Pipe and grain boundary diffusion of He in UO₂

Molecular dynamics simulations have been conducted to study the effects of dislocations and grain boundaries on He diffusion in UO2. Calculations were carried out for the {100}, {110} and {111} h110i edge dislocations, the screw h110i dislocation and Σ5, Σ13, Σ19 and Σ25 tilt grain boundaries. He diffusivity as a function of distance from the dislocation core and grain boundaries was investigated for the temperature range 2300 - 3000 K. An enhancement in diffusivity was predicted within 20 Å of the dislocations or grain boundaries. Further investigation showed that He diffusion in the edge dislocations follows anisotropic behaviour along the dislocation core, suggesting that pipe diffusion occurs. An Arrhenius plot of He diffusivity against the inverse of temperature was also presented and the activation energy calculated for each structure, as a function of distance from the dislocation or grain boundar

Controlling the polarisation correlation of photon pairs from a charge-tuneable quantum dot

Correlation between the rectilinear polarisations of the photons emitted from the biexciton decay in a single quantum dot is investigated in a device which allows the charge-state of the dot to be controlled. Optimising emission from the neutral exciton states maximises the operating efficiency of the biexciton decay. This is important for single dot applications such as a triggered source of entangled photons. As the bias on the device is reduced correlation between the two photons is found to fall dramatically as emission from the negatively charged exciton becomes significant. Lifetime measurements demonstrate that electronic spin-scattering is the likely cause.Comment: 3 figure

Quarkonia measurement in p+p and d+Au collisions at sqrt(s)=200 GeV by PHENIX Detector

We report new quarkonia measurements necessary to understand production mechanisms and cold nuclear matter effects in the yields observed at RHIC energy. Results obtained in p+p collisions collected during the 2006 RHIC Run include J/psi, Psi' and Upsilon differential cross sections as well as J/psi polarization. Revisited interpretations of the published J/psi nuclear modification factors and statistically improved observations in d+Au collisions taken in the 2008 Run are also discussed in the view of the recent understanding of the initial state effects and breakup cross section.Comment: 4 pages, 10 figures, Proceedings for Quark Matter 2009 Conference in Knoxville,TN,US

Continuous flow iodination using an automated computer-vision controlled liquid-liquid extraction system

Abstract A dynamic computer-vision control system incorporating open-source software technologies (Python, OpenCV) was used to automate a gravity based in-line liquid-liquid extraction during the iodination of enaminones in continuous flow. The system was able to cope with significant colouration of the organic reaction stream and with significant volume/flow changes in the aqueous and organic phase streams due to extraction of the water soluble acetonitrile co-solvent

The maritime heritage of Yemen: a focus on traditional wooden "dhows"

This paper investigates the disappearing heritage of Yemen’s large wooden boats (dhows), both in its current socio-economic context and in historical perspective. Fieldwork conducted by members of the MARES project in February 2009 along the coast between Aden and Salif sought to record remaining evidence of wooden boats and their related industries and practices. Wooden boat use has been in sharp decline in recent decades, as dhow-based commerce has declined, and fishing communities have switched to fibreglass vessels. The fieldwork sought to record remaining dhows through simple survey techniques including photography and illustration, as well as close observation. It also involved ethnographic interviews with people who worked on these vessels, either as builders or mariners. In terms of the vessels themselves, the aim was to produce a typology of Yemeni dhows; to record examples of each; to understand construction sequences; and to inventory the distribution of surviving craft. The findings are compared with previous literature on the subject.This research was conducted as part of the MARES Project, a three-year programme investigating the maritime past and heritage of the Red Sea and Arabian-Persian Gulf. MARES is based at the Institute of Arab and Islamic Studies of the University of Exeter (http://projects.exeter.ac.uk/mares). The programme is generously funded by the Golden Web Foundation, an educational charity registered in the UK (www.goldenweb.org). Thanks are also due to the Seven Pillars of Wisdom Trust, which provided additional financial support for the fieldwork. In addition, the MARES team would like to thank the following people for their assistance: Dr Abdulla M. Bawazir, President of Yemen’s General Organisation of Antiquities and Museums (GOAM); Dr Muhammad Taha al- Asbahi, General Director of Antiquities at GOAM; Dr Raja Batawil, head of GOAM in Aden; our GOAM-appointed field companion, Salah al-Mansuri; Mr. Hasan Saleh Shihab; Emily Allardyce, Fuad Mazid al-Matairi and their colleagues at the British Yemeni Language Institute; our driver and guide Muhammad al-Matairi; Edward Prados, Director of Amideast; Chris Evans; the British Council; and the British Embassy, Sanʿā. The team wishes to thank also the many individual informants along Yemen’s coast who generously gave of their time and expertise

