Three-dimensional magnetic resonance reconstruction images before and after surgical therapy of spontaneous canine brain tumors

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electrically detected and conventional magnetic resonance investigation of surface and bulk states in polyaniline thin films

Electrically detected magnetic resonance (EDMR) and electron paramagnetic resonance (EPR) were used to investigate emeraldine base polyaniline films. The magnetic susceptibility presented a Curie (localized spins)-Pauli (delocalized spins) transition at 240 K, when we also observed a transition in the dependence of the g factor with temperature (T). Peak-to-peak linewidth decreases with increasing temperature, reflecting that motional narrowing limits the hyperfine and dipolar broadening in this polymer. EDMR spectra could only be observed above 250 K in accordance to EPR results. Surface and bulk transport could be separated and their analysis reflected the effect of magnetic interaction with oxygen. (c) 2007 American Institute of Physics.

Use of on-line liquid chromatography-nuclear magnetic resonance spectroscopy for the rapid investigation of flavonoids from Sorocea bomplandii

This paper reports the identification of di- and triglycosylated flavonoids from Sorocea bomplandii (Moraceae) by liquid chromatography coupled on-line to nuclear magnetic resonance (LC-NMR). These glycosylated flavonoids may be used as a taxonomic marker in future work. (C) 2002 Elsevier B.V. B.V All rights reserved.

Structural studies of NaPO3-MoO3 glasses by solid-state nuclear magnetic resonance and raman spectroscopy

Vitreous samples were prepared in the (100 - x)% NaPO3-x% MoO3 (0 <= x <= 70) glass-forming system by a modified melt method that allowed good optical quality samples to be obtained. The structural evolution of the vitreous network was monitored as a function of composition by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), Raman scattering, and solid-state nuclear magnetic resonance (NMR) for P-31, Na-23, and Mo-95 nuclei. Addition of MoO3 to the NaPO3 glass melt leads to a pronounced increase in the glass transition temperatures up to x = 45, suggesting a significant increase in network connectivity. For this same composition range, vibrational spectra suggest that the Mo6+ ions are bonded to some nonbridging oxygen atoms (Mo-O- or Mo=O bonded species). Mo-O-Mo bond formation occurs only at MoO3 contents exceeding x = 45. P-31 magic-angle spinning (MAS) NMR spectra, supported by two-dimensional J-resolved spectroscopy, allow a clear distinction between species having two, one, and zero P-O-P linkages. These sites are denoted as Q(2Mo)((2)), Q(1Mo)((2)), and Q(0Mo)((2)), respectively. For x < 0.45, the populations of these sites can be described along the lines of a binary model, according to which each unit of MoO3 converts two Q(nMo)((2)) sites into two Q((n+1)Mo)((2)) sites (n = 0, 1). This structural model is consistent with the presence of tetrahedral Mo(=O)(2)(O-1/2)(2) environments. Indeed, Mo-95 NMR data suggest that the majority of the molybdenum species are four-coordinated. However, the presence of additional six-coordinate molybdenum in the MAS NMR spectra indicates that the structure of these glasses may be more complicated and may additionally involve sharing of network modifier oxide between the network formers phosphorus and molybdenum. This latter hypothesis is further supported by Na-23{P-31} rotational echo double resonance (REDOR) data, which clearly reveal that the magnetic dipole-dipole interactions between P-31 and Na-23 are increasingly diminished with increasing molybdenum content. The partial transfer of modifier from the phosphate to the molybdate network former implies a partial repolymerization of the phosphate species, resulting in the formation of Q(nMo)((3)) species and accounting for the observed increase in the glass transition temperature with increasing MoO3 content that is observed in the composition range 0 <= x <= 45. Glasses with MoO3 contents beyond x = 45 show decreased thermal and crystallization stability. Their structure is characterized by isolated phosphate species [most likely of the P(OMo)(4) type] and molybdenum oxide clusters with a large extent of Mo-O-Mo connectivity.

