Development of EM-CCD-based X-ray detector for synchrotron applications

A high speed, low noise camera system for crystallography and X-ray imaging applications is developed and successfully demonstrated. By coupling an electron-multiplying (EM)-CCD to a 3:1 fibre-optic taper and a CsI(Tl) scintillator, it was possible to detect hard X-rays. This novel approach to hard X-ray imaging takes advantage of sub-electron equivalent readout noise performance at high pixel readout frequencies of EM-CCD detectors with the increase in the imaging area that is offered through the use of a fibre-optic taper. Compared with the industry state of the art, based on CCD camera systems, a high frame rate for a full-frame readout (50 ms) and a lower readout noise (<1 electron root mean square) across a range of X-ray energies (6–18 keV) were achieved

Density-Matrix approach to a Strongly Coupled Two-Component Bose-Einstein Condensate

The time evolution equations for average values of population and relative phase of a strongly coupled two component BEC is derived analytically. The two components are two hyper-fine states coupled by an external laser that drives fast Rabi oscillations between these states. Specifically, this derivation incorporates the two-mode model proposed in [1] for the strongly coupled hyper-fine states of Rb. The fast Rabi cycle is averaged out and rate equations are derived that represents the slow dynamics of the system. These include the collapse and revival of Rabi oscillations and their subsequent dependence on detuning and trap displacement as reported in experiments of [1]. A proposal to create stable vortices is also given.Comment: 11 Latex pages, 2 figures (Figure 3 was removed and the text chnaged accordingly

Concrete pavements as a source of heating and cooling

There is great potential to use the large open space of pavement structures, equipped with an embedded pipe network, in conjunction with a heat pump, to provide heating and cooling for adjacent buildings, e.g. airport terminals, shopping centres etc, here termed a Pavement Source Heat Pump (PSHP). Due to the high thermal mass of pavement materials, seasonal temperature fluctuation under the pavement is much less than the temperature fluctuation of ambient air. Therefore, pavements can be utilised as a low grade heat source during winter and as a heat sink during summer. Airports, for example, provide a key potential application as they are very large consumers of energy, typically have very high cooling demands, have a large amount of adjacent pavement area, and are of a similar arrangement throughout the world. In this paper, the temperature distribution into pavements with different thermo-physical properties was modelled in order to evaluate their effects on depth of seasonal temperature fluctuation. The results show that there is a linear relationship between the thermal diffusivity and depth of seasonal temperature fluctuation and it decreases in relation to the thermal diffusivity of the pavement

Dissolution experiments in halite cores: comparisons in cavity shape and controls between brine and seawater experiments

There is an increasing need for underground storage of natural gas (and potentially hydrogen) to meet the UK’s energy demands and ensure its energy security. In addition, the growth of renewable energy technologies, such as wind power, will be facilitated by the development of grid-scale energy storage facilities to balance grid demand. One solution lies in creating large-scale compressed-air energy storage (CAES) facilities underground. Whilst a number of lithologies offer storage potential, only three operational CAES facilities exist in the UK. They are constructed in specifically designed solution-mined salt (halite) caverns, similar to those currently used for natural gas storage. The influences exerted on salt dissolution by petrology, structure and fabric during cavern construction are not fully understood, with some occurences of caverns with noncircular cross-sections being less than optimum for gas storage and especially CAES

Relic Abundance of Asymmetric Dark Matter

We investigate the relic abundance of asymmetric Dark Matter particles that were in thermal equilibrium in the early universe. The standard analytic calculation of the symmetric Dark Matter is generalized to the asymmetric case. We calculate the asymmetry required to explain the observed Dark Matter relic abundance as a function of the annihilation cross section. We show that introducing an asymmetry always reduces the indirect detection signal from WIMP annihilation, although it has a larger annihilation cross section than symmetric Dark Matter. This opens new possibilities for the construction of realistic models of MeV Dark Matter.Comment: 20 pages, 11 figures, Accepted by JCA

Symmetric-Asymmetric transition in mixtures of Bose-Einstein condensates

We propose a new kind of quantum phase transition in phase separated mixtures of Bose-Einstein condensates. In this transition, the distribution of the two components changes from a symmetric to an asymmetric shape. We discuss the nature of the phase transition, the role of interface tension and the phase diagram. The symmetric to asymmetric transition is the simplest quantum phase transition that one can imagine. Careful study of this problem should provide us new insight into this burgeoning field of discovery.Comment: 6 pages, 3 eps figure

Split vortices in optically coupled Bose-Einstein condensates

We study a rotating two-component Bose-Einstein condensate in which an optically induced Josephson coupling allows for population transfer between the two species. In a regime where separation of species is favored, the ground state of the rotating system displays domain walls with velocity fields normal to them. Such a configuration looks like a vortex split into two halves, with atoms circulating around the vortex and changing their internal state in a continuous way.Comment: 4 EPS pictures, 4 pages; Some errata have been corrected and thep resentation has been slightly revise

Dynamics of two colliding Bose-Einstein condensates in an elongated magneto-static trap

We study the dynamics of two interacting Bose-Einstein condensates, by numerically solving two coupled Gross-Pitaevskii equations at zero temperature. We consider the case of a sudden transfer of atoms between two trapped states with different magnetic moments: the two condensates are initially created with the same density profile, but are trapped into different magnetic potentials, whose minima are vertically displaced by a distance much larger than the initial size of both condensates. Then the two condensates begin to perform collective oscillations, undergoing a complex evolution, characterized by collisions between the two condensates. We investigate the effects of their mutual interaction on the center-of-mass oscillations and on the time evolution of the aspect ratios. Our theoretical analysis provides a useful insight into the recent experimental observations by Maddaloni et al., cond-mat/0003402.Comment: 8 pages, 7 figures, RevTe

Suggestion, hypnosis and hypnotherapy: a survey of use, knowledge and attitudes of anaesthetists

Publisher's copy made available with the permission of the publisher © Australian Society of AnaesthetistsClinical hypnosis is a skill of using words and gestures (frequently called suggestions) in particular ways to achieve specific outcomes. It is being increasingly recognised as a useful intervention for managing a range of symptoms, especially pain and anxiety. We surveyed all 317 South Australian Fellows and trainees registered with ANZCA to determine their use, knowledge of, and attitudes towards positive suggestion, hypnosis and hypnotherapy in their anaesthesia practice. The response rate was 218 anaesthetists (69%). The majority of respondents (63%) rated their level of knowledge on this topic as below average. Forty-eight per cent of respondents indicated that there was a role for hypnotherapy in clinical anaesthesia, particularly in areas seen as traditional targets for the modality, i.e. pain and anxiety states. Nearly half of the anaesthetists supported the use of hypnotherapy and positive suggestions within clinical anaesthesia. Those respondents who had experience of clinical hypnotherapy were more likely to support hypnosis teaching at undergraduate or postgraduate level when compared with those with no experience.http://www.aaic.net.au/Article.asp?D=200408

Testing Broken U(1) Symmetry in a Two-Component Atomic Bose-Einstein Condensate

We present a scheme for determining if the quantum state of a small trapped Bose-Einstein condensate is a state with well defined number of atoms, a Fock state, or a state with a broken U(1) gauge symmetry, a coherent state. The proposal is based on the observation of Ramsey fringes. The population difference observed in a Ramsey fringe experiment will exhibit collapse and revivals due to the mean-field interactions. The collapse and revival times depend on the relative strength of the mean-field interactions for the two components and the initial quantum state of the condensate.Comment: 20 Pages RevTex, 3 Figure