Advanced Fenton processing of aqueous phenol solutions:a continuous system study including sonication effects

Our previous report based on a batch reactor system for the Advanced Fenton Process (AFP) showed that pH, hydrogen peroxide and the organic substances treated are among the most important factors affecting the oxidation efficiency. As an extended study towards its commercialisation, this paper reports the effects of the main process parameters including those relating to a new AFP flow-through system. In order to systemise and correlate the results, the Taguchi experimental design method was used. Total organic carbon (TOC) removal was utilised as the measure of the oxidation efficiency and it was found that the removal of phenol from aqueous solution at pH 2.0 and 2.5 was very similar but hydrogen peroxide supply significantly affected the TOC removal with the change of flow rate from 14.4 mL/hr to 60 mL/hr. Also, the initial concentration of phenol was a highly significant factor, with higher concentrations resulting in a lower TOC removal rate. The temperature effects in the range of 14 °C to 42 °C were investigated and it was found that there was accelerated oxidation of phenol in the early stages but after 90 minutes there was no significant difference between the results. Sonication with a bath type sonicator resulted in relatively small enhancements of TOC removal but further studies with cup-horn and probe type sonicators showed that TOC removal increased with higher intensity of sonication on additional input of hydrogen peroxide

Sculpting the Extra Dimensions: Inflation from Codimension-2 Brane Back-reaction

We construct an inflationary model in 6D supergravity that is based on explicit time-dependent solutions to the full higher-dimensional field equations, back-reacting to the presence of a 4D inflaton rolling on a space-filling codimension-2 source brane. Fluxes in the bulk stabilize all moduli except the `breathing' modulus (that is generically present in higher-dimensional supergravities). Back-reaction to the inflaton roll causes the 4D Einstein-frame on-brane geometry to expand, a(t) ~ t^p, as well as exciting the breathing mode and causing the two off-brane dimensions to expand, r(t) ~ t^q. The model evades the general no-go theorems precluding 4D de Sitter solutions, since adjustments to the brane-localized inflaton potential allow the power p to be dialed to be arbitrarily large, with the 4D geometry becoming de Sitter in the limit p -> infinity (in which case q = 0). Slow-roll solutions give accelerated expansion with p large but finite, and q = 1/2. Because the extra dimensions expand during inflation, the present-day 6D gravity scale can be much smaller than it was when primordial fluctuations were generated - potentially allowing TeV gravity now to be consistent with the much higher gravity scale required at horizon-exit for observable primordial gravity waves. Because p >> q, the 4 on-brane dimensions expand more quickly than the 2 off-brane ones, providing a framework for understanding why the observed four dimensions are presently so much larger than the internal two. If uplifted to a 10D framework with 4 dimensions stabilized, the 6D evolution described here could describe how two of the six extra dimensions evolve to become much larger than the others, as a consequence of the enormous expansion of the 4 large dimensions we can see.Comment: 27 pages + appendices, 2 figure

The effects of increased freshwater inflow on metal enrichment in selected Eastern Cape estuaries, South Africa

The concentrations of select metals (Cd, Co, Cu, Fe, Pb, Ni and Zn) within the water column and sediment of the permanently open Kariega Estuary and temporary open / closed Riet and East Kleinemonde Estuaries were investigated during a dry and a wet season. Enrichment factors (EFs), using Fe as a reference element, and baseline linear regression models for metals vs Fe were used to assess the extent of metal enrichment in the sediments. The results of the study indicate that Cd, Co Ni and Pb were enriched above baseline concentrations (1.0 < EF < 4.1) in the sediments of all three estuaries. Co, Pb and Ni enrichment in the Kariega Estuary sediments was significantly higher during the dry season, and the mean concentrations of Pb and Cd in the water column were 19-fold and 66-fold higher in the dry season. The elevated concentration of metals during the dry season could be related to accumulation of diffuse pollution from human activities within the catchment area. Conversely, inflow of freshwater into the estuary had the net effect of reducing the concentration and enrichment of these metals within the Kariega Estuary due to scouring and outflow of estuarine water and sediment into the marine environment. The temporal variations in metal concentrations and enrichment factors were less pronounced in the temporary open / closed estuaries than the Kariega Estuary. The observed trend can probably be related to the low anthropogenic impact within the catchment areas of these systems, and the relatively smaller size of the catchments. Significant spatial variations existed in metal enrichment in the sediment of both the East Kleinemonde and Riet Estuaries, with the highest degrees of enrichment occurring in the sediments from the marine environment and lower reaches

