bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface modification of polycaprolactone monofilament by low pressure oxygen plasma
Authors: Gupta Bhuvanesh , Krishnanand Kumar , Deopura B. L. , Atthoff Björn 
Published: May 2012

AbstractSurface modification of polycaprolactone filament has been carried out using a low pressure oxygen plasma to introduce active centers in the form of radicals, peroxides, and hydroperoxides on the surface. Evaluation by 2, 2‐diphenyl‐1‐picrylhydrazyl method shows that there is an optimum value of exposure time, gas pressure, and discharge power for the generation of the maximum concentration of such groups. The plasma exposure time was thereafter varied to study the extent of the surface modification introduced by the plasma. It was found that only a short time of exposure to the oxygen plasma was necessary to make the surface highly wettable and polar with increased surface energy and work of adhesion. Surface chemical analysis by X‐ray photoelectron spectroscopy revealed that this happens because of oxidation of the top layer of the filament, which occurs primarily by the breaking of bonds and incorporation of oxygen containing functionalities. Morphological and topographical observations by scanning electron microscopy and atomic force microscopy revealed that etching is pronounced at longer exposure times leading to a rougher surface with hill‐valley features. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Study on high‐solid content Si/PU polyurethane dispersion with PES/PPG composite soft segment
Authors: Zhang Faxing , Wei Xiaoli , Xiao Zhongliang 
Published: May 2012

AbstractA polyol consists of silicone chains and epoxy acrylate structures, referred to as silicon polyether (PES), was used to prepare crosslinked Si/PU dispersions. Both PES and propylene oxide glycol (PPG) were mixed as soft segments. The effects weight ratios of PES to PPG on properties of the resultant polyurethane dispersions were studied. Morphology and properties of the Si/PU dispersions were characterized by particle size, transmission electron microscopy (TEM), and viscometer. It is shown that the Si/PU dispersions possessed wider particle size distribution and higher average particles diameter because of the use of PES, which contains crosslinked silicone side chains. The Si/PU dispersions have higher solid content as compared to the conventional water‐based polyurethane, because of the volume fraction ratio of bigger particle to small particle from the Si/PU dispersions. As increasing weight ratio of PES to PPG, the solid content of the Si/PU dispersions increased firstly, and then decreased. When the ratio ranges from 4 : 10 to 5 : 10, solid content of the Si/PU dispersions is up to 55%. It was also noticed that apparent viscosity of the Si/PU dispersions decreased with increasing PES to PPG ratio. In the Si/PU dispersions, solid content was increased and viscosity was decreased by the use of PES. Therefore, PES is a potential compound for the application of PU dispersions. In addition, stability of the crosslinked Si/PU dispersions decreases slightly at high‐ and low‐temperature; however, which can meet the basical requirements. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
The influence of melt‐mixing process conditions on electrical conductivity of polypropylene/multiwall carbon nanotubes composites
Authors: Tambe Pankaj B. , Bhattacharyya Arup R. , Kulkarni Ajit R. 
Published: May 2012

AbstractThe influence of melt‐mixing parameters on the development of “network‐like” structure of multiwall carbon nanotubes (MWNTs) in injection‐molded polypropylene (PP)/MWNTs composites was assessed through AC electrical conductivity measurements. A higher melt‐mixing temperature (260°C as compared to 200, 220, and 240°C) at a fixed rotational speed of the screws (150 rpm) and at a fixed mixing time (15 min) has yielded maximum improvement in electrical conductivity in PP/MWNTs composites of 3 wt % MWNTs content. Next to higher melt‐mixing temperature, a variation in the melt‐mixing time has also led to a variation in electrical conductivity of the composites. Raman spectroscopic analysis revealed an increase in the ratio of intensity due to G‐band over that of D‐band (IG/ID) of the MWNTs in the “skin” region as compared to the “core” region of the injection‐molded composites irrespective of the melt‐mixing conditions. Microscopic observations could not provide much insight into the variation of MWNTs network‐like structure in various PP/MWNTs composites. An attempt has been made to understand the variation of network‐like structure of MWNTs in PP/MWNTs composites as a function of melt‐mixing parameters through electrical conductivity measurements, Raman spectroscopic analysis, and morphological investigations. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Effect of interfacial chemistry on the linear rheology and thermal stability of poly(arylene ether nitrile) nanocomposite films filled with various functionalized graphite nanoplates
Authors: Zhan Yingqing , Meng Fanbin , Yang Xulin , Wei Junji , Yang Jian , Zou Yanke , Guo Heng , Zhao Rui , Liu Xiaobo 
Published: May 2012

