bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proton MR spectroscopic studies of chronic alcohol exposure on the rat brain
Authors: Lee Haakil , Holburn George H. , Price Ronald R. 
Published: July 2003

AbstractPurpose:To better understand the long‐term pathophysiologic mechanisms of alcoholism‐related organic brain damage by serially assessing brain metabolites in chronically exposed rats using both in vivo magnetic resonance spectroscopy (MRS) and high‐resolution nuclear magnetic resonance (NMR) from brain extracts.Materials and Methods:The alcoholic regimen was continued up to 60 weeks. In vivo proton MRS studies were performed at 200 MHz using a small animal imaging/spectrometer. In vitro rat brain extracts were also examined using a 500 MHz vertical bore magnet. Comparison measurements were also obtained in an age‐matched control group.Results:In vivo results showed that there is a significant increase in the Cho/NAA ratio in the chronic alcohol‐exposed group that reached a maximum around 16 weeks. After 44 weeks of alcohol exposure, Cho/NAA in the alcohol group decreased significantly from its maximum value to a value that was significantly lower than those from the control groups. Brain extract studies demonstrated that PC and GPC were the main components responsible for the observed in vivo spectral changes after 16 and 60 weeks of alcohol consumption, respectively.Conclusion:The fluctuation of choline‐containing metabolites during alcohol intoxication could explain sometimes seemingly conflicting and confusing results from MRS studies in human and animal studies in which the duration of alcohol consumption and amount are varied widely. J. Magn. Reson. Imaging 2003;18:147–151. © 2003 Wiley‐Liss, Inc.
Quantitative perfusion mapping of the human lung using 1H spin labeling
Authors: Wang Tungte , Schultz Georg , Hebestreit Helge , Hebestreit Alexandra , Hahn Dietbert , Jakob Peter M. 
Published: July 2003

AbstractPurpose:To evaluate the feasibility and reproducibility of a noninvasive, rapid and quantitative pulmonary perfusion mapping method using a two‐compartment tissue model in combination with a 1H spin labeling technique.Materials and Methods:Ten healthy volunteers and three patients with cystic fibrosis (CF) were examined on a 1.5‐T whole‐body scanner. Global and selective lung T1 maps based on an inversion recovery Snapshot FLASH technique were acquired from each subject with breath‐holds at end‐expiration. For comparison, corresponding Gd‐DTPA‐enhanced 1H MR perfusion images were also obtained from each CF patient.Results:Quantitative perfusion maps were calculated from the global and selective T1 maps. The measured perfusion rates of the upper right lung in volunteers ranged from 400 to 600 mL/100 g/minute. The method showed a high intra‐study reproducibility and low relative errors. In CF‐patients, perfusion defects detected using Gd‐DTPA‐enhanced MR imaging were also detected using the spin labeling method. The perfusion rates of diseased lung tissues were less than 200 mL/100 g/minute.Conclusion:Noninvasive, robust and quantitative 1H MR mapping of pulmonary perfusion was successfully performed using a rapid lung T1 mapping in combination with spin labeling within the imaging slice. The proposed method has the potential to provide both important qualitative functional information and quantitative pulmonary perfusion rates in various lung diseases at various stages without the need of contrast agents. J. Magn. Reson. Imaging 2003;18:260–265. © 2003 Wiley‐Liss, Inc.
Fat suppression gradient‐echo magnetic resonance imaging of experimental articular cartilage lesions: Comparison between phase‐contrast method at 0.23T and chemical shift selective method at 1.5T
Authors: Palosaari Kari , Ojala Risto , Blanco‐Sequeiros Roberto , Tervonen Osmo 
Published: July 2003

