The electrochemical deposition of mercury on glassy carbon electrodes : a thesis in partial fulfilment of the requirements for the degree of Masters in Science in Chemistry at Massey University, Palmerston North, New Zealand

The mechanism for the reduction of Hg2+ on glassy carbon in aqueous acetate and nitrate electrolyte was studied. This deposition process is of interest due to the wide electroanalytical applications of mercury thin film electrodes. It was found in the early stages of this work that even though the use of these electrodes is wide spread, there has been little investigation into how the deposition stage occurs. The electrochemical techniques used were cyclic voltammetry and chronoamperometry. A range of experiments were undertaken including concentration dependence, rotation dependence, scan rate dependence, electrochemical-cleaning, and the dependence of the length of time left at open potential. The acetate experiments were carried out at a constant pH of 5.0 and all experiments were carried out at a constant temperature of 20°C. Significant dependence was established in the cyclic voltammetry work for all the experimental conditions. In acetate electrolyte the development of peaks C1 and C2 were seen after cycling of the electrode without mechanical-cleaning. A shift in the reduction potential from a mechanically-cleaned electrode cycle to the next cycle without intervening cleaning was also observed. Two new anodic peaks, A2 and A3, were also seen in acetate electrolyte. At high concentrations cathodic current spikes were observed at the extreme cathodic limits of the voltammograms. The response that was observed in nitrate electrolyte was dissimilar to that in acetate. The shift in reduction potential, current spikes, peaks C1, C2, A2, and A3, were never observed for the deposition of Hg2+ in nitrate electrolyte. The chronoamperometry work on microelectrodes led to a number of new phenomena. Transients that were obtained from these experiments lead to the development of a quantitative nucleation and growth model for the growth of hemispherical mercury droplets. At the onset of reduction the transients follow a t2 function which is in accordance with surface area dependence growth of the droplet. However, after a short length of time, the transients start to follow a function of t 1/2, which is suggestive of perimeter growth control. This is assumed to be due to the formation of a semi-passivating Hg2(OAc)2 film over the mercury droplet where Hg2+2 forms as a result of a disproportionation reaction. A qualitative model was also developed to account for the observations of both the microelectrode results and most of the features seen in the cyclic voltammetry work

The human gaze at animals and the missing animal gaze in tourism studies

This research letter critically reflects on the missing animal gaze in tourism studies and elaborates on the urgency of including it in the discussion about the relationship between human and non-human animals. Drawing on the Foucauldian gaze and on the John Urry’s tourist gaze, we reflect on the unproblematised power imbalance between human and animal gazes that is inherent in tourist representations. Inspired by posthuman thinking, we use features of critical theory, sociology, and geography. This letter aims at casting a novel light to the human-animal relationship in tourism studies identifying a promising novel research line

Combined endophytic inoculants enhance nickel phytoextraction from serpentine soil in the hyperaccumulator Noccaea caerulescens

This study assesses the effects of specific bacterial endophytes on the phytoextraction capacity of the Ni-hyperaccumulator Noccaea caerulescens, spontaneously growing in a serpentine soil environment. Five metal-tolerant endophytes had already been selected for their high Ni tolerance (6 mM) and plant growth promoting ability. Here we demonstrate that individual bacterial inoculation is ineffective in enhancing Ni translocation and growth of N. caerulescens in serpentine soil, except for specific strains Ncr-1 and Ncr-8, belonging to the Arthrobacter and Microbacterium genera, which showed the highest indole acetic acid production and 1-aminocyclopropane-1-carboxylic acid-deaminase activity. Ncr-1 and Ncr-8 co-inoculation was even more efficient in promoting plant growth, soil Ni removal, and translocation of Ni, together with that of Fe, Co, and Cu. Bacteria of both strains densely colonized the root surfaces and intercellular spaces of leaf epidermal tissue. These two bacterial strains also turned out to stimulate root length, shoot biomass, and Ni uptake in Arabidopsis thaliana grown in MS agar medium supplemented with Ni. It is concluded that adaptation of N. caerulescens in highly Ni-contaminated serpentine soil can be enhanced by an integrated community of bacterial endophytes rather than by single strains; of the former, Arthrobacter and Microbacterium may be useful candidates for future phytoremediation trials in multiple metal-contaminated sites, with possible extension to non-hyperaccumulator plants

Liver involvement in pediatric celiac disease

Celiac disease (CD) is an intestinal inflammatory disease that manifests in genetically susceptible individuals when exposed to dietary gluten. It is a common chronic disorder, with a prevalence of 1% in Europe and North America. Although the disease primarily affects the gut, the clinical spectrum of CD is remarkably varied, and the disease can affect many extraintestinal organs and systems, including the liver. The hepatic dysfunction presenting in CD ranges from asymptomatic liver enzyme elevations or nonspecific reactive hepatitis (cryptogenic liver disorders), to chronic liver disease. In this article, we review the clinical presentations and possible mechanisms of CD-related liver injury to identify strategies for the diagnosis and treatment of these disorders in childhood

