bluuebunny/crossref_metadata_2025 huggingface dataset:
Tunable microwave photonic frequencies generation based on stimulated Brillouin scattering operating in the L‐band region
Authors: Ahmad Harith , Norizan Siti Fatimah , Awang Noor Azura , Zulkifli M.Z. , Ghani Z. A. , Harun Sulaiman Wadi
Published: May 2011

A tunable up frequencies of microwave photonics based on stimulated Brillouin scattering (SBS) for application in radio over fiber is demonstrated. The experimental setup consists of 7.7 km dispersion compensated fiber, which acts as the nonlinear medium for generating the SBS and is pumped by a narrow linewidth (0.015 nm) tunable laser operating in L‐band region. The input‐modulated RF at 2 GHz is upshifted to new frequencies of 7.71, 7.68, 7.65, 7.62, 7.58, and 7.56 GHz at Brillouin pump wavelengths of 1580, 1585, 1590, 1595, 1600, and 1605 nm, respectively. This system allows certain tunability in the upshifted frequencies by using a tunable laser source. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26106
Compact and high selectivity broadband bandpass filter with dual‐mode folded‐T‐type resonator
Authors: Deng Hong‐Wei , Zhao Yong‐Jiu , Zhang Xue‐Shun , Chen Wen , Qiang Li
Published: May 2011

A broadband bandpass filter (BPF) with compact size and high selectivity performances is proposed using the dual‐mode folded‐T‐type resonator and the identical short stub loaded parallel‐coupling feed structure.The resonator can generate one even‐mode and one odd‐mode in the desired band. Two resonant frequencies can be adjusted easily to satisfy the bandwidth of the BPF. The feed structure can generate four transmission zeros near the cutoff frequencies and in the stopband, leading to sharp skirt and deep stopband. One filter prototype with the fractional bandwidth of 58.89% is fabricated for experimental verification of the predicted results. The size for the resonator is only 0.156λg × 0.303λg in which λg is the guided wavelength of 50 Ω microstrip line at the center frequency. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26108
Indirect evaluation of radiated emissions from a bent signal line on a printed circuit board with two attached cables
Authors: Kim Dong‐Yeon , Lee Jae W. , Cho Choon Sik , Lee Haeng S. , Chung Yeon‐Choon
Published: May 2011

In this article, the radiated emissions mechanism and the variation of radiated emissions level have been analyzed and investigated, respectively, according to the ratio of the horizontal to vertical traces in a bent signal line when a bent signal line on a printed circuit board (PCB) with two attached cables is used.Though many papers concerning two cables attached to a PCB have appeared, it is seen that the two cables can be modeled as a dipole antenna. In addition, it is conjectured from two‐ port S‐parameters that the ratio between the horizontal and vertical traces in a bent signal line leads to the variation in magnitude of common‐mode voltage induced as a noise source of the dipole antenna. As the signal line in parallel with the attached cable becomes longer, the radiated emissions level due to the current‐driven mechanism becomes more dominant while the contribution from the voltage‐driven mechanism remains unchanged regardless of the ratio between two signal lines. Based on the analysis of measured and simulated S‐parameters, we propose an alternate and relatively simple estimation method replacing the 3‐m measuring method to measure the radiated emissions level and investigate the accuracy of our analysis using commercially available software CST MWS 2006B. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26114
An active tri‐band (AMPS/PCS/GPS) antenna with enhanced cellular‐to‐GPS isolation for automotive applications
Authors: Aloi Daniel N. , Sharawi Mohammad S.
Published: May 2011

The design and performance of an active tri‐band antenna for automotive applications that includes the global positioning system (GPS), analog mobile phone service (AMPS), and personal communication service (PCS) is presented. For automotive emergency applications, the close proximity of the GPS and cellular antenna elements demands stringent isolation requirements on the GPS low noise amplifier (LNA) design to prevent interference to GPS during cellular transmissions. The GPS low‐noise amplifier designed in this letter exhibited a power gain of 26.4 dB, an out of band rejection in excess of 31 dB at +/‐50 MHz around the center frequency, a noise figure of 1.5 dB, a 1dB power compression of 9.7 dBm, isolation over the AMPS band in excess of 62 dB, isolation over the PCS band in excess of 48 dB, an input 3rd order intercept of −6.5 dBm and an output 3rd order intercept of 20.6 dBm while operating at 5 volts with a current draw of 20mA. In addition, the antenna patterns measured on a ground plane are presented for the active GPS antenna, AMPS passive antenna and the PCS passive antenna. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26117
Optical generation of microwave/millimeter‐wave based on Brillouin‐Erbium fiber laser
Authors: Liu Lan , Shen Yichun , Zheng Shilie , Jin Xiaofeng , Chi Hao , Zhang Xianmin
Published: May 2011

A novel system configuration for optical generation of microwave/millimeter‐wave (mm‐wave), which is realized through Brillouin‐Erbium fiber laser (BEFL), is investigated.The microwave/mm‐wave is generated by the mixing of the nth‐order Stokes wave and the pump wave on the high‐speed photodetector. The nth‐order Stokes wave is generated in the BEFL and filtered out by fiber Bragg grating. The experiments are carried out based on such configuration, and experimental results verify the validity of it. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26118
Design of a Bethe‐hole directional coupler using substrate integrated waveguide technique
Authors: Amine Ali , Talbi Larbi , Sellal Kheireddine
Published: May 2011

