bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hyperpolarized lithium‐6 as a sensor of nanomolar contrast agents
Authors: van Heeswijk Ruud B. , Uffmann Kai , Comment Arnaud , Kurdzesau Fiodar , Perazzolo Chiara , Cudalbu Cristina , Jannin Sami , Konter Jacobus A. , Hautle Patrick , van den Brandt Ben , Navon Gil , van der Klink Jacques J. , Gruetter Rolf 
Published: April 2009

AbstractLithium is widely used in psychotherapy. The 6Li isotope has a long intrinsic longitudinal relaxation time T1 on the order of minutes, making it an ideal candidate for hyperpolarization experiments. In the present study we demonstrated that lithium‐6 can be readily hyperpolarized within 30 min, while retaining a long polarization decay time on the order of a minute. We used the intrinsically long relaxation time for the detection of 500 nM contrast agent in vitro. Hyperpolarized lithium‐6 was administered to the rat and its signal retained a decay time on the order of 70 sec in vivo. Localization experiments imply that the lithium signal originated from within the brain and that it was detectable up to 5 min after administration. We conclude that the detection of submicromolar contrast agents using hyperpolarized NMR nuclei such as 6Li may provide a novel avenue for molecular imaging. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
MR elastography as a method for the assessment of myocardial stiffness: Comparison with an established pressure–volume model in a left ventricular model of the heart
Authors: Kolipaka Arunark , McGee Kiaran P. , Araoz Philip A. , Glaser Kevin J. , Manduca Armando , Romano Anthony J. , Ehman Richard L. 
Published: April 2009

AbstractMagnetic resonance elastography (MRE) measurements of shear stiffness (μ) in a spherical phantom experiencing both static and cyclic pressure variations were compared to those derived from an established pressure–volume (P‐V)‐based model. A spherical phantom was constructed using a silicone rubber composite of 10 cm inner diameter and 1.3 cm thickness. A gradient echo MRE sequence was used to determine μ within the phantom at static and cyclic pressures ranging from 55 to 90 mmHg. Average values of μ using MRE were obtained within a region of interest and were compared to the P‐V‐derived estimates. Under both static and cyclic pressure conditions, the P‐V‐ and MRE‐based estimates of μ ranged from 98.2 to 155.1 kPa and 96.2 to 150.8 kPa, respectively. Correlation coefficients (R2) of 0.98 and 0.97 between the P‐V and MRE‐based estimates of shear stiffness measurements were obtained. For both static and cyclic pressures, MRE‐based measures of μ agree with those derived from a P‐V model, suggesting that MRE can be used as a new, noninvasive method of assessing μ in sphere‐like fluid‐filled organs such as the heart. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Noninvasive quantification of whole‐brain cerebral metabolic rate of oxygen (CMRO2) by MRI
Authors: Xu Feng , Ge Yulin , Lu Hanzhang 
Published: April 2009

AbstractCerebral metabolic rate of oxygen (CMRO2) is an important marker for brain function and brain health. Existing techniques for quantification of CMRO2 with positron emission tomography (PET) or MRI involve special equipment and/or exogenous agents, and may not be suitable for routine clinical studies. In the present study, a noninvasive method is developed to estimate whole‐brain CMRO2 in humans. This method applies phase‐contrast MRI for quantitative blood flow measurement and T2‐relaxation‐under‐spin‐tagging (TRUST) MRI for venous oxygenation estimation, and uses the Fick principle of arteriovenous difference for the calculation of CMRO2. Whole‐brain averaged CMRO2 values in young, healthy subjects were 132.1 ± 20.0 μmol/100 g/min, in good agreement with literature reports using PET. Various acquisition strategies for phase‐contrast and TRUST MRI were compared, and it was found that nongated phase‐contrast and sagittal sinus (SS) TRUST MRI were able to provide the most efficient and accurate estimation of CMRO2. In addition, blood flow and venous oxygenation were found to be positively correlated across subjects. Owing to the noninvasive nature of this method, it may be a convenient and useful approach for assessment of brain metabolism in brain disorders as well as under various physiologic conditions. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Temporally constrained reconstruction applied to MRI temperature data
Authors: Todd Nick , Adluru Ganesh , Payne Allison , DiBella Edward V.R. , Parker Dennis 
Published: April 2009

