Safety Analysis: Relative Risks of Ultraviolet Exposure from Fluorescence Spectroscopy and Colposcopy Are Comparable*

Fluorescence spectroscopy is a promising tool for use in the diagnosis of disease in human tissue. However, few published reports have evaluated the safety of this technique, despite the fact that many spectroscopic systems use UV illumination. This study determined the relative risk associated with light exposure from spectroscopic systems compared with the traditional light sources that are used to illuminate tissue and direct biopsies. We compared spectroscopic detection systems for the cervix to the colposcope, a low-power microscope routinely used to illuminate the cervix, which does not cause any known photochemical damage. We measured the average spectral irradiance (W/[cm²nm]) and the average tissue exposure time during a diagnostic colposcopy examination. To quantify the relative risks, we multiplied illumination spectra by several action spectra from the literature and compared the areas under the curves corresponding to each procedure. The risk associated with the average power colposcope served as our basis for comparison. We conclude that the risks of illumination using spectroscopic systems are lower than or comparable to those already encountered in routine diagnostic procedures such as colposcopy with an average power colposcope. Spectroscopic examination can be associated with a somewhat higher risk than a colposcopy with the lowest power colposcope or a shorter than average colposcopy. The analysis presented can be repeated to estimate the magnitude of risks associated with other spectroscopic diagnostic devices.     

One-step synthesis of low polydispersity, biotinylated poly(N-isopropylacrylamide) by ATRP

Low polydispersity poly(N-isopropylacrylamide) with a biotin end-group was obtained in one step from a biotinylated initiator for atom transfer radical polymerization and interacted with streptavidin to generate the thermosensitive polymer-protein conjugate.     

Structure and stability of Ne+He(n): experiment and diffusion quantum Monte Carlo theory with "on the fly" electronic structure

New data are reported for the mass-spectrometry fragmentation patterns of helium clusters, either pure or containing a Ne or an Ar atom. The patterns for He(n)+ and Ar+He(n) show clear evidence of structure, while those of Ne+He(n) do not. To better understand the surprising result for the Ne+He(n) fragments, diffusion quantum Monte Carlo (DMC) calculations of the energies and structural properties of these ions were performed using a diatomics-in-molecule (DIM) parametrization of the potential energy. Using DIM for electronic energy evaluation allows us to sample 10(9) configurations even for a cluster as large as Ne+He14. The results of the DMC calculation are very surprising. For n > 7, the DMC random walkers rarely venture within 100 cm(-1) of the minimum potential energy. Analysis of the resulting particle density distributions shows that the zero-point energy does more than spread the wave function around the potential-energy minima, resulting in very diffuse wave functions. For some of the clusters the quantum effects nearly exclude the region of the potential minimum from the overall wave function. An important result of this effect is that the incremental bonding energy of the nth helium atom varies quite smoothly with n, for n > 5. This eliminates the expected shell structure and explains the lack of magic-number-type features in the data.     

Preparation and crystallographic characterization of a new endohedral,Lu3N@C80.5 (o-xylene), and comparison with Sc3N@C80.5 (o-xylene)

The trimetallic nitride template (TNT) approach has been successfully utilized to prepare the new endohedral Lu(3)N@C(80). Well-ordered crystals of Lu(3)N@C(80).5 (o-xylene) and Sc(3)N@C(80).5 (o-xylene) form upon cooling of o-xylene solutions of these endohedrals and they are isomorphous. Although the positions of the fullerene cage (which is fully ordered and located at a crystallographic center of symmetry) and the o-xylene molecules are nearly identical in these two structures, the positioning of the metal ions in the two crystals differ in significant ways. However, the expected difference in sizes of lutetium and scandium does not affect the dimensions of the C(80) cage. Nevertheless, the positions of the metal atoms do produce a slight outward dislocation of the immediately adjacent carbon atoms.     

Centralized versus Decentralized Manpower Resource Planning: the Case of a Hong Kong Company

This paper considers the problem of planning effective servicing support of a Hong Kong-based company by providing sufficient technicians to repair/service copier machines at numerous customer sites throughout the city. As quality of service depends on its operational responsiveness, there is an urgent need to address the company's present and projected staffing.Mathematical modelling techniques based on the well-tested square-root response distance formulation of Kolesar et al. and a corresponding affine time-distance relationship are successfully applied to quantify the performance measure with respect to manpower resources. The numerical results enable model validation against collected data as well as analyses of different modes of centralized/decentralized, prioritized/non-prioritized service operations. Parametric study of performance versus resource offers further insights and directions towards the goal of optimal manpower planning.The approach is found to be very useful in an actual decision support setting, owing to its ease of adaptation, generalization and robust numerical modelling.