bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and morphology development in syndiotactic polypropylene during isothermal crystallization and subsequent melting
Authors: Wang Zhi‐Gang , Wang Xue‐Hui , Hsiao Benjamin S. , Phillips Roger A. , Medellin‐Rodriguez Francisco J. , Srinivas Srivatsan , Wang Howard , Han Charles C. 
Published: August 2002

AbstractStructure and morphology development during the isothermal crystallization and subsequent melting of syndiotactic polypropylene (sPP) was studied with differential scanning calorimetry (DSC), time‐resolved simultaneous small‐angle X‐ray scattering (SAXS), and wide‐angle X‐ray diffraction (WAXD) methods with synchrotron radiation. The morphology of sPP isothermally crystallized at 100 °C for 3 h was also characterized with transmission electron microscopy (TEM). Time‐ and temperature‐dependent parameters such as the long period (L), crystal lamellar thickness (lc), amorphous layer thickness (la), scattering invariant (Q), crystallinity (Xc), lateral crystal sizes (L200 and L010), and unit cell dimensions (a and b) were extracted from the SAXS and WAXD data. Results indicate that the decreases in L and lc with time are probably due to the formation of thinner crystal lamellae, and the decreases in a and b are due to crystal perfection. The changes in the morphological parameters (Q, Xc, L, and lc) during subsequent melting exhibited a two‐stage process that was consistent with the multiple melting peaks observed in DSC. The two high‐temperature peaks can be attributed to the melting of primary lamellae (at lower temperatures) and recrystallized lamellae (at higher temperatures). An additional minor peak, located at the lowest temperature, was also visible and was related to the melting of thin and defective secondary lamellae. TEM results are consistent with the SAXS data, which supports the assignment of the larger value (l1) from the correlation function analysis as lc. WAXD showed that the thermal expansion was greater along the b axis than the a axis during melting. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2982–2995, 2001
Spherulitic growth rates and morphology of absorbable poly(p‐dioxanone) homopolymer and its copolymer by hot‐stage optical microscopy
Authors: Andjelić Saša , Jamiolkowski Dennis , McDivitt James , Fischer Jerome , Zhou Jack 
Published: August 2002

AbstractHot‐stage optical microscopy was used to study the crystal morphology, nucleation, and spherulitic growth rates of poly(p‐dioxanone) (PDS) homopolymer and an 89/11 PDS/glycolide segmented block copolymer. A wide range of crystallization conditions were experimentally accessible, allowing the inspection of various morphological features and accurate estimations of characteristic growth parameters, including radial growth and nucleation rates. Although the regime analysis of the crystallization kinetics indicated no breaks in the growth rate curve, the isothermal data were in excellent agreement with the Hoffman–Lauritzen theory. Spherulitic growth rates obtained from optical measurements are compared with values of the half‐time of crystallization determined earlier by differential scanning calorimetry. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 3073–3089, 2001
Free volume, glass transition, and degree of branching in metallocene‐based propylene/α‐olefin copolymers: Positron lifetime, density, and differential scanning calorimetric studies
Authors: Dlubek G. , Bamford D. , Rodriguez‐Gonzalez A. , Bornemann S. , Stejny J. , Schade B. , Alam M. A. , Arnold M. 
Published: August 2002

AbstractPositron annihilation lifetime spectroscopy (PALS), density, and differential scanning calorimetric (DSC) measurements were used to study systematically the variation of the glass‐transition temperature (Tg) and the size v and number density Nh of local free volumes in n‐alkyl‐branched polypropylenes. The samples were metallocene‐catalyzed propylene copolymers with different α‐olefins (from C4 to C16) and a different α‐olefin content (between 0 and 20 mol %). From the total specific volume and crystallinity the specific volume of the amorphous phase Va was estimated and used to calculate the fractional free (hole) volume h and value of Nh. The variations of Tg, v, Va, h, and Nh were related to the degree (number and length) of branching. Tg decreases and v increases linearly with the number and length of n‐alkyl branches. This behavior was attributed to an increased segmental mobility caused by branching. Both values, Tg and v, follow linear master curves as a function of the degree of branching (DB) if this is defined as the number of all side‐chain carbons with respect to a total of 1000 (main‐chain and side‐chain) carbons. Only propylene/1‐butene copolymers deviated from these relations. A linear relation between v and Tg was also found. The number density of holes was estimated to be Nh = 0.49(±0.07) nm−3 and Nh′ = 0.58(±0.11) × 1021 g−1, respectively. It shows a slight variation with the DB, which is also seen in the behavior of the specific volume Va. This variation was explained by the appearance of sterical hindrances resulting from short‐chain branches that may prevent an efficient packing of the chains. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 434–453, 2002; DOI 10.1002/polb.10108
Mechanism for the phase transition of poly(butylene terephthalate)
Authors: Takahashi Yasuhiro , Murakami Kei , Nishikawa Sumiyo 
Published: August 2002

