The effect of carbon nanofillers on the performance of electromechanical polyaniline-based composite actuators.

Different types of crystalline carbon nanomaterials were used to reinforce polyaniline for use in electromechanical bilayer bending actuators. The objective is to analyze how the different graphitic structures of the nanocarbons affect and improve the in situ polymerized polyaniline composites and their subsequent actuator behavior. The nanocarbons investigated were multiwalled carbon nanotubes, nitrogen-doped carbon nanotubes, helical-ribbon carbon nanofibers and graphene oxide, each one presenting different shape and structural characteristics. Films of nanocarbon-PAni composite were tested in a liquid electrolyte cell system. Experimental design was used to select the type of nanocarbon filler and composite loadings, and yielded a good balance of electromechanical properties. Raman spectroscopy suggests good interaction between PAni and the nanocarbon fillers. Electron microscopy showed that graphene oxide dispersed the best, followed by multiwall carbon nanotubes, while nitrogen-doped nanotube composites showed dispersion problems and thus poor performance. Multiwall carbon nanotube composite actuators showed the best performance based on the combination of bending angle, bending velocity and maximum working cycles, while graphene oxide attained similarly good performance due to its best dispersion. This parallel testing of a broad set of nanocarbon fillers on PAni-composite actuators is unprecedented to the best of our knowledge and shows that the type and properties of the carbon nanomaterial are critical to the performance of electromechanical devices with other conditions remaining equal.

Successes and challenges of latent TB screening and treatment in a high-prevalence US region.

BACKGROUND: South Texas has higher TB disease incidence than much of the United States. We evaluated a multi-site South Texas interferon-gamma release assay (IGRA)-based testing and latent TB infection (LTBI) treatment program targeting high-risk populations.METHODS: Number of IGRA tests, test results, LTBI confirmation, and treatment outcomes were collected over 2.5 years. Sixteen semi-structured patient interviews and 10 site-based focus groups were conducted with providers, nurses, and administrators. Grounded theory identified themes associated with successful outcomes.RESULTS: Of 9,050 IGRA tests, 687 (8%) were positive; 340 (49%) confirmed as LTBI; 191 initiated LTBI treatment; and 130 (68% of initiators) completed treatment. Patient barriers to treatment completion included lack of knowledge, misconceptions, and treatment toxicities. Clinic staff concurred that toxicity was a barrier to treatment and requiring new processes with limited resources were implementation barriers.CONCLUSIONS: Over 9,000 patients were screened with a high prevalence of IGRA positivity, but confirming LTBI, initiating, and completing treatment were challenging. Qualitative evaluation supports low literacy patient education on LTBI and toxicities and expanded support for process implementation and provider training. These findings highlight challenges at all levels of the LTBI care cascade and provide patient, staff, and provider perspectives on implementation of these programs.

Production and characterization of coaxial nanotube junctions and networks of CNx/CNT.

Novel coaxial structures consisting of nitrogen-doped carbon nanotube (MWNTs-CNx) cores with external concentric shells of pure carbon were produced by the pyrolysis of toluene over Fe-coated MWNTs-CNx. These materials were thoroughly characterized by SEM, HRTEM, X-ray diffraction, and TGA; a possible growth scenario for their formation is also proposed. In addition, these coaxial structures were able to form 2D and 3D covalent networks that mainly exhibited T-, Y-, and on-type morphologies. The two-step technique presented here could be further developed to fully control the growth of these new coaxial structures, study of individual junctions, and it could be used to create periodic nanotube networks, in which the heterocable structure could find applications in nanoelectronics.

Effect of film thickness on the performance of photopolymers as holographic recording materials.

An important issue in developing applications for photopolymers in holography is the effect of film thickness on recording properties. Now it is possible to create these samples with a much wider range of thickness (d = 20-1400 mum) than was previously available. We exploit these recent advances in photopolymer processing to systematically evaluate how the dynamic range of a photopolymer depends on its thickness. The results illustrate that sample performance increases linearly with thickness as predicted by standard models of volume holography. However, above a critical thickness sample performance degrades, and the angular response of recorded plane-wave holograms shows evidence of grating curvature. These distortions are likely the result of photopolymer shrinkage, which in thicker samples occurs in a nonuniform fashion. This problem limits the performance of these photopolymers and is likely to be an issue for any photopolymer that undergoes comparable polymerization shrinkage.