8,975 research outputs found
Exoplanets - search methods, discoveries, and prospects for astrobiology
Whereas the Solar System has Mars and Europa as the best candidates for
finding fossil/extant life as we know it - based on complex carbon compounds
and liquid water - the 263 (non-pulsar) planetary systems around other stars as
known at 15 September 2008 could between them possess many more planets where
life might exist. Moreover, the number of these exoplanetary systems is growing
steadily, and with this growth there is an increase in the number of planets
that could bear carbon-liquid water life. In this brief review the main methods
by which exoplanets are being discovered are outlined, and then the discoveries
that have so far been made are presented. Habitability is then discussed, and
an outline presented of how a planet could be studied from afar to determine
whether it is habitable, and whether it is indeed inhabited. This review is
aimed at the astrobiology community, which spans many disciplines, few of which
involve exoplanets. It is therefore at a basic level and concentrates on the
major topics.Comment: 37 pages, 12 Figure
Mark my words: an exhibition about marginalia
The book, The Ghost In The Fog has been included in an exhibition about marginalia in the Upper Library, The Queen's College Library, Oxford
Teaching embedded software development utilising QNX and Qt with an automotive-themed coursework application
A Study of Vitrified Nuclear Wasteforms by Molecular Dynamics, Electron Microscopy and Raman Spectroscopy
In this study an attempt is made to create molecular dynamics (MD) models of borate glass, alkali borosilicate glasses, and UK vitreous High Level Radioactive Wasteforms. The study also includes experimental studies of vitrified wasteforms by helium pycnometry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray florescence spectroscopy (XRF) and Raman spectroscopy.
Molecular dynamics models of alkali borosilicate glasses were created using Buckingham and BHM potentials in the constant pressure and temperature ensemble. The models using BHM potentials showed more realistic boron coordination numbers than those using Buckingham potentials. However structural features such as Si-O, Li-O and Na-O nearest neighbour distances and O Si O and O B O bond angles were considered satisfactory using Buckingham potentials.
SEM images showing phase separation in four different vitrified wasteforms are presented. The chemical composition of the phases were determined using SEM EDX. XRF spectroscopy was obtained from the wasteforms in powder form and show qualitative agreement with nominal compositions.
Raman spectroscopy also revealed the presence of MoO4 tetrahedra in a glass environment and in phases such as CaMoO4 and Na(Gd,Nd)(MoO4)2. The presence of ruthenium, cerium and zirconium phases were also found in the Raman spectra of wasteforms.
MD models of three simplified vitrified wasteforms were created using Buckingham potentials. Two models of each wasteform were created. The first models used only two-body potentials and showed MoO6 octahedra connected to borosilicate network formers. In the second model of each wasteform, an additional O Mo O three-body potential was applied. The results of the second models showed MoO4 tetrahedra detached from the borosilicate network which is a realistic feature in comparison to the experimental observations
Dual wound dc brush motor gearhead
The design requirements, the design, development tests and problems, the qualification and life test and the findings of the strip examination of a dual wound DC brushed motor gearhead are described. It is the only space qualified dual wound dc brushed motor gearhead in Europe
Inflationary Baryogenesis in a Model with Gauged Baryon Number
We argue that inflationary dynamics may support a scenario where significant
matter-antimatter asymmetry is generated from initially small-scale quantum
fluctuations that are subsequently stretched out over large scales. This
scenario can be realised in extensions of the Standard Model with an extra
gauge symmetry having mixed anomalies with the electroweak gauge symmetry.
Inflationary baryogenesis in a model with gauged baryon number is considered in
detail.Comment: 11 pages, V3 - major revisio
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The influence of Widmanstätten ferrite, martensite and grain boundary carbides on the strength and impact behaviour of high Al (0.2%) and Nb containing hot rolled steels
The influence of Al and Nb on the strength and impact behaviour of hot rolled 0.06%C, 1.4%Mn steels has been determined after hot rolling to 15 and 30 mm thick plate. When 0.16%Al was added to the plain C-Mn steel, the impact behaviour significantly improved even though Widmanstätten ferrite (WF) was present. This improvement was due to refinement of the grain boundary carbides and removing the N from solution as AlN. The hot rolled steels all contained WF but when Nb was added more WF formed as well as MA giving poor impact behaviour. Reducing the hardenability from that shown in previous work by decreasing C from 0.1 to 0.06%, Nb from 0.03 to 0.02%, and cooling rate from 33 to 17 K/min had no effect in improving the impact performance of hot rolled Nb steels. To ensure optimum properties not only is it necessary to reduce the hardenability, but WF formation must be discouraged by having a high Ar3. This can only be presently achieved by refining the austenite grain size via control rolling the Nb containing steels; the benefit of adding Al can then, readily be seen. Suggestions are made as to how this might be achieved for hot rolling
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