bluuebunny/crossref_metadata_2025_split huggingface dataset:
On Alternative Thermal Methods for Discerning the Miscibility in Blends of Isotactic Polystyrene and Poly(cyclohexyl methacrylate) with Closely‐Spaced Glass Transitions
Authors: Chang Li‐Ling , Woo Ea‐Mor , Chiang Chih‐Pei 
Published: March 2004

AbstractSummary: Thermal characterizations were performed to further discern the miscibility and qualitative interactions in blends of isotactic polystyrene (iPS) and poly(cyclohexyl methacrylate) (PCHMA). A method based on the enthalpy relaxation of the blends was used to overcome the difficulty or ambiguity in resolving closely‐spaced glass transitions of these two constituent polymers. Interactions between the blend components were further estimated by two additional methods: the blend's glass transition temperature (Tg) and the melting point depression. The blend's Tg method yielded a χ12 value ranging from −0.0016 (i.e., almost 0) to −1.98 (with the values depending on the amorphous PCHMA contents in the blends) in the temperature range of 95–110 °C, whereas the melting point depression led to χ12 = −0.039 at 240 °C. The interaction parameters obtained from these two methods are negative, confirming the miscibility with weak interactions. The results of these alternative thermal characterizations further clarified that the iPS/PCHMA blends, whose Tg's are too close to allow the use of conventional Tg criteria, are indeed completely miscible.Specific heat increment (ΔCP) at Tg for the iPS/PCHMA blends.magnified imageSpecific heat increment (ΔCP) at Tg for the iPS/PCHMA blends.
What influences the relationship between customer satisfaction and repurchase intention? Investigating the effects of adjusted expectations and customer loyalty
Authors: Yi Youjae , La Suna 
Published: March 2004

AbstractThis study examines how loyalty influences the relationship between customer satisfaction (CS) and repurchase intention (RPI). Considering the effect of time, the study introduces adjusted expectations, which are expectations updated after consumption experience. The present study investigates the role of adjusted expectations in the CS–RPI link. With structural‐equation analysis, the proposed model was tested in the family‐restaurant setting. The results show that adjusted expectations can mediate the effect of CS on RPI. The results also indicate that processes underlying the CS–RPI link are different between low‐loyalty and high‐loyalty customers. Specifically, the transient route, which reflects the indirect path from CS to RPI via adjusted expectations, has a greater impact for nonloyals than for loyals. On the other hand, the chronic route, which represents the direct path from CS to RPI, has a greater impact for loyals than for nonloyals. CS is found to have no direct influence on RPI for low‐loyalty customers. © 2004 Wiley Periodicals, Inc.
Optical Probes for Monitoring Intercalation and Exfoliation in Melt‐Processed Polymer Nanocomposites
Authors: Maupin Paul H. , Gilman Jeffrey W. , Harris Richard H. , Bellayer Severine , Bur Anthony J. , Roth Steven C. , Murariu Marius , Morgan Alexander B. , Harris Joseph D. 
Published: March 2004

AbstractSummary: Laser‐induced fluorescence spectroscopy of the optical probe Nile Blue A in polymer clay nanocomposites is described. Concentration quenching of the fluorescence dominates the probe behavior until the clay platelets are physically separated by polymer intercalation. Further separation into an exfoliated structure results in an intense increase in probe fluorescence. Preliminary results indicate the ability to discriminate between intercalated and exfoliated structures in nanocomposites formed by melt processing.Polyamide 6 nanocomposites: Purple, 1 minute processing (left). Red, 7 minute processing (right).magnified imagePolyamide 6 nanocomposites: Purple, 1 minute processing (left). Red, 7 minute processing (right).
Rodlike Cellulose Microcrystals: Structure, Properties, and Applications
Authors: de Souza Lima M. Miriam , Borsali Redouane 
Published: March 2004

