A solution concentration dependent transition from self-stratification to lateral phase separation in spin-cast PS:d-PMMA thin films

Thin films with a rich variety of different nano-scale morphologies have been produced by spin casting solutions of various concentrations of PS:d-PMMA blends from toluene solutions. During the spin casting process specular reflectivity and off-specular scattering data were recorded and ex situ optical and atomic force microscopy, neutron reflectivity and ellipsometry have all been used to characterise the film morphologies. We show that it is possible to selectively control the film morphology by altering the solution concentration used. Low polymer concentration solutions favour the formation of flat in-plane phase-separated bi-layers, with a d-PMMA-rich layer underneath a PS-rich layer. At intermediate concentrations the films formed consist of an in-plane phase-separated bi-layer with an undulating interface and also have some secondary phase-separated pockets rich in d-PMMA in the PS-rich layer and vice versa. Using high concentration solutions results in laterally phase-separated regions with sharp interfaces. As with the intermediate concentrations, secondary phase separation was also observed, especially at the top surface

Four New Planets Orbiting Metal-enriched Stars

Peer reviewe

Stability analysis of motor drive interactions in aircraft electrical systems

More Electric Aircraft are currently being developed so that in the future all non-propulsive power on an aircraft can be provided by the electrical system. In this electrical system, it is expected that several motor loads will run in parallel from a single DC bus. The paper will investigate the interactions between five motor loads connected to a common DC bus, paying particular attention to the effects of the line impedance on the stability of the system, and how this interacts with any capacitance in the input filters to the motor drive loads. Based on the results of the tests carried out, guidelines to ensure the stability of a multiple load system are presented. To achieve this, a generic model for a motor load is proposed. Five of these motor loads are then connected to a DC bus and the stability of this system has been tested. The motor parameters have been scaled to represent models of different sizes, and they have different input filters. The impedance of the line has been included

Corallivory in tubelip wrasses: diet, feeding and trophic importance

This paper describes a 2 month study of the patterns of abundance, feeding pressure, diet and feeding selectivity in corallivorous tubelip wrasses (Labridae), rarely studied, yet widespread and abundant group of corallivores on Indo-Pacific coral reefs. The relative abundance and feeding pressure of corallivorous wrasses and butterflyfishes (Chaetodontidae) in Kimbe Bay, Papua New Guinea, were compared. Overall, tubelip wrasses were more than twice as abundant as corallivorous butterflyfishes and accounted for three times as many feeding bites on corals. The three most abundant tubelip wrasses (yellowtail tubelip Diproctacanthus xanthurus, Allen's tubelip Labropsis alleni and the tubelip wrasse Labrichthys unilineatus) were all obligate corallivores taking > 97% of bites from the surface of live corals. Labropsis alleni and D. xanthurus were highly selective, consuming preferred prey species in proportions significantly higher than expected given their availability. In contrast, L. unilineatus was fairly non-selective and consumed most corals in direct accordance with their availability. As coral predators, tubelip wrasses are highly comparable to coral-feeding butterflyfishes in the coral species consumed, range of dietary specialization and their reliance on live coral. Tubelip wrasses, however, may supersede butterflyfishes as the predominant corallivorous family in some Indo-Pacific locations, and coral-feeding tubelip wrasses are likely to be severely affected by coral decline

Maghemite-like regions at crossing of two antiphase boundaries in doped BiFeO3

We report the observation of a novel structure at the point where two antiphase boundaries cross in a doped bismuth ferrite of composition (Bi0.85Nd0.15)(Fe0.9Ti0.1)O0.3. The structure was investigated using a combination of high angle annular dark field imaging and electron energy loss spectroscopy spectrum imaging in the scanning transmission electron microscope. A three-dimensional model was constructed by combining the position and chemistry data with previous results and assuming octahedral coordination of all Fe and Ti atoms. The resulting structure shows some novel L shaped arrangements of iron columns, which are coordinated in a similar manner to FeO6 octahedra in maghemite. It is suggested that this may lead to local ferromagnetic orderings similar to those in maghemite

Nanostructure and paramagnetic centres in diamond-like carbon: Effect of Ar dilution in PECVD process

