bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystalline and supermolecular structure of polylactide in relation to the crystallization method
Authors: Pluta Mirosław , Galeski Andrzej 
Published: September 2002

AbstractThe effect of thermal treatment on the crystalline and supermolecular structure of polylactide was investigated. The samples were isothermally crystallized by two methods, the crystallization temperature being reached (1) via cooling from the melt and (2) via heating from the glassy, amorphous state. The samples were crystallized over a broad temperature range of 70–130°C. The glassy state was produced by the quenching of the polymer melt to ambient temperature. The morphology and structural features of the samples were examined with X‐ray techniques (wide‐angle and small‐angle X‐ray scattering), small‐angle light scattering, polarizing light microscopy, and differential scanning calorimetry. The results showed similar structures on the lamellar level for samples prepared by the two methods under similar time and temperature conditions. Crystal perfection increased with the crystallization temperature. This was accompanied by an evolution of the spherulitic structure: the spherulites were larger in samples crystallized via cooling from the melt than those in samples crystallized via heating from the glassy, amorphous state. The thermal properties were influenced markedly by the initial crystallinity of the polymer, but differentiation of the supermolecular structures between samples crystallized according to the two protocols did not affect their thermal behavior. The structure of each sample was correlated with its viscoelastic properties. The viscoelastic response was sensitive to the crystallinity level but depended less on the sizes of the spherulites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1386–1395, 2002
Deformation of high‐density polyethylene produced by rolling with side constraints. I. Orientation behavior
Authors: Bartczak Z. 
Published: September 2002

AbstractA new method of rolling with side constraints was applied to polyethylene. The process relies on the rolling of a material inside a channel formed on the circumference of one roll with another roll having a thickness matching the width of the channel in the first roll. The rolling inside a channel resembles to a large extent the plane‐strain compression in a channel die. The deformation processes of linear polyethylene by compression in a channel die and by rolling with side constraints proceed in very similar fashions and produce similarly strong single‐component crystal textures accompanied by chevronlike lamellar structures at comparable strains. The macromolecular chains are highly oriented along the rolling direction. At high rolling rates, {310} twinning takes place with both the channel die and rolling with side constraints because of tensile stress across the bar caused by strain recovery on unloading. The constraint rolling allows for the production of bars or profiles with relatively large cross sections (>1 cm2) in a continuous manner. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1396–1404, 2002
Deformation of high‐density polyethylene produced by rolling with side constraints. II. Mechanical properties of oriented bars
Authors: Bartczak Z. , Morawiec J. , Galeski A. 
Published: September 2002

AbstractThe mechanical behavior of oriented bars of polyethylene obtained by heavy rolling with side constraints was studied. The bars were rolled to a permanent deformation ratio (DR) of up to 8.3. The elastic modulus and ultimate strength measured along the rolling direction increase with increasing DR. For samples deformed to DR = 8.3, the ultimate strength exceeds 180 MPa, whereas an unoriented material exhibits a strength of merely 15 MPa. Because of the highly ordered lamellar structure of the rolled material, the tensile deformation of the bars along the rolling direction is reversible to a large extent. The oriented bars of polyethylene also demonstrate very high toughness, especially in the direction of side constraints. Izod impact tests revealed that the impact strength of the oriented bars exceeds 200 kJ/m2. The samples did not fracture on impact and showed only limited delamination in planes parallel to the rolling plane. Most of the delivered energy was consumed during specimen bending rather than fracture. In contrast to the tensile properties, there is an optimum DR around 5, for which the impact strength is the highest. Dynamical mechanical measurements showed that heavy rolling to a high strain, above DR = 6, produces not only a well‐developed orientation of the crystalline component but also high orientation and transverse ordering of the amorphous phase, which leads to the anisotropy of the material properties in the loading direction/constraint direction plane, perpendicular to the rolling direction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1405–1412, 2002
Determination of stresses around beads in stressed epoxy resin by photoelasticity
Authors: Pawlak Andrzej , Galeski Andrzej 
Published: September 2002

