bluuebunny/crossref_metadata_2025 huggingface dataset:
Risk factors for hysterectomy among Mexican‐American women in the U.S. southwest
Authors: Hautaniemi Susan I. , Leidy Sievert Lynnette
Published: January 2003

The purpose of this study was to assess risk factors associated with a history of hysterectomy among Mexican‐American women living in the United States Southwest. Mexican‐American women ages 20–74 at time of interview were defined as a subpopulation among adults in the Hispanic Health and Nutrition Examination Survey (HHANES), 1982–1984. Language preference, reproductive history, level of education, poverty status, generation of immigration, marital status, and insurance coverage were examined in relation to risk of hysterectomy using weighted tabulation and logistic regression for data resulting from complex survey designs. Heretofore, language preference has not been a variable considered in relation to risk of hysterectomy. In the HHANES, over 60% of women who spoke English most often rather than Spanish reported a history of hysterectomy. Women who had previously been pregnant were almost four times as likely (odds ratio 3.972) to have had a hysterectomy compared to women who had never been pregnant. Women who expressed any preference for English were twice as likely (odds ratio 2.050) to have had a hysterectomy than were those who responded that they exclusively preferred Spanish. Age, higher levels of education, and higher economic status also increased the risk of hysterectomy. In contrast, reproductive history, marital status, prior tubal ligation, generation of immigration, and health insurance did not have substantial effects on the risk of hysterectomy. This study suggests that, in the future, the effect of language preference should not be overlooked when considering risk factors for hysterectomy. Am. J. Hum. Biol. 15:38–47, 2003. © 2002 Wiley‐Liss, Inc.
Potential association between endogenous leptin and sympatho‐vagal activities in young obese Japanese women
Authors: Matsumoto Tamaki , Miyatsuji Aya , Miyawaki Takashi , Yanagimoto Yukio , Moritani Toshio
Published: January 2003

Leptin is an adipocyte‐derived hormone that decreases food intake and increases energy expenditure through the activation of the sympathetic nervous system (SNS). Notwithstanding recent intensive research, the underlying physiological mechanism of leptin as well as the etiology of obesity in humans remains elusive. The present study attempted to investigate the potential association between endogenous circulating leptin and sympatho‐vagal activities in age‐ and height‐matched obese and nonobese healthy young women. Plasma leptin concentrations were measured by radioimmunoassay. The autonomic nervous system activity was assessed during the resting condition by means of a recently devised power spectral analysis of heart rate variability, which serves to identify three separate frequency components, very low (VLO), low (LO), and high (HI). Plasma leptin concentrations were greater in the obese than in the control group (45.7 ± 5.89 vs. 11.2 ± 1.10 ng · ml−1, P < 0.01). As to the contribution of endogenous leptin to SNS activity, both the ratios of the VLO frequency component reflecting thermoregulatory sympathetic function and the global SNS index [(VLO + LO)/HI] to plasma leptin concentration were markedly reduced in the obese compared to the control group (VLO per leptin: 5.9 ± 1.39 vs. 37.8 ± 8.1 ms2 · ml · ng−1, P < 0.01; SNS index per leptin: 0.04 ± 0.008 vs. 0.33 ± 0.01 ml ċ· ng−1, P < 0.01). Additionally, a nonlinear regression analysis revealed that these ratios exponentially decreased as a function of body fat content (VLO per leptin r2 = 0.57, P < 0.01; SNS index per leptin r2 = 0.53, P < 0.01). Our data suggest that reduced sympathetic responsiveness to endogenous leptin production, implying peripheral leptin resistance, might be a pathophysiological feature of obesity in otherwise healthy young women. The findings regarding the association of leptin, body fat content, and SNS activity further indicate that the 30% of total body fat, which has been used as a criterion of obesity, might be a critical point at which leptin resistance is induced. Am. J. Hum. Biol. 15:8–15, 2003. © 2002 Wiley‐Liss, Inc.
Age differences in growth and physical abilities in trained and untrained girls 10–17 years of age
Authors: Loko J. , Aule R. , Sikkut T. , Ereline J. , Viru A.
Published: January 2003

The purpose of the present study was to assess the age differences in growth characteristics and physical abilities of physically active adolescent girls and to compare them to corresponding data for girls nonactive in sport. The cross‐sectional study was carried out on 643 Estonian girls, 10–17 years of age, who were regularly training track and field, and 902 nonactive girls. The organized physical activity of the studied girls consisted of lessons in the school curriculum (2 × 45 minutes per week) for both groups and special track and field training for the first group. Height, weight, and the body mass index (BMI) were used to characterize growth status. Physical ability was assessed with the 30‐m dash, standing long jump, medicine ball throw (2 kg), standing quintuplet jump, isometric strength of back extensor muscles, and 1‐minute ergocycling at the highest possible rate. Girls active in track and field were taller in all the age groups (P < 0.05–0.001) and lighter except at 17 years, when they were heavier (P > 0.05), but the differences at 12 and 13 years were not significant. BMI was also significantly lower in active girls (P < 0.05–0.001) in all age groups, except at 17 (P > 0.05). The actively training girls had higher physical abilities at all ages from 10–17. The annual differences in performance scores were significant (P < 0.05–0.001) up to 15 years except for the standing long jump. Differences in mean scores of most motor abilities were minimal or reduced significantly at 13–14 years in nonactive girls, but were significant in active girls. Am. J. Hum. Biol. 15:72–77, 2003. © 2002 Wiley‐Liss, Inc.
Allometric scaling of strength in an independently living population age 55–86 years
Authors: Amara Catherine E. , Rice Charles L. , Koval John J. , Paterson Donald H. , Winter Edward M. , Cunningham David A.
Published: January 2003