This article proposes the design of a Bethe‐hole (BH) directional coupler using substrate integrated waveguide (SIW) technique. The design can readily be coupled with, for instance, an antenna and is therefore suitable for millimeter‐wave communication systems. Good agreements have been achieved between simulated and experimental results for a 25‐dB BH SIW coupler operating in the X‐band. Directivity greater than 20‐dB and a coupling of 24.7 dB were obtained. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26119
Novel series‐fed microstrip array antenna with miniaturized feeding network for WLAN/RFID applications
Authors: Ku Chia‐Hao , Liu Hsien‐Wen , Lin Yu‐Shu
Published: May 2011

A novel series‐fed microstrip array antenna with a miniaturized feeding network suitable for wireless local area network (WLAN) and radio frequency identification (RFID) applications is presented.This array works with 10 patch elements and utilizes artificial transmission lines (ATL) to design the feeding network to well reduce the whole size. Compared to conventional series‐fed array designs, the proposed array can achieve not only a small size of merely 14 (L) × 230 (W) mm2 but also a wide operating bandwidth from 5 to 5.94 GHz. Experimental results exhibit that fairly good broadside radiation pattern with adequate half‐power beamwidth for practical application can be obtained with our array design. Therefore, the proposed microstrip array antenna with a compact size is well suitable to be integrated within the WLAN/RFID systems as a transmitting antenna. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26120
Monopole antenna based on wrench‐shaped slot on circular disc patch for UWB application
Authors: Moosazadeh Mahdi , Ghobadi Changiz , Esmati Zahra
Published: May 2011

A monopole antenna with circular‐shaped patch has been proposed for ultra wideband (UWB) applications.With lack of current at the center of circular‐shaped patch, a wrench‐shaped design has been used for modifying blind spot center of patch and reinforcement of currents. In ground plane, a square and circular shape linked notch has been placed for proper impedance matching. Proposed antenna has a small size, and operates in 3.1 to 11.91 GHz frequency band. Laboratory and simulated antenna results show that proposed antenna has an acceptable return loss level and radiation pattern characteristics for the UWB frequency band range. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26125
Design of a high‐resolution microfluidic microwave MEMS phase shifter
Authors: Ozbey Burak , Ozturk Sule , Aktas Ozgur
Published: May 2011

In this article, a novel microwave microelectromechanical phase shifter based on a microfluidic design is proposed and demonstrated.The design principles, the fabrication process, and experimental results (S‐parameters and phase shift plots) are presented. The proposed system has a high bandwidth, high‐power handling capacity, and a high‐resolution along with a small settling time. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26127
A band selected 3.1–30.1 GHz distributed amplifier in 0.18‐μm CMOS technology
Authors: Feng Wu‐Shiung , Wei Chien‐Cheng , Hsu Hui‐Chen , Chen Chia‐Hsun , Chatterjee Prasenjit , Kung Ling
Published: May 2011

A band‐selected 3.1–30.1 GHz CMOS distributed amplifier (DA) for extended UWB application is presented in this article. The proposed circuit was designed and fabricated with a 0.18‐μm CMOS technology. This circuit uses a sharpening technique to improve the frequency response from low‐pass to bandpass property, for the requirement of limited frequency band. This DA also adopts the inductive peaking technique to increase circuit's gain and bandwidth. This DA has a measured maximum power gain of 7.5 dB. The supply voltage and biasing current are 1.8 V and 28.6 mA, with total DC power of 51.48 mW. When compared with the standard DAs published over the past years, this circuit offers good abilities in band selectivity, acceptable power gain, low noise figures, and large‐signal performances. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26139
Adhesive‐fixed microbend long‐period fiber gratings with bandpass filter response
Authors: Sakata Hajime , Saito Takuya
Published: May 2011

We demonstrate an adhesive‐fixed periodic microbending whose transmission spectrum shows a bandpass filter response with the help of a fiber coil.In addition to thermal shift of the resonance wavelength, the transmission peak amplitude is varied with ambient temperature due to thermal expansion of the adhesive that maintains the microbend. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26146
Novel microwave filters based on Epsilon Near Zero waveguide tunnels
Authors: Corona‐Chavez Alonso , Murthy D. V. B , Olvera‐Cervantes Jose Luis
Published: May 2011

Microwave filters based on the concept of Epsilon Near Zero (ENZ) tunneling effect are presented. ENZ metamaterials provide interesting phenomena such as anomalous tunneling and energy squeezing through ultra narrow waveguide channels. Using this concept two filters are demonstrated with Chebyshev response and one with a quasi‐elliptic response by adding transmission zeroes with hairpin resonators. Experimental and simulated responses are presented with good agreement. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26147
Novel dual‐mode square patch bandpass filter using slot‐type SRR perturbation for mode splitting
Authors: Fu Shu‐Hong , Tong Chuang‐Ming , Li Xi‐Min , Zhou Ming
Published: May 2011

