bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of Hormesis in Life Extension by Caloric Restriction
Authors: Masoro Edward J.
Published: February 2007

Caloric restriction (CR) markedly extends the life of rats, mice and several other species, and it also modulates age-associated physiological deterioration and delays the occurrence and/or slows progression of age-associated diseases. The level of CR that retards the aging processes is a low-intensity stressor, which enhances the ability of rats and mice of all ages to cope with intense stressors. CR thus exhibits a hormetic action in these species, and therefore it is hypothesized that hormesis plays a role in the life-extending and anti-aging actions of CR. Both the findings in support of this hypothesis and those opposing it are critically considered. However, it is likely that hormesis is not the only process contributing to CR-induced life extension. It is proposed that two general processes are involved in CR-induced life extension. One is the reduced endogenous generation of damaging agents, such as reactive oxygen species. The second is hormesis, which enhances processes that protect against the action of damaging agents and also promotes processes that repair the damage once it occurs.
Radiation-Induced Neoplastic Transformation in vitro, Hormesis and Risk Assessment
Authors: Redpath J. Leslie , Elmore Eugene
Published: February 2007

Dose-response curves for various low-LET radiation sources have consistently been demonstrated to be J-shaped for the cancer-relevant endpoint of neoplastic transformation in vitro. Most of these studies have been performed where the radiation has been delivered at intermediate to high dose-rates (30–3000 mGy/min), where the threshold dose for induction of neoplastic transformation is around 100–200 mGy. Below these doses, the transformation frequency is less than that seen spontaneously, indicative of a hormetic effect. More recently, data have been obtained for low dose rates (<0.5 mGy/min) of low-LET radiation, and again hormetic effects are apparent but with threshold doses now being >1000 mGy. Similar trends have been reported in animal experiments as well as in human epidemiologic studies. Indeed, the relative risks for induction of neoplastic transformation in vitro in the dose range 1 to 1000 mGy agree well with those for incidence of radiation-induced breast cancer and leukemia in humans. These findings support the notion that the endpoint of neoplastic transformation in vitro is a plausible endpoint to not only study mechanisms involved in response to low doses of radiation, but also to provide information of potential importance to risk assessment.
Effects of Cobalt-60 Exposure on Health of Taiwan Residents Suggest New Approach Needed in Radiation Protection
Authors: Chen W.L. , Luan Y.C. , Shieh M.C. , Chen S.T. , Kung H.T. , Soong K.L. , Yeh Y.C. , Chou T.S. , Mong S.H. , Wu J.T. , Sun C.P. , Deng W.P. , Wu M.F. , Shen M.L.
Published: February 2007

The conventional approach for radiation protection is based on the ICRP's linear, no threshold (LNT) model of radiation carcinogenesis, which implies that ionizing radiation is always harmful, no matter how small the dose. But a different approach can be derived from the observed health effects of the serendipitous contamination of 1700 apartments in Taiwan with cobalt-60 (T1/2 = 5.3 y). This experience indicates that chronic exposure of the whole body to low-dose-rate radiation, even accumulated to a high annual dose, may be beneficial to human health. Approximately 10,000 people occupied these buildings and received an average radiation dose of 0.4 Sv, unknowingly, during a 9–20 year period. They did not suffer a higher incidence of cancer mortality, as the LNT theory would predict. On the contrary, the incidence of cancer deaths in this population was greatly reduced—to about 3 per cent of the incidence of spontaneous cancer death in the general Taiwan public. In addition, the incidence of congenital malformations was also reduced—to about 7 per cent of the incidence in the general public. These observations appear to be compatible with the radiation hormesis model. Information about this Taiwan experience should be communicated to the public worldwide to help allay its fear of radiation and create a positive impression about important radiation applications. Expenditures of many billions of dollars in nuclear reactor operation could be saved and expansion of nuclear electricity generation could be facilitated. In addition, this knowledge would encourage further investigation and implementation of very important applications of total-body, low-dose irradiation to treat and cure many illnesses, including cancer. The findings of this study are such a departure from expectations, based on ICRP criteria, that we believe that they ought to be carefully reviewed by other, independent organizations and that population data not available to the authors be provided, so that a fully qualified epidemiologically-valid analysis can be made. Many of the confounding factors that limit other studies used to date, such as the A-bomb survivors, the Mayak workers and the Chernobyl evacuees, are not present in this population exposure. It should be one of the most important events on which to base radiation protection standards.
What Becomes of Nuclear Risk Assessment in Light of Radiation Hormesis?
Authors: Cuttler Jerry M.
Published: February 2007

