bluuebunny/crossref_metadata_2025 huggingface dataset:
Paris‐Trousseau syndrome platelets in a child with Jacobsen's syndrome
Authors: Krishnamurti L. , Neglia J.P. , Nagarajan R. , Berry S.A. , Lohr J. , Hirsch B. , White J.G.
Published: August 2002

The thrombocytopenia in an infant with clinical features of Jacobsen's syndrome characterized by multiple congenital anomalies, cardiac defects, psychomotor retardation, and deletion of chromosome 11 at 11q23.3 has been evaluated. Study of his platelets in the electron microscope revealed giant alpha granules in his cells identical in appearance to those reported in the family with Paris‐Trousseau syndrome. As a result, the Paris‐Trousseau syndrome appears to be a variant of the Jacobsen syndrome, and the thrombocytopenia observed in all cases of chromosome 11q23.3 deletion due to dysmegakaryopoieses. Giant alpha granules are frequently observed in normal platelets during long‐term storage and may form in Jacobsen and Paris‐Trousseau platelets during prolonged residence in the bone marrow. Am. J. Hematol. 66:295–299, 2001. © 2001 Wiley‐Liss, Inc.
Evolutionary approach to below replacement fertility
Authors: Kaplan Hillard , Lancaster Jane B. , Tucker W. Troy , Anderson K.G.
Published: August 2002

The large human brain, the long period of juvenile dependence, long life span, and male support of reproduction are the co‐evolutionary result of the human niche based on skill‐intensive techniques of resource accrual. The regulation of fertility under traditional conditions is based upon a co‐evolved psychology and physiology where adjustments of investment in offspring depend upon the returns to skill and mortality hazards. When all wealth is somatic, the hormonal system controlling ovulation and implantation translates income into genetic descendants. In modern society the existence of extra‐somatic wealth is a critical condition to which our evolved proximate physiological mechanisms do not respond. However, psychological mechanisms regulating parental investment in offspring quality may lead to greater and greater investment in own and offspring education, a smaller desired family size, a delay in the onset of reproduction, and a reduction in the total numbers of offspring produced. This delay in reproduction can cause many individuals to produce fewer children than desired because fecundity falls during the reproductive part of the life course. As more individuals in a society follow this pattern, more will fail to reach their desired family size. At the same time the effective use of birth control decreases the numbers of families producing more children than desired. Below replacement fertility can result. Predictions from this model were tested using data from the National Survey of Families and Households and the Albuquerque Men study. Am. J. Hum. Biol. 14:233–256, 2002. © 2002 Wiley‐Liss, Inc.
An evolutionary ecological perspective on demographic transitions: Modeling multiple currencies
Authors: Low Bobbi S. , Simon Carl P. , Anderson Kermyt G.
Published: August 2002

Life history theory postulates tradeoffs of current versus future reproduction; today women face evolutionarily novel versions of these tradeoffs. Optimal age at first birth is the result of tradeoffs in fertility and mortality; ceteris paribus, early reproduction is advantageous. Yet modern women in developed nations experience relatively late first births; they appear to be trading off socioeconomic status and the paths to raised SES, education and work, against early fertility. Here, [1] using delineating parameter values drawn from data in the literature, we model these tradeoffs to determine how much socioeconomic advantage will compensate for delayed first births and lower lifetime fertility; and [2] we examine the effects of work and education on women's lifetime and age‐specific fertility using data from seven cohorts in the Panel Study of Income Dynamics (PSID). Am. J. Hum. Biol. 14:149–167, 2002. © 2002 Wiley‐Liss, Inc.
Performance of cochlear implant recipients with GJB2‐related deafness
Authors: Green Glenn E. , Scott Daryl A. , McDonald Joshua M. , Teagle Holly F.B. , Tomblin Bruce J. , Spencer Linda J. , Woodworth George G. , Knutson John F. , Gantz Bruce J. , Sheffield Val C. , Smith Richard J.H.
Published: August 2002

Congenital profound hearing loss affects 0.05–0.1% of children and has many causes, some of which are associated with cognitive delay. For prelingually‐deafened cochlear implant recipients, the etiology of deafness is usually unknown. Mutations in GJB2 have been established as the most common cause of heritable deafness in the United States. In this report, we identify cochlear implant recipients with GJB2‐related deafness and examine the performance of these individuals. Cochlear implant recipients received a battery of perceptive, cognitive, and reading tests. Neither subjects nor examiners knew the etiology of deafness in these individuals. The implant recipients were then examined for mutations in GJB2 using an allele‐specific polymerase chain reaction assay, single‐strand conformation polymorphism analysis, and direct sequencing. GJB2 mutations were the leading cause of congenital deafness among the cochlear implant recipients screened. Cochlear implant recipients with GJB2‐related deafness read within one standard deviation of hearing controls better than other congenitally deaf cochlear implant recipients and non‐cochlear implant recipients. Individuals with congenital deafness should be offered GJB2 screening. Positive results establish an etiologic diagnosis and provide prognostic, genetic, and therapeutic information. Effective rehabilitation for profoundly deaf individuals with GJB2‐related deafness is possible through cochlear implantation. © 2002 Wiley‐Liss, Inc.
Family‐based association study of serotonin transporter promoter in suicidal adolescents: No association with suicidality but possible role in violence traits
Authors: Zalsman Gil , Frisch Amos , Bromberg Michal , Gelernter Joel , Michaelovsky Elena , Campino Alon , Erlich Zippy , Tyano Samuel , Apter Alan , Weizman Abraham
Published: August 2002

