bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical investigation of amplified spontaneous emission in an active structure by extended (3×3)transfer matrix formalism: the case of a non-uniform longitudinal distribution of emitters
Authors: Boucher Yann G.
Published: February 2007

We use an extended (3×3) Transfer Matrix Formalism (TMF) to investigate the properties of Amplified Spontaneous Emission (ASE) in an active structure that exhibits a non-uniform spatial distribution of emitters along its longitudinal axis. The spectral density of power of the internal and emitted fields, both filtered into the transfer function of the structure, are expressed analytically in structural dimensionless parameters. We show that a periodically modulated distribution of emitters inside a cavity, in spite of their being spatially non-coherent, are responsible for a cross-interference product that can lead to an unexpected resonant enhancement of the spectral selectivity.
Multi-kernel deconvolution applied to confocal fluorescence microscopy with engineered point spread function
Authors: Simon Bertrand , Haeberlé Olivier
Published: February 2007

Fluorescence microscopy is a powerful technique in biology, because of the immense variety of markers now available. Compared to other methods, its resolution is however limited. In wide–field microscopy, the technique of structured illumination permits to improve the lateral resolution by a factor of two, even surpassing confocal microscopy, which permits a theoretical gain of about 40%. We propose an alternate technique, combining laterally interfering focused beams, which should permit the same gain of resolution in a confocal microscope. Furthermore, this technique, combined with multiple acquisition and multikernel deconvolution, permits a better object reconstruction than classical monokernel deconvolution using a regular excitation point spread function.
Polarization insensitive blazed diffraction gratings
Authors: Bonod Nicolas , Popov Evgeny , Enoch Stefan , Néauport Jérôme
Published: February 2007

Gratings insensitive to light polarization may be useful in many areas of optical engineering, particularly in light demultiplexing application. We study different kinds of binary gratings able to present reflected efficiencies higher than 98% in the –1st order. These are metallic gratings, dielectric gratings deposited on a metallic substrate, total internal reflection gratings and gratings lying on a dielectric multilayer. We study each configuration with respect to manufacturing constraints and optical performances to conclude by providing the most suitable design.
Plasmonic Marangoni forces
Authors: Lereu A. L. , Passian A. , Farahi R. H. , Zahrai S. , Thundat T.
Published: February 2007

Localized surface-tension-driven forces (microscale Marangoni effect) caused by a temperature inhomogeneity from the decay of optically excited surface plasmons into phonons have been engaged in the actuation of adsorbed and applied liquid on a thin metal film. Microfluidic operations of transport, separation, mixing, and sorting have been experimentally and theoretically demonstrated using this all-optical modulation scheme.
Inversion of a guided optical vortex
Authors: Carpentier A. V. , Michinel H. , Salgueiro J. R. , Doval S. , Ferrando A.
Published: February 2007

We demonstrate, both theoretically and experimentally, the inversion of the topological charge of a vortex that propagates through an optical fiber. In our experiment, we couple the vortex to a two-mode fiber and we control the charge inversion by deformation of the optical fiber.
Liquid-infiltrated photonic crystals: Ohmic dissipation and broadening of modes
Authors: Mortensen Niels Asger , Ejsing Simon , Xiao Sanshui
Published: February 2007

The pronounced light–matter interactions in photonic crystals make them interesting as opto–fludic “building blocks” for lab–on–a–chip applications. We show how conducting electrolytes cause dissipation and smearing of the density–of–states, thus altering decay dynamics of excited bio–molecules dissolved in the electrolyte. Likewise, we find spatial damping of propagating modes, of the order dB/cm, for naturally occurring electrolytes such as drinking water or physiological salt water.
Axial spectral scans of polarization dependent third harmonic generation in a multimode photonic crystal fiber
Authors: Lorenc D. , Bugar I. , Uherek F. , Szpulak M. , Urbanczyk W. , Zheltikov A. M.
Published: February 2007

We demonstrate a nondestructive axial scanning technique for the spectrally resolved analysis of femtosecond nonlinear–optical transformation in photonic crystal fibers. This technique is applied to map the generation of a polarization–switched third harmonic of femtosecond Cr:forsterite laser pulses in a multimode silica photonic crystal fiber. Obtained results confirmed the intermodal phase–matching to be responsible for the observed polarization dependent multipeak third–harmonic generation. The axial scans revealed, that it is necessary to distinguish between the low and high energy excitation regime of the fiber sample. The proposed technique allows to measure the spectra of nonlinear signals generated in a photonic crystal fiber as a function of the propagation distance without cutting the fiber.
Non-Bragg band gaps in 1D metamaterial aperiodic multilayers
Authors: Monsoriu Juan A. , Depine Ricardo A. , Silvestre Enrique
Published: February 2007

We investigate the existence of non–Bragg band gaps in 1D aperiodic photonic structures, namely the Fibonacci and Thue–Morse lattices combining ordinary positive index materials and dispersive metamaterials. Both structures present new band gaps which, in contrast with the usual Bragg gaps, are not based on interference mechanisms. One of these non–Bragg gaps, called zero–n̄ gap and corresponding to zero (volume) averaged refractive index, has been reported to be present in Fibonacci lattices. In this paper we extend this result to other aperiodic systems, showing the existence of a zero– n̄ gap also in Thue–Morse lattices. Furthermore, we show that these systems can also support two polarization–selective non–Bragg gaps: the zero permeability, and the zero permittivity gaps. Some distinctive aspects of these gaps are outlined and the impact on the photonic spectra produced by the level of the generation of the aperiodic structure is analyzed.
Concealment by uniform motion
Authors: Mackay Tom G. , Lakhtakia Akhlesh
Published: February 2007

