The effect of SO3-Ph-BTBP on stainless steel corrosion in nitric acid

SO3-Ph-BTBP is a hydrophilic tetra-N-dentate ligand proposed for An(III)/Ln(III) separation by solvent extraction, and a candidate for use in future advanced reprocessing schemes such as GANEX and SANEX. We present the first study of the effect of SO3-Ph-BTBP on the corrosion behavior of stainless steels. Specifically, studies have been performed using steels and conditions equivalent to those found in relevant nuclear reprocessing flow sheets. SO3-Ph-BTBP has been shown to have little effect on either steel passivation or reductive dissolution. However, if driven cathodically into a region of hydrogen evolution at the electrode surface or conversely anodically into a region of transpassive dissolution, observed currents are reduced in the presence of SO3-Ph-BTBP, suggesting corrosion inhibition of the steel potentially through weak absorption of a SO3-Ph-BTBP layer at the metal-solution interface. The lack of any observed corrosion acceleration via complexation of Fe3+ is surprising and has been suggested to be due to the slow extraction kinetics of SO3-Ph-BTBP as a result of a requirement for a trans- to cis-conformational change before binding

Promoting students’ sexual and reproductive health in peer-led programmes at two South African universities: Emergent tensions and dilemmas

Sexual and reproductive health programmes with students in higher education in South Africa, are a neglected area of intervention. We report on piloting the peer-facilitated Auntie Stella intervention material at two South African universities. This participatory methodology encourages critical thinking by opening discussion on managing relationships, sexual decision-making, gender-based violence and risk-safety. The format involves various cards featuring a letter, a facilitated discussion, an answer-response and action points. Six focus groups of participants were facilitated by postgraduate students over four months. Using thematic analysis four tensions were identified in the student discussions: HIV awareness was in tension with relationship practices; awareness of risk was in tension with denial of vulnerability; awareness of individuals’ rights was in tension with claims on these rights; and HIV knowledge was in tension with HIV stigma. The Auntie Stella material has the potential to open up discursive spaces amongst students, and to develop agency in sexual decision-making

Insight into the self-assembly of water-soluble perylene bisimide derivatives through a combined computational and experimental approach

We use a combination of computational and experimental techniques to study the self-assembly and gelation of water-soluble perylene bisimides derivatised at the imide position with an amino acid. Specifically, we study the likely structure of self-assembled aggregates of the alanine-functionalised perylene bisimide (PBI-A) and the thermodynamics of their formation using density functional theory and predict the UV-vis spectra of such aggregates using time-dependent density functional theory. We compare these predictions to experiments in which we study the evolution of the UV-Vis and NMR spectra and rheology of alkaline PBI-A solutions when gradually decreasing the pH. Based on the combined computational and experimental results, we show that PBI-A self-assembles at all pH values but that aggregates grow in size upon protonation. Hydrogel formation is driven not by aggregate growth but reduction of the aggregation surface-charge and a decrease in the colloidal stability of the aggregation with respect to agglomeration

The effect of hydrogen peroxide on uranium oxide films on 316L stainless steel

For the first time the effect of hydrogen peroxide on the dissolution of electrodeposited uranium oxide films on 316L stainless steel planchets (acting as simulant uranium-contaminated metal surfaces) has been studied. Analysis of the H2O2-mediated film dissolution processes via open circuit potentiometry, alpha counting and SEM/EDX imaging has shown that in near-neutral solutions of pH 6.1 and at [H2O2] 0.1 mol dm(-3) the uranium oxide film, again in analogy to common corrosion processes, behaves as if in a transpassive state and begins to dissolve. This transition from passive to transpassive behaviour in the effect of peroxide concentration on UO2 films has not hitherto been observed or explored, either in terms of corrosion processes or otherwise. Through consideration of thermodynamic solubility product and complex formation constant data, we attribute the transition to the formation of soluble uranyl-peroxide complexes under mildly alkaline, high [H2O2] conditions - a conclusion that has implications for the design of both acid minimal, metal ion oxidant-free decontamination strategies with low secondary waste arisings, and single step processes for spent nuclear fuel dissolution such as the Carbonate-based Oxidative Leaching (COL) process. (C) 2015 Elsevier B.V. All rights reserved

Photocatalytically Driven Dissolution of Macroscopic Nickel Surfaces

Photocatalytically generated H2O2-driven nickel dissolution has been studied as a novel, secondary waste minimal decontamination process for nuclear process steels. Nickel corrosion experiments in dilute H2SO4 show that at deliberately added [H2O2] ≤ 1 mM, nickel dissolution occurs via formation and dissolution of NiOH groups; at [H2O2] ≥ 10 mM (pseudo-)passivation by NiO prevents this. Furthermore, Nickel also dissolves slowly in mild acid, dissolution that is significantly accelerated in the presence of photogenerated peroxide – suggesting that photocatalytically generated H2O2 could be used to selectively increase dissolution of Ni, and potentially steel, surfaces that normally dissolve only slowly in mild acid

Hydrogen evolution from water using heteroatom substituted fluorene conjugated co-polymers

