PubMed Health⌕ Search

Biomedical subjects

B M Nichols

Publications and source records attributed to B M Nichols.

10 recordsLinked to original sources
PubMed2006

Effect of ozone oxidation on single-walled carbon nanotubes.

Exposing single-walled carbon nanotubes to room-temperature UV-generated ozone leads to an irreversible increase in their electrical resistance. We demonstrate that the increased resistance is due to ozone oxidation on the sidewalls of the nanotubes rather than at the end caps. Raman and X-ray photoelectron spectroscopies show an increase in the defect density due to the oxidation of the nanotubes. Using ultraviolet photoelectron spectroscopy, we show that these defects represent the removal of pi-conjugated electron states near the Fermi level, leading to the observed increase in electrical resistance. Oxidation of carbon nanotubes is an important first step in many chemical functionalization processes. Because the oxidation rate can be controlled with short exposures, UV-generated ozone offers the potential for use as a low-thermal-budget processing tool.

Carbon↗
PubMed1971

Sickling reversed and blocked by urea in invert sugar.

Optical and electron microscopic evidence is presented to support the finding that sickling of hemoglobin S can be reversed and blocked by urea in invert sugar (UIS). Erythrocytes from subjects having hemoglobin SS, AS or AA were treated with the UIS either before or after deoxygenation with Na(2)S(2)O(5). Light microscopic studies indicated that approximately one-fifth as much urea is required to block sickling as is necessary to reverse sickled poikilocytes to normal forms. Intracellular microfilaments apparent in transmission electron micrographs of sickled erythrocytes were eliminated by treating aliquots of the same deoxygenated erythrocytes with UIS. Scanning electron micrographs showed a reversion of sickled poikilocytes to a normal erythrocyte population of biconcave discs. The use of UIS was deduced from Murayama's hypothesis that the molecular mechanism of sickling clearly involves hydrophobic bonds formed between the number-6 valine substitution of the beta-chain S globins and the alpha-chain globins of interacting hemoglobin molecules. The use of UIS to arrest the formation of such hydrophobic bonds is advocated as an evident and effective therapeutic strategy to treat sickle cell crisis.

Anemia, Sickle Cell↗