bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of activity coefficient models for liquid solutions
Authors: Eubank Philip T. , Wang Xiaonian
Published: April 2004

Liquid–phase activity coefficient models (or excess Gibbs energy models) with three or fewer adjustable parameters are often sufficient to model the liquid solutions present for the vapor–liquid equilibria (VLE) or the vapor–liquid–liquid equilibria (VLLE) calculations of phase equilibria. Our purpose here is to show the flexibility of three such equations in the correlation and prediction of (1) extrema and inflection points on the popular ln γi vs. x1 diagram for binary solutions, (2) liquid–liquid phase splitting, and (3) homogeneous azeotropes. The empirical equations investigated here are (a) the two‐constant Margules model, (b) the van Laar model, and (c) the three‐constant NRTL model. New mathematical procedures lead to new graphs and equations, which allow the reader to identify the presence of any of the above three phenomena by inspection without performing detailed calculations such as a Gibbs energy minimization for liquid phase splitting. © 2004 American Institute of Chemical Engineers AIChE J, 50: 854–861, 2004
New method for ocean disposal of CO2 by a submerged kenics‐type static mixer
Authors: Tajima Hideo , Yamasaki Akihiro , Kiyono Fumio , Teng Ho
Published: April 2004

A new method for ocean disposal of anthropogenic CO2 is proposed. In this method, liquefied CO2 is transported through a pipeline to a Kenics‐type static mixer, submerged at a depth between 500 and 1,000 m below the ocean surface and mixed with seawater in the mixer and then released into the ocean. Because the pressure and temperature for seawater at depths > 500 m satisfy those for hydrate formation, CO2 hydrate may form at the CO2–seawater interface. Thus, the release from the mixer is a mixture of liquid CO2, hydrate, and seawater. The apparent CO2 concentration of the release can be determined by the CO2–seawater mixing rate and distribution of the CO2 drops (with or without a hydrate layer) produced in the mixer. This proposed disposal method was simulated experimentally. The laboratory‐scale simulation revealed that sizes of the dispersed CO2 drops and their distribution in the mixer were governed by the mixing rate and the Weber number on the basis of the continuous phase (seawater); larger Weber numbers led to smaller drop sizes and more uniform drop distribution. It was also observed that the drops with a hydrate layer were generally smaller than those without a hydrate layer under the same mixing rate and that a fairly uniform distribution for the dispersed CO2 drops was always obtained if the continuous‐phase flow was fully turbulent. Results of the laboratory simulation suggest that the environmental impact induced by the CO2 released by a Kenics‐type static mixer may be better predicted than from conventional injection methods. © 2004 American Institute of Chemical Engineers AIChE J, 50: 871–878, 2004
Kinetics and reactive mixing: Fragmentation and coalescence in turbulent fluids
Authors: Madras Giridhar , McCoy Benjamin J.
Published: April 2004

Reactive mixing in liquids can be quantitatively described by combining chemical kinetics and hydrodynamics so that dispersed reactants interact at evolving fluid–element interfaces. For the batch reactor we postulate that the dispersed fluid elements are fragmented in a cascade of increasingly smaller sizes and larger interfacial area. The reversible fragmentation–coalescence is described by a population dynamics equation that has an exact self‐similar solution for the size distribution as a function of time. Two types of competitive reaction kinetics incorporating a diffusion‐limited fast reaction satisfy nonlinear differential equations, written in terms of moments of the time‐dependent dispersed‐fluid size distribution. Applying a compressed time variable to transform to a simple system of differential equations readily solves the nonlinear equations. The straightforward solutions display realistic effects of dispersed fluid volume fraction, rate parameters, and initial concentrations. Final fractional conversions, occurring when the limiting reactant is depleted, are functions of a Damkohler number, volume fraction of dispersed reactant, and scaled initial conditions. © 2004 American Institute of Chemical Engineers AIChE J, 50: 835–847, 2004
Metabolic and molecular basis of peroxisomal disorders: A review
Authors: Wanders Ronald J.A.
Published: April 2004

The group of peroxisomal disorders now includes 17 different disorders with Zellweger syndrome as prototype. Thanks to the explosion of new information about the functions and biogenesis of peroxisomes, the metabolic and molecular basis of most of the peroxisomal disorders has been resolved. A review of peroxisomal disorders is provided in this paper. © 2004 Wiley‐Liss, Inc.
Positive associations of polymorphisms in the metabotropic glutamate receptor type 8 gene (GRM8) with schizophrenia
Authors: Takaki Hiromi , Kikuta Rumiko , Shibata Hiroki , Ninomiya Hideaki , Tashiro Nobutada , Fukumaki Yasuyuki
Published: April 2004

The glutamatergic dysfunction has been implicated in pathophysiology of schizophrenia. The Group III metabotropic glutamate receptor 4 (mGluR4), 6, 7, and 8 are thought to modulate glutamatergic transmission in the brain by inhibiting glutamate release at the synapse. We tested association of schizophrenia with GRM8 using 22 single nucleofide polymorphisms (SNPs) with the average intervals of 40.3 kb in the GRM8 region in 100 case‐control pairs for the SNPs. Although we observed significant associations of schizophrenia with two SNPs, SNP18 (rs2237748, allele: P = 0.0279; genotype: P = 0.0124) and SNP19 (rs2299472, allele: P = 0.0302; genotype: P = 0.0127), none of two SNPs showed significant association with disease after Bonferroni correction. Both SNP18 and SNP19 were included in a large region (>330 kb) in which SNPs are in linkage disequilibrium (LD) at the 3′ region of GRM8. We also tested haplotype association of schizophrenia with constructed haplotypes of the SNPs in LD. Significant associations were detected for the combinations of SNP5‐SNP6 (χ2 = 18.12, df = 3, P = 0.0004, P corr = 0.0924 with Bonferroni correction), SNP4‐SNP5‐SNP6 (χ2 = 27.50, df = 7, P = 0.0075, P corr = 0.015 with Bonferroni correction), and SNP5‐SNP6‐SNP7 (χ2 = 23.92, df = 7, P = 0.0011, P corr = 0.0022 with Bonferroni correction). Thus, we conclude that at least one susceptibility locus for schizophrenia is located within the GRM8 region in Japanese. © 2004 Wiley‐Liss, Inc.
Structural morphology and properties of star styrene–isoprene–butadiene rubber and natural rubber/star styrene–butadiene rubber blends
Authors: Zhao Suhe , Zou Hua , Zhang Xingying
Published: April 2004