AbstractPoly(arylene ether nitrile) (PEN) nanocomposites filled with functionalized graphite nanoplates (GNs) were prepared by a simple solution‐ casting method and then characterized by rheometer and thermogravimetric analysis (TGA). This study investigates how the surface treatment of GNs affects the GN dispersion state. The linear rheological test indicated that the 4‐aminophenoxyphthalonitrile‐grafted GN (GN‐CN) presented better dispersion in PEN matrix than purified GN because the corresponding composite showed the lower rheological percolation threshold, which was further confirmed by scanning electron microscopy and solution experiments. The TGA revealed that the presence of 4‐aminophenoxyphthalonitrile‐grafted GN retarded the depolymerization evidently compared with that of purified GN, showing remarkable increase in the temperatures corresponding to a weight loss of 5 wt % (increased by 21°C) and maximum rate of decomposition (increased by 9°C). Both the dispersion state and the surface functionalization of GN are very important to the thermal stability of PEN matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Thermal degradation behaviors and flame retardancy of epoxy resins with novel silicon‐containing flame retardant
Authors: Gao Ming , Wu Weihong , Xu Zhi‐qiang 
Published: May 2012

AbstractA novel macromolecular silicon‐containing intumescent flame retardants (Si‐IFR) was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus‐silicon characterized by IR. Epoxy resins (EP) were modified with Si‐IFR to get the flame retardant EP, whose flammability and burning behavior were characterized by UL 94 and limiting oxygen index (LOI). Twenty percentage of weight of Si‐IFR was doped into EP to get 27.5% of LOI and UL 94 V‐0. The degradation behavior of the flame retardant EP was studied by thermogravimetry, differential thermogravimetry, scanning electron microscopy, and X‐ray photoelectron spectroscopy analysis. The experimental results exhibited that when EP/Si‐IFR was heated, the phosphorus‐containing groups firstly decompose to hydrate the char source‐containing groups to form a continuous and protective carbonaceous char, which changed into heat‐resistant swollen char by gaseous products from the nitrogen‐containing groups. Meanwhile, SiO2 reacts with phosphate to yield silicophosphate, which stabilizes the swollen char. The barrier properties and thermal stability of the swollen char are most effective in resisting the transport of heat and mass to improve the flame retardancy and thermal stability of EP. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Photochromic behavior of naphthopyran in styrene–butadiene–styrene elastomer thin films: Effect of stretching of film and linker
Authors: Zhao Xiancai , Wang Guang , Zhang Kuo 
Published: May 2012

AbstractThermoplastic elastomers of styrene–butadiene–styrene (SBS) triblock copolymers containing grafts of naphthopyran as side‐chain polymer were prepared by polymerization of naphthopyran acrylate monomer with a solution of SBS in tetrahydrofuran. Thin films of all grafted SBS polymers displayed photochromism, the decoloration kinetics of naphthopyran in the films was modeled by fitting biexponential equations to the photochromic decay curves after UV light irradiation. Stretching of the grafted SBS film at room temperature affected the fading rate constant k1 of the naphthopyran. The length of linker between photochromic naphthopyran moiety and the acrylate unit in monomer also affected the fading rate constant k1 of the naphthopyran in SBS elastomers. This study presents an example of tuning the photochromic properties of naphthopyran via two approaches, polymer structure, and stretching of films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Study on reaction kinetics of epoxy resin cured by a modified dicyandiamide
Authors: Feng Libang , Wang Yulong , Wang Yanping , Liu Hao , Zhao Jianchang 
Published: May 2012

