bluuebunny/crossref_metadata_2025_split huggingface dataset:
γ‐Irradiation preparation of poly(acrylic acid)–chitosan hydrogels for in vitro drug release
Authors: Shim Jae‐Woon , Nho Young‐Chang 
Published: October 2003

AbstractBiocompatible and biodegradable pH‐responsive hydrogels based on poly(acrylic acid) and chitosan were prepared for controlled drug delivery. These interpolymeric hydrogels were synthesized by a γ‐irradiation polymerization technique. The degree of gelation was over 96% and increased as the chitosan or acrylic acid (AAc) content increased. The equilibrium swelling studies of hydrogels prepared under various conditions were carried out in an aqueous solution, and the pH sensitivity in a range of pH 1–12 was investigated. The AAc/chitosan hydrogels showed the highest water content when 30 vol % AAc and 0.1 wt % chitosan were irradiated with a 30 kGy dose of radiation. In addition, an increase of the degree of swelling with an increase in the pH was noticed and it had the highest value at pH 12. The drug 5‐fluorouracil was loaded into these hydrogels and the release studies were carried out in simulated gastric and intestinal fluids. The in vitro release profiles of the drugs showed that more than 90% of the loaded drugs were released in the first 1 h at intestinal pH and the rest of the drug was released slowly. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3270–3277, 2003
Poly(vinyl alcohol) nanocomposites with different clays: Pristine clays and organoclays
Authors: Chang Jin‐Hae , Jang Tae‐Gab , Ihn Kyo Jin , Lee Won‐Ki , Sur Gil Soo 
Published: October 2003

AbstractPoly(vinyl alcohol) (PVA)/clay nanocomposites were synthesized using the solution intercalation method. Na ion‐exchanged clays [Na+–saponite (SPT) and Na+–montmorillonite (MMT)] and alkyl ammonium ion‐exchanged clays (C12–MMT and C12OOH–MMT) were used for the PVA nanocomposites. From the morphological studies, the Na ion‐exchanged clay is more easily dispersed in a PVA matrix than is the alkyl ammonium ion‐exchanged clay. Attempts were also made to improve both the thermal stabilities and the tensile properties of PVA/clay nanocomposite films, and it was found that the addition of only a small amount of clay was sufficient for that purpose. Both the ultimate tensile strength and the initial modulus for the nanocomposites increased gradually with clay loading up to 8 wt %. In C12OOH–MMT, the maximum enhancement of the ultimate tensile strength and the initial modulus for the nanocomposites was observed for blends containing 6 wt % organoclay. Na ion‐exchanged clays have higher tensile strengths than those of organic alkyl‐exchanged clays in PVA nanocomposites films. On the other hand, organic alkyl‐exchanged clays have initial moduli that are better than those of Na ion‐exchanged clays. Overall, the content of clay particles in the polymer matrix affect both the thermal stability and the tensile properties of the polymer/clay nanocomposites. However, a change in thermal stability with clay was not significant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3208–3214, 2003
Isothermal crystallization of metallocene‐based polypropylenes with different isotacticity and regioregularity
Authors: Xu Jun‐Ting , Guan Fang‐Xiao , Yasin Tariq , Fan Zhi‐Qiang 
Published: October 2003

AbstractThree polypropylenes with various isotacticities and regioregularities were prepared with metallocene catalysts at different polymerization temperatures. WAXD results showed that the relative content of γ crystals in polypropylenes increased as isotacticity decreased. It was found that the γ crystal overcame the α crystal and became predominant in polypropylene of low isotacticity and high regioerrors. More γ crystals were also formed at higher crystallization temperatures. The isothermal crystallization kinetics of α and γ crystals were compared and the metastability of these two crystal phases was interpreted in terms of the crystallization kinetics. It was observed that the α crystal has a faster crystallization rate than that of the γ crystal and, thus, higher stability at low temperature. By contrast, the γ crystal tends to have a faster crystallization rate and becomes more stable at high temperature. The metallocene‐based polypropylenes with different isotacticities have similar Avrami exponents. As the content of the γ crystal increases, double melting peaks become more evident. Equilibrium melting temperatures were derived from Hoffman–Weeks analysis and very close equilibrium melting temperatures were obtained, 185.5 and 184.0°C, for two metallocene‐based polypropylenes containing major α crystals and one of 182.5°C for the polypropylene with predominant γ crystals. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3215–3221, 2003
Preparation and properties of novel polyimides with side chains containing biphenyl units
Authors: Liu Xikui , Xiang Hai , Yang Jin , Gu Yi 
Published: October 2003

