bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on high power single‐frequency erbium doped fiber laser for long distance communications
Authors: Wang Tianshu 
Published: March 2008

AbstractTo stabilize the frequency, a structure with fiber seed laser plus fiber amplifier module is designed. Using only one laser diode simultaneously pumps fiber amplifier and laser through a coupler with special ratio. Single‐frequency fiber laser with high‐output power and low‐noise is achieved. The center‐wavelength is 1550.16 nm while the 3 dB spectrum‐width of output laser is 0.08 nm and the side mode suppression ratio is 55 dB. The maximum output power exceeds 23 mW, the slope efficiency is more than 20%, and the stability is less than ±0.005 dB. A nice single‐frequency is observed and the modes adjacent to the lasing mode are completely suppressed. A 10 Gbps codes rate is used in the fiber laser transmission experiment. The signal is transmitted in 42 km without regeneration. The eye diagrams of optical transmission are measured, the performance of long‐haul transmission with high‐speed modulation is perfect. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1660–1662, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23449
Low‐cost flat metal‐plate dipole antenna for 2.4/5‐GHz WLAN operation
Authors: Su Saou‐Wen , Chou Jui‐Hung 
Published: March 2008

AbstractA low‐cost, one‐piece, flat‐plate dipole antenna for dual WLAN band operation is presented. The dipole antenna is rectangular in shape with the dimensions 10 mm × 37 mm and fed by 50‐Ω mini‐coaxial cable. By cutting two L‐shaped slits in each radiating arm, two dipole arms are obtained, which form a larger dipole and a smaller dipole antennas for the 2.4‐ and 5‐GHz band operation, respectively. The dipole arms are further short‐circuited, making it possible for the antenna to be fabricated by stamping a single, flat metal plate only. The impedance bandwidth for 2.4/5‐GHz WLAN operation is with VSWR below 1.5 and good omnidirectional radiation patterns are also observed. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1686–1687, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23461
Compact dual band Wilkinson power divider
Authors: Mohra Ashraf S. S. 
Published: March 2008

AbstractThis article presents the design of a compact Wilkinson power divider for dual applications. The design is accomplished by transforming the length and impedance of the quarter wave sections of the conventional Wilkinson power divider into dual band Π‐shaped sections. Simple design equations for basic design geometry are given. The dual band power divider geometry is analyzed using EM simulator and then realized at 1.8 and 4.775 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1678–1682, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23465
Accelerated whole‐heart 3D CSPAMM for myocardial motion quantification
Authors: Rutz Andrea K. , Ryf Salome , Plein Sven , Boesiger Peter , Kozerke Sebastian 
Published: March 2008

AbstractMyocardial tissue tagging using complementary spatial modulation of magnetization (CSPAMM) allows detailed assessment of myocardial motion. To capture the complex 3D cardiac motion pattern, multiple 2D tagged slices are usually acquired in different orientations. These approaches are prone to slice misregistration and associated with long acquisition times. In this work, a fast method for acquiring 3D CSPAMM data is proposed that allows measuring deformation of the whole heart in three breath‐holds of 18 heartbeats duration each. Three acquisitions are sequentially performed with line tag preparation in each orthogonal direction. Measurement acceleration is achieved by applying localized tagging preparation and a hybrid multishot, segmented echo‐planar imaging sequence. Five healthy volunteers and five patients with myocardial infarction were measured. Midwall contours were tracked throughout the cardiac cycle with an enhanced variant of the harmonic phase (HARP) technique. Circumferential shortening at end‐systole ranged from 14.1% (base) to 20.1% (apex) in healthy subjects. Hypokinetic regions in patients corresponded well with regions exhibiting hyperenhancement after contrast injection. Time to maximum circumferential shortening varied more significantly over the left ventricle in patients than in volunteers (P < 0.01). The proposed measurement scheme was well tolerated by patients and holds considerable potential to investigate cardiac mechanics in various diseases. Magn Reson Med 59:755–763, 2008. © 2008 Wiley‐Liss, Inc.
Radial single‐shot STEAM MRI
Authors: Block Kai Tobias , Frahm Jens 
Published: March 2008

