bluuebunny/crossref_metadata_2025 huggingface dataset:
Implications of Recreational Fishing on Juvenile Masu Salmon Stocked in a Hokkaido River
Authors: Miyakoshi Yasuyuki , Sasaki Yoshitaka , Fujiwara Makoto , Tanaka Keiko , Matsueda Naokazu , Irvine James R. , Kitada Shuichi
Published: February 2009

Freshwater recreational anglers in northern Japan sometimes catch significant numbers of juvenile masu salmon Oncorhynchus masou, thereby reducing the effectiveness of enhancement activities aimed at increasing marine catches of adult masu salmon. We stocked 66,500 juvenile masu salmon in the Shirai River, a major tributary of the Yoichi River in Hokkaido, northern Japan, during October 2005. Surveys conducted during the month after stocking revealed that approximately 65 fish/angler-day were caught, and catch varied between fishing gears (bait or fly) and locations (upper or lower reach). Estimated total number (mean ± SE) of fish harvested was 5,647 ± 2,394, equivalent to 8.5 ± 3.6% of the fish stocked. The estimated number of fish remaining in the river at the end of the angler survey was 57,246 ± 8,595, and survival rate during this month was 86.1 ± 12.9%. While releasing hatchery-reared masu salmon in late fall can reduce fishing mortality in rivers compared with earlier releases, mortality could be further reduced by dispersing fish over large areas that contain locations with suitable overwintering habitat.
DNA licensing as a novel androgen receptor mediated therapeutic target for prostate cancer
Authors: D'Antonio Jason M , Vander Griend Donald J , Isaacs John T
Published: February 2009

During middle G1 of the cell cycle origins of replication orchestrate the ordered assembly of the pre-replication complex (pre-RC), allowing licensing of DNA required for DNA replication. Cyclin-dependent kinase activation of the pre-RC facilitates the recruitment of additional signaling factors, which triggers DNA unwinding and replication, while limiting such DNA replication to once and only once per cell cycle. For both the normal and malignant prostate, androgen is the major stimulator of cell proliferation and thus DNA replication. In both cases, the binding of androgen to the androgen receptor (AR) is required. However, the biochemical cascade involved in such AR-stimulated cell proliferation and DNA synthesis is dramatically different in normal versus malignant prostate cells. In normal prostate, AR-stimulated stromal cell paracrine secretion of andromedins stimulates DNA replication within prostatic epithelial cells, in which AR functions as a tumor suppressor gene by inducing proliferative quiescence and terminal differentiation. By direct contrast, nuclear AR in prostate cancer cells autonomously stimulates continuous growth via incorporation of AR into the pre-RC. Such a gain of function by AR-expressing prostate cancer cells requires that AR be efficiently degraded during mitosis since lack of such degradation leads to re-licensing problems, resulting in S-phase arrest during the subsequent cell cycle. Thus, acquisition of AR as part of the licensing complex for DNA replication represents a paradigm shift in how we view the role of AR in prostate cancer biology, and introduces a novel vulnerability in AR-expressing prostate cancer cells apt for therapeutic intervention.
Model‐based assessment of persistence in proposed marine protected area designs
Authors: Kaplan David M. , Botsford Louis W. , O'Farrell Michael R. , Gaines Steven D. , Jorgensen Salvador
Published: February 2009

Assessment of marine protected areas (MPAs) requires the ability to quantify the effects of proposed MPA size and placement, habitat distribution, larval dispersal, and fishing on the persistence of protected populations. Here we describe a model‐based approach to assessment of the contribution of a network of marine protected areas to the persistence of populations with a sedentary adult phase and a dispersing larval phase. The model integrates the effects of a patchy spatial distribution of habitat, the spatial scale of larval dispersal, and the level of fishing outside of reserves into a calculation of the spatial distribution of equilibrium settlement. We use the amount of coastline predicted to have equilibrium settlement rates that saturate post‐settlement habitat as a response variable for the assessment and comparison of MPA network designs. We apply this model to a set of recently proposed MPA networks for the central coast of California, USA. Results show that the area of habitat set aside is a good predictor of the area over which population levels will be high for short‐distance dispersers. However, persistence of longer distance dispersers depends critically on the spatial distribution of habitat and reserves, ranging from not persistent anywhere to persistent over a greater area than that set aside in reserves. These results depend on the mechanisms of persistence, with self‐replacement supporting short‐distance dispersers and network effects supporting long‐distance dispersers. Persistence also depends critically on fishery status outside the MPAs, as well as how fishing effort is redistributed after MPA implementation. This assessment method provides important benchmarks, as well as a transparent modeling approach, for improving initial MPA configurations that may result from less‐comprehensive rule‐ or habitat‐based methods of designing MPAs.
Delayed conifer mortality after fuel reduction treatments: interactive effects of fuel, fire intensity, and bark beetles
Authors: Youngblood Andrew , Grace James B. , McIver James D.
Published: February 2009

