Dissolution of UO2 at Various Parametric Conditions: A Comparison Between Calculated and Experimental Results

1988 ◽  
Vol 127 ◽  
Author(s):  
Kaija Olliia
Keyword(s):  
Solid Phase ◽  
Reaction Pathway ◽  
Critical Factor ◽  
Limiting Factor ◽  
Carbonate Concentration ◽  
Reducing Conditions ◽  
Lower Solubility ◽  
Solubility Constant ◽  
Experimental Solubility ◽  
Bicarbonate Solutions

ABSTRACTThe solubilities of uranium measured in deionized water, in sodium bicarbonate solutions as a function of carbonate concentration and in two types of synthetic groundwaters have been compared with those predicted using the reaction pathway program, PHREEQE. All the measurements were carried out under both air-saturated, oxidizing and anoxic, reducing conditions.The experimental solubility values of uranium under oxidizing conditions are, in general, lower when compared to the corresponding theoretical ones calculated by PHREEQE. A critical factor is the choice of solubility constant for the solid phase. The reason for the lower solubility values may also be the mechanism of dissolution leading for example either to a situation where low dissolution rate is a limiting factor, or to formation of some solid phase of uranium with lower solubility. The experimental solubility values under reducing conditions appear to be in good agreement with the theoretical solubility values.

Static Dissolution of Uo2 in Interstitial Boom Clay Water

1999 ◽  
Vol 556 ◽  
Author(s):  
K. Lemmens ◽  
C. Cachoir ◽  
P. Van Iseghem
Keyword(s):  
Uranium Concentration ◽  
Solid Phase ◽  
Experimental Conditions ◽  
Boom Clay ◽  
Carbonate Concentration ◽  
Reducing Conditions ◽  
Ph Conditions ◽  
The Impact ◽  
Uranium Species ◽  
Sulfide Species

AbstractStatic dissolution experiments were performed with unirradiatcd UO2 in Boom Clay water. The objectives were (1) to measure the solubility of uranium species in Boom Clay water, with UO2 as the solid phase, and (2) to assess the impact of dissolved organic matter and carbonate concentration on this solubility. The tests were supported by calculations with geochemical codes to indicate possibly solubility controlling solid phases. The tests were performed in anoxic and reducing conditions, at 20 and 25°C. The following conclusions could be drawn: (1) Within 2 months in anoxic conditions, the uranium concentrations appear to approach saturation. (2) The “near-saturation” concentrations are between 2.4 and 7.8× 10−7 M. (3) The influence of the carbonate concentration and humic acids on the uranium concentration was apparently small, but the interpretation is hampered by pH and Eh variations. (4) The concentrations tend to be higher than the concentrations found in literature for similar Eh and/or pH conditions; this can probably be explained by small differences in experimental conditions. (5) The measured “near steadystate” uranium concentration in the real clay water agrees relatively well with the solubility calculated for uraninite. (6) Addition of sulfide species reduced the rcdox potential, but not the uranium concentrations, except in real Boom Clay water.

The mechanism of formation of 2,7-dimethyl-2,6-octadiene in the synthesis of 3-methylene-7-methyl-1,6-octadiene

1983 ◽  
Vol 48 (7) ◽  
pp. 1864-1866
Author(s):  
Jan Bartoň ◽  
Ivan Kmínek
Keyword(s):  
Mass Spectrometry ◽  
Nmr Spectroscopy ◽  
Alkali Metal ◽  
Chromatographic Analysis ◽  
Solid Phase ◽  
Reaction Pathway ◽  
Mechanism Of Formation ◽  
Gas Chromatographic Analysis ◽  
C Nmr ◽  
Visual Observations

2,7-Dimethyl-2,6-octadiene is formed in the catalytic solution for the dimerization of 2-methyl-1,3-butadiene to β-myrcene (3-methylene-7-methyl-1,6-octadiene), as revealed by mass spectrometry and 13C NMR spectroscopy. Visual observations together with the results of gas chromatographic analysis of the catalytic solution suggest that the formation of 2,7-dimethyl-2,6-octadiene is associated with the transition of the alkali metal (sodium) from the solid phase into the solution. A reaction pathway is suggested accounting for the formation of 2,7-dimethyl-2,6-octadiene in the system.

scholarly journals The Role of Electric Pressure/Stress Suppressing Pinhole Defect on Coalescence Dynamics of Electrified Droplet

Coatings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 503
Author(s):  
Jaehyun Lee ◽  
Ehsan Esmaili ◽  
Giho Kang ◽  
Baekhoon Seong ◽  
Hosung Kang ◽  
...  
Keyword(s):  
Solid Phase ◽  
Critical Factor ◽  
Air Pressure ◽  
Conical Shape ◽  
Electric Stress ◽  
Bottom Interface ◽  
Electric Pressure ◽  
Pressure Stress ◽  
Air Film

