bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Aging Performance of Virgin EPDM Roof-Sheeting Compounds with Amine-Devulcanized EPDM Weatherstrip Material
Authors: Dijkhuis K. A. J. , Dierkes W. K. , Noordermeer J. W. M. , Sutanto P.
Published: February 2011

Sulfur-cured EPDM building-profile material was reclaimed in a co-rotating twin-screw extruder using hexadecylamine as reclaiming aid. This reclaim was blended with increasing amounts of a virgin EPDM roof-sheeting masterbatch and cured at temperatures allowing for a reversion-free vulcanization. The trends in cure characteristics showed that increasing amounts of reclaim employed in the blends lowered the reversion-free cure temperature and the maximum torque values, while the vulcanization speed was increased. The insoluble fraction and crosslink density both decreased, while the ratio of mono- to di- and polysulfidic crosslinks increased with growing reclaim contents. A SEM-EDX morphology study of the blends, in order to evaluate the dispersion of the reclaim into the virgin rubber matrix showed, that even large amounts of reclaimed material resulted in homogeneous and smooth compounds. Tensile strength, modulus at 300% strain and hardness decreased, while elongation at break, tear strength and compression set at 70 °C increased with increasing reclaim ratios. Irrespective of the blend ratios, the mechanical properties all fulfilled the most stringent UEAtc specifications for EPDM roof-sheeting. Increasing reclaim contents improve the aging resistance and prolong the time before a practical limiting value for elongation at break of 250% for EPDM roof-sheeting purposes is reached.
Viscoelasticity of Asphalts Modified with SEBS Copolymers Functionalized with Various Amounts of Maleic Anhydride
Authors: Vargas M. A. , López N. N. , Cruz M. J. , Calderas F. , Manero O.
Published: February 2011

It is known that the microstructure of polymer-modified asphalts (PMA) depends strongly of the characteristics of the polymer. The modifier polymer improves the mechanical properties of pure asphalt when used in paved roads. In this work, asphalt is modified using reactive polymers obtained via functionalization of styrene-ethylene/butylene-styrene (SEBS) copolymers in solution using various amounts of benzoil peroxide (BPO) as initiator and maleic anhydride (MAH). The resulting functionalized copolymer (SEBS-g-MAH) with variable amounts of grafting (variable reactivity) is blended with the asphalt at small contents (2–4 wt. %). The amount of MAH grafting was determined by FTIR, 1HNMR, GPC, DSC and by titration with KOH, and this amount is readily correlated with the improvement of the mechanical properties and thermal stability of the asphalt. In addition, the limit of the polymer-asphalt compatibility is determined for these systems.
Recent Advances in Structural Characterization of Natural Rubber
Authors: Tanaka Yasuyuki , Tarachiwin Lucksanaporn
Published: February 2011

Structural characterization of rubber from Hevea brasiliensis (NR) has been carried out to elucidate the biosynthesis mechanism of rubber molecule as well as to find the relationship between physical properties characteristic of NR and its structure. Recent advances of structural studies have provided a series of new information on the structure of long-chain branching based on the result of selective decomposition of branch-points by chemical and enzymatic treatments as well as physical treatment such as polar solvent treatments and washing of NR latex by centrifugation in the presence of a surfactant. The measurement of the resulting rubber with NMR, FTIR, SEC and dilute solution viscosity provided confirming evidence that the initiating terminal (ω-terminal) with an unidentified functional group and phosphate terminal (α-terminal) form branch-points by hydrogen bond, ionic bond or micelle formation of phospholipids linked to both terminal groups. Based on these results, the origin of green properties characteristic of NR has been explained and a new mechanism of storage hardening has been proposed. The purification method by saponification of NR latex developed for the structural characterization has been applied to produce purified NR latex free from Type I allergic reaction. Instantaneous coagulation of saponified latex by the use of a flocculant and formic acid has provided solid saponified NR having good green and cured rubber properties.
Mixing, Curing and Reinforcement of NR/BR/EPDM Blends for Tire Sidewall Applications
Authors: Zhang H. , Datta R. N. , Talma A. G. , Noordermeer J. W. M.
Published: February 2011

Tire sidewalls generally consist of blends of natural rubber (NR) and butadiene rubber (BR), containing a high concentration of antiozonants to provide ozone resistance. However, the most widely used antiozonant, N-(1, 3-dimethyl-butyl)-N'-phenyl-p-phenylenediamine (6PPD), is a staining, toxic and environmentally unfriendly substance. Incorporation of Ethylene-Propylene-Diene rubber (EPDM) into NR/BR is a way of achieving non-staining ozone resistance. But blending of dissimilar rubbers is severely restricted due to viscosity mismatch, thermodynamic incompatibility, cure incompatibility and heterogeneous filler distribution. This chapter gives an overview of the various research approaches in the field of blending dissimilar rubbers so far, as well as the mechanism of ozone protection by incorporation of EPDM in tire sidewall applications.
Mechanistic Studies into the New Concept of Co-Agents for Scorch Delay and Property Improvement in Peroxide Vulcanization
Authors: Alvarez Grima M. M. , Eriksson J. G. , Talma A. G. , Datta R. N. , Noordermeer J. W. M.
Published: February 2011