AbstractSummary: In this article we present some interesting properties of rodlike cellulose microcrystals (so‐called “whiskers”). These microcrystals can be obtained from different cellulose sources such as wood, cotton, or animal origin. When submitted to acid hydrolysis, the cellulose fibers yield stable aqueous suspensions because of the presence of negative charges on the surface of the microcrystallites during the hydrolysis process. The obtained microcrystals are rod‐shaped particles, the dimensions of which depend on the cellulose origin. For instance, the cotton whiskers have typical dimensions varying from 100 to 300 nm in length, L, and 8 to 10 nm in diameter, d, while those of the tunicate whiskers range from 100 nm to few micrometers in length and 10 to 20 nm in diameter. At very low concentrations, these whiskers are randomly suspended in water and form an isotropic phase. When the concentration reaches a critical value, the whiskers spontaneously display ordered phases showing interesting liquid crystal properties (nematic and chiral nematic). The chiral nematic orders can be retained after evaporation of the solvent (generally water), leaving iridescent films. The reflected color can be controlled by changing either the ionic strength or by applying an electric field. These colloidal particles have been investigated using several techniques including small‐angle neutron scattering (SANS), small angle X‐ray scattering, rheology, and more recently dynamic and static light scattering techniques (DLS and SLS) to highlight their static and dynamic behavior. Because of their geometry, important axis ratio (L/d), and high crystallinity, these rods have been also extensively used to process nanocomposites based on polymer matrices, to reinforce their mechanical properties. All these properties are discussed in this contribution.Rodlike nanocrystals in aqueous suspension (left, Tunicate, 1 wt.‐%) and film (right), observed between cross‐polarizers.magnified imageRodlike nanocrystals in aqueous suspension (left, Tunicate, 1 wt.‐%) and film (right), observed between cross‐polarizers.
Glass Transition of Low‐Dimensional Polystyrene
Authors: Jiang Qing , Lang Xing You 
Published: March 2004

AbstractSummary: A unified model is developed for the finite size‐effect on the glass‐transition temperature of polymers, Tg(D), where D denotes the diameter of particles or thickness of films. In terms of this model, Tg depends on both the size and interface conditions. The predicted results are consistent with the experimental evidence for polystyrene (PS) particles and films with different interface situations.Tg(D) function of free‐standing PS films.magnified imageTg(D) function of free‐standing PS films.
Spontaneous Ring‐Opening Polymerization of Macrocyclic Aromatic Thioether Ketones under Transient High‐Temperature Conditions
Authors: Colquhoun Howard M. , Zolotukhin Mikhail G. , Zhu Zhixue , Hodge Philip , Williams David J. 
Published: March 2004

AbstractSummary: Spontaneous ring‐opening polymerization of macrocyclic aromatic thioether ketones [1,4‐SC6H4COC6H4]n (n = 3 and 4), in which the thioether linkages are para to the ketone, occurs during rapid, transient heating to 480 °C, to afford a soluble, semi‐crystalline poly(thioether ketone) of high molar mass (ηinh > 1.0 dL · g−1). Corresponding macrocyclic ether ketones, and a macrocyclic thioether ether ketone in which the thioether linkage is para to the ether rather than to the ketone, show no evidence of polymerization under analogous conditions.The uncatalysed ring‐opening polymerization of macrocycle 1, within the pores of an alumina microfiltration membrane, leads to formation of polymer 3 with the microstructure shown in the above scanning electron micrograph.magnified imageThe uncatalysed ring‐opening polymerization of macrocycle 1, within the pores of an alumina microfiltration membrane, leads to formation of polymer 3 with the microstructure shown in the above scanning electron micrograph.
Theoretical Consideration of the Grafting of Polymer Chains onto Fullerene C60
Authors: Kuchanov Semion , Pizik Ilya , Ivanov Viktor 
Published: March 2004

AbstractSummary: For the first time, the kinetics and statistics of the formation of polymer stars by grafting linear macromolecules onto the fullerene C60 are considered. Two kinetic models are put forward providing an explanation for some important experimentally observed peculiarities of these macromolecular reactions. The comparison of the results found from the solution of the kinetic equations and those obtained by Monte Carlo simulations demonstrates their good agreement. Due to the minimal number of the parameters involved, the theoretical approach proposed is rather convenient for the treatment of experimental data.image
On hybrid quantum–classical transport models
Authors: Ben Abdallah Naoufel , Tang Shaoqiang 
Published: March 2004

