<s>
Natural	B-General_Concept
time	I-General_Concept
analysis	I-General_Concept
is	O
a	O
statistical	O
method	O
applied	O
to	O
analyze	O
complex	O
time	O
series	O
and	O
critical	O
phenomena	O
,	O
based	O
on	O
event	O
counts	O
as	O
a	O
measure	O
of	O
"	O
time	O
"	O
rather	O
than	O
the	O
clock	O
time	O
.	O
</s>
<s>
Natural	B-General_Concept
time	I-General_Concept
analysis	I-General_Concept
has	O
been	O
primarily	O
applied	O
to	O
earthquake	O
prediction	O
/	O
nowcasting	O
and	O
secondarily	O
to	O
sudden	O
cardiac	O
death	O
/	O
heart	O
failure	O
and	O
financial	O
markets	O
.	O
</s>
<s>
Time	O
reversal	O
,	O
in	O
contrast	O
to	O
clock	O
time	O
,	O
is	O
applicable	O
when	O
studying	O
the	O
approach	O
of	O
a	O
system	O
to	O
criticality	O
with	O
natural	B-General_Concept
time	I-General_Concept
analysis	I-General_Concept
.	O
</s>
<s>
Thus	O
a	O
critical	O
state	O
of	O
a	O
system	O
can	O
be	O
estimated	O
by	O
applying	O
natural	B-General_Concept
time	I-General_Concept
analysis	I-General_Concept
upon	O
calculating	O
the	O
entropy	B-Algorithm
upon	O
both	O
normal	O
time	O
flow	O
and	O
time	O
reversal	O
and	O
studying	O
the	O
difference	O
of	O
the	O
two	O
results	O
.	O
</s>
<s>
Typical	O
applications	O
are	O
:	O
great	O
global	O
earthquakes	O
and	O
tsunamis	B-Application
,	O
aftershocks	O
and	O
induced	O
seismicity	O
,	O
induced	O
seismicity	O
at	O
gas	O
fields	O
,	O
seismic	O
risk	O
to	O
global	O
megacities	O
,	O
studying	O
of	O
clustering	B-Algorithm
of	O
large	O
global	O
earthquakes	O
,	O
etc	O
.	O
</s>
<s>
Natural	B-General_Concept
time	I-General_Concept
analysis	I-General_Concept
has	O
been	O
initially	O
applied	O
to	O
VAN	O
method	O
in	O
order	O
to	O
improve	O
the	O
accuracy	O
of	O
the	O
estimation	O
of	O
the	O
time	O
of	O
a	O
forthcoming	O
earthquake	O
that	O
has	O
been	O
indicated	O
to	O
occur	O
by	O
seismic	O
electric	O
signals	O
(	O
SES	O
)	O
.	O
</s>
<s>
Once	O
the	O
SES	O
are	O
deemed	O
valid	O
,	O
a	O
second	O
NT	O
analysis	O
is	O
started	O
in	O
which	O
the	O
subsequent	O
seismic	O
(	O
rather	O
than	O
electric	O
)	O
events	O
are	O
noted	O
,	O
and	O
the	O
region	O
is	O
divided	O
up	O
as	O
a	O
Venn	B-Application
diagram	I-Application
with	O
at	O
least	O
two	O
seismic	O
events	O
per	O
overlapping	O
rectangle	O
.	O
</s>
<s>
Natural	B-General_Concept
time	I-General_Concept
analysis	I-General_Concept
has	O
been	O
experimentally	O
used	O
for	O
the	O
diagnosis	O
of	O
heart	O
failure	O
syndrome	O
as	O
well	O
as	O
identifying	O
patients	O
at	O
high	O
risk	O
for	O
sudden	O
cardiac	O
death	O
,	O
even	O
when	O
measuring	O
solely	O
the	O
heart	O
rate	O
,	O
either	O
using	O
electrocardiography	B-Application
or	O
far	O
more	O
inexpensive	O
and	O
portable	O
equipment	O
(	O
i.e.	O
</s>
<s>
Due	O
to	O
similarities	O
of	O
the	O
dynamic	O
characteristics	O
between	O
earthquakes	O
and	O
financial	O
markets	O
,	O
natural	B-General_Concept
time	I-General_Concept
analysis	I-General_Concept
,	O
which	O
is	O
primarily	O
used	O
in	O
seismology	O
,	O
was	O
chosen	O
to	O
assist	O
in	O
developing	O
winning	O
strategies	O
in	O
financial	O
markets	O
,	O
with	O
encouraging	O
results	O
.	O
</s>
