bluuebunny/crossref_metadata_2025_split huggingface dataset:
Orientation development in solid‐state extrusion and hot forming of polypropylene tubes
Authors: Elnagmi Mohamed , Jain Mukesh , Britten James F. 
Published: May 2011

AbstractThe use of high‐strength polymer in automotive structural components is limited by insufficient understanding of microscopic aspects of deformation for accurate numerical predictions of the mechanical behavior during forming processes. One approach to meeting these critical data needs is a careful examination of the structure property relationships that directly influence formability. Different hot forming processes (solid‐state extrusion, axial feed hot oil tube forming, and biaxial ball stretching test) are utilized in this work for investigating the effect of process conditions on the molecular orientation of polypropylene (PP) tubes. White‐Spruiell representation of orientation factors based on the results form X‐ray diffraction (XRD) patterns is utilized to analyze the development of orientation under extrusion and various forming conditions. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Montmorillonite nanoclay filler effects on electrical conductivity, thermal and mechanical properties of epoxy‐based nanocomposites
Authors: Rashmi  , Renukappa N.M. , Chikkakuntappa Ranganathaiah , Kunigal N. Shivakumar 
Published: May 2011

AbstractEpoxy‐based nanocomposites with 2, 5, and 7 wt% of montmorillonite (MMT) nanoclay were prepared using high shear melt mixing technique. The microstructural features of the nanocomposites were investigated by transmission electron microscopy (TEM). The thermal and mechanical properties were measured using differential scanning calorimetry (DSC), thermogravimetric analyzer (TGA), and dynamic mechanical analyzer (DMA). Further, the effect of voltage, temperature, seawater aging on the electrical conductivity (σDC) of the nanocomposites was also measured. To understand the free volume behavior upon filler loading, and to observe the connectivity between microstructure and other properties, positron annihilation lifetime spectroscopy was used. The TEM results revealed that MMT nanoparticles were uniformly dispersed in the epoxy matrix. Experimental results showed that the inclusion of 2 wt% MMT nanofiller increased the Tg, electrical conductivity, thermal stability, modulus, free volume of the epoxy nanocomposite significantly. This is well explained from the results of Tg (DSC and DMA), thermal stability, TGA residue, free volume analysis, and electrical conductivity. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
The role of specific interaction and selective localization of multiwall carbon nanotubes on the electrical conductivity and phase morphology of multicomponent polymer blends
Authors: Bose Suryasarathi , Bhattacharyya Arup R. , Khare Rupesh A. , Kamath Srikanth S. , Kulkarni Ajit R. 
Published: May 2011

AbstractMulticomponent polymer blends involving polyamide6 (PA6), polypropylene (PP), acrylonitrile‐butadiene‐styrene (ABS) and high density polyethylene (HDPE) with multiwall carbon nanotubes (MWNT) were prepared by melt mixing technique to achieve conducting composites. MWNT were either compounded directly or by employing a masterbatch dilution approach in binary (PA6/ABS), ternary (PA6/PP/ABS) and quaternary (PA6/PP/ABS/HDPE) blends. To facilitate “network‐like'' structure MWNT were pretreated with either sodium salt of 6‐aminohexanoic acid or octadecyl tri‐phenyl phosponium bromide. Multicomponent blends with pretreated MWNT utilizing masterbatch dilution approach showed significant improvements in the bulk electrical conductivity as compared to blends prepared by direct addition approach at 2 wt % MWNT content. Phase morphology of these blends revealed co‐continuous type of morphology wherein MWNT were found to be selectively localized in the PA6 phase. The heteronucleating action of MWNT was manifested in increased crystallization temperature of mainly PA6 phase of the blends indicating preferential localization of MWNT in the PA6 phase. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Melt‐compounding of PP/clay nanocomposite and relationship between its microstructure and shear strain in the flow field based on rheological analysis
Authors: Jiang Guo , Huang Han‐Xiong 
Published: May 2011