Extended Dualization: a method for the Bosonization of Anomalous Fermion Systems in Arbitrary Dimension

The technique of extended dualization developed in this paper is used to bosonize quantized fermion systems in arbitrary dimension $D$ in the low energy regime. In its original (minimal) form, dualization is restricted to models wherein it is possible to define a dynamical quantized conserved charge. We generalize the usual dualization prescription to include systems with dynamical non--conserved quantum currents. Bosonization based on this extended dualization requires the introduction of an additional rank $0$ (scalar) field together with the usual antisymmetric tensor field of rank $(D-2)$. Our generalized dualization prescription permits one to clearly distinguish the arbitrariness in the bosonization from the arbitrariness in the quantization of the system. We study the bosonization of four--fermion interactions with large mass in arbitrary dimension. First, we observe that dualization permits one to formally bosonize these models by invoking the bosonization of the free massive Dirac fermion and adding some extra model--dependent bosonic terms. Secondly, we explore the potential of extended dualization by considering the particular case of \underbar{chiral} four--fermion interactions. Here minimal dualization is inadequate for calculating the extra bosonic terms. We demonstrate the utility of extended dualization by successfully completing the bosonization of this chiral model. Finally, we consider two examples in two dimensions which illuminate the utility of using extended dualization by showing how quantization ambiguities in a fermionic theory propagate into the bosonized version. An explicit parametrization of the quantization ambiguities of the chiral current in the Chiral Schwinger model is obtained. Similarly, for the sine--Gordon interaction in the massive Thirring model the quantizationComment: Revised version including major changes in section 3, to be published in Phys. Rev.

Bulk Axions, Brane Back-reaction and Fluxes

Extra-dimensional models can involve bulk pseudo-Goldstone bosons (pGBs) whose shift symmetry is explicitly broken only by physics localized on branes. Reliable calculation of their low-energy potential is often difficult because it requires details of the stabilization of the extra dimensions. In rugby ball solutions, for which two compact extra dimensions are stabilized in the presence of only positive-tension brane sources, the effects of brane back-reaction can be computed explicitly. This allows the calculation of the shape of the low-energy pGB potential and response of the extra dimensional geometry as a function of the perturbing brane properties. If the pGB-dependence is a small part of the total brane tension a very general analysis is possible, permitting an exploration of how the system responds to frustration when the two branes disagree on what the proper scalar vacuum should be. We show how the low-energy potential is given by the sum of brane tensions (in agreement with common lore) when only the brane tensions couple to the pGB. We also show how a direct brane coupling to the flux stabilizing the extra dimensions corrects this result in a way that does not simply amount to the contribution of the flux to the brane tensions. We calculate the mass of the would-be zero mode, and briefly describe several potential applications, including a brane realization of `natural inflation,' and a dynamical mechanism for suppressing the couplings of the pGB to matter localized on the branes. Since the scalar can be light enough to be relevant to precision tests of gravity (in a technically natural way) this mechanism can be relevant to evading phenomenological bounds.Comment: 36 pages, JHEP styl

Supersymmetric codimension-two branes and U(1)_R mediation in 6D gauged supergravity

We construct a consistent supersymmetric action for brane chiral and vector multiplets in a six-dimensional chiral gauged supergravity. A nonzero brane tension can be accommodated by allowing for a brane-localized Fayet-Iliopoulos term proportional to the brane tension. When the brane chiral multiplet is charged under the bulk U(1)_R, we obtain a nontrivial coupling to the extra component of the U(1)_R gauge field strength as well as a singular scalar self-interaction term. Dimensionally reducing to 4D on a football supersymmetric solution, we discuss the implication of such interactions for obtaining the U(1)_R D-term in the 4D effective supergravity. By assuming the bulk gaugino condensates and nonzero brane F- and/or D-term for the uplifting potential, we have all the moduli stabilized with a vanishing cosmological constant. The brane scalar with nonzero R charge then gets a soft mass of order the gravitino mass. The overall sign of the soft mass squared depends on the sign of the R charge as well as whether the brane F- or D-term dominates.Comment: 28 pages, no figures, version to appear in JHE

Modeling population structure and adaptation in a Hawaiian stream goby: Sicyopterus stimpsoni

