bluuebunny/crossref_metadata_2025 huggingface dataset:
Flutamide–metformin for post-menarcheal girls with preclinical ovarian androgen excess: evidence for differential response by androgen receptor genotype
Authors: Ong Ken K , de Zegher Francis , López-Bermejo Abel , Dunger David B , Ibáñez Lourdes
Published: November 2007

Objective

Addition of androgen receptor (AR) blockade (flutamide) to insulin-sensitising therapy (metformin) may confer synergistic benefits in girls with hyperinsulinaemic androgen excess. We hypothesised that girls with shorter AR gene CAG repeat alleles, and thus greater receptor sensitivity, might benefit more from the addition of low-dose flutamide.

Design

Open randomised crossover study.

Methods

In this study, 32 post-menarcheal girls (mean age 12.1 years) with a history of low birth weight and precocious pubarche were subgrouped by CAG genotype (‘short’: CAG mean length ≤20, n=14; ‘long’: CAG >20, n=18). Within each subgroup, girls were 1:1 randomised to metformin alone (850 mg/day) or in combination with flutamide (62.5 mg/day) for 12 months. To allow comparisons with no treatment, long-CAG girls randomised to flutamide–metformin, and short-CAG girls randomised to metformin alone were observed for 12 months before treatment. Body composition by absorptiometry, fasting lipid profiles and levels of insulin, glucose and androgens were measured during the first 12 months on each treatment.

Results

In all girls, 12 months flutamide–metformin lowered body fat and improved lipid profiles when compared with no treatment. Compared with metformin alone, flutamide–metformin achieved greater reductions in the percentage of body fat and abdominal fat mass in the short-CAG subgroup (P=0.001 to P<0.0001). In contrast, in the long-CAG subgroup, flutamide–metformin produced no further improvements when compared with metformin alone.

Conclusions

In young post-menarcheal girls with preclinical androgen excess, low-dose flutamide–metformin improved body composition and key endocrine–metabolic abnormalities. However, only those girls with genetic markers of greater AR sensitivity may benefit from the addition of flutamide above metformin alone.
Metformin improves polycystic ovary syndrome symptoms irrespective of pre-treatment insulin resistance
Authors: Tan Susanne , Hahn Susanne , Benson Sven , Dietz Tiina , Lahner Harald , Moeller Lars C , Schmidt Markus , Elsenbruch Sigrid , Kimmig Rainer , Mann Klaus , Janssen Onno E
Published: November 2007

Objective

Insulin resistance (IR) and obesity are common features of the polycystic ovary syndrome (PCOS). Insulin-sensitizing agents have been shown to improve both reproductive and metabolic aspects of PCOS, but it remains unclear whether it is also beneficial in lean patients without pre-treatment IR. The aim of this study was to determine the influence of metformin on the clinical and biochemical parameters of PCOS irrespective of the presence of basal obesity and IR.

Design

The effect of 6 months of metformin treatment was prospectively assessed in 188 PCOS patients, divided into three groups according to body mass index (BMI; lean: BMI<25 kg/m2, overweight: BMI 25–29 kg/m2, and obese: BMI≥30 kg/m2). Outcome parameters, which were also assessed in 102 healthy controls, included body weight, homeostasis model assessment for IR (HOMA-IR), fasting glucose and insulin levels, area under the curve of insulin response (AUCI), hyperandrogenism, and menstrual irregularities.

Results

In comparison with the respective BMI-appropriate control groups, only obese but not lean and overweight PCOS patients showed differences in fasting insulin and HOMA-IR. Metformin therapy significantly improved all outcome parameters except fasting glucose levels. Subgroup analyses revealed that in the group of lean PCOS patients without pre-treatment IR, metformin significantly improved HOMA-IR (1.7±1.0 vs 1.1±0.7 μmol/l×mmol/l2) and fasting insulin levels (7.7±4.2 vs 5.4±3.9 mU/l), in addition to testosterone levels (2.6±0.9 vs 1.8±0.7 nmol/l), anovulation rate (2.3 vs 59.5%), and acne (31.8 vs 11.6%; all P<0.017). In the overweight and obese PCOS groups, metformin also showed the expected beneficial effects.

Conclusion

Metformin improves parameters of IR, hyperandrogenemia, anovulation, and acne in PCOS irrespective of pre-treatment IR or obesity.
Distribution of neuropeptide Y Leu7Pro polymorphism in patients with type 1 diabetes and diabetic nephropathy among Swedish and American populations
Authors: Ma Jun , Nordman Sofia , Möllsten Anna , Falhammar Henrik , Brismar Kerstin , Dahlquist Gisela , Efendic Suad , Gu Harvest F
Published: November 2007

Objective

The distribution of Leu7Pro polymorphism in the neuropeptide Y gene shows a geographical north to south gradient of decreasing frequency, suggesting that it may be a population-specific causal variant. This polymorphism is found to be associated with diabetic nephropathy (DN) and coronary heart disease in Finnish women with type 1 diabetes (T1D). The present study aims to evaluate the susceptibility of this polymorphism to the development of DN in two different populations.

Design

One sample set consists of 174 (females 98 and males 76) Swedish T1D patients with DN and 249 (females 132 and males 117) patients without DN. Another sample set includes 597 (females 356 and males 241) American T1D patients without DN and 577 (females 264 and males 313) patients with DN, who were descents of European Caucasians and were from the Genetics of Kidneys in Diabetes (GoKinD) Study.

