bluuebunny/crossref_metadata_2025 huggingface dataset:
Negative pressure fixation device to reduce motion artifacts on contrast‐enhanced MRI of the breast: A clinical feasibility study
Authors: Balakrishnan Asha , Kacher Daniel F. , Gombos Eva , Smith Darrell N. , Carretero Macarena , Leon Bill , Freyre Carlos V. , Chavoustie Steven E.
Published: July 2009

Purpose

To investigate the effect of a negative pressure fixation device on misregistration artifacts in contrast‐enhanced (CE) MR subtraction images.

Materials and Methods

Nine patients, two of which had been previously diagnosed with breast cancer, were examined with T2‐weighted (T2‐w) turbo spin‐echo (TSE) and three‐dimensional (3D) spoiled gradient‐recalled echo (SPGR) CE dynamic MRI. Baselines images were subtracted from the dynamic images. A device consisting of two stiff plastic domes was placed on the breasts of each patient. Negative pressure of 27 to 37 mmHg within the domes was maintained. The patient was positioned prone in the coil without the device and imaged as a baseline. Subsequently, the patient was placed into the negative pressure domes and reimaged. One of the nine patients was also imaged supine to establish feasibility for this positioning.

Results

With the use of the negative pressure fixation device, a reduction in misregistration artifact has been demonstrated in prone imaging. Patients reported improved comfort with the device and feasibility has been shown for supine imaging.

Conclusion

The device was shown to be MRI‐compatible and successfully applied in this pilot study, opening other avenues of exploration. Supine positioning for breast imaging makes possible better access for biopsy and intervention. Further modifications to the device are in order for this purpose and to eliminate motion due to breathing in the prone position. J. Magn. Reson. Imaging 2009;30:430–436. © 2009 Wiley‐Liss, Inc.
Prostate cancer detection with multi‐parametric MRI: Logistic regression analysis of quantitative T2, diffusion‐weighted imaging, and dynamic contrast‐enhanced MRI
Authors: Langer Deanna L. , van der Kwast Theodorus H. , Evans Andrew J. , Trachtenberg John , Wilson Brian C. , Haider Masoom A.
Published: July 2009

Purpose

To develop a multi‐parametric model suitable for prospectively identifying prostate cancer in peripheral zone (PZ) using magnetic resonance imaging (MRI).

Materials and Methods

Twenty‐five radical prostatectomy patients (median age, 63 years; range, 44–72 years) had T2‐weighted, diffusion‐weighted imaging (DWI), T2‐mapping, and dynamic contrast‐enhanced (DCE) MRI at 1.5 Tesla (T) with endorectal coil to yield parameters apparent diffusion coefficient (ADC), T2, volume transfer constant (Ktrans) and extravascular extracellular volume fraction (ve). Whole‐mount histology was generated from surgical specimens and PZ tumors delineated. Thirty‐eight tumor outlines, one per tumor, and pathologically normal PZ regions were transferred to MR images. Receiver operating characteristic (ROC) curves were generated using all identified normal and tumor voxels. Step‐wise logistic‐regression modeling was performed, testing changes in deviance for significance. Areas under the ROC curves (Az) were used to evaluate and compare performance.

Results

The best‐performing single‐parameter was ADC (mean Az [95% confidence interval]: Az,ADC: 0.689 [0.675, 0.702]; Az,T2: 0.673 [0.659, 0.687]; Az,Ktrans: 0.592 [0.578, 0.606]; Az,ve: 0.543 [0.528, 0.557]). The optimal multi‐parametric model, LR‐3p, consisted of combining ADC, T2 and Ktrans. Mean Az,LR‐3p was 0.706 [0.692, 0.719], which was significantly higher than Az,T2, Az,Ktrans, and Az,ve (P < 0.002). Az,LR‐3p tended to be greater than Az,ADC, however, this result was not statistically significant (P = 0.090).

Conclusion

Using logistic regression, an objective model capable of mapping PZ tumor with reasonable performance can be constructed. J. Magn. Reson. Imaging 2009;30:327–334. © 2009 Wiley‐Liss, Inc.
Monitoring of acute axonal injury in the swine spinal cord with EAE by diffusion tensor imaging
Authors: Feng Song , Hong Yin , Zhou Zhang , JinSong Zhang , XiaoFeng Dai , ZaiZhong Wang , YaLi Ge , Ying Liu , YingJuan Chang , Yi Huan
Published: July 2009

Purpose

To evaluate the ability of diffusion tensor imaging (DTI) to detect and monitor acute axonal injury in swine spinal cord with acute experimental allergic encephalomyelitis (EAE).

Materials and Methods

Magnetic resonance imaging of the cervical spinal cord was performed in vivo at different time points through the onset and progression of EAE using a 3 Tesla clinical scanner. The DTI parameters were calculated in four separate regions of interest at the C2/C3 level. The quantitative DTI‐pathology and DTI‐clinical correlations were verified.

Results

In the monophasic acute course of EAE onset and progression, axial diffusivity (AD) decrease correlates with acute axonal injury (r = −0.84; P < 0.001). By contrast, radial diffusivity does not change and no demyelination in histopathology was detected. Moreover, a clear correlation between clinical disease and axial diffusivity was found in two swine EAE models (r = −0.86; P < 0.001 and r = −0.92; P < 0.001).

