bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and characterization of hydrogels based on gamma irradiation of acrylic acid and methacrylic acid
Authors: El‐Din Horia M. Nizam , Hegazy El‐Sayed A. , Ibraheim Doaa M. 
Published: October 2008

AbstractIn this work, hydrogels based on different ratios of acrylic acid (AAc) and methacrylic acid (MAc) monomers were prepared by gamma radiation copolymerization. The hydrogels were characterized by IR spectroscopy and thermogravimetric analysis (TGA). The effect of temperature and pH on the degree of swelling of AAc/MAc hydrogels was also studied. The results showed that the gel fraction of AAc is relatively higher than MAc, while the gel fraction of AAc/MAc hydrogels decreased slightly with increasing the ratio of MAc monomer in the initial solution. The IR spectroscopic analysis indicates the formation of copolymer networks and the presence of hydrogen bonding. The thermal study showed that PAAc hydrogel displayed higher thermal stability than PMAc and AAc/MAc hydrogels, over the studied compositions. The results showed that PAAc hydrogel reached equilibrium swelling state in water after 4 h, whereas PMAc and AAc/MAc hydrogels reached the equilibrium after 7 h. In this regard, AAc/MAc hydrogels showed degree of swelling in water lower than PAAc and higher than PMAc hydrogels. It was found that the swelling of the hydrogels based on AAc and MAc monomers or their copolymers increases with increasing temperature up to 50°C. Moreover, it was observed that the degree of swelling of hydrogels were not affected by increasing the pH values up to 4 and increased greatly within the pH values from 5 to 9. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Wollastonite‐reinforced polypropylene composites modified with novel metallocene EPR copolymers. I. Phase structure and morphology
Authors: Švab Iztok , Musil Vojko , Pustak Anđela , Šmit Ivan 
Published: October 2008

AbstractSupermolecular structure of isotactic polypropylene/wollastonite/metallocene propylene–ethylene copolymers (iPP/W/EPR) composites was studied as a function of elastomer content (from 0 to 20 vol%) by optical, scanning, and transmission electron microscopy, wide‐angle X‐ray diffraction, and differential scanning calorimetry. Both, wollastonite and dispersed EPR particles, homogeneously incorporated into the iPP matrix, and affected the final phase structure and morphology of the iPP/wollastonite/EPR composites. Wollastonite particles were orientated plane‐parallel to the sample surface and hindered spherulite growth of the iPP matrix. EPRs enhanced plane‐parallel orientation of wollastonite and simultaneously enhanced the spherulite and crystallite growth in the iPP matrix during the solidification of polymer melt. Ternary iPP/wollastonite/EPR composites exhibited significant prevalence of separated microphase morphology (over core‐shell morphology) because of constitution similarity of P‐E and iPP chains. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers.
Processing and modeling of the mechanical behavior of natural fiber thermoplastic composite: Flax/polypropylene
Authors: El‐Sabbagh A. , Steuernagel L. , Ziegmann G. 
Published: October 2008

AbstractA proposed modeling approach to calculate the mechanical properties of thermoplastic matrices reinforced with natural fibers is suggested. This model aims to solve the great deviation trends observed in the fiber content especially out of the range 10–40% volume fraction vf. The model considers the transfer of fiber load hand over from fibers pull out to fiber load bearing. Different cases of the matrices are studied. Namely, matrix with either elastic or elastic plastic behavior, matrix with either brittle or ductile failure strain in comparison with the reinforcing fiber. Length and orientation efficiency factors for stiffness and strength are exploited. Another factor describing the even distribution of the fibers and the amount of corresponding matrix in adhesion is developed. This factor gives insight to the compounding process. Experimental plan is carried out to investigate the fiber loading of 0–50% vf and different matrices namely polypropylene PP and maleated anhydride polypropylene MAPP. The suggested model is tested versus both the current experimental data and the literature results. The model shows good matching with the experimental results in a big domain of the fiber vf. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Dynamic mechanical study of clay dispersion in maleated polypropylene/organoclay nanocomposites
Authors: Wang Yeh , Huang Syh‐W. , Guo Jiang‐Y. 
Published: October 2008