A slot‐type split‐ring resonator (SRR) as a new type of perturbation element for dual‐mode square patch resonator is introduced in this article.The slot‐type SRR used in the patch resonator allows coupling between the two degenerate modes. Moreover, coupling characteristics can be adjusted by the location of slot‐type SRR. By adding two notches in the dual‐mode filter with slot‐type SRR, the high degenerate mode near the passband is eliminated, and the center frequency is lowered slightly. It has been verified by both simulation and measurement. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26148
Demonstration of a two‐user time domain spectral phase encoding OCDMA system with variable‐bandwidth spectrum shaper‐based decoder
Authors: Gao Zhensen , Wang Xu , Kataoka Nobuyuki , Wada Naoya
Published: May 2011

We propose and experimentally demonstrate a 2.5‐Gb/s two‐user optical‐code‐division‐multiple‐access (OCDMA) system with a novel time domain spectral phase encoding scheme and variable‐bandwidth spectrum shaper (VBS)‐based spectral phase decoder. The spectral phase encoded OCDMA signal is generated by using a pair of dispersive fibers with opposite dispersion and a high speed phase modulator with rapid programmable 8‐chip, 20 Gb/s optical code patterns in time domain, and spectrally decoded using a VBS with high controlling precision of amplitude and phase. A total of 2.5‐Gb/s time domain spectral phase encoded on‐off‐keying OCDMA signal data has been successfully transmitted over 34 km fiber with error‐free. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26151
Heuristic uniform 2D double wedge diffraction based on generalized Fresnel integral
Authors: Legendre J. F. , Marsault T. , Velé T. , Cueff D.
Published: May 2011

This article describes an uniform 2D double wedge diffraction coefficient.The transition function is based on generalized Fresnel integral. First, a closed form of the dielectric single wedge diffraction based on classical heuristic TUD introduction by Luebbers is recalled. Its drawback when applied twice on double single edge diffraction is evaluated. Next, an uniform double edge diffraction based on Marhefka's spectral theory work is proposed. It is compared with other methods. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26154
Fast broadband analysis of microstrip by interpolating both impedance and preconditioning matrices with MBPE
Authors: Liu Zhiwei , Li Mengmeng , Zhang Guozhong , Chen Rushan
Published: May 2011

An interpolation scheme using model‐based parameter estimation (MBPE) for fast analysis of the microstrip structures over a wideband is proposed.The microstrip structures are analyzed by the mixed potential integral equation with the generated dense impedance matrix partitioned and compressed hierarchically by the UV method. The linear systems are solved by the generalized minimal residual method with its convergence accelerated by the sparse approximate inversion (SAI) preconditioning technique. Over a wide frequency band, both the near field impedance matrix and the SAI preconditioning matrix are interpolated by MBPE. Numerical results show that the proposed method can reduce the computation time significantly. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26155
Double modes characterization and incident light angle tuning on the photonic band gap of SiO2 colloid crystal
Authors: Wang Xin , Fan Huiqing , Ren Pengrong , Li Jin
Published: May 2011

Photonic crystal of packed monodisperse silica submicron spheres were synthesized in this article. We investigated the optical properties of packed monodisperse silica submicron spheres by means of both optical transmission and reflection measurements. Research suggests that the two methods are consistent in essence, and the reflection mode is more suitable for colloidal crystal assembled of smaller colloidal spheres. Accurately tuning of photonic band gap by incident light angle was also studied in our article. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26156
Effect of antenna envelope correlation for 2 × 2 multi‐input multioutput system in WiMAX field measurements
Authors: Kim Dongjin , Yang Taesik , Kim Minchan
Published: May 2011

This article describes the effect of antenna envelope correlation in the throughput of multi‐input multioutput (MIMO) antenna system.Despite the fact that antenna envelope correlation is a critical factor that determines the data transmitting capability of a MIMO antenna system, an appropriate level of envelope correlation for MIMO antennas in mobile communication devices has never been proposed yet. In this article, we have examined various MIMO antenna systems designed with different correlation values to provide a guideline for industrial WiMAX MIMO applications. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26158
Erratum: A broadband Fabry–Pérot cavity antenna designed using an improved resonance prediction method
Authors: Kim Dongho , Ju Jeongho , Choi Jaeick
Published: May 2011

Originally published Microwave Opt Technol Lett 53:1065–1069, 2011.© 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26229 (Original article DOI 10.1002/mop.25898)
Complete 1H and 13C NMR data assignment of protolimonoids from the stem barks of Aphanamixis grandifolia
Authors: Wang Junsong , Zhang Yao , Luo Jun , Kong Lingyi
Published: May 2011

Seven new protolimonoids, named aphagranins A–G (1–7), along with four known compounds, were isolated from the ethanol extract of the stem barks of Aphanamixis grandifolia. Structure elucidation and signal assignments were achieved on the basis of spectral and chemical evidences. Copyright © 2011 John Wiley & Sons, Ltd.
Ca2+ signaling during maturation of cumulus–oocyte complex in mammals
Authors: Silvestre F. , Boni R. , Fissore R.A. , Tosti E.
Published: May 2011

Under the influence of gonadotropins or growth factors, a close cooperation develops between cumulus cells and the oocyte that is implicated in transmitting signals involved in maintaining or releasing the meiotic arrest in the oocyte. While cyclic adenosine 5′‐monophosphate (cAMP) is a key molecule in maintaining the meiotic arrest, calcium (Ca2+) may play a role in controlling either spontaneous or gonadotropin‐induced oocyte maturation, possibly by modulating intracytoplasmic cAMP concentrations via Ca2+‐sensitive adenylate cyclases. This review focuses on the mechanisms related to the origin of the Ca2+ wave that travels from the cumulus cells to the oocyte, and discusses the source of variations affecting the dynamics of this wave. Mol. Reprod. Dev. 78:744–756, 2011. © 2011 Wiley Periodicals, Inc.
Alternate ascending/descending directional navigation approach for imaging magnetization transfer asymmetry
Authors: Park Sung‐Hong , Duong Timothy Q.
Published: May 2011

