bluuebunny/crossref_metadata_2025 huggingface dataset:
Caveolins as tumour markers in lung cancer detected by combined use of cDNA and tissue microarrays
Authors: Wikman Harriet , Seppänen Jouni K , Sarhadi Virinder K , Kettunen Eeva , Salmenkivi Kaisa , Kuosma Eeva , Vainio‐Siukola Katri , Nagy Balint , Karjalainen Antti , Sioris Thanos , Salo Jarmo , Hollmén Jaakko , Knuutila Sakari , Anttila Sisko
Published: April 2004

To identify new potential diagnostic markers for lung cancer, the expression profiles of 37 lung tumours were analysed using cDNA arrays. Seven samples were from small‐cell lung cancer (SCLC), two from large‐cell neuroendocrine tumours (LCNEC), and 28 from other non‐small‐cell lung cancers (mainly squamous cell cancer and adenocarcinoma). Principal component analysis and the permutation test were used to detect differences in the gene expression profiles and a set of genes was found that distinguished high‐grade neuroendocrine carcinomas (SCLC and LCNEC) from other lung cancers. In addition, several genes, such as caveolin‐1 (CAV1) and caveolin‐2 (CAV2), were constantly deregulated in all types of tumour sample, compared with normal tissue. The expression of these two genes was investigated further at the protein level on a tissue microarray containing tumours from 161 patients and normal tissues. Immunostaining for CAV1 was negative in 48% of tumours, whereas 28% of the tumours did not express CAV2. Lack of CAV1 protein expression was not caused by methylation or mutation. In stage I adenocarcinomas, CAV2 protein expression correlated with shorter survival. In conclusion, the present study was able to identify genes that have not previously been implicated in lung cancer by the combined use of two different array techniques. Some of these genes may provide novel diagnostic markers for lung cancer. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Prion protein is ubiquitinated after developing protease resistance in the brains of scrapie‐infected mice
Authors: Kang Shin‐Chung , Brown David R , Whiteman Matthew , Li Ruliang , Pan Tao , Perry George , Wisniewski Thomas , Sy Man‐Sun , Wong Boon‐Seng
Published: April 2004

Although the key event in the pathology of prion diseases is thought to be the conversion of cellular prion protein (PrPC) to the protease‐resistant scrapie species termed PrPSc, the factors that contribute to neurodegeneration in scrapie‐infected animals are poorly understood. One probable determinant could be when the accumulation of PrPSc in infected brain overwhelms the ubiquitin–proteasome system and triggers the degenerative cascade. In the present study, it was found that in mouse brains infected with the ME7 scrapie strain, the level of ubiquitin protein conjugates increased significantly at ∼144 days post‐infection (pi) when clinical signs first become apparent. This elevation correlated with the detection of protease‐resistant PrPSc and a decline in two endopeptidase activities associated with proteasome function. However, ubiquitination of PrP was only detected at the terminal stage, 3 weeks after the development of clinical symptoms (∼165 days pi). These results suggest that ubiquitination of PrP is a late event phenomenon and this conjugation occurs after the formation of protease‐resistant PrPSc. Whether this post‐translational modification and the impairment of proteasome function are pivotal events in the pathogenesis of prion diseases remains to be determined. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Attenuating PP/PET bicomponent melt blown microfibers
Authors: Zhao Rongguo , Wadsworth Larry C.
Published: April 2004

This research investigated the attenuation of polypropylene (PP)/poly(ethylene terephthalate) (PET) bicomponent (bico) filaments during the melt blowing (MB) process. It was found that both mono‐ and bi‐component filaments attenuated from several hundred micrometers to a few micrometers in the first 5 centimeters from the die. However, fiber diameter distributions were found to be broad in these regions. The filaments were attenuated much slower but exhibited narrower diameter distributions as they moved further from the die. The diameters of bico MB filaments were between those of 100% PP and 100% PET filaments. The PET component in a bico filament controls the final fiber diameter. During melt blowing, filaments were aligned orderly with the airflow direction in a short distance near the die. Filament entanglements started at about 2.5 cm from the die and became more and more randomly oriented as the distance‐from‐the‐die (DFD) increased. The fiber diameter distribution of bico filaments was broader than that of 100% PP filaments. A higher airflow rate led to a narrower fiber size distribution for bico filaments.
Mechanical behavior of a semicrystalline polymer before necking. Part II: Modeling of uniaxial behavior
Authors: Brusselle‐Dupend N. , Lai D. , Feaugas X. , Guigon M. , Clavel M.
Published: April 2004

Based on the experimental mechanical characterization presented in Part I of this paper, a model allowing the prediction of the behavior of the studied semicrystalline polymer in the pre‐necking domain was constructed. The modeling of the viscoelastoplastic behavior of polypropylene (PP) was described by partitioning the total strain into a viscoelastic strain and a viscoplastic strain. After being improved with experimental observations, the rheological model of Zener was used to model the viscoelastic behavior of PP. As for viscoplastic behavior modeling, it was based on the characterization of the mechanical behavior performed in the first part of the study. Attention was focused on the strain reversal in order to predict the unloading path. Experimental data from the performed mechanical tests were employed to determine the parameters of the viscoelastoplastic model.
Microcellular model evaluation for the deformation of dynamically vulcanized EPDM/iPP blends
Authors: Wright Kathryn J. , Indukuri Kishore , Lesser Alan J.
Published: April 2004

