bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and properties of polyolefin‐clay nanocomposites
Authors: Lew C. Y. , Murphy W. R. , McNally G. M. 
Published: July 2004

AbstractPolyolefin‐organoclay nanocomposites containing a synthetic tetrasilisic fluoromica were prepared from metallocene‐catalyzed and conventional Ziegler‐Natta‐catalyzed linear low‐density polyethylenes (LLDPE) by means of melt‐compounding. The effects of maleic‐anhydride grafted compatibilizer (PE‐g‐MA) level, clay concentration, and blending procedure were investigated and compared. Morphology and structural analysis using transmission electron microscopy (TEM) and X‐ray diffraction (XRD) suggested the clay exfoliation was more intense in the metallocene LLDPE matrix, conceivably because of the controlled short‐chain branching and viscosity effects. When exfoliated, these silicate sheets were shown to restrict the lamellar crystallization, as seen by the decrease in crystallinity using differential scanning calorimetry analysis (DSC). The dynamic mechanical thermal analysis (DMTA) study suggested that the three α, β, and γ‐relaxations of the LLDPE were affected by polymer chain branching and clay exfoliation level. Polym. Eng. Sci. 44:1027–1035, 2004. © 2004 Society of Plastics Engineers.
Extrusion processing of TPO nanocomposites
Authors: Fasulo Paula D. , Rodgers William R. , Ottaviani Robert A. , Hunter Douglas L. 
Published: July 2004

AbstractNanocomposites are a class of materials that use molecular‐sized particles for reinforcing the polymer matrix. These materials blend an organoclay with polymer to produce a composite with physical and mechanical properties equal to or better than their conventionally filled counterparts but at lower filler loadings. Occasionally, when the processing conditions are not optimized, compaction of the filler materials can occur. This agglomeration of the filler can affect the final properties of the composite by lowering the effective filler concentration and by the creation of stress risers around these agglomerates. This paper addresses the role of extrusion processing as it relates to the dispersion of the organoclay filler. Polym. Eng. Sci. 44:1036–1045, 2004. © 2004 Society of Plastics Engineers.
Preparation and thermal properties of silica‐graft acrylonitrile‐butadiene‐styrene nanocomposites
Authors: Zheng Kang , Chen Lin , Li Yong , Cui Ping 
Published: July 2004

AbstractThe synthesis of silica‐graft acrylonitrile‐butadiene‐styrene (ABS) nanocomposites and their thermal properties are studied. The silica nanopowders are treated with silane to introduce reactive groups onto the silica surfaces. The dispersion of modified silica nanoparticles in tetrahydrofuran (THF) is significantly improved. The silica‐graft ABS composites were prepared by an open ring reaction and radical grafting copolymerization of modified silica, styrene, and maleic anhydride (MAH) in ABS/THF solution. Differential scanning calorimetry (DSC) results show that the glass transition temperature (Tg) of ABS‐graft‐SiO2 shifts obviously to high temperatures with increasing silica content. The TGA results indicate that the thermal stability is also improved with the increase of grafted silica. Polym. Eng. Sci. 44:1077–1082, 2004. © 2004 Society of Plastics Engineers.
Thermoset rubber/layered silicate nanocomposites. Status and future trends
Authors: Karger‐Kocsis J. , Wu C.‐M. 
Published: July 2004

AbstractThis paper surveys the recent achievements with thermoset rubber/layered silicate nanocomposites considering their production methods, cure characteristics, structure and basic properties (mechanical, thermal and barrier). It was shown that the properties of the “nanoreinforced” rubbers strongly depend on the dispersion state of the silicate. The latter can be influenced by various methods related to the production route (latex, solution or melt compounding), silicate type (natural and artificial origin mostly affecting the aspect ratio), surface modification of the silicate (chemical buildup of the surfactant used for “organophilization”), recipe (curatives, activators, compatibilizers, etc.) and compounding parameters (temperature, time, shear rate, etc.). A peculiar skeleton‐type reinforcing structure can be produced by latex compounding. Solution and melt intercalation techniques usually result in nanocomposites containing silicate layers in both intercalated and exfoliated forms. To detect the related structure the combined use of transmission electron microscopy (TEM) and X‐ray diffraction (XRD) techniques is inevitable. Confinement and deintercalation of the organophilic layered silicates occurring during compounding can be circumvented by the proper selection of the surfactants. Based on the present praxis some tendencies for future R&D activities with rubber nanocomposites were deduced and a strong impetus was forecasted to them owing to the fast development with thermoplastic/layered silicate systems. Polym. Eng. Sci. 44:1083–1093, 2004. © 2004 Society of Plastics Engineers.
Mechanical and rheological studies on polyethylene terephthalate‐montmorillonite nanocomposites
Authors: Sánchez‐Solís A. , Romero‐Ibarra I. , Estrada M. R. , Calderas F. , Manero O. 
Published: July 2004