Many low‐elevation dry forests of the western United States contain more small trees and fewer large trees, more down woody debris, and less diverse and vigorous understory plant communities compared to conditions under historical fire regimes. These altered structural conditions may contribute to increased probability of unnaturally severe wildfires, susceptibility to uncharacteristic insect outbreaks, and drought‐related mortality. Broad‐scale fuel reduction and restoration treatments are proposed to promote stand development on trajectories toward more sustainable structures. Little research to date, however, has quantified the effects of these treatments on the ecosystem, especially delayed and latent tree mortality resulting directly or indirectly from treatments. In this paper, we explore complex hypotheses relating to the cascade of effects that influence ponderosa pine (Pinus ponderosa) and Douglas‐fir (Pseudotsuga menziesii) mortality using structural equation modeling (SEM). We used annual census and plot data through six growing seasons after thinning and four growing seasons after burning from a replicated, operational‐scale, completely randomized experiment conducted in northeastern Oregon, USA, as part of the national Fire and Fire Surrogate study. Treatments included thin, burn, thin followed by burn (thin + burn), and control. Burn and thin + burn treatments increased the proportion of dead trees while the proportion of dead trees declined or remained constant in thin and control units, although the density of dead trees was essentially unchanged with treatment. Most of the new mortality (96%) occurred within two years of treatment and was attributed to bark beetles. Bark beetle‐caused tree mortality, while low overall, was greatest in thin + burn treatments. SEM results indicate that the probability of mortality of large‐diameter ponderosa pine from bark beetles and wood borers was directly related to surface fire severity and bole charring, which in turn depended on fire intensity, which was greater in units where thinning increased large woody fuels. These results have implications when deciding among management options for restoring ecosystem health in similar ponderosa pine and Douglas‐fir forests.
Litter drives ecosystem and plant community changes in cattail invasion
Authors: Farrer Emily C. , Goldberg Deborah E.
Published: February 2009

Invaded systems are commonly associated with a change in ecosystem processes and a decline in native species diversity; however, many different causal pathways linking invasion, ecosystem change, and native species decline could produce this pattern. The initial driver of environmental change may be anthropogenic, or it may be the invader itself; and the mechanism behind native species decline may be the human‐induced environmental change, competition from the invader, or invader‐induced environmental change (non‐trophic effects). We examined applicability of each of these alternate pathways in Great Lakes coastal marshes invaded by hybrid cattail (Typha × glauca). In a survey including transects in three marshes, we found that T. × glauca was associated with locally high soil nutrients, low light, and large amounts of litter, and that native diversity was highest in areas of shallow litter depth. We tested whether live T. × glauca plants or their litter induced changes in the environment and in diversity with a live plant and litter transplant experiment. After one year, Typha litter increased soil NH4+ and N mineralization twofold, lowered light levels, and decreased the abundance and diversity of native plants, while live Typha plants had no effect on the environment or on native plants. This suggests that T. × glauca, through its litter production, can cause the changes in ecosystem processes that we commonly attribute to anthropogenic nutrient loading and that T. × glauca does not displace native species through competition for resources, but rather affects them non‐trophically through its litter. Moreover, because T. × glauca plants were taller when grown with their own litter, we suggest that this invader may produce positive feedbacks and change the environment in ways that benefit itself and may promote its own invasion.
Complex population dynamics and control of the invasive biennial Alliaria petiolata (garlic mustard)
Authors: Pardini Eleanor A. , Drake John M. , Chase Jonathan M. , Knight Tiffany M.
Published: February 2009

Controlling species invasions is a leading problem for applied ecology. While controlling populations expanding linearly or exponentially is straightforward, intervention in systems with complex dynamics can have complicated, and sometimes counterintuitive, consequences. Most invasive plant populations are stage‐structured and density‐dependent—a recipe for complex dynamics—and yet few population models have been created to explore the effects of control efforts on such species. We examined the demography of the invasive biennial plant Alliaria petiolata (garlic mustard) on the front of its spread into a natural area and found evidence of strong density dependence in vital rates of first‐year rosette and second‐year adult stage classes. We parameterized a density‐dependent, stage‐structured projection model using field‐collected data. This model produces two‐point cycles with alternating years in which adults vs. rosettes are more prevalent. Such population dynamics match observations in natural populations, suggesting that these complicated population dynamics may result from deterministic rules. We used this model to evaluate simulated management strategies, including herbicide treatment of rosettes and clipping or pulling of adult plants. Management of A. petiolata by inducing mortality of either rosettes or adults will not be effective at reducing population density unless the induced mortality is very high (>95% for rosettes and >85% for adults) and repeated every year. Indeed, induced mortality of rosettes can be counterproductive, causing increases in the stationary distribution of A. petiolata density. This species is typical of many invasive plants (stage‐structured, short‐lived, high fertility) and exhibits common forms of density dependence. Thus, the management implications of our study should apply broadly to other species with similar life histories. We suggest that management should focus on managing adults rather than rosettes, and on creating efficient control in targeted areas of the population, rather than spreading less efficient efforts widely.
Self‐Supporting, Double Stimuli‐Responsive Porous Membranes From Polystyrene‐block‐poly(N,N‐dimethylaminoethyl methacrylate) Diblock Copolymers
Authors: Schacher Felix , Ulbricht Mathias , Müller Axel H. E.
Published: February 2009

