bluuebunny/crossref_metadata_2025_split huggingface dataset:
Melt compounding of different grades of polystyrene with organoclay. Part 1: Compounding and characterization
Authors: Tanoue Shuichi , Utracki Leszek A. , Garcia‐Rejon Andrés , Tatibouët Jacques , Cole Kenneth C. , Kamal Musa R. 
Published: July 2004

AbstractNanocomposites of polystyrene (PS) with up to 20 wt% organoclay were prepared by melt compounding in a co‐rotating, intermeshing twin‐screw extruder. Three grades of PS with different molecular weights were used. In this paper we discuss preparation and characterization of the mixtures. Residence time and its distribution were measured by ultrasonics (US). They were found to be independent of the PS grade, but the US attenuation and sound velocity varied with the organoclay loading. According to the XRD diffraction data, the organoclay was dispersed into two types of platelet stacks evidenced by the diffraction peaks at about 2θ = 2.1 and 5.5°, i.e., with the interlayer spacings of d001 = 4.20 and 1.6 nm, respectively. Since neat organoclay has d001 = 1.93 nm, the first peak indicates intercalation by PS and the other a collapse of the interlamellar gallery during compounding. The XRD spectra depended on the organoclay content, but not on PS grade. According to TEM analysis, the degree of intercalation of organoclay in the polymer matrix is highest for the low‐molecular‐weight polystyrene. TEM results also confirm the collapse of interlamellar spacing in parts of the samples. FT‐IR spectroscopy showed that there was some thermal degradation of the onium compound present in the nanoclay. Polym. Eng. Sci. 44:1046–1060, 2004. © 2004 Society of Plastics Engineers.
Melt compounding of different grades of polystyrene with organoclay. Part 2: Rheological properties
Authors: Tanoue Shuichi , Utracki Leszek A. , Garcia‐Rejon Andrés , Sammut Pierre , Ton‐That Minh‐Tan , Pesneau Isabelle , Kamal Musa R. , Lyngaae‐Jørgensen Jørgen 
Published: July 2004

AbstractPolystyrene‐based nanocomposites (PNC) were prepared using three grades of polystyrene (different molecular weights). The resin was melt‐compounded with 0 to 10 wt% of commercial organoclay in a co‐rotating twin‐screw extruder. Owing to thermo‐oxidative degradation the degree of dispersion was poor. The rheological properties of PNC were determined under dynamic and steady state shear as well as under extensional flow conditions. At the higher clay content, dynamic strain sweep demonstrated that the storage and loss moduli decrease continuously with an increase of strain. To characterize this nonlinear viscoelastic behavior, the Fourier‐transform rheology was applied. The low strain frequency sweep showed that the storage and loss moduli increase with organoclay content. The extracted zero‐shear viscosity data were used to calculate the intrinsic viscosity and then the aspect ratio of dispersions. In spite of nonlinear viscoelastic behavior, the time‐temperature superposition was observed in the full range of concentration. The horizontal and vertical shift factors were found to be almost independent of organoclay content and molecular weight of PS. For comparison, PNC was also prepared by the solution method. A high degree of dispersion was obtained, reflected in the aspect ratio: p = 269, to be compared with p = 16 calculated for the melt‐compounded PNC. Polym. Eng. Sci. 44:1061–1076, 2004. © 2004 Society of Plastics Engineers.
Relative energies, stereoelectronic interactions and conformational interconversions in silathiacyclohexanes
Authors: Freeman Fillmore , Cha Chansa , Fang Christine , Huang Angela C. , Hwang Jee H. , Louie Patricia L. , Shainyan Bagrat A. 
Published: July 2004