Conclusion

AD corresponds with axonal injury in the absence of demyelination and may be a useful noninvasive tool to investigate the underlying pathogenic processes of multiple sclerosis and to monitor the effects of experimental treatments for axonal injury. J. Magn. Reson. Imaging 2009;30:277–285. © 2009 Wiley‐Liss, Inc.
Evaluating the role of zinc in the occurrence of fibrosis of the skin: A preclinical study
Authors: Pietsch Hubertus , Pering Christiane , Lengsfeld Philipp , Walter Jakob , Steger‐Hartmann Thomas , Golfier Sven , Frenzel Thomas , Hütter Joachim , Weinmann Hans‐Joachim , Sieber Martin A.
Published: July 2009

Purpose

To investigate the possible role of Zn as a trigger for NSF we were using a previously established preclinical model. The depletion of endogenous Zinc ions (Zn) caused by the administration of gadolinium‐based contrast agents (GBCAs) has been suggested as a possible pathomechanism for nephrogenic systemic fibrosis (NSF).

Materials and Methods

In the Zn supplementation study, rats were injected with Gadodiamide, Omniscan, and Magnevist with or without Zn supplementation. In the Zn depletion study, animals were kept on a Zn‐deficient diet or a special control diet and received injections of Omniscan, OptiMARK, Magnevist, Gadovist, and Gd‐EDTA. Gd, Zn, and Cu concentrations in tissue were measured and histology of the skin was performed.

Results

As seen in earlier studies, a difference in Gd concentration in the skin was observed following treatment with the different GBCAs. High Gd concentration in the skin correlated with the occurrence of NSF‐like skin lesions. We observed no differences in the occurrence of skin lesions between the Zn supplementation and the Zn‐deficient groups compared to their respective control groups.

Conclusion

We found no significant effect of Zn on the initiation of NSF‐like skin lesions. The results further support data from previous studies highlighting the importance of complex stability of the investigated GBCAs. J. Magn. Reson. Imaging 2009;30:374–383. © 2009 Wiley‐Liss, Inc.
Susceptibility effects in hyperpolarized 3He lung MRI at 1.5T and 3T
Authors: Deppe Martin H. , Parra‐Robles Juan , Ajraoui Salma , Parnell Steven R. , Clemence Matthew , Schulte Rolf F. , Wild Jim M.
Published: July 2009

Purpose

To compare susceptibility effects in hyperpolarized 3He lung MRI at the clinically relevant field strengths of 1.5T and 3T.

Materials and Methods

Susceptibility‐related B0 inhomogeneity was evaluated on a macroscopic scale by B0 field mapping via phase difference. Subpixel susceptibility effects were quantified by mapping T. Comparison was made between ventilation images obtained from the same volunteers at both field strengths.

Results

The B0 maps at 3T show enhanced off‐resonance effects close to the diaphragm and the ribs due to susceptibility differences. The average T from a voxel (20 × 4 × 4) mm3 was determined as T = 27.8 msec ± 1.2 msec at 1.5T compared to T = 14.4 msec ± 2.6 msec at 3T. In ventilation images the most prominent effect is increased signal attenuation close to the intrapulmonary blood vessels at higher B0.

Conclusion

Image homogeneity and T are lower at 3T due to increased B0 inhomogeneity as a consequence of susceptibility differences. These findings indicate that 3He imaging at 3T has no obvious benefit over imaging at 1.5T, as signal‐to‐noise ratio (SNR) was comparable for both fields in this work. J. Magn. Reson. Imaging 2009;30:418–423. © 2009 Wiley‐Liss, Inc.
Imaging the vessel wall in major peripheral arteries using susceptibility‐weighted imaging
Authors: Yang Qi , Liu Jiantao , Barnes Samuel R.S. , Wu Zhen , Li Kuncheng , Neelavalli Jaladhar , Hu Jiani , Haacke E. Mark
Published: July 2009

Purpose

To demonstrate a novel contrast mechanism for imaging the vessel wall and vessel wall calcification using susceptibility‐weighted imaging (SWI).

Materials and Methods

Eighteen subjects were imaged with multidetector computed tomography (MDCT) and high‐resolution SWI at 3T. The SWI imaging parameters were optimized to allow for the best visualization of the femoral artery lumen and the arterial wall in magnitude and phase images, respectively. SWI‐filtered phase data were used to evaluate the diamagnetic susceptibility of vessel wall and of putative vessel wall calcification. Imaging was performed using TE = 15.6 msec (in‐phase for fat); TR = 25 msec, flip angle (FA) = 10°, bandwidth (BW) = 80 Hz/pixel, resolution = 0.5 × 0.5 mm in‐plane and 1.0 mm through‐plane, an acquisition matrix of 512 × 384 × 64 (for read, phase, and slice‐select directions), and a total scan time of 8 minutes.

Results

Nineteen calcifications were identified in CT and SWI and they correlated well in both size and position. The contrast‐to‐noise ratio between the blood signal in the lumen of the artery and arterial wall was 11.7:1 and 7.4:1 in magnitude and in phase images, respectively.

Conclusion

SWI provides a novel means to visualize vessel wall and recognize the presence of calcification. J. Magn. Reson. Imaging 2009;30:357–365. © 2009 Wiley‐Liss, Inc.
Impact of audio/visual systems on pediatric sedation in magnetic resonance imaging
Authors: Lemaire Colette , Moran Gerald R. , Swan Hans
Published: July 2009

Purpose

To evaluate the use of an audio/visual (A/V) system in pediatric patients as an alternative to sedation in magnetic resonance imaging (MRI) in terms of wait times, image quality, and patient experience.

Materials and Methods

Pediatric MRI examinations from April 8 to August 11, 2008 were compared to those 1 year prior to the installation of the A/V system. Data collected included age, requisition receive date, scan date, and whether sedation was used. A posttest questionnaire was used to evaluate patient experience. Image quality was assessed by two radiologists.

