A project and competition to design and build a simple heat exchanger

To address a declining interest in process engineering, a project to design and build a compact heat exchanger was initiated in the second year of a four-year, multidisciplinary degree programme in biotechnology. The heat exchangers had a double-pipe configuration and employed plastic outer pipes and copper inner pipes of various diameters. Designs produced ranged from coiled inner pipes to various multi-pass arrangements and were assessed on the basis of heat transfer achieved per unit mean temperature difference per unit cost. The project, which also formed the basis of a competition, was very well received by students and gave them hands-on experience of engineering design and construction, as well as team work, problem solving, engineering drawing and the use of simple tools. Based on the success of this project, a similar problem based learning approach will be initiated in the third year of the same degree programme and will focus on bioethanol production

High-efficiency generation of nanomaterials via laser ablation synthesis in solution with in-situ diagnostics for closed-loop control

Driven by an ever-increasing demand for nanomaterials with specific functionalities, physical synthesis techniques such as Laser Ablation Synthesis in Solution (LASiS) have gained significant interest over in recent years. Commercial wet chemical synthesis methods, while having significantly higher nanomaterial yields than LASiS, typically have considerable negative environmental impact through the use of harmful reagents and solvents. LASiS therefore represents a route towards the sustainable “green” production of nanomaterials however the significant challenge to its commercialization is that of comparably low nanomaterial yields. Significant effort has been made towards increasing the production rates of LASiS, however many of the reported advances have relied on the use of high power (>20 W) or short pulse (<10 ps) laser systems which have high capital costs. Other advances have examined moving from batch production in small volumes towards the use of continuous production through the use of solvent flow systems. Combining these advances, we have developed a new system for nanomaterial generation via LASiS incorporating a low cost, low power (< 4W) Nd:YAG laser and solvent flow system for high-efficiency nanomaterial generation. This study has shown an increase in productivity from 2.5± 0.5 mg/hr for an 11 mL batch colloid, to continuous production yields of 17± 0.7 mg/hr under flow conditions

Development of a heat transfer and artificial neural networks teaching laboratory practical for biotechnology students

The paper describes a newly developed laboratory practical that teaches students how to develop an Artificial Neural Network model and its possible use in bio-processing. An emphasis is placed on giving students "hands on" experience with bio-processing equipment, namely bio-reactors and data acquisition systems in an attempt to help prepare them for work in bio-processing and chemical engineering industries

Novel strategy for the calorimetry-based control of fed-batch cultivations of saccharomyces cerevisiae

Typical controllers for fed-batch cultivations are based on the estimation and control of the specific growth rate in real time. Biocalorimetry allows one to measure a heat signal proportional to the substrate consumed by cells. The derivative of this heat signal is usually used to evaluate the specific growth rate, introducing noise to the resulting estimate. To avoid this, this study investigated a novel controller based directly on the heat signal. Time trajectories of the heat signal setpoint were modelled for different specific growth rates, and the controller was set to follow this dynamic setpoint. The developed controller successfully followed the setpoint during aerobic cultivations of Saccharomyces cerevisiae, preventing the Crabtree effect by maintaining low glucose concentrations. With this new method, fed-batch cultivations of S. cerevisiae could be reliably controlled at specific growth rates between 0.075 h−1 and 0.20 h−1, with average root mean square errors of 15 ± 3%

Emergent magnetic state in (111)-oriented quasi-two-dimensional spinel oxides

We report on the emergent magnetic state of (111)-oriented CoCr2O4 ultrathin films sandwiched by Al2O3 in the quantum confined geometry. At the two-dimensional crossover, polarized neutron reflectometry reveals an anomalous enhancement of the total magnetization compared to the bulk value. Synchrotron x-ray magnetic circular dichroism (XMCD) demonstrates the appearance of long-range ferromagnetic ordering of spins on both Co and Cr sublattices. Brillouin function analyses further corroborates that the observed phenomena are due to the strongly altered magnetic frustration, manifested by the onset of a Yafet-Kittel type ordering as the new ground state in the ultrathin limit, which is unattainable in the bulk

Stable nano-silver colloid production via Laser Ablation Synthesis in Solution (LASiS) under laminar recirculatory flow

As nanomaterials find applications in an increasingly diverse range of fields such as wastewater treatment, biotechnology and flexible electronics, the demand for nanomaterials with specific properties has increased. This increase is coupled with an increasing emphasis on nanomaterials with highly specific properties for specialised applications. Industrially, nanomaterials are produced via wet- chemical techniques which employ the use of solvents and reagents which are environmentally harmful. As we move forward with the use of nanomaterials, the ability to produce nanomaterials in a sustainable manner has become a topic of great significance. Towards this end, Laser Ablation Synthesis in Solution (LASiS) is a physical production technique capable of producing tailored nanomaterial colloids in a sustainable manner. These colloids are produced by ablating a solid target immersed in a solvent using a laser. Typically, LASiS is conducted in a batch process and in small volumes limiting commercial viability. To overcome this, there has been a move towards the use of continuous production via LASiS using flow systems. This allows an increase in nanomaterial yield, resulting in colloid concentrations approaching those of commer- cial colloids. This work investigates a new production technique incorporating a laminar recirculatory flow system to produce stable high concentration nano-silver colloids