The perceived lateral position of a transmitted beam, upon propagating through a slab made of homogeneous, isotropic, dielectric material at an oblique angle, can be controlled through varying the velocity of the slab. In particular, on judiciously selecting the slab velocity, the transmitted beam can emerge from the slab with no lateral shift in position. Thereby, a degree of concealment can be achieved, as exemplified by numerical simulations involving a 2D Gaussian beam.
Slow light by means of coherent population oscillations: laser linewidth effects
Authors: Piredda Giovanni , Boyd Robert W.
Published: February 2007

Several groups have recently reported the observation of slow light propagation speeds based on the process of coherent population oscillations (CPO) under conditions such that the laser line width exceeds the width of the CPO transparency window. We explain this apparently paradoxical result by noting that the CPO effect is sensitive only to intensity variations of the incident laser field that occur on time scales comparable to or shorter than the population relaxation time of the material medium. Laser linewidths are associated primarily with phase fluctuations or with intensity fluctuations on much shorter time scales.
Microlenses with annular amplitude and phase masks
Authors: Paeder V. , Scharf T. , Ruffieux P. , Herzig H.–P. , Voelkel R. , Weible K. J.
Published: February 2007

We present theoretical and experimental investigations of microlenses with both amplitude and phase masks. The light field in the focal region has been measured with a high resolution Mach–Zehnder interferometer with z–scan. The experimental results show good agreement with simulation. We show that we can obtain effects as diverse as squeezing or expansion in longitudinal and lateral directions, focal point splitting and focal shift. These effects may be of interest for applications such as Shack–Hartmann wavefront sensing, integral imaging, optical tweezers and confocal microscopy.
A Model to Optimize a Microwave PBG Accelerator Based on Generic Unit Cell
Authors: Diana Roberto , Giorgio Agostino , Marani Roberto , Passaro Vittorio M. N. , Perri Anna Gina
Published: February 2007

In this paper a numerical method, based on the well known Floquet–Bloch theory, useful to analyze the physical properties of a PBG based accelerator, is presented. The proposed model has been developed to analyze a 2D lattice characterized by a generic inclination angle between the two primitive translation vectors, thus resulting very useful when a periodic structure without an equilateral triangular or square cell has to be investigated. The numerical method has been optimized in order to account several number of space harmonics with a low CPU time and memory consumption. Comparisons with more complex numerical methods demonstrate the accuracy of our model. Several simulations have been performed to find all the geometrical parameters including the inclination angle of the unit cell, filling factor and index contrast. The proposed method, through an optimization procedure of the photonic band structure, allows to obtain a large spectral purity, high order mode suppression and high Q–values.
Effects of partial coherence on frequency combs
Authors: Torres–Company Víctor , Lajunen Hanna , Friberg Ari T.
Published: February 2007

We give an analytical model to study the deviations from an ideal frequency comb when the effects of random variations, from pulse to pulse, in the amplitude, phase, shape, chirp, and timing jitter are simultaneously taken into account. This model is consistent with the previous experimental research and extends the theoretical work on spectral line widths of mode–locked lasers.
Strehl ratio and optimum focus of high-numerical-aperture beams
Authors: Janssen Augustus J.E.M. , van Haver Sven , Braat Joseph J.M. , Dirksen Peter
Published: February 2007

We analytically calculate the focus setting for a beam with a high numerical aperture (NA) that optimizes its Strehl ratio in the case of small aberrations up to the ’just’ diffraction-limited value (Strehl ratio ≥0.80). The optimum focus setting deviates from the one that follows from a minimization of the wavefront aberration with the aid of the Zernike aberration coefficients. This deviation stems largely from the fact that the common quadratic approximation of the focus term becomes inadequate in the high-NA case. Fundamental high-NA amplitude nonuniformity in the exit pupil of an optical system in the case of a linearly polarized incident beam also influences the optimum focus setting. Results for spherical aberration and astigmatism are presented for an NA-value of 0.95.
Animal Health Assurance
Authors: Donovan John , Brown Patricia
Published: February 2007

A program to ensure the health of laboratory animals and to provide a stable environment for their maintenance is necessary to reduce unwanted variables or complicating factors in experimentation. To ensure animal health throughout a research study, the animals involved should be procured in good health, monitored for continued health status, and protected from pathogenic organisms through testing of any biological materials. This unit addresses all three of these health management practices. Essential in support of these practices is a diagnostic laboratory capable of testing for rodent and rabbit pathogens.
Generation of Epstein‐Barr Virus (EBV)–Immortalized B Cell Lines
Authors: Tosato Giovanna , Cohen Jeffrey I.
Published: February 2007

Immortalization of B lymphocytes by EBV is an effective procedure for inducing long‐term growth of certain human B lymphocytes. The protocol described in this unit to accomplish this can be divided into three stages: preparation of virus, preparation of target cells to be immortalized, and EBV infection and growth of infected cells.
Characterization of Bacteria in Mixed Biofilm Communities Using Denaturing Gradient Gel Electrophoresis (DGGE)
Authors: Welsh Allana K. , McLean Robert J.C.
Published: February 2007

