bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intermolecular and intramolecular hydrogen bonding of poly(dimethylsiloxane)urethane‐graft–poly(methyl methacrylate) copolymers based on 2,4‐TDI and m‐XDI
Authors: Ma Chen‐Chi M. , Wang Feng‐Yih , Du Yi‐Chang , Wu Chen‐Li , Chiang Chin‐Lung , Hung Albert Y. C. 
Published: September 2002

AbstractIn this study, poly(dimethylsiloxane)urethane–graft–poly(methyl methacrylate) (PDMS urethane–g–PMMA) copolymers with low crosslinking density were synthesized. Glass transition temperatures of the copolymers were investigated by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). Results confirm that PDMS urethane–g–PMMA is miscible in the 2,4‐TDI (2,4‐ toluene diisocyanate) system, whereas it is partially miscible in the m‐XDI (m‐xylene diisocyanate) system. Free, intra‐ (urethane–urethane), and inter‐ (urethane–ester) association hydrogen bonding exist in the urethane group of copolymers. The inter‐association hydrogen bonding can improve the compatibility of the copolymer components. The relationship between the frequency shift and enthalpy confirm the distribution of hydrogen bonding in the macromonomer and copolymer. Ninety percent of the hydrogen bonding is by interassociation in the 2,4‐TDI system. The intra‐association hydrogen bonding in the m‐XDI system is higher than that in the 2,4‐TDI system. Consequently, aggregation may occur easily in the siloxane‐grafted chain in the m‐XDI system. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 962–972, 2002
Self‐affine fractal scaling in fracture surfaces generated in ethylene and propylene polymers and copolymers
Authors: Lapique Fabrice , Meakin Paul , Feder Jens , Jøssang Torstein 
Published: September 2002

AbstractThe fracturing of four different polyolefin materials was studied with the objective of developing a better understanding of the relationships between the morphology of the semicrystalline polymers, the morphology of their fracture surfaces and their mechanical properties. This article is focussed on the quantitative description of the fractures surfaces. The surface structure can be described in terms of self‐affine fractal models, and the Hurst exponent(s) and roughness measurements can be used to describe quantitatively the fracture surface topography. Fracture surfaces generated in homopolymers can be described by a single Hurst exponent, which differs for PE and PP. For copolymers with PE and PP matrices, the Hurst exponent measured on small‐length scales was the same as that obtained for the matrix material, but a crossover to a second regime, with a higher Hurst exponent, was found at longer length scales. The crossover was related to the average distance between rubber particles for the PP/PE rubber phase specimen (PP‐copo). The introduction of a second component seems to modify the crack propagation at long‐length scales, but the propagation at shorter length scales remains unchanged. Environmental stress cracking experiments indicate that each regime can be related to brittle or ductile fracturing processes. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 973–983, 2002
Nonisothermal bulk crystallization of high‐density polyethylene via a modified depolarized light microscopy technique: Further analysis
Authors: Supaphol Pitt , Spruiell Joseph E. 
Published: September 2002

AbstractThe quiescent nonisothermal bulk crystallization kinetics of high‐density polyethylene was investigated with a modified depolarized light microscopy technique, which allowed for studies at average cooling rates of approximately 5–2500 °C min−1. All of the samples crystallized at a pseudoisothermal temperature (i.e., the plateau or crystallization temperature), despite the nonisothermal nature of the cooling conditions. The rate of the crystallization process increased monotonically with increasing the cooling rate and decreasing the crystallization temperature. Moreover, the apparent crystallinity content was a certain decreasing function with the cooling rate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1009–1022, 2002
Synthesis and characterization of functionalized syndiotactic polystyrene copolymers
Authors: Li Chi‐Lan , Chan Shu‐Hua , Ting Ching , Jiang George J. 
Published: September 2002

