bluuebunny/crossref_metadata_2025 huggingface dataset:
The chemically initiated high pressure polymerization of ethylene
Authors: Buback Michael , Lendle Hubert
Published: April 2003

The kinetics of the high‐pressure ethylene polymerization initiated by di‐tert‐butyl peroxide were measured via quantitative near‐infrared spectroscopy at temperatures between 130°C and 165°C to a maximum pressure of 3 kbar. The overall polymerization rate was found to be first order in ethylene concentration and of the order 0,5 in peroxide concentration. The overall activation energy and the overall activation volume were determined to be E0 = 107,2 ± 7,5 kJ · mol−1 and Δ V0≠ = − 17,5 ± 5,0 cm3 · mol−1, respectively. From the overall quantities and from the decomposition rate of di‐tert‐butyl peroxide determined in independent spectroscopic high‐pressure high‐temperature experiments, kp · kt−1/2 (kp and kt are the propagation and termination rate constants, respectively) and the corresponding activation parameters, Ep – 1/2 Et and Δ vp≠ − 1/2 Δvt≠, were derived for the high‐pressure ethylene polymerization. These data enable the overall polymerization rate to be determined also for high‐pressure ethylene polymerizations initiated in any different way, provided the initiation rate law is known. The procedure is illustrated for the ethylene polymerization initiated by tert‐butyl peroxypivalate.
Crystallization of polydisperse polyethylene fractionated according to pennings' method
Authors: Hert Marius , Rault Jacques , Robelin Elisabeth
Published: April 2003

It is shown that the molten state and the semi‐crystalline state of polydisperse polyethylene are interrelated. Large polydisperse fractions obtained according to Pennings' fractionation method were studied by small angle X‐ray scattering and differential thermal analysis; the long period, depending on the molecular weight distribution, is shown to be given by the weight average end‐to‐end distance of the coils; the long chains with molecular weights M > 105 behave as a series of “sub‐chains” with molecular weight M* = 105 which crystallize independently. The same result is found for fractions with narrow molecular weight distribution and for mixtures of polyethylene fractions.
Asymmetric induction in the copolymerization of (–)‐3‐(β‐styryloxy)menthane with styrene
Authors: Yamaguchi Hidemasa , Sekioka Ken‐ichi , Kurokawa Masahiro , Doiuchi Tohru
Published: April 2003

Asymmetric induction in the copolymerization of (–)‐3‐(β‐styryloxy)menthane (1) with styrene was investigated. The copolymers obtained in the presence of BF3 · OEt2 are optically active. The absolute value of the specific rotation of the copolymers was found to be higher than that of the homopolymeric mixture, whatever the composition. After ether cleavage reaction of the copolymers, the products are still optically active. The result suggests that an asymmetric induction takes place in the polymer main chain.
Redox initiators for cationic polymerization: The diaryliodonium Salt/Sn(II) redox couple
Authors: Crivello J. V. , Lee J. L.
Published: April 2003

Diaryliodonium salts undergo facile copper catalyzed reduction in the presence of Sn(II) compounds. Such redox couples can be employed for the in situ generation of active initiators for cationic vinyl and ring opening polymerizations. Two mechanisms are proposed for the reduction reaction to explain the stoichiometry of the reactants and nature of the products formed. The polymerizations of several representative cationically polymerizable monomers were studied.
Vinyl polymerization initiated with systems of dimethylaniline N‐oxide and some chlorosilanes
Authors: Sato Tsuneyuki , Yamada Kentaro , Yasuda Takeyasu , Otsu Takayuki
Published: April 2003

Binary systems of dimethylaniline N‐oxide (DMAO) and some chlorosilanes were found to be effective initiators for vinyl polymerization. The initiating activity of the chlorosilanes decreases in the following order: SiCl4 > CH3SiCl3 > (CH3)SiCl2 > (CH3)3SiCl. The copolymerization of methyl methacrylate (MMA) with styrene, initiated with the system DMAO/SiCl4, propagates via a radical mechanism. The polymerization of MMA with the system DMAO/SiCl4 was investigated kinitically in acetonitrile. The overall activation energy of the polymerization was calculated to be 44,4 kJ/mol, an extremely low value. The initial poly‐merization rate(Rp) is of 1st order in monomer concentration. Rp is proportional to the square root of the DMAO concentration, and slightly dependent on the SiCl4 concentration for high SiCl4 concentrations. This suggests that a complex is formed between DMAO and SiCl4. Spec‐troscopic results on the system DMAO/SiCl4 also indicate the formation of a complex. A yellow crystalline compound was isolated from the reaction of DMAO with SiCl4 at room temperature in methylene chloride/diethyl ether (1:3, by vol.). The complex has a composition of four moles of DMAO and one mole of SiCl4. From these results and from spin trapping studies, a possible initiation mechanism is proposed for the polymerization initiated with the system DMAO/chlorosilane.
Polymerization of lactams, 55. Cyclic dimer of 6‐caprolactam and its polymerization
Authors: Krajník Václav , Kondelíková Jaroslava , Králíček Jaroslav , Karhan František
Published: April 2003

Polymerization of the cyclic dimer of 6‐caprolactam was investigated in N‐methyl‐2‐pyrroli‐done solution at 260°C under initiation with 6‐aminocaproic acid or anhydrous phosphoric acid on the one hand, and in the solid phase at 230, 260, and 280°C in the absence of any other component or under initiation with anhydrous phosphoric acid, on the other. Monomeric 6‐caprolactam was formed in all cases already at the beginning of reaction. It has been suggested that, in addition to the direct incorporation of the cyclic dimer into a polymer chain, the dimer is alos incorporated via the monomer, which is formed from the dimer by an intermolecular transamidation reaction.
Influence of water in the polymerization of tetrahydrofuran
Authors: Alamo Rufina , Guzmán Julio , Fatou José G.
Published: April 2003