The serotonin transporter–linked promoter region polymorphism (5‐HTTLPR) is thought to be associated with some serotonin dysfunction–related psychopathologies such as depression and anxiety disorders. Suicide and suicide‐related behaviors such as violence, aggression, and impulsivity have been reproducibly associated with serotonin dysfunction and are partially genetic. This study examined the association of 5‐HTTLPR with suicidal behavior and related traits in Israeli suicidal adolescent inpatients using the haplotype relative risk (HRR) method that controls for artifacts caused by population stratification. Forty‐eight inpatient adolescents who recently attempted suicide were assessed by structured interviews for detailed clinical history, diagnoses, suicide intent, suicide risk, impulsivity, violence, and depression. Blood samples were collected and DNA extracted from patients and their biological parents. The 5‐HTTLPR allele frequencies were tested for association with suicidality by the HRR method. In addition, the relationship between genotypes and phenotypic severity of several clinical parameters was analyzed. No significant allelic association of the 5‐HTTLPR polymorphism with suicidal behavior was found (chi square = 0.023; P = 0.88). Analysis of variance of the suicide‐related trait measures for the three genotypes demonstrated a significant difference in violence measures between patients carrying the LL and LS genotypes (9.50±4.04 vs. 5.36±4.03; P = 0.029). This study suggests that the 5‐HTTLPR polymorphism is unlikely to have major relevance to the pathogenesis of suicidal behavior in adolescence but may contribute to violent behavior in this population. © 2001 Wiley‐Liss, Inc.
Investigation of association of 13 polymorphisms in eight genes in southeastern African American Alzheimer disease patients as compared to age‐matched controls
Authors: Perry Rodney T. , Collins Julianne S. , Harrell Lindy E. , Acton Ronald T. , Go Rodney C.P.
Published: August 2002

Alzheimer disease (AD) is an emotionally devastating and exceptionally costly disease. Apolipoprotein E (APOE) is a major risk factor gene for AD regardless of age of onset or family history. However, this association may not be as strong or consistent in ethnic groups such as African Americans, raising the possibility of other modifier gene(s). In a group of African American AD patients, a significantly increased risk of AD was associated with two E4 alleles (OR = 5.6; 95% CI = 1.5–21.0) or one E4 allele (OR = 2.5; 95% CI = 1.3–5.0) when compared to E3/E3 genotype, and there was a significant lowering of age of onset for affecteds with E4/E4 genotype as compared to one E2 allele (P = 0.02) or all others (P = 0.03). We also found a significant increase in age of onset with the −308 #2 (A) allele of TNF when compared to AD cases with no #2 allele. A significant increase in age was also demonstrated with the #2 allele (99 base pairs) of the microsatellite TNFa, located ∼ 10.5 kb upstream of TNF. When these two alleles were combined with the TNF −238G (#1) allele to give a haplotype, the significant increase in age was still demonstrated. Polymorphisms in the APOE promoter and six other candidate genes did not appear to demonstrate any significant association with our African American AD patients. Our results confirm the established association of APOE4 to AD observed in several ethnic groups, including African Americans. In addition, TNF appears to have some modifying effect in AD, primarily on age of onset, or it could be in linkage disequilibrium with a modifier locus nearby. © 2001 Wiley‐Liss, Inc.
Paleopathological and biomolecular study of tuberculosis in a medieval skeletal collection from England
Authors: Mays S. , Taylor G.M. , Legge A.J. , Young D.B. , Turner‐Walker G.
Published: August 2002

Nine human skeletons of medieval date from a rural English burial site show signs of skeletal tuberculosis. They were subject to polymerase chain reaction (PCR) assays aimed at detecting traces of DNA from infecting mycobacteria, with the purpose both of confirming the paleopathological diagnosis of tuberculosis and determining in individual cases whether disease was due to M. tuberculosis or M. bovis. In all nine cases, evidence for M. tuberculosis complex DNA was found, and in all instances it appeared that disease was due to M. tuberculosis rather than M. bovis. The significance of the findings for understanding tuberculous infection in rural agrarian communities in medieval England is discussed. Am J Phys Anthropol 114:298–311, 2001. © 2001 Wiley‐Liss, Inc.
Ontogeny of locomotion in rhesus macaques (Macaca mulatta): II. Postural and locomotor behavior and habitat use in a free‐ranging colony
Authors: Wells James P. , Turnquist Jean E.
Published: August 2002

This study quantifies changes in postural and locomotor behavior as well as habitat use across the life span of free‐ranging rhesus macaques (Macaca mulatta) in the Cayo Santiago colony in Puerto Rico. It focuses on developmentally related changes from birth to adulthood, and complements an earlier study by Turnquist and Wells ([1994] J Hum Evol 26:487–499) on the early postnatal ontogeny of the musculoskeletal system of the same colony. A total of 6,551 locomotor and postural events was analyzed. Selection and use of substrate correlated well with age. The more sedentary adult and dependent infant select safe, wide, horizontal arboreal settings in contrast to the older Infant IIs and Juveniles, who are learning locomotor and postural skills through independent chase and play. Infant macaques, when independent, often employ a low center of gravity and widely abducted limbs in order to broaden their contact with the base of support. This study shows that the previously reported ontogenetic changes in morphology are closely paralleled by changes in postural and locomotor behavior, and these in turn are correlated to changes in habitat use, particularly during the formative years. Am J Phys Anthropol 115:80–94, 2001. © 2001 Wiley‐Liss, Inc.
A novel, blood‐based diagnostic assay for limb girdle muscular dystrophy 2B and miyoshi myopathy
Authors: Ho Mengfatt , Gallardo Eduard , McKenna‐Yasek Diane , De Luna Noemi , Illa Isabel , Brown Jr. Robert H.
Published: August 2002