AbstractRapid MR imaging using the stimulated echo acquisition mode (STEAM) technique yields single‐shot images without any sensitivity to resonance offset effects. However, the absence of susceptibility‐induced signal voids or geometric distortions is at the expense of a somewhat lower signal‐to‐noise ratio than EPI. As a consequence, the achievable spatial resolution is limited when using conventional Fourier encoding. To overcome the problem, this study combined single‐shot STEAM MRI with radial encoding. This approach exploits the efficient undersampling properties of radial trajectories with use of a previously developed iterative image reconstruction method that compensates for the incomplete data by incorporating a priori knowledge. Experimental results for a phantom and human brain in vivo demonstrate that radial single‐shot STEAM MRI may exceed the resolution obtainable by a comparable Cartesian acquisition by a factor of four. Magn Reson Med 59:686–691, 2008. © 2008 Wiley‐Liss, Inc.
Visualization of the coherence of the principal diffusion orientation: An eigenvector‐based approach
Authors: Wang JiunJie , Lin YuChun , Wai YauYau , Liu HaoLi , Lin ChingPo , Huang YingZu 
Published: March 2008

AbstractA novel method for spatially mapping anisotropy/orientation coherence of the eigenvector is presented. By using an eigenvector‐based approach, an intervoxel diffusion coherence (IVDC) index was used to quantify the coherence of the principal diffusion directions within a voxel neighborhood. This method may allow reconstruction of a whole brain map to be used for diagnostic purposes. The IVDC index is calculated by a scatter matrix‐based method in a voxel‐wise manner. A simulation was performed using two fiber populations crossing at various separation angles. We demonstrate that the IVDC index was more sensitive than fractional anisotropy (FA) to changes in separation between the fibers under a noise‐free condition. Diffusion‐tensor images of six healthy volunteers were acquired on a 3.0T MR imager. The FA, coherence index, and IVDC were then calculated. The results showed that IVDC improved the contrast in several brain areas including thalamus, middle cerebral peduncle, and pons. We therefore conclude that the IVDC index provides reliable and complementary information on water diffusion in the brain. It may be useful in white matter tractography, especially to determine the termination point of a trajectory. Magn Reson Med 59:764–770, 2008. © 2008 Wiley‐Liss, Inc.
Additive angle method for fast large‐tip‐angle RF pulse design in parallel excitation
Authors: Grissom William A. , Yip Chun‐Yu , Wright Steven M. , Fessler Jeffrey A. , Noll Douglas C. 
Published: March 2008

AbstractCurrent methods for parallel excitation RF pulse design are based on the small‐tip‐angle approximation, which provides a computationally efficient means of pulse calculation. In general, pulses designed with those methods are inaccurate when scaled to produce large‐tip angles, and methods for large‐tipangle pulse design are more computationally demanding. This paper introduces a fast iterative method for large‐tip‐angle parallel pulse design that is formulated as a small number of Bloch equation simulations and fast small‐tip‐angle pulse designs, the results of which add to produce large‐tip‐angle pulses. Simulations and a phantom experiment demonstrate that the method is effective in designingmultidimensional large‐tip‐angle pulses of high excitation accuracy, compared to pulses designed with small‐tip‐angle methods. Magn Reson Med 59:779–787, 2008. © 2008 Wiley‐Liss, Inc.
Modification of embolic‐PVA particles with MR contrast agents
Authors: Cilliers Renee , Song Ying , Kohlmeir Ellen K. , Larson Andrew C. , Omary Reed A. , Meade Thomas J. 
Published: March 2008

AbstractWe report the synthesis and characterization of polyvinyl alcohol (PVA) embolic particles modified with a clinically approved magnetic resonance (MR) contrast agent. PVA particles are used during transcatheter arterial embolization (TAE) procedures and this minimally invasive technique is a widely employed treatment for inoperable tumors. The PVA particles are injected into tumor vessels and prevent blood flow which results in tumor attenuation. An accurate assessment of the endpoint of embolization is critical to successful TAE procedures. Recent reports suggest that 20% of endpoint determination of TAE procedures by angiographic techniques are erroneous. Real time, in vivo imaging of the embolic particles would overcome this limitation. The contrast‐modified PVA particles described here show an 80% decrease in T1 relaxation times compared to unmodified particles. Images of particles in capillary tubes of similar size to catheters used in TAE procedures are clearly visible by MRI. Magn Reson Med 59:898–902, 2008. © 2008 Wiley‐Liss, Inc.
Fractionated feridex and positive contrast: In vivo MR imaging of atherosclerosis
Authors: Briley‐Saebo Karen C. , Mani Venkatesh , Hyafil Fabien , Cornily Jean‐Christophe , Fayad Zahi A. 
Published: March 2008

