Zastrau U.,Friedrich - Schiller University of Jena |
Zastrau U.,Helmholtz Center for Heavy Ion Research |
Vinko S.M.,University of Oxford |
Wark J.S.,University of Oxford |
And 11 more authors.
AIP Conference Proceedings | Year: 2012
We report on experiments aimed at the generation and characterization of solid density plasmas at the free-electron laser FLASH in Hamburg. Aluminum samples were irradiated with XUV pulses at 13.5 nm wavelength (92 eV photon energy). The pulses with duration of a few tens of femtoseconds and pulse energy up to 100 μJ are focused to intensities ranging from 10 13 to 10 17 W/cm 2. We investigate the absorption and temporal evolution of the sample under irradiation by use of XUV spectroscopy. We discuss the origin of saturable absorption, radiative decay, bremsstrahlung and ionic line emission. Our experimental results are in good agreement with hydrodynamic simulations. © 2012 American Institute of Physics.
Abdelal G.F.,Queenss University |
Robotham A.,Auckland University of Technology |
Carragher P.,United Technologies
Journal of Petroleum Science and Engineering | Year: 2015
For over 50 years bridge plugs and cement have been used for well abandonment, work over, and are still the material of choice. However the failures of cement abandonments using bridge plugs has been reported on many occasions, some of which have resulted in fatal consequences. A new patented product is designed to address the shortcomings associated with using bridge plugs and cement. The new developed tools use an alloy based on bismuth that is melted in situ using Thermite reaction. The tool uses the expansion properties of bismuth to seal the well. Testing the new technology in real field under more than 2. km deep sea water can be expensive. Virtual simulation of the new device under simulated thermal and mechanical environment can be achieved using nonlinear finite element method to validate the product and reduce cost. Experimental testing in the lab is performed to measure heat generated due to thermite reaction. Then, a sequential thermal mechanical explicit/implicit finite element solver is used to simulate the device under both testing lab and deep water conditions. © 2015 Elsevier B.V.
McCarter W.J.,Heriot - Watt University |
Chrisp T.M.,Heriot - Watt University |
Starrs G.,Heriot - Watt University |
Basheer P.A.M.,Queenss University |
And 3 more authors.
International Journal of Structural Engineering | Year: 2015
Implementation of both design for durability and performance-based standards and specifications are limited by the lack of rapid, simple, sciencebased test methods for characterising the transport properties and deterioration resistance of concrete. This paper presents developments in the application of electrical property measurements as a testing methodology to evaluate the relative performance of a range of concrete mixes. The technique lends itself to in-situ monitoring thereby allowing measurements to be obtained on the as-placed concrete. Conductivity measurements are presented for concretes with and without supplementary cementitious materials (SCM's) from demoulding up to 350 days. It is shown that electrical conductivity measurements display a continual decrease over the entire test period and attributed to pore structure refinement due to hydration and pozzolanic reaction. The term formation factor is introduced to rank concrete performance in terms of is resistance to chloride penetration. Copyright © 2015 Inderscience Enterprises Ltd.
Khudayer B.,Al-Buraimi University College |
Kadhum M.,Universiti Sains Malaysia |
Kadhum M.,Queenss University
Proceedings - IEEE COMNETSAT 2014: 2014 IEEE International Conference on Communication, Network and Satellite | Year: 2014
Mobile Ad Hoc Networks (MANETs) are increasingly being used in various applications for civilian, commercial, and military uses. However, unique characteristics of MANETs introduce several challenges such as routing and mobility management. Nodes frequent movements make routing more difficult due to frequent topology changes. Dynamic Source Routing (DSR) routing protocol is among the common routing protocols that suffer from poor performance in highly dynamic environment. This paper presents an extensive study of the performance of DSR in heterogeneous scalable MANET that involves different nodes with different resources where no prior information about the destinations is available. The study shows that DSR performance suffers significantly over heterogeneous MANETs with respect to network sizes and resources. © 2014 IEEE.
Schaible B.,University College Dublin |
Schaible B.,Queenss University |
McClean S.,Institute of Technology Tallaght |
Selfridge A.,University College Dublin |
And 4 more authors.
PLoS ONE | Year: 2013
Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen commonly associated with lung and wound infections. Hypoxia is a frequent feature of the microenvironment of infected tissues which induces the expression of genes associated with innate immunity and inflammation in host cells primarily through the activation of the hypoxia-inducible factor (HIF) and Nuclear factor kappaB (NF-κB) pathways which are regulated by oxygen-dependent prolyl-hydroxylases. Hypoxia also affects virulence and antibiotic resistance in bacterial pathogens. However, less is known about the impact of hypoxia on host-pathogen interactions such as bacterial adhesion and infection. In the current study, we demonstrate that hypoxia decreases the internalization of P. aeruginosa into cultured epithelial cells resulting in decreased host cell death. This response can also be elicited by the hydroxylase inhibitor Dimethyloxallyl Glycine (DMOG). Reducing HIF-2α expression or Rho kinase activity diminished the effects of hypoxia on P. aeruginosa infection. Furthermore, in an in vivo pneumonia infection model, application of DMOG 48 h before infection with P. aeruginosa significantly reduced mortality. Thus, hypoxia reduces P. aeruginosa internalization into epithelial cells and pharmacologic manipulation of the host pathways involved may represent new therapeutic targets in the treatment of P. aeruginosa infection. © 2013 Schaible et al.