Limb girdle muscular dystrophy 2B and Miyoshi myopathy were recently found to be allelic disorders arising from defects in the dysferlin gene. We have developed a new diagnostic assay for limb girdle muscular dystrophy 2B and Miyoshi myopathy, which screens for dysferlin expression in blood using a commercially available monoclonal antibody. Unlike current methods that require muscle biopsy for immunodiagnosis, the new method is simple and entails a significantly less invasive procedure for tissue sampling. Moreover, it overcomes some of the problems associated with the handling and storage of muscle specimens. In our analysis of 12 patients with limb girdle muscular dystrophy 2B or Miyoshi myopathy, the findings obtained using the new assay are fully consistent with the results from muscle immunodiagnosis.
Increased expression of the amyloid precursor β‐secretase in Alzheimer's disease
Authors: Holsinger R. M. Damian , McLean Catriona A. , Beyreuther Konrad , Masters Colin L. , Evin Geneviève
Published: August 2002

β‐Secretase cleavage represents the first step in the generation of Aβ polypeptides and initiates the amyloid cascade that leads to neurodegeneration in Alzheimer's disease. By comparative Western blot analysis, we show a 2.7‐fold increase in protein expression of the β‐secretase enzyme BACE in the brain cortex of Alzheimer's disease patients as compared to age‐matched controls. Similarly, we found the levels of the amyloid precursor protein C‐terminal fragment produced by β‐secretase to be increased by nearly twofold in Alzheimer's disease cortex.
Nigrostriatal collaterals to thalamus degenerate in parkinsonian animal models
Authors: Freeman Amanda , Ciliax Brian , Bakay Roy , Daley Joseph , Miller R. Daniel , Keating Glenda , Levey Allan , Rye David
Published: August 2002

Movement, cognition, emotion, and positive reinforcement are influenced by mesostriatal, mesocortical, and mesolimbic dopamine systems. Here, we describe a fourth major pathway originating from mesencephalic dopamine neurons: a mesothalamic system. The dopamine transporter, specific to dopamine containing axons, was histochemically visualized in thalamic motor and limbic‐related nuclei and regions that modulate behavioral state as opposed to sensory nuclei in rats, nonhuman primates, and humans. Anatomical tracing established this innervation's origin via axon collaterals from the mesostriatal pathway. These findings implicate the thalamus as a novel site for disease specific alterations in dopamine neurotransmission, such as exist with nigral degeneration attending Parkinson's disease. This was confirmed in hemiparkinsonian animals where reduction of thalamic dopamine innervation occurred coincident with signs of active axonal degeneration. Individual mesencephalic dopamine neurons therefore have the potential to modulate normal and pathologic behavior not only through traditional nigrostriatal pathways but also by way of axon collaterals that innervate the thalamus.
Frameshift mutation in the collagen VI gene causes Ullrich's disease
Authors: Higuchi Itsuro , Shiraishi Tadafumi , Hashiguchi Teruto , Suehara Masahito , Niiyama Takahito , Nakagawa Masanori , Arimura Kimiyoshi , Maruyama Ikuro , Osame Mitsuhiro
Published: August 2002

Patients with Ullrich's disease have generalized muscle weakness, multiple contractures of the proximal joints, and hyperextensibility of the distal joints. Recently, we found a deficiency of collagen VI protein in two patients with Ullrich's disease. In this study, we detected a homozygous 26 bp deletion in exon 14 of the collagen VI alpha 2 gene (COL6A2) in one patient. This mutation causes a frameshift and a premature termination codon, and results in a truncated collagen VI alpha 2 chain. Our data suggest that at least some cases of Ullrich's disease result from recessive mutations in COL6A2.
Preparation methodologies of polymer matrix nanocomposites
Authors: Avella M. , Errico M. E. , Martelli S. , Martuscelli E.
Published: August 2002

Recently, as a result of developments in nanotechniques, there has been a growing interest in the field of nanocomposites. The use of inorganic nanoparticle‐filled composites can provide high‐performance materials that find applications in several industrial fields. In the present work, preliminary studies concerning the preparation of polymethylmethacrylate (PMMA)/CaCO3­nanoparticles composites are reported. The preparation was performed by using an in situ polymerization methodology. In particular, the nanocomposites have been obtained by a modified radical polymerization of the MMA dispersing the nanoparticles directly into the acrylic monomer. Nanocomposites having 2, 3, 4 and 6 wt% of nanoparticles were prepared. The influence of the nanoparticles on the chemico‐physical properties of the polymeric matrix and the mode of dispersion were investigated by performing thermal, mechanical and morphological analyses. Copyright © 2001 John Wiley & Sons, Ltd.
Molecular mechanism of haemolysis induced by triphenyltin chloride
Authors: Burda Kvĕtoslava , Lekki Janusz , Cieślak Jakub , Kruk Jerzy , Lekka MaŁgorzata , Dubiel StanisŁaw , Stanek Jan , Stachura Zbigniew
Published: August 2002

