄[RuII2FeIIFeIII] 5+⇄[RuII2FeIII2]6+⇄[RuIIRuIIIFeIII2]7+⇄[RuIII2FeIII2]8+. Electrochemically generated [RuII2FeIIFeIII]5+ and [RuII2FeIII2]6+ showed new absorption bands at 2350 nm (ε=5500 M−1 cm−1) and 1560 nm (ε=10 500 M−1 cm−1), respectively, which were assigned to the intramolecular IT (intervalence transfer) bands from FeII to FeIII and from RuII to FeIII ions, respectively. The electronic interaction matrix elements (HAB) and the degrees of electronic delocalisation (α2) were estimated to be 1090 cm−1 and 0.065 for the [RuII2FeIIFeIII2]5+ state and 1990 cm−1 and 0.065 for the [RuII2FeIII2]6+ states.
A Practical High‐Throughput Screening System for Enantioselectivity by Using FTIR Spectroscopy
Authors: Tielmann Patrick , Boese Matthias , Luft Martin , Reetz Manfred T.
Published: August 2003

For the first time FTIR spectroscopy has been applied to the measurement of enantiomeric purity. The underlying concept is based on the use of pseudo‐enantiomers that are 13C‐labeled at appropriate positions. Upon applying Lambert–Beer's law in the determination of the concentrations of both enantiomers, the ee values are accessible, accuracy to within ±5 % of the true values being possible. The application of a commercially available high‐throughput FTIR system results in a slightly decreased accuracy (±7 % for the ee values), but this allows a throughput of up to 10 000 samples per day. The method is of interest in the area of combinatorial asymmetric catalysis and directed evolution of enantioselective enzymes.
Cation Sensors Based on Terpyridine‐Functionalized Boradiazaindacene
Authors: Goze Christine , Ulrich Gilles , Charbonnière Loïc , Cesario Michèle , Prangé Thierry , Ziessel Raymond
Published: August 2003

A new class of highly luminescent dyes is reported. The characteristic feature of these compounds is that a terpyridine fragment is closely appended to a boradiazaindacene moiety in such a way that cation binding to the vacant terpyridine causes strong perturbations of the photophysical properties of the boradiazaindacene unit. In particular, these sensors are especially applicable to the fluorescence detection of trace quantities of zinc(II) ions in solution. The mechanism of the cation‐induced quenching process has been investigated by a combination of electrochemistry, UV/Vis absorption, emission, and NMR spectroscopy. Highly luminescent arrays can be formed by doping transparent polymers with low concentrations of these new dyes. In such materials, the change in photophysical properties upon cation binding is so marked that “cation writing” becomes feasible under routine conditions.
Temperature‐Dependent Behavior of Protein‐Chromophore Interactions: A Theoretical Study of a Blue Fluorescent Antibody
Authors: Salsbury Freddie R. , Han Wen‐Ge , Noodleman Louis , Brooks Charles L.
Published: August 2003

The unusual temperature‐dependent excited‐state dynamics of a stilbene–antibody complex reported by Simeonov et al. are explored using theoretical methods. The anomalous temperature‐dependent fluorescence emission and lifetime are shown to be the result of interplay among temperature‐modulated protein flexibility, the excited‐state potential surface for the stilbene central twist, and changes in the stilbene charge distribution upon excitation. Stilbene is found to possess a similar geometry and orientation within the antibody binding pocket at all temperatures in the ground state and at low temperatures (≈240 K) in the excited state. At higher temperatures (≈260 K), the excited‐state conformation twists around the central double bond and adopts an alternate orientation within the binding pocket. These changes result from protein side chain and loop motions that are frozen out at lower temperatures and account for the observed red shift of the fluorescence emission spectrum (a calculated shift of 3.8 kcal mol−1 compares favorably with the ≈5 kcal. mol−1 observed experimentally). Approximately 3.0 kcal mol−1 of this stabilization is global in nature and is not attributable to specific local interactions. Local interactions between stilbene and Tyr‐B39 contribute ≈0.8 kcal mol−1 to the fluorescence shift. The primary structural change in simulations of the high temperature excited state involves a decrease in the stilbene–tyrosine distance and a relative change in orientation of the aromatic rings. We identify several nearby charged residues that contribute to the fluorescence emission shift and provide targets for mutagenesis to probe the temperature‐dependent dynamics of protein–chromophore interactions.
Evaluation of one‐ and two‐equation low‐Re turbulence models. Part II—Vortex‐generator jet and diffusing S‐duct flows
Authors: Yaras M. I. , Grosvenor A. D.
Published: August 2003