AbstractFunctionalized syndiotactic polystyrene copolymers were synthesized and characterized. The syndiotactic polystyrene copolymers, poly(styrene‐co‐4‐methylstyrene) (sPSMS), were prepared by styrene with 4‐methylstyrene with a metallocene/methylaluminoxane catalyst. In addition, grafted copolymers, chemically grafted with isoprene onto an sPSMS backbone [poly(styrene‐co‐4‐methylstyrene)‐g‐polyisoprene (sPSMS‐g‐PIP)] were synthesized by anionic grafting polymerization with a metallation reagent. In this study, we also examined the effect of the degree of functionalization (epoxidation) on the polymer structure of the sPSMS‐g‐PIP copolymers. Experimental results indicate that the crystallinity of the sPSMS‐g‐PIP copolymer was lower than that of the ungrafted sPSMS copolymer. Moreover, the epoxy‐containing sPSMS‐g‐PIP copolymer effectively increased the thermal stability more than did the sPSMS‐g‐PIP copolymer alone. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1038–1045, 2002
Morphology of iPP spherulites crystallized in a temperature gradient
Authors: Pawlak Andrzej , Chapel Jean‐Paul , Piorkowska Ewa 
Published: September 2002

AbstractThe influence of temperature gradient on the lamellar structure of isotactic polypropylene spherulites was studied. Polypropylene films were crystallized in a constant temperature gradient of 35 K/mm with the free surface and studied by means of atomic force microscopy and scaning electron microscopy. Samples crystallized isothermally were also prepared and examined for comparison. The results show that the temperature gradient influenced only the alignment of lamellae within spherulites. The lamellae deviated from a radial direction in a stepwise manner. The lamellae became less and less inclined and finally assumed a direction parallel to the temperature gradient. The change of the lamellae alignment in spherulites was the result of the competition of lamellae to fill the space during growth in the temperature gradient. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1318–1328, 2002
Modeling of polymer crystallization in a temperature gradient
Authors: Piorkowska Ewa 
Published: September 2002

AbstractThe crystallization of polymer films in a temperature gradient was simulated. The curvature of lamella growth directions observed experimentally was taken into account. The computer simulation permitted the visualization of the evolution of the spherulitic pattern and also the calculation of the conversion of the melt into spherulites. The mathematical model was also elaborated and allowed the prediction of the kinetics of conversion during the crystallization of polymers in the temperature gradient. A good agreement between the computer simulation results, the mathematical model predictions, and the experimental data for isotactic polypropylene crystallized in a temperature gradient was obtained. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1351–1362, 2002
Structure and properties of isotactic polypropylene oriented by rolling with side constraints
Authors: Bartczak Z. , Morawiec J. , Galeski A. 
Published: September 2002

AbstractThe rolling of isotactic polypropylene (iPP) with a new method of rolling with side constraints (inside a channel) was studied. It was found that deformation processes by compression in a channel die and by rolling with side constraints proceed in very similar fashions (plane‐strain conditions) and result in materials of similar orientations and mechanical properties. The difference between the two processes is that rolling causes the destruction of the lamellar structure at a higher strain than compression. Dynamic mechanical measurements showed that rolling to a high strain produces not only a well‐developed orientation of the crystalline component but also high orientation and transverse ordering of the amorphous phase, leading to its transverse anisotropy. iPP deformed by rolling with side constraints has tensile properties similar to those of iPP deformed by other methods, such as conventional rolling or plane‐strain compression. The elastic modulus and ultimate strength measured along the rolling direction increase with an increasing deformation ratio. For samples deformed to a deformation ratio of 10.4, the ultimate strength reaches 340 MPa and can be further increased by postdeformation annealing. The oriented iPP also demonstrates extremely high impact toughness, especially in the direction of side constraints. Izod impact tests demonstrated that the material fracture on impact is very limited and that the impact strength exceeds 170 kJ/m2. In contrast to the tensile properties, there is an optimum deformation ratio around 5, for which the impact strength is the highest. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1413–1425, 2002
High‐strength uniaxially drawn tapes from scrap recycled poly(ethylene terephthalate)
Authors: Morawiec J. , Bartczak Z. , Pluta M. , Galeski A. 
Published: September 2002