AbstractPurpose:To evaluate the diagnostic performance of a newly developed single‐scan phase‐contrast water‐fat imaging technique for fat suppression at 0.23T open magnet, compared to the conventional chemical shift selective fat suppression method at 1.5T, in the detection of experimental articular cartilage lesions.Materials and Methods:Sixty regions of 20 knee joint specimens of pigs with artificially created articular cartilage lesions were examined with 0.23T and 1.5T MR scanners. Sagittal fat‐suppressed three‐dimensional gradient‐echo (3D GRE) images, obtained with the phase‐contrast method at 0.23T, and fat‐suppressed three‐dimensional spoiled gradient recalled echo (3D SPGR) images, obtained with a chemical shift selective method at 1.5T, were evaluated. Diagnostic performance was analyzed. The conspicuity of the lesions, the amount of artifacts, and the uniformity of fat suppression were evaluated. The contrast‐to‐noise (CNR) values of cartilage‐to‐bone marrow, and cartilage‐to‐infrapatellar fat were calculated.Results:At 0.23T, sensitivity and specificity were 80% and 95% for partial cartilage lesions (grade 2), and 91% and 100% for full‐thickness lesions (grade 3). At 1.5T, sensitivity and specificity were 85% and 95% for grade 2 lesions, and 96% and 97% for grade 3 lesions. No significant difference was detected in the conspicuity of lesions. The uniformity of fat suppression was more constant with 3D SPGR images compared to 3D GRE images. More susceptibility artifacts, derived from the procedure of creating lesions, were detected at 1.5T. The cartilage‐to‐fat CNRs were significantly higher with high‐field images.Conclusion:Phase‐contrast method for fat suppression at 0.23T is a useful technique in detecting articular cartilage lesions. J. Magn. Reson. Imaging 2003;18:225–231. © 2003 Wiley‐Liss, Inc.
Serial MR imaging with MS‐325 for evaluating female sexual arousal response: Determination of intrasubject reproducibility
Authors: Maravilla Kenneth R. , Cao Yunyu , Heiman Julia R. , Garland Patricia A. , Peterson Barry T. , Carter Wayne O. , Weisskoff Robert M. 
Published: July 2003

AbstractPurposeTo determine if a similar sexual arousal response in normal, healthy women could be obtained and monitored by serial magnetic resonance (MR) imaging at two separate sessions.Materials and MethodsSerial imaging of the external genitalia was performed on nine healthy, sexually functional women at two separate MR sessions after administration of the contrast agent, MS‐325. Images were obtained every three minutes during a 45‐minute study period during each MR session. The second MR session began approximately 45 minutes after the end of the first MR session. While undergoing imaging, subjects viewed videotapes that contained neutral and sexually‐explicit material through an audiovisual system. Analysis performed at each time point consisted of visual evaluation of the images, clitoral and femoral vein signal intensity measurements, relative regional blood volume calculations, and clitoral volume measurements. Statistical analysis of the results consisted of calculating correlation coefficients of the two MR sessions by using the least square fit method.ResultsAll nine subjects reported sexual arousal on subjective questionnaires at each MR session. Post‐contrast MS‐325 MR images showed strong enhancement of the external genitalia at each session. There was excellent correlation between the two sessions for the clitoral volume measurements of all nine subjects. The correlation coefficient, r2, was 0.95.ConclusionThe sexual arousal response in normal, healthy women can be monitored by serial imaging combined with the use of the contrast agent, MS‐325, and similar results can be reproduced at two different MR sessions. This method holds promise for future studies of women with female sexual arousal dysfunction. J. Magn. Reson. Imaging 2003;18:216–224. © 2003 Wiley‐Liss, Inc.
Automated unwrapping of MR phase images applied to BOLD MR‐venography at 3 Tesla
Authors: Rauscher Alexander , Barth Markus , Reichenbach Jürgen R. , Stollberger Rudolf , Moser Ewald 
Published: July 2003

AbstractPurpose:To improve the diagnostic value of BOLD MR‐Venography by removing artifacts related to phase wrapping, particularly in regions of large background susceptibilities at high magnetic field strengths.Materials and Methods:High resolution, T‐weighted, single echo images were acquired on a 3 T system (Medspec 30/80 Avance, Bruker Medical, Ettlingen, Germany) with a three‐dimensional, first order velocity compensated gradient echo sequence using a quadrature transmit/receive birdcage head coil. Data of nine healthy subjects and 19 patients were evaluated (age range: 27 to 76 years). To achieve improved MR‐venograms, a fully automated region‐growing phase unwrapping algorithm and subsequent high pass filtering were applied to phase images prior to the computation of minimum intensity projections.Results:Considerably improved visualization of venous structures in regions of large background susceptibility‐induced field inhomogeneities is demonstrated in healthy subjects and patients with brain tumors.Conclusion:BOLD MR venograms are improved compared to previous post‐processing algorithms. It is now feasible to obtain high‐resolution images also in inhomogeneous regions, which increases the clinical potential of BOLD MR‐Venography. J. Magn. Reson. Imaging 2003;18:175–180. © 2003 Wiley‐Liss, Inc.
Acute infarct of the corpus callosum: Appearance on diffusion‐weighted MR imaging and MR spectroscopy
Authors: Riedy Gerard , Melhem Elias R. 
Published: July 2003