Most physiological functions vary allometrically with body size; however, few investigators have examined the relationship between strength and body size with allometric scaling. Thus, we hypothesized that allometric analysis would reveal that both the amount and quality of muscle are significant determinants of strength in the elderly. Allometric analyses were used to determine the influence of limb cross‐sectional area (CSA), physical activity, demispan (distance between index‐middle finger web and the sternal notch), leg length, and sex on grip and plantar flexor strength in men (n = 188) and women (n = 205) age 55–86 years. Physical activity was measured using a self‐reporting questionnaire (Taylor et al. [1978] J Chron Dis 31:741–755). Forearm and leg CSA was estimated from anthropometry. There was an age‐related decline in grip strength, independent of forearm CSA, demispan, and sex, equal to ≈12% per decade, whereas plantar flexor strength adjusted for leg CSA, physical activity, and sex was reduced at a rate of ≈15% per decade. The allometric models explained 71.4% (r = 0.845) and 38.8% (r = 0.623) of the variance in grip and plantar flexor strength, respectively. Model parameters were identified using multiple linear regression (P < 0.05). Thus, grip strength = forearm CSA0.435 · demispan0.161 · exp(3.905 − 0.012 age + 0.413 sex) and plantar flexor strength = leg CSA0.223 · physical activity 0.115 · exp(5.867 − 0.015 age + 0.366 sex). These findings indicate that age‐related reductions in muscle CSA do not fully account for strength declines with age. Physical activity is also important and partially explains these reductions. Am. J. Hum. Biol. 15:48–60, 2003. © 2002 Wiley‐Liss, Inc.
Genetic structure of seven Mexican indigenous populations based on five polymarker loci
Authors: Buentello‐Malo Leonora , Peñaloza‐Espinosa Rosenda I. , Loeza Francisco , Salamanca‐Gomez Fabio , Cerda‐Flores Ricardo M.
Published: January 2003

This descriptive study investigates the genetic structure of seven Mexican indigenous populations (Mixteca Alta, Mixteca Baja, Otomies, Purepecha, Nahuas‐Guerrero, Nahuas‐Xochimilco, and Tzeltales) on the basis of five PCR‐based polymorphic DNA loci: LDLR, GYPA, HBGG, D7S8, and GC. Genetic distance and diversity analyses indicate that these Mexican indigenous are similar and that more than 96% of the total gene diversity (HT) can be attributed to individual variation within populations. Mixteca‐Alta, Mixteca‐Baja, and Nahuas‐Xochimilco show indications of higher admixture with European‐derived persons. The demonstration of a relative genetic homogeneity of Mexican Indians for the markers studied suggests that this population is suitable for studying disease‐marker associations in the search for candidate genes of complex diseases. Am. J. Hum. Biol. 15:23–28, 2003. © 2002 Wiley‐Liss, Inc.
Physical activity, body fat, and serum c‐reactive protein in postmenopausal women with and without hormone replacement
Authors: Manns Patricia J. , Williams Daniel P. , Snow Christine M. , Wander Rosemary C.
Published: January 2003

The objective was to determine whether higher physical activity is associated with lower serum C‐reactive protein (CRP), independent of oral hormone replacement therapy (HRT) status and body fatness, in 133 postmenopausal women using a cross‐sectional exploratory design at a university research laboratory. The subjects were 133 postmenopausal women, age 50–73 years, with no evidence of coronary artery disease or diabetes. The main outcome measures were: serum CRP, physical activity as measured by Stanford 7‐day activity recall, body fat (both total and regional) as measured by dual energy X‐ray absorptiometry (DXA), and anthropometry (waist and hip circumference). Secondary outcome measures included fasting plasma glucose and insulin as well as fasting serum triglycerides, total cholesterol, high‐density lipoprotein cholesterol, and low‐density lipoprotein cholesterol. Higher physical activity energy expenditures were significantly associated with lower serum CRP levels (r = −0.18, P = 0.041), independent of oral HRT use, age, smoking behavior, alcohol consumption, aspirin use, and statin use. However, in the complete multivariate model, which included body fat, older ages (P = 0.047), greater trunk fat masses (P < 0.001), any oral HRT use (P < 0.001), and unopposed oral estrogen use (P = 0.012) were the sole independent predictors of higher serum CRP levels. The complete multivariate model accounted for 58% of the variance in serum CRP. We conclude that the association between higher physical activity and lower serum CRP levels is dependent on the lower body fat of the more active women, yet independent of oral HRT use. Future intervention trials should determine whether diet‐ and exercise‐related reductions in body fat may be effective ways to diminish the proinflammatory effects of oral HRT in postmenopausal women. Am. J. Hum. Biol. 15:91–100, 2003. © 2002 Wiley‐Liss, Inc.
Behavior of loci D1S1656 and D12S391 in a sample from Maracaibo, Venezuela
Authors: Bernal Lennie Pineda , Rodríguez‐Larralde Alvaro , Lareu María V. , Carracedo Angel , Borjas‐Fajardo Lisbeth
Published: January 2003