AbstractPolypropylene (PP)/clay nanocomposite was melt‐compounded using high shearing/mixing and chaotic mixing, the former provided by kneading block sections in twin‐screw extruder and the latter by a convective screw. Effect of mixing type on rheological behavior and microstructure of nanocomposites was investigated. Rheological property development along twin‐screw extruder was also tested. By numerical simulation, shear strain was calculated. Based on rheological analysis, the relationship between the shear strain and microstructure of nanocomposite was analyzed. Results show that chaotic mixing facilitates the dispersion of clay in PP matrix. Along twin‐screw extruder, the complex viscosity of samples is increased, and melt yield stress of end‐obtained samples is decreased with increase of the feeding rate. Observed from transmission electron microscopy photomicrographs, a better dispersion of clay in PP matrix was found when feeding rate is lowest, and the total strain calculated is largest at the lowest feeding rate. It is deduced that higher strain in flow field is important to obtain better dispersion and properties of polymer/clay nanocomposites. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers.
Rheological properties of cotton pulp cellulose dissolved in 1‐butyl‐3‐methylimidazolium chloride solutions
Authors: Liu Zhen , Wang Hui , Li Zengxi , Lu Xingmei , Zhang Xiangping , Zhang Suojiang , Zhou Kebin 
Published: May 2011

AbstractRheological properties of cotton pulp dissolved in 1‐butyl‐3‐methylimidazolium chloride ([Bmim]Cl) solutions were characterized using an advanced rheometer. The complex viscosity, dynamic modulus, and shear viscosity at different temperature were studied. In the steady shear measurements, all the solutions show a shear‐thinning behavior at high shear rates. The complex viscosity as a function of frequency was fitted by extended Carreau–Yasuda model. In all cotton pulp/[Bmim]Cl solutions, the complex dynamic viscosity (η*) and steady shear viscosity (ηa) followed the Cox–Merz rule only at lower frequency. The effects of tested temperature on viscosity and viscoelastic behavior of the solutions were also investigated. The value of activation energy for the dissolution of cotton pulp in ionic liquids was 65.28 kJ/mol at the concentration of 10 wt% and was comparable with the ones for the dissolution of cellulose in NMMO. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Surface‐active and associative properties of ionic polymeric surfactants based on carboxymethylcellulose
Authors: Tomanová Vladimíra , Sroková Iva , Ebringerová Anna , Sasinková Vlasta 
Published: May 2011

AbstractPolymeric biosurfactants were prepared by the transesterification reaction between rapeseed oil triacyl glycerides and carboxymethylcellulose (CMC). The reaction was performed in H2O/N,Ndimethylformamide (DMF) with potassium laurate as catalyst at various reaction conditions using microwave radiation as heating source. The structural features of the obtained water‐soluble CMC derivatives were characterized Fourier‐transform infrared (FT‐IR) spectroscopy and their behavior in dilute aqueous solutions was investigated by surface activity measurements, viscometry and with a polarity probe, the Coomassie Brilliant Blue dye. All derivatives showed a very low esterification extent and moderate surface tension lowering effect. Nevertheless, they exhibited significant emulsifying efficiency comparable to that of the synthetic surfactant, Tween 20. They establish hydrophobic associations in bulk solution while adsorbing on the air/water interface. The presence of hydrophobic substituents in CMC molecules enhanced the hydrophobicity resulting in higher emulsion stability than produced by Tween 20. The results suggested that suitable polymeric biosurfactants applicable as emulsifying agents can be prepared from CMC under microwave heating at low microwave power and reaction times in the range of few minutes, what represents a great advantage in comparison with transesterification reactions lasting up to 6 h at conventional heating. POLYM. ENG. SCI., 2011. ©2011 Society of Plastics Engineers.
A general quantitative structure–property relationship treatment for dielectric constants of polymers
Authors: Xu Jie , Wang Lei , Liang Guijie , Wang Luoxin , Shen Xiaolin 
Published: May 2011

