Investigation of the Causes of Violations of the Radioactive Balance between Radionuclides of the Uranium Decay Chain

Throughout the literature, it is mentioned that 15 radionuclides in the uranium decay chain have a constant radioactive equilibrium. Theoretical calculations give the value of the activity of each radionuclide in the uranium decay chain.This article examines various factors that affect the coefficient of radioactive equilibrium between radionuclides in the uranium decay chainThe concept of the coefficient of violations of nuclear equilibrium between radionuclides is adopted to determine the degree of violations in the uranium decay chain.Many nuclear-physical factors influence the radioactive balance between radionuclides. The most important of them is the recoil energy that the daughter nucleus receives when splitting from the mother nucleus.Another critical factor in the violation of the radioactive balance between radionuclides is the technological factor: leaching (acid, mini-reagent, bicarbonate, etc.) when leaching uranium by underground leaching of uranium.In addition, as a theoretical result of the study, the article presents a graphical relationship between the number of nuclear masses and the recoil energy of radionuclides in the uranium decay chain

Reversible Gelation of Poly(dimethylsiloxane) with Ionic and Hydrogen-Bonding Substituents

Poly(dimethylsiloxane) copolymers containing a small fraction of carboxylic acid or Zn-carboxylate groups were prepared and compared regarding reversible gelation by hydrogen-bonding and ion-pair interaction. The polymers were synthesized by condensation of a t-butylcarboxylate functionalized dichlorosilane with an α,ω-dihydroxy-poly(dimethylsiloxane), followed by thermal cleavage of the ester bond. Neutralization of the resulting carboxylic acid substituents was achieved by addition of Zn (acac)2. Reversible crosslinking was investigated by step stress and oscillating shear experiments. The carboxylic acid containing poly(dimethylsiloxane) became rubberlike upon increasing the temperature and liquified again when it was brought back to room temperature. This observation has been explained tentatively by segregation of the carboxylic acid groups into polar domains at high temperatures [i.e., a behavior like it is observed for systems with a lower critical solution temperature (LCST)]. At ambient temperature, the carboxylic acid groups undergo hydrogen bonding to the Si-O-Si backbone. Clustering of the carboxylic acid groups occurs only as these hydrogen bonds break upon raising temperature. Moisture was found to have a strong influence on the reversal of the crosslinking. Addition of zinc acetylacetonate resulted in the formation of an elastic network already at ambient conditions consistent with the concept of ionomers which undergo reversible gelation by formation of ion-pair multiplets and clusters in the hydrophobic polymer matrix in particularly at low temperatures. At high temperature, both the carboxylic acid and the carboxylate sample exhibited a rather similar viscoelastic behavior consistent with a common structure where transient crosslinks are formed by clusters of the carboxylic acid and the carboxylate groups. © 1999 John Wiley & Sons, Inc

Controlling aqueous sorption of humic substances on silica gel by directed alkoxysilyl-derivatization of their functionalities.

In this study we explored a possibility for enhancing aqueous sorption of humic substances (HS) onto hydroxylated surfaces (e.g., silica gel) by increasing modification rate of their most abundant functional groups - carboxyls with mineral-adhesive alkoxysilyl moieties. The synthesis included treatment of dried humic material with 3-aminopropyl trimethoxy silane (APTS) capable of forming amide bonds with carboxyl groups of HS under anhydrous conditions. The reaction was run at six different HS to APTS ratio for achieving different modification degrees of the carboxyl groups in the humic backbone. The obtained derivatives were characterized using elemental analysis, 13C NMR Spectroscopy, Fourier transform infrared spectroscopy, and size exclusion chromatography that confirmed quantitative incorporation of alkoxysilyl-moieties into HS structure. Aqueous adsorption was investigated in 0.028 M phosphate buffer using silica gel as a surrogate for mineral surface. Both distribution coefficients as well adsorption capacities paralleled the amount of alkoxysilyl-moieties incorporated into backbone of the parental HS. The adsorption capacity reached its maximum value of 210 mg of HS per g of SiO2 for the APTS derivative synthesized at the equimolar reagent ratio. This value was comparable to the amount of the same HS immobilized onto the APTS-treated silica gel (265 mg of HS per g of SiO2). Adsorption of alkoxysilyl-derivatives was found to be irreversible under conditions studied. Conclusively, we believe that the directed modification of HS by incorporating alkoxysilyl-moieties is well suited for producing humic derivatives with controllable affinity for aqueous sorption onto hydroxylated surfaces

Plasmonic fluorescence enhancement of DBMBF2 monomers and DBMBF2-toluene exciplexes using al-hole arrays

The optical properties of aluminum hole arrays fabricated via colloidal lithography were investigated. By tuning the hole diameter and hole spacing independently, their influence on the Bloch wave-surface plasmon polariton (BW-SPP) and localized surface plasmon resonances resonances (LSPR) could be identified. The aluminum hole arrays were used to enhance the fluorescence of a dibenzoylmethanatoboron difluoride (DBMBF2) dye. The dye exhibits the advantageous property of forming an exciplex with aromatic compounds. The interaction of DBMBF2 monomer fluorescence and DBMBF 2-toluene exciplexes with Al hole arrays is studied. Furthermore, the respective roles of the BW-SPPs and LSPRs were studied through tuning of the plasmon resonances from the UV excitation wavelength (λext = 385 nm) through the visible emission range (400-550 nm). Monomer emission was predominately enhanced by BW-SPPs while exciplex emission showed a contribution from both BW-SPPs and LSPRs. Fluorescence enhancement of 3.8 was observed for DBMBF2-toluene exciplex emission from 26 nm thick polymer films. Aluminum hole arrays are shown to be attractive structures for fluorescence enhancing applications with excitation in the UV and stable oxide coatings. © 2014 American Chemical Society