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Magnetic Resonance Spectroscopy (magnetic + resonance_spectroscopy)
Kinds of Magnetic Resonance Spectroscopy Terms modified by Magnetic Resonance Spectroscopy Selected AbstractsFUTURE OF MAGNETIC RESONANCE IMAGING AND MAGNETIC RESONANCE SPECTROSCOPY IN ONCOLOGYANZ JOURNAL OF SURGERY, Issue 6 2005Ferenc Jolesz MD No abstract is available for this article. [source] Molecular Dynamics of Podand Studied by Broadband Dielectric and Nuclear Magnetic Resonance Spectroscopies,,MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 19-20 2007Bakyt Orozbaev Abstract Nuclear magnetic resonance (NMR) and broadband dielectric spectroscopies (BDS) were used to analyze the molecular dynamics in P10.3H Podand. The temperature studies of NMR line and magnetic spin,lattice relaxation times accompanied by DS investigation enabled us to distinguish three main dynamical processes connected with the motions of the P10.3H Podand chains. In the low-temperature region the magnetic relaxation was associated with fast axial C3 rotation of methyl groups. Moreover, two other independent processes were observed and interpreted as (i) segmental motion of both oxyethylene and ethylene units, and (ii) the overall motion involved in the melting process. [source] 1H-Magnetic Resonance Spectroscopy for Quantifying Myocardial Lipid Content in Humans With the Cardiometabolic SyndromeJOURNAL OF CLINICAL HYPERTENSION, Issue 9 2009Robert D. O'Connor PhD First page of article [source] Research Article: Fingerprinting Analysis of Saposhnikovia divaricata using 1H Nuclear Magnetic Resonance Spectroscopy and High Performance Liquid ChromatographyJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2010Yue-Yang Xin The 1H nuclear magnetic resonance (1H NMR) fingerprints of fractionated non-polar and polar extracts (control substance for plant drug [CSPD] A and B) from the roots of 12 specimens of Saposhnikovia divaricata (Turcz.) Schischk were achieved with Fourier Transform (FT)-NMR spectrometer and assigned by comparison to each other and to the 1H NMR spectra of the isolated individual compounds. These fingerprints were found to be uniform in terms of the specificity for the implication of all 12 specimens being systematically of the same origin. The uniformity was further affirmed by high performance liquid chromatography (HPLC), which also revealed exactly identical specificity for the identified S. divaricata species with the 1H NMR appearances of corresponding CSPD on the part of the composition of characteristic constituents when comparing to corresponding individual compounds. This investigation unambiguously shows that the specific signals from the chemotaxonomically significant compounds of chromones and coumarins in S. divaricata are exhibited distinctively in the composite features of both 1H NMR fingerprints and HPLC profiles. The 1H NMR and HPLC profiles established can successfully be used as reference for the authentication of the origin of S. divaricata species as well as for chemotaxonomic studies. [source] Fingerprinting Analysis of Rhizoma Chuanxiong of Commercial Types using 1H Nuclear Magnetic Resonance Spectroscopy and High Performance Liquid Chromatography MethodJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2009Hai-Lin Qin Abstract The 1H nuclear magnetic resonance (1H NMR) fingerprints of fractionated non-polar extracts (control substance for a plant drug (CSPD) A) from Rhizoma chuanxiong, the rhizomes of Ligusticum chuanxiong Hort., of seven specimens from different sources were measured on Fourier Transform (FT)-NMR spectrometer and assigned by comparing them with the 1H NMR spectra of the isolated pure compounds. The 1H NMR fingerprints showed exclusively characteristic resonance signals of the major special constituents of the plant. Although the differences in the relative intensity of the 1H NMR signals due to a discrepancy in the ratio of the major constituents among these samples could be confirmed by high performance liquid chromatography analysis, the general features of the 1H NMR fingerprint established for an authentic sample of the rhizomes of L. chuanxiong exhibited exclusive data from those special compounds and can be used for authenticating L. Chuanxiong species. [source] Role of Proton Magnetic Resonance Spectroscopy in Differentiating Oligodendrogliomas from AstrocytomasJOURNAL OF NEUROIMAGING, Issue 1 2010Sanjeev Chawla PhD ABSTRACT BACKGROUND AND PURPOSE Preoperative differentiation of astrocytomas from oligodendrogliomas is clinically important, as oligodendrogliomas are more sensitive to chemotherapy. The purpose of this study was to assess the role of proton magnetic resonance spectroscopy in distinguishing astrocytomas from oligodendrogliomas. METHODS Forty-six patients [astrocytomas (n= 17) and oligodendrogliomas (n= 29)] underwent