AbstractWe made an effort to develop a manufacturing process for high‐strength packaging straps from recycled poly(ethylene terephthalate) (PET) beverage bottles. High‐strength tapes from low‐viscosity bottle‐grade PET cannot be obtained by single drawing to a natural draw ratio because the strength of such tapes is below expectation. To increase that strength, we developed a double‐drawing process, consisting of a second drawing step after free drawing with the natural draw ratio. The second stretching of tapes proceeded without necking and uniformly over the entire tape length. The extrusion/stretching was performed on the laboratory line, consisting of a single screw extruder, a chill roll, two sets of slow and fast rolls separated by a heating tunnel, and wind‐up roll. The tape drawn to a total draw ratio of 6 had a tensile strength slightly below 700 MPa and an initial slope of ≈ 15 GPa. Strain‐induced crystallization was the origin of strong texture after single drawing, whereas plastic deformation mechanisms of crystals were activated in the second step of drawing: the (100)[001] chain and (100)[010] transverse slips led to clear further refining of (1¯05) X‐ray pole figure. Industrial scale up of the double drawing delivered tapes with strength slightly below 700 MPa. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1426–1435, 2002
Remote hydrogen plasma chemical vapor deposition of silicon–carbon thin‐film materials from a hexamethyldisilane source: Characterization of the process and the deposits
Authors: Wróbel A. M. , Walkiewicz‐Pietrzykowska A. , Klemberg‐Sapieha J. E. , Hatanaka Y. , Aoki T. , Nakanishi Y. 
Published: September 2002

AbstractAmorphous, hydrogenated silicon–carbon (a‐Si:C:H) films were produced by remote hydrogen plasma chemical vapor deposition (RHP‐CVD) with hexamethyldisilane (HMDS) as the starting compound. Microwave hydrogen plasma was the source of the atomic hydrogen active species. The susceptibility of particular bonds in the HMDS molecule toward the initiation step was established with tetramethylsilane as a model compound. The reaction mechanisms proposed for the RHP‐CVD process revealed the important role of polymerization in film growth. The temperature dependence of the film growth rate implied that the investigated RHP‐CVD was a nonthermally activated process. The a‐Si:C:H films produced at different deposition temperatures were characterized in terms of their chemical structure, surface and bulk composition, surface morphology, surface free energy, density, corrosion resistance, mechanical properties (adhesion and hardness), and optical properties (refractive index and optical band gap). The deposition temperature appeared to be a key parameter, precisely controlling the structure and properties of the resulting films. Based on the results of these studies, reasonable structure–property relationships were found. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1445–1458, 2002
Surface plasmon resonance of azobenzene‐incorporated polyelectrolyte thin films as an H+ indicator
Authors: Uznanski Pawel , Pecherz Janusz 
Published: September 2002

AbstractAn azo‐dye‐incorporated polyionene was spin‐coated as thin films on silver evaporated glass substrates. The films were used in conjunction with surface plasmon resonance (SPR) spectroscopy to examine the utility of combining these techniques for optical H+‐ion sensing. A method suggested by Kano and Kawata was used to enhance the sensitivity of the classical SPR measurements toward absorption detection. With the exposure of the composite polyionene films to HCl vapor, changes in the reflectivity signal were obtained in proportion to the concentration of H+ ions and according to the analyzing wavelength. The transformation of the parent azobenzene into the azohydrazone polar form determined the displacement of the absorption band and was the basis for the absorption‐enhanced SPR measurements. The difference in the SPR signals for the neutral sample and that exposed to interaction with HCl was most demonstrated for the wavelength at which the sample spectrum changed from being nonabsorbing to absorbing. The results show that chromophoric polyionenes are good materials for the production of sensitive substrates and can be combined with SPR spectroscopy for the optical sensing of aggressive gaseous species. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1459–1464, 2002
Oriented films from recycled poly(ethylene terephthalate)/recycled high‐density polyethylene compatibilized blends
Authors: Morawiec J. , Krasnikova N. P. , Galeski A. , Pracella M. 
Published: September 2002

