bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interfacial chemistry and morphology of in‐situ compatibilised PA‐6 and PBT based blends
Authors: van Duin Martin , van Gurp Marnix , Leemans Luc , Walet Monique , Aussems Marcel , Martin Philippe , Legras Roger , Machado Ana V. , Covas Jose A. 
Published: August 2003

AbstractReactive blending is the preferred route for obtaining rubber‐toughened engineering plastics. In this study the chemistry and morphology of in‐situ compatibilised PA‐6/EPM‐g‐MA blends and PBT/E‐MA‐GMA blends are compared. Despite the different chemical structures formed (PA‐6: cyclic imide; PBT: ester), the different side‐reactions that take place (PA‐6: chain scission; PBT: rubber crosslinking) and the different reaction rates (PA‐6: very fast; PBT: rather slow), a general description of reactive blending is proposed. First, a very fast physics‐controlled dispersion of the rubber phase into the polycondensate matrix occurs (from milimeter to micrometer scale). Then the interface, thus generated, is covered via graft‐copolymer formation. This results in a stabilisation against coalescence and in a reduction of the interfacial tension, enabling further dispersion of the rubber phase. In the case of PA‐6/EPM‐g‐MA blends the graft formation occurs so quickly that when the physics‐controlled dispersion is completed, the final dispersion is achieved. In the case of PBT/E‐MA‐GMA blends the graft formation is much slower and the chemistry‐controlled dispersion can hence be considered as a secondary process, yielding the final morphology.
Functionalization of polyolefins by reactive processing: influence of starting reagents on content and type of grafted groups
Authors: Passaglia Elisa , Coiai Serena , Aglietto Mauro , Ruggeri Giacomo , Rubertà Marco , Ciardelli Francesco 
Published: August 2003

AbstractPrevious studies carried out in our laboratory on the functionalization of ethylene polymers (homo and copolymers) through free radical processes, using mechanical mixers and/or extruders with diethylmaleate (DEM) and dicumyl peroxide (DCP), have shown that the presence of branched α‐olefin blocks favours degradation versus functionalization and crosslinking whereas these last are more effective with linear ethylene blocks.In this contest the present paper reports about attempts to extend the same processes to propylene polymers by benefitting of the indications of previous results. In particular the one step functionalization of EPM with two or more different groups was carried through the use of different monomers. Moreover the procedure was extended to polypropylene thus obtaining a significant functionalization degree flanked by a remarkable decrease of molecular weight.
Morphology and mechanical properties of extruded ribbons of LDPE/PA6 blends compatibilized with an ethylene‐acrylic acid copolymer
Authors: La Mantia Francesco Paolo , Scaffaro Roberto , Valenza Antonino , Marchetti Augusto , Filippi Sara 
Published: August 2003

AbstractTwo grades of low density polyethylene (LDPE) were blended with polyamide‐6 (PA) in the 75/25 and 25/75 wt/wt ratios and shaped into ribbons with a Brabender single screw extruder. An ethylene‐acrylic acid copolymer (EAA) was used in the 2 phr concentration as a compatibilizer precursor (CP). The morphology of the ribbons and its evolution during high temperature annealing were investigated by scanning electron microscopy (SEM). The results confirmed that EAA does actually behave as a reactive compatibilizer for the LDPE/PA blends. In fact, in the presence of EAA, the interfacial adhesion is improved, the dispersion of the minor phase particles is enhanced and their tendency toward fibrillation is increased, especially for the blends with the higher molar mass LDPE grade. The mechanical properties of the latter blends were found to be considerably enhanced by the addition of EAA, whereas the improvement was relatively modest for the blends with the lower molar mass LDPE. The fracture properties of double end notched samples of the ribbons prepared with the blends containing the lower molar mass LDPE grade were also studied. It was shown that, despite of the increased interfacial adhesion caused by the presence of EAA, the latter plays a measurable positive effect on the fracture properties only for the blends with LDPE as the matrix.
Dependence of the interfacial reaction and morphology development on the functionality of the reactive precursors in reactive blending
Authors: Yin Z. , Koulic C. , Pagnoulle C. , Jérôme R. 
Published: August 2003