AbstractMicrophotoelasticity gives the possibility of determining stresses in systems with small inclusions. We studied four systems with the same matrix (epoxy resin) and different inclusions of spherical shapes. The distributions of stresses and pressure, after the application of external tensile forces, were determined. In a matrix with a hard inclusion, tensile stresses concentrated at the pole. For a soft inclusion, that is, a poly(vinyl acetate) bead or an air bubble, the tensile stresses concentrated at the equator with some compression at the pole. The soft inclusion promoted the stress relaxation by the change in its shape. In the matrix with a stiff inclusion, such as a steel or glass bead, debonding was observed at the interface near the pole area. In such a case, the stress concentration region moved toward the tip of the debonding. For a hard inclusion, the pressure at all points of the interface was negative, and the maximum was found at the pole near the inclusion surface from −6 to −10 MPa. This region was sensitive to the initiation of destruction processes such as cavitation and debonding. For a soft inclusion, the pressures at the pole and equator were comparable, but the signs were opposite, being positive at the pole (compression) and negative at the equator (expansion). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1436–1444, 2002
Ion exchange in (BO)2.4I3 microcrystals: A method for obtaining colorless, transparent, metallically conductive polymer films
Authors: Tracz Adam 
Published: September 2002

AbstractI obtained colorless, transparent, metallically conductive polymer films by anion exchange in the microcrystals of (BO)2.4I3 [BO = bis(ethylenedioxytetrathiafulvalene)], forming the conductive network in surface‐conducting reticulate‐doped polycarbonate (PC) films. Strongly absorbing I3− anions were replaced by I− or Br− anions, showing weaker absorption in visible light. Interestingly, this transformation proceeded without deterioration of the continuity of the network, and even the shape of the microcrystals was preserved. Particularly, the salt (BO)2.4I3 could be transformed to (BO)2Br(H2O)3 or to (BO)2I(H2O)x. I achieved this by immersing strongly colored PC/(BO)2.4I3 films in the KBr solution or by contact with a Cu plate in KI solution. Depending on the conditions of the ion‐exchange reaction, colorless films showing metallic conductivity down to helium temperatures or showing semiconducting behavior below 100 K were obtained. Electrical properties of some systems are very sensitive to the partial pressure of water. The (BO)2Br(H2O)3 and (BO)2I(H2O)x microcrystals could reversibly change their water content, as shown by comparative X‐ray diffraction and electrical studies performed under reduced pressure or dry atmosphere and under ambient conditions. The controlled anion exchange presented in this article can be considered as a new effective way of modifying the polycrystalline networks of (BO)2.4I3 and other similar salts. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1465–1472, 2002
Recycling of postconsumer poly(ethylene terephthalate) and high‐density polyethylene by compatibilized blending
Authors: Pawlak A. , Morawiec J. , Pazzagli F. , Pracella M. , Galeski A. 
Published: September 2002

AbstractTwo ways of recovering the properties of the scrap plastics poly(ethylene terephthalate) (PET) and high‐density polyethylene (HDPE) were analyzed: (1) blending incompletely segregated polymers with a compatibilizer and (2) blending nonsegregated polymers with a small amount (2 pph) of another compatibilizer. The advancement of the compatibilization reaction in a twin‐screw extruder depended on the residence time and intensity of mixing according to melt viscosity measurements and scanning electron microscopy observations. The acceptable mechanical properties for systems with different PET contents were obtained in blends compatibilized with ethylene–glycidyl methacrylate (EGMA) and styrene–ethylene–butylene–styrene grafted with maleic anhydride. For a blend with 75% PET and 25% HDPE, the optimum content of EGMA was determined to be about 4 pph, and a film was produced with this composition. Admixtures present in recycled HDPE migrated to PET during blending and accelerated the hydrolysis of PET. As a result of migration, differences in the mechanical properties of the blends were observed, depending on the brand of recycled HDPE used. EGMA was also successfully used for the improvement of mechanical properties of a nonsegregated mixture based on PET. Tensile properties of two compatibilized PET‐rich and HDPE‐rich commingled scraps indicated the possibility of using these blends for film extrusion, with potential applications in the packaging of technical products. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1473–1485, 2002
Polylactide/montmorillonite nanocomposites and microcomposites prepared by melt blending: Structure and some physical properties
Authors: Pluta M. , Galeski A. , Alexandre M. , Paul M.‐A. , Dubois P. 
Published: September 2002

