Surface oxidation study of single wall carbon nanotubes.

Functionalization of single wall carbon nanotubes (SWCNTs) is desirable to enhance their ability to be incorporated into polymers and enhance their bonding with the matrix. One approach to carbon nanotube functionalization is by oxidation via a strong oxidizing agent or refluxing in strong acids. However, this approach can damage the nanotubes, leading to the introduction of defects and/or shorter nanotubes. Such damage can adversely affect the mechanical, thermal, and electrical properties. A more benign approach to nanotube functionalization has been developed involving photo-oxidation. Chemical analysis by XPS revealed that the oxygen content of the photo-oxidized SWCNTs was 11.3 at.% compared to 6.7 at.% for SWCNTs oxidized by acid treatment. The photo-oxidized SWCNTs produced by this method can be used directly in various polymer matrices or can be further modified by additional chemical reactions.

Thoracic duct lymph. Relative contribution from splanchnic and muscle tissue.

We have shown previously that thoracic duct lymph insulin dynamics are well correlated with tracer-determined whole-body glucose uptake and have suggested that thoracic duct lymph insulin is representative of insulin concentration in muscle interstitial fluid. However, thoracic duct lymph is comprised of interstitial fluid from all sub-thoracic tissue beds. To investigate the relative contribution of muscle interstitial fluid to total thoracic duct lymph flow, the distribution and elimination of [14C]inulin was investigated in eight experiments with conscious dogs. Both plasma and thoracic duct lymph were measured, and a three-compartment model that was hypothesized to consist of plasma, splanchnic interstitial fluid, and muscle interstitial fluid was identified. Identifications were performed with either a bolus protocol (n = 4) or an infusion protocol (n = 4), and the predicted [14C]inulin dynamics in the splanchnic and muscle interstitial fluid compartments were compared with measured values in thoracic duct lymph. Neither compartment predicted the thoracic duct [14C]inulin dynamics; however, a model based on a percentage contribution from each tissue bed fit the thoracic data well. The relative contribution of splanchnic interstitial fluid to the total thoracic duct lymph flow averaged 78 +/- 5% for the bolus protocol and 54 +/- 5% for the infusion protocol. Thus, we conclude that in the conscious animal, approximately 25-50% of thoracic duct lymph originates from muscle interstitial fluid.

Field Emission and Radial Distribution Function Studies of Fractal-like Amorphous Carbon Nanotips.

The short-range order of individual fractal-like amorphous carbon nanotips was investigated by means of energy-filtered electron diffraction in a transmission electron microscope (TEM). The nanostructures were grown in porous silicon substrates in situ within the TEM by the electron beam-induced deposition method. The structure factor S(k) and the reduced radial distribution function G(r) were calculated. From these calculations a bond angle of 124 degrees was obtained which suggests a distorted graphitic structure. Field emission was obtained from individual nanostructures using two micromanipulators with sub-nanometer positioning resolution. A theoretical three-stage model that accounts for the geometry of the nanostructures provides a value for the field enhancement factor close to the one obtained experimentally from the Fowler-Nordheim law.

Effect of tree and grass pollens and fungal spores on spring allergic rhinitis: a comparative study.

BACKGROUND: Current literature indicates tree pollen is less important than grass pollen as the cause of spring allergic rhinitis. The role of fungal spores is secondary and uncertain. OBJECTIVE: To assess the relative allergenicity of tree and grass pollen and fungal spores as the cause of spring allergic rhinitis in central Indiana. METHODS: (1) Chart review of 189 Indiana natives with seasonal allergic rhinitis to ascertain clinical sensitivity to tree or grass pollens. (2) A prospective study conducted in the spring of 1997 in 51 patients, correlating patients' symptom and medication scores with daily pollen and spore counts, obtained with a Burkard spore trap. RESULTS: One hundred thirty of 189 patients (69%) reported symptoms before May with positive prick test to at least one tree pollen. One hundred thirty-four patients (71%) had symptoms in May and June with positive test to grass pollen. The ratio between the two groups is 1:1, in contrast to a ratio of 1:4 derived from the literature. The prospective study revealed a symptom score increase parallel to the rise of tree pollen counts beginning in mid-March and reaching a plateau in early May prior to the onset of grass season. Medication use continued to increase and peaked at the height of grass pollination. Spore counts increased in late May and stayed at high levels throughout June, yet symptom and medication scores steadily declined following the peak of grass pollination in early June. CONCLUSIONS: This study suggests that in central Indiana, tree pollen is more important as the cause of spring allergic rhinitis than that suggested by the literature. This study confirmed previous observations that fungal spores are substantially less allergenic than pollens.