Brownjohn J.M.W.,University of Exeter |
Bocian M.,University of Leicester |
Hester D.,Queenss University |
Quattrone A.,Polytechnic University of Turin |
And 4 more authors.
Journal of Sound and Vibration | Year: 2016
With the main focus on safety, design of structures for vibration serviceability is often overlooked or mismanaged, resulting in some high profile structures failing publicly to perform adequately under human dynamic loading due to walking, running or jumping. A standard tool to inform better design, prove fitness for purpose before entering service and design retrofits is modal testing, a procedure that typically involves acceleration measurements using an array of wired sensors and force generation using a mechanical shaker. A critical but often overlooked aspect is using input (force) to output (response) relationships to enable estimation of modal mass, which is a key parameter directly controlling vibration levels in service. This paper describes the use of wireless inertial measurement units (IMUs), designed for biomechanics motion capture applications, for the modal testing of a 109 m footbridge. IMUs were first used for an output-only vibration survey to identify mode frequencies, shapes and damping ratios, then for simultaneous measurement of body accelerations of a human subject jumping to excite specific vibrations modes and build up bridge deck accelerations at the jumping location. Using the mode shapes and the vertical acceleration data from a suitable body landmark scaled by body mass, thus providing jumping force data, it was possible to create frequency response functions and estimate modal masses. The modal mass estimates for this bridge were checked against estimates obtained using an instrumented hammer and known mass distributions, showing consistency among the experimental estimates. Finally, the method was used in an applied research application on a short span footbridge where the benefits of logistical and operational simplicity afforded by the highly portable and easy to use IMUs proved extremely useful for an efficient evaluation of vibration serviceability, including estimation of modal masses. © 2016 The Authors
Khudayer B.H.,Al-Buraimi University College |
Kadhum M.M.,Universiti Sains Malaysia |
Chee W.T.,Queenss University
Lecture Notes in Electrical Engineering | Year: 2015
The capabilities of Mobile Ad hoc Networks (MANETs) pave the way for wide range of potential applications personal, civilian, andmilitary environments as well as emergency operations.The characteristics of MANETS impose serious challenges in deploying these networks efficiently. The limitation of transmission range of mobile nodes emerge the use of multi-hop to exchange and route data between nodes across the network. Routing is the most important process that can affect the overall performance in MANETs. A variety of routing protocols have been developed for MANETs. These protocols present poor performance under different conditions due to their strategies in learning about routes to destinations. In this paper, we present an innovative Multi-disjoint Routes mechanism that is based on source routing concept to improve routing in MANTEs. The simulation evaluation results showed that the proposed routing mechanism outperforms the common routing protocols, DSR and AODV. © Springer-Verlag Berlin Heidelberg 2015.
Greencentre Canaga and Queenss University | Date: 2011-12-15
Methods and systems for use of switchable water, which is capable of reversibly switching between an initial ionic strength and an increased ionic strength, is described. The disclosed methods and systems can be used, for example, in distillation-free removal of water from solvents, solutes, or solutions, desalination, clay settling, viscosity switching, etc. Switching from lower to higher ionic strength is readily achieved using low energy methods such as bubbling with C0_(2), CS_(2 )or COS or treatment with Bronsted acids. Switching from higher to lower ionic strength is readily achieved using low energy methods such as bubbling with air, inert gas, heating, agitating, introducing a vacuum or partial vacuum, or any combination or thereof.
Hanshi S.M.,Universiti Sains Malaysia |
Kadhum M.M.,Universiti Sains Malaysia |
Kadhum M.M.,Queenss University
2013 IEEE International Conference on RFID-Technologies and Applications, RFID-TA 2013 | Year: 2013
Due to high mobility and nature of vehicular adhoc environment, routing decisions in such a network are becoming a hard task. Therefore, the routing protocol must be robust to frequent link disruptions and aware of the environment surrounding the network. It is noticeable that routing-based position protocols are more appropriate for high dynamic and fast topology change networks. Many routing protocols have been proposed to enhance the delivery of data packets in a vehicular network. The goal of this paper is to review the current position-based routing protocols, in order to get more insight on the capability of these routing protocols in handling different challenges of vehicular ad-hoc networks. © 2013 IEEE.
PubMed | Queenss University
Type: Historical Article | Journal: Bulletin of the history of medicine | Year: 2012
The role of climatic change in determining the shape of human evolution, a theme that came to prominence during the early years of the twentieth century, has resurfaced with renewed vigor. The author examines the rise and resurgence of the modern history of the idea that hominid evolutionary pathways have been trigged by climatic causes to illustrate the continuing vitality of environmental determinism and to highlight some continuities between early-twentieth-century and contemporary archaeoanthropology.