Methods

Genotyping of Leu7Pro polymorphism was performed by dynamic allele-specific hybridization.

Results

The C allele frequencies of Leu7Pro polymorphism in T1D patients between Swedish and American GoKinD populations were significantly different (6.3 vs 4.0%; P=0.006). Particularly, the C allele frequency in Swedish female T1D patients with DN was significantly higher in comparison with T1D patients without DN (10.2 vs 4.2%; P=0.011, OR=2.614, 95% confidence intervals: 1.249–5.467). No significant association of this polymorphism with DN was observed in Swedish male T1D patients and the patients from GoKinD.

Conclusions

The present study provides further evidence that Leu7Pro polymorphism confers the susceptibility to the development of DN in Swedish female T1D patients.
The association of interleukin-18 genotype and serum levels with metabolic risk factors for cardiovascular disease
Authors: Evans Juliet , Collins Malcolm , Jennings Courtney , van der Merwe Lize , Söderström Ingegerd , Olsson Tommy , Levitt Naomi S , Lambert Estelle V , Goedecke Julia H
Published: November 2007

Objective

Circulating levels of interleukin (IL)-18 are associated with the metabolic syndrome and risk for the development of cardiovascular disease (CVD). This study investigated the association between the circulating IL-18 levels and the −137 G/C polymorphism within theIL-18gene with metabolic risk factors for CVD in normal-weight and obese black South African women.

Methods

Blood pressure (BP), body composition (dual-energy X-ray absorptiometer), visceral adiposity (computerized tomography), as well as fasting glucose, insulin, lipid profile, IL-18 levels, andIL-18genotype were measured in 104 normal-weight (body mass index (BMI) ≤25 kg/m2) and 124 obese (BMI≥30 kg/m2) black South African women.

Results

Subjects with a GC genotype (23%) had a greater mean arterial pressure (MAP, 90.6±11.1 vs 85.5±10.3 mmHg,P<0.001) than the subjects with the GG genotype. Serum IL-18 levels were not associated with IL-18 genotype (P=0.985); however, they significantly correlated with percentage of body fat (r=0.25,P<0.001), visceral adiposity (r=0.32,P<0.001), MAP (r=0.22,P=0.001), HOMA-IR (r=0.33,P<0.001), fasting insulin (r=0.25,P<0.001), triglyceride (r=0.16,P<0.05), and high-density lipoprotein-cholesterol (r=−0.14,P<0.05) levels, after adjusting for age and body fatness.

Conclusions

We show for the first time that the GC genotype of theIL-18−137 G/C polymorphism and the circulating IL-18 levels are independently associated with raised BP. Moreover, fasting IL-18 levels are associated with the other metabolic risk factors for CVD in normal-weight and obese black South African women.
Effects of Dietary Arginine on Hematological Parameters and Innate Immune Function of Channel Catfish
Authors: Buentello J. Alejandro , Reyes-Becerril Martha , Jesús Romero-Geraldo María , Jesús Ascencio-Valle Felipe
Published: November 2007

The effects of elevated dietary arginine on the hematology and immune function of juvenile channel catfish Ictalurus punctatus were evaluated by means of in vivo and in vitro experiments. Healthy juvenile channel catfish (average weight, 34.8 g) were fed casein–gelatin-based diets containing 28% crude protein and supplemented with crystalline l-arginine (ARG) at 0.5, 1, 2, or 4% of diet. An intact-protein diet containing 1.3% arginine also was included to investigate the effects of amino acid form (crystalline-free amino acids versus intact protein). Each purified diet was fed to apparent satiation to triplicate groups of fish for 6 weeks. At the end of the experimental feeding period, the fish were injected intraperitoneally with two doses (3 d apart) of 2 mg lipopolysaccharide/kg body weight. Six days after the initial injection, the fish were anesthetized and tissue samples were obtained to evaluate hematological and humoral and cellular immune parameters, including phagocytic activity of peritoneal macrophages, hemoglobin, hematocrit, mean corpuscular volume (MCV), blood cell counts, plasma protein, and hepatic superoxide dismutase activity. High dietary levels (4% ARG) resulted in significantly higher levels of hemoglobin, hematocrit, and circulating erythrocytes. Dietary ARG did not significantly affect MCV and the number of circulating leukocytes, lymphocytes, eosinophils, and monocytes. In vitro, a moderate level (2 mM) of ARG in the culture media was found to be ideal in significantly enhancing phagocytosis. This study demonstrates that some aspects of the immune system of channel catfish are sensitive to changes in dietary ARG.
Stabilised mineral–biomass mixtures in groundwork: fundamentals
Authors: Tyrologou P. , Dudeney A. W. L. , Harrison J. P. , Grattoni C. A.
Published: November 2007

