Chemical and elemental mapping of spent nuclear fuel sections by soft X-ray spectromicroscopy

Soft X-ray spectromicroscopy at the O K-edge, U N 4,5-edges and Ce M 4,5-edges has been performed on focused ion beam sections of spent nuclear fuel for the first time, yielding chemical information on the sub-micrometer scale. To analyze these data, a modification to non-negative matrix factorization (NMF) was developed, in which the data are no longer required to be non-negative, but the non-negativity of the spectral components and fit coefficients is largely preserved. The modified NMF method was utilized at the O K-edge to distinguish between two components, one present in the bulk of the sample similar to UO2 and one present at the interface of the sample which is a hyperstoichiometric UO2+x species. The species maps are consistent with a model of a thin layer of UO2+x over the entire sample, which is likely explained by oxidation after focused ion beam (FIB) sectioning. In addition to the uranium oxide bulk of the sample, Ce measurements were also performed to investigate the oxidation state of that fission product, which is the subject of considerable interest. Analysis of the Ce spectra shows that Ce is in a predominantly trivalent state, with a possible contribution from tetravalent Ce. Atom probe analysis was performed to provide confirmation of the presence and localization of Ce in the spent fuel.

Disorder of Iron Metabolism as a Universal Pathogenetic Factor in Damage to Organs and Systems in Covid-19

Relevance. The pathogenesis of COVID-19 remains one of the most pressing. The literature discusses the role of iron as a factor supporting inflammatory processes, hypercoagulability and microcirculation crisis in severe COVID-19.The aim of study. was to identify changes in iron metabolism in patients with severe COVID-19 and hyperferritinemia.Material and methods. In this study, we used a content analysis of available scientific publications and our own observations of the peculiarities of the clinical picture and laboratory parameters in patients with a severe course of COVID-19 who had hyperferretinemia at the height of the disease. The main group consisted of 30 patients hospitalized in the Department of Anesthesiology, Resuscitation and Intensive Care of N.A. Semashko City clinical Hospital No. 38 with the diagnosis COVID-19, bilateral polysegmental pneumonia, severe course and hyperferritinemia. The diagnosis of a new coronavirus infection was confirmed by visualization of bilateral viral lung lesions with chest CT-scan, positive PCR test for SARS-CoV-2 and the presence of immunoglobulins to SARS-CoV-2. The control group consisted of 20 healthy volunteers. The study evaluated the biochemical parameters of iron metabolism, fibrinolysis and markers of inflammation. Changes associated with impaired iron metabolism were assessed by the level of serum iron, transferrin, daily and induced iron excretion in the urine. Statistical processing was carried out using nonparametric methods.Results. All patients with severe COVID-19 and hyperferritinemia showed signs of impaired iron metabolism, inflammation and fibrinolysis — a decrease in the level of transferrin (p<0.001), serum iron (p><0.005), albumin (p><0.001), lymphocytes (p><0.001) and an increase in leukocytes (p><0.001), neutrophils (p><0.001), CRP (p><0.005), IL-6 (p><0.001), D-dimer (p><0.005), daily urinary iron excretion (p><0.005) and induced urinary iron excretion (p><0.001). Conclusions The study showed that in the pathogenesis of the severe course of COVID-19, there is a violation of iron metabolism and the presence of a free iron fraction. The appearance of free iron can be caused by damage to cells with the “release” of iron from cytochromes, myoglobin, hemoglobin, or violation of the binding of iron to transferrin, which may be the result of a change in the protein structure or violation of the oxidation of iron to the trivalent state. When assessing the degree of viral effect on the body, one should take into account the effect of various regulators of iron metabolism, as well as an assessment of the level of free iron not associated with transferrin. Keywords: new coronavirus infection, COVID-19, SARS-CoV-2, iron metabolism, free iron, ferritin, transferrin, NTBI, nontransferrin bound iron>˂0.001), serum iron (p˂0.005), albumin (p˂0.001), lymphocytes (p˂0.001) and an increase in leukocytes (p˂0.001), neutrophils (p˂0.001), CRP (p˂0.005), IL-6 (p˂0.001), D-dimer (p˂0.005), daily urinary iron excretion (p˂0.005) and induced urinary iron excretion (p˂0.001).Conclusions. The study showed that in the pathogenesis of the severe course of COVID-19, there is a violation of iron metabolism and the presence of a free iron fraction. The appearance of free iron can be caused by damage to cells with the “release” of iron from cytochromes, myoglobin, hemoglobin, or violation of the binding of iron to transferrin, which may be the result of a change in the protein structure or violation of the oxidation of iron to the trivalent state. When assessing the degree of viral effect on the body, one should take into account the effect of various regulators of iron metabolism, as well as an assessment of the level of free iron not associated with transferrin.