In previous studies a new concept of a peroxide cure system for rubber has been reported where scorch safety and mechanical properties are improved at the same time. This new system consists of the use of a combination of a peroxide, a bismaleimide type co-agent and a sulfur spender for the cure of saturated or low-unsaturated rubber. Several mechanical properties have been studied and were found to be improved by using this curing system, such as tensile strength, moduli, compression set and aging. The present paper deals with the understanding of the reported phenomena. Mechanistic studies have been performed with the aim of comprehending the chemistry that takes place during peroxide vulcanization in the presence of a maleimide co-agent and a sulfur spender. From Nuclear Magnetic Resonance and Infrared analysis the loss of the maleimide unsaturation from the co-agent was observed, due to reaction with the sulfur spender. This reaction already takes place at room temperature, thus previous to peroxide decomposition. Further, Model Compound Vulcanization studies were performed using 3-methylpentane as representative model for the saturated rubber backbone. The reaction products of the peroxide vulcanization of 3-methylpentane in the presence of a maleimide type co-agent and a sulfur donor have been analyzed by means of Liquid Chromatography-Mass Spectrometry. Several reaction products have been identified and a reaction mechanism that explains the scorch delay and the property improvement by the new cure system is proposed.
Ischemic Monomelic Neuropathy: A Rare but Important Complication after Hemodialysis Access Placement - a Review
Authors: Thermann Florian , Kornhuber Malte
Published: February 2011

The creation of a vascular access for hemodialysis is a frequently performed procedure. Ischemic monomelic neuropathy (IMN) is a rare, but important complication of hemodialysis access (HA) procedures, which can lead to severe and nonreversible limb dysfunctions. Therefore, in any case of postoperative neurological malfunction, immediate neurological investigations should be undertaken. If IMN is diagnosed, improvement of distal perfusion should be established without delay. IMN is a form of hemodialysis-associated ischemic syndrome (as the so-called steal syndrome), but experiences with this complication are small. Every case of IMN should be carefully documented and if possible published, to gain more experience about this rare but important complication.
Calendering
Authors: Coaker A. William M.
Published: February 2011

Calendaring is essentially extruding a mass of material between successive pairs of corotating, parallel rolls to form a film or sheet. This process is widely used in the thermoplastics, rubber, textile, paper, and nonwoven fabrics industries.
Pelletizing
Authors: Todd Baker D. B.
Published: February 2011

In the production of thermoplastics, the primary products frequently leave the manufacturing facility in the form of pellets. Incorporation of antioxidants, stabilizers, colors, fillers, reinforcing agents, and other additives requires that the polymer be in the melt stage to assure uniform distribution. After incorporation the melt is pelletized into uniform sizes and shapes to facilitate handling.
Annealing
Authors: LeGrand D. G.
Published: February 2011

The annealing of plastics can be defined as a secondary process wherein the plastic is brought to a certain temperature, kept there for a time, and then cooled to room temperature. The primary reasons for annealing include the reduction or removal or residual stresses and strains, dimensional stabilization, reduction or elimination of defects, and improvement of physical properties.
Casting
Authors: Harbison William C.
Published: February 2011

Casting is the process whereby a liquid is poured into a mold and allowed to react, cure, or harden to form a rigid object that reproduces the mold cavity. Many resin systems may be utilized in this process, eg, acrylic, diethylene glycol bis(allyl carbonate), epoxy, phenol–formaldehyde, polystyrene, polysulfide, and silicone. Methyl methacrylate is the principle monomer used in the casting, or bulk polymerization, of acrylic plastics.
Specific Near‐IR Absorption Imaging of Glioblastomas Using Integrin‐Targeting Gold Nanorods
Authors: Choi Jihye , Yang Jaemoon , Park Joseph , Kim Eunjung , Suh Jin‐Suck , Huh Yong‐Min , Haam Seungjoo
Published: February 2011

Molecular imaging using nanoprobes with high resolution and low toxicity is essential in early cancer detection. Here we introduce a new class of smart imaging probes employing PEGylated gold nanorods (GNRs) conjugated to cRGD for specific optical imaging of αvβ3 integrins from glioblastoma. GNRs exhibiting an optical resonance peak in the near‐infrared (NIR) region were synthesized using the seed‐mediated growth method. CTAB (cetyl trimethylammonium bromide) bilayer on the GNRs was replaced with a biocompatible stabilizer, heterobifunctional polyethyleneglycol (COOH‐PEG‐SH). Further, the carboxylated GNRs (PGNRs; PEG‐coated GNRs) were functionalized with cRGD using EDC‐NHS chemistry to formulate cRGD‐conjugated GNRs (cRGD‐PGNRs) for αvβ3 integrins. In order to assess the potential of the cRGD‐PGNRs as a targeted imaging probe, we investigated their optical properties, biocompatibility, colloidal stability and in vitro/in vivo binding affinities for cancer cells. Consequently, cRGD‐PGNRs demonstrated excellent tumor targeting ability with no cytotoxicity, as well as sufficient cellular uptake due to stable and prolonged blood circulation of cRGD‐PGNRs.
Self‐Tuning the Carrier Concentration of PbTe/Ag2Te Composites with Excess Ag for High Thermoelectric Performance
Authors: Pei Yanzhong , May Andrew F. , Snyder G. Jeffrey
Published: February 2011

