Predicting Transitions in Fischer-Tropsch Reactors

The Fischer-Tropsch process has the potential to be fundamental to a future without dependence on fossil fuels. It converts syngas, a readily available resource, into high quality hydrocarbons, with water being the primary byproduct. Like many gas-to-liquid processes, it is catalysed on a transition metal surface, and the lifetime of the catalyst bed largely dictates the process’s economic viability. Predictive computational models can shed light on the mechanisms driving catalyst deactivation. This work focuses particularly on reactors with a titania-supported cobalt catalyst. One part of this project is an investigation using VASP studying the adsorption and mobility of several cobalt species that might form on the TiO2 support surface. It is found that reactor species generally have a strong effect on the binding properties of cobalt, and that this effect could either strengthen or weaken its bond to the surface depending on how reactive the functional group is with the support surface. In particular, the carbon monoxide feedstock was found to favourably bind to surface- adsorbed cobalt and create highly mobile species. In practice the support surface is rarely dry, and this effect is also found on a model hydrated surface. This painted a clear picture that the carbon monoxide feed may have an effect on the sintering process by inducing surface and gas-phase transport of highly dispersed cobalt. Plane-wave DFT suffers from unfavourable cubic scaling and its extended basis makes vacuum space costly, limiting its applicability to large clusters and surface structures. The linear-scaling DFT code ONETEP is a good candidate for investigating these classes of system. While its metals treatment for systems smaller than the thousands of atoms scale using ensemble DFT (EDFT) is also cubic-scaling, it is able to offload a lot of the cost of the calculation onto linear-scaling parts and also maintains a linear-scaling memory cost. Another part of this project was to develop ONETEP to be able to perform studies of chemistry on adsorbed and free catalyst nanoparticles. Two main pieces of crucial functionality have been added to ONETEP - free-spin EDFT and nudged elastic band transition-state searching. The former allows ensemble DFT to be performed at non-integer net spin and non-integer charge, and also adds the ability to relax the spin state during a calculation - previously ONETEP was constrained to fixed integer net spin. This is crucial in cases where the net spin of a magnetic system is not necessarily known or may be altered by, for example, surface adsorbates. The latter is a popular and robust transition state searching method that reliably minimizes a path connecting a product and reactant. The dimer method is also being developed for ONETEP primarily as a transition state refinement tool. Early applications of the new functionality in ONETEP is demonstrated in an investigation of carbon monoxide binding on cobalt HCP and FCC nanoparticles of around 50 atoms. These adsorption energies are compared, where available, to surface adsorption energies from literature. Generally, the abundance of edges on these small particles make surface adsorption energies site dependent and different to clean surface values, and adsorption sites near edges are generally stronger than the surface values. Additionally, two CO dissociation pathways on the FCC cluster are examined, starting from the surface making up the majority on the FCC Wulff particle. A modest decrease in activation energy is identified, and the presence of new pathways involving particle edges is highlighted for future study.This work was carried out with funding and advisor support from Shell Technology Center Bangalore. Funding was provided through the EPSRC CDT in Computational Methods for Materials Science. This work was performed in part using resources provided by the Cambridge Service for Data Driven Discovery (CSD3) operated by the University of Cambridge Research Computing Service (www.csd3.cam.ac.uk), provided by Dell EMC and Intel using Tier-2 funding from the Engineering and Physical Sciences Research Council (capital grant EP/P020259/1), and DiRAC funding from the Science and Technology Facilities Council (www.dirac.ac.uk). I am grateful to the UK Materials and Molecular Modelling Hub for computational resources, which is partially funded by EPSRC (EP/P020194/1)

Lighting Design in Europe: Aligning the Demands for Lower Energy Usage with Better Quality.

Lighting design is one of the fastest changing areas in building engineering. It has evolved significantly in recent years due to changing technology and demands for improved quality, better control, reduced energy and sustainability. This paper is an overview of what is happening in Europe and elsewhere and examines the literature to find that latest recommendations in the Code for Lighting issued by the SLL (Society of Light and Lighting) in the UK change previous demands for equal illuminance across a working plane to more specific and demanding criteria. There are recommendations for qualitative metrics and better distribution of light so as to enhance the visual appearance of interiors. European standards are also examined and the LENI (lighting energy numerical indicator) has been found to be a better way of reducing energy than installed load. New LED (light-emitting diode) lamp technology is examined and daylight is discussed in the context of these changing demands. It is found that lighting standards and design are changing for the better but that standards will need to evolve further if they are to ensure good quality lighting

A new approach to interior lighting design :early stage research in Ireland

Current standards for interior lighting design are discussed and an alternative design methodology proposed. Cuttle has previously suggested a new criterion be defined as perceived adequacy of illumination (PAI), and that the metric for specifying minimum illumination standards becomes mean room surface exitance (MRSE). This metric specifies the overall brightness of illumination, enabling its distribution to be planned in terms of target/ ambient illuminance ratio (TAIR). This new methodology is explained, analysed and discussed along with on-going research at the Dublin Institute of Technology

Rapid Responsiveness to Practice Predicts Longer-Term Retention of Upper Extremity Motor Skill in Non-Demented Older Adults