AbstractNovel polyimides with side chains containing various methylene spacers and biphenyl end groups were prepared. They were characterized by the inherent viscosity, mechanical properties, and solubility and by Fourier transform infrared, 1H‐nuclear magnetic resonance, X‐ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. All the polyimides with biphenyl side groups could be formed into tough films. WAXD showed that all the films were apparently amorphous. By incorporating side chains, the solubility was greatly enhanced and all the polyimides with side chains showed good solubility in polar aprotic solvents, while the high moduli and strength of typical polyimides were maintained and even improved. However, the heat‐resistant properties such as the thermal stability and glass transition temperature were generally decreased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3291–3298, 2003
Comparison of disperse dye exhaustion, color yield, and colorfastness between polylactide and poly(ethylene terephthalate)
Authors: Yang Yiqi , Huda Shah 
Published: October 2003

AbstractTen popular disperse dyes with different energy levels and chemical constitutions were used to compare their exhaustion, color yield, and colorfastness on polylactide (PLA) and poly(ethylene terephthalate) (PET). Only two out of the 10 dyes had exhaustions higher than 80% on PLA at 2% owf. Five out of the 10 dyes had exhaustions less than 50%. All 10 dyes had more than 90% exhaustion on PET, whereas six of them had exhaustions of 98% or higher. There was no obvious pattern as for which energy level or which structure class provided dye exhaustion better than that of others. Although PLA had lower disperse dye exhaustion than that of PET, it had higher color yield. Based on the 10 dyes examined, the color yield of PLA was about 30% higher than that of PET. This means that even with low dye uptake, PLA could have a similar apparent shade depth as that of PET if the same dyeing conditions are applied. Our study supported that the lower reflectance, or reflectivity, of PLA contributes to the higher color yield of PLA than that of PET. A quantitative relation between the shade depth of PLA and PET based on their dye sorption was developed. Disperse dyes examined had lower washing and crocking fastness on PLA than on PET. The differences in class were about 0.5 to 1.0. If the comparison was based on the same dye uptake, the differences might be larger. The differences in light fastness between the two fibers were smaller than that in washing and crocking fastnesses. The light fastness of disperse dyes on PLA is expected to be even better if the comparison is based on the same dye uptake on both fibers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3285–3290, 2003
Preparation of thermoplastic elastomers based on silicone rubber and polyethylene by thermomechanical reactive blending: Effects of polyethylene structural parameters
Authors: Jalali‐Arani A. , Katbab A. A. , Nazockdast H. 
Published: October 2003

AbstractAttempts have been made to prepare thermoplastic elastomers based on polyethylene and silicone rubber by thermomechanical reactive mixing of the two polymers. Occurrence of both grafting and vulcanization of the silicone rubber chains was evidenced by increase in the mixing torque, solvent extraction data, as well as FTIR and DSC analysis. Among different types of polyethylene, linear low‐density polyethylene (LLDPE) showed higher potential to promote reactions between the two phases. The blend based on LLDPE prepared at high temperature and shear rate exhibited distinct rheological behavior with a non‐Newtonian characteristic and higher dynamic viscosity measured by rheomechanical spectroscopy (RMS) than the two individual components at low frequencies. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3402–3408, 2003
Swelling kinetics of modified poly(vinyl alcohol) hydrogels
Authors: Kim Seon Jeong , Lee Ki Jung , Kim In Young , Lee Young Moo , Kim Sun I. 
Published: October 2003