Electrochemical and chronoamperometry assessment of nano‑gold sensor surfaces produced via novel laser fabrication methods

New developments in laser ablation have shown great potential as nanofabrication methodologies, offering many significant advantages over more traditional methods. Herein, we have developed a method for applying two of these techniques, confined atmospheric pulsed-laser (CAP) deposition and laser ablation synthesis in solution (LASiS), to the fabrication of a nanostructured sensor platform. Following deposition, additional steps were then used to crosslink the deposited nanostructures and fabricate counter and reference electrodes. Chronoamperometry and cyclic voltammetry (CV) were used to assess the effects of these crosslinking steps on the properties of the sensor surfaces. These experiments resulted in the development of a simple, inexpensive and readily scalable process for the fabrication of 3-electrode sensor systems. As an example of a readily measurable surface interaction, electrochemical impedance spectroscopy (EIS) was applied to demonstrate the use of these systems in the detection of 6-mercaptohexanol. This interaction was examined in real-time by measuring the change in the EIS of the sensor system over time following its exposure to the thiol. This experiment clearly showed a measurable EIS response, demonstrating the effectiveness of these newly fabricated sensors for the detection of a simple surface interaction and suggesting the future potential of these laser based methods as the basis for an inexpensive, facile, rapid and scalable sensor fabrication process

Digital afx: digital dressing and affective shifts in Sin City and 300

In Sin City (Robert Rodriguez, 2005) and 300 (Zack Snyder, 2006) extensive post-production work has created stylised colour palettes, manipulated areas of the image, and added or subtracted elements. Framing a discussion around the terms ‘affect’ and ‘emotion’, this paper argues that the digital technologies used in Sin City and 300 modify conventional interactions between representational and aesthetic dimensions. Brian Massumi suggests affective imagery can operate through two modes of engagement. One mode is embedded in a meaning system, linked to a speci?c emotion. The second is understood as an intensi?cation whereby a viewer reacts but that reaction is not yet gathered into an alignment with meaning. The term ‘digital afx’ is used to describe manipulations that produce imagery allowing these two modes of engagement to coexist. Digital afx are present when two competing aesthetic strategies remain equally visible within sequences of images. As a consequence the afx mingle with and shift the content of representation

Pulsed laser ablation in liquid (PLAL) for nanoparticle generation

Nanoparticles, broadly spherical pieces of material with diameters in the nanoscale range, have a number of advantageous physical, chemical, electrical, and optical properties. These unique properties make them suitable for a wide range of applications including sensing, medical therapeutics, printed electronics, and anti-fouling/anti-microbial surfaces. Pulsed laser ablation in liquid (PLAL), also known as laser ablation synthesis in solution (LASIS), is an attractive, green method for producing ligand-free nanoparticles in solution. These nanoparticles can be produced from a wide range of target materials and avoids the use of hazardous, environmentally-unfriendly chemicals. In this chapter, the key applications, conventional generation methods of nanoparticles, as well as the background and cutting edge of PLAL are reviewe

Simulations of bent-double radio sources in galaxy groups

Bent-double radio sources have been used as a probe to measure the density of intergalactic gas in galaxy groups. We carry out a series of high-resolution, 3D simulations of AGN jets moving through an external medium with a constant density in order to develop a general formula for the radius of curvature of the jets, and to determine how accurately the density of the intra-group medium (IGM) can be measured. Our simulations produce curved jets ending in bright radio lobes with an extended trail of low surface brightness radio emission. The radius of curvature of the jets varies with time by only about 25%. The radio trail seen in our simulations is typically not detected in known sources, but may be detectable in lower resolution radio observations. The length of this tail can be used to determine the age of the AGN. We also use our simulation data to derive a formula for the kinetic luminosity of observed jets in terms of the radius of curvature and jet pressure. In characterizing how well observations can measure the IGM density, we find that the limited resolution of typical radio observations leads to a systematic under-estimate of the density of about 50%. The unknown angles between the observer and the direction of jet propagation and direction of AGN motion through the IGM leads to an uncertainty of about 50% in estimates of the IGM density. Previous conclusions drawn using these sources, indicating that galaxy groups contain significant reservoirs of baryons in their IGM, are still valid when considering this level of uncertainty. In addition, we model the X-ray emission expected from bent-double radio sources. We find that known sources in reasonably dense environments should be detectable in ~100 ks Chandra observations. X-ray observations of these sources would place constraints on the IGM density and AGN velocity that are complementary to radio observations.Comment: 14 pages, 8 figures, accepted by MNRA