Manual pressing of nannochloropsis oculata dried biomass for enhanced lipid extraction

Microalgae offer significant potential to produce high value products and biofuels, whilst simultaneously being used to bio-remediate water or capture carbon dioxide (CO2). Microalgal cell disruption processes are often necessary to increase lipid extraction from microalgae before conventional solvent extraction processes are used to isolate lipids. The extracted lipids can be processed to produce biofuels. The combinations of hydraulic pressing with liquid nitrogen (LN2) treatment were applied to samples of dried Nannochloropsis oculata in the presented study to enhance the cellular destruction and lipid yields. The results indicated higher lipid extraction with LN2 treatment (0.159 g/g dry algae) compared to the LN2 untreated samples (0.070 g/g dry algae). The corresponding cell disruptions were found to be seventy-eight and fifty percent, respectively, at the same 10 bar (145 psi) pressure level. The control sample (without any treatment) lipid yield was 0.006 g/g dry algae, while the lipid yield varied between 0.192-0.213 g/g dry algae with LN2 treated biomass with pressure loadings of 70-100 bar (1015-1450 psi) and with a corresponding cell disruption of 93-98 percent. The presence of palmitate, oleate and linoleate found in the fatty acid methyl ester composition of the extracted lipids, shows a favourable profile to produce biodiesel

Context guided retrieval

This paper presents a hierarchical case representation that uses a context guided retrieval method The performance of this method is compared to that of a simple flat file representation using standard nearest neighbour retrieval. The data presented in this paper is more extensive than that presented in an earlier paper by the same authors. The estimation of the construction costs of light industrial warehouse buildings is used as the test domain. Each case in the system comprises approximately 400 features. These are structured into a hierarchical case representation that holds more general contextual features at its top and specific building elements at its leaves. A modified nearest neighbour retrieval algorithm is used that is guided by contextual similarity. Problems are decomposed into sub-problems and solutions recomposed into a final solution. The comparative results show that the context guided retrieval method using the hierarchical case representation is significantly more accurate than the simpler flat file representation and standard nearest neighbour retrieval

Magnetic annihilation and reconnection in two dimensions

The problems of incompressible, planar, magnetic annihilation and reconnection are discussed. We first emphasize that steady-state reconnection solutions can be constructed from annihilation models involving harmonic velocity fields. We show, however, that the only harmonic velocity profile capable of supporting inviscid magnetic annihilation is the traditional stagnation point flow φ= −αxy. The implication is that further steady-state planar reconnection models derived from annihilation solutions are impossible. We go on to show that certain classes of nonharmonic stream functions allow reconnection solutions to be developed, once the constraint of time independence is relaxed. In particular, we construct an exact reconnection model based on cellular inflows into a periodic assemblage of magnetic X-points

Dynamic planar magnetic reconnection solutions for incompressible plasmas

The planar magnetic reconnection problem for viscous, resistive plasmas is addressed. We show that solutions can be developed by superposing transient nonlinear disturbances onto quiescent “background” fields. The disturbance fields are unrestricted in form, but the spatial part of the background field must satisfy ∇2K= -λK. This decomposition allows previous analytic reconnection solutions, based on one-dimensional disturbance fields of “plane wave” form, to be recovered as special cases. However, we point out that planar disturbance fields must be fully two-dimensional to avoid the pressure problem associated with analytic merging models, that is, to avoid unbounded current sheet pressures in the limit of small plasma resistivities. The details of the reconnection problem are then illustrated using cellular background field simulations in doubly periodic geometries. The flux pile-up rate is shown to saturate when the pressure of the current sheet exceeds the hydromagnetic pressure of the background field. Although the presaturation regime is well described by one-dimensional current sheet theory, the nonlinear postsaturation regime remains poorly understood. Preliminary evidence suggests that, although after saturation the early evolution of the field can be described by slow Sweet-Parker scalings, the first implosion no longer provides the bulk of the energy release