Results

Over the 4 months in 2008 there was an increase of 7.2% (115; P < 0.05) of pediatric patients scanned and a decrease of 15.4%, (67; P = 0.32) requiring sedation. The average sedation wait time decreased by 33% (5.8 months) (P < 0.05). Overall, the most positively affected group was the 4–10 years. The questionnaire resulted in 84% of participants expressing a positive reaction to the A/V system. Radiological evaluation revealed no changes in image quality between A/V users and sedates.

Conclusion

The A/V system was a successful method to reduce patient motion and obtain a quality diagnostic MRI without the use of sedation in pediatric patients. It provided a safer option, a positive experience, and decreased wait times. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.
Assessment of mediastinal tumors with diffusion‐weighted single‐shot echo‐planar MRI
Authors: Razek Ahmed Abdel , Elmorsy Ahmed , Elshafey Mohsen , Elhadedy Tamer , Hamza Osama
Published: July 2009

Purpose

To assess the role of diffusion‐weighted single‐shot echo‐planar magnetic resonance imaging (MRI) in patients with mediastinal tumors.

Methods

Prospective study was conducted on 45 consecutive patients (29 male, 16 female, age 22–66 years, mean 41 years) with mediastinal tumor. They underwent diffusion‐weighted single‐shot echo‐planar MRI of the mediastinum with a b‐factor of 0, 300, and 600 sec/mm2. The apparent diffusion coefficient (ADC) value of the mediastinal tumor was correlated with the histopathological findings.

Results

The mean ADC value of malignant mediastinal tumors was 1.09 ± 0.25 × 10−3 mm2/sec, and of benign tumors was 2.38 ± 0.56 × 10−3 mm2/sec. There was a significant difference in the mean ADC value between malignant and benign tumors (P = 0.001) and within different grades of malignancy (0.001). When an ADC value of 1.56 × 10−3 mm2/sec was used as a threshold value for differentiating malignant from benign tumor, the best results were obtained with an accuracy of 95%, sensitivity of 96%, specificity of 94%, positive predictive value of 94%, negative predictive value of 96%, and area under the curve of 0.938.

Conclusion

The ADC value is a noninvasive parameter that can be used for differentiation of malignant from benign mediastinal tumors and grading of mediastinal malignancy. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.
Protein adsorption in porous adsorbent particles: A multiscale modeling study on inner radial humps in the concentration profiles of adsorbed protein induced by nonuniform ligand density distributions
Authors: Riccardi Enrico , Wang Jee‐Ching , Liapis Athanasios I.
Published: July 2009

Recently published results determined from molecular dynamics (MD) modeling and simulation studies have shown that the spatial distribution of the density of immobilized charged ligands in ion‐exchange porous adsorbent particles is most likely nonuniform and the adsorbent particles also exhibit local nonelectroneutrality. In this work, the functional forms of the nonuniform spatial distributions of the density of the immobilized ligands in four different porous adsorbent media that were determined by MD studies were employed in a macroscopic continuum model describing the transport and adsorption of a single protein in the porous particles of the four different adsorbent media. The results clearly show that inner radial humps in the concentration profiles of the adsorbed protein can occur when the spatial distribution of the density of the immobilized ligands in the porous adsorbent particles is nonuniform and also has local maxima or minima along the radial direction in the particle. The results also indicate that the rate at which the equilibrium condition is approached depends significantly on the functional form of the spatial distribution of the density of the immobilized ligands. When adsorption equilibrium has been reached, the concentration profile of the adsorbed protein exhibits the shape of the spatial distribution of the density of the immobilized ligands. The results suggest that the technique of confocal scanning laser microscopy could be used to measure the concentration profile of an adsorbed protein at equilibrium and this measurement could provide the spatial distribution of the density of the immobilized ligands, and such measurements could also be used for quality control of the adsorbent medium. The results in this work have also implications in the modeling, design, analysis, and quality control of systems involving biocatalysis. Furthermore, the results clearly indicate that it is very important to study the dynamic behavior of an adsorption system having a nonuniform spatial distribution in the density of the immobilized charged ligands and where (i) both monovalent and multivalent interactions between the single charged adsorbate and the immobilized charged ligands occur and (ii) the values of the pH and ionic strength are such that the electrophoretic effects are active.
Modeling the effect of species retention on the band broadening in perfectly ordered silica monolithic column mimics with variable external porosity and intra‐skeleton diffusivity
Authors: Detobel Frederik , Gzil Piotr , Desmet Gert
Published: July 2009

Computational fluid dynamics simulations of the band broadening in an idealized, and highly ordered 3‐D model of silica monoliths are reported. As this high degree of order induces only a minimal eddy‐dispersion, the band broadening is very sensitive to the intra‐skeleton diffusivity and retention factor of the analytes. The simulations hence provide a maximal view on how the Cm‐ and Cs‐contributions to the band broadening depend on the intra‐skeleton diffusivity and retention factor. By comparing two model‐structures with different external porosities, some interesting qualitative insights on the effect of the through‐pore diameter are obtained as well. Because of the precisely known intra‐skeleton diffusivity, the obtained plate height data also provide an ideal test case for the general plate height expression of chromatography. Writing out this model, identifying the geometrical parameters, and determining their value using a parameter fitting algorithm, a set of parameter values can be found which allows to accurately predict the retention factor dependency of the band broadening over a very broad range of mobile phase velocities. Remaining modeling problems are the apparent intra‐skeleton diffusion dependency of the shape factor describing the intra‐skeleton mass transfer, and the absence of mathematical expressions to predict the model shape factor values.
Polymeric strong cation‐exchange monolithic column for capillary liquid chromatography of peptides and proteins
Authors: Chen Xin , Tolley H. Dennis , Lee Milton L.
Published: July 2009

