bluuebunny/crossref_metadata_2025 huggingface dataset:
Moral Hazard and Consumer-Driven Health Care: A Fundamentally Flawed Concept
Authors: Geyman John P.
Published: April 2007

For more than 30 years, most health care economists in the United States have accepted a conventional theory of health insurance based on the concept of moral hazard: an assumption is made that insured people overuse health care services because they have insurance. The recent trend toward “consumer-driven health care” (CDHC) is advocated by its supporters based on this same premise, assuming that imprudent choices by patients can be avoided if they are held more financially responsible for their health care choices through larger co-payments and deductibles and other restrictions. This article examines how moral hazard–based CDHC plays out in both private plans and public programs. The author identifies seven ways in which this concept fails the public interest, while also failing to control health care costs. Uninsured and underinsured people, now including many in the middle class, underuse essential health care services, resulting in increased morbidity and more preventable hospitalizations and deaths among these groups than their more affluent counterparts. A case is made to reject moral hazard as an organizing rationale for health care, and the author offers some alternative approaches.
Massachusetts' Approach to Universal Coverage: High Hopes and Faulty Economic Logic
Authors: Himmelstein David U. , Woolhandler Steffie
Published: April 2007

Massachusetts' new universal coverage law has been lauded as a national model. The legislation expands Medicaid HMOs to cover all of the poor (free of charge) and near poor (with partial subsidies), and requires the rest of the uninsured to pay for private coverage. Large employers that don't offer coverage will pay a small tax. Other provisions raise Medicaid payment rates to providers; expand some smaller programs for the poor; allow dependents to remain on family policies up to age 25; and require increased public disclosure of medical price and quality data. Unfortunately, the legislation includes grossly inadequate funding for the promised subsidies and assumes that the uninsured, most of whom are in lower-income families, can afford substantial premiums. Moreover, the required coverage will leave gaping holes—co-payments and deductibles that will leave families vulnerable to bankruptcy. All of the new coverage will be purchased from private insurers with high overhead costs. The bill includes no credible cost-containment mechanisms. The legislation reflects a political calculus favoring private insurers, and ignores the imperative of cost control and the financial realities of cash-strapped families. Hence, it is unlikely to achieve universal coverage or to stabilize the state's health care financing system.
Symmetry of the pentacene molecule and classification of electron states studied in the frame of group action on a set
Authors: Potera Piotr , Stefaniuk Ireneusz , Kuźma Marian
Published: April 2007

Pentacene have recently become the subject of intense studies due to their physical properties which follow from the states of their outer-shell electrons that are able to take part in molecule bonding. The symmetry of these molecules provides the classification of quantum states according to the group theory method. In this paper, we apply a molecular state-space factorization scheme for the classification of pentacene molecules based on the structure of their electron states.
Numerical spherically symmetric static solution of the RTG equations outside of matter
Authors: Godizov Anton
Published: April 2007

There was obtained a numerical external solution for the exact system of the RTG equations using natural boundary conditions in the static spherically symmetric case. The properties of the solution are discussed.
Evaluation of the inelastic mean free path (IMFP) of electrons in polyaniline and polyacetylene samples obtained from elastic peak electron spectroscopy (EPES)
Authors: Gergely György , Menyhard Miklós , Sulyok Attila , Gurban Sándor , Lesiak Beata , Jablonski Aleksander , Kosinski Andrzej , Toth József , Varga Dezső
Published: April 2007

The inelastic mean free path (IMFP) of electrons was determined experimentally for selected polyaniline and polyacetylene samples with Ag and Ni references using elastic peak electron spectroscopy (EPES). The surface composition was determined by XPS and density by helium pycnometry. The high resolution hemispherical ESA-31 and ADES-400 spectrometers were used for measurements in the energy range E = 0.5–3.0 keV and E =0.4 − 1.6 keV, respectively. The integrated elastic peak intensity ratios for sample and reference were calculated using the Monte Carlo (MC) algorithm based on the electron elastic scattering cross-sections database NIST SRD64 version 3.1 and applying TPP-2M IMFPs for polymers. Surface excitation parameters (SEP) and material parameters (ach) for polymers were determined, using the model of Chen, from comparison of measured and MC calculated elastic peak intensity ratios. These corrections proved to be efficient in decreasing the percentage deviations between the obtained IMFPs and the TPP-2M formula IMFPs. The elastic peak of hydrogen was observed in the EPES spectra of polymers. The experimental contribution of the hydrogen to the total elastic peak was 0.58%, while this value obtained from the MC simulations was 1.98%.
Pulsed ytterbium-doped large mode area double-clad fiber amplifier in MOFPA configuration
Authors: Świderski J. , Zając A. , Skórczakowski M.
Published: April 2007

A pulsed master oscillator fiber power amplifier working in nanosecond range has been developed. An ytterbium-doped double-clad (large mode area) optical fiber was used as an amplifying medium. Actively Q-switched Nd:YVO laser was used as a seed of light pulses. The system worked at the repetition rate from 10 kHz to 40 kHz. At the amplifier output, pulses of 10.9 kW peak-power were achieved. The laser system worked at the slope efficiency of 30%.
Prepregnancy weight, inappropriate gestational weight gain, and smoking: Relationships to birth weight
Authors: May Richard
Published: April 2007