The origins of elasticity in thermoplastic vulcanizates have been debated for the past decade. Previous modeling attempts provide numerical solutions that make assessment of constituent concentration and interaction unclear. A microcellular modeling approach is proposed and evaluated herein to describe the steady‐state behavior of dynamically vulcanized blends of ethylene‐propylene‐diene monomer (EPDM) and isotactic polypropylene (iPP). This approach provides an analytic result including terms for composition and cure state. Three types of deformation are accounted for: elastic and plastic deformation of iPP, elastic deformation of EPDM, and localized elastic and plastic rotation about iPP junction points. The viability of the constitutive model is evaluated in terms of iPP concentration and EPDM cure state.
Effect of dissolved gas on the viscosity of HIPS in the manufacture of microcellular plastics
Authors: Chong Tae‐Hyong , Ha Young‐Wook , Jeong Dae‐Jin
Published: April 2004

The microcellular plastics (MCPs) process is a foaming process that has been developed to reduce the weight of a product without significant changes to the mechanical properties. To apply microcellular plastics to mass production systems such as extrusion, injection molding, and blow molding, research must be done on material properties, such as viscosity, glass transition temperature, and melt index of polymer resin. Among the properties, it is critical to predict the change in viscosity with the amount of inert gas, which can be an index of the injection molding working condition of polymer resin. The purpose of this paper is to study the relationship between the amount of dissolved gas and the viscosity of high impact polystyrene (HIPS) resin in extrusion. The experiment was carried out with newly designed gas supply equipment and with a screw and die modified for MCPs. In addition, a pressure gauge was set up on the end of a barrel for measuring the pressure change. The experiment has shown that the viscosity of polymer decreases with increasing amounts of inert gas. A new model was applied to estimate the viscosity change as a function of the amount of dissolved gas.
Mechanical properties and structural characteristics of dynamically photocrosslinked PP/EPDM blends
Authors: Wang Weizhi , Wu Qianghua , Qu Baojun
Published: April 2004

The mechanical properties and crystal morphological structures of dynamically photocrosslinked polypropylene (PP)/ethylene‐propylene‐diene terpolymer (EPDM) blends have been studied by mechanical tests, wide‐angle X‐ray diffraction (WAXD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Dynamically photocrosslinking of PP/EPDM blends can improve the mechanical propertiess considerably, especially the notched Izod impact strength at low temperature. Data obtained from mechanical tests show that the notched Izod impact strength of a dynamically photocrosslinked sample with 30% EPDM at −20°C is about six times that of an uncrosslinked sample with the same EPDM component. The results from the WAXD, SEM, and DSC measurements reveal the enhanced mechanism of impact strength for the dynamically photocrosslinked PP/EPDM blends as follows: (i) the β‐type crystal structure of PP is formed and the interplanar distance of β‐type crystal increases slightly with an increase in the EPDM component; (ii) the droplet size of the EPDM phase in the photocrosslinked PP/EPDM blends is obviously reduced and the droplet number is increased with an increase in the EPDM component during the dynamical photocrosslinking process; (iii) the graft copolymer of PP‐g‐EPDM is formed at the interface between PP and EPDM components. All the above changes from the crystal morphological structures are favorable for increasing the compatibility and enhancing the toughness of PP/EPDM blends at low temperatures.
A study of residence time distribution in co‐rotating twin‐screw extruders. Part II: Experimental validation
Authors: Poulesquen A. , Vergnes B. , Cassagnau P. , Michel A. , Carneiro O. S. , Covas J. A.
Published: April 2004

In the first part of this paper, a new approach to model the residence time distribution (RTD) in a co‐rotating twin‐screw extruder was proposed. It consists of coupling a continuum mechanics approach with a chemical engineering one, yielding an RTD curve without any fitting parameter. However, the choice of ideal reactors that depict the behavior of each particular profile is not evident. In this second part, we present an experimental study based on two types of extruder (Leistritz 30–34 and Clextral BC45), different screw profiles and two measurement techniques (off‐line and in‐line). Global, partial and local RTD curves were obtained, both experimentally and by means of a deconvolution technique. This series of experiments permitted the definition of the best association between ideal reactors and screw elements. Using this association, a comparison has been made between experimental results and theoretical calculations. A good agreement was generally obtained in terms of the RTD shape, delay time, mean residence time and variance.
Formation and properties of spontaneously polymerized fluorocoatings on aluminum
Authors: Zheng Haipeng , Davis Guy D. , Bell James P.
Published: April 2004

Spontaneous polymerization (S‐Poly) is a novel process to form protective polymer coatings on aluminum and other metals. Here we discuss polymerization and coating properties when two fluorinated monomers are introduced into the S‐Poly system. The resulting coatings were characterized using attenuated total reflectance fourier transform infrared (ATR‐FTIR), differential scanning calorimetry (DSC), optical microscope and other measurements. Fluorinated coatings showed excellent dielectric properties and strong hydrophobicity. Their dry adhesion strength was a little lower than the coatings in previous systems, but changed very little after immersion in hot water for several days. Some of the fluorinated coatings exhibited significantly improved corrosion resistance in most corrosion tests.
Optimization of a batch reactor to produce the elastomeric copolyester prepolymer copoly(ethylene‐polyoxyethylene terephthalate)(CEPT)
Authors: De La Cruz‐Guerra Cornelio , Hernández‐Rivera Miguel A. , Cruz‐Gómez M. Javier
Published: April 2004