AbstractStereoelectronic hyperconjugative interactions and the relative energies of conformers and transition states of 2‐, 3‐, and 4‐silathiacyclohexane were calculated at the B3LYP/6–311+G(d,p) level of theory. The chair conformer of 2‐silathiacyclohexane is 15.4 and 15.9 kcal mol−1 (1 kcal = 4.184 kJ), respectively, lower in energy than the chair conformers of 3‐ and 4‐silathiacyclohexane. Intrinsic reaction path calculations were used to connect the transition states between the respective chair and twist conformers and different chair–chair conformational interconversion paths were located for 3‐ and 4‐silathiacyclohexane. The energy of the transition state that connects the chair and 2,5‐twist conformers of 3‐silathiacyclohexane is 5.58 kcal mol−1 higher in energy than the chair. The transition state that connects the chair and 2,5‐twist conformers of 4‐silathiacyclohexane is 4.82 kcal mol−1 higher in energy than the chair. The energy differences (ΔE, kcal mol−1) between the chair conformer of 2‐silathiacyclohexane and the respective 1,4‐twist (ΔE = 4.16), 2,5‐twist (ΔE = 3.20) and 3,6‐twist (ΔE = 3.87) conformers were calculated. Small relative energy differences were calculated between the chair conformer and the respective 1,4‐twist (ΔE = 3.95), 2,5‐twist (ΔE = 4.07) and 3,6‐twist (ΔE = 3.46) conformers of 3‐silathiacyclohexane. The calculated energy differences (ΔE) between the chair conformer and the 1,4‐twist and 2,5‐twist conformers of 4‐silathiacyclohexane were 3.50 and 4.04 kcal mol−1, respectively. The geometric parameters and stereoelectronic hyperconjugative interactions in the silathiacyclohexanes are compared and discussed. Copyright © 2004 John Wiley & Sons, Ltd.
Block copolymers of styrene andn‐alkyl methacrylates with long alkyl groups. Micellization behavior in selective solvents
Authors: Pitsikalis Marinos , Siakali‐Kioulafa Ekaterini , Hadjichristidis Nikos 
Published: July 2004

AbstractThe micellization properties of well‐defined block copolymers of styrene and decyl methacrylate (SDMA) were studied in two different solvents, methyl acetate (MAc) selective for the polystyrene (PS) block and dodecane, selective for the poly(decyl methacrylate) (PDMA) block. The results were compared with those obtained, in the same solvents, from block copolymers of styrene and stearyl methacrylate (SSMA). In MAc, SDMA copolymers with a decyl methacrylate (DMA) content of 15% or less formed unimolecular micelles, whereas those with a content of 18.5% or higher formed multimolecular micelles. The degrees of association were lower than the corresponding SSMA samples. In dodecane, SDMA form large, monodisperse, spherical, and thermally stable micelles with degrees of association higher than the corresponding SSMA samples. The different behaviors can be attributed to the steric hindrance effect and the ability of the long alkyl groups of the polymethacrylate, MA blocks to crystallize. When the MA blocks are in the soluble corona of the micelles, the steric hindrance effect prevails, thus leading to higher degrees of association for the less bulky alkyl group. In the case where the MA block is in the insoluble core of the micelles, the higher the tendency for crystallization the higher the degree of association. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4177–4188, 2004
Segmental cystic malformation of the lung with chondrolipomatous component
Authors: Cohen Marta , Diez Graciela , Segal Edgardo , Drut Ricardo 
Published: July 2004

AbstractA peculiar cystic and chondrolipomatous malformation affecting the right upper lobe of the lung as presented in a 10‐year‐old girl with a history of recurrent pneumonia and pneumothorax is reported. The lesion combined bronchial‐type cavities with intervening stroma containing adipose tissue, with cartilage nodules of different sizes. The findings do not fit with any already‐known malformations of the lung. Pediatr Pulmonol. © 2004 Wiley‐Liss, Inc.
Aggressive and non‐violent videogames: short‐term psychological and cardiovascular effects on habitual players
Authors: Baldaro Bruno , Tuozzi Giovanni , Codispoti Maurizio , Montebarocci Ornella , Barbagli Francesco , Trombini Elena , Rossi Nicolino 
Published: July 2004