Inversion of exciton level splitting in quantum dots

The demonstration of degeneracy of exciton spin states is an important step toward the production of entangled photon pairs from the biexciton cascade. We measure the fine structure of exciton and biexciton states for a large number of single InAs quantum dots in a GaAs matrix; the energetic splitting of the horizontally and vertically polarized components of the exciton doublet is shown to decrease as the exciton confinement decreases, crucially passing through zero and changing sign. Thermal annealing is shown to reduce the exciton confinement, thereby increasing the number of dots with splitting close to zero

The simulation of action disorganisation in complex activities of daily living

Action selection in everyday goal-directed tasks of moderate complexity is known to be subject to breakdown following extensive frontal brain injury. A model of action selection in such tasks is presented and used to explore three hypotheses concerning the origins of action disorganisation: that it is a consequence of reduced top-down excitation within a hierarchical action schema network coupled with increased bottom-up triggering of schemas from environmental sources, that it is a more general disturbance of schema activation modelled by excessive noise in the schema network, and that it results from a general disturbance of the triggering of schemas by object representations. Results suggest that the action disorganisation syndrome is best accounted for by a general disturbance to schema activation, while altering the balance between top-down and bottom-up activation provides an account of a related disorder - utilisation behaviour. It is further suggested that ideational apraxia (which may result from lesions to left temporoparietal areas and which has similar behavioural consequences to action disorganisation syndrome on tasks of moderate complexity) is a consequence of a generalised disturbance of the triggering of schemas by object representations. Several predictions regarding differences between action disorganisation syndrome and ideational apraxia that follow from this interpretation are detailed

Boat and ship engravings at Al Zubarah, Qatar: the dāw exposed?

This is the author accepted manuscript. The final version is available from ArchaeopressOn-going excavations at the site of the 18th–19th century walled town of Al Zubarah, Qatar, have uncovered a number of engravings of seagoing craft etched into the dry plasterwork of buildings within the settlement. The engravings are essentially graffiti, carved into the interiors of rooms without aesthetic reference to the original decorative schema of their settings. The resulting images are of varying sophistication and detail — dependent, no doubt, on the skill and inclination of their executors. While the crudest images are rudimentary outlines of hulls, others show detail that demonstrates the familiarity of their creators with boat construction and type — not surprising in a settlement whose raison d’être was the livings to be made from the sea. This iconographic vestige provides an insight into the types of vessel their creators used and encountered, and allows us to venture our own identifications of them. It also prompts us to reflect on the nature of the relationship between Al Zubarah’s some-time residents and the sea: the vessels depicted are for the most part a mixture of ocean-going types built within the Gulf or western Indian Ocean region. One, however, is of a European naval vessel, perhaps suggesting the shadow of British imperial power in the Gulf. Finally, the process of identification of these watercraft inspires renewed reflection on the word ‘dhow’ and its variants, from both a typological and an etymological perspective; these new reflections are presented at the end of this paper

Cold atoms in micromachined waveguides: A new platform for atom-photon interactions

