bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of spongin derived from Hymeniacidon sinapium on bone mineralization
Authors: Kim Moon‐Moo , Mendis Eresha , Rajapakse Niranjan , Lee Sang‐Hoon , Kim Se‐Kwon
Published: January 2009

Marine sponges have been known to provide a source of novel bone and cartilage replacements because of their secondary metabolites and specific skeleton structures. In particular, it has been reported that spongin as a component of fibrous skeleton, pseudokeratin, neurokeratin, horny protein, and collagen‐like protein in sponges can be used in several biomedical applications including osteoarthritis (OA). However, the pharmacological mechanism of action of spongin remains obscure. In this study, it was investigated whether spongin derived from Hymeniacidon sinapium can promote bone mineralization of osteoblast‐like MG‐63 cells. Our present study provides the first evidence that spongin is effective in activating bone mineralization. Furthermore, spongin increased ALP activity, collagen synthesis, and osteocalcin secretion in addition to bone mineralization in osteoblastic cells in vitro. In addition, it was demonstrated that spongin exerted the inhibitory effect on production of inflammatory mediators such as TNF‐α, IL‐1β, and PGE2 in macrophage, RAW264.7 cells. These results suggest that the anti‐inflammatory effect of spongin derived from Hymeniacidon sinapium can play a critical role in bone mineralization of osteoblast‐like MG‐63 cells. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009
Collagen nanofilm immobilized on at surfaces by electrodeposition method
Authors: Yang Xiudong , Jiang Bo , Huang Yi , Tian Yunfei , Chen Hong , Chen Jiyong , Yang Bangcheng
Published: January 2009

A simple electrodeposition method is presented for the preparing of collagen nanofilms (EAT) on anodic oxidized titanium surfaces (AT). The nanofilms were observed by scanning electron microscopy and atomic force microscopy. Functional TiOx layers with anionic groups of PO4, SO4 and OH were investigated on the AT surface by X‐ray photoelectron spectroscopy; X‐ray diffraction results indicated that the AT surface was composed mainly of anatase and rutile. The bioactive electrodeposited TiOx layers on the AT surface showed lower water contact angles and higher surface energy than pure titanium surfaces (CT) and displayed higher collagen molecule immobilization. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009
A kernel‐based method to determine optimal sampling times for the simultaneous estimation of the parameters of rival mathematical models
Authors: Donckels Brecht M. R. , De Pauw Dirk J.W. , Vanrolleghem Peter A. , De Baets Bernard
Published: January 2009

When several models are proposed for one and the same process, experimental design techniques are available to design optimal discriminatory experiments. However, because the experimental design techniques are model‐based, it is important that the required model predictions are not too uncertain. This uncertainty is determined by the quality of the already available data, since low‐quality data will result in poorly estimated parameters, which on their turn result in uncertain model predictions. Therefore, model discrimination may become more efficient and effective if this uncertainty is reduced first. This can be achieved by performing dedicated experiments, designed to increase the accuracy of the parameter estimates. However, performing such an additional experiment for each rival model may undermine the overall goal of optimal experimental design, which is to minimize the experimental effort. In this article, a kernel‐based method is presented to determine optimal sampling times to simultaneously estimate the parameters of rival models in a single experiment. The method is applied in a case study where nine rival models are defined to describe the kinetics of an enzymatic reaction (glucokinase). The results clearly show that the presented method performs well, and that a compromise experiment is found which is sufficiently informative to improve the overall accuracy of the parameters of all rival models, thus allowing subsequent design of an optimal discriminatory experiment. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009
N2O in small para‐hydrogen clusters: Structures and energetics
Authors: Zhu Hua , Xie Daiqian
Published: January 2009

We present the minimum‐energy structures and energetics of clusters of the linear N2O molecule with small numbers of para‐hydrogen molecules with pairwise additive potentials. Interaction energies of (p‐H2)–N2O and (p‐H2)–(p‐H2) complexes were calculated by averaging the corresponding full‐dimensional potentials over the H2 angular coordinates. The averaged (p‐H2)–N2O potential has three minima corresponding to the T‐shaped and the linear (p‐H2)–ONN and (p‐H2)–NNO structures. Optimization of the minimum‐energy structures was performed using a Genetic Algorithm. It was found that p‐H2 molecules fill three solvation rings around the N2O axis, each of them containing up to five p‐H2 molecules, followed by accumulation of two p‐H2 molecules at the oxygen and nitrogen ends. The first solvation shell is completed at N = 17. The calculated chemical potential oscillates with cluster size up to the completed first solvation shell. These results are consistent with the available experimental measurements. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009
Hydrodynamic behaviour of a full‐scale anaerobic contact reactor using residence time distribution technique
Authors: Capela Isabel , Bilé Maria João , Silva Flávio , Nadais Helena , Prates António , Arroja Luís
Published: January 2009

BACKGROUND: The knowledge of the fluid pattern of full‐scale anaerobic reactors is of fundamental importance for the optimisation of biological processes. High solids concentrations often lead to inefficient mixing conditions, which may reduce treatment capacity due to heterogeneity within the biomass.

RESULTS: The hydrodynamic characteristics of a full‐scale anaerobic contact reactor treating evaporator condensate from a sulphite pulp mill were investigated. The methodology applied was based on the residence time distribution (RTD) technique using lithium as a tracer. Different non‐ideal hydraulic flow models were tested and the best model fitting RTD data was the Gamma distribution model with by‐pass. It was concluded that the full‐scale bioreactor presents a good degree of mixing with about 22% of non‐effective volume due to the presence of high amounts of inorganic materials.

