bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time‐Dependent Permeabilities of Hydrophobic, pH‐Sensitive Hydrogels Exposed to pH Gradients
Authors: Dhanarajan Anish P. , Siegel Ronald A. 
Published: August 2005

AbstractpH‐dependent changes in permeability to glucose of a poly(N‐isopropylacrylamide‐co‐methacrylic acid) hydrogel membrane were measured with the membrane clamped between two cells. The donor cell was maintained at pH 7.0 and the receptor cell was subjected to a set of ramps in pH. Starting with the membrane in a state of high permeability to glucose, a ramp of decreasing pH led ultimately to shutoff of glucose flux. With passage of time at a fixed, low pH, however, permeability was restored to an intermediate value. Upon ramping pH back to its initial value, the initial permeability was restored. Based on light microscopy, the nonstationary permeability behavior is attributed to lateral stress‐induced morphological changes that occur in a collapsed “skin” formed on the side of the membrane facing the acidic donor solution.
Electric and Magnetic Field‐Structured Smart Composites
Authors: Varga Zsolt , Filipcsei Genovéva , Szilágyi András , Zrínyi Miklós 
Published: August 2005

AbstractThe combination of polymers with nanomaterials displays novel and often enhanced properties compared to the traditional materials. They can open up possibilities for new technological applications. The electric‐ and magnetic‐ field‐sensitive elastomers represent a new type of composites consisting of small particles, usually from nanometer range to micron range, dispersed in high elastic polymeric matrix. Coupling of electric and/or magnetic fields with elastic properties leads to a number of striking phenomena that are exhibited in response to impressed external fields.The ability of such materials to change their size and mechanical properties in a reversible manner has inherent interest, if for no other reason than the uniqueness having giant elastic response to polarization. The giant deformational effect, high elasticity, anisotropic properties, and quick response to either electric or magnetic fields open new opportunities for using such materials for various applications. Since electric and magnetic fields are convenient stimuli from the point of signal control, it is of great importance to develop and study such flexible, smart polymeric systems.
Internal Tension: A Novel Hypothesis Concerning the Mechanical Properties of the Vitreous Humor
Authors: Nickerson Charles S. , Karageozian Hampar L. , Park John , Kornfield Julia A. 
Published: August 2005

AbstractThe vitreous humor is a soft viscoelastic gel composed of a complex network of biomolecules (primarily collagen and polyhyaluronic acid, “hyaluronan”). While extensive progress has been made in identifying the components of the vitreous, lack of sufficient experimental methods has hampered previous efforts to quantitatively define its mechanical properties. To address this issue, we have developed a novel “cleat” tool geometry for dynamic shear rheometry. Using this geometry we find that the shear moduli of vitreous decline by roughly a factor of five to steady‐state values within an hour after removal from the eye. Steady‐state values (Porcine: G′ = 2.6 ± 0.9 Pa, and G″ = 0.65 ± 0.41 Pa, n = 9; Bovine: G′ = 6.5 ± 2.0 Pa, and G″ = 2.0 ± 0.6 Pa, n = 17) are significantly larger than previously reported. The decrease in modulus also correlates with a decrease in mass (65 ± 11 %, n = 8) that occurs spontaneously after the vitreous is extracted. Rheological findings, taken in combination with biochemical analyses suggest that hyaluronan, a ubiquitous polyelectrolyte in connective tissue, contributes to vitreous stiffness by inducing tension in the network in vivo.
Fluorescence Correlation Spectroscopy Study of Probe Diffusion in Poly(vinyl alcohol) Solutions and Gels
Authors: Michelman‐Ribeiro Ariel , Boukari Hacène , Nossal Ralph , Horkay Ferenc 
Published: August 2005

