Redox, solubility and sorption chemistry of technetium in dilute to concentrated saline systems (KIT Scientific Report ; 7703)

This PhD work represents a comprehensive investigation of redox processes, solubility and sorption behaviour of technetium in the absence of complexing ligands extending from dilute to concentrated NaCl, MgCl2 and CaCl2 systems. The complete chemical, thermodynamic and activity models derived in this work provide key input for understanding the chemical behaviour of Tc in conditions relevant for nuclear waste disposal

A Computational Model of Cell Spreading, Movement, and Alignment on Micro-Wavy Surfaces

Mechanical behavior of cells plays a crucial role in response to external stimuli and environment. It is very important to elucidate the mechanisms of cellular activities like spreading and alignment as it would shed light on further biological concepts. A multi-scale computational approach is adopted by modeling the cytoskeleton of cell as a tensegrity structure. The model is based on the complementary force balance between the tension and compression elements, resembling the internal structure of cell cytoskeleton composed of microtubules and actin filaments. The effect of surface topology on strain energy of a spread cell is investigated by defining strain energy of the structure as the main criterion in the simulation process of the cell spreading. Spreading as a way to decrease internal energy toward a minimum energy state is the main hypothesis that is investigated. The cell model is placed at different positions along the wavy surface and the spreading and alignment behavior is observed. The implementation of the model illustrates the effect of topological factors on spreading and alignment of the cell. The proposed computational model can be explanatory in terms of understanding mechanical characteristics of cells

Thermodynamic description of Tc(IV) solubility and hydrolysis in dilute to concentrated NaCl, MgCl₂ and CaCl₂ solutions

We present the first systematic investigation of Tc(IV) solubility, hydrolysis and speciation in dilute to concentrated NaCl, MgCl2 and CaCl2 systems, and comprehensive thermodynamic and activity models for the system Tc4+–H+–Na+–Mg2+–Ca2+–OH−–Cl−–H2O using both SIT and Pitzer approaches. The results are advancing the fundamental scientific understanding of Tc(IV) solution chemistry and are highly relevant in the applied context of nuclear waste disposal. The solubility of Tc(IV) was investigated in carbonate-free NaCl–NaOH (0.1–5.0 M), MgCl2 (0.25–4.5 M) and CaCl2 (0.25–4.5 M) solutions within 2 ≤ pHm ≤ 14.5. Undersaturation solubility experiments were performed under an Ar atmosphere at T = 22 ± 2 °C. Strongly reducing conditions (pe + pHm ≤ 2) were imposed with Na2S2O4, SnCl2 and Fe powder to stabilize technetium in the +IV redox state. The predominance of Tc(IV) in the aqueous phase was confirmed by solvent extraction and XANES/EXAFS spectroscopy. Solid phase characterization was accomplished after attaining thermodynamic equilibrium using XRD, SEM–EDS, XANES/EXAFS, TG–DTA and quantitative chemical analysis, and indicated that TcO2·0.6H2O(s) exerts solubility-control in all evaluated systems. The definition of the polyatomic Tc3O52+ species instead of TcO2+ is favoured under acidic conditions, consistently with slope analysis (mTcvs. pHm) of the solubility data gained in this work and spectroscopic evidence previously reported in the literature. The additional formation of Tc(IV)–OH/O–Cl aqueous species in concentrated chloride media ([Cl−] = 9 M) and pHm ≤ 4 is suggested by solubility and EXAFS data. The pH-independent behaviour of the solubility observed under weakly acidic to weakly alkaline pHm conditions can be explained with the equilibrium reaction TcO2·0.6H2O(s) + 0.4H2O(l) ⇔ TcO(OH)2(aq). Solubility data determined in dilute NaCl systems with pHm ≥ 11 follow a well-defined slope of +1, consistent with the predominance of TcO(OH)3− previously selected by NEA–TDB. In concentrated MgCl2 and CaCl2 solutions with pHm ≥ 8, the formation of the ternary Mg3[TcO(OH)5]3+ and Ca3[TcO(OH)5]3+ species is proposed based on the slope analysis of the solubility data, model calculations and previous observations for analogous An(IV) and Zr(IV) systems. The formation and stability of these hitherto unknown Tc(IV) species are supported by DFT calculations. Based on the newly generated experimental data and previous spectroscopic observations, new comprehensive chemical, thermodynamic and activity models (SIT, Pitzer) for these systems are derived

Application of Neodymium Isotope Ratio Measurements for the Origin Assessment of Uranium Ore Concentrates

A novel procedure has been developed for the measurement of 143Nd/144Nd isotope ratio in various uranium-bearing materials, such as uranium ores and ore concentrates (UOC) in order to evaluate the usefulness and applicability of variations of 143Nd/144Nd isotope ratio for provenance assessment in nuclear forensics. Neodymium was separated and pre-concentrated by extraction chromatography and then the isotope ratios were measured by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The method was validated by the measurement of standard reference materials (La Jolla, JB-2 and BCR-2) and the applicability of the procedure was demonstrated by the analysis of uranium samples of world-wide origin. The investigated samples show distinct 143Nd/144Nd ratio depending on the ore type, deposit age and Sm/Nd ratio. Together with other characteristics of the material in question, the Nd isotope ratio is a promising signature for nuclear forensics and suggests being indicative of the source material, the uranium ore.JRC.E.7-Nuclear Safeguards and Forensic

Aerogel‐Based Biomaterials for Biomedical Applications: From Fabrication Methods to Disease‐Targeting Applications

Abstract Aerogel‐based biomaterials are increasingly being considered for biomedical applications due to their unique properties such as high porosity, hierarchical porous network, and large specific pore surface area. Depending on the pore size of the aerogel, biological effects such as cell adhesion, fluid absorption, oxygen permeability, and metabolite exchange can be altered. Based on the diverse potential of aerogels in biomedical applications, this paper provides a comprehensive review of fabrication processes including sol‐gel, aging, drying, and self‐assembly along with the materials that can be used to form aerogels. In addition to the technology utilizing aerogel itself, it also provides insight into the applicability of aerogel based on additive manufacturing technology. To this end, how microfluidic‐based technologies and 3D printing can be combined with aerogel‐based materials for biomedical applications is discussed. Furthermore, previously reported examples of aerogels for regenerative medicine and biomedical applications are thoroughly reviewed. A wide range of applications with aerogels including wound healing, drug delivery, tissue engineering, and diagnostics are demonstrated. Finally, the prospects for aerogel‐based biomedical applications are presented. The understanding of the fabrication, modification, and applicability of aerogels through this study is expected to shed light on the biomedical utilization of aerogels

Development of ²²⁵Ac Production from Low Isotopic Dilution ²²⁹Th

The promise of 225Ac targeted alpha therapies has been on the horizon for the last two decades. TerraPower Isotopes are uniquely suited to produce clinically relevant quantities of 225Ac through the decay of 229Th. Herein, a rapid processing scheme to isolate radionuclidic and radioisotopically pure 225Ac in good yield (98%) produced from 229Th that contains significant quantities of 228Th activity is described. The characterization of each step of the process is presented along with the detailed characterization of the resulting 225Ac isotopic starting material that will support the cancer research and development efforts