The polymerization of tetrahydrofuran by acetyl perchlorate as initiator in methylene dichloride solution in the presence of water shows the same rate‐constant and yields polymer of the same number average degree of polymerization as its polymerization in anhydrous systems provided that [H2O] < [CH3CO+ClO4−]. The fact that water causes neither retardation nor transfer is explained.
Etude par 13C NMR d'alcanes lourds mono‐ et diramifiés. Modèles de polyoléfines
Authors: Frêche Patrick , Grenier‐Loustalot Marie‐Florence , Metras Franck , Gascoin Alain
Published: April 2003

13C NMR spectra were obtained for a series of branched, heavy alkanes at 37°C and 100°C, which provide a model set for describing the branched sequences in low density polyethylene (LDPE) and copolymers of α‐olefines. In addition, they provide a model set for revising the empirical Grant‐Paul and Lindeman‐Adams additive coefficients and corrective terms for pre‐dicting 13C chemical shifts of alkanes. The resulting revised parameters (for 37°C and 100°C) produce more accurate predictions of 13C NMR spectra for branched alkanes and it is noted that some corrective terms can be temperature‐sensitive.
Determination of poly(ethylene oxide) crystallinity by inverse gas chromatography
Authors: Fernández‐Berridi M. J. , Martín Guzmán G. M. , Iruin J. J. , Elorza J. M.
Published: April 2003

Specific retention volumes Vg for acetone, 1‐propanol, ethyl acetate, hexane, and tetrahydrofuran were obtained by inverse gas chromatography using poly(ethylene oxide) as stationary phase. Measurements were done at different flow rates, different injected sample amounts, and with three columns of different packing. Retention volumes were measured above and below the melting temperature of the polymer. The shape of the flow diagram and the variation of retention time tr with the sample amount depend on the temperature, flow rate, and the nature of the probe. Moreover, and due to the polymer polarity, the retention volume is a linear function of the column coating. All these factors must be controlled in order to obtain an accurate value of Vg which allows the determination of the crystallinity of the stationary phase. Above Tm, Vg is independent of flow, packing, and amount of the injected sample.
Polyvinylpyridine complexes of ruthenium(III) chloride
Authors: Clear James M. , Kelly John M. , Vos Johannes G.
Published: April 2003

A series of polymeric materials were prepared by reacting poly(2021840311vinylpyridine) or poly‐(4‐vinylpyridine) with ruthenium (III) chloride in refluxing methanol. Mole ratio of RuCl3 to vinylpyridine (Ru: PVP ratio) was varied from 2:1 to 1:20. From IR and UV/VIS spectroscopic data it is shown that several kinds of ruthenium‐PVP complexes are present, their relative proportions depending on the Ru: PVP ratio of the original reaction mixture and on the reaction time. The spectroscopic properties of the polymer complexes are compared to those of methylpyridine complexes of ruthenium(III) chloride.
Polymeric schiff's base chelates and their precursors, 4. Syntheses of schiff's base chelates from diaminomaleonitrile and investigation of their activity for the valence isomerisation of quadricyclane to norbornadien
Authors: Wöhrle Dieter , Bohlen Heike , Rothkopf Hans‐Werner
Published: April 2003

Various low molecular and polymeric Schiff's base chelates 9 – 13, 15 – 19, and 22 were synthesized from Z‐2,3‐diamino‐2‐butene dinitrile (3), the corresponding o‐hydroxyaldehydes, and Co(II), Ni(II), or Cu(II) acetate. Their IR, UV, and MS data are discussed. The cobalt containing Schiff's base chelates including the polymeric ones, were found to be effective catalysts for the isomerization of quadricyclane (24) into norbornadiene (23). First results are reported.
Promotion of charge‐transfer complex formation by β‐ or γ‐cyclodextrin
Authors: Kobayashi Nagao , Saito Rumiko , Ueno Akihiko , Osa Tetsuo
Published: April 2003

The formation of charge‐transfer (CT) complexes between eleven naphthalene derivatives and eight di‐ or trinitrobenzene derivatives in water and in water‐organic solvent systems has been studied in the presence and absence of β‐ or γ‐cyclodextrin (β‐ or γ‐CDx), respectively. Data of UV absorption and circular dichroism (CD) clearly revealed that γ‐CDx, in several cases, assists CT complex formation by accommodating both electron donor (D) and acceptor (A) molecules in its cavity simultaneously. Thus the weak CT band was intensified and even some systems in which CT complex formation was usually not observed produced CT complexes by the addition of γ‐CDx. In contrast, β‐CDx did not promote markedly the CT complex formation except in one case. It did promote the CT complex formation between α‐naphthylacetic acid (α‐NAA) and picric acid (PA), manifesting the capability of β‐CDx to include two aromatic molecules. Magnetic circular dichroism (MCD) associated with the CT bands was detected for a π ‐ π* type CT complex for the first time, but its intensity was quite weak as anticipated from theory.
Kinetics of the nitrogen dioxide initiated polymerization of acrylic acid
Authors: Mishra Mahendra K. , Bhadani Suraj N.
Published: April 2003