AbstractMorphological characteristics and the dynamic mechanical properties of maleic anhydride grafted polypropylene (PPgMA) and its clay‐filled nanocomposites with different degrees of clay exfoliation have been investigated. Fully and partially exfoliated samples were prepared through powered sonication and melt blending, respectively. Our results indicated that both mechanical α and β relaxations can be identified. The glass (β) transition of the nanocomposites shifted to slightly lower temperatures for nearly all formulations because of reduced chain cooperative motion. However, the broad α transition became more distinct with increasing clay loading for sonicated nanocomposites, and shifted to higher temperatures due to chain confinement of amorphous polymer chains in the crystalline region. The reinforcement in the glassy storage modulus E′ of PPgMA was examined by the Halpin–Tsai theory. The high aspect ratio of clay stacks in the fully exfoliated nanocomposites resulted in a significant increase in reinforcing efficiency. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Statistical characteristics of out‐of‐plane permeability for plain‐woven structure
Authors: Song Young Seok , Heider Dirk , Youn Jae Ryoun 
Published: October 2008

AbstractSince out‐of‐plane permeability of fiber preforms is a function of the number and arrangement of stacked layers, either many layers of preforms or numerous experiments are required to obtain an exact out‐of‐plane permeability experimentally. The reason is that there exist nesting and phase shifting when the preforms are laid up. From a statistical viewpoint, the effect of the number of preform layers on the out‐of‐plane permeability was analyzed by adopting an analytical model proposed in this study. Numerical simulation for a unit‐cell constructed based on geometry of the preform was carried out to validate the analytical model as well as experimental measurements of the permeability. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Numerical analysis of parametric effects on consolidation of angle‐bended composite laminates
Authors: Li Yanxia , Li Min , Zhang Zuoguang , Gu Yizhuo 
Published: October 2008

AbstractIn the previous study, the finite element formulation has been developed by our group based on two‐dimensional resin flow and fiber compaction model. Good agreement between simulations and experimental results was found under the one‐dimensional flow condition. In this article, the two‐dimensional model was used to simulate the consolidation of angle‐bended laminates with the convex tool in autoclave process. The effects of material properties on the consolidation were studied. It was found that the fiber bed shear modulus significantly affects the compaction behavior in the corner section of angle‐bended laminate, the fiber bed compaction property decide the laminate deformation, and the resin viscosity and fiber bed permeability affect the rate of laminate compaction and consolidation time. The angle‐bended T700/BMI QY8911‐Ilaminates were manufactured in autoclave process. The experimental data validate the numerical simulation method for the consolidation of the angle‐bended laminates. These results are greatly helpful for the optimization of processing parameters, improvement of composite parts quality, and reduction of the fabrication cost. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Repeated impact behavior of glass/epoxy laminates
Authors: Icten Bulent Murat 
Published: October 2008

AbstractThe response of glass–epoxy composites to repeated impact for various impact energies ranging from 5 to 15 J was investigated. Specimens with two different stacking sequences were studied; [0/90/0/90]S and [0/90/+45/−45]S. In addition to the room temperature, impact tests were also performed at −40°C environmental test temperature for impact energy of 15 J. Contact force‐deflection and energy‐time curves at each test and the number of impacts to failure (Nf) were obtained for each experiment. Compression after impact (CAI) tests were also conducted to determine the residual load carrying capacity of the damaged specimens. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Increasing the mass accuracy of high‐resolution LC‐MS data using background ions – a case study on the LTQ‐Orbitrap
Authors: Scheltema Richard A. , Kamleh Anas , Wildridge David , Ebikeme Charles , Watson David G. , Barrett Michael P. , Jansen Ritsert C. , Breitling Rainer 
Published: October 2008