AbstractTo improve the disadvantage of the low reactivity and reduce the high curing temperature of epoxy resin cured by dicyandiamide (DICY), DICY is chemically modified with phenyl hydrazine and a new curing agent, LB‐A, is developed in this research. The structure, the curing behavior, and reaction kinetics of LB‐A curing epoxy resin are investigated. Results show that the DICY is modified successfully and the well‐defined structure of DICY is destroyed after modification. Consequently, a new curing agent in a noncrystal form is resulted. Thereupon, the reactivity and compatibility between the epoxy resin and the curing agent are improved appreciably using LB‐A instead of DICY. Meanwhile, the curing temperature and activation energy of the curing reaction decrease outstanding, whereas the rate constant increases remarkably. In addition, the compressive strength and the adhesive strength in shear by tension loading of the resulting epoxy resins have been increased using LB‐A instead of DICY as the curing agent. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Diffusivity of alcohols in amorphous polystyrene
Authors: Bernardo Gabriel 
Published: May 2012

AbstractGravimetry is used to study the diffusion of a homologous series of alcohols (Cn, with n = 1, 2, 3, 4, 6, 10, and 16) in amorphous polystyrene at temperatures from 35 to 145°C, that is both below and above the polymer glass transition temperature of 100°C. All the mass uptake results are well described by a simple Fickian model (for t < t1/2) and are used to calculate the corresponding diffusion coefficients using the thin‐film approximation. At any particular temperature, the alcohols Cn with n = 3, 4, and 6 possess very similar diffusivities despite the fact that the chain length doubles from C3 to C6. This peculiar diffusivity behavior is explained based on the variation of the polymer–solvent chemical affinity along the homologous series. As expected, at any particular temperature, the diffusivity decreases considerably from C6 to C10 and from C10 to C16. For each alcohol, its log(D) increases linearly with the decrease in liquid viscosity associated with an increase in temperature. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Covalent immobilization of β‐galactosidase onto electrospun nanofibers of poly (AN‐co‐MMA) copolymer
Authors: El‐Aassar M. R. , Al‐Deyab Salem S. , Kenawy El‐Refaie 
Published: May 2012

AbstractImmobilization of β‐galactosidase in poly (acrylonitrile‐co‐methyl methacrylate) poly (AN‐co‐MMA) Nanofibers was studied by electrospinning, and a spacer‐arm i.e., (Polyethyleneimine (PEI)) was covalently attached by the reaction of carbonyl groups of Poly (AN‐co‐MMA) nanofibers. β‐galactosidase was then covalently immobilized through the spacer‐arm of the Poly (AN‐co‐MMA) nanofibers by using glutaraldehyde (GA) as a coupling agent. Nanofibers mode of interaction was proven by FTIR and thermal gravimetric analysis and supported by morphological changes recognized through SEM examination. Factors affecting the modification process such as PEI concentration, reaction time, and reaction temperature have been studied. Its influence on the amount of coupled PEI was consequently correlated to the changes of the catalytic activity and the retained activity of immobilized enzyme, the main parameters judging the success of the immobilization process. Evidences of Poly (AN‐co‐MMA) nanofibers modification were extracted from morphological changes recognized through SEM examination. The maximum activity (Vmax) and michaelis constant (Km) of immobilized enzyme were found to be 8.8 μmole/min mg protein and 236.7 mM, respectively. Stabilities of the immobilized β‐galactosidase were obviously improved. The optimum temperature for β‐galactosidase immobilized on the spacer‐arm attached nanofiber was 5°C higher than that of the free enzyme and was also significantly broader. The immobilized β‐galactosidase had better resistance to temperature inactivation than did the free form. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Fundamental thermo‐mechanical property modeling of triglyceride‐based thermosetting resins
Authors: La Scala John , Wool Richard P. 
Published: May 2012