This second segment of the two‐part paper systematically examines several turbulence models in the context of two flows, namely a vortex flow created by an inclined jet in crossflow, and the flow field in a diffusing S‐shaped duct. The test cases are chosen on the basis of availability of high‐quality and detailed experimental data. The tested turbulence models are integrated to solid surfaces and consist of: Rodi's two‐layer k–ε model, Wilcox's k–ω model, Menter's two‐equation shear–stress‐transport model, and the one‐equation model of Spalart and Allmaras. The objective of the study is to establish the prediction accuracy of these turbulence models with respect to three‐dimensional separated flows with streamline curvature. At the same time, the study establishes the minimum spatial resolution requirements for each of these turbulence closures, and identifies the proper low‐Mach‐number preconditioning and artificial diffusion settings of a Reynolds‐averaged Navier–Stokes algorithm for optimum rate of convergence and minimum adverse impact on prediction accuracy. Copyright © 2003 John Wiley & Sons, Ltd.
Isolation of volatile oil from thyme (Thymbra spicata) by steam distillation
Authors: Hancı Serap (Sonsuzer) , Sahin Serpil , Yılmaz Levent
Published: August 2003

The effects of steam flow rate (1.03 and 0.64 L/h( distillation time, and particle size (0.50, 1.00, 2.05 mm) of Thymbra spicata on essential oil yield and sequence of extraction of compounds were studied. A logarithmic model fitted well to experimental data. The composition of the essential oil obtained by steam distillation was investigated for whole leaves only since the grinding had an adverse effect on yield. The oil obtained was very rich with respect to its carvacrol content. For both steam flow rates, oxygenated monoterpenes were recovered the most rapidly. Using whole leaves (2.05 mm) and a higher steam flow rate (1.03 L/h) for 75 min of distillation was chosen as the optimum which gives the lowest amount of monoterpene hydrocarbons, the complete recovery of oxygenated compounds, and the highest yield in a shorter time. Yield was 1.57% at this optimum condition. The oil was composed of 53.1% oxygenated compounds, 25.7% monoterpene hydrocarbons, 4.4% sesquiterpenes, and 14.1% p‐cymene.
Assessment of protein nutritional quality and effects of traditional processes: A comparison between Ethiopian quality protein maize and five Ethiopian adapted normal maize cultivars
Authors: Fufa Habtamu , Akalu Girma , Wondimu Asrat , Taffesse Samson , Gebre Takele , Schlosser Karla , Noetzold Horst , Henle Thomas
Published: August 2003

The present study was designed to quantitatively measure and compare the levels and variations of total protein, individual amino acids, and computed protein efficiency ratio (C‐PER) in raw and traditionally processed products of one recently released quality protein maize (QPM BH542) with four high‐yield maize hybrids, namely flint BH660, semi‐dent BH140, Pioneer 30H83, and Pioneer 30G97, as well as one local maize cultivar. The total protein content was variable among the cultivars ranging from 7% for BH660 to 8.6% for Pioneer 30H83, 8.9% for BH140, 9.8% for QPM BH542, 10.1% for local maize cultivar, and 11.8% for Pioneer 30G97, respectively. However, the QPM BH542 maize protein proved to be higher in nutritional quality than common maize proteins because it contained 30% to 82% more lysine, higher levels of arginine, tryptophan, histidine, threonine, cysteine, and valine. As a result, the QPM BH542 amino acid profile gives a good balance of total essential amino acids, limited only in lysine, and has a C‐PER ratio of 2.2 compared to 1.14, 1.2, 1.4, 1.66, and 1.67 for Pioneer 30G97, local, BH‐140, BH660, and Pioneer 30H83, respectively. The various traditional processes of maize have no significant effect on the protein nutritional quality of the new quality protein maize. Hence, the widely dissemination of it in agricultural cultivation as well as consumption by the general population is recommended.
Linkage disequilibrium assessment via log‐linear modeling of SNP haplotype frequencies
Authors: Morris Andrew , Pedder Alan , Ayres Karen
Published: August 2003

