All posts by gp

Expert System

One of the more mature and successful applications of AI (Artificial Intelligence) is the Expert System, in which a knowledge base (domain) is stored on a computer, and then delivered back to users via an ‘inference engine’. An inference engine is a sort of active decision tree, wherein branches can be taken according to current conditions, and thinking can even be ‘backtracked’. Backtracking is necessary if the current conditions change or if an unfruitful path is taken (perhaps a wrong guess). The goal is to have a machine-based, portable ‘expert’ that can make decisions within this domain using varying problem parameters like a human can. One person or persons contribute knowledge, and a different set of people then can use that knowledge. These two groups may be widely separated in time and location, perhaps even in areas of sparse population or hazardous conditions. Interestingly, the user is not necessarily another human. Expert Systems are sometimes employed in automated systems to enable machines to make (artificially) intelligent decisions.

Expert systems are usually created within a ‘shell’. This is a framework that allows rules to be defined and stored along with the facts that define the domain. The human expert imparts her knowledge using the development tools in the shell. Once created, users can then use the shell to apply that stored expertise, by means of an interactive dialog, to new sets of problems within the domain.

Of course, machines lack the ability to apply emotional, cultural, and social context. This can be a hinderance or a benefit depending on the application.

Water Chemistry and Life

Life on earth (and presumably elsewhere) depends on water. The biochemistry of life takes place in aqueous solution. Even organisms that live on dry land are mostly water (cells are liquid internally). Water has several key properties that life depends on.

The water molecule (H2O) is slightly polarized. The hydrogen end is positive and the oxygen end is negative. This makes water a powerful solvent (it is commonly known as a ‘universal solvent’). This is important because once in solution, chemicals can easily interact.

The two hydrogen atoms form an angle of 105° with the oxygen atom. This angle allows water to form a loose lattice with each molecule bonding to three or four others. These are very weak bonds that are constantly breaking and re-forming. This gives water some remarkable properties. First, it’s transparent to visible light. This lets sunlight penetrate the top few meters of the ocean, giving photosynthesis some working space. However, water absorbs harmful radiation like UV and microwaves, which would damage or even prevent life. Next, water has a very high specific heat, which moderates (buffers) the earth’s surface temperature, keeping it from getting too hot or too cold – again, important for life. Next, water actually gets less dense as it freezes into a solid, which is strange. Ice floats. Imagine what would happen if it didn’t. Layers of ice that formed on the surface would sink to the bottom of the ocean, where they they would stay frozen. Eventually, the whole ocean would freeze solid, and life wouldn’t be possible at all. Next, water has a high surface tension and resulting capillary activity. This allows water to be carried up plant stems, against gravity. Next, water can be either a base or an acid in chemical reactions.

Water is so fundamental for life that it’s what we look for whenever we search for life on other planets or even in deep space. The temperature range where water is liquid is the ‘sweet spot’ for life.

Chaotic Evolution

Keith Bennett
“The chaos theory of evolution”
New Scientist 2782
Oct 18 2010

Found at
www.newscientist.com/
article/mg20827821.000-
the-chaos-theory-of-evolution.html

Description
An attempt to separate the concepts of microevolution (more Darwinian) and macroevolution (more chaotic). The weak dependence of speciation on environmental change and the eerily fractal nature of the tree of life are examined.

Gliese 581g Earth-like planet

Steven S. Vogt et al.
“The Lick-Carnegie Exoplanet Survey: A 3.1M Planet in the
Habitable Zone of the Nearby M3V Star Gliese 581″

Astrophysical Journal
29 Sep 2010
arXiv:1009.5733v1 

found at
www.ucolick.org/~vogt/gj581_rev205.pdf

Description
The 11 year study that resulted in the discovery of Gliese 581g, the ‘Goldilocks’ planet. Much more advocacy and passion than usual scientific papers.