Energy-based operator splitting approach for the time discretization of coupled systems of partial and ordinary differential equations for fluid flows: The Stokes case

The goal of this work is to develop a novel splitting approach for the numerical solution of multiscale problems involving the coupling between Stokes equations and ODE systems, as often encountered in blood flow modeling applications. The proposed algorithm is based on a semi-discretization in time based on operator splitting, whose design is guided by the rationale of ensuring that the physical energy balance is maintained at the discrete level. As a result, unconditional stability with respect to the time step choice is ensured by the implicit treatment of interface conditions within the Stokes substeps, whereas the coupling between Stokes and ODE substeps is enforced via appropriate initial conditions for each substep. Notably, unconditional stability is attained without the need of subiterating between Stokes and ODE substeps. Stability and convergence properties of the proposed algorithm are tested on three specific examples for which analytical solutions are derived

Effects of field inoculation with VAM and bacteria consortia on root growth and nutrients uptake in common wheat

This study investigated the effects of a commercial biofertilizer containing the mycorrhizal fungus Rhizophagus irregularis and the diazotrophic N-fixing bacterium Azotobacter vinelandii on root and shoot growth, yield, and nutrient uptake in common wheat (Triticum aestivum L.) in order to improve the sustainable cultivation of this widespread crop. The trials were carried out in controlled conditions (rhizoboxes) and in open fields over two years to investigate the interaction between inoculation and three doses of nitrogen fertilization (160, 120 and 80 kg ha1) in a silty-loam soil of the Po Plain (NE Italy). In rhizoboxes, efficient root colonization by R. irregularis was observed at 50 days after sowing with seed inoculation, together with improved root tip density and branching (+~30% vs. controls), while the effects of post-emergence inoculation by soil and foliar spraying were not observable at plant sampling. In the open, field spraying at end tillering significantly increased the volumetric root length density (RLD, +22% vs. controls) and root area density (+18%) after about two months (flowering stage) in both years under medium and high N fertilization doses, but not at the lowest N dose. In absence of inoculation, RLD progressively decreased with increased N doses. Inoculation had a negligible effect on grain yield and N uptake, which followed a typical N dose-response model, while straw Zn, P, and K concentrations were seldom improved. It is concluded that medium-high N fertilization doses are required to achieve the target yield and standards of quality (protein contents) in wheat cultivation, while the use of this mixed VAM-PGPR biofertilizer appears to be a sustainable mean for minimizing the adverse effects of chemical N fertilizers on root expansion and for improving the uptake of low-mobility nutrients, which has potentially relevant environmental benefits

Effetti dell'intensità di utilizzazione sulla produzione foraggera e sull'azotofissazione della sulla

Objectives of this research were (I) to quantify nitrogen fixation under field conditions of sweetvetch in relation to the cutting intensity; (II) to evaluate the effect of the control species on the reliability of the estimate of nitrogen fixation, using the nitrogen balance method (NB); (III) to verify the possibility of application of the natural abundance method (NA) in the environmental conditions of the experimental site. Two cutting intensities were compared: intensive (2 early cuts in spring and 1 autumn cut) and extensive (1 cut in spring + possible cleaning cut in summer). Three control species were tested: Lolium hybridum, Cicorium inthybus and Phalaris aquatica. The intensive cutting regime showed higher levels of nitrogen fixation in the above ground phytomass compared to those achievabie through extensive utilization (about 300 vs. 235 kg N ha-1). The nitrogen fixation assessed by the NB method was underestimated when Phalaris aquatica was used as control species, while nitrogen fixation was not affected by the control species using the NA method. The results show that soil δ 15N in the experimental site was sufficient for the application of NA method. The δ 15N of sulla cultivated in a soil without combined nitrogen was obtained indirect1y (B = -2,4) by assuming that the percentage of nitrogen fixation on total nitrogen of sulla is never higher than 95%. Further investigations are required to verify this parameter and to evaluate the fate of fixed nitrogen in the following crop after a legume crop. The dynamics of the morphological stage of deveIopment, of the leaf to stem ratio and of the total nitrogen of the aboveground phytomass influenced the reliability of the control species using the NB method

The equilibrium measure for a nonlocal dislocation energy

In this paper we characterize the equilibrium measure for a nonlocal and anisotropic weighted energy describing the interaction of positive dislocations in the plane. We prove that the minimum value of the energy is attained by a measure supported on the vertical axis and distributed according to the semicircle law, a well-known measure that also arises as the minimizer of purely logarithmic interactions in one dimension. In this way we give a positive answer to the conjecture that positive dislocations tend to form vertical walls. This result is one of the few examples where the minimizer of a nonlocal energy is explicitly computed and the only one in the case of anisotropic kernels.</p