Most microorganisms in nature, including those within biofilms, live in mixed populations. PCR‐based molecular genetic techniques are very useful in studying microbial diversity since unculturable as well as culturable organisms can be investigated. One such technique is denaturing gradient gel electrophoresis (DGGE), which separates PCR‐amplified community 16S rRNA (and other gene) sequences on the basis of G+C content. Unlike other community fingerprinting techniques, bands from DGGE gels can be excised, and sequenced to identify community members. Thus DGGE can be used to describe overall microbial diversity as well as to identify individual community members. This protocol describes a method for using DGGE to study microbial diversity within biofilm populations.
Isolation and Culture of Human Umbilical Vein Endothelial Cells (HUVEC)
Authors: Cheung Ambrose L.
Published: February 2007

Human‐derived endothelial cells can now be routinely harvested from human umbilical veins. Studies with human umbilical vein endothelial cells (HUVEC) have been conducted with cells from passage 2 to 5. It is now also possible to cryopreserve primary and early‐passaged HUVEC for future propagation and for forwarding to an end user by express courier. Stored HUVEC have been stably retrieved even after several years. These retrieval techniques have facilitated the deployment of HUVEC for many studies, including those for homeostasis, inflammatory disorders, atherosclerosis, cancer, and microbial adhesion and invasion. In this unit, we will delineate the procedure for harvesting, propagation, and storage of HUVEC.
Direct sulfation of limestone
Authors: Hu Guilin , Dam‐Johansen Kim , Wedel Stig , Hansen Jens Peter
Published: February 2007

The direct sulfation of limestone was studied in a laboratory fixed‐bed reactor. It is found that the direct sulfation of limestone involves nucleation and crystal grain growth of the solid product (anhydrite). At 823 K and at low‐conversions (less than about 0.5 %), the influences of SO2, O2 and CO2 on the direct sulfation of limestone corresponds to apparent reaction orders of about 0.2, 0.2 and −0.5, respectively. Water is observed to promote the sulfation reaction and increase the apparent reaction orders of SO2 and O2. The influence of O2 at high O2 concentrations (> about 15 %) becomes negligible. In the temperature interval from 723 K to 973 K, an apparent activation energy of about 104 kJ/mol is observed for the direct sulfation of limestone. At low temperatures and low conversions, the sulfation process is most likely under mixed control by chemical reaction and solid‐state diffusion. The nucleation and crystal grain growth of the solid product, and this mixed control mechanism provide satisfactory explanations of the various phenomena related to the direct sulfation of limestone, such as porosity in the product layer, the variation of the apparent reaction orders of SO2, O2 and CO2 with reaction conditions and the influence of water. © 2007 American Institute of Chemical Engineers AIChE J, 53: 948–960, 2007
Treatment of diuretic refractory pleural effusions with bevacizumab in four patients with primary systemic amyloidosis
Authors: Hoyer Robert J. , Leung Nelson , Witzig Thomas E. , Lacy Martha Q.
Published: February 2007

Refractory pleural effusions present a challenging management problem and are associated with a poor prognosis in patients with primary systemic amyloidosis (AL). We report a series of four patients with AL who presented with bilateral pleural effusions that were refractory to diuretic therapy. After treatment with bevacizumab, an antivascular endothelial growth factor (VEGF) antibody, three of the four patients had improvement in their pleural effusions, peripheral edema, and functional status. Additional studies are needed to further define the role of bevacizumab in the management of this group of patients. Am. J. Hematol., 2007. © 2007 Wiley‐Liss, Inc.
Unkonventionelle gemischtvalente Komplexe des Rutheniums und Osmiums
Authors: Kaim Wolfgang , Lahiri Goutam Kumar
Published: February 2007

In den letzten Jahren ist es gelungen, das Repertoire gemischtvalenter Ruthenium‐ und Osmiumkomplexe über konventionelle Systeme hinaus zu erweitern, indem anspruchsvollere Liganden eingesetzt und vielgestaltigere Koordinationssituationen herbeigeführt wurden. Zu den angewendeten Strategien zählen sowohl die Nutzung mehrzähniger Liganden (die zu mehrkernigen Komplexen und Chelatkomplexen führen) als auch der Einsatz einer oder mehrerer selbst redoxaktiver Komponenten (“nicht‐unschuldige” Liganden; Stichwort: Oxidationsstufenambivalenz). Diese Untersuchungen geben tiefere Einblicke in die Abläufe von Elektronentransfers zwischen Metallen und Liganden. Gemischtvalente Materialien können in der molekularen Elektronik und im “molecular computing” Anwendung finden.
Titelbild: Shaping Mesoporous Silica Nanoparticles by Disassembly of Hierarchically Porous Structures (Angew. Chem. 11/2007)
Authors: Li Fan , Wang Zhiyong , Stein Andreas
Published: February 2007

Kolloidkristalle aus monodispersen sphärischen Partikeln wurden als Template für makroporöse Abgüsse mit inverser Opalstruktur genutzt. Stein et al. stellen in ihrer Zuschrift auf S. 1917 ff. die Synthese von einheitlichen mesoporösen Siliciumoxidwürfeln, ‐tetrapoden und ‐kugeln durch gesteuerten Abbau von Siliciumoxidproben mit inverser Opalstruktur vor. Die Nanopartikel können durch Nanogießen repliziert werden, wobei Kohlenstoff‐ oder polymere Nanopartikel mit ähnlichen Morphologien entstehen.
Innentitelbild: Porphine Dimeric Assemblies in Organic‐Pillared Coordination Cages (Angew. Chem. 11/2007)
Authors: Ono Kosuke , Yoshizawa Michito , Kato Tatsuhisa , Watanabe Kentaro , Fujita Makoto
Published: February 2007