Collective Intelligence

Collective behaviour allows a group of individuals to behave as a single unit eg. flock, school, swarm. This has the advantages of common and wider awareness of food/predators as well as confusing predators (safety in numbers). This behaviour is achieved by each individual following simple rules, such as: stay aligned with neighbours, match neighbours’ velocity, maintain fixed distance from neighbours, etc. This behaviour produces the illusion of orchestration.

Collective action allows a group of individuals to coordinate their actions. An example is quorum sensing, which enables honeybees to choose a new hive location. This mechanism is also used by bacteria to coordinate the release of digestive enzymes and toxins, and formation of biofilm.

Swarm intelligence allows a group of individuals to make better decisions than any single individual could. It has three main components: independence, diversity, and positive feedback. An example is an ant colony. One of the tasks of the colony is to locate and fetch food with a minimum expenditure of time and energy. Since no single ant is intelligent enough, or well-informed enough to direct this effort, swarm intelligence is employed. A few ants go out and explore for food. Individual ants explore independent routes. This makes for a very diverse and widespread search. Although most of them will find low-value, inefficient routes, a few will find more efficient routes to food sources. These will be the first to return to the nest, thus inspiring others to follow their path. The current hypothesis is that subsequent trekkers lay down pheromone at key junctions, thus reinforcing the best path(s) via positive feedback. Very quickly, the entire effort of the colony is concentrated on the most efficient route(s). A good decision has been made.

How does such swarm intelligence evolve? In the particular case of ants, why would scouts evolve to lead such dangerous, solitary, often fruitless lives? Isn’t that the antithesis of Darwinism?

The answer is that evolution applies not to individual ants, but to the gene pool of the species. It is the ants’ DNA that is evolving. Natural selection screens for those mutations that are beneficial to the colony. The more independent are the scouts, the more diverse will be the search for food, the greater will be the likelihood of success of the colony and therefore reproduction. The colony’s gene pool will then propagate the trait of independence in scouts.

Human intelligence allows a single person to be sentient. It incorporates mechanisms such as inference, pattern-seeking, goal-seeking, perception, complex memory, imagination, and language. However, it has been speculated that the basis of this higher intelligence may be some form of collective intelligence amongst neurons.

Pulsar found by Einstein@Home

B. Knispel et al.
“Pulsar Discovery by Global Volunteer Computing”


Science 10 September 2010:
Vol. 329. no. 5997, p. 1305
DOI: 10.1126/science.1195253

Found at
www.sciencemag.org/cgi/rapidpdf/329/5997/1305.pdf

Description
Details of the discovery on July 11, 2010 of a pulsar in Arecibo data by the Einstein@Home volunteer distributed computing project (using the BOINC platform).

Evolution

Living things reproduce with variation and are subject to natural selection. Reproductive variation results from random genetic mutations. Natural selection is the non-random screening (via death or survival of individuals) of those mutations which aid the life form in its struggle to survive long enough to reproduce. For example, even a slight improvement in eyesight will tend to aid in survival and thus help to propagate the genes that carry that trait within the gene pool of a species. Eventually, a single species will diverge into new ones (speciation), each better adapted to its particular environment, which includes geography, competition, predation, etc. Over geological time, this process has produced all the species that have ever existed (until humans began artificial selection and even direct synthesis of new species).

Evolution is perhaps the simplest, most profound, and most verified scientific theory ever conceived.

Article & Publication – Altruistic Bacteria

“Researchers Discover Bacterial Charity Work”
Howard Hughes Medical Institute (HHMI)

Found at
Article:
www.hhmi.org/news/collins20100901.html
Full publication:
Henry H. Lee, Michael N. Molla, Charles R. Cantor & James J. Collins
“Bacterial charity work leads to population-wide resistance”
Nature 467, pp. 82-85 (02 September 2010) doi:10.1038/nature09354

Description
Selfless defense of an E. coli colony. Given that evolution is gene based, altruism makes sense. W.D. Hamilton rides again.