Isotopic Mixtures Research Articles

Визначення дезактивуючих властивостей шампунів до цезію, стронцію та кобальту

The decontamination properties of shampoos for cesium, strontium, and cobalt were determined. The method has been developed for determining the decontaminating properties of shampoos. The chemical part of the study includes the preparation of hair, which consists of forced pollution and subsequent washing. Stable isotopes were used in the work. This has increased the safety of staff during chemical hair research. The analytical part includes the quantitative determination of the cesium, strontium, and cobalt in the hair, which was carried out by the Particle-Induced X-ray Emission (PIXE) method using the analytical nuclear-physical complex "Sokol". Various shampoos were analyzed, and their decontamination properties were determined. During the research, various samples of shampoos, which are presented on the market of Ukraine, were considered. It has been established that TM "Ringo" shampoo has the best deactivating properties for cesium (Kd - 574.0) and insignificant deactivating properties for strontium (Kd - 3.1) and cobalt (Kd - 3.6). It was determined that with multi-isotope contamination (a mixture of cesium, strontium, and cobalt isotopes) decrease in the deactivation coefficient for all isotopes was observed, which is due to the competition factor of the isotopes in the complexation process with shampoo. Reduction of decontaminating properties was observed on all samples of shampoos.

Visualizing Lithium Ion Transport in Solid‐State Li–S Batteries Using 6Li Contrast Enhanced Neutron Imaging

AbstractThe elucidation of lithium ion transport pathways through a solid electrolyte separator is a vital step toward development of reliable, functional all‐solid‐state batteries. Here, advantage has been taken of the significantly higher neutron attenuation coefficient of one of the most abundant stable isotopes of lithium, 6Li, with respect to that of naturally occurring lithium isotope mixture, to perform neutron imaging on a purpose built all‐solid‐state lithium–sulfur battery. Increasing the 6Li content in the anode while using natural lithium in the solid electrolyte separator and the cathode enhances the contrast such that it is possible to differentiate, during the initial discharge, between the mobile lithium ions diffusing through the cell from the anode and those that are initially located in the solid electrolyte. The sensitivity of neutrons to the different lithium isotopes means that operando neutron radiography allows demonstration of the lithium ion diffusion through the cell while in situ neutron tomography has permitted presentation, in three dimensions, of the distribution of the trapped lithium ions inside the cell in charged and discharged states.

Source analysis of metals in the tea plant using linear correlation analysis combined with a lead-strontium isotope tracer

Many studies have focused on the concentrations of heavy metals (HMs) in Tieguanyin tea plants and surrounding soil; however, limited information is available on the specific sources of HMs in tea plantation trees. In this study, HMs in tea plants (roots, stems, old leaves, and young leaves) from Anxi County of the Fujian Province were determined by inductively coupled plasma mass spectrometry (ICP-MS). Additionally, correlation analysis, principal component analysis (PCA), and isotope tracers were used to analyze the sources of HMs pollution. The contribution rate of HMs in tea from different specific sources was further quantified by establishing a relative isotope mixing model. Our results showed that the highest Pb content in the roots was 23.89 μg·g−1 and was positively correlated with Sr and Ni in the roots, indicating that these three metals in the roots are from the same source, mainly from the soil. PCA analysis showed that Sr and Pb in factor 1 have higher positive charges in the young leaves, and their contribution rate was 27.16%. Sr is commonly used in the cement industry, indicating that factor 1 was mainly affected by industrial activities. The Pb and Sr isotope ratio showed that the average values of 208Pb/206Pb and 206Pb/207Pb in young leaves were 2.1124 and 1.1619, respectively, while the average values of 87Sr/86Sr in young leaves was 0.709774. The contribution rate of each potential source was quantitatively analyzed using the Pb-Sr multiple isotope mixture model, and agricultural activities were found to be the biggest contributors of HMs in tea. For example, agricultural sources of HMs found in old leaves and young leaves were 62% and 31%, respectively. Using multivariate statistical analysis methods combined with isotope tracing techniques, this study was able to identify sources of multiple heavy metals in Tieguanyin tea plants.

