North American Fruit Explorers mailing list at ibiblio

["Joe Hecksel" <jhecksel@voyager.net>]

Hello all:

This will be just a quick note on a very large topic.

Epidemics:
Diseases in fruit trees, worms in the fruit and on the computer.  
Bacteria and viruses in birds/mosquitoes and humans.  What do they have 
in common.  They can be described as epidemics.

Ed Fackler, one of the two smartest men I know, once said that it is 
(nearly) impossible to grow a natural apple orchard in the Eastern US, 
in part, because an orchard looks nothing like a woodland ecosystem.  
Seldom do you see a single clone covering five acres.  It does happen 
(aspen and some herbacious plants) but it is rare.

A key component in understanding epidemics is a concept of the distance 
between hosts.  That is, the distance between organisms that can become 
infected and spew spoors.  Epidemics fizzle when the distance between 
hosts becomes too large.  Epidemics explode when DBH becomes small.  It 
is absolutely essential to understand the nuances of "distance" if you 
want to manage epidemics.

Aside:  I once had a Professor correct me when I called a set of 
differential equations "Governing Equations" as I am sure I had heard 
somebody else use that term.  He told me that physical phenomena are 
not "Governed" by mathematical equations.  Rather, they are *Described* 
by equations.  The beauty of calling them "Descriptive" equations is 
that it opens up all kinds of simulations that can be run.  Running a 
simulation on a "safe" system that has similar underlying descriptive 
equations can give you much insight....at a lower cost.

So, what other physical phenomena have similar underlying descriptive 
equations:
-Thermonuclear reactions 
-Certain kinds of heat transfer problems
-Others that I will think of in a minute

The following heat transfer experiment/simulation is one that I ran 
with my 11 year old boy.  We both had a ball.

-Take a common soda pop bottle screw cap.
-Put play-doh or clay in it
-Place cap on concrete surface with open end up
-Give the kid a box of common, wooden kitchen matches.
-Tell kid to see how many matches he can put in the cap, business end 
up.  You will light one of the matches.  The "score" is the number of 
matches that remain un-ignited after the flames die down.

Each match is a potential host.  It must absorb a significant amount of 
heat before it ignites.  After ignition, it radiates a large amount of 
heat and puts other, nearby matches at risk.

My boy's first effort resulted in 21 ignited matches and no survivors.

Among the things that were evaluated were 
-reducing the density of matches
-Lobing or grouping the matches to look like villages separated by 
fields
-Installing some alumninum beverage can material to further separate 
villages  

My boy's final effort resulted in 30 of 40 survivors.  I think he could 
have gone farther but he got the point.


-- 
Joe Hecksel
Personal Webpage http://my.voyager.net/~jhecksel