bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessing the accuracy of high‐resolution x‐ray computed tomography of primate trabecular bone by comparisons with histological sections
Authors: Fajardo Roberto José , Ryan T.M. , Kappelman J.
Published: August 2002

Different lines of evidence suggest that trabecular bone architecture contains a functional signal related to an organism's locomotor behavior. An understanding of the interspecific and intraspecific variation in extant nonhuman primate trabecular structure is needed to evaluate its usefulness as a tool to reconstruct the locomotor habits of extinct primates. High‐resolution X‐ray computed tomography (HRXCT) is a new imaging approach with a resolution in the tens of microns that allows nondestructive access to the internal structure of bony elements. Previous studies indicate that such resolution is necessary to accurately quantify structural parameters of trabecular bone.

The primary goal of this study was to test the accuracy of HRXCT by comparing stereological measurements from HRXCT images and histological thin sections of cancellous bone taken from the proximal femur and humerus of baboons. To this end, 11 bone samples were scanned on an HRXCT scanner and then thin‐sectioned to reveal the scanned plane. HRXCT images were thresholded using a modified half‐maximum height protocol. The stereological measurements included bone volume fraction (BV/TV), trabecular number (Tb.N), bone surface to volume ratio (BS/BV), trabecular thickness (Tb.Th), and trabecular spacing (Tb.Sp). The measurement errors on the HRXCT images were 10.90% for BV/TV, 6.06% for Tb.N, 14.19% for BS/BV, 14.33% for Tb.Th, and 7.09% for Tb.Sp, but none of these measurements were significantly different from the histological standards (α = 0.05).

A second goal of this study was to examine the influence of thresholding, a necessary step in any morphometric study using computed tomography, on the accuracy of the quantitative morphometry. Threshold values derived from a modified half‐maximum height protocol showed that parameters derived from the region of interest (area in which stereological measurements were later taken) produced better reconstructions of the actual bone structure than threshold values derived from more inclusive areas of bone.

We conclude that HRXCT can accurately reconstruct the complex architecture of trabecular bone, and that thresholding is a nontrivial step in trabecular bone studies, with even slight changes in the protocol greatly affecting the morphometric data. HRXCT represents a valuable analytical tool that should be of interest to a great many researchers in physical anthropology because it allows nondestructive access to internal morphology, thereby preserving valuable and limited skeletal collections. Am J Phys Anthropol 118:1–10, 2002. © 2002 Wiley‐Liss, Inc.
Selective hippocampal neuron loss in dementia with Lewy bodies
Authors: Harding Antony J. , Lakay Bronwyn , Halliday Glenda M.
Published: August 2002

Hippocampal volume and neuron number were measured using stereological techniques in pathologically confirmed dementia with Lewy bodies (n = 8), Parkinson's disease only (n = 4), and controls (n = 9). We, and others, have previously shown considerable cell loss in the CA1 and subiculum subregions in Alzheimer's disease. In contrast, these regions were spared in dementia with Lewy bodies where a selective loss of lower presubiculum pyramidal neurons was found. These findings suggest a selective loss of frontally projecting hippocampal neurons in dementia with Lewy bodies versus those projecting to temporal lobe regions in Alzheimer's disease.
Novel delta subunit mutation in slow‐channel syndrome causes severe weakness by novel mechanisms
Authors: Gomez Christopher M. , Maselli Ricardo A. , Vohra Bhupinder P. S. , Navedo Manuel , Stiles Joel R. , Charnet Pierre , Schott Kelly , Rojas Legier , Keesey John , Verity Anthony , Wollmann Robert W. , Lasalde‐Dominicci Jose
Published: August 2002

We investigated the basis for a novel form of the slow‐channel congenital myasthenic syndrome presenting in infancy in a single individual as progressive weakness and impaired neuromuscular transmission without overt degeneration of the motor endplate. Prolonged low‐amplitude synaptic currents in biopsied anconeus muscle at 9 years of age suggested a kinetic disorder of the muscle acetylcholine receptor. Ultrastructural studies at 16 months, at 9 years, and at 15 years of age showed none of the typical degenerative changes of the endplate associated with the slow‐channel congenital myasthenic syndrome, and acetylcholine receptor numbers were not significantly reduced. We identified a novel C‐to‐T substitution in exon 8 of the δ‐subunit that results in a serine to phenylalanine mutation in the region encoding the second transmembrane domain that lines the ion channel. Using Xenopus oocyte in vitro expression studies we confirmed that the δS268F mutation, as with other slow‐channel congenital myasthenic syndrome mutations, causes delayed closure of acetylcholine receptor ion channels. In addition, unlike other mutations in slow‐channel congenital myasthenic syndrome, this mutation also causes delayed opening of the channel, a finding that readily explains the marked congenital weakness in the absence of endplate degeneration. Finally, we used serial morphometric analysis of electron micrographs to explore the basis for the progressive weakness and decline of amplitude of endplate currents over a period of 14 years. We demonstrated a progressive widening and accumulation of debris in the synaptic cleft, resulting in loss of efficacy of released neurotransmitter and reduced safety factor. These studies demonstrate the role of previously unrecognized mechanisms of impairment of synaptic transmission caused by a novel mutation and show the importance of serial in vitro studies to elucidate novel disease mechanisms.
A new locus for Parkinson's disease (PARK8) maps to chromosome 12p11.2–q13.1
Authors: Funayama Manabu , Hasegawa Kazuko , Kowa Hisayuki , Saito Masaaki , Tsuji Shoji , Obata Fumiya
Published: August 2002