magnetic resonance imaging and multi voxel proton magnetic resonance spectroscopic imaging before treatment. Peak areas for N-acetylaspartate (NAA), creatine (Cr), choline (Cho), myo-inositol (mI), glutamate/glutamine (Glx), and lipids + lactate (Lip+Lac) were analyzed from voxels that exhibited hyperintensity on fluid-attenuated inversion recovery images and were normalized to Cr from each voxel. The average metabolite/Cr ratios from these voxels were then compared between astrocytomas and oligodendrogliomas. Receiver-operating curve analyses were used as measures of differentiation accuracy of metabolite ratios. A threshold value for a metabolite ratio was estimated by maximizing the sum of sensitivity and specificity. RESULTS A significant difference in mI/Cr was observed between astrocytomas and oligodendrogliomas (.50 ± .18 vs. 0.66 ± 0.20, P < .05). Using a threshold value of .56 for mI/Cr ratio, it was possible to differentiate oligodendrogliomas from astrocytomas with a sensitivity of 72.4% and specificity of 76.4%. CONCLUSION These results suggest that mI/Cr might aid in distinguishing oligodendrogliomas from astrocytomas. J Neuroimaging 2010;20:3-8. [source] Combined Use of F-18 Fluorocholine Positron Emission Tomography and Magnetic Resonance Spectroscopy for Brain Tumor EvaluationJOURNAL OF NEUROIMAGING, Issue 3 2004Sandi A. Kwee MD ABSTRACT Background. Choline metabolism is often abnormal in malignant brain tumors.Methods. Brain positron emission tomography (PET) imaging with F-18 fluorocholine (FCH) was performed on 2 patients with intracranial lesions suspected to be high-grade malignant gliomas on the basis of magnetic resonance (MR) imaging and multivoxel 1H-MR spectroscopic imaging (MRSI) findings. Standardized uptake value (SUV) measurements on PET were compared with measurements of choline/creatine metabolite ratio on MRSI in corresponding regions. Brain biopsy revealed glioblastoma multiforme (GBM) in one case and demyelinating disease in the other.Results. In the case of GBM, the tumor demonstrated increased FCH uptake on PET. The mean and maximum SUV in areas of the tumor correlated with regional choline/ creatine ratio measurements (r= 0.76,P < .001;r= 0.83,P < .001, respectively). In the case of tumefactive demyelinating lesions, the lesion demonstrated low FCH uptake, which did not correlate with choline/ creatine ratio measurements.Conclusions. Assessments of choline metabolism may aid in evaluating intracranial mass lesions. [source] Neonatal Alcohol-Induced Region-Dependent Changes in Rat Brain Neurochemistry Measured by High-Resolution Magnetic Resonance SpectroscopyALCOHOLISM, Issue 10 2008Shonagh K. O'Leary-Moore Background:, Maternal drinking during pregnancy can lead to a range of deleterious outcomes in the developing offspring that have been collectively termed fetal alcohol spectrum disorders (FASDs). There is interest and recognized value in using non-invasive neuroimaging techniques such as magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) to characterize, respectively, structural and biochemical alterations in individuals with FASDs. To date, however, results with MRS have been inconsistent regarding the degree and/or nature of abnormalities. Methods:, High-resolution magic angle spinning (HR-MAS) proton (1H) MRS is an ex vivo neuroimaging technique that can acquire spectra in small punches of intact tissue, providing clinically relevant neurochemical information about discrete brain regions. In this study, HR-MAS 1H MRS was used to examine regional neurochemistry in frontal cortex, striatum, hippocampus, and cerebellum of young rats previously exposed to ethanol as neonates. Key neurochemicals of interest included N-acetyl-aspartate (NAA), glutamate, GABA, glutamine, creatine, choline and myo -inositol. Results:, Daily neonatal alcohol exposure from postnatal day 4 (PN4) through PN9 significantly reduced levels of NAA and taurine in the cerebellum and striatum, and induced sex-dependent reductions in cerebellar glutamate when measured on PN16. In addition, myo -inositol was significantly increased in cerebellum. The frontal cortex and hippocampus were virtually unaffected by this neonatal alcohol exposure. Conclusion:, Results of this research may have implications for understanding the underlying neurobiology associated with FASDs and aid in testing treatments in the future. Ongoing studies are assessing the developmental persistence of and/or maturational recovery from these changes. [source] Longitudinal Brain Metabolic Characterization of Chronic Alcoholics With Proton Magnetic Resonance SpectroscopyALCOHOLISM, Issue 9 2002Mitchell H. Parks Background Proton magnetic resonance spectroscopy may elucidate the molecular underpinnings of alcoholism-associated brain shrinkage and the progression of alcohol dependence. Methods Using proton magnetic resonance