AbstractThe α and β forms of poly(butylene terephthalate) transform reversibly by elongation and relaxation. The conformation change occurs in the tetramethylene glycol part, from GGTGG conformation to TSTS̄T conformation. In this study, by using a doubly oriented sample, we measured the positions, intensities, and half‐widths of the (100) and (010) reflections of the α and β forms of poly(butylene terephthalate) with a position‐sensitive proportional counter system. During the transformation, the molecules translate only slightly. These slight molecular translations, or distortions, accumulate, and the crystallite of the α form breaks into the small crystallites of the β form as the α–β transformation proceeds, and the crystallite of the α form grows with the relaxation of the distortion accumulated in the crystal and amorphous regions and on the crystallite surface as the β–α transformation proceeds. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 765–771, 2002
Diffusion of small molecules through modified poly(vinyl chloride) membranes
Authors: Tiemblo P. , Guzmán J. , Riande E. , Mijangos C. , Herrero M. , Espeso J. , Reinecke H. 
Published: August 2002

AbstractThe transport properties of a set of four copolymers based on poly(vinyl chloride) (PVC) have been studied. The nucleophilic substitution of chlorine atoms with 4‐mercaptophenol sodium salt, 2‐thionaphthalene, 4‐(1‐adamantyl) thiophenol, and thiophenolate sodium salt as the nucleophiles has been performed, from low conversion levels (3%) to high levels (40%), and the permeability, solubility, and diffusivity of oxygen, nitrogen, carbon dioxide, and methane have been measured. The introduction of bulky groups to the PVC chain leads to chain separation and results in large increases in the free volume at conversions up to 10%. This brings about a 5‐fold increase in the diffusion coefficients that is almost independent of the bulkiness of the substituent. Solubility is little affected and instead tends to decrease as substitution progresses. The substitution of more than 10% of the chlorine atoms does not result in an improvement in the transport properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 964–971, 2002
Transport of toluene/methyl ethyl ketone mixtures in polyisobutylene
Authors: Hong Seong U. , Barbari Timothy A. 
Published: August 2002

AbstractIn this study, the diffusion behavior of methyl ethyl ketone (MEK)/toluene mixtures, with MEK molar fractions (x1) in the liquid source lower than 0.2, in polyisobutylene (PIB) was investigated with vapor‐sorption Fourier transform infrared attenuated total reflectance (FTIR‐ATR) spectroscopy. FTIR‐ATR Fickian diffusion models for both binary and ternary systems were used to determine diffusion coefficients. Obtained diffusion coefficients for MEK from the binary diffusion model did not agree with those determined previously for the diffusion of MEK/toluene mixtures, with x1 > 0.2, in PIB. When the ternary diffusion model was used, the main‐term and cross‐term diffusion coefficients of MEK were comparable. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 908–914, 2001
Frequency‐dependent conductivity of interpenetrating polymer network composites of polypyrrole–poly(vinyl acetate)
Authors: Bhattacharyya S. , Saha S. K. , Chakravorty M. , Mandal B. M. , Chakravorty D. , Goswami K. 
Published: August 2002

AbstractThe frequency‐dependent conductivity of interpenetrating polymer network composites of polypyrrole (PPy) and poly(vinyl acetate) (PVAc) synthesized by FeCl3‐impregnated PVAc films being dipped into solutions of pyrrole in water was investigated over a frequency range of 100 Hz to 2 MHz and a temperature range of 110–300 K. For specimens with a PPy content less than the percolation threshold, the quantum mechanical tunneling of electrons was the conduction mechanism. For specimens with a higher PPy content, correlated barrier hopping of electrons appeared to be operative. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1935–1941, 2001
Glass‐formation kinetics of miscible blends of atactic polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide)
Authors: Robertson Christopher G. , Wilkes Garth L. 
Published: August 2002