AbstractIn this work, a detailed investigation of the rheological and mechanical properties of nanocomposites based on polyethylene terephthalate (PET) and montmorillonite clays is presented. A series of additives [maleic anhydride (MAH), pentaerythritol (PENTA), and alkylammonium chlorides from amines of various chain lengths] were used as compatibilizers. The influence of the additives on the mechanical and rheological behavior of the PET matrix was evaluated separately, through their individual contributions. To shed more light on the reported decrease in melt viscosity of organoclay composites with respect to the matrix viscosity, observed in nylon and PET nanocomposites, the polymer molecular weight was related to the resulting rheological and mechanical properties of the systems. Results reveal that the PET nanocomposites behave quite differently in shear as opposed to elongation. The viscoelastic properties in shear present low values when the molecular weight decreases because of the processing operations. However, properties under tension increase over those of the matrix, manifesting the presence of a network formed between the clay and the polymer. Polym. Eng. Sci. 44:1094–1102, 2004. © 2004 Society of Plastics Engineers.
Evaluation of the emotional status of patients on a waiting list for thoracic surgery during the outbreak of Severe Acute Respiratory Syndrome (SARS)
Authors: Wan Innes Y. P. , Wat Karen H. Y. , Ng Calvin S. H. , Thung K. H. , Lam Shirley , Lee T. W. , Wan Song , Yim Anthony P. C. 
Published: July 2004

AbstractThe objective of this study was to examine the emotional status of patients on the waiting list for thoracic surgery operations during the outbreak of Severe Acute Respiratory Syndrome (SARS) in Hong Kong. Telephone interviews were conducted on patients awaiting thoracic surgery including major lung resection, mediastinal, pleural, tracheal and chest wall operations during the outbreak of SARS in April 2003 at the Prince of Wales Hospital, Hong Kong. The anxiety and depressive symptoms were assessed by the Hospital Anxiety and Depression Scale (HADS). Fifty‐seven patients participated in the interview (31.67 per cent response rate) of whom 18 were female. On the HADS, using the cut‐off point for psychiatric cases, 17 patients (29.82 per cent) scored above 15 for the full scale indicating significant psychiatric problems. Within the anxiety sub‐scale, 24 patients (42.11 per cent) reached the level of high anxiety (HADS score > 5). Fifteen patients (26.3 per cent) were above the cut‐off score of significant depression (HADS score > 8) for the depression sub‐scale. There was no relationship between the waiting time on the list and the level of depression and anxiety. The outbreak of SARS and the anticipation of surgery contributed to the high levels of anxiety and depression among patients awaiting thoracic surgical operations. A multi‐disciplinary and holistic approach to the management of this group of patients should be considered. Copyright © 2004 John Wiley & Sons, Ltd.
Knowledge spillovers and the assignment of R&D responsibilities to foreign subsidiaries
Authors: Feinberg Susan E. , Gupta Anil K. 
Published: July 2004

AbstractResearch on R&D location choice by MNCs has focused largely on host country factor endowments and overlooked the role that the potential to capture and utilize knowledge spillovers from competitors may also play in determining such choices. Using a large‐scale panel database of the foreign subsidiaries of U.S.‐based MNCs in above‐average R&D‐intensive industries, we examine the extent to which external spillover opportunities as well as internal firm‐specific capabilities to utilize such knowledge affect MNCs' new R&D location decisions. Our findings suggest that MNCs appear to anticipate potential spillover opportunities and are discriminating in assessing these opportunities not only across locations but also across categories of competitors within the same location. Further, our findings provide stronger support to predictions regarding the salience of global utilization capacity than they do to predictions regarding the salience of local utilization capacity. Copyright © 2004 John Wiley & Sons, Ltd.
Where do resources come from? The role of idiosyncratic situations
Authors: Ahuja Gautam , Katila Riitta 
Published: July 2004