CONCLUSION: As a result of this study it was possible to both improve the full‐scale bioreactor performance and decrease the running costs by changes in the plant operation strategies which allowed reduction of the huge amount of inorganic materials contributing to the non‐effective volume. The methodology is simple and results from a unique RTD experiment and confirms the importance of considering mixing characteristics when assessing complex full‐scale treatment processes. Copyright © 2009 Society of Chemical Industry
In situ TEM observation of magnetic materials
Authors: Tanase Mihaela , Petford‐Long Amanda K.
Published: January 2009

Magnetic nanostructures and thin films display novel magnetization reversal behavior as a function of size and shape, which makes them appropriate for a range of technological applications. The spatial resolution of in situ transmission electron microscopy techniques such as Lorentz TEM (LTEM) and off‐axis electron holography are well suited to analysis of the magnetic domain structure and magnetization behavior of these magnetic nanostructures and thin films. In this article the various techniques that are applicable are described, including the qualitative LTEM imaging modes and the differential phase contrast technique. In addition, quantitative methods for mapping the magnetic induction via phase reconstruction are discussed. In each case the advantages and limitations are presented. Application of the techniques to various types of magnetic structures is then presented, and the article ends with a short summary and a discussion of future developments in this field. Microsc. Res. Tech., 2009. Published 2009 Wiley‐Liss, Inc.
Ultrashort TE spectroscopic imaging (UTESI): Application to the imaging of short T2 relaxation tissues in the musculoskeletal system
Authors: Du Jiang , Takahashi Atsushi M. , Chung Christine B.
Published: January 2009

Purpose

To investigate ultrashort TE spectroscopic imaging (UTESI) of short T2 tissues in the musculoskeletal (MSK) system.

Materials and Methods

Ultrashort TE pulse sequence is able to detect rapidly decaying signals from tissues with a short T2 relaxation time. Here a time efficient spectroscopic imaging technique based on a multiecho interleaved variable TE UTE acquisition is proposed for high‐resolution spectroscopic imaging of the short T2 tissues in the MSK system. The projections were interleaved into multiple groups with the data for each group being collected with progressively increasing TEs. The small number of projections in each group sparsely but uniformly sampled k‐space. Spectroscopic images were generated through Fourier transformation of the time domain images at variable TEs. T2* was quantified through exponential fitting of the time domain images or line shape fitting of the magnitude spectrum. The feasibility of this technique was demonstrated in volunteer and cadaveric specimen studies on a clinical 3T scanner.

Results

UTESI was applied to six cadaveric specimens and four human volunteers. High spatial resolution and contrast images were generated for the deep radial and calcified layers of articular cartilage, menisci, ligaments, tendons, and entheses, respectively. Line shape fitting of the UTESI magnitude spectroscopic images show a short T2* of 1.34 ± 0.56 msec, 4.19 ± 0.68 msec, 3.26 ± 0.34 msec, 1.96 ± 0.47 msec, and 4.21 ± 0.38 msec, respectively.

Conclusion

UTESI is a time‐efficient method to image and characterize the short T2 tissues in the MSK system with high spatial resolution and high contrast. J. Magn. Reson. Imaging 2009;29:412–421. © 2009 Wiley‐Liss, Inc.
Quantitation of brain tissue changes associated with white matter hyperintensities by diffusion‐weighted and magnetization transfer imaging: The LADIS (leukoaraiosis and disability in the elderly) study
Authors: Ropele Stefan , Seewann Alexandra , Gouw Alida A. , van der Flier Wiesje M. , Schmidt Reinhold , Pantoni Leonardo , Inzitari Domenico , Erkinjuntti Timo , Scheltens Philip , Wahlund Lars O. , Waldemar Gunhild , Chabriat Hugues , Ferro José , Hennerici Michael , O'Brien John , Wallin Anders , Langhorne Peter , Visser Marieke C. , Barkhof Frederik , Fazekas Franz
Published: January 2009

Purpose

To explore the value of diffusion‐weighted imaging (DWI) and magnetization transfer imaging (MTI) for the improved detection and quantification of cerebral tissue changes associated with ageing and white matter hyperintensities (WMH).

Materials and Methods

DWI (n = 340) and MTI (n = 177) were performed in nine centers of the multinational Leukoaraiosis And DISability (LADIS) study investigating the impact of WMH on 65‐ to 85‐year‐old individuals without prior disability. We assessed the apparent diffusion coefficient (ADC) and magnetization transfer ratio (MTR) of normal appearing brain tissue (NABT) and within WMH and related them to subjects' age and WHM severity according to the Fazekas score.

Results

ADC and MTR values showed a significant inter‐site variation, which was stronger for the MTR. After z‐transformation multiple regression analysis revealed WMH severity and age as significant predictors of global ADC and MTR changes. Only lesional ADC, but not MTR was related to WMH severity.

Conclusion

ADC and MTR are both sensitive for age and WMH related changes in NABT. The ADC is more sensitive for tissue changes within WMH and appears to be more robust for multicenter settings. J. Magn. Reson. Imaging 2009;29:268–274. © 2009 Wiley‐Liss, Inc.
Non‐contrast‐enhanced MR angiography for selective visualization of the hepatic vein and inferior vena cava with true steady‐state free‐precession sequence and time‐spatial labeling inversion pulses: Preliminary results
Authors: Shimada Kotaro , Isoda Hiroyoshi , Okada Tomohisa , Kamae Toshikazu , Maetani Yoji , Arizono Shigeki , Hirokawa Yuusuke , Shibata Toshiya , Togashi Kaori
Published: January 2009

Purpose

To selectively visualize the hepatic vein and inferior vena cava (IVC) using three‐dimensional (3D) true steady‐state free‐precession (SSFP) MR angiography with time‐spatial labeling inversion pulse (T‐SLIP), and to optimize the acquisition protocol.