A strong cation‐exchange (SCX) monolithic stationary phase was prepared in 75 μm id capillaries by direct in situ polymerization of sulfopropyl methacrylate and polyethylene glycol diacrylate in a ternary porogen system consisting of methanol, cyclohexanol, and water. The resulting monolith exhibited good dynamic binding capacity, fast kinetic adsorption of proteins, and high permeability. The monolith had a dynamic binding capacity of ˜52 mg/mL of column volume for lysozyme and cytochrome C. The monolith was evaluated for SCX capillary LC of synthetic peptides, natural peptides, and protein standards. Fast separation of proteins was achieved in less than 4 min. The average peak capacity for peptides was 28 using a relatively steep gradient when hydrophobic interactions were suppressed with 40% acetonitrile.
Synthesis and Characterization of Hyperbranched Poly(arylene ether)s from a New Activated Trifluoro B3 Monomer Adopting an A2 + B3 Approach
Authors: Banerjee Susanta , Komber Hartmut , Häußler Liane , Voit Brigitte
Published: July 2009

A new trifluoromethyl‐activated trifluoro monomer was successfully prepared by Pd‐initiated coupling of 1,3,5‐tribromobenzene with 4‐fluoro‐3‐trifluoromethylphenylboronic acid. 1,3,5‐Tris(4‐fluoro‐3‐trifluoromethylphenyl)benzene (B3) leads to several hyperbranched poly(arylene ether)s when reacted with three different bisphenols (A2) in different molar ratios. The 1.5:1 molar product of A2/B3 showed very high molecular weight without significant gelation. The products have been well characterized by GPC, DSC, TGA, FTIR, and NMR techniques. The 19F NMR signals were used to calculate the degree of branching. The 1.5:1 molar products have excellent thermal stability and higher glass transition temperatures than their linear analogs.

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Heterophase Polymerization as Synthetic Tool in Polymer Chemistry for Making Nanocomposites
Authors: Tauer Klaus , Weber Nancy , Nozari Samira , Padtberg Klaus , Sigel Reinhard , Stark Arne , Völkel Antje
Published: July 2009

Summary: The paper considers various possibilities to produce inorganic – polymeric nanocomposites via aqueous heterophase polymerization. Special emphasis is placed on strategies to synthesize nanocomposite particles via joint nucleation or joint polymerization. The former strategy is used to make composite particles with CaCO3 as inorganic component. The strategy of joint polymerization takes advantage from the condition that aqueous heterophase polymerization is a convenient possibility to synthesize amphiphilic block copolymers. This method relies on the fact that polymeric radicals can survive in isolated latex particles that are stabilized by hydrophilic blocks. This strategy can be successfully applied to produce silica‐containing block copolymer particles in a one‐step procedure.
Synthesis of Poly(vinyl acetate)‐block‐poly(dimethylsiloxane)‐block‐poly(vinyl acetate) Copolymers by Iodine Transfer Photopolymerization in Miniemulsion
Authors: Tonnar Jeff , Pouget Emmanuel , Lacroix‐Desmazes Patrick , Boutevin Bernard
Published: July 2009

Summary: Iodine transfer polymerization of vinyl acetate in aqueous miniemulsion, initiated by UV radiation in the presence of an α,ω‐diiodo‐poly(dimethylsiloxane) macrophotoiniferter has been performed. The formation of a triblock copolymer latex PVAc‐b‐PDMS‐b‐PVAc has been evidenced by 1H‐NMR and size exclusion chromatography. The size of the PDMS and PVAc blocks were modulated thus opening the way to a wide range of copolymers with different properties. A detailed study of the reaction mechanism showed the importance of the aqueous dispersed medium to achieve a controlled polymerization.
Emulsification for Latex Production Using Static Mixers
Authors: El‐Jaby Ula , Farzi Ghomali , Bourgeat‐Lami Elodie , Cunningham Michael , McKenna Timothy F.L.
Published: July 2009

Summary: Evolution of droplets generated by static mixers have been investigated in terms of surfactant concentration, flow rate through the pump, monomer hydrophobicity and the type of static mixer. Operating at faster pump flow rates and using the PAC static mixers generated smaller miniemulsion droplets. Similar effects were observed at higher surfactant concentrations (3.0 vs. 1.0 g/L) and using monomers of increasing hydrophilicity (MMA vs. St). When comparing the efficiency of PAC static mixers to SMX mixing elements it was found that SMX was capable of generating droplets approximately 100 nm smaller at similar pump flow rates in the same time period. Based on these promising results, the SMX mixers were further evaluated based on surfactant concentration. The miniemulsion droplets were polymerized and their distribution was evaluated.
Latex Film Formation in the Environmental Scanning Electron Microscope
Authors: Dragnevski Kalin , Donald Athene , Taylor Phil , Murray Martin , Davies Simon , Bone Elizabeth
Published: July 2009

