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Ongoing Research Projects supported by Research IT

Listing of project codes and abstracts, describing work undertaken which use the resources of the compute clusters hosted by the Research IT team.

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Project Title Microscopic approach to understand the charge and spin transport properties of pi-conjugated polymers
Project Code HPC_11_00368
Principal Investigator Prof Stefano Sanvito
Start Date 2011-09-26
End Date 2013-09-30
Abstract The field of organic spintronics has grown by leaps and bounds over the last few years because of the potential of organic semiconductors to match or even perform better than their inorganic counterparts in spintronic applications. It is now conceivable for organic materials to open new avenues to cheap, low-weight, mechanically flexible, chemically inert and bottom-up fabricated spin-devices. Furthermore the mechanisms responsible for the interaction of spins with their environment during transport are minimal for organic materials. This present project aims at providing insights into the challenging problem of charge and spin transport through organic semiconductors using fundamental microscopic models. We will expand on our work on Monte Carlo study [1] of the finite temperature properties of a Hubbard-Peierls model describing pi-conjugated polymers. The model also incorporates spin-orbit coupling and hyperfine interactions and it is solved at the mean field level. In particular we explored the model as a function of the strength of electron-electron and electron-phonon interactions. In this work the transport set-up consists, a network of polymer molecules described by the Hubbard-Peierls model sandwiched between two metallic leads. We measure the low-biased spin-polarized conductance using a Greens function approach [4] and the carrier mobility using linear response Kubo formalism. From these parameters we are able to extract useful quantities that characterize spin and charge transport, described by our microscopic theory. This part of the work, aims at understanding which out of hyperfine interaction or spin-orbit coupling is the more dominant contributor to spin scattering which would inhibit an efficient spin transport through organic polymers. We are also are interested in explaining the charge transport across model in different regimes of el-ph interaction strength and temperatures, with the model parameters extracted from first-principle constrained DFT calculations. [1] S. Bhattacharya, M.S. Ferreira and S. Sanvito, J. Phys.: Condens. Matter 23, 316001 (2011). [2] S.Sanvito, Chem. Soc. Rev, 40, 3336-3355, (2011). [3] G. Szulczewski, S. Sanvito and M. Coey, Nat. Mat. 8, 693-695, (2010). [4] I. Rungger and S.Sanvito, Phys Rev B 78, 035407, (2008).
Project Title Schroedinger Functional with 4 staggered quarks on the lattice
Project Code HPC_11_00367
Principal Investigator Dr Stefan Sint
Start Date 2011-09-26
End Date 2012-06-30
Abstract We want to examine the behaviour of the strong running coupling and correlation functions using the Schroedinger Functional set up with 4 flavours of staggered quarks in the framework of lattice QCD
Project Title Tuning Machine Translation Engines
Project Code HPC_11_00365
Principal Investigator Prof Carl Vogel
Start Date 2011-09-21
End Date 2012-08-31
Abstract This demonstrator is part of the CNGL project, in collaboration with DCU. It aims at improving the performance of MT (Machine Translation) engines by adapting them to the particular context in which they are used. In this framework this set of experiments are intended to select the "best" training data: given a reference corpus of forum data in English and a more general English corpus (Europarl data), the goal is to select the parts of the latter which are the most similar to the former in order to use it as training data. This way we hope the resulting MT engine to be better at translating sentences (the DCU team is responsible for this part). More precisely, in this set of experiments we are interested in comparing different methods and different parameters with our text similarity program. Additionally, one of the important issues is efficiency, since the data is very big in this case; several new optimization techniques have been implemented and will be tested this way.