Materials and Methods

Respiratory‐gated 3D true SSFP scans were conducted in 23 subjects in combination with two different T‐SLIPs (one placed in the thorax to suppress the arterial signal and the other in the abdomen to suppress the portal venous signal). One of the most important factors was the inversion time (TI) of abdominal T‐SLIP, and the image quality was evaluated at four different TIs of 800, 1200, 1600, and 2000 msec in terms of relative signal‐to‐noise ratio (SNR), contrast‐to‐noise ratio (CNR), and mean visualization scores.

Results

No significant difference was observed in SNR and CNR between each TI. However, IVC visualization scores were better at TIs of 1600 and 2000 msec, and overall image quality was better at TIs of 1200 and 1600 msec. Therefore, the TI of 1600 msec was considered to provide the optimal balance between IVC visualization and signal suppression of the portal vein in our protocol.

Conclusion

True SSFP scan with T‐SLIPs enabled selective visualization of the hepatic vein and IVC without an exogenous contrast agent. J. Magn. Reson. Imaging 2009;29:474–479. © 2009 Wiley‐Liss, Inc.
Assessment of anterior cruciate ligament reconstruction using 3D ultrashort echo‐time MR imaging
Authors: Rahmer Jürgen , Börnert Peter , Dries Sebastian P.M.
Published: January 2009

This work demonstrates the potential of ultrashort TE (UTE) imaging for visualizing graft material and fixation elements after surgical repair of soft tissue trauma such as ligament or meniscal injury. Three asymptomatic patients with anterior cruciate ligament (ACL) reconstruction using different graft fixation methods were imaged at 1.5T using a 3D UTE sequence. Conventional multislice turbo spin‐echo (TSE) measurements were performed for comparison. 3D UTE imaging yields high signal from tendon graft material at isotropic spatial resolution, thus facilitating direct positive contrast graft visualization. Furthermore, metal and biopolymer graft fixation elements are clearly depicted due to the high contrast between the signal‐void implants and the graft material. Thus, the ability of UTE MRI to visualize short‐T2 tissues such as tendons, ligaments, or tendon grafts can provide additional information about the status of the graft and its fixation in the situation after cruciate ligament repair. UTE MRI can therefore potentially support diagnosis when problems occur or persist after surgical procedures involving short‐T2 tissues and implants. J. Magn. Reson. Imaging 2009;29:443–448. © 2009 Wiley‐Liss, Inc.
Value of precontrast T1 for dGEMRIC of native articular cartilage
Authors: Li Wei , Du Hongyan , Scheidegger Rachel , Wu Ying , Prasad Pottumarti V.
Published: January 2009

Purpose

To evaluate if the difference between pre‐ and post‐Gd‐DTPA2‐ relaxation rate (ΔR1) provides better differentiation of osteoarthritic patients (OA) from healthy subjects (HS) with dGEMRIC, as compared to post‐Gd‐DTPA2‐ spin‐lattice relaxation time (T1Gd).

Materials and Methods

Seventeen OA and 14 HS underwent pre‐ and 90 minutes postcontrast (Gd‐DTPA2‐) magnetic resonance imaging (MRI) of the knee, using inversion recovery fast spin‐echo and/or Lock–Locker sequences for T1 mapping. Effect sizes for T1pre, T1Gd, and ΔR1 were calculated, and receiver operating characteristic (ROC) curve and regression analysis were also performed to assess the effectiveness of each parameter in the separation of OA and HS.

Results

T1Gd and ΔR1 were almost identical in terms of areas under ROC curves (0.903 and 0.914, respectively), and effect sizes (1.34 and 1.31, respectively). These were significantly higher than T1pre. In addition, a high inverse correlation was observed between ΔR1 vs. T1Gd (R = 0.96).

Conclusion

Either T1Gd or ΔR1 could be used as an index in the evaluation of native cartilage. However, considering the practical logistical cost involved in terms of time and effort to acquire precontrast T1 measurements, our data further support the continued use of T1Gd as the dGEMRIC index in the evaluation of native cartilage. J. Magn. Reson. Imaging 2009;29:494–497. © 2009 Wiley‐Liss, Inc.
Improved fat suppression using multipeak reconstruction for IDEAL chemical shift fat‐water separation: Application with fast spin echo imaging
Authors: Kijowski Richard , Woods Michael A. , Lee Kenneth S. , Takimi Kuya , Yu Huanzhou , Shimakawa Ann , Brittain Jean H. , Reeder Scott B.
Published: January 2009

Purpose

To evaluate and quantify improvements in the quality of fat suppression for fast spin‐echo imaging of the knee using multipeak fat spectral modeling and IDEAL fat‐water separation.

Materials and Methods

T1‐weighted and T2‐weighted fast spin‐echo sequences with IDEAL fat‐water separation and two frequency‐selective fat‐saturation methods (fat‐selective saturation and fat‐selective partial inversion) were performed on 10 knees of five asymptomatic volunteers. The IDEAL images were reconstructed using a conventional single‐peak method and precalibrated and self‐calibrated multipeak methods that more accurately model the NMR spectrum of fat. The signal‐to‐noise ratio (SNR) was measured in various tissues for all sequences. Student t‐tests were used to compare SNR values.