A nuclear probabilistic risk or safety assessment (PRA or PSA) is a scientific calculation that uses assumptions and models to determine the likelihood of plant or fuel repository failures and the corresponding releases of radioactivity. Estimated radiation doses to the surrounding population are linked inappropriately to risks of cancer death and congenital malformations. Even though PRAs use very pessimistic assumptions, they demonstrate that nuclear power plants and fuel repositories are very safe compared with the health risks of other generating options or other risks that people readily accept. Because of the frightening negative images and the exaggerated safety and health concerns that are communicated, many people judge nuclear risks to be unacceptable and do not favour nuclear plants. Large-scale tests and experience with nuclear accidents demonstrate that even severe accidents expose the public to only low doses of radiation, and a century of research has demonstrated that such exposures are beneficial to health. A scientific basis for this phenomenon now exists. PRAs are valuable tools for improving plant designs, but if nuclear power is to play a significant role in meeting future energy needs, we must communicate its many real benefits and dispel the negative images formed by unscientific extrapolations of harmful effects at high doses.
Cancer Control Related to Stimulation of Immunity by Low-Dose Radiation
Authors: Liu Shu-Zheng
Published: February 2007

Previous studies showed that low dose radiation (LDR) could stimulate the immune system in both animal and human populations. This paper reviews the present status of relevant research as support to the use of LDR in clinical practice for cancer prevention and treatment. It has been demonstrated that radiation-induced changes in immune activity follows an inverse J-shaped curve, i.e., low dose stimulation and high dose suppression. The stimulation of immunity by LDR concerns most anticancer parameters, including antibody formation, natural killer activity, secretion of interferon and other cytokines as well as other cellular changes. Animal studies have revealed that LDR retards tumor growth, decreases cancer metastasis, and inhibits carcinogenesis induced by high dose radiation. These effects of LDR on cancer control were found to be related to its stimulation on immunity. The experimental data may well explain the efficacy of the clinical trial of LDR in the treatment of cancer.
Low Doses of Radiation Reduce Risk in Vivo
Authors: Mitchel R. E. J.
Published: February 2007

The “Linear No Threshold” hypothesis, used in all radiation protection practices, assumes that all doses, no matter how low, increase the risk of cancer, birth defects and heritable mutations. In vitro cell based experiments show adaptive processes in response to low doses and dose rates of low LET radiation, and do not support the hypothesis. This talk will present cellular data and data from animal experiments that test the hypothesis in vivo for cancer risk. The data show that a single, low, whole body dose (less than about 100 mGy) of low LET radiation, given at low dose rate, increased cancer latency and consequently reduced both spontaneous and radiation-induced cancer risk in both genetically normal and cancer-prone mice. This adaptive response lasted for the entire lifespan of all the animals that developed these tumors, and effectively restored a portion of the life that would have been lost due to the cancer in the absence of the low dose. Overall, the results demonstrate that the assumption of a linear increase in risk with increasing dose in vivo is not warranted, and that low doses actually reduce risk.
Shrinking the Borders: Globalization, Culture, and Belonging
Authors: Turner Graeme
Published: February 2007

This article argues that the political success of the economic discourses of globalization within Australia over the last two decades has been accompanied by a compensatory and regressive revival of an exclusivist model of cultural nationalism. Within a society that once prided itself upon developing the tolerance required to manage the cultural policy of multiculturalism, the reappearance of a nostalgic, monocultural nationalism has been unexpected. It has thrown into question those narratives used within Australian cultural studies to understand the process of nation formation as directed toward the production of hybridity. Further, and despite the continuing presence of an official policy of multiculturalism, these developments have highlighted the highly provisionalized forms of national belonging now available to Australian citizens in certain immigrant communities, particularly to those from Middle Eastern backgrounds.
Resistance Becomes Ballistic: Vanishing Point and the End of the Road
Authors: Beck John
Published: February 2007

Richard C. Sarafian's Vanishing Point (1971) is the apotheosis of the Vietnam-era exploitation/arthouse existentialist road movies produced in the wake of Easy Rider. Vanishing Point is about speed and technology, surveillance and control, acceleration and catastrophe, roads, deserts, and perspective. It explores the compression of time through the acceleration of movement and measures the velocity of a counterculture that has “hopped up” the machinery of repression as it approaches final impact. This essay discusses the film in the context of issues surrounding individual liberty and national security which, while historically specific to the moment of production – the late 1960s and early 1970s – are also provocatively contemporary in their identification of the limits of resistance. Vanishing Point is read as a film that refuses the escapism of the road movie genre and instead pursues the logic of maximum efficiency internalized by the film's protagonist. As such the film questions the libertarian rhetoric of the open road and instead proposes that American fictions of free mobility mask the fact of containment by military-industrial imperatives.
The NematodeC. elegansas an Animal Model to Explore Toxicology In Vivo: Solid and Axenic Growth Culture Conditions and Compound Exposure Parameters
Authors: Nass Richard , Hamza Iqbal
Published: February 2007

