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Magnetic Resonance Techniques (magnetic + resonance_techniques)
Selected AbstractsThe future of magnetic resonance-based techniques in neurologyEUROPEAN JOURNAL OF NEUROLOGY, Issue 1 2001European Federation of Neurological Societies Task Force Magnetic resonance techniques have become increasingly important in neurology for defining: 1,brain, spinal cord and peripheral nerve or muscle structure; 2,pathological changes in tissue structures and properties; and 3,dynamic patterns of functional activation of the brain. New applications have been driven in part by advances in hardware, particularly improvements in magnet and gradient coil design. New imaging strategies allow novel approaches to contrast with, for example, diffusion imaging, magnetization transfer imaging, perfusion imaging and functional magnetic resonance imaging. In parallel with developments in hardware and image acquisition have been new approaches to image analysis. These have allowed quantitative descriptions of the image changes to be used for a precise, non-invasive definition of pathology. With the increasing capabilities and specificity of magnetic resonance techniques it is becoming more important that the neurologist is intimately involved in both the selection of magnetic resonance studies for patients and their interpretation. There is a need for considerably improved access to magnetic resonance technology, particularly in the acute or intensive care ward and in the neurosurgical theatre. This report illustrates several key developments. The task force concludes that magnetic resonance imaging is a major clinical tool of growing significance and offers recommendations for maximizing the potential future for magnetic resonance techniques in neurology. [source] Magnetic resonance techniques for the in vivo assessment of multiple sclerosis pathology: Consensus report of the white matter study groupJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2005Massimo Filippi MD Abstract On October 9,11, 2003, the third meeting of the White Matter Study Group of the International Society for Magnetic Resonance in Medicine was held in Venice, Italy. This article is the report of the meeting on how to use MRI in the diagnostic workup of multiple sclerosis (MS) and allied white matter disorders, and to define the nature and the extent of MS pathology in vivo. Both of these steps are central to the design of future treatment strategies aimed at limiting the functional consequences of the most disabling aspects of this disease. J. Magn. Reson. Imaging 2005;21:669,675. © 2005 Wiley-Liss, Inc. [source] Spins as probes of different electronic statesCONCEPTS IN MAGNETIC RESONANCE, Issue 2 2007Dieter Suter Abstract Nuclear spins are efficient probes of electronic states. Because most NMR experiments are performed in thermal equilibrium, they probe the electronic ground state,the only state that is significantly populated under ambient conditions. Probing electronically excited states becomes possible, if magnetic resonance techniques are combined with optical (laser) excitation. Depending on the nature of the electronic state, drastic changes of the magnetic resonance parameters may be observed. We discuss the basic principles of this type of investigation. Depending on the lifetime of the electronically excited state, it is possible to measure separate spectra of ground and excited state if the lifetime is long on the NMR timescale, or an averaged spectrum if the lifetime is short. We present examples for both limiting cases using rare earth ions and semiconductor heterostructures. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 116,126, 2007. [source] The future of magnetic resonance-based techniques in neurologyEUROPEAN JOURNAL OF NEUROLOGY, Issue 1 2001European Federation of Neurological Societies Task Force Magnetic resonance techniques have become increasingly important in neurology for defining: 1,brain, spinal cord and peripheral nerve or muscle structure; 2,pathological changes in tissue structures and properties; and 3,dynamic patterns of functional activation of the brain. New applications have been driven in part by advances in hardware, particularly improvements in magnet and gradient coil design. New imaging strategies allow novel approaches to contrast with, for example, diffusion imaging, magnetization transfer imaging, perfusion imaging and functional magnetic resonance imaging. In parallel with developments in hardware and image acquisition have been new approaches to image analysis. These have allowed quantitative descriptions of the image changes to be used for a precise, non-invasive definition of pathology. With the increasing capabilities and specificity of magnetic resonance techniques it is becoming more important that the neurologist is intimately involved in both the selection of magnetic resonance studies for patients and their interpretation. There is a need for considerably improved access to magnetic resonance technology, particularly in the acute or intensive care ward and in the neurosurgical theatre. This report illustrates several key