Biology Reference
In-Depth Information
Exercise 4.31.
In this question, you will develop code that models two axons
that (due to differences in their receptors) respond react differently to the effect two
chemicals in the environment.
Use your previous work to create a program to the following specifications:
a.
There are two (C1 and C2) chemicals, with sources at (0, 10) for chemical C1
and at (0,
10) for chemical C2, both of which have diffusion rates that are
user-defined via a slider.
b.
There are two
agents
:
−
The first
agent
starts at (30,10) and reacts to chemical C1 via chemotaxis and is
unaffected by chemical C2.
The second
agent
starts at (30,
10) and initially acts in the same way as the
first
agent
. However, when this
agent
crosses the middle of the environment (
y
−
=
0) the response switches and the
agent
no longer responds to chemical C1 and is
chemorepulsed by chemical C2.
Exercise 4.32.
Project: Construct a model of axon guidance.
Important aspects that you will need to include are: A midline where there are two
sources of chemical (C1 and C2) that can act as chemoattractants/chemorepulsants.
C1 and C2 both diffuse through the environment.
Four types (A-D) of axon (
agent
) that act in the following ways:
type A: attracted to C1, until it crosses the midline, then repulsed by C2
type B: repulsed by C1 and C2, however the repulsion by C2 is contact mediated
type C: repulsed by C2 (contact mediated)
type D: attracted to C1, repulsed by C2
Make sure there are sliders for the diffusion rates. (A slider can be added using
Button
on the NetLogo Interface: an example can be found in the model
Diffusion1.
nlogo
.)
4.3
AN AGENT-BASED MODEL FOR CHOLERA AND
THE IMPORTANCE OF REPLICATION
Cholera is a diarrheal disease caused by human ingestion of the bacteria
Vibr io
cholerae
, a bacteria that can live in environments that lack proper sanitation. An
outbreak typically begins through contact with a contaminated water source, but
becomes amplified by a fecal-oral spread among humans [
37
]. The rapid dehydra-
tion that accompanies a cholera illness can lead to death within a few hours if not
treated. Cholera causes millions of illnesses each year, and leads to more than 100,000
annual deaths worldwide, primarily in countries which lack the infrastructure to pro-
vide clean water and adequate sanitation [
38
]. As an illustration of how an ABM
might be used to implement the scientific method, we consider the setting of an out-
break of cholera in a small village, such as one in a developing African country,
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