Significant limitations in vertebrate animal model systems include the time involved, the expense, the fact that in vitro results may not reflect live animal pathology, difficulties in transporting the toxin past the blood brain barrier, and the inability to identify the mechanism of action without some a priori knowledge of the toxin's target. The availability of the complete genome sequence of the nematodeC. elegans, coupled with the worm's size, growth rate, ease of culturing, and the realization that basic biological mechanisms and disease processes between worms and humans are highly conserved, makes this genetically tractable model a remarkable opportunity to dissect and identify in vivo the cellular processes involved in toxin‐induced cell dysregulation and death. This unit includes protocols for culturing worms on solid and axenic media and acute and chronic exposure parameters for Parkinson's disease–associated toxins and hemin chloride. These methods provide the groundwork for using this powerful model system to further elucidate and understand the molecular mechanisms involved in nutrition as well as toxicological responses relevant to human diseases.
Mouse Models for Human Hemato‐Lymphopoiesis
Authors: Ziegler Patrick , Manz Markus G.
Published: February 2007

By transplanting human hematopoietic stem and progenitor cells in newborn immunodeficient mice, researchers have recently achieved development of a human adaptive immune system, consisting of B cells, T cells, dendritic cells, and some cells of the myeloid lineage, which together form respective structured lymphoid organs as thymus, spleen, and lymph nodes, and produce some functional immune responses. These will provide valuable models to analyze the impact of chemicals, pharmaceuticals, or species‐specific infections on human hematolymphoid cells in vivo. This unit describes methods for isolation of the progenitor human cells and their injection into mouse to constitute an adaptive immune system.
Automated Large‐Scale Purification of a Recombinant G‐Protein‐Coupled Neurotensin Receptor
Authors: White Jim F. , Grisshammer Reinhard
Published: February 2007

Structure determination of G‐protein‐coupled receptors and other applications, such as nuclear magnetic resonance (NMR) studies, require milligram quantities of purified, functional receptor protein on a regular basis. This unit presents a step‐by‐step procedure for the automated two‐column purification at the 10‐milligram scale of a G protein‐coupled receptor for neurotensin, expressed in functional form in Escherichia coli.
Crystallization of Integral Membrane Proteins
Authors: Barnard Travis J. , Wally Jeremy L. , Buchanan Susan K.
Published: February 2007

Over the last 20 years, the use of X‐ray crystallography has become a viable technique for the structure determination of integral membrane proteins. However, standard crystallizaton protocols must be modified to account for difficulties involved in handling membrane proteins, which arise primarily from having detergent present. This unit provides protocols that can be used to crystallize a purified membrane protein, including detergent exchange, sample concentration, initial screening using a crystallization robot, and finally, optimization of crystallization conditions to obtain diffraction‐quality crystals. These protocols were established for outer membrane proteins, but can be used for inner membrane proteins as well. Advice on alternative protocols, detergent selection, and optimization of crystallization conditions is provided.
Toxicity Testing in Chemical Safety Evaluation
Authors: Bus James S.
Published: February 2007

The modern era of chemistry has resulted in dramatic improvements in the overall human condition. In addition to new pharmaceuticals, modern chemistry has brought with it enormous health and social benefits Introduction of chemistry‐based technologies, however, has also been clearly associated with potential human health risks. The dramatic increase in pharmaceutical and chemical technologies in the post World War II era, coupled with associated examples of demonstrated human toxicity, led to development and application of an expanded and standardized battery of animal and other toxicity tests designed to characterize the potential hazards and risks associated with chemical exposures. This unit discusses the current approach to industrial chemical and pesticide toxicity testing.
Detection of Protein‐Protein Interactions by Coprecipitation
Authors: Elion Elaine A.
Published: February 2007

Coprecipitation of proteins from whole‐cell extracts is a valuable approach to test for physical interactions between proteins of interest. This unit describes basic approaches to immunoprecipitating tagged proteins from whole‐cell extracts. The approaches described can be adapted for other systems. In a typical experiment, as described here, cells are lysed and a whole‐cell extract is prepared under nondenaturing conditions. The protein is precipitated from the lysate with a solid‐phase affinity matrix, and the precipitate is tested for the presence of a second specifically associated protein. The approach can be used for native or epitope‐tagged proteins for which antibodies are available, or for recombinant proteins that have been engineered to bind with high affinity to a molecule that can be coupled to a solid‐phase matrix.
Preparation and Inoculation of Mesophyll Protoplasts from Monocotyledenous and Dicotyledenous Hosts
Authors: Rao A.L.N.
Published: February 2007

This unit describes a simple and efficient protocol for inoculating mesophyll protoplasts of either monocotyledonous or dicotyledenous host plants using polyethylene glycol. The unit covers isolation of biologically active protoplasts, their transfection with viral RNA, and conditions for the maintenance of transfected protoplasts. It also highlights critical aspects of these steps and discusses common problems and their solutions.
Northern Analysis of Viral Plus‐ and Minus‐Strand RNAs
Authors: Palani Paramasivan Vijaya , Lin Na‐Sheng
Published: February 2007

Replication is a fundamental activity of viruses. Replication of positive‐sense RNA viruses involves the synthesis of complementary minus‐strand intermediates from the parental RNA template followed by synthesis of nascent plus strands. Negative‐sense RNA genome and double‐stranded RNA are copied into positive‐sense mRNA before translation. To detect and estimate the abundance of plus‐ and minus‐strand viral transcripts in the infected samples, northern analysis is the most commonly used method.
Cover Picture: Mechanical Properties and Impact Resistance of a New Transparent Glass‐Ceramic (Adv. Eng. Mater. 3/2007)
Authors: Berthier da Cunha T. , Wu J. P. , Peitl O. , Fokin V. M. , Zanotto E. D. , Iannucci L. , Boccaccini A. R.
Published: February 2007

