XPS and NEXAFS study of fluorine modified TiO2 nano-ovoids reveals dependence of Ti3+ surface population on the modifying agent

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (http://creativecommons.org/licenses/by/3.0/)Crystalline titanium dioxide was synthesised under mild conditions by the thermal degradation of peroxotitanic acid in the presence of a number of fluoride-containing surface modifying agents (NH4F, NH4BF4, NH4PF6, NBu4F, NBu4BF4, NBu4PF6). The resulting materials were characterised by PXRD, SEM, HRTEM, XPS and NEXAFS. Particle phase, size, and surface area were noticeably affected by the choice of surface modifying agent. Both the cation and anion comprising the modifying agent affect the surface Ti3+ population of the materials, with two apparent trends observed: F− > BF4− > PF6− and NBu4+ > NH4+. All materials displayed evidence of fluorine doping on their surfaces, although no evidence of bulk doping was observed

Outlook and appraisal [June 1993]

First quarter GDP figures signal the end of the recession. Recent falls in unemployment and rising house prices should stimulate greater expenditure from consumers now that the threat of redundancy has receded

Population policies and education: exploring the contradictions of neo-liberal globalisation

The world is increasingly characterised by profound income, health and social inequalities (Appadurai, 2000). In recent decades development initiatives aimed at reducing these inequalities have been situated in a context of increasing globalisation with a dominant neo-liberal economic orthodoxy. This paper argues that neo-liberal globalisation contains inherent contradictions regarding choice and uniformity. This is illustrated in this paper through an exploration of the impact of neo-liberal globalisation on population policies and programmes. The dominant neo-liberal economic ideology that has influenced development over the last few decades has often led to alternative global visions being overlooked. Many current population and development debates are characterised by polarised arguments with strongly opposing aims and views. This raises the challenge of finding alternatives situated in more middle ground that both identify and promote the socially positive elements of neo-liberalism and state intervention, but also to limit their worst excesses within the population field and more broadly. This paper concludes with a discussion outling the positive nature of middle ground and other possible alternatives

Genome sequencing of the lizard parasite Leishmania tarentolae reveals loss of genes associated to the intracellular stage of human pathogenic species

The Leishmania tarentolae Parrot-TarII strain genome sequence was resolved to an average 16-fold mean coverage by next-generation DNA sequencing technologies. This is the first non-pathogenic to humans kinetoplastid protozoan genome to be described thus providing an opportunity for comparison with the completed genomes of pathogenic Leishmania species. A high synteny was observed between all sequenced Leishmania species. A limited number of chromosomal regions diverged between L. tarentolae and L. infantum, while remaining syntenic to L. major. Globally, >90% of the L. tarentolae gene content was shared with the other Leishmania species. We identified 95 predicted coding sequences unique to L. tarentolae and 250 genes that were absent from L. tarentolae. Interestingly, many of the latter genes were expressed in the intracellular amastigote stage of pathogenic species. In addition, genes coding for products involved in antioxidant defence or participating in vesicular-mediated protein transport were underrepresented in L. tarentolae. In contrast to other Leishmania genomes, two gene families were expanded in L. tarentolae, namely the zinc metallo-peptidase surface glycoprotein GP63 and the promastigote surface antigen PSA31C. Overall, L. tarentolae's gene content appears better adapted to the promastigote insect stage rather than the amastigote mammalian stage

The steady-state transcriptome of the four major life-cycle stages of Trypanosoma cruzi

<p>Abstract</p> <p>Background</p> <p>Chronic chagasic cardiomyopathy is a debilitating and frequently fatal outcome of human infection with the protozoan parasite, <it>Trypanosoma cruzi</it>. Microarray analysis of gene expression during the <it>T. cruzi </it>life-cycle could be a valuable means of identifying drug and vaccine targets based on their appropriate expression patterns, but results from previous microarray studies in <it>T. cruzi </it>and related kinetoplastid parasites have suggested that the transcript abundances of most genes in these organisms do not vary significantly between life-cycle stages.</p> <p>Results</p> <p>In this study, we used whole genome, oligonucleotide microarrays to globally determine the extent to which <it>T. cruzi </it>regulates mRNA relative abundances over the course of its complete life-cycle. In contrast to previous microarray studies in kinetoplastids, we observed that relative transcript abundances for over 50% of the genes detected on the <it>T. cruzi </it>microarrays were significantly regulated during the <it>T. cruzi </it>life-cycle. The significant regulation of 25 of these genes was confirmed by quantitative reverse-transcriptase PCR (qRT-PCR). The <it>T. cruzi </it>transcriptome also mirrored published protein expression data for several functional groups. Among the differentially regulated genes were members of paralog clusters, nearly 10% of which showed divergent expression patterns between cluster members.</p> <p>Conclusion</p> <p>Taken together, these data support the conclusion that transcript abundance is an important level of gene expression regulation in <it>T. cruzi</it>. Thus, microarray analysis is a valuable screening tool for identifying stage-regulated <it>T. cruzi </it>genes and metabolic pathways.</p

Towards fabrication of novel photocatalysts: investigation of morphology control of metal oxide nanoparticles