AbstractThe glass transition temperature (Tg) of acrylated triglycerides was clearly a function of the level of acrylation of triglyceride‐based polymers and was modeled using simple empirical relationships. We began by calculating the distribution of unsaturation sites in plant oils. We assumed a binomial distribution of chemical functionality that was added to these unsaturation sites to calculate the distribution of epoxides, acrylates, and reacted acrylates to predict the crosslink density, thermal softening, and dynamic mechanical behavior. The glass transition temperatures of n‐acrylated triglycerides were used as the relaxation temperatures of acrylated oils with a broad distribution of functionality for prediction of the modulus as a function of temperature. Essentially, the percent drop in the elastic modulus is equal to the percentage of n‐acrylated triglycerides in the acrylated oil with Tg less than that of the ambient temperature. The tan (δ) was also accurately predicted based on the percentage change of n‐functional triglycerides as the temperature changes from one relaxation temperature to the next. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Recruitment of the threatened mussel Margaritifera margaritifera in relation to mussel population size, mussel density and host density
Authors: Arvidsson Björn L. , Karlsson Jens , Österling Martin E. 
Published: May 2012

ABSTRACT

Anthropogenic, abiotic factors are considered the main cause of recruitment failure of unionid mussels, including the freshwater pearl mussel (Margaritifera margaritifera). This large‐scale investigation instead examined the relationship between biotic factors and mussel recruitment.
Mussel population size and density were positively related to recruitment and to juvenile mussel density. Juvenile mussel density appeared to be the more accurate measure of recruitment of the two.
Host fish density of young‐of‐the‐year and older brown trout (Salmo trutta) were positively related to recruitment. Moreover, the mean density of both age classes of fish, when grouped into density classes, was positively related to juvenile mussel density, an effect that decreased at trout densities above 10 trout 100 m‐2.
Mussel population size and density were relatively more important to recruitment than trout density.
To increase recruitment of juvenile mussels, managers should apply measures that increase mussel density, and trout density up to about 10 trout 100 m‐2 in proximity to mussel beds. Mussel beds may also be managed; one possible measure within small and sparse mussel populations may be to concentrate the remaining mussels in areas where trout density is high. Likewise, young‐of‐the‐year trout may also be moved to areas of high mussel density, as young trout individuals tend not to move far during their first year. This may increase mussel larval infection rates and mussel recruitment. Copyright © 2012 John Wiley & Sons, Ltd.
Skull Mechanics and the Evolutionary Patterns of the Otic Notch Closure in Capitosaurs (Amphibia: Temnospondyli)
Authors: Fortuny Josep , Marcé‐Nogué Jordi , Gil Lluis , Galobart Àngel 
Published: May 2012

AbstractCapitosaurs were among the largest amphibians that have ever lived. Their members displayed an amphibious lifestyle. We provide new information on functional morphology data, using finite element analysis (FEA) which has palaeoecological implications for the group. Our analyses included 17 taxa using (2D) plate models to test four loading cases (bilateral, unilateral and lateral bitings and skull raising system simulation). Our results demonstrates that, when feeding, capitosaurs concentrated the stress at the circumorbital region of the capitosaur skull and cranial sutures probably played a key role in dissipating and absorbing the stress generated during biting. Basal members (as Wetlugasaurus) were probably less specialized forms, while during Middle‐ and Late Triassic the group radiated into different ecomorphotypes with closed otic notch forms (as Cyclotosaurus) resulting in the strongest skulls during biting. Previous interpretations discussed a trend from an open to closed otic notch associated with lateral repositioning of the tabular horns, but the analysis of the skull‐raising system reveals that taxa exhibiting posteriorly directed tabular horns display similar results during skull raising to those of closed otic notch taxa. Our results suggest that various constraints besides otic notch morphology, such as the elongation of the tabular horns, snout length, skull width and position, and size of the orbits affect the function of the skull. On the light of our results, capitosaur skull showed a trend to reduce the stresses and deformation during biting. Capitosaurs could be considered crocodilian analogues as they were top‐level predators in fluvial and brackish Triassic ecosystems. Anat Rec, , 2012. © 2012 Wiley Periodicals, Inc.
Quality management of body donation program at the University of Padova
Authors: Porzionato Andrea , Macchi Veronica , Stecco Carla , Mazzi Anna , Rambaldo Anna , Sarasin Gloria , Parenti Anna , Scipioni Antonio , De Caro Raffaele 
Published: May 2012