Digital camera images showing macroscopic damage induced on transparent glass or glass‐ceramic discs after ballistic test at low impact energy. Glass beads were used as projectiles in a gas gun. More details can be found in the article of A. R. Boccaccini et al. on page 191.
Rectification of multiscale data with application to life cycle inventories
Authors: Yi Heui‐Seok , Bakshi Bhavik R.
Published: February 2007

The quality of life cycle inventory (LCI) data is crucial to the reliability of decisions made via life cycle analysis (LCA). However, many LCI data, be they from commercial software or public domain databases, violate the laws of thermodynamics due to errors, missing data, and other inconsistencies. The process engineering method of data rectification is appealing for improving the quality of LCI data, but applying this approach poses many new challenges that are not addressed in traditional rectification. One such challenge is due to the availability of life cycle data at multiple overlapping scales. This includes engineering data at the equipment and process scales, process LCA data at the value chain scale, and economic input–output and toxic release inventory data at the economy scale. This article develops a method for rectification of such multiscale data. Rectification is accomplished via a mixed integer optimization‐based approach, and it is integrated with the existing computational methods for different types of traditional and hybrid LCA. The developed method may also be used for multiscale data from process engineering. It is applied to data for a caustic soda process from a public domain LCI database to illustrate the benefits of the proposed approach and identify further challenges. © 2007 American Institute of Chemical Engineers AIChE J, 2007
Flammability properties and mechanical performance of epoxy modified phenolic foams
Authors: Auad Maria L. , Zhao Lihua , Shen Hongbin , Nutt Steven R. , Sorathia Usman
Published: February 2007

This work has been mainly focused on the development and optimization of the processing methodology to produce epoxy modified phenolic foams. This study analyzes the relation between the composition and the structure as well as the mechanical and flammability performance of epoxy‐phenolic (E‐P)‐based foams. Phenolic foams modified with different types and compositions of epoxy resin were successfully synthesized and characterized, showing uniform pore structure. Two epoxy resins were used for this approach. One is regular diglycidyl ether of bisphenol A (Epon 826) type and the other is a brominated bisphenol A (DER 542), which has halogen groups in the structure to improve the flammability properties of the resulting foams. Cone calorimeter (ASTM E 1354) was used to measure the heat release rate, the time to ignition, and other flammability properties of the E‐P foams with different types of epoxy resins, under well‐controlled combustion conditions. The mechanical performance of the system was studied and compared with competing foams, such us phenolic, epoxy, and polyurethanes, in aspects of compression, friability, and shear performances. Compared with conventional phenolic foams, E‐P foams exhibit significant improvement in mechanical performance, lower friability and similar resistance to flame. These results demonstrate the potential of the E‐P foam as a flame resistant and high performance core material for sandwich structure. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1399–1407, 2007
Radiation synthesis of interpenetrating polymer networks based on N‐vinyl pyrrolidone – acrylic acid copolymer and gelatin. I. Swelling, morphology, and thermal characterization for biomedical applications
Authors: Singh Dipti , Choudhary Veena , Koul Veena
Published: February 2007

Interpenetrating polymer networks (IPNs) based on N‐vinyl pyrrolidone (NVP) : gelatin (Ge), and a copolymer of NVP – acrylic acid (AA) : gelatin (Ge) were prepared using N‐N′methylenebisacrylamide (BIS) (0.5, 1% w/w) and glutaraldehyde (GLU) (0.5% v/v) as crosslinkers, respectively, by gamma irradiation technique. GLU was incorporated after irradiation to crosslink the gelatin chains, whereas BIS was placed in the respective solutions before irradiation. Several samples were prepared by varying the composition of gelatin to NVP or by changing the ratio of NVP : AA in preparing IPNs. The swelling behavior of the hydrogels was investigated as a function of variable doses, crosslinker (BIS) concentration, copolymer composition (NVP : AA ratio) or Ge : NVP ratio and pH of the immersion medium (3, 7.4, and 11). As expected, the swelling ratio increased with increasing acrylic acid content and decreased with increasing BIS content. No definite trend in the swelling behavior was observed as a function of dose. The interpenetration of the polymeric chains was established by morphological and thermal characterization. Scanning electron microscopy of IPNs showed a hybrid of coral and honeycomb structures as compared with the crosslinked polymers based on Ge and NVP (Gx and PVPx). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1456–1463, 2007
Efficiency of Egyptian drilling muds in the presence of cationic polyethylene imine and anionic polyacrylamide
Authors: Mostafa Bassem A. , Assaad Faiz F.
Published: February 2007