A mathematical algorithm that optimizes the reactor to produce the elastomeric copolyester copoly(ethylene‐polyoxyethylene terephthalate), CEPT, is shown in this work. The optimization was carried out this way: First, an initial isothermal guess of temperature profile is made and the differential equtions system, which describes the CEPT production process, is solved, Second, the reaction time is fixed and the objective function is calculated. Third, the adjoint variable equations system is solved and the Hamiltonian's function is calculated. Fourth, a new temperature profile is found by using the control vector iteraction procedure. Finally, steps one to three are repeated until the objective function reaches a minimum value. The results of the optimization establish that the copolytransesterification reactor should be operated initially to high temperature (about 285°C), which should be reduced quickly to near 250°C to purposely diminish the production of by‐products.
Effect of interdiffusion regions on penetrant flux through multilayer films
Authors: Sankhe Shilpa Y. , Hirt Douglas E. , Zumbrunnen David A.
Published: April 2004

Barrier properties of polymer films can be improved in various ways, such as formation of multilayer structures by coextrusion, surface treatment, and coatings. This work explores the use of thousands of alternating layers of polymer (xyxy…) to modify the resistance to permeation. A model is presented to predict the number of layers needed in a laminate to change the flux of a permeant by a given amount. An important feature of the model is the species transport across the interdiffusion regions at the polymer‐polymer interfaces where diffusivity of the penetrant, Di, is assumed to be a constant or a function of the volume fractions (ϕ) of the interdiffusing polymers. For constant Di, the modeling results show that increasing the number of interfacial regions decreases the flux for a given condition, and a large number of layers are required to achieve appreciable flux reduction. For ϕ‐dependent Di a balanced interdiffusion region was modeled in which the interdiffusing polymers were assumed to interpenetrate one another equally. In this particular case, the flux was predicted to always increase with the number of layers.
The effect of flame retardants on the hot‐plate welding of talc‐filled polypropylene
Authors: Oliveira M. J. , Bernardo C. A. , Hemsley D. A.
Published: April 2004

The effect of a flame retardant on the weldability of polypropylene with two different talc loadings was studied by microscopy and mechanical tests on hot‐plate welded injection molded tensile test bars. Welding changes the orientation of the talc particles, which align parallel to the weld interface, and can cause voiding of the material with a consequent decrease of weld strength. Welds of the material containing a flame retardant, which melts and volatizes at the temperatures used in welding, exhibited higher voiding and lower relative weld strengths on welding than the grade without a flame retardant. Voiding may be reduced using lower hot plate temperatures and higher welding displacements, but that results in an increase in the transverse orientation of the talc particles in the weld zone. The relative weld strength, which is affected by the composition of the material, was about 50% for the 20% talc‐filled polypropylene and about 45% for the 30% talc‐filled grade containing a flame retardant.
Plasma surface treatments of melt‐extruded sheets of poly(L‐lactic acid)
Authors: Hirotsu Toshihiro , Nakayama Kazuo , Tsujisaka Toshiyuki , Mas Andre , Schue Francois
Published: April 2004

Poly(L‐lactic acid) sheets, prepared by melt extrusion, were treated with O2−, He−, and N2−plasmas generated in radio frequency (RF) at 13.56 MHz. Atmospheric pressure discharge at 20 kHz in helium was also applied to the modification of the sheets. The surface of the PLLA sheets was etched to form the characteristic morphology, and the patterns were different depending on the type of plasma. Polar groups composed of –COOH and –OH were incorporated by plasma treatment, and the surface became wettable. Surface modification became effective after a short treatment period, e.g., 30 seconds. Receding contact angles (θr) changed remarkably, and the surface properties were closely related to the increase in the surface energy of the polar contribution (γsp). Biodegradation of the poly(L‐lactic acid) sheets was not enhanced practically, even though the surface became hydrophilic after plasma treatment.
Verification of extensional viscosity effects in injection mold filling simulation
Authors: Moller James C. , Lee Daeyong
Published: April 2004

The effect of extensional viscosity upon wall pressure and front progression in injection molding is presented through experiments and simulations. In order to compare materials having distinctly different responses to extensional flow, unfilled and glass‐filled polypropylenes were examined. Wall pressure agreement was best with an extensional viscosity included in the simulation, particularly for the filled material. Pressure gradients were large enough to indicate significant density variations in the part at the end of filling, Examination of the test materials' viscoelastic properties indicates that extensional, rather than viscoelastic, effects predominate in the behaviors shown. Flow front progression was recorded by strobe photography. Results indicate that, when cavity thickness gradient is not aligned with the the direction of flow, there is disagreement among predictions and measurements. This is principally due to the violation of the Hele‐Shaw assumption that forms the basis for the simulation.
Development of a curvilinear viscoelastic constitutive relationship for time dependent materials. Part B: Example problems
Authors: Stephenson M. J. , Dargush G. F.
Published: April 2004