Asymmetric membranes are prepared via the non‐solvent‐induced phase separation (NIPS) process from a polystyrene‐block‐poly(N,N‐dimethylaminoethyl methacrylate) (PS‐b‐PDMAEMA) block copolymer. The polymer is prepared via sequential living anionic polymerization. Membrane surface and volume structures are characterized by scanning electron microscopy. Due to their asymmetric character, resulting in a thin separation layer with pores below 100 nm on top and a macroporous volume structure, the membranes are self‐supporting. Furthermore, they exhibit a defect‐free surface over several 100 µm2. Polystyrene serves as the membrane matrix, whereas the pH‐ and temperature‐sensitive minority block, PDMAEMA, renders the material double stimuli‐responsive. Therefore, in terms of water flux, the membranes are able to react on two independently applicable stimuli, pH and temperature. Compared to the conditions where the lowest water flux is obtained, low temperature and pH, activation of both triggers results in a seven‐fold permeability increase. The pore size distribution and the separation properties of the obtained membranes were tested through the pH‐dependent filtration of silica particles with sizes of 12–100 nm.
Doping of the Metal Oxide Nanostructure and its Influence in Organic Electronics
Authors: Park Mi‐Hyae , Li Juo‐Hao , Kumar Ankit , Li Gang , Yang Yang
Published: February 2009

Synthesizing metal oxides through the sol–gel process provides a convenient way for forming a nanostructured layer in wide band gap semiconductors. In this paper, a unique method of introducing dopants into the metal oxide semiconductor is presented. The doped TiO2 is prepared by adding a Cs2CO3 solution to a nanocrystalline TiO2 solution that is synthesized via a non‐hydrolytic sol–gel process. The properties of the TiO2:Cs layer are investigated and the results show stable nanostructure morphology. In addition to providing morphological stability, Cs in TiO2 also gives rise to a more desirable work function for charge transport in organic electronics. Polymer solar cells based on the poly(3‐hexylthiophene) (P3HT): methanofullerene (PC70BM) system with the addition of a TiO2:Cs interfacial layer exhibit excellent characteristics with a power conversion efficiency of up to 4.2%. The improved device performance is attributed to an improved polymer/metal contact, more efficient electron extraction, and better hole blocking properties. The effectiveness of this unique functionality also extends to polymer light emitting devices, where a lower driving voltage, improved efficiency, and extended lifetime are demonstrated.
Synthesis and structural peculiarities of 1,1‐dimethylhydrazine‐based polyurethanes
Authors: Savelyev Y. V. , Veselov V. Y. , Kharitonova V. K. , Savelyeva O. A. , Shtompel V. I. , Perekhrest A. I. , Travinskaya T. V. , Kanapitsas A. , Pissis P.
Published: February 2009

Novel polyurethanes (PUs) based on poly(oxytetramethylene glycol), 4,4′‐methylenediphenyl diisocyanate, and 1,1‐dimethylhydrazine (DMH) were prepared. Stoichiometric (1 : 1) and nonstoichiometric (2 : 1 to 20 : 1) prepolymer/DMH ratios were studied. The number‐average molecular masses and possible structures of the obtained polymers were evaluated by potentiometric nonaqueous titration analysis of terminal groups, the Kieldal method (the evaluation of the nitrogen atom content), the aminolysis method, viscosimetry, IR spectroscopy, rheology, and small‐angle X‐ray scattering. Only in the case of the stoichiometric (1 : 1) ratio was a low‐molecular‐mass PU with a linear structure formed, whereas for all studied nonstoichiometric ratios, PUs with branched structures were formed. The level of hard and flexible block segregation increased with the increase in the prepolymer/DMH ratio. Dielectric results for the dynamic glass transition and water sorption measurements provided additional support to the structural studies. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Enhanced hydrolytic stability of poly(p‐dioxanone) with polycarbodiimide
Authors: Liu Zhong‐Ping , Ding Song‐Dong , Sui Ying‐Jia , Wang Yu‐Zhong
Published: February 2009

The effect of polycarbodiimide (PCD) on hydrolytic stability of poly(p‐dioxanone) (PPDO) was investigated by hydrolytic degradation of PPDO and PPDO added with PCD (PPDOCD) in phosphate buffer solution (pH = 7.4) at 37°C. The variation of weight, water absorption, pH, molecular weight, tensile properties, surface morphologies, and thermal properties with degradation time were evaluated. After 11 weeks, the weight loss and water absorption of PPDO was 24 and 30%, respectively, but the corresponding values were only 3 and 5% for PPDOCD5, where 5 represents the weight percentage of PCD added; the molecular weight of PPDO decreased much faster than that of PPDOCD. The pH of the solution was monitored for 15 weeks and a final pH value of the solution involving PPDOCD5 was 6.81 whereas that of PPDO solution was 3.77, indicating that more acid fragments from PPDO samples migrate into the buffer solution. Surface morphological changes showed a better physical integrity for PPDOCD samples and they also kept their mechanical properties for a longer time than PPDO samples. These results revealed that PCD can retard the hydrolysis degradation of PPDO and enhance its hydrolytic stability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Effects of pretreatment reagents on the hydrolysis and physical properties of PET fabrics
Authors: Kim Eun Seon , Lee Chang Hwan , Kim Seong Hun
Published: February 2009