A new method for imaging magnetization transfer (MT) asymmetry with no separate saturation pulse is proposed in this article. MT effects were generated from sequential two‐dimensional balanced steady‐state free precession imaging, where interslice MT asymmetry was separated from interslice blood flow and magnetic field inhomogeneity with alternate ascending/descending directional navigation (ALADDIN). Alternate ascending/descending directional navigation provided high‐resolution multislice MT asymmetry images within a reasonable imaging time of ∼3 min. MT asymmetry signals measured with alternate ascending/descending directional navigation were 1–2% of baseline signals (N = 6), in agreement with those from the conventional methods. About 70% of MT asymmetry signals were determined by the first prior slice. The frequency offset ranges in this study were >8 ppm from the water resonance frequency, implying that the MT effects were mostly associated with solid‐like macromolecules. Potential methods to make alternate ascending/descending directional navigation feasible for imaging amide proton transfer (∼3.5 ppm offset from the water resonance frequency) were discussed. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.
The feasibility of endorectal MR elastography for prostate cancer localization
Authors: Arani Arvin , Plewes Donald , Krieger Axel , Chopra Rajiv
Published: May 2011

The objectives of this study were to evaluate the feasibility of using a rigid radio‐frequency receiver endorectal coil for intracavitary prostate magnetic resonance elastography (MRE) and to demonstrate the capability of this technique for generating stiffness maps over a typical prostate volume. An endorectal coil is currently used to help improve the signal‐to‐noise ratio of images acquired with multiparametric magnetic resonance imaging. We propose that this same coil could also serve to generate shear waves in the prostate gland during imaging, opening up the possibility of incorporating prostate stiffness characterization into multiparametric magnetic resonance imaging. Prostate cancer has been shown to change the elasticity of tissue, suggesting that stiffness imaging (elastography) may provide supplementary diagnostic information. A rigid endorectal coil was mechanically coupled to a piezoceramic actuator and used to investigate full volume (27 slices, 2‐mm thick) endorectal MRE in a prostate mimicking phantom. The low‐amplitude vibrations (±8–38 μm displacements) necessary to perform endorectal MRE did not affect the signal‐to noise ratio of the coil and endorectal MRE was capable of resolving 0.1cc (0.6 cm diameter) spherical inclusion volumes. Therefore, the results of this study, in combination with current clinical practice, motivate clinical evaluation of endorectal MRE in patients. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.
Influence of shotcrete composition on load‐level estimation in NATM‐tunnel shells: Micromechanics‐based sensitivity analyses
Authors: Ullah S. , Pichler B. , Scheiner S. , Hellmich C.
Published: May 2011

Displacement measurement‐based estimations of loads and utilization degrees in shotcrete tunnel shells as part of the New Austrian Tunneling Method (NATM), have become standard tools in tunnel practice; their quality, however, may crucially depend on the knowledge of the actual shotcrete composition after spraying. To shed light on this issue, we here determine, based on experimentally validated micromechanical representations of shotcrete, the hydration degree‐dependent elastic, creep, and strength properties of different shotcretes, characterized by water cement ratios (w/c) between 0.4 and 0.6, aggregate cement ratios (a/c) between 3.5 and 5, and Young's modulus of aggregates (Eagg) between 40 and 80 GPa. These properties are fed into a structural shell model of the Sieberg tunnel, and this model is subjected to displacement fields approximated from daily displacement measurements at five selected points along the shell's inner surface. Resulting stresses and forces in the tunnel shell allow for analyzing the influence of shotcrete composition on load‐level estimation in NATM tunnel shells: The magnitudes of circumferential and longitudinal normal forces increase significantly with decreasing w/c, while a/c and Eagg have the inverse and relatively minor effect. The utilization degree is virtually insensitive to changes in w/c(especially at early ages), and only slightly decreases with decreasing a/c and Eagg. The location of maximum loading is unaffected by the shotcrete composition underlying the analysis. Conclusively, location and magnitude of maximum utilization degrees are very robust estimates (not affected by limited knowledge on the shotcrete composition), whereas realistic estimation of stresses and forces does require more accurate consideration of shotcrete composition. Copyright © 2011 John Wiley & Sons, Ltd.
Public affairs and mining in Australia—a rescued license to operate
Authors: Allen Geoff
Published: May 2011

In 2010, the Australian Government was caught by surprise at the high level of public support for the mining industry over the proposed introduction of a mining industry 'super profits tax'. While the industry's exports helped the economy through the global financial crisis, this support was only possible because of a major turnaround in its community license to operate. After many years of poor reputation, consequent on practices that fell short of changing community expectations and strident advocacy strategies, a major turnaround in public affairs strategies and operational practice in Australia and internationally has led to a new level of community acceptance. Copyright © 2011 John Wiley & Sons, Ltd.
Novel imidazolium‐based poly(ionic liquid)s: preparation, characterization, and absorption of CO2
Authors: Xiong Yu‐Bing , Wang Hong , Wang Yu‐Jiao , Wang Rong‐Min
Published: May 2011