π‐π‐Stapelwechselwirkungen induzieren die Stapelung von Porphin‐Gästen im schachtelförmigen Hohlraum eines Koordinationskäfigs mit organischen Säulen. M. Fujita und Mitarbeiter beschreiben in ihrer Zuschrift auf S. 1835 ff., wie zwei Porphinmoleküle je nach Hohlraumgröße entweder direkt oder mit einer aromatischen Zwischenschicht stapeln (siehe Bild). Wenn der Porphin‐Gast ein Kupfer(II)‐Ion enthält, zeigt das direkt gestapelte Dimer eine spezifische CuII‐CuII‐Spin‐Spin‐Austauschwechselwirkung.
Cover Picture: Shaping Mesoporous Silica Nanoparticles by Disassembly of Hierarchically Porous Structures (Angew. Chem. Int. Ed. 11/2007)
Authors: Li Fan , Wang Zhiyong , Stein Andreas
Published: February 2007

Colloidal crystals assembled from monodisperse spherical particles, have been used to template macroporous replicas with an inverse opal structure. Stein and co‐workers describe in their Communication on page 1885 ff. that uniform mesoporous silica cubes, tetrapods, and spheroids are produced by controlled disassembly of inverse opal silica samples. The shaped nanoparticles can be replicated into carbon or polymer shapes by nanocasting techniques.
Inside Cover: Porphine Dimeric Assemblies in Organic‐Pillared Coordination Cages (Angew. Chem. Int. Ed. 11/2007)
Authors: Ono Kosuke , Yoshizawa Michito , Kato Tatsuhisa , Watanabe Kentaro , Fujita Makoto
Published: February 2007

π–π‐Stacking interactions induce the discrete stacking of porphine guests in the box‐shaped cavity of organic‐pillared coordination cages. M. Fujita and co‐workers describe in their Communication on page 1803 ff. how two porphine molecules are stacked directly or layered with an aromatic spacer depending on the cavity size (see picture). When the porphine guest contains a copper(II) ion, a CuII–CuII spin–spin exchange interaction is observed for the directly stacked dimer only.
Studies on the reaction of organotin phenoxides with ethyl propiolate catalysed by triethylamine and tin(IV) chloride
Authors: Kinart Wojciech J. , Kinart Andrzej
Published: February 2007

Different tributyltin phenoxides react at room temperature with ethyl propiolate in benzene, in the presence of tin(IV) chloride, triethylamine and their mixture to give the derivatives of 3‐phenoxyacrylic acid ethyl ester. Exceptionally, 3‐(2‐hydroxyphenyl)acrylic acid ethyl ester and 3‐(2‐hydroxy‐5‐methylphenyl)acrylic acid ethyl ester have been obtained from the reaction of tributylphenoxytin and tributyl(p‐tolyloxy)tin, respectively catalysed by SnCl4, and they have been easily hydrolysed to coumarin and 6‐methylcoumarin. Copyright © 2007 John Wiley & Sons, Ltd.
Kinetics of isothermal and nonisothermal crystallization of nylon 1313
Authors: Wang Yudong , Liu Minying , Wang Zhimin , Li Xiaoguang , Zhao Qingxiang , Fu Peng‐Fei
Published: February 2007

The crystallization process of a new polyamide, nylon 1313, from the melt has been thoroughly investigated under isothermal and nonisothermal conditions. During isothermal crystallization, relative crystallinity develops in accordance with the Avrami equation with the exponent n ≈ 2 based on DSC analysis. Under nonisothermal conditions, several different analysis methods were used to elucidate the crystallization process. The Avrami exponent n is greater in the isothermal crystallization process, indicating that the mode of nucleation and the growth of the nonisothermal crystallization for nylon 1313 are more complicated, and that the nucleation mode might include both homogeneous and heterogeneous nucleation simultaneously. The calculated activation energy is 214.25 kJ/mol for isothermal crystallization by Arrhenius form and 135.1 kJ/mol for nonisothermal crystallization by Kissinger method, respectively. In addition, the crystallization ability of nylon 1313 was assessed by using the kinetic crystallizability parameters G. Based on this parameter, the crystallizability of many different polymers was compared theoretically. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1415–1422, 2007
Ultrasound‐assisted coating of nylon 6,6 with silver nanoparticles and its antibacterial activity
Authors: Perkas N. , Amirian G. , Dubinsky S. , Gazit S. , Gedanken A.
Published: February 2007

A silver/nylon 6,6 nanocomposite containing 1 wt % metallic silver has been produced from an aqueous solution of silver nitrate in the presence of ammonia and ethylene glycol by an ultrasound‐assisted reduction method. The structure and properties of nylon 6,6 coated with silver have been characterized with X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, energy‐dispersive X‐ray, X‐ray photoelectron spectroscopy, Raman spectroscopy, and diffused reflection spectroscopy measurements. The nanocrystals of pure silver, 50–100 nm in size, are finely dispersed on the polymer surface without damaging the nylon 6,6 structure. This silver–nylon nanocomposite is stable to many washing cycles and thus can be used as a master batch for the production of nylon yarn by melting and spinning processes. The fabric knitted from this yarn has shown excellent antimicrobial properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1423–1430, 2007
Effect of fullerenes on the structure and properties of linear and crosslinked polyesterurethane ureas
Authors: Olkhov Y. A. , Jurkowski B.
Published: February 2007