AbstractPMMA containing 50 wt% of anthracene‐labeled PMMA chains end‐capped by a phthalic anhydride group (anth‐PMMA‐anh) has been melt blended at 180°C with PS containing 33 wt% of chains end‐capped by an aliphatic primary amine (PS‐NH2) and PS bearing 3.5 pendant amine groups (as an average) along the chains (PS‐co‐PSNH2), respectively. The reactive chains have been synthesized by atom transfer radical polymerization. Conversion of anth‐PMMA‐anh into PS‐b‐PMMA and PS‐g‐PMMA copolymers has been monitored by SEC with a UV detector. The interfacial reaction mainly occurs in the initial melting and softening stage (<1.0 min.), although at a rate which strongly depends on the number of reactive groups attached to PS chains, the higher conversion being observed for the PS‐co‐PSNH2 containing blends. The phase morphology depends on the architecture of the in‐situ formed copolymer. Indeed, a coarser phase dispersion is observed in case of the graft copolymer compared to the diblock.
Phase separation by continuous quenching: similarities between cooling experiments in polymer blends and reaction‐induced phase separation in modified thermosets
Authors: Alig Ingo , Rüllmann Maximilian , Holst Marco , Xu Jianjun 
Published: August 2003

AbstractSmall angle light scattering (SALS) has been applied to study the phase separation kinetics in a binary polymer mixture of poly(ethyl methyl siloxane) (PEMS) and poly(dimethyl siloxane) (PDMS). The phase separation was induced by cooling an initially homogeneous mixture with well defined cooling rates. The results have been compared to time resolved SALS and microscopy in the course of reaction‐induced phase separation in mixtures of an epoxy resin and polysulfone (PSU).For the critical PEMS/PDMS mixture with an upper critical point it was found in a continuous quenching experiment that the time evolution of the scattered light intensity I(q,t) scales with the cooling rate. The similarity to the scaling behavior of I(q,t) in isothermal experiments after fast quenches (scaled by the quench depth) is discussed. A secondary phase separation was found and has been explained by the competition between the growth of the two phase structure during cooling and the mutual diffusion without the assumption of gelation or vitrification.For the epoxy/PSU mixture with 15% PSU, after the appearance of a bicontinuous structure a secondary phase separation was observed. Mixtures with higher PSU‐contents formed epoxy‐rich droplets in the PSU‐rich matrix by nucleation and growth mechanism. The frustration of the structure growth can be explained by approaching vitrification of one or both phases.The similarity between continuous cooling experiments in blends and the reaction‐induced phase separation have been discussed in the generalized χN vs. composition phase diagram (N: degree of polymerization, χ: Flory‐Huggms interaction parameter).
Reactive compatibilization of epoxy/polyorganosiloxane blends
Authors: Prolongo S.G. , Cabanelas J.C. , Baselga J. 
Published: August 2003

AbstractA new thermoset material based on DGEBA with polyaminosiloxane curing agents is presented. The system shows reaction‐induced compatibilization which prevents coalescence of polysiloxane and DGEBA rich domains, leading to gradient structured morphologies. The influence of curing temperature and/or chemical nature of the siloxane on the morphology and surface microhardness were examined. When siloxane is pre‐reacted with epoxypropylphenylether (EPPE), a more homogeneous material is obtained. Microhardness profiles on the material are strongly influenced by the extension of the compositional gradients.
A new class of epoxy thermosets
Authors: Girard‐Reydet Emmanuel , Pascault Jean‐Pierre , Bonnet Anthony , Court François , Leibler Ludwik 
Published: August 2003

