965 research outputs found
The imperial war museum’s social interpretation project
This report represents the output from research undertaken by University of Salford and MTM
London as part of the joint Digital R&D Fund for Arts and Culture, operated by Nesta, Arts
Council England and the AHRC. University of Salford and MTM London received funding from
the programme to act as researchers on the Social Interpretation (SI) project, which was led by
the Imperial War Museum (IWM) and their technical partners, The Centre for Digital
Humanities, University College London, Knowledge Integration, and Gooii. The project was
carried out between October 2011 and October 2012
Towards Novel Alkaline Earth Metal Pyrazolates: Opportunities in Materials Chemistry
Until recent years, the coordination chemistry of the alkaline earth metals remained relatively unexplored. Owing to the development of new synthetic methods and improved techniques for the exclusion of air and moisture, great progress has been made into our understanding of the alkaline earth metals and their compounds. These compounds are useful in a wide variety of applications, including as polymerization initiators, precursors for chemical vapor deposition (CVD) and in metal-organic frameworks (MOFs) for gas separation and storage. Current work in alkaline earth metal chemistry focuses on designing and tailoring ligand systems to expand their potential applications in materials chemistry.
The pyrazole ligand system, previously explored in alkaline earth chemistry, becomes a promising candidate, due to its facile synthesis and substitution and the variety of available binding modes with which coordinative saturation of the metal can be achieved. One novel approach includes introducing “pendant arms,” extended substituents in the 3 and 5 positions, capable of stabilizing metal centers through potential Lewis base donation. These pendant arm pyrazoles are applicable in the synthesis of CVD precursors. Current precursors often contain neutral donors which can cause premature decomposition upon heating, therefore reducing or eliminating the need for donors by utilizing pendant arms is advantageous.
Also of interest is the synthesis of potential alkaline earth metal-organic frameworks for hydrogen storage. 2-D geometry can be introduced into the target MOFs by synthesizing bidentate dipyrazole ligands, allowing them to act as “linkers” between adjacent metal nodes. Furthermore, the pyrazole substituents can be modified in order to introduce intermolecular stabilizing forces and tune pore sizes. A novel ligand, 3,5,3’,5’-tetraphenyl-1,4-xylylene-4,4’-dipyrazole, has been synthesized to explore the effect of these substituents on metal-organic frameworks.
This work presents novel approaches in the design and preparation of ligands for the aforementioned applications. The utility of alkaline earth metal compounds for these applications may be enhanced through the utilization of these new ligands. This work also presents novel applications of synthetic routes toward the preparation of alkaline earth organometallic compounds
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Transposon mutagenesis in a hyper-invasive clinical isolate of Campylobacter jejuni reveals a number of genes with potential roles in invasion
Transposon mutagenesis has been applied to a hyper-invasive clinical isolate of Campylobacter jejuni, 01/51. A random transposon mutant library was screened in an in vitro assay of invasion and 26 mutants with a significant reduction in invasion were identified. Given that the invasion potential of C. jejuni is relatively poor compared to other enteric pathogens, the use of a hyper-invasive strain was advantageous as it greatly facilitated the identification of mutants with reduced invasion. The location of the transposon insertion in 23 of these mutants has been determined; all but three of the insertions are in genes also present in the genome-sequenced strain NCTC 11168. Eight of the mutants contain transposon insertions in one region of the genome (∼14 kb), which when compared with the genome of NCTC 11168 overlaps with one of the previously reported plasticity regions and is likely to be involved in genomic variation between strains. Further characterization of one of the mutants within this region has identified a gene that might be involved in adhesion to host cells
A penny for your thoughts : the practice of rewarding research participants with shopping vouchers
This briefing addresses whether giving shopping vouchers to research participants in receipt of government welfare benefits will be harmful if they have to declare it to benefit entitlement officials or if it causes them to exceed the amount they are allowed to earn before losing benefits, otherwise known as their ‘work allowance’. This guidance will aid researchers when writing proposals, methodological statements and completing ethics review forms
Self-assembled germanium islands grown on (001) silicon substrates by low-pressure chemical vapor deposition
The time evolution of self-assembled Ge islands, during low-pressure chemical vapor deposition (LPCVD) of Ge on Si at 650 Deg C using high growth rates, has been investigated by atomic force microscopy, transmission electron microscopy, and Rutherford backscattering spectrometry. We have found three different island structures The smallest islands are "lens-shaped" and characterized by a rather narrow size distribution, ~4nm high and ~20nm wide. Next to form are a distinct population of multifaceted "dome shaped" islands, up to 25nm high and 80-150 nm wide. Finally, the largest islands that form are square-based truncated pyramids with a very narrow size distribution ~50nm high and ~250nm wide. The pyramidal islands normally seen in the intermediate size range (~150nm) are not observed. The small lens-shaped islands appear to be defect free, while some of the multifaceted islands as well as all the large truncated pyramids contain misfit dislocations. The existence of multifaceted islands, in the size range where multifaceted "dome shaped" islands have previously been reported, is attributed to the high growth rate used. Furthermore, under the growth conditions used, the truncated-pyramid-shaped islands are characterized by a very narrow size distribution
Tunable reflection minima of nanostructured antireflective surfaces
Broadband antireflection schemes for silicon surfaces based on the moth-eye principle and comprising arrays of subwavelength-scale pillars are applicable to solar cells, photodetectors, and stealth technologies and can exhibit very low reflectances. We show that rigorous coupled wave analysis can be used to accurately model the intricate reflectance behavior of these surfaces and so can be used to explore the effects of variations in pillar height, period, and shape. Low reflectance regions are identified, the extent of which are determined by the shape of the pillars. The wavelengths over which these low reflectance regions operate can be shifted by altering the period of the array. Thus the subtle features of the reflectance spectrum of a moth-eye array can be tailored for optimum performance for the input spectrum of a specific application
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