AbstractFew reports of corpus callosum infarction are published in the radiologic literature. We present a case of an atypical infarction of the corpus callosum and adjacent gyri involving both anterior cerebral artery territories. Standard magnetic resonance (MR) imaging was performed including diffusion weighted imaging. In addition, perfusion‐weighted imaging and MR spectroscopy were employed to further characterize the patient's corpus callosal lesion. On MR imaging and spectroscopic examination, the lesion demonstrated T2 hyper‐intensity, restricted diffusion, and the metabolite lactate. While the MR imaging appearance of this bilateral infarction has some characteristics that mimic tumor, employment of the full range of MR techniques can obviate the need for biopsy in acute infarcts of the corpus callosum. J. Magn. Reson. Imaging 2003;18:255–259. © 2003 Wiley‐Liss, Inc.
Improvement in the quantification of myocardial perfusion using an automatic spline‐based registration algorithm
Authors: Dornier Christophe , Ivancevic Marko K. , Thévenaz Philippe , Vallée Jean‐Paul 
Published: July 2003

AbstractPurpose:To improve the quantification of myocardial perfusion by registering the time series of magnetic resonance (MR) images with injection of gadolinium.Materials and Methods:Eight patients underwent MR scans to perform myocardial perfusion exam. Two short axis views of the left ventricle (LV) were acquired in free breathing. Two masks for performing the spatial registration of the images were evaluated. The registration was based on pixel intensity in a multi‐resolution scheme. The efficiency of this correction was evaluated by calculating geometric residual displacement of the LV and by fitting the data to a compartment model fit with two parameters: K1, the blood‐to‐myocardium transfer coefficient, and Vd, the distribution volume of the contrast media.Results:The registration stage allowed a decrease in the observed motion of the LV from more than 1.98 ± 0.68 mm to less than 0.56 ± 0.18 mm (mean ± SD). Variability obtained in the perfusion analysis decreased from 46 ± 103% to 5± 4% for K1 parameter and from 18 ± 21% to 5 ± 5% for Vd parameter.Conclusion:As with manual correction, this automatic motion correction leads to accurate perfusion parameters in dynamic cardiac MR imaging after contrast agent injection. This automatic stage requires placing only one mask over one frame of the perfusion study instead of manually shifting each image to fit a reference image of the perfusion study. J. Magn. Reson. Imaging 2003;18:160–168. © 2003 Wiley‐Liss, Inc.
Dendritic polymers: from efficient catalysis to drug delivery
Authors: Kakkar Ashok K. 
Published: July 2003

AbstractDendritic polymers constitute an intriguing class of macromolecules that offer tremendous potential in designing new materaisl for applications in areas such as catalysis and small molecule loading and delivery. Synthesis of a variety of dendritic polymers using a simple and highly versatile synthetic methodology has enabled us to carry out a detailed investigation of dendritic effects in transition metal catalyzed organic transformations. Small dye molecules such as p‐nitroaninline and DR1 could be loaded into the intrinsic cavities of the backbone of 3,5‐dihydroxybenzyl alcohol based dendrimers, leading to a change in physical properties of both the dye and the dendrimer. We are also exploring the use of dendrimers as templates to prepare network carriers containing cavities of predetermined size and disposition.
Electron transport in conjugated metallopolymers
Authors: Cameron Colin G. , MacLean Brian J. , Pickup Peter G. 
Published: July 2003

AbstractSuperexchange interactions between metal centers coordinated to various conjugated polymer backbones have been shown to enhance the rate of electron transport through the polymer. Results for Ru and Os bipyridine moieties complexed to polybenzimidzoles and poly(bithiophene‐co‐bithiazole)s are reviewed. The evidence for superexchange mediated electron transport, and the factors that influence the rate of electron hopping between metal centers, are discussed.
Phosphine‐based coordination cages and nanoporous coordination polymers
Authors: James Stuart L. , Xu Xingling , Law Robert V. 
Published: July 2003