AbstractWith the advent of a new generation of high‐resolution mass spectrometers, the fields of proteomics and metabolomics have gained powerful new tools. In this paper, we demonstrate a novel computational method that improves the mass accuracy of the LTQ‐Orbitrap mass spectrometer from an initial ±1–2 ppm, obtained by the standard software, to an absolute median of 0.21 ppm (SD 0.21 ppm). With the increased mass accuracy it becomes much easier to match mass chromatograms in replicates and different sample types, even if compounds are detected at very low intensities. The proposed method exploits the ubiquitous presence of background ions in LC‐MS profiles for accurate alignment and internal mass calibration, making it applicable for all types of MS equipment. The accuracy of this approach will facilitate many downstream systems biology applications, including mass‐based molecule identification, ab initio metabolic network reconstruction, and untargeted metabolomics in general.
Control of the mushroom phorid fly, Megaselia halterata (Wood), with plant extracts
Authors: Erler Fedai , Polat Ersin , Demir Halil , Cetin Huseyin , Erdemir Tugba 
Published: October 2008

AbstractBACKGROUND: The most serious insect pest problems affecting the cultivation of mushroom [Agaricus bisporus (Lange) Imbach] in Turkey are mushroom flies (sciarids, cecids and phorids). Mushroom phorid fly, Megaselia halterata (Wood), is the most common insect pest species during April‐October. The aim of this study was to evaluate the potential for eight botanical materials (two commercial neem‐based products and six hot‐water plant extracts) to control M. halterata populations in three successive growing periods.RESULTS: Treatment efficacy was evaluated by assessing adult emergence and sporophore damage rates compared with that of a standard insecticide, chlorpyrifos‐ethyl (positive control). All plant extracts caused significant reductions in the mean number of emerging adults and sporophore damage rates compared with the water‐treated control (negative control). Reduction in adult emergence in both neem treatments, Neemazal and Greeneem oil, was greater than that in the positive control. While Neemazal and Origanum onites L. extract had significantly lower sporophore damage rates than the positive control, there were no significant differences between the chlorpyrifos‐ethyl, Greeneem oil and Pimpinella anisum L. extract treatments.CONCLUSION: The results suggest that both neem products and hot‐water extracts of O. onites and P. anisum may be potential alternatives to conventional pesticides for the control of mushroom phorid fly. Copyright © 2008 Society of Chemical Industry
Kinetics of the thermal decomposition in CsH2PO4 superprotonic crystal
Authors: Baranov A. I. , Kopnin E. M. , Grebenev V. V. , Sin A. , Dubitsky Yu. , Caracino P. 
Published: October 2008

AbstractThermal stability of CsH2PO4 was investigated in an extended temperature range below and above the superprotonic transition. Single and polycrystalline samples were studied by optical microscopy and measurements of ac conductivity using different electrodes. The kinetics of CsH2PO4 thermal decomposition and the influence of different factors such as quality of the sample and especially its surface, heating rate, type of electrodes and atmosphere were studied in detail. Different stages of this process were identified such as induction time, surface nucleation, intensive growth of the nuclei until decomposition products completely cover the surface of the sample and growth of this layer into bulk of the crystal. Two clearly different high‐conductive states with the conductivities 0.04 S cm–1 and 0.003 S cm–1, which appear during the decomposition process, were found for the first time. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron paramagnetic resonance and electron‐nuclear double resonance of nonequivalent Yb3+ centers in stoichiometric lithium niobate
Authors: Malovichko Galina , Bratus1 Victor , Grachev Valentin , Kokanyan Edward 
Published: October 2008

AbstractLithium niobate crystals doped with ytterbium were studied using Electron Paramagnetic Resonance (EPR) and Electron Nuclear Double Resonance (ENDOR). The tremendous narrowing of EPR lines in nearly stoichiometric samples, when compared to those in congruent samples, allowed us to distinguish nine non‐equivalent centers, as well as line splitting caused by the hyperfine interaction of ytterbium electrons with the nuclear spins of two magnetic isotopes, 171Yb and 173Yb. Eight of the nine centers are described for the first time. It was found that three of the centers have axial C3 symmetry, and all others have the lowest C1 symmetry due to the presence of intrinsic defects and/or charge compensation defects in the near neighborhood of Yb3+. Characteristics of the g ‐tensor for all of the centers and hyperfine tensors for axial centers were determined. The ENDOR observations of Nb nuclei in the nearest neighborhood of Yb13+ gave direct evidence that the dominated axial Yb1 center has no charge compensator in its nearest surroundings (distant charge compensation mechanism). Both the EPR and ENDOR data for the main axial ytterbium center are explained by a supposition that Yb3+ ions substitute for Li+. Possible models for low‐symmetry centers are discussed. The obtained numerous spectroscopic parameters can be used as cornerstones for model calculations of Yb3+ centers in lithium niobate. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The FM/AFM bilayer Bethe lattice with FM or AFM interlayer interactions
Authors: Albayrak Erhan 
Published: October 2008

