bluuebunny/crossref_metadata_2025_split huggingface dataset:
Peroxide‐Grafted PDMS: Hydrosilylation Reaction and Thiol‐Ene Chemistry as an Alternative Pathway
Authors: Lucas Patrice , Fleury Etienne , Estur Jean‐François , Lapinte Vincent , Robin Jean‐Jacques 
Published: September 2009

AbstractPeroxide‐containing PDMS was synthesized according to a new pathway. Although hydrosilylation is one of the main reactions carried out in silicone chemistry, the catalysts used are very sensitive to the chemical nature of the reactants and remained inefficient to graft allylic peroxide. Radical catalyzed thiol‐ene chemistry was involved for the first time to yield an initiator group containing polymer. The peroxide‐grafted polysiloxane structure and decomposition were characterized using 1H, 13C and 29Si NMR, FT‐IR and Raman spectroscopies, SEC and DSC. These macroinitiators can be used to obtain polysiloxane able to undergo crosslinking.magnified image
Modification of Oligomeric Cyanate Ester Polymer Properties with Multi‐Walled Carbon Nanotube‐Containing Particles
Authors: Dominguez Dawn D. , Laskoski Matthew , Keller Teddy M. 
Published: September 2009

AbstractThe properties of an oligomeric cyanate ester polymer were modified by the addition of 0.01–3 wt.‐% multi‐walled carbon nanotube (MWNT) containing particles. The dynamic mechanical behavior and thermal properties of the cyanate ester/MWNT nanocomposites were evaluated. The storage modulus, G′, of the nanocomposite with 1 wt.‐% MWNT particles was nearly 60 and 600% higher than the neat polymer at 100 and 200 °C, respectively. The glass transition temperature of the nanocomposite was also raised by 30 °C and its thermal stability in air and nitrogen was increased by 58 and 25 °C, respectively. The property improvements are attributed to reinforcement of the cyanate ester as a result of good nanotube dispersion and effective polymer‐MWNT interaction.magnified image
Extraction of Contamination of Automotive Gas Tank Material by Extrusion with Supercritical Carbon Dioxide
Authors: Michaeli Walter , Rothe Bernd , Elas Athanassios 
Published: September 2009

AbstractDuring their working life, plastics can be exposed to contaminating media which limit their recyclability. A continuous extraction process with supercritical CO2 has been developed. Contaminated material is extruded through two twin‐screw extruders in a cascade. The first extruder purifies with scCO2 and the second extruder is for degassing and hot‐cut pelletisation. Post‐consumer automotive diesel fuel tank material has been processed. A direct flow and a counter‐flow process with different screw configurations have been developed. Characterisation has been performed by headspace gas chromatography. Results show that contaminants were extracted out of the plastic for both process variants. However, direct flow yielded better extraction efficiency.magnified image
Bio‐Based Rubbers by Concurrent Cationic and Ring‐Opening Metathesis Polymerization of a Modified Linseed Oil
Authors: Jeong Wonje , Mauldin Timothy C. , Larock Richard C. , Kessler Michael R. 
Published: September 2009

AbstractBio‐based rubbers prepared by tandem cationic polymerization and ROMP using a norbornenyl‐modified linseed oil, Dilulin™, and a norbornene diester, NBDC, have been prepared and characterized. Increasing the concentration of the NBDC in the mixture results in a decrease in the glass transition temperature. The new bio‐based rubbers exhibit tensile test behavior ranging from relatively brittle (18% elongation) to moderately flexible (52% elongation) and with decreasing values of tensile stress with increasing NBDC content. Thermogravimetric analysis reveals that the bio‐based rubbers have maximum decomposition temperatures of over 450 °C with their thermal stability decreasing with increasing loadings of NBDC.magnified image
Fabrication and Characterization of Sb2O3/Carboxymethyl Cellulose Sodium and the Properties of Plasticized Starch Composite Films
Authors: Chang Peter R. , Yu Jiugao , Ma Xiaofei 
Published: September 2009