The effects of pretreatment reagents on the hydrolysis and physical properties of PET fabrics were investigated under various alkaline hydrolysis treatment and pretreatment conditions. Before alkaline hydrolysis, solvent treatment with pretreatment reagents, including benzyl alcohol (PET‐b) or 2‐phenyl ethanol (PET‐p), modified the structure of the PET fabric, thus affecting the hydrolysis and physical properties of the PET fabrics. Fabric weight loss increased with increasing hydrolysis time. The rate constant (k) increased markedly with increasing methyl groups in the pretreatment reagents. The activation energy (Ea) of untreated fabrics was higher than those of the treated fabrics. The crystallinity of the PET fabrics increased with increasing hydrolysis times (t) and methyl groups in the pretreatment reagents. The weight loss of PET‐b increased with increasing pretreatment temperature (T). However, the weight loss of PET‐p increased up to 100°C but decreased above 120°C. The shrinkage of all samples increased with increasing hydrolysis times (t). Shrinkage of PET‐b and PET‐p was greater than that of untreated fabrics. PET‐b displayed greater shrinkage than PET‐p because byproducts polluted the PET fibers. Both the initial and maximum water absorption of the fabrics increased with increasing hydrolysis times (t). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Physicochemical characterization of poly(ethylene glycol) plasticized poly(methyl vinyl ether‐co‐maleic acid) films
Authors: Singh Thakur Raghu Raj , McCarron Paul A. , Woolfson A. David , Donnelly Ryan F.
Published: February 2009

The influence of the poly(ethylene glycol) (PEG) plasticizer content and molecular weight on the physicochemical properties of films cast from aqueous blends of poly(methyl vinyl ether‐co‐maleic acid) (PMVE/MA) was investigated with tensile mechanical testing, thermal analysis, and attenuated total reflectance/Fourier transform infrared spectroscopy. Unplasticized films and those containing high copolymer contents were very difficult to handle and proved difficult to test. PEG with a molecular weight of 200 Da was the most efficient plasticizer. However, films cast from aqueous blends containing 10% (w/w) PMVE/MA and either PEG 1000 or PEG 10,000 when the copolymer/plasticizer ratio was 4 : 3 and those cast from aqueous blends containing 15% (w/w) PMVE/MA and either PEG 1000 or PEG 10,000 when the copolymer/plasticizer ratio was 2 : 1 possessed mechanical properties most closely mimicking those of a formulation we have used clinically in photodynamic therapy. Importantly, we found previously that films cast from aqueous blends containing 10% (w/w) PMVE/MA performed rather poorly in the clinical setting, where uptake of moisture from patients' skin led to reversion of the formulation to a thick gel. Consequently, we are now investigating films cast from aqueous blends containing 15% (w/w) PMVE/MA and either PEG 1000 or PEG 10,000, where the copolymer/plasticizer ratio is 2 : 1, as possible Food and Drug Administration approved replacements for our current formulation, which must currently be used only on a named patient basis as its plasticizer, tripropylene glycol methyl ether, is not currently available in pharmaceutical grade. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Morphology‐related packetlike space‐charge behavior in linear low‐density polyethylene doped with Al2O3 nanoparticles
Authors: Zheng Feihu , Hao Shujuan , Wang Wenyan , Xiao Chun , An Zhenlian , Zhang Yewen
Published: February 2009

Packetlike space‐charge behavior and the isothermal decay processes of the injected charge in neat linear low‐density polyethylene (LLDPE) and LLDPE doped with Al2O3 nanoparticles were investigated by the pressure wave propagation method. The 1‐mm sheet samples, sandwiched by semiconductive electrodes, were submitted to 40 kV/mm of direct current field at various temperatures for 3 h. The charge‐injecting rate and the apparent mobility of packetlike space charge under direct‐current stress were compared among the samples subjected to different blending processes with or without nanoparticles. The slight doping concentration showed a significant influence on the space‐charge dynamics, with a lower injecting rate and apparent mobility for higher doped samples. The isothermal decay processes of the injected charge indicated trap‐modulated features. The phenomena were considered to be related to the changing morphology of the matrix material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Double‐network hydrogel with high mechanical strength prepared from two biocompatible polymers
Authors: Zhang Xiaoyan , Guo Xinglin , Yang Shuguang , Tan Shuaixia , Li Xiaofeng , Dai Hongjun , Yu Xiaolan , Zhang Xiaoli , Weng Ning , Jian Bin , Xu Jian
Published: February 2009

Novel double‐network (DN) hydrogels with high mechanical strength have been fabricated with two biocompatible polymers, poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG), through a simple freezing and thawing method. Some properties of the obtained hydrogels, such as the mechanical strength, rheological and thermodynamic behavior, drug release, and morphology, have been characterized. The results reveal that in sharp contrast to most common hydrogels made with simple natural or synthetic polymers, PVA/PEG hydrogels can sustain a compressive pressure as high as several megapascals, highlighting their potential application as biomedical materials. In addition, a model for describing the structural formation of PVA/PEG DN hydrogels is proposed: the condensed PVA‐rich phase forms microcrystals first, which bridge with one another to form a rigid and inhomogeneous net backbone to support the shape of the hydrogel, and then the dilute PEG‐rich phase partially crystallizes among the cavities or voids of the backbone; meanwhile, there are entanglements of molecular chains between the two polymers. Moreover, a mechanism is also proposed to explain the high mechanical strength of PVA/PEG DN hydrogels. It is suggested that the free motion of PEG clusters in the cavities of PVA networks can prevent the crack from growing to a macroscopic level because the linear PEG chains in the cavities effectively absorb the crack energy and relax the local stress either by viscous dissipation or by large deformation of the PEG chains. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Preparation and characterization of LDPE and PP—Wood fiber composites
Authors: Taşdemır Münir , Biltekin Hasan , Caneba Gerald T.
Published: February 2009