AbstractIn this study, we demonstrate how the diffusion of probe particles in aqueous poly(vinyl alcohol) (PVA) solutions and gels is affected by: (i) the presence of cross‐links, (ii) the cross‐link density, (iii) the polymer concentration. We apply fluorescence correlation spectroscopy (FCS) to measure the diffusion time of a rhodamine‐based fluorescent particle (TAMRA) and TAMRA‐labeled dextran in PVA solutions and gels prepared at various polymer concentrations (1% to 8.6% w/v) and cross‐link densities (1/400 to 1/50 cross‐link monomers per PVA monomers). The measurements indicate that the probe particles are slowed down with increasing polymer concentration and with increasing cross‐link density. Also, FCS can detect differences in the diffusion times measured in “fresh” and “aged” PVA solutions. We find that FCS provides a quantitative measure of network inhomogeneities.
Synthesis and Characterization of Poly(ethylene glycol) Dimethacrylate Hydrogels
Authors: Lin‐Gibson Sheng , Bencherif Sidi , Antonucci Joseph M. , Jones Ronald L. , Horkay Ferenc 
Published: August 2005

AbstractFacile synthesis and detailed characterization of photo‐polymerizable and biocompatible poly(ethylene glycol) dimethacrylates (PEGDM) and their hydrogels are described. Combined analyses of 1H NMR and MALDI‐TOF MS confirmed the formation of prepolymers of high purity and narrow mass distribution (PD < 1.02). A systematic investigation into the structure and mechanical properties of PEGDM hydrogels was performed to characterize the relationships between the network structure and gel properties. Small‐angle neutron scattering was used to characterize the structural features of hydrogels with respect to their semidilute solution precursors. A well‐defined structural length scale (correlation length) manifested as a maximum in the scattering intensity was observed for hydrogels derived from high molecular mass PEGDMs and/or high oligomer mass fractions. Hydrogels derived from lower molecular mass PEGDMs and/or low oligomer mass fractions exhibited multiple correlation lengths suggesting the formation of inhomogeneous gel structures. The shear moduli, determined from uniaxial compression measurement, showed that the gel structures correlate well with the gel mechanical properties.
New Nanophase Separated Intelligent Amphiphilic Conetworks and Gels
Authors: Iván Béla , Haraszti Márton , Erdődi Gábor , Scherble Jonas , Thomann Ralf , Mülhaupt Rolf 
Published: August 2005

AbstractAmphiphilic conetworks (APCN) are new materials composed of covalently bonded otherwise immiscible hydrophilic and hydrophobic polymer chains. The amphiphilic nature of these new crosslinked polymers is indicated by their swelling ability in both hydrophilic and hydrophobic solvents. Special synthetic techniques have been developed for the preparation of these new unique materials, such as poly(2‐hydroxyethyl methacrylate)‐l‐polyisobutylene (PHEMA‐l‐PIB), poly(methacrylic acid)‐l‐polyisobutylene (PMAA‐l‐PIB) and poly(N,N‐dimethylaminoethyl methacrylate)‐l‐polyisobutylene (PDMAEMA‐l‐PIB) (‐l‐ stands for linked by). Due to their unique architecture, macrophase separation of the immiscible components is prevented by the chemical bonding in the conetworks. As a results, phase separation leads to nanodomains with usually 2‐20 nm domain sizes as shown by AFM measurements. The nanophase separated morphology may also lead to smart temperature responsive gels with high mechanical stability, such as in the case of poly(N,N‐dimethylaminoethyl methacrylate)‐l‐polyisobutylene APCNs as discovered during these studies. In another approach, poly(2‐hydroxyethyl methacrylate)‐l‐polyisobutylene and poly(methacrylic acid)‐l‐polyisobutylene APCNs were prepared by a special two‐step process. The new PMAA‐l‐PIB polyelectrolyte APCNs possess smart (intelligent) reversible pH‐responsive properties in aqueous media. These unique conetwork structures and properties of these new emerging materials may lead to numerous new potential applications, such as smart materialk products, sustained drug release matrices, biomaterials, nanohybrids, nanotemplates etc.
Ionic Diffusion in Polymers
Authors: Boeykens Susana P. , Daraio Marta E. , Temprano Norma , Rosen Marta 
Published: August 2005

AbstractScleroglucan aqueous solutions and gels were selected to study the dependence of diffusion behavior of alkali and alkaline‐earth metal ions on matrix structural characteristics. Stokes and free diffusion experimental methods for obtaining diffusion coefficients were contrasted. Three different behaviors, corresponding to three well‐defined concentration regimes of the polymeric system were found.
Ion‐Dependent Hydration and Transparency of the Corneal Stroma, a Polyelectrolyte Biogel
Authors: Huff Joseph William , Jimoh Olanrewaju , Uhakheme Maxwell , Sukhitashvili George 
Published: August 2005