The dimple occurs by sudden pressure inversion at the droplet’s bottom interface when a droplet collides with the same liquid-phase or different solid-phase. The air film entrapped inside the dimple is a critical factor affecting the sequential dynamics after coalescence and causing defects like the pinhole. Meanwhile, in the coalescence dynamics of an electrified droplet, the droplet’s bottom interfaces change to a conical shape, and droplet contact the substrate directly without dimple formation. In this work, the mechanism for the dimple’s suppression (interfacial change to conical shape) was studied investigating the effect of electric pressure. The electric stress acting on a droplet interface shows the nonlinear electric pressure adding to the uniform droplet pressure. This electric stress locally deforms the droplet’s bottom interface to a conical shape and consequentially enables it to overcome the air pressure beneath the droplet. The electric pressure, calculated from numerical tracking for interface and electrostatic simulation, was at least 108 times bigger than the air pressure at the center of the coalescence. This work helps toward understanding the effect of electric stress on droplet coalescence and in the optimization of conditions in solution-based techniques like printing and coating.

Impact of sulfate on the solubility of Tc(IV) in acidic to hyperalkaline aqueous reducing systems

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sarah B. Duckworth ◽  
Xavier Gaona ◽  
Alexander Baumann ◽  
Kathy Dardenne ◽  
Jörg Rothe ◽  
...  
Keyword(s):  
Solid Phase ◽  
Correction Factors ◽  
Mixed Salt ◽  
Ph Values ◽  
Reducing Conditions ◽  
Upper Limits ◽  
Salt Systems ◽  
Amorphous Character ◽  
Good Agreement

Abstract The solubility of 99Tc(IV) was investigated from undersaturation conditions in NaCl–Na2SO4 (0.3 M ≤ I ≤ 5.0 M), MgCl2–MgSO4 (I = 13.5 M) and CaCl2–CaSO4 (I = 13.5 M) systems with 0.001 M ≤ [SO4 2−]tot ≤ 1.0 M and 1 ≤ pH m  ≤ 12 (with pH m  = −log[H+], in molal units). Reducing conditions were set by either Sn(II) or Fe(0). Special efforts were dedicated to accurately characterize the correction factors A m required for the determination of pH m from the experimentally measured pH values in the mixed salt systems investigated, with pH m  = pHexp + A m . The combination of (pe + pH m ) measurements with Pourbaix diagrams of Tc suggests that technetium is present in its +IV redox state. This hypothesis is confirmed by XANES, which unambiguously shows the predominance of Tc(IV) both in the aqueous and solid phases of selected solubility samples. XRD and SEM–EDS support the amorphous character of the solid phase controlling the solubility of Tc(IV). EXAFS data confirm the predominance of TcO2(am, hyd) at pH m  > 1.5, whereas the formation of a Tc(IV)–O–Cl solid phase is hinted at lower pHm values in concentrated NaCl–Na2SO4 systems with ≈5 M NaCl. Solubility data collected in sulfate-containing systems are generally in good agreement with previous solubility studies conducted in sulfate-free NaCl, MgCl2 and CaCl2 solutions of analogous ionic strength. Although the complexation of Tc(IV) with sulfate cannot be completely ruled out, these results strongly support that, if occurring, complexation must be weak and has no significant impact on the solubility of Tc(IV) in dilute up to highly saline media. Solubility upper-limits determined in this work can be used for source term estimations including the effect of sulfate in a variety of geochemical conditions relevant in the context of nuclear waste disposal.

scholarly journals Purification and properties of α-mannosidase II from Golgi-like membranes of baculovirus-infected Spodoptera frugiperda (IPLB-SF-21AE) cells

1997 ◽  
Vol 324 (3) ◽  
pp. 951-956 ◽  
Author(s):  
Jianxin REN ◽  
Francis J. CASTELLINO ◽  
Roger K. BRETTHAUER
Keyword(s):  
Spodoptera Frugiperda ◽  
Reaction Pathway ◽  
Gel Filtration ◽  
Deae Cellulose ◽  
Enzymic Activity ◽  
Mannose Residue ◽  
Lepidopteran Insect ◽  
Reducing Conditions ◽  
Apparent Homogeneity ◽  
Purification And Properties

