A heuristic model of bounded route choice in urban areas

There is substantial evidence to indicate that route choice in urban areas is complex cognitive process, conducted under uncertainty and formed on partial perspectives. Yet, conventional route choice models continue make simplistic assumptions around the nature of human cognitive ability, memory and preference. In this paper, a novel framework for route choice in urban areas is introduced, aiming to more accurately reflect the uncertain, bounded nature of route choice decision making. Two main advances are introduced. The first involves the definition of a hierarchical model of space representing the relationship between urban features and human cognition, combining findings from both the extensive previous literature on spatial cognition and a large route choice dataset. The second advance involves the development of heuristic rules for route choice decisions, building upon the hierarchical model of urban space. The heuristics describe the process by which quick, 'good enough' decisions are made when individuals are faced with uncertainty. This element of the model is once more constructed and parameterised according to findings from prior research and the trends identified within a large routing dataset. The paper outlines the implementation of the framework within a real-world context, validating the results against observed behaviours. Conclusions are offered as to the extension and improvement of this approach, outlining its potential as an alternative to other route choice modelling frameworks

BeppoSAX observations of low-energy spectral features in AGN

The combination of the broad band coverage and moderate spectral resolution of the LECS and MECS instruments on-board BeppoSAX allow the spectra of AGN to be studied in unprecedented detail down to 0.1 keV. We describe the calibration and the performance of the LECS and report on observations of low-energy absorption features in the spectra of both a low (MCG-6-30-15) and a high luminosity (3C 273) AGN. These features provide important diagnostics on the location and nature of the material surrounding the AGN. A comparison of LECS and ASCA/SIS low energy performance is also presented in the case of 3C 273.Comment: 5 pages. To appear in symposium proceedings: The Active X-Ray Sky, Rome, October 199

'Unlicensed' natural killer cells dominate the response to cytomegalovirus infection.

Natural killer (NK) cells expressing inhibitory receptors that bind to self major histocompatibility complex (MHC) class I are 'licensed', or rendered functionally more responsive to stimulation, whereas 'unlicensed' NK cells lacking receptors for self MHC class I are hyporesponsive. Here we show that contrary to the licensing hypothesis, unlicensed NK cells were the main mediators of NK cell-mediated control of mouse cytomegalovirus infection in vivo. Depletion of unlicensed NK cells impaired control of viral titers, but depletion of licensed NK cells did not. The transfer of unlicensed NK cells was more protective than was the transfer of licensed NK cells. Signaling by the tyrosine phosphatase SHP-1 limited the proliferation of licensed NK cells but not that of unlicensed NK cells during infection. Thus, unlicensed NK cells are critical for protection against viral infection

Lurcher, nPIST, and Autophagy

AbstractPrevious work has shown that neurodegeneration in the lurcher mouse is due to a mutation in the GluRδ2 gene that results in a constitutively active glutamate receptor ion channel. Characterization of the cell death pathway in these animals reported by Yue et al. 2002, in this issue of Neuron provides important insight into the toxicity induced by the abundant transmitter glutamate. Through protein-protein interactions, the GluRδ2Lc mutant channel activates autophagy