The flow properties of Egyptian bentonite were studied using a combination of anionic polyacrylamide (MW = 1,000,000 g mol−1) and cationic polyethylene imine (MW = 700,000 g mol−1). This combination gave a significant effect on the clay suspensions to be qualified in the field of drilling mud depending on the sequence their addition. It was found that, by adding 50 mg/L cationic polyethylene imine followed by 10 mg/L anionic polyacrylamide, the rheological properties were improved using 6% Egyptian bentonite suspension, especially at 20°C. But, by reversing this addition sequence, the rheological properties of bentonite suspension were declined. The zeta‐potential value of bentonite suspension in the presence of 50 mg/L polyethylene imine was −47 mV, while at 10 mg/L polyacrylamide was −55 mV. But, on addition of 10 mg/L polyacrylamide to bentonite suspension followed by 50 mg/L polyethylene imine induced a reduction of the zeta‐potential value to −51 mV when compared with that of polyacrylamide alone. By reversing the addition sequence, a very high stable suspension having zeta‐potential values of −82 mV was obtained. Potential energy profiles were constructed to investigate the relation between rheological and electrical properties. Potential energy profile at 50 mg/L polyethylene imine followed by 10 mg/L polyacrylamide to bentonite suspension produced a high repulsion potential energy between clay surfaces, i.e. the suspension stability improved. By reversing that sequence, a significant decrease in the energy barrier was observed. The most reliable clay suspension as a drilling mud could be obtained by using 6% clay suspension concentration, with 50 mg/L polyethylene imine followed by 10 mg/L polyacrylamide, at 20°C up to 24 h aging time. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1487–1495, 2007
Investigation of electrical and dielectric properties of prelocalized graphite/poly(vinyl chloride) composites near the percolation threshold
Authors: Srivastava N. K. , Sachdev V. K. , Mehra R. M.
Published: February 2007

Present article reports the effect of percolation threshold on the electrical and dielectric properties of prelocalized graphite‐filled poly(vinyl chloride) composite. The variation of room temperature electrical conductivity, D‐shore hardness, and relative permittivity as a function of graphite concentration has been studied below and above percolation concentration of the filler. The percolation threshold at which insulator to conductor transition takes place is estimated to be 0.0026 volume fraction of graphite. The current density‐electric field characteristics of the composites having different filler concentrations are also studied. It has been observed that the nonlinear electrical characteristics become linear when the composite undergoes insulator to conductor transition. The dielectric constant and dissipation factor are found to increase slowly up to the percolation concentration and beyond it, a sudden increase in its value is observed. The D‐shore hardness is found to decrease by nearly 10% at the point of percolation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2027–2033, 2007
Controlled synthesis of low‐molecular‐weight polyethylene waxes by titanium–biphenolate–ethylaluminum sesquichloride based catalyst systems
Authors: Umare Prashant S. , Rao Karumanchi , Tembe Gopal L. , Dhoble Deepa A. , Trivedi Bhavna
Published: February 2007

Soluble complexes of titanium(IV) bearing sterically hindered biphenols, such as biphenol, 1,1′‐methylene di‐2‐naphthol, 2,2′‐methylene bis(4‐chlorophenol), 2,2′‐methylene bis(6‐tert‐butyl‐4‐ethyl phenol), and 2,2′ ethylidene bis(4,6‐di‐tert‐butyl phenol), were prepared and characterized. These catalyst precursors, formulated as [Ti(O∧O)X2], were active in the polymerization of ethylene at high temperatures in combination with ethylaluminum sesquichloride as a cocatalyst. The ultra‐low‐molecular‐weight polyethylenes (PEs) were linear and crystalline and displayed narrow polydispersities. The catalytic polymerization leading to PE waxes in this reaction exhibited unique properties that have potential applications in surface coatings and adhesive formulations. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1531–1539, 2007
Determination of the molecular characteristics of commercial polyethylenes with different architectures and the relation with the melt flow index
Authors: Teresa Rodríguez‐Hernández M. , Angulo‐Sánchez J. L. , Pérez‐Chantaco A.
Published: February 2007

The molecular weight distribution curves of several commercial polyethylene samples were evaluated by high‐temperature gel permeation chromatography with two detectors (a refractive‐index detector and a viscometer) to determine the molecular sizes and architectures (branching). The polymer samples included high‐ and low‐density polyethylenes with different molecular weight distributions (wide, medium, unimodal, and bimodal) from nine producers. The results were tested against the melt flow index and zero‐shear melt viscosity to find correlations. The data for high‐density polyethylene correlated well with the molecular weight, whereas the data for low‐density polyethylene did not correlate. However, when the weight‐average molecular weight was corrected by the branching parameter and a factor form, all the polyethylene samples fit a single equation. These results indicate that the melt flow index is dependent not only on the molecular weight but also on the molecular shape, including branching. The relation accounted for samples of different resin producers, molecular weights (65,000–638,000), and polydispersities (2.9–20). The use of the branching parameter for the correction of the molecular weight allowed the correlation of these parameters despite differences in the technologies, molecular weights, and molecular architectures. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1572–1578, 2007
Thermomechanical history effects on rigid PVC microstructure and impact properties
Authors: Fillot Louise‐Anne , Hajji Philippe , Gauthier Catherine , Masenelli‐Varlot Karine
Published: February 2007