AbstractSb2O3 nanoparticles were prepared using CMC as the stabilizing agent. The nanocomposite was fabricated with Sb2O3/CMC nanoparticles as the filler in a GPS matrix. Characterization of Sb2O3/CMC nanoparticles revealed that Sb2O3 (about 84 wt.‐%) was encapsulated by CMC (about 16 wt.‐%) with the size of about 30–50 nm. Because there was good interaction between the Sb2O3/CMC filler and the GPS matrix, Sb2O3/CMC nanoparticles could be uniformly dispersed in the GPS matrix at a low filler loading level, resulting in obvious improvement in tensile strength and UV absorbance, and in the resistance of water vapor permeability. However, introduction of the nanoparticles into the matrix, decreased the elongation at break and the thermal stability of the nanocomposites.magnified image
Microwave and Ionic Liquids: Inverse Temperature Dependence of Viscosity in Aqueous Medium of Grafted Copolymers
Authors: Bezdushna Ella , Ritter Helmut 
Published: September 2009

AbstractWe elaborated a route to the thermosensitive polyelectrolyte system composed of 1‐methyl‐3‐vinylimidazolium salt with β‐cyclodextrin complexed counterions and mono‐(meth)acrylic functionalized poly(N‐isopropylacrylamide) as grafted side chains via a three‐step synthetic procedure. The aqueous solution of the polyelectrolyte displays partially inverse thermoresponsive behavior; it exhibits enhancement of shear viscosity up to body temperature. Furthermore, based on classically prepared poly(NIPAAm) bearing terminal amino groups, corresponding (meth‐) acrylamide‐type of macromonomers were easily obtained under microwave conditions.magnified image
Improved signal spoiling in fast radial gradient‐echo imaging: Applied to accurate T1 mapping and flip angle correction
Authors: Lin Wei , Song Hee Kwon 
Published: September 2009

AbstractIn conventional spoiled gradient echo imaging utilizing quadratic radio frequency (RF) spoiling, nonideal signal intensities are often generated, particularly when repetition time is short and/or excitation flip angle (FA) becomes larger. This translates to significant errors in various quantitative applications based on T1‐weighted image intensities. In this work, a novel spoiling scheme is proposed, based on random gradient moments and RF phases. This scheme results in a non‐steady‐state condition, but achieves ideal mean signal intensity. In order to suppress artifacts created by the inter‐TR signal variations and at the same time attain the ideal signal intensity, radial data acquisition is utilized. The proposed method achieves ideal spoiling for a wide range of T1, T2, TR, and FAs. Phantom and in vivo experiments demonstrate improved performance for T1 mapping and FA correction when compared with conventional RF spoiling methods. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Estimation of brain iron concentration in vivo using a linear relationship between regional iron and apparent transverse relaxation rate of the tissue water at 4.7T
Authors: Mitsumori Fumiyuki , Watanabe Hidehiro , Takaya Nobuhiro 
Published: September 2009

AbstractMaps of the apparent transverse relaxation time (T2†) were collected on a transaxial plane across the basal ganglia in 54 healthy subjects at 4.7T using a multiecho adiabatic spin‐echo (MASE) imaging sequence. We attempted to quantify the nonhemin iron concentration ([Fe]) in various brain regions in vivo based on the linear relationship between the apparent relaxation rate constant (R2† = 1/T2†) and regional [Fe], as demonstrated previously in 12 subjects. The calculated [Fe] in five gray matter (GM) regions agreed well with the previously reported regional iron distribution as well as reproduced its age‐dependent change. In particular, a decrease of iron in the thalamus region in subjects over 30 years of age was demonstrated while an upward trend was shown in other regions. Furthermore, the average R2† in each GM region in subjects over 30 years of age showed a deviation from the regression line with [Fe] in an identical manner to that obtained in the previous 12 subjects. This strongly suggests that there is a systematic regional factor affecting R2†, in addition to iron. Interregional difference in the macromolecular mass fraction (fM) explained this systematic deviation well. When accounting for fM in the analysis, the apparent transverse relaxation rate seems to give a significantly better estimation of regional [Fe]. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Tyrosine polyethylene glycol (PEG)‐micelle magnetic resonance contrast agent for the detection of lipid rich areas in atherosclerotic plaque
Authors: Beilvert Anne , Cormode David P. , Chaubet Frédéric , Briley‐Saebo Karen C. , Mani Venkatesh , Mulder Willem J.M. , Vucic Esad , Toussaint Jean‐François , Letourneur Didier , Fayad Zahi A. 
Published: September 2009