Star styrene–isoprene–butadiene rubber (SIBR) was synthesized with a new kind of star anionic initiator made from naphthalene lithium and an SnCl4 coupled agent. The relationship between the structure and properties of star SIBR was studied. Star block styrene–isoprene–butadiene rubber (SB‐SIBR), having low hysteresis, high road‐hugging, and excellent mechanical properties, was closer to meeting the overall performance requirements of ideal tire‐tread rubber according to a comparison of the morphology and various properties of SB‐SIBR with those of star random SIBR and natural rubber/star styrene–butadiene rubber blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 336–341, 2004
Surface and electrical characteristics of poly(amide imide)–poly(dimethylsiloxane) nanocomposites
Authors: Park Young‐Wook , Lee Dong‐Sung
Published: April 2004

A series of poly(amide imide)–poly(dimethylsiloxane) (PDMS) nanocomposites were fabricated through the reaction of poly(amide imide), epoxysilane (coupling agent), and diethoxydimethylsilane (DEDMS) via a sol–gel process. Nanocomposite films were obtained through the hydrolysis and condensation of DEDMS in poly(amide imide) solutions. The existence of the condensation product of DEDMS in the poly(amide imide) matrix was confirmed with Fourier transform infrared (FTIR). The concentration of PDMS on the surface of the poly(amide imide) matrix was observed through a comparison of FTIR and attenuated total reflection spectra. The contact angle of the poly(amide imide)–PDMS composites increased more than 40° with respect to that of pure poly(amide imide). The alternating‐current (ac) breakdown strength was obtained through the measurement of the ac breakdown voltage at the temperature of liquid nitrogen. As the PDMS concentration in poly(amide imide) increased, the characteristics of the insulation breakdown improved greatly. The best ac breakdown strength was observed in a poly(amide imide)–epoxysilane (30 wt %) nanocomposite with 30 wt % PDMS. The samples at the temperature of liquid nitrogen were brittle, as in a glassy state. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 342–347, 2004
Visible‐light‐induced controlled/living radical polymerization of styrene with a phenyl seleno group at one terminal chain end: 1‐(Phenylseleno)ethyl benzene as a photoiniferter
Authors: Rathore K. , Reddy K. Raghunatha , Tomer N. S. , Desai S. M. , Singh R. P.
Published: April 2004

The photopolymerization of styrene with a well‐defined molecular architecture and a low polydispersity index and with methyl and phenylseleno (SePh) groups at α‐ and ω‐chain ends, respectively, was performed via a controlled/living radical polymerization with a new initiating system, 1‐(phenylseleno)ethyl benzene/tert‐butyl diphenyl (phenylseleno) silane, through the absorption of visible light at room temperature. A novel initiating living radical polymerization was examined. The yield and number‐average molecular weight (Mn) of the resulting polymer increased with the reaction time. Furthermore, a linear relationship was found in a plot of Mn versus the polymer yield. These results indicated that this polymerization proceeded through a living radical mechanism. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 348–355, 2004
Solid freeform fabrication of epoxidized soybean oil/epoxy composites with di‐, tri‐, and polyethylene amine curing agents
Authors: Liu Z. S. , Erhan S. Z. , Calvert P. D.
Published: April 2004

Soybean oil/epoxy‐based composites are prepared by solid freeform fabrication (SFF) methods. SFF methods built materials by the repetitive addition of thin layers. The mixture of epoxidized soybean oil and epoxy resin is modified with di‐, tri‐, or polyethylene amine gelling agent to solidify the materials until curing occurs. The high strength and stiffness composites are formed through fiber reinforcement. E‐glass, carbon, and mineral fibers are used in the formulations. The type of fiber affects the properties of the composites. It was found that a combination of two types of fibers could be used to achieve higher strength and stiffness parts than can be obtained from a single fiber type. In addition, the effects of curing temperature, curing time, and fiber concentration on mechanical properties of composites are studied and reported. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 356–363, 2004
Solution and solid‐state NMR investigation of poly(methyl methacrylate)/poly(vinyl pyrrolidone) blends
Authors: Diniz Teresinha M. F. F. , Tavares Maria I. B.
Published: April 2004

The development of polymer blends has become very important for the polymer industry because these blends have shown to be a successful and versatile alternative way to obtain a new polymer. In this study, binary blends formed by poly(methyl methacrylate) (PMMA) and poly(vinyl pyrrolidone) were prepared by solution casting and evaluated by solution and solid‐state NMR. Variations in the microstructure of PMMA were analyzed by 13C solution NMR. Solid‐state NMR promotes responses on physical interaction, homogeneity, and compatibility to use these blends to understand the behavior of the ternary blends. The NMR results led‐us to acquire information on the polymer blend microstructure and molecular dynamic behavior. From the NMR solution, it was possible to evaluate the microstructure of both polymer blend components; they were atactic. From the solid state, good compatibility between both polymer components was characterized. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 372–377, 2004
Use of N,N‐dimethylaniline end‐functional polymers in photoinduced block copolymerization
Authors: Muftuoglu A. Ekrem , Cianga Ioan , Yurteri Seda , Yagci Yusuf
Published: April 2004