An α-mannosidase II-like activity was identified in baculovirus-infected Spodoptera frugiperda (IPLB-SF21-AE) cells. The enzyme responsible was purified from Golgi-type membranes to apparent homogeneity by using a combination of steps including DEAE-cellulose, hydroxyapatite, concanavalin A–Sepharose and gel filtration chromatography. The molecular mass of this purified protein was approx. 120 kDa by SDS/PAGE under reducing conditions and approx. 240 kDa under non-reducing conditions, indicating that the enzyme is a disulphide-linked dimer. Substrates demonstrated to undergo hydrolysis with this enzyme were GlcNAc-Man5-GlcNAc-GlcNAc (non-reduced and reduced) and p-nitrophenyl α-d-mannopyranoside. The oligosaccharide substrate was converted into GlcNAc-Man3-GlcNAc-GlcNAc through an intermediate GlcNAc-Man4-GlcNAc-GlcNAc. Treatment of the isolated intermediate oligosaccharide with endoglycosidase H resulted in its conversion into GlcNAc-Man4-GlcNAc. This indicated that it contained the α-1,3-linked mannose residue on the α-1,6-linked mannose arm and showed that the α-1,6-linked mannose residue on the α-1,6-linked mannose arm had been preferentially hydrolysed by the mannosidase. The oligosaccharide lacking the β-1,2-linked GlcNAc residue on the α-1,3-linked mannose arm (Man5-GlcNAc-GlcNAc) was not hydrolysed in the presence of the enzyme. Metal ions were not required for enzymic activity on any of the substrates, but Cu2+ was strongly inhibitory. The activity of the enzyme was inhibited at low concentrations of swainsonine, but much higher concentrations of 1-deoxymannojirimycin were required to achieve inhibition. All of these properties are characteristic of mannosidase II enzymes from other eukaryotic tissues. The presence of mannosidase II in lepidopteran insect cells would allow entry of N-linked glycoproteins into the complex processing reaction pathway or into the terminal Man3-GlcNAc-GlcNAc pathway.

Electrochemical Dissolution of Goethite by Abrasive Stripping Voltammetry

1995 ◽  
Vol 60 (6) ◽  
pp. 950-959 ◽  
Author(s):  
Tomáš Grygar ◽  
Jan Šubrt ◽  
Jaroslav Boháček
Keyword(s):  
Solid Phase ◽  
Reaction Pathway ◽  
Stripping Voltammetry ◽  
Electrode Reaction ◽  
Reductive Dissolution ◽  
Quantitative Characterization ◽  
Acid Media ◽  
Qualitative And Quantitative ◽  
Spectroscopic Examination

Abrasive stripping voltammetry was applied to the investigation of the reductive dissolution of some iron(III) oxides and hydroxy-oxides, particularly goethite (α-FeOOH), in acid media. The electrode reaction directly involves the solid phase, and the reaction pathway depends on the phase composition and particle shape. This can be used for a qualitative and quantitative characterization of goethite. The results of a quantitative analysis of a mixture of goethite (α-FeOOH) and lepidocrocite (γ-FeOOH) are compared with those of IR and Moessbauer spectroscopic examination. The effects of the particle appearance (shape, crystal intergrowth) on the results of the voltammetric and chronoamperometric measurements are discussed.

Assessment of Redox Conditions in the Near Field of Nuclear Waste Repositories: Application to the Swiss high-level and intermediate level waste disposal concept

2003 ◽  
Vol 807 ◽  
Author(s):  
Paul Wersin ◽  
Lawrence H. Johnson ◽  
Bernhard Schwyn
Keyword(s):  
Solid Phase ◽  
Near Field ◽  
Intermediate Level ◽  
Redox Conditions ◽  
High Level Waste ◽  
Redox Potentials ◽  
Spent Fuel ◽  
Reducing Conditions ◽  
High Level ◽  
Waste Repositories

ABSTRACTRedox conditions were assessed for a spent fuel and high-level waste (SF/HLW) and an intermediate-level waste (ILW) repository. For both cases our analysis indicates permanently reducing conditions after a relatively short oxic period. The canister-bentonite near field in the HLW case displays a high redox buffering capacity because of expected high activity of dissolved and surface-bound Fe(II). This is contrary to the cementitious near field in the ILW case where concentrations of dissolved reduced species are low and redox reactions occur primarily via solid phase transformation processes.For the bentonite-canister near field, redox potentials of about -100 to -300 mV (SHE) are estimated, which is supported by recent kinetic data on U, Tc and Se interaction with reduced iron systems. For the cementitious near field, redox potentials of about -200 to -800 mV are estimated, which reflects the large uncertainties related to this alkaline environment.

Aqueous Dissolution of Silver Iodide and Associated Iodine Release under Reducing Conditions with Sulfide

2006 ◽  
Vol 985 ◽  
Author(s):  
Yaohiro Inagaki ◽  
Toshitaka Imamura ◽  
Kazuya Idemitsu ◽  
Tatsumi Arima ◽  
Osamu Kato ◽  
...  
Keyword(s):  
Thin Layer ◽  
Phase Analysis ◽  
Thermodynamic Equilibrium ◽  
Silver Iodide ◽  
Solid Phase ◽  
Reducing Conditions ◽  
Dissolution Tests ◽  
Iodine Release

AbstractAqueous dissolution tests of AgI were performed in Na2S solutions in order to evaluate, empirically, dissolution of AgI to release iodine under reducing conditions with sulfide. The results indicated that AgI dissolves to release iodine being controlled by mainly precipitation of Ag2S. However, the dissolution of AgI can be depressed to proceed, and the thermodynamic equilibrium cannot be attained easily. Solid phase analysis for the reacted AgI suggested that a thin layer of solid silver forming at AgI surface may evolve to be protective against transportation of reactant species, which can lead to the depression in the dissolution of AgI.