This study was designed to test predictors of infant birth weight based on categories of prepregnancy body mass index (BMI), gestational weight gain, and smoking. Data were collected retrospectively from records of 233 mother‐infant pairs enrolled in the Siouxland Women, Infants, and Children (WIC) Program in Sioux City, Iowa. Prepregnancy BMI and gestational weight gain were coded according to Institute of Medicine guidelines. Smoking behavior was coded based on reported smoking during the last 3 months of pregnancy. Multiple regression analysis was used to test predictors of infant birth weight. Forty‐two percent of women gained more weight than recommended, and 16% gained less than recommended. Based on prepregnancy BMI, women were classified as underweight (12%), overweight (16%), or obese (31%). Twenty‐four percent of mothers reported smoking late in gestation. Higher birth weight was predicted by prepregnancy obesity (+144 g). Lower infant birth weight was predicted by lower (−162 g) and higher (−153 g) than recommended weight gain, and by lower (−299 g) and higher (−168 g) levels of smoking. Depression of birth weight among women who gained excess weight may relate to inadequate early weight gain or pregnancy complications. More research is needed regarding physiological consequences of these maternal factors and their associated demographic risk factors.Am. J. Hum. Biol. 19:305–310, 2007. © 2007 Wiley‐Liss, Inc.
HLA genes and surnames show a similar genetic structure in Lombardy: Does this reflect part of the history of the region?
Authors: Lisa Antonella , De Silvestri Annalisa , Mascaretti Luca , Degiuli Alberto , Guglielmino Carmela R.
Published: April 2007

Lombardy, in northern Italy, is the most populated and industrialized Italian region. We attempt to study its genetic structure with two independent sets of data: HLA allele frequencies and surnames. According to our results, it is plausible to deduce that ancient history, more than genetic isolation and drift, may have contributed to the present genetic structure of Lombardy. The hypothesis seems to be confirmed by the results of the cluster analysis of the 11 provinces of the region, which was performed using two different types of markers. Both genes and surnames show approximately the same structure. Not only Celts but also ancient Ligurians (and Etruscans) probably shaped the region into the present three clusters in which the 11 provinces appear to be genetically structured. In particular, an ancient historic, archaeological, and linguistic boundary, along the Adda River, seems to be preserved in present‐day Lombardy's population structure.Am. J.Hum. Biol. 19:311–318, 2007. © 2007 Wiley‐Liss, Inc.
Size at birth and growth trajectories to young adulthood
Authors: Adair Linda S.
Published: April 2007

Few studies in developing countries follow growth trajectories from birth to adulthood. Such studies are important because size at birth and postnatal growth affect risk of chronic disease in adulthood. This study examines the inter‐relationships of maternal factors during pregnancy, infant birth weight and length, early postnatal growth, and young adult height, weight, BMI, and skinfold thicknesses, with particular attention to patterns of growth associated with increased chronic disease risk. Women were recruited in pregnancy, and offspring were followed from birth to age 21 in the community‐based Cebu (Philippines) Longitudinal Health and Nutrition Survey. Birth weight and length are independently, positively associated with height, BMI and sum of skinfolds in young adult males and females, and inversely associated with the subscapular to triceps ratio in males only. The effects of size at birth on adult size were modified by birth order, and remained significant after adjusting for maternal nutritional status, socioeconomic status at birth and throughout the growth period, and maturation. Early postnatal growth was strongly influenced by BMI at birth, with rapid early infant weight gain associated with thinness. The growth pattern of the at‐risk group most often associated with increased risk of chronic disease (small at birth, relatively heavy as an adult), was characterized by more rapid growth in the first 4 postnatal months. The high level of inter‐relatedness of maternal nutrition in pregnancy, prenatal growth, and postnatal growth emphasizes the need to consider the full growth trajectory in studies of developmental origins of adult disease.Am. J. Hum. Biol. 19:327–337, 2007. © 2007 Wiley‐Liss, Inc.
Secular trends in anthropometric characteristics, physical fitness, physical activity, and biological maturation in Flemish adolescents between 1969 and 2005
Authors: Matton Lynn , Duvigneaud Nathalie , Wijndaele Katrien , Philippaerts Renaat , Duquet William , Beunen Gaston , Claessens Albrecht L. , Thomis Martine , Lefevre Johan
Published: April 2007