AbstractPolylactide (PLA)/clay nanocomposites loaded with 3 wt % organomodified montmorillonite and PLA/clay microcomposites containing 3 wt % sodium montmorillonite were prepared by melt blending. We investigated the morphology and thermal properties of the nanocomposites and microcomposites and compared them with unfilled PLA, keeping the same thermomechanical history. The influence of the processing temperature on the structural characteristics of the investigated systems was determined. The investigations were performed with differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X‐ray diffraction (XRD), size exclusion chromatography (SEC), and polarized light microscopy (LM). XRD showed that the good affinity between the organomodified clay and the PLA was sufficient to form intercalated structure in the nanocomposite. The microcomposite featured a phase‐separated constitution. DSC and LM studies showed that the nature of the filler affected the ordering of the PLA matrix at the molecular and supermolecular levels. According to TGA, the PLA‐based nanocomposites exhibited improvement in their thermal stability in air. Reduced flammability, together with char formation, was also observed for nanocomposites, compared to the microcomposites and pure PLA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1497–1506, 2002
Development of the coronary blood supply: Changing concepts and current ideas
Authors: Bernanke David H. , Velkey J. Matthew 
Published: September 2002

AbstractEarlier views of the development of the coronary vasculature included angiogenic budding and growth of arteries from the aortic sinuses and veins from the coronary sinus. The current concept begins with the establishment of the epicardium from the proepicardial organ, an outgrowth of the dorsal wall of the pericardial cavity. Capillaries form in a subepicardial mesenchymal population, extending as a plexus toward the truncus arteriosus and the atria. Multiple vessels grow from a peritruncal ring of capillaries, preferentially invading the newly formed aorta. In a process involving apoptotic changes of both the aortic wall and the invading capillaries, orifices open at the level of the aortic sinuses. Smooth muscle cells and pericytes, recruited from the surrounding mesenchyme, contribute to the vessel walls, and the definitive coronary artery pattern is established. Similar events are occurring on the venous side of the coronary circulation, following a slightly earlier time course. Multiple factors govern this process, including VEGF and FGF‐1 stimulating vasculogenesis and angiogenesis, and the angiopoietins and their tyrosine kinase receptors modulating interactions between endothelial cells and the mural components. As remodeling of the capillary plexus and the coronary orifices progresses, TGFβ released by apoptotic cells or from other sources likely modulates VEGF and FGF‐1, and also contributes to further apoptotic changes. A better appreciation of the controls of the mechanisms of coronary vessel development may direct further research in the prevention of arteriosclerosis and ischemic tissue injuries. Anat Rec (New Anat) 269:198–208, 2002. © 2002 Wiley‐Liss, Inc.
Magnetic anisotropy of the radula of chiton Acanthochiton rubrolinestus LISCHKE
Authors: Qian Xia , Zhao Jian‐gao , Liu Chuan‐lin , Guo Cheng‐hua 
Published: September 2002

AbstractThe magnetic anisotropy of the whole radula, the major lateral radula teeth, and magnetic material in the major lateral radula teeth of the chiton Acanthochiton rubrolinestus LISCHKE have been studied by a magnetic torque meter and superconducting quantum interference device (SQUID) magnetometer. The length and width axes of the teeth are the easily magnetized axes, while the thickness axis is difficult to magnetize. The width and thickness axes of the radula are the easily magnetized axes, and the length axis is difficult to magnetize. The measurement results of the whole radula and the major lateral radula teeth agree well with each other. The magnetic anisotropy of the magnetic material is given as well as a possible distribution of the magnetic material in the major lateral radula teeth. Bioelectromagnetics 23:480–484, 2002. © 2002 Wiley‐Liss, Inc.
Bioelectrical parameters of the whole human body obtained through bioelectrical impedance analysis
Authors: Lafargue Alcibiades Lara , Cabrales Luis Bergues , Larramendi Ricardo Morales 
Published: September 2002