AbstractWe present a detailed investigation of the kinetics associated with the glass transitions of miscible blends composed of atactic polystyrene (a‐PS) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO). According to both dynamic mechanical analysis and differential scanning calorimetry, relaxation times displayed an enhanced temperature dependence (i.e., more fragile or more cooperative behavior) for the blends compared with additive behavior based on the responses of neat a‐PS and PPO. This is consistent with the notion that specific interactions between the blend components heighten the intermolecular cooperativity. The compositional dependence of fragility provided insight into physical aging results for the properties of volume and enthalpy. The combination of our research and a previously reported pressure–volume–temperature study by Zoller and Hoehn (J Polym Sci Polym Phys Ed 1982, 20, 1385) provided evidence that the observation of increased glassy densities for the blends compared with those of the pure polymers was kinetic in origin and was not a feature of the thermodynamics of miscibility. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2118–2129, 2001
Replacement of thrombin residue G184 with Lys or Arg fails to mimic Na+ binding
Authors: Roy Dolly Banerjee , Rose Thierry , Di Cera Enrico 
Published: August 2002

AbstractNa+ binding to thrombin enhances the catalytic activity toward numerous synthetic and natural substrates. The bound Na+ is located in a solvent channel 16 Å away from the catalytic triad, and connects with D189 in the S1 site through an intervening water molecule. Molecular modeling indicates that the G184K substitution in thrombin positions the protonated ϵ‐amino group of the Lys side‐chain to replace the bound Na+. Likewise, the G184R substitution positions the guanidinium group of the longer Arg side‐chain to replace both the bound Na+ and the connecting water molecule to D189. We explored whether the G184K or G184R substitution would replace the bound Na+ and yield a thrombin derivative stabilized in the highly active fast form. Both the G184K and G184R mutants lost sensitivity to monovalent cations, as expected, but their activity toward a chromogenic substrate was compromised up to 200‐fold as a result of impaired diffusion into the S1 site and decreased deacylation rate. Interestingly, both G184K and G184R substitutions compromised cleavage of procoagulant substrates fibrinogen and PAR1 more than that of the anticoagulant substrate protein C. These findings demonstrate that Na+ binding to thrombin is difficult to mimic functionally with residue side‐chains, in analogy with results from other systems. Proteins 2001;43:315–318. © 2001 Wiley‐Liss, Inc.
Efficacy and residues of phloxine B and uranine for the suppression of Mediterranean fruit fly in coffee fields
Authors: Licudine Jocelyn A , McQuate Grant T , Cunningham Roy T , Liquido Nicanor J , Li Qing X 
Published: August 2002

AbstractThe field efficacy of a bait containing phloxine B, uranine and Provesta 621 protein was tested against Mediterranean fruit fly (Ceratitis capitata; Medfly) by aerial and ground spraying in about 84 ha of coffee fields in Kauai, Hawaii, USA. Concurrently, soil and crop samples were collected from the aerially sprayed field and its unsprayed control field for residue studies. Efficacy of the sprays was assessed through trapping with both protein‐baited and trimedlure‐baited traps and through the infestation level of coffee cherries collected at least three‐quarters ripe. The C capitata population was low at the start of the aerial and ground spray studies, but dramatically increased in the control fields. This increase coincided with initial ripening of coffee cherries. During times of peak population levels, C capitata populations were reduced by more than 91% in the ground‐sprayed field and 99% in the aerial‐sprayed field, relative to the populations in their respective control fields and based on protein‐baited trap catches. Results of residue analyses indicated that uranine dissipated quickly compared with phloxine B on coffee and soil. Coffee samples collected at pre‐spray periods had phloxine B residues of 7.2–25.5 ng g−1 on berries. Phloxine B concentrations were much higher on coffee leaves (163–1120 ng g−1). Lower concentrations of the dye were found from coffee samples collected during rainy days. Average phloxine B concentrations immediately after spraying were 56 and 2840 ng g−1 in coffee berries and leaves, respectively. Dissipation of phloxine B on berries was fast, with a half‐life (t1/2) of 3 days. Dissipation of phloxine B on leaves was fitted to two linear phases: the initial (0–4 days) with a shorter t1/2 of 3 days and the later phase (4–28 days) with a longer t1/2 of 15 days. Average concentrations of phloxine B in the top soil ranged from 50 to 590 ng g−1 at pre‐spray. Phloxine B initial concentration (770 ng g−1) reached a plateau immediately after the last spraying, but showed a steady decline over time with t1/2 of 16 days. Fast dissipation of the dyes in the field indicates that these chemicals may be environmentally compatible and therefore a promising alternative for fruit fly control.© 2001 Society of Chemical Industry
Active packaging as an opportunity to create package design that reflects the communicational, functional and logistical requirements of food products
Authors: Meroni Anna 
Published: August 2002

