An amusing paper (geek alert - you should understand the basics of TCP before wading in...) The analogies are interesting. Flow control, slow start and time out ...
The Regulation of Ant Colony Foraging Activity without Spatial Information
Balaji Prabhakar1, Katherine N. Dektar2, Deborah M. Gordon3*
1 Departments of Computer Science and Electrical Engineering, Stanford University, Stanford, California, United States of America, 2 Biomedical Computation, School of Engineering, Stanford University, Stanford, California, United States of America, 3Department of Biology, Stanford University, Stanford, California, United States of America
Many dynamical networks, such as the ones that produce the collective behavior of social insects, operate without any central control, instead arising from local interactions among individuals. A well-studied example is the formation of recruitment trails in ant colonies, but many ant species do not use pheromone trails. We present a model of the regulation of foraging by harvester ant (Pogonomyrmex barbatus) colonies. This species forages for scattered seeds that one ant can retrieve on its own, so there is no need for spatial information such as pheromone trails that lead ants to specific locations. Previous work shows that colony foraging activity, the rate at which ants go out to search individually for seeds, is regulated in response to current food availability throughout the colony's foraging area. Ants use the rate of brief antennal contacts inside the nest between foragers returning with food and outgoing foragers available to leave the nest on the next foraging trip. Here we present a feedback-based algorithm that captures the main features of data from field experiments in which the rate of returning foragers was manipulated. The algorithm draws on our finding that the distribution of intervals between successive ants returning to the nest is a Poisson process. We fitted the parameter that estimates the effect of each returning forager on the rate at which outgoing foragers leave the nest. We found that correlations between observed rates of returning foragers and simulated rates of outgoing foragers, using our model, were similar to those in the data. Our simple stochastic model shows how the regulation of ant colony foraging can operate without spatial information, describing a process at the level of individual ants that predicts the overall foraging activity of the colony.
Social insect colonies operate without any central control. Their collective behavior arises from local interactions among individuals. Here we present a simple stochastic model of the regulation of foraging by harvester ant (Pogonomyrmex barbatus) colonies, which forage for scattered seeds that one ant can retrieve on its own, so there is no need for pheromone trails to specific locations. Previous work shows that colony foraging activity is regulated in response to current food availability, using the rate of brief antennal contacts inside the nest between foragers returning with food and outgoing foragers. Our feedback-based algorithm estimates the effect of each returning forager on the rate at which foragers leave the nest. The model shows how the regulation of ant colony foraging can operate without spatial information, describing a process at the level of individual ants that predicts the overall foraging activity of the colony.
NASA imaging of fires around the world over 12 years compiled by Andy Revkin
Here is where he got the images to stitch together - and an explanation of the imaging:
News reports portray wildfires as terrifying, accidental episodes in which people and animals flee as roiling flames consume houses and trees, and send massive plumes of thick smoke billowing into the sky. While wildfires can bring death and destruction, not all wildfires are bad and some can even be good for forest ecosystems.
High-latitude forests regularly experience wildfires, triggered mostly by lightning strikes hitting the surface. Some coniferous trees are resistant to fire, and evolved to use the flames as a means for spreading their seeds. When seen from above, the high-latitude forests of Alaska, Canada, Northern Europe, and Asia look like a patchwork mosaic of areas in different stages of re-growth after a wildfire. Scientists have come to see wildfire as a natural part of the boreal ecosystem.
Fire clears away dead and dying underbrush, which can help restore an ecosystem to good health. Thus, humans use fire as tool in what are sometimes called "prescribed burns." Humans also use fire in slash-and-burn agriculture to expedite the process of returning unwanted vegetation back to the soil. Humans also use fire to clear away old-growth forests and grasslands to make room for living spaces, roads, and fields for raising crops and cattle. Scientists estimate humans burn an average of 175 million acres of forest and grassland every year. So, by far, humans are leading cause of fire around the world.
Some fires are not good. Because humanity's biomass burning is so widespread around the world, it significantly impacts Earth's carbon cycle. Not only does burning biomass release the carbon that was fixed in plants into the atmosphere (in the form of various gaseous and particle pollutants), but it also destroys plants and trees that would otherwise be removing carbon dioxide from the atmosphere during photosynthesis.
Scientists need better measurements of how much area burns every year so they can better understand the roles fire plays in Earth's environment — how it changes the land surface, how it impacts life and the health of ecosystems, and how it changes the chemistry of the atmosphere. Using fire data collected globally every day by NASA's Terra and Aqua satellites, scientists produce maps like these to show the number and extent of fire around the world. The fire maps are helping scientists to better understand Earth's environment and climate system.
The red, orange, and yellow splotches on these maps show the locations where the MODIS instrument aboard NASA's Terra satellite detects actively burning fires. Don't be fooled by sizes of some of the bright splotches on these maps. The colors represent a count of the number of fires observed within a 1,000-square-kilometer area. White pixels show the high end of the count — as many as 100 fires in a 1,000-square-kilometer area per day. Yellow pixels show as many as 10 fires, orange shows as many as 5 fires, and red areas as few as 1 fire in a 1,000-square-kilometer area per day.
Paul Ryan seems to have something of a problem when it comes to telling the truth - his marathon "time" is an example. There was no reason to lie, but he did anyway.
The difference between an under 3 hour and a something over four hour time is enormous. To qualify in the NY Marathon you need a sub 3 hour time if you are male in the age range he mentions. A four hour tine is required for a male to qualify at age 70... Perhaps that's why he lied.