In this study, secular trends in anthropometric characteristics, physical fitness, physical activity, and biological maturity over the past 25–35 years in Flemish adolescents were investigated. Representative cross‐sectional samples of 12–18‐year‐old secondary school children (11,899 assessments in boys in 1969–1974, 4,899 girls in 1979–1980, 1,429 boys and 1,772 girls in 2005) and parent‐offspring pairs tested at approximately the same age during adolescence (55 father‐son pairs, mean age fathers = 15.47 years, mean age sons = 15.38 years; 62 mother‐daughter pairs, mean age mothers = 16.63 years, mean age daughters = 15.01 years) were used. The cross‐sectional data were analyzed in 6 yearly age‐categories using Wilcoxon rank sum tests. For the parent‐offspring data paired t‐tests, simple linear regressions to adjust for parent‐offspring differences in chronological age and multiple linear regressions to adjust for parent‐offspring differences in chronological and skeletal age were conducted. The cross‐sectional study generally revealed an increase in weight, stature, BMI, skinfolds and trunk‐extremity index, and a decrease in the performance on several physical fitness tests. In the parent‐offspring study, only sons were maturationally advanced compared to fathers. Even after adjustment for parent‐offspring differences in chronological age and in chronological and skeletal age, results for stature, trunk‐extremity index and physical fitness were generally similar to the cross‐sectional study. No secular trend was observed for sports participation. The fact that the positive secular trends in weight, BMI, and skinfolds of the cross‐sectional study were not entirely confirmed in the parent‐offspring study is probably due to higher similarity in genetic and familial background, higher socio‐economic status, and more health‐consciousness of the latter.Am. J. Hum. Biol. 19:345–357, 2007. © 2007 Wiley‐Liss, Inc.
Focused life history data and linear enamel hypoplasia to help explain intergenerational variation in relative leg length within Taiwanese families
Authors: FLOYD B.
Published: April 2007

This study first examines the hypothesis that significant intergeneration increases in stature within 85 Taiwanese families in two study locations were primarily the result of increases in subischial leg length. It then evaluates a second hypothesis that independent assessments of the extent of intergenerational change in childhood environments within these families helped account for parent–offspring differences in relative leg length. Childhood environments were assessed using two criteria: developmental environment scores derived from life history data and evidence of linear enamel hypoplasia (LEH). Relative leg length was represented in two ways, as either the difference between internally estimated sex‐specific z‐scores of sitting height and subischial leg length (zD = zSH − zLL) or as relative sitting height (RSH; sitting height/height × 100). Paired Student t tests indicated intergenerational increases in relative leg length were significantly greater than zero in both study locations (P ≤ 0.012). The second hypothesis, tested using a hierarchical model with maximum likelihood estimation that allowed for nesting of more than one offspring per family, received support as midparent–offspring differences in composite scores were significantly positively associated with midparent–offspring differences in relative leg length. This was true alone (P = 0.018), and when significant associations with LEH prevalence among mothers and offspring were statistically controlled for (P = 0.010). Evidence also indicated that while the large majority of offspring were taller than their midparental average height (84.3%; 91/108), offspring who were taller were also more likely to have relatively longer legs than by chance alone (Fishers exact, P = 0.027).Am. J. Hum. Biol. 19:358–375, 2007. © 2007 Wiley‐Liss, Inc.
Endurance running and digit ratio (2D:4D): Implications for fetal testosterone effects on running speed and vascular health
Authors: Manning John T. , Morris Laura , Caswell Noreen
Published: April 2007

There is anatomical and physiological evidence that endurance running (ER), i.e., running one or more kilometers using aerobic metabolism, originated early in the evolution of Homo, and the consequences of early selection for ER may be important in modern Homo. Here we examine ER performance in competitive ER. ER is sex dependent such that men tend to run faster than women, and the influence of sex on ER suggests that it may be modified by testosterone (T). It is shown that a putative proxy for prenatal T, the ratio of the length of the 2nd and 4th digits (2D:4D), is correlated with ER. Thus performance in training for ER was associated with high prenatal T, as measured by low 2D:4D, in both men and women. In cross‐country races from 1 to 4 miles, 2D:4D explained about 25% of the variance in both male and female ER. Therefore, speed in ER was dependent on a proxy for prenatal T. 2D:4D correlates with performance in sport and exercises, which test a mix of strength and fitness, but the associations are in general quite weak with 2D:4D accounting for less than 10% of the variance in performance. Our finding that 2D:4D explains about 25% of the variance in ER suggests that prenatal T is important in determining efficiency in aerobic exercise. Early populations of Homo may have been strongly selected for ER and high prenatal T. The implications of this for patterns of predisposition to cardiovascular disease in modern Homo are discussed.Am. J. Hum. Biol. 19:416–421, 2007. © 2007 Wiley‐Liss, Inc.
Y‐chromosome lineages in São Tomé e Príncipe islands: Evidence of European influence
Authors: Gonçalves Rita , Spínola Hélder , Brehm António
Published: April 2007

The Y‐chromosome haplogroup composition of the population of São Tomé e Príncipe (STP) archipelago was analyzed using 25 biallelic markers and compared with populations of different origins from Europe, Africa, and the Middle East. Two main Y‐chromosome haplogroups were found: E3a, very common among sub‐Saharans accounts for 84.2% of the paternal lineages and R1b, typical of West Eurasia, represents 8.7% of the overall male population. Nevertheless, we detected in the population of STP a significant heterogeneous distribution of R1b among the two main ethnic groups of the archipelago: Forros (10.3%) and Angolares (6.6%). Together, haplogroups known to be prevalent in West Eurasia reach 12.5% of the chromosomes analyzed unequally distributed among the two groups: Forros present 17.7% while Angolares display only 8.2% of west Eurasian haplogroups. Our findings suggest that, despite its sub‐Saharan genetic background, a relevant contribution of European paternal lineages is present in nowadays STP population. This influence has shown to be stronger in Forros than in Angolares, which could be explained by the social isolation that these have last experienced through their history.Am. J. Hum. Biol. 19:422–428, 2007. © 2007 Wiley‐Liss, Inc.
Validation of hand‐held bioelectrical impedance analysis with magnetic resonance imaging for the assessment of body composition in overweight women
Authors: Varady Krista A. , Santosa Sylvia , Jones Peter J. H.
Published: April 2007