Summary: Environmental scanning electron microscopy (ESEM) was used to study the film formation mechanisms and extent of coalescence of three acrylic latex compositions with different glass transition temperatures (Tg), here defined as standard‐low Tg, standard‐high Tg (both carboxymethyl cellulose‐ stabilised) and novel (stabilised with a novel polysaccharide derived from agricultural waste). The ESEM analysis revealed that the microstructure of the standard – low‐Tg system consisted of individual particles in dispersion and upon evaporation a continuous film formed, whereas in the case of the standard ‐ high Tg latex particle deformation was not observed, but particle aggregation resulted in the formation of crystal‐like structures that have formed via the formation of stacking faults. However, in the case of the novel system the microstructure consisted of individual particles and clusters and during evaporation a discontinuous film formed with voids present within its structure and some of the clusters accumulating on the surface of the specimens.
Polarity and Temperature‐Dependent Properties of Poly(N‐isopropylacrylamide) and Poly(N,N‐diethylacryl‐amide) Hydrogels Studied by Liquid Chromatography
Authors: Hradil Jiří , Macková Hana , Horák Daniel
Published: July 2009

Summary: Superporous N‐isopropylacrylamide (NIPAAm) and N,N‐diethylacrylamide (DEAAm) copolymers with N,N'‐methylenebisacrylamide (MBAAm) were prepared by radical polymerization with the aim to determine their temperature‐dependent changes in polarity by liquid chromatography. Superpores were formed by the salt‐leaching technique using NaCl as a porogen. Porosities of the hydrogels characterized by water regain and mercury porosimetry, ranging from 81 to 91%, were proportional to the volume of NaCl porogen in the feed. The retention volumes of several phenols decreased with increasing temperature as polarity of the hydrogels decreased. A jump change in solute retention volume was observed at ca. 32 °C in PNIPAAm and at ca. 35 °C in PDEAAm indicating a change in the mechanism of interaction. The Gibbs energy changes ΔGCH2 were rather low, increasing in the order phenol < benzyl alcohol < ethanol < butan‐1‐ol. In contrast to the solutes, retention volumes of bovine serum albumin and dextrans were higher at higher temperature confirming thus hydrophobic interactions of the compounds with the studied hydrogels.
Critical Exponents of Thermal Phase Transitions ofκ‐Carrageenan in Various Salt Solutions
Authors: Tarı Özlem , Pekcan Önder
Published: July 2009

Summary: The steady state fluorescence (SSF) technique was employed to study the phase transitions of κ‐carrageenan in NaCl and KCl solutions. Pyranine was used as a fluorescence probe for monitoring these transitions. Scattered light, Isc, and fluorescence intensity, I, was monitored against temperature to determine transition temperatures and exponents. It was observed that transition temperatures are strongly correlated with the NaCl and KCl contents. The weight‐average degree of polymerization, DPw and gel fraction G, exponents (γ and β) were measured and found to be in accord with the classical Flory‐Stockmayer model.
Surfactant and Electrolyte Effects on Latex Depletion Flocculation by Thickeners
Authors: Kostansek E. C.
Published: July 2009

Summary: Polymer thickeners can induce good dispersion, bridging, or depletion flocculation of latexes depending on the polymer structure and concentration. Unlike non‐associative polymers, associative polymers have the ability to create a good latex dispersion. However, when the associative interactions are destroyed, depletion flocculation of the latex can result. This happens when an excess of ionic surfactant is added to the system. In addition, the surfactant may associate with the thickener backbone, thus modifying the molecular volume of the polymer thickener. This paper explores the effect of anionic surfactant and electrolyte on the molecular volume of both associative and non‐associative thickeners. Both HEUR and HASE structures are included. For HEUR thickeners, formation of a pseudo‐polyelectrolyte through the association of anionic surfactant with the polyethylene oxide backbone is confirmed. Further, the ability of the thickener to depletion flocculate latexes as a function of surfactant and electrolyte is explored. Experimental critical flocculation concentrations (CFC) are compared to values expected based on molecular volume and potential energy calculations. A good correlation is found between molecular volume and CFC for a wide range of thickener compositions.
Compact CPW‐fed tri‐band monopole antenna for PCS and 2.4/5GHz WLAN applications
Authors: Chen Lei , Shi Xiao‐wei , Zhang Tian‐ling , Song Yue
Published: July 2009

A compact tri‐band monopole antenna with coplanar waveguide (CPW)‐fed structure is presented for applications in PCS and 2.4/5 GHz WLAN systems. By using a spiral strip and a meandered strip closed to an inverted‐L ground strip, the proposed antenna with a compact size of 30 × 30 × 1.6 mm3 including the ground can not only meet the impedance bandwidth requirements for PCS band (1.85–1.99 GHz) and WLAN bands (2.4–2.484 GHz and 5.15–5.825 GHz), but also can provides good radiation characteristics and antenna gains for the operating bands, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2495–2498, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24593
A novel K‐shaped dual‐band antenna with a shorting pin for WLAN communications
Authors: Choi Sun‐Ho , Lee Hwa‐Choon , Kwak Kyung‐Sup
Published: July 2009

In this article, a novel K‐shaped dual‐band antenna with a shorting pin for 5.2/5.8 GHz wireless local area network (WLAN) operations is designed and fabricated. To obtain sufficient bandwidth when return loss (RL) < −10 dB, a shorting pin is inserted in the patch and a coaxial probe source is used. The measured result of the fabricated antenna has 221 MHz bandwidth from 5.145 to 5.366 GHz and a 187 MHz bandwidth from 5.695 to 5.882 GHz (RL < −10 dB) with the gain ranging from 3.66 to 4.58 dBi. A good radiation pattern is achieved for the WLAN band (5.150–5.350 GHz and 5.725–5.825 GHz) range. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2442–2444, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24609
Study of a uniplanar printed internal WWAN laptop computer antenna including user's hand effects
Authors: Lee Cheng‐Tse , Wong Kin‐Lu
Published: July 2009