Skill acquisition is a form of motor learning that may provide key insights into the aging brain. Although previous work suggests that older adults learn novel motor tasks slower and to a lesser extent than younger adults, we have recently demonstrated no significant effect of chronological age on the rates and amounts of skill acquisition, nor on its longterm retention, in adults over the age of 65. To better understand predictors of skill acquisition in non-demented older adults, we now explore the relationship between early improvements in motor performance due to practice (i.e., rapid responsiveness) and longer-term retention of an upper extremity motor skill, and whether the extent of rapid responsiveness was associated with global cognitive status. Results showed significant improvements in motor performance within the first five (of 150) trials, and that this “rapid responsiveness” was predictive of skill retention 1 month later. Notably, the extent of rapid responsiveness was not dependent on global cognitive status, as measured by the Montreal Cognitive Assessment (MoCA). Thus, rapid responsiveness appears to be an important variable in longer-term neurorehabilitative efforts with older adults, regardless of their cognitive status

Evaluting Domestic Lighting: an Investigation into the Use of Compact Fluorescent Lamps in the Domestic Environment

The Irish government, UK Government and European Commission have recently passed a ban on the sale of all incandescent/GLS lamps above 100W, which commenced in September 209 with smaller Wattages to be phased out by 2012. This paper sets out to investigate if CFLs are an adequate, suitable and appropriate replacement for GLS lamps in domestic environments. The main areas examined are power factor and total harmonic distortion, but other CFL characteristics are also investigated by means of literature review, to provide a complete overview of CFL performance. The measured power factor of all CFLS averaged 0.57 and ranged between 0.52 and 0.62. The effects of harmonic distortion on the current waveform of CFL circuit was significant and reached levels up to 80% of the fundamental frequency. However, this large harmonic distortion is returned on the waveform of a smaller current than would be drawn by a GLS lamp and hence, effects on the national grid and risks of an overloaded three phase neutral conductor are less than sometimes claimed by researchers

Network-layer reservation TDM for ad-hoc 802.11 networks

Ad-Hoc mesh networks offer great promise. Low-cost ad-hoc mesh networks can be built using popular IEEE 802.11 equipment, but such networks are unable to guarantee each node a fair share of bandwidth. Furthermore, hidden node problems cause collisions which can cripple the throughput of a network. This research proposes a novel mechanism which is able to overcome hidden node problems and provide fair bandwidth sharing among nodes on ad-hoc 802.11 networks, and can be implemented on existing network devices. The scheme uses TDM (time division multiplexing) with slot reservation. A distributed beacon packet latency measurement mechanism is used to achieve node synchronisation. The distributed nature of the mechanism makes it applicable to ad-hoc 802.11 networks, which can either grow or fragment dynamically

Incidence of Delirium and Associated Mortality in Hematopoietic Stem Cell Transplantation Patients

AbstractDelirium has been associated with a high risk of mortality in medical patients. Despite the high incidence of delirium in patients who undergo hemapoietic stem cell transplantation (HSCT), delirium as a risk factor for death has not been examined in this population. Thirty adult patients undergoing HSCT who were admitted to the University of Iowa Blood and Marrow Transplantation Program inpatient unit were assessed prospectively from 1 to 2 weeks before transplantation, throughout their inpatient stay, and at 100 days after transplantation. The Delirium Rating Scale and Memorial Delirium Assessment Scale were used twice weekly during the inpatient period to assess delirium severity and occurence. Patients’ self-reports of medical history, computerized medical records, and neuropsychological and psychiatric assessments were used to identify pretransplantation risk factors. The incidence of delirium (Delirium Rating Scale score >12 or Memorial Delirium Assessment Scale score ≥8) was 43% and occurred with highest frequency in the first 2 weeks after transplantion. The presence of delirium at any point during hospitalization after transplantation and transplant type (allogeneic) were highly predictive of mortality (p < .0005; odds ratios, 14.0 and 14.4). In conclusion, this study highlights the importance of monitoring for delirium during the acute recovery period after transplantation and suggests that early or even prophylactic treatment for delirium should be studied. Studies to determine the factors that connect delerium soon after transplantation to mortality are highly warranted

Stacking non-BPS D-Branes

We present a candidate supergravity solution for a stacked configuration of stable non-BPS D-branes in Type II string theory compactified on T^4/Z_2. This gives a supergravity description of nonabelian tachyon condensation on the brane worldvolume.Comment: 10 pages, revte

Anticancer and Antifungal Activity of Copper(II) Complexes of Quinolin-2(1H)-one-Derived Schiff Bases

The condensation of substituted aromatic aldehydes with 7-amino-4-methyl-quinolin-2(1H)-one (1) has lead to the isolation of quinolin-2(1H)-one derived Schiff bases (2–14). The copper(II) complexes (2a–14a) of the ligands were also prepared, and together with their corresponding free ligands were fully characterised by elemental analyses, spectral methods (IR, 1H and 13C NMR, AAS, UV–Vis), magnetic and conductance measurements. The bidentate ligands coordinated to the copper(II) ion through the deprotonated phenolic oxygen and the azomethine nitrogen of the ligands in almost all cases. X-ray crystal structures of two of the complexes, 5a and 8a, confirmed the bidentate coordination mode. All of the compounds were investigated for their antimicrobial activities against the fungus, Candida albicans, and against Gram-positive and Gram-negative bacteria. The compounds were found to have excellent anti-Candida activity but were inactive against Staphylococcus aureus and Escherichia coli. Selected compounds (2–8 and 2a–8a) were also screened for their in vitro anticancer potential using the human hepatic carcinoma cell line, Hep-G2. Several derivatives were shown to be active comparable to that of cisplatin