Environmental radionuclide monitoring of Canadian harbours: a decade of analyses in support of due diligence activities by the Royal Canadian Navy.

The Royal Canadian Navy has conducted a comprehensive programme of safety, security and environmental monitoring since the first visits of nuclear powered and nuclear capable vessels (NPV/NCVs) to Canadian harbours in the late 1960s. The outcomes of baseline monitoring and vessel visit sampling for the period 2003-2012 are described for vessel visits to Halifax (NS), Esquimalt (BC) and Nanoose (BC). Data were obtained by gamma-ray spectroscopy using high purity germanium detectors. No evidence was found for the release of radioactive fission or activation products by NCV/NPVs during the study period, although anthropogenically produced radionuclides were observed as part of the study's baseline monitoring. Background activities of Cs-137 can be observed in sediments from all three locations which are derived from well-documented radioactivity releases. The detection of I-131 in aquatic plants is consistently observed in Halifax at activities as high as 15,000 Bq kg(-1) dry weight. These data are tentatively assigned to the release of medical I-131, followed by bioaccumulation from seawater. I-131 was also observed in aquatic plants samples from Esquimalt (33 Bq kg(-1)) and Nanoose (20 Bq kg(-1)) for a single sampling following the Fukushima Daiichi accident.

Validation of an inductively coupled plasma mass spectrometry (ICP-MS) method for the determination of cerium, strontium, and titanium in ceramic materials used in radiological dispersal devices (RDDs).

In radiological dispersal device (RDD) studies, sintered ceramics made of CeO2 and SrTiO3 were used to simulate actinide oxides and (90)SrTiO3, respectively. Instrumental neutron activation analysis (INAA), inductively coupled plasma optical emission spectroscopy (ICP-OES), and inductively coupled plasma mass spectrometry (ICP-MS) were investigated as possible analytical techniques for the measurement of SrTiO3 and CeO2 constituents in powder forms, sintered ceramics, and air particulates collected following a detonation. For ICP-OES and ICP-MS analysis, new digestion procedures were developed using a closed-vessel microwave apparatus. Acid mixtures (HNO3:H2O2:HF (16:2:1) and HNO3:H2O2 (1:4)) were found to be effective for the digestion of SrTiO3 and CeO2, respectively. The intercomparison study confirmed that the results obtained by ICP-OES/MS are in good agreement with INAA results. This also confirms the efficiency of the digestion procedures for these refractory materials and the inter-exchangeability of the instrumentation tested. Comparison between the ICP-OES and the ICP-MS instrumentation for the determination of air particulates shows, that although the two methods are equivalent, ICP-MS provides better detection limits (0.11, 0.02, and 0.04 microg per filter for Ti, Sr, and Ce, respectively) and the possibility to determine isotopic fractionation as the result of an explosion.

The role of disulfide bonds in the structure and function of murine epidermal growth factor (mEGF).

A systematic study using solid phase peptide synthesis has been undertaken to examine the role of the disulfide bonds in the structure and function of mEGF. A combination of one, two and three native disulfide pair analogues of an active truncated (4-48) form of mEGF have been synthesised by replacing specific cysteine residues with isosteric a-amino-n-butyric acid (Abu). Oxidation of the peptides was performed using either conventional aerobic oxidation at basic pH, in DMSO under acidic conditions or via selective disulfide formation using orthogonal protection of the cysteine pairs. The contribution of individual, or pairs of, disulfide bonds to EGF structure was evaluated by CD and (1)H-NMR spectroscopy. The mitogenic activity of each analogue was determined using Balb/c 3T3 mouse fibroblastsAs we have reported previously (Barnham et al. 1998), the disulfide bond between residues 6 and 20 can be removed with significant retention of biological activity (EC50 20-50 nM). The overall structure of this analogue was similar to that of native mEGF, indicating that the loss of the 6-20 disulfide bridge did not affect the global fold of the molecule. We now show that removal of any other disulfide bond, either singly or in pairs, results in a major disruption of the tertiary structure, and a large loss of activity (EC50>900 nM). Remarkably, the linear analogue appears to have greater activity (EC50 580 nM) than most one and two disulfide bond analogues although it does not have a definable tertiary structure.