This paper considers the fundamentals of mechanical structures and fluid flow characteristics in lime-stabilised mineral—biomass mixtures for potential novel applications in low-value bulk industrial products or wastes. As contained organic matter is expected to be essentially stable indefinitely under anaerobic conditions, the composites represent a form of solid carbon sequestration. Laboratory specimens containing designed combinations of coarse mineral (4 or 10 mm quartz) and fines (wet digested sewage sludge, pulverised-fuel ash and quicklime) were evaluated as possible precursors to composite emplacements in engineering groundwork. The volume proportion of coarse mineral to mixed fines was nominally 3:2, a value that allowed complete sludge infilling between coarse particles while ensuring particles remained in point contact to form a supporting matrix. The results showed that compositions of digested sewage (25% solids) and fuel ash in the approximate mass ratio 2:1, together with 3% quicklime, underwent pozzolanic strengthening to give an unconfined compressive strength of typically 250 ± 30 kPa after several months' ageing. This is similar in strength to stiff soil or soft rock and, in principle, indicates sufficient mechanical integrity for use as foundations beneath light building development or as a bulk fill underlying open amenities. Porosity (4–10%) and hydraulic conductivity (10−5–10−7 m/s) were moderate to low. Interstitial water contained significant concentrations of ammonia and heavy metals, suggesting that effective isolation from the outside environment would be required in field applications.
Die Haftung des Waldeigentümers im Waldbestand und entlang von Strassen (Essay)|The forest owner's liability within the stand and along the road (essay)
Authors: Leuch Andreas
Published: November 2007

The author investigates under which circumstances the forest owner is liable for damage caused by falling branches and trees. In particular, he outlines the potential for liability issues raised with traffic roads. According to the general legal terms, it is the owner of the road and not the forest owner who is liable under this circumstance. By the example of the law in the canton Zürich the author shows how the community as owner of the public roads may shift its risk of liability to the forest owner by legislatory instruments. To avoid this liability the forest owner has to implement actions to secure the traffic roads. These actions are associated with high costs.
Gran Paradiso: Erkenntnisse aus der sich natürlich regulierenden Steinbockpopulation|Gran Paradiso: Conclusions from the naturally regulated Capricorn population
Authors: Amos Grégory , Marchand Ambroise , Schneiter Anja , Sorg Annina
Published: November 2007

The last Capricorns (Capra ibex ibex) in the Alps survived during the nineteenth century in the Aosta valley thanks to the royal hunting reservation (today Gran Paradiso national park). Capricorns from this reservation were successfully re-introduced in Switzerland after its Capricorn population had disappeared. Currently in Switzerland there are 13200 Capricorns. Every year 1000 are hunted in order to prevent a large variation and overaging of their population and the damage of pasture. In contrast, in the Gran Paradiso national park the game population regulates itself naturally for over eighty years. There are large fluctuations in the Capricorn population (2600–5000) which are most likely due to the climate, amount of snow, population density and to the interactions of these factors. The long-term surveys in the Gran Paradiso national park and the investigations of the capacity of this area are a valuable example for the optimal management of the ibexes in Switzerland.
Inside Front Cover: Direct Patterning, Conformal Coating, and Erbium Doping of Luminescent nc‐Si/SiO2 Thin Films from Solution Processable Hydrogen Silsesquioxane (Adv. Mater. 21/2007)
Authors: Hessel C. M. , Summers M. A. , Meldrum A. , Malac M. , Veinot J. G. C.
Published: November 2007

Patterned nanostructure arrays of luminescent, oxide‐embedded silicon nanocrystals (nc‐Si) are formed by reductively thermally processing e‐beam patterns of hydrogen silsesquioxane (HSQ). While traditionally employed as a negative type e‐beam resist, HSQ is shown to produce thin films, non‐flat conformal coatings, and sub‐10 nm structures that contain luminescent nc‐Si. The variety of morphologies (structures) that can be produced by this method highlights the versatility of HSQ as a nc‐Si precursor, report Jonathan Veinot and co‐workers from the University of Alberta, Canada on p. 3513.
A subordinate status position increases the present value of financial resources for low 2D:4D men
Authors: Millet Kobe , Dewitte Siegfried
Published: October 2007

It has been suggested that the ratio of the length of the 2nd and 4th fingers (digit ratio or 2D:4D) is related to prenatal testosterone with lower ratios thought to be influenced by higher prenatal testosterone levels. Accordingly, low 2D:4D has been associated to a number of fitness‐related factors, such as high status in competitive sports and in music. Recent evidence suggests that 2D:4D is also related to economic decision making. We combine both streams of research in the present paper. In two studies we manipulated status in two different ways. We found that a subordinate position raises discount rates, consistent with the reasoning that the present utility of money is higher for men in this position. Moreover, the effect was more pronounced for men with a low 2D:4D. There was a significant negative relationship between 2D:4D and level of discounting in a subordinate status position, but no significant relationship emerged in the dominant status position. Our studies add evidence to the recent line of research associating digit ratio and economic decision making. Moreover, our studies show that future 2D:4D research should focus on plausible interactions between 2D:4D and context cues rather than on linear relations. Am. J. Hum. Biol., 2008. © 2007 Wiley‐Liss, Inc.
Descent, lineage, and pedigree of the Trojans in Homer's Iliad
Authors: Bazopoulou‐Kyrkanidou Euterpe
Published: November 2007