AbstractThe cornea is the clear outer window of the eye, composed primarily of dense regular connective tissue called the stroma. The tissue is composed of 70% water and parallel collagen fibrils surrounded by proteoglycans containing high concentrations of acidic and neutral glycosaminoglycans (GAGs) and contains ∼2 – 10% cells by volume. When the surface membranes covering the stroma are damaged by injury or disease, the stroma swells due to the hydrophilic nature of the polysaccharides. At the same time, swelling spreads the collagen fibrils apart and the tissue loses transparency. We investigated the role of different salts in modifying swelling behavior and transparency loss. In saline (148 mM NaCl) solution, hydration increases as a multi exponential function of time: Initially the stroma gains hydration at a fast rate, then slows down. In the presence of divalent cations, swelling behavior significantly decreased, and the effect was weakly anion‐dependent. Under imposed stromal swelling pressures, Ca++ and Mg++ inhibited hydration equally, and their effects were additive, indicating that they work by similar mechanisms. They were also concentration‐dependent, with no apparent ceiling to the effect within normal biological ionic strengths. As stated above, Mg++ and Ca++ both dehydrate stromas and decrease swelling rates compared to saline, and as a stroma hydrates, it loses transparency: visible spectrophotometry of stromas bathed in NaCl lose transparency faster than those bathed in MgSO4, because MgSO4 solutions hydrate stromas slower. Stromas bathed in Ca++ hydrated slower than those bathed in NaCl, but interestingly, high (49 – 148 mM) concentrations of Ca++ caused transparency loss almost instantly. In hyaluronin (a collagen fibril‐free polyanionic biogel), when similar concentrations of Ca++ were added, transparency also decreased. Our conclusion is that the dehydrating effects of Mg++ and low concentrations of Ca++ are due to shielding of electrostatic repulsion between anionic GAGs. The higher concentrations of Ca++ dehydrate by a combination of covalent binding to (precipitating) GAGs and/or shielding their electrostatic repulsions, and scatter light by precipitating GAGs and disrupting collagen fibril order. These techniques and ionic probes are useful for studying the structure and function of polyionic hydrogels and may be useful for modifying the materials properties of biological and synthetic gels.
Laser Micropatterning of Polylactide Microspheres into Neuronal‐Glial Coculture for the Study of Axonal Regeneration
Authors: Bakken Daniel E. , Narasimhan Sriram V. , Burg Karen J.L. , Gao Bruce Z. 
Published: August 2005

Abstract250,000 Americans suffer from spinal cord injury caused by vehicular, work, and sports related accidents[1]. After injury to the spinal cord, axons do not have the capability of regenerating across the lesioned site. To understand the mechanisms of axon regeneration and to identify a better method of regeneration, a new technique for mimicking and studying the in vivo cellular environment is needed. To meet this goal, we have developed a laser cell micropatterning system that uses a weakly focused laser beam to pattern both biological cells and nonbiological particles for the study of various cell‐cell‐polymer interactions. Using this system, we have successfully copatterned neurons, glial cells, and polymer microspheres into a viable matrix. These copatterns allow us to study the effects nerve growth factor has, when released from a degradable polymer microsphere, on a single neuron within a specific arrangement of multiple cell types.
A new concept for front‐end circuit integration: From single‐ended antenna to differential‐input connection without any external balun
Authors: Chen Hsien‐Ku , Juang Ying‐Zong , Chiu Chin‐Fong 
Published: August 2005

AbstractA new concept for a single‐ended input front‐end circuit design is proposed. The coupling of a single‐ended low‐noise amplifier (LNA) to a double‐balanced cross‐coupled mixer using a single‐to‐differential transformer is successfully implemented and then tested in the 5.725–5.825‐GHz band in order to show its feasibility. Furthermore, this idea is even useful for wide‐receive‐band applications when the bandwidth of the LNA is designed widely. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 1–4, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21063
A novel genetic‐algorithm‐based artificial magnetic conductor structure
Authors: Qiang Gao , Yan Dun‐Bao , Fu Yun‐Qi , Yuan Nai‐Chang 
Published: August 2005