The photocatalytic performance of fluorene-type polymer photocatalysts for hydrogen production from water in the presence of a sacrificial hole scavenger is significantly improved by the incorporation of heteroatoms into the...</p

Direct mass analysis of water absorption onto ceria thin films

Plutonium oxide (PuO2) is one of the most highly radioactive components of nuclear fuel waste streams and its storage poses particular challenges due to the high temperatures produced by its decay and the production of gases (particularly H2 and steam). Its high radiotoxicity necessitates the use of analogues, such as CeO2, to allow the comprehensive study of its interaction with water under storage conditions. We have developed a method which enables direct gravimetric measurement of water adsorption onto CeO2 thin films with masses in the microgram region. Porous CeO2 films were fabricated from a surfactant based precursor solution. The absorption of water onto the CeO2 coating at different relative humidities was studied in a closed reactor. Quartz Crystal Microbalance (QCM) gravimetry was used as a signal transducer, as changes in crystal resonant frequency due to absorbed mass are directly and linearly related to mass changes occurring at the crystal surface. Using this method, we have determined the enthalpy of absorption of water onto CeO2 to be 49.7 kJmol–1 at 75°C, 11 kJmol-1 greater than the enthalpy of evaporation. This enthalpy is within the range predicted for the absorption of water onto PuO2, indicating this method allows for investigation of water absorption using microgram samples

Cardiac effects of amiselimod compared with fingolimod and placebo: results of a randomised, parallel-group, phase I study in healthy subjects.

AIM: Amiselimod (MT-1303) is a selective sphingosine 1-phosphate 1 (S1P1 ) receptor modulator which is currently being developed for the treatment of various autoimmune diseases. Unlike some other S1P receptor modulators, amiselimod seemed to show a favourable cardiac safety profile in preclinical, phase I and II studies. The aim of the current study was to characterize the cardiac effects of amiselimod by directly comparing it with fingolimod and placebo. METHODS: A total of 81 healthy subjects aged 18-55 years were equally randomized to receive amiselimod 0.4 mg, amiselimod 0.8 mg, placebo or fingolimod 0.5 mg once daily for 28 days. The chronotropic/dromotropic and inotropic effects were evaluated using intensive Holter electrocardiogram and echocardiography. RESULTS: Unlike fingolimod, neither amiselimod dose exerted acute (1-6 h) negative chronotropic effects on Days 1 and 2. The lowest nadir mean hourly heart rate was observed on Day 14 in the amiselimod 0.4 mg group (least squares mean difference: -4.40 bpm, 95% confidence interval -7.15, -1.66) and Day 7 in the 0.8 mg group [-3.85 bpm (-6.58, -1.11)] compared with placebo, but these changes were smaller than those with fingolimod on Day 1 [-6.49 bpm (-8.95, -4.02)]. No clinically significant bradyarrhythmia or cardiac functional abnormalities were observed in either amiselimod group. Both amiselimod doses were well tolerated and no serious adverse events were reported. Fingolimod was also generally well tolerated, although one subject was withdrawn owing to highly frequent 2:1 atrioventricular blocks on Day 1. CONCLUSION: The study demonstrated a more favourable cardiac safety profile for amiselimod than fingolimod when administered over 28 days in healthy subjects

Structure–activity relationships in well-defined conjugated oligomer photocatalysts for hydrogen production from water

Most organic semiconductor photocatalysts for solar fuels production are linear polymers or polymeric networks with a broad distribution of molecular weights. Here, we study a series of molecular dibenzo[b,d]thiophene sulfone and fluorene oligomers as well-defined model systems to probe the relationship between photocatalytic activity and structural features such as chain length and planarity. The hydrogen evolution rate was found to vary significantly with bridge head atom, chain length, and backbone twisting. A trimer (S3) of only three repeat units has excellent activity for proton reduction with an EQE of 8.8% at 420 nm, approaching the activity of its polymer analogue and demonstrating that high molar masses are not a prerequisite for good activity. The dynamics of long-lived electrons generated under illumination in the S3 oligomer are very similar to the corresponding polymer, both under transient and quasi-continuous irradiation conditions

Accelerated Discovery of Organic Polymer Photocatalysts for Hydrogen Evolution from Water through the Integration of Experiment and Theory

Conjugated polymers are an emerging class of photocata-lysts for hydrogen production where the large breadth of potential synthetic diversity presents both an opportunity and a challenge. Here, we integrate robotic experimentation with high-throughput computation to navigate the available structure-property space. A total of 6354 co-polymers was considered computationally, followed by the synthesis and photocatalytic characterization of a sub-library of more than 170 co-polymers. This led to the discovery of new pol-ymers with sacrificial hydrogen evolution rates (HERs) of more than 6 mmol g-1 h-1. The variation in HER across the library does not correlate strongly with any single physical property but a machine learning model involving four sepa-rate properties can successfully describe up to 68% of the variation in the HER data between the different polymers. The four variables use in the model were the predicted elec-tron affinity, the predicted ionization potential, the optical gap, and the dispersibility of the polymer particles in solu-tion, as measured by optical transmittance