AbstractThe packaging of industrial food products is the most important means of transmitting a product's image and taste value. When the nature of its interface and its contents are the product of carefully planned imaging, the product has notable advantages in defining its image and product identity. Modern food trends dictate an ever‐increasing amount of services: The so‐called ‘functional packaging’ and ‘active packaging’ are prime examples of this service. The greatest innovation within this category of products consists literally of their interaction with food. These features create numerous fallbacks within all stages of the life‐cycle of a product, requiring a complex and multidisciplinary evaluation. The evaluation strategy of services which this packaging will offer to the consumer is still to be defined, and still to be identified within the key applications are the interests of the intermediary links of the production process. This requires the evaluation of the semantic and communicative aspects of the packaging which tend to be confused with the foodstuffs, the individualization of appropriate user profiles, control of logistical and location aspect of production, and a careful analysis of a comprehensive environmental balance, all issues that are parts of the objectives of the European project, Actipak. It is hoped, therefore, that the elaboration of these packaging systems will become a motive to try out a more knowledgeable and systematic design process for foodstuffs, in which innovative technology is used to provide effective benefits to the consumer. Copyright © 2000 John Wiley & Sons, Ltd.
Partition experimental designs for sequential processes: Part I—First‐order models
Authors: Perry Leonard A. , Montgomery Douglas C. , Fowler John W. 
Published: August 2002

AbstractThe output quality or performance characteristics of a product often depend not only on the effect of the factors in the current process but on the effect of factors from preceding processes. Statistically‐designed experiments provide a systematic approach to study the effects of multiple factors on process performance by offering a structured set of analyses of data collected through a design matrix. One important limitation of experimental design methods is that they have not often been applied to multiple sequential processes. The objective is to create a first‐order experimental design for multiple sequential processes that possess several factors and multiple responses. The first‐order design expands the current experimental designs to incorporate two processes into one partitioned design. The designs are evaluated on the complexity of the alias structure and their orthogonality characteristics. The advantages include a decrease in the number of experimental design runs, a reduction in experiment execution time, and a better understanding of the overall process variables and their influence on each of the responses. Copyright © 2001 John Wiley & Sons, Ltd.
Structural properties of PbTiO3 and PbZrxTi1−xO3: A quantum‐chemical study
Authors: Stashans Arvids , Zambrano Cesar , Sanchez Alfredo , Procel Luis Miguel 
Published: August 2002

AbstractWe investigate the structural and electronic properties of pure and Zr‐doped PbTiO3 crystals. The nature of atomic relaxation around the Zr impurity is studied through quantum‐chemical simulations based on the Hartree–Fock theory and a periodic large unit cell model adopted within the so‐called intermediate neglect of differential overlap approximation. The most stable defect configurations are predicted for different impurity concentrations. The results obtained are compared with those from other theoretical studies and a number of experimental measurements carried out on this technologically important perovskite‐type crystal. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Quantum chemical study of the reaction mechanism of ozone and methane with fluorine and chlorine atoms
Authors: Li Lai‐Cai , Wang Jing , Wang Xin , Tian An‐Min , Wong Ning‐Bew 
Published: August 2002