AbstractRecent findings in the use of multidentate phosphines to synthesise porous coordination polymers (metal‐organic frameworks) and their possible precursor cages are reviewed. Additional recent investigations into using large adamantoid Age cages as polymer vertices in giant diamandoid structures are also presented. The results are discussed in terms of possible strategies for the controled synthesis of porous coordination polymers.
Nano‐scale metallodendritic complexes in electron‐transfer processes and catalysis
Authors: Astruc Didier , Blais Jean‐Claude , Daniel Marie‐Christine , Martinez Victor , Nlate Sylvain , Ruiz Jaime 
Published: July 2003

AbstractNano‐sized metallodendrimers in which the equivalent metal fragments are located at the periphery can be assembled covalently, by H‐bonding (supramolecular) or onto dendronized nanoparticles. They can be used as electron‐reservoirs, i.e. molecular batteries, redox catalysts and sensors for the recognition of biologically relevant anions. They can also be deposited on metal surfaces or electrodes, which optimizes their use as recoverable sensors.
Iridium(III) complexes as polymer bound oxygen sensors
Authors: DeRosa Maria C. , Mosher Peter J. , Evans Christopher E.B. , Crutchley Robert J. 
Published: July 2003

AbstractNew luminescent oxygen sensors have been prepared by covalent attachment of iridium complex luminophores to a silicone polymer. The oxygen sensor properties of these novel materials were compared to related sensors in which the luminophore is dispersed within the polymer matrix. Covalently bound luminophore materials showed increased sensitivity to oxygen over dispersions in pure silicone polymer as well as in blends with polystyrene, which was added to improve the mechanical properties of the material.
Synthesis and properties of new phosphorus‐functionalized bithiophene materials
Authors: Baumgartner Thomas 
Published: July 2003

AbstractThe synthesis and reactivity of the novel dithieno[3,2‐b:2′,3′‐d]‐phosphole system and its potential use in polymeric sensory materials was investigated. Due to the nucleophilic nature of the phosphorus atom, these materials were found to be easily tunable. Classical reactions at the phosphorus center were performed to modify the electronic structure of the system and the corresponding changes were detected by UV/Vis and fluorescence spectroscopy. Depending on the oxidation state of the central phosphorus atom or its substitution pattern, the dithieno[3,2‐b:2′,3′‐d]‐phospholes show varying wavelengths for absorption and emission allowing to distinguish between different compounds by means of optical spectroscopy.
Organometallic conducting polymers synthesized by metallacycling polymerization
Authors: Nishihara Hiroshi , Kurashina Masashi , Murata Masaki 
Published: July 2003

AbstractThe study on the synthesis of π‐conjugated polymers using cobaltacyclopentadiene formation reaction of CpCo(PPh3)2 and conjugated diacetylene and the structure and physical properties of the polymers is overviewed. The substituents on the diacetylene affect crucially the solubility, the degree of polymerization, redox properties, and electronic structures and so on. Recent synthesis of a ruthenacyclopentatriene polymers by metallacyling polymerization is also described.
Hybrid inorganic/organic crosslinked resins containing polyhedral oligomeric silsesquioxanes
Authors: Pittman Jr. Charles U. , Li Gui‐Zhi , Ni Hanli 
Published: July 2003

AbstractThe incorporation of both monofunctional and multifunctional polyhedral oligomeric silsesquioxane (POSS) derivatives into crosslinked resins has been conducted as a route to synthesize hybrid organic/inorganic nanocomposites. The central cores of POSS molecules contain an inorganic cage with (SiO1.5)n stoichiometry where n=8,10 and 12. Each Si atom is capped with one H or R function giving an organic outer shell surrounding the nanometer‐sized inorganic inner cage. By including polymerizable functions on the R groups, a hybrid organic/inorganic macromer is obtained which can be copolymerized with organic monomers to create thermoplastic or thermoset systems. We have focused on incorporating POSS derivatives into crosslinking resins of the following types: (1) dicyclopentadiene (2) epoxies (3) vinyl esters (4) styrene‐DVB (5) MMA/1,4‐butane dimethacrylate (6) phenolics and (7) cyanate esters. One goal has been to determine if molecular dispersion of the POSS macromers has been achieved or if various degrees of aggregation occur during crosslinked resin formation. As network formation proceeds, a kinetic race between POSS molecular incorporation into the network versus phase separation into POSS‐rich regions (which then polymerize) occurs. Ultimately, we hope to determine the effects of such microstructural features on properties. Combustion of these hybrids creates a SiO2‐like surface layer that retards flame spread. Dynamic mechanical properties have been studied.
Exploiting catalytic dehydrogenative coupling in the synthesis and study of polysilanes
Authors: Rosenberg Lisa 
Published: July 2003