Methods of assessing body composition suitable for use in clinical trials should be accurate, reliable, and easy to perform. One such technique routinely implemented is hand‐held bioelectrical impedance analysis (BIA). The validity of this method, however, in body composition assessment of overweight women is not known. The aim of this study was to validate the hand‐held BIA technique with magnetic resonance imaging (MRI) for the assessment of body composition in overweight women. Fat mass, percent fat mass, fat‐free mass, and percent fat‐free mass values estimated by hand‐held BIA were compared to those measured by MRI. Thirty‐one Caucasian women (50.1 ± 8.2 years, body mass index of 26.9 ± 3.1 kg/m2) participated in the study. BIA measurements were highly reproducible (technical error (TE) was 0.06 ± 0.07 kg for fat mass and 0.08 ± 0.11% for percent fat mass), but were significantly different (P < 0.0001) for each body composition parameter when compared to MRI. BIA underestimated fat mass by 2.3 ± 3.3 kg and percent fat mass by 5.6 ± 3.9%. Likewise, BIA overestimated fat free mass by 7.4 ± 2.7 kg and percent fat free mass by 5.6 ± 3.2%. No relationship between the bias and the mean of the two measurements was noted suggesting that bias is not related to measurement size. Although hand‐held BIA gives reproducible findings, the bias noted for all body composition parameters puts into question the validity of this regional impedance device for use in clinical trials in overweight women.Am. J. Hum. Biol. 19:429–433, 2007. © 2007 Wiley‐Liss, Inc.
Enzyme immunoassay for total immunoglobulin E in dried blood spots
Authors: Tanner Susan , Mcdade Thomas W.
Published: April 2007

Elevated circulating levels of total immunoglobulin E (IgE) are associated with both allergic disease and repeated macro‐parasitic infections. Population‐based research on IgE has been limited by the logistical constraints associated with obtaining and processing venipuncture blood samples. In this short report, we present an enzyme immunoassay protocol for quantifying circulating total IgE levels in capillary whole blood, collected from a finger prick and dried on filter paper. The assay demonstrated acceptable levels of accuracy, precision, and reliability. IgE remained stable at room temperature for only 2–4 days and degraded rapidly at higher temperatures suggesting that samples should be refrigerated or frozen within 1–2 days of collection. It is hoped that the relative ease of blood spot collection will expand opportunities for population‐based research on IgE.Am. J. Hum. Biol. 19:440–442, 2007. © 2007 Wiley‐Liss, Inc.
Association analysis of COMT polymorphisms and schizophrenia in a Chinese Han population: A case‐control study
Authors: Yu Rui , Zhang Xian‐Ning , Huang Xiao‐Xiao , Ding Shi‐Ping , Li Ji‐Cheng
Published: April 2007

Schizophrenia is a common disease with complex mode of inheritance; great efforts have been made to identify the susceptible genes. Catechol‐O‐methyltransferase (COMT) gene has long been considered as a candidate gene mainly because of two reasons: First, it encodes a key dopamine catabolic enzyme. Second, it maps to the velocardiofacial syndrome (VCFS) region of chromosome 22q11, which is associated with schizophrenia predisposition. Numerous case‐control and family‐based studies have been conducted, majority of them focused on a functional Val/Met polymorphism (rs4680). Unfortunately, these studies have produced conflicting results. In a previous report, Shifman et al. found a three‐marker haplotype (rs737865–rs4680–rs165599) that showed significant association with schizophrenia. In this study, we try to replicate their findings in Chinese Han population and failed to find any associations. © 2007 Wiley‐Liss, Inc.
Association of the neuropilin‐2 (NRP2) gene polymorphisms with autism in Chinese Han population
Authors: Wu Suping , Yue Weihua , Jia Meixiang , Ruan Yan , Lu Tianlan , Gong Xiaohong , Shuang Mei , Liu Jing , Yang Xiaoling , Zhang Dai
Published: April 2007

Autism is a pervasive neurodevelopmental disorder, with a significant role of genetic factors in its development. The neuropilin‐2 (NRP2) gene is localized to 2q34, an autism susceptibility locus. NRP2 has been demonstrated to both guide axons and to control neuronal migration in the central nervous system. It has been reported that NRP2 may be required in vivo for sorting migrating cortical and striatal interneurons to their correct destination. We examine the association between the NRP2 gene and autism using a cohort of 169 Chinese Han family trios. Four single nucleotide polymorphisms (SNPs) were genotyped by the polymerase chain reaction‐based restriction fragment length polymorphism (PCR‐RFLP) analyses. The transmission disequilibrium tests (TDT) of SNPs and haplotype association were carried out using the TDTPHASE program. We found significant genetic association between autism and two of the SNPs of the NRP2 gene (rs849578: P = 0.017, rs849563: P = 0.027), as well as specific haplotypes, especially those formed by rs849563. Furthermore, haplotypes constructed with all markers showed significant excess transmission in both global and individual haplotype analyses (P = 0.004 and 0.017, respectively). The polymorphisms in the NRP2 gene are associated with autism, implying that the NRP2 gene may render individuals to be predisposed to autism. © 2007 Wiley‐Liss, Inc.
Why do young women smoke? IV. Role of genetic variation in the dopamine transporter and lifetime traumatic experience
Authors: Segman Ronnen H. , Kanyas Kyra , Karni Osnat , Lerer Elad , Goltser‐Dubner Tanya , Pavlov Vera , Lerer Bernard
Published: April 2007

