"Bushmeat" and the Origin of HIV/AIDS: A Case Study of Biodiversity, Population Pressures, and Human Health

The Center for Health and the Global Environment at Harvard Medical School, Population Action International, the Jane Goodall Institute, and the Environmental and Energy Study Institute co-hosted a Congressional briefing, entitled "Bushmeat and the Origin of HIV/AIDS: A Case Study of Biodiversity, Population Pressures and Human Health." The AIDS epidemic is a global problem with challenging social implications and no easy solutions. In the United States and around the world, citizen groups and governments are rallying to help scientists find a cure for HIV/AIDS and encouraging widespread education about the disease. To date, over 60 million people have been infected with HIV (human immunodeficiency virus), approximately five million more become infected each year, and over 20 million have died from the disease. In their quest to understand more about this deadly disease, researchers have sought to understand where it came from, and how humans contracted it. What they have discovered is that many answers about HIV and even the potential cure will most likely come from the same place as the original source of the disease -- from chimpanzees and a monkey called the sooty mangabey in the West Central African forests. Unfortunately, it is also becoming frighteningly clear that human actions and population pressures are destroying these forests and the species that inhabit them at alarming rates, which may have significant implications for human health

Percolation in Networks with Voids and Bottlenecks

A general method is proposed for predicting the asymptotic percolation threshold of networks with bottlenecks, in the limit that the sub-net mesh size goes to zero. The validity of this method is tested for bond percolation on filled checkerboard and "stack-of-triangle" lattices. Thresholds for the checkerboard lattices of different mesh sizes are estimated using the gradient percolation method, while for the triangular system they are found exactly using the triangle-triangle transformation. The values of the thresholds approach the asymptotic values of 0.64222 and 0.53993 respectively as the mesh is made finer, consistent with a direct determination based upon the predicted critical corner-connection probability.Comment: to appear, Physical Review E. Small changes from first versio

On the critical behavior of the Susceptible-Infected-Recovered (SIR) model on a square lattice

By means of numerical simulations and epidemic analysis, the transition point of the stochastic, asynchronous Susceptible-Infected-Recovered (SIR) model on a square lattice is found to be c_0=0.1765005(10), where c is the probability a chosen infected site spontaneously recovers rather than tries to infect one neighbor. This point corresponds to an infection/recovery rate of lambda_c = (1-c_0)/c_0 = 4.66571(3) and a net transmissibility of (1-c_0)/(1 + 3 c_0) = 0.538410(2), which falls between the rigorous bounds of the site and bond thresholds. The critical behavior of the model is consistent with the 2-d percolation universality class, but local growth probabilities differ from those of dynamic percolation cluster growth, as is demonstrated explicitly.Comment: 9 pages, 5 figures. Accepted for publication, Physical Review

High Performance School Buildings: Energy-Smart Schools That Make a Difference

Over seventy percent of U.S. schools still in use today were built before 1960, according to the General Accounting Office. In the next decade, school districts around the nation will have to replace or renovate over six thousand of these buildings, and the school's administrators will aim to construct the best possible learning environments while using limited budgets. At this EESI Congressional briefing, co-hosted by the Sustainable Buildings Industry Council, a panel of experts discussed the concept of a "whole building design" as a way to attain a high performance school building. With an integrated design, a school's various components work together as a whole system to produce an efficient and well-operating building. Another key aspect to creating a high performance building is implementing an energy management program to monitor and reduce energy use wherever possible. In recent years, many legislators, architects, engineers and school officials have begun to embrace this holistic approach to building design and function. Not only will it lower a school building's overall energy costs and environmental impact, initial studies indicate that high performance school buildings also improve student performance

Boundary conditions in random sequential adsorption

The influence of different boundary conditions on the density of random packings of disks is studied. Packings are generated using the random sequential adsorption algorithm with three different types of boundary conditions: periodic, open, and wall. It is found that the finite size effects are smallest for periodic boundary conditions, as expected. On the other hand, in the case of open and wall boundaries it is possible to introduce an effective packing size and a constant correction term to significantly improve the packing densities.Comment: 9 pages, 7 figure

Corrections to scaling for percolative conduction: anomalous behavior at small L

Recently Grassberger has shown that the correction to scaling for the conductance of a bond percolation network on a square lattice is a nonmonotonic function of the linear lattice dimension with a minimum at $L = 10$, while this anomalous behavior is not present in the site percolation networks. We perform a high precision numerical study of the bond percolation random resistor networks on the square, triangular and honeycomb lattices to further examine this result. We use the arithmetic, geometric and harmonic means to obtain the conductance and find that the qualitative behavior does not change: it is not related to the shape of the conductance distribution for small system sizes. We show that the anomaly at small L is absent on the triangular and honeycomb networks. We suggest that the nonmonotonic behavior is an artifact of approximating the continuous system for which the theory is formulated by a discrete one which can be simulated on a computer. We show that by slightly changing the definition of the linear lattice size we can eliminate the minimum at small L without significantly affecting the large L limit.Comment: 3 pages, 4 figures;slightly expanded, 2 figures added. Accepted for publishing in Phys. Rev.