Analyses of high‐density single‐nucleotide polymorphism (SNP) data, such as genetic mapping and linkage disequilibrium (LD) studies, require phase‐known haplotypes to allow for the correlation between tightly linked loci. However, current SNP genotyping technology cannot determine phase, which must be inferred statistically. In this paper, we present a new Bayesian Markov chain Monte Carlo (MCMC) algorithm for population haplotype frequency estimation, particulary in the context of LD assessment. The novel feature of the method is the incorporation of a log‐linear prior model for population haplotype frequencies. We present simulations to suggest that 1) the log‐linear prior model is more appropriate than the standard coalescent process in the presence of recombination (>0.02 cM between adjacent loci), and 2) there is substantial inflation in measures of LD obtained by a “two‐stage” approach to the analysis by treating the “best” haplotype configuration as correct, without regard to uncertainty in the recombination process.Genet Epidemiol25:106–114, 2003. © 2003 Wiley‐Liss, Inc.
Perceived organizational support and work status: a comparison of the employment relationships of part‐time and full‐time employees attending university classes
Authors: Gakovic Anika , Tetrick Lois E.
Published: August 2003

Employees who were attending classes at a local university responded to measures of perceived organizational support, the content of their psychological contracts (e.g., relational and transactional obligations), social and economic exchange, the level of fulfillment of both employee and organizational obligations, and organizational commitment. Part‐time employees (N=319) reported higher levels of perceived organizational support and stronger economic exchange relationships, while full‐time employees (N=282) reported higher levels of continuance commitment—sacrifice and greater relational and transactional obligations to their organizations. There were no significant differences between the two groups in terms of the strength of social exchange relationships, the levels of their organizations' relational and transactional obligations to them, the degree to which they had fulfilled their obligations to their organizations or their organizations had fulfilled their obligations to them, the level of continuance commitment—perceived alternatives, affective commitment, and normative commitment. There were no differences in the strength of the relations between perceived organizational support and the other exchange variables depending on work status. Overall, the findings suggested that social exchange processes operate similarly for part‐time and full‐time employees. Copyright © 2003 John Wiley & Sons, Ltd.
Employment relationships and firm performance: evidence from an emerging economy
Authors: Wang Duanxu , Tsui Anne S. , Zhang Yichi , Ma Li
Published: August 2003

Defining employment relationships from the employer's perspective and based on the inducement‐contribution framework, this study examined the link between employment relationships and firm performance in a heterogeneous sample of firms in the largest emerging economy in the world, i.e., the People's Republic of China. It also analyzed the contingent role of both the firm's strategic orientation and its ownership structure. The results demonstrated that it is the combination of a high level of expected contributions coupled with a high level of provided inducements (i.e., organization‐focused employment relationship approach) rather than a high level of either expected contributions or provided inducements alone that is critical for firm performance. Further, we found that it is not the organization‐focused but the underinvestment employment relationship approach that offers a competitive advantage if the firm pursues the prospector strategy or if the firm is a domestic privately owned enterprise. In particular, the domestic privately owned enterprises reported the highest firm performance when they used the underinvestment approach with their middle managers, in contrast to the state‐owned or foreign‐invested enterprises. These results support both the universalistic and the contingency perspectives on the relationship between employment relationships and firm performance. They also contribute to our understanding of employment relationships in the global context. Copyright © 2003 John Wiley & Sons, Ltd.
Development of SNMP‐XML translator and gateway for XML‐based integrated network management
Authors: Yoon Jeong‐Hyuk , Ju Hong‐Taek , Hong James W.
Published: August 2003

The research objective of our work is to develop a SNMP MIB to XML translation algorithm and to implement an SNMP‐XML gateway using this algorithm. The gateway is used to transfer management information between an XML‐based manager and SNMP‐based agents. SNMP is widely used for Internet management, but SNMP is insufficient to manage continuously expanding networks because of constraints in scalability and efficiency. XML–based network management architectures are newly proposed as alternatives to SNMP‐based network management, but the XML‐based Network Management System (XML‐based NMS) cannot directly manage legacy SNMP agents. We also implemented an automatic specification translator (SNMP MIB to XML Translator) and an SNMP‐XML gateway. Copyright © 2003 John Wiley &Sons, Ltd.
Differential effects of dopamine on a potassium current in cultured rutabaga and wild‐type Drosophila cells
Authors: Alshuaib Waleed B. , Mathew Mini V. , Hasan Mohammed Y. , Fahim Mohamed A.
Published: August 2003