Small concentrations up to 10−6 mol/cm3 of C60 fullerenes influence on both the molecular and topological structures changing at synthesis and the related mechanical properties of linear (pseudonetworked) and crosslinked polyester urethane ureas (PEUU). A crosslinked PEUU was synthesized on the base of poly(oxypropylene) macrodiisocyanate (POPMDIC) and 3,3′‐dichloro‐4,4′‐diaminodiphenylmethane (MOCA) with virtually an equimolar ratio of amine and isocyanate groups, but the linear polymer was obtained with twofold molar excess of amine groups. Fullerenes change the network density, the share of the physical branching junctions and molecular weight distribution (MWD) of the chain segments between the networking junctions. Additionally, molecular weight and the polydispersity index increase with C60 concentration in the reaction blend. This evidences to a branching role of C60 during their interaction with terminating amine groups. An influence of MWD of the chain segments between the networking junctions on tensile strength of the crosslinked and linear polymers was assumed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1431–1442, 2007
Sulfonated poly(ether ether sulfone) copolymers for proton exchange membrane fuel cells
Authors: Wang Zhe , Li Xianfeng , Zhao Chengji , Ni Hongzhe , Na Hui
Published: February 2007

Novel aromatic sulfonated poly(ether ether sulfone)s (SPEESs) with tert‐butyl groups were synthesized by aromatic nucleophilic polycondensation of disodium 3,3′‐disulfonate‐4,4′‐dichlorodiphenylsulfone (SDCDPS), 4,4′‐dichlorodiphenylsulfone (DCDPS), and tert‐butylhydroquinone (TBHQ). The resulting copolymers showed very good thermal stability and could be cast into tough membranes. The morphology of the membranes was investigated with atomic force microscopy. The proton conductivity of SPEES‐40 membranes increased from 0.062 S/cm at 25°C to 0.083 S/cm at 80°C, which was higher than the 0.077 S/cm of Nafion 117 under the same testing conditions. These copolymers are good candidates to be new polymeric electrolyte materials for proton exchange membrane fuel cells. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1443–1450, 2007
pH‐controlled uphill transport of boric acid through a poly(vinyl alcohol) (PVA) membrane
Authors: Shimada Toshio , Iizuka Atsushi , Shiojiri Kazuhiro , Yamasaki Akihiro , Yanagisawa Yukio
Published: February 2007

The uphill transport of boric acid in aqueous solutions through a thermal‐crosslinked poly(vinyl alcohol) (PVA) membrane was investigated. A normal permeation caused by the concentration difference of the boron along the PVA membrane was observed for equal pH conditions at both sides of the membrane, and higher flux was observed under an acidic condition at pH = 5.0 than under a basic condition at pH = 10.0. When the pH of one side is kept pH = 5.0 (acid side) and the other side was kept at pH = 10.0 (base side), uphill transport of boric acid from the acid side to the base side was observed under an equal initial concentration of both sides. Such an uphill transport was also observed against the concentration difference under the condition in which the initial concentration of the base side was higher than that of the acid side. The uphill transport could be explained by the difference in the permeation rates through the PVA membrane between B(OH)3, the dominant form under lower pH, and B(OH)4−, the dominant form under higher pH, which makes a complex with diols in PVA. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1451–1455, 2007
Phase structure and thermal stability of crosslinked polyurethane elastomers based on well‐defined prepolymers
Authors: Król Piotr , Pilch‐Pitera Barbara
Published: February 2007

Taking advantage of the DSC method, general procedures were presented for qualitative and quantitative evaluation of the phase separation degree and the crystalline phase content in polyurethane elastomers with well‐defined structures. Those elastomers were obtained not only in a typical one‐step method but also in the prepolymer method with the use of urethane oligomers with controlled molecular weight distribution (MWD). Prepolymers with well defined chain structures and narrow distributions of their molecular weights (MWD) Mw/Mn = 1.1–1.3 were produced in a multistage method, i.e., in step‐by‐step polyaddition of 2,4‐ and 2,6‐TDI with polyoxyethylenediols or with polycaprolactonediols of varied molecular weights. Isocyanate oligomers obtained at individual stages were then crosslinked with triethanolamine, whereas hydroxyl‐terminated oligomers were crosslinked with 4,4′,4″‐triphenylmethane triisocyanate (Desmodur RE). The obtained polyurethane elastomers were found to be characterized by the presence of five phases: soft phase consisted of flexible polyol‐type segments, crystalline phase made of soft segments, crystalline and amorphous hard phase made of hard segments, and intermediate phase, which was a composition of the soft and hard segments. The polyurethanes obtained out of prepolymers with defined MWD were characterized by better phase separation of the soft segments and increased structural order inside the hard phase as well as by better thermal stability than polyurethanes obtained from the typical one‐step method. The structural effects were also discussed on the thermal properties of the synthesized elastomers as analyzed by the TG and DTA methods. © 2007 Wiley Periodicals, Inc. J Appl PolymSci 104: 1464–1474, 2007
Pore collapse during the fabrication process of rubber‐like polymer scaffolds
Authors: Diego Raúl Brígido , Ribelles José Luis Gómez , Sánchez Manuel Salmerón
Published: February 2007

