  In a previous study we showed that D0-branes (particles) can operate as
sources of very-high-energy radiation, as a result of an unstable spacetime
distortion that follows a D0-particle/closed string state scattering. The
effect can happen only if the energy of the incident particle/closed string
state exceeds a certain threshold, which is of order of the subsequently
radiated energy. In this letter we speculate on the possibility of detection of
the D-particles due to this phenomenon. The energies of the emitted radiation
range in a narrow window of size less than one order of magnitude.
Observation-wise, this radiation will appear as an excess of photons in a
narrow band in the spectrum of high energy cosmic rays. From their energy we
can then read off the value of the product of the string mass scale times the
string coupling. We speculate on the possibility that high energy neutrinos
from GRB's play the r\^ole of the necessary high energy flux that triggers the
effect, by striking D-particles lying inside the mean free path of the photons
as measured from Earth. The possibilty of this effect operating as a mechanism
of GZK cutoff violation is also pointed out.