Thermoelectric materials can be optimized by tuning the carrier concentration with chemical doping. However, because the optimum dopant concentration typically increases with temperature, the optimum efficiency can not normally be achieved for a uniform material in a temperature gradient. Here, we show Ag‐doped PbTe/Ag2Te composites exhibit high thermoelectric performance (∼50% greater than La‐doped composites) because of a temperature induced gradient in the doping concentration caused by the temperature‐dependent solubility of Ag in the PbTe matrix. This demonstrates a new mechanism to achieve a higher thermoelectric efficiency afforded by a given material system, and should be applicable to other thermoelectric materials.
Another case of multiple juxtasutural hyperostoses, cervical exostoses, and fatty infiltration of myocardium
Authors: Kannu Peter , Perry David , Rees Martin , O'Donnell Clare , Aftimos Salim
Published: February 2011

We report on an individual affected by multiple juxtasutural cranial hyperostoses who later developed cervical spine hyperostoses with associated fusion anomalies. The propositus was not affected by a disorder of generalized overgrowth. An echocardiogram revealed areas of abnormal signal within the myocardium which were consistent with fatty infiltration on magnetic resonance imaging of the heart. We compare our case with a few previously reported cases that share phenotypic similarities but differ in some other clinical aspects. It is possible that these patients represent a phenotypic continuum resulting from a somatic mutation in an unknown gene. © 2011 Wiley‐Liss, Inc.
Hajdu–Cheney syndrome with severe dural ectasia
Authors: Avela Kristiina , Valanne Leena , Helenius Ilkka , Mäkitie Outi
Published: February 2011

Hajdu–Cheney syndrome (HCS) is an autosomal dominant condition comprising osteolysis of the terminal phalanges, characteristic craniofacial abnormalities, dental anomalies, and proportionate short stature. The clinical and radiological findings develop and progress with age. Here, we report on a HCS patient with severe scoliosis and exceptionally massive dural ectasia. Congenital scoliosis and dural ectasia have not been reported previously in HCS. © 2011 Wiley‐Liss, Inc.
Variable expression of neurofibromatosis 1 in monozygotic twins
Authors: Rieley Margaret B. , Stevenson David A. , Viskochil David H. , Tinkle Brad T. , Martin Lisa J. , Schorry Elizabeth K.
Published: February 2011

Neurofibromatosis 1 (NF1) is a common autosomal dominant disorder with high penetrance but extreme variability of expression. Monozygotic (MZ) twins with NF1 who have phenotypic discordances are a useful tool in evaluating which traits are influenced by non‐hereditary influences such as second hit somatic events, environmental agents, epigenetic modification, or post‐zygotic mutations. We evaluated nine sets of MZ twins and one set of MZ triplets, ages 4–18 years, for NF1 features and calculated probandwise concordance (PC) for each feature. MZ twins were highly concordant in numbers of café‐au‐lait spots (PC = 0.89) and cutaneous neurofibromas. IQ scores were within 10 points for all twin pairs tested, and similar patterns of learning disabilities and speech disorders were observed. Twin pairs showed significant discordance for tumors, particularly plexiform neurofibromas (PC = 0.40) and malignant peripheral nerves sheath tumors (MPNST), as expected if post‐natal second‐hit events were contributing to these features. One set of twins was concordant for multiple, large paraspinal neurofibromas, suggesting that there may be more hereditary factors involved in production of paraspinal neurofibromas. Four sets were concordant for pectus deformities of the chest (PC = 0.80). Three sets of twins were discordant for scoliosis (PC = 0.40); an additional set was concordant for scoliosis but differed in presence of dystrophic features and need for surgery. Our data suggest there are additional non‐hereditary factors modifying the NF1 phenotype and causing discordancies between MZ twins. Future studies may focus on differences in epigenetic changes or somatic mosaicism which have been documented for other disease genes in MZ twins. © 2011 Wiley‐Liss, Inc.
Genetic dosage compensation in a family with velo‐cardio‐facial/DiGeorge/22q11.2 deletion syndrome
Authors: Alkalay Avishai A. , Guo Tingwei , Montagna Cristina , Digilio M. Cristina , Dallapiccola Bruno , Marino Bruno , Morrow Bernice
Published: February 2011

Cytogenetic studies of a male child carrying the 22q11.2 deletion common in patients with velo‐cardio‐facial/DiGeorge syndrome showed an unexpected rearrangement of the 22q11.2 region in his normal appearing mother. The mother carried a 3 Mb deletion on one copy and a reciprocal, similar sized duplication on the other copy of chromosome 22q11.2 as shown by fluorescence in situ hybridization and array comparative genome hybridization analyses. The most parsimonious mechanism for the rearrangement is a mitotic non‐allelic homologous recombination event in a cell in the early embryo soon after fertilization. The normal phenotype of the mother can be explained by the theory of genetic dosage compensation. This is the second documented case of such an event for this or any genomic disorder. This finding helps to reinforce this phenomenon in a human model, and has significant implications for recurrence risks for the dose‐compensated mother. © 2011 Wiley‐Liss, Inc.
Descriptive study of nonsyndromic atrioventricular septal defects in the National Birth Defects Prevention Study, 1997–2005
Authors: Hartman Robert J. , Riehle‐Colarusso Tiffany , Lin Angela , Frías Jaime L. , Patel Sonali S. , Duwe Kara , Correa Adolfo , Rasmussen Sonja A. ,   The National Birth Defects Prevention Study
Published: February 2011