Rubbery polymer scaffolds for tissue engineering were produced using templates of the pore structure. The last step in the fabrication process consists of dissolving the template using a solvent that, at the same time, swells the scaffolding matrix that was a polymer network. Sometimes the polymer matrix is stretched so strongly that when the solvent is eliminated, i.e., the network is dried, it shrinks and is not able to recover its original shape and, consequently, the porous structure collapses. In this work we prepared, using the same fabrication process (the same template and the same solvent), a series of polymer scaffolds that results in collapsed or noncollapsed porous structures, depending on the polymer network composition. We explain the collapse process as a consequence of the huge volume increase in the swelling process during the template extraction due to the large distance between crosslinking points in the scaffolding matrix. By systematically increasing the crosslinking density the porous structure remains after network drying and the final interconnected pores were observed. It is shown that this problem does not take place when the scaffolding matrix consists of a glassy polymer network. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1475–1481, 2007
Cation exchange resin cum polymeric indicator based on sulfonated styrene/methyl acrylate copolymers
Authors: Ratna D. , Dalvi V. , Chakraborty B. C.
Published: February 2007

Styrene (ST)/methyl acrylate (MA) copolymers, having various MA contents (0–50 wt %), were synthesized in the form of a crosslinked bead and characterized by FTIR, solid state nuclear magnetic resonance (NMR) spectroscopy and elemental analysis. The copolymers were sulfonated using concentrated sulfuric acid. The copolymers with a higher MA content (20 wt % or above) undergo sulfonation even at room temperature, and higher temperature was required for the completion of sulfonation in case of the samples having lower MA content. This has been explained in terms of the polarity and porosity of the beads as has been analyzed by scanning electron microscope (SEM). The sulfonated copolymer beads show built‐in acid–base indicator property: yellow color in an acid medium changes to intense pink color at the equivalence point. FTIR and NMR studies clearly indicate that intramolecular cyclization takes place during sulfonation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1517–1522, 2007
Comparison of the curing kinetics of a DGEBA/acid anhydride epoxy resin system using differential scanning calorimetry and a microwave‐heated calorimeter
Authors: Navabpour P. , Nesbitt A. , Mann T. , Day R. J.
Published: February 2007

The cure of an epoxy resin system, based upon a diglycidyl ether of bisphenol‐A (DGEBA) with HY917 (an acid anhydride hardener) and DY073 (an amine–phenol complex that acted as an accelerator), was investigated using a conventional differential scanning calorimeter and a microwave‐heated power‐compensated calorimeter. Dynamic cure of the epoxy resin using four different heating rates and isothermal cure using four different temperatures were carried out and the degree of cure and reaction rates were compared. The cure kinetics were analyzed using several kinetics models. The results showed different activation energies for conventional and microwave curing and suggested different reaction mechanisms were responsible for curing using the two heating methods. Resins cured using conventional heating showed higher glass transition temperatures than did those cured using microwave heating. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2054–2063, 2007
Flame retardancy and char microstructure of nylon‐6/layered silicate nanocomposites
Authors: Shanmuganathan Kadhiravan , Deodhar Sarang , Dembsey Nicholas , Fan Qinguo , Calvert Paul D. , Warner Steven B. , Patra Prabir K.
Published: February 2007

We investigated the effect of organically modified clay alone and in combination with zinc borate on the thermal/flammability behavior of nylon‐6 nanocomposites. Differential thermogravimetric analysis indicated that the peak decomposition temperature was not affected by the addition of clay, but the rate of weight loss decreased with increase in clay concentration. Nanocomposite films of approximately 0.5 mm thickness with 2.5 and 5 wt % clay burned for almost the same duration as neat nylon‐6 but with reduced dripping in horizontal flame test. The 10 wt % clay nanocomposite sample burned without any dripping and the flame spread rate was reduced by 25–30%. Zinc borate/clay containing nanocomposite developed into a very good intumescent system in cone calorimeter test, swelling about 10–13 mm height prior to ignition forming a cellular char structure. This was found to be an effective composition in reducing the heat release and mass loss rate of nylon‐6 by about 65% and at par with 10 wt % clay nanocomposite. Flame retardant behavior could be attributed to distinct char morphologies observed through scanning electron microscopy. Fourier transform infrared spectroscopy of the 10 wt % clay nanocomposite char showed the presence of amides, indicating possible residual polymer within the shielded char. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1540–1550, 2007
Design, synthesis and characterization of novel electroactive polyamide with amine‐capped aniline pentamer in the main chain via oxidative coupling polymerization
Authors: Chao Danming , Ma Xiaobo , Lu Xiaofeng , Cui Lili , Mao Hui , Zhang Wanjin , Wei Yen
Published: February 2007

By oxidative coupling polymerization of the macromonomer of oligoaniline and p‐phenylenediamine we have prepared a novel electroactive polyamide, exhibiting well‐defined molecular structure, interesting spectroscopic and electrochemical properties. The well‐defined molecular structure of the electroactive polyamide was confirmed by FTIR, NMR spectroscopy, elemental analysis and X‐ray powder diffraction (XRD) and the resulting polyamide exhibit an enhanced solubility in most of the organic solvents as compared with polyaniline. The UV–Vis spectra were used to monitor the chemical oxidation process of the reduced polyamide. Electrochemical activity of the polyamide was tested in 1.0M H2SO4 aqueous solution and it shows three redox peaks, which is different from the polyaniline. Moreover, the thermal properties of the polyamide were evaluated by thermogravimetric analysis (TGA) and it shows moderate thermal resistance in the N2 atmosphere. Its electrical conductivity is about 1.04 × 10−4 S cm−1 at room temperature upon preliminarily protonic‐doped experiment. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1603–1608, 2007
Crystallization behavior of PP/PP‐g‐MAH/GFR PA66 blends: Establishment of their continuous‐cooling‐transformation of relative crystallinity diagrams
Authors: Safidine Z. , Fellahi S. , Frick A.
Published: February 2007