spectroscopy, we determined absolute concentrations of N -acetylaspartate (NAA), creatine/phosphocreatine (Cr), and choline (Cho)-containing compounds and myo -inositol (mI) in the anterior superior cerebellar vermis and frontal lobe white matter in 31 alcoholics and 12 normal controls. All patients were examined within 3 to 5 days of their last drink. Patients who did not relapse were again studied after 3 weeks and 3 months of abstinence by using an on-line repositioning technique that allows reliable localization of volumes of interest (VOIs). Results At 3 to 5 days after the last drink, frontal white matter metabolite concentrations were not significantly different from those of normal controls, whereas brain tissue in the VOI was reduced. Cerebellar [NAA] and [Cho] and brain and cerebellar volumes were decreased, but [Cr], [mI], and VOI brain tissue volume were not significantly different. Eight patients relapsed before 3 weeks (ER), 12 relapsed between 3 weeks and 3 months (LR), and 11 did not relapse (NR) during 3 months. Cerebellar [NAA] was reduced only in ER patients, despite the fact that ER patients drank for significantly fewer years and earlier in life than LR or NR patients. After 3 months, in the 11 continuously abstinent patients, cerebellar [NAA] and brain and cerebellar volumes increased; cerebellar [Cho], [Cr], and [mI] and VOI brain tissue did not change significantly. Conclusions Decreased [NAA] and [Cho] in cerebellar vermis indicate a unique sensitivity to alcohol-induced brain injury. Cerebellar [NAA] increased with abstinence, but reduced [Cho] persisted beyond 3 months. Further studies are needed to determine whether low cerebellar [NAA] is a risk factor for, or consequence of, malignant, early-onset alcoholism. [source] Characterization of Phase Separation and Thermal History Effects in Magnesium Silicate Glass Fibers by Nuclear Magnetic Resonance SpectroscopyJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2009Jonathan F. Stebbins Liquid,liquid immiscibility, leading to the separation of silica-rich and silica-poor domains, is a common phenomenon in binary silicate glasses, but can be difficult to detect and characterize when rapid cooling results in nano-scale domain dimensions. 29Si nuclear magnetic resonance (NMR) spectroscopy can be very useful for detecting such phase separation, because the exclusion of paramagnetic impurity ions from the silica-rich regions can greatly slow their spin-lattice relaxation rates. Properly designed experiments can therefore largely isolate the NMR signals from high-silica and low-silica domains, and thus provide information about their proportions, compositions, and short- to intermediate-range structures. We demonstrate this approach here for fiber glasses that are predominantly magnesium, or calcium-magnesium silicates, with minor contents of alumina. For bulk compositions within the known region of stable liquid immiscibility, phase separation occurs even when extremely rapid cooling yields fibers less than 1 ,m in mean diameter. Slower cooling increases the extent of separation, while the addition of small amounts of alumina reduces it. [source] Metabolic changes detected in vivo by 1H MRS in the MPTP-intoxicated mouseNMR IN BIOMEDICINE, Issue 6 2010Carine Chassain Abstract We used in vivo proton (1H) Magnetic Resonance Spectroscopy (MRS) to measure the levels of the main excitatory amino acid, glutamate (Glu) and also glutamine (Gln) and GABA in the striatum and cerebral cortex in the MPTP-intoxicated mouse, a model of dopaminergic denervation, before and after dopamine (DA) replacement. The study was performed at 9.4T on control mice (n,=,8) and MPTP-intoxicated mice (n,=,8). In vivo spectra were acquired in a voxel (8,µL) centered in the striatum, and in the cortex (4.6,µL). Three days after basal MRS acquisitions new spectra were acquired in the striatum and cortex, after levodopa (200,mg.kg,1). Glu, Gln and GABA concentrations obtained in the basal state were significantly increased in the striatum of MPTP-lesioned mice (Glu: 20.2,±,0.8 vs 11.4,±,0.9,mM, p,<,0.001; Gln: 5.4,±,1.6 vs 2.0,±,0.6,mM, p,<,0.05; GABA: 3.6,±,0.8 vs 1.6,±,0.2,mM, p,<,0.05). Levodopa lowered metabolites concentrations in the striatum of MPTP-lesioned mice (Glu: 20.2,±,0.8 vs 11.2,±,0.4,mM (+ Ldopa), p,<,0.001; Gln: 5.4,±,1.6 vs 1.6,±,0.4,mM (+ Ldopa), p,<,0.05; GABA: 3.6,±,0.8 vs 1.7,±,0.4,mM (+ Ldopa), p,<,0.01). Metabolite levels in the striatum of MPTP-intoxicated mice + levodopa were not significantly different from those in the striatum of controls. No change was found in the cortex after DA denervation and after DA replacement between the two animals groups. These results strongly support a predominant change in striatal Glu synaptic activity in the cortico-striatal pathway. Acute levodopa administration reverses the increase of metabolites