We performed genomewide linkage analysis of a Japanese family with autosomal dominant parkinsonism, which exhibits clinical features compatible with those of common Parkinson's disease. Parametric two‐point linkage analysis yielded a highest log odds (LOD) score of 4.32 at D12S345 (12p11.21). Parametric multipoint linkage analysis of the 13.6cM interval around this marker yielded LOD scores almost uniformly of >4.0 with a Zmax of 4.71 at D12S85 (12q12). Haplotype analysis detected two obligate recombination events at D12S1631 and D12S339 and defined the disease‐associated haplotype in the 13.6cM interval in 12p11.2–q13.1. This haplotype was shared by all the patients and by some unaffected carriers, suggesting that disease penetration in this family is incomplete. This low penetrance suggests that environmental or other genetic factors modify expression of the disease. Nonparametric two‐point and multipoint linkage analyses, which are penetrance‐independent, yielded Zmax LOD scores of 14.2 and 24.9 at D12S345, respectively, strongly supporting the mapping of the parkinsonism locus in this family to 12p11.23–q13.11. This chromosome region is different from any known locus for hereditary parkinsonism, in keeping with the unique genetic features of the parkinsonism in this family. The nomenclature of PARK8 was assigned to the new locus.
Interferon β‐1a for early multiple sclerosis: CHAMPS trial subgroup analyses
Authors: Beck Roy W. , Chandler Danielle L. , Cole Stephen R. , Simon Jack H. , Jacobs Lawrence D. , Kinkel R. Philip , Selhorst John B. , Rose John W. , Cooper Joanna A. , Rice George , Murray Thomas J. , Sandrock Alfred W.
Published: August 2002

The objective of this work was to assess the effect of interferon β‐1a (Avonex®) on the rate of development of clinically definite multiple sclerosis and brain magnetic resonance imaging changes in subgroups based on type of presenting event, baseline brain magnetic resonance imaging parameters, and demographic factors in the Controlled High‐Risk Subjects Avonex Multiple Sclerosis Prevention Study (CHAMPS) trial. After the onset of a first demyelinating event, 383 patients with brain magnetic resonance imaging evidence of subclinical demyelination were treated with corticosteroids and randomly assigned to receive weekly intramuscular injections of 30μg interferon β‐1a or placebo. The treatment effect within subgroups was assessed in proportional hazards models both for the development of clinically definite multiple sclerosis and for a combined outcome of development of clinically definite multiple sclerosis or >1 new or enlarging T2 lesions on brain magnetic resonance imaging. A beneficial effect of treatment was noted in all subgroups evaluated. Adjusted rate ratios for the development of clinically definite multiple sclerosis in the optic neuritis, brainstem–cerebellar, and spinal cord syndrome subgroups were 0.58 (p = 0.05), 0.40 (p = 0.03), and 0.30 (p = 0.01) and for the development of the combined clinically definite multiple sclerosis/magnetic resonance imaging outcome were 0.50 (p < 0.001), 0.41 (p = 0.001), and 0.40 (p = 0.004), respectively. A treatment benefit on both outcome measures also was seen in subgroups based on baseline brain magnetic resonance imaging parameters, gender, and age. Interferon β‐1a is beneficial when initiated at the first clinical demyelinating event in patients with brain magnetic resonance imaging evidence of subclinical demyelination. The beneficial effect is present for optic neuritis, brainstem–cerebellar syndromes, and spinal cord syndromes.
Alzheimer's disease versus dementia with Lewy bodies: Cerebral metabolic distinction with autopsy confirmation
Authors: Minoshima Satoshi , Foster Norman L. , Sima Anders A. F. , Frey Kirk A. , Albin Roger L. , Kuhl David E.
Published: August 2002

Seeking antemortem markers to distinguish Dementia with Lewy bodies (DLB) and Alzheimer's disease (AD), we examined brain glucose metabolism of DLB and AD. Eleven DLB patients (7 Lewy body variant of AD [LBVAD] and 4 pure diffuse Lewy body disease [DLBD]) who had antemortem position emission tomography imaging and autopsy confirmation were compared to 10 autopsy‐confirmed pure AD patients. In addition, 53 patients with clinically‐diagnosed probable AD, 13 of whom later fulfilled clinical diagnoses of DLB, were examined. Autopsy‐confirmed AD and DLB patients showed significant metabolic reductions involving parietotemporal association, posterior cingulate, and frontal association cortices. Only DLB patients showed significant metabolic reductions in the occipital cortex, particularly in the primary visual cortex (LBVAD −23% and DLBD −29% vs AD −8%), which distinguished DLB versus AD with 90% sensitivity and 80% specificity. Multivariate analysis revealed that occipital metabolic changes in DLB were independent from those in the adjacent parietotemporal cortices. Analysis of clinically‐diagnosed probable AD patients showed a significantly higher frequency of primary visual metabolic reduction among patients who fulfilled later clinical criteria for DLB. In these patients, occipital hypometabolism preceded some clinical features of DLB. Occipital hypometabolism is a potential antemortem marker to distinguish DLB versus AD.
Nanoparticles by chemical synthesis, processing to materials and innovative applications
Authors: Schmidt Helmut
Published: August 2002