AbstractThe purpose of this study is to evaluate the short‐term effects on several physiological (arterial pressure and heart rate) and psychological (anxiety and aggressiveness) indexes of playing violent and non‐violent videogames in young adults. The study was carried out on a sample of 22 male participants. Subjects invited to participate in the study were recruited from a videogame leisure club. Before and during playing either a violent or non‐violent computer game, blood pressure and heart rate were measured. Before and after the game session, the subjects completed the State‐Anxiety Inventory‐Y (STAI‐Y) and the Buss–Durkee Hostility Inventory. The results of the study showed a range of short‐term effects of playing violent and non‐violent videogames on arterial pressure and on the state anxiety of subjects, but not on hostility measurements. More specifically, the group that played the violent videogames showed a significant increase in the state anxiety score at the end of the game, as compared to the pre‐game self‐evaluation, and an increase in the systolic blood pressure while the subjects were playing as compared to pre‐ and post‐game values. A decrease in diastolic blood pressure after playing any game was also found. Copyright © 2004 John Wiley & Sons, Ltd.
R&D, organization structure, and the development of corporate technological knowledge
Authors: Argyres Nicholas S. , Silverman Brian S. 
Published: July 2004

AbstractWe explore the link between a firm's organization of research—specifically, its choice to operate a centralized or decentralized R&D structure—and the type of innovation it produces. We propose that by reducing the internal transaction costs associated with R&D coordination across units, centralized R&D will generate innovations that have a larger and broader impact on subsequent technological evolution than will decentralized research. We also propose that, by facilitating more distant (‘capabilities‐broadening’) search, centralized R&D will generate innovations that draw on a wider range of technologies. Our empirical results provide support for our predictions concerning impact, and mixed results for our predictions concerning breadth of search. We also find that control over research budgets complements direct authority relations in contributing to innovative impact. We propose several extensions of this research. Copyright © 2004 John Wiley & Sons, Ltd.
The scope and governance of international R&D alliances
Authors: Oxley Joanne E. , Sampson Rachelle C. 
Published: July 2004

AbstractParticipants in research and development alliances face a difficult challenge: how to maintain sufficiently open knowledge exchange to achieve alliance objectives while controlling knowledge flows to avoid unintended leakage of valuable technology. Prior research suggests that choosing an appropriate organizational form or governance structure is an important mechanism in achieving a balance between these potentially competing concerns. This does not exhaust the set of possible mechanisms available to alliance partners, however. In this paper we explore an alternative response to hazards of R&D cooperation: reduction of the ‘scope’ of the alliance. We argue that when partner firms are direct competitors in end product or strategic resource markets even ‘protective’ governance structures such as equity joint ventures may provide insufficient protection to induce extensive knowledge sharing among alliance participants. Rather than abandoning potential gains from cooperation altogether in these circumstances, partners choose to limit the scope of alliance activities to those that can be successfully completed with limited (and carefully regulated) knowledge sharing. Our arguments are supported by empirical analysis of a sample of international R&D alliances involving electronics and telecommunications equipment companies. Copyright © 2004 John Wiley & Sons, Ltd.
How do multinational companies leverage technological competencies? Moving from single to interdependent explanations
Authors: Hansen Morten T. , Løvås Bjørn 
Published: July 2004

AbstractThis paper explores the relationships among four fundamental determinants of intrafirm competence transfers that have hitherto been analyzed only separately: formal organization structure, informal relations, geographical distance, and relatedness of competencies across subsidiaries. Using a data set consisting of 4840 dyads between new product development teams and subsidiaries that were potential targets for competence transfers in a high‐technology multinational company, we find that these determinants interact in surprising ways to explain different patterns of transfers. Results revealed that teams preferred to approach people they knew rather than people who knew related technologies well. They also showed that teams steered away from spatially distant subsidiaries that had related competencies and that the negative effect of large spatial distances could be overcome through established informal relations. These findings indicate that studying one of the determinants separately can yield biased results, as their net effect may change when the moderating effects of the other determinants are considered. Research on synergies, integration, technology transfers, and geographical and cultural differentiation in multinational enterprises therefore needs to be broadened by analyzing multiple determinants of competence transfers. Copyright © 2004 John Wiley & Sons, Ltd.
Technological and product‐market experience and the success of new product introductions in the pharmaceutical industry
Authors: Nerkar Atul , Roberts Peter W. 
Published: July 2004