AbstractInterpenetrating polymer network (IPN) hydrogels composed of poly(vinyl alcohol) (PVA) and monomer, N‐isopropylacrylamide (NIPAAm), diallyldimethylammonium chloride (DADMAC), or methacrylic acid (MAA) were prepared by using the sequential‐IPN method. The equilibrium swelling ratios of PVA/NIPAAm (VANP), PVA/DADMAC (VADC), and PVA/MAA (VAMA) are 412, 370, and 297 at 25°C, respectively. VANP had the highest swelling ratio in time‐dependent swelling behavior, whereas the swelling ratio of VAMA had the lowest. The n values of VANP, VADC, and VAMA are 0.72, 0.81, and 0.96, respectively. Transport of all IPN hydrogels is anomalous and their transport mechanisms are dominated by a combination of diffusion‐controlled and relaxation‐controlled systems. VAMA has the highest activation energy and VANP has the lowest activation energy. The values of all IPN hydrogels are from 4.66 to 16.49 kJ/mol, which proves that all IPN hydrogels are hydrophilic. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3310–3313, 2003
Energy‐based predictive criterion for LCP fibrillation in LCP/thermoplastic polymer blends under shear
Authors: Joshi S. C. , Lam Y. C. , Yue C. Y. , Tam K. C. , Li L. , Hu X. 
Published: October 2003

AbstractThis article relates the fibrillation of liquid crystalline polymer (LCP) under shear in its blend with a thermoplastic polymer (TP) to the relative rate of energy utilization in the LCP and TP phases. The development of a criterion based on the energy relationship for predicting LCP fibrillation in the blend is discussed. The formation of LCP fibers in the blends of LCP with polycarbonate (PC), polyethylene naphthalate (PEN), high‐density polyethylene (HDPE), polypropylene (PP), and silica‐filled polypropylene (PP) was studied to validate the criterion and to demonstrate its applicability. For all the blends, viscosity data were obtained by using a capillary rheometer, which was subsequently used to estimate the rate of energy utilization in the LCP and the matrix phases. The predictions based on the proposed criterion were verified through the morphological investigations carried out on the extrudates obtained from the same capillary experiments. The energy‐based criterion was easy to implement, could account for the effect of variable LCP concentration and fillers in the blend, and could provide reliable predictions for a variety of LCP/TP blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3314–3324, 2003
Structure–properties relationship of starch/waterborne polyurethane composites
Authors: Cao Xiaodong , Zhang Lina , Huang Jin , Yang Guang , Wang Yixiang 
Published: October 2003

AbstractThe blend materials from waterborne polyurethane (WPU)/starch (ST) with different contents (10–90 wt %) were satisfactorily prepared by using the solution casting method. Their miscibility, structure, and properties were investigated by wide‐angle X‐ray diffraction (WAXD), scanning electron microscope (SEM), different scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and the tensile tests, respectively. The results indicated that tensile strength of composite materials not only depended on the starch content, but also related to the microstructure of WPU. The sample WPU2 (1.75 of NCO/OH molar ratio) exhibited hard‐segment order, but WPU1 (1.25 of NCO/OH molar ratio) had no hard‐segment order. The appropriate starch filled into WPU not only decreased the ordered region of soft‐segment matrix, but also hindered the formation of hard‐segment ordered structure. The blend material from 80 wt % WPU1 and 20 wt % starch exhibited better tensile strength (27 MPa), elongation at break (949%), and toughness than others. With an increase of starch content, the WPU matrix with dispersed starch in the blends transited to dual‐phase continuity and then to starch matrix with dispersed WPU. The results suggested that a certain extent of miscibility existed between WPU and starch in the blend materials on the whole composition ratio. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3325–3332, 2003
Soybean oil based polyisocyanurate cast resins
Authors: Javni Ivan , Zhang Wei , Petrović Zoran S. 
Published: October 2003

AbstractTwo series of polyisocyanurates were prepared from polymeric 4,4′‐diphenylmethane diisocyanate (MDI) and soy‐based or polypropylene oxide polyols by varying isocyanate indexes from 105 to 350. Increasing isocyanate index gave polyisocyanurates with increased thermal stability, flame resistance, tensile strength, modulus, and glass transition. Impact was lower. Soy‐based polyisocyanurates displayed better thermal stability, higher rigidity (modulus), and higher strength than those based on the propylene oxide polyols of the same molecular weight and functionality. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3333–3337, 2003
Crystallization kinetics of low‐density polyethylene and polypropylene melt‐blended with a low‐Tg tin‐based phosphate glass
Authors: Guschl Peter C. , Otaigbe Joshua U. 
Published: October 2003