A uniplanar monopole antenna to be printed on a thin (0.4 mm) and small‐size FR4 substrate and capable of GSM850/900/1800/1900/UMTS penta‐band WWAN operation for thin‐profile laptop computer application is presented. The antenna is formed by a direct‐fed shorter radiating strip for upper‐band operation at about 1900 MHz and a coupled‐fed longer radiating strip which is also short‐circuited to the antenna ground for lower‐band operation at about 900 MHz. Note that the two radiating strips are fed using different excitation mechanisms. With the coupling excitation and short‐circuiting, which functions as an internal printed matching circuitry, the longer radiating strip can provide a wide dual‐resonant lower band at around 900 MHz for GSM850/900 operation. A wide upper band can also be generated at about 1900 MHz for the antenna to cover GSM1800/1900/UMTS operation. The antenna is studied in the article, and the user's hand effects on the performances of the antenna are analyzed. The obtained results are useful for the antenna employed in the laptop computer with a touch panel. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2341–2346, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24614
Attenuation fitting functions
Authors: Fugihara Meire C. , Pinto Armando Nolasco
Published: July 2009

The usual exponential approximation for ultraviolet UV absorption in optical fibers could not fit the attenuation coefficient over a broad spectral range. As the UV absorption spectrum is a result of electronic transitions, we propose a Lorentzian function to model this contribution. Experimental results show a good agreement. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2294–2296, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24617
All‐optical clock division with simultaneous wavelength conversion using an optically injected Fabry‐Perot laser diode
Authors: Lv Yu‐Xiang , Sun Shuai , Yang Xing
Published: July 2009

The authors propose and experimentally demonstrate a novel technique that uses a single Fabry‐Perot laser diode (FP‐LD) to perform simultaneous all‐optical clock division and wavelength conversion. By utilizing the nonlinear dynamical period‐one oscillation and the cross‐gain modulation effect of the light injection semiconductor laser, we achieve the all optical clock frequency division of 12.36 GHz to 6.18 GHz with simultaneous wavelength conversion from 1550.24 nm to 1545.91 nm. The phase noise of the extracted optical clock is less than −105 dBc/Hz. It was empirically found that the best clock division and wavelength conversion occurred when the injected signal power was approximately 2–2.5 times as the injected probe light power, and the range of optimum wavelength detuning was about from −0.01 nm to 0.06 nm. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2428–2431, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24626
A highly efficient class‐F power amplifier for wideband linear power amplifier applications
Authors: Kim Jangheon , Moon Junghwan , Hong Sungchul , Kim Bumman
Published: July 2009

In this letter, a highly efficient class‐F power amplifier (PA) is developed as a new main block of the wideband base‐station linear power amplifier. The class‐F PA is implemented using Eudyna EGN010MK GaN HEMT with a 10‐W peak envelop power. The nonlinearity and memory effects of class‐F PA are explored to apply the wideband application. The maximum power‐added efficiency of the implemented PA is 68% at a saturated output power of 40 dBm for the 2.14‐GHz CW signal. The PA delivers a good efficiency of 35% at an average output power of 32.3 dBm for wide‐band code division multiple access 3FA signal with 15‐MHz bandwidth, and the linearity can be improved to about −48 dBc using the digital feedback predistortion linearization technique. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2323–2326, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24631
Tunable medium power multiwavelength fiber laser
Authors: Dastmalchi Mansour , Das Gautam
Published: July 2009

The authors report a medium power spacing tunable multiwavelength fiber laser operating at room temperature. A double‐clad erbium‐ytterbium co‐doped fiber was used to produce high output power. An unpumped polarization‐maintaining fiber and a Lyot‐Sagnac loop filter with multiple segments of polarization‐maintaining fibers were used as a saturable absorber to stabilize the laser wavelengths and tunable filter to tune the separation between lasing wavelengths, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2517–2519, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24648
Solution of very large integral‐equation problems with single‐level FMM
Authors: Landesa L. , Taboada J. M. , Obelleiro F. , Rodríguez J. L. , Mouriño C. , Gómez A.
Published: July 2009

We present a massively parallel version of the single‐level fast multipole method, which allows the efficient use of hundreds of processors. A very large problem with more than 32 millions of unknowns is solved in 512 processors, which becomes a new record in scalability for this kind of problems. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2451–2453, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24651
Circularly polarized ceramics dielectric resonator antenna excited by Y‐shaped microstrip
Authors: Li Li‐Xian , Zhong Shun‐Shi , Xu Sai‐Qing , Chen Min‐Hua
Published: July 2009

A circularly polarized ceramics dielectric resonator antenna fed by a Y‐shaped microstrip is proposed and analyzed. The CP design is achieved by simply adjusting the lengths and widths of two quadrate shorted stubs. The antenna is compact in structure, whose radius is only 4.5 mm. The reflection, polarization, and radiation characteristics of the antenna are studied. For the proposed antenna, with relative dielectric constant of resonator εr1 = 38, a measured impedance bandwidth of 6.8%, a measured minimum axial ration of 0.8 dB, and a wide beamwidth of 164°are achieved. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2416–2418, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24653
A slot‐coupling coplanar waveguide‐fed fan‐shaped antenna embedded in semicircle aperture
Authors: Li Qin‐Yi , Zhao Gang , Jiao Yong‐Chang
Published: July 2009

