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- Aguilar, A., et al.
(författare)
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Double photodetachment from the Cl[-]ion
- 2004
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 69:2
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Tidskriftsartikel (refereegranskat)abstract
- The correlated process involving the photodetachment of two electrons from the [Formula Presented] ion has been investigated over the photon energy range 20–45 eV. In the experiment, a beam of photons from the Advanced Light Source (ALS) was collinearly merged with a counterpropagating beam of [Formula Presented] ions from a sputter ion source. The [Formula Presented] ions produced in the interaction region were detected, and the normalized signal was used to monitor the relative cross section for the reaction. An absolute scale for the cross section was established by measuring the spatial overlap of the two beams and by determining the efficiency for collection and detection of the [Formula Presented] ions. The overall magnitude and shape of the measured cross section for this process agrees well with an R-matrix calculation. The calculation identifies the dominant mechanism leading to the production of the [Formula Presented] ion as being a direct nonresonant process involving the ejection of a pair of electrons from the valence shell. Less important is the indirect nonresonant process that involves the production and decay of core-excited and doubly excited states of the Cl atom in an intermediate step. Direct and indirect resonant mechanisms involving the excitation of a single [Formula Presented] core electron or more than one valence electron of the [Formula Presented] ion were found to be insignificant in the energy range studied.
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- deWeert, Michael J., et al.
(författare)
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Analysis of spatial variability in hyperspectral imagery of the uterine cervix in vivo
- 2003
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Ingår i: Proceedings of SPIE. - : SPIE. ; 4959, s. 67-76
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Tidskriftsartikel (refereegranskat)abstract
- The use of fluorescence and reflectance spectroscopy in the analysis of cervical histopathology is a growing field of research. The majority of this research is performed with point-like probes. Typically, clinicians select probe sites visually, collecting a handful of spectral samples. An exception to this methodology is the Hyperspectral Diagnostic Imaging (HSDI®) instrument developed by Science and Technology International. This non-invasive device collects contiguous hyperspectral images across the entire cervical portio. The high spatial and spectral resolution of the HSDI instruments make them uniquely well suited for addressing the issues of coupled spatial and spectral variability of tissues in vivo. Analysis of HSDI data indicates that tissue spectra vary from point to point, even within histopathologically homogeneous regions. This spectral variability exhibits both random and patterned components, implying that point monitoring may be susceptible to significant sources of noise and clutter inherent in the tissue. We have analyzed HSDI images from clinical CIN (cervical intraepithelial neoplasia) patients to quantify the spatial variability of fluorescence and reflectance spectra. This analysis shows the spatial structure of images to be fractal in nature, in both intensity and spectrum. These fractal tissue textures will limit the performance of any point-monitoring technology.
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- McLaughlin, David, et al.
(författare)
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Specific modification of heparan sulphate is required for normal cerebral cortical development
- 2003
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Ingår i: Mechanisms of Development. - : Elsevier. - 0925-4773 .- 1872-6356. ; 120:12, s. 1481-1488
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Tidskriftsartikel (refereegranskat)abstract
- Proteoglycans are cell surface and extracellular matrix molecules to which long, unbranched glycosaminoglycan side chains are attached. Heparan sulphate, a type of glycosaminoglycan chain, has been proposed as a co-factor necessary for signalling by a range of growth factors. Here we provide evidence that loss of 2-O-sulphation in heparan sulphate leads to a significant reduction in cell proliferation in the developing cerebral cortex. The gene encoding heparan sulphate 2-sulphotransferase (Hs2st) is expressed in embryonic cortex and histological analysis of mice homozygous for a null mutation in Hs2st indicated a reduction in the thickness of the embryonic cerebral cortex. Using 5′-bromodeoxyuridine (BrdU) incorporation assays we found a reduction of approximately 40% in labelling indices of cortical precursor cells at E12. Comparison of the fates of cortical cells born on E13 and E15 in Hs2st−/− mutant and wildtype littermate embryos revealed no differences in the pattern of cell migration. Our findings suggest a critical role for 2-O-sulphation of heparan sulphate proteoglycan (HSPG) in regulating cell proliferation during development of the cerebral cortex, perhaps through the modulation of cellular responses to growth factor signalling.
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