AbstractThe reinforcing strategies of epoxy thermosets rely on the control of the phase separation between the additive and the growing thermoset. With standard additives, such as reactive liquid rubbers, the length scale of the resulting domains is the micrometer. Here, we present a route that enable a control of the morphology down to the nanometer scale. This strategy is based upon the self‐assembly process of blends of epoxy and SBM triblock copolymers, namely Poly(Styrene‐b‐1,4 Butadiene‐b‐Methyl methacrylate). It relies on the respective affinities between the epoxy precursors and each of the three blocks. Liquid epoxy has a strong affinity for PMMA, whilst it is not miscible with polystyrene nor polybutadiene at standard processing temperatures. Thus, within the reactive system, microphase separation leads to a regular network of S‐B domains. This nanostructure is governed by thermodynamics. The size and geometry of the dispersed domains are controlled by the concentration and the ratio between blocks lengths. The domain size is of the order of magnitude of the chain length, ranging typically from 10 to 30 nanometers. What controls the blend's morphology throughout the curing process of the thermoset was one topic on which we focused our interest. Nanostructured thermosets have been obtained. These supramolecular architectures yield significant toughness improvements while preserving the transparency of the material. The reinforcing mechanisms are not yet fully understood : it is intriguing to induce significant toughening with elastomer domains smaller than 30 nanometers in diameter. Besides being efficient epoxy tougheners, SBM can broaden the scope of applications of thermosets due to specific rheological behaviors. Thanks to the self assembly process taking place in the blend of the SBM block copolymers with the epoxy thermosets precursors, the reactive solvent can be turned into a reactive gel or solid (before curing). This physical gelation is induced by the microphase separation and is thus thermoreversible. At relatively moderate loadings of block copolymers the reactive blend behaves like a thermoplastic material, with adjustable modulus and tackiness. These results evidence that SBM block copolymers open a broad area for designing new class of thermoset materials.
Blends of a new thermoplastic in a thermoset epoxy matrix
Authors: Constantin François , Fenouillot Françoise , Guillaume Jean‐Luc , Koenig Raymond , Pascault Jean‐Pierre 
Published: August 2003

AbstractProperties of thermoplastic modified epoxy network have been studied. The particularity of this work is the use of new thermoplastic epoxies whose structure is close to the final matrix. Blends of thermoset epoxy (Diglycidyl Ether of Bisphenol A/4‐4′ methylenebis [3‐chloro 2,6‐diethylaniline]) with a thermoplastic content from 5 to 40%w have been realised. Initial miscibility in the thermoset precursors shows an UCST behaviour with a maximal value near 130°C for a thermoplastic content of 10%. Due to the presence of tertiary amine and pendant hydroxyl groups on the thermoplastic backbone, epoxy amine reactions are faster than for the neat system but the thermoplastic seems not to have reacted with the thermoset network. The final blends are transparent but toughening increase is rather low.
Critical DNA damage recognition functions of XPC‐hHR23B and XPA‐RPA in nucleotide excision repair
Authors: Thoma Brian S. , Vasquez Karen M. 
Published: August 2003

AbstractIt has been reported that 80–90% of human cancers may result, in part, from DNA damage. Cell survival depends critically on the stability of our DNA and exquisitely sensitive DNA repair mechanisms have developed as a result. In humans, nucleotide excision repair (NER) protects the DNA against the mutagenic effects of carcinogens and ultraviolet (UV) radiation from sun exposure. By preventing mutations from forming in the DNA, the repair machinery ultimately protects us from developing cancers. DNA damage recognition is the rate‐limiting step in repair, and although many details of NER have been elucidated, the mechanisms by which DNA damage is recognized remain to be fully determined. Two primary protein complexes have been proposed as the damaged DNA recognition factor in NER: xeroderma pigmentosum protein A–replication protein A (XPA‐RPA) and xeroderma pigmentosum protein C‐human homolog of RAD23B (XPC‐hHR23B). Here we compare the evidence that supports damage detection by these protein complexes and propose a model for DNA damage recognition in NER based on the current understanding of the roles these proteins may play in the processing of DNA lesions. © 2003 Wiley‐Liss, Inc.
Biallelic expression of the H19 gene during spontaneous hepatocarcinogenesis in the albumin SV40 T antigen transgenic rat
Authors: Manoharan Herbert , Babcock Karlee , Willi Jonathan , Pitot Henry C. 
Published: August 2003