Cavitation generated by vibrating quartz tuning fork in concentrated 3He–4He mixture

The state of the problem of cavitation in superfluid helium and the content of previous works on this topic are analyzed. The transition between turbulent flow and cavitation under oscillations of a quartz tuning fork in a normal and superfluid isotopic mixture containing 15% of 3He in the temperature range of 0.5–3 K is studied experimentally. The temperature dependences of the critical velocity for the cavitation onset and the critical transition excitation force are obtained. We compare the results of our measurements with the data obtained by other groups. The results of measurements with tuning forks in restricted and unrestricted geometries suggest that the presence of acoustic emission facilitates the conditions for the onset of cavitation and indirectly confirms the role of vortex lines. A comparison of the temperature dependences of the critical velocity of cavitation onset in pure 4He and a concentrated 3He–4He mixture did not give an unambiguous answer to the reason for the sharp increase of this velocity, at the transition to the superfluid state, and the contributions of both thermal effects and the 3He impurities to the velocity increase.

Isotopic Creation of New Materials

Most of the physical properties of substances depend to a greater or lesser on isotopic composition. 95% or more of substances are mixture of different isotopes. We analyze and overview the main characteristics of the new isotope - based materials. Mainly the results of isotope - substituted substances based on lithium hydride and carbon are used. LiH has the largest isotopic shift. Carbon, being the second element after silicon on Earth, has unusually wide range of allotropic compounds with completely different physical properties that a highly dependent on isotopic composition. The use of our object allows the investigation of not only the isotope effects in lattice dynamics (vibrational, elastic and thermal properties), but also the influence of such effects on the electronic excitations (for example, the renormalization of the band - to - band transition energy Eg). We emphasize that the study of the isotope effect remains at the forefront not only in materials science, but also nuclear and high energy physics. The latter one is associated with the non - accelerating manifestation of strong nuclear interaction as well as the origin of mass in Nature.

Phonon transition across an isotopic interface

Isotopic mixtures result in distinct properties of materials such as thermal conductivity and nuclear process. However, the knowledge of isotopic interface remains largely unexplored mainly due to the challenges in atomic-scale isotopic identification. Here, using electron energy-loss spectroscopy in a scanning transmission electron microscope, we reveal momentum-transfer-dependent phonon behavior at the h−10BN/h-11BN isotope heterostructure with sub-unit-cell resolution. We find the phonons’ energy changes gradually across the interface, featuring a wide transition regime. Phonons near the Brillouin zone center have a transition regime of ~3.34 nm, whereas phonons at the Brillouin zone boundary have a transition regime of ~1.66 nm. We propose that the isotope-induced charge effect at the interface accounts for the distinct delocalization behavior. Moreover, the variation of phonon energy between atom layers near the interface depends on both of momentum transfer and mass change. This study provides new insights into the isotopic effects in natural materials.

Startup methods analysis of a cryogenic distillation system with two interlinked columns for hydrogen isotope separation

Effective startup methods are crucial for the successful operation of a distillation facility. In order to design a viable startup method for a cryogenic distillation demonstration system with two interlinked columns for hydrogen isotope separation, which is under construction at Institute of Materials, China Academy of Engineering Physics, Aspen Plus and Aspen Dynamics were employed in combination to generate a dynamic numerical model for the startup analysis. Total four conventional startup methods were analysed. The most time-effective method was identified and the other of the four startup methods were found to be able to lead to successful startup results but with varied operation complexity and length of time to reach the steady state. The effective startup method that involved in charging the two distillation columns with equilibrated hydrogen isotope mixtures respectively, took only 50.36 h to reach the target steady state. And the identified method would be employed into the cryogenic distillation demonstration system to check its startup efficient.

