20-minute background counts were taken during a 24-hour period.
From November 24 to the end of December,
were made with counter No.
127 background counts
185, and the mean value was 50.25
c/m with a standard deviation of 2.63; for the other counter,
No. 184, 135 background counts were made during the same perjod with a mean value of 53.51 c/m and a standard deviation of
3.84.
These background values are less than those recorded in
the 1949 report because the counting chambers are now shielded
with two inches of lead.
Decay.
At the time of counting,
were decaying at an appreciable rate.
were corrected for decay and the date
the post test samples
Therefore these samples
to which they were cor-
rected arbitrarily chosen as December 1,
one month after the
Mike test and &lso near the mid-point of the counting period
for these samples.
Although the activity of the samples is
corrected to that of December 1,
the distribution of activity
is that of the date of collection, November 2 to 10.
In the
period immediately following the shot the activity in the organisms would be expected to vary greatly within short periods,
due to changes
in geographical distribution of the radioactive
materials and to length of time of exposure of the organisms.
The curve from which the correction factors were determined was the decay curve for a sand sample that had been
dredged from Rojoa and Aaraanbiru on November 7 at a depth of
30 feet. The principal reason for selecting this curve was that,
by inspection, the "composite" of 91 decay curves from various
types of organisms and tissues closely resembled the sand
- 13 .
OoMe Hives