Organometals are known to cause lysis of cells, but the molecular mechanism of their action is not recognized. In this work, we have examined the interaction of triphenyltin with erythrocyte membranes. We determined the order of haemolytic activity of the investigated organometal species as being: triphenyllead > tripropyltin = triphenyltin > triethyllead > trimethyltin. Such an order suggests that the haemolytic activity increases with the increasing hydrophobicity of the organic ligands. Compounds containing lead are more toxic than the respective complexes of tin. Triphenyltin chloride (Ph3SnCl) is very effective in lysis of erythrocytes. Using 119Sn Mössbauer spectroscopy we showed that triphenyltin interacts with the protein components of pig erythrocyte membranes in a highly specific way, but we did not detect any interaction of triphenyltin with pig haemoglobin. The Mössbauer spectrum was fitted with a single doublet characterized by hyperfine parameters that differ considerably from those reported for other organotin compounds in membranes of red blood cells. Applying the point charge model of the electric field gradient for the analysis of the environment of tin bonds from the quadrupole splitting, we could indicate Nhet from histidine and/or Sthiol from cysteine as the only possible ligands of Ph3Sn(IV). We expect that protein components of erythrocyte membranes having similar cysteine and histidine arrangement, such as in cat or rat haemoglobins, which provide high‐affinity binding sites for organotins, can bind triphenyltin with high affinity. We give some arguments that ankyrin and β‐spectrin are the most probable targets of Ph3Sn(IV) action and indicate its potential binding sites within the proteins. The highly specific interaction of triphenyltin with the membrane cytoskeleton components, postulated by us, should already influence the rigidity of red blood cells at the stage preceding the lysis of erythrocytes. To support this hypothesis, we carried out scanning force microscopy measurements of red blood cells elasticity. We have observed a lower stiffness for erythrocytes treated with concentrations of Ph3SnCl that caused less than 20% of haemolysis. Copyright © 2002 John Wiley & Sons, Ltd.
Separation of phenol–water mixture by membrane pervaporation using polyimide membranes
Authors: Pradhan Narayan C. , Sarkar Chandra Sekhar , Niyogi Sobhan , Adhikari Basudam
Published: August 2002

Separation of components of aqueous waste streams containing organic pollutants is not only industrially very important but also is a challenging process. In this study, separation of a phenol–water mixture was carried out by using a membrane pervaporation technique with indigenously developed polyimide membranes. The membranes were found to permeate water selectively. The total flux as well as that of the individual components were measured. The effect of lithium chloride modification of polyimide film on total flux was investigated. The total flux obtained with 2% lithium chloride modification was about 3.6 times higher than that obtained with virgin membrane. The effects of different parameters such as feed composition and temperature on flux, and separation factor were determined. With modified membrane, a separation factor as high as 18.0 was obtained for water at 27°C and with 8.0 wt % phenol solution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 822–829, 2002
Sugarcane bagasse reinforced phenolic and lignophenolic composites
Authors: Paiva Jane M. F. , Frollini E.
Published: August 2002

Lignin, extracted from sugarcane bagasse by the organosolv process, was used as a partial substitute of phenol (40 w/w) in resole phenolic matrices. Short sugarcane fibers were used as reinforcement in these polymeric matrices to obtain fiber‐reinforced composites. Thermoset polymers (phenolic and lignophenolic) and related composites were obtained by compression molding and characterized by mechanical tests such as impact, differential mechanical thermoanalysis (DMTA), and hardness tests. The impact test showed an improvement in the impact strength when sugarcane bagasse was used. The inner part of the fractured samples was analyzed by scanning electron microscopy (SEM), and the results indicated adhesion between fibers and matrix, because the fibers are not set free, suggesting they suffered a break during the impact test. The modification of fiber surface (mercerization and esterification) did not lead to an improvement in impact strength. The results as a whole showed that it is feasible to replace part of phenol by lignin in phenolic matrices without loss of properties. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 880–888, 2002
Biodegradation studies of LDPE filled with biodegradable additives: Morphological changes. I
Authors: Contat‐Rodrigo L. , Ribes Greus A.
Published: August 2002

Low‐density polyethylene (LDPE) samples filled with three commercial biodegradable additives (Mater‐Bi, Cornplast, and Bioefect) have been subjected to an accelerated soil burial test in a culture oven for 1 year. By means of Differential Scanning Calorimetry (DSC), the effect of the degradation in soil in the samples morphology has been analyzed, in terms of their melting temperature, their crystalline content, and their lamellar thickness distribution. These morphological parameters evolve in different stages, depending on the additive used. It has been found that the LDPE–Mater‐Bi samples are the ones exhibiting faster changes in their crystalline content. However, the LDPE blends with Cornplast and Bioefect display more significant changes in their lamellar thickness distribution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1683–1691, 2002
Preparation and properties of polyimide films codoped with barium and titanium oxides
Authors: Tong Yuejin , Li Yuesheng , Liu Jieping , Ding Mengxian
Published: August 2002