Polypropylene/polypropylene‐grafted‐maleic anhydride/glass fiber reinforced polyamide 66 (PP/PP‐g‐MAH/GFR PA 66) blends‐composites with and without the addition of polypropylene‐grafted‐maleic anhydride (PP‐g‐MAH) were prepared in a twin screw extruder. The effect of the compatibilizer on the thermal properties and crystallization behavior was determined using differential scanning calorimetry analysis. The hold time was set to be equal to 5 min at 290°C. These conditions are necessary to eliminate the thermomechanical history in the molten state. The crystallization under nonisothermal conditions and the plot of Continuous‐Cooling‐Transformation of relative crystallinity diagrams of both PP and PA 66 components proves that PP is significantly affected by the presence of PP‐g‐MAH. From the results it is found that an abrupt change is observed at 2.5 wt % of PP‐g‐MAH as a compatibilizer and then levels off. In these blends, concurrent crystallization behavior was not observed for GFR PA66. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1620–1626, 2007
Radiopacity evaluation of Bis‐GMA/TEGDMA/opaque mineral filler dental composites
Authors: Amirouche A. , Mouzali M. , Watts D. C.
Published: February 2007

The purpose of this work was to determine radiopacity values of composites based on (Bis‐GMA/TEGDMA) monomers, at varying monomer compositions: (25/75), (50/50), and (75/25), mixed with five different radiopacifying filler agents: BaO, BaSO4, La2O3, ZrO2, and SrO at varying loadings ranging from 0 to 80 wt %. The radiopacity of four commercial dental composites were also evaluated and used as a comparative data. Following standard radiographic technique, X‐ray radiography of 2.5 mm thickness dental composite specimens along with pure aluminum step‐wedge, a reference, were performed. The optical density of specimens was measured using a transmission densitometer and the radiopacity values of samples were expressed in term of equivalent thickness of aluminum per mm thickness of material. The lanthanum oxide filler containing composites, which is a new radiopacifying agent, exhibited the greatest radiopacity levels than all other composites, for all monomer and filler loadings studied. The radiopacity values of these composites were greater than that of human dental enamel. Strontium oxide containing composites were less radiopaque than other materials especially in the case of composites based on (Bis‐GMA/TEGDMA): (25/75). The composites containing more than 10 wt % of BaO, BaSO4, and ZrO2 for monomer compositions of (75/25) and (50/50) had radiopacity values greater than that of enamel. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1632–1639, 2007
Tensile, flow, and thermal properties of CaCO3‐filled LDPE/LLDPE composites
Authors: Liang Ji‐Zhao
Published: February 2007

Calcium carbonate (CaCO3)‐filled low‐density polyethylene (LDPE)/linear low‐density polyethylene (LLDPE) composites were fabricated by means of a twin‐screw extruder, and the tensile mechanical properties of the tubing with thickness of 0.5 mm made from these composites were measured at room temperature to identify the effect of the filler concentration on the properties of these composites. The results showed that the tensile elastic modulus increased roughly linearly with increasing weight fraction (ϕf) of the fillers. The tensile fracture strength (σb) along longitudinal direction was obviously higher than that along transverse direction under the same test conditions, especially at higher filler concentration. The values of σb of the specimens along both the two directions achieved minimum at ϕf = 20%. Furthermore, the melt flow rate (MFR) and heat enthalpy (ΔH) of the composite materials were measured. It was found that both the MFR and the ΔH decreased with the addition of ϕf. The ΔH for the composite with LDPE/LLDPE ratio of 70/30 was higher than that of the composite with LDPE/LLDPE ratio of 50/50 at the same filler concentration, but contrary to the MFR. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1692–1696, 2007
Morphologies and properties of cured epoxy/brominated‐phenoxy blends
Authors: Yokoyama Naoki , Nonaka Yasushi , Kurata Toshiharu , Sakai Shunsuke , Takahashi Shinya , Kasemura Tomoyuki
Published: February 2007

Morphologies of cured epoxy/brominated‐phenoxy blends were observed by scanning transmission electron microscopy (STEM) and energy dispersive X‐ray fluorescence spectroscopy (EDX). When brominated‐phenoxy content was 30 wt %, cocontinuous phase structures between cured epoxy and brominated‐phenoxy were found. Since every loss tangent (tan δ) curve as a function of temperature on dynamic mechanical analysis (DMA) showed 2 peaks at 128°C and 155°C respectively, cured epoxy phases and brominated‐phenoxy phases were incompatible together and Tgs of cured epoxy phases were not decreased. Tensile strength and tensile elongation of the cured blends were increased together. T‐peel adhesion strength and the lap‐shear adhesion strength were also increased together. These phenomena could be due to the cocontinuous structures consisted by the rigid cured epoxy phases of thermosets and ductile the brominated‐phenoxy phases of thermoplastics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1702–1713, 2007
Thermoanalytical, spectroscopic, and morphological study of poly(ethylene glycol)/poly(2‐acrylamido‐2‐methylpropanesulfonic acid‐co‐N‐isopropylacrylamide) semi‐interpenetrating network gels
Authors: Zhang Chi , Easteal Allan J.
Published: February 2007

