Streamlined life cycle assessment of transparent silica aerogel made by supercritical drying

This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2011 ElsevierWhen developing sustainable building fabric technologies, it is essential that the energy use and CO2 burden arising from manufacture does not outweigh the respective in-use savings. This study investigates this paradigm by carrying out a streamlined life cycle assessment (LCA) of silica aerogel. This unique, nanoporous translucent insulation material has the lowest thermal conductivity of any solid, retaining up to four times as much heat as conventional insulation, whilst being highly transparent to light and solar radiation. Monolithic silica aerogel has been cited as the ‘holy grail’ of future glazing technology. Alternatively, translucent granular aerogel is now being produced on a commercial scale. In each case, many solvents are used in production, often accompanied by intensive drying processes, which may consume large amounts of energy and CO2. To date, there has been no peer-reviewed LCA of this material conducted to the ISO 14000 standard. Primary data for this ‘cradle-to-factory gate’ LCA is collected for silica aerogel made by low and high temperature supercritical drying. In both cases, the mass of raw materials and electricity usage for each process is monitored to determine the total energy use and CO2 burden. Findings are compared against the predicted operational savings arising from retrofitting translucent silica aerogel to a single glazed window to upgrade its thermal performance. Results should be treated as a conservative estimate as the aerogel is produced in a laboratory, which has not been developed for mass manufacture or refined to reduce its environmental impact. Furthermore, the samples are small and assumptions to upscale the manufacturing volume occur without major changes to production steps or equipment used. Despite this, parity between the CO2 burden and CO2 savings is achieved in less than 2 years, indicating that silica aerogel can provide a measurable environmental benefit.This work is funded by the EPSRC, Brunel University and Buro Happold Ltd, the University of Bath is funded by the EPSRC grant EP/F018622/1

The Nanoaquarium: A Nanofluidic Platform for in SiTu Transmission Electron Microscopy in Liquid Media

There are many scientifically interesting and technologically relevant nanoscale phenomena that take place in liquid media. Examples include aggregation and assembly of nanoparticles; colloidal crystal formation; liquid phase growth of structures such as nanowires; electrochemical deposition and etching for fabrication processes and battery applications; interfacial phenomena; boiling and cavitation; and biological interactions. Understanding of these fields would benefit greatly from real-time, in situ transmission electron microscope (TEM) imaging with nanoscale resolution. Most liquids cannot be imaged by traditional TEM due to evaporation in the high vacuum environment and the requirement that samples be very thin. Liquid-cell in situ TEM has emerged as an exciting new experimental technique that hermetically seals a thin slice of liquid between two electron transparent membranes to enable TEM imaging of liquid-based processes. This work presents details of the fabrication of a custom-made liquid-cell in situ TEM device, dubbed the nanoaquarium. The nanoaquarium’s highlights include an exceptionally thin sample cross section (10s to 100s of nm); wafer scale processing that enables high-yield mass production; robust hermetic sealing that provides leak-free operation without use of glue, epoxy, or any polymers; compatibility with lab-on-chip technology; and on-chip integrated electrodes for sensing and actuation. The fabrication process is described, with an emphasis on direct wafer bonding. Experimental results involving direct observation of colloid aggregation using an aqueous solution of gold nanoparticles are presented. Quantitative analysis of the growth process agrees with prior results and theory, indicating that the experimental technique does not radically alter the observed phenomenon. For the first time, in situ observations of nanoparticles at a contact line and in an evaporating thin film of liquid are reported, with applications for techniques such as dip-coating and drop-casting, commonly used for depositing nanoparticles on a surface via convective-capillary assembly. Theoretical analysis suggests that the observed particle motion and aggregation are caused by gradients in surface tension and disjoining pressure in the thin liquid film

The Effects of Visual Cue Facilitation in Spatial Pattern Learning in Rats

Recently published research has shown that a consistent but not coincident visual pattern facilitated the learning of a diamond spatial pattern in humans (Katz, Brown & Sturz, 2014). The purpose of the present experiment was to examine if this could be done in rats, using a square spatial pattern. For each trial, 16 towers were arranged in a 4 X 4 matrix, with one of the nine possible 2 X 2 baiting patterns baited with cheese. The visual pattern group also had four striped towers placed in a 2 X 2 spatial pattern within the larger matrix, while the visual random group had four striped towers placed randomly throughout the matrix. On 25% of the trials, there was overlap between one baited tower and a striped tower, while the remaining 75% of the trials contained no overlap. There were 50 trials, and the goal for the rats was to find all four of the baited towers in each. Results of the experiment revealed that the visual pattern group performed significantly better than the visual random group in the last 20 trials, showing that that the visual pattern facilitated the learning of baited 2 X 2 pattern. As well, both groups were significantly faster at finding all the baited towers during the non-overlap trials than on the overlap trials. Finally, both groups showed that they were making a good tower choice relative to chance after visiting the second and third baited towers

The role of social relationships in the association between adolescents' depressive symptoms and academic achievement

While research has established that depression interferes with academic achievement, less is understood about the processes by which social relationships may buffer the relationship between depression and academic outcomes. In this study we examined the role of positive relationships in the school, family and peer contexts in the association between depressive symptoms and academic achievement among 894 adolescents aged 12-17 years living in Santiago, Chile. Depressive symptoms were associated with lower levels of academic achievement; parental monitoring, school belonging, positive mother relationships, and having academically inclined peers moderated this relationship, though some interactions differed by sex and age. Implications for promoting the academic success of adolescents experiencing depressive symptoms are discussedR01 DA021181 - NIDA NIH HHS; R01 HD033487 - NICHD NIH HH