Homer's Iliad, is an epic poem that describes the last 70 days of the Trojan War, which was waged against the city of Troy by the Achaeans. Here, the descent, lineage, and the pedigree of the Trojans are presented. In the Illiad, they are said to have originated from Zeus. Beginning with him, the Trojan pedigree comprised 17 men in 8 generations with Dardanus, founder of Dardania in the second generation; Tros, King of the Trojans in the fourth generation; and the two heroes Hector and Aeneas in the eighth generation. In the seventh generation, Priam, as King of the Trojans, had a huge family, including 50 sons: 19 children with his wife Hecabe, other sons with many different wives, and some daughters as well. Hector, the first born, became leader of the Trojans. Hector's brother, Paris, in abducting Helen of Sparta, the wife of King Menelaus, caused the Trojan War to break out. © 2007 Wiley‐Liss, Inc.
Mutualism, reciprocity, or kin selection? Cooperative rescue of a conspecific from a boa in a nocturnal solitary forager the gray mouse lemur
Authors: Eberle Manfred , Kappeler Peter M.
Published: October 2007

Predator mobbing is a widespread phenomenon in many taxa but the evolution of cooperative mobbing as an adaptive behavior is still subject to debate. Here, we report evidence for cooperative predator defense in a nocturnal solitarily foraging primate, the gray mouse lemur (Microcebus murinus). Several mouse lemurs mobbed a snake that held a non‐related male conspecific until he could escape. Evolutionary hypotheses to explain cooperative mobbing include (1) by‐product mutualism, when individuals defend others in the process of defending themselves; (2) reciprocity, where animals achieve a higher fitness when helping each other than when they do not cooperate; and (3) kin selection where animals help each other only if they share genes by common descent. Owing to the solitary activity of this species, reciprocity seems to be least likely to explain our observations. By‐product mutualism cannot be ruled out entirely but, if costs of snake mobbing are relatively low, the available detailed socio‐genetic information indicates that kin selection, rather than any of the other proposed mechanisms, is the primary evolutionary force behind the observed cooperative rescue. Am. J. Primatol. 70:410–414, 2008. © 2007 Wiley‐Liss, Inc.
The effect of branch diameter on primate gait sequence pattern
Authors: Stevens Nancy Jeanne
Published: October 2007

Most mammals use lateral sequence gaits during quadrupedal locomotion, a pattern characterized by the touchdown of a forelimb directly following the ipsilateral hind limb in a given stride cycle. Primates, however, tend to use diagonal sequence (DS) gaits, whereby it is the touchdown of a contralateral forelimb that follows that of a given hind limb most closely in time. A number of scenarios have been offered to explain why primates favor DS gaits, most of them relating to the use of the arboreal habitat and, in particular, the exploitation of a narrow branch niche. This experimental study explores the potential explanation for the use of DS gaits by examining the relationship between branch diameter and gait patterns in 360 strides collected from six species of quadrupedal strepsirrhine primates on broad and narrow diameter supports. Gait sequence is quantified using limb phase, or the percentage of time during a stride cycle that a forelimb touchdown follows an ipsilateral hind limb touchdown. Although Loris, Nycticebus and Eulemur rubriventer individuals in this study did exhibit significantly lower locomotor velocities on narrower supports (P<0.01 in all three species), analyses of covariance showed no significant differences in limb phase values between broad and narrow diameter supports. Hence, results indicate surprisingly little evidence to suggest that alterations in gait sequence pattern provide a specific advantage for negotiating narrow supports. Am. J. Primatol. 70:356–362, 2008. © 2007 Wiley‐Liss, Inc.
Effect of structure of aromatic imide–amines on curing behavior and thermal stability of diglycidyl ether of bisphenol‐A
Authors: Sharma Pooja , Choudhary Veena , Narula Anudeep Kumar
Published: October 2007

The curing behavior of diglycidyl ether of bisphenol‐A (DGEBA) with aromatic imide–amines having aryl ether, sulfone, and methylene linkages was studied using differential scanning calorimetry (DSC). Six imide–amines of varying structure were synthesized by reacting 1 mol of naphthalene 1,4,5,8‐tetracarboxylic dianhydride (N) or 4,4′‐oxodiphthalic anhydride (O) with excess (>2 mol) of 4,4′‐diaminodiphenylether [E] or 4,4′‐diaminodiphenyl methane [M] or 4,4′‐diaminodiphenyl sulfone [S]. The imide–amines prepared by reacting O or N with S, M, and E have been designated as OS/NS; OM/NM, and OE/NE, respectively. Structural characterization of imide–amines was done using FTIR, 1H NMR, 13C NMR, and elemental analysis. The curing behavior of DGEBA in the presence of stoichiometric amount of imide–amines was investigated by recording DSC scans. A broad exothermic transition was observed and the peak exotherm temperature was found to be dependent on the structure of imide–amines. The peak exotherm temperature (Tp) was lowest in case of imide–amines OE and highest in case of imide–amines NS/OS. Thermal stability of isothermally cured DGEBA in the presence of imide–amines was evaluated by dynamic thermogravimetry. The char yield was highest for resin cured with imide–amines NE. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Activated carbon‐polyethylenedioxythiophene composite electrodes for symmetrical supercapacitors
Authors: Selvakumar M. , Krishna Bhat D.
Published: November 2007

A symmetrical (p/p) supercapacitor has been fabricated by making use of activated carbon (AC)‐polyethylenedioxythiophene (PEDOT)‐composite electrodes for the first time. The composite electrodes have been prepared via electrochemical deposition of β‐napthalenesulphonate doped PEDOT onto AC electrodes. The characteristics of the electrodes and the fabricated supercapacitor have been investigated using cyclic voltammetry (CV) and AC impedance spectroscopy. The electrodes show a maximum specific capacitance of 158 Fg−1 at a scan rate of 10 mV s−1. This indicates that the in situ electro‐polymerization of ethylenedioxythiophene (EDOT) onto AC could improve the performance of carbon electrodes for use in supercapacitors. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008
In vitro release study of diltiazem hydrochloride from poly(vinyl pyrrolidone)/sodium alginate blend microspheres
Authors: Şanlı Oya , Biçer Emine , Işıklan Nuran
Published: October 2007

