Complexation of plutonium(IV) with sulfate at variable temperatures

The complexation of plutonium(IV) with sulfate at variable temperatures has been investigated by solvent extraction method. A NaBrO₃ solution was used as holding oxidant to maintain the plutonium(IV) oxidation state throughout the experiments. The distribution ratio of Pu(IV) between the organic and aqueous phases was found to decrease as the concentrations of sulfate were increased. Stability constants of the 1:1 and 1:2 Pu(IV)-HSO₄ ⁻ complexes, dominant in the aqueous phase, were calculated from the effect of [HSO₄ ⁻] on the distribution ratio. The enthalpy and entropy of complexation were calculated from the stability constants at different temperatures using the Van’t Hoff equation.     

Mass resolved MPI spectra of methyl iodide in the 430-490 nm region

The mass resolved multiphoton ionization (MPI) spectra of methyl iodide were obtained in the 430-490 nm region using a time-of-flight (TOF) mass spectrometer. They have the same vibrational structure, which testifies that the fragment species, in the wavelength region under study, are from the photodissociation of multiphoton ionized molecular parent ions. Some features in the spectra are identified as three-photon excitations to 6p and 7s Rydberg states of methyl iodide. Two new vibrational structures of some Rydberg states are observed. The mechanism of ionization and dissociation is also discussed.     

High-throughput cytochrome p450 inhibition assays by ultrafast gradient liquid chromatography with tandem mass spectrometry using monolithic columns

A generic method employing ultrafast liquid chromatography with tandem mass spectrometry (LC/MS/MS) was developed and employed for routine screening of drug candidates for inhibition of five major human cytochrome p450 (CYP) isozymes, CYP3A4, CYP2D6, CYP2C9, CYP2C19, and CYP1A2. The method utilized a monolithic silica rod column to allow fast flow rates to significantly reduce chromatographic run time. The major metabolites of six CYP-specific probe substrates for the five p450 isoforms were monitored and quantified to determine IC(50) values of five drug compounds against each p450 isozyme. Human liver microsomal incubation samples at each test compound concentration were combined and analyzed simultaneously by the LC/MS/MS method. Each pooled sample containing six substrates and an internal standard was separated and detected in only 24 seconds. The combination of ultrafast chromatography and sample pooling techniques has significantly increased sample throughput and shortened assay turnaround time, allowing a large number of compounds to be screened rapidly for potential p450 inhibitory activity, to aid in compound selection and optimization in drug discovery.     

Polyurethane cationomers. I. Structure–properties relationships

Polyurethane (PU) cationomers have been synthesized by quaternizing tertiary amine-containing linear polyurethanes using different quaternizers containing acid groups. The effect of chemical structure of PU cationomers on the physical properties was studied. The mechanical properties of PU cationomers were improved with decreasing molecular weight of poly(caprolactone) glycol, and increasing concentration of quaternary ammonium. Decreasing the carbon number in the alkyl group of the N-alkyl diethanol-amine chain-extenders, and using rigid symmetrical diisocyanates, the mechanical properties of the PU cationomers were increased. The effects of these factors on the glass transition temperature of PU cationomers were also examined. The mechanical properties of the PU cationomers decreased by immersion in water and recovered after removal of the water.     

Synthesis of cation-exchanged laponite suspensions by laser ablation of microsized-metal particles in liquid

Laser ablation in the liquid technique has been used to synthesize cation-exchanged laponite suspensions. In summary, laser ablation of the microsize-metal powder (Co, Al, and Cu) dispersed in an aqueous solution containing deionized water laponite crystals was carried out using laser beam generated by a single-mode, Q-switched Nd-Yag laser operating at 532 nm with a pulse duration of 5.5 ns and 10 Hz repetition rate. Laser fluence was 0.265 J/cm² for all tests. For all samples, the mass fraction of laponite was 1%. General observations of the prepared samples indicated that an aqueous suspension of 1 wt% laponite retained its free flowing liquid phase characteristics even after aging for several weeks. When bivalent cationic metals (Cu, Co, Al) were ablated in it for about 1 h, even with a small amount of the metal (0.025% and 0.050%) were generated, the suspension became highly viscous and behaved as a shear-thinning and thixotropic material. That is, the suspension gelled strongly when it was allowed to rest. The gels, however, could easily be reverted to a low viscosity liquid with simple shaking. Information from TEM and XRD analysis indicated that such a sol-gel transformation might be due to the charge exchange between the cationic species produced during the laser ablation and the sodium ions in the interlayers of the clay sheets.     

