Developing systems for the commercial culture of Ulva species in the UK

PhD ThesisThe green seaweed, Ulva, is highly valued in terms of animal feed, food and biofuel, as well in the delivery of crucial remediation services including wastewater treatment and CO2 removal. Accordingly, Ulva cultivation has gained significant research interest worldwide. Notwithstanding these research efforts, Ulva cultivation is still in its infancy and knowledge to underpin such developments remains limited. A common challenge in Ulva cultivation is the fluctuating productivity with time due to vegetative fragmentation and/or periodic reproduction. In this study, three methods were employed to address this challenge. Firstly, culture conditions were optimised to establish a balance between growth and reproduction. Secondly, a refined culture method was developed, which more than tripled growth of Ulva over an 18-day cultivation as compared to a standard method. Thirdly, a sterile strain was obtained by mutating a wild strain with ultraviolet radiation. This new strain grew five times faster over an 18-day cultivation and absorbed nitrate and phosphate 40.0% and 30.9% quicker compared to the wild strain respectively. The chemical composition of the sterile strain showed a lipid content of more than double that of the wild strain, while the protein content was 26.3% lower than the wild strain. Several tissue preservation techniques were developed to enable settlement and growth trials to be conducted on demand. The merits or otherwise of the preservation techniques were determined for gametes, germlings and thalli. In addition to cultivation-related techniques, the co-effects of climate change factors (global warming and ocean acidification) and eutrophication on Ulva cultivation were investigated. These three variables interacted in a complex pattern to differentially affect life history stages, as well as altering the chemical composition and functional properties of Ulva. These findings make tangible contributions to the ability to successfully and commercially cultivate Ulva in terms of culture conditions, tissue preservation and the development of mutant strains. Further, by placing Ulva culture in a climate change context, this work provides valuable insight into the limits to resilience of Ulva to a changing climate. This will inform the future development of the Ulva culture industry over the coming decades.MaST in Newcastle Universit

Multi-scale simulation of capillary pores and gel pores in Portland cement paste

The microstructures of Portland cement paste (water to cement ratio is 0.4, curing time is from 1 day to 28 days) are simulated based on the numerical cement hydration model, HUMOSTRUC3D (van Breugel, 1991; Koenders, 1997; Ye, 2003). The nanostructures of inner and outer C-S-H are simulated by the packing of monosized (5 nm) spheres. The pore structures (capillary pores and gel pores) of Portland cement paste are established by upgrading the simulated nanostructures of C-S-H to the simulated microstructures of Portland cement paste. The pore size distribution of Portland cement paste is simulated by using the image segmentation method (Shapiro and Stockman, 2001) to analyse the simulated pore structures of Portland cement paste. The simulation results indicate that the pore size distribution of the simulated capillary pores of Portland cement paste at the age of 1 day to 28 days is in a good agreement with the pore size distribution determined by scanning electron microscopy (SEM). The pore size distribution of the simulated gel pores of Portland cement paste (interlayer gel pores of outer C-S-H and gel pores of inner C-S-H are not included) is validated by the pore size distribution obtained by mercury intrusion porosimetry (MIP). The pores with pore size of 20 nm to 100 nm occupy very small volume fraction in the simulated Portland cement paste at each curing time (0.69% to 1.38%). This is consistent with the experimental results obtained by nuclear magnetic resonance (NMR)

Mechanism of microstructural modification of the interfacial transition zone by using blended materials

Applying blended materials with finer particle size or high reactivity could be an effective and economic way for improving the microsturcture of interfacial transition zone (ITZ). In this study, the porosity characteristics of ITZ in concrete made with OPC and blended binders were determined quantitatively by using backscattered electron microscopy (BSE) image analysis and mercury intrusion porosimetry (MIP) measurements. This paper especially focused on the effects of slag and limestone filler on the thickness and pore structure of the ITZ. Results indicated that the porosity at each distance reduces with increasing limestone filler from 0 to 5%, and a significant increase is observed in the sample with 10% of limestone filler. The addition of 5% of limestone filler is able to densify the pore structure of both ITZ and bulk matrix. The reduction in pore volume in the range coarser than 100 nm contributed to the largest decrease in the total pores. Increasing the incorporation level of limestone filler to 10% resulted in an increase in the total porosity. The influences of slag on the porosity characteristics were highly dependent on the replacement level and the determined pore size regions. The addition of 35% of slag reduces the porosity at all distances and produces a denser microstructure both in the ITZ and bulk cement matrix. However, this improvement disappears when the substitution amount reaches to 70%. The incorporation of slag as a partial substitute for Portland cement tends to refine the pore structure

Investigation of the deterioration of blended cement concrete under sulfate attack in terms of interfacial transition zone

The importance of the porous interfacial transition zone to the chemical aggression of concrete is obvious when one considers the relations existing between porosity, permeability, chemical composition and the sulfate attack. In this study, the effect of ITZ quantity through varying aggregate content on the deterioration of blended cement concrete under sulfate attack, was determined to understand better the relationship between sulfate ions and concrete microstructure. The ITZ quantity was directly proportional to the aggregate volume fraction. Therefore, the effect of ITZ on sulfate resistance ability of concrete made with pure OPC and blended binders was evaluated by a comparison among mortars with systematically varied aggregate volume fraction. The porosity distribution with the ITZ was determined by using a quantitative backscattered electron microscopy (BSE) image analysis. It was found that the incorporation of moderate amount of Limestone filler is able to compact the microstructure of both ITZ and bulk matrix by filling effect and nucleation sites effect. The effects of slag on the porosity of ITZ were dependent on the replacement rate. The degree of deterioration had a slight tendency to increase for the samples prepared with higher aggregate volume content, which means high ITZ volume fraction. For the sulfate to reach the interior of the samples, it must move through the bulk cement matrix. The effect of aggregate and ITZ can only be notable when the interior structure was exposed to the sulfate ions. The presence of ITZ was normally accompanied by a denser bulk cement matrix. This could limit the ingress of sulfate ions and delay the formation of expansive products in initial stage. After the sulfate penetrates into the interior of the samples, the inner structure was expected to exert more significant influences on the deterioration

[N,N′-Bis(3-meth­oxy-2-oxidobenzyl­idene)ethyl­enediammonium-κ4 O,O′,O′′,O′′′]tris­(nitrato-κ2 O,O′)dysprosium(III)

In the title mononuclear Schiff base complex, [Dy(NO3)3(C18H20N2O4)], the DyIII ion is ten-coordinated in a distorted hexa­deca­hedral geometry by six O atoms of three nitrate anions and four O atoms of the Schiff base ligand. An intra­molecular N—H⋯O hydrogen bond occurs. The crystal structure is stabilized by inter­molecular C—H⋯O hydrogen bonds