AbstractThe process for the compatibilized blending of recycled poly(ethylene terephthalate) and recycled high‐density polyethylene with ethylene/glycidyl methacrylate copolymer was enlarged to the scale of a pilot plant. The addition of a compatibilizer effectively reduced the size of dispersed inclusions with better bonding to the matrix. The optimum contents of the compatibilizer were found to be around 4 pph. The extrusion and orientation of films from the blend were developed on an industrial scale, and the structure and properties of the obtained films were characterized. The crystalline phase of poly(ethylene terephthalate) in oriented films assumed a strong texture resulting from the plane‐strain state of the deformation of the films on the industrial machinery. The origin of the texture was mostly strain‐induced crystallization. The chain segments in the amorphous phase were oriented along the machine direction, but there was significant anisotropy of the chain packing in the amorphous phase in the plane perpendicular to the drawing direction, the pseudohexagonal packing of chain fragments being in register over the whole film. Such a texture of an oriented amorphous phase of poly(ethylene terephthalate) is reported here for the first time. The nonoriented and oriented films obtained with the industrial machinery showed good mechanical properties, with strengths up to 120 MPa and elongations to break of 40%. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 02: 1486–1496, 2002
Anatomy of a successful K–12 educational outreach program in the health sciences: Eleven years experience at one medical sciences campus
Authors: Burns E. Robert 
Published: September 2002

AbstractThe Department of Anatomy and Neurobiology, College of Medicine, University of Arkansas for Medical Sciences (UAMS) is the administrative home of a nationally recognized educational outreach program in the health sciences for K–12 teachers (includes school nurses, counselors, etc.) and students. This program is called the Partners in Health Sciences (PIHS) program. It began in the summer of 1991 and is based on an annual needs assessment of the state's teachers. PIHS is a program available to all teachers and students in the state. It has several different components: (1) a cafeteria of 21 days of mini‐courses offered in the summer to meet the professional development needs of K–12 biology/health teachers and other school personnel; (2) weekly, interactive telecommunication broadcasts for students during the academic year; (3) intensive, 5‐day workshops that train five selected teachers at a time (10 per year) to use an authoring software program to develop grade‐appropriate interactive, computer‐assisted, instructional (CAI) modules for Internet (http://k14education.uams.edu) use by teachers and students; (4) a monthly science night for students and their parents at a local science magnet high school; (5) field trips to the UAMS campus for teachers and their students; (6) community‐requested presentations by program faculty; and (7) availability of earning undergraduate and graduate credit for science education majors in the College of Education, University of Arkansas at Little Rock. The data presented in this report span the period from 1991 through 2001. For all program activities, 14,084 different participants have consumed a total of 50,029 hours of education. Anat Rec (New Anat) 269:181–193, 2002. © 2002 Wiley‐Liss, Inc.
Infective agents in fixed human cadavers: A brief review and suggested guidelines
Authors: Demiryürek Deniz , Bayramoǧlu Alp , Ustaçelebi Şemsettin 
Published: September 2002

AbstractCadavers remain a principal teaching tool for anatomists and medical educators teaching gross anatomy. Infectious pathogens in cadavers that present particular risks include Mycobacterium tuberculosis, hepatitis B and C, the AIDS virus HIV, and prions that cause transmissible spongiform encephalopathies such as Creutzfeldt‐Jakob disease (CJD) and Gerstmann‐Straussler‐Scheinker syndrome (GSS). It is often claimed that fixatives are effective in inactivation of these agents. Unfortunately cadavers, even though they are fixed, may still pose infection hazards to those who handle them. Specific safety precautions are necessary to avoid accidental disease transmission from cadavers before and during dissection and to decontaminate the local environment afterward. In this brief review, we describe the infectious pathogens that can be detected in cadavers and suggest safety guidelines for the protection of all who handle cadavers against infectious hazards. Anat Rec (New Anat) 269:194–197, 2002. © 2002 Wiley‐Liss, Inc.
Adult onset acute myelogenous leukemia and electromagnetic fields in Los Angeles County: Bed‐heating and occupational exposures
Authors: Oppenheimer Mark , Preston‐Martin Susan 
Published: September 2002

AbstractIn a large matched population‐based case‐control study of acute myelogenous leukemia (AML), we did not find incident AML in Los Angeles County (1987–1994) to be associated with previous exposure to electric blankets, electrically heated waterbeds, or occupations with presumed high exposure to electromagnetic fields. Bioelectromagnetics 23:411–415, 2002. © 2002 Wiley‐Liss, Inc.
Current density threshold for the stimulation of neurons in the motor cortex area
Authors: Kowalski T. , Silny J. , Buchner H. 
Published: September 2002