AbstractThe growth and development of a firm depend on its ability to introduce new products over time. To do this successfully, it requires technological knowledge, the ability to combine knowledge elements into valuable new products, and the complementary assets that facilitate the manufacturing, sales, and distribution of those products. We argue that these all develop as a function of a firm's experience in its technological and product‐market domains. Moreover, given the prospect of complementarities among technological and product‐market experience, the value of any one type of experience may be enhanced by the presence of another. Therefore, new products will be more successful when a firm possesses the appropriate stocks of technological and product‐market experience. We test this idea by analyzing whether pharmaceutical firms' experience in their technological and product‐market domains confer early advantages to their new product offerings, and lead to higher initial sales levels. Copyright © 2004 John Wiley & Sons, Ltd.
Are we all global now? Local vs. foreign sources of corporate competence: the case of the Japanese pharmaceutical industry
Authors: Thomas L. G. 
Published: July 2004

AbstractThis study links the highly distinctive national contexts of the pharmaceutical industry to the evolution of innovative capabilities for Japanese drug firms from 1975 to 1995. During these two decades, the Japanese domestic environment for pharmaceuticals changed radically, encouraging a ‘bubble’ of trivial innovations. Experience by Japanese firms in their domestic market predominantly determined their innovative capabilities, pushing these firms towards trivial innovation. Corporate experience in the socially ‘proximate’ markets of Southern Europe served as a strategic complement for significant innovation by Japanese drug firms, and thus as a partial counterweight to the home market. Unfortunately, corporate diversification was a strategic substitute for significant innovation, and many Japanese drug firms are significantly diversified. The resulting degradation of innovative capability for Japanese drug firms has locked most of them into an increasingly unattractive home market. Copyright © 2004 John Wiley & Sons, Ltd.
EPR Studies of Spin Correlation in Some Ion Radical Salts
Authors: Chesnut D. B. , Phillips W. D. 
Published: July 2004

Electron spin resonance studies have been carried out on a number of ion-radical salts based on the strong π-acceptor tetracyanoquinodimethane (TCNQ). These studies have established that spin correlation exists between the magnetic electrons in these salts, giving rise to a ground singlet state and a thermally accessible triplet state. Typical singlet-triplet separations (J) derived from observed temperature dependences of EPR signal intensities are 0.034 ev for the [(C2H5)3NH]+(TCNQ)2− salt, 0.062 ev for the (φ3PCH3)+(TCNQ)2− and (φ3AsCH3)+(TCNQ)2− salts, and 0.41 ev for the (morpholinium)+(TCNQ)− salt.
The triplet states of the (φ3PCH3)+(TCNQ)2− and (φ3AsCH)+(TCNQ)2− salts are further manifested by an anisotropic splitting of the resonance into a doublet (zero-field splitting) and the appearance of half-field Δm=±2 transitions. Detailed analysis reveals that both salts may be represented by the spin Hamiltonian H=βH·g·S+DSz2+E(Sx2−Sy2),with | D/hc |=0.0062 cm−1, | E/hc |=0.00098 cm−1, and gx, gy, and gz equal to 2.0040, 2.0031, and 2.0027, respectively. Temperature-dependent exchange interactions observed for the (φ3PCH3)+(TCNQ)2− and (φ3AsCH3)+(TCNQ)2− salts cause the doublet zero-field components to broaden, move together, and collapse into a single, progressively sharper line as the temperature is increased. The exchange frequency follows an exponential temperature dependence and is governed by the concentration of triplet entities in the solid (J=0.062 ev).
The importance of paramagnetic impurities in studies of the magnetic properties of organic solids is emphasized. Examples are given which illustrate how a percent or so of doublet-state impurity species can dominate resonances near g=2.002 in molecular solids obeying singlet-triplet statistics.
Cohesive Energies of Europium, Gadolinium, Holmium, and Erbium
Authors: Trulson O. Conrad , Hudson Donald E. , Spedding Frank H. 
Published: July 2004

A mass spectrometric method has been employed to study the solid-gas phase change in four rare-earth metals. The enthalpies of sublimation in kcal/M reducted to 298°K are: Eu, 43.11±0.25; Gd, 81.22±0.32; Ho, 75.04±0.44; and Er, 75.39±0.34. The corresponding cohesive energies in kcal/M as determined from presently available thermodynamic data are: Eu, 43.4; Gd, 81.9; Ho, 75.5; and Er, 75.7.
A summary of the cohesion in the rare-earth series is included. A qualitative explanation of the unexpected variations is given in terms of the energetics of the metallic and gaseous states.
Nuclear Quadrupole Resonance in TiCl4, ThCl4, NbCl5, and TaCl5
Authors: Reddoch Allan H. 
Published: July 2004