Project Title A strongly interacting electroweak symmetry breaking sector
Project Code HPC_11_00364
Principal Investigator Dr Stefan Sint
Start Date 2011-09-21
End Date 2015-06-30
Abstract One of the main tasks of the Large Hadron Collider is to find out why the weak nuclear force is truly weak, and how the known elementary particles acquire their mass. In the Standard Model this is accomplished by the Higgs mechanism and the associated Higgs particle. Theoretical physicists agree that this description is inconsistent theoretically and needs to be replaced by a more fundamental theory. Several alternative scenarios have been proposed and need to be investigated as to their phenomenological viability. This research project proposes to do this for a particular class of so-called technicolor models. In particular we intend to study the scale evolution of the gauge coupling and the fermion mass using techniques adapted from lattice QCD.
Project Title In-vivo mechanisms of new glutamatergic antidepressants in humans and animal models of depression
Project Code HPC_11_00362
Principal Investigator Dr Andrew Harkin
Start Date 2011-10-01
End Date 2014-09-29
Abstract A novel glial ablation based animal model of depression will be assessed using MRI techniques and standard behavioural tests of depression and anxiety. An astrocyte specific toxin (L-Aminoadipic Acid) will be used to induce depressive like behaviour in rats. The effect of the administration of this glial toxin will then be accessed via standardised behavioural tests including the Porsolt behavioural despair test, saccharin preference test, as well as open field and elevated plus maze. Recent evidence suggests that neurovascular blood flow is mediated by glial regulation of cerebral microvasculature. Recent advances in magnetic resonance imaging (MRI) have enabled measurement of cerebral blood flow (CBF) using contrast agent free approaches such as bolus tracking arterial spin labelling (btASL). We will use this method as well as structural MRI imaging and a novel T1 and T2 relaxometry based method for determination of inflammatory activation to acquire neuro-imaging markers for this model. These markers may then be used at a later date to assess novel glutamatergic anti-depressants such as S-Ketamine. They may also be useful in a clinical setting to enable us to identify altered cerebral blood perfusion caused by loss of glial cells from the frontal cortex as well as the associated structural changes. Hence the aims of this study are 1.To assess the ability of a novel astrocyte specific toxin to induce depressive like behaviours in animals. 2. To use this model to gather neuro-imaging markers. 3. To observe the effect of loss of pre-frontal cortex glia on regional blood flow as characterised by btASL. 4. To use this model and this imaging data to help further elucidate the action of novel anti-depressant S-Ketamine.
Project Title The Effect of Divalent Dopants on the Oxygen Storage Capacity and Catalytic Reactivity of CeO2
Project Code HPC_11_00361
Principal Investigator Prof Graeme Watson
Start Date 2011-09-07
End Date 2012-09-07
Abstract Ceria (CeO2) is recognised as a key material in modern heterogeneous catalysis, both as a support and as a catalyst itself. Its efficacy is in part due to its high oxygen storage capacity, which results from the relatively facile reduction of Ce(IV) to Ce(III) upon the formation of oxygen vacancies. The incorporation of divalent noble metals such as Pt and Pd into the ceria lattice to form Ce1−xMxO2 is seen to improve ceria’s reducibility by creating weakly or undercoordinated oxygen ions which are more easily removed than those in pure ceria. Density functional theory calculations (with the +U correction to account for on-site Coulombic interactions) will be performed on bulk and the low index surfaces of ceria doped with a range of divalent ions to ascertain how the dopant size, coordination environment, and electronic structure affect oxygen storage capacity, reducibility, and catalytic reactivity and selectivity.
Project Title Glassy lithium-ion conductors
Project Code HPC_11_00360
Principal Investigator Prof Graeme Watson
Start Date 2011-09-07
End Date 2012-09-07
Abstract Secondary lithium-ion batteries have aided the portable electronics revolution during the past two decades because they store much higher energy per unit weight or volume compared to rechargeable battery systems. For this reason, lithium ion batteries are now also being intensively pursued for transportation applications. However, cost, safety, cycle life, energy ad power density are some of the major issues in successfully adopting the lithium ion battery technology for transportation and energy storage purposes and these are, in turn, linked to the electrode and electrolyte materials used. In this work, we propose to study the conduction mechanism of SiS2-Li2S, one of the most promising electrolytes for all-solid state lithium secondary batteries. We plan to use state-of-the-art Density Functional Theory to get a preliminary understanding of the factors affecting Li-ion conduction in this material. Then, we will use these calculations to parameterize interionic potentials for SiS2-Li2S and we will perform extensive Molecular Dynamics simulations to elucidate and further understand the conduction mechanism of this system. Special focus will be dedicated to those factors (different cations, addition of a network modifier, etc) which are know to affect the conductivity of SiS2-Li2S.
