Biosorption and Bioreduction\u27s Impact on the Mobility of Uranium and Cesium

Microbial interactions with radionuclides in the environment are multi-faceted and play an important role on the fate and the extent of transport of these metals within the biosphere. Understanding how these biotic interactions affect radionuclides could prove useful in developing more suitable waste containment facilities and improve the overall risk management strategies at legacy waste sites around the world. This study investigates two microbial interactions with these metals: biosorption and bioreduction. To elucidate the impact of biosorption on uranium and cesium, active and inactive biomass were analyzed using batch sorption experiments in the presence of complexing ligands, EDTA and citrate, to determine whether whole cells or cell lysate increased sorption. Results demonstrated systems without soil showed a decrease in free aqueous uranium with biomass present in EDTA. Adding a second complexing ligand decreased the amount of biosorption to active biomass, but not inactive biomass. With soil present in the system, biomass increased the sorption of uranium to the soil regardless of the complexing ligand. In contrast, cesium was unaffected by the biomass and complexing ligands due to its affinity to sorption sites associated with the soil. Therefore, remedial strategies incorporating biomass as biosorbents increase the retention of uranium but have no effect on cesium. Further, the transformation of U(VI) to U(IV) via bioreduction was studied to quantify the rate and extent of U(VI) reduction using various electron donors. Re-oxidation of U(IV) experiments followed in the presence of nitrate or oxygen to determine the long-term viability of bioreduction as a remedial strategy for treating groundwater contaminated with uranyl carbonate. Results showed the various electron donors tested were sufficient to allow bioreduction of U(VI) to U(IV). However, re-oxidation occurred on the magnitude of days in the presence of oxygen or nitrate. Therefore, bioreduction of uranium as a remedial strategy does not offer long-term solutions for groundwater contaminated with uranyl carbonate

Student expectations: what is university really about?

Students spend 12 to 14 years in school learning in a carefully controlled and structured system.  It appears that many students enter university with unrealistic conceptions of what is expected of them in many aspects of teaching and learning, including assessment. Hence, when they reach university they are faced with the challenge of adjusting to radically different styles of teaching, learning and assessment. It follows that this lack of preparedness is key reason why students drop out or take longer to complete their studies.  To compound the issue, university teachers may not fully appreciate students' expectations and are unable to anticipate and address these in curriculum development and delivery.  Therefore, developing a better understanding of students’ perceptions, expectations and experiences is crucial to being able to deliver programmes of study that support students in the transition from school to university and as they move through their university life.  This paper explores the perceptions of Level 5 and Level 6 students on two LJMU programmes in the Faculty of Education, Health and Community with the overarching aim to investigate key aspects of the student experience relating to induction, support and transition.  By exploring students’ ideas around key areas we hope to be able to better understand what the student expectation is and identify strategies to bridge any gap that exists between staff and student beliefs

The Dynamics of a Collapsing Polyelectrolyte Gel

We analyse the dynamics of different routes to collapse of a constrained polyelectrolyte gel in contact with an ionic bath. The evolution of the gel is described by a model that incorporates non-linear elasticity, Stefan-Maxwell diffusion and interfacial gradient free energy to account for phase separation of the gel. A bifurcation analysis of the homogeneous equilibrium states reveals three solution branches at low ion concentrations in the bath, giving way to only one above a critical ion concentration. We present numerical solutions that capture both the spatial heterogeneity and the multiple timescales involved in the process of collapse. These solutions are complemented by two analytical studies. Firstly, a phase-plane analysis that reveals the existence of a depletion front for the transition from the highly swollen to the new collapsed equilibrium state. This depletion front is initiated after the fast ionic diffusion has set the initial condition for this time regime. Secondly, we perform a linear stability analysis about the homogeneous states that show that for a range of ion concentrations in the bath, spinodal decomposition of the swollen state gives rise to localized solvent-rich(poor) and, due to the electroneutrality condition, ion-poor(rich) phases that coarsen on the route to collapse. This dynamics of a collapsing polyelectrolyte gel has not been described before

