The geology and mineralization of some Northern Rhodesian pegmatites

Imperial Users onl

Teachers as Writers research report

Teachers as Writers is a two-year research project offering teachers sustained opportunities to write and build co-mentoring relationships with professional writers in order to improve student outcomes. The project set out to determine the impact of professional writers’ engagement with teachers, both in changing teachers’ classroom practices in the teaching of writing, and in improving student outcomes in writing. The report summarises the insights gained

SSNN, a method for neural network protein secondary structure fitting using circular dichroism data

Circular dichroism (CD) spectroscopy is a quick method for measuring data that can be used to determine the average secondary structures of proteins, probe their interactions with their environment, and aid in drug discovery. This paper describes the operation and testing of a self-organising map (SOM) structure-fitting methodology named Secondary Structure Neural Network (SSNN), which is a methodology for estimating protein secondary structure from CD spectra of unknown proteins using CD spectra of proteins with known X-ray structures. SSNN comes in two standalone MATLAB applications for estimating unknown proteins' structures, one that uses a pre-trained map and one that begins by training the SOM with a reference set of the user's choice. These are available at http://www2.warwick.ac.uk/fac/sci/chemistry/research/arodger/arodgergroup/research_intro/instrumentation/ssnn/ as SSNNGUI and SSNN1_2 respectively. They are available for both Macintosh and Windows formats with two reference sets: one obtained from the CDPro website, referred to as CDDATA.48 which has 48 protein spectra and structures, and one with 53 proteins (CDDATA.48 with 5 additional spectra). Here we compare SSNN with CDSSTR, a widely-used secondary structure methodology, and describe how to use the standalone SSNN applications. Current input format is Δε per amino acid residue from 240 nm to 190 nm in 1 nm steps for the known and unknown proteins and a vector summarising the secondary structure elements of the known proteins. The format is readily modified to include input data with e.g. extended wavelength ranges or different assignment of secondary structures

Understanding the "rules of engagement" for membrane protein folding : chemical biology and computational approaches for determination of structure and dynamics

Approximately one third of genes in the human genome (1) encode transmembrane (TM) proteins and form more than half of all drug targets (2). However, our understanding of how these proteins fold into their functional form, as well as how they may misfold into a disease-associated form, remains a difficult area of study. By observing the effects of single point mutations in the context of a native sequence, in addition to adding and mutating interhelical interaction motifs on a low complexity sequence background, we aim to elicit ‘rules’ of TM protein domain association. For the single point mutation in the context of a native sequence, the TM domain of the sequence Neu, along with its oncogenic substitution V664E form Neu*, were selected. Using molecular dynamics (MD) a united atom model of each dimer in a model bilayer system was subjected to umbrella sampling along an interhelical reaction coordinate to yield a free energy profile of self-association. The lipid order, bilayer thickness, and peptide tilt angle were calculated from trajectories taken from three points along the reaction coordinate. Helical composition, solvent accessible surface area, and hydrogen bond analysis (for the V664E substitution) were performed at the free energy minimum. Low complexity sequences of polyleucine and polyleucine-alanine heptad repeat sequences, with and without interaction motifs similar to those present in the Neu model, were ligated into PBLM100 plasmids. Transformed E. coli cells were subjected to semi-quantitative homo-interaction analysis using the GALLEX assay. The same TM sequences were modelled using a coarse grained (CG) forcefield. Umbrella sampling along an interhelical reaction coordinate was performed to yield a free energy profile of self-association. Single-linkage cluster analysis of peptides was performed at the global free energy minimum. A representative structure from each set was compared to an averaged structure from the clusters of an atomistic conformational search. The results presented in this study, could contribute to what in theory would be a large database of motif-driven rules for TM helical domain oligomerisation. This may encourage further investigation into TM protein design for novel application

Retention of Mechanical Properties After Water Immersion for Glass-Fibre Polymer Composite Laminates with Thermoset & Thermoplastic Infusible Resins