AbstractIn this paper, we examine the emergence of resources. Our analysis of technological capability acquisition by global U.S.‐based chemical firms shows that the emergence of resources is inherently evolutionary. We find thatpath‐creating searchthat generates resource heterogeneity is a response to idiosyncratic situations faced by firms in their local searches. Two such idiosyncratic situations—technology exhaustion and expansion beyond national markets—trigger firms in our sample to create unique innovation search paths. We also find that along a given path firms experiment in order to find the correct investment—in fact, some organizations seem to take a step backward for two steps forward—further demonstrating the evolutionary nature of the resource creation process. Copyright © 2004 John Wiley & Sons, Ltd.
Momentum and serendipity: how acquired leaders create value in the integration of technology firms
Authors: Graebner Melissa E. 
Published: July 2004

AbstractMerger and acquisition activity is a critical means by which technology firms obtain the resources needed to compete in global markets. Effective implementation is essential to making these acquisitions successful, yet prior research on the implementation process has yielded paradoxical findings. I argue that a closer examination of the role of the acquired managers helps to resolve the implementation dilemmas found in prior research, which has focused on the role of the acquiring firm. I use grounded theory‐building techniques to examine the integration of eight technology acquisitions, and find that acquired managers play a key role in achieving two types of value: expected and serendipitous. In promoting the realization of these two types of value, acquired leaders maintain the advantages of both integration and autonomy. Moreover, these leaders enable their organizations to simultaneously experience two often‐conflicting forms of change: exploration and exploitation. Copyright © 2004 John Wiley & Sons, Ltd.
The global acquisition, leverage, and protection of technological competencies
Authors: McEvily Susan K. , Eisenhardt Kathleen M. , Prescott John E. 
Published: July 2004

AbstractHow managers acquire, leverage, and protect technological competencies in order to innovate successfully and enhance firm performance is central to the field of strategic management. When tensions across acquisition, leverage, and protection activities are resolved and synergies are captured, the value derived from technological competencies can be used to fuel a virtuous cycle in which fewer resources are needed to perpetuate a firm's advantage. The papers in this issue examine the mechanisms underlying acquisition, leverage, and protection, and are particularly useful in resolving these tensions and highlighting potential synergies. We develop a typology to describe the research domain and relate these papers to one another. Based on gaps in this typology and issues raised by these papers, we offer observations for future research on the acquisition, leverage, and protection of technological competencies. Copyright © 2004 John Wiley & Sons, Ltd.
Hyperfine Structure and g-Tensor Anisotropy of the Paramagnetic Resonances of Manganese in TiO2
Authors: Andresen Harro G. 
Published: July 2004

Several characteristic resonances of the paramagnetic spectrum of a manganese-doped TiO2 single crystal in its rutile structure were measured with high precision in order to improve the accuracy of the spin Hamiltonian parameters. The measurements were performed at room temperature and at X-band frequencies. Especially, the anisotropy of the g tensor and that of the A tensor were evaluated using the resonance data measured at orientations of the magnetic field parallel to the three magnetic axes of the rutile crystal. The hyperfine structure patterns of the manganese resonances are discussed qualitatively for various crystal orientations; two properly selected |ΔmI|=1 transitions were used to estimate the upper limit of the quadrupole-term parameters of the spin Hamiltonian.
The paramagnetic resonances of manganese in rutile were also investigated at liquid nitrogen temperature and at X-band frequencies. Aside from a spectrum that is very similar to the spectrum already observed at room temperature and assigned to tetravalent manganese atoms, having a spin value of S=32, additional manganese resonances of strong intensity were observed. Though it is very likely that these resonances can be attributed to manganese atoms of a different valence state, the paramagnetic data at X-band frequencies are insufficient to determine the origin of these resonances unambiguously.
Self-Nucleation in the Sulfuric Acid-Water System
Authors: Doyle George J. 
Published: July 2004

Howard Reiss' ``Vector model'' was adapted to calculate the self-nucleation rate for the sulfuric acid-water system and similar systems.
A numerical calculation was carried out for the typical case of 50% relative humidity at 25°C. It was concluded that rapid self-nucleation would take place at sulfuric acid partial pressures in the range 10-8-10-10 mm Hg. The considerable uncertainty is principally due to lack of data on the partial pressure of sulfuric acid above its aqueous solutions and on the dominant sulfuric acid-bearing species in humid atmospheres.
Interaction of Rare Gases with Semiconductor Surfaces
Authors: Green Mino , Seiwatz Ruth 
Published: July 2004