Rigid PVC microstructure strongly depends on processing conditions: under both shear and heat influence, gelation process occurs, and the resulting morphology can be characterized by the so‐called gelation level parameter. But thermomechanical history also affects several other features of the microstructure. In this work, two different aspects mainly related to (i) orientation and (ii) molecular mobility are pointed out, and their respective effects on poly(vinyl chloride) (PVC) impact properties are described. Charpy impact tests have been carried out on a typical extruded window profile formulation, evidencing a strong anisotropy effect in those extrudates. It turned out that modulated differential scanning calorimetry was able to evidence macromolecular orientation. Then, the effects of heat treatments on impact properties were investigated. Below the glassy transition temperature (Tg) of PVC, physical ageing results in a decrease of the impact performance, without affecting PVC anisotropy. The reason of this performance loss is the reduction of the molecular mobility, as evidenced by dynamical mechanical analysis experiments. After performing a heat treatment above Tg, another important decrease of the impact performance was observed. This decrease was attributed to (i) partial disorientation of the PVC macromolecular chains and (ii) reduction of the molecular mobility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2009–2017, 2007
Synthesis and evaluation of novel light‐curable amino acid‐constructed glass–ionomer cements
Authors: Xie Dong , Park Jong‐Gu , Faddah Mona
Published: February 2007

Poly(alkenoic acid)s constructed with β‐alanine and glutamic acid were synthesized and grafted with glycidyl methacrylate (GM). The purified polymers were further formulated with water, acrylic acid (AA), and Fuji II LC glass filler to form photocurable dental cements. Compressive strength (CS) and flexural strength (FS) of the cement, and viscosity of the resin liquid were used as screening tools to find the optimal formulation. The specimens were conditioned in distilled water at 37°C for 24 h, prior to testing. The results show that the effects of grafting ratio, polymer content, powder liquid (P/L) ratio, initiator concentration, and light exposure time were significant, but the effect of molecular weight was not. Aging study shows that the experimental cement showed a constant increase in mechanical strength for up to 1 week and then kept constant over 1 month. The formulation with 50/25/25 (liquid composition of polymer/AA/water), 70% (grafting ratio of GM), 3.2/1 (P/L ratio) as well as 0.9% (camphorquinone) and 1‐min light exposure time were found to be the optimal. The experimental cement was 19% higher in CS, 47% higher in diametral tensile strength and 176% higher in FS, compared to Fuji II LC. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1587–1595, 2007
Synthesis and characterization of hindered amine light stabilizers based on end functionalization of polypropylene
Authors: Reddy K. Raghunatha , Kumar Bijendra , Rana Sravendra , Tevtia Amit K. , Singh R. P.
Published: February 2007

A polymeric hindered amine light stabilizer (HALS), where HALS moiety was attached at the terminal end of the polypropylene chain via end‐functionalized vinylidine PP through simple organic reactions, was synthesized. It comprises the synthesis of vinylidine‐terminated polypropylene by using Cp2ZrCl2/MAO as catalyst system and epoxidation of vinylidene polypropylene. The final product was synthesized by carrying out the reaction between epoxy end functionalized polypropylene and 4‐amino‐2,2,6,6‐tetrametyl piperidine. The final product was characterized by using 1H NMR, 13C NMR, and FT‐IR spectra. Functionality was calculated by using vapor phase osmometry and 1H NMR. The solubility and diffusion coefficient of the product were calculated and also its stabilization performance was checked. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1596–1602, 2007
A study of some equation‐of‐state parameters of poly(methylhydrosiloxane‐co‐dimethylsiloxane) with some solvents by gas chromatography
Authors: Coskun Selin , Cankurtaran Özlem , Eran Belkis B. , Sarac Ayfer
Published: February 2007

Trace amount of methyl acetate, ethyl acetate, tert‐butyl acetate, pentane, hexane, and heptane were passed through the chromatographic column loaded with poly(methylhydrosiloxane‐co‐dimethylsiloxane) coated on Chromosorb W. The retention diagrams of the solvents on the copolymer were plotted by means of specific retention volumes at temperatures between 40 and 80°C by inverse gas chromatography technique. In this study, some thermodynamic interaction parameters such as Flory–Huggins polymer–solvent interaction parameter, equation‐of‐state polymer–solvent interaction parameter, effective exchange energy parameter, and weight fraction activity coefficients at infinite dilution of the solvent were determined. Then, the exchange enthalpy parameter and entropy parameter were determined by using a relation for the enthalpy interaction parameter of the equation‐of‐state theory, which is arranged for the inverse gas chromatography conditions. Later, the partial molar heat of sorption and the partial molar heat of mixing were obtained. The solubility parameter of this copolymer was determined as 6.64 (cal/cm3)1/2 at room temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1627–1631, 2007
Poly(lactide) nanofibers produced by a melt‐electrospinning system with a laser melting device
Authors: Ogata Nobuo , Yamaguchi Shinji , Shimada Naoki , Lu Gang , Iwata Toshiharu , Nakane Koji , Ogihara Takashi
Published: February 2007