Cigarette smoking is a complex behavior to which environmental, psychological, and genetic factors contribute. Applying a multifactorial model, we examined the role of genetic variation in the dopamine transporter (DAT1) in smoking initiation (SI) and nicotine dependence. The participants were female college students who had never smoked (n = 148) or had smoked daily for at least a year (n = 242). All participants provided extensive background information and completed a series of psychological instruments. Five SNPs were genotyped in the 3′ and 5′ regions of DAT1. Data were analyzed by logistic regression. The best fitting model for SI (P = 1.9 × 10−17, Nagelkerke R2 = 0.33) revealed novelty seeking (OR = 1.14, P = 0.000004) and lifetime traumatic experience (OR = 2.3, P = 0.001) as risk factors and a DAT1_E15 + 274—DAT1_VNTR G‐9 haplotype as protective (OR = 0.57, P = 0.03). In the model for nicotine dependence (P = 1.4 × 10−8, Nagelkerke R2 = 0.27) novelty seeking was a risk factor (OR = 1.07, P = 0.03); the DAT1_E15+274—DAT1_VNTR G‐9 haplotype (OR = 0.37, P = 0.001) and the interaction between trauma and a DAT1_E15 + 274—DAT1_VNTR C‐9 haplotype (OR = 0.15, P = 0.01) were protective. Lifetime experience of trauma was associated with high nicotine dependence among non‐carriers of the C‐9 haplotype but not among carriers of this haplotype. These findings indicate that in the context of a multifactorial model, haplotypes in the 3′ region of DAT1 influence the propensity of young women to initiate smoking as well as the severity of nicotine dependence once the habit is established. A haplotype in the 3′ untranslated region of DAT1 modifies the effect of lifetime traumatic experience on the severity of nicotine dependence. © 2007 Wiley‐Liss, Inc.
Future of neuroprotection for acute stroke: In the aftermath of the SAINT trials
Authors: Savitz Sean I. , Fisher Marc
Published: April 2007

The concept of neuroprotective therapy for acute ischemic stroke to salvage tissue at risk and improve functional outcome is based on sound scientific principles and extensive preclinical animal studies demonstrating efficacy. The failure of most neuroprotective drugs in clinical trials has been due to inadequate preclinical testing and flawed clinical development programs. The Stroke Therapy Academic Industry Roundtable (STAIR) group has outlined rational approaches to preclinical and clinical studies. The positive results from the first Stroke‐Acute‐Ischaemic‐NXY‐Treatment (SAINT‐I) trial of the free‐radical spin‐trap drug, NXY‐059, which followed many of the STAIR guidelines, reinvigorated enthusiasm in neuroprotection, but the SAINT‐II trial did not replicate the positive effect on the same primary prespecified outcome measure. This has led to concerns about the future of neuroprotection as a therapeutic strategy for acute ischemic stroke. We discuss new suggestions to bridge the chasm between preclinical animal modeling and acute human stroke trials to potentially enhance the future assessment of novel neuroprotective drugs. Ann Neurol 2007
Oxygen‐transport properties of liquid‐crystalline polyesters based on 4,4′‐bibenzoic acid
Authors: Hu Y. S. , Wang H. P. , Schiraldi D. A. , Hiltner A. , Baer E.
Published: April 2007

This study examined the oxygen‐transport properties of aromatic liquid‐crystalline (LC) polyesters of 4,4′‐bibenzoic acid (BB) and an aliphatic diol. The effect of the spacer length was probed by the number of methylene groups in the diol being increased from 3 to 6. Parallel studies were performed on polymers in which the LC character was reduced or removed by copolymerization with 30 mol % nonmesogenic isophthalic acid (BB‐30I) or by the replacement of BB with 4,4′‐oxybis(benzoic acid) (OBB). The oxygen‐transport properties were interpreted in terms of the solid‐state structure as revealed by the thermal behavior and wide‐angle X‐ray diffraction. The strong odd–even effect of the spacer length that characterized the thermal transitions of the BB polyesters was weak or absent from the oxygen‐transport properties when the effect of crystallinity was considered. Permeability and diffusivity tended to increase with the spacer length. The lower oxygen permeability of all the BB polyesters compared with that of the BB‐30I copolyesters and the OBB polyesters was due primarily to lower oxygen solubility. The low solubility of the noncrystalline LC phase was ascribed to a smaller free‐volume hole size and possibly to a lower free‐volume hole density in comparison with an amorphous glass. The solubility of oxygen in the noncrystalline regions of the BB‐30I copolyesters and in the amorphous OBB polyesters conformed to the relationship between the solubility and the glass‐transition temperature previously established for amorphous and glassy aromatic polyesters. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 105: 30–37, 2007
Atom transfer radical polymerization of methyl acrylate with molybdenum halides as catalysts in an ionic liquid
Authors: Maria Sebastien , Biedroń Tadeusz , Poli Rinaldo , Kubisa Przemysaw
Published: April 2007

