High-resolution, multiple gradient-echo functional MRI at 1.5 T

A multiple gradient echo, high resolution imaging method is proposed to better visualize different sources of activation in functional magnetic resonance imaging (fMRI) experiments. Eight echoes are collected from 30 ms to 205 ms with an echo spacing of 25 ms. All echoes show significant activation, but each echo reveals its own pattern of activation. From this variability, it appears that large vessel contributions can be separated from small vessel contributions using a fuzzy cluster analysis across echo times. The results demonstrate the importance of a multiple gradient echo data acquisition approach in localizing various vascular contributions to brain activation in fMRI.     

Fabrication of Nanostructured Self‐Detoxifying Nanofiber Membranes that Contain Active Polymeric Functional Groups

Military soldiers, medicinal doctors, and ordinary people require protection against chemical and biological warfare (C&B) agents. Activated charcoal impregnated with metal ions is currently used in protective clothing applications, which has some disadvantages. Electrospinning is emerging as one of the cheapest technologies to produce continuous nanofibers with a high surface area‐to‐volume ratio. In the present study, electrospinning of a poly(ethylene imine) (PEI)/nylon blend has been carried out in which PEI acts as a support material as well as a catalytic media. The membrane is combined with non‐selective metal oxide nanoparticles to degrade C&B agents into non‐toxic products. In addition, these membranes possess hydrophilic properties, hence they are suitable candidates for protective clothing applications.

     

Hydroxyl space-time correlation measurements in partially premixed turbulent opposed-jet flames

A high repetition-rate, two-point, time-resolved, laser-induced fluorescence technique is used to perform simultaneous two-point OH time-series measurements in a series of turbulent opposed-jet partially premixed flames with varying fuel-side equivalence ratio and bulk Reynolds number. Time scales of OH in these flames have previously been reported; however, the extension to two-point detection permits measurements of new spatial and temporal statistics previously unavailable in such flames. In particular, the simultaneous OH time series are used here to compute spatial and temporal autocorrelation functions. Filtered OH length scales (l_r,OH), corresponding to radial OH fluctuations in turbulent stagnation flames, are obtained from the spatial autocorrelation function, including their variation across the stagnation plane. In general, maximum OH fluctuations occur at the stagnation plane, thus minimizing the OH integral length scale at the axial location of peak OH. For all flames of this study, trends in OH length scale follow those of axial time scale (τ_I,OH). For flames with constant Re, l_r,OH decreases with less partial premixing. However, this change in integral length scale appears to be more significant for flames at lower Re in comparison to those at higher Re. Similar to OH integral time scales, for flames with the same fuel composition, l_r,OH decreases with increasing Re. Moreover, fuel-lean mixtures appear to be more sensitive to Re variations as compared to fuel-rich mixtures. PACS 47.70.Pq; 32.50.+d; 47.27.wg     

Optical pulse tailoring and termination by self-sweeping of a fabry-perot cavity

Utilizing optically induced refractive index changes, optical pulses have been shown to self sweep Fabry-Perot cavity resonances resulting in shorter pulses or abrupt self-termination. Using a glass filter of a GaAs interferometer, 150 μs and 150 ns pulses have been shortened to 10 μs and 20 ns respectively.