Natural fiber reinforced composites is an emerging area in polymer science. These natural fibers are low cost fibers with low density and high specific properties. These are biodegradable and nonabrasive. The natural fiber composites offer specific properties comparable to those of conventional fiber composites. However, in development of these composites, the incompatibility of the fibers and poor resistance to moisture often reduce the potential of natural fibers, and these draw backs become critical issue. Wood‐plastic composites (WPC) are a relatively new class of materials and one of the fastest growing sectors in the wood composites industry. Composites of wood in a thermoplastic matrix (wood–plastic composites) are considered a low maintenance solution to using wood in outdoor applications. WPCs are normally made from a mixture of wood fiber, thermoplastic, and small amounts of process and property modifiers through an extrusion process. In this study, Wood–plastic composites (WPC) are produce by adding a maleic anhydride modified low density polyethylene coupling agent to improve interfacial adhesion between the wood fiber and the plastic. Mixing is done with twin screw extruder. Subsequently, tensile strength, the modulus of elasticity, % elongation, hardness, Izod impact strength, melt flow index (MFI), and heat deflection temperature (HDT) are determined. Thermal transition temperatures and microstructure are determined with DSC and SEM, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Polylactide/nano‐ and micro‐scale silica composite films. II. Melting behavior and cold crystallization
Authors: Huang Jiann‐Wen , Chang Hung Yung , Wen Ya‐Lan , Kang Chiun‐Chia , Yeh Mou‐Yung
Published: February 2009

Nonisothermal crystallization of polylactide (PLA)/silica composites prepared by (i) directly blending the PLA with nanoscale colloidal silica sol and by (ii) a sol–gel process are studied by differential scanning calorimeter (DSC) at various heating rates. Samples quenched from the molten state exhibited two melting endotherms (Tml and Tmh) due to melt‐recrystallization during the DSC scans. Lower heating rate and the presence of silica particles generate a lower peak intensity ratio of Tml /Tmh. The nonisothermal crystallization kinetics is analyzed by modified Avrami model, Ozawa model, and Liu‐Mo models. The modified Avrami and Liu‐Mo models successfully described the nonisothermal cold crystallization processes, but Ozawa is inapplicable. The nucleation constant (Kg) is calculated by modified Lauritzen‐Hoffman equation and the activation energy by Augis‐Bennett, Kissinger, and Takhor models. These calculated parameters indicate consistently that the nanoscale silica particles seem to form more heterogeneous nucleation to increase crystallization, but microscale one form hindrance to retard crystallization. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis and characterization of polyurethane elastomers based on chitosan and poly(ε‐caprolactone)
Authors: Barikani Mehdi , Honarkar Hengameh , Barikani Majid
Published: February 2009

Biodegradable polyurethane (PU) elastomers with potential for biomedical and industrial applications were synthesized by the reaction of poly(ε‐caprolactone) (PCL) and isophorone diisocyanate (IPDI), extended with different mass ratio of chitosan and 1,4‐butane diol (BDO). Their chemical structures were characterized using FTIR, 1HNMR, and 13CNMR, and thermal properties were determined by TGA and DMTA. Incorporation of chitosan contents into the polyurethane backbone caused improvement in thermal stability and thermal degradation rate. Optimum thermal properties and degradation profile were obtained from elastomer extended with chitosan. The crystallinity and hydrophilicity of the prepared polymers were also examined by X‐ray and contact angle measurements. The results showed that hydrophilicity decreased and crystallinity increased with increasing of chitosan content in polyurethane backbone. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Investigation of nanostructure and properties of aromatic–aliphatic polyamide‐based nanocomposites with clay additives
Authors: Zulfiqar Sonia , Shabbir Saima , Ishaq Muhammad , Sarwar Muhammad Ilyas
Published: February 2009

Aromatic–aliphatic polyamide/clay nanocomposites were produced using solution intercalation technique. Surface modification of the clay was performed with ammonium salt of aromatic diamine and the polyamide chains were produced by condensation of 4‐aminophenyl sulfone with sebacoyl chloride (SCC) in dimethyl acetamide. Carbonyl chloride endcapped polymer chains were prepared by adding extra SCC near the end of polymerization reaction. The nanocomposites were investigated for organoclay dispersion, water absorption, mechanical, and thermal properties. Formation of delaminated and intercalated nanostructures was confirmed by X‐ray diffraction and TEM studies. Tensile strength and modulus improved for nanocomposites with optimum organoclay content (8 wt %). Thermal stability and glass transition temperatures of nanocomposites increased relative to pristine polyamide with augmenting organoclay content. The amount of water uptake for these materials decreased as compared with the neat polyamide. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Structure and properties of new thermoforming bionanocomposites based on chitin whisker‐graft‐polycaprolactone
Authors: Feng Liangdong , Zhou Ziyan , Dufresne Alain , Huang Jin , Wei Ming , An Lijia
Published: February 2009