Acrylic acid (AA) was polymerized with NO2 in tetrahydrofuran (THF) and in 1,4‐dioxane. The effects of monomer and initiator concentration and of temperature on polymer conversion, initial rate of polymerization, and molecular weight were studied. The overall activation energy of polymerization was found to be 16,3 kcal mol−1 (68,23 kJ · mol−1) and 15,54 kcal · mol−1 (65,05 kJ · mol−1) in THF and in 1,4‐dioxane, respectively. High molecular weight polymers (M ca. 105) were obtained. The polymerization appears to be initiated by free radicals.
The solid‐state polymerization and physical properties of 2,4‐hexadiynylene bis(N‐ethylcarbamate), 1 crystal modifications and polymerization kinetics
Authors: Galiotis Costas , Young Robert J. , Ando David J. , Bloor David
Published: April 2003

Three distinct crystal modifications of 2,4‐hexadiynylene bis(N‐ethylcarbamate), (1c) are isolated under different conditions. The conditions necessary for the growth of crystals of the different modifications are described and their melting and phase transitions determined by differential thermal analysis. X‐Ray diffraction studies yielded unit cell dimensions for some modifications of the monomer 1c as well as the polymer 2c, but full structural analyses were impossible to obtain. Molecular models of 1c with different conformations have been constructed and shown to be compatible with the observed cell dimensions and solid‐state reactivities. The thermal and radiation polymerization kinetics of the two reactive modifications of 1c were studied. Despite the fact that the thermal polymerization of modification I of 1c is not a single‐phase process, the kinetics are well described by the crystal‐strain model, this fit being clearly fortuitous. A more detailed study of the kinetics reveals a second‐order behaviour and a model for a two‐phase polymerization process is proposed.
Functional monomers and polymers, 105. Synthesis of poly(β‐alanine) from a new type of active amino acid ester
Authors: Kondo Koichi , Miwa Yoshiyuki , Takemoto Kiichi
Published: April 2003

Active β‐alanine esters having dipeptide groups, which are capable of forming hydrogen bonds between the side chains, were prepared in the form of hydrogen chloride salts. The polycondensation of these salts was studied in non‐polar solvents, in the presence of triethylamine. In the case of the ester with β‐alanyl‐β‐alanine as dipeptide moiety, the polycondensation proceeded smoothly in chloroform solution. To explain the characteristic feature of the polycondensation, an ordered aggregation of the ester molecules is assumed to play an important role. The ester with glycylglycine as dipeptide moiety, however, did not undergo a polycondensation.
Polymers based on p‐aminophenol, 3. Synthesis of the simplest aromatic poly(imide‐ester) from p‐aminophenol derivatives
Authors: Kurita Keisuke , Matsuda Shoko
Published: April 2003

The pyrolytic behavior of N‐(4‐hydroxyphenyl)phthalimide‐4‐carboxylic acid (3) and its two ester derivatives 4 and 5 was studied with the intention to synthesize the simplest aromatic poly(imide‐ester). Self‐polycondensation of 3 at elevated temperatures was not successful, but a pyrolytic ester exchange reaction of monomers 4 and 5 led to the poly(imide‐ester) 1. Though the viscosity was not high, the polymer was confirmed to exhibit excellent thermooxidative stability.
Aliphatische azoverbindungen, 14. Eine kinetische analyse des thermischen zerfalls aliphatischer azonitrile
Authors: Barbe Werner , Rüchardt Christoph
Published: April 2003

Ketenimines 4 are known to be formed in a side equilibrium during the thermal decomposition of azonitrile initiators 1, as e.g. 2,2′‐azoisobutyronitrile (1a). The concentration of 4 was monitored by IR during the decomposition reaction of 1, and the final yield ratio of substituted succinonitrile 3 and nitrile 5 was determined by GC. Together with the rate constant k1 of 1, these data suffice for calculating k‐3, the rate of decomposition of 4, and k3/k2 the rate ratio of the two possible modes of dimerisation of α‐cyanoalkyl radicals 2.
Hydrolysis of phenyl esters catalyzed by alternating copolymers containing imidazolyl and carboxyl groups
Authors: Tanaka Jiro , Yamada Akira
Published: April 2003

The alternating copolymer, poly(N‐vinylimidazole‐co‐maleic acid) (4), and the random copolymer, poly(N‐vinylimidazole‐co‐acrylic acid) (5), with nearly the same ratio of carboxyl groups to imidazolyl groups, were found to catalyze the hydrolysis of 3‐acetoxy‐N‐trimethyl‐anilinium iodide (1), 4‐nitrophenyl acetate (2), and 4‐acetoxy‐3‐nitrobenzoic acid (3). For these esters, the catalytic activity of 4 at pH >9 was found to be in the following order: 3 > 2 > 1 that for 1 being a retarding one. Copolymer 5 shows a reverse catalytic activity of the order 1 > 2 > 3. The catalytic site of the alternating copolymer 4 is the free imidazolyl group, and the reaction rate is enhanced by the carboxylate anion, whereas the reaction rate in the presence of the random copolymer 5 is controlled predominantly by electrostatic interaction forces between the substrate and sequential carboxylate anions.
Association of two‐block copolymer polystyrene‐block‐poly(2‐vinylpyridine) in toluene
Authors: Sikora Antonín , Tuzar Zdeněk
Published: April 2003

The association of two‐block copolymers polystyrene‐block‐poly(2‐vinylpyridine) has been studied in toluene (a solvent selective for polystyrene) by osmometry, viscometry, and light scattering. Polystyrene‐block‐poly(2‐vinylpyridine) in toluene forms polymolecular micelles having a poly(2‐vinylpyridine) core and a polystyrene shell, and micellization conforms to the model of closed association. The phenomenon of so‐called anomalous micellization has been observed within a certain temperature interval where unusually large particles are formed.
Preliminary results on ethylene/propene copolymerization in the presence of Cp2Ti(CH3)2/Al(CH3)3/H2O
Authors: Busico Vincenzo , Mevo Lorenzo , Palumbo Giuseppe , Zambelli Adolfo , Tancredi Teodorico
Published: April 2003