in the striatum. Copyright © 2010 John Wiley & Sons, Ltd. [source] Magnetic Resonance Spectroscopy of Iron-Doped Glasses: From Isolated Ions to Clusters and NanoparticlesCHEMINFORM, Issue 31 2005Janis Kliava Abstract For Abstract see ChemInform Abstract in Full Text. [source] Quantitative Determination of Sodium Dodecatungstosilicate Speciation by 183W Nuclear Magnetic Resonance Spectroscopy.CHEMINFORM, Issue 41 2002Bradley J. Smith Abstract For Abstract see ChemInform Abstract in Full Text. [source] Magnetic resonance spectroscopy (MRS) and its application in Alzheimer's diseaseCONCEPTS IN MAGNETIC RESONANCE, Issue 1 2007Pravat K. Mandal Abstract Magnetic resonance spectroscopy (MRS) is a noninvasive tool to measure the chemical composition of tissues (in vivo) and characterize functional metabolic processes in different parts of the human organs. It provides vital biological information at the molecular level. Combined with magnetic resonance imaging (MRI), an integrated MRI/MRS examination provides anatomical structure, pathological function, and biochemical information about a living system. MRS provides a link between the biochemical alterations and the pathophysiology of disease. This article provides a comprehensive description of the MRS technique and its application in Alzheimer's disease (AD) research. This review is a primer for students and researchers seeking a firm theoretical understanding of MRS physics as well as its application in clinical AD research. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 40,64, 2007. [source] Linking structural, metabolic and functional changes in multiple sclerosisEUROPEAN JOURNAL OF NEUROLOGY, Issue 4 2001Massimo Filippi In patients with multiple sclerosis (MS), conventional magnetic resonance imaging (MRI) has markedly improved our ability to detect the macroscopic abnormalities of the brain and spinal cord. New quantitative magnetic resonance (MR) approaches with increased sensitivity to subtle normal-appearing white matter (NAWM) and grey matter changes and increased specificity to the heterogeneous pathological substrates of MS may give information complementary to conventional MRI. Magnetization transfer imaging (MTI) and diffusion-weighted imaging (DWI) have the potential to provide important information on the structural changes occurring within and outside T2-visible lesions. Magnetic resonance spectroscopy (MRS) adds information on the biochemical nature of such changes. Functional MRI might quantify the efficiency of brain plasticity in response to MS injury and improve our understanding of the link between structural damage and clinical manifestations. The present review summarizes how the application of these MR techniques to the study of MS is dramatically changing our understanding of how MS causes irreversible neurological deficits. [source] Lactate Detection by MRS in Mitochondrial Encephalopathy: Optimization of Technical ParametersJOURNAL OF NEUROIMAGING, Issue 1 2008Antônio José da Rocha MD ABSTRACT Mitochondriopathies are a heterogeneous group of diseases with variable phenotypic presentation, which can range from subclinical to lethal forms. They are related either to DNA mutations or nuclear-encoded mitochondrial genes that affect the integrity and function of these organelles, compromising adenosine triphosphate (ATP) synthesis. Magnetic resonance (MR) is the most important imaging technique to detect structural and metabolic brain abnormalities in mitochondriopathies, although in some cases these studies may present normal results, or the identified brain abnormalities may be nonspecific. Magnetic resonance spectroscopy (MRS) enables the detection of high cerebral lactate levels, even when the brain has normal appearance by conventional MR scans. MRS is a useful tool for the diagnosis of mitochondriopathies, but must be correlated with clinical, neurophysiological, biochemical, histological, and molecular data to corroborate the diagnosis. Our aim is to clarify the most relevant issues related to the use of MRS in order to optimize its technical parameters, improving its use in the diagnosis of mitochondriopathies, which is often a challenge. [source] Amelioration of disease severity by intraarticular hylan therapy in bilateral canine osteoarthritisJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2000K. W. Marshall Because of its high molecular weight, the glycosaminoglycan molecule hyaluronan is responsible for the viscoelastic properties of normal synovial fluid. In osteoarthritis, the concentration and molecular weight of hyaluronan in synovial fluid is diminished; this impairs the ability of synovial fluid to effectively lubricate joints, absorb loads, and exert anti-inflammatory effects. Using a bilateral anterior cruciateligament transection and partial neurectomy canine model of osteoarthritis, this study examined