Nanoparticles have been fabricated by using chemical synthesis routes under specific conditions. During a precipitation process from liquid phases, surface controlling agents (SCAs) have been added during or shortly after the formation of precipitates. These interfere with the nucleating and growing particle to avoid agglomeration and to control size. Nanoparticles from many systems have been fabricated. If the SCAs are bifunctional, the surfaces chemistry could be tailored and the zeta potential of these particles was tailored also. SiO2 particles have been used for gene targeting using this approach. In other investigations, FeO
x nanoparticles have been surface modified by amino groupings together with a sonochemical route to obtain very stable coatings. These particles have been used for in vitro tumor cell penetration and hyperthermal treatment. Boehmite nanoparticles were used to serve as condensation catalysts to prepare very hard transparent coatings for polycarbonate and an overcoat with polymerizable nanoparticles was used to produce anti‐reflective and ultrahard coatings. In systems with incorporated fluoro silanes, leading to low surface free energy coatings, nanoparticles were used to tailor the fluorine depth profile in self‐aligning transparent easy‐to‐clean coatings by influencing the critical micelle concentration. The examples show the usefulness of the chemical nanoparticle approach for nanocomposite fabrication and the high potential of these materials for medical and industrial application. Copyright © 2001 John Wiley & Sons, Ltd.
Dimethylarsinoylacetate from microbial demethylation of arsenobetaine in seawater
Authors: Khokiattiwong Somkiat , Goessler Walter , Pedersen Søren N. , Cox Raymond , Francesconi Kevin A.
Published: August 2002

The fate of 11 arsenic compounds in microbially enriched seawater was monitored for up to 10 days by HPLC–ICPMS. Most of the arsenicals underwent little or no change in this medium, whereas two of the compounds, arsenobetaine and arsenocholine, were completely degraded. Arsenobetaine (Me3As+CH2COO−), the predominant form of arsenic in marine animals, was transformed within hours, initially to dimethylarsinoylacetate (Me2As(O)CH2COO−) and then to dimethylarsinate (Me2As(O)O−). Arsenocholine behaved similarly but degraded at a slower rate. The identity of the new metabolite, dimethylarsinoylacetate, was confirmed by LC electrospray MS. A repeat experiment with arsenobetaine and dimethylarsinoylacetate, and employing LC electrospray MS to monitor the metabolites, produced results qualitatively identical with those from the first experiment. The rapidity of the degradation processes offers an explanation for the apparent absence of arsenobetaine in natural waters. Copyright © 2001 John Wiley & Sons, Ltd.
Determination of total mercury and monomethylmercury compounds in water samples from Minamata Bay, Japan: an interlaboratory comparative study of different analytical techniques
Authors: Logar M. , Horvat M. , Akagi H. , Ando T. , Tomiyasu T. , Fajon V.
Published: August 2002

Concentration levels of mercury and its organic compounds in natural water samples are very low, so accurate analysis is still a major problem. To ensure the validity of such measurements a proper quality control/quality assurance programme should be implemented. In the absence of reference materials, the best way to check the accuracy of the results is through interlaboratory comparisons and comparisons of the results obtained by different analytical methods. The purpose of the present work was to compare independent analytical techniques used by two different laboratories for determination of total mercury (Hg‐T) and monomethylmercury compounds (MeHg) in seawater samples from Minamata Bay, Japan. The interlaboratory study was carried out between the Jožef Stefan Institute, Ljubljana, Slovenia and the National Institute for Minamata Disease, Minamata, Japan. Copyright © 2001 John Wiley & Sons, Ltd.
Comparison of three methods for the extraction of arsenic compounds from the NRCC standard reference material DORM‐2 and the brown alga Hijiki fuziforme
Authors: Kuehnelt Doris , Irgolic Kurt J. , Goessler Walter
Published: August 2002

The NRCC standard reference material DORM‐2 and the marine brown alga Hijiki fuziforme were extracted with water, methanol/water (9 + 1), and 1.5 M orthophosphoric acid. The extracts from DORM‐2 were analyzed by HPLC–ICP‐MS for arsenobetaine, arsenocholine, trimethylarsine oxide, and the tetramethylarsonium cation and the extracts from H. fuziforme for arsenous acid, arsenic acid, dimethylarsinic acid, methylarsonic acid, and four arsenoriboses. Almost no differences between the three extractants were observed when DORM‐2 was investigated. Only arsenobetaine was slightly better extracted with 1.5 M orthophosphoric acid or methanol/water (9 + 1) than with water. The sum of all extractable compounds (arsenobetaine, the tetramethylarsonium cation, and a formerly unknown compound recently identified as the trimethyl(2‐carboxyethyl)arsonium ion) accounted for 94% of the total arsenic when 1.5 M orthophosphoric acid was used, for 92% when methanol/water (9 + 1) was used, and for 87% when water was used. Significant differences in the extraction yields obtained for the alga were observed for arsenic acid and one of the arsenoriboses (‘glycerol‐ribose’). Orthophosphoric acid removed twice as much of this ribose from the algal material than water and three times more than methanol/water (9 + 1). Arsenic acid was 1.2 times better extracted with orthophosphoric acid than with water and ten times better than with methanol/water (9 + 1). Almost no differences in the extraction yields were found for dimethylarsinic acid and the other three riboses. Orthophosphoric acid extracted 76%, water 65%, and methanol/water 33% of the total arsenic from H. fuziforme. Copyright © 2001 John Wiley & Sons, Ltd.
Identification of [(GS)2AsSe]− in rabbit bile by size‐exclusion chromatography and simultaneous multielement‐specific detection by inductively coupled plasma atomic emission spectroscopy
Authors: Gailer Jürgen , Madden Sean , Buttigieg Gavin A. , Denton M. Bonner , Younis Husam S.
Published: August 2002