AbstractThe monitoring of thermal ablation procedures would benefit from an acceleration in the rate at which MRI temperature maps are acquired. Constrained reconstruction techniques have been shown to be capable of generating high quality images using only a fraction of the k‐space data. Here, we present a temporally constrained reconstruction (TCR) algorithm applied to proton resonance frequency shift (PRF) data. The algorithm generates images from undersampled data by iteratively minimizing a cost function. The unique challenges of using an iterative constrained reconstruction technique to generate real‐time images were addressed. For a set of eight heating experiments on ex vivo porcine tissue, a maximum reduction factor of 4 was achieved while keeping the root mean square error (RMSE) of the temperature below 0.5°C. For a set of three heating experiments on in vivo canine muscle tissue, the maximum reduction factor achieved was 3 while keeping the temperature RMSE below 1.0°C. At these reduction factors, the TCR algorithm underpredicted the thermal dose by an average of 6% for the ex vivo data and 28% for the in vivo data. Compared with sliding window and low resolution reconstructions, the RMSE of the TCR algorithm was significantly lower (P < 0.05 in all cases). Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
A note on fast approximate minimum degree orderings for symmetric matrices with some dense rows
Authors: Dollar H. S. , Scott J. A. 
Published: April 2009

AbstractRecently, a number of variants of the approximate minimum degree algorithm have been proposed that aim to efficiently order symmetric matrices containing some dense rows. We compare the performance of these variants on a range of problems and highlight their potential limitations. This leads us to propose a new variant that offers both speed and robustness. Copyright © 2009 John Wiley & Sons, Ltd.
A meshless method using the radial basis functions for numerical solution of the regularized long wave equation
Authors: Shokri Ali , Dehghan Mehdi 
Published: April 2009

AbstractThis article discusses on the solution of the regularized long wave (RLW) equation, which is introduced to describe the development of the undular bore, has been used for modeling in many branches of science and engineering. A numerical method is presented to solve the RLW equation. The main idea behind this numerical simulation is to use the collocation and approximating the solution by radial basis functions (RBFs). To avoid solving the nonlinear system, a predictor‐corrector scheme is proposed. Several test problems are given to validate the new technique. The numerical simulation, includes the propagation of a solitary wave, interaction of two positive solitary waves, interaction of a positive and a negative solitary wave, the evaluation of Maxwellian pulse into stable solitary waves and the development of an undular bore. The three invariants of the motion are calculated to determine the conservation properties of the algorithm. The results of numerical experiments are compared with analytical solution and with those of other recently published methods to confirm the accuracy and efficiency of the presented scheme.© 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2010
Compatibility of softwood flour and commercial biopolymers in injection molding
Authors: Sykacek Eva , Schlager Wolfgang , Mundigler Norbert 
Published: April 2009

AbstractThis study is focused on wood flour‐reinforced biopolymers for injection molding. Eight commercial biopolymers were compounded with 30 and 50% wood flour and injection molded. Thermal processability via extrusion was evaluated by use of the resulting melt pressure, melt temperature, and machine load, during injection molding the injection pressure was taken. Clear increases of melt‐ and injection pressures could be determined at rising fiber load and better shaping of the molded parts was observed. The mechanical performance of the composites and the neat polymers was evaluated by tensile‐, bending‐, and impact properties. To study the effects of different fiber concentrations, multiple comparison tests were calculated. High variations in the mechanical properties and in hygroscopic behavior were found between the different biopolymers. Through incorporation of wood flour, the E‐modules of all polymers were significantly improved. The strength values of the various biopolymers offered different trends because of the reinforcement. The polylactic acid (PLA) and the cellulose‐based polymer Biograde showed significant decreases in strength by addition of wood flour. Scanning electron micrographs of a 50% filled PLA compound revealed low fiber matrix adhesion. Impactstrength and elongation at yield of all investigated polymers dropped dramatically with rising fiber content. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Effects of carbon fillers in thermally conductive polypropylene based resins
Authors: King Julia A. , Johnson Beth A. , Via Michael D. , Ciarkowski Charles J. 
Published: April 2009