Ethylene/propene copolymerizations were carried out in the presence of the catalyst system Cp2Ti(CH3)2/Al(CH3)3/H2O (Cp = cyclopentadienyl group), and the reactivity ratios r1, r2 were determined through the Fineman and Ross equation and via 13C NMR. A nearly alternating copolymer structure was pointed out. The yields as well as the molecular weights of the copolymers strongly decrease with increasing propene mole fraction in the copolymers.
Memory of a polymeric matrix, stabilizing the initial conformation of potassium bis[N‐(5‐methacryloylamino)‐salicylidene‐(S)‐norvalinato]‐cobaltate(III) in the deuterium exchange
Authors: Belokon Yuri N. , Tararov Vitali I. , Savel'eva Tatiana F. , Vorob'ev Mikhail M. , Vitt Sergei V. , Sizoy Vladimir F. , Sukhacheva Nina A. , Vasil'ev Gleb V. , Belikov Vasili M.
Published: April 2003

Copolymerization of potassium Λ‐ and Δ‐bis[N‐(5‐methacryloylamino)salicylidene‐(S)‐norvalinato]‐cobaltate(III) (1 and 2) with acrylamide and N,N′‐methylenediacrylamide gives crosslinked gels. The behaviour of the amino acid moiety in the gel obtained from the isomer with the Δ(S,S) configuration does not differ from that of the monomeric model compound 4. The Λ(S,S) isomer gives gels, in which a part of the complex proves to be attached by both phenyl moieties to one polymeric chain forming a macrocycle. Deuterium exchange in such complexes proceeds with full retention of the configuration of the amino acid.
Study of photopolymers, 18. Synthesis and photochemical reaction of novel polymers with pendant photosensitive and photosensitizing groups
Authors: Lizawa Takashi , Nishikubo Tadatomi , Takahashi Eiji , Hasegawa Masaki
Published: April 2003

Self‐sensitized photosensitive polymers with pendant photosensitive and photosensitizing groups were prepared by reaction of polystyrene containing pendant chloromethyl and photosensitizing groups, with the potassium salts of photosensitive compounds such as cinnamic acid, crotonic acid, or 2‐cyano‐3‐(α‐styryl)acrylic acid in DMF using tetrabutylammonium bromide as phase transfer catalyst. The photochemical reactivity and the practical photosensitivity of the resulting polymers were measured by IR spectrometry and by the gray‐scale method, respectively. Pendant 4‐nitro‐1‐naphthyloxy and 4‐nitrophenoxy groups in the polymers show the highest photosensitizing activity for pendant cinnamoyl groups. The photochemical reactivity and the sensitivity of these polymers are affected by the content of photosensitizing units in the polymer skeleton, the glass transition temperature of the polymers, however, is not influenced. Pendant 2‐benzoylbenzoyl groups act as excellent photosensitizers for pendant crotonoyl groups, however, the photochemical reactivity of this polymer was found to be lower than that of the polymer with pendant cinnamoyl and suitable photosensitizing groups. Pendant 2‐cyano‐3‐(α‐styryl)acryloyl groups in the polymer, which exhibit high photochemical activity, are also sensitized by pendant methyleosin moieties.
Synthesis and characterization of some new polyamides containing azomethine groups in the polymer backbone, 2
Authors: Subramanian Pethannan , Venkatarao Krishnan
Published: April 2003

New aromatic polyamides containing azomethine groups in the backbone and also having different linking groups like CH2, CH2CH2, and O were synthesized by reacting 4,4′‐[1,4‐phenylenebis(methylidynenitrilo)]dibenzoyl dichloride (2) with some diamines 1a – d, 4, and 6 by the low temperature solution polycondensation method. The physical, spectral, and thermal properties of the synthesized polyamides were investigated. The effect of the nature of different linking groups on the properties of these aromatic polymides was explored by comparing their spectral and thermal data.
Synthese der cyclischen oligomere des butylenterephthalats
Authors: Müller Franz‐Josef , Kusch Peter , Windeln Johannes , Zahn Helmut
Published: April 2003

Cyclic oligomers of butylene terephthalate (16a – d) were synthesized by cyclocondensations of the corresponding dicarboxylic acid dichlorides (2 or 13) with diols (4, 10, or 15). The linear educts 2, 4, 10, 13, and 15 were obtained by stepwise synthesis. The resulting cyclic esters 16a – d were characterized by IR, NMR, and mass spectroscopy.
Polymer‐solvent interactions in mixed solvents, 5. Ionized ethyl, butyl, and hexyl vinyl ether‐maleic acid alternating copolymers in water/2‐chloroethanol mixtures
Authors: Apostolopoulos Michel , Morcellet Michel , Loucheux Claude
Published: April 2003

Viscosity and preferential solvation measurements were carried out on ionized maleic acidethyl, ‐butyl, and ‐hexyl vinyl ether alternating copolymers (i‐MA/EVE, i‐MA/BVE, and i‐MA/HVE, respectively) in water‐2‐chloroethanol mixtures. i‐MA/EVE and i‐MA/BVE are completely coiled and their preferential and absolute solvation by water and 2‐chloroethanol reflects their more or less hydrophilic or hydrophobic nature. For i‐MA/HVE, the viscosimetric and preferential solvation measurements suggest that, in 2‐chloroethanol rich mixtures, the polymer retains a hypercoiled conformation in which an important part of the hexyl side chains are screened form contact with both componenets of the solvent mixture.
Interaction between polynucleotides in aqueous NaCl solution, 5. Temperature dependence of the heat of formation of poly(I) · poly(C) duplex
Authors: Baba Yoshihiro , Kagemoto Akihiro , Beatty Charles L.
Published: April 2003