AbstractIn this paper, a novel genetic algorithm (GA)‐based AMC structure, which is made up of a high‐impedance frequency‐selective surface, is introduced. The aperture‐coupled microstrip antenna using this structure has 10‐dB less back radiation and 3–4‐dB more gain than a conventional one. This structure has important reference value for antenna manufacturing. A practical antenna is fabricated, and the measured results basically agree well with the simulated ones. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 20–22, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21069
Characterization and applications of a compact CPW defected ground structure
Authors: Karyamapudi Bindu M. , Hong J.‐S. 
Published: August 2005

AbstractA compact coplanar waveguide (CPW) defected ground structure is investigated. Its frequency characteristics are modeled by full‐wave EM simulations. Some applications are investigated, including two electronic bandgap (EBG) devices which are constructed based on a periodical structure of the proposed defected ground without and with loading of lumped‐element capacitors. Also, a varactor‐tuned defected ground structure of this type has been demonstrated. The theoretical, simulated, and experimental results are presented. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 26–31, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21071
A concurrent multiband SiGe LNA for 1.8/1.9‐GHz GSM, 2.4/5.2/5.7‐GHz WLAN, and 5–7‐GHz ultrawideband (UWB) system applications
Authors: Lin Yo‐Sheng , Liao Kun‐Nan 
Published: August 2005

AbstractA concurrent multiband low‐noise amplifier (LNA) for 1.8/1.9‐GHz GSM, 2.4/5.2/5.7‐GHz WLAN, and 5–7‐GHz ultra‐wideband (UWB) system applications is realized using 0.35‐μm SiGe BiCMOS technology. The LNA occupies an area of only 600 × 300 μm, excluding the test pads, because only two inductors are used. The first stage of the LNA provides high gain and input matching simultaneously at the 1.8/1.9‐GHz GSM and 2.4/5.2/5.7‐GHz WLAN bands. The output matching of the second stage is realized by shunt‐shunt feedback. It consumes only 14.4‐mW power and achieved transducer gains (S21) of 26.6, 26.3, 24.6, 15.8, and 14.8 dB, input return losses (S11) of‐8.4,‐9.9,‐22.4,‐12.3, and‐17.1 dB, noise figures of 1.81, 1.9, 2.41, 3.4, and 2.81 dB (for fully on‐chip input matching), and noise figures of 1.5, 1.6, 2.0, 2.82, and 2.32 dB (for off‐chip input matching) at 1.8, 1.9, 2.4, 5.2, and 5.7 GHz, respectively. In addition, very low and very flat NF versus frequency characteristics (below 3.0 dB) are achieved over a very wide frequency range (from 5 to 7.2 GHz), which means the implemented LNA is also very suitable for 5–7‐GHz UWB‐system applications. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 36–41, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21074
Image technique for multiresolution time‐domain using nonsymmetric basis functions
Authors: Kovvali Narayan , Lin Wenbin , Carin Lawrence 
Published: August 2005

AbstractThe image technique is required in order to model perfect‐electric‐conductor and perfect‐magnetic‐conductor boundary conditions using the multiresolution time‐domain (MRTD) method. The strategy of directly imposing the image principle on the field‐expansion coefficients is valid only if the basis functions of the multiresolution analysis are symmetric or satisfy the interpolation property. Here we address the rigorous incorporation of the image principle into the framework of the multiresolution time‐domain using nonsymmetric basis functions which do not satisfy the interpolation property. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 44–47, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21076
Compact slot‐coupled microstrip antennas with circular polarization
Authors: Chuo Feng‐Pin , Han Tuan‐Yung , Chen Tsair‐Rong 
Published: August 2005