AbstractThe nonisothermal and isothermal crystallizations of low‐density polyethylene (LDPE) and polypropylene (PP) in phosphate glass (Pglass)–polymer hybrid blends were studied through differential scanning calorimetry (DSC). As the Pglass volume fraction was increased, the percentage crystallinity decreased. The half‐time for crystallization decreased as the propagation rate constant rose, for both of the polymer matrices, with increasing Pglass concentrations. The Pglass was observed to be a nucleating agent for formation of two‐ or three‐dimensional spherulites in the hybrids. Tensile modulus improved for both of the Pglass–polymer hybrids up to 40% Pglass, but the energy to break decreased. Tensile strength changed slightly with the addition of Pglass to the LDPE matrix, exhibiting a larger value than that of pure LDPE at 30%. The tensile strength decreased as more Pglass was added to the PP matrix. The observed differences between tensile properties of the Pglass–PP and Pglass–LDPE hybrids at identical Pglass volume concentration were found to be consistent with that of the crystallization behavior of the hybrids. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3445–3456, 2003
Real‐time functional MRI using a PC cluster
Authors: Bagarinao Epifanio , Matsuo Kayako , Nakai Toshiharu 
Published: October 2003

AbstractA system for the real‐time analysis of functional magnetic resonance imaging (fMRI) time series is evaluated. The system exploits the advantages of parallel computing, coupled with an efficient general linear model (GLM) coefficient estimation algorithm, to overcome several issues constraining the analysis of the whole‐brain fMRI data in real time. The highly parallel, voxel‐wise processing of fMRI data motivated the use of a cluster of personal computers for parallel computation. Aside from gaining a significant increase in computational speed, the PC cluster provides a versatile way to handle the computational requirements of the system. The use of GLM in the supporting software allows substantial parametric analysis to be performed. Results of the real‐time analysis of the whole‐brain fMRI data of a normal subject performing a simple finger‐tapping task demonstrated the capabilities of the system. For a real‐time statistical analysis including real‐time image reconstruction, realignment for motion correction, smoothing, GLM coefficient estimation, statistical analysis, and update of the displayed activation map, the time required to process the data for each image volume is about 1.034 s for a 64 × 64 × 30 image volume and 2.561 s for a 128 × 128 × 20 image volume, less than the TR set to 3 s. © 2003 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 19B: 14–25, 2003.
A fast calculation method for magnetic field inhomogeneity due to an arbitrary distribution of bulk susceptibility
Authors: Salomir Rares , de Senneville Baudouin Denis , Moonen Chrit TW 
Published: October 2003

AbstractA fast calculation method for the magnetic field distribution due to (dynamic) changes in susceptibility may allow real‐time interventional applications. Here it is shown that a direct relationship can be obtained between the magnetic field perturbation and the susceptibility distribution inside the MR magnet using a first order perturbation approach to Maxwell's magneto‐static equations, combined with the Fourier transformation technique to solve partial derivative equations. The mathematical formalism does not involve any limitation with respect to shape or homogeneity of the susceptibility field. A first order approximation is sufficient if the susceptibility range does not exceed 10−4 (or 100 ppm). The formalism allows fast numerical calculations using 3D matrices. A few seconds computation time on a PC is sufficient for a 128 × 128 × 128 matrix size. Predicted phase maps fitted both analytical and experimental data within 1% precision. © 2003 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 19B: 26–34, 2003.
Cellular interactions between axon terminals containing endogenous opioid peptides or corticotropin‐releasing factor in the rat locus coeruleus and surrounding dorsal pontine tegmentum
Authors: Tjoumakaris S.I. , Rudoy C. , Peoples J. , Valentino R.J. , Van Bockstaele E.J. 
Published: October 2003