N,N‐Dimethylaniline functional polystyrenes with well‐defined structures and low polydispersities were synthesized by atom transfer radical polymerization of styrene in bulk at 110°C using 4‐(dimethylamino)benzyl 4‐(bromomethyl) benzoate as initiator in conjunction with a cuprous complex [Cu(I)Br/bipyridine]. These polymers were further used in block copolymerization with methyl methacrylate and cyclohexene oxide (CHO) by photoinduced radical and radical‐promoted cationic polymerization routes, respectively. In the former case, macroradical generation was achieved with benzophenone sensitizer by photoexcitation followed by hydrogen abstraction from amino end groups. A visible light initiating system was used in the radical‐promoted cationic polymerization of CHO. The system involves a xanthene dye (erythrosin B) as the sensitizer, an aromatic N,N‐dimethyl amino group and diphenyl iodonium hexafluorophosphate as the radical source and radical oxidizer, respectively. Whereas pure block copolymers were obtained in the free‐radical route, the free‐radical–promoted cationic polymerization yielded both block and homopolymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 387–394, 2004
Effects of plasma treatment on CO2 plasticization of poly(methyl methacrylate) gas‐separation membranes
Authors: Hu Chien‐Chieh , Tu Chen‐Yuan , Wang Yi‐Chieh , Li Chi‐Lan , Lee Kueir‐Rarn , Lai Juin‐Yih
Published: April 2004

To suppress undesirable plasticization effects of condensable gas (CO2) in high pressure gas‐separation process, a surface‐modified poly(methyl methacrylate) (PMMA) membrane prepared by a plasma treatment was synthesized in this study. The pressure dependencies of permeability were analyzed to characterize the plasticization phenomenon and how it can be controlled by the plasma modification. FTIR‐ATR and TGA results suggest that the plasma treatment leads to surface crosslinking of PMMA membrane. Thus, the plasticization effect resulting from sorbed CO2 on the Ar‐plasma–treated PMMA membrane was significantly reduced, but the reduction in permeability was lower than that of other crosslinking modification methods. The reduction of the CO2 permeability contributes to a major part to the selectivity of He/CO2 for the Ar‐plasma–treated PMMA membranes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 395–401, 2004
Structure and morphology of an intumescent polypropylene blend
Authors: Almeras X. , Renaut N. , Jama C. , Le Bras M. , Tóth A. , Bourbigot S. , Marosi Gy. , Poutch F.
Published: April 2004

This article deals with the study of the efficiency of different compatibilizing agents in the intumescent polypropylene/polyamide‐6/ammonium polyphosphate (PP/PA‐6/APP) blend. The migration of additive was first investigated by X‐ray photoelectron spectroscopy. The study showed that ethylene–butyl acrylate–maleic anhydride is not efficient in preventing the exudation of APP to the surface. However, ethylene vinyl acetate (EVA) prevented such a phenomenon. Second, the modifications in the blends were analyzed as a function of their compositions. Optical microscopy analysis showed that adding EVA to PP/PA‐6/APP promoted a decrease in the size of PA‐6 droplets. X‐ray diffraction was used to characterize the effect of each component on the PP crystallinity. It was clearly shown that the crystallinity depends on the composition of the blend. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 402–411, 2004
Study on poly(propylene)/ammonium polyphosphate composites modified by ethylene‐1‐octene copolymer grafted with glycidyl methacrylate
Authors: Lu Mingfu , Zhang Shijun , Yu Dingsheng
Published: April 2004

The compatibilization effect of ethylene‐1‐octene copolymer grafted with glycidyl methacrylate (POE‐g‐GMA) as an interface compatibilizer on the mechanical and combustion properties, and the morphology and structures of the cross sections of ammonium polyphosphate (APP)–filled poly(propylene) (PP) were investigated by thermogravimetry, dynamic mechanical analysis, and differential scanning calorimetry. The results indicated that the toughness of the PP/APP composites increased rapidly with adding POE‐g‐GMA; the dynamic mechanical spectra revealed that the increase of the toughness was closely related to the peaks of loss modulus (E″) and mechanical loss (tan δ). The improvement of the dispersion of APP in the PP matrix was attributed to the addition of POE‐g‐GMA; it was found that the interfacial adhesion between the filler and matrix was enhanced when the grafting material was added to the composites. Under such circumstances, the ratio of char formation was increased when the PP composites were heated, although the content of flame retardant was not changed, so the flame retardance of the material was improved. The addition of POE‐g‐GMA increased the rate of crystallization. At the same time, the degree of crystallinity and the temperature at the beginning of crystallization were decreased, although exerting little influence on the melt behavior of the crystallization of the composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 412–419, 2004
Chemiluminescence of lucigenin is dependent on experimental conditions
Authors: Hyrsl Pavel , Lojek Antonin , Ciz Milan , Kubala Lukas
Published: April 2004