Polyimide hybrid films containing bimetalic compounds were obtained by codoping poly(amic acid) with a barium and titanium precursor prepared from BaCO3, Ti(OBu)4, and lactic acid followed by casting and thermal curing. FTIR, WAXD, and XPS measurements showed that barium and titanium precursor could be transformed to BaTiO3 at a temperature above 650°C, while the mixed oxides were only found in hybrid films. The measurements of TEM and AFM indicated a homogeneous distribution of inorganic phase with particle sizes less than 50 nm. The hybrid films exhibited fairly high thermal stability, good optical transparency, and promising mechanical properties. The incorporation of 10 wt % barium and titanium oxide lowered surface and volume electrical resistivity by 2 and 5 orders, respectively, increasing dielectric constant from 3.5 to 4.2 and piezoelectric constant from 3.8 to 5.2 × 10−12 c/N, relative to the nondoped polyimide film. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1810–1816, 2002
Red phosphorus–controlled decomposition for fire retardant PA 66
Authors: Schartel B. , Kunze R. , Neubert D.
Published: August 2002

The thermal degradation and the combustion behavior of glass fiber–reinforced PA 66 materials containing red phosphorus were investigated. Thermogravimetry (TG), TG coupled with FTIR, and TG coupled with mass spectroscopy were used to investigate the thermal decomposition. The flame retardant red phosphorus was investigated with respect to the decomposition kinetics and the release of volatile products. The combustion behavior was characterized using a cone calorimeter. Fire risks and fire hazards were monitored versus external heat fluxes between 30 and 75 kW/m2. Red phosphorus acts in the solid phase and its efficiency depends on the external heat flux. The use of red phosphorus results in an increased amount of residue and in a corresponding decrease in total heat release. The decrease of the mass loss rate peak results in a corresponding decrease of the peak heat release. With increasing external heat flux applied the first effect on the total heat release decreases linearly, whereas the second effect on the peak heat release expands linearly. The investigation provides insight into the mechanisms of how the fire retardant PA 66 is achieved by red phosphorus controlling the degradation kinetics. Taking into account that a decrease of the volatile products also leads to a decrease of heat production in the flame zone and that the char acts as heat transfer barrier, a reduced pyrolysis temperature is suggested as a further feedback effect. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2060–2071, 2002
Preparation and characterization of microporous polyethylene hollow fiber membranes
Authors: Shen Li‐Qiang , Xu Zhi‐Kang , Xu You‐Yi
Published: August 2002

Microporous polyethylene (PE) hollow fiber membrane with a porosity of 43% and N2 permeation of 4.96 cm3 (STP)/cm2 s cmHg was prepared by melt‐spinning and cold‐stretching method. It was found that PE with a density higher than 0.96 g/cm3 should be used for the preparation of microporous PE hollow fiber membranes. By increasing the spin–draw ratio, both the porosity and the N2 permeation of the hollow fiber membranes increased. Annealing the nascent hollow fiber at 115°C for 2 h was suitable for attaining membranes with good performance. By straining the hollow fiber to higher extensions, the amount and size of the micropores in the hollow fiber wall increased, and the N2 permeation of the membranes increased accordingly. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 203–210, 2002; DOI 10.1002/app.10305
Multiple‐beam Fizeau fringe‐pattern analysis using Fourier transform method for accurate measurement of fiber refractive index profile of polymer fiber
Authors: El‐Morsy M. A. , Yatagai T. , Hamza A. , Mabrouk M. A. , Sokkar T. Z. N.
Published: August 2002

In this article the Fourier transform method is applied to analyze multiple‐beam interference Fizeau fringes. The real part of the inverse Fourier transform is used to estimate a theoretical pattern. This pattern coincides with the experimental one. A derivative‐sign binary image of the interference pattern is also used in automated determination of the contour line of the fringe pattern, regardless of the quality of this pattern. A correlation between the pixel size and the accuracy of the measured fiber refractive index is presented. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 475–484, 2002
Epoxy‐toughened, unsaturated polyester interpenetrating networks
Authors: Shaker Z. G. , Browne R. M. , Stretz H. A. , Cassidy P. E. , Blanda M. T.
Published: August 2002

A series of translucent interpenetrating polymer networks (IPNs) made of a reactive elastomer [linear (D) and branched (T) with varying molecular weights] (Jeffamine™), a commercially available epoxy (D.E.R. 331), and an unsaturated polyester (15:85 wt %) were prepared. DSC data indicated complete cure after 8 h at 90°C. DMTA data showed a single glass‐transition temperature (Tg) for all elastomer‐containing IPNs, an indication of homogeneity. As expected, all IPNs showed a decrease in Tg with incorporation of elastomer, from 16 to 114°C or lower, the largest decrease being with T‐5000. Izod impact strengths were increased by 28–44%, but with no apparent pattern among structure and molecular weight variations. In several cases the standard deviation of impact data increased significantly. Flexural data were measured using a three‐point bend test. The highest flexural modulus obtained was that which incorporated linear D‐2000 with a decrease of only 22% upon incorporation of the elastomer, whereas other compositions dropped up to 55% in flexural modulus. The strongest material obtained was that using D‐2000 with a flexural strength increase of 65% upon incorporation of the elastomer. Two of the three branched elastomer components showed flexural strength increases of about 53%, but one was only equal to the base polyester resin. TGA data were recorded for all IPNs and values compared well to that of the pure polyester resin, with the exception of T‐403, which showed a 20°C decrease, and D‐2000 with a 10°C decrease. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2283–2286, 2002
Structural investigations of poly(ethylene terephthalate)‐graft‐polystyrene copolymer films
Authors: Nasef Mohamed Mahmoud
Published: August 2002