The heat of mixing of equimolar solutions of poly(I) and poly(C) containing various NaCl concentrations was measured at 288 and 308 K, and the heat of formation of Poly(I) · poly(C) duplex from the randomly coiled constituents, poly(I) and poly(C), was estimated from the heat of mixing with the aid of CD measurements. The temperature dependence of this heat of formation, ΔH, differs at lower and higher NaCl concentrations: In the region of NaCl concentration less than 0,5 mol · dm‐3, ΔH increases with temperature, while in the region of NaCl concentrations higher than 0,5 mol · dm‐3, ΔH decreases with temperature. The free energy change, ΔG, of the formation of poly(I) · poly(C) duplex decreases as the NaCl concentration increases, that is, the stability of poly(I) · poly(C) duplex increases with NaCl concentration. Moreover, the conformation of poly(I) · poly(C) duplex seems to differ at lower and higher NaCl concentration as derived from the CD spectra and the thermodynamic quantities.
Proton NMR studies on n‐paraffins in restricted molecular motion
Authors: Ando Isao , Hirai Toru , Fujii Yuji , Nishioka Atsuo , Shoji Akira
Published: April 2003

The 1H NMR spectra of guest molecules, n‐paraffins (n‐C5H12, n‐C6H14, n‐C7H16, n‐C9H20, nC10H22, nC11H24, n‐C12H26, n‐C15H32, n‐C16H34, n‐C21H44 and n‐C22H46), were measured in poly(γ‐benzyl‐L‐glutamate) liquid crystalline solution. The methylene signal of n‐paraffins is a doublet due to magnetic dipole‐dipole interaction. These results suggest that an n‐paraffin takes predominantly the extended form in the restricted molecular motion state and that its long axis orients in the same direction as the helical axis of poly(γy‐benzyl‐L‐glutamate) parallel to the magnetic field. The results are compared with the molecular motion and conformation of η n‐paraffins in α‐chloronaphthalene.
Controller order reduction with guaranteed performance via coprime factorization
Authors: Wang Jin‐Zhi , Huang Lin
Published: April 2003

In this paper the problems of the suboptimalH∞controller order reduction and strictly positive real (SPR) controller order reduction via coprime factorization are studied. The sufficient conditions to ensure the reduced order controllers also being suboptimalH∞controllers and SPR are given, respectively. The conditions presented may be considered as frequency weighted model reduction problems. We generalize the result ofCℱ(θ) approach in Goddard (Ph.D. Thesis, Trinity College, Cambridge, 1995) for controller order reduction with anH∞framework and the relationship between our results and some other existing results is established. Copyright © 2003 John Wiley & Sons, Ltd.
Turnaround in East Asian firms: evidence from ethnic Overseas Chinese communities
Authors: Bruton Garry D. , Ahlstrom David , Wan Johnny C. C.
Published: April 2003

Research done primarily in the United States has shown that firms in decline enjoy better odds of returning to health when strong measures are taken. The culture of the Overseas Chinese of East Asia has helped to shape the region's prior commercial success but it also impacts responses to firm decline and turnaround. This research provides the first empirical investigation of the turnaround strategies of Overseas Chinese firms in East Asia. The evidence gathered shows that the utility of the predominantly U.S. model of firm turnaround has limits in East Asia. In particular, the role of strong owner‐managers and the importance of relationships among business people constrain the applicability of prior U.S. research to East Asia. Copyright © 2003 John Wiley & Sons, Ltd.
Obstetric aspects of the Prader–Willi syndrome
Authors: Fong B. F. , de Vries J. I. P.
Published: April 2003

The Prader–Willi syndrome (PWS) is a complex, multisystem disorder. The syndrome affects the central nervous system, with a predilection for the hypothalamus. The clinical picture in PWS is very variable, and depends on the age of the affected child. Frequently, the most prominent features such as obesity, mental retardation and behavioral disorders do not become evident until the later childhood stage, which can lead to underdiagnosis or late diagnosis in early childhood. Because of the long‐term implications of this syndrome, it is important to recognize its features as soon as possible so that early counseling of parents and the affected child is possible. Because PWS can also lead to complications in both pregnancy and labor, proper diagnosis in the fetus can also help optimize perinatal care in affected children. In three cases we illustrate that certain combinations of obstetric symptoms such as polyhydramnios, diminished fetal movements, malpresentation and abnormal fetal heart rhythm can help alert clinicians to the possibility of this syndrome in fetuses. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
On conformally invariant differential operators in odd dimensions
Authors: Alexakis Spyros
Published: April 2003

This is a brief announcement in which we identify all the conformally invariant differential operators acting on densities other than −(
n
/2) +
k
and other than
l
, where
k
is a positive integer and
l
is a nonnegative integer.
A reexamination of human-induced environmental change within the Lake Pátzcuaro Basin, Michoacán, Mexico
Authors: Fisher Christopher T. , Pollard Helen P. , Israde-Alcántara Isabel , Garduño-Monroy Victor H. , Banerjee Subir K.
Published: April 2003

This paper presents 2,000 years of settlement and land use within the Lake Pátzcuaro Basin, Mexico. Three findings challenge the conclusions of previous research. We show (i) that initial land degradation was caused by settlement, not by agriculture; (ii) that population density inversely correlates with erosion; and (iii) that land degradation was associated with European Conquest but not from the introduction of the Euro-agro suite. Instead, demographic collapse caused by European-introduced disease prevented human-generated landscapes from being maintained, resulting in widespread degradation. These findings support the use of indigenous landscape technology for modern conservation if past failings can be resolved.
Genetic architecture and evolutionary constraint when the environment contains genes
Authors: Wolf Jason B.
Published: April 2003