An arsenic–selenium metabolite that exhibited the same arsenic and selenium X‐ray absorption near‐edge spectra as the synthetic seleno‐bis(S‐glutathionyl) arsinium ion [(GS)2AsSe]− was recently detected in rabbit bile within 25 min after intravenous injection of rabbits with sodium selenite and sodium arsenite. X‐ray absorption spectroscopy did not (and cannot) conclusively identify the sulfur‐donor in the in vivo sample. After similar treatment of rabbits, we analyzed the collected bile samples by size‐exclusion chromatography (SEC) using inductively coupled plasma atomic emission spectroscopy (ICP‐AES) to monitor arsenic, selenium and sulfur simultaneously. The bulk of arsenic and selenium eluted in a single peak, the intensity of which was greatly increased upon spiking of the bile samples with synthethic [(GS)2AsSe]−. Hence, we identify [(GS)2AsSe]− as the major metabolite in bile after exposure of rabbits to selenite and arsenite. The reported SEC–ICP‐AES method is the first chromatographic procedure to identify this biochemically important metabolite in biological fluids and is thus a true alternative to X‐ray absorption spectroscopy, which is not available to many chemists. Copyright © 2001 John Wiley & Sons, Ltd.
Enzymatic degradation of blends of poly(ε‐caprolactone) and poly(styrene‐co‐acrylonitrile) by Pseudomonas lipase
Authors: Cho Kilwon , Lee Jaeyoung , Xing Pexiang
Published: August 2002

In polymer blends, the composition and microcrystalline structure of the blend near surfaces can be markedly different from the bulk properties. In this study, the enzymatic degradation of poly(ε‐caprolactone) (PCL) and its blends with poly(styrene‐co‐acrylonitrile) (SAN) was conducted in a phosphate buffer solution containing Pseudomonas lipase, and the degradation behavior was correlated with the surface properties and crystalline microstructure of the blends. The enzymatic degradation preferentially took place at the amorphous part of PCL film. The melt‐quenched PCL film with low crystallinity and small lamellar thickness showed a higher degradation rate compared with isothermally crystallized (at 36, 40, and 44°C) PCL films. Also, there was a vast difference in the enzymatic degradation behavior of pure PCL and PCL/SAN blends. The pure PCL showed 100% weight loss in a very short time (i.e., 72 h), whereas the PCL/SAN blend containing just 1% SAN showed ∼50% weight loss and the degradation ceased, and the blend containing 40% SAN showed almost no weight loss. These results suggest that as degradation proceeds, the nondegradable SAN content increases at the surface of PCL/SAN films and prevents the lipase from attacking the biodegradable PCL chains. This phenomenon was observed even for a very high PCL content in the blend samples. In the blend with low PCL content, the inaccessibility of the amorphous interphase with high SAN content prevented the attack of lipase on the lamellae of PCL. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 868–879, 2002
Thermal and rheological studies on the molecular composition and structure of metallocene‐ and Ziegler–Natta‐catalyzed ethylene–α‐olefin copolymers
Authors: Starck P. , Malmberg A. , Löfgren B.
Published: August 2002

The relationship between the molecular structure and the thermal and rheological behaviors of metallocene‐ and Ziegler–Natta (ZN)‐catalyzed ethylene copolymers and high‐density polyethylenes was studied. Of special interest in this work were the differences and similarities of the metallocene‐catalyzed (homogeneous) polymers with conventional coordination‐catalyzed (heterogeneous) polyethylenes and low‐density polyethylenes. The short‐chain branching distribution was analyzed with stepwise crystallization by differential scanning calorimetry and by dynamic mechanical analysis. The metallocene copolymers exhibited much more effective comonomer incorporation in the chain than the ZN copolymers; they also exhibited narrower lamellar thickness distributions. Homogeneous, vanadium‐catalyzed ZN copolymers displayed a very similar comonomer incorporation to metallocene copolymers at the same density level. The small amplitude rheological measurements revealed the expected trend of increasing viscosity with weight‐average molecular weight and shear‐thinning tendency with polydispersity for the heterogeneous linear low‐density polyethylene and very‐low‐density polyethylene resins. The high activation energy values (34–53 kJ/mol) and elevated elasticity found for some of our experimental metallocene polymers suggest the presence of long‐chain branching in these polymers. This was also supported by the comparison of the relationship between low shear rate viscosity and molecular weight. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1140–1156, 2002
Reinforcement of poly(dimethylsiloxane) networks by montmorillonite platelets
Authors: Osman Maged A. , Atallah Ayman , Kahr Günter , Suter Ulrich W.
Published: August 2002