Thermoformable bionanocomposites of chitin whisker‐graft‐polycaprolactone (CHW‐g‐PCL) were synthesized by initiating the ring‐opening polymerization of caprolactone monomer onto the CHW surface under microwave radiation. In this case, the “graft from” strategy contributed to long and dense “plasticizing” PCL tails onto the CHW surface as the key of thermoforming, and, therefore, such bionanocomposites were injection‐molded as the sheets with a structure of cocontinuous phase mediated with the entanglement of grafted PCL chains. The structure and properties of the molded CHW‐g‐PCL sheets were investigated by FTIR, XRD, SEM, DSC, DMTA, contact angle measurement, and tensile test. With an increase of the PCL content in CHW‐g‐PCL, the strength and elongation as well as the hydrophobicity of the nanocomposites increased at one time. This is the first report on the thermoformable polymer‐grafted nanocrystal derived from natural polysaccharide. Moreover, such new bionanocomposites with good mechanical performances could have great potential applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Studies on the complexation between generation‐4.5 methyl ester‐terminated poly(amidoamine) dendrimer and Pd2+ ions in methanol
Authors: Lu Wenting , Li Guoping , Luo Yunjun , Jin Yujuan
Published: February 2009

Poly(amidoamine) (PAMAM) dendrimers have attracted attention because of their well‐defined molecule structures and chemical versatility, which also complicate the mechanism of interactions between metal ions and PAMAM dendrimers. To further understand the complexation of dendrimers with metal ions, the interactions between Pd2+ ions and G4.5‐COOCH3 PAMAM dendrimers were investigated by UV‐vis and FTIR spectrophotometric method. The results show that the addition of K2PdCl4 results in covalent attachment of the PdCl alcoholysis product of this complex to tertiary amines within the dendrimers under the appropriate conditions. This process was also supported by X‐ray photoelectron spectroscopy data of the new complex which indicated a 1 : 3 Pd/Cl ratio. The maximum loading of 80 Pd2+ ions within the G4.5‐COOCH3 dendrimers and the best pH value of 8.3 for complexation system are also obtained. Details regarding the Pd species present in solution of different chemical environments are reported. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Preparation and characterization of venlafaxine hydrochloride‐loaded chitosan nanoparticles and in vitro release of drug
Authors: Shah Sunil , Pal Angshuman , Kaushik V. K. , Devi Surekha
Published: February 2009

The venlafaxine hydrochloride (VHL)‐loaded chitosan nanoparticles were prepared by ionic gelation of chitosan (CS) using tripolyphosphate (TPP). The nanoparticles were characterized using FTIR, differential scanning calorimetry, X‐ray diffraction, dynamic light scattering, transmission electron microscopy, and X‐ray photoelectron spectroscopy. The effect of concentration of CS, polyethylene glycol (PEG), VHL and CS/TPP mass ratio on the particle size and zeta potential of nanoparticles was examined. The particle size of CS/TPP nanoparticles and VHL‐loaded CS/TPP nanoparticles was within the range of 200–400 nm with positive surface charge. In the case of VHL‐loaded nanoparticles and PEG‐coated CS/TPP nanoparticles, the particle size increases and surface charge decreases with increasing concentration of VHL and PEG. Both placebo and VHL‐loaded CS/TPP nanoparticles were observed to be spherical in nature. PEG coating on the surface of CS/TPP nanoparticles was confirmed by XPS analysis. Maximum drug entrapment efficiency (70%) was observed at 0.6 mg/mL drug concentration. In vitro drug release study at 37°C ± 0.5°C and pH 7.4 exhibited initial burst release followed by a steady release. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Immobilization of manganoporphyrin on a novel polymeric support and catalytic oxidation characteristic of supported catalyst
Authors: Gao Baojiao , Wang Ruixin , Zhang Yan
Published: February 2009

Monomer glycidyl methacrylate (GMA) was grafted on silica gel particles in the manner of “grafting from,” and the grafted particles PGMA/SiO2 was prepared. The grafted particles PGMA/SiO2 is a kind of novel support for the immobilization of metalloporphyrin catalysts. In the presence of basic catalysts, the ring‐opening reaction of the epoxy groups of the grafted PGMA occurred and the bonding of meso‐tetra (4‐hydroxylphenyl) porphyrin (THPP) on the particles PGMA/SiO2 was realized, resulting in the bonded particles HPP‐PGMA/SiO2. Subsequently, the metallation of the bonded particles HPP‐PGMA/SiO2 was carried out via the coordination reaction between HPP‐PGMA/SiO2 and manganese salt, resulting in the supported manganoporphyrin (MnP) catalyst MnP‐PGMA/SiO2. The supported catalyst was used in the catalytic oxidation of ethyl benzene into acetophenone by molecular oxygen. In this article, the effects of various factors such as the species and amount of the catalyst on the bonding process of THPP were studied because of the importance of the bonding reaction of THPP in the preparation of the catalyst MnP‐PGMA/SiO2. Finally, the catalytic performance of MnP‐PGMA/SiO2 in the catalytic oxidation process of ethyl benzene was investigated. The experimental results show that triethylamine is a suitable catalyst for the bonding of THPP on the grafted particles PGMA/SiO2 and for the forming of MnP‐PGMA/SiO2. The supported catalyst MnP‐PGMA/SiO2 can effectively activate molecular oxygen, and obviously catalyze the oxidation process of ethyl benzene to acetophenone by molecular oxygen. It was found that the immobilization density of MnP on MnP‐PGMA/SiO2 has a great effect on the catalytic activity of the catalyst. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Comparison of chemical and enzymatic emulsion polymerization of styrene
Authors: Kwon Hyuk‐Sung , Chung Eunyong , Lee Dong‐Ig , Lee Chang‐Ha , Ahn Ik‐Sung , Kim Ju‐Young
Published: February 2009