The atom transfer radical polymerization of methyl acrylate in 1‐butyl‐3‐methylimidazolium hexafluorophosphate was studied with a molybdenum halide catalytic system. A combination of a bromine‐containing initiator (ethyl‐2‐bromopropionate) with a chloride‐containing catalyst [MoCl3(PMe3)3/MoCl4(PMe3)3] led to a controlled polymerization, and matrix‐assisted laser desorption/ionization time‐of‐flight analysis of the polymers indicated that the reversibly deactivated macromolecules contained both bromine and chloride end groups. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 105: 278–281, 2007
Influence of thermal history on the nonisothermal crystallization of poly(L‐lactide)
Authors: Masirek R. , Piorkowska E. , Galeski A. , Mucha M.
Published: April 2007

The effect of thermal history on the nonisothermal crystallization of poly(L‐lactide) (PLA) was studied. The cold crystallization of PLA by heating from the glassy state was dominated by the heating rate. However, the temperature to which PLA was cooled before crystallization markedly affected the crystallization kinetics. The lower the temperature was to which PLA was cooled, the lower the nonisothermal crystallization peak temperature was and the larger the crystallization enthalpy was, which indicated enhanced nucleation of spherulites. Fast heating from the glassy state reduced the time available for the growth of spherulites and also suppressed the number of nuclei stable at elevated temperatures by limiting the recrystallization of nuclei formed at low temperatures and their overgrowth by thicker and more perfect crystals. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 105: 282–290, 2007
Deformation mechanism of nylon 6/layered silicate nanocomposites: Role of the layered silicate
Authors: Kim G.‐M. , Goerlitz S. , Michler G. H.
Published: April 2007

Polymer/layered silicate nanocomposites, depending on the molecular weight of nylon 6 as the matrix, were prepared through melt blending with a twin‐screw extruder to study their morphology and the role of layered silicates (i.e., montmorillonite) on local deformation processes. A thermal analysis of the nanocomposites was performed with differential scanning calorimetry. The dispersion of the layered silicates and nanocomposite morphology were investigated with wide‐angle X‐ray scattering and transmission electron microscopy. The results showed that the layered‐silicate surfaces predominantly induced γ‐form crystals of nylon 6, whereas α‐form crystals were nucleated far away from the clay surface. The fraction of γ‐form crystals and the degree of exfoliation increased with the molecular weight of the nylon 6 matrix. In a high‐molecular‐weight nanocomposite, a well‐defined exfoliated nanomorphology was observed, in which fine nylon 6 lamellae were most likely to be oriented with their planes perpendicular to the injection‐molding direction, although to a great extent the layered silicates were arranged on planes parallel to the injection‐molding direction. On the contrary, a mixed nanomorphology appeared in a low‐molecular‐weight nanocomposite, intercalated and exfoliated nanomorphologies coexisting; the layered silicates were randomly dispersed in the nylon 6 matrix, and the nylon 6 lamellae grew in no preferential direction with respect to the layered‐silicate surface. The dispersion of the layered silicates and the orientation of the layered silicates as well as the lamellae were directly reflected in the mechanical deformation processes. The results of in situ deformation experiments under a high‐voltage electron microscope (1000 kV) indicated that the main deformation mechanism was microvoid formation either within the intercalated tactoids or in the vicinity of layered silicates in the matrix for intercalated and exfoliated nanomorphology systems, respectively. In the exfoliated nanocomposite, that is, the high‐molecular‐weight nanocomposite, the external applied stresses were much more effectively transferred from the polymer matrix to the layered silicates; furthermore, microvoid formation took place more uniformly and homogeneously throughout the deformed specimen, and thus a well‐improved stiffness/strength/ toughness balance was achieved in comparison with the mixed nanomorphology system (the low‐molecular‐weight nanocomposite). © 2007 Wiley Periodicals, Inc. JAppl Polym Sci 105: 38–48, 2007
Refractive‐index anisotropy and optical dispersion in films of deoxyribonucleic acid
Authors: Samoc Anna , Miniewicz Andrzej , Samoc Marek , Grote James G.
Published: April 2007

We have determined the refractive indices in the directions parallel and perpendicular to the surface plane of films of deoxyribonucleic acid (DNA) and their wavelength dispersion. These parameters are fundamental for understanding the properties of waveguiding structures containing DNA‐based photonic materials. The orientation of DNA molecules in films and their optical properties are sensitive to the film fabrication and environmental conditions influencing the structure. Prism coupling measurements show ambient‐humidity‐related changes in the refractive index, birefringence, and anisotropy of the alignment of the DNA molecules in the films studied. These films were 0.5–5 μm thick, were prepared by both spin coating and casting from aqueous solutions containing 0.1–3 wt % DNA, and were measured in ambient air with relative humidities of 37–58%. The optical properties of the films and the orientation of the DNA molecules are discussed with respect to the mechanism for the formation of the polymer liquid‐crystalline phases during film deposition. The dispersion of the refractive indices in films of native DNA has been derived from interference fringes in absorption and reflection spectra in the wavelength range of 350–2700 nm through the fitting of the positions of the fringes with the Sellmeier dispersion formula in combination with the prism coupling data. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 105: 236–245, 2007
Silicon carbonitride thin‐film coatings fabricated by remote hydrogen–nitrogen microwave plasma chemical vapor deposition from a single‐source precursor: Growth process, structure, and properties of the coatings
Authors: Wrobel A. M. , Blaszczyk‐Lezak I. , Walkiewicz‐Pietrzykowska A.
Published: April 2007