A PDMS network, synthesized from a vinyl‐terminated precursor, was reinforced by plate‐like montmorillonite (volclay) particles with different surface cations. The optimal ratio of crosslinker‐to‐PDMS precursor was ascertained from the mechanical properties of networks prepared with different crosslinker concentrations. The elastic modulus of the polymer was enhanced by the montmorillonite particles. The increase in modulus was higher in the Li– than in the Na–volclay composites. The ultimate strength of the composites was also strongly enhanced by the small platelets, especially in presence of surface Li+. The stronger influence of Li–volclay on the mechanical properties of the composites can be attributed to the partial formation of an intercalated structure, which leads to thinner particles with a high aspect ratio. Both composite strength and modulus were proportional to the filler‐volume‐fraction, but the increase in strength was limited by rising particle agglomeration at high loading. In contrast to organic‐modified montmorillonite, the inorganic surface of volclay catalyzed the thermal degradation of PDMS. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2175–2183, 2002
Mechanism of migration from agglomerated cork stoppers: I. An electron spin resonance investigation
Authors: Six Thérèse , Feigenbaum Alexandre , Riquet Anne‐Marie
Published: August 2002

Related to the study of interactions between food and packaging, migration from agglomerated cork stoppers was studied by electron spin resonance. Paramagnetic probes were incorporated separately in the adhesive or in the cork granules. The finished cork was obtained by an individual molding procedure. The behavior of aminoxyl probes, differing by their functional groups, was studied. Free probes, initially incorporated into the adhesive phase, partitioned into cork during processing. Their migration occurred from both the cork and the adhesive phases. With amino‐TEMPO, a probe covalently bonded to the adhesive phase, it was possible to study the penetration of the alcoholic simulant of wine (12% ethanol) into the whole structure of the cork and to demonstrate that strong swelling took place. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2644–2654, 2002
Correlation among crystalline morphology of PEEK, interface bond strength, and in‐plane mechanical properties of carbon/PEEK composites
Authors: Gao Shang‐Lin , Kim Jang‐Kyo
Published: August 2002

The effect of the cooling rate on in‐plane and interlaminar properties of carbon fiber/semicrystalline PEEK matrix composites was studied. Strengths and moduli were measured in tension, flexure, and interlaminar shear, all of which were shown to correlate, to different degrees, with the fiber–matrix interface adhesion and the bulk matrix properties. The in‐plane and interlaminar properties, in general, increased with a decreasing cooling rate, which was attributed to changes in the failure mechanism from adhesive failure involving fiber–matrix interface debonding at high cooling rates to matrix‐dominant cohesive failure at low cooling rates. The present study demonstrates that the mechanical properties of semicrystalline thermoplastic composites can be tailored for desired applications by controlling the processing conditions, especially the cooling rate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1155–1167, 2002; DOI 10.1002/app.10406
Orientation and crystallinity in film casting of polypropylene
Authors: Lamberti Gaetano , Brucato Valerio , Titomanlio Giuseppe
Published: August 2002

In the cast film process a polymer melt is extruded through a slit die, stretched in air, and cooled on a chill roll. During the path in air the melt cools while being stretched. Film casting experiments were carried out with an isotactic polypropylene resin. The temperature and width distributions were measured along the draw direction. Further, the crystallinity and Hermans orientation factor were measured on the final film. The process was described by a simple thermomechanical model derived elsewhere. The evolution of the molecular orientation parameters was calculated on the basis of a dumbbell model coupled with velocity and temperature distributions provided by the thermomechanical model. The experimental crystalline orientations of the final films collapsed into a single step‐shaped curve (from low to high orientation) if plotted versus the stress calculated by the model at the frozen line. The experimental values of the crystallinity and Hermans orientation factors are discussed on the basis of predictions of the dumbbell model for melt orientation at the frozen line and the crystallinity data obtained in quiescent conditions under the same cooling rate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1981–1992, 2002; DOI 10.1002/app.10422
Mechanical properties of natural rubber filled with flyash
Authors: Hundiwale D. G. , Kapadi U. R. , Desai M. C. , Bidkar S. H.
Published: August 2002

The mechanical properties of flyash‐filled natural rubber were investigated and compared with those filled with calcium carbonate. A number of composites with varying percentage of the fillers were prepared using a two‐roll mill and molded on compression molding press. Specimens were subjected to mechanical testing. The properties studied were tensile strength, modulus at various elongations, hardness, density, etc. From the results it was observed that flyash‐filled composites were better in mechanical properties compared to those filled with calcium carbonate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 995–1001, 2002
Hardness evaluation of epoxy resin filled with mineral waste
Authors: D'Almeida J. R. M. , Manfredini B. H. P.
Published: August 2002

The care of the world environment poses many challenges to the proper disposal of mineral wastes. Particulate wastes can be used to modify the properties or lower the cost of polymers. The influence of an iron–silica rich waste on the hardness of an epoxy resin is evaluated in this work. It is shown that the hardness values are polymer dominated for volume fractions of waste lower than 0.30, but for higher volume fractions a useful increase in the hardness numbers can be achieved. The coarser the particles are the more heterogeneous is the microstructure of the composite. Nevertheless, particulate rich layers increase the hardness of the material several times. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2178–2184, 2002
Morphology and micromechanical deformation behavior of SB‐block copolymers. II. Influence of molecular architecture of asymmetric star block copolymers
Authors: Adhikari R. , Michler G. H. , Lebek W. , Goerlitz S. , Weidisch R. , Knoll K.
Published: August 2002