The development of novel materials for carbon dioxide (CO2) capture is of great importance in resource utilization and environmental preservation. In this study, imidazolium‐based ionic liquids (ILs) with symmetrical ester and hydroxyl groups were prepared, and their corresponding polymer were synthesized by melt condensation polymerization. The structure and properties of the poly(ionic liquid)s (PILs) were characterized by proton nuclear magnetic resonance, gel permeation chromatograph, differential scanning calorimetry, X‐ray diffraction, and scanning electron microscopy. In addition, the CO2 sorption behavior of the IL monomers and PILs were studied at a low pressure (648.4 mmHg CO2) and under a temperature of 25°C using a thermogravimetric analyzer. The CO2 sorption capacity of 1,3‐bis(2‐hydroxyl ethyl)‐imidazolium hexafluorophosphate ([HHIm]PF6, 10 mol%) was the highest among all the IL monomers and PILs studied. This capacity is also much higher than those reflected of previously reported ILs. Moreover, the sorption equilibrium of [HHIm]PF6 was achieved within a short time. Copyright © 2011 John Wiley & Sons, Ltd.
Porous poly(vinylidene fluoride) membrane modified with hyperbranched poly(amine‐ester)
Authors: Wei Xiu‐Zhen , Yang Jia , Zhu Bao‐Ku , Xu You‐Yi , Zhang Guo‐Liang
Published: May 2011

Poly(vinylidene fluoride) (PVDF) membranes were hydrophilic modified with hydroxyl group terminated hyperbranched poly(amine‐ester) (HPAE). Fourier transform infrared spectroscopy (FT‐IR) was used to study the chemical change of PVDF membranes. X‐ray photoelectron spectroscopy (XPS) indicated that some HPAE molecules were retained in PVDF membrane through polymer chain coiling. The presence of HPAE would improve the hydrophilicity of PVDF membrane. Scanning electron microscopy (SEM) was employed to characterize the morphology of different membranes. The thermodynamic stability for PVDF/DMAc/HPAE/Water system was characterized by the determination of the gelation values. Precipitation kinetics for PVDF/DMAc/HPAE/Water system was studied by precipitation time measurement. The water contact angle indicated that the hydrophilicity and the biocompatibility corresponding to protein adsorption of PVDF membrane were improved significantly after blending with hydrophilic HPAE molecules. Copyright © 2011 John Wiley & Sons, Ltd.
Structure, thermal stability, and mechanical properties of nanocomposites based on an amorphous polyamide
Authors: Zabaleta A. , González I. , Eguiazábal J.I. , Nazábal J.
Published: May 2011

Polymer nanocomposites based on an amorphous polyamide (aPA) modified with three organoclays were obtained in the melt state. The observed Tg decreases indicated that some organic modifier of the OMMT (surfactant) migrated to the matrix during mixing. The decrease in the thermal stability of the aPA in nitrogen atmosphere on organoclay addition was attributed to the instability of the organoclays. The smaller decrease in the thermal stability of the nanocomposites in air atmosphere was attributed to a barrier effect. The largest dispersion (an average of only 1.2 layers per particle) occurred using the octadecylamine‐modified organoclay (I30) that has the maximum uncovered surface; this indicates the basic importance of this parameter on exfoliation. Despite the bulky nature of the aPA that hinders the matrix/inorganic surface interactions, this dispersion level is comparable to that of semicrystalline polyamides with similar polarity. This indicates that the relation between high polarity of the matrix and high dispersion level also works in bulky aPAs, as that of this study. The significant modulus increases (56% for the nanocomposite with 5% I30) are consistent with the measured high dispersion level. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Fabrication of nanostructured polycarbonate/poly(methyl methacrylate) blends with improved optical and mechanical properties by high‐shear processing
Authors: Li Yongjin , Shimizu Hiroshi
Published: May 2011

The structure and properties of polycarbonate (PC)/poly(methyl methacrylate) (PMMA) blends fabricated using a high‐shear extruder at different shear rates were investigated. It was found that the morphologies of the blends were greatly dependent on the shear rate exerted during melt processing. High‐shear processing leads to a nanostructured PC/PMMA blend, in which PMMA domains with a size of less than 50 nm are homogeneously dispersed in the PC matrix. The prepared nanostructured blends exhibit not only excellent optical properties with a transmittance of more than 90% in the visible region but also a higher modulus than pure PC. In contrast, the PMMA domain size ranges from submicron to micrometer for the same blends processed at a low‐shear rate. These blends are opaque and display much lower elongation at break compared with the blends processed at a high‐shear rate. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Effects of acrylonitrile content and molecular weight on the scratch behavior of styrene‐acrylonitrile random copolymers
Authors: Browning Robert , Sue Hung‐Jue , Minkwitz Rolf , Charoensirisomboon Piyada
Published: May 2011

