This week's fun papers

From: Anders Sandberg (
Date: Fri Apr 14 2000 - 07:08:43 MDT

* Nerd theology
* Monkey economics
* Jelly hydraulics
* Technology avalanches
and the logic of life...

This week I have been quite busy preparing a lecture on models of
pattern formation and morphogenesis for a local course (my notes can
be found at Some of the
links I found that I can strongly recommend are - Kurt Fleischer has done
        lovely work on simulated development, applied both to
        artificial life and computer graphics.
        - Biological pattern formation: How cell talk with each other
        to achieve reproducible pattern formation by Hans
        Meinhardt. Great lecture with animations. - an old classic
        when it comes to reaction-diffusion models.

Other fun papers:

Kevin Kelly, Nerd Theology, in Technology in Society 21 (1999)

Points out that the term god has acquired new meanings in the computer
world different from traditional theology. Instead of being a term for
supreme being, it denotes a creator entity of a system, something that
creates something else out of a state of nothingness. Kelly also
points out (as does several of the other papers in this issue) that
"'God created man in His own image' is a recursive statement" (from
Sussman's Ph.D. thesis) and that there can be chains of entities
creating other entities - and that later entities doesn't have to be
inferior to their creators.

Frans B.M. de Waal and Michelle L.Berger
Payment for Labour in Monkeys
Nature 404: 6778 (2000)

It turns out that capuchin monkeys coluntarily share treats with other
monkeys that helped to secure them. The researchers put two monkeys in
a cage divided by a mesh, and placed bowls with or without food in
front of the cage on a plate that could be hauled in by one or both
monkeys drawing on rods depnding on the experiment. Each monkey could
get just its own bowl of food. It turned out that when there was only
food in one of the bowls significantly more food was shared when both
monkeys had to work to haul it in than when just one monkey could do
the job. It seems that the capuchins have something similar to
scorekeeping, gratuity or reciprocity.

Functional hydrogel structures for autonomous flow control inside
microfluidic channels
David J. Beebe, Jeffrey S. Moore, Joseph M. Bauer, Qing Yu, Robin H. Liu,
Chelladurai Devadoss & Byung-Ho Jo
Nature 404: 6778 (2000)

Hydrogels can respond to many kinds of stimuli, but since they change
volume slowly on a macroscopic scale they have not been used
extensively. This paper shows that swelling processes on the
micrometre scale can be quite fast and used in microfluidic systems by
allowing self-regulated flow control. They made gels in exact shapes
in microfluid channels using photopatterning to polymerize the gels,
and then the exactly shaped gels could be used as valves,
"transistors" and a pH separator that let fluid through to two
different output channels depending on its acidity.

Self-organised evolution in a socioeconomic environment
A. Arenas, A Diaz-Guilera, C.J. Perez and F. Vega-Redono
Physical Review E vol 61: 4 3466--3469

A model of technological changes in socioeconomic environments. The
idea is that agents get a base payoff depending on their technological
level, but decreased by the difference between themselves and their
neighbours they have to cooperate with. If this decrease is small,
then of course it is favorable to adopt new technologies as soon as
they become available and everybody rushes along. If the penalty is
large, then the system gets locked in. This paper analyses the
behavior of intermediate levels, where self-organised criticality
seems to develop (wow! who could have expected that? :-) as agents
undergo avalanches when new technology spreads through the system and
people adopt. The most interesting result is that there exists an
optimal level of penalty due to technological differences, and the
advance rate is highest at this point regardless of the size of the
system. The paper predicts that there are different regimes of
technological evolution depending on the cost of improvement; I guess
economists would just say this is obvious (?).

Anders Sandberg                                      Towards Ascension!                  
GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y

This archive was generated by hypermail 2b29 : Thu Jul 27 2000 - 14:09:18 MDT