Development of Technology of Arsenic Removal from Acidic Waste Solutions in the Form of Arsenic Trisulfide

During the laboratory tests the conditions of arsenic removal from acidic waste solutions of metallurgical enterprise in the form of arsenic trisulfide were determined. The technology based on the reduction of pentavalent arsenic to trivalent state with sodium pyrosulfite solution and following arsenic trisulfide precipitation from acidic solution after treatment with sodium sulfide solution was proposed. The arsenic removal proceeds with mechanical stirring, dosing the calculated amounts of reagents and collecting emissions of hydrogen sulfide. With such treatment, about 95% of arsenic, which was in the initial solution, passes into the precipitate. An enlarged laboratory experiment was carried out and the precipitate with 42.6% of arsenic and 46.9% of sulfur was obtained. The precipitate yield was ∼25.7 kg (dry weight) out of 1 m3 of the initial arsenic containing solution. Keywords: arsenic, arsenic trisulfide, acidic waste solutions, sodium sulfide, sodium pyrosulfite

SYNTHESIS AND SPECTRAL CHARACTERISTICS OF PERSPECTIVE NANOSIZED CARBON QUANTUM DOTS FOR ADSORPTION AND CATALYTIC PROCESSES

Processes of interaction between carbon quantum dots (CQDs) and solutions of rhodium, ruthenium and palladium chlorides in the surface layer have been investigated by electron and IR spectroscopy. When rhodium chloride is added to a solution of CQDS, a bathochromic shift of the β- and p-absorption bands (ABs) at 48725 and 41711 cm-1 as well as hypsochromic shift of the α-AB at 28935 cm-1 indicate that rhodium adsorption occurs on the surface of CQDs. The bathochromic shift of the absorption bands at 22400 сm1 together with the hypsochromic shift of ABs corresponding to d-d electron transitions in the metal ions indicates the formation of rhodium with CQDs. When ruthenium and palladium chlorides are added to an aqueous solution of CQDs, the intensive of ABs characterizing the complex anions [RuCl6]3-, [RuCl6]2- or [PdCl4]2- are absent in the UV-Vis spectra. This indicates the passage of adsorption processes of metals on the surface of CQDs. The present of ABs (at 27055 and 25125 сm-1) indicate the trivalent state of ruthenium ion; the p-ABs bathochromic shift as well as α-ABs hypsochromic shift indicates the probable complex formation of CQDs with Ru3+ ions. The change in the position of the absorption bands of d-d electron transitions (at 25448 сm1) together with the bathochromic shift of p-ABs and hypsochromic shift of α-ABs indicates a change in coordination environment in the palladium ion with the possible formation of Pd → N bond. The IR-spectra data of CQDs showed the presence of a number of characteristic ABs for functionalized CQDs: ν(N–H) at 3260 сm1, (C=O) at 1830, 1840 and 1850 сm1, –С=O(NH) at 1770 сm1, ν(C=N) at 1680 and δ(N–H) at 1640 сm1, which confirms the coordination of metals on the surface of CQDs.