Fundamental understanding of the scratch behavior of styrene‐acrylonitrile (SAN) random copolymers with variation in acrylonitrile (AN) content and molecular weight (MW) is pursued using the methodology outlined in ASTM D7027‐05/ISO 19252:08. Two sets of SAN model systems are employed: One that varies the AN content with similar MW and another that varies the MW at the same AN content. Key scratch damage mechanisms (scratch groove formation, periodic micro‐cracking, and plowing) are identified and correlated with the compressive and tensile properties of the SAN systems. Scratch visibility is analyzed through the use of a commercial software package. A fundamental structure–property relationship of SAN scratch behavior is proposed by the fact that increasing the AN content or the MW can have a positive effect on increasing the scratch resistance of SAN as it improves its tensile strength and ductility. The implication of material properties and their effect on polymer scratch behavior is discussed. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Improvement in toughness and crystallization of poly(L‐lactic acid) by melt blending with poly(epichlorohydrin‐co‐ethylene oxide)
Authors: Zhang Kunyu , Ran Xianghai , Wang Xuemei , Han Changyu , Han Lijing , Wen Xin , Zhuang Yugang , Dong Lisong
Published: May 2011

Melt blending of poly(lactic acid) (PLA) and poly(epichlorohydrin‐co‐ethylene oxide) copolymers (ECO) was performed to improve the toughness and crystallization of PLA. Thermal and scanning electron microscopy analysis indicated that PLA and ECO were not thermodynamically miscible but compatible to some extent. The addition of a small amount of ECO accelerated the crystallization rate and increased the final crystallinity of PLA in the blends. Significant enhancement in toughness and flexibility of PLA were achieved by the incorporation of the ECO elastomer. When 20 wt% ECO added, the impact strength increased from 5 kJ/m2 of neat PLA to 63.9 kJ/m2, and the elongation at break increased from 5% to above 160%. The failure mode changed from brittle fracture of neat PLA to ductile fracture of the blend. Rheological measurement showed that the melt elasticity and viscosity of the blend increased with the concentration of ECO. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers.
Effect of nanoclay addition on the foaming behavior of linear polypropylene‐based soft thermoplastic polyolefin foam blown in continuous extrusion
Authors: Zhai Wentao , Park Chul B.
Published: May 2011

The goal of this study is to fabricate a soft foam with high cell density and high foam expansion based on thermoplastic polyolefin (TPO), and to supply a potential candidate for soft thermoset foams. It was found that a linear polypropylene (PP)‐based TPO foam exhibited very poor cell morphology because of its weak melt strength. Nanoclay was introduced into the TPO to improve its foaming behavior. The extrusion foaming experiments demonstrated that the introduction of 0.5 wt% nanoclay significantly increased the cell morphology and expansion ratio of TPO/clay nanocomposite foams due to the enhanced cell nucleation and the possible cell coalescence suppression at low temperatures. At a high nanoclay content of 2.0 wt%, the cell density and foam expansion of foams increased continuously compared with the 0.5 wt% nanoclay addition. Our study suggested that it was possible to produce soft TPO foams with a well‐defined cell structure and high foam expansion using a continuous method, but that a proper PEOc content control was needed to maximize foam expansion. POLYM. ENG. SCI., 2011. ©2011 Society of Plastics Engineers.
Co‐injection molding of immiscible polymers: Skin‐core structure and adhesion studies
Authors: Gomes M. , Martino D. , Pontes A.J. , Viana J.C.
Published: May 2011

In this article, the microstructure and the adhesion developed in co‐injected specimens obtained with polypropylene (PP; core) and polystyrene (PS; skin) were studied as a function of process conditions and additives used. The study shows that the incorporation of low amounts of fillers such as Nanoclays and styrene‐ethylene‐butadiene‐styrene (SEBS) copolymer to the core material, working as compatibilizers, improves the adhesion at lower and higher polymer melt temperatures, respectively. The authors concluded as well that the use of such fillers, also improves the reproducibility of the process. The adhesion was assessed by shear tests using double lap shear specimens. A data acquisition system was attached to the mold to evaluate the pressure inside the cavity. Results of the in‐mold pressure profiles corresponded well when compared with MoldFlow predictions, and demonstrated that the adhesion of both materials is also related to their behavior and shrinkage inside the mold. POLYM. ENG. SCI., 2011. ©2011 Society of Plastics Engineers.
Discovery of biomarker candidates for coronary artery disease from an APOE‐knock out mouse model using iTRAQ‐based multiplex quantitative proteomics
Authors: Jing Linhong , Parker Carol E. , Seo David , Hines Maria Warren , Dicheva Nedyalka , Yu Yanbao , Schwinn Debra , Ginsburg Geoffrey S. , Chen Xian
Published: May 2011