AbstractVulnerable or high‐risk atherosclerotic plaques often exhibit large lipid cores and thin fibrous caps that can lead to deadly vascular events when they rupture. In this study, polyethylene glycol (PEG)‐micelles that incorporate a gadolinium diethylenetriamine pentaacetic acid (Gd‐DTPA) amphiphile were used as an MR contrast agent. In an approach inspired by lipoproteins, the micelles were functionalized with tyrosine residues, an aromatic, lipophilic amino acid, to reach the lipid‐rich areas of atherosclerotic plaque in a highly efficient manner. These micelles were applied to apolipoprotein E−/− (ApoE−/−) mice as a model of atherosclerosis. The abdominal aortas of the animals were imaged using T1‐weighted (T1W) high‐resolution MRI at 9.4T before and up to 48 h after the administration of the micelles. PEG‐micelles modified with 15% tyrosine residues yielded a significant enhancement of the abdominal aortic wall at 6 and 24 h postinjection (pi) as compared to unmodified micelles. Fluorescence microscopy on histological sections of the abdominal aorta showed a correlation between lipid‐rich areas and the distribution of the functionalized contrast agent in plaque. Using a simple approach, we demonstrated that lipid‐rich areas in atherosclerotic plaque of ApoE−/− mice can be detected by MRI using Gd‐DTPA micelles. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Sources of hepatic glycogen synthesis during an oral glucose tolerance test: Effect of transaldolase exchange on flux estimates
Authors: Delgado Teresa C. , Silva Claúdia , Fernandes Isabel , Caldeira Madalena , Bastos Margarida , Baptista Carla , Carvalheiro Manuela , Geraldes Carlos F. G. C. , Jones John G. 
Published: September 2009

AbstractSources of hepatic glycogen synthesis during an oral glucose tolerance test were evaluated in six healthy subjects by enrichment of a 75‐g glucose load with 6.67% [U‐13C]glucose and 3.33% [U‐2H7]glucose and analysis of plasma glucose and hepatic uridine diphosphate–glucose enrichments (sampled as urinary menthol glucuronide) by 2H and 13C nuclear magnetic resonance. The direct pathway contribution, as estimated from the dilution of [U‐13C]glucose between plasma glucose and glucuronide, was unexpectedly low (36 ± 5%). With [U‐2H7]glucose, direct pathway estimates based on the dilution of position 3 2H‐enrichment between plasma glucose and glucuronide were significantly higher (51 ± 6%, P = 0.05). These differences reflect the exchange of the carbon 4, 5, and 6 moiety of fructose‐6‐phosphate and glyceraldehyde‐3‐phosphate catalyzed by transaldolase. As further evidence of this exchange, 2H‐enrichments in glucuronide positions 4 and 5 were inferior to those of position 3. From the difference in glucuronide positions 5 and 3 enrichments, the fraction of direct pathway carbons that experienced transaldolase exchange was estimated at 21 ± 4%. In conclusion, the direct pathway contributes only half of hepatic glycogen synthesis during an oral glucose tolerance test. Glucose tracers labeled in positions 4, 5, or 6 will give significant underestimates of direct pathway activity because of transaldolase exchange. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
SSFP signal with finite RF pulses
Authors: Bieri Oliver , Scheffler Klaus 
Published: September 2009

AbstractThe theoretical description of steady state free precession (SSFP) sequences is generally well accepted and unquestioned, although it is based on instantaneously acting radiofrequency (RF) pulses. In practice, however, all excitation processes are finite, thereby questioning the overall validity of the common SSFP signal description for use with finite RF pulses. In this paper, finite RF pulse effects on balanced SSFP signal formation are analyzed as a function of the RF time, the pulse repetition time, the flip angle (α) and relaxation times (T1,2). The observed signal modulations from finite RF pulses (compared to infinitesimal ones) can range from only a few percent (for RF time/pulse repetition time ≪ 1, α ≪ 90°, T2/T1 ∼ 1) to over 10% (for RF time/pulse repetition time ≪ 1, α ∼ 90°, T2/T1 ≪ 1) and may even exceed 100% in the limit of RF time/pulse repetition time → 1 (for α ∼ 90°, T2/T1 ≪ 1). As a result, a revision of SSFP signal theory is indicated not only for reasons of completeness but also seems advisable, e.g., for all quantitative SSFP methods. A simple modification for the common balanced SSFP equation is derived that provides an accurate framework for SSFP signal description over a wide variety of practical and physiologic parameters. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
An internal reference model–based PRF temperature mapping method with Cramer‐Rao lower bound noise performance analysis
Authors: Li Cheng , Pan Xinyi , Ying Kui , Zhang Qiang , An Jing , Weng Dehe , Qin Wen , Li Kuncheng 
Published: September 2009