Seasonal variation of 129I species in the Baltic Proper

Iodine speciation plays a significant role in iodine volatilizing into atmosphere from the seas, as well as serving as a biological indicator. Despite this importance, the data on iodine species revealed inconclusive evidence of what factors controlling speciation transformation. We here present new data on profiles of ¹²⁹I speciation in the Baltic Proper during November 2009. Along with the two earlier investigations (August 2006 and April 2007), an assessment of seasonal variation of ¹²⁹I species is presented. The results show that, due to the anoxic nature of Baltic Proper, presence of ¹²⁹IO₃ ^? in the Baltic Proper does not follow an obvious seasonal cycle, as the case with ¹²⁹I^?. Concentrations of ¹²⁹I^? in the Baltic Proper exhibit higher values in summer than the other two seasons (spring and winter), which might be associated with degrading of organic matter and release from sediment to water column that is more pronounced during summer. ¹²⁹I^? in surface water from the three seasons does not reflect the release function from the reprocessing facilities during the period April 2007 to November 2009. Consequently variability of ¹²⁹I^? in surface seawater of the Baltic Proper depends, to some extent, on local physical as well as biochemical conditions.     

Molecular dynamics studies of ultrafast laser-induced nonthermal melting

Molecular Dynamics (MD) is employed to investigate nonthermal melting triggered by coherent phonon excitation in bismuth telluride, which has Peierls distortion in the lattice structure. Results showed that the structural distortion caused by coherent phonons appears as early as 80 fs, while it takes several picoseconds for the whole phonon-excited area to evolve into a liquid state. It was also found that the temperature in the phonon-excited area rises quickly within tens of femtoseconds, while the rest of the lattice remains at the initial temperature even after several picoseconds, which is separated from the high temperature region across a thin transition area. This phenomenon is analogous to the heat transfer across a solid–liquid interface, even though in our case there is no abrupt solid-liquid interface between the cold lattice and the quasiliquid.     

Off-center Li defects in KCl: Parameters for isolated Li+ as a function of hydrostatic pressure and evidence for other Li centers

Abstract

We have measured all three tunneling parameters for the KCl:Li system as a function of hydrostatic pressure; all increase with pressure. Our measurements show that the off-center tunneling model works exceedingly well for this system. Surprisingly, the pressure dependence of the electric dipole moment shows a sharp break near 900 bar. In some samples, additional lines indicate other Li centers are present, possibly Li pairs.     

Anionic surfactant selective electrode for the titrimetric determination of anionic surfactant

The construction and characteristic performance of a PVC membrane electrode responsive for sodium dodecylsulfate (SDS) are described in this paper. The electrode based on CTA⁺DS^? ion pair as ionophore in PVC membrane displays a Nernstian slope of ?58.8 ± 0.7 mV/decade in a 1.32 × 10^?6 to 3.75 × 10^?3 mol L^?1 concentration range and a limit of detection of 1.13 × 10^?6 mol L^?1. The electrode can be used for 3 months without showing significant changes in the value of slope or working range. The electrode has been utilized as an end point indicator electrode for potentiometric titration involving Hyamine as titrant. More than 100 titrations were carried out for the evaluation of the electrode parameters: the standard deviations of the equivalent volume and the equivalent potential, the height of the potential jump and the number of faulty titrations. The behavior of the electrode was assessed with regard to their usefulness in routine analysis.