Due to the lack of precise markers indicative of its occurrence and progression, coronary artery disease (CAD), the most common type of heart diseases, is currently associated with high mortality in the United States. To systemically identify novel protein biomarkers associated with CAD progression for early diagnosis and possible therapeutic intervention, we employed an iTRAQ‐based quantitative proteomic approach to analyze the proteome changes in the plasma collected from a pair of wild‐type versus apolipoprotein E knockout (APOE−/−) mice which were fed with a high fat diet. In a multiplex manner, iTRAQ serves as the quantitative ‘in‐spectra’ marker for ‘cross‐sample’ comparisons to determine the differentially expressed/secreted proteins caused by APOE knock‐out. To obtain the most comprehensive proteomic data sets from this CAD‐associated mouse model, we applied both MALDI and ESI‐based mass spectrometric (MS) platforms coupled with two different schemes of multidimensional liquid chromatography (2‐D LC) separation. We then comparatively analyzed a series of the plasma samples collected at 6 and 12 wk of age after the mice were fed with fat diets, where the 6‐ or 12‐wk time point represents the early or intermediate phase of the fat‐induced CAD, respectively. We then categorized those proteins showing abundance changes in accordance with APOE depletion. Several proteins such as the γ and β chains of fibrinogen, apolipoprotein B, apolipoprotein C‐I, and thrombospondin‐4 were among the previously known CAD markers identified by other methods. Our results suggested that these unbiased proteomic methods are both feasible and a practical means of discovering potential biomarkers associated with CAD progression.
Proteomic profiling between CNE‐2 and its strongly metastatic subclone S‐18 and functional characterization of HSP27 in metastasis of nasopharyngeal carcinoma
Authors: Li Guo‐Ping , Wang Hua , Lai Yiu‐Kay , Chen Shao‐Chun , Lin Marie C. M. , Lu Gang , Zhang Jing‐Fang , He Xiao‐Guang , Qian Chao‐Nan , Kung Hsiang‐Fu
Published: May 2011

Metastasis to secondary sites remains the leading cause of nasopharyngeal carcinoma (NPC)‐associated death. In order to identify the candidate protein(s) responsible for the differential metastatic capacity, the protein expression profiling between NPC cell line CNE‐2 and its highly metastatic subclone S‐18 were compared by 2‐DE. In total, 18 spots were differentially expressed between these two cell lines. Among all, seven proteins were identified with further MS analysis. Western blotting further validated upregulation of HSP27 and ezrin, and downregulation of valosin containing protein and keratin 18 in S‐18. Moreover, the knockdown of HSP27 was found to significantly decrease the invasive ability of S‐18. On the other hand, overexpression of HSP27 in NP460 cells, which generated little endogenous HSP27 and less invasive, was noted to gain enhanced metastatic capability. Real‐time PCR confirmed that the transcriptional levels of NF‐κB and MMP9, MMP11 were downregulated after inhibition of HSP27 in S‐18, which implicated that HSP27 enhanced the metastatic property of NPC cells probably via the NF‐κB‐mediated activation of MMPs. The findings in this work provided us a platform for further elucidating the underlying mechanisms of NPC metastasis and demonstrated that HSP27 would be a valid target for anti‐cancer drug development.
The Role of Interannual Climate Variability in Controlling Solifluction Processes, Endalen, Svalbard
Authors: Harris Charles , Kern‐Luetschg Martina , Christiansen Hanne H. , Smith Fraser
Published: May 2011

A continuous record is presented of active layer processes at Endalen, Svalbard, over the period 2005–08. The monitored slope has a gradient of around 7° and in 2005, active layer depth was 94 cm, but this increased by around 14 cm over the next three years. The presence of an ice‐rich transient layer proved highly significant in determining the timing and profiles of solifluction movement. Frost heaving was 4.2 cm in 2005–06, 6.6 cm in 2006–07 and 3.2 cm in 2007–08, but thaw settlement exceeded frost heave in each year, giving a net total ground surface lowering of 6.2 cm. In winter, segregation ice was concentrated within the upper and lower active layer, leaving the central parts ice‐poor. During the summers of 2006 and 2008, thawing of the transient layer was associated with artesian pore pressures at 90 cm depth and basal soil shearing, but in 2007, when the thaw front failed to reach the ice rich basal zone, pore pressures during thaw were sub‐hydrostatic and no basal shearing was observed. Solifluction shear strain during thaw settlement resulted in downslope surface displacements of 2.3 cm in 2005–06, 1.2 cm in 2006–07 and 1 cm in 2007–08. Copyright © 2011 John Wiley & Sons, Ltd.
Toward accurate prediction of pKa values for internal protein residues: The importance of conformational relaxation and desolvation energy
Authors: Wallace Jason A. , Wang Yuhang , Shi Chuanyin , Pastoor Kevin J. , Nguyen Bao‐Linh , Xia Kai , Shen Jana K.
Published: May 2011

Proton uptake or release controls many important biological processes, such as energy transduction, virus replication, and catalysis. Accurate pKa prediction informs about proton pathways, thereby revealing detailed acid‐base mechanisms. Physics‐based methods in the framework of molecular dynamics simulations not only offer pKa predictions but also inform about the physical origins of pKa shifts and provide details of ionization‐induced conformational relaxation and large‐scale transitions. One such method is the recently developed continuous constant pH molecular dynamics (CPHMD) method, which has been shown to be an accurate and robust pKa prediction tool for naturally occurring titratable residues. To further examine the accuracy and limitations of CPHMD, we blindly predicted the pKa values for 87 titratable residues introduced in various hydrophobic regions of staphylococcal nuclease and variants. The predictions gave a root‐mean‐square deviation of 1.69 pK units from experiment, and there were only two pKa's with errors greater than 3.5 pK units. Analysis of the conformational fluctuation of titrating side‐chains in the context of the errors of calculated pKa values indicate that explicit treatment of conformational flexibility and the associated dielectric relaxation gives CPHMD a distinct advantage. Analysis of the sources of errors suggests that more accurate pKa predictions can be obtained for the most deeply buried residues by improving the accuracy in calculating desolvation energies. Furthermore, it is found that the generalized Born implicit‐solvent model underlying the current CPHMD implementation slightly distorts the local conformational environment such that the inclusion of an explicit‐solvent representation may offer improvement of accuracy. Proteins 2011. © 2011 Wiley‐Liss, Inc.
Anodic repassivation of low energy Au‐implanted ultra‐thin anodic Al2O3
Authors: Mardare Andrei Ionut , Melnikov Alexander , Wieck Andreas Dirk , Hassel Achim Walter
Published: May 2011