AbstractPrevious studies in this laboratory have demonstrated that the earliest cytogenetic alteration in the development of hepatic neoplasms in a transgenic strain of rats bearing the albumin Simian virus 40 T antigen (Alb SV40 T Ag) construct was a duplication of the chromosome 1q4.1‐1q4.2 band. In this region, in the rat genome a cluster of linked imprinted genes occurs. One of these imprinted genes, H19, which is expressed in fetal liver but not in adult liver, was found to be expressed in virtually all neoplasms investigated. A single‐nucleotide polymorphic marker in the H19 coding sequence was identified in two rat strains and utilized for the investigation of H19 imprinting. Our results reveal monoallelic expression of the maternal gene in fetal liver, but biallelic expression of the H19 gene in liver neoplasms, thus demonstrating the basis for the deregulation of the imprinted gene expression during hepatocarcinogenesis. These results suggest that the loss of genomic imprinting of the H19 gene found in the liver neoplasms of the Alb SV40 T Ag rat may result not from allelic loss, but from adverse changes in the epigenetic imprints present in the 5′‐upstream region of the H19 promoter of the parental alleles. © 2003 Wiley‐Liss, Inc.
Tunable electromagnetic bandgap performance of coplanar waveguides periodically loaded by ferroelectric varactors
Authors: Kuylenstierna D. , Subramanyam G. , Vorobiev A. , Gevorgian S. 
Published: August 2003

AbstractTo achieve tunable electromagnetic bandgap (EBG) performance, ferroelectric varactors are considered, in LC circuits, for periodically loading coplanar waveguides (CPWs). Asymmetric or symmetric tuning of the bandgap width may be achieved by changing the capacitance of the varactors in the LC circuits. To validate this concept, tunable EBG arrays based on silicon substrate CPWs, including thin film SrTiO3 (STO) varactors, are fabricated and tested experimentally. The EBGs are designed so that the first band gap starts between 20 and 30 GHz. Up to 10% tuning is achieved, under 20‐V DC applied bias, in the EBG structures. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 81–86, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11134
Lossy effects on the transient propagation in LTCC coplanar waveguides (CPWs)
Authors: Yin W. Y. , Guo B. , Dong X. T. , Gan Y. B. 
Published: August 2003

AbstractThe effects of dielectric, radiative leakage and ohmic losses in CPWs on the propagation of Gaussian and sinusoidally modulated Gaussian pulses are investigated. These CPWs are assumed to be fabricated on a single‐layer low‐temperature co‐fired ceramic (LTCC) substrate. It is shown that, based on the improved empirical formula for accurate prediction of the ohmic attenuation constant presented by Liao et al., the lossy effects in LTCC CPWs are dominated by the ohmic loss of the center and ground conductive planes in the frequency range up to 40 GHz. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 94–97, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11137
A hybrid implicit‐explicit FDTD scheme with weakly conditional stability
Authors: Huang Binke , Wang Gang , Jiang Yansheng , Wang Wenbing 
Published: August 2003

AbstractA hybrid implicit‐explicit FDTD (HIE‐FDTD) algorithm is proposed in this paper. In the HIE‐FDTD algorithm, semi‐implicit‐ and explicit‐difference schemes are imposed on two different field components, respectively, and the field component with implicit difference is updated by solving simple tridiagonal matrix equations. The HIE‐FDTD method, although conditionally stable, allows for larger time‐step size than the conventional FDTD method because the stability condition of the HIE‐FDTD method is weaker than that of the conventional Yee's FDTD algorithm. The demonstrated numerical dispersion relation of the HIE‐FDTD method is found to be identical to that of the ADI‐FDTD method. The accuracy and efficiency of the HIE‐FDTD are verified by numerical simulation results. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 97–101, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11138
Analysis of four‐wave mixing in optical fiber links with non‐uniform chromatic dispersion
Authors: Souza J. R. , Harboe P. B. 
Published: August 2003

AbstractThe four‐wave mixing (FWM) process in single‐mode optical fibers is investigated by considering that a zero‐dispersion wavelength varies along the length of the fiber link, which is represented as a series of segments with different lengths, propagation constants, and zero‐dispersion wavelengths. The results indicate that new optical frequencies are efficiently generated for particular combinations of the input‐signal wavelengths, even when the phase‐matching condition is not fully met. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 102–105, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11139
Analysis of the mixing effect in InAlAs/InGaAs metal‐semiconductor‐metal photodetectors
Authors: Aliberti K. , Stann B. , Svensson S. , Mehandru R. , Ren F. , Shen H. 
Published: August 2003