AbstractThe thermal conductivity of insulating polymers can be increased by adding conductive fillers. One potential market for these thermally conductive resins is for fuel cell bipolar plates. In this study, varying amounts of three different carbon fillers (carbon black, synthetic graphite particles, and carbon nanotubes) were added to polypropylene. The effects of single fillers and combinations of the different fillers were studied via a factorial design. Each single filler caused a statistically significant increase in composite through‐plane thermal conductivity at the 95% confidence level, with synthetic graphite causing the largest increase. All of the composites containing combinations of the different fillers caused a statistically significant increase in composite through‐plane thermal conductivity. It is possible that thermally conductive pathways are formed that ‘link’ these carbon fillers, which results in increased composite thermal conductivity. Composites containing 80 wt% synthetic graphite had an in‐plane thermal conductivity of 28.0 W/m·K, which is desired for bipolar plates (>20 W/m·K). POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Prenatal screening for chromosome abnormalities in a region with no access to termination of pregnancy
Authors: Paolini Cynthia I. , Gadow Andrea , Petracchi Florencia , Igarzabal Laura , Quadrelli Roberto , Gadow Enrique C. 
Published: April 2009

AbstractObjectiveTo analyze the different variables that affect couples' decision‐making about prenatal screening of chromosome abnormalities in a population with limited access to prenatal diagnosis and no legal termination of pregnancy (TOP).MethodsFrom February through August 2004, 79 couples who requested for prenatal screening at centers from Argentina and Uruguay participated in a study. A cross‐sectional survey was administered to assess attitudes toward prenatal screening, the decision‐making process, and knowledge and attitudes toward TOP.ResultsMean maternal age was 32.8 ± 0.4 years. Among the couples, 88.61% knew that TOP due to fetal anomalies is not legal in their countries. When asked about the possibility of TOP in case of a serious fetal anomaly, 53% would contemplate this option.ConclusionPrenatal screening is a common practice worldwide. However, unlike most developed countries, our region has a limited access to prenatal diagnosis and no legal TOP. Those couples who stated that ‘reassurance about fetal well‐being’ was the most important reason to perform prenatal screening had more positive attitudes toward TOP than those who considered this screening important ‘to be better prepared to receive the baby’. Our findings can be used to inform and revise current health‐care policies. Copyright © 2009 John Wiley & Sons, Ltd.
(Meth)acrylate vinyl ester hybrid polymerizations
Authors: Lee Tai Yeon , Cramer Neil B. , Hoyle Charles E. , Stansbury Jeffrey W. , Bowman Christopher N. 
Published: April 2009

AbstractIn this study, vinyl ester monomers were synthesized by an amine catalyzed Michael addition reaction between a multifunctional thiol and the acrylate double bond of vinyl acrylate. The copolymerization behavior of both methacrylate/vinyl ester and acrylate/vinyl ester systems was studied with near‐infrared spectroscopy. In acrylate/vinyl ester systems, the acrylate groups polymerize faster than the vinyl ester groups resulting in an overall conversion of 80% for acrylate double bonds in the acrylate/vinyl ester system relative to only 50% in the bulk acrylate system. In the methacrylate/vinyl ester systems, the difference in reactivity is even more pronounced resulting in two distinguishable polymerization regimes, one dominated by methacrylate polymerization and a second dominated by vinyl ester polymerization. A faster polymerization rate and higher overall conversion of the methacrylate double bonds is thus achieved relative to polymerization of the pure methacrylate system. The methacrylate conversion in the methacrylate/vinyl ester system is near 100% compared to only ∼60% in the pure methacrylate system. Utilizing hydrophilic vinyl ester and hydrophobic methacrylate monomers, polymerization‐induced phase separation is observed. The phase separated domain size is in the order of ∼1 μm under the polymerization conditions. The phase separated domains become larger and more distinct with slower polymerization and correspondingly increased time for diffusion. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2509–2517, 2009
Ferrocenyl‐functionalized long chain branched polydienes
Authors: Wurm Frederik , Villanueva Francisco Javier López , Frey Holger 
Published: April 2009

AbstractA convenient two‐step approach for the synthesis of ferrocenyl‐functionalized long chain branched polydienes, based on both butadiene and isoprene, respectively, is presented. Classical living anionic polymerization was used to synthesize different ABn type poly(diene) macromonomers with moderate molecular weights between 1700 and 3200 g/mol and narrow polydispersity. Quantitative end‐capping with chlorodimethylsilane resulted in the desired ABn macromonomer structures. In the ensuing Pt‐catalyzed hydrosilylation polyaddition, branched, functionalized polydienes were obtained by a concurrent ABn + AR type of copolymerization with mono‐ and difunctional ferrocenyl silanes (fcSiMe2H or fc2SiMeH). Molecular weights of the branched polymers were in the range of 10,000 to 44,000 g/mol (SEC/MALLS). Because of the large number of functional end groups, high loading with ferrocene units up to 63 wt % of ferrocene was achieved. Detailed studies showed full conversion of the functional silanes and incorporation into the branched polymer. Further studies using DSC, TGA, and cyclovoltammetry (CV) measurements have been performed. Electrochemical studies demonstrated different electrochemical properties for fcSiMe2‐ and fc2SiMe‐units. The CVs of polymers modified with diferrocenylsilane units exhibit the pattern of communicating ferrocenyl sites with two distinct, separate oxidation waves. The polymers were also deposited on an electrode surface and the electrodes investigated via CV, showing formation of electroactive films with promising results for the use of the materials in biosensors. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2518–2529, 2009
Synthesis of amphiphilic copolymer brushes possessing alternating poly(methyl methacrylate) and poly(N‐isopropylacrylamide) grafts via a combination of ATRP and click chemistry
Authors: Yin Jun , Ge Zhishen , Liu Hao , Liu Shiyong 
Published: April 2009