The influence of molecular architecture on morphology, mechanical properties, and micromechanical deformation behavior of asymmetric styrene/butadiene star block copolymers is investigated by transmission electron microscopy (TEM) and uniaxial tensile testing. In contrast to diblock copolymers, star block copolymers having 74% polystyrene (PS) show a lamellar morphology. Furthermore, tapered asymmetric star block copolymers having a PS core reveal additional PS domains inside the PB lamellae not observed in untapered star block copolymers. The introduction of tapered sequences in star block copolymers results in a significant improvement of tensile properties due to the increased interfacial width between the phases as well as differences in morphology. The investigated star block copolymers show a homogeneous plastic deformation of PS lamellae. This mechanism is called thin‐layer yielding of PS lamellae. The lamellae are locally deformed via inhomogeneous necking and drawing. Lamellae which are not oriented parallel to the load direction are twisted to the deformation direction. Neat star block copolymers (without tapered chains) exhibit a premature failure of PS lamellae arising from the decreased interfacial width, which results in a decrease of their ultimate strain. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 701–713, 2002
Seeded dispersion polymerization
Authors: Wang Danni , Dimonie Victoria L. , Sudol E. David , El‐Aasser Mohamed S.
Published: August 2002

Micron‐size poly(n‐butyl acrylate) (PBA) and polystyrene (PSt) particles were used as seed in second‐stage seeded dispersion polymerizations. The effects of various polymerization parameters on the morphology of the structured particles resulting from the second‐stage seeded dispersion polymerizations were studied, and a series of uniform micron‐size structured particles was successfully prepared. In addition to the polymerization medium, the type of stabilizer (i.e., the molecular weight of the polyvinylpyrrolidone [PVP] stabilizer) that was used in the seed preparation and the subsequent seeded dispersion polymerization was found to be important. The final outcome of a seeded dispersion polymerization, that is, the morphology of the structured particles and the formation of secondary particles, was found to be primarily governed by thermodynamic factors. It was also found that the latex particles in these dispersion systems are virtually stabilized by the small amount of grafted PVP molecules. The dispersions maintain colloidal stability after repeated washing of the particles, which removes all of the soluble PVP. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2710–2720, 2002
Influence of vinyl ester/styrene network structure on thermal and mechanical behavior
Authors: Shan L. , Robertson C. G. , Verghese K. N. E. , Burts E. , Riffle J. S. , Ward T. C. , Reifsnider K. L.
Published: August 2002

The influence of vinyl ester/styrene network structure on thermal and mechanical properties was investigated. The crosslink density of the resins was altered by changing the molecular weight of the vinyl ester oligomer and by varying the amount of styrene used during the crosslinking reaction leading to variations in both the physical network structure and the chemical composition of the polymeric networks. The glass transition temperatures of the network polymers were found to increase systematically with increasing crosslink density without the additional influence of the chemical composition as determined from both differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The breadth of the glass transition regions increased with crosslink density for the DSC data, but the breadth assessed from the DMA data did not vary significantly for the network materials. A secondary relaxation was observed for the materials using DMA, and this relaxation did not appear to be significantly affected by changes in either the crosslink density or the composition of the network. Cooperativity studies involving time–temperature scaling of dynamic mechanical data in the glass formation temperature region were also conducted. The degree of segmental cooperativity at Tg appeared to be primarily influenced by the chemical composition of the networks. These issues dealing with the structure of the networks provided insight into the associated fracture properties in the glassy state (ambient temperature). Specifically, an empirically based linear correlation was found between the fracture toughness of the networks and the cooperative domain size at the glass transition temperature normalized by the crosslink density. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 917–927, 2001
Hydrolysis, polycondensation, and catalytic properties of Ru(II) complex of 3‐4,5‐dihydroimidazol‐1‐yl‐propyltriethoxysilane
Authors: Seçkin Turgay , Özdemir İsmail , Çetinkaya Bekir
Published: August 2002

The preparation and measurements of some properties of organic–inorganic hybrid materials derived from Ru(II)‐3‐4,5‐dihyroimidazol‐1‐yl‐propyltriethoxysilane inside a polysiloxane network have been achieved. The hydrolysis and polycondensation of Ru(II)‐3‐4,5‐dihyroimidazol‐1‐yl‐propyltriethoxysilane were performed in different experimental conditions, producing a new organic–inorganic silica. The alkoxysilyl groups available were used for the construction of inorganic backbone by the sol‐gel process, and the imidazole group was found suitable for incorporating Ru(II) by coordination. The coordination of metal complex is retained because there is no leaching from the metal complex containing gels. To ensure sufficient catalytic properties, a series of hybrid materials from tetraethoxysilane was prepared. These materials were identified and catalytic activities were tested for cyclization of (Z)‐3‐methylpent‐2‐en‐4‐yn‐1‐ol to 2,3‐dimethylfuran. Heterogeneous Ru(II) catalyst can also be recycled and reused without significant loss of selectivity or activity. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1329–1334, 2001
Photoaging and stabilization of rigid PVC/wood‐fiber composites
Authors: Matuana Laurent M. , Kamdem Donatien P. , Zhang Jun
Published: August 2002

