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| 2. |
- Allard, Stefan, 1968, et al.
(författare)
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Complexing Properties of α-Isosaccharinate: Stability Constants, Enthalpies and Entropies of Th-complexation with Uncertainty Analysis
- 2006
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Ingår i: Journal of Solution Chemistry. - : Springer Science and Business Media LLC. - 0095-9782 .- 1572-8927. ; 25:8, s. 1173-1186
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Tidskriftsartikel (refereegranskat)abstract
- The complexation of Th-alpha-isosaccharinate has been examined using liquid-liquidextraction technique. An organic phase consisting of 0.025 M acetylacetone in toluene was used with a 1.0 M NaClO4 aqueous phase kept at pH 8 in a thermostated AKUFVE unit. Two temperatures, 15 degrees C and 35 degrees C, were investigated and the stability constants for the complexation reaction Th4+ + pISA Th(ISA(-))(p)((4-p)+) were determined by curve fitting of a distribution ratio equation to experimental data employing a chi(2) method to estimate the standard deviation. By incorporating data from a previous study at 25 degrees C, Delta H degrees and AS' for the reaction were also obtained, using randomly generated, binomially distributed, data points around the stability constant values with one standard deviation in two dimensions. Three alpha-isosaccharinate ligands were found to be involved in the complexation with thorium.
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| 4. |
- Allard, Stefan, 1968
(författare)
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Investigations of α-D-isosaccharinate: Fundamental Properties and Complexation
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Waste products containing cellulose will be present in the planned underground radioactive waste repositories. It will be exposed to an alkaline environment for long periods of time. Under such conditions cellulose will degrade forming mainly isosaccharinate. Sorption studies have shown that tetra- and trivalent actinides and lanthanides form strong complexes with α D isosaccharinate which increases the amount substance that goes into solution. Information relating to fundamental properties of the isosaccharinic system is scarce and needs to be attained to properly assess its long term impact on a repository.This thesis is focused on such properties of the isosaccharinic system. The acid dissociation constant of α D isosaccharinic acid and the associated enthalpy and entropy has been determined by means of potentiometric titrations. The isosaccharinic system is comprised of the three conformations α D-isosaccharinate, α-D-isosaccharinic acid and α D-isosaccharino-1,4-lactone. The equilibrium constant for the lactonization reaction has been determined by transformation rate and equilibrium studies. This information was used in complexation studies. The stability constants of thorium and americium α D-isosaccharinate have been determined using solvent extraction technique. The enthalpies and entropies associated with the thorium α D-isosaccharinate complexation have been established
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| 5. |
- Brown, P. L., et al.
(författare)
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Dissociation Constants of alpha-D-Isosaccharinic Acid: "Composite" and "Intrinsic" Values
- 2010
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Ingår i: Journal of Chemical & Engineering Data. - : American Chemical Society (ACS). - 0021-9568 .- 1520-5134. ; 55:11, s. 5207-5213
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Tidskriftsartikel (refereegranskat)abstract
- The transformation of alpha-D-isosaccharinic acid into alpha-D-isosaccharino-1,4-lactone proceeds relatively slowly. Consequently, the transformation constant, K-L, has been determined kinetically in 1.0 mol center dot dm(-3) NaClO4 and at 23 degrees C. A previous determination in 0.1 mol center dot dm(-3) NaClO4 and at 23 degrees C has been reinterpreted. The values obtained have been coupled with other data in the literature to demonstrate that the magnitude of the transformation constant is independent of ionic strength, and its value was determined to be log K-L degrees = 0.80 +/- 0.02. Data from the literature for the dissociation of alpha-D-isosaccharinic acid have been re-evaluated to determine both the "intrinsic" and "composite" dissociation constants at zero ionic strength, namely, log K-u degrees = -4.04 +/- 0.06 and log K-c degrees = -4.90 +/- 0.07, respectively. The present data permit a much more thorough understanding of the aqueous chemistry of alpha-D-isosaccharinic acid to be ascertained than has previously been possible.
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| 6. |
- Chernikova, Dina, 1982, et al.