AbstractThe conventional phase difference method for MR thermometry suffers from disturbances caused by the presence of lipid protons, motion‐induced error, and field drift. A signal model is presented with multi‐echo gradient echo (GRE) sequence using a fat signal as an internal reference to overcome these problems. The internal reference signal model is fit to the water and fat signals by the extended Prony algorithm and the Levenberg‐Marquardt algorithm to estimate the chemical shifts between water and fat which contain temperature information. A noise analysis of the signal model was conducted using the Cramer‐Rao lower bound to evaluate the noise performance of various algorithms, the effects of imaging parameters, and the influence of the water:fat signal ratio in a sample on the temperature estimate. Comparison of the calculated temperature map and thermocouple temperature measurements shows that the maximum temperature estimation error is 0.614°C, with a standard deviation of 0.06°C, confirming the feasibility of this model‐based temperature mapping method. The influence of sample water:fat signal ratio on the accuracy of the temperature estimate is evaluated in a water‐fat mixed phantom experiment with an optimal ratio of approximately 0.66:1. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Application of DENSE‐MR‐elastography to the human heart
Authors: Robert Benjamin , Sinkus Ralph , Gennisson Jean‐Luc , Fink Mathias 
Published: September 2009

AbstractTypically, MR‐elastography (MRE) encodes the propagation of monochromatic acoustic waves in the MR‐phase images via sinusoidal gradients characterized by a detection frequency equal to the frequency of the mechanical vibration. Therefore, the echo time of a conventional MRE sequence is typically longer than the vibration period which is critical for heart tissue exhibiting a short T2. Thus, fast acquisition techniques like the so‐called fractional encoding of harmonic motions were developed for cardiac applications. However, fractional encoding of harmonic motions is limited since it is two orders of magnitude less sensitive to motion than conventional MRE sequences for low‐frequency vibrations. Here, a new sequence is derived from the so‐called displacement encoding with stimulated echoes (DENSE) sequence. This sequence is more sensitive to displacement than fractional encoding of harmonic motions, and its spectral specificity is equivalent to conventional MRE sequences. The theoretical spectral properties of this new motion‐encoding technique are validated in a phantom and excised pork heart specimen. An excellent agreement is found for the measured displacement fields using classic MRE and displacement encoding with stimulated echoes MRE (8% maximum difference). In addition, initial in vivo results on a healthy volunteer clearly show propagating shear waves at 50 Hz. Thus, displacement encoding with stimulated echoes MRE is a promising technique for motion encoding within short T2* materials. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Magnetic resonance elastography: Inversions in bounded media
Authors: Kolipaka Arunark , McGee Kiaran P. , Manduca Armando , Romano Anthony J. , Glaser Kevin J. , Araoz Philip A. , Ehman Richard L. 
Published: September 2009

AbstractMagnetic resonance elastography is a noninvasive imaging technique capable of quantifying and spatially resolving the shear stiffness of soft tissues by visualization of synchronized mechanical wave displacement fields. However, magnetic resonance elastography inversions generally assume that the measured tissue motion consists primarily of shear waves propagating in a uniform, infinite medium. This assumption is not valid in organs such as the heart, eye, bladder, skin, fascia, bone and spinal cord, in which the shear wavelength approaches the geometric dimensions of the object. The aim of this study was to develop and test mathematical inversion algorithms capable of resolving shear stiffness from displacement maps of flexural waves propagating in bounded media such as beams, plates, and spherical shells, using geometry‐specific equations of motion. Magnetic resonance elastography and finite element modeling of beam, plate, and spherical shell phantoms of various geometries were performed. Mechanical testing of the phantoms agreed with the stiffness values obtained from finite element modeling and magnetic resonance elastography data, and a linear correlation of r2 ≥ 0.99 was observed between the stiffness values obtained using magnetic resonance elastography and finite element modeling data. In conclusion, we have demonstrated new inversion methods for calculating shear stiffness that may be more appropriate for waves propagating in bounded media. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
High spatial and temporal resolution cardiac cine MRI from retrospective reconstruction of data acquired in real time using motion correction and resorting
Authors: Kellman Peter , Chefd'hotel Christophe , Lorenz Christine H. , Mancini Christine , Arai Andrew E. , McVeigh Elliot R. 
Published: September 2009