Differential scanning calorimetry, x-ray diffraction and F-19 nuclear magnetic resonance investigations of the crystallization of InF3-based glasses

Results of differential scanning calometry (DSC), x-ray diffraction (XRD), and F-19 nuclear magnetic resonance (NMR) of InF3-based glasses, treated at different temperatures, ranging from glass transition temperature (T-g) to crystallization temperature (T-c), are reported. The main features of the experimental results are as follows. DSC analysis emphasizes several steps in the crystallization process. Heat treatment at temperatures above T-g enhances the nucleation of the first growing phases but has little influence on the following ones. XRD results show that several crystalline phases are formed, with solid state transitions when heated above 680 K, the F-19 NMR results show that the spin-lattice relaxation, for the glass samples heat treated above 638 K, is described by two time constants. For samples treated below this temperature a single time constant T-1 was observed. Measurements of the F-19 spin-lattice relaxation time (T-1), as a function of temperature,made possible the identification of the mobile fluoride ions. The activation energy, for the ionic motion, in samples treated at crystallization temperature was found to be 0.18 +/- 0.01 eV. (C) 1998 American Institute of Physics.

Small-angle X-ray and nuclear-magnetic resonance study of siloxane-PMMA hybrids prepared by the sol-gel process

Transparent siloxane-polymethylmethacrylate (PMMA) hybrids were synthesized by the sol-gel process through hydrolysis of methacryloxyproyltrimethoxysilane (TMSM), tetramethoxysilane (TMOS) and polymerization of methylmethacrylate (MMA) using benzol peroxide (BPO) as catalyst. These composites have a good chemical stability due to the presence of covalent bonds between the inorganic (siloxane) and organic (PMMA) phases. The effects of siloxane content, pH of the initial sol and BPO content on the structure of the dried gels were analyzed by small-angle X-ray scattering (SAXS). SAXS results revealed the presence of an interference (or correlation) peak at medium q-range for all compositions, suggesting that siloxane groups located at the ends of PMMA chains form isolated clusters that are spatially correlated. The average intercluster distance - estimated from the q-value corresponding to the maximum in SAXS spectra - decreases for samples prepared with increasing amount of TMSM-TMOS. This effect was assigned to the expected increase in the number density of siloxane groups for progressively higher siloxane content. The increase of BPO content promotes a more efficient polymerization of MMA monomers but has no noticeable effect on the average intercluster distance. High pH favors polycondensation reactions between silicon species of both TMOS and TMSM silicon alcoxides, leading to a structure in which all siloxane clusters are bonded to PMMA chains. This effect was confirmed by Si-29 nuclear-magnetic resonance (NMR) measurements.

Exciton formation in dye doped OLEDs using electrically detected magnetic resonance

Electrically Detected Magnetic Resonance (EDMR) was used to investigate the influence of dye doping molecules on spin-dependent exciton formation in Aluminum (III) 8-hydroxyquinoline (Alq(3)) based OLEDs with different device structures and temperature ranges. 4-(dicyanomethylene)-2-methyl-6-{2-[(4-diphenylamino-phenyl]ethyl}-4H-pyran (DCM-TPA) and 5,6,11,12-tetraphenylnaphthacene (Rubrene) were used as dopants. A strong temperature dependence have been observed for doped OLEDs, with a decrease of two orders of magnitude in EDMR signal for temperatures above similar to 200 K. The signal temperature dependence were fitted supposing different spin-lattice relaxation processes. The results suggest that thermally activated vibrations of dopants molecules induce spin pair dissociation, reducing the signal.

Magnetic resonance study of the crystallization behavior of InF3-based glasses doped with Cu2+, Mn2+ and Gd3+