The aim of the study was to test the effect of experimental conditions such as light radiation and temperature on chemiluminescence (CL) of 10−2–10−5 mol/L lucigenin dissolved in various types of solvents. Irradiation by UV light (280, 297, 313 or 400 nm) induced a signiﬁcant increase in CL of lucigenin dissolved in borate buffer. This effect was the most obvious for 10−2–10−3 mol/L lucigenin. All wavelengths used had a similar effect. UV irradiation did not induce changes in the CL activity of lucigenin dissolved in dH2O or in dimethyl sulphoxide (DMSO). Different results for various solvents were not dependent on pH. The CL activity of 10−2 mol/L and 10−3 mol/L lucigenin dissolved in borate buffer increased depending on the solution temperature (25°C, 30°C, 37°C or 40°C) already at the beginning of the analysis, with a further increase during 16 h incubation period. It can be summarized that temperatures higher than 25°C and intensive light irradiation are among those factors which signiﬁcantly affect the result of analysis when lucigenin is used as a luminophor. Copyright © 2004 John Wiley & Sons, Ltd.
Hypohalites and related oxidants as chemiluminescence reagents: a review
Authors: Francis Paul S. , Barnett Neil W. , Lewis Simon W. , Lim Kieran F.
Published: April 2004

This review concerns the use of hypochlorite, hypobromite and related oxidants (such as N‐bromosuccinimide and 1,3‐dibromo‐5,5‐dimethylhydantoin) as chemiluminescence reagents and includes references to 249 papers that were published prior to mid‐2003. Particular emphasis has been placed on proposed emitting species and the mechanisms of the light‐producing pathways. The analytical applications of this chemistry have been summarized in three tables: (1) quantiﬁcation of hypohalites and related compounds (including halides, which are initially oxidized); (2) enhancement or inhibition of luminol chemiluminescence; and (3) direct chemiluminescence reactions with hypohalite reagents. Copyright © 2004 John Wiley & Sons, Ltd.
Flow injection chemiluminescent determination of tetracycline using a tris(2,2′‐bipyridine)ruthenium(II)–cerium(IV) sulphate system
Authors: Guo Liangqia , Xie Zenghong , Lin Xucong , Liu Xiaohua , Zhang Weilin , Chen Guonan
Published: April 2004

A ﬂow‐injection chemiluminescence method for the determination of tetracycline was developed. The method is based on an enhancement by tetracycline of the chemiluminescence light emission of tris(2,2′‐bipyridine)ruthenium(II). In sulphuric acid medium, the chemiluminescence is generated by the continuous oxidation of tris(2,2′‐bipyridine)ruthenium(II) by cerium (IV) sulphate. The light‐emission intensity is greatly enhanced in the presence of tetracycline. Under the optimum conditions, the calibration curve is linear over the range 3.75 × 10−8 g/mL–1.5 × 10−5 g/mL for tetracycline with the linear equation: ΔINT = 205.898 × C − 20.442 (R2 = 0.9974). The detection limit is 3.27 × 10−8 g/mL. The proposed method was also successfully used to determine tetracycline in pharmaceutical formulation (mean recovery of tetracycline, 100.7%). Copyright © 2004 John Wiley & Sons, Ltd.
Photochemical attachment of biomolecules onto ﬁbre‐optics for construction of a chemiluminescent immunosensor
Authors: Leshem Boaz , Sarfati Gadi , Novoa Andres , Breslav Igor , Marks Robert S.
Published: April 2004

We report herein a simple and effective way to photochemically immobilize biomolecules onto a ﬁbre‐optic silica surface. The system is based on a photoreactive benzophenone derivative that is bound to SiO2 surfaces of the optical ﬁbre via a silane anchor. The benzophenone derivative was 4‐allyloxybenzophenone, synthesized by standard procedures that were later used to synthesize the 4‐(3′‐chlorodimethylsilyl) propyloxybenzophenone and 4‐(3′‐dichloromethylsilyl) propyloxybenzophenone by regular hydrosilation procedures. After silanization with the benzophenone derivatives, the ﬁbres were immersed in a cholera toxin B subunit solution and illuminated with UV light (wavelength > 345 nm). As a result of the photochemical reaction, a thin layer of the antigen was covalently bound to the benzophenone‐modiﬁed surface. The photochemically modiﬁed ﬁbre‐optics were then tested as immunosensors in the detection of cholera anti‐toxin antibody and revealed through chemiluminescence measurements. A secondary antibody labelled with horseradish peroxidase acted as the marker for the cholera toxin antibody. A photo‐electronic set‐up was designed speciﬁcally to monitor the signal. The immunosensor system was shown to be both speciﬁc and sensitive. The lowest rabbit serum titre detected was 1:1 700 000. Copyright © 2004 John Wiley & Sons, Ltd.
A rapid method for fractionation and puriﬁcation of a 92 kDa cartilage glycoprotein
Authors: Roussidis Andreas E. , Anagnostides Stavros T.
Published: April 2004

Matrix glycoproteins are among the main components that contribute to the properties of cartilage. In this article we report on the development of a rapid method for the fractionation and puriﬁcation of a 92 kDa glycoprotein from chick sternal cartilage. The developed procedure involves ion‐exchange chromatography on DEAE‐Sephacel, gel permeation chromatography on Sepharose CL‐6B and semi‐preparative SDS‐polyacrylamide gel electrophoresis. Identiﬁcation of protein was performed by western blotting using speciﬁc antibodies and purity by capillary electrophoresis. The proposed method is superior to those previously published since it eliminates the step of density gradient centrifugation. Copyright © 2003 John Wiley & Sons, Ltd.
Stability indicating reversed‐phase high‐performance liquid chromatographic and thin layer densitometric methods for the determination of ziprasidone in bulk powder and in pharmaceutical formulations
Authors: El‐Sherif Zeinab A. , El‐Zeany Badr , El‐Houssini Ola M. , Rashed Mohamed S. , Aboul‐Enein Hassan Y.
Published: April 2004

