Results 1 - 10 of 173
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[en] We make use of the ionisation energy theory, Ramachandran interaction theory and the energy-level spacing renormalisation group technique to extend the Drude Hamiltonian to derive the Ramachandran pairing mechanism. This particular mechanism is exploited to explain the notorious discontinuous jumps in the specific heat data at critical points in both He-4 and He-3 superfluids. The well-known spin states (due to Balian–Werthamer and Anderson–Brinkman–Morel theories) and the Leggett’s spontaneously broken spin-orbit symmetry are shown to enhance Ramachandran attraction between two He-3 atoms without the need to invoke the spin-induced pairing or the phonon-mediated Cooper pairing mechanism in superconductors. In addition, we shall show physically that the spin-exchange mechanism can neither cause pairing between electrons nor between He-3 atoms. (author)
[en] The worldwide comparison of stable 15N and 13C isotope measurements provides confidence in the analytical performance of stable isotope laboratories and hence an important tool for external quality control. The 2020 Proficiency Test (PT) on 15N and 13C isotopic abundance in plant materials, organized by the University of Wageningen, the Netherlands, and funded by the SWMCN Laboratory has been successfully completed. The Wageningen Evaluating Programs for Analytical Laboratories (WEPAL, http://www.wepal.nl) is accredited for the organization of Inter-Laboratory Studies by the Dutch Accreditation Council. Every year, one FAO/IAEA 15N-enriched and three not 15N-enriched test samples are included in one round of the WEPAL IPE (International Plant-Analytical Exchange) programme. A special evaluation report for IAEA participants on the analytical performance in stable isotope analysis is issued by the SWMCN Laboratory and sent to the participants together with a certificate of participation in addition to the regular WEPAL evaluation report.
[en] The Joint Research Centre, in cooperation with the Commissariat a l'Energie Atomique et aux Energies Alternatives, produced a novel 243Am spike reference material for mass spectrometry. Americium solution with an isotopic composition of 88% 243Am and 12% 241Am was used as the source for the preparation of the spike material. The certified value of 5.696 (11) nmol g-1 for the amount content of 243Am and 0.136138 (54) for the n(241Am)/n(243Am) amount ratio were assigned. The assigned values from mass spectrometry were confirmed by alpha-particle spectrometry, alpha-particle counting at a defined solid angle, and high-resolution gamma-ray spectrometry. Furthermore, an external validation of the certified values was obtained from the results of an interlaboratory comparison exercise, using this americium reference solution as the test sample. (author)
[en] The inflow of Atlantic Water to the Arctic Ocean is a crucial determinant for the future trajectory of this ocean basin with regard to warming, loss of sea ice, and ocean acidification. Yet many details of the fate and circulation of these waters within the Arctic remain unclear. Here, we use the two long-lived anthropogenic radionuclides I and U together with two age models to constrain the pathways and circulation times of Atlantic Water in the surface (10– 35 m depth) and in the mid-depth Atlantic layer (250–800m depth). We thereby benefit from the unique time-dependent tagging of Atlantic Water by these two isotopes. In the surface layer, a binary mixing model yields tracer ages of Atlantic Water between 9–16 years in the Amundsen Basin, 12–17 years in the Fram Strait (East Greenland Current), and up to 20 years in the Canada Basin, reflecting the pathways of Atlantic Water through the Arctic and their exiting through the Fram Strait. In the mid-depth Atlantic layer (250–800 m), the transit time distribution (TTD) model yields mean ages in the central Arctic ranging between 15 and 55 years, while the mode ages representing the most probable ages of the TTD range between 3 and 30 years. The estimated mean ages are overall in good agreement with previous studies using artificial radionuclides or ventilation tracers. Although we find the overall flow to be dominated by advection, the shift in the mode age towards a younger age compared to the mean age also reflects the presence of a substantial amount of lateral mixing. For applications interested in how fast signals are transported into the Arctic’s interior, the mode age appears to be a suitable measure. The short mode ages obtained in this study suggest that changes in the properties of Atlantic Water will quickly spread through the Arctic Ocean and can lead to relatively rapid changes throughout the upper water column in future years.
[en] We would like to confirm our commitment to support our Member States in improving nutrition in these difficult times. Have a look at the suggestions for conducting IAEA nutrition studies during the COVID-19 pandemic. Mainly working from home, we continued with our activities in the second half of 2020 and conducted meetings and training workshops in a virtual format. We have discussed progress of research projects, identified new research agendas, strengthened expertise in deuterium-based isotope techniques and established new collaborations with nutrition societies. We contributed to the Micronutrient Forum 5th Global Conference CONNECTED 2020 and to the 11th Africa Day for Food and Nutrition Security. Check out new publications presenting results from different IAEA-supported projects.