AbstractRecent evidence suggests that certain stressors release both endogenous opioids and corticotropin‐releasing factor (CRF) to modulate activity of the locus coeruleus (LC)‐norepinephrine (NE) system. In ultrastructural studies, axon terminals containing methionine5‐enkephalin (ENK) or CRF have been shown to target LC dendrites. These findings suggested the hypothesis that both neuropeptides may coexist in common axon terminals that are positioned to have an impact on the LC. This possibility was examined by using immunofluorescence and immunoelectron microscopic analysis of the rat LC and neighboring dorsal pontine tegmentum. Ultrastructural analysis indicated that CRF‐ and ENK‐containing axon terminals were abundant in similar portions of the neuropil and that approximately 16% of the axon terminals containing ENK were also immunoreactive for CRF. Dually labeled terminals were more frequently encountered in the “core” of the LC vs. its extranuclear dendritic zone, which included the medial parabrachial nucleus (mPB). Triple labeling for ENK, CRF, and tyrosine hydroxylase (TH) showed convergence of opioid and CRF axon terminals with noradrenergic dendrites as well as evidence for inputs to TH‐labeled dendrites from dually labeled opioid/CRF axon terminals. One potential source of ENK and CRF in the dorsal pons is the central nucleus of the amygdala (CNA). To determine the relative contribution of ENK and CRF terminals from the CNA, the CNA was electrolytically lesioned. Light‐level densitometry revealed robust decreases in CRF immunoreactivity in the LC and mPB on the side ipsilateral to the lesion but little or no change in ENK immunoreactivity, confirming previous studies of the mPB. Degenerating terminals from the CNA in lesioned rats were found to be in direct contact with TH‐labeled dendrites. Together, these data indicate that ENK and CRF may be colocalized to a subset of individual axon terminals in the LC “core.” The finding that the CNA provides, to dendrites in the area examined, a robust CRF innervation, but little or no opioid innervation, suggests that ENK and CRF axon terminals impacting LC neurons originate from distinct sources and that terminals that colocalize ENK and CRF are not from the CNA. J. Comp. Neurol. 466:445–456, 2003. © 2003 Wiley‐Liss, Inc.
Differential expression of nitric oxide in serotonergic projection neurons: Neurochemical identification of dorsal raphe inputs to rodent trigeminal somatosensory targets
Authors: Simpson Kimberly L. , Waterhouse Barry D. , Lin Rick C.S. 
Published: October 2003

AbstractThe dorsal raphe (DR) is invested with nitric oxide synthase (NOS)‐expressing profiles. To characterize the connections of NO‐containing cells and further assess neurochemical relationships maintained by DR, the transmitter identity of the raphe projection to the trigeminal somatosensory system was examined. Rats were injected with retrograde tracer into vibrissae‐related target areas or with anterograde tracer into DR. NADPH‐diaphorase (NADPHd) histochemistry or NOS‐immunostaining was combined with serotonin (5HT)‐ or serotonin transporter (SERT)‐immunolabeling to examine: 1) the presence of NO in 5HT‐containing axons from DR; 2) the distribution of NO‐containing fibers with respect to other nitrergic profiles in the somatosensory system; and 3) the propensity for individual projection neurons in specific subdivisions of DR to colocalize 5HT and NO. Results confirm that “barrel‐like” patches can be identified in several adult trigeminal relay nuclei by NADPHd histochemistry and demonstrate that fibers from DR contain 5HT and NO. Observations include a high percentage of cortical midline projection neurons which contained NADPHd (70–80%) and coexpressed 5HT. In contrast, ∼40% of retrogradely labeled DR‐thalamus cells in the lateral wing demonstrated NADPHd or 5HT expression, but not both in the same neuron. Colocalization of NADPHd and 5HT within individual DR projection neurons indicates that: i) DR is a source of nitrergic input to trigeminal structures, and ii) NO and 5HT may be simultaneously released to influence information‐processing within somatosensory targets. Disparities in NADPHd expression between retrogradely labeled DR neuronal subpopulations further suggest functional differences in the impact of NO on cortical and subcortical targets. J. Comp. Neurol. 466:495–512, 2003. © 2003 Wiley‐Liss, Inc.