Two recently reported short tandem repeat polymorphisms characterized by PCR, D1S1656 and D12S391, were investigated in a sample from Maracaibo, an admixed population of Venezuela, in order to evaluate their application in forensic and population genetics studies. The unbiased heterozygosities were 0.9011 and 0.8444 for locus D1S1656 and D12S391, respectively. The joint discrimination power and joint probability of exclusion were 0.99972 and 0.93287. When allele frequencies of locus D1S1656 from Maracaibo were compared with eight other populations, our group clustered with the European or European‐derived samples, mainly from Spain. In the comparison of locus D12S391 with 16 populations, Maracaibo clustered with 3 Asian samples. The high heterozygosity and discrimination power make these two loci important candidates to be considered for STR packages for forensic and population genetic purposes. Am. J. Hum. Biol. 15:68–71, 2003. © 2002 Wiley‐Liss, Inc.
Effect of husbands' education on fatness of wives
Authors: Lipowicz Anna
Published: January 2003

The aim of the study was to examine the relationship between social position of females achieved by marriage and level of fatness and relative fat distribution. The data of 588 healthy, occupationally active, married women, age 21–62 years, with 12 years of education (completed secondary school) were used. The body mass index (BMI, kg/m2 ), triceps and subscapular skinfold thicknesses, and summed skinfold thicknesses were used as indicators of fatness. The waist–hip ratio, the waist–thigh ratio, and waist, hip, and thigh circumferences were used as indicators of fat distribution. According to the educational level of husbands, women were grouped as 1) moving up the social scale (spouse with complete university education), 2) stable (equal level of education), and 3) moving down the social scale (spouse who never passed beyond the level of basic vocational school, i.e., skilled and unskilled manual workers). The two opposite groups were analyzed, i.e., moving up and moving down. Women with secondary schooling who married up were consistently leaner than women who married down. A similar pattern was observed for fat distribution. Women marrying down had more abdominal body fat compared to women marrying up. Am. J. Hum. Biol. 15:1–7, 2003. © 2002 Wiley‐Liss, Inc.
Beta‐globin gene cluster haplotypes as evidence of African gene flow to the northeastern coast of Venezuela
Authors: Vívenes De Lugo Merlyn , Rodríguez‐Larralde Alvaro , Castro de Guerra Dinorah
Published: January 2003

In order to study the origin of mutation HBB*S in Sucre and Anzoátegui states and the genetic affinities of these Venezuelan populations with other human groups, the β‐globin gene cluster haplotypes were determined for 28 sickle cell and/or S‐beta thalassemia patients and for 37 individuals with normal hematological parameters. Bantu, Benin, Senegal, and atypical haplotypes were identified in 50%, 36%, 2%, and 12% of the HBB*S chromosomes, respectively. Similar results have been published for Venezuelan patients from the central states, but a different trend is shown in a publication based on a group of patients from different regions of the country. For HBB*A, haplotype 2 (+ − − − −), characteristic of non‐African groups, was the most common (39%), followed by haplotype 3 (− − − − +) of African origin, and haplotype 6 (− + + − +), also typical of non‐Africans. The results reveal a high level of admixture of the Sucre–Anzoátegui population. The importance of specific conditions which have acted differently in the Venezuelan populations, such as founder effect, genetic drift, isolation, and endogamy are discussed. Genetic distances between the Sucre–Anzoátegui sample and several other human populations calculated on the basis of the HBB*S and HBB*A haplotypes revealed similar results, the closest genetic relationships being observed in relation to Bantu‐speaking groups. These results confirm the utility of the β‐globin haplotypes for population studies and contribute to knowledge of the Venezuelan gene pool. Am. J. Hum. Biol. 15:29–37, 2003. © 2002 Wiley‐Liss, Inc.
Obesity correlates with increased blood pressures in urban native American youth
Authors: Smith Chery , Rinderknecht Kimberly
Published: January 2003

Although obesity is a growing problem with Native American youth living on reservations, little research has been conducted examining the prevalence of obesity and correlations between age, body composition, dietary intake, and blood pressures (BP) for urban Native youth. The purpose of this study was to investigate the relationship of these variables in urban Native American youth. Height and weight were measured for 155 Native American youth, age 5–18 years, and the body mass index (BMI) was calculated and classified into percentile categories. Skinfold thicknesses at the biceps, triceps, suprailiac, and subscapular sites, arm and waist circumferences, and systolic (SBP) and diastolic (DBP) blood pressures were also measured. There was a high proportion of obesity (>95 percentile) for youth in all age groups. The prevalence was 38% for the 5–10‐year‐olds and 45% for the 11–18‐year‐olds youth. There were no significant correlations between SBP and DBP and dietary variables. Mean SBP and DBP increased with increasing BMI percentiles. Stepwise regression analyses showed that waist circumference, age, and BMI were strong predictors for SBP, while waist circumference and age were predictors for DBP in the total sample. The findings suggest that overweight/obesity is very prevalent among urban Native American youth and the increased adiposity is associated with increased SBP and DBP. Am. J. Hum. Biol. 15:78–90, 2003. © 2002 Wiley‐Liss, Inc.
Minor physical anomalies in mentally healthy subjects: Internal consistency of the Waldrop Physical Anomaly Scale
Authors: Sivkov Stefan T. , Akabaliev Valentin H.
Published: January 2003