Polymeric blend microspheres of poly(vinyl pyrrolidone) (PVP) with sodium alginate (NaAlg) were prepared by cross‐linking with calcium ions and used to deliver a calcium channel blocker drug, diltiazem hydrochloride (DT). The prepared microspheres were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Scanning electron microscopy confirmed the spherical nature of the particles. Preparation conditions for the microspheres were optimized by considering the percentage entrapment efficiency, particle size, and swelling capacity. Effects of variables such as PVP/NaAlg ratio, molecular weight of PVP, cross‐linker concentration, and drug/polymer ratio on the release of DT were discussed at two different pH values (1.2, 6.8) at 37°C. It was observed that DT release from the microspheres decreased with increasing molecular weight of PVP and extent of cross‐linking. However, DT release increased with increasing PVP content and drug/polymer ratio (d/p) of the blend microspheres. The highest DT release percentage was obtained as 99% for PVP/NaAlg ratio of 1/2 with d/p ratio of 1/2 at the end of 4 h. It was also observed from release results that DT delivery from the microspheres through the external medium are much higher at low pH (1.2) value than that of high pH (6.8) value. The drug release from the microspheres mostly followed Fickian transport. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and characterization of polyaniline–organoclay nanocomposites
Authors: Salahuddin N. , Ayad M. M. , Ali M.
Published: October 2007

Polyaniline (PANI)–organoclay nanocomposites were prepared. Intercalation of aniline monomer into montmorillonite (MMT) modified by polyoxyalkylene was followed by subsequent oxidative polymerization of the aniline in the interlayer spacing. The organoclay was prepared by cation exchange process between sodium cation in MMT and onium ion in four different types of polyoxyalkylene diamine and triamine with different molecular weight. Infrared spectra confirm the electrostatic interaction between the positively charged onium group (NH3+) and the negatively charged surface of MMT. X‐ray diffraction analysis provides a structural information. The absence of d001 diffraction band in the nanocomposites was observed at certain types and contents of organoclay. Scanning electron microscopy and transmission electron microscopy were employed to determine the dispersion of the clay into PANI. The thermal degradation behavior of PANI in the nanocomposites has been investigated by thermogravimetric analysis. The weight loss suggests that the PANI chains in the nanocomposites are more thermally stable than pristine PANI. This improvement is attributed to the presence of nanolayers with high aspect ratio acting as barriers, thus shielding the diffusion of degraded PANI from the nanocomposites. The electrical conductivity of the nanocomposites was increased 30 times more than that of pure MMT at a certain concentration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Study on PVC composites containing Eugenia jambolana wood flour
Authors: Saini Gajender , Choudhary Veena , Bhardwaj Rashmi , Narula A. K.
Published: November 2007

This article describes the properties of composites using unplasticized PVC matrix and wood flour (obtained by crushing the bark of Eugenia jambolana) as filler. Composites were prepared by mixing PVC with varying amounts of wood flour (ranging from 10–40 phr; having particle sizes of 100–150 μm and <50μm) using two‐roll mill followed by compression molding. The effect of wood flour content and its particle size on the properties, i.e., mechanical, dynamic mechanical, and thermal was evaluated. Tensile strength, impact strength, and % elongation at break decreased with increasing amounts of wood flour. Stiffness of the composites (as determined by storage modulus) increased with increasing amounts of the filler. Modulus increased significantly when wood flour having particle size <50 μm was used. Morphological characterization (SEM) showed a uniform distribution of wood flour in the composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008
Study of the formulations and process conditions in the crosslinking of polyethylene foams at atmospheric pressure
Authors: Marcilla A. , García‐Quesada J. C. , Beltran M. I. , Ruiz‐Femenia R.
Published: October 2007

The aim of this work is the study of the foaming process of a commercial polyethylene in the presence of a crosslinking agent. Foams have been produced under nearly atmospheric pressure conditions, which commonly occur during polymer rotomolding. Different processingtemperatures and different combinations of blowing agent/kicker (azodicarbonamide/zinc oxide) and crosslinking agent (dicumyl peroxide) concentrations have been employed. Thus, the melt viscosity, crosslinking degree, and temperature of the gas evolution and its rate have been changed to a certain degree. The obtained results have revealed that all these factors are critical to obtaining uniform and low‐density foams. Under certain processing temperatures and with an appropriate formulation, foam densities have been reduced up to 70% with respect to nonfoamed polymer. The interactions among the different components of the formulation have also been observed, and the results have led to the conclusion that in this kind of process, when a low pressure is applied, the foam density can be controlled by an adequate synchronization of the melt‐crosslinking, foaming, and gas‐expansion processes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Graft copolymerization of methyl methacrylate with an N‐substituted maleimide–liquid‐crystalline copolymer by atom transfer radical polymerization
Authors: Çakır T. , Önen A. , Serhatlı I. E.
Published: October 2007