(författare)
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The neutron-gamma Feynman variance to mean approach: Gamma detection and total neutron-gamma detection (theory and practice)
- 2015
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 782, s. 47-55
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Tidskriftsartikel (refereegranskat)abstract
- Two versions of the neutron gamma variance to mean (Feynman-alpha method or Feynman-Y function) formula for either gamma detection only or total neutron gamma detection, respectively, are derived and compared in this paper. The new formulas have particular importance for detectors of either gamma photons or deleclors sensitive to both neutron and gamma radialion. If applied to a plastic or liquid deleclor, he total neutron-gamma detection Feynman-Y expression corresponds Lo a situation where no discrimination is made between neutrons and gamma parlicles. The gamma variance Lo mean formulas are useful when a detector of only gamma radialion is used or when working with a combined neutron-gamma deleclor at high count rates. The theoretical derivation is based on the Chapman-Kolmogorov equation with the inclusion of general reactions and corresponding intensities for neutrons and gammas, but with the inclusion of prompt reactions only. A one energy group approximation is considered. The comparison of the two different theories is made by using reaction intensities obtained in MCNPX simulations with a simplified geometry for two scintillation detectors and a Cf-252-source. In addition, the variance to mean ratios, neutron, gamma and total neutron-gamma are evaluated experimentally for a weak Cf-252 neutron-gamma source, a Cs-137 random gamma source and a Na-22 correlated gamma source. Due to the focus being on the possibility of using neutron-gamma variance to mean theories for both reactor and safeguards applications, we limited the present study to the general analytical expressions for Feynman-alpha formulas.
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| 7. |
- Dubois, Isabelle, 1983, et al.
(författare)
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Dependency of BET surface area on particle size for some granitic minerals.
- 2011
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Ingår i: Proc. Radiochimica Acta. - : Oldenbourg Wissenschaftsverlag. - 2193-2875. ; 1, s. 75-82, s. 75-82
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Tidskriftsartikel (refereegranskat)abstract
- In order to assess the geochemical retention properties of rocks, which will be the final barrier for radionuclide transport to the biosphere in the case of a failed deep underground repository for spent nuclear fuel, radionuclide sorption experiments are usually made with crushed material. This raises the issue of extrapolating results obtained from laboratory experiments to the field scale. As sorption is generally related to the surface area of the geological material, it is then important to consider the dependency of the specific surface area on the particle size. In this work, BET surface area determinations of samples of different particle sizes are conducted on two minerals commonly found in granite: labradorite and magnetite. The results show a linear relationship between BET surface area and the inverse of the particle size, up to a certain particle size. Furthermore, results also show that the specific surface area for intact, larger pieces is much smaller than the one predicted by a linear extrapolation of results on crushed material. Therefore, extrapolation of BET area for fine particles to the field situation will lead to an overestimation of the surface area and thereby also the radionuclide sorption, if sorption coefficients are extrapolated as well. Also of importance is that these results show that sorption experiments on crushed material may dominantly reflect properties of new surface, created during the mechanically treatment of the samples.
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| 8. |
- Dubois, Isablle E., et al.
(författare)
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Correlation between particle size and surface area for chlorite and K-feldspar
- 2010
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Ingår i: Water-Rock Interaction - Proceedings of the 13th International Conference on Water-Rock Interaction, WRI-13. - 9780415604260 ; , s. 717-720, s. 717-720
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Konferensbidrag (refereegranskat)abstract
- The specific surface area as determined by BET analysis is often used for scaling mineral surface reaction capacities and rates between particles of different sizes as found in nature. Generally, an inverse proportionality between BET area and particle size is assumed, based on geometry. However, macroscopic laboratory studies of mineral surface reactions generally employ crushed material that may have been mechanically disturbed, potentially leading to an artificial increase in the specific surface area, and a change in the apparent surface reactivity. In this study, we determine the BET area for natural K-feldspar and chlorite samples from Sweden as function of particle size in a first step towards relating the surface reactivity for these minerals to grain size.
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| 9. |
- Karlsson, Johan, 1984, et al.
(författare)
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Ex vivo alendronate localization at the mesoporous titania implant/bone interface
- 2015
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Ingår i: Journal of materials science. Materials in medicine. - : Springer Science and Business Media LLC. - 1573-4838 .- 0957-4530. ; 26
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Tidskriftsartikel (refereegranskat)abstract
- An attractive approach in implant technology is local drug delivery, and design of efficient, safe and reliable treatments. Ourhitherto strategy has been to coat Ti implants with a thin mesoporous TiO2 film that in turnis loaded with an osteoporosis drug, such as Alendronate (ALN) that is known to suppress osteoclastic activity. This system has proven highly successful and results in excellent osseointegration. However, more detailed information about drug-release and distribution at the bone/implant interface is needed. In this study, (14)C-ALN loaded titanium implants were placed up to 8weeks into rat tibia and the spatial-temporal distribution of the drug was evaluated. Autoradiography data demonstrated a sustained release of (14)C-ALN and the releaseddrug remained bound to bone in close vicinity, within 500 micrometers,of the implants. Liquid scintillation counting experiments confirmed that the distal transport of released (14)C-ALN was extremely low. The results are favorable as they show that ALN stays for a long time in the vicinity of the implant and may therefore improve for a long time the mechanical fixation of bone anchored implants. Moreover, these findings suggest due to the low systemic spreading a minimal risk of Alendronate related systemic side effects.
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