Results

Precalibrated and self‐calibrated multipeak IDEAL had significantly greater suppression of signal (P < 0.05) within subcutaneous fat and bone marrow than fat‐selective saturation, fat‐selective partial inversion, and single‐peak IDEAL for both T1‐weighted and T2‐weighted fast spin‐echo sequences. For T1‐weighted fast spin‐echo sequences, the improvement in the suppression of signal within subcutaneous fat and bone marrow for multipeak IDEAL ranged between 65% when compared to fat‐selective partial inversion to 86% when compared to fat‐selectivesaturation. For T2‐weighted fast spin‐echo sequences, the improvement for multipeak IDEAL ranged between 21% when compared to fat‐selective partial inversion to 81% when compared to fat‐selective saturation.

Conclusion

Multipeak IDEAL fat‐water separation provides improved fat suppression for T1‐weighted and T2‐weighted fast spin‐echo imaging of the knee when compared to single‐peak IDEAL and two widely used frequency‐selected fat‐saturation methods. J. Magn. Reson. Imaging 2009;29:436–442. © 2009 Wiley‐Liss, Inc.
Determination of spiramycin and neospiramycin antibiotic residues in raw milk using LC/ESI‐MS/MS and solid‐phase extraction
Authors: Wang Jian , Leung Daniel
Published: January 2009

A simple confirmatory method for the determination of spiramycin and its metabolite neospiramycin in raw milk using LC ESI MS/MS is presented. Macrolide residues in raw milk were extracted by ACN, and sample extracts were further cleaned up and concentrated using SPE cartridges. Both spiramycin and neospiramycin were protonated in electrospray positive ion mode to form singly and/or doubly charged pseudomolecular ions. Data acquisition was achieved using multiple reaction monitoring, i.e., two transitions, for quantification and confirmation. Matrix‐matched standard calibration curves were utilized to achieve the best accuracy for the method. The method performance was evaluated according to both a conventional validation procedure and a designed experimental result. The measurement uncertainty arising from accuracy and precision was estimated. The method accuracy, expressed as a percentage of an overall recovery, was from 82.1 to 108.8%, and its intermediate precision was less than 20%. LC/ESI‐MS/MS method LODs (S/N ⪈ 3:1) of spiramycin and neospiramycin were less than 1.0 μg/kg.
Porous Biodegradable Scaffold: Predetermined Porosity by Dissolution of Poly(ester‐anhydride) Fibers from Polyester Matrix
Authors: Rich Jaana , Korhonen Harri , Hakala Risto , Korventausta Joni , Elomaa Laura , Seppälä Jukka
Published: January 2009

A novel selective leaching method for the porogenization of the biodegradable scaffolds was developed. Continuous, predetermined pore structure was prepared by dissolving fast eroding poly(ε‐caprolactone)‐based poly(ester‐anhydride) fibers from the photo‐crosslinked poly(ε‐caprolactone) matrix. The porogen fibers dissolved in the phosphate buffer (pH 7.4, 37 °C) within a week, resulting in the porosity that replicated exactly the single fiber dimensions and the overall arrangement of the fibers. The amount of the porosity, estimated with micro‐CT, corresponded with the initial amount of the fibers. The potential to include bioactive agents in the porogen fibers was demonstrated with the bioactive glass.

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Reactive Compatibilization in Brominated Poly(isobutylene‐co‐p‐methylstyrene) and Polyamide Blends
Authors: Tsou Andy H. , Favis Basil D. , Hara Yuichi , Bhadane Prashant A. , Kirino Yoshiaki
Published: January 2009

The blending of BIMSM and PA results in interfacial reactions between pendant benzylic bromines of BIMSM and terminal amines and backbone amides of PA as determined by FT‐IR. The emulsification study at 40 (IMSM/BIMSM)/60 PA composition demonstrates a rapid initial drop in elastomer phase size at lower BIMSM concentrations due to inhibited coalescence effects. However, at higher BIMSM concentrations, unlike classical compatibilized systems, a plateau‐value phase size is never attained. Instead, a linear dependence of the elastomer particle size on BIMSM concentration is found. Particle sizes as small as 80–100 nm are obtained. A 3D PA transcrystalline network bridging BIMSM dispersions to PA matrix is obtained after dynamic vulcanization.

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Hierarchical Assembly of Collagen‐Like Peptides in vitro Provides Structural Causes of Osteogenesis Imperfecta
Authors: Huang Jia , Cebe Peggy , Kaplan David L.
Published: January 2009

Collagen type I peptides, representative of native to disease states for the bone disease, Osteogenesis imperfecta, were studied with regard to self‐assembly into triple helices and liquid crystalline mesophases. The purpose of the study was to establish insight into collagen mutations in terms of propagation of single chain defects up the scale of materials hierarchy, toward solid state fibril assemblies formed from collagen. Studies carried out in vitro demonstrated the value of this approach in establishing in vitro disease models, as the degree of collagen disruption could be recapitulated by the point mutations to show major impact on macroscopic features. Fourier transform infrared spectroscopy, circular dichroism, atomic force microscopy and optical ellipsometry were used to assess the structural and morphological changes at the various length scales post assembly. The results demonstrated that glycine to alanine to aspartic acid single substitutions in the collagen peptides progressively disrupted normal assembly, reflected in lower thermal stability, loss of triple helical structure and loss of mesophase formation. This approach can provide a basis upon which to study collagen biomaterial templates for controlled hydroxyapatite formation and changes in cell signaling related to bone remodeling, related to the severity of the disease.