Trophic niche and potential carbon source of three reef-associated fishes of Zhongjieshan Islands.

To clarify the trophic relationship of important rock fishes, we analyzed trophic niche of three typical rockfish species (Oplegnathus fasciatus, Sebastiscus marmoratus and Conger myriaster) in the Zhongjieshan Islands in summer 2020, based on the carbon and nitrogen stable isotope techniques. We calculated the contributions of major carbon sources [macroalgae, phytoplankton, suspended particulate organic matter (POM) and substrate organic matter (SOM)]. The results showed that: 1) the δ13C values of the three species ranged from -21.44‰ to -15.21‰, with an average value of (-16.85±1.12)‰, while the δ15N values ranged from 8.32‰ to 10.96‰, with an average value of (9.69±0.66)‰. There were significant differences in carbon and nitrogen stable isotopes among the three species. 2) There was small niche overlap between O. fasciatus and S. marmoratus, indicating that the interspecific competition was not intense. There was no overlap between C. myriaster and the first two, indicating feeding differentiation. 3) The total ecotone area, corrected core ecotone area, and food source diversity of C. myriaster were the highest, indicating that it had a more generalized diet and richer food sources. 4) With Mytilus coruscus as a baseline organism, the trophic level of C. myriaster was the highest (3.38), followed by S. marmoratus (3.09), and the trophic level of O. fasciatus was the smallest (3.00). 5) Results of the stable isotope mixture model (SIAR) showed that POM was the main carbon source of the three species, contributing 57.4%, 57.9%, and 92.0% of the total, respectively. In addition, the contribution rate of SOM was also high for O. fasciatus and S. marmoratus, which was 21.5% and 33.9%, respectively. This study could provide basic information and reference for understanding trophic structure and marine food web in Zhongjiashan Islands.

The role of isotope mass and transport for H-mode access in tritium containing plasmas at JET with ITER-like wall

The required heating power, , to access the high confinement regime (H-mode) in tritium containing plasmas is investigated in JET with ITER-like wall at a toroidal magnetic field of T and a plasma current of MA. , also referred to as the L-H power threshold, is determined in plasmas of pure tritium as well as mixtures of hydrogen with tritium (H-T) and mixtures of deuterium with tritium (D-T), and is compared to the L-H power threshold in plasmas of pure hydrogen and pure deuterium. It is found that, for otherwise constant parameters, is not the same in plasmas with the same effective isotope mass, , when they differ in their isotope composition. Thus, is not sufficient to describe the isotope effect of in a consistent manner for all considered isotopes and isotope mixtures. The electron temperature profiles measured at the L-H transition in the outer half of the radius are very similar for all isotopes and isotope mixtures, despite the fact that the L-H power threshold varies by a factor of about six. This finding, together with the observation of an offset linear relation between the L-H power threshold, , and an effective heat diffusivity, , indicates that the composition-dependent heat transport in the low confinement mode (L-mode) determines, how much power is needed to reach the necessary electron temperatures at the edge, and hence .

Enhance Hydrogen Isotopes Separation by Alkali Earth Metal Dopant in Metal-Organic Framework.

Kinetic quantum sieving (KQS) based on pore size and chemical affinity quantum sieving (CAQS) based on adsorption site are two routes of porous materials to separate hydrogen isotope mixtures. Alkali earth metals (Be, Mg, and Ca) were doped into UiO-67 to explore whether these metal sites can promote H2/D2 separation. Based on the zero-point energy and adsorption enthalpy calculated by density functional theory calculations, the Be dopant shows better H2/D2 separation performance than other alkali earth metal dopants and unsaturated metal sites in metal-organic frameworks based on CAQS. Orbital interaction strongly relates to the chemical affinity and further influences the D2/H2 selectivity. Moreover, the predicted D2/H2 selectivity of Be-doped sites (49.4) at 77 K is even larger than the best experimental result (26). Finally, the different dynamic behaviors of H2 and D2 on Be-doped UiO-67 indicate its strong H2/D2 separation performance via KQS.

