This paper considers the distribution of technogenic
137
Cs and naturally occurring radionuclides:
238
U,
232
Th and
40
К concentrations in soils and
137
Cs in atmospheric dry depositions by ...altitudinal belts of the Aragats mountain massif, Republic of Armenia. Undisturbed soil samples were collected at altitudes from 1000 to 3200 m. For the determination of geochemical variability, two soil sampling campaigns were undertaken. Atmospheric dry depositions were sampled from five stations at 1100–3200 m collected onto organic fiber filters between June and December 2016.
137
Cs activity was measured using a high-purity Germanium detector coupled to a multichannel analyzer (Canberra). Results indicated that specific activity of
137
Cs in soils at 1000 m is 495–528 Bq m
−2
, and at 3200 m is 10,500–11,470 Bq m
−2
. No correlation observed for
137
Cs versus naturally occurring radionuclides, which varies in distribution by altitude. Specific activities of
137
Cs in dry atmospheric depositions varies from 1.06 at 846 m to 2.37 Bq m
−2
per quarter at 3200 m and increases as the altitude increases. Activities of
137
Cs in soil and dry atmospheric deposition correlated significantly, and
137
Cs activity in soils and atmospheric dry depositions decrease as the absolute altitude decreases. The 50-year effective dose from exposure to
137
Cs fallout varies with altitude from 0.007 to 1.42 mSv.
New determination of the 229Th half-life Essex, Richard M.; Mann, Jacqueline L.; Collé, Ronald ...
Journal of radioanalytical and nuclear chemistry,
2018/10, Letnik:
318, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A new determination of the
229
Th half-life was made based on measurements of the
229
Th massic activity of a high-purity solution for which the
229
Th molality had previously been measured. The
229
...Th massic activity was measured by direct comparison with SRM 4328C using 4παβ liquid scintillation counting, NaI counting, and standard addition liquid scintillation counting. The massic activity was confirmed by isotope dilution alpha spectrometry measurements. The calculated
229
Th half-life is (7825 ± 87) years (
k
= 2), which is shorter than the three most recent half-life determinations but is consistent with these values within uncertainties.
Nuclear forensics is a multidisciplinary science that uses a variety of analytical methods and tools to explore the physical, chemical, and isotopic characteristics of nuclear and radiological ...materials. These characteristics, when evaluated alone or in combination, become signatures that may reveal how and when the material was fabricated. The signatures contained in samples of dirt collected at two different uranium metal processing facilities in the United States were evaluated to determine uranium isotopic composition and compare results with processes that were conducted at these sites. One site refined uranium and fabricated uranium metal ingots for fuel and targets and the other site rolled hot forged uranium and other metals into dimensional rods. Unique signatures were found that are consistent with the activities and processes conducted at each facility and establish confidence in using these characteristics to reveal the provenance of other materials that exhibit similar signatures.
Neurodegenerative processes associated with Alzheimer’s disease (AD) are accompanied by reactive astrogliosis and microglia activation and a role for chronic inflammation in the brain degeneration of ...these patients has been suggested. Moreover impaired immune functions in AD brains might also influence the disease’s progression. Therefore, it is of interest to further characterized inflammatory molecules in the peripheral blood of patients with AD and its relationship with cognitive decline. A complex picture emerged in this pilot study and IL-8, IFN-gamma, MCP-1 and VEGF levels were increased in AD. Levels of P-selectin and L-selectin were decreased in AD and lowest in AD patients with highest cognitive decline. Our findings suggest that these molecules may induce alterations of endothelial regulation and influence neurodegenerative processes of AD.
MARC IX Introduction LaMont, Stephen P.; Glover, Samuel E.
Journal of radioanalytical and nuclear chemistry,
04/2013, Letnik:
296, Številka:
1
Journal Article
Radiological chronometry of uranium metal samples Meyers, Lisa A.; Glover, Samuel E.; LaMont, Stephen P. ...
Journal of radioanalytical and nuclear chemistry,
03/2014, Letnik:
299, Številka:
3
Journal Article
Recenzirano
Radiological chronometry is an important tool in nuclear forensics that uses several methods to determine the length of time that has elapsed since a material was last purified. One of the ...chronometers used in determining the age of metallic uranium involves measuring the fractional ingrowth of
230
Th from its parent
234
U with the assumption that the uranium metal contained no impurities, especially thorium, when it was purified. The affects of different etching procedures were evaluated for the removal of surface oxidation with three different types of uranium metal samples to determine whether the etching procedure affects the radiological age. The sample treated with a rigorous etching procedure had exhibited the most reliable radiological age while less rigorous etching yields a radiological age from 15 years to hundreds of years older than the known age. Any excess thorium on the surface of a uranium metal sample presents a bias in age determination and the sample will appear older than the true age. Although this research demonstrates the need for rigorous surface etching, a bias in the radiological age could have arisen if the uranium in the metal was heterogeneously distributed.