The environment provided by conspecifics is often the most important component of the environment experienced by individuals, frequently having profound effects on fitness and trait expression. Although these social effects on fitness and trait expression may appear to be purely environmental, they differ from other sorts of environmental influences, because they can have a genetic basis and thus can contribute to evolution. Theory has shown that these effects modify the definition of genetic architecture by making the phenotype the property of the genotypes of multiple individuals and alter evolutionary dynamics by introducing additional heritable components contributing to trait evolution. These effects suggest that genetic and evolutionary analyses of traits influenced by social environments must incorporate the genetic components of variation contributed by these environments. However, empirical studies incorporating these effects are generally lacking. In this paper, I quantify the contribution of genetically based environmental effects arising from social interactions during group rearing to the quantitative genetics of body size inDrosophila melanogaster. The results demonstrate that the genetic architecture of body size contains an important component of variation contributed by the social environment, which is hidden to ordinary genetic analyses and opposes the direct effects of genes on body-size development within a population. Using a model of trait evolution, I show that these effects significantly alter evolutionary predictions by providing hidden constraints on phenotypic evolution. The importance of relatedness of interactants and the potential impact of kin selection on the evolution of body size are also examined.
MAN1 and emerin have overlapping function(s) essential for chromosome segregation and cell division in
Caenorhabditis elegans
Authors: Liu Jun , Lee Kenneth K. , Segura-Totten Miriam , Neufeld Ester , Wilson Katherine L. , Gruenbaum Yosef
Published: April 2003

Emerin and MAN1 are LEM domain-containing integral membrane proteins of the vertebrate nuclear envelope. The function of MAN1 is unknown, whereas emerin is known to interact with nuclear lamins, barrier-to-autointegration factor (BAF), nesprin-1α, and a transcription repressor. Mutations in emerin cause X-linked recessive Emery–Dreifuss muscular dystrophy. Emerin and MAN1 homologs are both conserved in
Caenorhabditis elegans
, but loss of Ce-emerin has no detectable phenotype. We therefore used
C. elegans
to test the hypothesis that Ce-MAN1 overlaps functionally with Ce-emerin. Supporting this model, Ce-MAN1 interacted directly with Ce-lamin and Ce-BAF
in vitro
and required Ce-lamin for its nuclear envelope localization. Interestingly, RNA interference-mediated removal of ≈90% of Ce-MAN1 was lethal to ≈15% of embryos. However, in the absence of Ce-emerin, ≈90% reduction of Ce-MAN1 was lethal to all embryos by the 100-cell stage, with a phenotype involving repeated cycles of anaphase chromosome bridging and cytokinesis [“cell untimely torn” (
cut
) phenotype]. Immunostaining showed that the anaphase-bridged chromatin specifically retained a mitosis-specific phosphohistone H3 epitope and failed to recruit detectable Ce-lamin or Ce-BAF. These findings show that LEM domain proteins are essential for cell division and that Ce-emerin and Ce-MAN1 share at least one and possibly multiple overlapping functions, which may be relevant to Emery–Dreifuss muscular dystrophy.
Microfluidics without microfabrication
Authors: Lutz Barry R. , Chen Jian , Schwartz Daniel T.
Published: April 2003

Microfluidic devices create spatially defined, chemically controlled environments at microscopic dimensions. We demonstrate the formation and control of microscopic hydrodynamic and chemical environments by impinging a low-intensity acoustic oscillation on a cylindrical electrode. The interaction of small-amplitude (≤203 μm), low-frequency (≤515 Hz) fluid oscillations with a submillimeter cylinder creates four microscopic eddies that circulate adjacent to the cylinder. This steady flow is known as acoustic streaming. Because the steady circulation in the eddies has closed streamlines, reagent dosed from the electrode can escape the eddies only by slow molecular diffusion. As a result, reagent dosing rates of 10 nmol/s produce eddy concentrations as high as 8 mM, without a correspondingly large rise in bulk solution composition. Imaging Raman spectroscopy is used to visualize the eddy concentration distribution for various acoustic oscillation conditions, and point Raman spectra are used to quantify eddy compositions. These results, and corresponding numerical simulations, show that each eddy acts as a microchemical trap with size determined by acoustic frequency and the concentration tuned via reagent dosing rate and acoustic amplitude. Low-intensity acoustic streaming flows can serve as microfluidic elements without the need for microfabrication.
High-fidelity
in vivo
replication of DNA base shape mimics without Watson–Crick hydrogen bonds
Authors: Delaney James C. , Henderson Paul T. , Helquist Sandra A. , Morales Juan C. , Essigmann John M. , Kool Eric T.
Published: April 2003

We report studies testing the importance of Watson–Crick hydrogen bonding, base-pair geometry, and steric effects during DNA replication in living bacterial cells. Nonpolar DNA base shape mimics of thymine and adenine (abbreviated F and Q, respectively) were introduced into
Escherichia coli
by insertion into a phage genome followed by transfection of the vector into bacteria. Genetic assays showed that these two base mimics were bypassed with moderate to high efficiency in the cells and with very high efficiency under damage-response (SOS induction) conditions. Under both sets of conditions, the T-shape mimic (F) encoded genetic information in the bacteria as if it were thymine, directing incorporation of adenine opposite it with high fidelity. Similarly, the A mimic (Q) directed incorporation of thymine opposite itself with high fidelity. The data establish that Watson–Crick hydrogen bonding is not necessary for high-fidelity replication of a base pair
in vivo
. The results suggest that recognition of DNA base shape alone serves as the most powerful determinant of fidelity during transfer of genetic information in a living organism.
Joining comes of age: from pragmatic process to enabling technology
Authors: Messler Robert W.
Published: April 2003