Two sensitive and reproducible methods were developed and validated for the determination of ziprasidone (ZIP) in the presence of its degradation products in pure form and in pharmaceutical formulations. The ﬁrst method was based on reversed‐phase high‐performance liquid chromatography (HPLC), on a Lichrosorb RP C18 column using water:acetonitrile:phosphoric acid (76:24:0.5 v/v/v) as the mobile phase at a ﬂow rate of 1.5 mL min−1 at ambient temperature. Quantiﬁcation was achieved with UV detection at 229 nm over a concentration range of 10–500 µg mL−1 with mean percentage recovery of 99.71 ± 0.55. The method retained its accuracy in presence of up to 90% of ZIP degradation products. The second method was based on TLC separation of ZIP from its degradation products followed by densitometric measurement of the intact drug spot at 247 nm. The separation was carried out on aluminium sheet of silica gel 60 F254 using choloroform:methanol:glacial acetic acid (75:5:4.5 v/v/v) as the mobile phase, over a concentration range of 1–10 µg per spot and mean percentage recovery of 99.26 ± 0.39. Both methods were applied successfully to laboratory prepared mixtures and pharmaceutical capsules. Copyright © 2003 John Wiley & Sons, Ltd.
The Effect of Pressure on Hydrogen Transfer Reactions with Quinones
Authors: Wurche Frank , Sicking Wilhelm , Sustmann Reiner , Klärner Frank‐Gerrit , Rüchardt Christoph
Published: April 2004

The effect of pressure on the oxidation of hydroarenes3–9with 2,3‐dichloro‐5,6‐dicyano‐1,4‐quinone (DDQ;1 a) oro‐chloranil (10), leading to the corresponding arenes, has been investigated. The activation volumes were determined from the pressure dependence of the rate constants of these reactions monitored by on‐line UV/Vis spectroscopic measurements in an optical high‐pressure cell (up to 3500 bar). The finding that they are highly negative and only moderately dependent on the solvent polarity (ΔV≠= −13 to −25 in MTBE and −15 to −29 cm3 mol−1in MeCN/AcOEt, 1:1) rules out the formation of ionic species in the rate‐determining step and is good evidence for a hydrogen atom transfer mechanism leading to a pair of radicals in the rate‐determining step, as was also suggested by kinetic measurements, studies of kinetic isotope effects, and spin‐trapping experiments. The strong pressure dependence of the kinetic deuterium isotope effect for the reaction of 9,10‐dihydroanthracene5/5‐9,9,10,10‐D4with DDQ (1 a) can be attributed to a tunneling component in the hydrogen transfer. In the case of formal 1,3‐dienes and enes possessing two vicinal CH bonds, which have to be cleaved during the dehydrogenation, a pericyclic hydrogen transfer has to considered as one mechanistic alternative. The comparison of the kinetic deuterium isotope effects determined for the oxidation of tetralin9/9‐1,1,4,4‐D4/9‐2,2,3,3‐D4/9‐D12either with DDQ (1 a) or with thymoquinone1 cindicates that the reaction with DDQ (1 a) proceeds in a stepwise manner through hydrogen atom transfer, analogously to the oxidations of 1,4‐dihydroarenes, whereas the reaction with thymoquinone1 cis concerted, following the course of a pericyclic hydrogen transfer. The difference in the mechanistic courses of these two reactions may be explained by the effect of the CN and Cl substituents in1 a, which stabilize a radical intermediate better than the alkyl groups in1 c. The mechanistic conclusions are substantiated by DFT calculations.
Preparation and Reactions of 1,3‐Diphosphacyclobutane‐2,4‐diyls That Feature an Amino Substituent and/or a Carbonyl Group
Authors: Sugiyama Hiroki , Ito Shigekazu , Yoshifuji Masaaki
Published: April 2004

The preparation and properties of a 1‐amino‐1,3‐diphosphacyclobutane‐2,4‐diyl and a 1‐benzoyl‐1,3‐diphosphacyclobutane‐2,4‐diyl, which can be regarded as functionalized cyclic biradical derivatives, were investigated. Hydrolysis of 1‐diisopropylamino‐3‐methyl‐2,4‐bis(2,4,6‐tri‐tert‐butylphenyl)‐1,3‐diphosphacyclobutane‐2,4‐diyl (7), which is formed by reaction of Mes*CP (4; Mes*=2,4,6‐tBu3C6H2) with lithium diisopropylamide and iodomethane, resulted in ring‐opening of the 1,3‐diphosphacyclobutane‐2,4‐diyl skeleton, as well as de‐aromatization of one of the Mes* rings. 3‐Oxo‐1,3‐diphosphapropene 8 and 7‐phosphabicyclo[4.2.0]octa‐1(8),2,4‐triene 9 were the resultant products, and these were subsequently characterized. Isomerization and oxidation of 7 occurred in the presence of TEMPO (2,2,6,6‐tetramethyl‐1‐piperidinoxy) to give the first example of a cyclic dimethylenephosphorane derivative, namely 3‐oxo‐1,3‐diphospha‐1,4‐diene 10. 1‐Benzoyl‐3‐tert‐butyl‐2,4‐bis(2,4,6‐tri‐tert‐butylphenyl)‐1,3‐diphosphacyclobutane‐2,4‐diyl (12) was isolated and characterized from the reaction of 4 with tert‐butyllithium and benzoyl chloride. Compound 12 was subsequently heated and underwent rearrangement of the benzoyl group and ring‐expansion to afford 1‐oxo‐1H‐[1,3]diphosphole 13. Reaction of 4 with lithium diisopropylamide and benzoyl chloride afforded the 2H‐[1,2,4]oxadiphosphinine 15, which was probably formed through the 1,3‐diphosphacyclobutane‐2,4‐diyl intermediate 14. Thermolysis of 15 afforded 1‐oxo‐1H‐[1,3]diphosphole 16 in an Arbuzov‐type rearrangement.
The Ground and Excited States of Polyenyl Radicals C2n−1H2n+1 (n=2–13): A Valence Bond Study
Authors: Luo Yan , Song Lingchun , Wu Wei , Danovich David , Shaik Sason
Published: April 2004