Single crystal investigation of the YbAl2 compound

A sample of nominal composition Yb33,3Al66,7 was synthesized from high-purity elements (Yb ≥ 98.9 wt.% and Al ≥ 99.999 wt.%) by arc-melting under a purified argon atmosphere, using Ti as a getter and a tungsten electrode. To achieve high efficiency of the interaction between the components, the sample was melted twice. The ingot was annealed at 500°C in an evacuated quartz ampoule for 720 h and subsequently quenched in cold water. The weight loss during the preparation of the sample was less than 1 % of the total mass, which was 2 g. The chemical composition of the selected crystals was checked with a field-emission scanning electron microscope (FEINovaNanoSEM 230) equipped with an EDS analyzer. Laue and rotation diffraction patterns of selected single crystals showed cubic symmetry. Integrated intensities measured with graphite-monochromatized Мо Kα radiation (l = 0.71073 Å) on an Xcalibur Atlas CCD diffractometer confirmed the cubic lattice. The structure type MgCu2 was assigned and the structure was refined using the program SHELXL (full-matrix least-squares refinement on F2)] with anisotropic displacement parameters for all of the atoms: Pearson symbol cF24, space group Fd-3m, a = 7.7011(4) Å, V = 456.73(7) Å3, Z = 8, R = 0.0261, Rw = 0.0726 for 42 reflections. It is well-known that the trivalent state is usual one for the rare earth metals. The dependence of the mean atomic volume of the RAl2 binary showed of the so-called “valence” fluctuation state for Eu and Yb.

How Plants Handle Trivalent (+3) Elements

Plant development and fitness largely depend on the adequate availability of mineral elements in the soil. Most essential nutrients are available and can be membrane transported either as mono or divalent cations or as mono- or divalent anions. Trivalent cations are highly toxic to membranes, and plants have evolved different mechanisms to handle +3 elements in a safe way. The essential functional role of a few metal ions, with the possibility to gain a trivalent state, mainly resides in the ion’s redox activity; examples are iron (Fe) and manganese. Among the required nutrients, the only element with +3 as a unique oxidation state is the non-metal, boron. However, plants also can take up non-essential trivalent elements that occur in biologically relevant concentrations in soils. Examples are, among others, aluminum (Al), chromium (Cr), arsenic (As), and antimony (Sb). Plants have evolved different mechanisms to take up and tolerate these potentially toxic elements. This review considers recent studies describing the transporters, and specific and unspecific channels in different cell compartments and tissues, thereby providing a global vision of trivalent element homeostasis in plants.

Stabilization of Cr-rich tannery waste in fly ash matrices

In the present work, the stabilization/solidification of a Cr-rich ash obtained from the anoxic incineration of tannery hazardous wastes was studied. Chromium in the starting waste was exclusively in amorphous form and in trivalent state. The waste was embedded in fly ash-based cementitious material matrices. Calcium and sodium hydroxides, as well as sodium silicate, were used as activators. The proposed process combines mechanical activation with hydrothermal curing. Successful immobilization of chromium was achieved, as attested by standard leaching tests. Backscattered electron images revealed the existence of the C-S-H gel, and elemental mapping by energy dispersive X-ray spectroscopy showed a good interdispersion of chromate and aluminosilicate species, verifying that chromium was well distributed in the final amorphous cementitious matrix. X-ray diffraction confirmed the absence of Cr-rich crystalline phases of calcium aluminosilicates, where chromium can enter in hexavalent state. The stiffness of the stabilized samples was reduced with increasing the amount of added Cr-rich ash, as attested by measurements of the dynamic Young’s modulus.

Valencies of the lanthanides

The valencies of the lanthanides vary more than was once thought. In addition to valencies associated with a half-full shell, there are valencies associated with a quarter- and three-quarter-full shell. This can be explained on the basis of Slater’s theory of many-electron atoms. The same theory explains the variation in complexing constants in the trivalent state (the “tetrad effect”). Valency in metallic and organometallic compounds is also discussed.