The crystallization of fluoroindate glasses doped with Gd3+, Mn2+ and Cu2+ heat treated at different temperatures, ranging from the glass transition temperature (Tg) to the crystallization temperature (Tc), are investigated by electron paramagnetic resonance (EPR) and 19F nuclear magnetic resonance (NMR). The EPR spectra indicate that the Cu2+ ions in the glass are located in axially distorted octahedral sites. In the crystallized glass, the g-values agreed with those reported for Ba2ZnF6, which correspond to Cu2+ in a tetragonal compressed F- octahedron and to Cu2+ on interstitial sites with a square-planar F- co-ordination. The EPR spectra of the Mn2+ doped glasses exhibit a sextet structure due to the Mn2+ hyperfine interaction. These spectra suggest a highly ordered environment for the Mn2+ ions (close to octahedral symmetry) in the glass. The EPR spectra of the recrystallized sample exhibit resonances at the same position, suggesting that the Mn2+ ions are located in sites of highly symmetric crystalline field. The increase of the line intensity of the sextet and the decrease of the background line in the thermal treated samples suggest that the Mn2+ ions move to the highly ordered sites which contribute to the sextet structure. The EPR spectra of the Gd3+ doped glasses exhibit the typical U-spectrum of a s-state ion in a low symmetry site in disordered systems. The EPR of the crystallized glasses, in contrast, have shown a strong resonance in g ≈ 2.0, suggesting Gd3+ ions in environment close to cubic symmetry. The 19F NMR spin-lattice relaxation rates were also strongly influenced by the crystallization process that takes over in samples annealed above Tc. For the glass samples (doped or undoped) the 19F magnetization recoveries were found to be adjusted by an exponential function and the spin-lattice relaxation was characterized by a single relaxation time. In contrast, for the samples treated above Tc, the 19F magnetization-recovery becomes non-exponential. A remarkable feature of our results is that the changes in the Cu2+, Mn2+, Gd3+ EPR spectra and NMR relaxation, are always observed for the samples annealed above Tc. © 2006 Elsevier B.V. All rights reserved.

Electrically detected magnetic resonance modeling and fitting: An equivalent circuit approach

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Retrospective study of 32 encephalic tumors diagnosed by advanced - image magnetic resonance imaging and computed tomography

The incidence of encephalic tumors in dogs and cats has increased in recent years due to the constant advancement of methods of specialist Diagnostic Imaging: Magnetic Resonance Imaging (MRI) and Computed Tomography (CT), used in small animals. These tools, which were distant in the past, are now becoming increasingly important as an additional aid to the identification of tumor processes in the Central Nervous System. The objective, of the present study, was describe imaging findings obtained in 32 cases of encephalic tumors, through techniques of CT and MR imaging procedures during the years 2004 to 2011. Were diagnosed 19/32 by MRI and 13/32 by CT, being the most affected breed Boxer (9/32), the mean age was 10 years.

Usefulness of computed tomography and magnetic resonance imaging in radiotherapy planning for the treatment of brain tumors

Advanced diagnostic techniques such as magnetic resonance imaging and computed tomography have become useful tools for confirmation of presumptive diagnosis of structural lesions in the brain such as encephalic neoplasms in small animal veterinary practice in Colombia, allowing an effective treatment planning that is more specific and less invasive for this type of pathology.

Contribution of magnetic resonance in acute spinal cord trauma - case report

Acute spinal cord trauma is a common injury that occurs frequently in small animals. In order to acertain a prognosis of the lesion generated in the spinal cord, it is necessary to perform a complete neurological and physical examination, aided by complementary images. Magnetic resonance imaging may be advantageous over other types of images, because it can determine with greater definition the structural damage to the nervous tissue. The objective of this report was to demonstrate the contribution of magnetic resonance imaging in a case of acute spinal cord trauma in a dog.

Fast determination of beef quality parameters with time-domain nuclear magnetic resonance spectroscopy and chemometrics

The noteworthy of this study is to predict seven quality parameters for beef samples using time-domain nuclear magnetic resonance (TD-NMR) relaxometry data and multivariate models. Samples from 61 Bonsmara heifers were separated into five groups based on genetic (breeding composition) and feed system (grain and grass feed). Seven sample parameters were analyzed by reference methods; among them, three sensorial parameters, flavor, juiciness and tenderness and four physicochemical parameters, cooking loss, fat and moisture content and instrumental tenderness using Warner Bratzler shear force (WBSF). The raw beef samples of the same animals were analyzed by TD-NMR relaxometry using Carr-Purcell-Meiboom-Gill (CPMG) and Continuous Wave-Free Precession (CWFP) sequences. Regression models computed by partial least squares (PLS) chemometric technique using CPMG and CWFP data and the results of the classical analysis were constructed. The results allowed for the prediction of aforementioned seven properties. The predictive ability of the method was evaluated using the root mean square error (RMSE) for the calibration (RMSEC) and validation (RMSEP) data sets. The reference and predicted values showed no significant differences at a 95% confidence level.

Classification of intact fresh plums according to sweetness using time-domain nuclear magnetic resonance and chemometrics

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)