Silicon carbonitride (Si:C:N) films were produced by remote hydrogen–nitrogen microwave plasma chemical vapor deposition (RP‐CVD) from a 1,1,3,3‐tetramethyldisilazane precursor with a nitrogen content {[N2]/([H2] + [N2])} of 0.88 in the plasma‐generating mixture and a substrate temperature in the range of 30–400°C. The effects of the substrate temperature on the rate and yield of the RP‐CVD process and chemical structure (examined by Fourier transform infrared spectroscopy) of the resulting films were investigated. The Si:C:N film properties were characterized in terms of the density, hardness, elastic modulus, and friction coefficient. With the IR structural data, reasonable structure–property relationships were determined. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 105: 122–129, 2007
Glass transition as a key to identifying solid phases
Authors: Wunderlich Bernhard
Published: April 2007

The earlier suggested definition, “a solid is a condensed phase at a temperature below its glass transition,” has developed into the key to the understanding of macromolecular materials. Its importance and implications for the understanding of not only polymers but all materials are reviewed in this article. A macromolecular sample can be a system consisting of a single amorphous phase or be a molecularly coupled multiphase system of different degrees of order and metastability in its subsystems. It is well known that liquid crystals, plastic crystals, and conformationally disordered crystals are still ordered above the glass transition, but recently even the monoclinic crystals of poly (oxyethylene) have been shown to have an additional glass transition below the melting temperature. This supports the inference that in the delineation of the solid state, the glass transitions take preference to melting transitions. The main tools for recognizing the different equilibrium and nonequilibrium phases are differential scanning calorimetry and temperature‐modulated differential scanning calorimetry. Such calorimetry yields quantitative heat capacities to be interpreted in terms of molecular motion and latent heats. Separated into reversible and irreversible contributions, the entropy changes connected to ordering and disordering can be evaluated. The value of the recognition of phase transitions lies in the fact that materials must be pliable for being manufactured into a final shape but often need high modulus and strength in their applications. Near the glass transition, forming is easy, whereas below the glass‐transition temperature, a high modulus is reached for properly oriented polymer molecules. By the identification of the glass transitions of materials with different states of order, a better understanding of the solid state of soft materials is reached. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 105: 49–59, 2007
Block copolymers of cyclohexene oxide and ketonic resins via condensation and promoted cationic polymerization
Authors: Ergun Selin , Kızılcan Nilgün , Önen Ayşen
Published: April 2007

Block copolymers of cyclohexene oxide (CHO) and ketonic resin were prepared by using ketonic resins as free radical photoinitiators via two‐step procedure. In the first step, cyclohexanone–formaldehyde and acetophenone–formaldehyde resins were modified during their preparation with benzoin and benzoin isobutyl ether. Then, AB or ABA type block copolymers depending on the resin employed were obtained by irradiation of these resins in the presence of pyridinium salt and CHO as a cationically polymerizable monomer. By this way, block copolymers of CHO with ketonic resin were prepared and characterized by GPC, DCS, FTIR, and 1H NMR spectral measurements. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Self‐assembly of pH‐responsive acrylate latex particles at emulsion droplets interface
Authors: He Xiao Dong , Ge Xue Wu , Liu Hua Rong , Deng Ming Ge , Zhang Zhi Cheng
Published: April 2007

The self‐assembly of pH‐responsive poly (methyl methacrylate‐co‐acrylic acid) latex particles at emulsion droplet interfaces was achieved. Raising pH increases the hydrophilicity of the latex particles in situ and the latex particle acts as an efficient particulate emulsifier self‐assembling at emulsion droplet interface at around pH 10–11 but exhibits no emulsifier activity at higher pH. This effect can be reversibly induced simply by varying the aqueous phase pH and thus the latex emulsifier can be reassembled. The effect factors, including the aqueous phase pH, the surface carboxyl content, ζ‐Potential of the latex particles and oil phase solvent have been investigated. Using monomer as oil phase, the latex particles could stabilize emulsion droplets during polymerization and cage‐like polymer microspheres with hollow core/porous shell structure were obtained after polymerization. The mechanism of the latex particles self‐assembly was discussed. The morphologies of emulsion and microspheres were characterized by optical microscopy, scanning electron microscopy, and transmission electron microscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Effects of amphoteric copolymer structure on the properties of barium titanate suspensions
Authors: Chen Chin‐Hao , Hsu Kung‐Chung
Published: April 2007