A novel design of a fan‐shaped antenna embedded in semicircle aperture is proposed and experimentally studied in this article. The proposed antenna is fed by a tapered coplanar waveguide (CPW) and has an ultrawide band owing to the coupling between the fan‐shaped radiation unit and the ground. From experimental results, the measured impedance bandwidth of the antenna, determined by −10 dB return loss, can reach an operating bandwidth of 23.36 GHz (1.64–25 GHz), more than 175% with the center frequency operating at about 13.32 GHz. Good radiation patterns and gains covering the operating band have been observed. Details of the antenna design and experimental results are discussed in this article. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2385–2387, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24655
An ultra‐wideband bandpass filter using hybrid structure of microstrip and CPW
Authors: Luo Xun , Ma Jian‐Guo , Ma Kaixue , Yeo Kiat Seng
Published: July 2009

An ultra‐wideband (UWB) bandpass filter is proposed based on the hybrid structure of microstrip and coplanar waveguide (CPW). First, the detached‐mode resonator is formed on the CPW layer, which composes a quarter‐wavelength (λ/4) multiple‐mode resonator (MMR) with a short‐stub and a λ/4 single‐mode resonator. Then, two λ/4 microstrip open‐stubs on the top side of the common substrate are introduced for bandwidth enhancement to meet the UWB passband limit. Quasi‐elliptic function response and UWB operation are achieved. The simulated and measured results show an excellent agreement. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2470–2473, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24658
A suspended microstripline‐fed K‐band linear‐tapered slot antenna element and its 4 × 4 array designed by the finite‐difference time‐domain method
Authors: Wu Chen
Published: July 2009

A linear‐tapered slot antenna (LTSA) element fed by a novel suspended microstripline (SML) feed structure is presented in this article. The element is designed using the finite‐difference time‐domain (FDTD) method. It shows that the element has a wide impedance bandwidth in K‐band. Using the new element, a 4 × 4 SML parallel‐feed array has been designed and built. The measured results demonstrate that the array matches its 50‐ohm SML feed line in a wide frequency band, has better than 16 dBi gain from 17.7 to 23.3 GHz, and has low cross polarizations in both the E‐ and H‐plane. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2406–2410, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24662
Design of X‐band 6‐bit CMOS phase shifter for phased array T/R modules
Authors: Kang Dong‐Woo , Ku Bon‐Hyun , Hong Songcheol
Published: July 2009

This article presents the design of a 6‐bit phase shifter in a 0.18‐μm CMOS technology for X‐band phased array radar application. Meandered microstrip lines and compact circuit designs techniques yield a chip with 1.9 mm2 die area. The fabricated phase shifter demonstrates a typical 15.7 ± 1.1 dB insertion loss and a 4° rms phase shift error at 9.5 GHz. To the author's knowledge, this is the first demonstration of a 6‐bit phase shifter using CMOS switches with the lowest die area among reciprocal digital phase shifters at X‐band. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2404–2406, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24663
Transmission 32 × 10 Gb/s using LEAF and RDF in C band and L band for DWDM dispersion compensation
Authors: Lin Hsiu‐Sheng , Lai Po‐Chou
Published: July 2009

We propose the experiment transport of 32 channels 10 Gbit/s dense wavelength division multiplexing (DWDM) system which uses large effective area fiber (LEAF) in combination with reverse dispersion fiber (RDF), which is a dispersion compensation device, in C and L band wavelength range to solve the dispersion program. The system structure transmission length of 800‐km consisted of 75‐km LEAF and 5‐km RDF for ten fiber spans. Q factor should be greater than 6 dB for good performance, corresponding to a bit error rate (BER) of less than 10−9, and all 32 channels have been measured for both Q factor and BER. The proposed system is applicable for ultra long‐haul transmission in DWDM systems. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2489–2492, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24667
Structure elucidation and complete NMR spectral assignments of two new oleanane‐type pentacyclic triterpenoid saponins from the husks of Xanthoceras sorbifolia Bunge
Authors: Guo Ying , Dou De‐Qiang , Kang Ting‐Guo , Wang Shi‐Cheng , Kuang Hai‐Xue
Published: July 2009

Two new saponins were isolated from husks of Xanthoceras sorbifolia Bunge and their structures were elucidated as 3‐O‐[β‐D‐galactopyranosyl(1→2)]‐α‐L‐arabinofuranosyl(1→3)‐β‐D‐methyl glucuronic acid‐21‐O‐(3,4‐diangeloyl)‐α‐L‐rhamnose‐3β, 16α, 21β, 22α, 28β‐pentahydroxyl‐22‐acetoxy‐olean‐12‐ene(1) and 3‐O‐[β‐D‐galactopyranosyl(1→2)]‐α‐L‐arabinofuranosyl(1→3)‐β‐D‐methyl glucuronic acid‐21,22‐O‐diangeloyl‐3β,15α,16α,21β,22α,28β‐hexahydroxyl‐olean‐12‐ene(2) on the basis of 1D and 2D NMR (including 1H, 13C‐NMR, 1H1H COSY, HSQC, HMBC and DEPT), ESI‐MS spectrometry and chemical methods. Copyright © 2009 John Wiley & Sons, Ltd.
Structural studies on aryl‐substituted enaminoketones and their thio analogues. Part II. Experimental and DFT calculated carbon–carbon coupling constants, nJ(CC)'s (n = 1–3)
Authors: Bugaj Marta , Baran Piotr A. , Kamieńska‐Trela Krystyna , Krówczyński Adam
Published: July 2009