Hybrid quantum devices, incorporating both atoms and photons, can exploit the benefits of both to enable scalable architectures for quantum computing and quantum communication, as well as chip-scale sensors and single-photon sources. Production of such devices depends on the development of an interface between their atomic and photonic components. This should be compact, robust, and compatible with existing technologies from both fields. Here we demonstrate such an interface. Cold cesium atoms are trapped inside a transverse, 30μm-diameter through hole in an optical fiber, created via laser micromachining. When the guided light is on resonance with the cesium D2 line, up to 87% of it is absorbed by the atoms. The corresponding optical depth per unit length is ∼700 cm−1, higher than any reported for a comparable system. This is important for miniaturization and scalability. The technique can be equally effective in optical waveguide chips and other existing photonic systems, providing a promising platform for fundamental research

The Dhow's last redoubt? Vestiges of wooden boatbuilding traditions in Yemen

This is an accepted version of an article that went on to be published in the Proceedings of the Seminar for Arabian Studies in 2010. The reference for the published version is: Agius, D.A., Cooper, J.P., Jansen van Rensburg, J.and Zazzaro, C., 2010 " The dhow's last redoubt? Vestiges of wooden boatbuilding traditions in Yemen". Proceedings of the Seminar for Arabian Studies 40: 71—84. Please use the published version in any citations.The final version of the article is available from Archaeopress via the link in this record.Researchers from the MARES Project visited Yemen in February 2009 in order to investigate the building and use of traditional wooden boats (‘dhows’, in English parlance) in the country. The survey covered the coastline from Aden to Salif in the Red Sea, and visited centres of traditional dhow building and use, including Ghureira, Mocha and Khokha. The project aimed to assess the state of the industry, establish a vessel typology, understand construction processes, learn about the use of these vessels, and compile a lexicon of boatbuilding and nautical terms. This article offers the preliminary findings of the survey, pending more comprehensive publication in the future. The survey found that, in all locations visited, the building of new vessels had rapidly diminished in the preceding decade, and had now all but ceased. The only ongoing activity witnessed during the survey was repairs to existing wooden craft. In formerly large boat-building centres, wooden boat-builders, mostly elderly, have ceased work, while younger men were building fishing craft using fibreglass – the material used in the great majority of vessels in Yemen today. A preliminary typology of surviving vessel was established. The doubleended cargo-carrying za<īmahs and zārūqs were recorded only as 2 abandoned hulks. Double-ended <obrīs and transom-sterned ‘large hūrīs’, with their stern-quarter ‘fins’, continued to be used in small numbers for sein fishing and transporting livestock. Again, most examples were abandoned. Various forms of small log and plank hūrī ‘canoes’ were observed, few still in use, while the log-raft ramas survives on the Red Sea coast. The terms used for these vessel types form part of a linguistic survey of dhow activity in Yemen.This research was conducted as part of the MARES Project, a three-year programme investigating the maritime past and heritage of the Red Sea and Arabian-Persian Gulf. MARES is based at the Institute of Arab and Islamic Studies at the University of Exeter (http://projects.exeter.ac.uk/mares). The programme is funded by the Golden Web Foundation, an educational charity registered in the UK (www.goldenweb.org), to which our gratitude is due. 27 Thanks are also due to the Seven Pillars of Wisdom Trust, which provided additional financial support for the fieldwork. In addition, the MARES team would like to thank the following people for their assistance: Dr Abdulla M. Bawazir, President of Yemen’s General Organisation of Antiquities and Museums (GOAM); Dr Muhammad Taha al-Asbahi, General Director of Antiquities at GOAM; Dr Raja Batawil, head of GOAM in Aden; our GOAMappointed field companion, Salah al-Mansuri; Mr. Hasan Saleh Shihab; Emily Allardyce, Fuad Mazid al-Matairi and their colleagues at the British Yemeni Language Institute; our driver and guide Muhammad al-Matairi; Edward Prados, Director of Amideast; Chris Evens; the British Council; and the British Embassy. Last but not least, the team wishes to thank the many individual informants along Yemen’s coast who gave their assistance to its research