Efficacy of Damage Annealing in Advanced Ultra-Shallow Junction Processing

2008 ◽  
Vol 1070 ◽  
Author(s):  
Paul J Timans ◽  
Yao Zhi Hu ◽  
Jeff Gelpey ◽  
Steve McCoy ◽  
Wilfried Lerch ◽  
...  
Keyword(s):  
Leakage Current ◽  
Crystalline Silicon ◽  
Solid Phase ◽  
Rapid Assessment ◽  
Critical Factor ◽  
Defect Annealing ◽  
Residual Damage ◽  
B Doping ◽  
Low Thermal Budget ◽  
Spike Annealing

ABSTRACTLow thermal budget annealing approaches, such as millisecond annealing or solid-phase epitaxy (SPE) of amorphized silicon, electrically activate implanted dopants while minimizing diffusion. However, it is also important to anneal damage to the crystal lattice in order to minimize junction leakage. Annealing experiments were performed on low-energy B implants into both crystalline silicon and into wafers pre-amorphized by Ge implantation. Some wafers also received As implants for halo-style doping, and in some cases the halo implants were pre-annealed at 1050°C before the B-doping. The B-implants were annealed by either SPE at 650°C, spike annealing at 1050°C, or by millisecond annealing with flash-assisted RTP™ (fRTP™) at temperatures between 1250°C and 1350°C. Residual damage was characterized by photoluminescence and non-contact junction leakage current measurements, which permit rapid assessment of damage removal efficacy. Damage from the heavy ions used for the halo and pre-amorphization implants dominates the defect annealing behaviour. The halo doping is the critical factor in determining junction leakage current. Millisecond annealing at high temperatures helps to minimize residual damage while limiting diffusion.

scholarly journals Evaluation of molecular assays to detect Leishmania donovani in Phlebotomus argentipes fed on post-kala-azar dermal leishmaniasis patients

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Md Anik Ashfaq Khan ◽  
Khaledul Faisal ◽  
Rajashree Chowdhury ◽  
Rupen Nath ◽  
Prakash Ghosh ◽  
...  
Keyword(s):  
Leishmania Donovani ◽  
Control Strategies ◽  
Reference Method ◽  
Critical Factor ◽  
Sand Fly ◽  
Accurate Estimation ◽  
Limiting Factor ◽  
Sand Flies ◽  
Real Time Quantitative Pcr ◽  
Kala Azar

Abstract Background Post-kala-azar dermal leishmaniasis (PKDL) caused by Leishmania donovani (LD) is a skin disorder that often appears after treatment of visceral leishmaniasis (VL) patients. PKDL patients are potential reservoirs of LD parasites, which can initiate a new epidemic of anthroponotic VL. Therefore, host infectiousness to its sand fly vector is a critical factor for transmission, and its accurate estimation can facilitate control strategies. At present, conventional microscopy serves as the reference method to detect parasites in its vector. However, low sensitivity of microscopy can be a limiting factor. Methods In this study, real-time quantitative PCR (LD-qPCR) and recombinase polymerase amplification (LD-RPA) assays were evaluated against microscopy for the detection of LD DNA extracted from live sand flies five days after controlled feeding on PKDL cases. Results The sensitivity of LD-qPCR and LD-RPA assays were found to be 96.43 and 100%, respectively, against microscopy for the selected fed sand flies (n = 28), and an absolute specificity of both molecular tools for apparently unfed sand flies (n = 30). While the proportion of infectious cases among 47 PKDL patients was estimated as 46.81% as defined by microscopic detection of LD in at least one fed sand fly per case, LD-RPA assay evaluation of only the microscopy negative sand flies fed to those 47 PKDL cases estimated an even greater proportion of infectious cases (51.06%). In overall estimation of the infectious cases in retrospective manner, discordance in positivity rate was observed (p < 0.05) between LD-RPA (59.57%) assay and microscopy (46.81%), while LD-RPA had slightly better positivity rate than LD-qPCR (55.32%) as well. Conclusions Considering the sensitivity, cost, detection time, and field applicability, RPA assay can be considered as a promising single molecular detection tool for investigations pertaining to LD infections in sand flies and/or host infectiousness in PKDL, while it can also be useful in confirmation of microscopy negative sand fly samples. Graphical abstract

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