Nonsyndromic atrioventricular septal defects (AVSDs) are serious congenital heart defects for which information on prevalence and descriptive characteristics based on large, geographically, and ethnically diverse populations has been limited. To describe the birth prevalence and phenotype of nonsyndromic AVSDs, we used data from the National Birth Defects Prevention Study (NBDPS), a multisite, population‐based case–control study aimed at identifying genetic and environmental risk factors for birth defects. For this analysis, infants born during the period 1997–2005 and meeting the NBDPS case definition for AVSDs were included. Infants with an AVSD associated with recognized or strongly suspected chromosomal abnormalities or single‐gene disorders (syndromic case infants) were excluded. We identified 302 infants with a nonsyndromic AVSD for a birth prevalence of 0.83/10,000 livebirths. Over 20% of infants with an AVSD had an additional major birth defect, with gastrointestinal, renal or urinary, and central nervous system defects being the most common. A lower prevalence of AVSDs was seen among infants born to Hispanic mothers compared with those born to non‐Hispanic White mothers [prevalence ratio = 0.63 (95% confidence interval: 0.46–0.86)]. Understanding the prevalence of nonsyndromic AVSDs, demographic factors associated with their occurrence, and associated defects could help guide clinical care, as well as contribute to a better understanding of pathogenesis. © 2011 Wiley‐Liss, Inc.
Carnitine and coenzyme Q10 levels in individuals with Prader–Willi syndrome
Authors: Miller Jennifer L. , Lynn Christy H. , Shuster Jonathan , Driscoll Daniel J.
Published: February 2011

Carnitine deficiency or coenzyme Q10 (CoQ10) deficiency may present with hypotonia, poor growth, easy fatigability, and apnea. This constellation of findings can also be seen in individuals with Prader–Willi syndrome (PWS). Animal studies indicate that increased fat mass due to obesity negatively correlates with both carnitine and CoQ10 levels in skeletal muscle. Increased body fat and obesity are characteristic of individuals with PWS. Currently, there is no documentation of serum carnitine levels, and only one study investigating plasma CoQ10 levels, in individuals with PWS. Fasting serum carnitine and plasma CoQ10 levels were measured in 40 individuals with molecularly confirmed PWS (ages 1–27 years; 19 F/21 M), 11 individuals with early‐onset morbid obesity of unknown etiology (ages 3–13 years; 5 F/6 M), and 35 control siblings from both groups (ages 1–24 years; 19 F/16 M). There were no significant differences among the three groups in either total carnitine, free carnitine, or CoQ10 levels. However, individuals with PWS had higher serum levels of carnitine esters (P = 0.013) and higher ester‐to‐free carnitine ratios (P = 0.0096) than controls suggesting a possible underlying impairment of peripheral carnitine utilization and mitochondrial energy metabolism in some individuals with PWS. Serum sampling identified no significant differences in total and free carnitine or CoQ10 levels between individuals with PWS, obese individuals, and sibling control groups. Muscle biopsy or measurement in leukocytes or cultured skin fibroblasts could be a better method to identify abnormalities in carnitine and CoQ10 metabolism in individuals with PWS than peripheral blood sampling. © 2011 Wiley‐Liss, Inc.
Eye‐tracking with nonhuman primates is now more accessible than ever before
Authors: Machado Christopher J. , Nelson Eric E.
Published: February 2011

Human and nonhuman primates rely almost exclusively on vision for social communication. Therefore, tracking eye movements and examining visual scan paths can provide a wealth of information about many aspects of primate social information processing. Although eye‐tracking techniques have been utilized with humans for some time, similar studies in nonhuman primates have been less frequent over recent decades. This has largely been owing to the need for invasive manipulations, such as the surgical implantation of devices to limit head movement, which may not be possible in some laboratories or at some universities, or may not be congruent with some experimental aims (i.e., longitudinal studies). It is important for all nonhuman primate researchers interested in visual information processing or operant behavior to realize that such invasive procedures are no longer necessary. Here, we briefly describe new methods for fully noninvasive video eye‐tracking with adult rhesus monkeys (Macaca mulatta). We also describe training protocols that require only ∼30 days to accomplish and quality control measures that promote reliable data collection. It is our hope that this brief overview will reacquaint nonhuman primate researchers with the benefits of eye‐tracking and promote expanded use of this powerful methodology. Am. J. Primatol. 73: 562–569, 2011. © 2011 Wiley‐Liss, Inc.
Brain alkalosis causes birth asphyxia seizures, suggesting therapeutic strategy
Authors: Helmy Mohamed M. , Tolner Else A. , Vanhatalo Sampsa , Voipio Juha , Kaila Kai
Published: February 2011

Objective:

The mechanisms whereby birth asphyxia leads to generation of seizures remain unidentified. To study the possible role of brain pH changes, we used a rodent model that mimics the alterations in systemic CO2 and O2 levels during and after intrapartum birth asphyxia.

Methods:

Neonatal rat pups were exposed for 1 hour to hypercapnia (20% CO2 in the inhaled gas), hypoxia (9% O2), or both (asphyxic conditions). CO2 levels of 10% and 5% were used for graded restoration of normocapnia. Seizures were characterized behaviorally and utilizing intracranial electroencephalography. Brain pH and oxygen were measured with intracortical microelectrodes, and blood pH, ionized calcium, carbon dioxide, oxygen, and lactate with a clinical device. The impact of the postexposure changes in brain pH on seizure burden was assessed during 2 hours after restoration of normoxia and normocapnia. N‐methyl‐isobutyl‐amiloride, an inhibitor of Na+/H+ exchange, was given intraperitoneally.