From when we, as humans, first lashed a pointed stone to a split straight stick to make a more effective spear for hunting to now when we fasten and bond ablative ceramic tiles to the frail metal skin of the Space Shuttle to allow safe re‐entry from manned excursions into space, joining has been a pragmatic, albeit critically important, fabrication process. As we move beyond the Industrial Age to the ages of Information Technology, Nanotechnology, and Biotechnology, joining must move from a secondary process for manufacturing objects or articles from pre‐synthesized and pre‐shaped materials to a primary process for combining materials into fundamental structures as these structures and even materials are being synthesized; where the boundary between the materials and the structure becomes blurred. This paper attempts to catch a glimpse of the future where joining comes of age to become an enabling technology practiced as much or more by technicians or physicians than as a trade practiced by helmeted welders or hard‐hatted riveters.
Productivity and quality improvements through orbital forming
Authors: Stutz Werner R.
Published: April 2003

Orbital forming is an efficient and precise process to assemble component parts. It provides strength, an attractive finished appearance, and batch‐to‐batch uniformity. Orbital forming machines can produce high‐torque assemblies and also freely swinging joints, and any degree of built‐in resistance in between. These machines quietly flare and form all malleable materials, including many engineering thermoplastics, and work safely on delicate and brittle parts. The machine controls provide infinitely variable cycle times (speed), forming pressure and tool stroke on the micrometer dial with resolution to 0.001 in.
Robotic “layup” of composite materials
Authors: Groppe David
Published: April 2003

This paper describes the history and current technology behind composite manufacturing and the development of a precision feed endeffector (PFE). The PFE is used on the end of a robot arm and performs many functions associated with the handling of prepreg and semipreg materials. The PFE helps to achieve higher levels of accuracy and productivity for automated layup systems.
Facing the threats to electronic commerce
Authors: McCrohan Kevin F.
Published: April 2003

Presidential Decision Directive 63 concerning critical infrastructure protection, was signed on May 22, 1998. This order created a Presidential Commission charged with formulating policy recommendations to the President on measures to protect the critical infrastructures of the USA from cyber‐based attack. These initiatives were advanced in the Bush Administration with Executive Order 13231 – Critical Infrastructure Protection in the Information Age, October 16, 2001. Critical infrastructures are defined as those that are so vital that their incapacity or destruction would have a debilitating impact on the defence or economic security of the country. Among these are finance and banking, and telecommunications, the pillars of commerce and the nascent electronic commerce (e‐commerce) industry. Subsequent to this, the new century began with the publication of Defending America’s Cyberspace: The National Plan for Information Systems Protection, the distributed denial of service attacks on Yahoo!, and other major sites, and the hundreds of millions of dollars in damage due to the Code Red and Nimda viruses. One month after the publication of The National Strategy to Secure Cyberspace was distributed for comments (September 2002), the core domain name system root servers were attacked. In spite of these events, the reality is that market forces will continue to fuel the interest in e‐commerce regardless of concerns over security. Additionally, it will also remain difficult to encourage private sector openness and investment in security solutions in the absence of a major commercial catastrophe even in the face of rising customer expectations in service, security, and privacy. This paper explores these issues as they affect e‐commerce and suggests strategies to limit the potential impact of the array of threats facing critical infrastructures and e‐commerce. In doing so the paper discusses the importance of e‐commerce, the critical infrastructures, the threats to e‐commerce, and policies for protecting the organizations’ e‐commerce operations.
Oxygen Exchange Profile in Rat Muscles of Contrasting Fibre Types
Authors: Behnke Brad J. , McDonough Paul , Padilla Danielle J. , Musch Timothy I. , Poole David C.
Published: April 2003

To determine whether fibre type affects the O2 exchange characteristics of skeletal muscle at the microcirculatory level we tested the hypothesis that, following the onset of contractions, muscle comprising predominately type I fibres (soleus, Sol, 86 % type I) would, based on demonstrated blood flow responses, exhibit a blunted microvascular PO2 (PO2,m, which is determined by the O2 delivery (Q̇O2) to O2 uptake (V̇O2) ratio) profile (assessed via phosphorescence quenching) compared to muscle of primarily type II fibres (peroneal, Per, 84 % type II). PO2,m was measured at rest, and following the rest‐contractions (twitch, 1 Hz, 2–4 V for 120 s) transition in Sol (n= 6) and Per (n= 6) muscles of Sprague‐Dawley rats. Both muscles exhibited a delay followed by a mono‐exponential decrease in PO2,m to the steady state. However, compared with Sol, Per demonstrated (1) a larger change in baseline minus steady state contracting PO2,m (ΔPO2,m) (Per, 13.4 ± 1.7 mmHg; Sol, 8.6 ± 0.9 mmHg, P < 0.05); (2) a faster mean response time (i.e. time delay (TD) plus time constant (τ); Per, 23.8 ± 1.5 s; Sol, 39.6 ± 4.3 s, P < 0.05); and therefore (3) a greater rate of PO2,m decline (ΔPO2,m/τ; Per, 0.92 ± 0.08 mmHg s−1; Sol, 0.42 ± 0.05 mmHg s−1, P < 0.05). These data demonstrate an increased microvascular pressure head of O2 at any given point after the initial time delay for Sol versus Per following the onset of contractions that is probably due to faster Q̇O2 dynamics relative to those of V̇O2.
Holistic obstetrics: the origins of “natural childbirth” in Britain
Authors: Moscucci O
Published: April 2003