AbstractThe bilayer Bethe lattice with the Ising spins of the top layer having only ferromagnetic (FM) interactions and the spins of the bottom one having only antiferromagnetic (AFM) interactions were allowed to interact via the interlayer interaction either FM or AFM type. The problem was analyzed by using the exact recursion relations in a pairwise approach for given coordination numbers q = 3, 4 and 6 with equal external magnetic fields acting on the layers. The phase diagrams of the model were obtained on different planes for given system parameters by studying the ground state (GS) phase diagrams and the thermal variations of the order parameters and the response functions, i.e. the susceptibility and the specific heat, in detail. The model with five distinct GS configurations presents only the second‐order phase transition lines, i.e. the lines of the Néel temperatures TN. Two TN's were obtained for q = 6 in the transition regions from the AFM phases to the FM phases at low temperatures, as a result the TN lines show reentrant behavior for q = 6. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the band gap location and core spectra of orthorhombic IV–VI compounds SnS and SnSe
Authors: Makinistian L. , Albanesi E. A. 
Published: October 2008

AbstractWhile the orthorhombic IV–VI compounds show the typical layered behavior of that crystallography, we show that the presence of sulphur induces important changes to the band gap behaviour: both in its location, and in its character as well. Our modelling of tin sulfide (SnS) and tin selenide (SnSe), performed within an ab initio density‐functional theory (DFT) with a FP‐LAPW method, shows that the spin–orbit interaction produces slight splittings of bands in both compounds, especially in the conduction band, which are in very good agreement with measured values of the core spectra. In addition to these splittings, for SnS we found the novel feature that the spin–orbit relocates the band gap in the BZ, while it does not affect that of SnSe. Furthermore, several aspects of the crystals anisotropy may be explained upon our results on the hybridized band structure, the density of states (DOS) and the optical spectra (complex dielectric function and absorption coefficient). We satisfactorily compare our results with those available in the literature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hypothetically superhard boron carbide structures with a B11C icosahedron and three‐atom chain
Authors: Aydin Sezgin , Simsek Mehmet 
Published: October 2008

AbstractThe structural and mechanical properties are investigated for the phases of superhard boron carbide, B4C, by performing DFT/PW91 level calculations. In addition to B12 icosahedra and CCC chains, we suggest new types of hypothetically stable rhombohedral structures of boron carbide, configurations that consist of one icosahedron, B11C, and a three‐atom chain such as CBC, CCB and BCC. Our results indicate that all phases are promising superhard materials, the hardness of all of them being greater than 40 GPa. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
General form of Maxwell equations for metamaterials study
Authors: Cho Kikuo 
Published: October 2008

AbstractBased on a new, more complete form of macroscopic Maxwell equations, we discuss its influence on the studies of metamaterials, where coexisting electric and magnetic polarizations make unusual EM responses. The new scheme is derived by applying a long‐wavelength approximation to the fundamental equations of microscopic non‐local response theory, and it requires only one susceptibility tensor χcm (ω, k) to take care of all the electric and magnetic polarizations and their mutual interference in the different‐order terms of the wave vector k. This scheme reduces to the conventional one in the absence of chiral symmetry, while the Drude–Born–Fedorov equations for the phenomenological description of a chiral medium turn out to be incorrect near the resonance frequency. In the conventional description of a non‐chiral medium in terms of ε and μ, it is required to use the magnetic susceptibility defined with respect, not to H, but to B with poles at magnetic transition energies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase‐relaxation processes of excitons in semiconducting single‐walled carbon nanotubes
Authors: Ichida Masao , Kiyohara Yumie , Saito Shingo , Miyata Yasumitsu , Kataura Hiromichi , Ando Hiroaki 
Published: October 2008