In this work titanium dioxide (TiO2) was synthesised using hydrothermal methods. Initial studies were based on TiO2 oxalic acid passivated sols previously synthesised by Dr Tim Kemmitt. These sols were hydrothermally treated in the presence of ammonium fluoride (NH4F) as a morphology directing agent. The hydrothermally treated titanium dioxide was characterised using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and dynamic light scattering (DLS). It was found the phase, size and shape of the TiO2 nanoparticles produced could be controlled by tuning the NH4F concentration, temperature profile and time of the hydrothermal treatment. The high-temperature hydrothermal treatment caused the decomposition of organic species present in the reaction mixture, which resulted in a partial reduction of the TiO2 observed as a blue colouration Characterising the blue colour-causing defect and identify the mechanisms behind the formation of this defect quickly became the focus of the forthcoming studies. The hydrothermal synthesis was tuned to produce a phase-pure blue anatase TiO2, which was a better candidate for an in-depth study of the electronic features of the blue TiO2. The conditions need to generate the blue colour were studied and the blue TiO2 was characterised by the following techniques: synchrotron powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectric spectroscopy (XPS), valence band spectroscopy (VBS), near edge absorption fine structure spectroscopy (NEXAFS), electron paramagnetic resonance (EPR), superconducting quantum interference device (SQUID), Raman spectroscopy, ultraviolet-visible light spectroscopy diffuse reflectance (UV-VIS DRS), infrared spectroscopy (IR), thermal gravitational analysis (TGA), particle induce gamma emission spectroscopy (PIGE), nitrogen adsorption isotherms and gas mass spectrometry (GC-MS). Evidence from the various characterisation techniques showed that bulk phase self-doping with Ti3+ occurred during synthesis of the blue TiO2. The Ti3+ was stabilised by fluorine ions (F-) substituted for oxygen in the lattice. The reduction of Ti4+ to Ti3+ was a consequence of in-situ H2 formation due to the thermal decomposition of the isopropanol liberated from the hydrolysis of titanium isopropoxide (the titanium precursor). The reduced Ti3+ ions were incorporated into the growing nanocrystals where F- would substitute for O2- forming a stable defect. The Ti3+ defect produced an intermediate band below the conduction band which allowed the absorption of red light to produce the blue colour observed. Although the Ti3+ was causing the blue colouration, the synthesis conditions and F- doping had other effects. First, it was found the anatase crystals grew preferentially along the c axis, this was found to be as a result of ammonium titanate formation. The ammonium titanate also encouraged the growth of very large crystals in a narrow concentration range. Secondly, the Ti3+ defects where found to be mostly located close to the surface. Finally, the TiO2 was very deficient in Ti as a result of Ti vacancies possibly due to hydroxyl inclusions. Having determined the synthetic methodology to produce the blue colouration, the synthesis was reworked to produce even more novel blue brookite and blue rutile phase TiO2 which was characterised using many of the same methods as above. It was found that the brookite was formed via the conversion of anatase via a sodium titanate mechanism. The temperature of hydrothermal treatment and NaF ratio could be used to control the aspect ratio of the brookite formed. Finally, it was found that Ti3+ was present as both a bulk and surface dopant causing the blue colour. Blue rutile was formed by adding oxalic acid to the synthesis. The NH4F was found to change the shape of the rutile crystallites so there was a greater exposure of the {001} facet. The blue rutile was found to have the highest concentration of Ti3+ defects and was hence very blue. Lastly, studies were carried out on the TiO2 to assess the effects the synthesis conditions and blue colour on the photocatalytic activity of the TiO2. In particular, there was an interest as to whether the absorption of red light could drive photocatalytic activity into the visible-light range (>400 nm). Reactive blue (RB-19) and methylene blue (MB) was used as a model dyes to examine the photocatalytic activity of the TiO2. The blue TiO2 was found to be more active than commercial photocatalyst under broad-spectrum light. The TiO2 was also capable of harnessing the energy of visible-light to degrade the dye, making it visible light active. Furthermore, the blue brookite and rutile were found to be effective photocatalysts

Outlook and appraisal [Spetmber 1993]

The level of activity in the Scottish Manufacturing sector remains, to some extent, at the mercy of the United States and the European Community

The world economy [June 1993]

In the fourth quarter of 1992 quarterly GDP/GNP growth averaged 0.9% in the four major world economies. The world economy remained in the doldrums as growth slowed in the USA and both Japan and Western Europe stagnated. This brief analysis sets out growth rates for each country and provides a provisional estimate for the USA and the UK in the first quarter

The Scottish economy [June 1993]

The latest official release of the seasonally adjusted output index for Scottish production industries (Divisions 1 to 4 of the 1980 SIC) shows a marked increase (4.7%) in the final quarter over the previous quarter last year. This increase is due largely to a dramatic 30% increase in the output of the electrical and instrument engineering industries in the final quarter. However, considering the overall performance of the UK manufacturing industry (including the electrical and instrument engineering industries which experienced a more modest growth of 3% in the same period), and given all the information contained in various business surveys, such a substantial increase in Scottish production output should, we think, be treated with caution

The British economy [June 1993]

The recession is over. All the available evidence suggests that the economy 'bottomed out' in the second quarter of 1992. However, the recovery was weak until the turn of the year. In the first quarter of this year, the momentum of recovery appears to have moved up a gear