The synthesis of novel copolymers consisting of a side‐group liquid‐crystalline backbone and poly (methyl methacrylate) grafts were realized by the use of atom transfer radical polymerization (ATRP). In the first stage, the bromine‐functional copolymers 6‐(4‐cyanobiphenyl‐4′‐oxy)hexyl acrylate and (2,5‐dioxo‐2,5‐dihydro‐1H‐pyrrole‐1‐yl)methyl 2‐bromopropanoate were synthesized by free‐radical polymerization. These copolymers were used as initiators in the ATRP of methyl methacrylate to yield graft copolymers. Both the macroinitiator and graft copolymers were characterized by 1H‐NMR, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. The ATRP graft copolymerization was supported by an increase in the molecular weight of the graft copolymers compared to that of the macroinitiator and also by their monomodal molecular weight distribution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Characterization of oxidized cellulose with ultraviolet–visible spectroscopy
Authors: Milichovsky Miloslav , Milichovska Svatava
Published: October 2007

This article describes some properties and behavior of oxidized cellulose evaluated with ultraviolet–visible spectroscopy. Newly defined analytical parameters are described. Mechanisms of poly(1,4‐β‐D‐anhydroglucuronic acid) degradation and destruction are formulated. The feasibility of using the same Staudinger–Mark–Houwink equation to calculate the degree of polymerization of cellulose and the degree of polymerization of oxidized cellulose is demonstrated. Utilization of ultraviolet–visible spectroscopy is shown for the optimization of oxidized cellulose production and aging. Advantages and limitations of this method are discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Modeling the solids conveying zone of a novel extruder
Authors: Jia Mingyin , Wang Kejian , Xue Ping , Zhu Fuhua
Published: October 2007

On the basis of the theory of relative motions, a novel nested screw extruder was invented in which one rotating outer screw acted as the barrel for an inner screw; the combination of the outer screw and outer barrel was the other extrusion system. It was realized that centrifugal force resulted in the difference between the forces acting on the solids by the screw and by the barrel, which further compacted the solid pellet or powder. These factors benefited the frictional drag of solids and the early melting. This was consistent with the fact that the solids conveying flow rate increased greatly when the barrel and screw rotated oppositely at the same time. Thus, centrifugal force and material compressibility were significant in the feeding zone. A mathematical model was developed to calculate the output, pressure, and velocity of the solids in the screw down‐channel with consideration of the centrifugal force and material compressibility. The predicted pressure distribution and output were better than those by previous models in fitting the experimental data. The simulations revealed that the maximum traction angle was close to 90° − the helix angle for maximum output in contrast to the maximum traction angle of 90° predicted by the Darnell–Mol theory. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Preparation of polyurea microcapsules containing pyrethroid insecticide with hexamethylene diisocyanate isocyanurate
Authors: Takahashi Tadatsugu , Taguchi Yoshinari , Tanaka Masato
Published: October 2007

Polyurea microcapsules containing a pyrethroid insecticide were prepared by the reaction between hexamethylene diisocyanate isocyanurate and ethylenediamine in an oil‐in‐water emulsion. This study was performed to establish the operational conditions of preparing microcapsules by interfacial polymerization and to investigate how the operational conditions affected the characteristics of microcapsules such as the morphology, wall thickness, mean diameter, and particle size distribution. Microcapsules prepared in this study were found to be spherical and monocore. The microcapsule yields, ranging from 94 to 98%, were almost equal to the theoretical values. The wall thickness of the microcapsules increased with the diameter of the microcapsules and the concentration of hexamethylene diisocyanate isocyanurate. In comparison with the results for microcapsules prepared with a mixture of hexamethylene diisocyanate uretidione and isocyanurate, the diameters and wall thickness of the microcapsules were found to be larger. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Microwave hall mobility studies on polymer–metal oxide nanocomposites
Authors: Murthy D. V. B. , Subramanian V. , Pavan Kumar V. S. , Natarajan T. S. , Raghuraman G. K. , Dhamodharan R. , Murthy V. R. K.
Published: October 2007

Films of polymer metal oxide composites with poly(methyl methacrylate) and metallic powders (CuO, Ni, and brushed Fe3O4) were prepared with a spin‐casting method. Electric transport studies indicated that the compositions surpassed the percolation threshold limit. Alternating current (AC) conductivity studies confirmed a hopping mechanism with power‐law behavior in frequency. For the first time, the mobility values of the carriers in these films were measured by the contactless microwave Hall effect technique with a bimodal cavity operating at 14 GHz. In this technique, a circular bimodal cavity is used to measure the change in the transmission coefficient (proportional to the carrier mobility) due to the application of a static magnetic field perpendicular to the microwave electric fields. The mobility measurements indicated a decrease in mobility with increasing quantity of CuO and Ni and showed an increase in the carrier–lattice scattering, whereas the mobility increased with increasing Fe3O4 due to the negative magneto resistance. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Mechanical properties of thermoplastic elastomeric blends of chitosan and natural rubber latex
Authors: Rao Vijayalakshmi , Johns Jobish
Published: November 2007

Thermoplastic chitosan/natural rubber blends (Cs/NR) were prepared from natural rubber latex and chitosan by solution casting technique. The blends were characterized by mechanical analysis (stress–strain) and the mechanical properties were found to vary with chitosan/natural rubber ratios. Experimental values were compared with different theoretical models. Effect of thermal aging on mechanical properties was also investigated. Dicumyl peroxide was used as the crosslinking agent. The effect of crosslinking on mechanical properties of Cs/NR has also been studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Using anionic polymerizable surfactants in ultrasonically irradiated emulsion polymerization to prepare polymer nanoparticles
Authors: He Yuhui , Cao Ya , Fan Ying
Published: October 2007