Fast magnetic reconnection via jets and current microsheets

Numerical simulations of highly nonlinear magnetic reconnection provide evidence of ultrathin current microsheets. These small-scale sheets are formed by strong exhaust jets from a primary large-scale current layer. The overall size of the secondary microsheet is determined by the thickness of the primary sheet. Preliminary scalings show that the thickness of the microsheet varies linearly with the plasma resistivity. This scaling suggests that microsheets may provide fast reconnection sites in magnetically complex plasmas such as the solar corona and planetary magnetospheres

Exact models for hall current reconnection with axial guide fields

This paper employs an analytic reconnection model to investigate the conditions under which Hall currents can influence reconnection and Ohmic dissipation rates. It is first noted that time dependent magnetohydrodynamic systems can be analyzed by decomposing the magnetic and velocity fields into guide field and reconnecting field components. A formally exact solution shows that Hall currents can speed up or slow down the reconnection rate depending on the strength and orientation of the axial guide field. In particular, merging solutions are developed in which the axial guide field is the dominant driver of the reconnection. The extent to which Hall currents can alleviate the buildup of back pressures in flux pile-up reconnection models is also examined. The analysis shows that, although enhancements of the merging rate can be expected under certain conditions, it is unlikely that Hall currents can completely undo the fundamental pressure limitations associated with flux pile-up reconnection

Construction and Operation of a Two-place Diver's Sled

Fisheries gear researchers have employed scuba diver-operated sleds to evaluate towed fishing systems since the early 1950's. One of the earliest sled designs was a converted Stokes litter in which two divers sat tandem with the forward diver operating the diving controls (Sand, 1956). The litter was relatively easy to maneuver and provided a comfortable platform for observing operational fishing gear. However, the use of underwater photographic equipment to document gear performance was difficult due to the limited mobility of the observer-cameraman

Characterisation of hydraulic and hydrogeochemical processes in a reducing and alkalinity-producing system (RAPS) treating mine drainage, South Wales, UK

A series of tracer tests has been carried out in the compost and limestone Tan-y-Garn Reducing and Alkalinity-Producing System (RAPS), designed to treat iron-rich net acidic mine water (mean pH 6.18, Fe = 47 mg L-1, alkalinity 1.70 meq L-1 and mineral acidity 1.82 meq L-1) in South Wales, UK. Conservative tracer breakthrough time in the RAPS basal effluent is approximately inversely related to throughflow rate. Repeat tracer tests indicate a long term decrease in hydraulic conductivity, but not in total porosity. A specific sodium chloride tracer test from June 2008 is reported, when 15 kg salt was added to a raw mine water inflow rate of 0.87 L s-1. Electrical conductivity and major ion chemistry were monitored for a 170 hour period. Sodium exhibited a retardation of 1.15 to 1.2 in the RAPS medium relative to chloride, due to cation exchange. Simple 1-D advection-diffusion analytical modelling succeeded in simulating the early portion of tracer breakthrough in the RAPS effluent. More complex analytical modelling, accounting for (i) mixing and dilution effects in the supernatant water input signature and (ii) matrix diffusion effects, was found to be required to adequately simulate the later-stage tail of the breakthrough curve in the RAPS effluent

The power output of spine and fan magnetic reconnection solutions

The ability of three-dimensional magnetic “spine” and “fan” reconnection solutions to provide flarelike energy release is discussed. It is pointed out, on the basis of exact analytic solutions, that fast dissipation is possible only if the hydromagnetic pressure in the reconnection region becomes unbounded in the limit of small plasma resistivities. The implication is that some “saturation” of the power output is inevitable for realistic coronal plasmas. Estimates of the saturated power, based on limiting the flux pileup in the field, suggest that the geometry of the spine reconnection mechanism precludes significant flare energy release. However, the current sheet structures involved in fan reconnection seem able to release sufficient magnetic energy fast enough to account for modest flares, even under the conservative assumption of classical plasma resistivities