Results:

Whereas hypercapnia or hypoxia alone did not result in an appreciable postexposure seizure burden, recovery from asphyxic conditions was followed by a large seizure burden that was tightly paralleled by a rise in brain pH, but no change in brain oxygenation. By graded restoration of normocapnia after asphyxia, the alkaline shift in brain pH and the seizure burden were strongly suppressed. The seizures were virtually blocked by preapplication of N‐methyl‐isobutyl‐amiloride.

Interpretation:

Our data indicate that brain alkalosis after recovery from birth asphyxia plays a key role in the triggering of seizures. We question the current practice of rapid restoration of normocapnia in the immediate postasphyxic period, and suggest a novel therapeutic strategy based on graded restoration of normocapnia. Ann Neurol 2011
Transition to adult care for children with chronic neurological disorders
Authors: Camfield Peter , Camfield Carol
Published: February 2011

Chronic neurological disorders in children have significant effects on adult medical and social function. Transition and then formal transfer of care from pediatric to adult services is a complex process, although there are virtually no objective data to inform physicians about the most effective approach. Some neurological disorders that start in children are a danger to society if poorly treated in adulthood, some disorders that were previously lethal in childhood now permit survival well into adulthood, and others are static in childhood but progressive in adulthood. Some disorders remit or are cured in childhood but continue to have serious comorbidity in adulthood, whereas others are similar and persistent in children and adults. Maturity, provision of information, and cognitive problems are confounders. We discuss several models of transition/transfer but prefer a joint pediatric/adult transition clinic. We make a series of suggestions about how to improve the transition/transfer process with the hope of better medical and social adult outcome for children with neurological disorders. ANN NEUROL 2011
Predictors of seizure freedom after surgery for malformations of cortical development
Authors: Chang Edward F. , Wang Doris D. , Barkovich A. James , Tihan Tarik , Auguste Kurtis I. , Sullivan Joseph E. , Garcia Paul A. , Barbaro Nicholas M.
Published: February 2011

Objective:

Malformations of cortical development (MCDs) are a major cause of medically refractory epilepsy. Our aim was to examine a surgical series of patients with cortical malformations to determine the prognostic factors associated with long‐term seizure control.

Methods:

We conducted a retrospective review of 143 patients with MCD who underwent resective surgery for medically refractory epilepsy. Demographic, imaging, histopathologic, and surgical variables were analyzed for potential association with seizure freedom. Preoperative magnetic resonance imaging (MRI) was evaluated in a blind fashion and classified according to a new imaging/embryologic MCD classification system.

Results:

Gray‐white blurring on MRI, smaller lesions, complete resection of structural lesions, complete resection of abnormal electrocorticographic areas, and locally confined electrocorticographic abnormalities are favorable prognosticators of seizure freedom on univariate analysis. Imaging features consistent with abnormal proliferation (Barkovich class I) were associated with better outcome compared to those related to abnormal neuronal migration (class II) or abnormal cortical organization (class III). Multivariate logistic regression revealed complete resection of tissue manifesting electrocorticographic and/or MRI anatomic abnormalities as the main independent predictor of seizure freedom. Other histopathologic or demographic factors were not associated with seizure control. Long‐term follow‐up of patients demonstrated sustained overall rates of seizure control (72% at 2 years, 65% at 5 years, and 67% at 10 years).

Interpretation:

Surgery for MCDs can result in high rates of seizure freedom. Complete resection of electrocorticographic and anatomic abnormalities appears to be most predictive of long‐term seizure control. ANN NEUROL 2011
The generalized SIC‐OEP formalism and the generalized SIC‐Slater approximation (stationary and time‐dependent cases)
Authors: Messud J. , Dinh P.M. , Reinhard P.‐G. , Suraud E.
Published: February 2011

We present a generalized formulation of the Optimized Effective Potential (OEP) approach to the Self Interaction Correction (SIC) problem in Time Dependent (TD) Density Functional Theory (DFT). The formulation relies on the introduction of a double set of single electron orbitals. It allows the derivation of a generalized Slater approximation to the full OEP formulation, which extends the domain of validity of the standard Slater approximation. We discuss both formal aspects and practical applications of the new formalism and give illustrations in cluster and molecules. The new formalism provides a valuable ansatz to more elaborate (and computationally very demanding) full TD OEP and full TD SIC calculations especially in the linear domain.
Synthesis and characterization of magnetic nanocomposites of fullerene‐containing polyurethane films for microwave applications
Authors: Chopra Swati , Pandey Mritunjay Kr. , Alam Sarfaraz
Published: February 2011

Novel nanocomposites of barium hexaferrite‐ and fullerene‐containing polyurethane were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, X‐ray diffractometry, and energy‐dispersive X‐ray diffraction. The nanoparticles showed good dispersion in the polyurethane matrix. Their thermal, mechanical, and electromagnetic absorbance properties were studied. The complex permeability and permittivity were measured in the frequency range of 8.2–12.4 GHz. The maximum reflection loss of the nanocomposites was found to increase with increasing the ferrite content from 1% to 5%, with maximum value of −7.5 dB at only 5% composition. The incorporation of nanofiller not only imparts mechanical strength to the nanocomposite but also shows good radar‐absorbing properties at only 5% filler concentration. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Development of porous polymer monolith by photoinitiated polymerization
Authors: Yu Suzhu , Ng Feng Lin , Ma Khin Cho Cho , Ng Fern Lan , Zhao Jianhong , Tong Steven Kin Kong
Published: February 2011