Parameters of the UNIQUAC model for describing the vapor-liquid phase equilibrium of D<sub>2</sub>-T<sub>2</sub>, D<sub>2</sub>-DT, DT-T<sub>2</sub> hydrogen isotope mixtures

Objectives. Determination of the parameters of the binary energy interaction of the (UNIversal QUAsiChemical) UNIQUAC model on the basis of mathematical processing of experimental literature data on the phase equilibrium of hydrogen isotopic mixtures D2-T2, D2-DT, DT-T2 to calculate the activity coefficients of the components D2, DT, and T2.Methods. The method of successive approximations was used in junction with the “from stage to stage” method, which consists in calculating a single evaporation process on a theoretical plate.Results. Equations were written for calculating the activity coefficients of hydrogen isotopes on the basis of the Sherwood theory as applied to binary D2-T2, D2-DT, DT-T2 and ternary D2-DT-T2 hydrogen isotope mixtures. The graphical dependences of the activity coefficients and separation coefficients of mixtures D2-T2, D2-DT, and DT-T2 are compared in the range of the concentration of a highly volatile component from 0 to 100 mol % at atmospheric pressure for three options: ideal mixtures; non-ideal mixtures using the Sherwood theory; non-ideal mixtures on the basis of the UNIQUAC model. The dependences of the separation coefficients a were found to be similar for all binary isotopic mixtures. However, when considering mixtures as ideal, a increases.According to Sherwood's theory, a remains a practically constant value, which is independent of the composition of the mixture. The UNIQUAC model predicts a decrease in a with an increase in the concentration of a less volatile component in the mixture. The profile of the distribution of hydrogen isotopes D2, DT, and T2 of a three-component mixture D2-DT-T2, along the height of a distillation column operating in a closed mode was calculated for three variants. It was accepted that: pressure along the height of the column is constant and equal to atmospheric 760 mm Hg. Art.; number of theoretical plates 21; concentration of components in the liquid phase on the first plate (stage), in mol %: XD₂ = 65; XDT= 10; XT₂= 25; the accuracy of calculating the composition of the vapor phase is 10-10.Conclusions. The parameters of the binary energy interaction of the UNIQUAC model of hydrogen isotopic mixtures D2-T2, D2-DT, and DT-T2 are determined. The UNIQUAC model is adequate in relation to experimental data on the coefficient of separation. Due to systematic deviations in the theoretical Sherwood and ideal models, they are not suitable for further calculations of phase equilibrium of isotopic mixtures of hydrogen D2-T2, D2-DT, DT-T2, and D2-DT-T2.

Highly Effective H2/D2 Separation within the Stable Cu(I)Cu(II)-BTC: The Effect of Cu(I) Structure on Quantum Sieving.

Realizing ideal deuterium separation from isotopic mixtures remains a daunting challenge because of their almost identical sizes, shapes, and physicochemical properties. Using the quantum sieving effect in porous materials with suitable pore size and open metal sites (OMSs) enables efficient hydrogen isotope separation. Herein, synthetic HKUST-1-derived microporous mixed-valence Cu(I)Cu(II)-BTC (BTC = benzene-1,3,5-tricarboxylate), featuring a unique network of distinct Cu(I) and Cu(II) coordination sites, can remarkably boost the D2/H2 isotope separation, which has a high selectivity (SD2/H2) of 37.9 at 30 K, in comparison with HKUST-1 and other porous materials. Density functional theory (DFT) calculations indicate that the introduction of Cu(I) macrocycles in the framework decreases the pore size and further leads to relatively enhanced interaction of H2/D2 molecules on Cu(II) sites. The significantly enhanced selectivity of Cu(I)Cu(II)-BTC at 30 K can be mainly attributed to the synergistic effect of kinetic quantum sieving (KQS) and chemical affinity quantum sieving (CAQS). The results reveal that Cu(I) OMSs exhibit counterintuitive behaviors and play a crucial role in tuning quantum sieving without a complex structural design, which provides a deeper insight into quantum sieving mechanisms and a new strategy for the intelligent design of highly efficient isotope systems.