The aim of the study was to investigate the prevalence of minor physical anomalies in mentally healthy subjects by using the Waldrop Physical Anomaly Scale and to assess the reliability (internal consistency) of the scale. The subjects were 82 mentally healthy individuals (42 men, 40 women) of Bulgarian origin who were examined for minor physical anomalies. Mentally healthy individuals show a low mean score of minor physical anomalies. The anomalies prevail in the craniofacial region. The correlations between the anomalies are low, which implies poor internal consistency of the scale, probably due to the heterogeneity of the anomalies in terms of location, character, and time of prenatal development and adversity. Providing a base for comparative studies of developmental disorders, the findings infer the necessity of a more reliable scale for examination of informative morphogenetic variants which can distinguish between minor malformations and phenogenetic variants and suggest the period of prenatal adversity. Am. J. Hum. Biol. 15:61–67, 2003. © 2002 Wiley‐Liss, Inc.
Modification of cyanate ester resin by soluble polyimides
Authors: Iijima Takao , Kaise Tomohiro , Tomoi Masao
Published: January 2003

Soluble polyimides (PIs) were prepared as random or multiblock types with 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (s‐BPDA) as acid dianhydride components and 4,4′‐bis(m‐aminophenoxy) diphenyl sulfone (m‐BAPS) as a diamine component by a one‐pot process and used to improve the brittleness of the cyanate ester resin. Random‐type PIs were more effective as modifiers than multiblock‐type PIs. The morphologies of the modified resins depended on PI structure, molecular weight, and concentration. The most effective modification of the cyanate ester resin was attained because of a heterogeneous phase structure composed of a flat matrix phase and phase‐inverted structures of the modified resin; a 15 wt % inclusion of a random PI (weight‐average molecular weight = 63,400) composed of 6FDA, s‐BPDA, and m‐BAPS (0.5/0.5/1.0 molar ratio) led to a 65% increase in the fracture toughness for the modified resin with a slight loss of flexural strength and a retention of flexural modulus and glass‐transition temperature, compared with the values for the unmodified resin. Water absorptivity of the modified resin was comparable to that of the unmodified resin up to 400 h, and then, water absorption of the modified resins increased considerably. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1–11, 2003
Relationship between interfacial tension and dispersed‐phase particle size in polymer blends. II. PP/PA6
Authors: Shariatpanahi H. , Nazokdast H. , Hemmati M.
Published: January 2003

Simple blends with different viscosity ratios of the components as well as compatibilized blends varying both in type and content of the compatibilizers were used to study the relation between the interfacial tension and the dispersed‐phase particle size for PP/PA6 (80/20 wt %) blends in this work. Four compatibilizing systems including poly(ethylene‐co‐methacrylic acid) ionomers, a maleic anhydride‐grafted propylene copolymer, maleic anhydride‐grafted polypropylene, and a maleic anhydride‐grafted styrene ethylene butylene copolymer were used. For blends prepared in an internal mixer, a power‐law relation was found between the capillary number and the torque ratio of the blends' components. This relation was used to estimate the interfacial tension for the compatibilized blends. The relation between the steady‐state torque of the blends as a measure of viscosity and the estimated values of interfacial tension were also investigated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 54–63, 2003
Mechanical properties and morphology of PP/ABS blends compatibilized with PP‐g‐2‐HEMA
Authors: Patel Alpesh C. , Brahmbhatt Ragesh B. , Devi Surekha
Published: January 2003

Polypropylene (PP) and acrylonitrile–butadiene–styrene blends of different composition were prepared using a single‐screw extruder. The binary blend of PP/ABS was observed to be incompatible and shows poor mechanical properties. PP‐g‐2‐hydroxyethyl methacrylate (2‐HEMA) was used as a compatibilizer for the PP/ABS blends. The ternary compatibilized blends of PP/ABS/PP‐g‐2‐HEMA showed improvement in the mechanical properties. Electron micrographs of these blends showed a homogeneous and finer distribution of the dispersed phase. The mechanical performance increased particularly in the PP‐rich blend. The 2.5‐phr (part per hundred of resin) compatibilizer was observed to bring improvement to the properties. The suitability of various existing theoretical models for the predication of the tensile moduli of these blends was examined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 72–78, 2003
Physical properties of PVA/PSSNa blends
Authors: Xu Ning , Zhou Dongshan , Li Liang , He Jinbo , Chen Wei , Wan Fen , Xue Gi
Published: January 2003

