Frustration Effects in Antiferromagnetic FCC Heisenberg Films

We study the effects of frustration in an antiferromagnetic film of FCC lattice with Heisenberg spin model including an Ising-like anisotropy. Monte Carlo (MC) simulations have been used to study thermodynamic properties of the film. We show that the presence of the surface reduces the ground state (GS) degeneracy found in the bulk. The GS is shown to depend on the surface in-plane interaction $J_s$ with a critical value at which ordering of type I coexists with ordering of type II. Near this value a reentrant phase is found. Various physical quantities such as layer magnetizations and layer susceptibilities are shown and discussed. The nature of the phase transition is also studied by histogram technique. We have also used the Green's function (GF) method for the quantum counterpart model. The results at low-$T$ show interesting effects of quantum fluctuations. Results obtained by the GF method at high $T$ are compared to those of MC simulations. A good agreement is observed.Comment: 11 pages, 19 figures, submitted to J. Phys.: Condensed Matte

Nitrogen removal enhancement using lactic acid fermentation products from food waste as external carbon sources: Performance and microbial communities

© 2018 Elsevier Ltd In this study, nitrogen removal using the lactic acid fermentation products from food waste and other external chemical carbon sources (sodium acetate, sodium lactate and starch) was investigated. Similar to sodium acetate and lactate, the lactic acid-enriched fermentation liquid from food waste (FLFW) exhibited a high denitrification rate (5.5 mg NOx-N/(g-VSS h)) and potential (0.16 g NO3−-N/g COD), and could achieve high NH4+-N and total nitrogen (TN) removal efficiencies during long-term operation. Using FLFW as supplementary carbon sources reduced the extracellular polymeric substances (EPS) content, improved the settleability and achieved a satisfactory biomass yield of activated sludge. Additionally, the increased microbial metabolic activity and bacterial community diversity and the accumulation of unique bacteria in the activated sludge cultured with FLFW further promoted the organics utilization rate and nitrogen removal efficiency, indicating that the FLFW prepared from solid waste was an ideal carbon source for wastewater treatment

The impact of gas slug flow on microfiltration performance in an airlift external loop tubular membrane reactor

© 2016 The Royal Society of Chemistry. This work investigated the impact of gas slug flow on microfiltration in an airlift external loop tubular membrane reactor. A complete description for the characteristics of the slug flow was obtained as the aeration rate increased from 30 to 120 L h-1 with an interval of 30 L h-1. The shear stress of the falling film region could reach 6.37 × 10-3 Pa with the aeration rate of 90 L h-1. Experimental results showed that the growth of transmembrane pressure (TMP) could be controlled effectively by increasing the aeration rate and the optimal aeration rate in a slug flow was around 90 L h-1. However, a subsequent increase in the aeration rate had no significant effect on slowing down the TMP growth rate. Turning the constant air-flow into periodic pulsatile air-flow, low gas-velocity and high gas-velocity led to alternate operation in filtration. When the alternate interval of pulsatile air-flow was 60 s at the alternate aeration rates of 30/90 L h-1 and 60/90 L h-1, it could delay membrane fouling and save a lot of gas compared with implementing a constant air-flow of 90 L h-1. Finally, for different water outlet positions along the membrane tube, membrane fouling gradually slowed down from the bottom to the top

Enhanced low C/N nitrogen removal in an innovative microbial fuel cell (MFC) with electroconductivity aerated membrane (EAM) as biocathode

© 2016 Elsevier B.V. A novel microbial fuel cell (MFC) was developed to enhance simultaneous nitrification and denitrification (SND) by employing electrons from the anode. The cathode chamber of the reactor consisted of a membrane aerated biofilm reactor (MABR) which was made of an electroconductivity aerated membrane. The maximum power density of 4.20 ± 0.12 W m−3was obtained at a current density of 4.10 ± 0.11 A m−2(external resistance = 10 Ω). Compared with an open-circuit system, the removal rates of NH4+-N and TN were improved by 9.48 ± 0.33% and 19.80 ± 0.84%, respectively, which could be ascribed to the electrochemical denitrification. The anode (chemical oxygen demand, COD) and cathode (NO3−) chambers reached the maximum coulombic efficiencies (CEs) of 40.67 ± 1.05% and 42.84 ± 1.14%, respectively. It suggested that the electroconductivity MABR has some advantages in controlling aeration intensity, thus improving SND and CEs. Overall, EAM-MFC could successfully generate electricity from wastewater whilst showing high capacity for removing nitrogen at a low COD/N ratio of 2.8 ± 0.07 g COD g−1N