The interaction of krypton with clean germanium surfaces has been analyzed in terms of dispersion forces, assuming a 6:12 potential. Using the experimental value for the heat of adsorption and a computed value for the attractive term in the 6:12 potential, the repulsive term in the potential was calculated. The interaction energy at various positions on the (111) crystal plane of germanium was then computed. The method used involves recently developed techniques for the summation over a semi-infinite crystal. From this analysis an effective van der Waals radius for the surface germanium atoms can be deduced, and the value (1.8 A) seems to be, from several points of view, physically reasonable. Using an empirical combination rule, it is then possible to predict heats of adsorption for other germanium-rare gas systems, viz., (Ge–Ar) 3.3 kcal/mole; (Ge–Xe) 4.1 kcal/mole.
The contribution of the induction effect to the heat of adsorption at various positions on the (111) plane has been calculated for a specific model, and the results show that while there is a significant contribution, roughly 0.8 kcal/mole, the dominant adsorption force is the dispersion interaction. The possible contribution of surface heterogeneity to the heat of adsorption is discussed in terms of adsorption at a surface step. A description of the method of summation over the semi-infinite crystal is dealt with in an Appendix.
Energy Value of the Octahedral-Tetrahedral Coordination Change
Authors: Katzin Leonard I. 
Published: July 2004

The equilibrium oct(CoCl2Py4) = tet(CoCl2Py2) +2Py for cobaltous chloride solutions in pyridine is followed over a temperature range, yielding ΔH = +13.4 kcal/mole. At 38°C the equilibrium constant is estimated as (CoPy2Cl2) (Py)2/(CoCl2Py4) = 0.04, and the ΔS for the reaction is about 36.7 eu. It is pointed out that the average bond strength in the tetrahedral species is about 17 kcal greater than for the same groups in the octahedral configuration, and that the strength of binding and the dissociation energy for the two ligands released according to the equation above are significant factors in determining the equilibrium reaction.
Detailed arguments are given against the view that the relative stability of octahedrally and tetrahedrally coordinated complexes, such as the pair discussed, reflect principally the difference in ``ligand-field stabilization'' of the nonbonding d electrons between octahedral and tetrahedral fields.
Molecular Detachment Processes in the Vacuum uv Photolysis of Gaseous Hydrocarbons. I. Ethylene. II. Butane
Authors: Sauer Myran C. , Dorfman Leon M. 
Published: July 2004

The photolysis of ethylene and of butane has been studied at room temperature with light of 1470 A. The results of isotopic studies, along with a detailed examination of the products of reaction, establish conclusively that molecular detachment processes are of major importance in the primary decomposition of the photoexcited states formed.
In the photolysis of ethylene at 1470 A the primary processes are C2H4*=C2H2+H2φ1C2H4**=C2H2+2Hφ2with φ1≅φ2. Rupture of only a single carbon-hydrogen bond is not an important primary process. The foregoing reactions, along with the subsequent interactions of ethyl radicals, formed by hydrogen atom addition to ethylene, furnish a unique description of almost all the photochemistry observed under the conditions of the experiments.
In the photolysis of butane at 1470 A, molecular detachment of hydrogen: C4H10*=C4H8+H2is a major primary process. The detailed nature of any other primary reactions has not been established.
Uranium Monosulfide. I. Vaporization, Thermodynamics, and Phase Behavior
Authors: Cater E. David , Gilles Paul W. , Thorn R. J. 
Published: July 2004