Blends of conductive polymers with conventional nonconductive ones have, together, the virtues of good electroconductivity and good mechanical properties, whose prospect for electronic industrial application is very good. We prepared poly(vinyl alcohol) (PVA)–sodium polystyrene–sulfonate (PSSNa) blends through aqueous solution casting; the films are flexible and transparent, with electroconductivity that could reach 10−5 S/cm. The dependence of the electroconductivity on the weight fraction of PSSNa was found to follow the percolation theory. A general discussion is given on the factors that could influence the percolation threshold and the exponent. The films are stable in a 30% KOH solution and keep their conductivity after 10 days' exposure. Some mechanical properties are measured and the best mixing ratio is obtained for future use. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 79–87, 2003
Modeling of molecular weight distribution of gas‐phase polymerization of butadiene
Authors: Fang Dongyu , Sun Jianzhong , Zhou Qiyun
Published: January 2003

A mathematical model of the molecular weight distribution (MWD) based on a multilayer model and an improved intrinsic kinetics model was proposed to simulate the MWD of the gas‐phase polymerization of butadiene with a heterogeneous catalyst. Intrinsic kinetics and heat and mass‐transfer resistances based on the multilayer model of a polymeric particle were considered in the modeling of the MWD. The effects of the reaction conditions, catalyst particle size, mass‐transfer resistance, deactivation of active sites, and transfer of the polymer chain on the molecular weight and MWD were simulated. The results show that the effects of the deactivation of active sites and transfer of the polymer chain on the average molecular weight are significant and that the effect of the catalyst particle size on the MWD is not significant. The simulation results of the molecular weight and MWD are compared with the experimental results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 88–103, 2003
Electron spin resonance and ultraviolet spectral analysis of UV‐irradiated PVA films filled with MnCl2 and CrF3
Authors: Zidan H. M.
Published: January 2003

PVA films with various filling levels of CrF3 and MnCl2 were prepared. ESR and UV/VIS optical analysis were used to shed more light on the structural modification that occur due to filling with different levels and/or UV irradiation. The ESR analysis revealed that the spin configuration of CrF3, MnCl2, and CoBr2‐filled PVA are different. The filling level dependence of ESR parameters was discussed. The UV‐VIS spectral analysis for pure PVA shows absorption bands at 265 and 280 nm, which were assigned to the presence of carbonyl groups. The addition of CrF3 led to the appearance of another bands at 418 and 596 nm. The filling level and/or UV irradiation have no effect on the position of absorption bands but the intensity of these bands has been changed. The addition of MnCl2 led to a new band at about 350 nm due to charge transfer transition. The ligand field parameters and optical energy gaps can be calculated and discussed. The results of optical and ESR analysis indicated that the Cr3+ or Mn2+ are present in its octahedral symmetrical form within the PVA Matrix. SEM micrographs of CrF3 filled PVA is discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 104–111, 2003
Thermally conductive nylon 6,6 and polycarbonate based resins. I. Synergistic effects of carbon fillers
Authors: Weber Erik H. , Clingerman Matthew L. , King Julia A.
Published: January 2003

Increasing the thermal conductivity of typically insulating polymers, such as nylon 6,6, opens new markets. A thermally conductive resin can be used for heat‐sink applications. This research focused on performing compounding runs followed by injection molding and thermal conductivity testing of carbon filled nylon 6,6 and polycarbonate based resins. The three carbon fillers investigated included an electrically conductive carbon black, synthetic graphite particles, and a milled pitch‐based carbon fiber. For each polymer, conductive resins were produced and tested that contained varying amounts of these single carbon fillers. In addition, combinations of fillers were investigated by conducting a full 23 factorial design and a complete replicate in each polymer. The objective of this article was to determine the effects and interactions of each filler on the thermal conductivity properties of the conductive resins. From the through‐plane thermal conductivity results, it was determined that for both nylon 6,6 and polycarbonate based resins, synthetic graphite particles caused the largest increase in composite thermal conductivity, followed by carbon fibers. The combination of synthetic graphite particles and carbon fiber had the third most important effect on composite thermal conductivity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 112–122, 2003
Thermally conductive nylon 6,6 and polycarbonate based resins. II. Modeling
Authors: Weber Erik H. , Clingerman Matthew L. , King Julia A.
Published: January 2003

Increasing the thermal conductivity of typically insulating polymers opens new markets. A thermally conductive resin can be used for heat‐sink applications. This research focused on extruding followed by injection molding and thermal conductivity testing of carbon filled nylon 6,6 and polycarbonate‐based resins. The three carbon fillers investigated included an electrically conductive carbon black, synthetic graphite particles, and a milled pitch‐based carbon fiber. For each polymer, conductive resins were produced and tested that contained varying amounts of these single carbon fillers. In addition, combinations of fillers were investigated by conducting a full 23 factorial design and a complete replicate in each polymer. These through‐plane thermal conductivity experimental results were then compared to results predicted by several different thermal conductivity models. An improved thermal conductivity model was developed that fit the experimental results well for resins that contained single fillers and combinations of different fillers. This improved model was based on the original Nielsen model. A single value for the shape parameter, A (which is needed in Nielsen's model), was used for all three different fillers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 123–130, 2003
Structural and physical properties of biodegradable copolyesters from poly(ethylene terephthalate) and polycaprolactone blends
Authors: Lim Kyung Yul , Kim Byoung Chul , Yoon Kee Jong
Published: January 2003

