643 research outputs found
Aristotle's four conceptions of time
In this paper I will describe four theories of time that can be found in Aristotle. I will
compare these four theories with modern notions of time, and propose that the ancient
and modern views are substantively the same. Of course, all four theories cannot be
true together. I will present four ways to resolve the inconsistencies, and conclude that
the contradictions can be resolved
Aristotle and real possibility
Ross, Hintikka, Waterlow and Makin have all suggested that there is something problematic
about Aristotle’s treatment of possibility. I will canvas their concerns and propose
that the problem is not so much with Aristotle as the fact that the notion of
possibility is not a single simple concept. I will present eight different components of
the notion of possibility and suggest that Aristotle may have been aware of all of them.
I will conclude whilst his treatment can appear inconsistent, it is instead, an attempt
to give a complete description of a complex notion
Hedging Housing Risk
An unusually rich source of data on housing prices in Stockholm is used to analyze the investment implications of housing choices. This empirical analysis derives market-wide price and return series for housing investment during a 13-year period, and it also provides estimates of the individual-specific, idiosyncratic, variation in housing returns. Because the idiosyncratic component follows an autocorrelated process, the analysis of portfolio choice is dependent upon the holding period. We analyze the composition of household investment portfolios containing housing, common stocks, stocks in real estate holding companies, bonds and t-bills. For short holding periods, the efficient portfolio contains essentially no housing. For longer periods, low risk portfolios contain 15 to 50 percent housing. These results suggest that there are large potential gains from policies or institutions that would permit households to hedge their lumpy investments in housing. We estimate the potential value of hedges in reducing risk to households, yet yielding the same investment returns. The value is surprisingly large, especially to poorer homeowners.Portfolio Risk; House Price Index; Hedging
Enhancement of island size by dynamic substrate disorder in simulations of graphene growth
We demonstrate a new mechanism in the early stages of sub-monolayer epitaxial island growth, using Monte Carlo simulations motivated by experimental observations on the growth of graphene on copper foil. In our model, the substrate is “dynamically rough”, by which we mean (i) the interaction strength between Cu and C varies randomly from site to site, and (ii) these variable strengths themselves migrate from site to site. The dynamic roughness provides a simple representation of the near-molten state of the Cu substrate in the case of real graphene growth. Counterintuitively, the graphene island size increases when dynamic roughness is included, compared to a static and smooth substrate. We attribute this effect to destabilisation of small graphene islands by fluctuations in the substrate, allowing them to break up and join larger islands which are more stable against roughness. In the case of static roughness, when process (ii) is switched off, island growth is strongly inhibited and the scale-free behaviour of island size distributions, present in the smooth-static and rough-dynamic cases, is destroyed. The effects of the dynamic substrate roughness cannot be mimicked by parameter changes in the static cases
Audio-visual integration during overt visual attention
How do different sources of information arising from different modalities interact to control where we look? To answer this question with respect to real-world operational conditions we presented natural images and spatially localized sounds in (V)isual, Audio-visual (AV) and (A)uditory conditions and measured subjects' eye-movements. Our results demonstrate that eye-movements in AV conditions are spatially biased towards the part of the image corresponding to the sound source. Interestingly, this spatial bias is dependent on the probability of a given image region to be fixated (saliency) in the V condition. This indicates that fixation behaviour during the AV conditions is the result of an integration process. Regression analysis shows that this integration is best accounted for by a linear combination of unimodal saliencies
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