For the reasonable comparison of chemical and enzymatic polymerization, manganese(III) acetate and manganese peroxidase (MnP)‐catalyzed synthesis of polystyrenes were chosen and studied with respect to the yield and the polydispersity of polymer particles. MnP allowed the production of polystyrene in a higher yield and higher polydispersity (82.34% and 2.61) than manganese(III) acetate (77.90% and 1.75). This is believed to be due to a gradual supply of initiator radicals via a catalytic cycle in MnP‐catalyzed polymerization, whereas radicals are generated all at once in Mn(III)‐mediated polymerization. NMR spectroscopy revealed that atactic polystyrene was produced by emulsion polymerization using Mn(III) or MnP. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Substituent effect on the optoelectronic properties of poly(p‐phenylenevinylene) based conjugated‐nonconjugated copolymers
Authors: Palai Akshaya K. , Rath Sangram K. , Srivastava Ritu , Kamalasanan Modeeparampil Narayanan , Patri Manoranjan
Published: February 2009

Two classes of light emitting Poly(p‐phenylenevinylene) (PPV) based conjugated‐nonconjugated copolymers (CNCPs) have been synthesized. The conjugated chromophores containing 2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene (MEHPV) and 2,5‐dimethyl‐1,4‐phenylenevinylene (DMPV) moieties are rigid segments and nonconjugated portion containing hexyl units are flexible in nature. All copolymers were synthesized by well‐known Wittig reaction between the appropriate bisphosphonium salts and the dialdehyde monomers. The resulting polymers were found to be readily soluble in common organic solvents like chloroform, THF and chlorobenzene. The effect of chromophore substituents on the optical and redox properties of the copolymers has been investigated. Color tuning was carried out by varying the molar percentage of the comonomers. The UV‐Vis absorption and PL emission of the copolymers were in the range 314–395 nm and 494–536 nm respectively. All the polymers show good thermal stability. Polymer light‐emitting diodes (PLEDs) were fabricated in ITO/PEDOT:PSS/emitting polymer/cathode configurations of selected polymers using double‐layer, LiF/Al cathode structure. The emission maxima of the polymers were around 499–536 nm, which is a blue‐green part of the color spectrum. The threshold voltages of the EL polymers were in the range of 5.4–6.2 V. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Polyvinylidene fluoride‐based novel polymer electrolytes for magnesium‐rechargeable batteries with Mg(CF3SO3)2
Authors: Aravindan Vanchiappan , Karthikaselvi G. , Vickraman P. , Naganandhini S. P.
Published: February 2009

Magnesium trifluoromethanesulfonate (Mg (CF3SO3)2)‐based polymer electrolytes (PEs) have been prepared with polyvinylidene fluoride (PVdF) as a host matrix. Tetraglyme and tetrabutyl ammonium chloride (TBACl) were used as plasticizer and filler, respectively, in the matrix by solution‐casting technique. The electrolyte containing 5 wt % TBACl exhibits the conductivity of 0.442 mS cm−1 at ambient temperature. X‐ray diffraction study reveals the amorphous nature of the PE. Linear sweep voltammetry was also performed to evaluate the decomposition potential of the electrolyte. The morphological features were analyzed by scanning electron microscope. The activation energy has also been calculated, which corroborates the ionic conductivity results. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Effects of the incorporation of low‐molecular‐weight diurethanes on thermal and rheological properties of thermoplastic polyurethane
Authors: Fiorio Rudinei , Zattera Ademir José , Ferreira Carlos Arthur
Published: February 2009

In this study, two low‐molecular‐weight diurethanes were synthesized and blended with thermoplastic polyurethane (TPU). The effects of the incorporation on the thermal and rheological properties of TPU were evaluated. The diurethanes were obtained from the reaction of 4,4′‐diphenylmethane‐diisocyanate (MDI) with 1‐butanol (Additive 1) or 1‐octanol (Additive 2). Blending of the additives with TPU was carried out in a torque rheometer, and the blends obtained were analyzed by differential scanning calorimetry (DSC), torque rheometry, and capillary rheometry. The torque rheometry showed that an increase in the amount of both additives displaced the charging peaks to longer times and reduced the torque values after melting. The DSC analysis showed that the incorporation of the additives did not affect the glass transition temperature (Tg) of the flexible phase of TPU. However, an increase in the amount of Additive 1 led to a reduction in the Tg of the rigid phase, while increasing the amount of Additive 2 caused an increase in the Tg of this phase. Capillary rheometry results showed that blends with up to 2 wt % of additive led to intrinsic viscosity and melt‐flow stability values higher than those of processed TPU. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
The representation of national political freedom on Web interface design: The indicators
Authors: Li Rowena
Published: February 2009