The relationship between the degree of ester‐interchange reactions and the physical properties in the melt blending of poly(ethylene terephthalate) (PET) and polycaprolactone (PCL) was investigated in terms of the blending time. 1H‐NMR and 13C‐NMR spectra confirmed that poly(ethylene terephthalate caprolactone) copolyesters were generated and became dominant at a blending time of more than 15 min, and this result may be related to the degree of the thermal decomposition of PCL. The spectra disclosed the effect of the blending time on the block characteristics of the ethylene terephthalate (ET) and caprolactone (CL) units of the copolyesters. The melting temperatures and heats of fusion assigned to the ET units in the copolyesters decreased with the blending time. However, the melting peak of the CL units disappeared when the blending time exceeded 20 min. For the CL block, the number of the average repeating units (5) proved to be the least critical value for crystallization. The crystallinity of the copolyesters was most notably reduced with a blending time up to 20 min. The total organic carbon (TOC) content of the copolyesters, a quantitative measure of biodegradability, increased steeply with the blending time up to 20 min. However, the TOC content increased slowly during extended blending. This agrees well with the recognized fact that the accession and penetration of lipase into copolyesters initiate in the amorphous region of the polymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 131–138, 2003
Preparation and properties of highly functional copolyetheresters
Authors: Park Yun Heum , Kim Ki Young , Han Myong Hee
Published: January 2003

Block copolyetheresters with hard segments of poly(trimethylene 2,6‐naphthalene dicarboxylate) and soft segments of poly(tetramethylene ether)glycol 2,6‐naphthalene dicarboxylate were prepared by the melt polycondensation of dimethyl 2,6‐naphthalene dicarboxylate (NDC), 1,3‐propanediol (PD), and poly(tetramethylene ether)glycol (PTMEG) with molecular weights of 1000. The block copolyetheresters were characterized by 1H‐NMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. The block copolyetheresters synthesized with NDC/PD/PTMEG were more heat resistant than those synthesized with dimethyl terephthalate/PD/PTMEG. The block copolyetheresters synthesized with NDC/PD/PTMEG showed stronger elastoplastic behavior than those synthesized with NDC/1,4‐butanediol/PTMEG. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 139–145, 2003
Graft mechanism of acrylonitrile onto starch by potassium permanganate
Authors: Zhang Liming , Gao Jianping , Tian Ruchuan , Yu Jiugao , Wang Wei
Published: January 2003

The graft mechanism of acrylonitrile (AN) onto starch under the initiation of potassium permanganate was investigated. The relationships of the grafting rate and the concentrations of potassium permanganate, AN, and backbone starch, as well as the reaction temperature, were established. On this basis, the equation for the rate of the graft copolymerization was derived, and the apparent activation energy for the graft copolymerization was obtained. Through the study of the oxidation reaction of starch with manganic ions, the valence changes of manganic ions during the graft copolymerization, and the grafting ability of different starch derivatives, together with electron spin resonance analysis, the grafting mechanism for the graft copolymerization of AN onto starch under the initiation of potassium permanganate was determined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 146–152, 2003
Thermotropic liquid‐crystalline polymers: Synthesis, characterization, and properties of poly(azomethine esters)
Authors: Shukla Utkarsh , Rao K. V. , Rakshit Animesh Kumar
Published: January 2003

A series of poly(azomethine ester) copolymers were synthesized by the solution polycondensation method with different diamines. The synthesized polymers were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), hot‐stage polarized microscopy, wide‐angle X‐ray diffraction, and solution viscosity. All polymers showed good thermal stability. The thermotropic liquid‐crystalline properties were examined by DSC and by microscopic observations. Except for one, all of the polymers showed nematic liquid‐crystalline behavior. The effects of temperature on crystallinity and the substituent on solubility, thermal stability, melting temperature, and viscosity were also studied. The voluminosity and shape factor were also computed from the viscosity data. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 153–160, 2003
Mathematical modeling of diffusion‐controlled free‐radical terpolymerization reactions
Authors: Keramopoulos Anastasios , Kiparissides Costas
Published: January 2003

A comprehensive mathematical model is developed to describe the kinetics and molecular and compositional developments in a free‐radical terpolymerization batch reactor. This model is based on a fairly general kinetic mechanism, including chain‐transfer and terminal double‐bond reactions. We take into account the effects of diffusion‐controlled phenomena (i.e., gel, glass, and cage effects) on polymerization kinetics by extending our previous model on diffusion‐controlled reactions to terpolymerization systems. Triple moments for the live and dead trivariate chain‐length terpolymer composition distributions are introduced to describe the molecular and compositional developments in the terpolymerization system. The predictive capabilities of this model are demonstrated by simulation of the free‐radical, bulk terpolymerization of butyl acrylate/methyl methacrylate/vinyl acetate under different experimental conditions. It is shown that the model predictions are in good agreement with experimental data on monomer conversion, average molecular weights, and terpolymer composition, as reported by Dube and Penlidis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 161–176, 2003
Optical properties of block copolymers containing pendant carbazole groups and in situ synthesized CdS nanoclusters
Authors: Gratt Jason A. , Cohen Robert E.
Published: January 2003