developments. The task force concludes that magnetic resonance imaging is a major clinical tool of growing significance and offers recommendations for maximizing the potential future for magnetic resonance techniques in neurology. [source] Polyelectrolyte-in-Ionic-Liquid ElectrolytesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2003Churat Tiyapiboonchaiya Abstract Novel polymer electrolyte materials based on a polyelectrolyte-in-ionic-liquid principle are described. A combination of a lithium 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSLi) and N,N,-dimethylacrylamide (DMMA) are miscible with the ionic liquid, 1-ethyl-3-methylimidazolium dicyanamide (EMIDCA). EMIDCA has remarkably high conductivity (,,2,·,10,2 S,·,cm,1) at room temperature and acts as a good solvating medium for the polyelectrolyte. At compositions of AMPSLi less than or equal to 75 mol-% in the copolymer (P(AMPSLi- co -DMAA)), the polyelectrolytes in EMIDCA are homogeneous, flexible elastomeric gel materials at 10,,,15 wt.-% of total polyelectrolyte. Conductivities higher than 8,·,10,3 S,·,cm,1 at 30,°C have been achieved. The effects of the monomer composition, polyelectrolyte concentration, temperature and lithium concentration on the ionic conductivity have been studied using thermal and conductivity analysis, and pulsed field gradient nuclear magnetic resonance techniques. Comparison of the measured and calculated lithium conductivity at 30,°C. [source] Conformational states of human H-Ras detected by high-field EPR, ENDOR, and 31P NMR spectroscopy ,MAGNETIC RESONANCE IN CHEMISTRY, Issue S1 2005Michael Spoerner Abstract Ras is a central constituent of the intracellular signal transduction that switches between its inactive state with GDP bound and its active state with GTP bound. A number of different X-ray structures are available. Different magnetic resonance techniques were used to characterise the conformational states of the protein and are summarised here. 31P NMR spectroscopy was used as probe for the environment of the phosphate groups of the bound nucleotide. It shows that in liquid solution additional conformational states in the GDP as well as in the GTP forms coexist which are not detected by X-ray crystallography. Some of them can also be detected by solid-state NMR in the micro crystalline state. EPR and ENDOR spectroscopy were used to probe the environment of the divalent metal ion (Mg2+ was replaced by Mn2+) bound to the nucleotide in the protein. Here again different states could be observed. Substitution of normal water by 17O-enriched water allowed the determination of the number of water molecules in the first coordination sphere of the metal ion. In liquid solution, they indicate again the existence of different conformational states. At low temperatures in the frozen state ENDOR spectroscopy suggests that only one state exists for the GDP- and GTP-bound form of Ras, respectively. Copyright © 2005 John Wiley & Sons, Ltd. [source] Diffusion-weighted imaging and magnetization transfer imaging of tardive and edentulous orodyskinesiaMOVEMENT DISORDERS, Issue 9 2008Abdesslem Khiat PhD Abstract Oral dyskinesias occur in elderly individuals in relation to drug use (tardive dyskinesia, TD) or edentulousness (edentulous orodyskinesia, EOD) but their characterization remains incomplete. Our aim was to investigate whether magnetic resonance techniques such as diffusion-weighted imaging (DWI) and magnetization transfer imaging (MTI) of the brain could be used to differentiate dyskinetic patients from control subjects. Eight drug-treated patients with TD, 12 EOD patients, 8 drug-treated patients without TD, and 10 control subjects were recruited and examined by DWI and MTI. Measurements in the caudate nucleus, putamen, and globus pallidus yielded globally different apparent diffusion coefficient (ADC) values between drug treated patients with TD and control subjects but the magnetization transfer ratios showed no significant variations. The discrimination between dyskinetic patients and control subjects offered by ADC values was however slightly poorer than the discrimination offered by the previously published choline/creatine ratios measured by MR spectroscopy in the basal ganglia. The results are consistent with the pathophysiological hypothesis of damage to cholinergic interneurons. © 2008 Movement Disorder Society [source] Endotoxemia does not limit energy supply in exercising rat skeletal muscleMUSCLE AND NERVE, Issue 4 2008Benoit Giannesini PhD Abstract Although depletion in high-energy phosphorylated compounds and mitochondrial impairment have been reported in septic skeletal muscle at rest, their impact on energy metabolism has not been documented during exercise. In this study we aimed to investigate strictly gastrocnemius muscle function non-invasively, using magnetic resonance techniques in endotoxemic rats. Endotoxemia was induced by injecting animals intraperitoneally at t0 and t0 + 24 h with Klebsiella pneumoniae lipopolysaccharides (at 3 mg kg,1). Investigations were performed at t0 + 48 h during a transcutaneous electrical stimulation protocol consisting of 5.7 min of repeated