A piece of scrap uranium metal bar buried in the dirt floor of an old, abandoned metal rolling mill was analyzed using multi-collector inductively coupled plasma mass spectroscopy (MC-ICP-MS). The ...mill rolled uranium rods in the 1940 and 1950s. Samples of the contaminated dirt in which the bar was buried were also analyzed. The isotopic composition of uranium in the bar and dirt samples were both the same as natural uranium, though a few samples of dirt also contained recycled uranium; likely a result of contamination with other material rolled at the mill. The time elapsed since the uranium metal bar was last purified can be determined by the in-growth of the isotope
230
Th from the decay of
234
U, assuming that only uranium isotopes were present in the bar after purification. The age of the metal bar was determined to be 61 years at the time of this analysis and corresponds to a purification date of July 1950 ± 1.5 years.
In the framework of a collaboration between laboratories involved in bulk U and Pu analysis of environmental samples (DIF centre of the French Commissariat à l’Energie Atomique, US National ...Laboratories of New Brunswick, Lawrence Livermore, Pacific Northwest, Oak Ridge, and Los Alamos), two round-robins were organised, each one consisting of the complete analysis (chemical preparation and isotope measurement) of three Quality Control samples. The samples were 10 × 10 cm cotton tissues (“swipe samples”) containing low amounts of U (from ~20 to ~150 ng) and Pu (from ~0.15 to ~10 pg). Despite using different spikes, different methods of sample preparation and different analytical instrumentation, the results for U and Pu contents and isotopic compositions reported by all laboratories are globally in good agreement. All laboratories are able to measure sub-pg amounts of U and Pu isotopes with acceptable accuracy and reproducibility, even if limited discrepancies are observed affecting one or other measurement and/or laboratory. General and laboratory specific recommendations were discussed and adopted to continue to improve the accuracy and precision of the measurements.
The dissolution rate of a material in the lung is an important parameter in evaluating the risk to humans following accidental inhalation of a substance and is also a parameter that may be useful in ...characterizing particles for nuclear forensics analysis. Conventional methods of measuring dissolution rates in vitro involve exposing the material or particles to a solvent, such as water, saline, or solutions that simulate lung fluid, and measuring the fraction of material that dissolves with time. A new device for measuring dissolution rates for small samples, especially individual particles, was evaluated that incorporates a regenerated cellulose dialysis membrane fixed to the bottom of a small, 2 mL plastic cup that fits into the top of a 50 mL plastic centrifuge tube. The cup is easily transferred among a series of tubes containing solvent to measure rate of dissolution. The dialysis membrane has a diffusion rating of 20 kDa molecular weight cut off which greatly exceeds the size of the dissolved uranium molecule. The performance of the dialysis cup device was evaluated by measuring the dissolution rate of uranyl acetate in distilled water, phosphate buffered saline (PBS), and simulated lung fluid (SLF). These results were compared to the dissolution rate measured using the traditional filter sandwich method in which a sample is sealed between two hydrophilic membranes. Although the majority of uranyl acetate dissolved in SLF within 30 min using the filter sandwich method, most of the uranyl acetate was undissolved in PBS and SLF using the dialysis membrane device. Reactions between the dissolved uranyl acetate, solvent, and the dialysis membrane likely caused the membrane to swell, shrinking the pore size, and thus reducing the transport of dissolved uranium across the membrane. Use of the dialysis cup device for evaluating dissolution rates for uranium-bearing materials in solvents containing a high concentration of salts is therefore not recommended.
Background: Proteomics' requirement for simultaneous measurement of multiple markers is now possible with biochip array technology. Many laboratories utilise in-house, manual procedures for biochip ...fabrication and sample testing. Reproducibility and standardisation of biochip processes is vital to ensure quality of results and offer the best tool for elucidation of complex relationships between multiple proteins in diseased conditions. Methods: Various novel control checks have been implemented in biochip fabrication, reagent manufacture, automation and imaging processes for the Evidence analyser. Reference spots enable location of discrete test regions on the surface of the biochip and simultaneous quantification of multiple markers. Performance and standardisation methods are presented. Results: Formulation of dispense solution for discrete test regions had a direct effect on their shape, stability and integrity on the biochip surface. Assays for fertility hormones and drugs of abuse demonstrated excellent precision, stability and comparison with other commercial methods. Conclusion: Control processes employed in the manufacture and analysis of Evidence components ensure reproducibility of assays for a range of routine and novel markers.
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