Electron probe microanalysis of ion exchange of selected elements between dentine and adhesive restorative materials

The document attached has been archived with permission from the Australian Dental Association. An external link to the publisher’s copy is included.Background: There have been numerous attempts to demonstrate the phenomenon of ion exchange between auto cure glass ionomer cements (GICs) and dentine. The purpose of this study was to employ an electron probe microanalysis (EPMA) technique to examine the interchange of elements between non-demineralized dentine and two types of restorative material, auto cure GICs and a resin composite. Methods: Restorations of auto cure GICs (Riva Fast, Fuji IX Fast, Ketac Molar Quick and Fuji VII) and a bonded composite resin were placed in each of 10 recently extracted human third molar teeth. After two weeks the restorations were sectioned and prepared for EPMA. Percentage weights of calcium, phosphorus aluminum, strontium and fluoride were calculated in the restorations 200μm from the restorative interface and 200μm into the dentine at 5μm intervals. Results: There was evidence of calcium and phosphorus in all five auto cure GICs to a depth of 50μm. Aluminum and strontium ions were also present in dentine except subjacent to Ketac Molar restorations. There was evidence of element transfer into composite resin and resin-bonded dentine. Conclusions: The findings of this paper support the concept of ion exchange as a bonding mechanism between auto cure GIC and dentine. Element penetration into tooth structure and GIC exceeded beyond the “ion exchange layer” observed in scanning electron microscopy studies. Penetration of calcium and phosphorus into composite resin from dentine likely occurred as a result of the self-etching process dissolving calcium and phosphorus and incorporating these elements into the hybrid layer. The presence of Al and Sr ions in dentine were likely to be associated with resin tags extending into the dentine.GM Knight, JM McIntyre, GG Craig and Mulyan

Improvement of bioavailable carbon source and microbial structure toward enhanced nitrate removal by Tubifex tubifex

© 2018 Elsevier B.V. The research provides new insights into how T. tubifex affects microbe-available organic carbon transformation, microbial community, and related inorganic nitrogen transformation. With different T. tubifex densities under enriched NO3-N concentration with different C/N ratio, the groups with low and high T. tubifex abundance had 17.1% and 27.2% higher TOC concentrations compared to control group under C/N ratio of 3.0 and 2.0, respectively. According to the OC characteristics analyzed by GC–MS and EEM, the group with T. tubifex contained higher dissolved organic carbon (DOC) content and short-chain compounds. As the NO3-N concentration increased and C/N ratio decreased, the proportions of carboxylic acid derivatives (methyl acetate), sulfur-containing compounds, humic-like products and the emission of CO2 were enhanced with T. tubifex, which could be utilized by denitrifiers directly. The OC degradation was highly correlated with the effect of T. tubifex on microbial community and nutrient removal. The T. tubifex can increase OC transformed into sediment and change the microbial community similarity to that in their digestive system. According to the principal component analysis (PCA), the improved proportions of OC that available for microbes and altered microbial community with T. tubifex could enhance denitrification, which experienced a 21% higher denitrifiers and threefold increased NO3-N removal efficiency than that in control group

Re-orientation Transition in Molecular Thin Films: Potts Model with Dipolar Interaction

We study the low-temperature behavior and the phase transition of a thin film by Monte Carlo simulation. The thin film has a simple cubic lattice structure where each site is occupied by a Potts parameter which indicates the molecular orientation of the site. We take only three molecular orientations in this paper which correspond to the 3-state Potts model. The Hamiltonian of the system includes: (i) the exchange interaction $J_{ij}$ between nearest-neighbor sites $i$ and $j$ (ii) the long-range dipolar interaction of amplitude $D$ truncated at a cutoff distance $r_c$ (iii) a single-ion perpendicular anisotropy of amplitude $A$. We allow $J_{ij} =J_s$ between surface spins, and $J_{ij}=J$ otherwise. We show that the ground state depends on the the ratio $D/A$ and $r_c$. For a single layer, for a given $A$, there is a critical value $D_c$ below (above) which the ground-state (GS) configuration of molecular axes is perpendicular (parallel) to the film surface. When the temperature $T$ is increased, a re-orientation transition occurs near $D_c$: the low-$T$ in-plane ordering undergoes a transition to the perpendicular ordering at a finite $T$, below the transition to the paramagnetic phase. The same phenomenon is observed in the case of a film with a thickness. We show that the surface phase transition can occur below or above the bulk transition depending on the ratio $J_s/J$. Surface and bulk order parameters as well as other physical quantities are shown and discussed.Comment: 7 pages, 11 figures, submitted for publicatio