Spin–spin carbon–carbon coupling constants across one, two and three bonds, J(CC), have been measured for a series of aryl‐substituted Z‐s‐Z‐s‐E enaminoketones and their thio analogues. As a result, a large set, altogether 178, of J(CC)s has been obtained. It consists of 82 couplings across one bond, 31 couplings across two bonds and 65 couplings across three bonds. Independently, the DFT calculations at the B3PW91/6‐311++G(d,p)//B3PW91/6‐311++G(d,p) level yielded a set of theoretical J(CC) values. A comparison of these two sets of data gave an excellent linear correlation with parameters a and b close to ideal; a = 0.9978 which is not far from unity and b = 0.22 Hz which is close to zero. The 1J(CC) couplings determined for the crucial fragment of the molecules, i.e. CCCO (or CCCS), are: 1J(CC) ≈ 68 Hz (67 Hz) and 1J(CC) = 60.5 Hz (60.0 Hz). The corresponding couplings found for the Z‐s‐Z‐s‐E isomer of the parent enaminoketone, 4‐methylamino‐but‐3‐en‐2‐one are 64.1 and 59.3 Hz, respectively. The most sensitive towards substitution of the oxygen atom by sulfur are two‐bond couplings between the α‐vinylic and aromatic Cipso carbon atoms, which attain 12 Hz in the enaminoketone derivatives and decrease to 5 Hz in their thio analogues. Copyright © 2009 John Wiley & Sons, Ltd.
Torsion angle relationship of the 17O NMR chemical shift in α,β‐unsaturated carbonyl compounds
Authors: Mocci Francesca
Published: July 2009

The torsion angle effect on the isotropic shielding of 17O nucleus in α,β‐unsaturated carbonyl groups is studied by means of density functional theory (DFT) calculations using a polarizable continuum model (PCM) for the solvent, employing the PBE0 functional together with the 6‐311G(d,p) basis set for geometry optimization, and the 6‐311+G(2d,p) basis set for calculating the NMR shielding with the gauge‐including atomic orbitals (GIAO) method.

This study adds new information on the sensitivity of the 17O nucleus to conformational changes, revealing a strong dependence of the 17O NMR chemical shift on the dihedral angle between the carbonyl and the vinyl moiety in all studied compounds; remarkable differences are observed with the data reported for α‐diketones. Copyright © 2009 John Wiley & Sons, Ltd.
Green and rapid preparation of thermally stable and highly organosoluble polyamides containing L‐phenylalanine‐9,10‐dihydro‐9,10‐ethanoanthracene‐11,12‐dicarboximido moieties
Authors: Mallakpour Shadpour , Rafiee Zahra
Published: July 2009

A chiral diacid monomer containing L‐phenylalanine‐9,10‐dihydro‐9,10‐ethanoanthracene‐11,12‐dicarboximido unit was successfully synthesized in four steps and used in the preparation of a series of novel optically active polyamides by direct polycondensation with diverse aromatic diamines using 1,3‐dipropylimidazolium bromide under microwave dielectric heating. Ionic liquids (ILs) efficiently absorb microwave energy and thus are employed as solvent. By controlling the concentration of 1,3‐dipropylimidazolium bromide, reaction time and power level, high yield and moderate inherent viscosity polymers could be achieved in a very short period of time. All the resulting polymers exhibited excellent solubility in various organic solvents. The polyamides were found to have inherent viscosities in the range of 0.54–0.85 dL g−1. These polyamides had glass‐transition temperatures (Tg) above 180°C, and a 10% weight‐loss temperatures in excess of 340°C with char yield at 800°C in nitrogen higher than 40%. A comparative study on effects exerted by microwave technique with conventional method is also presented. Copyright © 2009 John Wiley & Sons, Ltd.
O‐glycoside sequence of pentacyclic triterpene saponins from Phytolacca bogotensis using HPLC‐ESI/multi‐stage tandem mass spectrometry
Authors: Montoya Guillermo , Arango Gabriel J. , Unger Matthias , Holzgrabe Ulrike
Published: July 2009

Introduction – The lack of pharmacopoeial methodologies for the quality control of plants used for therapeutic purposes is a huge problem that impacts directly upon public health. In the case of saponins, their great structural complexity, weak glycoside bonds and high polarity hinder their identification by conventional techniques.

Objective – To apply high‐performance liquid chromatography–electrospray tandem mass spectrometry (HPLC‐ESI/MSn) to identify the O‐glycoside sequence of saponins from the roots of Phytolacca bogotensis.

Methodology – Saponins were isolated by preparative HPLC and characterised by NMR spectroscopic experiments. Collision‐induced dissociation (CID) of isolated saponins was performed producing typical degradation reactions that can be associated with several glycosidic bonds as empirical criteria. A method using solid‐phase extraction (SPE) and HPLC/ESI‐MSn for the characterisation of saponins and identification of novel molecules is described.

Results – Three saponins reported for the first time in P. bogotensis were isolated and characterised by NMR spectroscopy. Characteristic cross ring cleavage reactions have been used as empirical criteria for the characterisation of the glycosidic bonds most frequently reported for Phytolacca saponins. One new saponin was proposed on the basis of empirical criteria, and other five saponins were identified for the first time for P. bogotensis using HPLC‐ESI/MSn.

Conclusion – Electrospray ionisation in combination with tandem mass spectrometry has been established as a powerful tool for the profiling of saponins from roots of P. bogotensis. CID proved to be a useful tool for the characterisation and identification of known and novel saponins from the plant family Phytolaccaceae and can be used for quality control purposes of crude plant extracts. Copyright © 2009 John Wiley & Sons, Ltd.