LC12531
Low temperature melting of water nanoparticles
Water nanoparticles play a crucial role in environmental and atmospheric
chemistry as well as in astrophysics. Nevertheless, no experimental data
even of their most fundamental thermodynamic property, the melting
point, was available until now. We present measured caloric curves of
unsupported, size selected 1.4 and 1.9 nm diameter water clusters, which
show a clear onset of melting at about 100 K. This unusually low melting
point demonstrates the peculiarity of the hydrogen bond network
dynamics, and will help to calibrate theoretical models. Our results
represent a first step towards an urgently needed size dependent phase
diagram of water.
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EDR1044
Percolation and epidemics in clustered networks
The social networks that infectious diseases spread along are
typically clustered. Because of the close relation between percolation
and epidemic spread, the behavior of percolation in such networks
gives insight into infectious disease dynamics. A number of authors
have studied percolation or epidemics in clustered networks, but the
networks often contain preferential contacts in high degree nodes. We
introduce a class of random clustered networks and a class of random
unclustered networks with the same preferential mixing. Percolation in
the clustered networks reduces the component sizes and increases the
epidemic threshold compared to the unclustered networks.
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EA10490
Heat transfer in low pressure gas is abysmally low
The amount of heat that can be transferred from a hot surface to cooler fluid flowing
over it, or vice-versa, is of great practical significance. Although results for a large
number of cases are available, the problem of rarefied (low pressure) gas flow over a
surface is not very amenable to measurements and is poorly studied. The available
theoretical results show some contradiction amongst themselves, while experimental
data is totally missing. We have made detailed measurements of heat transfer
coefficient for nitrogen flowing in a heated tube. Our results suggest that the
experimental values are substantially (by up to four orders of magnitude) smaller than
expected from any calculations. Such wide disagreement between experiments and
theory is worth noting. These results suggest that a relook at the governing equations
and/or boundary conditions in in order. The results are therefore expected to trigger
development of new theories and further measurements. Our work would have
significant implications for micro and nanoscale science as well.