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Amphiphilic Patchy Composite Colloids
Authors: Ding Shujiang , Zhang Chengliang , Wei Wei , Qu Xiaozhong , Liu Jiguang , Yang Zhenzhong
Published: January 2009

A new approach to fabricate patchy silica/polymeric gel composite colloids with amphiphilic performance is reported. The amphiphilic performance is rendered by selectively modifying the silica framework with a silane that contains an oleophilic alkyl chain. The patchy composite colloids are dispersible in both water and oil, and may be used as a solid particle surfactant. The modified silica framework can also assist other functional materials to disperse in a desired media. The corresponding silica/carbon composite colloids become amphiphilic after a sequential activation of carbon and modification of silica, and meanwhile possess as good electron conductivity as the as‐prepared silica/carbon composite colloids.

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A modified extended ZY T‐chart for conjugately characteristic‐impedance transmission lines with active characteristic impedances
Authors: Vudhivorn K. , Torrungrueng D.
Published: January 2009

Conjugately characteristic‐impedance transmission lines (CCITLs) implemented by lossless periodic transmission‐line structures can exhibit active characteristic impedances; that is, negative characteristic resistances. In this case, the magnitude of the voltage reflection coefficient is always greater than or equal to unity for passive load terminations. The extended ZY T‐chart developed earlier for these CCITLs is modified, called a modified extended ZY T‐chart, by mapping the region outside the unit circle of the former to the inside one of the latter using an appropriate bilinear transformation. The modified chart is plotted in the plane of the inverse of the voltage reflection coefficient. It is found that the modified chart also depends on the angle Ø, the argument of CCITL characteristic impedances, and it is more convenient in usage than the extended ZY T‐chart. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 621–625, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24124
A compact dual‐band bandpass filter using stub‐loaded two‐mode resonators and direct source‐load coupling to obtain improved stopband characteristics
Authors: He Wenqing , Ma Zhewang , Chen Chun‐Ping , Anada Tetsuo , Kobayashi Yoshio
Published: January 2009

In this article, a dual‐band bandpass filter is designed by using microstrip stub‐loaded two‐mode resonators. Because the resonant frequencies of the odd‐mode and even‐mode of the stub‐loaded resonator can be varied individually, the midband frequencies of the dual‐bands of filter can be controlled separately. Direct coupling between the source and load of the filter is introduced, and four transmission zeros in the stopband of the filter are produced. As a consequence, excellent performance of the filter with sharp passband skirts and wide stopbands is realized. For example, dual‐band filter has midband frequencies of 2.4 GHz and 3.6 GHz, respectively, with fractional bandwidths of 11.35% and 5.21%, correspondingly. The measured frequency response of the filter agrees excellently with the predicted result. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 618–621, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24129
Finite element analysis and experimental verification of SOI waveguide bending loss
Authors: Srinivasan H. , Bommalakunta B. , Chamberlain A. , Hastings J. T.
Published: January 2009

Bending and transition losses in silicon‐on‐insulator rib waveguides were calculated using finite‐element analysis of equivalent straight waveguides with perfectly matched boundary layers. Experimental loss measurements of silicon‐on‐insulator waveguides with various bend radii reveal that this technique accurately predicts loss and minimum bend radius for efficient design. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 699–702, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24135
Electrically small square loop antenna with a capacitive split ring resonator cover structure
Authors: Kim Yong‐Jin , Lee Hong‐Min
Published: January 2009

In this article, electrically small square loop antenna with a capacitive split ring resonator (SRR) cover structure is built and tested. The size of the proposed antenna (ka = 0.34) is smaller than the corresponding Chu limiting value and it is efficiently matched without additional matching network. An electrically small loop antenna has a large inductive reactance. Therefore, a capacitive SRR can be used to achieve impedance matching of the antenna. The equivalent circuit model of the antenna structure is applied to analyze and qualify the design correctness. The experimental result shows that the resonant frequency and impedance bandwidth (VSWR ≤ 2) are 906 MHz and 5.8 MHz (901.7–907.5 MHz), respectively. The proposed antenna has a radiation efficiency of 42.85% and maximum gain of −0.59 dBi at 906 MHz and it is fabricated on a Teflon substrate (εr = 2.2) without using a ground plane. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 831–835, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24137
A novel compact low‐pass filter using defected ground structure
Authors: Chen XiaoQun , Wang LingXia , Shi XiaoWei
Published: January 2009

In this article, a novel gradual change defected ground structure (DGS) for low‐pass filter (LPF) design is presented and analyzed. The proposed DGS combined with open stubs is presented to enhance the out‐band suppression. The equivalent circuit model and simulated results for the DGS are used to determine the dimension parameters. Based on gradual change structure, the LPF with cutoff frequency fc of 3.1 GHz has presented good measured characteristics, including low insertion loss of 0.325 dB and wide stopband from 3.4 to 10 GHz below −35 dB. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 792–795, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24139
A 58‐GHz wide‐locking range CMOS direct injection‐locked frequency divider using input‐power‐matching technique
Authors: Chen Chang‐Zhi , Hsu Wei‐Lun , Lin Yo‐Sheng
Published: January 2009

