Narrow Results

Accurate quantifications of aerosol components are crucial to predict global atmospheric transport models. Recently developed International Monitoring System (IMS) network represents an opportunity to enhance comprehensive systematic aerosol observations on a global scale because it provides a global infrastructure. As such, a local pilot study utilizing several state-of-the-art instruments has been conducted at the peak of the Rattlesnake Mountain, Washington, USA, during three month periods (June-August) in 2003 to explore this opportunity. In this study, routine aerosol samples were collected using a 3-stage Cascade Impactor Beam Analyzer (0.07 to 2.5 µm) with time resolution about 6 hours on long Teflon strips while radionuclide aerosols were collected using Radionuclide aerosol sampler/analyzer (RASA) developed at Pacific Northwest National Laboratory. The elemental composition and hydrogen concentration were measured using proton induced x-ray emission (PIXE) and proton elastic scattering analysis (PESA), respectively. In addition, short and long-lived radionuclides that exist in nature were measured with same time resolution (6 hours) using RASA. In this method, high-resolution gamma-ray spectra were analyzed for radionuclide concentration. Combination of trace radioactive and non-radioactive element analysis in aerosols makes this investigation unique.

The direct detection of galactic dark matter particles requires ultra-low background conditions. NaI(Tl) crystals are applied in the search for these dark matter particles through their interactions in the detector by measuring the scintillation signal produced. The production of long-lived isotopes in materials due to the exposure to cosmic rays on Earth’s surface can be an hazard for these ultra-low background demanding experiments, typically performed underground. Therefore, production rates of cosmogenic isotopes in all the materials present in the experimental set-up, as well as the corresponding cosmic rays exposure history, must be both well-known in order to assess the relevance of this effect in the achievable sensitivity of a given experiment.

Here, analysis of the cosmogenic studies developed from the ANAIS experiment NaI(Tl) detectors are presented. Installed inside a convenient shielding at the Canfranc Underground Laboratory just after finishing surface exposure to cosmic rays and thanks to the prompt data taking developed, identification and quantification of isotopes with half-lives of the order of tens of days were allowed, and thanks to the long-term operation of the detectors long-lived isotopes have been also identified and quantified. Main results for the activation yields of iodine and tellurium isotopes, ${}^{22}$Na, ${}^{113}$Sn, ${}^{109}$Cd, and tritium are presented in this work, together with the estimate of the production rates for their activation by cosmic nucleons while on Earth’s surface based on a selection of excitation functions over the entire energy range of cosmic nucleons.

Pyropheophorbide-a and the corresponding 3-(1'-hexyloxyethyl)-3-devinyl derivative (HPPH), the tumor-avid photosensitizers were conjugated with mono- or di-bisaminoethanethiols (N₂S₂ ligand). The in vivo biodistribution study of the related ^99mTc complexes was performed in F-344 rats bearing Ward colon tumors at 4 h and 24 h post injection. These data show that the complexes are stable and among four tracers, HPPH di-^99mTc N₂S₂ conjugate reaches the highest tumor uptake (%ID/g). The larger tumors reach higher concentrations of the tracer. However, the short 6 h half life of ^99mTc is incompatible with the 24 h imaging time, suggesting that the use of a longer-lived isotope such as ¹¹¹In could still provide a useful scanning agent, or that further structure-activity screening could yield an HPPH analog with more appropriate pharmacokinetics for tumor imaging with ^99mTc.

Radioactive contamination of natural and anthropogenic landscapes has become a significant factor in radionuclide uptake by humans since 20^th century. Contamination of soils by radionuclides occurs as a result of nuclear weapon tests, major radiation accidents, waste deposition, and using phosphate fertilizers with a high content of natural radionuclides. Various methods of rehabilitation of radioactively contaminated lands, such as plowing, liming, addition of sorbents, and addition of mineral and organic fertilizers, as well as phytoremediation techniques, have been developed. Among them, elimination of the upper soil layer and phytoremediation allow decreasing the real activity of a soil but generate secondary radioactive waste, whereas the other methods are focused on suppression of radionuclide transfer from soil to plants. Plowing the upper soil layer to deeper horizons and using ferrocyanide sorbents result in the maximum decrease in radionuclide transfer to plants among the developed methods.