AbstractThis paper contains a review on the coupling between classical models and quantum models for electron transport in semiconductors. Starting from the quantum analogue of the boundary value problem for the Vlasov equation, the coupling with the Boltzmann equation in the one‐dimensional stationary situation is reviewed for the stationary and time‐dependent problems. Then a numerical scheme based on the characteristics method is applied to the stationary hybrid model. Some mathematical properties of the scheme are proven and illustrated in some numerical experiments. Copyright © 2004 John Wiley & Sons, Ltd.
Magnetic relaxation dispersion of lithium ion in solutions of DNA
Authors: Victor Ken G. , Teng Ching‐Ling , Dinesen T. R. D. , Korb Jean‐Pierre , Bryant Robert G. 
Published: March 2004

AbstractThe magnetic field dependence of the nuclear spin–lattice relaxation rate constant defines the magnetic relaxation dispersion (MRD) and provides a direct characterization of the molecular dynamics that cause fluctuations in the magnetic couplings in the system and may also indicate the dimensional constraints on the motion. The counterion cloud surrounding a linear polyelectrolyte ion, such as DNA in solution, provides an interesting opportunity for ion confinement that helps in understanding the thermodynamics and the dynamics of the interactions between the polyion and other solutes. The MRD profiles of lithium ion and tetramethylammonium ion were recorded in dilute aqueous solutions of native calf thymus DNA, which provides a long, charged rod that reorients slowly. The 7Li ion relaxes through the nuclear electric quadrupole coupling and the proton–lithium dipole–dipole coupling; the protons of the tetramethylammonium ion relax by dipole–dipole coupling. MRD profiles of the 7Li+ ion are dominated by transient interactions with the DNA that yield a linear dependence of the spin–lattice relaxation rate constant on the logarithm of the Larmor frequency. This magnetic field dependence is consistent with diffusive ion motions that modulate two spatial coordinates that characterize the relaxation couplings in the vicinity of the polyion. Motions around the rod and fluctuations in the ion distance from the rod are consistent with these constraints for lithium. The magnetic field dependence of the tetramethylammonium ion proton relaxation rate constant is weak, but also approximately a linear function of the logarithm of the Larmor frequency, which implies that the field dependence is caused in part by local order in the DNA solution. Copyright © 2004 John Wiley & Sons, Ltd.
Modeling 1H exchange: An estimate of the error introduced in MRI by assuming the fast exchange limit in bolus tracking
Authors: Moran G.R. , Prato F.S. 
Published: March 2004

AbstractA simulation is presented which calculates the MRI signal expected from a model tissue for a given pulse sequence after a bolus injection of a contrast agent. The calculation assumes two physiologic compartments only, the intravascular and extravascular spaces. The determination of the concentration of contrast in each compartment as a function of time and position has been outlined in a previous publication (Moran and Prato, Magn Reson Med 2001;45:42–45). These contrast agent concentrations are used here to determine the NMR relaxation times as a function of time and position within the tissue. Knowledge of this simulated tissue ‘map’ of relaxation times as a function of time provides the information required to determine whether the proton exchange rate is fast or slow on the NMR timescale. Since with a bolus injection the concentration of contrast and hence the relaxation time may vary with position along the capillary, some segments of the capillary are allowed to be in fast exchange with the extravascular space, while others may be in slow exchange. Using this information, and parameters specific to a given tissue, the MRI signal for a given pulse sequence is constructed which correctly accounts for differences in proton exchange across the length of the capillary. It is shown that extravascular contrast agents show less signal dependence on water exchange, and thus may be more appropriate for quantitative imaging when using fast exchange assumptions. It is also shown that nondistributed compartment models can incorrectly estimate the water exchange that is occurring at the capillary level if exchange‐minimizing pulse sequences are not used. Magn Reson Med 51:816–827, 2004. © 2004 Wiley‐Liss, Inc.
Designing acceptance sampling schemes for life testing with mixed censoring
Authors: Chen Jianwei , Chou Winlin , Wu Hulin , Zhou Haibo 
Published: March 2004