AbstractThe dielectric constant (ε) of a polymer represents the capacitance of the polymer relative to a vacuum and is important in many industrial applications. Nevertheless, accurate experimental ε values of polymers are often unavailable, and current prediction methods lack universality and suitability. Reported here is the development and testing of a new QSPR (quantitative structure property relationship) correlation of ε for polymers. The entire set of 57 polymers was divided into a training set of 45 polymers and a test set of 12 polymers according to Kennard and Stones algorithm. A nine‐descriptor model, with squared correlation coefficient (R2) of 0.9384 and standard error of estimation (s) of 0.0873, was produced by using the stepwise multilinear regression analysis (MLRA) on the training set. The reliability of the proposed model was further illustrated using various evaluation techniques: leave‐one‐out cross‐validation procedure, randomization tests, and validation through the test set. POLYM. ENG. SCI., 2011. ©2011 Society of Plastics Engineers.
The chlorosome of Chlorobaculum tepidum: Size, mass and protein composition revealed by electron microscopy, dynamic light scattering and mass spectrometry‐driven proteomics
Authors: Kouyianou Kalliopi , De Bock Pieter‐Jan , Müller Shirley A. , Nikolaki Antigoni , Rizos Apostolos , Krzyžánek Vladislav , Aktoudianaki Aikaterini , Vandekerckhove Joël , Engel Andreas , Gevaert Kris , Tsiotis Georgios 
Published: May 2011

AbstractChlorosomes, the antenna complexes of green bacteria, are unique antenna systems in which pigments are organized in aggregates. Studies on isolated chlorosomes from Chlorobaculum tepidum based on SDS‐PAGE, immunoblotting and molecular biology have revealed that they contain ten chlorosomal proteins, but no comprehensive information is available about the protein composition of the entire organelle. To extend these studies, chlorosomes were isolated from C. tepidum using three related and one independent isolation protocol and characterized by absorption spectroscopy, tricine SDS‐PAGE, dynamic light scattering (DLS) and electron microscopy. Tricine SDS‐PAGE showed the presence of more than 20 proteins with molecular weights ranging between 6 and 70 kDa. The chlorosomes varied in size. Their hydrodynamic radius (Rh) ranged from 51 to 75 nm and electron microscopy indicated that they were on average 140 nm wide and 170 nm long. Furthermore, the mass of 184 whole chlorosome organelles determined by scanning transmission electron microscopy ranged from 27 to 237 MDa being on average 88 (±28) MDa. In contrast their mass‐per‐area was independent of their size, indicating that there is a strict limit to chlorosome thickness. The average protein composition of the C. tepidum chlorosome organelles was obtained by MS/MS‐driven proteomics and for the first time a detailed protein catalogue of the isolated chlorosomal proteome is presented. Based on the proteomics results for chlorosomes isolated by different protocols, four proteins that are involved in the electron or ion transport are proposed to be tightly associated with or incorporated into C. tepidum chlorosomes as well as the ten Csm proteins known to date.
Proteomic changes in articular cartilage of human endemic osteoarthritis in China
Authors: Ma Wei‐Juan , Guo Xiong , Liu Jiang‐Tao , Liu Rui‐Yu , Hu Jian‐Wen , Sun An‐Guo , Yu Yue‐Xiang , Lammi Mikko J. 
Published: May 2011

AbstractKashin–Beck disease (KBD) is a chronic endemic osteochondropathy with unclear pathogenesis. It is a degenerative disease similar to osteoarthritis, but with different manifestations of cartilage damage. The aim of this investigation was to show the protein changes in KBD cartilage and to identify the candidate proteins in order to understand the pathogenesis of the disease. Proteins were extracted from the media of primary cell cultures of KBD and normal chondrocytes, and separated by two‐dimensional fluorescence difference gel electrophoresis (2‐D DIGE). MALDI‐TOF/TOF analysis revealed statistically significant differences in 27 proteins from KBD chondrocyte cultures, which consisted of 17 up‐regulated and ten down‐regulated proteins. The results were further validated by Western blot analysis. The proteins identified are mainly involved in cellular redox homeostasis and stress response (MnSOD, Hsp27, Peroxiredoxin‐1, and Cofilin‐1), glycolysis (PGK‐1, PGM‐1, α‐enolase), and cell motility and cytoskeletal organization (Actin, Calponin‐2, and Keratin). These KBD‐associated proteins indicate that cytoskeletal remodeling, glycometabolism, and oxidative stress are abnormal in KBD articular cartilage.
Adhesive and Structural Failures of Oxide Coatings on Plasma‐Treated Polymers
Authors: Yun Jungheum , Lee Sunghun , Bae Tae‐Sung , Yun Youngmok , Lee Seunghoon , Kwon Jung‐Dae , Lee Gun‐Hwan 
Published: May 2011