AbstractMacrophages have been identified as a critical factor in the pathogenesis of atherosclerosis. Ultrasmall iron oxide particles (USPIOs) have been used to passively target intraplaque macrophages. For dextran‐based USPIOs, uptake into macrophages may be modulated by particle size. The aim of the current study was to test the efficacy of fractionated Feridex with respect to macrophage uptake in atherosclerotic rabbits. Fractionation of Feridex resulted in a 15‐nm USPIO that exhibited a blood half‐life of 15.9 h and liver retention of 6.4%. Blood clearance and liver retention of Feridex was 0.46 h and 60%, following administration of 4.8 mg Fe/kg Feridex. Atherosclerotic rabbits were administered 0.5 or 4.8 mg Fe/kg dosages of either fractionated Feridex or Feridex. MRI was performed at 1.5T over a 24‐h time period postinjection. Perls and RAM‐11 staining was performed to identify iron deposition. MRI showed a dose‐dependent signal loss using conventional gradient echo (GRE) sequences following administration of fractionated Feridex. Even at low dose, significant signal loss was observed that correlated with histology. No signal attenuation or iron deposition was observed in the vessel wall of rabbits administered Feridex. Results of this study suggest that it may be possible to optimize USPIOs for intraplaque macrophage detection. Magn Reson Med 59:721–730, 2008. © 2008 Wiley‐Liss, Inc.
Spinal cord blood flow measurement by arterial spin labeling
Authors: Duhamel Guillaume , Callot Virginie , Cozzone Patrick J. , Kober Frank 
Published: March 2008

AbstractThe assessment of spinal cord (SC) hemodynamics, and especially SC blood flow (SCBF), plays a key role in the pathophysiological description and understanding of many SC diseases such as ischemia, or spinal cord injury. SCBF has been previously measured in animals with invasive techniques such as autoradiography or labeled microspheres; no MR technique, however, has been proposed so far. The possibility of quantitatively measuring SCBF in mice using MRI was investigated using a presaturated FAIR (flow‐sensitive alternating inversion recovery) arterial spin labeling (ASL) technique. SCBF measurements were performed at the cervical level of the mouse as well as on the brain so as to use cerebral blood flow (CBF) values as internal references. With a spatial resolution of 133 × 133 μm2 for the SCBF maps, absolute regional perfusion values could be measured within the different structures of the SC (gray matter, white matter, and cerebrospinal fluid area). Similar perfusion values were found in SC gray matter (330 ± 90 mL/100g/min) and in brain (295 ± 22 mL/100g/min for thalamus). This result, in agreement with SCBF/CBF measurements performed with non‐MR techniques, opens new perspectives for noninvasive longitudinal and in vivo animal studies. Application to human experiments may also be possible. Magn Reson Med 59:846–854, 2008. © 2008 Wiley‐Liss, Inc.
Imaging brain vasculature with BOLD microscopy: MR detection limits determined by in vivo two‐photon microscopy
Authors: Park Sung‐Hong , Masamoto Kazuto , Hendrich Kristy , Kanno Iwao , Kim Seong‐Gi 
Published: March 2008

AbstractRat brain vasculature was imaged at 9.4T with blood oxygenation level‐dependent (BOLD) microscopy. Data were acquired without exogenous contrast agent in <35 min using 3D gradient‐echo imaging with 78‐μm isotropic resolution. Detailed vascular patterns including intracortical veins and some branches were observed in simple magnitude‐contrast data acquired at an experimentally optimized echo time. The venous origin of the dark patterns was confirmed by oxygenation‐dependent studies, and when the systemic arterial oxygen saturation level was <80% BOLD microscopy revealed additional intracortical vessels presumed to be of arterial origin. Quantification shows a decrease of intracortical venous density with depth. The full width at half‐minimum intensity was 90–190 μm for most intracortical venous vessels identifiable by BOLD venography. Since actual diameters are not directly quantifiable by BOLD, we also measured diameter‐dependent intracortical venous density in vivo by two‐photon excitation fluorescent microscopy. Density comparisons between the two modalities, along with computer simulations, show that venous vessels as small as ≈16–30 μm diameter are detectable with 9.4T BOLD microscopy under our experimental conditions. Magn Reson Med 59:855–865, 2008. © 2008 Wiley‐Liss, Inc.
Melt polycondensation of L‐lactic acid catalyzed by 1,3‐dialkylimidazolium ionic liquids
Authors: Wang Weichao , Wu Linbo , Huang Yuan , Li Bo‐Geng 
Published: March 2008