Structural investigations of poly(ethylene terephthalate)‐graft‐polystyrene (PET‐g‐PS) films prepared by radiation‐induced grafting of styrene onto commercial poly(ethylene terephthalate) (PET) films were carried out by FTIR, X‐ray diffraction (XRD), and differential scanning calorimetry (DSC). The variation in the degree of crystallinity and the thermal characteristics of PET films was correlated with the amount of polystyrene grafted therein (i.e., the degree of grafting). The heat of melting was found to be a function of PET crystalline fraction in the grafted films. The grafting is found to take place by incorporation of amorphous polystyrene grafts in the entire noncrystalline (amorphous) region of the PET films and at the surface of the crystallites. This results in a decrease in the degree of crystallinity with the increase in the degree of grafting, attributed to the dilution of PET crystalline structure with the amorphous polystyrene, without almost any disruption in the inherent crystallinity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1949–1955, 2002; DOI 10.1002/app.10515
Core–shell latex containing fluorinated polymer rich in shell
Authors: Cheng Shiyuan , Chen Yanjun , Chen Zhengguo
Published: August 2002

Core–shell latex with polyacrylate rich in core and fluoropolymer rich in shell was prepared by semicontinuous emulsion polymerization in the presence of mixed emulsifiers. The solids content of the latex was about 25 wt %. The polymerization conditions for the latex were discussed. The morphology of latex particles was characterized by transmission electron microscopy and the surface properties were determined by the Wilhelmy method. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1147–1153, 2002
Ion‐exchange membranes prepared by blending sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide) with polybenzimidazole
Authors: Kosmala Barbara , Schauer Jan
Published: August 2002

New ion‐exchange acid/base‐blend (SPPO/PBI) membranes were prepared by mixing N,N‐dimethylacetamide (DMA) solutions of sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPO) in the ammonium form and of polybenzimidazole (PBI), casting the solution as a thin film, evaporating the solvent, and treating the membrane with aqueous hydrochloric acid. The resulting membranes were found insoluble in DMA. The preliminary tests of the membranes were carried out in an H2/O2 fuel cell at room temperature. Their performance in the fuel cell increased with the increase in the concentration of SPPO sulfonic acid groups in the blend, but the membranes formed with the highly sulfonated SPPO alone or predominanting, which swelled excessively in water, did not give reproducible results, and their performance was usually inferior to that of the membranes having an optimum ratio of both components. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1118–1127, 2002
Weathering characteristics of modified rubberwood (Hevea brasiliensis)
Authors: Pandey K. K. , Pitman A. J.
Published: August 2002

Surfaces of rubberwood treated with dilute aqueous solutions of chromium trioxide, chromic nitrate, ferric chloride, and ferric nitrate and modified with acetic anhydride were weathered outdoors for periods from 1 day to 1 year. Fourier transform infrared (FTIR) spectroscopy, fluorescence spectroscopy, light microscopy (LM), and scanning electron microscopy (SEM) were used to analyze chemical and microscopic changes in treated and untreated weathered wood surfaces. Severe delignification and hemicellulose degradation occurred in untreated samples, evident from rapid decreases in IR band intensities at 1505 and 1740 cm−1, respectively. Surface delignification occurred after 1 day's exposure, with severe lignin loss within 2–3 days and almost complete surface delignification after 1 week of exposure. Fluorescence spectra of weathered wood surfaces showed a rapid decrease in intensity and a large red shift in emission maxima. Scanning electron microscopy of untreated wood surfaces exposed for 125 and 360 days showed them to have ridges in the S3 cell‐wall layer adjacent to the lumen, together with wall checking and pit degradation. Fungal spores and hyphae were observed in wood cell lumens. Pretreatment of wood surfaces with chromium trioxide (chromium VI compound) significantly restricted weathering deterioration and microbial colonization, whereas ferric chloride was most effective in preventing microbial colonization. Acetylation also partially prevented delignification and fungal staining. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 622–631, 2002
Rheological behavior of controlled‐rheology polypropylenes obtained by peroxide‐promoted degradation during extrusion: Comparison between homopolymer and copolymer
Authors: Berzin F. , Vergnes B. , Delamare L.
Published: August 2002

In the present work, experimental studies of the free‐radical‐initiated molecular weight degradation of polypropylene in a modular self‐wiping corotating twin‐screw extruder are investigated. The control of the molecular weight distribution of polypropylene resins by peroxide degradation is widely used in the polymer industry. It allows one to adjust the viscosity of these resins to the level required for processing applications. The purpose of this work was to characterize the influence of peroxide degradation on the rheological behavior of a polypropylene homopolymer and a block polypropylene/polyethylene copolymer, which includes an addition of a low percentage of polyethylene (around 7%). The homopolymer exhibits a classical behavior: When the peroxide amount is increased, we observe a decrease in the viscosity corresponding to a decreasing molecular weight and a pronounced shift toward more Newtonian behavior. The rheological behavior of the copolymer is influenced by the presence of the polyethylene phase which greatly modifies the viscoelastic properties and increases the viscosity when the polypropylene matrix is highly degraded. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1243–1252, 2001
Studies on high‐speed melt spinning of noncircular cross‐ section fibers. I. Structural analysis of as‐spun fibers
Authors: Takarada Wataru , Ito Hiroshi , Kikutani Takeshi , Okui Norimasa
Published: August 2002