In this work, we conducted an extensive comparative study of the water absorption behavior and retention of mechanical properties of a group of GRP composite laminates manufactured with a range of infusible thermosetting and thermoplastics resins. All laminates were manufactured by Vacuum-Assisted Resin Transfer Moulding (VARTM; the most relevant manufacturing technique in shipbuilding) with a range of state-of-the-art thermosetting resins (Urethane acrylate Crestapol 1210, Epoxy SR1125, Bio-epoxy Supersap CLR, Phenolic Cellobond J2027X) and a novel infusible acrylic thermoplastic resin (Acrylic Elium 150). The reinforcement of choice for each laminate was a unidirectional glass fabric of 996 gsm. Sample preparation for water immersion studies was according to ASTM D5229. This study was part of a comprehensive down-selection of commercially available resins in terms of their suitability for shipbuilding applications, as part of the EU H2020 project FIBRESHIP2 .  A selection of relevant properties of the laminates with different resin systems is presented in this paper including fibre volume fraction, apparent interlaminar shear strength (dry and wet condition), flexural strength (dry and wet condition) and flexural modulus (dry and wet condition)

Thermoplastic infusible resin systems: candidates for the marine sector?

This work investigated the feasibility of the use of a novel infusible thermoplastic resin (Elium 150 from Arkema) for composite laminate manufacture by resin infusion methods and possible application in the shipbuilding sector. We compared the properties of Elium glass-fibre laminates with those of laminates infused with state-of-the-art thermosetting epoxy and urethane acrylate resins. The Elium laminates matched the mechanical performance (flexure and interlaminar shear strength) of the epoxy and surpassed that of the urethane acrylate counterpart. However, the mechanical performance of the Elium laminates after immersion in water at 35 oC for 28 days deteriorated compared to urethane acrylate, but was comparable in flexural properties to that of the epoxy. The combination of superior mechanical performance coupled with acceptable environmental resistance and comparable composite laminate manufacturing conditions makes the infusible thermoplastic a possible future candidate matrix over commercial thermosetting resin options

Modelling water diffusion in plasticizers: development and optimization of a force field for 2,4-dinitroethylbenzene and 2,4,6-trinitroethylbenzene

A classical all-atom force field has been developed for 2,4,6-trinitroethylbenzene and 2,4-dinitroethylbenzene and applied in molecular dynamics simulations of the two pure and two mixed plasticizer systems. Bonding parameters and partial charges were derived through electronic and geometry optimization of the single molecules. The other required parameters were derived from values already available in the literature for generic nitro aromatic compounds, which were adjusted to reproduce to a high level of accuracy the densities of 2,4-dinitroethylbenzene, 2,4,6-trinitroethylbenzene and the energetic plasticizers K10 and R8002. This force field has been applied to both K10 and R8002, which when used as plasticizers form an energetic binder with nitrocellulose. Nitrocellulose decomposes in storage, under varying conditions, but in particular where it may become increasingly dry. Following the derivation of the force field, we have therefore applied it to calculate water diffusion coefficients for each of the different materials at 298 K and 338 K, thereby providing a starting point for understanding water behaviour in a nitrocellulose binder

Effect of Environmental Conditioning on the Properties of Thermosetting and Thermoplastic-Matrix Composite Materials by Resin Infusion for Marine Applications (PREPRINT)

Glass-fibre reinforced polymer (GFRP) laminates were manufactured using Vacuum assisted Resin Transfer Moulding (VaRTM) with a range of thermosetting resins and a novel infusible thermoplastic resin as part of a comprehensive down-selection to identify suitable commercially available resin systems for the manufacture of marine vessels greater than 50 m in length. The effect of immersion in deionised water and in an organic liquid (diesel) on the interlaminar shear strength (ILSS) and glass transition temperature (Tg) was determined. The thermoplastic had the highest Tg of all materials tested and comparable ILSS properties to the epoxy. Immersion in water, however, caused larger reductions in ILSS properties of the thermoplastic compared to the other systems. SEM showed a transition from matrix-dominated failure in the dry condition to failure at the fibre-matrix interface in the wet and organic-wet specimens. The overall performance of the infusible thermoplastic is good when compared to well-established marine resin systems; however, the environmental performance could be improved if the thermoplastic resin is used in conjunction with a fibre sizing that is tailored for use with acrylic-based resin systems