The semiempirical valence bond (VB) method, VBDFT(s), is applied to the ground states and the covalent excited states of polyenyl radicals C2n−1H2n+1 (n=2–13). The method uses a single scalable parameter with a value that carries over from the study of the covalent excited states of polyenes (W. Wu, D. Danovich, A. Shurki, S. Shaik, J. Phys. Chem. A, 2000, 104, 8744). Whenever comparison is possible, the VB excitation energies are found to be in good accord with sophisticated molecular orbital (MO)‐based methods like CASPT2. The symmetry‐adapted Rumer structures are used to discuss the state‐symmetry and VB constitution of the ground and excited states, and the expansion to VB determinants is used to gain insight on spin density patterns. The theory helps to understand in a coherent and lucid manner the properties of polyenyl radicals, such as the makeup of the various states, their geometries and energies, and the distribution of the unpaired electrons (the neutral solitons).
Hybrid Integral‐Equation/Simulation Models: From Complexation Thermodynamics to Direct Free Energies
Authors: Kast Stefan M.
Published: April 2004

Statistical‐mechanical integral equation theory, an approximate methodology for computing distribution functions and thermodynamic properties of the liquid state, can be advantageously combined with molecular simulations to overcome inherent limitations of both approaches. This Concept discusses a number of conceptual applications that illustrate the capabilities of hybrid models: A study of complex formation in solution by explicit simulation of only the solute molecules, the correction of artefacts induced by truncated potentials, and an approach to the direct computation of free energies from a simulation of a single state.
Simulated Annealing Study of Diblock Copolymer Thin Films Confined between Two Homogeneous Surfaces
Authors: Yin Yuhua , Sun Pingchuan , Chen Tiehong , Li Baohui , Jin Qinghua , Ding Datong , Shi An‐Chang
Published: April 2004

Thin films of symmetric diblock copolymers confined between two parallel surfaces have been systematically investigated by means of simulated annealing on a simple cubic lattice. The study was carried out for systems with different film thicknesses and surface–polymer interactions. Very regular equilibrium morphologies of lamella are formed in almost all cases. The dependence of lamellar orientations, total energy, chain‐conformation entropy, and free energy of the confined films on the film thickness and the strength of surface–polymer interactions has been studied systematically. The influence of packing frustration on morphology is observed and the mechanisms of lamellar orientations are investigated.
Solvate‐Supported Proton Transport in Zeolites
Authors: Franke Marion E. , Simon Ulrich
Published: April 2004

Solvate‐supported proton transport in zeolite H‐ZSM‐5 was studied by means of complex impedance spectroscopy. The zeolite shows enhanced proton mobility in the presence of NH3 and H2O that depends on the concentration of the solvate molecule, temperature (298–773 K), and the SiO2/Al2O3 ratio of the zeolite (30–1000). In general, proton conductivity in H‐ZSM‐5 is most effectively supported in the presence of NH3 and H2O at high concentrations, low temperatures, and low SiO2/Al2O3 ratios (≤80). For the aluminum‐rich samples desorption measurements reflect different transport mechanisms that depend on the respective temperature range. Up to about 393 K a Grotthus‐like proton transport mechanism is assumed, whereas at higher temperatures (393–473 K) vehiclelike transport seems to dominate. The activation energies for NH4+ and H3O+ vehicle conductivity depend on the SiO2/Al2O3 ratio, and the values are in the range of 49–59 and 39–49 kJ mol−1, respectively, and thus significantly lower than those for “pure” proton conduction in solvate‐free samples.
Ground and Excited‐State Electronic Interactions in Poly(propylene amine) Dendrimers Functionalized with Naphthyl Units: Effect of Protonation and Metal Complexation
Authors: Pina Fernando , Passaniti Paolo , Maestri Mauro , Balzani Vincenzo , Vögtle Fritz , Gorka Marius , Lee Sang‐Kyu , van Heyst Jeroen , Fakhrnabavi Hassan
Published: April 2004

We report the absorption spectra and the photophysical properties (fluorescence spectrum, quantum yield, and lifetime) of four dendrimers of the poly(propylene amine) family (POPAMs) functionalized at the periphery with naphthylsulfonamide (hereafter called naphthyl) units. Each dendrimer Gn, where n=1 to 4 is the generation number, comprises 2n+1 (i.e., 32 for G4) naphthyl functions in the periphery and 2n+1−2 (i.e., 30 for G4) tertiary amine units in the branches. All the experiments have been carried out in acetonitrile solutions. Comparison with two reference compounds (N‐methyl‐naphthalene‐2‐sulfonamide, A, and N‐(3‐dimethylamino‐propyl)‐2‐naphthalene‐1‐sulfonamide, B) has shown that the absorption spectra of the dendrimers are significantly different from those expected from the component units. Furthermore, the intense fluorescence band of the naphthyl unit (λmax=343 nm; Φ=0.15, τ=8.5 ns) is strongly quenched in the dendrimers. The quenching effect increases with increasing generation and is accompanied by the appearance of a weak and broad emission tail at lower energy. Protonation of the amine units of the dendrimers by addition of CF3SO3H (triflic) acid causes a strong increase in the intensity of the naphthyl luminescence and a change in the form of the emission tail. The shapes of the titration curves depend on dendrimer generation, but in any case, the effect of the acid can be fully reversed by successive addition of a base (tributylamine). The results obtained show that in the dendrimers there are interactions (both in the ground and excited states) between naphthyl units as well as between naphthyl units and amine units of the branches; this gives rise to dimer/excimer and charge‐transfer/exciplex excited states. Titration with Zn(CF3SO3)2 has the same effect as acid titration, as far as the final emission spectrum is concerned, but a much higher concentration of Zn(CF3SO3)2 has to be used and the shapes of the titration plots are very different. Titration with Co(NO3)2.6H2O causes a much smaller increase in the intensity of the naphthyl fluorescence compared with Zn(CF3SO3)2 . The results obtained have shown that protonation and metal coordination can reveal the presence of ground and excited state electronic interactions in functionalized poly(propylene amine) dendrimers, and that the presence of photoactive units in the dendrimers can be useful to reveal some peculiar aspects of the protonation and metal coordination processes.
Hydrogen Bonding in Mimics of Watson–Crick Base Pairs Involving CH Proton Donor and F Proton Acceptor Groups: A Theoretical Study
Authors: Guerra Célia Fonseca , Bickelhaupt F. Matthias , Baerends Evert Jan
Published: April 2004