AbstractQuality management improvement has become a recent focus of attention in medical education. The program for the donation of bodies and body parts (Body Donation Program) at the University of Padova has recently been subjected to a global quality management standard, the ISO 9001:2008 certification. The aim of the present work is to show how the above standard is useful in enhancing the efficiency of body donation procedures and the quality and output of medical education. The program is managed by means of the following interlinked procedures: the collection of body donations, death certificates, data, and body parts from living donors; the transportation and identification of cadavers; the management of bodies, body parts, equipment, instruments, purchasing of necessary materials, and setting up anatomical training sessions; the management of preventive and corrective actions; the management of documents and registration; the management of internal and external quality audits; and the review of outcomes and improvement planning. Monitoring indicators are identified in the numbers of donors and of donated body parts per year, education sessions, and satisfaction of learners and donors, as evaluated by questionnaires. The process management approach, the integrated involvement of medical, technical, and administrative staff in defining procedures, and the application of monitoring indicators allow quality improvement in all aspects of the Body Donation Program. Anat Sci Educ. © 2012 American Association of Anatomists.
Observer‐based Reliable Control for Discrete Time Systems: An Average Dwell Time Approach
Authors: Du Dongsheng , Jiang Bin , Shi Peng , Mao Zehui 
Published: May 2012

AbstractThis paper deals with the problem of reliable control for discrete time systems with actuator failures. The actuator is assumed to fail occasionally and can recover over a time interval. During the time of suffering failures, the considered closed‐loop system is assumed unstable. Using an average dwell time method and under the condition that the activation time ratio between the system without actuator failures and the system with actuator failures is not less than a specified constant, an observer‐based feedback controller is developed in terms of linear matrix inequalities such that the resulting closed‐loop system is exponentially stable. An example is included to demonstrate the effectiveness of the proposed approach.
Use of a greasy effluent floater treatment station from the slaughterhouse for biosurfactant production
Authors: Borges Wesley da Silva , Cardoso Vicelma Luiz , Resende Miriam Maria de 
Published: May 2012

AbstractMost commercially available surfactants are produced from petroleum. However, increasing concerns about the environment have stimulated the search for biosurfactant production. This work examines biosurfactant production from the greasy effluent floater treatment station from the slaughterhouse of poultry and pigs. The biosurfactant production was evaluated using two strains of Pseudomonas aeruginosa [American Type Culture Collection (ATCC) 9027 and 10145] in a kinetic study to determine which strain produces a higher rhamnolipid concentration, which is characterized by the rhamnose concentration. The strain of P. aeruginosa was selected via a central composite design based on the following variables: fat concentration, nitrogen concentration, added ammonium nitrate (AN), and brewery residual yeast (BRY). The preliminary results show that the P. aeruginosa strain ATCC 10145 produced biosurfactant more efficiently than ATCC 9027. After optimizing the variables that were studied, the best fat, BRY, and AN concentrations (in g/L) were found to be 12, 15, and 0, respectively.
Lipid composition is a determinant for human defensin hnp1 selectivity
Authors: Gonçalves Sónia , Abade João , Teixeira Alexandre , Santos Nuno C. 
Published: May 2012

AbstractHuman neutrophil peptide 1 (HNP1) is a human defensin with antimicrobial activity against different bacteria (both Gram‐positive and negative), fungi, and viruses. HNP1 is stored in the cytoplasmic azurophilic granules of neutrophils. To elucidate the mode of action of this antimicrobial peptide, studies based on its lipid selectivity were carried out. Large unilamellar vesicles with different lipid compositions were used as biomembranes model systems (mammal, fungal, and bacterial models). Changes on the intrinsic fluorescence of HNP1 upon membrane binding/insertion show that HNP1 has quite distinct preferences for mammalian and fungal membrane model systems. HNP1 showed low interaction with glucosylceramide rich membranes, but high sterol selectivity: it has a higher partition for ergosterol‐containing membranes (as fungal membranes) and lower interaction with cholesterol‐containing membranes (as in mammalian cells). These results reveal that lipid selectivity is a determinant step for HNP1 action. Fluorescence quenching data obtained using acrylamide indicate that HNP1 interacts with membranes without a full insertion in the lipid bilayer. Generalized polarization of laurdan indicates a change in membrane fluidity in the presence of HNP1 for POPC membranes but not for ergosterol‐enriched membranes. © 2012 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 98:313‐321, 2012.