AbstractThe aim of this study was to determine a current density threshold for exciting the motor cortex area of the brain. The current density threshold for excitation of nerve fibres (20 μm in diameter) found in the literature is approximately 1 A/m2at frequencies lower than 1 kHz. In consideration of a safety factor of 100, the International Commission on Non‐Ionizing Radiation Protection (ICNIRP) recommends to restrict the exposure to 0.01 A/m2. The electromagnetic stimulation of neurons in the motor cortex is used in the clinical diagnosis of nerve lesions and neuropathy by means of magnetic or electrical transcranial stimulation. Combining medical data from clinical studies and technical specifications of the Magstim®Model 200 stimulator, we were able to compute the current density threshold for the excitation of the human motor cortex by means of the finite element method (FEM). A 3D‐CAD head model was built on the basis of magnetic resonance imaging (MRI) slices and segmented into four anatomical structures (scalp, skull, brain, and ventricular system) with different conductivities. A current density threshold for the stimulation of the motor cortex area of the upper limbs of 6 and 2.5 A/m2at 2.44 kHz and 50 Hz, respectively, was calculated. As these values lie above the recommended ICNIRP values by two orders of magnitude there is no need for lower safety standards with regard to stimulation of the brain. Bioelectromagnetics 23:421–428, 2002. © 2002 Wiley‐Liss, Inc.
Effect of ultraviolet B radiation and 100 Hz electromagnetic fields on proliferation and DNA synthesis of Jurkat cells
Authors: Nindl G. , Hughes E.F. , Johnson M.T. , Spandau D.F. , Vesper D.N. , Balcavage W.X. 
Published: September 2002

AbstractThe use of ultraviolet B light (UVB) has been proven to be highly effective for treatment of various inflammatory skin diseases, but UVB phototherapy is limited by its carcinogenic side effects. It is necessary to uncover effectors that augment UVB so that similar or improved efficacy can be obtained with lower UVB doses. We found that low frequency, low intensity electromagnetic fields (EMFs) can act as such an effector and synergistically inhibit T lymphocyte proliferation. We first characterized the effects of UVB on Jurkat cells, a model for cutaneous T lymphocytes, and determined UVB's dose dependent inhibition of cell proliferation and induction of apoptosis. Cells exposed to a sublethal UVB dose retained their sensitivity to UVB, but repetitive irradiation seemed to cause accumulation of delayed DNA damage. We then exposed cells to combinations of UVB plus EMFs and found that 100 Hz, 1 mT EMFs decrease DNA synthesis of UVB‐activated Jurkat cells by 34 ± 13% compared to UVB alone. The decrease is, however, most effective when relatively high UVB doses are employed. Since EMFs alone had only a very weak inhibitory effect (10 ± 2%), the data suggest that EMFs augment the cell killing effects of UVB in a synergistic way. These findings could provide the basis for development of new and improved clinical phototherapy protocols. Bioelectromagnetics 23:455–463, 2002. © 2002 Wiley‐Liss, Inc.
Developmental changes in Drosophila melanogaster following exposure to alternating electromagnetic fields
Authors: Mirabolghasemi Ghadire , Azarnia Mahnaz 
Published: September 2002

AbstractThis study investigated the biological effects of alternating electromagnetic fields (EMFs) on developmental stages of Drosophila melanogaster eggs and the first, second and third instar larvae stages. D. melanogaster eggs and larval stages were exposed to a 11 mT 50 Hz field produced by a pair of Helmholtz coils. Each stage was exposed to aEMFs for 2, 4, 6 and 8 h. Features of adult flies such as head, thorax, abdomen and other morphological changes were studied and compared. The frequency of abnormal flies was calculated using statistical methods at P < .05. The results obtained from exposing larvae in different stages of development showed a significant increase in the number of abnormal adult flies, whereas no significant increase was observed in the group arising from eggs exposed to aEMFs. Also, it appeared that duration of exposure correlates with the increase in the number of abnormal flies. There was no significant difference in mortality rate and sex distribution of the abnormal flies between field exposed and the control groups. Bioelectromagnetics 23:416–420, 2002. © 2002 Wiley‐Liss, Inc.