SYNTHESIS, ELECTRONIC STRUCTURE AND STUDY OF YTTERBIUM TETRAPHENYLPORPHYRIN COMPLEXES STABILITY BY PHOTOELECTRON SPECTROSCOPY AND THERMOGRAVIMETRY

Metalloorganic complexes of rare earth elements with porphyrins have attracted attention over the past years in view of potential applications as templates for biology, nanotechnology and medicine. For deeper understanding and studying of their properties the knowledge of electronic structure and bonding in these compounds is required and should be investigated essentially by a photoelectron spectroscopy. In present work the electronic structure and stability of tetrakis-porphyrins and its ytterbium complexes were studied experimentally by X-ray (XPS) photoemission spectroscopy. The X-ray photoemission data show the different atomic constituents in accordance with its states in molecules which can be related to the peaks of N1s, C1s, O1s, Yb4d appearing in the electronic spectra. In the tetraphenylporphyrin free base spectrum of the N1s state core levels there are two peaks of N1s which were assigned to sp3 and sp2 nitrogen respectively (pyrrol- and azastates). In Yb metalloporphyrin charge distribution is more uniform for N1s spectra and thus wide single peak of N1s states reflects small difference between pyrol- and aza-nitrogen. The analysis of Yb4d electronic states shows that spectra do not consist of the spin-orbit split doublet, but instead is composed of asymmetric peak with multiplet splitting. Divalent Yb has a filled 4f shell, i.e. a 4f14 configuration, and the 4d spectra shows the doublet with 3:2 ratio, while for trivalent Yb, 4f13, the 4d peaks consist of a multiplet. The spectrum analysis demonstrated the multiplet splitting of Yb 4d and trivalent state in Yb(acac)-5,10,15,20-tetrakis-porphyrins. The research of thermal stability of tetraphenylporphyrin, octabrominetetraphenylporphyrin, ytterbium acetylacetonate octabrominetetraphenylporphyrin by X-ray photoelectron spectroscopy and thermogravimetry measurements in the range of temperatures of 30-450°C (when heating in ultrahigh vacuum) has shown destruction of the octabrominetetraphenylporphyrin and ytterbium acetylacetonate octabrominetetraphenylporphyrin after warming up higher than 150ºС while free base porphyrines (tetraphenylporphyrines) have shown thermal stability under vacuum conditions.

Preparation and Characterization of Cellulose Crystallites via Fe(III)-, Co(II)- and Ni(II)-Assisted Dilute Sulfuric Acid Catalyzed Hydrolysis Process

Hydrolyzing the cellulose amorphous regions with high selectivity while protecting the crystallite phases unaltered during acid hydrolysis is still a great challenge in nanocellulose industry. Due to this reason, transition metal based catalysts such as Fe (NO3)3-, Co (NO3)2- and Ni (NO3)2metal salts were chosen as promoter to co-catalyze with H2SO4 in order to develop a facile hydrolysis technique for the preparation of cellulose crystallites inform nanodimension from native cellulose source. This study investigated the hydrolysis efficiency of three different transition metals (Fe3+, Co2+ and Ni2+) on cellulose crystallinity index, structure and morphology of the products.Results showed that the transition metal salts (Ni2+, Co2+ and Fe3+) were capable to selectively degraded cellulose amorphous structure with increase of crystallite sizes (8.12-27.8 nm) and improved of crystallinity index (65.5-70.3 %), as compared to native cellulose. Furthermore, surface morphology study indicated the cellulose fibers were successfully disintegrated into smaller fragments (diameter ranges of 18.5-31.5 nm) with spider-web-like nanostructured surfaces. Higher oxidation state of Fe (III)-cation with trivalent state rendered more effective hydrolysis effect in preparing the cellulose crystallites as compared to divalent state of Co (II)- and Ni (II)-cations.