Spinodal decomposition and collapse of a polyelectrolyte gel

The collapse of a polyelectrolyte gel in a (monovalent) salt solution is analysed using a new model that includes interfacial gradient energy to account for phase separation in the gel, finite elasticity and multicomponent transport. We carry out a linear stability analysis to determine the stable and unstable spatially homogeneous equilibrium states and how they phase separate into localized regions that eventually coarsen to a new stable state. We then investigate the problem of a collapsing gel as a response to increasing the salt concentration in the bath. A phase space analysis reveals that the collapse is obtained by a front moving through the gel that eventually ends in a new stable equilibrium. For some parameter ranges, these two routes to gel shrinking occur together

Asymptotic study of the electric double layer at the interface of a polyelectrolyte gel and solvent bath

An asymptotic framework is developed to study electric double layers that form at the inter-face between a solvent bath and a polyelectrolyte gel that can undergo phase separation. The kinetic model for the gel accounts for the finite strain of polyelectrolyte chains, free energy ofinternal interfaces, and Stefan?Maxwell diffusion. By assuming that the thickness of the doublelayer is small compared to the typical size of the gel, matched asymptotic expansions are used toderive electroneutral models with consistent jump conditions across the gel-bath interface in two-dimensional plane-strain as well as fully three-dimensional settings. The asymptotic frameworkis then applied to cylindrical gels that undergo volume phase transitions. The analysis indicatesthat Maxwell stresses are responsible for generating large compressive hoop stresses in the double layer of the gel when it is in the collapsed state, potentially leading to localised mechanicalinstabilities that cannot occur when the gel is in the swollen state. When the energy cost of in-ternal interfaces is sufficiently weak, a sharp transition between electrically neutral and chargedregions of the gel can occur. This transition truncates the double layer and causes it to have finitethickness. Moreover, phase separation within the double layer can occur. Both of these featuresare suppressed if the energy cost of internal interfaces is sufficiently high. Thus, interfacial freeenergy plays a critical role in controlling the structure of the double layer in the gel

Spinodal decomposition and collapse of a polyelectrolyte gel

The collapse of a polyelectrolyte gel in a (monovalent) salt solution is analysed using a new model that includes interfacial gradient energy to account for phase separation in the gel, finite elasticity and multicomponent transport. We carry out a linear stability analysis to determine the stable and unstable spatially homogeneous equilibrium states and how they phase separate into localized regions that eventually coarsen to a new stable state. We then investigate the problem of a collapsing gel as a response to increasing the salt concentration in the bath. A phase space analysis reveals that the collapse is obtained by a front moving through the gel that eventually ends in a new stable equilibrium. For some parameter ranges, these two routes to gel shrinking occur together

Breakdown of electroneutrality in polyelectrolyte gels

Mathematical models of polyelectrolyte gels are often simplified by assuming the gel is electrically neutral. The rationale behind this assumption is that the thickness of the electric double layer (EDL) at the free surface of the gel is small compared to the size of the gel. Hence, the thin-EDL limit is taken, in which the thickness of the EDL is set to zero. Despite the widespread use of the thin-EDL limit, the solutions in the EDL are rarely computed and shown to match to the solutions for the electrically neutral bulk. The aims of this paper are to study the structure of the EDL and establish the validity of the thin-EDL limit. The model for the gel accounts for phase separation, which gives rise to diffuse interfaces with a thickness described by the Kuhn length. We show that the solutions in the EDL can only be asymptotically matched to the solutions for an electrically neutral bulk, in general, when the Debye length is much smaller than the Kuhn length. If the Debye length is similar to or larger than the Kuhn length, then phase separation can be initiated in the EDL. This phase separation spreads into the bulk of the gel and gives rise to electrically charged layers with different degrees of swelling. Thus, the thin-EDL limit and the assumption of electroneutrality only generally apply when the Debye length is much smaller than the Kuhn length