Novel poly(ethylene glycol)/poly(2‐acrylamido‐ 2‐methylpropanesulfonic acid‐co‐N‐isopropylacrylamide) semi‐interpenetrating network gels were synthesized with free‐radical initiation at 70°C and characterized with differential scanning calorimetry, Fourier transform infrared and X‐ray photoelectron spectroscopy, X‐ray diffraction, and scanning electron microscopy. The first thermal decomposition peaks for semi‐interpenetrating network gels with various proportions of 2‐acrylamido‐2‐methylpropanesulfonic acid and N‐isopropylacrylamide were in the range of 278–289°C, whereas for poly (2‐acrylamido‐2‐methylpropanesulfonic acid‐co‐N‐isopropylacrylamide) copolymer gels with corresponding proportions of the comonomers, decomposition began at about 203°C. A significant proportion of the amide groups in the semi‐interpenetrating network gels with a high proportion of 2‐acrylamido‐2‐methylpropanesulfonic acid were found to be protonated as a result of the relatively strong acid strength of 2‐acrylamido‐2‐methylpropanesulfonic acid. The surface morphology of the dried gels varied with the relative proportions of the comonomers and was significantly different for the semi‐interpenetrating network gels and corresponding copolymer gels. Strong hydrophobic and hydrogen‐bonding interactions between poly (ethylene glycol) with an average molecular weight of approximately 6000 g/mol and the copolymer network were responsible for different thermal behaviors of the poly(2‐acrylamido‐2‐methylpropanesulfonic acid‐co‐N‐isopropylacrylamide) copolymer gels and the semi‐interpenetrating network gels. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1723–1731, 2007
Sonochemical deposition of silver nanoparticles on wool fibers
Authors: Hadad Liraz , Perkas Nina , Gofer Yosef , Calderon‐Moreno Jose , Ghule Anil , Gedanken Aharon
Published: February 2007

Silver nanoparticles were deposited on the surface of natural wool with the aid of powered ultrasound. The average particle size was 5–10 nm, but larger aggregates of 50–100 nm were also observed. The sonochemical irradiation of a slurry containing wool fibers, silver nitrate, and ammonia in an aqueous medium for 120 min under an argon atmosphere yielded a silver–wool nanocomposite. By varying the gas and reaction conditions, we could achieve control over the deposition of the metallic silver particles on the surface of the wool fibers. The resulting silver‐deposited wool samples were characterized with X‐ray diffraction, transmission electron microscopy, high‐resolution transmission electron microscopy, high‐resolution scanning electron microscopy, electron‐dispersive X‐ray analysis, Brunauer, Emmett, and Teller physical adsorption method, X‐ray photoelectron spectroscopy, and Raman and diffused reflection optical spectroscopy. The results showed that the strong adhesion of the silver to the wool was a result of the adsorption and interaction of silver with sulfur moieties related to the cysteine group. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1732–1737, 2007
Antimicrobial activity of cotton fabrics containing immobilized enzymes
Authors: Ibrahim N. A. , Gouda M. , El‐shafei A. M. , Abdel‐Fatah O. M.
Published: February 2007

Immobilization of α‐amylase, alkaline pectinase, and laccase enzymes onto ester‐crosslinked as well as Cu‐chelated cotton fabrics were carried out. Factors affecting the extent of enzyme‐loading and retention activities of immobilized enzymes were studied. Proper conditions for attaining higher extent of fixation along with better retained activity were studied. The degree of antimicrobial activity of treated fabric samples against gram‐negative and gram‐positive bacteria, filamentous, and nonfilamentous fungi were evaluated. The antimicrobial activity is determined by the type of substrate, i.e., Cu‐chelated > ester‐crosslinked and activated cotton substrate, and the nature of immobilized enzyme, i.e., alkaline pectinase > α‐amylase > laccase, irrespective of the used microorganism. The antimicrobial activities of the treated fabrics are completely maintained after laundering at least ten consecutive wash cycles. Further consecutive wash cycles, i.e., 20 or 30 cycles, has practically negative impact on the retained antimicrobial efficacy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1754–1761, 2007
Comparison of the kinetics of conventional and microwave methyl methacrylate polymerization
Authors: Jovanovic Jelena , Adnadjevic Borivoj
Published: February 2007

A comparative investigation of the conventional and microwaves kinetics of methyl methacrylate (MMA) polymerization was performed. A method for determining the increase of the reaction rate in the microwave field (β) was presented. It was found that at all of the investigated temperatures and powers the polymerization rates increased in the presence of microwave energy by up to 8.9 times compared with conventional polymerization. Isothermal kinetics of the conventional MMA polymerization was investigated and its parameters were determined using isoconversion method. It was found that the calculated kinetics parameters changes complexly with degree of MMA conversion (α) and are in the mutual linear functional relationship, which is so called “compensation effect.” The complex changes of the kinetics parameters with α are explained with the postulated model for the mechanism of the MMA polymerization. The kinetics of the MMA polymerization under the microwave field (MWF) with different input power was investigated and its parameters were determined on the basis of the conversion‐temperature curves and Arrhenius equation. The values of the kinetics parameters for MMA polymerization in the MWF are dependent on α and are from 1.2 to 12 times lower than that for conventional MMA polymerization. A new method for the determination of activation energy (Ea) of the investigated process in the MWF was described. Decreased Ea value of the polymerization process in the MWF compared with the conventional polymerization is explained with the formation of the nonequilibrium energetic distribution of the reactants due to the rapid transfer of energy in the reaction system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1775–1782, 2007