Chemically specifi C multiscale modeling of clay-polymer nanocomposites reveals intercalation dynamics, tactoid self-assembly and emergent materials properties

A quantitative description is presented of the dynamical process of polymer intercalation into clay tactoids and the ensuing aggregation of polymerentangled tactoids into larger structures, obtaining various characteristics of these nanocomposites, including clay-layer spacings, out-of-plane clay-sheet bending energies, X-ray diffractograms, and materials properties. This model of clay-polymer interactions is based on a three-level approach, which uses quantum mechanical and atomistic descriptions to derive a coarse-grained yet chemically specifi c representation that can resolve processes on hitherto inaccessible length and time scales. The approach is applied to study collections of clay mineral tactoids interacting with two synthetic polymers, poly(ethylene glycol) and poly(vinyl alcohol). The controlled behavior of layered materials in a polymer matrix is centrally important for many engineering and manufacturing applications. This approach opens up a route to computing the properties of complex soft materials based on knowledge of their chemical composition, molecular structure, and processing conditions.This work was funded in part by the EU FP7 MAPPER project (grant number RI-261507) and the Qatar National Research Fund (grant number 09–260–1–048). Supercomputing time was provided by PRACE on JUGENE (project PRA044), the Hartree Centre (Daresbury Laboratory) on BlueJoule and BlueWonder via the CGCLAY project, and on HECToR and ARCHER, the UK national supercomputing facility at the University of Edinburgh, via EPSRC through grants EP/F00521/1, EP/E045111/1, EP/I017763/1 and the UK Consortium on Mesoscopic Engineering Sciences (EP/L00030X/1). The authors are grateful to Professor Julian Evans for stimulating discussions during the course of this project. Data-storage and management services were provided by EUDAT (grant number 283304)

Drying Properties and Rice Production Potential of Cracking Soils in the Muda Irrigation Scheme

Three previously puddled rice soils, namely the Chengai, Tebengau, and Tualang series of the Muda Irrigation Scheme were studied both in the field and in the glass house. The objectives of this study were to understand the processes of drying, cracking and re-wetting and relate these to soil properties, to develop a simple model for estimating bypass flow and bypass ratio of cracking soil during land soaking, and to simulate the ORYZA_ W model for determining the optimum sowing date, quantifying rice yield, net water use, and crop duration under future climate change scenarios, and assessing the drought effect on irrigated rice yield. Calculated volumetric and linear shrinkage of the Chengai and Tebengau series were similar and greater than those of the Tualang series. The measured shrinkage geometric factor rs, with values of around 3 , indicated that shrinkage of these three series was isotropic. Comparatively faster moisture depletion and absorption were observed in the Chengai and Tebengau series than in the Tualang series both in the glasshouse and field conditions. Chengai and Tebengau soils showed similar crack width, depth, area, length and volume, these properties being significantly different from those of the Tualang soil. The deepest crack depth below the puddled layer measured by the paint method were 77, 73, and 52 cm in the Chengai, Tebengau, and Tualang series, respectively. A model was developed to quantify bypass flow during land soaking. According to the model, the amount of water that bypassed the topsoil of the three soil series accounted for 59-67% of total input water. Higher yields (1 0.2 to 1 0.6 t ha-I) were predicted for the off season (56-98 Day of the Year - DOY) than the main season (9.2 to 9.7 t ha-I during 1 96-238 DOY). The higher off season yields were associated with higher radiation and longer crop duration. The impact of 15 different climatic scenarios was evaluated. Crop duration (TGP) was shortened by 3 and 2 days during the off and main seasons, respectively, following a 4°C increase in the daily maximum temperature. Increased CO2 levels predicted an increase in yield in both seasons. The combinations of increased CO2 levels and temperatures predicted increased yields for both seasons. The scenarios of three General Circulation Models (GCM) predicted yield reduction in the off season while in the main season, predicted yields were almost similar to current yields. The net water use (NWU) increased with increase in temperature in both seasons for all cases. Increments in CO2 level did not predict any change for NWU in both seasons. The combinations of increased temperatures and CO2 levels, and the scenarios of three GCMs predicted an increase of NWU in both seasons. Increased NWU was mainly influenced by temperature increments. Yield differences between crops temporarily stressed at mid-tillering and panicle initiation stages and nonstressed crops were smaller. However, maturity was delayed in both seasons. Large yield reductions were predicted for temporary drought stress at the flowering stage, while maturity was delayed by 3 and I-day in the off and main seasons, respectively

An Overview of the Alabama Burst Energetics eXplorer (ABEX) Mission

The Alabama Burst Energetics eXplorer (ABEX) project is a 12U scientific and educational mission to investigate Gamma-Ray Bursts (GRB) through spectral analysis and localization of joint gravitational-wave GRB mergers using wavefront timing analysis. The project is in development by a multi-university collaboration across Alabama with design work conducted by students under faculty advisement. The effort is organized and funded by the Alabama Space Grant Consortium and includes the University of Alabama, University of Alabama in Birmingham, University of South Alabama, Auburn University, and the University of Alabama in Huntsville. ABEX will deploy on a super-synchronous orbit and propulsively maneuver to a high eccentricity orbit of 300 km perigee by 60,000 km apogee at 27° inclination. From this high apogee destination, ABEX will observe GRB events using a suite of detectors that measure a broad energy range from keV to MeV. The highly eccentric orbit allows ABEX to perform wavefront timing between LEO gamma-ray missions as it passes through apogee. ABEX has several engineering systems being developed by cohort universities as part of its educational mission, specifically the On-Board Computers, Electrical Power System, Flight Software, chassis, and instrumentation. In this paper we present a broad overview of the mission, including the scientific and educational goals, spacecraft design, instrument design, and operations concept

The effect of applied and magnetic fields on the crystallisation of hydrocarbons

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This thesis provides a background on the effects of applied and magnetic fields on crystallisation, and summarises the analytical techniques employed for characterisation and analysis. The study of applied fields was carried out on the crystallisation of one main system-solid nonadecane. This was then studied further to establish the effects of a solvent and a mixed solid system on the crystallisation of nonadecane. The systems studied were the crystallisations of: static and dynamic nonadecane, static and dynamic nonadecane in heptane, static and dynamic nonadecane and heneicosane, static and dynamic nonadecane and heneicosane in heptane and static and dynamic nonadecane and crude oil. The results of these studies showed that the magnetic and applied fields can affect electrostatic forces in molecular solids. It also showed that even the weakest of these forces, Van der Waals forces are affected by applied and magnetic fields