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15.2.3.2. Computational Tasks. Besides the nanocomputers and control
systems similar to those previously described for other nanorobots, clottocytes
crucially require special control protocols to ensure that these nanorobots cannot
release their mesh packets in the wrong places inside the body, or at an
inappropriate time. These protocols will demand that carefully specified con-
stellations of sensor readings must be observed before device activation is
permitted. Reliable communications protocols will be required to control co-
ordinated mesh releases from multiple neighboring devices and to regulate the
maximum multidevice-activation radius within the local clottocyte population.
Detection of the ''bled out of body'' condition will be an especially
important component of these protocols. Atmospheric concentrations of gases
such as carbon dioxide and oxygen are different than the concentrations of those
same gases in blood serum. As clottocyte-rich blood enters a breach in a blood
vessel, nanorobot onboard sensors can rapidly detect the change in partial
pressures, often indicating that the nanodevice is being bled out of the body. At
a nanorobot whole-blood concentration of 20mm 3 , mean device separation is
370 microns. If the first device to be bled from the body lies 75 microns from the
air-serum interface, oxygen molecules from the air can diffuse through serum at
human body temperature (310K) from the interface to the nanodevice surface in
B
1 second [1aj]. Detection of
this change can be rapidly broadcast
to
neighboring clottocytes using
1500m/sec waterborne acoustic pulses that are
received by devices up to several millimeters away in times on the order of
microseconds, allowing rapid propagation of a carefully controlled device-
enablement cascade. Similarly, air temperature is normally lower than body
temperature. The thermal equilibration time [1ak] across a distance L in serum
at 310K is t EQ B
B
(6.7 10 6 )L 2 , hence a device that lies 75 microns from the air-
plasma interface can detect a change in temperature in t EQ B
40millisec. Other
relevant sensor readings may include blood pressure profiles, bioacoustic
monitoring, bioelectrical field measurements, optical and ultraviolet radiation
detection, and sudden shifts in pH or other ionic concentrations. At some cost in
rapidity of response, clottocytes also could eavesdrop [1am] on natural biological
platelet control signals, using sensors with receptors for the natural prostaglan-
dins produced by endothelial cells that normally induce or inhibit platelet
activation, and then take appropriate action upon receipt of those natural
biochemical signals.
Biocompatibility [2] requirements engender additional needs for specialized
clottocyte control protocols. For instance, the rapid mechanical action of
clottocytes could interfere with the much slower natural platelet adhesion and
aggregation processes, or disturb the normal equilibrium between the clotting and
fibrinolytic systems [2i]. Thus it may be necessary for artificial platelets to release
quantities of various chemical substances that will encourage the remainder of the
coagulation cascade to proceed normally or at an accelerated pace, including
timed localized vasodilation and vasoconstriction, control of endothelial cell
modulation of natural platelet action, and finally clot retraction and fibrinolysis
much later during tertiary hemostasis.
 
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