isometric contractions at a frequency of 3.3 HZ. Endotoxin treatment produced a depletion in basal phosphocreatine content and a pronounced reduction in oxidative adenosine triphosphate (ATP) synthesis capacity, whereas the resting ATP concentration remained unchanged. During the stimulation period, endotoxemia caused a decrease in force-generating capacity that was fully accounted for by the loss of muscle mass. It further induced an acceleration of glycolytic ATP production and an increased accumulation of adenosine diphosphate (ADP, an important mitochondrial regulator) that allowed a near-normal rate of oxidative ATP synthesis. Finally, endotoxemia did not affect the total rate of ATP production or the ATP cost of contraction throughout the whole stimulation period. These data demonstrate that, in an acute septic phase, metabolic alterations in resting muscle do not impact energy supply in exercising muscle, likely as a result of adaptive mechanisms. Muscle Nerve, 2008 [source] Pulsed electrically detected magnetic resonance in organic semiconductorsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11-12 2009C. Boehme Abstract Carbon-based materials have an intrinsically weak spin,orbit coupling which imposes spin selection rules on many electronic transitions. The spin degree of freedom of electrons and nuclei can therefore play a crucial role in the electronic and optical properties of these materials. Spin-selection rules can be studied via magnetic resonance techniques such as electron,spin resonance and optically detected magnetic resonance as well as electrically detected magnetic resonance (EDMR). The latter has progressed in recent years to a degree where the observation of coherent spin motion via current detection has become possible, providing experimental access to many new insights into the role that paramagnetic centers play for conductivity and photoconductivity. While mostly applied to inorganic semiconductor materials such as silicon, this new, often called pulsed-(p) EDMR spectroscopy, has much potential for organic (carbon-based) semiconductors. In this study, progress on the development of pEDMR spectroscopy on carbon-based materials is reviewed. Insights into materials properties that can be gained from pEDMR experiments are explained and limitations are discussed. Experimental data on radiative polaron-pair recombination in poly[2-methoxy-5-(20-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) organic light emitting diodes (OLEDs) are shown, revealing that under operating conditions the driving current of the device can be modulated by spin-Rabi nutation of the polaron spin within the charge carrier pairs. From this experimental data it becomes clear that for polaron pairs, the precursor states during exciton formation, exchange interaction is not the predominant influence on the observed pEDMR spectra. [source] A Morphological and 13C NMR Study of the Extramandibular Fat Bodies of the Striped Dolphin (Stenella coeruleoalba)THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 7 2007C. Maxia Abstract The molecular and histological structure of the fat bodies covering externally the posterolateral region of the jaw of the striped dolphin (Stenella coeruleoalba) was investigated by means of morphological and nuclear magnetic resonance techniques. The analyses of samples belonging to adult and juvenile individuals were performed with the aim of seeking the presence of age-related differences. In our study, the level of isovalerate (iso5:0) in the extramandibular fat of the juvenile individuals is comparable with those of the adult counterparts; conversely, longer isobranched fatty acids were detected in lower quantities in the juveniles together with a higher degree of unsaturation. The morphologic analyses revealed that, in both adults and juveniles, this fatty tissue is similar to univacuolar adipose tissue. However, in the juveniles, a muscular component was present, whereas only in adult subjects, enlarged and irregularly shaped cavities may be seen within the adipose tissue. These cavities, structurally organized as veins, may regulate blood flow in response to changing water temperature and stabilize thermal gradient within the jaw lipids. These data suggest that the molecular components and the histological organization can indicate a maturation of the organ with age that probably may reflect different sound reception properties. Anat Rec, 2007. © 2007 Wiley-Liss, Inc. [source] Conformational Stability of A, -(25,35) in the Presence of Thiazolidine DerivativesCHEMICAL BIOLOGY & DRUG DESIGN, Issue 2 2007Pietro Campiglia In the attempt to identify a new lead compound able to modify the conformational preferences of the , -amyloid peptides, a set of new compounds characterized by a thiazolidine ring linked to several different aryl moieties were synthesized. The ability of these compounds to prevent the , -amyloid aggregation was evaluated using circular dichroism and nuclear magnetic resonance techniques. Molecular docking procedure allowed an interpretation of spectroscopic in the key of molecular interaction. [source] | |||||||||||||||||||||||||