Large Seebeck coefficients in Iron-oxypnictides : a new route towards n-type thermoelectric materials

The iron-oxypnictide compounds, recently reported as a new class of superconductors when appropriately doped, exhibit large Seebeck coefficients, of the order of -100 microV/K, while keeping good electrical conductivity. Their power factor shows a peak at low temperatures, suggesting possible applications of these materials in thermoelectric cooling modules in the liquid nitrogen temperature range

Old Comrades: A study of the formation of ex-military communities in Tyne and Wear since the Great War

Although veterans are a permanent feature of British society, how ex-service men and women have come to understand their identities as individuals has not received the attention from historians this subject deserves and requires. Tyne and Wear, traditionally said to be a productive recruiting ground for the Armed Forces, is no exception to this lack of research. The examination of oral memory in this thesis demonstrates an approach to understanding veterans’ identities in Tyne and Wear since 1914, analysing individuals’ interpretations of their experiences, their identity, and their perceptions of participation in communities and wider society. Using a collection of newly created and re-evaluated oral histories, this thesis challenges established notions of a single ‘veteran identity’. It argues that the relationship between the communities and identities formed by ex-service personnel since 1914 have been directly linked to the influence of military service in a more complex and heterogeneous manner than has been previously recognised by scholars

Coupling slot-waveguide cavities for large-scale quantum optical devices

By offering effective modal volumes significantly less than a cubic wavelength, slot-waveguide cavities offer a new in-road into strong atom-photon coupling in the visible regime. Here we explore two-dimensional arrays of coupled slot cavities which underpin designs for novel quantum emulators and polaritonic quantum phase transition devices. Specifically, we investigate the lateral coupling characteristics of diamond-air and GaP-air slot waveguides using numerically-assisted coupled-mode theory, and the longitudinal coupling properties via distributed Bragg reflectors using mode-propagation simulations. We find that slot-waveguide cavities in the Fabry-Perot arrangement can be coupled and effectively treated with a tight-binding description, and are a suitable platform for realizing Jaynes-Cummings-Hubbard physics.Comment: 11 pages, 7 figures, submitte

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Remarkable preservation of brain tissues in an Early Cretaceous iguanodontian dinosaur

It has become accepted in recent years that the fossil record can preserve labile tissues. Here we report highly detailed mineralisation of soft tissues associated with a naturally occurring brain endocast of an iguanodontian dinosaur, found in ~133 Ma fluvial sediments of the Wealden at Bexhill, Sussex, U.K. Moulding of the braincase wall, and mineral replacement of adjacent brain tissues by phosphates and carbonates, permits direct examination of petrified brain tissues. SEM imaging and CT-scanning reveal preservation of the tough membranes (meninges) that enveloped and supported the brain proper. Collagen strands of the meningeal layers are preserved in collophane. Blood vessels, also preserved in collophane, are either lined by, or infilled with, microcrystalline siderite. Meninges are preserved in the hindbrain region, and exhibit structural similarities with those of living archosaurs. Greater definition of the forebrain (cerebrum) compared to the hindbrain (cerebellar and medullary regions) is consistent with the anatomical and implied behavioural complexity previously described in iguanodontian-grade ornithopods. However, we caution that the observed proximity of probable cortical layers to the braincase walls likely results from settling of brain tissues against the roof of the braincase following inversion of the skull during decay and burial

Fabrication of Diamond Nanowires for Quantum Information Processing Applications

We present a design and a top-down fabrication method for realizing diamond nanowires in both bulk single crystal and polycrystalline diamond. Numerical modeling was used to study coupling between a Nitrogen Vacancy (NV) color center and optical modes of a nanowire, and to find an optimal range of nanowire diameters that allows for large collection efficiency of emitted photons. Inductively coupled plasma (ICP) reactive ion etching (RIE) with oxygen is used to fabricate the nanowires. Drop-casted nanoparticles (including $\mathrm{Au}$, $\mathrm{SiO_{2}}$ and $\mathrm{Al_2O_3}$) as well as electron beam lithography defined spin-on glass and evaporated $\mathrm{Au}$ have been used as an etch mask. We found $\mathrm{Al_2O_3}$ nanoparticles to be the most etch resistant. At the same time FOx e-beam resist (spin-on glass) proved to be a suitable etch mask for fabrication of ordered arrays of diamond nanowires. We were able to obtain nanowires with near vertical sidewalls in both polycrystalline and single crystal diamond. The heights and diameters of the polycrystalline nanowires presented in this paper are \unit[\approx1]{\mu m} and \unit[120-340]{nm}, respectively, having a \unit[200]{nm/min} etch rate. In the case of single crystal diamond (types Ib and IIa) nanowires the height and diameter for different diamonds and masks shown in this paper were \unit[1-2.4]{\mu m} and \unit[120-490]{nm} with etch rates between \unit[190-240]{nm/min}.Comment: 11 pages, 26 figures, submitted to Diamond and related Materials; http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TWV-4Y7MM1M-1&_user=10&_coverDate=01%2F25%2F2010&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=6dc58b30f4773a710c667306fc541cc

High Temperature Long Period Grating Thermo-Mechanically Written

An optical fiber transducer able to work in high temperature environments is experimentally demonstrated in the laboratory. It is based on a permanent long period grating (LPG) written using a new technique based on a thermo-mechanical approach. Device precision was experimentally checked by means of repetitive thermal cycles between 25 and 950 °C. In addition device stability was assured by maintaining the temperature in steady state at 800 °C during 23 hours

Remarkable preservation of brain tissues in an Early Cretaceous iguanodontian dinosaur

It has become accepted in recent years that the fossil record can preserve labile tissues. We report here the highly detailed mineralization of soft tissues associated with a naturally occurring brain endocast of an iguanodontian dinosaur found in c. 133 Ma fluvial sediments of the Wealden at Bexhill, Sussex, UK. Moulding of the braincase wall and the mineral replacement of the adjacent brain tissues by phosphates and carbonates allowed the direct examination of petrified brain tissues. Scanning electron microscopy (SEM) imaging and computed tomography (CT) scanning revealed preservation of the tough membranes (meninges) that enveloped and supported the brain proper. Collagen strands of the meningeal layers were preserved in collophane. The blood vessels, also preserved in collophane, were either lined by, or infilled with, microcrystalline siderite. The meninges were preserved in the hindbrain region and exhibit structural similarities with those of living archosaurs. Greater definition of the forebrain (cerebrum) than the hindbrain (cerebellar and medullary regions) is consistent with the anatomical and implied behavioural complexity previously described in iguanodontian-grade ornithopods. However, we caution that the observed proximity of probable cortical layers to the braincase walls probably resulted from the settling of brain tissues against the roof of the braincase after inversion of the skull during decay and burial