Porous polymer monoliths have been successfully prepared by photoinitiated polymerization of butyl methacrylate (BMA) and ethylene glycol dimethacrylate (EDMA) monomers in porogenic solvent of methanol. Mercury intrusion porosimetry and scanning electron microscope are used to characterize the porous properties; nevertheless, the pore size obtained from both techniques is not comparable. The porous structure of the porous polymers is controlled by the phase separation during the polymerization and crosslinking. By varying the composition of the starting solution such as initiator fraction, BMA/EDMA ratio, porogen fraction, and UV intensity, porous polymers with median pore size from about 140 nm to 3 μm can be obtained, and the pore size distribution for majority of the porous polymers is also narrow. The results present a very positive prospect to microfluidic applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
The effect of hybrid nanoparticle additives on epoxy‐nanocomposite behavior and morphology
Authors: Jahren Susannah , Männle Ferdinand , Graff Joachim Moe , Olafsen Kjell
Published: February 2011

Amine modified polyhedral oligomeric silsesquioxane (POSS‐NH2) was used to modify sodium montmorillonite (MMT) nanoclays for improved dispersion in epoxy resin. The dispersion of the clay particles was inspected using scanning electron microscopy, energy dispersive spectroscopy (EDS) and X‐Ray diffraction and the thermal properties compared using differential scanning calorimetry (DSC) and thermogravametric analysis. The introduction of the amine‐POSS was found to have a positive effect on the dispersion of the MMT clays and prevented agglomeration. The absence of clay agglomerates lead to an increase in glass transition temperature (Tg) from 44°C in the samples with the untreated clay up to 54°C in the samples with 10% additional POSS‐NH2. The addition of POSS‐NH2 initial increase of the weight loss (Td
5%) but slowed down the rate of degradation due to the formation of an inert silica layer and eventually leading to an increased charyield. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Thermal degradation and pyrolysis study of phosphorus‐containing polysulfones
Authors: Petreus Oana , Lisa Gabriela , Avram Ecaterina , Rosu Dan
Published: February 2011

This article deals with the thermal decomposition behavior of a polysulfone containing 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide versus the initial chloromethylated polysulfone under an inert atmosphere and in air. Thermogravimetric characteristics from thermogravimetry and differential thermogravimetry data revealed important differences related to the employed atmosphere, the types of substituted functional groups, or the degree of substitution. The introduction of the 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide pendent group into polysulfone enhanced the thermal stability of the initial chloromethylated polysulfone in both an inert atmosphere and air. Thermal degradation in nitrogen consisted of one degradation step, whereas thermooxidative degradation in air involved more steps. In air, the degradation mechanism was more complex. The volatile products and solid residues that resulted after pyrolysis in an inert atmosphere and in air were analyzed with Fourier transform infrared and mass spectrometry. Environmental scanning electron microscopy showed that the char residues had different morphologies, which suggested that a more compact structure led to better resistance to heat and oxygen. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 000: 000–000, 2011
Hybridized reinforcement of natural rubber with silane‐modified short cellulose fibers and silica
Authors: Lopattananon Natinee , Jitkalong Dolmalik , Seadan Manus
Published: February 2011

Natural‐rubber‐based hybrid composites were prepared by the mixture of short cellulose fibers and silica of different relative contents with a 20‐phr filler loading with a laboratory two‐roll mill. The processability and tensile properties of the hybrid composites were analyzed. The tensile modulus improved, but the tensile strength and elongation at break decreased with increasing cellulose fiber content. The scorch safety improved with the addition of 5‐phr cellulose fiber in the composites. The Mooney viscosity significantly decreased with increasing cellulose fiber content. To modify the surface properties of the cellulose fiber and silica fillers, a silane coupling agent [bis(triethoxysilylpropyl)tetrasulfide, or Si69] was used. The effects of Si69 treatment on the processing and tensile properties of the hybrid composites were assessed. We found that the silane treatment of both fillers had significant benefits on the processability but little benefit on the rubber reinforcement. The strength of the treated hybrid composite was comparable to that of silica‐reinforced natural rubber. Furthermore, to investigate the filler surface modification and to determine the mixing effects, infrared spectroscopic and various microscopic techniques, respectively, were used. From these results, we concluded that the fillers were better dispersed in the composites, and the compatibility of the fillers and natural rubber increased with silane treatment. In conclusion, the hybridized use of short cellulose fibers from a renewable resource and silica with Si69 presented in this article offers practical benefits for the production of rubber‐based composites having greater processability and more environmental compatibility than conventional silica‐filler‐reinforced rubber. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Preparation of Cu(II)‐chelated poly(vinyl alcohol) nanofibrous membranes for catalase immobilization
Authors: Feng Quan , Xia Xin , Wei Anfang , Wang Xueqian , Wei Qufu , Huo Dayin , Wei Anjing
Published: February 2011

