Chemical Properties of 2‐Bromodecanoic Acid

Abstract

Some chemical equilibrium constants for 2‐bromodecanoic acid were investigated. The dimerization constant of 2‐bromodecanoic acid, k₂ =278 M^?1, in tert‐butylbenzene was first derived from IR spectroscopy measurements. Secondly, the distribution coefficient, k _d =799, was found by combining the value of k₂ with distribution data obtained from solvent extraction experiments evaluated with the aid of neutron activation analysis. Finally the dissociation constant, k _a =3.18 ?10^?3 M, was estimated from two‐phase titrations. A theoretical calculation was made based on the obtained constants and this calculation was validated by a second solvent extraction experiment that gave a good correspondence between calculated and experimental values.     

Milling machine spindle analysis using FEM and non-contact spindle excitation and response measurement

In this paper a method for analysing lateral vibrations in a milling machine spindle is presented including finite-element modelling (FEM), magnetic excitation and inductive displacement measurements of the spindle response. The measurements can be conducted repeatedly without compromising safety procedures regarding human interaction with rotating high speed spindles. The measurements were analysed and compared with the FEM simulations which incorporated a spindle speed sensitive bearing stiffness, a separate mass and stiffness radius and a stiffness radius sensitive shear deformation factor. The effect of the gyroscopic moment and the speed dependent bearing stiffness on the system dynamics were studied for different spindle speeds. Simulated mode shapes were experimentally verified by a scanning laser doppler vibrometer. With increased spindle speed, a substantial change of the eigenfrequencies of the bearing-related eigenmodes was detected both in the simulations and in the measurements. The centrifugal force that acted on the bearing balls resulted in a softening of the bearing stiffness. This softening was shown to be more influential on the system dynamics than the gyroscopic moment of the rotor. The study performed indicates that predictions of high speed milling stability based on 0 rpm tap-test can be inadequate.     

COEXTRACTION OF URANIUM AND TECHNETIUM IN TBP-SYSTEMS

Abstract

The coextraction of technetium with uranium in TBP/HNO systems has been studied. The extraction mechanism,

has been found to agree well with experimental data at 5 M HNO,.The extraction constant, K_TC,e for this reaction Is given by

where T is temperature (K) and C_T total TBP concentration (%). This equation is valid for 5 M HNO, DSFS–30% TBP, and from 20 to 60°C, with an average error of 2·8% in log K_TC,e     

Separation of Actinides(III) from Lanthanides(III) in Simulated Nuclear Waste Streams using 6,6′‐Bis‐(5,6‐dipentyl‐[1,2,4]triazin‐3‐yl)‐[2,2′]bipyridinyl (C5‐BTBP) in Cyclohexanone

Abstract

An extraction system comprising 6,6′‐bis‐(5,6‐dipentyl‐[1,2,4]triazin‐3‐yl)‐[2,2′]bipyridinyl (C5‐BTBP) dissolved in cyclohexanone was investigated. The main purpose of this investigation was to extract and separate actinides(III) from lanthanides(III), both of which are present in the waste from the reprocessing of spent nuclear fuel. The system studied showed high distribution ratios for the actinides(III) and a high separation factor between actinides and lanthanides (SF_Am/Eu around 150). The extraction kinetics were fast with equilibrium being reached in 5 minutes. The effects of temperature on the extraction and the stoichiometry of the extracted complex were investigated. The extraction of californium(III) was studied and it was found that the BTBP molecule has a higher affinity for californium than for americium (SF_Cf/Am around 4). This system could be used to separate actinides(III) from lanthanide fission products with high efficiency, if used in conjunction with a pre‐equilibrium step.     

EXTRACTION BEHAVIOUR OF TECHNETIUM AND ACTINIDES IN THE ALIQUAT-336/NITRIC ACID SYSTEM

ABSTRACT

The extraction behaviour of technetium, thorium, uranium, neptunium, plutonium, americium and curium in the Aliquat-336 (diluted with 1,3-diisopropyl benzene) - nitric acid system have been studied. Aliquat-336 (tricapryl-methyl ammonium nitrate) is a quaternary ammonium salt extracting different species with an anion exchange mechanism. Distribution data obtained are modeled by anion exchange (technetium) and ion-pair formation mechanisms (actinides) with the extraction of nitric acid included to account for the lowering of the free extractant concentration. Reasonably high distribution ratios were obtained for technetium and the tetravalent elements (Th, Np and Pu) and Aliquat-336 can therefore be useful for partitioning of these elements.     