A new melt‐electrospinning system equipped with a CO2‐laser melting device was developed. Rod‐like samples were prepared from poly(lactide) pellets, and then fibers were produced from the samples using the new system. The effects of producing conditions on the fiber diameter were investigated. Furthermore, the physical properties of the fibers were investigated. The following conclusions were obtained: (i) in a special case, fibers having an average fiber diameter smaller than 1 μm could be obtained using the system developed; (ii) the fiber diameter could be decreased with increased laser output power, but the physical properties of the fibers such as the melting point and the molecular weight were decreased; and (iii) the electrospun fibers exhibited an amorphous state, and the annealed fibers exhibited an isotropic crystal orientation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1640–1645, 2007
Preparation of super‐hydrophobic film with fluorinated‐copolymer
Authors: Chang Kuei‐Chien , Chen Hui , Huang Chih‐Kai , Huang Shi‐Ing
Published: February 2007

Organic superhydrophobic films were prepared by utilizing TA‐N fluoroalkylate (TAN) and methyl methacrylate (MMA) copolymer as water‐repellent materials and inorganic silica powder as surface roughness material has been developed. Coating solutions prepared by adding silica powders into copolymer solution directly (one‐step method) and by adding silica powders into monomers and allowing them to react (two‐step method). The results showed that contact angles of the films prepared by one‐step method (37.6 wt % of silica powders in the coating solution) were greater than 150°, but the transmittance of the film at visible light was only 30%. On the other hand, the contact angle of films prepared by two‐step method (20 wt % of silica powders in the coating solution) was greater than 160° and the transmittance of the film was greater than 90%. The contact angle of the film prepared by poly(octyl acrylate), POA, was 32.1°, but while introducing silica powder into the system, the contact angle of the film was reduced to be smaller than 5°. Thus, superhydrophobic and superhydrophilic films can be obtained by introducing a roughening material on the hydrophobic surface and the hydrophilic surface, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1646–1653, 2007
Glass‐transition‐temperature depression in chemically crosslinked low‐density polyethylene and high‐density polyethylene and their blends with ethylene vinyl acetate copolymer
Authors: Khonakdar H. A. , Jafari S. H. , Hässler R.
Published: February 2007

A reduction in the glass‐transition temperature (Tg) was found for polyolefins chemically crosslinked by peroxide. This tendency, which was observed for low‐density and high‐density polyethylenes, was also validated for their blends with Ethylene Vinyl Acetate copolymer. It is proposed that the constrained crystallization process, as a result of a restriction imposed on the chain packing by the chemical crosslinks, results in an increasing net free volume in the amorphous phase and hence reduces Tg. The Tg depression becomes greater with increasing crosslink density, whereas at the same time, the degree of crystallinity and consequently the density of the system decreases with an increase in the peroxide content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1654–1660, 2007
Styrene/tetradecyl methyl acrylate/3‐methacryloxylpropyl trimethoxyl silane triblock copolymers: Atom transfer radical polymerization synthesis and effects on the glass‐fiber/polypropylene interphase properties as a macromolecular coupling agent
Authors: Zhou Shanhua , Gao Yan , Wang Yantao , Hu Chunpu , Dong Qingzhi
Published: February 2007

Styrene/tetradecyl methyl acrylate/3‐methacryloxylpropyl trimethoxyl silane triblock copolymers (PSTKs), with well‐defined structures and narrow molecular weight distributions, were synthesized by atom transfer radical polymerization. They were investigated as macromolecular coupling agents for the surface treatment of glass fibers. The reaction kinetics for the triblock copolymers were studied. The contact angles of the copolymers with water and diiodomethane showed that a modified‐glass‐fiber surface treated with a PSTK solution had strong hydrophobicity and that the impregnation of polypropylene on glass fibers was improved dramatically. In comparison with a film of 3‐methacryloxylpropyl trimethoxyl silane, the polarity of the surface free energy of a PSTK film decreased, whereas the dispersion increased greatly. The critical concentration of the macromolecular coupling agents was obtained, and the monolayer saturated adsorptive capacity was calculated with the Gibbs absorption isotherm equation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1661–1670, 2007
Reactive‐extrusion route for the closed‐loop recycling of poly(ethylene terephthalate)
Authors: Kiliaris P. , Papaspyrides C. D. , Pfaendner R.
Published: February 2007