AbstractMixed censoring is useful extension of Type I and Type II censoring and combines some advantages of both types of censoring. This paper proposes a general Bayesian framework for designing a variable acceptance sampling scheme with mixed censoring. A general loss function which includes the sampling cost, the time‐consuming cost, the salvage value, and the decision loss is employed to determine the Bayes risk and the corresponding optimal sampling plan. An explicit expression of the Bayes risk is derived. The new model can easily be adapted to create life testing models for different distributions. Specifically, two commonly used distributions including the exponential distribution and the Weibull distribution are considered with a special decision loss function. We demonstrate that the proposed model is superior to models with Type I or Type II censoring. Numerical examples are reported to illustrate the effectiveness of the method proposed. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004
A sequential dynamic pricing model and its applications
Authors: Lin Kyle Y. 
Published: March 2004

AbstractConsider a sequential dynamic pricing model where a seller sells a given stock to a random number of customers. Arriving one at a time, each customer will purchase one item if the product price is lower than her personal reservation price. The seller's objective is to post a potentially different price for each customer in order to maximize the expected total revenue. We formulate the seller's problem as a stochastic dynamic programming model, and develop an algorithm to compute the optimal policy. We then apply the results from this sequential dynamic pricing model to the case where customers arrive according to a continuous‐time point process. In particular, we derive tight bounds for the optimal expected revenue, and develop an asymptotically optimal heuristic policy. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004.
Cribra orbitalia and cribra cranii in Roman skeletal remains from the Ravenna area and Rimini (I–IV century AD)
Authors: Facchini F. , Rastelli E. , Brasili P. 
Published: March 2004

AbstractCribra orbitalia and cribra cranii are considered good indicators of the health and nutritional status of ancient populations, as their presence is often associated with chronic acquired anaemia. The distribution of these lesions in two Roman samples from the Ravenna area and Rimini was considered as a measure of health in relation to their respective environments. Enamel hypoplasia was also assessed as it is symptomatic of childhood physiological stresses such as malnutrition, infectious diseases, physiological traumas, and the like. The differential analysis suggests that the lesions observed are due to chronic acquired anaemia, probably caused by a poor diet, worm infestation, infections and parasitic diseases. Copyright © 2004 John Wiley & Sons, Ltd.
Large‐scale extrusion processing and characterization of hybrid nylon‐6/SiO2nanocomposites
Authors: García Monserrat , van Vliet Gerhard , ten Cate Mattijs G. J. , Chávez Francisco , Norder Ben , Kooi Bart , van Zyl Werner E. , Verweij Henk , Blank Dave H. A. 
Published: March 2004

AbstractSolution impregnations, pulltrusion and film stacking are widely used methods to prepare thermoplastic composite materials. Extruders are used to melt the polymer and to incorporate fibers into the polymer in order to modify physical properties. In this article, the compounding of colloidal silica nanoparticles filled polyamide‐6 (PA‐6) is achieved using a twin‐screw extruder, which has a significant market share due to its low cost and easy maintenance. The experiments were performed at 250 rpm and the bulk throughput was 6 kg h−1with a pump pressure of 30 bars. The composites were characterized with nuclear magnetic resonance (NMR), wide angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). As determined by WAXD, the PA‐6 showed higher amounts ofγ‐phase when compared to other synthesis methods such asin situpolymerization. TEM pictures showed that the silica particles aggregated nevertheless, upon addition of 14% (w/w) silica the E‐modulus increased from 2.7 to 3.9 GPa indicating that an effective mechanical coupling with the polymer was achieved. The behavior, illustrated with dynamic mechanical analysis (DMA) curves, indicated that in general when a filled system is compared to unfilled material, the values of the moduli (E′ and E″) increased and tanδdecreased. Determination of molecular mass distribution of the samples by means of size exclusion chromatography (SEC) coupled to a refractive index (RI), viscosity (DV) and light scattering (LS) detector revealed that the addition of silica did not decrease the average molecular weight of the polymer matrix, which is of importance for composite applications. Copyright © 2004 John Wiley & Sons, Ltd.
Compaction of thick composites: Simulation and experiment
Authors: Shin Daniel D. , Hahn H. Thomas 
Published: March 2004