AbstractWe report on the synthesis of well‐defined amphiphilic copolymer brushes possessing alternating poly(methyl methacrylate) and poly(N‐isopropylacrylamide) grafts, poly(PMMA‐alt‐PNIPAM), via a combination of atom transfer radical polymerization (ATRP) and click reaction (Scheme 1). Firstly, the alternating copolymerization of N‐[2‐(2‐bromoisobutyryloxy)ethyl]maleimide (BIBEMI) with 4‐vinylbenzyl azide (VBA) affords poly(BIBEMI‐alt‐VBA). Bearing bromine and azide moieties arranged in an alternating manner, multifunctional poly(BIBEMI‐alt‐VBA) is capable of initiating ATRP and participating in click reaction. The subsequent ATRP of methyl methacrylate (MMA) using poly(BIBEMI‐alt‐VBA) as the macroinitiator leads to poly(PMMA‐alt‐VBA) copolymer brush. Finally, amphiphilic poly(PMMA‐alt‐PNIPAM) copolymer brush bearing alternating PMMA and PNIPAM grafts is synthesized via the click reaction of poly(PMMA‐alt‐VBA) with an excess of alkynyl‐terminated PNIPAM (alkynyl‐PNIPAM). The click coupling efficiency of PNIPAM grafts is determined to be ∼80%. Differential scanning calorimetry (DSC) analysis of poly(PMMA‐alt‐PNIPAM) reveals two glass transition temperatures (Tg). In aqueous solution, poly(PMMA‐alt‐PNIPAM) supramolecularly self‐assembles into spherical micelles consisting of PMMA cores and thermoresponsive PNIPAM coronas, which were characterized via a combination of temperature‐dependent optical transmittance, micro‐differential scanning calorimetry (micro‐DSC), dynamic and static laser light scattering (LLS), and transmission electron microscopy (TEM). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2608–2619, 2009
Well‐defined poly[(dimethylamimo)ethyl methacrylate]‐b‐poly(fluoroalkyl methacrylate) diblock copolymers: Effects of different fluoroalkyl groups on the solution properties
Authors: Liu Cuicui , He Jinlin , Zhao Qun , Zhang Mingzu , Ni Peihong 
Published: April 2009

AbstractA series of well‐defined, fluorinated diblock copolymers, poly[2‐(dimethylamino)ethyl methacrylate]‐b‐poly(2,2,2‐trifluoroethyl methacrylate) (PDMA‐b‐PTFMA), poly[2‐(dimethylamino)ethyl methacrylate]‐b‐poly(2,2,3,4,4,4‐hexafluorobutyl methacrylate) (PDMA‐b‐PHFMA), and poly[2‐(dimethylamino)ethyl methacrylate]‐b‐poly(2,2,3,3,4,4,5,5‐octafluoropentyl methacrylate) (PDMA‐b‐POFMA), have been synthesized successfully via oxyanion‐initiated polymerization. Potassium benzyl alcoholate (BzO−K+) was used to initiate DMA monomer to yield the first block PDMA. If not quenched, the first living chain could be subsequently used to initiate a feed F‐monomer (such as TFMA, HFMA, or OFMA) to produce diblock copolymers containing different poly(fluoroalkyl methacrylate) moieties. The composition and chemical structure of these fluorinated copolymers were confirmed by 1H NMR, 19F NMR spectroscopy, and gel permeation chromatography (GPC) techniques. The solution behaviors of these copolymers containing (tri‐, hexa‐, or octa‐ F‐atom)FMA were investigated by the measurements of surface tension, dynamic light scattering (DLS), and UV spectrophotometer. The results indicate that these fluorinated copolymers possess relatively high surface activity, especially at neutral media. Moreover, the DLS and UV measurements showed that these fluorinated diblock copolymers possess distinct pH/temperature‐responsive properties, depending not only on the PDMA segment but also on the fluoroalkyl structure of the FMA units. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2702–2712, 2009
Facile one‐pot synthesis and characterization of novel nanostructured organic dispersible polyaniline
Authors: Han Youn‐Gyu , Kusunose Takafumi , Sekino Tohru 
Published: April 2009

