Lfil = Ö(k/l)
k is effective diffusivity
l is strain rate
For exponential growth,
final width of filament is independent of growth rate
    identical to that for an inert tracer
Typical values:
k=5m2s-1, l=5x10-6 s-1
Lfil~1km
Converges in ~ 1-2 days
For limited growth, (McLeod et al., 2001)
2 regimes:
m/l<2.5:  as exponentially growing/inert tracer
m/l>2.5:  width dependent on growth rate
                larger than for exponential growth
Lfil ~ Ö(km/l2)
Go through
Counter-intuitive that growth is irrelevant except for time.
Solution allows for time varying growth rate
Obvious extension to explicitly include limitation
EXPLAIN LIMITATION
   - if less near exponential
   - if greater decay
Regimes
Confirms earlier model for beta<2.5
For beta>2.5
   - biology now important
   - width larger than for exponential growth
     - counter-intuitive
All nice theory, but what use?