AbstractKnowledge of electrical properties of body tissues across the frequency spectrum is useful for tissue characterization. The bioelectric impedance analysis method, operating from 1 to 250 kHz (multi‐frequency), was used in 23 normal male human subjects between the ages of 21 and 52 years, for estimation of their bioelectrical parameters. Amplitude of the output current was set to 800 μARMS. The experimental data showed that bioelectric parameters were highly dependent on frequency and the presence of a threshold frequency around 4 kHz. In order to explain the unusual features observed in our experimental data, the human body was simulated through the Cole–Fricke–Cole model (RC circuit) and the Extended Cole–Fricke–Cole model (RLC circuit). The simulated data showed that the Extended Cole–Fricke–Cole model had a higher accuracy than the traditional Cole–Fricke–Cole model. These results suggest that the unusual features could be due to the possible existence of inductive effects in biological cells and body tissues and that the inductive parameter and the threshold frequency could be used for characterizing the healthy tissues as well as the traditional bioelectric parameters. © 2002 Wiley‐Liss, Inc. Bioelectromagnetics 23:450–454, 2002. © 2002 Wiley‐Liss, Inc.
Effects of non‐uniform static magnetic fields on the rate of myosin phosphorylation
Authors: Engström Stefan , Markov Marko S. , McLean Michael J. , Holcomb Robert R. , Markov Julia M. 
Published: September 2002

AbstractThe effect on myosin phosphorylation from exposure to a magnetic field generated by an array of four permanent magnets was investigated. Two lateral positions in the non‐uniform field over the array were explored, each at four vertical distances over the surface of the device. The rate of myosin phosphorylation was found to depend on the position laterally over the array as well as the distance from the device surface. The square magnet array was comprised of axially magnetized, cylindrical NdFeB permanent magnets arranged with poles of alternating polarity in a plane (MagnaBloc™ therapeutic device). Detailed dosimetry of the magnet array was compiled: the magnetic flux density averaged over the exposure volume spanned the range 0.7–86 mT for the eight different exposure positions. The corresponding range for the absolute field gradient was 0.4–20 T/m. Comparing the dosimetry to the experimental outcome, our results imply that magnetic field amplitude alone is not sufficient to describe the influence of the field in this preparation. Bioelectromagnetics 23:475–479, 2002. © 2002 Wiley‐Liss, Inc.
Determination of safety distance limits for a human near a cellular base station antenna, adopting the IEEE standard or ICNIRP guidelines
Authors: Cooper Justin , Marx Bernd , Buhl Johannes , Hombach Volker 
Published: September 2002

AbstractThis paper investigates the minimum distance for a human body in the near field of a cellular telephone base station antenna for which there is compliance with the IEEE or ICNIRP threshold values for radio frequency electromagnetic energy absorption in the human body. First, local maximum specific absorption rates (SARs), measured and averaged over volumes equivalent to 1 and to 10 g tissue within the trunk region of a physical, liquid filled shell phantom facing and irradiated by a typical GSM 900 base station antenna, were compared to corresponding calculated SAR values. The calculation used a homogeneous Visible Human body model in front of a simulated base station antenna of the same type. Both real and simulated base station antennas operated at 935 MHz. Antenna‐body distances were between 1 and 65 cm. The agreement between measurements and calculations was excellent. This gave confidence in the subsequent calculated SAR values for the heterogeneous Visible Human model, for which each tissue was assigned the currently accepted values for permittivity and conductivity at 935 MHz. Calculated SAR values within the trunk of the body were found to be about double those for the homogeneous case. When the IEEE standard and the ICNIRP guidelines are both to be complied with, the local SAR averaged over 1 g tissue was found to be the determining parameter. Emitted power values from the antenna that produced the maximum SAR value over 1 g specified in the IEEE standard at the base station are less than those needed to reach the ICNIRP threshold specified for the local SAR averaged over 10 g. For the GSM base station antenna investigated here operating at 935 MHz with 40 W emitted power, the model indicates that the human body should not be closer to the antenna than 18 cm for controlled environment exposure, or about 95 cm for uncontrolled environment exposure. These safe distance limits are for SARs averaged over 1 g tissue. The corresponding safety distance limits under the ICNIRP guidelines for SAR taken over 10 g tissue are 5 cm for occupational exposure and about 75 cm for general‐public exposure. Bioelectromagnetics 23:429–443, 2002. © 2002 Wiley‐Liss, Inc.
Contact voltage measured in residences: Implications to the association between magnetic fields and childhood leukemia
Authors: Kavet Robert , Zaffanella Luciano E. 
Published: September 2002