Ultraviolet–visible absorption spectra and photoluminescence spectra were used to demonstrate efficient charge‐carrier migration in a novel bulk heterogeneous block copolymer system. One moiety of the block copolymer was functionalized with charge‐transporting carbazole groups, whereas the other block formed domains suitable for the in situ synthesis of CdS nanoclusters. The excitation of the cluster‐free copolymers with 350‐nm‐wavelength radiation led to a strong emission peak at 450 nm that was associated with the carbazole groups. When CdS clusters were present in nearby but spatially distinct domains, the carbazole emission was completely quenched and replaced by a very broad emission in the visible range (near 560 nm). The implications of these observations are discussed in the context of the energy‐transfer mechanism and possible device applications. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 177–182, 2003
Effect of nanosilica on the properties of polyester‐based polyurethane
Authors: Zhou Shu‐Xue , Wu Li‐Min , Sun Jian , Shen Wei‐Dian
Published: January 2003

Polyester‐based polyurethanes with embedded nanosilica particles were prepared. The viscosity of polyester resins without and with nanosilica was determined by rheoviscometry. The morphology and mechanical and optical properties of the polyurethane coatings were studied intensively with a transmission electron microscope, a pendulum hardness tester, a scanning probe microscope, an Instron testing machine, an abrader and an ultraviolet–visible spectrophotometer. The viscosity of the polyester resins increased as the nanosilica content increased. Nanosilica could basically be dispersed into the polyester and its polyurethane on a nanoscale. The addition of a small amount of nanosilica increased the hardness, abrasion resistance, and tensile properties of the polymer films. However, these mechanical properties could be worsened at higher nanosilica contents. The ultraviolet–visible spectra showed that the absorbance and reflection of ultraviolet–visible light by the polyurethane films increased as the nano‐SiO2 content increased, especially at wavelengths of 290–400 nm. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 189–193, 2003
An X‐ray scattering study of water‐conditioned injection‐molded starch during isothermal heating
Authors: Cagiao M. E. , Bayer R. K. , Rueda D. R. , Baltá Calleja F. J.
Published: January 2003

The in situ structure variation of injection‐molded starch (as processed and after water conditioning) during heat treatment was investigated by means of wide‐angle X‐ray scattering using synchrotron radiation. Results confirm that the crystal structure of potato starch is destroyed after injection molding, while as‐processed corn starch preserves some degree of crystallinity. This residual crystallinity in corn starch is related to the crystalline Vh‐form, made of complexes of amylose with lipids. Furthermore, it is shown that both starch types can develop crystallinity by water conditioning: potato starch yields the crystal B‐form, while corn starch yields the crystal A‐form coexisting with the persistent Vh‐form. Upon isothermal heating of samples under vacuum, a rapid decrease of crystallinity, which is a function of both time and treatment temperature, is detected. Crystallinity variations are discussed in terms of water evaporation, the leveling‐off values of crystallinity being dependent on the temperature of the isothermal treatment. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 17–21, 2003
Nonisothermal cure kinetics in the synthesis of polybenzoxazine–clay nanocomposites
Authors: Shi Zixing , Yu Dingsheng , Wang Yizhong , Xu Riwei
Published: January 2003

The ability to understand and model the mechanism of cure kinetics accurately is crucial for the production of thermosetting resin‐based nanocomposites. This article reports on work performed to elucidate an accurate model of cure kinetics for the formation of polybenzoxazine–montorillonite nanocomposites through the use of differential scanning calorimetry with nonisothermal methods, including single‐heating and multiple‐heating methods. The results indicated that both the Kissinger and Ozawa methods for calculating the activation energy gave fairly close results of 115 and 120 kJ/mol, respectively. The reaction order was about 1.31, calculated from the single‐heating method based on the autocatalytic method, and a comparison was made of the dynamic curing behaviors in the syntheses of polybenzoxazine and polybenzoxazine–montorillonite nanocomposites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 194–200, 2003
Investigation of electropolymerized polypyrrole composite film: Characterization and application to gas sensors
Authors: Bhat N. V. , Gadre A. P. , Bambole V. A.
Published: January 2003

Polypyrrole–Polymethylmethacrylate (PMMA + PPy) composite films were prepared electrochemically by means of codeposition at constant potential. The films were characterized by using Infrared spectroscopy, wide‐angle X‐ray diffraction analysis, and scanning electron microscopy. The appearance of standard and some new absorption bands for PPy and PMMA confirms the composite formation. The mechanical properties of the conducting PMMA+ PPy films were studied and found to be improved with respect to the control PPy films. The electrical conductivity of the PMMA + PPy film was measured by using standard four‐ and two‐probe methods. The conductivity of the films was found to depend on the pyrrole content. These conducting composites were further used as gas sensors by observing the change in the current when exposed to ammonia gas. The film gives a fast and reproducible response towards ammonia gas. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88:22–29, 2003
Properties of poly(vinyl chloride) blended with an emulsion copolymer of N‐cyclohexylmaleimide and methyl methacrylate
Authors: Yang Liting , Sun Donghai , Li Yanfang , Liu Guodong , Gao Jungang
Published: January 2003