AbstractCine MRI is used for assessing cardiac function and flow and is typically based on a breath‐held, segmented data acquisition. Breath holding is particularly difficult for patients with congestive heart failure or in pediatric cases. Real‐time imaging may be used without breath holding or ECG triggering. However, despite the use of rapid imaging sequences and accelerated parallel imaging, real‐time imaging typically has compromised spatial and temporal resolution compared with gated, segmented breath‐held studies. A new method is proposed that produces a cardiac cine across the full cycle, with both high spatial and temporal resolution from a retrospective reconstruction of data acquired over multiple heartbeats during free breathing. The proposed method was compared with conventional cine images in 10 subjects. The resultant image quality for the proposed method (4.2 ± 0.4) without breath holding or gating was comparable to the conventional cine (4.4 ± 0.5) on a five‐point scale (P = n.s.). Motion‐corrected averaging of real‐time acquired cardiac images provides a means of attaining high‐quality cine images with many of the benefits of real‐time imaging, such as free‐breathing acquisition and tolerance to arrhythmias. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Simplified 13C metabolic modeling for simplified measurements of cerebral TCA cycle rate in vivo
Authors: Valette Julien , Boumezbeur Fawzi , Hantraye Philippe , Lebon Vincent 
Published: September 2009

Abstract13C NMR spectroscopy is a unique tool to measure the cerebral tricarboxylic acid (TCA) cycle rate in vivo. The measurement relies on metabolic modeling of glutamate C3 and C4 enrichment time courses during a 13C‐glucose intravenous infusion. Usual metabolic models require the plasma glucose and 13C‐glucose time courses as input functions, as well as the knowledge of Michaelis‐Menten kinetics parameters governing passage through the blood‐brain barrier. It is shown in the present work that, when using an infusion protocol yielding a rapidly stable plasma glucose fractional enrichment, metabolic modeling can be simplified in such a manner that this additional information on input function and glucose transport is no longer required, significantly simplifying the measurement of cerebral TCA cycle rate in vivo. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Flat boundaries and their effect on sand testing
Authors: Marketos G. , Bolton Malcolm D. 
Published: September 2009

AbstractA study of the effect of the use of flat boundaries on the stressing of a sample of an idealized granular material with no applied shear is presented. Discrete element method (DEM) data of 1D compression were analysed and the local strain field inside the sample was investigated as the sample was stressed. A best‐fit strain was seen to best describe the material behaviour free from boundary effects. The individual particle displacements were probed, providing insight into the behaviour of particles adjacent to the boundaries. In addition, the porosity and force distribution inside the sample were observed, allowing for estimates of the width of a boundary region to be made. This region, non‐representative of far‐field material behaviour, will affect the behaviour of a granular sample in DEM or laboratory tests, with local porosity differences leading to a change in the transport properties of the sample, and force distribution changes leading to a bias in the location of grain cracking or crushing events for sufficiently high stress levels. Nevertheless, the largest effect of the boundary region was a severe underestimation of the stiffness of a granular material. Copyright © 2009 John Wiley & Sons, Ltd.
Synthesis and characterization of temperature‐responsive copolymers based on N‐vinylcaprolactam and their grafting on fibres
Authors: Crespy Daniel , Golosova Anastasia , Makhaeva Elena , Khokhlov Alexei R , Fortunato Giuseppino , Rossi René 
Published: September 2009

AbstractBACKGROUND: Responsive materials are able to respond reversibly to an environmental stimulus. When the stimulus is temperature in the physiological range, the responsive material is particularly interesting for textile applications. We describe here the synthesis and characterization of reactive temperature‐responsive copolymers and their subsequent grafting on cotton fabrics.RESULTS: Copolymers of N‐vinylcaprolactam and various reactive monomers were synthesized via free radical polymerization in solution. The copolymers were characterized in terms of chemical structure, molecular weight and temperature‐responsive properties. The copolymer of N‐vinylcaprolactam and methacrylic acid (11 or 22 wt%) and the hydrolysed copolymer of N‐vinylcaprolactam and acryloyl chloride were found to be temperature responsive. They were subsequently grafted on cotton fabrics. The grafting was studied using X‐ray photoelectron spectroscopy and scanning electron microscopy measurements and was found to be effective. Finally, the modified cotton fabrics were found to exhibit temperature‐responsive water regain and water vapour transmission rates.CONCLUSION: Temperature‐responsive copolymers were synthesized, characterized and successfully grafted on cotton fabrics, yielding responsive fabrics. Such fabrics can hence be used to modulate the skin microclimate under textiles. Copyright © 2009 Society of Chemical Industry