AbstractThis study discloses (i) the chemical and morphological modifications in acrylate hard‐coat and bare polyethylene terephthalate polymers occurring in the course of Ar plasma treatments and (ii) the effects of these modifications on the adhesion, barrier performance, and cohesion of silicon oxide coatings deposited on the polymers. It is concluded that the deterioration in these coating properties is dominated by the formation of nanoscopic globular polymer protrusions on the polymer surface as a result of plasma treatment. The protrusions evolve even under very mild plasma conditions in which an ion fluence of less than 1 × 1016 ions · cm−2 is applied with low‐energy ion irradiation of 6 eV. The polymer protrusions dictate the nucleation and subsequent growth of a coating by promoting the development of a three‐dimensional granular morphology in the coating. At the initial oxide nucleation stage, the wetting behavior of silicon oxide on the polymer surface in the presence of nanoscopic protrusions is directly limited by the area number density and size of the protrusions. Incomplete wetting of the protrusions with a silicon oxide coating hinders adhesion between the oxide and the polymer surface. The reduction in the contact area between the oxide and the protrusions is identified as the reason that a weak boundary layer forms at the oxide–polymer interface. Furthermore, the formation of nanoscopic defects, predominantly pinholes, is inevitable in the granular coating morphology on the polymer protrusions and weakens the oxide coating's barrier performance and cohesion strength. Variations in the polar surface free energy and chemical composition of the plasma‐treated polymer surface are irrelevant to the wetting dynamics whenever the protrusions develop on the polymer surface. The effects of the polar surface free energy and chemical composition are valid only to the extent that the plasma treatment improves the wettability of a polymer surface without protrusion formation. magnified image
Grain boundary electrochemistry of β‐type Nb–Ti alloy using a scanning droplet cell
Authors: Woldemedhin Michael Teka , Raabe Dierk , Hassel Achim Walter 
Published: May 2011

AbstractLocalized oxide spots were grown at the grain boundaries of a technically relevant 30 at.% Nb–Ti β‐type titanium alloy to study the local electrochemical response. The grain boundaries selected were combinations of grains having different orientations and grain boundary angle. Crystallographic information of the grains and boundary angles were revealed by electron back scattering diffraction (EBSD) technique. Cyclic voltammetry is the electrochemical technique used to grow the oxides starting from 0 V and increasing the potential in steps of 1 V till 8 V at a scan rate of 100 mV s−1 in an acetate buffer of pH 6.0. Electrochemical impedance spectroscopy was used to investigate the electrical properties of the oxide/electrolyte interface in the frequency range between 100 kHz and 100 mHz. Important oxide parameters such as formation factor and dielectric number were determined from these measurements. Significant differences were observed for different grain boundaries. The semiconducting properties of the oxides at the grain boundaries were assessed by using Mott–Schottky analysis on a potentiostatically grown oxide. All the oxides showed n‐type semiconducting properties where the donor concentration varies with the grain boundaries mentioned above. A flat band potential −0.25 ± 0.02 V versus standard hydrogen electrode is more or less the same for all the boundaries studied.magnified image
Optical gain in AlGaN/AlGaN multiple quantum wells grown on high temperature AlN multiple buffers
Authors: Gong Y. P. , Xing K. , Wang T. 
Published: May 2011

AbstractAmplified spontaneous emission spectra measurements have been carried out on two AlGaN/AlGaN multiple quantum well (MQW) structures grown using two different kinds of high‐temperature AlN buffers, both showing a clear stimulated emission at 340 nm. This allows for investigation of optical gain of the MQWs. Based on a classic method of stripe‐length dependent optical pumping, the gain spectra have been obtained, showing a higher gain along m‐axis than that along a‐axis (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Why are nitride lasers limited to the spectral range from ∼340 to 530 nm?
Authors: Sharma Tarun Kumar , Towe Elias 
Published: May 2011