An ionic polymerizable surfactant, sodium sulfopropyl‐laurylmaleate (M12), was synthesized and used as an emulsifier, an initiator, and a comonomer in ultrasonically irradiated emulsion polymerization. FTIR spectra and gravimetric method results indicated that copolymers P(Styrene‐M12) and P(Butylacrlate‐M12) were prepared successfully by ultrasonically irradiated emulsion polymerization and the composition of M12 elevated with the increasing concentration of M12 added. TEM photographs of P(St‐M12) showed that the nanoparticles with small diameters (20–45 nm) were prepared. With the increase of M12 concentration, the particle size became smaller and the size distribution became wider. The P(BA‐M12) particles size was also small (<100 nm) but the size distribution was wide due to the high reactivity of BA. Because surfmer M12 was chemically bonded with the latex particles, the stability of the copolymer latex prepared by ultrasonically irradiated emulsion polymerization was much better than that of the homopolymer latex (PSt or PBA) prepared by the same way. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Development of a mathematical model for studying bioethanol–water separation using hydrophilic polyetherimide membrane
Authors: Alvarez M. E. T. , Moraes E. B. , Araujo W. A. , Maciel Filho R. , Wolf‐Maciel M. R.
Published: November 2007

An essentially predictive mathematical model was developed to simulate pervaporation process. The group contribution method UNIFAC was used for calculating the upstream activity coefficients. The diffusion coefficient in the membrane was predicted using free‐volume theory. Free‐volume parameters were determined with viscosity and temperature data, and the binary interaction solvent–polymer parameter was calculated by a group‐contribution lattice‐fluid equation of state (GCLF‐EOS). A simulator named PERVAP was developed applying the mathematical model. Pervaporation process was simulated for separating bioethanol–water through polyetherimide membrane. The simulated results were validated using experimental data of bioethanol/water separation through polyetherimide membrane. The model presented a satisfactory performance compared to experimental data. Related to the simulation of the studied separation, a 99% molar enriched bioethanol stream was obtained with a recovery of 94%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and electrorheological properties of polyaniline‐coated barium titanate composite particles
Authors: Yan Hua , Liao Zi Jun , Zhu Xia , Wang Xue Mei , Chen Yong , Zhang Bin , Chen Shui Lian , Za Zhong Yong
Published: October 2007

Polyaniline‐coated barium titanate composite particles were synthesized by surface grafting polymerization, in which five silane coupling agents with different terminal groups were used. The structure of composite particles was characterized by SEM, XRD, FTIR, and TGA, and the electrorheological properties were tested by rotational rheometer. The results show that polyaniline was coated on the surface of barium titanate particles to form the shell‐core structure. The yield stress of the electrorheological fluids based on polyaniline‐coated barium titanate composite particles is higher than that of polyaniline and barium titanate. Compared with PANI‐based electrorheological fluids (ERFs), the composite particles‐based ERFs have lower field‐off viscosity due to the molecular interaction. The yield stress of the ERFs, as well as density of the composite particles, was affected by the groups at terminal of silane coupling agents. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Correlation between current–voltage (I–V) characteristic in the electric–thermal equilibrium state and resistivity‐temperature behavior of electro‐conductive silicone rubber
Authors: Zhang Jie , Feng Dacheng , Feng Shengyu , Han Jianjun , Diao Guangzhao , Liu Da
Published: October 2007

In the electric–thermal equilibrium state the current–voltage (I–V) characteristics of conductive silicone rubbers above the percolation threshold are found to be nonlinear. A mathematic model as I = a1U ± (a2U2 + C) has been built for the nonlinear I–V relations. Constant C and quadratic term a2U2 can be considered as deviation from Ohm's law. For the first time, a correlation is found for conductive silicone rubber between the I–V characteristic in the electric–thermal equilibrium state and the resistivity–temperature characteristic. Samples with positive temperature coefficient (PTC) resistivity effect exhibit negative deviation from linearity, with an I–V relation as I = a1U − (a2U2 + C). Samples with negative temperature coefficient (NTC) resistivity effect exhibit positive deviation, with an I–V relation as I = a1U + (a2U2 + C). The higher the loaded voltage, the more pronounced the deviation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Novel jute yarns grafted with methyl methacrylate
Authors: Montazer M. , Salehi A.
Published: October 2007

This research work involves graft copolymerization of jute fibers with methyl methacrylate (MMA), initiated by cerric ions, and optimization of the grafting parameters as a function of different polymerization conditions. It was considered to produce a hydrophobic jute fiber with enhanced properties. To achieve this, the effects of monomer concentration and grafting percentage on FTIR spectra, mechanical properties, moisture regain, oil‐adsorption capacity, and surface morphology were investigated, and optimum percentage of MMA with reasonable properties was suggested. The results indicated that cerric ions initiated graft copolymerization of MMA onto jute with 30% of weight of monomers at optimum conditions of acid concentration and temperature. The FTIR studies proposed grafting of MMA onto jute at hydroxyl groups. The results showed that mechanical properties and moisture regain (%) of samples decrease with increasing of graft percentage. The most remarkable features of this investigation include reducing oil‐adsorption capacity with increasing of lipophilic monomer percentages after one limitation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Thermal and rheological behavior of ultrafine fly ash filled LDPE composites
Authors: Hashmi S. A. R. , Sharma Pratibha , Chand Navin
Published: November 2007

