Biomedical subjects
Jeffrey Peterson
Publications and source records attributed to Jeffrey Peterson.
Single carbon nanotube optical spectroscopy.
This Minireview discusses novel insights into the electronic structure of carbon nanotubes obtained using single-molecule fluorescence spectroscopy. Fluorescence spectra from single nanotubes are well described by a single, Lorentzian lineshape. Nanotubes with identical structures fluoresce with different energies due to local electronic perturbations. Carbon nanotube fluorescence unexpectedly does not-show any intensity or spectral fluctuations at 300 K The lack of intensity blinking or bleaching demonstrates that carbon nanotubes have the potential to provide a stable, single-molecule infrared photon source, allowing for the exciting possibility of applications in quantum optics and biophotonics.
Anterior cingulate, gyrus rectus, and orbitofrontal abnormalities in elderly depressed patients: an MRI-based parcellation of the prefrontal cortex.
OBJECTIVE: To examine structural abnormalities in subregions of the prefrontal cortex in elderly patients with depression, the authors explored differences in gray matter, white matter, and CSF volumes by applying a parcellation method based on magnetic resonance imaging (MRI). METHOD: Twenty-four elderly patients with major depression and 19 group-matched comparison subjects were studied with high-resolution MRI. Cortical surface extraction, tissue segmentation, and cortical parcellation methods were applied to obtain volume measures of gray matter, white matter, and CSF in seven prefrontal subregions: the anterior cingulate, gyrus rectus, orbitofrontal cortex, precentral gyrus, superior frontal cortex, middle frontal cortex, and inferior frontal cortex. RESULTS: Highly significant bilateral volume reductions in gray matter were observed in the anterior cingulate, the gyrus rectus, and the orbitofrontal cortex. Depressed patients also exhibited significant bilateral white matter volume reductions and significant CSF volume increases in the anterior cingulate and the gyrus rectus. Finally, the depressed group showed significant CSF volume reductions in the orbitofrontal cortex relative to the comparison subjects. None of the other regions examined revealed significant structural abnormalities. CONCLUSIONS: The prominent bilateral gray matter deficits in the anterior cingulate and the gyrus rectus as well as the orbitofrontal cortex may reflect disease-specific modifications of elderly depression. The differential pattern of abnormalities detected in the white matter and CSF compartments imply that distinct etiopathological mechanisms might underlie the structural cortical changes in these regions.
Post-tonsillectomy hemorrhage and pediatric emergency care.
A cross-sectional, retrospective review of consecutive patients who presented to 1 of 2 pediatric emergency departments with post-tonsillectomy hemorrhage was undertaken. The study population included children who had secondary hemorrhage (bleeding at greater than 24 hours after tonsillectomy). Over a period of 2 years, 90 children received emergency care for secondary post-tonsillectomy hemorrhage. The average age was 8.5 years and there were 40 (44%) males. The average time from tonsillectomy to emergency department (ED) presentation was 7.3 days. One patient was hypotensive, and 7 had hemoglobins <10 mg/dL. Signs of bleeding on examination of the tonsillar fossa were active (4), oozing (18), clots (48), and none (14). Of the 70 children with signs of bleeding, 63 (90%) were treated surgically and 7 (10%) were observed. Four (6%) of the 63 children who had signs of bleeding and were managed surgically and 3 (43%) of the 7 children who had signs of bleeding and were managed by observation had repeat episodes of bleeding. Of the 14 patients with no signs of bleeding, all were observed and none had repeat episodes of bleeding. Signs of bleeding were not documented in 6 patients. Active hemorrhage and cardiovascular compromise were uncommon in this study population. Surgical management is recommended for children who have signs of bleeding, while observation appears to be appropriate for children who have no signs of bleeding.