Flat fibers and hollow fibers were prepared through the high‐speed melt spinning of poly(ethylene terephthalate) (PET), and the structures of these fibers were compared with those of circular fibers. The cross‐sectional shape of each fiber changed to a dull shape in comparison with that of the respective spinning nozzle. The change in the cross‐sectional shape was slightly suppressed with an increase in the take‐up velocity. There was a significant development of structural variation in the cross section of flat fibers in that the molecular orientation and crystallization were enhanced at the edge. Despite the difference in the cross‐sectional shape, the structural development of flat, hollow, and circular fibers with increasing take‐up velocity showed almost similar behavior. Considering that the tensile stress at the solidification point of the spin line is known to govern the structure development of high‐speed spun PET fibers, it was speculated that the effects of the enhancement of cooling and air friction on the tensile stress at the solidification point cancel each other. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1575–1581, 2001
Ionic conductivity of a novel solid polymer electrolyte
Authors: Xie Wenming , Xu Peixin , Liu Qing , Xie Yi
Published: August 2002

A novel kind of solid polymer electrolyte, the solvation unit of which is OCNHR, has been studied. The effects of host polymer structure, ion species, salt concentration, and plasticizers on ionic conductivity are discussed in detail. The solvability of host polymers is a very important factor that affects the ionic conductivity of electrolytes and is fully decided by the structure of solvation units and their density in polymer chain. The latter two rest with monomers structure and copolymerization ratio. Effects of alkali metal salts and divalent metal salts on ionic conductivity are different because of their different leading factor of cation radius. Salt concentration dependence of ionic conductivity appears as a double‐peak shape when alkali metal salts are added because of the total contribution of two kinds of ionic conductance modes, and appears as similar shapes when divalent metal salts are added. Different influences of plasticizers on ionic conductivity result from their different action ways. Ethylene glycol acts well because of its effective action from three different modes. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2176–2184, 2001
Bismaleimide resin modified with diallyl bisphenol A and diallyl p‐phenyl diamine for resin transfer molding
Authors: Li Zhongming , Yang Mingbo , Huang Rui , Zhang Meidong , Feng Jianmin
Published: August 2002

O,O′‐diallyl bisphenol A (DBA) and N,N′‐diallyl p‐phenyl diamine (DPD) were used for the reactive diluents of 4,4′‐bismaleimidodiphenol methane (BDM). The objective was to obtain a modified BDM resin system suitable for resin transfer molding (RTM) process to prepare the advanced composites. The processing behavior was determined by time–temperature–viscosity curves, gel characteristics, and differential scanning calorimetry (DSC). The injection temperature of the resin system in RTM could be 80°C, at which its apparent viscosity was only 0.31 Pa/s, and the apparent viscosity was still less than 1.00 Pa/s after the resin was held at 80°C for 16 h. The gel time test result indicated that at low temperatures, the reactivity of the resin system is low, whereas at high temperatures, the resin could cure very fast, which was beneficial to RTM. The postcure of the cured resin at a given temperature was necessary because the resin had a wide and flat cure exothermic peak, observed by DSC curve. The cured resin displayed both high heat and hot/wet resistance and high mechanical properties, especially tensile strength, tensile modulus, and flexural strength at room temperature, which reached 96.2 MPa, 4.8 GPa, and 121.4 MPa, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2245–2250, 2001
Preparation and characterization of chitosan/poly(vinyl alcohol) blend fibers
Authors: Zheng Hua , Du Yumin , Yu Jiahui , Huang Ronghua , Zhang Lina
Published: August 2002

Chitosan and poly(vinyl alcohol) blend fibers were prepared by spinning their solution through a viscose‐type spinneret at 25°C into a coagulating bath containing aqueous NaOH and ethanol. The influence of coagulation solution composition on the spinning performance was discussed, and the intermolecular interactions of blend fibers were studied by infrared analysis (IR), X‐ray diffraction (XRD), and scanning electron micrograph (SEM) and by measurements of mechanical properties and water‐retention properties. The results demonstrated that the water‐retention properties and mechanical properties of the blend fibers increase due to the presence of PVA in the chitosan substract, and the mechanical strength of the blends is also related to PVA content and the degree of deacetylation of chitosan. The best mechanical strength values of the blend fibers, 1.82 cN/d (dry state) and 0.81 cN/d (wet state), were obtained when PVA content was 20 wt % and the degree of deacetylation of chitosan was 90.2%. The strength of the blend fibers, especially wet tenacity could be improved further by crosslinking with glutaraldehyde. The water‐retention values (WRV) of the blend fibers were between 170 and 241%, obviously higher than pure chitosan fiber (120%). The structure analysis indicated that there are strong interaction and good miscibility between chitosan and poly(vinyl alcohol) molecular resulted from intermolecular hydrogen bonds. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2558–2565, 2001
The use of metal‐containing monomer in the preparation of molecularly imprinted polymer to increase the adsorption capacity
Authors: Sreenivasan K.
Published: August 2002