We have theoretically analyzed mimics of Watson–Crick adenine–thymine (AT) and guanine–cytosine (GC) base pairs in which NH⋅⋅⋅O and N⋅⋅⋅HN hydrogen bonds are replaced by NH⋅⋅⋅F and N⋅⋅⋅HC, respectively, by using the generalized gradient approximation of density functional theory at BP86/TZ2P. The general effect of the above substitutions is an elongation and weakening of the hydrogen bonds that hold together the base pairs. However, the precise effects depend on how many and, in particular, on which hydrogen bonds are substituted in AT and GC. Another purpose of this work is to clarify the relative importance of electrostatic attraction versus orbital interaction in the weak hydrogen bonds involved in the mimics, by using a quantitative bond‐energy decomposition scheme. At variance with widespread believe, the orbital interaction component in these weak hydrogen bonds is found to contribute 34–42 % of the attractive interactions and is thus of the same order of magnitude as the electrostatic component, which provides the remaining attraction component.
Consumer adoption of wireless services: Discovering the rules, while playing the game
Authors: Kleijnen Mirella , de Ruyter Ko , Wetzels Martin
Published: April 2004

This research aims to explain the adoption of mobile gaming based on a refined model of Rogers’ adoption theory, including context-specific factors and consumer traits. Overall, the empirical findings suggest that perceived risk plays a crucial role in the adoption process, followed by complexity and compatibility. Moreover, through cluster analysis we identified three consumers segments, termed “Value Seekers,” “Risk Avoiders,” and “Game Players.” Whereas perceived risk remains the most important factor for the Risk Avoiders, Value Seekers also are concerned about compatibility. Game Players emphasize navigation, communicability, and payment options.
The evolving role of the Internet in marketing strategy: An exploratory study
Authors: Sultan Fareena , Rohm Andrew J.
Published: April 2004

This research investigates the evolution of Internet marketing strategies in a longitudinal, exploratory study. The key research questions are “How does Internet strategy evolve over time, and what factors seem to drive this evolution?” To investigate these questions, we conducted in-depth interviews of senior managers at three manufacturing companies (Reebok International, Saturn, AB Dick) competing in different industries. By comparing past and current practices, we find that applications of Internet marketing strategy involve more than just e-commerce. Our research indicates that firms are using the Internet for creating value chain efficiencies, reducing costs, and enhancing customer and channel relationships.
The integration of direct marketing and field sales to form a new B2B sales coverage model
Authors: Coe John M.
Published: April 2004

Today's sales organization operates in a much different environment than that of the past. Sales and marketing must work together for the organization to operate at peak efficiency. It is only with such integration that sales can focus on the customers and channels most likely to provide the revenue necessary to reach their goals. The 21st century sales coverage model is built upon a multistepped process which integrates the tools and techniques of direct marketing with measurements, quantifiable business benefits, and capabilities that help salespeople remain fixed to an optimal set of goals. The process includes (a) benchmarking the existing sales and marketing process, (b) establishing gaps between the benchmarks and company goals, (c) developing required capabilities to close the gaps, (d) engineering the new sales coverage model, and (e) executing, measuring, and adjusting the model. While seeming to be deceptively simple, this framework realigns the sales organization to make best use of the company's full resources and capabilities.
The elasticity of customer value to retention: The duration of a customer relationship
Authors: Pfeifer Phillip E. , Farris Paul W.
Published: April 2004

A cornerstone of the customer relationship management (CRM) and interactive marketing literature is the Reichheld and Sasser statement that “reducing defections by 5% boosts profits 25% to 85%.” The basic premise is that a relatively small increase in customer retention (loyalty) will drive relatively large increases in profits. As the practice of CRM matures, we believe that managers and researchers will be interested in a more exact quantification of the economic benefits of increased customer retention. This article develops methods for determining percentage increases in expected customer (and prospect) lifetime values due to increased retention. In particular, we derive an equation for the elasticity of expected customer future value, the component of customer lifetime value contingent on retention. This equation for “retention elasticity” is based on a general model of a customer-retention relationship in which margins, retention spending, and retention probabilities vary with tenure. Using a numerical example, we investigate the factors that affect retention elasticity. We also show that this retention elasticity is equal to the financial duration of the customer asset. This connection between retention elasticity and financial duration offers a new perspective from which to understand and interpret retention elasticity. For example, just as duration is an important measure of a bond's risk, so too is retention elasticity a measure of one source of volatility in the value of a customer relationship.
Electrocatalysis of Nitrate Reduction at Copper‐Nickel Alloy Electrodes in Acidic Media
Authors: Simpson Brett K. , Johnson Dennis C.
Published: April 2004