The effectiveness of the reactive extrusion technique was investigated for poly(ethylene terephthalate) to promote the concept of closed‐loop recycling, that is, the reuse of waste material in the initial application. More specifically, a chain‐extender system, consisting of pyromellitic dianhydride, polyol, and a catalyst, was employed, and its efficiency regarding the improvement of the recyclate quality was evaluated. Accordingly, rheological and thermal characterizations were performed and used as criteria of the modification induced in the polymer molecular structure during processing due to the counteracting degradation and chain‐extension reactions. In particular, the molecular weight, related to intrinsic viscosity and melt flow rate measurements, of modified poly(ethylene terephthalate) samples was found to increase with the additive content. Simultaneously, a decrease in the crystallinity was observed, attributed to the branching effect of the chain extender, which restricted the ability of the macromolecules to organize in the crystal structure. Beyond a critical concentration of the additive system, the molecular weight of the treated samples started to decrease again, and this was accompanied by a small increase in the crystallinity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1671–1678, 2007
Effect of curing moisture on the indentation force deflection of flexible polyurethane foam
Authors: Ni Haifeng , Yap Chee Keong , Jin Yan
Published: February 2007

The moisture effect on the indentation force deflection (IFD) of flexible polyurethane foam was examined through the curing of the foam with different moisture contents. The employed foam was cured at 30, 40, 50, 60, 70, and 80% relative humidity, and the corresponding curing temperature was constant at 23°C. The experiments showed that the measured IFD and support factor of the flexible polyurethane foam decreased, and the hysteresis increased with the curing moisture. A statistical conversion formula was generated experimentally to correct the measured IFD of the flexible polyurethane foam to eliminate the deviation caused by the moisture effect. The measured IFD was inversely exponentially proportional to the curing moisture. The accuracy of the correction formula was verified by the conditioning of the foam again with different moisture contents. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1679–1682, 2007
Tensile properties of hollow glass bead‐filled polypropylene composites
Authors: Liang Ji‐Zhao
Published: February 2007

The tensile properties of polypropylene (PP) filled with hollow glass beads have been measured at room temperature to identify the effects of the particle contents, size and its distribution on them in the present article. The mean diameters of the fillers were 11, 35, and 70 μm, and they were named as TK10, TK35, and TK70 respectively. The surface of these particles was pretreated with silane coupling agent. The results showed that the yield stress (σy) decreased gently for PP/TK70 systems, whereas decreased relatively obviously for PP/TK35 systems with increasing the volume fraction (ϕf) of the fillers. When ϕf was less than 5%, the tensile strength at break (σb) of the composites increased with the increase of ϕf. When ϕf was more than 5%, σb was almost a constant for PP/TK70 systems, while σb decreased linearly for PP/TK35 systems. The tensile fracture strain (εb) of the composites decreased suddenly when ϕf was less than 5%, and then decreased slightly with increasing ϕf. When ϕf was 10%, σy and σb increased while εb decreased with the increase of the bead diameter. Furthermore, the σy was predicted by means an equation proposed in the previous work, and good interfacial adhesion was shown between the hollow glass beads and the matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1697–1701, 2007
Effect of metal ions and pH values on the conformational transition of the copolymer chain in aqueous solutions
Authors: Wang Bin , Liu Mingzhu , Chen Yong , Liang Rui , Chen Shilan , Jin Shuping
Published: February 2007

A novel salts‐ and pH‐responsive copolymer, poly(acrylic acid‐co‐ethyl 1‐(4‐chlorophenyl)‐5‐acrylamino‐1,2,3‐triazol‐4‐carboxylate), poly(AA‐co‐ECATC), was prepared by radical polymerization in methanol at room temperature with L‐ascorbic acid (Vc) and peroxide hydrogen (H2O2) as initiators. The copolymer was characterized by Fourier Transform Infrared (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC). The copolymer possessed excellent fluorescence properties. The effects of metal ions with different charges, radius and outer‐layer electron constructions and pH values on the conformation transition of copolymer chains were systematically investigated by the fluorescence intensity and the fluorescence anisotropy. It was found that fluorescence intensity and fluorescence anisotropy curves waved with the change of metal ions concentrations and pH values. Additionally, FTIR Subtraction spectroscopy was also carried out to confirm our results. The work provided a theory basis for the study of salts‐ and pH‐sensitive smart hydrogels, which were always used in the slow‐ or controlled‐release drugs. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1714–1722, 2007
Mechanical and electrical properties of hydrous electrorheological elastomers based on gelatin/glycerin/water hybrid
Authors: Gao Lingxiang , Zhao Xiaopeng
Published: February 2007

Aimed at improving the stability of geometrical shape, mechanical performance, and particles dispersion of electrorheological (ER) hydrous elastomers, a new gelatin water‐based elastic gels containing starch particles were prepared under an applied dc electric field, and their ER effects were described with the compression modulus and the electric resistivity. The result demonstrates that the mechanical and electrical properties of the ER elastomers are dominated by an externally applied electric field as well as the weight fraction of particles. On comparing with the same chemical composition, elastomers cured without a field and with barium titanate/gelatin water‐based elastomer, some conclusions are suggested: the object elastomer has stronger responses to a field than the same chemical composition elastomer, especially with higher weight fractions of particles. The object elastomer has steady geometrical shape and mechanical performance because of the addition of glycerin into the matrix, and has a better dispersion of particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1738–1743, 2007