the effect of viscosupplementation with hylan G-F 20 as a treatment for osteoarthritis, this study examined the effect of viscosupplementation with hylan G-F 20 as a treatment for osteoarthritis. Twelve dogs underwent bilateral arthroscopic anterior cruciate-ligament transections and partial neurectomy of the knee joints. Beginning 1 week after the operation, six dogs received three weekly 500-,l injections of hylan G-F 20 in one knee and a sham injection of saline solution in the contralateral knee (early-treatment group). The remaining six animals underwent the same treatment 2 months following the procedure (late-treatment group). All dogs were killed at 8 months, and both knees were evaluated for gross pathology, histology, and proteoglycan content. In addition, with use of 500-MHz [1H] magnetic resonance spectroscopy, the synovial fluid from both knees was assessed for changes in metabolic profile. Differences in outcome were analyzed with paired t tests. Gross pathological and histological examination revealed significantly less severe changes of osteoarthritis in knees treated with hylan G-F 20 2 months after surgery than in the contralateral untreated knees. Magnetic resonance spectroscopy of the specimens in this late-treatment group showed significantly decreased glucose concentrations and significantly elevated isoleucine levels in the synovial fluid from knees treated with hylan G-F 20 compared with the controls. Previous magnetic resonance spectroscopy had shown that glucose concentrations increase with the onset of osteoarthritis and eventually diminish in end-stage osteoarthritis. The three injections of hylan were given after osteoarthritis was established, and the severity of the disease was ameliorated in the treated knees 6 months after treatment. This occurred although hylan G-F 20 is almost certainly cleared from joints by lymphatics within 4 weeks of injection, suggesting that hylan therapy can retard the progression of osteoarthritis for periods of time extending beyond the intraarticular residence time of the injected molecules and that hylan injections given at relatively early stages of osteoarthritis may have a chondroprotective effect. No changes in outcome were noted in the animals that received hylan G-F 20 immediately following surgery. [source] In vivo magnetic resonance spectroscopy of gynaecological tumours at 3.0 TeslaBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 2 2009SJ Booth Background, Magnetic resonance spectroscopy (MRS) uses the same hardware as MR imaging and allows us to analyse the biochemistry of tissues in vivo. Published data for gynaecological lesions are limited and are largely based on MRS carried out at the lower magnetic field strength of 1.5 Tesla (T). Objective, The purpose of this study was to determine whether in vivo proton MRS could be performed at the higher magnetic field strength of 3 T to characterise the spectra of a variety of benign and malignant gynaecological lesions. Design, Prospective, non-randomised study. Setting, MRI department within a tertiary referral centre for gynaecological cancers. Sample, All women with a pelvic mass under going 3T MRI. Methods, We carried out MRS on nonrandomised women undergoing routine 3 T MRI within our MRI department during investigation for gynaecological lesions from February 2006 to April 2008. Only those women for whom histopathological data were available were included. Main outcome measures, The presence of choline detected by in vivo 3T MRS. Results, Eighty-seven women underwent MRS, 57 of whom had newly diagnosed neoplasms. MRS data for 39 of these new women (18 were excluded because of technical errors or missing data) were used to detect the presence of choline, an indicator of basement membrane turnover. Overall, choline was present in 13 of the 14 ovarian cancers, 8 of the 11 cervical tumours and all 4 of the uterine cancers. There was no statistical significant difference between choline levels in various lesion types (P= 0.735) or between benign and malignant disease (P= 0.550). Conclusions,In vivo MRS can be performed at 3 T to provide biochemical information on pelvic lesions. The way in which this information can be utilised is less clear but may be incorporated into monitoring tissue response in cancer treatments. [source] Magnetic resonance spectroscopy in anxiety disordersACTA NEUROPSYCHIATRICA, Issue 2 2008Clarissa Trzesniak Objective:, Magnetic resonance spectroscopy (MRS) is a non-invasive in vivo method used to quantify metabolites that are relevant to a wide range of brain processes. This paper briefly describes neuroimaging using MRS and provides a systematic review of its application to anxiety disorders. Method:, A literature review was performed in the PubMed, Lilacs and Scielo databases using the keywords spectroscopy and anxiety disorder. References of selected