Combination of BOLD-fMRI and VEP recordings for spin-echo MRI detection of primary magnetic effects caused by neuronal currents

In the present paper, for the first time, the feasibility to detect primary magnetic field changes caused by neuronal activity in vivo by spin-echo (SE) magnetic resonance imaging (MRI) is investigated. The detection of effects more directly linked to brain activity than secondary hemodynamic–metabolic changes would enable the study of brain function with improved specificity. However, the detection of neuronal currents by MRI is hampered by such accompanying hemodynamic changes. Therefore, SE image acquisition, rather than gradient-echo (GE) image acquisition, was preferred in the present work since the detection of primary neuronal and not blood oxygenation level-dependent (BOLD)-related effects may be facilitated by this approach. First of all, a precise spatiotemporal synchronization of image acquisition with the neuronal event had to be performed to avoid refocusing of the dephasing phenomenon during the course of the SE sequence. At this aim, we propose the combined use of visual evoked potential (VEP) recordings and BOLD-fMRI measurements prior to SE MRI scanning. Moreover, we exemplify by theory and experimentation how the control of artefactual signal changes due to BOLD and movement effects may be further improved by the experimental design. Finally, results from a pilot study using the proposed combination of VEP recordings and MRI techniques are reported, suggesting the feasibility of this method.     

Application of High Temperature High Resolution Gas Chromatography to Crude Extracts of Propolis

The underivatized acetone and hexane fractions from propolis samples (predominant flora Citrus spp. and Vernonia polyanthes) were analyzed by HT-HRGC (high temperature high resolution gas chromatography) and HT-HRGC coupled to mass spectrometry (HT-HRGC-MS). Several compounds, including flavonoid aglycones, phenolic acids, and high molecular weight compounds were characterized in crude extracts by HT-HRGC-MS. HT-HRGC and HT-HRGC-MS were shown to be quick and informative tools for rapid analysis of crude extracts without need for prior derivatization and purification.     

Fractionated crystallization in blends of functionalized poly(tetrafluoroethylene) and polyamide

Blends of poly(tetrafluoroethylene)/polyamide (PTFE/PA) were prepared to combine the good processing properties of PA with the excellent sliding properties of PTFE. For the compatibilizing of the immiscible components the chemical reaction of functional groups of modified PTFE (micro powder produced by electron irradiation in air) and polar PA during a reactive extrusion process was used. The parameter influencing the efficiency of the in‐situ reaction between both components were varied. The crystallization and melting behaviour of the different blends was investigated by DSC. In dependence on the degree of compatibilization the phenomenon of fractionated crystallization of the dispersed PTFE component was observed. In this way a qualitative characterization of the dispersity of PTFE in dependence on the functionality of the components and the processing conditions is possible, and therefore an estimation of the efficiency of the in‐situ reaction.