A 58‐GHz (V‐band) CMOS direct injection‐locked frequency‐divider (DILFD) using input‐power‐matching technique for locking‐range enhancement is reported for the first time. In an input‐power‐matching technique, an inductive input‐matching‐network is added to the gate of the NMOS switch to optimize the input‐power‐matching, i.e. to maximize the internal power, over the frequency band of interest. This DILFD architecture also features a very low input capacitance; therefore, high operating frequency of 58.2 GHz can be achieved. The DILFD dissipated 8.45 mW power from a 1.3 V power supply, and achieved a total locking range of 9.3 GHz (48.9–58.2 GHz; 17.4%), which is 400% higher than that (1.86 GHz (3%)) of a traditional DILFD without the input‐matching‐network for comparison. The chip area was only 0.585 × 0.492 mm2 excluding the test pads. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 685–689, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24158
An effective NF‐FF transformation with a hybrid cylindrical and bipolar scanning
Authors: D'Agostino F. , Ferrara F. , Gennarelli C. , Gennarelli G. , Guerriero R.
Published: January 2009

An efficient and innovative near‐field‐far‐field transformation technique with a hybrid cylindrical and bipolar scanning is proposed in this article. It allows one to considerably reduce the truncation error, which unavoidably affects the cylindrical near‐field‐far‐field transformation. To this end, nonredundant measurements are acquired by employing a cylindrical facility integrated with a rotating arm, which allows to collect the bipolar data on the upper and lower surfaces of the cylinder. Then, by applying the equivalence theorem, the knowledge of the electric field tangential components on the top and bottom of the cylinder is properly exploited to recover the nonredundant cylindrical near‐field data external to the measurement zone. At last, the near‐field data needed to perform the classical near‐field‐far‐field transformation with cylindrical scanning are efficiently computed via an optimal sampling interpolation algorithm. The effectiveness of the approach in reducing the truncation error is assessed by numerical tests. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 772–779, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24165
Compact dualband filter with wide upper stopband
Authors: Singh Pramod K. , Basu Sarbani , Wang Yeong‐Her
Published: January 2009

A compact dualband filter with wide upper stopband using folded stepped impedance resonators (SIRs) and open stub is presented in this letter. The anti‐parallel coupled SIRs are used for the realization of the dual passband and open stubs for the widening of the upper stopband. The SIRs are folded for the compact filter size. Two different folding structures are investigated for the size compactness and the frequency response of the filter. The wide stopband is useful for suppressing harmonics and noise in the RF circuit. Dualband filters at frequencies of 2.45/5.25 GHz and 2.45/5.75 GHz are realized. The wide and deep upper stopband as well as deep mid‐stopband are achieved. The size of the filters are less than 190 mm2 on a RO 4003C (εr = 3.38, h = 0.81 mm) substrate. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 804–808, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24174
A 60‐GHz millimeter‐wave CMOS Marchand balun using 0.18‐μm CMOS technology
Authors: Liu C.‐H. , Hsu C.‐Y. , Chuang H.‐R. , Chen C.‐Y.
Published: January 2009

A novel 60‐GHz wideband Marchand balun fabricated with a standard 0.18 μm six‐metal‐layer CMOS process for millimeter‐wave applications is presented. A technique for achieving good balance with the fourth metal layer microstrip conductor is used in the designed Marchand balun. The fabricated CMOS balun uses multilayer coupling with the top two layers. An output matching network is added to improve the output return loss. The measured amplitude imbalance was about ±1.5 dB from 25 to 65 GHz, over the 89% operating frequency band. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 766–770, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24176
Extended stop‐band band pass filter using new spurious suppression technique
Authors: Ma Kaixue , Yeo Kiat Seng
Published: January 2009

A spurious suppression method by using the “T” feeders is proposed and investigated. A novel band pass filter using “T” feeders is implemented. The measured results of the filter demonstrate good spurious suppression. The experimental results of the filter operating at the center frequency f0 = 1.87 GHz are the fractional bandwidth of 9%, the insertion loss of 1.7 dB, the return loss better than 25 dB. The spurious frequency with rejection larger than 25 dB is up to 5f0. Below 1 GHz, the stop‐band rejection is larger than 51.5 dB, and the largest stop‐band rejection is 54 dB in the upper stop‐band. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 706–709, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24179
A folded substrate integrated waveguide cavity filter using novel negative coupling
Authors: Wang Rui , Zhou Xi‐Lang , Wu Lin‐Sheng
Published: January 2009

This article presents a cross‐coupled folded substrate integrated waveguide (FSIW) cavity bandpass filter. A novel type of negative coupling between FSIW cavities has been investigated and demonstrated. A prototype of four‐pole FSIW cavity bandpass filter has been designed, fabricated with multilayer standard printed circuit board process. The filter has good selectivity which is demonstrated by the measured results, indicating 7.5% bandwidth and more than 14‐dB return loss, with good agreement obtained when compared with the simulated ones. In addition, the rejection band of this filter is quite wide, implying good harmonic rejection. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 866–871, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24181
Optically envelope detected QAM and QPSK RF modulated signals in hybrid wireless‐fiber systems
Authors: Tafur Monroy Idelfonso , Prince Kamau , Seoane Jorge , Yu Xianbin
Published: January 2009

We experimentally demonstrate optical envelope detection of 40 Mbaud 16‐QAM and QPSK RF modulated signals. The proposed system employs an electro‐absorption modulator performing the function of an optical halfwave rectifier. In this experiment, the QAM and QPSK signals are frequency down converted from a 1.6 GHz carrier frequency to an IF at 500 MHz, requiring no high frequency local oscillator and mixer at the remote base station. This result proves the feasibility of optical envelope detection for complex modulation formats of RF signals for hybrid wireless‐fiber transmission links. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 864–866, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24182
Thin absorbers using space‐filling curve artificial magnetic conductors
Authors: McVay John , Hoorfar Ahmad , Engheta Nader
Published: January 2009