The term “natural childbirth” denotes an approach to childbirth characterised by a bias towards physical and mental hygiene in the management of pregnancy and labour. It emerged in Britain in the interwar period, partly as a response to the growing interventionism of mainstream obstetrics. Its appeal since then has rested on the belief that it could provide a holistic approach to maternity care, capable of addressing the needs of the “whole” patient. At the same time, “natural childbirth” has provided a means of expressing anxieties about the social, economic and political upheavals of the 20th century. This paper explores this complex set of beliefs and practices by examining the ideas of some British pioneers.
Raynaud’s phenomenon after radical radiotherapy for tumours of the head and neck
Authors: Westbury C B , Harrington K J , Rhys-Evans P , Archer D J , Searle A E , Henk J M , Black C M , Nutting C M
Published: April 2003

Endothelial cell injury is implicated in the development of radiation induced tissue damage and may also be involved in the pathophysiology of secondary Raynaud’s phenomenon. Two patients are presented in whom the typical symptoms and signs of Raynaud’s phenomenon developed as a late complication of radical radiotherapy. One had Raynaud’s of the tongue and one of the lip. Both patients had a prior history of primary Raynaud’s phenomenon and in each case the symptoms were repeatedly precipitated by sudden cold exposure. The possible pathogenesis of radiation induced Raynaud’s phenomenon in the head and neck region is discussed.
Birkhoff‐Kellogg theorems on invariant directions for multimaps
Authors: Agarwal Ravi P. , O′Regan Donal
Published: April 2003

We establish Birkhoff‐Kellogg type theorems on invariant directions
for a general class of maps. Our results, in particular, apply to Kakutani, acyclic, O′Neill, approximable, admissible, and maps.
Iterative algorithms with seminorm‐induced oblique projections
Authors: Censor Yair , Elfving Tommy
Published: April 2003

A definition of oblique projections onto closed convex sets that
use seminorms induced by diagonal matrices which may have zeros
on the diagonal is introduced. Existence and uniqueness of such projections are secured via directional affinity of the sets with respect to the diagonal
matrices involved. A block‐iterative algorithmic scheme for solving the convex feasibility problem, employing seminorm‐induced oblique projections, is constructed and its
convergence for the consistent case is established. The fully simultaneous algorithm converges also in the inconsistent case to the minimum of a certain proximity function.
Efferents and Centrifugal Afferents of the Main and Accessory Olfactory Bulbs in the Snake Thamnophis sirtalis
Authors: Lanuza Enrique , Halpern Mimi
Published: April 2003

This study reinvestigates the efferent projections of the main and accessory olfactory bulbs and describes for the first time the centrifugal projections to the main and accessory olfactory bulbs in the snake Thamnophis sirtalis, using the intraaxonal transport of the anterograde and retrograde tracer biotinylated dextran amine and the retrograde tracer horseradish peroxidase. The olfactory projection consists of three tracts: the lateral olfactory tract, which projects bilaterally to the lateral cortex and the rostral amygdala, crossing the midline through the stria medullaris-habenular commissure system; the intermediate olfactory tract, which projects ipsilaterally to the olfactory tubercle and contributes to the contralateral projection; and the medial olfactory tract, which projects ipsilaterally to the dorsomedial retrobulbar formation. The vomeronasal projection is formed by a single tract, the accessory olfactory tract, that projects ipsilaterally to the nucleus of the accessory olfactory tract, the medial amygdala and the nucleus sphericus. The centrifugal projections to the main and accessory olfactory bulb are composed of two components: one that arises in areas that receive the olfactory or vomeronasal input (neurons in the olfactory tubercle, retrobulbar formation and lateral cortex project to the main olfactory bulb; and neurons in the nucleus of the accessory olfactory tract, the medial amygdala and the nucleus sphericus project to the accessory olfactory bulb), and another that arises in areas not directly implicated in processing the chemosensory information (the nucleus of the diagonal band of Broca and the dorsal cortex). These data allow the recognition of the general pattern of organization of the reptilian olfactory and vomeronasal systems.
The Effects of Telencephalic Lesions on Visually Mediated Prey Orienting Behavior in the Leopard Frog (Rana pipiens)
Authors: Patton Paul , Grobstein Paul
Published: April 2003

In this paper, we report studies aimed at characterizing the relationship between forebrain and midbrain systems involved in the control of prey orienting behavior in the leopard frog. In frogs, unilateral forebrain lesions, like unilateral tectal lobe lesions, have their most prominent effects in the contralateral monocular visual field. Such lesions produce partial reductions in response frequency in the binocular visual field as well. Similar sequelae follow unilateral tectal lobe removal. These findings suggest that the effects of unilateral forebrain removal can be largely attributed to removal of a facilitating influence on the tectal lobe on the same side of the brain. In the case of both forebrain and midbrain lesions, behavior was assayed not only in terms of the frequency with which animals responded to stimuli at various locations in the visual field (as is usually done) but also in terms of the latency of whatever responses were observed. A striking inverse relationship between response frequency and response latency was found, both in lesioned and in normal frogs. This relationship has not previously been noticed, doesn’t appear to be an obvious consequence of any existing models of the neuronal circuitry underlying anuran orienting behavior, and is difficult to account for in terms of the time scales associated with axonal conduction times and synaptic delays. It may be easier to account for in terms of the responses to perturbation of large interacting systems of neurons, and this possibility seems worthy of further exploration.