Vibrational spectroscopies in liquid water: on temperature and coordination effects in Raman and infrared spectroscopies

Water is an ubiquitous liquid that has several exotic and anomalous properties. Despite its apparent simple chemical formula, its capability of forming a dynamic network of hydrogen bonds leads to a rich variety of physics. Here we study the vibrations of water using molecular dynamics simulations, mainly concentrating on the Raman and infrared spectroscopic signatures. We investigate the consequences of the temperature on the vibrational frequencies, and we enter the details of the hydrogen bonding coordination by using restrained simulations in order to gain quantitative insight on the dependence of the frequencies on the neighbouring molecules. Further we consider the differences due to the different methods of solving the electronic structure to evaluate the forces on the ions, and report results on the angular correlations, isotopic mixtures HOD in H2O/D2O and and the dielectric constants in water.

Anomalously supercooled H2-D2 mixtures flowing inside a carbon nano tube.

H2 and D2 molecules condensed in a carbon nano tube (CNT) and their nonequilibrium flow through nano pores offer a key test to reveal mass molecular transport and separation of purely isotopic molecules that possess the same electronic potential but a two-times difference in mass inducing differently enhanced nuclear quantum effects (NQEs) such as nuclear delocalization and zero-point energy. Taking advantage of the non-empirical quantum molecular dynamics method developed for condensed H2-D2 molecules that can describe various kinds of condensed phases and thermodynamic states including uneven density and a shear flow, we investigated condensed isotopic H2-D2 mixtures flowing inside nanoscale adsorbable CNTs. We found that, in any mixture, the more delocalized H2 molecules are more supercooled than the less delocalized D2 molecules in a two-dimensional liquid film adsorbed around the CNT well, and that the stronger supercooling of the H2 molecules than the D2 molecules in an equilibrium state becomes more enhanced under the nonequilibrium flow due to the isotope-dependent flow-induced condensation, demonstrating the anomalous condensed-phase quantum sieving under the nonequilibrium flow and its dependence on the mixing ratio and temperature. The differently enhanced NQEs of the purely isotopic molecules essentially influence the condensed adsorption and their flows occurring in the nanoscale CNT, which should be distinguished from a dilute gas adsorption. The predicted properties and obtained physical insights in this paper will help in experimentally controlling condensed H2-D2 mixtures, and open a new strategy and innovative design of nanoporous materials for adsorptive separation of condensed-phase mixtures under a nonequilibrium flow not of a dilute gas mixture in an equilibrium state.

Determination of the isotopic composition of copper in a certified reference material HICU-1 by MC-ICP-MS using gravimetric isotope mixture calibration

An independent and fully calibrated copper isotope ratio measurement of a high-purity copper certified reference material, HICU-1, was achieved by MC-ICP-MS with use of gravimetric isotope mixture calibration.

Regenerative fission chambers with low variation of sensitivity for high fluence incore measurements

Fission chambers are widely used for online neutron flux monitoring in nuclear reactors. However, the depletion of the fissile deposit of the fission chamber with irradiation limits the life duration of the detector when used in a permanent incore location within the vessel of a power reactor. The addition of a fertile material has been considered, at the cost of yielding a non-monotonous evolution of the sensitivity which could be difficult to distinguish from a genuine flux evolution.In this paper, our goal is to find, for a given neutron flux, a feasible mixture of fissile and fertile isotopes to obtain the more stable sensitivity over a high fluence. We devise a methodology based on the DARWIN suite with no simplification of the evolution chains of isotopes and applicable to any neutron flux. All the isotopes that are routinely used in fission chambers are investigated. It is illustrated with a flux that is representative of the one of a Pressurized Water Reactor: we obtain a mixture of 235U−232Th the sensitivity of which is stable up to 3% over four years at full power corresponding to a fluence about 3⋅1022n/cm2. The practical realization of such a mixture for a fission chamber is described. We discuss the robustness of the stability performance with respect to nuclear data, initial isotopic composition and prior knowledge of the neutron flux. The spectral index, which quantifies the amount of thermalized neutrons, needs to be assessed with a precision about 8%. As a result, such a stable and long-living regenerative fission chamber has to be specifically conceived for a dedicated reactor and measurement location.