AbstractBACKGROUND: In syntheses of biodegradable and bioresorbable polymers, efficient metal‐free catalysts are very desirable as the resulting products may be more biocompatible. As an attempt to find new metal‐free catalysts, 1,3‐dialkylimidazolium salts, the most commonly used ionic liquids or organic melt salts, were used as single‐component catalysts in the melt polycondensation of L‐lactic acid for the first time. The resulting poly(L‐lactic acid) (PLLA) was characterized using gel permeation chromatography, 13C NMR, DSC and polarimetry.RESULTS: It has been found that less bulky substituents on the imidazolium ring are conducive to catalytic activity. PLLA with molar mass of about 20 000 g mol−1 was synthesized at high yield (over 70%) in the presence of various 1,3‐dialkylimidazolium salts. The product exhibits satisfactory color (white to slightly yellow), optical purity (89–95%) and crystallinity (40–55%). A possible catalytic mechanism is proposed.CONCLUSION: As compared with the well‐known binary catalyst system SnCl2 · 2H2O/toluene sulfonic acid, the catalysts used in this investigation are better in terms of increasing PLLA yield and preventing discoloration and comparable in terms of racemization. Copyright © 2008 Society of Chemical Industry
Synthesis and characterization of hydrogels containing biodegradable polymers
Authors: Cretu Adina , Kipping Martin , Adler Hans‐Jürgen , Kuckling Dirk 
Published: March 2008

AbstractBACKGROUND: Amphiphilic block and graft copolymers constitute a very interesting class of polymers with potential for biomedical applications, due to their special characteristics, which derive from the combination of properties of hydrophilic and hydrophobic moieties. In this work, the synthesis and biodegradation of poly(2‐hydroxyethyl methacrylate)‐graft‐poly(L‐lactide) are studied.RESULTS: The graft copolymers were synthesized using the macromonomer technique. In a first step, methacryloyl‐terminated poly(L‐lactide) macromonomers were synthesized in a wide molecular weight range using different catalysts. Subsequently, these macromonomers were copolymerized with 2‐hydroxyethyl methacrylate in order to obtain a graft copolymer. These new materials resemble hydrogel scaffolds with a biodegradable component. The biodegradation was studied in hydrolytic and enzymatic environments. The influence of different parameters (molecular weight, crystallinity, ratio between hydrophilic and hydrophobic components) on the degradation rate was investigated.CONCLUSION: Based on this study it will be possible to tailor the release properties of biodegradable materials. In addition, the materials will show good biocompatibility due to the hydrophilic poly(2‐hydroxyethyl methacrylate) hydrogel scaffold. This kind of material has potential for many applications, like controlled drug‐delivery systems or biodegradable implants. Copyright © 2008 Society of Chemical Industry
Plasma Amination of Low‐Density Polyethylene by DBD Afterglows at Atmospheric Pressure
Authors: Klages Claus‐Peter , Grishin Artur 
Published: March 2008

AbstractSurfaces of LDPE can be functionalized with primary amino groups using the afterglows from dielectric barrier discharges in N2, N2 + H2, and N2 + NH3 mixtures at atmospheric pressure. Quantitative analysis by a recently developed ATR FT‐IR spectroscopic method allows calculation of the number of NH2 groups generated per unit area. Treatment in N2 + H2 afterglows was found to be most efficient in terms of area densities of primary amines achieved (more than 15 nm−2), but appreciable quantities of NH2, up to about 3 nm−2, are also obtained in pure N2. Possible mechanisms of the amination reaction and the roles of gas additives are discussed.magnified image
Potential Use of CL‐20 in TNT/ETPE‐Based Melt Cast Formulations
Authors: Thiboutot Sonia , Brousseau Patrick , Ampleman Guy , Pantea Dana , Côté Sébastien 
Published: March 2008