The specimens containing different volume fractions of ultrafine fly ash in LDPE were prepared with the help of two roll mixing mill and the hot‐plate compression‐molding machine. Thermal and rheological properties were evaluated using DSC and parallel‐plate rotational‐rheometer. The effect of composition variation on melt enthalpy, crystallinity, shear viscosity, shear stress and first normal stress difference was studied and reported here. The addition of ultrafine fly ash in LDPE decreased the melt enthalpy of the specimen. Slight decrease in the crystallinity of LDPE was observed on addition of fly ash. The shear stress as well as the shear viscosity both increased with the addition of ultrafine fly ash in LDPE. Two regions of shear thinning were observed at 200°C for fly ash filled LDPE. The first normal stress difference (N1) reduced with fly ash content and with the increased temperature. The values of N1 remained almost invariable at low shear region however a proportional increase was observed beyond the shear stress of 10 kPa. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008
New Method for Predicting the Lumbar Lordosis Angle in Skeletal Material
Authors: Been Ella , Pessah Hayuta , Been Laurence , Tawil Arie , Peleg Smadar
Published: October 2007

Reconstructing the lordotic curvature of the lumbar spine in humans is essential for understanding their posture and locomotion. To date there is still no reliable method for predicting the lordotic curvature of disarticulated spines (in the absence of intervertebral disks). This article examines two possible methods for predicting the lordotic curvature of the lumbar spine. The first—the traditional method—is based on the degree of wedging of the vertebral bodies, and the second—the suggested new method—is based on a lateral view of the orientation of the inferior articular processes. We propose a linear regression model for predicting the lordotic curvature of the lumbar spine (lordosis angle) in disarticulated human spines. This model, derived directly from our new method, is a more reliable predictor of the lumbar lordosis angle in disarticulated spines. Anat Rec, 2007. © 2007 Wiley‐Liss, Inc.
Classification and Development of Myofiber Types in the Superior Oblique Extraocular Muscle of Chicken
Authors: Baryshnikova Larisa M. , Croes Scott A. , von Bartheld Christopher S.
Published: October 2007

Precise control of contractile force of extraocular muscles is required for appropriate movements and alignment of the eyes. It is unclear how such precise regulation of contractile force is achieved during development and maturation. By using the posthatch chicken as a model, we describe and quantify critical parameters of the developing superior oblique extraocular muscle from hatching to 16 weeks of age, including contractile force, muscle mass, myofiber diameters, classification of fiber types, and distribution and quantification of mitochondria. Analysis at the light‐ and electron microscopic levels shows that chicken myofiber types largely correspond to their mammalian counterparts, with four fiber types in the orbital and four types in the global layer. Twitch tension muscle force and muscle mass gradually increase and stabilize at approximately 11 weeks. Tetanic tension continues to increase between 11 and 16 weeks. Myofiber diameters in both the orbital and global layer increase from hatching to six weeks, and then stabilize, whereas the myofiber number is constant after hatching. This finding suggests that muscle mass increases during late maturation due to increasing fiber length rather than fiber diameter. Quantitative ultrastructural analysis reveals continuing changes in the composition of the four muscle fiber types, suggesting ongoing fiber type conversion or differential replacement of myofiber types. Muscle fiber composition continues to change into late juvenile and adult age. Our study provides evidence for gradual, incremental, and continuing changes in avian myofiber composition and function that is similar to postnatal oculomotor maturation in visually oriented mammals such as kitten. Anat Rec, 2007. © 2007 Wiley‐Liss, Inc.
Rechnerischer Nachweis der Randverformungen bei Wärmedämmverbundsystemen (WDVS) mit Holzfaserdämmplatten und großer Dämmdicke bis ca. 200 mm
Authors: Rüther Norbert
Published: October 2007

In Deutschland unterliegen Wärmedämmverbundsysteme (WDVS) mit Holzfaserdämmplatten einer bauaufsichtlichen Zulassung. Bisher war die Dämmdicke auf 120 mm begrenzt. Einige Firmen sind bestrebt, größere Dämmdicken einzusetzen, was eine genauere Untersuchung der Spannungen und Verformungen im System erforderlich macht. Dieser Artikel beschreibt Methoden zur Beurteilung von Verformungen in WDVS mit mechanisch befestigten Holzfaserdämmplatten. Aufgrund der komplexen Thematik ist der Artikel wie folgt strukturiert:

– hygrische und thermische Dehnung der Wärmedämmung und

– hygrische und thermische Dehnung des Putzes planparallel zur Oberfläche.

Der Artikel kommt zu dem Ergebnis, dass für Dämmstärken von mehr als 120 mm keine zusätzlichen Maßnahmen erforderlich sind. Die berechnete Verformung von ca. 1,8 mm im Belastungszustand “Primärschwindung und Temperaturänderung” eines theoretisch unendlichen WDVS führt zu Haarrissen, die im Allgemeinen unkritisch sind. Der Artikel beschreibt außerdem Methoden zur genaueren Berechnung der Verformungen von WDVS.