AbstractA reinvestigation of the catalytic activity of Wilkinson's catalyst, (Ph3P)3RhCl (1), for the dehydrogenative coupling reactions of secondary silanes has pointed the way toward the synthesis of key oligosilane reagents for structure property correlation studies of polysilanes. Implications are discussed for understanding the mechanisms of coupling and redistribution reactions of silanes mediated by such late metal centres. Also described are attempts to derivatize Si‐H bonds in the resulting oligosilanes, which is highly relevant to the development of improved methods for the post‐polymerization functionalization of polysilanes containing Si‐H bonds.
Polymer science with main group elements and transition metals
Authors: Manners Ian 
Published: July 2003

AbstractThe efficient formation of soluble, processable polymers with main chains containing inorganic elements provides a synthetic challenge but represents potentially important approach to new macromolecular and supramolecular materials with interesting properties. This talk will survey some of the recent research performed in our group concerning the development of controlled routes to a variety of different inorganic polymer systems and the use of the resulting materials in self‐assembly processes.
Towards photonic ink (P‐ink): a polychrome, fast response metallopolymer gel photonic crystal device
Authors: Arsenault André C. , Míguez Hernán , Kitaev Vladimir , Ozin Geoffrey A. , Manners Ian 
Published: July 2003

AbstractWe demonstrate here a new kind of planarized and oriented colloidal photonic crystal device whose optical stop‐band position, width and intensity can be reversibly redox and solvent tuned over a broad wavelength range by an anisotropic expansion of the photonic lattice. The material is composed of silica microspheres in a matrix of crosslinked polyferrocenylsilane[1], a metallopolymer network with a continuously variable state of oxidation[2]. Optical data was fitted using a scalar wave approximation, with a congruence to experimental data, allowing facile extraction of information concerning polymer swelling behaviour. The chemomechanical polychrome optical response of the material was exceptionally fast, attaining its fully swollen state from the dry shrunken state on a sub‐second time‐scale.
Lithographic applications of highly metallized polyferrocenylsilanes
Authors: Clendenning Scott B. , Manners Ian 
Published: July 2003

AbstractOrganometallic polymers are excellent candidates for the introduction of metals into nanostructures using lithographic techniques due to their inherently high and uniform metal loadings and processibility. Soluble, high molecular weight polyferrocenylsilanes possess unique physical properties and function as excellent ceramic precusors. Recent advances in the use of lithographic techniques with a highly metallized PFS resist to form new nanopatterned materials will be presented.
A Computational Study of the Polymerization‐Induced Phase Separation Phenomenon in Polymer Solutions under a Temperature Gradient
Authors: Lee Kam‐Wa D. , Chan Philip K. , Feng Xianshe 
Published: July 2003

AbstractThis paper studied the polymerization‐induced phase separation phenomenon (spinodal decomposition) in a model binary polymer solution under a linear spatial temperature gradient for the purpose of fabricating anisotropic polymeric materials by using mathematical modeling and computer simulation. Reaction kinetics were incorporated with the non‐linear Cahn‐Hilliard theory and the Flory‐Huggins free energy expression in the model. Moreover, the slow mode theory and Rouse law were used to account for polymer diffusion. It was found that an anisotropic morphology was obtained when a temperature gradient was imposed along the polymer solution sample. The direction of the structural anisotropy, however, depended significantly on the overall phase separation time. The presence of a temperature gradient along the polymer solution sample generated a spatial variation in polymerization rate, which resulted in a spatial variation of quench depth. Consequently, at a given instant, the phase separation at different locations of the polymer solution was at different stages of spinodal decomposition. The droplet size formed along the polymer solution was therefore dependent on the polymerization rate, the quench depth and the stage of spinodal decomposition. Furthermore, the spatial temperature gradient produced a spatial variation in the process induction time, which contains the polymerization induction time and phase separation induction time. It was also found that the polymerization induction time played a significant role on the spatial variation in the overall process induction time.image