The rate of evaporation of uranium monosulfide has been measured over the 900-deg temperature range 1840° to 2730°K and a pressure range 10—3 to 10—8 atm, with an estimated accuracy of ±4%, by collection of vapor effusing from tungsten effusion cells containing the solid. The congruently evaporating composition was shown to be S/U=1.00. The effusion rate is expressed in terms of an ``effective'' vapor pressure PE calculated as though the entire vapor consisted of gaseous US molecules. An empirical equation derived by the method of least squares from the data is logPE(atm)=−1.7382+3.127×104/T−1.3181×108/T2+0.093776×1012/T3.Mass spectrometric measurements [E. D. Cater, E. G. Rauh, and R. J. Thorn, J. Chem. Phys. 35, 619 (1961)] show that the vaporization actually occurs both to gaseous US and to gaseous U+S. The present data are treated to yield the heats of sublimation at 2300°K to gaseous molecules, 150.3±2.1, and to gaseous elements, 271.2±4.0 kcal/mole, where the quoted uncertainties are estimated errors. The corresponding entropies of sublimation are: to molecules, 38.4±0.6, and to atoms, 65.5±1.6 cal/degmole. The lattice parameter of uranium monosulfide is 5.4903±0.0002 A. The melting point is 2735+30–5°K. The monosulfide solid phase appears to encompass a small composition range. Values derived from the experimental data and the literature for absolute entropies at 2300°K are 45±2 eu for solid, and 83±3 eu for gaseous US, where estimated errors are given. The heat of formation of solid US at 298°K from the gaseous atoms is estimated to be —273±5 kcal/mole and from the solid elements, —90±5. The free energies of formation of solid and gaseous monosulfide between 2100 and 2400°K are expressed by the equations ΔFf∘(US,s)=64.0T−268000cal/moleΔFf∘(US,g)=38.8T−152000cal/mole
A semitheoretical treatment gives nonlinear equations for the temperature dependences of the free energies and entropies of vaporization.
Statistics of Orientation Effects in Linear Polymer Molecules
Authors: DiMarzio Edmund A. 
Published: July 2004

This paper is concerned with the effects of orientation on the combinatorial term g for the number of ways to pack together Nx linear polymers (x mers). Accordingly g is evaluated as a function of the number of molecules in each permitted direction for the case of straight rigid rods. The permitted directions can be continuous so that g is derived as a function of the continuous function f(r) which gives the density of rods lying in the solid angle Δr, or the permitted directions can be discrete so that g is the number of ways to pack molecules onto a lattice. To illustrate the usefulness of the orientation dependent combinatorial terms, liquid crystals are discussed. Another phase is found to exist in addition to the previously predicted nematic phase. This phase is tentatively identified with the cholesteric phase.
A procedure is developed for the calculation of the orientation dependent combinatorial term associated with the packing together of molecules of arbitrary shape. A very approximate application of this procedure results in an approximate expression for the combinatorial term which allows one to predict qualitatively the change in the entropy of packing as a function of stretch. It is found that the entropy of packing has the proper behavior to explain the initial deviation of the experimental stress-strain curve from the previous theoretical predictions.
The Effect of Water, Sugars, and Proteins on the Pattern of Ice Nucleation and Propagation in Acclimated and Nonacclimated Canola Leaves
Authors: Gusta L.V. , Wisniewski M. , Nesbitt N.T. , Gusta M.L. 
Published: July 2004

AbstractInfrared video thermography was used to observe ice nucleation temperatures, patterns of ice formation, and freezing rates in nonacclimated and cold acclimated leaves of a spring (cv Quest) and a winter (cv Express) canola (Brassica napus). Distinctly different freezing patterns were observed, and the effect of water content, sugars, and soluble proteins on the freezing process was characterized. When freezing was initiated at a warm subzero temperature, ice growth rapidly spread throughout nonacclimated leaves. In contrast, acclimated leaves initiated freezing in a horseshoe pattern beginning at the uppermost edge followed by a slow progression of ice formation across the leaf. However, when acclimated leaves, either previously killed by a slow freeze (2°C h−1) or by direct submersion in liquid nitrogen, were refrozen their freezing pattern was similar to nonacclimated leaves. A novel technique was developed using filter paper strips to determine the effects of both sugars and proteins on the rate of freezing of cell extracts. Cell sap from nonacclimated leaves froze 3-fold faster than extracts from acclimated leaves. The rate of freezing in leaves was strongly dependent upon the osmotic potential of the leaves. Simple sugars had a much greater effect on freezing rate than proteins. Nonacclimated leaves containing high water content did not supercool as much as acclimated leaves. Additionally, wetted leaves did not supercool as much as nonwetted leaves. As expected, cell solutes depressed the nucleation temperature of leaves. The use of infrared thermography has revealed that the freezing process in plants is a complex process, reminding us that many aspects of freezing tolerance occur at a whole plant level involving aspects of plant structure and metabolites rather than just the expression of specific genes alone.