The chlorine resonance in titanium tetrachloride has been re-examined, confirming the existence of four resonances. A chlorine-35 resonance at about 6 Mc has been discovered in thorium tetrachloride. The frequency suggests highly ionic bonding, which contradicts earlier conclusions from x-ray studies. Some double-bond character may be present in the Th–Cl bond.
Niobium and chlorine resonances have been discovered in niobium pentachloride. The niobium resonances are described by a single set of parameters, the coupling constant eqQ being approximately 78 Mc, and the asymmetry parameter, η=0.32. Because of the large asymmetry parameter, it was possible to observe two ΔM=2 and one ΔM=3 transitions. Only a single Cl35 resonance was found at about 13 Mc, although two more chlorine resonances would be expected on the basis of crystal structure. The frequency of the chlorine resonance suggests appreciable covalency in the niobium-chlorine bond in niobium pentachloride.
A single resonance has been found in tantalum pentachloride at about 13 Mc. It is believed to be a chlorine-35 resonance. A fairly simple method is outlined for determining the asymmetry parameter of the electric-field gradient from the observed transition frequencies without directly solving the secular equations.
Transition Probabilities in Multilevel Systems: Calculation from Impulsive and Steady-State Experiments
Authors: Carrington Tucker 
Published: July 2004

The study of collision-induced transitions of molecules in a system of many energy levels is discussed in an analysis of time-dependent and steady-state experiments. These results are used in a discussion, with numerical examples, of the difficulties in calculating the transition probabilities from observed population distributions.
An intimate conceptual and mathematical relationship is established between two types of experiments which are possible at present. One is an impulse, or time-dependent experiment such as excitation with a fast flash lamp and snapshot observation after a known delay time. The other is a steady-state experiment in which molecules are fed into the system (a gas or a surface) at a single energy level, for example, and undergo transitions among the available levels in competition with a first-order removal process such as spontaneous radiation or desorption from a surface.
The ideas summarized above are used to develop procedures for calculating transition probabilities from observed population distributions. Numerical examples and qualitative considerations indicate that when transitions involving more than single quantum jumps are involved, the experimental data must be known to much higher accuracy than that desired in the transition probabilities. The difficulties increase rapidly as the number of levels in the system increases.
Electrical Conductivity and Thermodynamic Equilibrium in Nickel Oxide
Authors: Mitoff S. P. 
Published: July 2004

The electrical conductivity of nickel oxide has been studied at temperatures between 600° and 1350°C and partial pressures of oxygen between 1 atm and 10−4 atm. The slope of log conductivity vs reciprocal temperature plots increases when the temperature is high enough for the sample to come into thermodynamic equilibrium with the atmosphere, and the temperature at which the change in slope occurs is observed to depend on the rate of heating or cooling of the crystal. The heat of formation of nickel vacancies may be determined from the magnitude of the change in slope by a simple calculation. Nickel oxide is a p-type semiconductor [M. Verwey, M. Haaijman, H. Romeijn, and M. van Oosterhout, Philips Research Repts. 5, 173 (1950)] in which the conductivity is proportional to the concentration of Ni3+ ions in the lattice. When thermodynamic equilibrium is established with the atmosphere the conductivity is proportional to the ⅙th power of the oxygen partial pressure.
The analysis of the conduction mechanism and the conduction data may be self-consistently correlated with nickel diffusion, nickel vacancy diffusion, and weight changes resulting from equilibration with different oxygen partial pressures. The following constants may be determined from these correlations: heat of formation of nickel vacancies, activation energy for nickel vacancy migration, activation energy for electron hole migration, and concentrations of nickel vacancies and Ni3+ ions as a function of temperature and oxygen pressure. Combined results give the following for the concentration of nickel vacancies: 0.11 (PO2)⅙ exp(−17 800/RT) vacancies per ion pair.