The boundary value problem of a two‐dimensional viscoelastic beam clamped at two ends and subjected to both a dead load and normal surface traction is solved using a finite element method here in Part B. The constitutive relationship between stress and strain developed in Part A uses a convected coordinate system and body tensor mathematics. Maxwell elements (springs and dashpots) describe the material for both fluid and solid characterizations. The overall finite element results calculated were physically reasonable. However, the assumed boundary conditions produce a stress singularity at the boundary, a singularity that is also seen in small deformation elastic theory.
Effect of curing temperature on the morphology of unsaturated polyester resin blended with poly(vinyl acetate)
Authors: Liu Chun‐Hsiu , Yu T. Leon , Chen Chih‐Cheng
Published: April 2004

Phase separation of unsaturated polyester/styrene (UPE/styrene) resin blended with 5 and 10 wt% of poly(vinyl acetate) (PVAc) cured at various temperatures ranging from 75°C to 150°C was studied using low angle laser light scattering (LALS) and scanning electron microscopy (SEM). For UPE/styrene resin blended with 5 wt% PVAc cured at a temperature below 90°C, a discrete phase‐separated structure was observed. As curing temperature was raised above 90°C, SEM micrographs revealed that more and more cured UPE globules fused together with increasing curing temperature. The LALS intensity profile became broader with increasing curing temperature, indicating a less discrete phase‐separated structure at a higher curing temperature. As PVAc content was increased to 10 wt%, SEM micrographs revealed a co‐continuous phase‐separated structure. The LALS intensity decayed slowly from the center of the scattering pattern to a high scattering angle without the appearance of maximum scattering peak intensity. The morphology of the cured sample did not change too much with curing temperature for UPE/styrene resin blended with 10 wt% of PVAc.
Gas transport properties in chlorosulfonated polyethylene‐acrylate based adhesives
Authors: Tiemblo P. , Guzmán J. , Riande E. , Fernández A. , Bosch P.
Published: April 2004

The permeability and diffusivity properties of four gases—oxygen, nitrogen, carbon dioxide and methane—have been obtained for membranes prepared by the photocrosslinking of a mixture of chlorosulfonated polyethylene, acting as a binder, and a series of acrylic and methacrylic monomers. These measurements have been performed in the range 20°C to 50°C, and the activation energies have also been determined. These data are presented in comparison with those previously obtained in a crosslinked system in which the binder was not chlorosulfonated polyethylene but an aliphatic polyurethane. Both polymeric systems show similar permselectivities for the gas pairs O2/N2 (near 5) and CO2/CH4 (near 12), though overall permeability is about three times lower in the chlorosulfonated polyethylene—based polymer because of the smaller diffusion coefficients. The permeation and diffusion results are discussed in terms of the final structure of the photocrosslinked polymeric system, and it is concluded that it is the binder which is mostly responsible for the gas transport properties of these crosslinked materials.
Viscoelastic stress calculation in multi‐layer coextrusion dies: Die design and extensional viscosity effects on the onset of ‘wave’ interfacial instabilities
Authors: Zatloukal M. , Sáha P. , Vlček J. , Tzoganakis C.
Published: April 2004

Non‐isothermal calculation of flow history‐dependent viscoelastic stresses in an annular coextrusion die is performed using the 8‐mode modified Leonov constitutive equation and the deformation rate field from finite element simulations. The study shows how the recently proposed total normal stress difference (TNSD) sign criterion, which quantifies the relative stretching of coextruded layers across an interface, can be used to investigate the role of the die design and elongational viscosities of coextruded materials from the point of view of interfacial instability. It is shown that both the die geometry and the elongational strain hardening have a crucial effect on the interfacial wave instability.
Toughness of nanoscale and multiscale polyamide‐6,6 composites
Authors: Nair Shanti V. , Goettler Lloyd A. , Lysek Bruce A.
Published: April 2004

Fracture initiation and fracture propagation toughening (R‐curve behavior) of polyamide 6,6 (PA‐66) polymers with different types of layered silicate clay having nanoscale (fully dispersed) or multiscale (mixed nanoscale/microscale) structure were studied. These results were compared to fracture data for conventional kaolin clay particulate reinforcements and a PA‐66 polyblend containing rubber and rigid poly(styrene‐co‐acrylonitrile) particulates. The stiffness increase due to the intercalated clay was the same as would be predicted by classical models for conventional elongated reinforcements at the same volume fraction level. The special benefit of the nanoscale reinforcement derived from their high surface area of contact with the matrix. Toughness in layered silicate clay composites was enhanced by better dispersion of the clay, by exfoliation of the clay layers, and by a stronger clay/matrix interface. A multiscale microstructure was found to be the more desirable microstructure, combining toughness from the nanodispersed clay with resistance curve behavior from the micrometer‐sized particulates. Fracture toughness was proportional to the crack‐tip plastic zone size at fracture, indicating that the clay reinforcements, by influencing shear deformation in the crack tip region, played an important role in promoting toughness. There was indirect evidence for the formation of a zone of damage within the crack‐tip plastic zone that could explain why toughness was not optimal.
The role of crystallinity and reinforcement in the mechanical behavior of polyamide‐6/clay nanocomposites
Authors: Bureau M. N. , Denault J. , Cole K. C. , Enright G. D.
Published: April 2004

The mechanical behavior of compression‐molded polyamide‐6 (PA6) reinforced with 2 wt% of organo‐nanoclay (montmorillonite intercalated with ω‐amino dodecanoic acid) has been studied and compared to that of PA6. The tensile strength and the Young's modulus of the PA6/clay were 15% higher than those of PA6. Differential scanning calorimetry, Fourier transform infrared spectroscopy, and X‐ray diffraction showed that the crystalline structures of PA6 and PA6/clay differed considerably. A crystallinity of 25% with a dual structure composed of the γ and α forms was obtained in PA6/clay, while a crystallinity of 31% with the α form as the dominant crystalline structure was obtained in PA6. To understand the role of the crystalline structure of PA6, the molding process was modified to obtain PA6 specimens with different levels of crystallinity and different crystalline forms. Quenching molten PA6 at a cooling rate sufficiently high to prevent crystallization gave a material that was predominantly amorphous (crystallinity of 7%) with traces of the mesomorphic β or γ* form. Annealing this material at 80°C considerably increased crystallinity to 21%, which was also of the mesomorphic β or γ* form. PA6 with a predominant crystalline γ form could not be generated. Comparisons with PA6/clay in terms of crystallinity and mechanical behavior lead to the conclusion that the improvements in rigidity and strength observed when montmorillonite is added to PA6 are related to the reinforcing filler and not to a modification of the crystalline structure.
From polymer blends to in situ polymer/polymer composites: Morphology control and mechanical properties
Authors: Pesneau I. , Kadi A. Aït , Bousmina M. , Cassagnau Ph. , Michel A.
Published: April 2004

In situ polymer/polymer short fiber composites were generated by a two‐step process. In the first step, a polyamide (PA) dispersed phase is blended with a polypropylene (PP) matrix in a twin‐screw extruder at a temperature at which both polymers are in molten state. The extrudate was then stretched at the die exit to generate long and thin fibers of PA in the PP matrix well oriented in the direction of flow. Adhesion between the phases was promoted by addition of PP grafted with maleic anhydride (PP‐g‐MA). During the second step, the chopped extrudates were molded by injection or compression molding at a temperature at which PA in the form of fibers is in the solid state and the PP matrix is molten. The control of the formation of such ultrafine fibers was obtained by quantitative analyses for the deformation of the minor PA‐phase during twin‐screw extrusion and stretching at the exit of the die that involve both shear and extensional flows. Morphology and mechanical properties of such polymer/polymer composites were compared to equivalent blends with dispersed spherical particles‐type morphology prepared in a batch mixer device.
PP/EMA TPV: Dynamic cross‐linking through an alcoholysis reaction
Authors: Pesneau Isabelle , Champagne Michel F. , Huneault Michel A.
Published: April 2004

Dynamically cross‐linked polypropylene/ethylene‐methyl acrylate copolymer (PP/EMA) blends were prepared by reactive extrusion in a twin‐screw extruder. A transesterification reaction catalyzed by an organotin compound and involving the acrylic moieties of EMA with the hydroxyl functions of pentanediol was used to cross‐link the elastomeric EMA. The extent of cross‐linking was estimated through the insoluble content of the blend. The alcohol‐to‐acrylic ratio and the dibutyltin oxide content were both found to increase the extent of EMA cross‐linking. Processing conditions such as screw rotation rate and extrusion temperature profile also had large effects on the reaction extent. Conditions leading to improved pentanediol dispersion were found to generate larger insoluble fraction. Gel contents of EMA phase as high as 75% to 85% were obtained. Interestingly, the stress‐strain curves of the cross‐linked PP/EMA TPV are very well represented by a single master curve. Dynamically cross‐linked blends show systematically better tensile properties than the non‐reactive system. Blends with higher insoluble content show strain at break in the 650%–750% range. Material processability was maintained, even for the systems with high insoluble content.
Rheology of concentrated solutions of hyperbranched polyesters
Authors: Andrady Anthony L. , Nunez Carlos M. , Chiou Bor‐Sen , Khan Saad A.
Published: April 2004

The solution rheology of different generations of hyperbranched polyesters in N‐methyl‐2‐pyrrolidinone (NMP) solvent was examined in this study. The solutions exhibited Newtonian behavior over a wide range of polyester concentrations. Also, the relative viscosities of poly(amidoamine) (PAMAM) dendrimers in ethylenediamine were compared with those of the hyperbranched polyesters in NMP. Both types of dendritic polymers have relative viscosities that are exponential functions of their molar fraction in solution. The slopes of these relative viscosity curves show a linear relationship with respect to the generation number. PAMAM dendrimers have the greater slopes for each generation, reflecting their relatively larger intrinsic viscosity values.
Influence of side‐chain structures on the viscoelasticity and elongation viscosity of polyethylene melts
Authors: Lin Gwo‐Geng , Shih Hsi‐Hsin , Chai Ping‐Chang , Hsu Shio‐Jin
Published: April 2004

Metallocene‐catalyzed, low‐density and linear low‐density polyethylenes with similar melt indexes were used to investigate how side‐chain structures influence the elongation viscosity and viscoelastic properties. The viscoelastic properties were determined with a rotation rheometer, while the elongation viscosities were acquired by using isothermal fiber spinning. The Phan‐Thien‐Tanner (PTT) model was also used to understand how the side‐chain structure affects the elongation behavior. Experimental results demonstrate that the log G′ vs. log G″ plot can qualitatively describe the effects of the side chain branch on the rheological properties of polyethylene melts. According to the results determined by the PTT model, low‐density polyethylene (LDPE) has low elongation viscosities at high strain rates. This low elongation viscosity can be attributed to the fact that LDPE has high shear thinning behavior. The long‐chain branching tends to increase entanglements, thereby enhancing the storage modulus, elongation viscosity and shear‐thinning behaviors. Uniform side‐chain distribution lowers the entanglements, which results in a low storage modulus, elongation viscosity and shear‐thinning behavior.
Rheological behavior of brominated isobutylene‐co‐paramethylstyrene: Effect of fillers, oil and blending with EPDM
Authors: Kumar Bhuwneesh , De S. K. , Bhowmick A. K. , De P. P. , Peiffer D. G.
Published: April 2004

The melt flow properties of unfilled and filled brominated isobutylene‐co‐paramethylstyrene (BIMS) were measured by means of a capillary viscometer at three different temperatures (90°C, 110°C and 130°C) and four different shear rates (61, 122, 245 and 306 s−1). The effect of addition of EPDM rubber on melt flow properties of unfilled BIMS was also studied. Evaluation of the processability was done by measuring the extrudate roughness (ER) of the extrudates obtained from the MPT. The viscosity of the systems decreased with the shear rate, indicating their pseudoplastic or shear thinning nature. As expected, the viscosity of BIMS increased with the addition of fillers and decreased with the addition of oil. For the neat systems, viscosity increased with the addition of EPDM, and the blends showed a positive deviation, indicating interdiffusion of the polymer chains across the phase boundaries. The activation energy of the filled systems at constant filler loading increased with increasing filler surface area (N330 > N550 > N774, each at 30 phr loading), and filler loading (50 > 30 > 10 phr, for N330) and decreased with the addition of oil (2.5 > 5.0 > 7.5 phr, for system containing 30 phr of N330). The silica filled system showed a higher activation energy and ER than the carbon black‐filled systems. With addition of N330 and N550 carbon blacks to BIMS, the extrudate roughness (ER) decreased, whereas it increased with the addition of N774 carbon black. With an increase in filler loading, ER initially increased and then decreased as compared to the neat system. For the filled systems, ER initially decreased up to 5 phr of oil, beyond which it increased.
Effects of molecular weight and clay organo‐ions on the melt intercalation of poly(ethylene oxide) into layered silicates
Authors: Shen Zhiqi , Simon George P. , Cheng Yi‐Bing
Published: April 2004

A useful and desirable method of synthesizing nanoscale organic‐inorganic composites is to intercalate polymers into layered silicates by melt intercalation. Nanocomposites of poly(ethylene oxide) with a sodium montmorillonite and an organoions exchanged bentonite have been prepared by melt intercalation. The effects of polymer molecular weight, the nature of the clay (one unmodified, the other with organo‐ion) and the presence of water molecules in the clay galleries have been investigated. Based on X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA), a distorted helical conformation is thought to describe the conformation of the PEO chains in the hybrid materials.
Characterization of monopolymer blend of virgin and recycled polyamide 6
Authors: Scaffaro R. , La Mantia F. P.
Published: April 2004

It is a common industrial practice to blend virgin polymer with the same recycled polymer coming from plastic scraps that, in general, has not undergone relevant degradation. In this work, the characteristics of blends of virgin and recycled polyamide have been considered by changing the amount of recycled polymer and the presence of humidity and a stabilizer. Neither dry nor wet stabilized recycled polyamide samples show significant variations of the molecular weight, but the melt Newtonian viscosity of the blends are slightly different from that predicted by an additive rule, despite the same chemical nature of the two components. This holds true even more for the humid unstabilized sample, as its noticeably lower molecular weight implies values lower than those expected on a linearity basis. The situation is different for the mechanical properties; here the morphology reached in the solid state determines a more rigid and brittle material, compared to the pure components, with relevant deviations from linearity for all the recycled samples used to prepare the blends. A different crystallinity as a function of the composition can be invoked to explain this phenomenon. The blends containing dry and wet stabilized recycled polyamide show almost the same behavior, confirming the reduced degradation of these samples.
A novel pH‐sensitive gelatin–DNA semi‐interpenetrating polymer network hydrogel
Authors: Liu Wen Guang , Li Xiao Wei , Ye Gui Xiang , Sun Shu Jun , Zhu Dunwan , Yao Kang De
Published: April 2004

Gelatin and DNA were mixed together in various ratios followed by the addition of glutaraldehyde as a cross‐linker. FT‐IR spectroscopy confirmed the formation of a semi‐interpenetrating polymer network (semi‐IPN) between the gelatin and DNA. The gelatin–DNA semi‐IPN hydrogel underwent, reversibly, remarkable changes in swelling degree in response to the variation of pH. In the low‐pH range, the hydrogel showed a lower swelling degree; with an increment in pH, the hydrogel was highly swollen, which is considered to originate from the complexation and de‐complexation between gelatin and DNA, as was verified by turbidity measurements. Higher contents of DNA result in an increase in the swelling degree, which is presumably due to the easy outward expansion of free DNA moieties. The permeability coefficient, P, for a model molecule, cimetidine, through the semi‐IPN hydrogel membranes was determined in pH 1.0 and pH 12.0 buffer solutions. The results show that the permeation of cimetidine is responsive to pH change, and an evident variation in the P values occurs in response to the pH of the media. Copyright © 2004 Society of Chemical Industry
Electroless recovery of gold chloride using inherently conducting polymers
Authors: Ding Jie , Price William E , Ralph Stephen F , Wallace Gordon G
Published: April 2004

Conducting polymers deposited onto reticulated vitreous carbon (RVC) were shown to remove gold from aqueous solutions in a facile and highly efficient fashion. For acidic solutions with initial [AuCl4]− concentrations between 0.1 and 1000 ppm, gold recoveries >90% were obtained. Experiments, conducted using solutions containing 0.1 ppm [AuCl4]−, also demonstrated that the composite materials were significantly more effective at recovering gold than activated carbon. Gold removal from solutions containing [AuCl4]− and much higher concentrations of iron was highly selective. Copyright © 2004 Society of Chemical Industry
Two‐dimensional maps and databases of the human macrophage proteome and secretome
Authors: Dupont Annabelle , Tokarski Caroline , Dekeyzer Olivia , Guihot Anne‐Laure , Amouyel Philippe , Rolando Christian , Pinet Florence
Published: April 2004

Macrophages exert a crucial, but still incompletely known, role in complex disorders such inflammatory, immunological, and infectious diseases. A differential proteomic approach should help to elucidate the macrophage dysfunctions involved in these diseases. With this goal in mind, we established the first two‐dimensional maps of the human macrophage proteome and secretome. Intracellular and secreted proteins were extracted from monocyte‐derived macrophages obtained from healthy donors (n = 16), and separated by two‐dimensional gel electrophoresis. Silver‐stained gels were analyzed using Progenesis software. A high level of between‐gel reproducibility was obtained, allowing us to generate two patterns specific of the macrophage proteome and secretome, respectively. A total of 127 and 66 distinct intracellular and secreted polypeptide spots, corresponding to 100 and 38 different proteins, respectively, were identified by matrix assisted laser desorption/ionisation‐mass spectrometry. The two‐dimensional reference maps and databases resulting from this study confirm that macrophages are involved in a wide range of biological functions, and that they provide a useful tool for a wide array of investigators involved in macrophage biology, allowing to investigate the macrophage protein changes associated with various disorders or environmental stimuli.
Dispensable role for interferon‐γ in the burn‐induced acute phase response: A proteomic analysis
Authors: Duan Xunbao , Yarmush David M. , Jayaraman Arul , Yarmush Martin L.
Published: April 2004

We examined the role of the pleiotropic cytokine interferon‐γ (IFN‐γ) in initiating the burn injury‐induced acute phase response (APR). Two‐dimensional (2‐D) electrophoresis was used to obtain serum protein profiles from wild‐type (WT) and IFN‐γ knockout mice following sham‐burn or 20% burn injury. Serum 2‐D images from both groups of burn‐injured mice were characterized by the upregulation of a similar panel of protein spots. These included the three major murine acute phase proteins haptoglobin, serum amyloid A, and serum amyloid P, that were identified by matrix‐assisted laser desorption/ionization‐time of flight (MALDI‐TOF)‐mass spectrometry. Furthermore, the changes in the levels of these protein spots were very similar between these two groups of mice, as determined by image analysis. Other features of burn‐induced APR such as a decrease in total serum protein concentration, an elevated circulation level of the cytokine interleukin‐6 (IL‐6), and activation of the IL‐6 signal transduction protein STAT3 were also evaluated and found to be similar between wild‐type and IFN‐γ knockout mice. These results suggest a dispensable role of IFN‐γ in the induction of the hepatic APR in mice following burn injury.
Unimod: Protein modifications for mass spectrometry
Authors: Creasy David M. , Cottrell John S.
Published: April 2004

Unimod is a database of protein modifications for use in mass spectrometry applications, especially protein identification and de novo sequencing. It contains accurate and verifiable values, derived from elemental compositions, for the mass differences introduced by both natural and artificial modifications.
The RESID Database of Protein Modifications as a resource and annotation tool
Authors: Garavelli John S.
Published: April 2004