Ultraviolet (UV) weathering performance of unpigmented and rutile titanium dioxide pigmented rigid polyvinyl chloride (PVC)/wood‐fiber composites has been studied. The composite samples were manufactured by dry‐blending PVC, wood fibers, and other processing additives in a high‐intensity mixer. The dry‐blended compounds were extruded and compression molded into panel samples. The manufactured samples were artificially weathered using laboratory accelerated UV tests. Composite samples were exposed to 340‐nm fluorescent UV lamps and assessed every 200 h, for a total of 1200 h of accelerated weathering. Each assessment consisted of a visual examination of surface roughness or erosion, a contact angle measurement, a FTIR collection, and a color measurement. The experimental results indicated that wood fibers are effective sensitizers and that their incorporation into a rigid PVC matrix has a deleterious effect on the ability of the matrix to resist degradation caused ultraviolet irradiation. The light stability of these composites could be improved quite efficiently with the addition of rutile titanium dioxide photoactive pigment during formulation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1943–1950, 2001
Crystallization of Nylon 11 under compressive high strain rates
Authors: Fernandez J. O. , Swallowe G. M. , Lee S. F.
Published: August 2002

The mechanical behavior of semicrystalline Nylon 11 was studied at strain rates between 10−3 and 8800 s−1. X‐ray diffraction and DSC were employed to examine the crystal structure and the crystallinity content. The as‐received material comprised a mixed structure of a predominately triclinic (α) form. DSC revealed that the material gave rise to two melting peaks. The compressive flow stress of Nylon 11 experienced a large increase at 1200 s−1 and decreased at higher strain rates. The maximum level of the flow stress corresponded with a higher level of crystallinity and a structure mainly of a pseudohexagonal form. The subsequent drop in stress at higher rates was associated with a decrease in the crystallinity content and a mixed crystal structure, different from that observed in the as‐received material. After compression, the low melting peak disappeared and the material melted over an increased temperature range. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2031–2038, 2001
On oxidation and adhesion of copper‐filled PE
Authors: Lin D. G. , Vorobieva E. V.
Published: August 2002

The IR‐spectroscopy and MVCIR technique were used to study the role of technological factors (filler content, film thickness) in oxidation of polyethylene coatings filled with copper powder. It was learned that copper powder introduced into polyethylene reduces the ultimate level of oxidation of both the outer surface layer and deep‐seated layers of the polymer; also, the layer thickness of the specimens oxidized at diffusion conditions was observed to be decreased. Besides, the oxidation gradient determined through the specimen thickness was decreased on increasing the filler content. For example, with copper concentration over 3 vol %, the ultimate level of oxidation within the polymer layer that undergoes diffusive oxidation remains unchanged. The filler exerts its influence on bonding of the coatings, first of all through variations in the oxidation level of the polymer layer bordering on the substrate. For example, at the filler concentration above 3 vol %, the achievable level of adhesional strength does not depend on the coat thickness (the coat thickness being smaller than that of the diffusively oxidized layer). In thicker coatings, oxidative transformations do not, in fact, take place in the zone of adhesional contact, and the adhesion strength remains unchanged during thermal treatment. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2047–2052, 2001
Rheological study of crosslinking and gelation in bismaleimide/cyanate ester interpenetrating polymer network
Authors: Hu Xiao , Fan Jing , Yue Chee Yoon
Published: August 2002

In searching for high performance polymer resins that have a combination of low dielectric constant and loss, high temperature resistance, ease of being processed, and other desirable properties, an interpenetrating polymer network (IPN) based on cyanate ester (CE) and 2,2′‐diallylbisphenol A (DBA) modified bismaleimide resin (BMI) was prepared via prepolymerization followed by thermal curing. This work discusses the use of multiple waveform rheological technique to investigate the crosslinking and gelation behavior of this resin system at various temperatures. The gel point can be accurately determined from a single experiment using this technique. At the point of gelation, both the storage modulus (G′) and loss modulus (G″) of the IPN follow a similar power law equation with oscillation frequency used in the rheological measurement. Both the relaxation exponent n, a viscoelastic parameter related to the cluster size of the gel, and gel strength S, related to the mobility of the crosslinked chain segments, were determined via a curve fitting method. Both n and S were found to be temperature dependent in this BMI/DBA–CE IPN system. The apparent activation energy of gelation or curing reaction was found to be approximately 47.6 kJ/mol. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2437–2445, 2001
Physical properties of PP‐g‐AA prepared by melt extrusion and its effects on mechanical properties of PP
Authors: Mai Kancheng , Li Zhengjun , Zeng Hanmin
Published: August 2002

Polypropylene grafting with acrylic acid, PP‐g‐AA (FPP), was prepared by melt extrusion. The physical properties of FPP and effect of FPP on mechanical properties of polypropylene (PP) were investigated. Experimental results showed that an increase in the grafting rate of FPP resulted in an increase in the crystallization peak temperature, melt peak temperature, and degree of crystallization of PP. Double melting peaks were observed for OPP prepared by adding dicumyl peroxide into PP and FPP with low grafting rate due to the degradation of PP. As the grafting rate was increased, the double melt peaks converted into a single melt peak. It is suggest that FPP with higher grafting rate resulted in enhanced nucleation and crystallization ability of PP. The grafting of AA onto the PP chain improved the thermal stability and mechanical properties of PP materials. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2609–2616, 2001
Graft copolymerization of PU membranes with acrylic acid and crotonic acid using benzoyl peroxide initiator
Authors: Pulat Mehlika , Babayiğit Doğan
Published: August 2002