The rutabaga mutation which has a low intracellular cyclic adenosine monophosphate (cAMP) concentration is defective in short‐term memory. The aim of this study was to compare modulation effects of dopamine on the delayed‐rectifier potassium current (IKDR) in rutabaga and wild‐type Drosophila neurons. The conventional whole‐cell patch‐clamp technique was applied to cultured Drosophila neurons derived from embryonic neuroblasts. IKDR was measured from cultured (2 days) wild‐type and rutabaga neurons. IKDR was smaller in rutabaga neurons (373 ± 38 pA) than in wild‐type neurons (519 ± 40 pA) but there was no difference in IKDR activation in wild‐type inactivation between the two genotypes. We examined the effects of dopamine on IKDR in wild‐type and rutabaga neurons. IKDR was measured from neurons before and after addition of dopamine to the external solution. Dopamine application reduced IKDR in wild‐type neurons but did not significantly affect IKDR in rutabaga neurons (single‐cell studies). In the presence of dopamine there was no difference in IKDR between wild‐type (344 ± 29 pA) and rutabaga (338 ± 27pA) neurons (population studies). These results indicate that dopamine differentially affects the delayed‐rectifier channel in wild‐type and rutabaga neurons. This can alter neuronal excitability in rutabaga and may affect the processing of neural signals necessary for learning and memory.
Response properties of cat striate neurons to simulated optic flow stimuli
Authors: Li Bao‐Wang , Li Bing , Chen Yao , Diao Yun‐Cheng
Published: August 2003

Optic flow analysis has been extensively investigated in several extrastriate visual areas of the primate, but it remains unclear whether and how the striate cortex is involved in the processing. In the present study 156 striate neurons in anaesthetized cats were tested with simulated optic flow patterns. More than 80% of the cells responded to the stimuli, about 30% significantly preferred translation to radiation and rotation, but few, if any, displayed clear preference for radial or circular motion. Most responsive neurons had fairly good direction sensitivity for their optimal stimuli. Generally, the differences between simple and complex cells were small and insignificant. Although translation obviously prevailed over radiation and rotation in driving more cells and eliciting stronger responses, the responsivity to complex flow fields was not predictable with the direction preference to planar motion. These results suggest that the striate contribution to optic flow analysis may go beyond the direction selectivity to local translation and there might be some kind of specific mechanism to complex motion features.
Sense of coherence and adjustment to divorce among Muslim Arab citizens of Israel
Authors: Cohen Orna , Savaya Rivka
Published: August 2003

This study examined the distinctiveness and causal relationships of Antonovsky's (1979) Sense of Coherence Scale and the Mental Health Index of Veit and Ware (1983) in a sample of 306 divorced Muslim Arab men and women in Israel. The findings, based on confirmatory factor analysis and latent‐variable structural modelling, suggest that in the present sample sense of coherence (SOC) and mental health are two independent but correlated constructs. They also suggest that, consistent with Antonovsky's theory, SOC may be better viewed as a mediator between stress and mental health than as a concurrent outcome of stress, although the latter possibility is not ruled out. Finally, the findings indicate that the SOC of the sample was relatively low in comparison with other groups. Copyright © 2003 John Wiley & Sons, Ltd.
Reactions of halo‐ and dihaloadamantanes with nitromethane anions by the SRN1 mechanism
Authors: Santiago Ana N. , Toledo Carlos A. , Rossi Roberto A.
Published: August 2003

The reactions of 1‐bromo‐, 2‐bromo‐, 1,3‐dibromo‐ and 1,4‐dibromoadamantane with −CH2NO2 anions were studied in DMSO and in liquid ammonia. The photostimulated reaction of 1‐haloadamantane (1‐AdX, X = Br, I) or 2‐AdBr with −CH2NO2 anions gave good yields of the substitution product 1‐AdCH2NO2 and 2‐AdCH2NO2, respectively, in the presence of the enolate anions of acetone (entrainment conditions). On the other hand, 1‐adamantanol was the main product of the reaction performed in DMSO without irradiation, but not in liquid ammonia. 1,3‐Dibromo and 1,4‐dibromoadamantane reacted with −CH2NO2 anions under irradiation in the presence of the enolate anions of acetone. The first compound gave the disubstitution product 11, and the second the monobromo‐substitution products 15 and 16, together with the disubstitution product 17. Compounds 15 and 16 were shown to be intermediates in the formation of 17. Copyright © 2003 John Wiley & Sons, Ltd.
Editorial
Authors: Siehl Hans‐Ullrich , Humeres Eduardo , Tokitoh Norihiro
Published: August 2003