AbstractNovel polyaniline (PANI) with nanotube, nanosheet, and nanofiber shapes was facilely synthesized by a self‐templating one‐pot process. Anilinium‐dodecylsulfate (DS) complex, obtained by mixing equivalent amounts of aniline and sodium dodecylsulfate (SDS), played a template‐like role in forming PANI nanostructures. It was found that the morphology and electrical conductivity of the PANI nanostructures changed with the amount of SDS and the reaction temperature. Nanotube‐shaped PANI synthesized at the temperature of anilinium‐DS complex formation in presence of SDS (concentration <0.12 M) showed high conductivity (12.9 S/cm). At higher temperature, the morphology changed to shape of a rose flower and electrical conductivity decreased to 3.95 S/cm. This suggested that both temperature and SDS concentration were key parameters for controlling the formation of the anilinium‐DS complex that acted as a template. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1024–1029, 2009
Piezoresistive characteristics of single wall carbon nanotube/polyimide nanocomposites
Authors: Kang Jin Ho , Park Cheol , Scholl Jonathan A. , Brazin Amy H. , Holloway Nancy M. , High James W. , Lowther Sharon E. , Harrison Joycelyn S. 
Published: April 2009

AbstractA systematic study of the effect of single wall carbon nanotubes (SWCNTs) on the enhanced piezoresistive sensitivity of polyimide nanocomposites from below to above percolation was accomplished. The maximum piezoresistive stress coefficient (Π) of 1.52 × 10−3 MPa−1 was noted at just above the percolation threshold concentration (Φ ∼ 0.05 wt %) of SWCNT. This coefficient value exceeds those of metallic piezoresistive materials by two orders of magnitude (4.25 × 10−5 MPa−1 for aluminum). The high piezoresistive characteristics appear to originate from a change in the intrinsic resistivity of the composite caused by the variation of the tunneling distance between conducting inclusions (SWCNTs) under compression or tension. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 994–1003, 2009
Reduction of Biofilm Formation on a‐C:H Coated Implants: Investigation of Biofilm‐Surface Interactions by Variation of Thin Film Properties
Authors: Kleinen Lisa , Syring Isabella , Laube Norbert 
Published: April 2009

AbstractFormation of crystalline bacterial biofilms (encrustations) on urological implants remains a major complication in patient care. Recently, it was shown that amorphous carbon (a‐C:H) coatings deposited on polyurethane (PU) stents provide a distinct reduction in biofilm formation with an effect more pronounced in‐vivo than in‐vitro. To investigate the underlying mechanisms, the influence of surface properties on the encrustation tendency of plasma coated and uncoated PU tubes was tested in an extended in‐vitro model with protein‐spiked artificial urine and urease. In the presence of albumin the formation of hollow crystalline spheres was observed mainly on uncoated PU. We suggest that evolving gas bubbles influence protein adherence and attachment of crystalline bacterial biofilm to the implant surfaces.
Wear Behaviour of UHMWPE Against DC‐Pulsed Plasma Nitrided and Duplex Treated AISI 316L Used in Hip Joint Replacements
Authors: Perez Ezequiel , Pazos Leonardo , Heras Evangelina De Las , Parodi Belén , Corengia Pablo , Braceras Iñigo 
Published: April 2009

AbstractWear behaviour of the artificial joint replacements plays a critical role in implant failure. The UHMWPE‐AISI 316L tribological system, widely used on joint prostheses, was studied. Two surface modifications were applied to the stainless steel counterface: DC‐pulsed plasma nitriding and duplex (DC‐pulsed plasma nitriding + TiN coating by cathodic‐arc evaporation) treatments. An Amsler Disc Machine Type A‐135 was used as an approximation to real loading conditions. Worn surfaces, weight loss curves and wear debris were analysed. The results show that the nitriding and duplex treatments improve the wear resistance of the tribological system. Different types of damages were observed on the UHMWPE worn surfaces depending on the surface treatment of the stainless steel.