AbstractAn attempt was made to introduce CL‐20 in a TNT/energetic thermoplastic elastomer (ETPE)‐based melt cast formulation, to obtain an insensitive composition with reduced adverse environmental properties. A loading limit of 42% w/w of CL‐20 in melted TNT was observed, while it should have been around 70%. This paper describes the investigation that was undertaken to understand the observed phenomena. It was demonstrated that CL‐20 undergoes structural alterations in melted TNT. The relative solubility of CL‐20, RDX and HMX in melted TNT was determined and the α‐, β‐, γ‐ and ε‐CL‐20 were prepared and characterized using Raman spectroscopy and DTA. CL‐20 was mixed in melted TNT, as much as 4.2 g of CL‐20 dissolved in 100 g of TNT. This allowed a transformation from ε to β‐CL‐20 and a modification of CL‐20 particle size and distribution. The later modification induced a raise in CL‐20 specific surface and was responsible for the loading limit, while the transformation to β‐CL‐20 caused an increase in sensitivity and a decrease in density. This indicates that the use of CL‐20 in TNT melt cast is not promising. Our study also showed that CL‐20 is sensitive to morphological transformations, which should be taken into consideration in future processing using this compound.
Mechanism of Solid Propellant Combustion Submitted to a High Plasma Flux
Authors: Alimi Roger , Berdichevsky Vadim 
Published: March 2008

AbstractA simplified mechanism of the plasma effect on the combustion on different types of propellants is presented. The model provides a semi‐quantitative prediction of the burning rate enhancement that should be expected for a given propellant composition and structure. Depending on the propellant structure and composition, one expects a burning rate enhancement either to disappear or to survive a certain time after the plasma injection has been turned off. In order to estimate the internal front propagation rate, we have built a simplified model of the RDX ignition inside the matrix. A cubic lattice topology has been assumed and the ignition front extends from one layer to its nearest neighbor. The propagation rate was found to be dependent on the lattice constant, the particle size, the thermo‐chemical properties of the RDX particles and the matrix background.
Cross‐resistance between a Bacillus thuringiensis Cry toxin and non‐Bt insecticides in the diamondback moth
Authors: Sayyed Ali H , Moores Graham , Crickmore Neil , Wright Denis J 
Published: March 2008

AbstractBACKGROUND: Bacillus thuringiensis Berliner (Bt) crystal (Cry) toxins are expressed in various transgenic crops and are also used as sprays in integrated pest management and organic agricultural systems. The diamondback moth (Plutella xylostella L.) is a major worldwide pest of crucifer crops and one that has readily acquired field resistance to a broad range of insecticides.RESULTS: Selection of a subpopulation of the P. xylostella SERD4 population with the pyrethroid deltamethrin increased resistance to both deltamethrin and Cry1Ac relative to an unselected subpopulation. Selection of a second subpopulation with the Bt toxin Cry1Ac also increased resistance to both Cry1Ac and deltamethrin. A complementation test between the Cry1Ac‐selected and deltamethrin‐selected subpopulations suggested the presence of a common genetic locus or loci that control resistance to both insecticides. A piperonyl butoxide analogue with potent inhibitory activity against insect esterases significantly increased the toxicity of Cry1Ac and deltamethrin against the respective resistant subpopulations, but showed no such synergism with the unselected subpopulation of SERD4.CONCLUSION: Selection of one resistance phenotype resulted in the simultaneous selection of the other. This phenomenon could be due to a single mechanism acting against both classes of insecticide or to genetically linked, but separate, mechanisms. Copyright © 2008 Society of Chemical Industry
Informing the selection of futility stopping thresholds: case study from a late‐phase clinical trial
Authors: Hughes Sara , Cuffe Robert L. , Lieftucht Alfons , Garrett Nichols W. 
Published: March 2008

AbstractIn an environment where (i) potential risks to subjects participating in clinical studies need to be managed carefully, (ii) trial costs are increasing, and (iii) there are limited research resources available, it is necessary to prioritize research projects and sometimes re‐prioritize if early indications suggest that a trial has low probability of success. Futility designs allow this reprioritization to take place. This paper reviews a number of possible futility methods available and presents a case study from a late‐phase study of an HIV therapeutic, which utilized conditional power‐based stopping thresholds. The two most challenging aspects of incorporating a futility interim analysis into a trial design are the selection of optimal stopping thresholds and the timing of the analysis, both of which require the balancing of various risks. The paper outlines a number of graphical aids that proved useful in explaining the statistical risks involved to the study team. Further, the paper outlines a decision analysis undertaken which combined expectations of drug performance with conditional power calculations in order to produce probabilities of different interim and final outcomes, and which ultimately led to the selection of the final stopping thresholds. Copyright © 2008 John Wiley & Sons, Ltd.