AbstractWe have investigated the phase‐relaxation process of excitons in semiconducting single‐walled carbon nanotubes (SWNTs) by a time‐resolved degenerate four‐wave mixing (DFWM) method. The phase‐relaxation time (T2) estimated from the time evolution of the diffracted DFWM signals strongly depends on the temperature and excitation intensity, shorter T2 with higher temperature and excitation intensity. The experimental trend can be explained by the enhancement of phase‐relaxation rate due to frequent exciton–phonon scattering at high temperature and exciton–exciton scattering under high‐density excitation conditions. The T2 value at the weak excitation limit measured for semiconducting SWNT with a tube diameter of 1.1 nm at 2 K is estimated to be 350 fs. This T2 value is in good agreement with the homogeneous width estimated from microluminescence measurements. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exciton energy transfer in mixed J‐aggregates
Authors: Lemaistre J. P. 
Published: October 2008

AbstractA computational method to analyze the exciton energy transfer and trapping mechanisms in mixed J‐aggregates featuring a donor–acceptor system is provided. For a given geometrical configuration, the intermolecular interactions are calculated using the extended dipole method. Numerical diagonalization of the aggregate Hamiltonian is performed taking into account the static disorder. The density of states, the absorption lineshapes and the relative number of coherently coupled molecules within the donor and acceptor bands are obtained. The excitation energy transfer processes among the excited states of the donor–acceptor system (intraband and interband scatterings) are described through an exciton‐phonon coupling model. The scattering rates are calculated and used in a Master Equation to obtain the time evolution of the exciton populations after initial excitation. Our simulation method is used to analyze the excitation energy transfer between two kinds of closely spaced linear parallel chains featuring the so‐called blue (donor) and red (acceptor) structures of pseudoisocyanine molecules (PIC). It is also applied to describe the energy transfer in the mixed J‐aggregate of oxacyanine (donor) and thiacyanine (acceptor) molecules. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low‐temperature excitons produced by two‐photon excitation in high‐purity diamond crystals
Authors: Naka N. , Kitamura T. , Omachi J. , Kuwata‐Gonokami M. 
Published: October 2008

AbstractWe have observed edge emission due to free excitons and electron–hole droplets in diamond by two‐photon excitation using subpicosecond laser pulses at 257 nm. We find that excitonic temperatures under two‐photon excitation are much lower than the case of one‐photon excitation. A minimum excitonic temperature of 3.4 K is extracted by spectral analysis. In order to understand the difference of the excitonic temperatures under two‐photon and one‐photon excitations, we discuss a heating mechanism which depends on the density distribution of the electron–hole pairs in the crystal along the laser beam. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
s‐polarization Brewster's angle of stratified metal–dielectric metamaterial in optical regime
Authors: Watanabe Ryosuke , Iwanaga Masanobu , Ishihara Teruya 
Published: October 2008

AbstractWe demonstrate that the optical reflectivity for s‐polarized light vanishes at a certain angle in a stratified metal–dielectric metamaterial numerically and experimentally. The metamaterial consists of a unit cell where a Ag layer of 30 nm thickness is sandwiched by Al2O3 layers of 60 nm thickness. In order to understand the phenomenon in terms of effective permittivity and permeability, we extended a field‐sampling method. The permeability is found to be significantly different from unity, which is the origin of Brewster's angle for s‐polarization. The microscopic field distribution is readily coarse grained with the effective optical parameters. The present result is a manifestation of the magnetic response in the optical regime. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of transmission line meta‐materials at optical wavelength
Authors: Baba Takeshi , Ishihara Teruya 
Published: October 2008

AbstractFollowing the transmission line formalism, we design a metamaterial structure that exhibts negative refraction in the red part of the visible spectrum.The structure is a waveguide consisting of an Al2O3 top layer, 2D array of Au dots, an Al2O3 spacer and a Ag ground plane. The Au dot array with period of 250 nm were patterned by an electron beam lithography technique. We confirm experimentally and numerically that threre is a mode shifting to the lower energy side as the wavevector increases. Both permittivity and permeability are found to be negative in that region. Focussing effect of a flat structure, which is a characteristic feature of a negative index metamaterial, is also confirmed with FDTD caculation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)