The cathodic reduction of NO$\rm{ {_{3}^{-}}}$ in 1.0 M HClO4 is investigated by voltammetry at pure Ni and Cu electrodes, and three Cu‐Ni alloy electrodes of varying composition, all configured as rotated disks. Voltammetric data obtained using these hydrodynamic electrodes demonstrate significantly improved activity for NO$\rm{ {_{3}^{-}}}$ reduction at Cu‐Ni alloy electrodes as compared to the pure Ni and Cu electrodes. This observation is explained on the basis of the synergistic benefit of different surface sites for adsorption of H‐atoms, generated by cathodic discharge of H+ at Ni‐sites, and adsorption of NO$\rm{ {_{3}^{-}}}$ at Cu‐sites on these binary alloy electrodes. Koutecky‐Levich plots indicate that the cathodic response for NO$\rm{ {_{3}^{-}}}$ at a Cu75Ni25 electrode corresponds to an 8‐electron reduction, which is consistent with production of NH3. In comparison, the cathodic response at Cu50Ni50 and Cu25Ni75 electrodes corresponds to a 6‐electron reduction, which is consistent with production of NH2OH. Flow injection data obtained using Cu50Ni50 and Cu25Ni75 electrodes with 100‐μL injections exhibit detection limits for NO$\rm{ {_{3}^{-}}}$ of ca. 0.95 μM (ca. 95 pmol) and 0.60 μM (ca. 60 pmol), respectively.
Voltammetric Study of Some Synthetic Antioxidants on Platinum Microelectrodes in Acetic Acid Medium
Authors: Michalkiewicz Slawomir , Mechanik Monika , Malyszko Jan
Published: April 2004

The electrochemical oxidation of the antioxidants tert‐butylhydroquinone (BHQ), tert‐butyl‐4‐hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) has been investigated by voltammetry at platinum microelectrodes in glacial acetic acid containing sodium perchlorate or sodium acetate as a background electrolyte. BHQ, a compound with para‐diphenyl groups, was typically found to have lower oxidation potential than isolated phenols BHA and BHT. Particular attention has been devoted to the mechanism of the electrode processes. Linear scan voltammograms recorded under steady‐state conditions showed well‐defined oxidation waves of the compounds studied even at relatively high concentrations (2 mM), due to a low proclivity for adsorption of the oxidation products on the electrode surface in acetic acid. The optimal conditions for the voltammetric determination of BHQ, BHA and BHT have also been studied. The results reveal that sensitive response for all the oxidants studied can be obtained in solution containing 0.1 M NaClO4 and 0.1 M CH3COONa by using the differential pulse voltammetry and square‐wave voltammetry. Peak currents were found to vary linearly with the antioxidant concentration over the range 3×10−5−1×10−3 M.
Lead Sulfide Nanoparticle as Oligonucleotides Labels for Electrochemical Stripping Detection of DNA Hybridization
Authors: Zhu Ningning , Zhang Aiping , Wang Qingjiang , He Pingang , Fang Yuzhi
Published: April 2004

We report a method for the detection of DNA hybridization in connection to lead sulfide (PbS) nanoparticle tags and electrochemical stripping measurement of the lead. A kind of lead sulfide nanoparticle with free carboxyl groups on its surface was synthesized in aqueous solution. The nanoparticle was used as a marker to label a sequence‐known oligonucleotide, which was then employed as a DNA probe for identifying a target ssDNA immobilized on a PPy modified electrode based on a specific hybridization reaction. The hybridization events were monitored by the oxidation dissolution of the lead sulfide anchored on the hybrids and the indirect determination of the lead ions by anodic stripping voltammetry (ASV). The detection limit is 0.3 pmol L−1 of target oligonucleotides. The PbS nanoparticle combining its easy conjugation to the DNA molecule with the highly sensitive stripping voltammetry detection of lead shows its promising application in the electrochemical DNA hybridization analysis assay.
The Mediated Reduction of Lindane in DMF
Authors: Birkin P. R. , Evans A. , Milhano C. , Montenegro M. I. , Pletcher D.
Published: April 2004

The direct and mediated reductions of the hexachlorocyclohexane, lindane, in DMF are reported. 9,10‐diphenylanthracene (DPA) is a particularly effective mediator. The reaction of DPA− with lindane is a very fast reaction and, indeed, with ratios of [lindane]/[DPA]<5, the mediated reduction of lindane is mass transfer limited with respect to lindane. During the mediated reduction, light emission can be seen even in an undarkened laboratory; this is due to the formation of DPA*.
Power calculations for familial aggregation studies
Authors: Rabbee Nusrat , Betensky Rebecca A.
Published: April 2004

Family studies are frequently undertaken as the first step in the search for genetic determinants of disease. Significant familial aggregation of disease is suggestive of a genetic etiology for the disease, and may lead to more focused genetic analyses. Many methods have been proposed in the literature for the analysis of family studies. One model that is appealing for its simplicity of computation and the conditional interpretation of its parameters is the quadratic exponential model (e.g., Zhao and Prentice [1990] Biometrika 77:642–648; Betensky and Whittemore [1996] Appl. Stat. 45:422–429; Hudson et al. [2001a] Am. J. Epidemiol. 153:500–514). However, a limiting factor in its application, as well as that of the other proposed methods, is that power and sample size calculations have not been derived. These calculations are essential for investigators who are designing family studies. Here we derive analytic approximations for power for testing for familial aggregation, for both randomly sampled and nonrandomly sampled families. We also present simulation studies of power for both single‐ and two‐disease cases, both under random and nonrandom sampling. © 2004 Wiley‐Liss, Inc.