AbstractA realistic process simulation model for heat transfer and compaction along the bleeder‐composite assembly was developed. Two case studies were presented with this model in which one took advantage of variable resin properties while the other used constant values. The predicted results were then experimentally validated with 228‐ply and 380‐ply AS4/3501‐6 graphite/epoxy laminates cured under one‐dimensional resin flow condition. The model‐experiment correlation was quite good for the 228‐ply laminate although results with variable resin properties predicted better through‐the‐thickness temperature distribution than with constant resin properties. The model also predicted faster compaction rate because the compressibility model appeared to predict higher fiber volume fraction for given effective stress. As for the 380‐ply laminate, notable deviations were observed for both the temperature and compaction predictions. The discrepancies appeared to have manifested from inaccurate resin property and compressibility models.
Structure characterization and conductive performance of polypyrrol‐molybdenum disulfide intercalation materials
Authors: Wang Tingmei , Liu Weimin , Tian Jun , Shao Xin , Sun Dacheng 
Published: March 2004

AbstractTwo types of polypyrrol/molybdenum disulfide nanocomposites were prepared by means of in situ polymerization of the intercalated monomers. The nanocomposites were characterized by means of powder X‐ray diffraction, Fourier transformation infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The charge transport properties of the nanocomposites were determined by four‐probe electrical conductivity measurement of pressed pellet samples. The relationship between the electrical conductivity at various temperatures and conformation of the polypyrrol/ molybdenum disulfide nanocomposites were investigated. Results indicated that polypyrrol took two kinds of conformation in the interlayer of MoS2. The electrical conductivity of the intercalation nanocomposites at room temperature was dependent on the conformation and stereo‐regular characteristics of the polypyrrol molecules in the MoS2 layers, it was mainly determined by the number of the active charge carriers in polypyrrol at −60°C. The intercalation of polypyrrol into MoS2 led to an increase in the electrical conductivity by six orders of magnitude.
Prenatal diagnosis of congenital Chagas' disease (American trypanosomiasis)
Authors: Okumura Maria , Aparecida dos Santos Vera , Camargo Mário E. , Schultz Regina , Zugaib Marcelo 
Published: March 2004

AbstractThe prenatal diagnosis of congenital transmission of Chagas' disease in a pregnant woman with the indeterminate form of the disease is reported. Sonography revealed fetal hydrops at 31 weeks' gestation. Anti‐Trypanosoma cruzi IgM and IgG antibodies were negative in the fetal blood sampled by cordocentesis, but T. cruzi trypomastigotes were found in its buffy coat. Owing to anemia, in utero exchange transfusion was undertaken, but fetal demise ensued. Labor was induced and a stillborn infant weighing 2030 g was delivered. The pathological examination revealed placentitis and meningoencephalitis, myocarditis and splenitis in the stillborn fetus. Amastigotes were found in the myocardium, brain and placenta. Copyright © 2004 John Wiley & Sons, Ltd.
Sonographic findings in Beckwith–Wiedemann syndrome related to H19 hypermethylation
Authors: Le Caignec C. , Gicquel C. , Gubler M. C. , Guyot C. , You M. C. , Laurent A. , Joubert M. , Winer N. , David A. , Rival J. M. 
Published: March 2004

AbstractBeckwith–Wiedemann syndrome (BWS) is an overgrowth syndrome associated with congenital malformations and tumour predisposition. BWS results from variable mutations or epigenetic modifications of imprinted genes in the 11p15 chromosomal region. We present a fetus with mild general overgrowth and bilateral enlarged echogenic kidneys with loss of the corticomedullary differentiation in which prenatal diagnosis of BWS was suspected. The rest of the fetal anatomy and the amniotic fluid volume appeared normal. After termination of the pregnancy, molecular analysis confirmed the diagnosis of BWS by showing an isolated hypermethylation of the H19 gene. Copyright © 2004 John Wiley & Sons, Ltd.