No Absract.
Reactions of lithiated aromatic heterocycles with carbon monoxide
Authors: Liñares Guadalupe E. García , Nudelman Norma S.
Published: August 2003

The reaction of lithium derivatives of aromatic heterocycles with carbon monoxide was studied under several reaction conditions: 2‐furyllithium afforded only one product, the tetrahydro‐2‐furaldehyde (25% yield). On the other hand, 2‐thienyllithium and 5‐methyl‐2‐furyllithium gave two and five products, respectively. Although in relatively low yields, formation of highly functionalized compounds takes place in a fast process under mild conditions. For 1,4‐dihydroxy‐1,4‐bis(5‐methyl‐2‐furanyl)butane‐2,3‐dione, reaction conditions were achieved to obtain this difficult to prepare derivative in 50% yield. To the best of our knowledge, this is the first report on the reaction of lithiated aromatic heterocycles with CO: evidence is given on the involvement of proton transfers in the reactions of 2‐furyllithium and 2‐thienyllithium, while the reaction of 5‐methyl‐2‐furyllithium seems to proceed through an electron transfer as the first step. Copyright © 2003 John Wiley & Sons, Ltd.
Antioxidant properties of extracts from Alchornea laxiflora (Benth) Pax and Hoffman
Authors: Olatunde Farombi E. , Ogundipe Oluyemisi O. , Samuel Uhunwangho E. , Adeyanju Mary A. , Olarenwaju Moody J.
Published: August 2003

The antioxidant activities of the leaf and root extracts of Alchornea laxiflora, a plant used locally for the preservation of food items in Nigeria, were evaluated using the ferric thiocyanate method, horseradish peroxidase catalysed oxidation of 2,2 azinobis‐(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS), β‐carotene linoleate model system and Fe2+/ascorbate/H2O2‐induced rat liver microsomal lipid peroxidation. The crude hexane root (HR), methanol root (MR), methanol leaf (ML) and hexane leaf (HL) extracts from A. laxiflora were tested for antioxidant activities. Antioxidant activity decreased in the following order: HR (76.4%), MR (63%), ML (40%) and HL (38%) at a concentration of 0.05% v/v. The antioxidant activity of HR compared to that of butylated hydroxyanisole (BHA) (80%), a standard antioxidant. The total antioxidant activity (TAA) of the crude extracts suggests that activity is highest in the HR compared with the others. The TAA value was estimated to be 8.0 measured as mm of vitamin C equivalent. Six column chromatographic fractions (FI–FVI) from HR showed antioxidant activity to varying extents in the β‐carotene model system in the order of FII > FI > FVI > FIII > FIV > FV. FII exhibited the highest antioxidant activity in all model systems utilized, it recorded a higher antioxidant activity than BHA and quercetin in the β‐carotene linoleate and Fe2+/ascorbate/H2O2. TLC analysis of fraction II revealed the presence of terpenoid compounds (radiant green coloration with 2,4 dinitrophenylhydrazine). Our results suggest that A. laxiflora contains potent natural antioxidants and may therefore be relevant in the preservation of lipid food products, which are prone to oxidation and rancidity. Copyright © 2003 John Wiley & Sons, Ltd.
Unexpected high testis‐specific transcriptional activity of the cyclin T1 promoter in transgenic mice
Authors: Mata X , Besnard N , Le Roux K , Tilly G , Andréoletti O , Hudrisier M , Costa Da Silva J , Laude H , Vilotte J.L
Published: August 2003

The ubiquitously expressed cyclin T1 gene encodes for a protein involved in human immunodeficiency virus type 1 (HIV‐1) transcription activation. The goat gene was recently shown to share an expression pattern similar to that of its endogenous counterpart when incorporated into mice using a BAC insert. To assess if its promoter could target ubiquitous expression of the bovinePrnpin transgenic mice, two constructs carrying either 1 or 30 kb of cyclin T1 5′‐flanking sequences were built and microinjected. Both constructs resulted in the unexpected high male germ cell‐specific expression of the prion protein. These data re‐question the suspected location of the cyclin T1 gene regulatory elements.