A study of the partitioning and sorptive behaviour of butyltins in the aquatic environment

This study was designed to investigate the partitioning and sorptive behaviour of tributyltin(TBT), and its degradation products dibutylitin (DBT) and monobutyltin (MBT), in the aquatic environment. Factorial experiments were undertaken to determine the importance of pH and particulate matter concentration in the sorption of butyltin compounds to solid phases. Results indicate that in freshwaters MBT, and to a lesser extent TBT, will be partitioned towards the particulate phase, whereas DBT exhibits a 50:50 partitioning between particulate and solution phases. In estuarine waters, whilst MBT will almost exclusively sorb on to particulates, TBT will be predominantly in the solid-phase fractions but 10–30% may remain in solution. DBT, in contrast, is solubilized in estuarine waters. A more detailed investigation of TBT sorption and particulate matter concentration was undertaken using adsorption isotherms on different sediment types. The results from batch isotherm tests plotted according to the Freundlich adsorption model revealed that TBT adsorption varied with sediment type, increasing in the order sandy-silt < silty-sand < silty-clay. TBT sorption was found to be reversible, indicating that contaminated sediments may release TBT to overlying waters following sediment distrubance. Interstitial water partitioning studies indicate that TBT predominates in the particulate phase with partition coefficients for TBT higher than for DBT and MBT. The TBT partition coefficient in interstitial waters appears to be related to total organic carbon loadings.     

Observation of persistent photoconductivity in conducting polyaniline thin films

Conducting polyaniline thin films have been deposited by a laser-based vaporization technique. The films have been characterized by infrared spectroscopy, UV-Vis spectroscopy, four-point conductivity measurements, thermogravimetric analysis, and fluorescence measurements. In addition, the films have been characterized with respect to their photoconductive response to 532-nm laser light. It is found that the films exhibit persistent photoconductivity and it is proposed that defect base sequences may be responsible for the charge localization that results in such a photoconductive response. PACS 78.66.Qn; 81.15.Fg; 72.80.Le     

A study of the centrally produced π+π−π0 system formed in the reactionpp→p f (π+π−π0)p s at 300 GeV/c

The reactionpp→p _f (π⁺π^?π⁰)p _s , where the π⁺π^?π⁰ system is centrally produced, has been studied at 300 GeV/c. The π⁺π^?π⁰ mass spectrum shows evidence for the η, ω anda ₂ (1320) as well as an enhancement in thea ₁ (1260) region. A Dalitz plot analysis of the π⁺π^?π⁰ system has been performed. Thea ₁ (1260) parameters coming from the fit of the 1⁺ S wave arem=1208±15 MeV and Γ=430±50 MeV. No evidence is found for theh ₁(1170) orh ₁(1380).     

The production ofJ/ψ in 200 GeV/A oxygen-uranium interactions

The dimuon production in 200 GeV/nucleon oxygen-uranium interactions is studied by the NA 38 Collaboration. The production ofJ/ψ, correlated with the transverse energyET, is investigated and compared to the continuum, as a function of the dimuon massM and transverse momentumPT. A value of 0.64±0.06 is found for the ratio (ψ/Continuum at highET)/(ψ/Continuum at lowET), from which theJ/ψ relative suppression can be extracted. This suppression is enhanced at lowPT.     

Production ofρ +, −, 0 (770),η(550), ω(783) andf 2(1270) mesons in\bar v neon and ν neon charged current interactions

The production of the meson resonances ?(770) (all three charge states), η(550), ω(783) andf ₂(1270) in \(\bar v\) Ne and ν Ne charged current interactions is investigated in a bubble chamber experiment with BEBC at CERN. Except for thef ₂, the main features of resonance production are reasonably well described by the Lund model, although the average resonance multiplicities are overestimated by the model by (67±30)%. The average multiplicities of all resonances, including thef ₂, are well reproduced by a semiempirical model, whose parameters were determined from hadron interaction data.     

Improved J-compensated sequences based on short composite pulses

Efficient J-compensated sequences that are shorter in duration and use less RF pulses have been created from short but very efficient composite 90 degrees RF pulses. The improved J-compensation transforms in-phase into antiphase magnetization and can be incorporated in any pulse sequence that involves evolution of heteronuclear J-couplings. The compensated sequences were tested and incorporated into an HMBC sequence. J-compensated experiments referred to as HMBC-J45 + 90A and HMBC-J45 + 90B, were found to be effective over a wide range of J values.     

Neuropeptide delivery to the brain: a von Willebrand factor signal peptide to direct neuropeptide secretion

Background  

Multiple neuropeptides, sometimes with opposing functions, can be produced from one precursor gene. To study the roles of the different neuropeptides encoded by one large precursor we developed a method to overexpress minigenes and establish local secretion.