articles were also hand-searched for additional citations. Results:, Recent studies have shown that there are significant metabolic differences between patients with anxiety disorders and healthy controls in various regions of the brain. Changes were mainly found in N -acetylaspartate, which is associated with neuronal viability, but some of them were also seen in creatine, a substance that is thought to be relatively constant among individuals with different pathological conditions. Conclusions:, MRS is a sophisticated neuroimaging technique that has provided useful insights into the biochemical and neurobiological basis of many anxiety disorders. Nevertheless, its utilization in some anxiety disorders is still modest, particularly social phobia and generalised anxiety. Although it is an extremely useful advance in neuroimaging, further research in other brain areas and patient populations is highly advisable. [source] Delayed changes in T1 -weighted signal intensity in a rat model of 15-minute transient focal ischemia studied by magnetic resonance imaging/spectroscopy and synchrotron radiation X-ray fluorescenceMAGNETIC RESONANCE IN MEDICINE, Issue 3 2006Xuxia Wang Abstract Previous studies have found that rats subjected to 15-min transient middle cerebral artery occlusion (MCAO) show neurodegeneration in the dorsolateral striatum only, and the resulting striatal lesion is associated with increased T1 -weighted (T1W) signal intensity (SI) and decreased T2 -weighted (T2W) SI at 2,8 weeks after the initial ischemia. It has been shown that the delayed increase in T1W SI in the ischemic region is associated with deposition of paramagnetic manganese ions. However, it has been suggested that other mechanisms, such as tissue calcification and lipid accumulation, also contribute to the relaxation time changes. To clarify this issue, we measured changes in relaxation times, lipid accumulation, and elemental distributions in the brain of rats subjected to 15-min MCAO using MRI, in vivo 1H MR spectroscopy (MRS), and synchrotron radiation X-ray fluorescence (SRXRF). The results show that a delayed (2 weeks after ischemia) increase in T1W SI in the ischemic striatum is associated with significant increases in manganese, calcium, and iron, but without evident accumulation of MRS-visible lipids or hydroxyapatite precipitation. It was also found that 15-min MCAO results in acutely reduced N-acetylaspartate (NAA)/creatine (Cr) ratio in the ipsilateral striatum, which recovers to the control level at 2 weeks after ischemia. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source] Preparation, characterization, and properties of fluorene-containing benzoxazine and its corresponding cross-linked polymerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2010Ying-Ling Liu Abstract A benzoxazine compound (FDP-FBz), which possesses a fluorene group and two terminal furan groups, and its corresponding cross-linked polymer (CR-FDP-FBz) have been prepared using 4,4,-(9-fluorenylidene)diphenol (FDP), furfurylamine, and formaldehyde as precursors. The chemical structure of FDP-FBz has been characterized with Fourier-transform infrared and 1H nuclear magnetic resonance spectroscopies. FDP-FBz displays a melting point at about 173 °C and a processing window of 52 °C as well as good solubility in common organic solvents. As a result, FDP-FBz can be fabricated in both molten and solution processes. Under an excitation at 365 nm, FDP-FBz exhibits a photoluminescent (PL) emission at about 445 nm. The PL intensity of FDP-FBz is as high as sixfolds of the intensity recorded with FDP. CR-FDP-FBz displays a glass transition temperature of 215 °C, a high storage modulus of 3.1 GPa, a 10% weight loss at 384 °C, and a high char yield of 56 wt % (900 °C, in nitrogen). Moreover, CR-FDP-FBz has a high refractive index of about 1.65 as a result of incorporating fluorene groups to its structure. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4020,4026, 2010 [source] Hyperbranched polycarbosiloxane with dendritic boron cores: Synthesis, characterization, and structure regulationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2006Jie Kong Abstract The synthesis, characterization, and structure regulation of hyperbranched polycarbosiloxane with dendritic boron cores were realized in this paper. First, dendritic boron core was synthesized via hydroboration with borane dimethylsulfide and bis(allyloxy)dimethylsilane. Then, the hyperbranched polycarbosiloxanes with dendritic boron cores were synthesized via hydrosilylation with AB2 type monomer of bis(allyloxy)methylsilane and dendritic boron cores. The molecular structures of the dendritic boron core and resulting hyperbranched polymers were characterized by using Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance, and 13C nuclear magnetic resonance spectroscopies. Size exclusion chromatography/multiangle laser light scattering analysis reveals that the structures of hyperbranched polycarbosiloxane can be regulated effectively by incorporation of functional dendritic boron cores. Compared with hyperbranched polycarbosiloxane of the same molecular weight level, the hyperbranched polycarbosiloxane with dendritic boron cores presents narrower molecular weight distribution as well as much smaller hydrodynamic radius and intrinsic viscosity. Thermalgravimetric analyzer analysis indicates that both the decomposition temperature and ceramic yields are increased as the results of the incorporation of dendritic boron cores into hyperbranched polycarbosiloxane. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3930,3941, 2006 [source] Synthesis and vibrational analysis of N-(2,-Furyl)-ImidazoleJOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2009A. E. Ledesma Abstract The N-(2,-furyl)-imidazole (1) has been prepared and characterized using infrared, Raman and multidimensional nuclear magnetic resonance spectroscopies. Theoretical calculations have been carried out by employing the Density Functional Theory (DFT) method, in order to optimize the geometry of their two conformers in the gas phase and to support the assignments of the vibrational bands of 1 to their normal modes. For a complete assignment of the compound, DFT calculations were combined with Scaled Quamtum Mecanic Force Field (SQMFF) methodology in order to fit the theoretical wavenumber values to the experimental one. Furthermore, Natural Bond Orbital (NBO) and topological properties by Atoms In Molecules (AIM) calculations were performed to analyze the nature and magnitude of the intramolecular interactions. The result reveals that two conformers are expected in liquid phase. Copyright © 2009 John Wiley & Sons, Ltd. [source] ,-Zein secondary structure in solution by circular dichroismBIOPOLYMERS, Issue 3 2008Tatiana C. Bicudo Abstract The proline-rich N-terminal domain of ,-zein has been reported in relevant processes, which include its ability to cross the cell membranes. Evidences indicate that synthetic hexapeptide (PPPVHL), naturally found in N-terminal portion of ,-zein, can adopt the polyproline II (PPII) conformation in aqueous solution. The secondary structure of ,-zein in maize protein bodies had been analyzed by solid state Fourier transform infrared and nuclear magnetic resonance spectroscopies. However, it was not possible to measure PPII content in physiological environment since the ,-sheet and PPII signals overlap in both solid state techniques. Here, the secondary structure of ,-zein has been analyzed by circular dichroism in SDS aqueous solution with and without ditiothreitol (DTT), and in 60% of 2-propanol and water with DTT. The results show that ,-zein has high helical content in all solutions. The PPII conformation was present at about 7% only in water/DTT solution. © 2007 Wiley Periodicals, Inc. Biopolymers 89: 175,178, 2008. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley. com [source] The hydrogen atom, revisited: Parallel-field magnetic resonance,CONCEPTS IN MAGNETIC RESONANCE, Issue 5 2006John A. Weil Abstract Consideration of the magnetic resonance spectroscopy of the free hydrogen atom (1H0) reveals that, in addition to the well-known transitions (EPR and NMR) occurring between the four spin states when the excitation magnetic field B1 is perpendicular to the static external field B, there exists a combination line (simultaneous electronic and nuclear spin flips) when B1 , B, which becomes strong under some circumstances. The latter phenomenon is focused on and discussed herein, in some detail. © 2006 Wiley Periodicals, Inc. Concepts Magn Reson Part A 28A: 331,336, 2006 [source] Signal de-noising in magnetic resonance spectroscopy using wavelet transformsCONCEPTS IN MAGNETIC RESONANCE, Issue 6 2002Hector F. Cancino-De-Greiff Abstract Computer signal processing is used for quantitative data analysis (QDA) in magnetic resonance spectroscopy (MRS). The main difficulty in QDA is that MRS signals appear to be contaminated with random noise. Noise reduction can be achieved by coherent averaging, but it is not always possible to average many MRS waveforms. Wavelet shrinkage de-noising (WSD) is a technique that can be employed in this case. The potentialities of WSD in MRS, alone and combined with the Cadzow algorithm, are analyzed through computer simulations. The results can facilitate an appropriate application of WSD, as well as a deeper understanding of this technique. © 2002 Wiley Periodicals, Inc. Concepts Magn Reson 14: 388,401, 2002 [source] ,Proton magnetic resonance spectroscopy (1H-MRS) in children with spastic diplegia'DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 4 2004Wojciech Kulaka No abstract is available for this article. [source] Elevated fasting plasma