Biomedical subjects

William S Brocklesby

Publications and source records attributed to William S Brocklesby.

4 recordsLinked to original sources

PubMed2006

Observation of the developing optical continuum along a nonlinear waveguide.

We describe what is to our knowledge the first nondestructive measurement of the evolution of an optical continuum as a function of distance along a nonlinear waveguide. Spectral mapping is achieved on a subwavelength scale by utilizing near-field microscopy to probe the waveguide's evanescent field. The measured continuum broadening along the waveguide agrees in general form with predictions of broadening from theoretical calculations, but differs in some important details. Subwavelength resolution measurements are made both along and across the waveguide to reveal spectral variations not seen before by other techniques.

Journal Article↗

PubMed2006

Soft-x-ray wavelength shift induced by ionization effects in a capillary.

Coherent soft x rays are produced by high-harmonic generation in a capillary filled with Ar gas. We demonstrate that the tuning of the harmonic wavelengths with intensity and chirp arises from changes in the Ar ionization level. Control over the tuning can be achieved either by changing the average intensity of the laser pulse or by varying the quadratic spectral phase of the laser pulse. We observe an ionization-dependent blueshift of the fundamental wavelength that is directly imprinted on the harmonic wavelengths. The harmonic tuning is shown to depend on nonlinear spectral shifts of the fundamental laser pulse that are due to the plasma created by ionization, rather than directly on any chirp imposed on the fundamental wavelength.

Journal Article↗

PubMed2005

Resin bead micro-UV-visible absorption spectroscopy.

The construction and design of a microscope coupled with a miniature UV-vis spectrometer is described. This was applied to the study of dyes linked to solid supports and displayed good correlation in spectral shape and lambda(max) values when compared to the dyes in solution, as well as showing a linear relationship between dye loading and UV-vis absorbance. The spectral profiles of these dyes at various pH's were measured and used to determine the pK(a) of the dyes on the beads, which were compared with the pK(a) values of the dyes in solution, thus enabling the dye-loaded beads to act as pH sensors.

Journal Article↗

PubMedDate not supplied

Which sites react first? Functional site distribution and kinetics on solid supports investigated using confocal Raman and fluorescence microscopy.

Fluorescence microscopy is a powerful technique for analyzing beads with very low loadings of fluorophores; however, the method is flawed when looking at more highly loaded beads as a result of severe problems with absorption. To probe distributions at higher loading levels, Raman spectroscopy avoids many of these issues. These studies show that there is a uniform distribution of reactive sites throughout the beads but that the spatial distribution of reacted sites depends on the polymer type, with a fine balance between reaction and diffusion rate.

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