Due to the environmental problem of climate change, it has been forecasted that the Hawaiian islands can expect increased drought and increased rainfall variability. This could cause a change in stream flow and threaten the amphidromous waterfall climbing gobies, Sicyopterus stimpsoni. To study the impact of these projected changes, we used spatially-explicit, individual-based population models with four levels drought and three levels of rainfall variability for three islands with different topographies (Hawai\u27i, O\u27ahu and Kaua\u27i) and looked at the effect on the goby population dynamics after 10 years. Our results showed that total abundance was impacted by drought, variability, and island shape, especially under extreme conditions. The rate of morphological change and percent of juveniles was also negatively affected by the extreme conditions. Overall, the populations were stable under moderate drought conditions, but suffered when conditions reached extreme levels

Volume stabilization in a warped flux compactification model

We investigate the stability of the extra dimensions in a warped, codimension two braneworld that is based upon an Einstein-Maxwell-dilaton theory with a non-vanishing scalar field potential. The braneworld solution has two 3-branes, which are located at the positions of the conical singularities. For this type of brane solution the relative positions of the branes (the shape modulus) is determined via the tension-deficit relations, if the brane tensions are fixed. However, the volume of the extra dimensions (the volume modulus) is not fixed in the context of the classical theory, implying we should take quantum corrections into account. Hence, we discuss the one-loop effective potential of the volume modulus for a massless, minimally coupled scalar field.Comment: 25 pages, 8 figures, typos correcte

The role of selenium supplementation in cardiovascular disease prevention: an in vitro study to identify the molecular mechanism(s).

Obesity is a worldwide epidemic, with two thirds of the UK population either overweight or obese (body mass index (BMI) 25–29·9 and >30 kg/m2 respectively). Obesity is characterised by systemic oxidative stress (OS), which itself results from chronically high levels of reactive oxidative species (ROS) and reduced antioxidant status. OS is considered to play a key role in cardiovascular disease (CVD) development by initiating atherosclerosis. In particular, increased monocyte ROS generation instigates atherosclerotic plaque formation by increasing the recruitment, binding and transmigration of monocytes across arterial endothelial cells into the arterial wall. An increased intake of dietary antioxidants or up-regulation of endogenous antioxidant enzymes may counteract this OS state and therefore lower CVD risk. Selenium is an essential dietary micronutrient which is incorporated within the catalytic site of endogenous antioxidant Glutathione Peroxidase (GPx) enzymes and protects cells from OS and consequent cell damage. There is, however, a lack of knowledge concerning both the effect of selenium supplementation in an OS state representative of sedentary overweight/obese individuals and the mechanisms involved. The aim of this work was to investigate the effect of selenium supplementation in modulating, in vitro, monocyte cell viability, ROS generation and antioxidant enzymes gene expression (GPx1/GPx4) when under OS. U937 monocyte cells were either supplemented, or not with sodium selenite (Na2SeO3; 100nM or 200nM) and cultured for 48 hours at 37°C. Paraquat (1 mM) and S-Nitroso-N-acetyl-DL-penicillamine (0·7 mM) (SNAP) were added to cells overnight to induce OS. Cell viability was assessed via MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay, ROS generation was determined by Flow Cytometry using CM-H2DC-FDA, while GPx1/GPx4 gene expression was quantified by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). PQ/SNAP treatment significantly reduced U937 cell viability and increased ROS generation compared to untreated control U937 cells; confirming the induction of OS. Supplementation with 100nM Na2SeO3, before PQ/SNAP treatment, significantly increased cell viability by 33% (p 0·05). Furthermore, 100nM Na2SeO3 supplementation significantly reduced ROS generation by 32% (p < 0·001) in cells treated with PQ/SNAP. Correspondingly, this increased GPx1 by 146% (p < 0·01) and GPx4 gene expression by 77% (p < 0·05), when compared to un-supplemented PQ/SNAP treated cells. This study indicates that selenium supplementation may be effective in counteracting the detrimental effects of OS by significantly increasing the expression of antioxidant genes; reinforcing endogenous antioxidant protection to quench ROS generation more effectively and improve cell viability. This preliminary data, in monocyte cells, indicates that GPx1 gene expression is affected considerably more by both selenium supplementation and OS when compared with GPx4. This suggests GPx1 may play a more important role in CVD prevention, with regards to selenium supplementation in overweight/obese individuals