#### Resource
delivery

The CA is
a string of cells consisting of a core which does not interact with other
CA, and a rim which produces cells. When the CA elongates cells are
produced, and when cells are delivered (exfoliated) it shrinks. The
core consists of everlasting progenitors. The inner most cells are stem
cells. During each time step CA cells accumulate resources, which are
depicted by the graph below.
Since core cells continually accumulate resources the graph rises. Whenever
cells are shed off, the graph declines (*).The CA cycle is 46 days,
and it produces 44 cells. On the average it delivers daily 0.94 cells.

The experiment
illustrates the effect of a rising demand for resources on CA structure.
The system is a two CA proliferon, consisting of
a stem and a
transitory process. Only the transitory process is depicted. The timing
of resource delivery is determined by a **set
point**. When CA length
reaches it resources are delivered. At the set point all CA cells deliver some of
their resources, and when their resources are exhausted, they die and
are shed off. The set point of CA-1 is 25 cells and it delivers on the
average 0.94 cells daily.

The set point
of CA-2 is 24 cells. Initially it grows, and when attaining the length
of 25 cells, all its cells deliver some of their resources. Some exhaust
their resources and die. The CA shrinks below the set point and stops
delivering resources. Gradually it recuperates starts growing and when
reaching the set point it delivers.

The
declining set point determines the maximal CA-
length.

The
following images depict resource variation of two CA.
Both start with 700 resource units.
Their initial lengths exceed their set points and they delivered
resources. When their length dropped
below the set point they accumulated resources until the set point was
reached, and so on.

The
graphs below depict maximal CA length and average daily cell production.
Initially as set point decline so does cell production. When CA become smaller their average daily
cell production rises.

**Cell
death**

Two factors
cause cell death. 1. Rule dependent cell elimination like in the CA-1 rim,
and 2. death due to resource depletion, which occurs
when CA length reaches the set point. Some cell exhaust their
resources and dies. In the subsequent states death is determined by the
rule.

**Setup**

nca=2; restoreparams[1,1,1];
restoreparams[2,1,1]; If [sa[[2]]
>=k, deleteon =1; {k, 25, 7,-1};
If [sa[[2]] <=2, deleteon
= 0]; If[ deleteon == 1, donate[2,2]]; If[nowdat[[2,8]]<
0, newzygote[2]];

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