Following our previous work, here an artificial magnetic conducting (AMC) surface, comprised of Hilbert and/or Peano space‐filling curve inclusions is utilized as a thin electromagnetic absorber. Numerical results are presented to show the effects of the incident angle, conducting strip widths and substrate thicknesses on the absorbing properties of such surfaces. The performance of a fabricated thin absorber in reducing the RCS of a conducting plate is demonstrated through measurement. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 785–790, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24186
Structure elucidation and NMR assignments for three anthraquinone derivatives from the marine fungus Fusarium sp. (No. ZH‐210)
Authors: Chen Yiguang , Cai Xiaoling , Pan Jiahui , Gao Junping , Li Jing , Yuan Jie , Fu Liwu , She Zhigang , Lin Yongcheng
Published: January 2009

The structure elucidations and complete 1H and 13C NMR assignments are reported for three new anthraquinone derivatives: Fusaquinon A (1), B (2), and C (3) isolated from the fermentation medium of the marine fungus Fusarium sp. (No. ZH‐210). HREIMS, Fourier transform infrared absorption spectrometry (FT‐IR), NMR experiments including gCOSY, gHMQC, gHMBC, and NOESY were used for the determination of the structures and NMR spectral assignments. Preliminary pharmacological test showed that they exhibited low cytotoxic activity towards KB, KBv200, and MCF‐7 cell lines. Copyright © 2009 John Wiley & Sons, Ltd.
Consistency of iterative operator‐splitting methods: Theory and applications
Authors: Geiser Jürgen
Published: January 2009

In this article, we describe a different operator‐splitting method for decoupling complex equations with multidimensional and multiphysical processes for applications for porous media and phase‐transitions. We introduce different operator‐splitting methods with respect to their usability and applicability in computer codes. The error‐analysis for the iterative operator‐splitting methods is discussed. Numerical examples are presented. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2010
Role of polyethylene‐graft‐glycidyl methacrylate compatibilizer on the biodegradation of poly(ε‐caprolactone)/cellulose acetate blends
Authors: Rosa D. S. , Bardi M. A. G. , Guedes C. G. F. , Angelis D. A.
Published: January 2009

Biodegradable polymers provide an attractive solution to reduce environmental pollution caused by the accumulation of plastic waste in landfills. In this study, the effect of polyethylene‐graft‐glycidyl methacrylate (PE‐g‐GMA) on the biodegradation of blends of poly(ε‐caprolactone) (PCL) and cellulose acetate (CA) (80/20, 60/40, 40/60, and 20/80 PCL/CA, w/w) was assessed by mass retention, tensile strength, and morphological properties. The principal fungal strains present in the soil after biodegradation were also identified. PCL and the blends containing 60% and 80% PCL showed greater mass loss and superficial change in simulated soil. PE‐g‐GMA increased the tensile strength retention during 3 months of aging in simulated soil. Scanning electron microscopy (SEM) indicated that pure PCL was more porous, which enhanced the hydrolysis and biodegradation of PCL. PE‐g‐GMA decreased the mass loss of the polymers, possibly by enhancing the interaction between PCL and CA, with the formation of hydrogen bonds between the carbonyl groups of PCL and the hydroxyl groups of CA. This effect was marked in blends with >40% PCL. Microbiological analysis revealed the presence of several species of fungi in the soil. Copyright © 2009 John Wiley & Sons, Ltd.
N‐Isopropylacrylamide/monoalkyl itaconate copolymers and N‐isopropylacrylamide/itaconic acid/dimethyl itaconate terpolymers
Authors: Erbil Candan , Yıldız Yalçın , Uyanık Nurseli
Published: January 2009

Temperature‐ and pH‐sensitive copolymers and terpolymers of N‐isopropylacrylamide (NIPAAm) with itaconic acid (IA), monomethyl itaconate (MMeI), monobutyl itaconate (MBuI), monooctyl itaconate (MOcI), monocetyl itaconate (MCeI), and dimethyl itaconate (DMI) were prepared by free radical solution polymerization method. The dependence of coil‐to‐globule transition on pH and composition, molecular structures, and reactivities of monoalkyl itaconates, molecular weight distributions, and glass transition temperatures of copolymers and terpolymers were investigated using FT‐IR and UV–visible spectroscopic techniques, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and acid–base titration methods. The temperature‐/pH‐dependent coil‐to‐globule transition measurements showed that, upon increasing the content and length of alkyl chains, the lower critical solution temperatures (LCSTs) were shifted to higher temperatures. This meant that with increase in the length of hydrophobic alkyl chain in the monoitaconates intramolecular intreactions between the carboxyl groups were suppressed and LCSTs increased. The aqueous solution behaviors of NIPAAm/IA/DMI terpolymers also revealed that, even if the terpolymer hydrophobicity is increased by adding DMI units, the presence of IA units overcame the decrease in hydrophilicity of the terpolymers. The presence of DMI units in the terpolymers balanced the hydrophilic character of IA. DSC results supported the ones obtained from the pH‐dependent coil‐to‐globule transition measurements. An increase in both the chain length of alkyl groups attached to the monoitaconates and the contents of the mono‐ and dialkyl itaconates in the copolymers and terpolymers decreased the Tgs. In the case of NIPAAm/IA and NIPAAm/MMeI copolymers, the presence of the carboxyl groups forming hydrogen bonds increased the Tg, while the monoalkyl and dialkyl itaconates such as MBuI, MOcI, MCeI and DMI lead to a decrease in Tg of copolymers and terpolymers because of the suppression of intramolecular interactions (resulting from the COOH and COO− groups) through the longer alkyl spacers. The dependence of the thermosensitivity of these NIPAAm copolymers and terpolymers on different conditions of pH, and the nature and content of comonomers suggests that they can be useful in biotechnology and drug delivery applications which involve small changes in pH and temperature. Copyright © 2009 John Wiley & Sons, Ltd.
Preparation and applications of novel cross‐linked fluoroalkyl end‐capped oligomeric nanocomposites possessing aromatic siloxane segments as core units
Authors: Goto Yuki , Mugisawa Masaki , Sawada Hideo
Published: January 2009

