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Biomedical subjects

V C Moore

Publications and source records attributed to V C Moore.

17 recordsLinked to original sources
PubMed2006

FEV1 decline in occupational asthma.

BACKGROUND: In occupational asthma continued workplace exposure to the causative agent is associated with a poor prognosis. However, there is little information available on how rapidly lung function declines in those who continue to be exposed, nor how removal from exposure affects lung function. METHODS: Forced expiratory volume in 1 second (FEV1) was studied in 156 consecutive subjects with occupational asthma (87% due to low molecular weight agents) using simple regression analyses to provide estimates of the decline in FEV1 before and after removal from exposure. RESULTS: In 90 subjects in whom FEV1 measurements had been performed for at least 1 year before removal from exposure (median 2.9 years), the mean (SE) rate of decline in FEV1 was 100.9 (17.7) ml/year. One year after removal from exposure FEV1 had improved by a mean (SE) of 12.3 (31.6) ml. The mean (SE) decline in FEV1 was 26.6 (18.0) ml/year in 86 subjects in whom measurements were made for at least 1 year (median 2.6 years) following removal from exposure. The decline in FEV1 was not significantly worse in current smokers than in never smokers, nor was it affected by the use of inhaled corticosteroids. CONCLUSION: FEV1 declines rapidly in exposed workers with occupational asthma. Following removal from exposure, FEV1 continued to decline but at a slower rate, similar to the rate of decline in healthy adults.

Adult↗
PubMed2006

Excitons in carbon nanotubes with broken time-reversal symmetry.

Near-infrared magneto-optical spectroscopy of single-walled carbon nanotubes reveals two absorption peaks with an equal strength at high magnetic fields (>55 T). We show that the peak separation is determined by the Aharonov-Bohm phase due to the tube-threading magnetic flux, which breaks the time-reversal symmetry and lifts the valley degeneracy. This field-induced symmetry breaking thus overcomes the Coulomb-induced intervalley mixing which is predicted to make the lowest exciton state optically inactive (or dark).

Journal Article↗
PubMed2005

Stability of high-density one-dimensional excitons in carbon nanotubes under high laser excitation.

Through ultrafast pump-probe spectroscopy with intense pump pulses and a wide continuum probe, we show that interband exciton peaks in single-walled carbon nanotubes (SWNTs) are extremely stable under high laser excitations. Estimates of the initial densities of excitons from the excitation conditions, combined with recent theoretical calculations of exciton Bohr radii for SWNTs, suggest that their positions do not change at all even near the Mott density. In addition, we found that the presence of lowest-subband excitons broadens all absorption peaks, including those in the second-subband range, which provides a consistent explanation for the complex spectral dependence of pump-probe signals reported for SWNTs.

Journal Article↗
PubMed2004

Interband recombination dynamics in resonantly excited single-walled carbon nanotubes.

Wavelength-dependent pump-probe spectroscopy of micelle-suspended single-walled carbon nanotubes reveals two-component dynamics. The slow component (5-20 ps), which has not been observed previously, is resonantly enhanced whenever the pump photon energy coincides with an absorption peak and we attribute it to interband carrier recombination, whereas we interpret the always-present fast component (0.3-1.2 ps) as intraband carrier relaxation in nonresonantly excited nanotubes. The slow component decreases drastically with decreasing pH (or increasing H+ doping), especially in large-diameter tubes. This can be explained as a consequence of the disappearance of absorption peaks at high doping due to the entrance of the Fermi energy into the valence band, i.e., a 1D manifestation of the Burstein-Moss effect.

Journal Article↗
PubMed1977

Physical aspects of electron-beam arc therapy.

The effect of different parameters on dose distribution in electron-beam arc therapy was studied in order to develop a technique for routine clinical use. A special diaphragm was designed to facilitate telecentric rotation. Dosimetry was performed with an ion chamber, film, and LiF powder in cylindrical polystyrene phantoms and an Alderson Rando phantom. Dose distributions were evaluated with regard to dose homogeneity, and a method of sharpening the dose fall-off near the ends of the arc was proposed. Criteria for selection of isocenter depth and field size were developed. Methods of dose calculation, calibration, and treatment planning are discussed.

Electrons↗
PubMed1976

Field shaping in electron beam therapy.

In the treatment of superficial lesions with 8-13 MeV electrons, lead shields are often used to protect the underlying tissue. Measurements were made with film and ion chamber to analyse various aspects of external and internal shielding in electron beam therapy. Data were obtained on the thickness of lead required for shielding, the effect of blocking on dose-rate, electron-backscattering from lead and X-ray contamination. Practical applications of a lead clay for shielding are discussed.

Electrons↗