Diamond-like carbon (DLC) films were deposited utilising plasma enhanced chemical vapour deposition (PECVD) with acetylene precursor, diluted with 0 – 45% argon. Electron paramagnetic resonance (EPR) measurements show the presence of one paramagnetic centre with no change in spin population over the range of film deposition conditions. However, the EPR linewidth decreases with increasing argon content of the precursor mix, suggesting an enhancement of motional narrowing due to an increase in electron delocalization, related to an increase in the sp2 cluster size. Atomic force microscopy (AFM) measurements indicate the surface of the DLC is formed of nanoscale asperities of material. With radii of tens of nanometres for films deposited with zero argon, the size of the features increases with the argon dilution of the acetylene. Energy dispersive x-ray analysis and electrical measurements further elucidate the changes in film structure

Design, characterisation and properties of Mo-Ti-Fe alloys reinforced by ordered intermetallic precipitates

Reinforcement of solid solution matrices with ordered intermetallic precipitates is known to be an effective strategy for obtaining high strength, damage tolerant alloys and has been central to the success of nickel based superalloys. This strategy has also been exploited in a number of bcc-based systems, for example in maraging steels where ferrite is strengthened by L21 (Heusler) and/or B2 structured intermetallic precipitates. However, only limited studies have explored the possibility of extending this approach to bcc alloys based on refractory metals and titanium. Recent research has shown that titanium-iron alloys comprising eutectic A2 Ti and B2 TiFe phases may be produced with strengths of over 2.5 GPa, alongside elongations to failures of ~15%. These impressive properties are thought to be a result of a fine microstructural length scale and a high lattice misfit between the phases. Here, we report on the phase equilibria in the Mo-Ti-Fe ternary system. In this system, an extensive two-phase field was identified between B2 TiFe intermetallic phase and the A2 (Ti, Mo) solid solution, that extended to Mo rich compositions. Knowledge of how this phase equilibrium varies with temperature enabled the design of alloys that could be homogenised in the single-phase solid solution and subsequently reinforced by solid state precipitates following a lower temperature heat treatment. The microstructure obtained was finer than has been produced through an invariant reaction and an initial assessment of their mechanical properties revealed substantial strength. The prospects for modifying these alloys to enable their use at higher temperatures will be discussed. This work was supported through the Rolls-Royce/EPSRC Strategic Partnership under EP/H022309/1 and EP/H500375/1, as well as the DARE project under EP/L025213/1

Design of Off - Grid Solar Photovoltaic (PV) System for Cottage Hospital

The provision of adequate and sustainable power supply to the country’s citizen has been a mirage since the 1980’s when the nation neglected to improve its power generation capacity. The rapid population and increase in industrial activities necessitate the injection of solar photovoltaic technology into nation’s energy mix. The need to power cottage hospital in developing country like Nigerian is too enormous. This seminar paper is an attempt to design off-grid solar PV system for cottage hospitals. In this study, I consider the appliances needed for cottage hospital to function effectively, the end used application include (Energy saving bulb, fan, DVD player, radio, television and refrigerator). The power is derived from fifteen 100W PV solar panel unit and the total load power of these appliances is 4925Wh/day. Keywords: PV array, Cottage Hospital, Rural Development, Storage battery, Charge Controller, inverter, Wire

Petrography and Geochemistry of Metals in Almahata Sitta Ureilites

Ureilites are ultramafic achondrites, predominantly composed of olivine and pyroxenes with accessory carbon, metal and sulfide. The majority of ureilites are believed to represent the mantle of the ureilite parent body (UPB) [1]. Although ureilites have lost much of their original metal [2], the metal that remains retains a record of the formative processes. Almahata Sitta is predominantly composed of unbrecciated ureilites with a wide range of silicate compositions [3,4]. As a fall it presents a rare opportunity to examine fresh ureilite metal in-situ, and analyzing their highly siderophile element (HSE) ratios gives clues to their formation. Bulk siderophile element analyses of Almahata Sitta fall within the range observed in other ureilites [5]. We have examined the metals in seven ureilitic samples of Almahata Sitta (AS) and one associated chondrite fragment (AS#25)