AbstractWe measured magnetic fields and two sources of contact current in 36 homes in Pittsfield, MA. The first source, VP–W, is the voltage due to current in the grounding wire, which extends from the service panel neutral to the water service line. This voltage can cause contact current to flow upon simultaneous contact with a metallic part of the water system, such as the faucet, and the frame of an appliance, which is connected to the panel neutral through the equipment‐grounding conductor. The second is VW–E, the voltage between the water pipe and earth, attributable to ground currents in the water system and magnetic induction from nearby power lines. In homes with conductive water systems and drains, VW–E can produce a voltage between the faucet and drain, which may produce contact current into an individual contacting the faucet while immersed in a bathtub. VP–W was not strongly correlated to the magnetic field (both log transformed) (r = 0.28; P < 0.1). On the other hand, VW–E was correlated to the residential magnetic field (both log transformed) (r = 0.54; P < 0.001), with the highest voltages occurring in homes near high voltage transmission lines, most likely due to magnetic induction on the grounding system. This correlation, combined with both frequent exposure opportunity for bathing children and substantial dose to bone marrow resulting from contact, lead us to suggest that contact current due to VW–E could explain the association between high residential magnetic fields and childhood leukemia. Bioelectromagnetics 23:464–474, 2002. © 2002 Wiley‐Liss, Inc.
Melanophore aggregation in strong static magnetic fields
Authors: Testorf Martin F. , Åke Öberg P. , Iwasaka Masakazu , Ueno Shoogo 
Published: September 2002

AbstractContradicting results can be found in the literature on effects from magnetic exposure to pigment cells. We have studied the influence of strong, static, homogenous magnetic fields of 8 and 14 T on melanophore aggregation during exposure to the field. Melanophores, black pigment cells, in fish are large flat cells having intracellular black pigment granules. Due to large size, high optical contrast, and quick response to drugs, melanophores are attractive as biosensors as well as for model studies of intracellular processes. This is especially true for modeling nerve cells, since melanophores share stem cells with axons. Twenty experiments on black tetra fish fins were carried out in the two magnetic flux densities. The same number of control experiments were carried out in the magnet with the magnetic field turned off. Several factors, such as the degree of maximal aggregation, speed of aggregation, and irregularity of the speed, were examined. The statistical analysis showed no significant field effects on the aggregation, with one exception: the irregularity in aggregation speed in the 8 T field, compared to control. The believed reorientation of the cytoskeleton (microtubules) in the field or the induced Lorentz force on moving pigment granules, did not affect the aggregation. Bioelectromagnetics 23:444–449, 2002. © 2002 Wiley‐Liss, Inc.
Secreted Frizzled‐related proteins: searching for relationships and patterns
Authors: Jones Steve E. , Jomary Catherine 
Published: September 2002

AbstractSecreted Frizzled‐related proteins (SFRPs) are modulators of the intermeshing pathways in which signals are transduced by Wnt ligands through Frizzled (Fz) membrane receptors. The Wnt networks influence biological processes ranging from developmental cell fate, cell polarity and adhesion to tumorigenesis and apoptosis. In the five or six years since their discovery, the SFRPs have emerged as dynamically expressed proteins able to bind both Wnts and Fz, with distinctive structural properties in which cysteine‐rich domains from Fz‐ and from netrin‐like proteins are juxtaposed. The abundant expression of SFRP genes in the early embryo, altered expression patterns in disease states, and potential significance in the evolution of the vertebrate body plan, make these intriguing molecules relevant to investigations in diverse fields of biology and biomedical sciences. BioEssays 24:811–820, 2002. © 2002 Wiley Periodicals, Inc.