Ultrathin anodic alumina with a film thickness of 11 nm was implanted by Au atoms with low energy of 2, 5 or 10 keV. Stopping range simulations yielded three essentially different geometries ranging from surface near implantation over well penetrated oxide to near oxide metal interface implantation, covering the entire range of possible implantation modifications. This work aims at demonstrating how to perform band gap engineering in alumina not only on an energetic level but also targeting a certain geometrical position of the doping atoms by means of the implantation parameters. Beside the intended implantation the oxide destruction in the implantation path and its possible repair was of interest. The repassivation behaviour was considerably different showing a significant redox contribution of the gold nanoclusters on top of the simple oxide repassivation. Near surface implanted Au remained electrochemically active for low repassivation potentials. Higher repassivation potentials always buried the implanted Au atoms under anodic alumina. The repassivation charge determined allowed determining the volume destructed by the implantation.
Single walled carbon nanotubes functionalized with hydrides as potential hydrogen storage media: A survey of intermolecular interactions
Authors: Surya V. J. , Iyakutti K. , Venkataramanan N. S. , Mizuseki H. , Kawazoe Y.
Published: May 2011

In this paper, we have analyzed the intermolecular interactions between H2and single walled carbon nanotube (SWCNT)–hydride complexes and project their capability as a practicable hydrogen storage medium (HSM). In this respect, we have investigated the type of interactions namely van der Waals, electrostatic, and orbital interactions to understand the molecular hydrogen binding affinity of various systems. We found that the charge transfer effects coupled with induced electrostatic interactions are responsible for synergetic action of SWCNT and hydrides on adsorption of H2molecules at ambient conditions. Also we have calculated the thermodynamically usable capacity of hydrogen in all the systems. This study enables one to identify and design potential hydrogen storage materials.
Green high‐power light sources using InGaN multi‐quantum‐well structures for full conversion
Authors: Galler B. , Sabathil M. , Laubsch A. , Meyer T. , Hoeppel L. , Kraeuter G. , Lugauer H. , Strassburg M. , Peter M. , Biebersdorf A. , Steegmueller U. , Hahn B.
Published: May 2011

We investigate the possibility to obtain efficient green light sources for high‐power applications by full luminescence conversion via InGaN/GaN multi‐quantum‐well (MQW) structures. Using an ultraviolet (UV) light‐emitting diode (LED) for optical pumping of a forty‐period (40x) MQW structure emitting in the green spectral range, we show that a luminous flux comparable to the best reported values for direct green LEDs can be achieved. The position of the efficiency maximum on the excitation density axis is shifted by an order of magnitude to an equivalent of 28 Acm–2 while maintaining comparable absolute values. We propose the concept of processing suitable platelets placed directly on a pump LED as a general experimental tool to determine absolute efficiency values of structures that cannot be pumped by electrical means (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AlN/GaN HEMTs with high‐κ ALD HfO2 or Ta2O5 gate insulation
Authors: Deen David , Storm David , Meyer David , Katzer D. Scott , Bass Robert , Binari Steven , Gougousi Theodosia
Published: May 2011

AlN/GaN Metal‐Insulator‐Semiconductor High Electron Mobility Transistors (HEMTs) have been grown and fabricated which utilize a 6 nm thick atomic layer deposited film of either Ta2O5 or HfO2 for gate insulation. Drain, transfer, and gate current characteristics are compared between both structures, showing a measurable difference in threshold voltage and transconductance. The cause is highlighted by the results of capacitance‐voltage analysis which showed 10 MHz dielectric constants of 8.7 and 11.7 for the HfO2 and Ta2O5 films, respectively. Furthermore, interface trap state density was extracted by Terman's method and compared between films. HEMT small signal frequency performance was representative of the different sub‐micron gate lengths. Consideration of the compared electrical results suggests that at this stage in ALD development, Ta2O5 appears better suited for gate insulation of AlN/GaN HEMTs. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Drain bias stress and memory effects in AlGaN/GaN heterostructure field‐effect transistors with p‐GaN gate
Authors: Sugiyama Takayuki , Honda Yoshio , Yamaguchi Masahito , Amano Hiroshi , Oshimura Yoshinori , Iida Daisuke , Iwaya Motoaki , Akasaki Isamu
Published: May 2011

We measured the drain bias stress effects in normally off mode AlGaN/GaN (JHFETs) with a p‐GaN gate, whose AlGaN barrier was exposed to air by dry etching. A large current collapse and a memory effect decreased the drain current (IDS). IDS of an unpassivated sample became the off leakage level of normally off mode JHFETs at a drain stress bias of 15 V. On the other hand, IDS in SiN‐passivated JHFETs decreased at a slow rate upon applying drain stress bias. The decrease in IDS in SiN‐passivated JHFETs was almost the same as that in as‐grown HFETs. These drain stress and memory effects were perfectly deletable by light exposure, and were rewritable similarly in an EPROM. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)