Fluoroalkyl end‐capped N,N‐dimethylacrylamide oligomer and N‐(1,1‐dimethyl‐3‐oxobutyl)acrylamide oligomer were reacted with phenylene‐ and biphenylene‐bridged ethoxysilanes under alkaline conditions to yield cross‐linked fluoroalkyl end‐capped oligomeric composites possessing aromatic siloxane segments as core units. These isolated fluorinated composite powders were found to be nanometer size‐controlled fine particles with a good dispersibility and stability in water and organic solvents. Nitrogen adsorption–desorption isotherms confirmed the presence of micropores in these nanocomposites; the micropore size estimated by the HK method was 0.7–0.8 nm. Interestingly, fluorinated nanocomposites possessing a higher micropore volume ratio were found to exhibit a selective encapsulation ability of fullerene into their composite cores. These fluorinated nanocomposites were also applied to the surface modification of poly(methyl methacrylate) film, resulting in a good oleophobicity imparted by fluorine on the surface. In addition, fluorescence emission was visibly observed only from the modified PMMA film surface treated with fluorinated nanocomposites possessing biphenylene units when irradiated by light. Copyright © 2009 John Wiley & Sons, Ltd.
A novel calixarene‐containing hyperbranched aliphatic polyester incorporated with pendant europium complexes
Authors: Feng Jichang , Liu Kuan , Li Yang , Yang Mujie
Published: January 2009

A novel calixarene‐containing hyperbranched aliphatic polyester incorporated with pendant europium complexes (H20‐Cal‐Eu) was synthesized and characterized by FTIR, UV, and element analysis. The polymer H20‐Cal‐Eu shows a glass‐transition temperature (Tg) of 127°C, and a deposition temperature in the range of 280–600°C, as revealed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. The investigation on its photoluminescence (PL) properties revealed that the polymer emitted a remarkably strong red luminescence. Furthermore, its half spectral bandwidth of the polymer film is only about 10 nm as determined from luminescence spectra, suggesting that the light is nearly monochromatic. It is proposed that the hyperbranched polymer (HBP) containing rare earth element exhibits great potential as a red light emitting material. Copyright © 2009 John Wiley & Sons, Ltd.
Composite polymer electrolytes prepared by in situ copolymerization of poly(methyl methacrylate‐acrylonitrile) on the surface of poly(methyl methacrylate)‐coated nano‐TiO2
Authors: Zhang P. , Zhang H. P. , Li Z. H. , Wu Y. P. , van Ree T.
Published: January 2009

Composite polymer electrolytes (CPE) for lithium ion batteries are reported. Initially, nano‐TiO2 was modified by coating with a layer of poly(methyl methacrylate) (PMMA) by emulsion polymerization. CPE with this modified nano‐TiO2 were then prepared by the in situ copolymerization of poly(methyl methacrylate‐acrylonitrile) (P(MMA‐AN)). Morphology, thermal, electrochemical, and spectroscopic measurements were used to characterize the electrolytes. The PMMA‐coated nano‐TiO2 was well dispersed in the polymer matrix due to the PMMA coating layer making the nanoparticles hydrophobic to effectively avoid the aggregation of the nanoparticles. The homogeneous CPEs of this PMMA‐coated nano‐TiO2 have better thermal tolerance, higher ionic conductivity, and wider electrochemical stability, thus providing a practical route to improved polymer electrolytes. Copyright © 2009 John Wiley & Sons, Ltd.
Scratch behavior of epoxy nanocomposites containing α‐zirconium phosphate and core‐shell rubber particles
Authors: Moghbelli Ehsan , Sun Luyi , Jiang Han , Boo Woong J. , Sue Hung‐Jue
Published: January 2009

The effects of nanoscale core‐shell rubber (CSR) particles and α‐zirconium phosphate (ZrP) nanoplatelet fillers on the scratch behavior of epoxy have been examined using a newly established ASTM scratch testing method. The critical load for onset of microcrack formation is utilized to determine scratch resistance of the epoxy nanocomposites. Optical microscopy and scanning electron microscopy were performed to determine failure and fracture patterns caused by the scratch. The findings of this study suggest that the introduction of nanoparticles or nanoplatelets does not necessarily enhance the scratch resistance of epoxy. This implies that increases in ductility and fracture toughness alone, i.e., the epoxy/CSR case, and enhancements in modulus and tensile strength alone, i.e., the epoxy/ZrP case, will not necessarily improve scratch resistance of epoxy matrix. A combination of material property attributes is needed to prepare scratch resistant polymers. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers