bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ethanol exposure alters neurotrophin receptor expression in the rat central nervous system: Effects of prenatal exposure
Authors: Blaine Moore D. , Madorsky Irina , Paiva Michael , Barrow Heaton Marieta 
Published: April 2004

AbstractDevelopmental ethanol exposure produces significant central nervous system (CNS) abnormalities. The cellular mechanisms of ethanol neurotoxicity, however, remain elusive. Recent data implicate altered neurotrophin signaling pathways in ethanol‐mediated neuronal death. The present study investigated ethanol‐induced alterations in neurotrophin receptor proteins in the rat CNS following chronic ethanol treatment during gestation, via liquid diet to pregnant dams. Brains were dissected on P1 and P10, and Western blots for the neurotrophin receptors TrkA, TrkB, TrkC, and p75 were quantified. Such ethanol treatment produced significant changes in neurotrophin receptor levels in the hippocampus, septum, cerebral cortex, and cerebellum. Receptor levels in hippocampus, septum, and cerebellum, tended to be decreased, while levels in cortex were consistently increased. Males were generally more affected than females. While most of these alterations were transient, sustained or delayed changes were present in P10 septum, cortex, and cerebellum. These results indicate that developmental ethanol exposure produces major changes in the normal physiological levels of the neurotrophin receptors throughout the CNS. These changes in the receptor complement during critical prenatal stages could relate to the anomalous development of the CNS seen in the fetal alcohol syndrome. This relationship is discussed, together with the potential biological effects of such dramatic changes in neurotrophin receptor expression. © 2004 Wiley Periodicals, Inc. J Neurobiol 60: 101–113, 2004
Ethanol exposure alters neurotrophin receptor expression in the rat central nervous system: Effects of neonatal exposure
Authors: Moore D. Blaine , Madorsky Irina , Paiva Michael , Barrow Heaton Marieta 
Published: April 2004

AbstractThe detrimental effects of ethanol exposure during nervous system development have been well established. The cellular mechanisms of ethanol neurotoxicity, however, have not been clearly defined. Recent studies suggest that neurotrophin signaling pathways may be involved in ethanol‐mediated neuronal death. The present investigation, therefore, was designed to examine ethanol‐induced alterations in neurotrophin receptor protein levels in the developing central nervous system (CNS) following chronic ethanol treatment administered during the early neonatal period. For this study, rats were exposed to ethanol via vapor inhalation from postnatal day 4 (P4) to P10. Brains were then dissected on P10 or P21, and Western blots used to quantify expression of neurotrophin receptors TrkA, TrkB, TrkC, and p75. This early postnatal ethanol treatment produced significant alterations in receptor levels in hippocampus, septum, cerebral cortex, and cerebellum. The alterations seen were variable, with decreases generally found in hippocampus and cerebellum, increases noted in septum, and changes in both directions occurring in cortex. These alterations were generally more prevalent in males than in females. While most of the receptor changes observed were transient, sustained or delayed alterations were occasionally seen in hippocampus, cortex, and cerebellum. These results suggest that developmental ethanol exposure modulates expression of these neurotrophin receptors throughout the CNS, alterations which could have wide‐ranging effects on functional CNS development. The possible linkage between such changes and abnormalities encountered in the fetal alcohol syndrome are considered. © 2004 Wiley Periodicals, Inc. J Neurobiol 60: 114–126, 2004
A weak‐derivative form for linear hyperbolic systems
Authors: Cooke Charlie H. , Chen Tze‐Jang 
Published: April 2004

AbstractDifference schemes for linear hyperbolic systems are considered. As a main result, a weak derivative form (WDF) of the governing equations is derived, which is also valid near flow discontinuities. The occurrence of one‐sided derivatives in the WDF structure indicated how to difference near discontinuities. When first‐order differencing is applied to the WDF result, the (linearly identical) schemes by Godunov, Roe, and Steger‐Warming are reproduced. The extension to nonlinear systems is via a local linearization. Choosing Roe's averaging reduces the WDF algorithm to Roe's scheme, whereas other nonlinear WDF schemes are possible. The suitability of various kinds of averaging is numerically investigated. For weak shocks a surprising lack of sensitivity of the method to a particular averaging is exhibited. However, for strong shocks and where the ordinary arithmetic average is used, a slightly more pronounced difference in performance exists between Roe's scheme and WDF. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2004
An error estimate for finite volume methods for the Stokes equations on equilateral triangular meshes
Authors: Blanc Philippe , Eymard Robert , Herbin Raphaèle 
Published: April 2004

AbstractWe give here an error estimate for a finite volume discretization of the Stokes equations in two space dimensions on equilateral triangular meshes. This work was initiated by an analogous result presented by Alami‐Idrissi and Atounti for general triangular meshes. However, in this latter article, the result is not actually proven. We state here the restricting assumptions (namely equilateral triangles) under which the error estimate holds, using the tools which were introduced by Eymard, Gallouet and Herbin and used by Alami‐Idrissi and Atounti. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2004
Functional and molecular characterization of interleukin‐2 transgenic Ewing tumor cells for in vivo immunotherapy
Authors: Staege Martin S. , Hansen Gesine , Baersch Gudrun , Burdach Stefan 
Published: April 2004

AbstractBackgroundInterleukin‐2 (IL‐2) is a potent cytokine with potential activity against several tumors including Ewing tumors (ET). Side effects of systemic IL‐2 can be circumvented by the use of transgenic tumor cells. However, in vitro manipulation may change the overall gene expression profile of tumor cells unfavorably. Therefore, we assessed gene expression profiles, safety, and immunomodulatory efficacy of IL‐2 transgenic (IL‐2‐tg) ET cells in vitro and in NOD/scid mice.ProcedureViable wild type A673 tumor cells were co‐cultured together with irradiated IL‐2‐tg or mock‐transfected cells and HLA matched peripheral blood mononuclear cells. Activation of T and NK cells was assessed by FACS analysis. The effect of irradiated IL‐2‐tg cells on tumor growth in vivo was investigated by using NOD/scid mice. Gene expression profiles of wild type and transfected cells were analyzed with Affymetrix HG‐U95A microarrays.ResultsIL‐2‐tg cells activated and in creased the number of T cells and NK cells in vitro. Co‐culture with IL‐2‐tg but not with mock‐transfected cells almost completely suppressed wild type tumor cell growth in vitro. Cell depletion experiments indicated a major contribution of NK cells to this tumor cell suppression. Co‐transfer of irradiated IL‐2‐tg cells significantly reduced wild type tumor growth in NOD/scid mice. Side effects in the treated animals were not observed and no tumor growth was observed after injection of irradiated IL‐2‐tg cells alone. Gene expression profiling revealed a substantial degree of homogeneity of gene expression in transfected and wild type cells and suggests that transfection and selection procedures had no major impact on the gene expression profile.ConclusionsNext to a high degree of homogeneity between transgenic and wild type cells, our data suggest that irradiated IL‐2‐tg ET cells can activate cytolytic effector cells. These cells may have therapeutic potential for ET patients. © 2004 Wiley‐Liss, Inc.
Residual stresses, shrinkage, and warpage of complex injection molded products: Numerical simulation and experimental validation
Authors: Kabanemi K. K. , Vaillancourt H. , Wang H. , Salloum G. 
Published: April 2004

AbstractA numerical simulation model for predicting residual stresses and residual deformations which arise during the injection molding of thermoplastic polymers in the post‐packing stage has been developed. A thermoviscoelastic model with volume relaxation is used for the calculation of residual stresses. The finite element method employed is based on the theory of shells as an assembly of flat elements. This theory is well suited for thin injection molded products of complex shape. The approach allows the prediction of residual deformations and residual stresses layer by layer like a truly three‐dimensional calculation, while reducing the computational cost significantly. The hole drilling technique is used to measure the residual stresses across the thickness of the product. A three‐dimensional laser digitizing system, an image processing technique and a dual displacement transducer system are used to measure the warpage. Experiments are carried out on polycarbonate and high density polyethylene parts. Numerical results are in qualitative agreement with experimental observations, i.e., the skin of the box is surrounded by a compressive region while the core region is in traction. The trend of both the experimental and the predicted residual stress profiles is close. Different examples are presented to illustrate the influence of the geometrical complexity of the shape on the final deformations and residual stresses. The influence of the mold temperature on residual stresses and warpage is also analyzed.
Analysis of high strain hysteresis loss of nonlinear rubbery polymer
Authors: Kar Kamal K. , Bhowmick Anil K. 
Published: April 2004

AbstractWith the use of the Boltzmann superposition principle, a statistical theory of rubber elasticity, and phenomenological theory, the hysteresis loss at high strain (greater than 100%) of nonlinear viscoelastic materials has been quantified in terms of material parameters. The theory incorporates both experimental and analytical parameters. The experimental results for natural rubber (NR) and styrene‐butadiene rubber (SBR) vulcanizates having variations of loading of carbon black, silica, clay, resin and curatives are in good accord with the theoretical predictions.
Fracture failure processes in polymers. I: Mechanical tests and results
Authors: Liu K. , Piggott M. R. 
Published: April 2004

AbstractTensile tests and Izod impact tests were carried out on eight thermoplastics and an epoxy. The results are compared with shear strengths determined previously, and it is shown that for seven of the polymers, the nominal tensile strength is equal to the yield strength and is approximately the same as the shear strength measured by the punch test. (The true ultimate tensile strength is not always a useful concept because the more ductile polymers are radically changed during the tensile testing process.) In shear tests the shear strains can be extremely high before eventual failure. Because of this the Iosipescu test appears to be unsuitable for measuring the ultimate shear strengths of polymers. Classical shear sliding of failure appears to be rare, and instead most of the polymers appear to be failing in tension when tested in the punch test. (Shear is equivalent to tension at +45° and compression at −45° to the shear directions.) The polymers with shear Strengths that are significantly less than the tensile strengths are brittle ones, and these differences are probably due to flaw statistics. Thus the idea first advanced to explain unduly high interface shear strengths in centrosymmetric systems, i.e., that most polymers ultimately fail in tension when tested in shear, appears to be validated.
Relationship between strain rate, temperature, and impact failure mechanism for poly(vinyl chloride) and poly(ethylene terephthalate)
Authors: Green Janet L. , Petty Charles A. , Gillis Peter P. , Grulke Eric A. 
Published: April 2004

AbstractOne approach to the purification of recycled thermoplastic mixtures is selective grinding to induce differences in sizes and shapes between polymers with different compositions. These mixtures can then be separated using one of several technologies including conventional sieving or hydrocyclones. Recycled poly(vinyl chloride) and poly(ethylene terephthalate) often are cross‐contaminated with each other since they have overlapping density ranges and are very difficult to separate using methods such as flotation. Selective grinding followed by physical separation might be a preferred method for separating such a polymer pair if processing “windows” for inducing differences in failure mechanisms can be found. There is a temperature range over which PET fails in a ductile mode while PVC fails in a brittle mode for impact grinding experiments. This range is not accurately predicted by failure mechanism and β‐transition temperature diagrams.
Toughening of unsaturated polyester with rubber particles. Part I: Morphological study
Authors: Maspoch M. L. L. , Martinez A. B. 
Published: April 2004

AbstractThe morphology of rubber‐modified unsaturated polyester is described. In order to modify the particle‐matrix interface, different rubbers were used; BFGoodrich Hycar liquid rubbers and high molecular weight rubbers. Blends of different compositions were prepared. The microstructure of the materials was investigated using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The volume fraction and the particle size of the rubbers' second phase was determined by applying quantitative metallography. The volume fraction of the precipitated phase was higher than the amount of added rubber. Such blends show phase inversion above 35 wt% of rubber.
Protective coatings on aluminum by spontaneous polymerization
Authors: Agarwal Rajat , Bell James P. 
Published: April 2004

AbstractA novel process to form protective polymer coatings on aluminum using spontaneous polymerization is described. When an aluminum sample is immersed in a partly aqueous monomer solution, polymerization proceeds rapidly on the metal surface, without the addition of initiator, at room temperature. The polymer coatings studied here were formed using styrene (St), N‐phenyl maleimide (NPMI), 2‐methacryloyloxy acetoacetate (MEA), and bis‐maleimide (BMI), monomers, from solutions of different compositions. A possible mechanism for spontaneous initiation and propagation is proposed. The effects of process variables such as polymerization time, monomer concentration, and monomer ratios in feed on the coating thickness and properties are presented. The glass transition temperatures, adhesion strength to aluminum, thermal stability and corrosion resistance of these coatings are reported. The coatings obtained are up to 50 μm thick and conform to the shape of the substrate. They have excellent thermal stability, low dielectric constant, and show very good resistance to corrosion under the ASTM B‐117 accelerated salt fog test. Other monomers and metals may also be used.
Free radical branching of polylactide by reactive extrusion
Authors: Carlson Denise , Dubois Philippe , Nie Li , Narayan Ramani 
Published: April 2004

AbstractThe reactive extrusion of polylactide (PLA) with a free radical initiator resulting in a branched polymer was accomplished. Reaction conditions were in the range of 160°C to 200°C with an initiator concentration between 0.0 and 0.5%. Triple detector size exclusion chromatography, melt flow index, thermal gravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis were used to characterize the polylactide polymers. PLA without initiator showed extensive degradation as was evidenced by a decrease in both molecular weight and melt viscosity. The optimum range for branching resulting in a high molecular weight and low melt flow index polylactide was found to be around 170°C to 180°C and 0.1 to 0.25% initiator.
Modification of nylon‐polyethylene blends via in situ fiber formation
Authors: Chen J. C. , Harrison I. R. 
Published: April 2004

AbstractExtrusion of nylon‐PE films has resulted in the successful in situ formation of high aspect ratio (possibly continuous) nylon fibers as desired. However, these fibers surprisingly provide no significant reinforcement in uncompatibilized blends. While certain compatibilizing agents appear to give properties more characteristic of a fiber reinforced system, achieving higher levels of reinforcement (approaching those anticipated for fibers containing highly oriented molecules) is judged to be difficult using current methods. Based on analysis of yield stress versus modulus, the act of drawing films appears to have the greatest potential for improving reinforcement beyond the limiting case for unmodified polymers. However, the greatest challenge in realizing this potential lies in overcoming the limited extensibility allowed by nylon under normal conditions.
Segmented block copolymers of natural rubber and propylene glycol‐toluene diisocyanate oligomers
Authors: Paul C. J. , Nair M. R. Gopinathan , Neelakantan N. R. , Koshy Peter 
Published: April 2004

AbstractSegmented block copolymers were synthesized from hydroxyl terminated liquid natural rubber (HTNR) and polyurethane oligomers based on 1,2‐propylene glycol and toluene diisocyanate (TDI) by one‐shot and two‐shot processes in solution. They were completely phase segregated. Structural features were characterized by infrared and nuclear magnetic resonance spectroscopies. The two‐phase morphology was deducted from thermal analysis and dynamic mechanical analysis (DMA). The soft segment glass transition temperature was about −64°C and the hard segment glass transition was between 70°C and 100°C depending on the polyurethane content. The two‐phase morphology was corroborated by a two‐stage thermal decomposition of the products. The morphology consisted of a heterogeneous dispersion of beads in a continuous matrix. The large size and the nature of the beads suggest that they are independent of the block copolymer structure and are formed by the agglomeration of the polyurethane homopolymers, which remain unbonded to the rubber chains during chain extension. At lower hard segment contents the materials behaved like quasi‐elastomers, and at higher hard segment contents, they were like tough plastics. At intermediate compositions they behaved as rigid elastomers. Variations in hardness and tear strength were consistent with this behavior.
Radiation grafting functionalization of poly (vinylidene fluoride) to compatibilize its blends with polyolefin ionomers
Authors: Valenza A. , Carianni G. , Mascia L. 
Published: April 2004

AbstractBlends of a crystalline vinylidene fluoride copolymer (PVDF) and a polyolefin ionomer were produced by melt mixing and characterized by a variety of techniques to examine the effect of increasing the level of salt formation on morphology. The PVDF component was also grafted with methacrylic acid by irradiating the polymer powder and subsequently treating it with an aqueous monomer solution. The effect of neutralizing the acid in both polymer components to produce the corresponding zinc salt was also investigated. Compatibilization was accomplished by the addition of zinc acetyl acetonate (ZnAcAc) to the mixture. This increased the viscosity of the polyolefin ionomer phase, comparable to that of the PVDF. The viscosity of the grafted PVDF component did not increase appreciably after neutralization with ZnAcAc. The grafted polymer precipitated and formed a particulate dispersion with in a largely graft‐free polymer matrix. The addition of ZnAcAc to the blend of grafted PVDF and polyolefin ionomer produced a large enhancement in compatibilization, giving rise to the formation of co‐continuous phases that contained encapsulated particles of different size and in various locations.
Interrelationships between P‐V‐T and flow behavior of linear and nonlinear hydrocarbons
Authors: Yahsi Ugur 
Published: April 2004

AbstractThe aim of this work is to determine the branching effect on the flow behavior of alkanes. For this purpose, the zero‐shear viscosity, η0, was analyzed in terms of the Simha‐Somcynsky equation of state, SS‐EOS, using the hole fraction, h = h(P, T) computed from it. For the analysis, η0‐data of the linear and three‐branch alkanes measured in a wide range of temperature and pressure, were used. For the linear species, Utracki proposed a relation, viz. ln η0 = a0 + a1/(h + a2), where a1 = 0.79 and a2 = 0.07 are the universal parameters for linear hydrocarbons and their mixtures. In this work, this relation was found to be valid for the linear but not for the branched alkanes.
Study of electrical phenomena in carbon black–filled HDPE composite
Authors: Lee Gun Joo , Suh Kyung Do , Im Seung Soon 
Published: April 2004

AbstractPercolation, positive temperature coefficient (PTC), and negative temperature co‐efficient (NTC) in carbon black‐filled HDPE composites, were studied by measuring AC electrical properties. An equivalent single parallel circuit model, which consists of a resistor and a capacitor, was adapted to explain the distribution of carbon black in composite. The electrical conductivity and admittance and phase angle were characterized by measuring the distribution of carbon black aggregates with an impedance analyzer. It was concluded that PTC is due to the deagglomeration or the breakage of the conduction networks caused by thermal expansion and/or crystalline melting of the matrix polymer, and NTC is due to the reagglomeration of the network of carbon black aggregates.
The influence of nucleating agents on the extrusion and thermoforming of polypropylene
Authors: Macauley N. J. , Harkin‐Jones E. M. A. , Murphy W. R. 
Published: April 2004

AbstractA large proportion of thin‐gauge containers for the food packaging sector is produced via the thermoforming of extruded thermoplastic sheet (1–4). The production of high quality thermoformed parts is critically dependent on the standard of extruded sheet feedstock used. One method of optimizing the properties of extruded sheet and those of the final thermoformed article is through the incorporation of nucleating agents (5–10). This paper discusses the influence of nucleating agents on the extrusion and thermoforming characteristics of polypropylene. The potential of white titanium dioxide pigment particles as a viable nucleation source for polypropylene is addressed. Evidence is also presented that suggests that nucleating agents may play an important role in controlling the extent of physical change taking place in extruded sheet as a direct result of post‐production aging.
A parametric study of the shock characteristics of expandable polystyrene foam protective packaging
Authors: Lye S. W. , Lee S. G. , Tor S. B. 
Published: April 2004

AbstractThe design of expandable polystyrene foam buffers, used as protective packaging for a range of goods, is by and large steeped in heuristics because the design procedures have not been formalized. This paper discusses the application of Taguchi's Method of Parameter Design to the determination of the key design parameters of expandable polystyrene foam end cap buffers. An L18 orthogonal array was adopted for the planned experiments. The eight design parameters considered critical in the design of the cushioning buffers were product centroid‐to‐buffer centroid distance, cushioning area, buffer thickness, wall thickness, material density, rib configuration, rib width, and rib spacing; of these, only buffer thickness, wall thickness and buffer density were found to be significant at a 99% confidence interval. The height of the ribs, being the difference between the buffer and wall thicknesses, is the single most important factor. The buffer cushioning area was found to be not as important as its distribution over the entire load‐bearing area and the buffer configuration. The buffers were designed in Unigraphics II, and the post‐processing of the NC part program for machining on the Hamai vertical machining center. The impact shock testing of the end cap buffers was conducted on the Lansmont Model 65/81 Shock Test System.