C-peptide occurs in non-diabetic individuals with fatty liver, irrespective of insulin resistanceDIABETIC MEDICINE, Issue 9 2009G. Perseghin Abstract Aims Studies have pointed to insulin resistance as a pathogenic factor in fatty liver. Although pancreatic B-cell function is believed to be involved, its role is unclear. This study was undertaken to test whether fasting C-peptide, an index of fasting B-cell function, was related to intra-hepatic fat (IHF) content in non-diabetic humans. Methods We assessed, retrospectively, fasting plasma C-peptide concentration in 31 patients with fatty liver and 62 individuals without fatty liver. The IHF content was measured by proton magnetic resonance spectroscopy (1H-MRS), while insulin sensitivity was estimated based on fasting plasma glucose and insulin with the homestasis model assessment (HOMA) 2 method. Results Age, sex and body mass index (BMI) were not different between groups. Patients with fatty liver had higher fasting insulin (P < 0.01), C-peptide (P < 0.005) and lower insulin sensitivity (HOMA2-%S). Fasting insulin alone explained 14% of the IHF content variability (P < 0.001); inclusion of fasting C-peptide in multivariate regression explained up to 32% (P < 0.001). A subgroup analysis was performed by matching 1 : 1 for HOMA2-%S. These data were analysed by conditional logistic regression which showed that, when HOMA2-%S was matched between groups, fasting C-peptide remained the only significant predictor of fatty liver. Conclusions Non-diabetic individuals with fatty liver are characterized by increased fasting plasma C-peptide concentration, irrespective of their insulin resistant state. [source] Relative increase in choline in the occipital cortex in chronic fatigue syndromeACTA PSYCHIATRICA SCANDINAVICA, Issue 3 2002B. K. Puri Puri BK, Counsell SJ, Zaman R, Main J, Collins AG, Hajnal JV, Davey NJ. Relative increase in choline in the occipital cortex in chronic fatigue syndrome. Acta Psychiatr Scand 2002: 106: 224,226. © Blackwell Munksgaard 2002. Objective:,To test the hypothesis that chronic fatigue syndrome (CFS) is associated with altered cerebral metabolites in the frontal and occipital cortices. Method:,Cerebral proton magnetic resonance spectroscopy (1H MRS) was carried out in eight CFS patients and eight age- and sex-matched healthy control subjects. Spectra were obtained from 20 × 20 × 20 mm3 voxels in the dominant motor and occipital cortices using a point-resolved spectroscopy pulse sequence. Results:,The mean ratio of choline (Cho) to creatine (Cr) in the occipital cortex in CFS (0.97) was significantly higher than in the controls (0.76; P=0.008). No other metabolite ratios were significantly different between the two groups in either the frontal or occipital cortex. In addition, there was a loss of the normal spatial variation of Cho in CFS. Conclusion:,Our results suggest that there may be an abnormality of phospholipid metabolism in the brain in CFS. [source] Insights into the acute cerebral metabolic changes associated with childhood diabetesDIABETIC MEDICINE, Issue 5 2005F. J. Cameron Abstract Aims Type 1 diabetes is a prevalent chronic disease in childhood with the commonest single cause of death being cerebral oedema in the context of diabetic ketoacidosis (DKA). The nature of the alterations in cerebral metabolism that may result in vulnerability to neuronal injury remains unknown. The aim of this study was to analyse the magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) brain data from eight children with diabetes following acute presentation with hyperglycaemia with or without ketoacidosis, to determine the nature and timing of any alterations in cerebral structure and metabolism. Methods This study used MRI and MRS to investigate regional cerebral abnormalities in a small series of diabetic patients with and without DKA. Changes were compared with the clinical and biochemical features of the patients studied. Results Our small series of patients all demonstrated abnormal signal changes in the frontal region on fluid attenuated inversion recovery (FLAIR) MR imaging, suggestive of oedema, and spectroscopic abnormalities of increased taurine, myoinositol and glucose levels. The MR abnormalities varied in severity but did not correlate with any clinical or biochemical parameters. Conclusions These changes indicate that many diabetic children, particularly at presentation, may have alterations in cerebral metabolism with implications for the pathogenesis and treatment of the cerebral complications of DKA. In addition, our findings suggest that increased taurine may be one of the important differentiating factors in the response of the brain of diabetic children to DKA that may reflect an increase in their vulnerability to cerebral oedema compared with diabetic adults. [source] | |||||||||||||||||||||||||||||||||||||||||||