Project Title Glassy lithium-ion conductors
Project Code HPC_11_00359
Principal Investigator Prof Graeme Watson
Start Date 2011-09-07
End Date 2012-09-07
Abstract Secondary lithium-ion batteries have aided the portable electronics revolution during the past two decades because they store much higher energy per unit weight or volume compared to rechargeable battery systems. For this reason, lithium ion batteries are now also being intensively pursued for transportation applications. However, cost, safety, cycle life, energy ad power density are some of the major issues in successfully adopting the lithium ion battery technology for transportation and energy storage purposes and these are, in turn, linked to the electrode and electrolyte materials used. In this work, we propose to study the conduction mechanism of SiS2-Li2S, one of the most promising electrolytes for all-solid state lithium secondary batteries. We plan to use state-of-the-art Density Functional Theory to get a preliminary understanding of the factors affecting Li-ion conduction in this material. Then, we will use these calculations to parameterize interionic potentials for SiS2-Li2S and we will perform extensive Molecular Dynamics simulations to elucidate and further understand the conduction mechanism of this system. Special focus will be dedicated to those factors (different cations, addition of a network modifier, etc) which are know to affect the conductivity of SiS2-Li2S.
Project Title Resting-state connectivity deficits associated with impaired inhibitory control in children at-risk for psychosis
Project Code HPC_11_00358
Principal Investigator Dr Hugh Garavan
Start Date 2011-09-06
End Date 2011-12-01
Abstract This study investigated intrinsic functional connectivity (iFC) during resting-state fMRI (rs-fMRI) in 11 youths at-risk for psychosis (aged 11-13) compared to 14 age and gender-matched controls. Seed regions of interest (ROIs) were identified on the basis of a previous task-based neuroimaging study performed in this at-risk sample, which showed reduced fronto-temporal activity on a response inhibition GO/NOGO task. At-risk children exhibited reduced intra-hemispheric iFC within the inferior frontal gyrus (IFG) and between the IFG and the anterior cingulate and striatum, relative to controls. Additional brain regions showing reduced connectivity in the at-risk group were between the anterior cingulate and claustrum and also between the precuneus and supramarginal gyrus. The at-risk group revealed increased long-range functional connectivity in contralateral brain regions between the superior frontal gyrus and claustum and also inferior frontal gyrus and lingual gyrus. Thus, the same regions that previously showed response inhibition-related hypofrontality show reduced local connectivity in the at-risk group compared to controls, suggesting that reduced intra-hemispheric connectivity may underlie the dysfunctional task-related activity. Moreover, these findings echo the disrupted patterns of aberrant functional organization of the frontal cortex previously found in patients with schizophrenia during rs-fMRI indicating their potential as early biomarkers of risk for the disease.
Project Title Computational Studies of Foam Structures and Drainage
Project Code HPC_11_00343
Principal Investigator Dr Stefan Hutzler
Start Date 2011-09-01
End Date 2012-10-01
Abstract Our numerical studies of foam drainage concern the modelling and interpretation of experimental data for liquid metal foams, produced and observed under conditions of microgravity. We are able to de- termine several key physical parameters of the liquid phase, including bulk surface tension and bulk viscosity. We examine the structure of confined and bulk ordered foams, and the response to wetting and perturbations. While the stability and energy of dry foams have been studied, wet foams (including the Weaire-Phelan) have not. As real foams found in experiment are wet, we hope to use these simulations to better understand real-world systems.