Molecular imprinting is an elegant approach to induce antibody like recognition ability in synthetic polymers. The technique of molecular imprinting has been used extensively in the preparation of tailor‐made stationary phases in chromatography, sorbents in solid phase extraction, sensor elements, etc. Though several of the reported molecularly imprinted polymers (MIPs) possess substrate selectivity comparable to antibodies, they are poor in adsorption capacity. The adsorption capacity could be improved presumably through enhanced interaction between the functionalities of the monomers and the print molecule. A simple approach to improve the interaction is perhaps the use of chemically modified monomers in the synthesis of the MIPs. This article explores this possibility by using a metal‐containing monomer in the synthesis of MIP. The data obtained using a copper acrylate based MIP and cholesterol as substrate indicates the adsorption capacity can be improved considerably through the simple chemical modification of the functional monomer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2795–2799, 2001
Conifer fibers as reinforcing materials for polypropylene‐based composites
Authors: Chuai Chengzhi , Almdal Kristoffer , Poulsen Lars , Plackett David
Published: August 2002

Conifer fibers were used to reinforce polypropylene (PP). To improve the compatibility between the conifer fibers and the PP matrix, the fibers were either grafted with maleated PP (MAPP), treated by adding MAPP, or mixed with ethylene/propylene/diene terpolymer (EPDM). The treatments resulted in improved processing, as well as improvements in the thermal and mechanical properties of the resultant composites compared with the composites filled with untreated conifer fibers. Moreover, MAPP grafting and MAPP treating displayed more obvious benefits than EPDM treating in terms of thermal properties, processing flowability, and tensile strength improvements. EPDM treating also produced more significant benefits than either MAPP grafting or MAPP treating in terms of impact strength and tensile elongation improvements. These improvements were attributed to surface coating of the fibers when EPDM was used. In addition, the effect of the concentration of the conifer fibers on the properties of the composites and the difference between MAPP grafting and MAPP treating were evaluated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2833–2841, 2001
Rheological behavior and processability of polypropylene blends with rubber ethylene propylene diene terpolymer
Authors: López Manchado Miguel A. , Biagiotti Jerico , Kenny José M.
Published: August 2002

A study of the dynamic complex and steady shear viscosity of isotactic polypropylene (iPP), ethylene–propylene diene terpolymer rubber (EPDM) and three different blends of both polymers are presented over a range of temperatures and frequencies. Moreover, the processability of these materials is studied through torque measurements during blend mixing. The results obtained show that the viscosity gradually increases with rubber content in the blend and decreases with both temperature and frequency. Plots of η″ versus η′ (Cole–Cole plots) show that the blend with the lower rubber content (25%), has a certain rheological compatibility with neat PP. Furthermore, torque curves measured during blend mixing confirm these results, demonstrating that the blend with 25% of elastomer has a similar behavior of iPP during processing. To analyze the morphological structure of the blends, a dynamic mechanical analysis of the solid state is also presented. It is observed that the blends have two distinct values of Tg close to the corresponding values of the pure polymers, confirming that this type of blends based on a semicrystalline polymer and an amorphous elastomer forms a two‐phase system with a limited degree of miscibility between both components. In addition, the polymer present with the higher concentration forms the continuous phase and controls the rheological properties of the blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1–10, 2001
Dissolution/reprecipitation: A model process for PET bottle recycling
Authors: Poulakis J. G. , Papaspyrides C. D.
Published: August 2002

A dissolution/reprecipitation route was followed for the recycling of poly(ethylene terephthalate) (PET). Model experiments on virgin material, either in the form of pellets or blow‐molded bottles, are presented. The process proposed comprises dissolution of the plastic in an appropriate solvent, reprecipitation by using a nonsolvent, thorough washing of the material obtained, and drying. The solvent mixtures involved are separated by fractional distillation for further reuse. N‐Methyl‐2‐pyrrolidone (NMP)/n‐octane + n‐hexane proved to be a particularly effective solvent/nonsolvent system. Further investigation was focused on the effect of the sample history through successive recycling cycles. The recycled material was evaluated in terms of molecular weight, crystallinity, and grain‐size analysis, resulting in an excellent quality, competing with the virgin grade. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 91–95, 2001
Thermal decomposition kinetics of an epoxy resin with rubber‐modified curing agent
Authors: Lee J. Y. , Shim M. J. , Kim S. W.
Published: August 2002

Thermal decomposition kinetics of diglycidyl ether of bisphenol A (DGEBA)/4,4′‐methylene dianiline (MDA) system with rubber‐modified MDA was studied by the methods of Ozawa, Kissinger, and Friedman, and the kinetic parameters were compared. The thermal decomposition data of the cured epoxy resin were analyzed by thermogravimetric analysis (TGA) at different heating rates. TG curves showed that the thermal decomposition of the epoxy system occurred in one stage regardless of rubber‐modified MDA content. The apparent activation energies for the DGEBA/MDA system with 10 phr of rubber‐modified MDA, as determined by the Ozawa, Kissinger, and Friedman methods, are 184, 182, and 222 kJ/mol, respectively. The thermal stability of the epoxy system increased with the increasing content of rubber‐modified MDA, which has four benzene rings with high thermal resistance due to the resonance structure. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 479–485, 2001