AbstractWe recently suggested that careful optimization of residual strain in nitride laser structures could be used to extend the operating wavelength into the red and infrared spectral region (Sharma and Towe, J. Appl. Phys. 106, 104509 (2009) and Appl. Phys. Lett. 96, 191105 (2010) [1, 2]). At the other wavelength extreme, in the ultraviolet, non‐optimal residual strain in nitride emitters with AlGaN layers and large crystal‐field splitting energies can cause a switching in emitted light polarization characteristics, leading to less efficient devices. Although Al‐rich AlGaN quantum wells favour shorter emission wavelengths, these structures also exhibit poor carrier confinement. These factors suggest that even in the ultra‐violet, the key limiting constraint for the development of lasers is the amount of residual strain in the structures. To properly resolve these issues, a critical analysis of strain, quantum confinement, and the polarization properties of nitride quantum well structures is warranted (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical and EDX‐analysis of CF4 and Ar plasma treated AlGaN/GaN HEMTs
Authors: Kotara P. , Hilt O. , Kirmse H. , Würfl J. , Neumann W. , Tränkle G. 
Published: May 2011

AbstractIn this paper we have investigated the effect of CF4 plasma treatment on AlGaN/GaN HEMTs and compared it with Ar plasma treated devices. We have investigated the electrical characteristics of the devices using transistor characteristics as wells as CV measurements in order to verify the impacts of the different treatments on the electron concentration in the 2DEG. Furthermore, a TEM‐EDX analysis was performed to find out if any fluorine incorporation in the AlGaN barrier during the CF4 plasma treatment occurs. No significant impact of the fluorine on the threshold voltage could be determined, We conclude that fluorine incorporation is not responsible for the threshold voltage shift. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Intrinsic origin of the breakdown of quasi‐cubic approximation in nitride semiconductors
Authors: Ebihara Yasuhiro , Kamiya Katsumasa , Shiraishi Kenji , Yamaguchi Atsushi A. 
Published: May 2011

AbstractWe investigate the intrinsic origin of the breakdown of the quasi‐cubic approximation in hexagonal GaN (h‐GaN) on the basis of first‐principles calculations. It is found that the breakdown is caused by the third‐nearest‐neighbour interactions as well as deviations from the “ideal wurtzite structure” in the lattice‐constant ratio (c /a) and the internal parameter (u). This means that the breakdown appears even in ideal structures. Furthermore, we investigate large strain effects on the deformation potentials. We find that the potentials of h‐GaN under large biaxial strain are significantly different from those of unstrained material, although no such difference is seen in cubic GaN. It is suggested that the nonlinearity is linked with the internal parameter (u), an additional degree of freedom. These results imply that these effects should be considered in the design of nitride‐based optical devices using strained active layers (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inner‐core vacillation cycles during the intensification of Hurricane Katrina
Authors: Nguyen Mai C. , Reeder Michael J. , Davidson Noel E. , Smith Roger K. , Montgomery Michael T. 
Published: May 2011

AbstractA simulation of Hurricane Katrina (2005) using the Australian Bureau of Meteorology's operational model for tropical‐cyclone prediction (TCLAPS) shows that the simulated vortex vacillates between almost symmetric and highly asymmetric phases. During the symmetric phase, the eyewall comprises elongated convective bands and both the low‐level potential vorticity (PV) and pseudo‐equivalent potential temperature θe fields exhibit a ring structure, with the maximum at some radius from the vortex centre. During this phase the mean flow intensifies comparatively rapidly, as the maximum acceleration of the mean tangential wind occurs near the radius of maximum mean tangential wind (RMW). In contrast, during the asymmetric phase the eyewall is more polygonal, with vortical hot towers (VHTs) located at the vertices. The low‐level PV and θe fields have monopole structures with the maximum at the centre. The intensification rate is lower than during the symmetric phase because the mean tangential wind accelerates most rapidly well within the RMW.The symmetric‐to‐asymmetric transition is accompanied by the development of VHTs within the eyewall. The VHTs are shown to be initiated by barotropic–convective instability associated with the ring‐like structure of PV in the eyewall where the convective instability is large. During the reverse asymmetric‐to‐symmetric transition, the VHTs weaken as the local vertical wind shear increases and the convective available potential energy is consumed by convection. The weakened VHTs move outwards, similar to vortex Rossby waves, and are stretched by the angular shear of the mean vortex. Simultaneously, the rapid filamentation zone outside the RMW weakens, becoming more favourable for the development of convection. The next symmetric phase emerges as the convection reorganizes into a more symmetric eyewall. It is proposed that vacillation cycles occur in young tropical cyclones and are distinct from the eyewall replacement cycles that tend to occur in strong and mature tropical cyclones. Copyright © 2011 Royal Meteorological Society