Poly(vinyl alcohol) (PVA) nanofibers were formed by electrospinning. Metal chelated nanofibrous membranes were prepared by reaction between Cu(II) solution and nanofibers, and which were used as the matrix for catalases immobilization. The constants of Cu(II) adsorption and properties of immobilized catalases were studied in this work. The Cu(II) concentration was determined by atomic absorption spectrophotometer (AAS), the immobilized enzymes were confirmed by the Fourier transform infrared spectroscopy (FTIR), and the amounts of immobilized enzymes were determined by the method of Bradford on an ultraviolet spectrophotometer (UV). Adsorption of Cu(II) onto PVA nanofibers was studied by the Langmuir isothermal adsorption model. The maximum amount of coordinated Cu(II) (qm) was 2.1 mmol g−1 (dry fiber), and the binding constant (Kl) was 0.1166 L mmol−1. The immobilized catalases showed better resistance to pH and temperature inactivation than that of free form, and the thermal and storage stabilities of immobilized catalases were higher than that of free catalases. Kinetic parameters were analyzed for both immobilized and free catalases. The value of Vmax (8425.8 μmol mg−1) for the immobilized catalases was smaller than that of the free catalases (10153.6 μmol mg−1), while the Km for the immobilized catalases were larger. It was also found that the immobilized catalases had a high affinity with substrate, which demonstrated that the potential of PVA‐Cu(II) chelated nanofibrous membranes applied to enzyme immobilization and biosensors. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Preparation of monodisperse magnetic polystyrene microspheres and its surface chemical modification
Authors: Liu Gang , Guan Yueping , Ge Ying , Xie Li
Published: February 2011

Monodisperse magnetic polystyrene (PS) microspheres were prepared in the presence of PS seed particles and styrene‐based magnetic colloid by the method of magnetic colloid swelling polymerization. The PS seed particles were prepared in advance by soap‐free emulsion polymerization. Styrene‐based magnetic colloid was used for swelling the PS seed particles in the magnetic colloid swelling polymerization process. After polymerization, functional amino groups were introduced onto the surface of the magnetic PS microspheres by surface Friedel‐Crafts acylation reaction. The morphology, size distribution, and magnetic properties of magnetic PS microspheres were characterized with scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM), respectively. SEM showed that the magnetic PS microspheres had an average size of 1078 nm with a narrow size distribution. VSM showed that the magnetic PS microspheres were superparamagnetic, and saturation magnetization was found to be 5.714 emu/g. The concentration of functional amino groups on the surface of magnetic PS microspheres was measured by atomic absorption spectroscopy and UV−Vis spectroscopy, and the concentration of amino groups was found to be 0.168 mmol/g. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
On the structure‐properties relationship in montmorillonite‐filled polyamide 6 nanocomposites
Authors: Motovilin Mladen , Denchev Zlatan , Dencheva Nadya
Published: February 2011

Polyamide 6/montmorillonite (MMT) nanocomposites were prepared by melt compounding method comprising 1–7.5 wt % of Nanomer I.24 TL or 5 and 10 wt % of Cloisite 15A organically modified nanoclays. The composite samples were characterized by synchrotron X‐ray, thermal and FT‐IR spectroscopy methods looking for changes in the micro‐ and nanostructure of both PA6 matrix and MMT reinforcement as a function of the clay content and type. These data were discussed in conjunction with the mechanical properties of the respective nanocomposites. Generally, the Young's modulus was found to increase proportionally to the clay content being the highest in samples with strong aggregation of MMT at micron length scale. The tensile strength passed through a maximum at 2.5 wt % clay load presenting a homogeneous microstructure with almost no agglomeration. Increasing the amount of MMT produced less crystalline PA6 matrices, richer in γ‐PA6 polymorph and resulted in larger long spacings of PA6 due to expansion of both crystalline and amorphous domains. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.
Preparation and characterization of silver‐chitosan nanocomposite particles with antimicrobial activity
Authors: An Jing , Luo Qingzhi , Yuan Xiaoyan , Wang Desong , Li Xueyan
Published: February 2011

A nanocomposite of silver nanoparticles (AgNPs) embedded in chitosan (Cts) matrix was successfully synthesized by crosslinking technology. Colloidal AgNPs formed in situ by chemical reduction of silver ions in presence of Cts showed a good stability. Transmission electron micrographs, X‐ray diffraction patterns, and UV‐visible spectra of Ag‐Cts composite particles confirmed the formation of silver nanocrystals. Fourier transform infrared spectroscopy verified the presence of Cts as a stabilizing agent surrounded AgNPs. Thermogravimetric‐differential scanning calorimeter analysis revealed Ag‐Cts nanocomposite had a higher thermal stability than Cts. X‐ray photoelectron spectroscopy suggested that the Ag‐O bond in the nanocomposite coule lead to the tight combination between silver and Cts. Microbial experiments showed the nanocomposite had excellent and wide spectrum antibacterial properties, and were more efficient than either AgNPs or Cts alone for inactivating bacteria. Therefore, the resultant nanocomposite could be used as antimicrobial materials for medical and biological applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.
Employing of some hyperbranched polyesteramides as new polymeric admixtures for cement
Authors: Amin A. , Darweesh H. H. M. , Ramadan A. M. , Morsi S. M. M. , Ayoub M. M. H.
Published: February 2011