[en] A comparative evaluation adsorption of 140La and 144Ce from water solutions on chemical ZnO (ZnO-C) and green synthesis ZnO (ZnO-G) by Nerium oleander flowers extract. Various parameters including pH, time and concentration were optimized to achieve maximum adsorption capacity. The adsorption efficiency of 140La and 144Ce was 59 and 69 on ZnO-G and 61 and 44% on ZnO-C respectively. Langmuir and pseudo-second order kinetic models were best suited to explain the adsorption process. The amount adsorbed of 140La and 144Ce ions at equilibrium (qe) was 23.9 and 27.8 on ZnO-G and 17.8 and 24.5 mg/g on ZnO-C respectively. (author)
[en] A primary goal of the IAEA’s activities relating to reference products for science and trade is to assist Member States in the use of stable isotope and radioisotope analytical techniques to understand, monitor and protect the environment. Through its Environment Laboratories, the IAEA provides reference materials to laboratories as a key measure for calibration and quality assurance worldwide. The Terrestrial Environment Laboratory, part of the IAEA Environment Laboratories, provides assistance to Member State laboratories in maintaining and improving the reliability of analytical measurement results, in carrying out stable isotope analysis, and in assessing environmental level radionuclides and trace elements. In the field of stable isotope ratio analysis, the Terrestrial Environment Laboratory provides more than forty different reference materials for various applications covering mainly the stable isotopes of hydrogen, carbon, nitrogen, oxygen and sulphur. In all ecosystems, water supports all life functions. Understanding the details of its origin, availability, behaviour and movement is of the utmost importance for understanding these ecosystems . The use of stable isotopes as tracers of water origin and of its possible vulnerability to pollution is of primary importance for many scientific studies. The reliability and comparability of the analyses performed by laboratories in this context are crucial for a meaningful interpretation of any sample data, for management of the environment, and for taking decisions on policy or at an administrative level. Comparability of measurement results can be achieved only when the results are traceable to conventionally agreed standards, such as to the established δ-value scales and the corresponding reference materials for relative stable isotope ratio measurements. The IAEA has supported such scientific investigations since the 1960s by providing basic support through analytical networks like the Global Network of Isotopes in Precipitation and associated databases, and in its international role of providing reference materials for stable isotope measurement and calibration in laboratories worldwide. As custodian of the isotope measurement scales and their realization by primary reference materials, the IAEA has a fundamental role in the application of such methods worldwide. The two most important reference materials produced by the IAEA are VSMOW2 (Vienna Standard Mean Ocean Water 2) and SLAP2 (Standard Light Antarctic Precipitation 2), which are used to realize the δ-value scales. Further quality control materials are used by laboratories to verify proper calibration with these two materials. This publication describes the production of the certified reference material GRESP (Greenland Summit Precipitation) for use as a quality control material. The reference material GRESP was produced following the applicable international ISO standards and characterized by laboratories with demonstrated competence.
[en] An analysis of natural radioactivity in soils collected around Chinese Nuclear Test site is presented. The radioactivities of 238U, 226Ra, 232Th, 40K, and 137Cs were determined by HPGe gamma-ray spectrometry, and potential radiological hazards were evaluated. The depth profiles of radionuclides in three selected areas of Gansu were analyzed, and a new method for detection of 137Cs specific activities were measured using ultra-low background gamma spectrometer named GeTHU-II developed by Tsinghua University at China Jinping Underground Laboratory. The radioactivity concentrations of 137Cs were significantly different in these three areas and gradually decreased from surface to underground 15 cm. (author)
[en] Production of different Radioisotopes i.e. Mo-99, Mo-99/Tc-99m generators, I-131 , P-32, Lu-177, Au-198 etc, diagnostic cold kits MIBI, MDP, DTPA, and adenosine injection (for different body organ imaging) as well as research and development is carried out at Isotopes Production Division (IPD) at PINSTECH. Pakistan has a population of ~200 Million and the number of nuclear medical centres practicing nuclear medicine are more than 36, in which 18 belongs to Pakistan Atomic Energy Commission (PAEC), and other belongs to private entities, whereas some more are expected to function in the coming years. The big cities like Karachi and Lahore, as well as capital city of Islamabad, has most of these nuclear medical centres. More than 500,000 patients are treated each year in PAEC Nuclear Medical Centres. Molybdenum-99 (Half-Life: 66 hours) is used to manufacture Technetium- 99m generators, the most widely used isotope in Nuclear Medicine. Its short half-life of six hours and the energy emitted (140 keV) makes it an ideal imaging agent. The Isotope Production Division is producing molybdenum- 99 weekly for manufacturing of PAKGEN 99Mo/99mTc generators in Mo-99 Loading Facility at PINSTECH, Islamabad. PAKGEN 99Mo/99mTc generators and I-131 supplied to all medical centres throughout Pakistan on weekly basis. These Radioisotopes are being produced in Pakistan Research Reacor-1. IPD/PINSTECH also producing diagnostic cold kits for different body organs imaging. These products are produced under Good Manufacturing Practices (GMP) and pass through strict quality control as laid down in the European Pharmacopeia and IAEA guides. All the IPD laboratories are ISO 9001-2015 certified and are licensed by PNRA. The division also holds Drug Manufacturer Registration of the Government of Pakistan. (author)
[en] The aim of this study is to determine activity concentrations of natural radionuclides (226Ra, 232Th, 40K and 222Rn) and radiological risks due to the contamination of radionuclides in surface soil in Ho Chi Minh City, Vietnam. Based on the activity concentration of 226Ra in the surface soil, we proposed a method for estimation of the radon concentration in the indoor air. The assessments of radiation dose and excess lifetime cancer risk show that the utilization of surface soils for human residences or routine activities in the studied area poses no risk to the public health. (author)