This study is designed to validate 10 Power Distance indicators identified from previous research on cultural dimensions to establish a measurement for determining a country's national political freedom represented on Web content and interface design. Two coders performed content analysis on 156 college/university Web sites selected from 39 countries. One‐way analysis of variance was applied to analyze each of the proposed 10 indicators to detect statistical significant differences among means of the three freedom groups (free‐country group, partly‐free‐country group, and not‐free‐country group). The results indicated that 6 of the 10 proposed indicators could be used to measure a country's national political freedom on Web interface design. The seventh indicator, symmetric layout, demonstrated a negative correlation between the freedom level and the Web representation of Power Distance. The last three proposed indicators failed to show any significant differences among the treatment means, and there are no clear trend patterns for the treatment means of the three freedom groups. By examining national political freedom represented on Web pages, this study not only provides an insight into cultural dimensions and Web interface design but also advances our knowledge in sociological and cultural studies of the Web.
Question types in public libraries' digital reference service in Finland: Comparing 1999 and 2006
Authors: Numminen Piritta , Vakkari Pertti
Published: February 2009

This study analyzes to which degree the question types addressed to a digital reference service run by a consortium of public libraries have changed between the Years 1999 and 2006. The data consist of representative samples of reference questions to a Finnish “Ask a Librarian” digital reference service in the years studied. Questions were classified based on a taxonomy refining earlier major taxonomies. The proportion of ready reference questions had increased from 33 to 45% whereas the proportion of subject‐based research questions had decreased from 57 to 47%. Among the former, fact‐finding questions had especially increased, and among the latter, topical search questions had decreased. These changes in the popularity of question types are likely related to the way people are searching on the Internet. It is concluded that the Internet has somewhat reduced the traditional role of public libraries in mediated topical searching.
Comparative effects of interferon alpha‐2b and pegylated interferon alpha‐2b on menstrual cycles and ovarian hormones in cynomolgus monkeys
Authors: Enright Brian P. , Compton David R. , Collins Nathaniel , Davis Thomas , McIntyre Barry S.
Published: February 2009

BACKGROUND: The covalent modification of interferon (IFN) α2b with monomethyoxy polyethylene glycol (PEG) reduces its clearance rate and increases its half‐life. High doses of interferon (IFN) α2b have previously been shown to affect maintenance of pregnancy in rhesus monkeys. Given the role of ovarian hormones in reproductive function and pregnancy, this study was conducted to assess the effects of PEG‐IFNα2b or IFNα2b (comparative control) on ovarian hormones and menstrual cyclicity in cynomolgus monkeys. In addition, the potential for reversibility of PEG‐IFNα2b or IFNα2b‐related observations was assessed. METHODS: Monkeys were administered 3,105 µg/m2 human recombinant (hr) IFNα2b or 52, 262, or 4,239 µg/m2 PEG‐hr‐IFNα2b every other day for one menstrual cycle, followed by a post‐dose period of up to two menstrual cycles. RESULTS: Monkeys administered 3,105 µg/m2 hr‐IFNα2b or 52, 262, or 4,239 µg/m2 PEG‐hr‐IFNα2b exhibited transient decreases in food consumption, leukocyte and erythrocyte parameters. Monkeys administered 3,105 µg/m2 hr‐IFNα2b exhibited lengthened menstrual cycles that were associated with a delay in reaching peak ovarian hormone levels and lower respective peak concentrations. Similarly, monkeys administered 4,239 µg/m2 PEG‐hr‐IFNα2b exhibited lengthened menstrual cycles and a delay in reaching peak ovarian hormone levels and slightly lower respective peak concentrations. Post‐dosing menstrual cycle length, estradiol and progesterone profiles exhibited evidence of recovery in both the hr‐IFNα2b and the high‐dose PEG‐hr‐IFNα2b groups. CONCLUSIONS: Administration of hr‐IFNα2b or PEG‐hr‐IFNα2b at high doses to cynomolgus monkeys resulted in similar effects on menstrual cycles, estradiol and progesterone profiles, and exhibited evidence of reversibility upon cessation of dosing. These results suggest that the previously observed high‐dose IFNα‐related effects on the maintenance of pregnancy in monkeys are likely the result of altered ovarian function. Birth Defects Res (Part B) 86:29‐39, 2009. © 2009 Wiley‐Liss, Inc.
Comparing four different approaches for the determination of inter‐residue interactions provides insight for the structure prediction of helical membrane proteins
Authors: Gao Jun , Li Zhijun
Published: February 2009

Studying inter‐residue interactions provides insight into the folding and stability of both soluble and membrane proteins and is essential for developing computational tools for protein structure prediction. As the first step, various approaches for elucidating such interactions within protein structures have been proposed and proven useful. Since different approaches may grasp different aspects of protein structural folds, it is of interest to systematically compare them. In this work, we applied four approaches for determining inter‐residue interactions to the analysis of three distinct structure datasets of helical membrane proteins and compared their correlation to the three individual quality measures of structures in these datasets. These datasets included one of 35 structures of rhodopsin receptors and bacterial rhodopsins determined at various resolutions, one derived from the HOMEP benchmark dataset previously reported, and one comprising of 139 homology models. It was found that the correlation between the average number of inter‐residue interactions obtained by applying the four approaches and the available structure quality measures varied quite significantly among them. The best correlation was achieved by the approach focusing exclusively on favorable inter‐residue interactions. These results provide interesting insight for the development of objective quality measure for the structure prediction of helical membrane proteins. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 547–556, 2009.

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