Measurements of Argon-39 at the U20az underground nuclear explosion site.

Pacific Northwest National Laboratory reports on the detection of 39Ar at the location of an underground nuclear explosion on the Nevada Nuclear Security Site. The presence of 39Ar was not anticipated at the outset of the experimental campaign but results from this work demonstrated that it is present, along with 37Ar and 85Kr in the subsurface at the site of an underground nuclear explosion. Our analysis showed that by using state-of-the-art technology optimized for radioargon measurements, it was difficult to distinguish 39Ar from the fission product 85Kr. Proportional counters are currently used for high-sensitivity measurement of 37Ar and 39Ar. Physical and chemical separation processes are used to separate argon from air or soil gas, yielding pure argon with contaminant gases reduced to the parts-per-million level or below. However, even with purification at these levels, the beta decay signature of 85Kr can be mistaken for that of 39Ar, and the presence of either isotope increases the measurement background level for the measurement of 37Ar. Measured values for the 39Ar measured at the site ranged from 36,000 milli- Becquerel/standard-cubic-meter-of-air (mBq/SCM) for shallow bore holes to 997,000 mBq/SCM from the rubble chimney from the underground nuclear explosion.

The potential detection of low-level aerosol isotopes from new civilian nuclear processes.

As the world faces a challenging future in maintaining the commercial availability of radioactive isotopes for medical use, new methods of medical isotope production are being pursued. Many of these are small in size and could effectively operate continuously. With the potential for much shorter retention times, a new suite of isotopes may soon be found in the environment. The authors estimate that many more aerosols containing low-level isotopes of gas/volatile origin could be detectable at short range and times, and a few at longer ranges and times as compared to those released in more common nuclear reactor operations.

First measurement of the ionization yield of nuclear recoils in liquid argon.

This Letter details a measurement of the ionization yield (Q(y)) of 6.7 keV(40)Ar atoms stopping in a liquid argon detector. The Q(y) of 3.6-6.3 detected e(-)/keV, for applied electric fields in the range 240-2130 V/cm, is encouraging for the use of this detector medium to search for the signals from hypothetical dark matter particle interactions and from coherent elastic neutrino-nucleus scattering. A significant dependence of Q(y) on the applied electric field is observed and explained in the context of ion recombination.

Expression of resistance to potato virus X in isolated potato protoplasts.

Resistance to Potato Virus X (PVX) in potato cultivars is conferred by the genes Nx and/or Nb. The Nx gene is activated by group 3 strains of PVX. When protoplasts from the cultivars King Edward containing the Nx gene and Pentland Crown containing neither resistance gene were inoculated with a group 3 strain of PVX resistance was expressed in the King Edward protoplasts. Replication of PVX occurred in King Edward protoplasts but only at a very low level as compared with the level observed in the susceptible Pentland Crown protoplasts. Similar results were obtained when protoplasts obtained from leaf discs mechanically inoculated with PVX were used. Virus levels were assayed by immunofluorescence and ELISA. Maintenance of resistance in protoplasts of King Edward following inoculation with PVX RNA was confirmed suggesting that resistance probably operates at the transcription stage in replication. These results clearly demonstrate single gene resistance in potato protoplasts inoculated with PVX.

Optimisation of conditions for infection of isolated potato protoplasts with potato virus X.

Conditions for the reproducible infection of potato protoplasts with PVX were determined. Successful virus infection was achieved when potato protoplasts at a concentration of 3 X 10(5) cells/ml were incubated with 20 micrograms/ml PVX and 2 micrograms/ml Poly-L-ornithine (MW 100,000) for 15 minutes at 0 degrees C. Numbers of protoplasts infected varied between 30 and 50 per cent. Preincubation of PVX with PLO for a minimum of 10 minutes was essential for good infection. The type and molecular weight of polycation used had a major effect on virus infection. PLO at 100,000 MW was the most efficient.