AbstractAb initio calculations of the potential energy surface for the F + O3 and Cl + O3 reactions have been performed using the G3 and G3MP2 methods, which optimize the geometry configuration of reactants, products, intermediates, and transition states. The results show that fluorine atoms react with ozone as violently as chlorine atoms. At the same time, we have studied the reaction mechanisms of F atoms and Cl atoms with methane. It is found that fluorine atoms prefer to react with methane and chlorine atoms with ozone when there is competition between ozone and methane. Therefore, we can reasonably explain why chlorine atoms play the main role of reactants depleting ozone, while the more active fluorine atoms deplete less ozone. © 2002 Wiley Periodicals, Inc.; DOI 10.1002/qua.10119
Examination of several density functionals in numerical Kohn–Sham calculations for atoms
Authors: Andrae Dirk , Brodbeck Ralf , Hinze Juergen 
Published: August 2002

AbstractWe studied several exchange‐only and exchange–correlation energy density functionals in numerical, i.e., basis‐set‐free, nonrelativistic Kohn–Sham calculations for closed‐shell 1S states of atoms and atomic ions with N electrons, where 2≤N≤120. Accurate total energies are presented to serve as reference data for algebraic approaches, as do the numerical Hartree–Fock results, which are also provided. Gradient‐corrected exchange‐only functionals considerably improve the total energies obtained from the usual local density approximation, when compared to the Hartree–Fock results. Such an improvement due to gradient corrections is not seen in general for highest orbital energies, neither for exchange‐only results (to be compared with Hartree–Fock results), nor for exchange–correlation results (to be compared with experimental ionization energies). © 2001 John Wiley & Sons, Inc. Int J Quant Chem 82: 227–241, 2001
Theoretical study of CnCl, CnCl+, CnCl− (n=1–7) clusters
Authors: Largo Antonio , Cimas Alvaro , Redondo Pilar , Barrientos Carmen 
Published: August 2002

AbstractA theoretical study of CnCl, CnCl+, and CnCl− (n=1–7) clusters has been carried out. Predictions for their electronic structures, dipole moments, and vibrational frequencies have been made at the B3LYP/6‐311G(d) level. According to our calculations the lowest‐lying geometry of all these species (with the only exception of neutral C3Cl) is predicted to be either a linear or quasi‐linear structure with chlorine located at the end of the carbon chain. CnCl clusters all have doublet ground states, whereas the anionic clusters, with the only exception of CCl−, all have singlet ground states. For CnCl+ species, n‐even clusters have triplet ground states whereas n‐odd ones have singlet ground states. An even–odd parity effect (n‐even clusters more stable than n‐odd ones) is found for both the neutral and anionic species, whereas in the case of the cations the alternation in stability is reversed. The ionization potential (IP) and electron affinity (EA) also exhibit regular variations with the size of the cluster, with n‐even clusters having both higher IP and EA than n‐odd ones. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 84: 127–135, 2001
Evaluation of protein modification during anti‐viral heat bioprocessing by electrospray ionization mass spectrometry
Authors: Smales C. Mark , Pepper Duncan S. , James David C. 
Published: August 2002

AbstractDuring the preparation of therapeutic plasma and recombinant protein biopharmaceuticals heat‐treatment is routinely applied as a means of viral inactivation. However, as most proteins denature and aggregate under heat stress, it is necessary to add thermostabilizing excipients to protein formulations destined for anti‐viral heat‐treatment in order to prevent protein damage. Anti‐viral heat‐treatment bioprocessing therefore requires that a balance be found between the bioprocessing conditions, virus kill and protein integrity. In this study we have utilized a simple model protein, β‐lactoglobulin, to investigate the relationship between virucidal heat‐treatment conditions (protein formulation and temperature) and the type and extent of protein modification in the liquid state. A variety of industrially relevant heat‐treatments were undertaken, using formulations that included sucrose as a thermostabilizing excipient. Using liquid chromatography/electrospray ionization mass spectrometry (LC/ESI‐MS) we show here that protein modifications do occur with increasingly harsh heat‐treatment. The predominant modification under these conditions was protein glycation by either glucose or fructose derived from hydrolyzed sucrose. Advanced glycation end products and additional unidentified products were also present in β‐lactoglobulin protein samples subjected to extended heat‐treatment. These findings have implications for the improvement of anti‐viral heat‐treatment bioprocesses to ensure the safety and efficacy of protein biopharmaceuticals. Copyright© 2001 John Wiley & Sons, Ltd.