AbstractThe optoelectronic mixing effect in InAlAs Schottky‐enhanced InGaAs‐based metal‐semiconductor‐metal photodetectors (MSM‐PDs) is analyzed. The measured frequency bandwidth of the optoelectronic mixer (OEM) is less than that of a corresponding photodetector. The mixing efficiency depends on the light‐modulation, local‐oscillator, and mixed‐signal frequencies and decreases nonlinearly with a decrease in optical power. We present a circuit model of the OEM to explain the experimental results. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 108–112, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11141
Design of broadband and arbitrary profile filters using large chirped fiber grating
Authors: Xia Li , Li Xuhui , Chen Xiangfei , Wang Peng , Xie Shizhong 
Published: August 2003

AbstractA method is presented for designing and fabricating broadband and arbitrary profile filters using large chirped fiber grating. The relationship between grating reflectivity and chirp coefficient is discussed. By changing the ultraviolet (UV) light exposure dose along the grating, the complex refractive index modulation profile can be obtained. A broadband filter used for sensing with a linear reflectivity profile is produced through this method. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 115–117, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11143
Bandwidth enhancement of plastic optical fiber with multi‐step core by thermal diffusion
Authors: Lee Seihyoung , Paek Un‐Chul , Chung Youngjoo 
Published: August 2003

AbstractWe propose a novel method to enhance the bandwidth of plastic optical fiber with a multi‐step core by forming a graded‐index core through thermal diffusion in the performance stage. The numerical simulation results indicate that the bandwidth of the optical fiber can be significantly enhanced by this method. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 129–131, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11147
Accurate CAD formulas with physical insight on microstrip‐line couplers by synthetic asymptote
Authors: Tang Wanchun , Chow Y. Leonard 
Published: August 2003

AbstractThis paper obtains simple CAD formulas of a microstrip‐line coupler in even and odd modes by synthetic asymptote. The formulas relate the line structure to the even‐ and odd‐mode impedances and the effective dielectric constants. The formulas are simple and accurate, and they provide good physical insights on the design properties. The average errors are less than 2%. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 131–135, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11148
A folded metal‐plate monopole antenna for multiband operation of a PDA phone
Authors: Lin Chia‐Ching , Tung Hao‐Chun , Chen Hong‐Twu , Wong Kin‐Lu 
Published: August 2003

AbstractA novel monopole antenna, constructed easily by folding a simple metal plate, is presented. The folded metal‐plate monopole antenna shows a compact size of 10 × 10 × 70 mm3 and has three wide impedance bandwidths at about 0.9, 2.0, and 5.0 GHz, thus covering the operating bandwidths of most of the present‐day mobile communication systems (AMPS, GSM, DCS, PCS, and UMTS) and the WLAN systems in the 2.4/5.2/5.8‐GHz bands. With the antenna performance obtained, the proposed antenna is suitable for application in a PDA phone for both mobile communications and WLAN applications. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 135–138, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11149
Parabolic dish antenna with offset elliptical multi‐mode feeds for space‐borne remote‐sensing applications
Authors: Sharma S. B. , Singh V. K. , Chakrabarty S. B. 
Published: August 2003

AbstractThis paper presents the design and development of a pencil‐beam scanning parabolic reflector antenna with new multi‐mode elliptical feeds for space‐borne scatterometer application. The feeds have been laterally displaced in the focal plane of the reflector in order to achieve two squinted elliptical beams with the required angular spacing. The asymmetry in the secondary beams has been realized by illuminating the reflector with elliptic sectoral patterns of the elliptical feeds. Sectoral patterns have been synthesized by coupling power into higher‐order modes at the feed aperture. Using this new type of feed, a gain improvement on the order of 0.7 dBi has been achieved, as compared to the reflector antennas illuminated by elliptic feeds of nonsectoral patterns. The computed and measured data on primary and secondary radiation patterns have been presented. The desired gain, beam widths, beam asymmetry, angular spacing between the beams, side‐lobe level, and cross‐polarization level have been achieved. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 138–141, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11150
A dual‐band Chebyshev impedance transformer
Authors: Castaldi G. , Fiumara V. , Pinto I. M. 
Published: August 2003

AbstractThis paper presents a simple extension of the Chebyshev quarter‐wave multisection transformer synthesis to dual‐band operation. The method is a variation of the classical Chebyshev transformer design procedure, using a suitable 2nd‐order trigonometric polynomial as the argument of the Chebyshev polynomial. As compared to a single‐band Chebyshev transformer encompassing both required passbands, the proposed design yields significantly better performance. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 141–145, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11151