Selenolthiol and dithiol C-terminal tetrapeptide motifs for one-step purification and labeling of recombinant proteins produced in E. coli

We have previously shown that a redox-active selenocysteine-containing tetrapeptide-Sel-tag (Gly-Cys-Sec-Gly)-can be used as a C-terminal fusion motif for recombinant proteins produced in Escherichia coli. This Sel-tag allows selenolate-targeted one-step purification, as well as fluorescent labeling or radiolabeling either with gamma emitters (75Se) or with positron-emitting radionuclides (11C). Here we have analyzed four different redox-active C-terminal motifs, carrying either dithiol (Gly-Cys-Cys-Gly or Ser-Cys-Cys-Ser) or selenolthiol (Gly-Cys-Sec-Gly or Ser-Cys-Sec-Ser) motifs. Utilizing these different functional motifs with the same recombinant protein (Fel d 1), we were able to assess their relative reactivities and potential usefulness for biotechnological applications. We found that all four redox-active tags could be utilized for efficient one-step purification to provide pure protein from a crude bacterial lysate through reversible binding to phenylarsine oxide sepharose, with yields and purities comparable to those obtained for a His-tagged protein purified by the more common approach with use of a Ni2+ column. For labeling with electrophilic fluorescent or radioactive compounds, however, the selenolthiol motifs were considerably more efficient than their dithiol counterparts. The results thus show that both the selenolthiol- and the dithiol-containing tags can serve as efficient alternatives to His-tags for protein purification, while the selenolthiol motifs offer additional and unique potential for Sec-targeted labeling. It should therefore be possible to utilize these multifunctional tetrapeptide motifs to develop a wide range of novel biotechnological applications based on Sec targeting with electrophilic compounds.     

SULFONATION AND PERFORMANCE OF SURFACE SULFONATED 5 AND 10 /μm DIAMETER,HIGHLY CROSSLINKED POROUS AND 15 μm DIAMETER, 10% CROSSLINKED GEL TYPE RESINS

Improved column efficiencies and decreased tailing of Eu³⁺ and Lu³⁺ elution peaks with 2-hydroxy isobutyric acid, HIBA, were obtained by partial sulfonation of experimental monodisperse 5 and 10 μm, highly (>40%) crosslinked porous beads. Blocking of micropores of such highly crosslinked porous gels with n-dodecane before sulfonation further reduces the extent of sulfonation and improves column efficiency. Simultaneous choice of a smaller particle size and less sulfonation improves the column performance. The normalized performance of a monodisperse 10 μm, highly crosslinked porous resin of 0.058 meq/ml capacity was similar to that of a monodisperse 15 μm, 10% crosslinked surface sulfonated gel type resin of 0.031 meq/ml capacity for Lu³⁺/HIBA.     

Fabrication and luminescence of ZnS:Mn2+ nanoflowers

Visually striking nanoflowers composed of ZnS:Mn2+ nanoparticles are prepared and characterized. The configurations of these fractal structures are very sensitive to both the pH values of the particle solutions from which they are precipitated and the substrates on which they are deposited. At pH 2.2, the fractal structures resemble trees without leaves; at pH 7.7, they are tree-like with four arms and at pH 11.0 they resemble trees with six arms. High resolution transmission microscopy reveals that the nanoflowers are composed of ZnS:Mn2+ nanoparticles of 2-5 nm in size. X-ray photoelectron spectral data indicate that the sample compositions of nitrogen, chlorine, and sulfur vary gradually with pH values of the solutions. These changes may have an impact on both the fractal configuration and the luminescence properties. The emission spectra of the particle solutions at pH values of 2.2 and 11.0 are similar with the emission maximum at 475 nm. As the pH value approaches 7.7, the emission spectral maximum shifts to longer wavelengths. At a pH value of 7.7, the emission peak wavelength is the reddest, 520 nm. The emission peak of the nanoflowers at a pH value of 9.3 is 510 nm, while the emission spectrum of the nanoflowers at 5.2 has two peaks at 500 nm and 440 nm, respectively. These blue-green emissions are attributed to defects and are the dominant luminescence from the nanoflowers. The emission from Mn2+ dopant is only observed in the delayed spectra of the fractal solid samples.