Serum profile changes in postpartum women with a history of childhood maltreatment: a combined metabolite and lipid fingerprinting study

Koenig AM, Karabatsiakis A, Stoll T, et al. Serum profile changes in postpartum women with a history of childhood maltreatment: a combined metabolite and lipid fingerprinting study. Scientific Reports. 2018;8(1): 3468

Needle size for vaccination procedures in children and adolescents

Background: This is an update of a Cochrane Review first published in 2015. The conclusions have not changed. Hypodermic needles of different sizes (gauges and lengths) can be used for vaccination procedures. The gauge (G) refers to the outside diameter of the needle tubing. The higher the gauge number, the smaller the diameter of the needle (e.g. a 23 G needle is 0.6 mm in diameter, whereas a 25 G needle is 0.5 mm in diameter). Many vaccines are recommended for injection into muscle (intramuscularly), although some are delivered subcutaneously (under the skin) and intradermally (into skin). Choosing an appropriate length and gauge of a needle may be important to ensure that a vaccine is delivered to the appropriate site and produces the maximum immune response while causing the least possible harm. Guidelines conflict regarding the sizes of needles that should be used for vaccinating children and adolescents. Objectives: To assess the effects of using needles of different sizes for administering vaccines to children and adolescents on vaccine immunogenicity (the ability of the vaccine to elicit an immune response), procedural pain, and other reactogenicity events (adverse events following vaccine administration). Search methods: We updated our searches of CENTRAL, MEDLINE, Embase, and CINAHL to October 2017. We also searched proceedings of vaccine conferences and two trials registers. Selection criteria: Randomised controlled trials evaluating the effects of using hypodermic needles of any gauge or length to administer any type of vaccine to people aged from birth to 24 years. Data collection and analysis: Three review authors independently extracted trial data and assessed the risk of bias. We contacted trial authors for additional information. We rated the quality of evidence using the GRADE system. Main results: We included five trials involving 1350 participants in the original review. The updated review identified no new trials. The evidence from two small trials (one trial including infants and one including adolescents) was insufficient to allow any definitive statements to be made about the effects of the needles evaluated in the trials on vaccine immunogenicity and reactogenicity. The remaining three trials (1135 participants) contributed data to comparisons between 25 G 25 mm, 23 G 25 mm, and 25 G 16 mm needles. These trials included infants predominantly aged from two to six months undergoing intramuscular vaccination in the anterolateral thigh using the World Health Organization (WHO) injection technique (skin stretched flat, needle inserted at a 90° angle and up to the needle hub in healthy infants). The vaccines administered were combination vaccines containing diphtheria, tetanus, and whole‐cell pertussis antigens (DTwP). In some trials, the vaccines also contained Haemophilus influenzae type b (DTwP‐Hib) and hepatitis B (DTwP‐Hib‐Hep B) antigen components. Primary outcomes: Incidence of vaccine‐preventable diseases: No trials reported this outcome. Procedural pain and crying: Using a wider gauge 23 G 25 mm needle may slightly reduce procedural pain (low‐quality evidence) and probably leads to a slight reduction in the duration of crying time immediately after vaccination (moderate‐quality evidence) compared with a narrower gauge 25 G 25 mm needle (one trial, 320 participants). The effects are probably not large enough to be clinically relevant…Authors' conclusions: Using 25 mm needles (either 23 G or 25 G) for intramuscular vaccination procedures in the anterolateral thigh of infants using the WHO injection technique probably reduces the occurrence of local reactions while achieving a comparable immune response to 25 G 16 mm needles. These findings are applicable to healthy infants aged two to six months receiving combination DTwP vaccines with a reactogenic whole‐cell pertussis antigen component. These vaccines are predominantly used in low‐ and middle‐income countries. The applicability of the findings to vaccines with acellular pertussis components and other vaccines with different reactogenicity profiles is uncertain