AbstractA compact circularly‐polarized (CP) design of a microstrip patch antennas is presented. The proposed antenna is fed by the coupling of a ring slot in the ground plane of a microstrip line. The results show that the required patch size of the proposed design at a fixed CP operating frequency has a reduction of 48%, as compared to a conventional CP microstrip antenna but, at the same time, its CP bandwidth is not decreased. Details of the simulated and experimental results are presented and discussed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 57–59, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21080
A phase‐conjugating pair of coupled, dual‐gate, self‐oscillating mixers
Authors: Christodoulou Michael G. , Chrissoulidis Dimitrios P. 
Published: August 2005

AbstractA novel phase conjugator for active retro‐directive operation is made by using twin, dual‐gate, self‐oscillating mixers mutually locked through a 12‐dB hybrid coupler. The coupling network incorporates the load of both oscillators. Reduced LO penetration is achieved at the IF port in two steps: (i) by trapping the LO signal within the dc bias lines of each self oscillating mixer and (ii) by the out‐of‐phase addition of any LO signal leakage. The input RF signal leaking through the mixers has also been suppressed by out‐of‐phase addition at the IF port. The measured results are presented for a phase conjugator designed for nominal operation at 900 MHz. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 59–62, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21081
Broadband 40‐GHz coherent source based on supercontinuum generation in highly nonlinear fiber
Authors: Xia Ge , Huang Dexiu , Chen Xiaogang , Yuan Xiuhua 
Published: August 2005

AbstractA broadband 40‐GHz coherent source, which utilizes supercontinuum (SC) generated in highly nonlinear fiber (HNLF) with large normal dispersion is investigated for the first time. In order to enhance the SC generation in the HNLF, a new scheme that applies the chirp‐pulse compensation technique is presented and confirmed by the theoretical and experimental results. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 73–76, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21085
An EMC foam‐base chip antenna for WLAN operation
Authors: Wong Kin‐Lu , Chang Chih‐Hwa 
Published: August 2005

AbstractA novel foam‐base chip antenna having an attractive property of electromagnetic compatibility (EMC) with the nearby conducting elements is presented. With the EMC property, the proposed antenna is very suitable to be applied in a mobile‐communication device as an internal antenna. For this kind of application, the antenna can be placed in very close proximity to the RF‐shielding metal case in the mobile device, without very small or negligible effects on the antenna performance, which can lead to a compact integration of the internal antenna with associated elements in the mobile device. A design example of the proposed antenna for wireless local‐area network (WLAN) operation in the 2.4‐GHz band is demonstrated. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 80–82, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21087
Circuit modeling of power/ground plane structures for printed circuit boards
Authors: Huang Chien‐Chang 
Published: August 2005

AbstractWith the increase of operating frequency and circuit‐component density, signal/power integrity issues due to ground bounces become more important for high‐speed digital systems. This paper presents a modal analysis resulting in a multiport equivalent circuit model for the power/ground plane structures in printed circuit boards including effects of dielectric, conductor, and radiation losses. Numerical results represented inZ‐parameters verified by the measured data are shown to validate the proposed approach. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 97–99, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21092
Crystallization and stereocomplexation governed self‐assembling of poly(lactide)‐b‐poly(ethylene glycol) to mesoscale structures
Authors: Slager Joram , Brizzolara Davide , Cantow Hans J. , Domb Abraham J. 
Published: August 2005

AbstractThe stereocomplex formation between enantioselective poly(lactide) (PLA) homopolymers is well understood. In this report an attempt is made to analyze the influence on the self‐assembling of the stereocomplex of enantiomorphic PLA‐PEG di‐ and tri‐blocks in different solvents. Powder diffraction studies showed the poly(ethylene glycol) (PEG) and the PLA blocks crystallize separately forming unique supra structures like rods, discs and coiled coils with dimensions in the micrometer scale in length and sub‐micrometer scale in diameter. The influence of the solvents on the crystal formation was shown in the formation of uniform structures. Discs emerged from equimolar mixtures of the D‐ and L‐configured di‐ and tri‐block copolymers, in dioxan and acetonitrile and in water the stereocomplexes crystallized mainly as rods. In some cases the rods were observed as coiled coils. The shape, the hydrophobic/hydrophilic content and the PEG coated surface of the discs give them a future potential as matrix for the controlled and targeted delivery of bioactive agents. Copyright © 2005 John Wiley & Sons, Ltd.