Hyperbranched polyesteramides (HBPA1 and HBPA2) were synthesized by the bulk polycondensation of maleic anhydride (MAn) as an A2 monomer with both of diisopropanolamine (DIPA) and diethanolamine (DEA), respectively, as B′B2 monomer. The prepared polymers were analyzed with IR, GPC, 1H NMR, TGA, and DSC. The hyperbranched polyesteramides were applied as polymeric admixtures in two different types of cement, namely ordinary Portland cement (OPC) and Portland limestone cement (PLC). Several parameters were studied to evaluate the action of HBPA1 and HBPA2 polymers as cement admixtures. Adding HBPA1 and HBPA2 decreased the water of consistency and increased the compressive strength with no effect on the chemical composition of the cement phases. The combined water content and bulk density displayed the same trend as compressive strength. The IR spectra of the formed phases for the mixed cement pastes with HBPA1 and HBPA2 illustrated increased intensities of the absorption bands than those of the pristine cement pastes. The SEM photos showed that the incorporation of HBPA1 and HBPA2 in cement phases affected the morphology and microstructure of the formed hydrates. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Immobilization of microorganisms within porous polymeric capsules
Authors: Nagashima Ryohichi , Hirose Haruko , Matsuyama Hideto
Published: February 2011

Porous capsules suitable for immobilizing yeast and Escherichia coli were prepared by the phase separation of poly(m‐phenylene isophthalamide) solution. The microorganisms were coated with starch or dextrin, which was subsequently extracted after capsule formation but served both to position the microorganisms in the capsule pores and to form spaces around the microorganisms. Fermentation experiments were carried out with capsules immobilizing yeast. Yeasts could be cultivated in the capsules, and effective release of CO2 produced by the fermentation was observed with capsules prepared using polyethylene glycol because of the porous structure at the capsule surfaces. Notably, yeasts could be cultivated at high density even after 1 year. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Investigation of electrospun and film‐cast PVC membranes incorporated with aliquat 336 for efficient Cd extraction: A comparative study
Authors: Wong Lisa , Shen Wei , Truong Yen Bach
Published: February 2011

This article was aimed to investigate the cadmium extraction behaviors of the two different polyvinyl chloride membranes incorporating Aliquat 336—electrospinning and film‐casting. An optimal investigation condition for membranes used in the extraction process was produced at 25 kV with 10 cm tip‐to‐collector distance. Membranes were electrospun for 8 h at 200 μL/h. Membrane extraction studies were carried out using a 127 mg/L Cd(II) solution. Scanning electron microscope (SEM) images revealed differences in fiber diameters and membrane morphology. The addition of Aliquat produced very fine fibers (7–722 nm) resulting Brunauer‐Emmett‐Teller (BET) surface areas of 4.67–11.3 m2/g for electrospun membranes and 1.70–5.44 m2/g for film‐casted membranes. Extraction studies using membranes with different levels of Aliquat (0–40% w/w) revealed that the cadmium extraction performance of electrospun membranes was significantly better than conventional film‐cast membranes. For 40% Aliquat 336, with an initial concentration of 127 mg/L Cd, the cast membrane extracted down to concentration to 115 mg/L as compared to electrospun membrane, which extracted down to 88 mg/L within 40 h. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Solvent‐assisted extrusion of polypropylene/clay nanocomposites
Authors: Castel Charles Dal , Oviedo Mauro A. S. , Liberman Susana A. , Oliveira Ricardo V. B. , Mauler Raquel S.
Published: February 2011

Polypropylene (PP) nanocomposites were prepared by a melting‐compounding process with a montmorillonite (MMT) suspension. In this process, an organically modified MMT was swollen in a polar solvent and blended with molten PP in an extruder; this was followed by solvent removal. The effect of a coswelling agent was also evaluated. The nanocomposites were characterized with X‐ray diffraction, transmission electron microscopy, differential scanning calorimetry, and scanning electron microscopy. In addition, the mechanical properties of the materials were studied. The nanocomposites prepared with the clay suspension presented a remarkable increase in the impact strength with the maintenance of their flexural modulus. The mechanical properties of the nanocomposites were found to be related to the interaction between PP and the clay. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Preparation of mesophase pitch‐based carbon foams with supercritical toluene
Authors: Lu Yonggen , Li Zhiqiang , Wang Peng , Yang Changling
Published: February 2011

Mesophase pitch‐based carbon foams were prepared with supercritical toluene. The effects of the foaming conditions, such as the solvent proportions, temperatures, initial pressures, and pressure drop rates, on the cell densities and mean cell diameters of the carbon foams were studied. The foaming mechanism was analyzed with the theories of homogeneous nucleation. The carbon foams varied in cell densities and cell structure from three‐dimensional interconnected to closed sizing in the range 200 to 800 μm when they were generated under different conditions. The carbon foam structure could be optimized with cell densities of 10–16 × 103 cm−3 and cell diameters from 400 to 450 μm, under the conditions where the temperature was 588 K, the initial pressure was 3.0 MPa, the pressure drop rate was 1.5 MPa/s, and the solvent proportion was 30 wt %. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Structure and tensile properties of Nanoclay–Polypropylene fibers produced by melt spinning
Authors: Rangasamy Loganathan , Shim Eunkyoung , Pourdeyhimi Behnam
Published: February 2011

Nanocomposite fibers of polypropylene and montmorillonite‐based organoclay were produced by a melt‐spinning process, and their structures and mechanical properties were studied. The addition of nanoclay in polypropylene increased the rate of crystallization and altered the microstructures of the fibers. Increases in the crystal size and a reduction in the molecular orientation were observed in the nanoclay–polypropylene composite fibers. The tensile properties of nanoclay composite fibers were also studied, and decreases in the fiber modulus and tenacity and increases in the strain at break were observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011