Isotope selective three-step photoionization of 174Yb

A three-step photoionization scheme has been theoretically studied for the laser isotope separation of 174 Y b from natural Yb using density matrix formalism. The effects of bandwidth and peak power density of lasers, Doppler broadening, and the number density of atoms on the degree of enrichment and production rate have been studied, and the optimum conditions for the efficient separation of 174 Y b have been derived. It has been shown that it is possible to enrich the 174 Y b isotope up to ∼ 90 % using lasers with a bandwidth of 500 MHz with a production rate up to 48 mg/h. On the whole, the system required for the laser isotope separation of 174 Y b is much simpler than that required for the separation of any of the 176 L u , 177 L u , and 176 Y b isotopes. 1 g of the enriched isotope mixture upon irradiation for 21 days in widely available low flux reactors produces 759 doses (7.4 GBq each) of 175 Y b radionuclide for peptide receptor radionuclide therapy (PRRT) with 98.6% radionuclidic purity. It is envisaged that the production of the 175 Y b isotope through this route will be economical and widely available to the public at large as a PRRT drug for cancer therapy.

The immunotoxicity of natural and depleted uranium: From cells to people

Uranium is a naturally occurring element found in the environment as a mixture of isotopes with differing radioactive properties. Enrichment of mined material results in depleted uranium waste with substantially reduced radioactivity but retains the capacity for chemical toxicity. Uranium mine and milling waste are dispersed by wind and rain leading to environmental exposures through soil, air, and water contamination. Uranium exposure is associated with numerous adverse health outcomes in humans, yet there is limited understanding of the effects of depleted uranium on the immune system. The purpose of this review is to summarize findings on uranium immunotoxicity obtained from cell, rodent and human population studies. We also highlight how each model contributes to an understanding of mechanisms that lead to immunotoxicity and limitations inherent within each system. Information from population, animal, and laboratory studies will be needed to significantly expand our knowledge of the contributions of depleted uranium to immune dysregulation, which may then inform prevention or intervention measures for exposed communities.

Method of Calculating and Optimizing Multiflow Cascades for Separating Multicomponent Isotopic Mixtures

Method of Calculating and Optimizing Multiflow Cascades for Separating Multicomponent Isotopic Mixtures

Isotope selective three-step photoionization of 177Lu

A 540-535-618 three-step photoionization scheme has been theoretically investigated for the laser isotope separation of 177 L u through density matrix formalism. Equations of motion for the three-step photoionization of odd isotopes have been derived. The effects of Doppler broadening, bandwidth and peak power density of excitation lasers, number density of atoms on the degree of enrichment of 177 L u and production rate have been studied. Optimum conditions for the laser isotope separation of 177 L u for the cases of initial abundances corresponding to the irradiation of natural Lu in low, medium, and high flux reactors have been derived. Under optimum conditions, the production rates of 177 L u in ranges of 0.87, 14.5, and 92.5 mg/h can be achieved with degrees of enrichment of 66%, 97%, and 100%, respectively, for the cases of initial abundances corresponding to the irradiation of natural Lu in low, medium, and high flux reactors. It has also been shown that the content of 177 m L u in the enriched isotope mixture will be in the range of 10 − 2 % to 10 − 4 % . This provides a comprehensive solution to the application of 177 L u for cancer therapy.