Emulsion‐polymerized copolymers of methyl methacrylate and N‐cyclohexylmaleimide were synthesized and used for blending with poly(vinyl chloride) (PVC) to improve the heat resistance of PVC. The thermal stabilities of the blends with different copolymer contents were characterized by thermogravimetric analysis, torsional braid analysis, and the Vicat softening temperature. The mechanical properties and rheological behavior of the blends were also determined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 201–205, 2003
Rheological properties and morphology of compatibilized poly(butylene terephthalate)/linear low‐density polyethylene alloy
Authors: Yang Jinghui , Shi Dean , Gao Ying , Song Yongxian , Yin Jinghua
Published: January 2003

The rheological behavior of PBT/LLDPE and PBT/LLDPE‐g‐AA blends [where PBT is poly(butylene terephthalate), LLDPE is linear low‐density polyethylene, and AA is acrylic acid] under a capillary flow was investigated with a capillary rheometer. The Utracki equation was used to describe the viscosity–composition dependence of PBT/LLDPE and PBT/LLDPE‐g‐AA blends at low shear stresses. However, at high shear stresses, this equation was not suitable for these blending systems. There existed a maximum on the curves of the entrance pressure drop versus the blending compositions, and the interlayer slip factor β in the Utracki equation was related not only to the shear stress but also to the elasticity difference of the two blending components. Morphological observations indicated that at high shear rates, there existed two different morphologies at different positions of the extrudates, and this was the reason that the Utracki equation failed. Near the wall of the capillary, low‐viscosity PBT stratified, and this resulted in an additional decrease in the viscosities of the blending systems. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 206–213, 2003
Peel‐strength behavior of bilayer thermal‐sprayed polymer coatings
Authors: Yan F. Y. , Gross K. A. , Simon G. P. , Berndt C. C.
Published: January 2003

We prepared various bilayer polymer coatings of ethylene methacrylic acid (EMAA) copolymer and ionomer by the thermal‐spray process under a range of preheat temperatures (PTs) to investigate their ability to be repaired. The thermal properties, crystallinity, microstructure, and interface strength of the coatings were investigated with differential scanning calorimetry, X‐ray diffraction, scanning electron microscopy, and mechanical testing. Processing parameters influenced the final morphological structure of the coatings. The crystallinity of the coatings increased with a higher final temperature, whereas the coating density decreased. The decrease in density was attributed to the appearance of bubbles, 250 μm in size, formed in the coatings during the spray process. For the monolayer coating of polymer on a metal substrate, a higher PT produced a greater contact area of the coating to the substrate. The adhesion of EMAA ionomer to steel was always lower than that of EMAA copolymer to steel. This may have been largely due to the interfacial adhesion between the polymer and steel being dominated by strong secondary bond interactions. Experimental results also indicate that the peel strength between polymers was at least twofold stronger than that between the polymer and the steel substrate for PTs greater than 100°C. The mixed bilayer coating of ionomer on copolymer produced the highest peel strength. The interface between the plastic layers was clearly visible under the scanning electron microscope at lower PTs, becoming more diffuse with an increase in PT. On the basis of these observations, the adhesion mechanism between polymers was explained by the formation of welding points. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 214–226, 2003
Analysis of the development of isotropic residual stresses in a bismaleimide/spiro orthocarbonate thermosetting resin for composite materials
Authors: Alcoutlabi Mataz , McKenna Gregory B. , Simon Sindee L.
Published: January 2003

In this article, we extend our model of isotropic residual stress development in thermosets to a novel thermosetting resin system: bismaleimide/spiro orthocarbonate. In this system, the cure shrinkage and resulting isotropic residual stresses are reduced through a ring‐opening reaction that occurs independently of the addition reaction. The modeling effort includes a parametric analysis of the effects of various parameters, including the volume changes involved in the reactions, the relative rates and orders of the reactions, the cure history, and the values of the bulk moduli and thermal expansion coefficients. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 227–244, 2003
Properties of n‐butyl methacrylate copolymer latex films derived from crosslinked latex particles
Authors: Mohd Ghazaly H. , Daniels E. S. , Dimonie V. L. , Klein A. , Sperling L. H. , El‐Aasser M. S.
Published: January 2003

Films obtained from copolymer latexes of n‐butyl methacrylate (BMA) with a series of crosslinking monomers [i.e., a macromonomer crosslinker (Mac), ethylene glycol dimethacrylate (EGDMA), and aliphatic urethane acrylate] exhibited differences in their tensile properties and swelling behaviors. For P(BMA‐co‐EGDMA) copolymer, a dependence on the initiator type was obtained. It is postulated that the network microstructures for the various copolymers evolved as the result of the copolymerization reactions between the monomer pairs during the synthesis in the miniemulsion free‐radical copolymerization. These network microstructures are, therefore, hypothesized to influence the mechanical properties of the resultant films. Copolymers prepared with Mac were tough in comparison with copolymers made with EGDMA. The presence of longer linear or lightly crosslinked poly(n‐butyl methacrylate) (PBMA) chains and the looseness of the crosslinked network structures in the PBMA‐co‐Mac copolymers appear to be the factors responsible for the differences. All of the copolymer films disintegrated into swollen individual microgels when they were immersed in tetrahydrofuran. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 42–49, 2003