The RESID Database of Protein Modifications is a comprehensive collection of annotations and structures for protein modifications and cross‐links including pre‐, co‐, and post‐translational modifications. The database provides: systematic and alternate names, atomic formulas and masses, enzymatic activities that generate the modifications, keywords, literature citations, Gene Ontology (GO) cross‐references, protein sequence database feature table annotations, structure diagrams, and molecular models. This database is freely accessible on the Internet through resources provided by the European Bioinformatics Institute (http://www.ebi.ac.uk/RESID), and by the National Cancer Institute – Frederick Advanced Biomedical Computing Center (http://www.ncifcrf.gov/RESID). Each RESID Database entry presents a chemically unique modification and shows how that modification is currently annotated in the protein sequence databases, Swiss‐Prot and the Protein Information Resource (PIR). The RESID Database provides a table of corresponding equivalent feature annotations that is used in the UniProt project, an international effort to combine the resources of the Swiss‐Prot, TrEMBL and PIR. As an annotation tool, the RESID Database is used in standardizing and enhancing modification descriptions in the feature tables of Swiss‐Prot entries. As an Internet resource, the RESID Database assists researchers in high‐throughput proteomics to search monoisotopic masses and mass differences and identify known and predicted protein modifications.
Preparation and properties of new polyimides and polyamides based on 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)naphthalene
Authors: Hsiao Sheng‐Huei , Yang Chin‐Ping , Huang Sheng‐Ching
Published: April 2004

A novel, trifluoromethyl‐substituted, bis(ether amine) monomer, 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)naphthalene, was synthesized through the nucleophilic displacement of 2‐chloro‐5‐nitrobenzotrifluoride with 1,4‐dihydroxynaphthalene in the presence of potassium carbonate in dimethyl sulfoxide, followed by catalytic reduction with hydrazine and Pd/C in ethanol. A series of new fluorine‐containing polyimides with inherent viscosities of 0.57–0.91 dL/g were prepared by reacting the diamine with six commercially available aromatic dianhydrides via a conventional, two‐step thermal or chemical imidization method. Most of the resulting polyimides were soluble in strong polar solvents such as N‐methylpyrrolidone and N,N‐dimethylacetamide (DMAc). All the polyimides afforded transparent, flexible, and strong films with good tensile properties. These polyimides exhibited glass‐transition temperatures (Tg's) (by DSC) and softening temperatures (by thermomechanical analysis) in the ranges of 252–315 and 254–301 °C, respectively. Decomposition temperatures for 5% weight loss all occurred above 500 °C in both air and nitrogen atmospheres. The dielectric constants of these polyimides ranged from 3.03 to 3.71 at 1 MHz. In addition, a series of new, fluorinated polyamides with inherent viscosities of 0.32–0.62 dL/g were prepared by the direct polycondensation reaction the diamine with various aromatic dicarboxylic acids by means of triphenyl phosphite and pyridine. All the polyamides were soluble in polar solvents such as DMAc and could be solution‐cast into tough and flexible films. These polyamides had Tg's between 228 and 256 °C and 10% weight‐loss temperatures above 400 °C in nitrogen or air. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2377–2394, 2004
Melt‐processable thermosetting polyimide: Synthesis, characterization, fusibility, and property
Authors: Kuroki T. , Shibuya A. , Toriida M. , Tamai S.
Published: April 2004

To obtain a melt‐processable thermosetting polyimide having a high glass‐transition temperature (Tg) and good solvent resistance, the effect of introducing a crosslinkable agent into the polymer chain ends of the melt‐processable polyimide on its physical properties was studied. The polyimide (calculated number‐average molecular weight (Mn) = 11,600 g/mol) capped with the crosslinkable agent exhibited poor melt flowability because its crosslinkable agent reacted at the processing temperature of 360 °C. To reduce the rate of crosslink reaction, two methods were investigated. One was lowering the processing temperature, and the other was decreasing the amount of crosslinkable agent. The low‐molecular‐weight oligomer (calculated Mn = 6300 g/mol) capped with the crosslinkable agent exhibited good melt flowability at the lower processing temperature of 340 °C where the crosslinkable agent did not react. However, the obtained molded part of this oligomer was too brittle to maintain its shape. However, the polyimide (calculated Mn = 11,600 g/mol) partially capped with the crosslinkable agent demonstrated good melt flowability at the processing temperature of 360 °C. Furthermore, the molded part of this resin was strong and tough. In addition, the cured part exhibited high Tg and good solvent resistance. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2395–2404, 2004
Synthesis of hydrophilic/CO2‐philic poly(ethylene oxide)‐b‐poly(1,1,2,2‐tetrahydroperfluorodecyl acrylate) block copolymers via controlled/living radical polymerizations and their properties in liquid and supercritical CO2
Authors: Ma Zhi , Lacroix‐Desmazes Patrick
Published: April 2004

Hydrophilic/CO2‐philic poly(ethylene oxide)‐b‐poly(1,1,2,2‐tetrahydroperfluorodecyl acrylate) block copolymers were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization, iodine transfer polymerization (ITP), and atom transfer radical polymerization (ATRP) in the presence of either degenerative transfer agents or a macroinitiator based on poly(ethylene oxide). In this work, both RAFT and ATRP showed higher efficiency than ITP for the preparation of the expected copolymers. More detailed research was carried out on RAFT, and the living character of the polymerization was confirmed by an ultraviolet (UV) analysis of the SC(S)Ph or SC(S)SC12H25 end groups in the polymer chains. The quantitative UV analysis of the copolymers indicated a number‐average molecular weight in good agreement with the value determined by 1H NMR analysis. The properties of the macromolecular surfactants were investigated through the determination of the cloud points in neat liquid and supercritical CO2 and through the formation of water‐in‐CO2 emulsions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2405–2415, 2004