To improve water wettability of polyurethane (PU), graft copolymerization with acrylic acid (AA) and crotonic acid (CA) was performed using a benzoyl peroxide (BO) initiator. The grafting reaction was carried out by placing the membranes in aqueous solutions of AA and CA at constant temperatures. Variations of graft yield with time, temperature, initiator, and monomer concentrations were investigated. The optimum temperature, polymerization time, monomer, and initiator concentrations for AA were found to be 70°C; 3 h; 1.5 M; 5.0 × 10−2 M, and for CA 70°C; 1 h; 1.5 M; 4.0 × 10−2 M, respectively. The grafting membranes were characterized by FTIR spectroscopy and scanning electron microscopy (SEM) analysis, and the effect of grafting on equilibrium water content (EWC) of PU membranes was obtained by swelling measurements. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2690–2695, 2001
Peroxosalts initiated graft copolymerization of aniline onto rayon fiber—A kinetic approach
Authors: Anbarasan R. , Jayaseharan J. , Sudha M. , Devi J. Lakshmi , Nirmala P. V. , Gopalan A.
Published: August 2002

Oxidative chemical polymerization of aniline was carried out using peroxydisulphate and peroxomonosulphate as a lone initiator in an aqueous acidic medium in the presence of Rayon fiber. The Rayon fiber was tested for the chemical grafting of polyaniline onto it. The content of polyaniline (wt %) in the backbone was found to vary while varying the [M], [I], and (amount of Rayon fiber) during the polymerization of aniline. Various graft parameters like rate of grafting, % grafting, and % efficiency were calculated. Rate of homopolymerization was also followed for both cases. The chemical grafting was confirmed using FTIR spectroscopy, cyclic voltammetry, weight loss study, and conductivity measurements. Probable mechanism has been proposed to explain the experimental results obtained. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 468–478, 2001
Mechanical properties and superstructure of isotactic polypropylene fibers prepared by continuous vibrating zone‐drawing
Authors: Suzuki Akihiro , Sugimura Toshio , Kunugi Toshio
Published: August 2002

A continuous vibrating zone‐drawing (CVZD) was applied to study the effect of vibration on the mechanical properties and superstructure of isotactic polypropylene fibers. The CVZD treatment was a new drawing method by which the fiber was continuously drawn at a rate of 0.5 m/min under vibration using the specially designed apparatus. The CVZD treatment was carried out in five steps at a drawing temperature of 150°C and a frequency of 100 Hz, and applied tensions increased step by step with processing in the range of 14.8 to 207 MPa. The obtained fiber had a birefringence of 0.0373, crystallinity of 62.4%, tensile modulus of 17.6 GPa, and tensile strength of 1.11 GPa. These values are higher than those of the continuous zone‐drawn isotactic polypropylene fiber previous reported. The vibration added to the fibers during the zone‐drawing was effective in developing amorphous orientation and improving the mechanical properties. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 600–608, 2001
Synthesis, characterization of polyacrylate‐g‐carbon black and its application to soap‐free waterborne coating
Authors: Li Wei , Xie Zhiming , Li Zhuomei
Published: August 2002

Polyacrylate‐g‐Carbon Black (abbrev. as gCB) was prepared by free radical polymerization of acrylate monomers on the carbon black surface, which was initiated by a redox system consisting of cerium ammonium nitrate and hydroxymethyl carbon black. gCB was ascertained by X‐ray Photoelectron Spectrometry (XPS). The optimum conditions of synthesis were studied. The stabilities of gCB dispersing in water were studied by zeta potential measurement and spectrophotometric analysis. The results showed that gCB could disperse in water better than the ungrafted carbon black. gCB could be dispersed in the soap‐free hydrosol forming a colored soap‐free water‐borne coating with satisfactory comprehensive performance. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1100–1106, 2001
Adsorption of blood proteins on glow‐discharge‐modified polyurethane membranes
Authors: Kayirhan Nesrin , Denizli Adil , Hasirci Nesrin
Published: August 2002

Polyurethanes are a class of polymers that have a wide range of applications in the medical field although their blood compatibility still needs improvement. In order to obtain medical purity, this study prepared membrane‐form polyurethanes from toluene 2,4‐diisocyanate (TDI) and poly(propylene ethylene glycol) without the addition of any ingredients such as solvents, catalysts, or chain extenders. The aim was to increase surface hydrophilicity and improve blood compatibility. Therefore, the prepared membranes were modified by treatment with oxygen or argon plasmas. Characterizations of the samples were achieved by contact‐angle and water‐uptake studies as well as from atomic force microscope (AFM) pictures. It was found that oxygen‐modified samples were more hydrophilic than argon‐modified samples. The AFM images showed that surface roughness increased with plasma treatment. The protein adsorption experiments carried out with single protein solutions demonstrated that the adsorption of bovine serum albumin and fibrinogen decreased drastically by increasing the applied power and exposure time of the glow discharge. A similar decrease in the adsorption of protein was also observed for human blood proteins. The alterations of the conformational structures of the adsorbed proteins were examined by fluorescence spectrophotometry. Similar spectra with the same maximum wavelength were observed for native and desorbed proteins. These results showed that no denaturation of the proteins occurred upon adsorption on the surfaces of the prepared membranes. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1322–1332, 2001