The effect of the molecular structure of an amphoteric copolymer, i.e., poly[acrylamide/(α‐N,N‐dimethyl‐N‐(3‐(β‐carboxylate)acrylamino)propyl)ammonium ethanate)] (PAD) on the interactions with BaTiO3 (BT) particles in water and on the stability of BT suspensions was examined by means of adsorption, ζ potential, sedimentation, and viscosity measurements. The results indicate that the adsorption of PAD onto BT particles follows the Langmuir adsorption isotherm. As the added PAD containing greater ionic group fraction, both the saturated amount of adsorbed polymer and the amount of the polymer required to reach the minimal ζ potential decrease. Whatever the ionic group fraction in PAD, BT suspensions become stable and less viscous when saturated amount of the polymer was adsorbed on particle surface. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
PTC effect in HDPE filled with carbon blacks modified by Ni and Au metallic particles
Authors: Pourabbas Behzad , Peighambardoust S. Jamal
Published: April 2007

Several types of positive temperature coefficient (PTC) composites are prepared by using Ni and Au modified carbon black. The major aim of this work was the lowering of the room temperature resistivity of the composites by enhancement of electrical conduction of the CB particles by incorporating metallic particles. Investigations showed that the metal particles fill the cavities and surface defects of the CB and thus surface free area reduces after modification. Metallic particles also change the nature of the CB particles after modification. Several types of PTC composites were prepared by using modified and unmodified CB by several loading level of filler. Measuring electrical properties of the PTC samples showed that the Ni modified CB reduce room temperature resistivity to lower than that of PTC composites prepared by unmodified CB. PTC composites prepared by Au modified CBs showed very different properties compared to PTC composites prepared by Ni modified CB. Their resistivities were quite higher than the others showing a poor compatibility between the matrix and Au modified CB. The effect of thermal annealing also investigated on the electrical properties of the prepared composites. Room temperature resistivities reduced for most of the samples while PTC intensities increased after annealing. Theoretical bases are employed to discuss the room temperature resistivity and PTC behavior of the composites before and after annealing. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
High molecular weight polypropylene nanospheres: Synthesis and characterization
Authors: Paik Pradip , Kar Kamal K.
Published: April 2007

The high molecular weight (MW) polypropylene with average particle size of 60 nm was synthesized by controlled growth mechanism using Ziegler–Natta catalyst. The atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies showed that PP nanoparticles were spherical in shape. Structure and crystallinity were concomitantly studied through Fourier transform infrared spectroscopy and X‐ray diffraction, respectively. It shows nanospherical PP particles with more crystallinity (∼ 75%) compared with macrosized PP (∼ 59%). In addition, differential scanning calorimetry studies revealed the finite particle size effect on Tg and the scale dependence Tg followed a first order exponential trend. As particle size goes down to nano‐ scale from macrosize, continuous elevation of Tg's were observed from −25 to −11°C. This phenomenon was directed to configuration entropy of single spherical nanoparticles of PP. The mechanical properties and surface roughness were also evaluated through AFM. At last, the properties of nanosized PP were compared with micron and macrosized particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Effects of meta and para diamines on the properties of polyetherimide nanocomposite films prepared by the sol‐gel process
Authors: Chen Bor‐Kuan , Fang Yu‐Ting , Cheng Jing‐Ru , Tsay Sun‐Yuan
Published: April 2007

The effects of chemical structure of diamines on the properties of polyetherimide (PEI) nanocomposite films prepared by the sol‐gel process were investigated. For meta diamine, nanocomposites with improved thermal, mechanical, and dielectric properties can be prepared by a sol‐gel process from soluble PEI via chemical imidization, with silica content up to 10%. However, for the PEI with pPDA as diamine and bisphenol A dianhydride, a two‐stage sol‐gel process via thermal imidization was necessary to prepare the nanocomposites. The thermal stability and mechanical properties were improved with the addition of up to 5 wt % of silica content. The variation could be attributed to the fact that differences in the compatibility between PEI and SiO2 for two kinds of PEI with the different meta and para structure of the diamine monomer. The morphology of the fracture surfaces investigated by SEM showed a finely interconnected or cocontinuous phase for PEI nanocomposites with the silica content of up to 10% and 5 wt % for mPDA and pPDA as diamine, respectively. At higher silica contents, thermal and mechanical properties were reduced due to the aggregation of SiO2. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
A novel method of encapsulating and cultivating adherent mammalian cells within collagen microcarriers
Authors: Wu Ta‐Jen , Huang Hsiu‐Hsuan , Hsu Yuan‐Ming , Lyu Shaw‐Ruey , Wang Yng Jiin
Published: April 2007

A novel method of preparing collagen microcarriers was developed and used to entrap adherent cells for cell culturing. This new technique involved seeding of cells in micro gel beads comprised of collagen fibrils dispersed in alginate. The gel beads were washed with phosphate buffered saline (PBS) to remove alginate and the resulting microspheres, about 300–500 µm in diameter, contained evenly distributed collagen fibrils which provided a 3D biomimetic environment for cell growth. The applicability of this microencapsulating system was demonstrated by its ability to support the growth of C2C12 myoblast cells. When seeded and cultured within the 3D collagen microcarriers, the population of C2C12 cells entrapped within the microcarriers increased by 1.5 folds in 7 days after inoculation. This encapsulation technique is potentially useful for culturing cells and especially useful for adherent cells that require a 3D fibrillar collagen environment. Biotechnol. Bioeng. 2007;98: 578–585. © 2007 Wiley Periodicals, Inc.