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Search Results: 1 - 10 of 323966 matches for " Peter J Bailey "
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Using graphs to find the best block designs
R. A. Bailey,Peter J. Cameron
Statistics , 2011,
Abstract: A statistician designing an experiment wants to get as much information as possible from the data gathered. Often this means the most precise estimate possible (that is, an estimate with minimum possible variance) of the unknown parameters. If there are several parameters, this can be interpreted in many ways: do we want to minimize the average variance, or the maximum variance, or the volume of a confidence region for the parameters? In the case of block designs, these optimality criteria can be calculated from the concurrence graph of the design, and in many cases from its Laplacian eigenvalues. The Levi graph can also be used. The various criteria turn out to be closely connected with other properties of the graph as a network, such as number of spanning trees, isoperimetric number, and the sum of the resistances between pairs of vertices when the graph is regarded as an electrical network. In this chapter, we discuss the notions of optimality for incomplete-block designs, explain the graph-theoretic connections, and prove some old and new results about optimality.
Stage-specific fluorescence intensity of GFP and mCherry during sporulation In Bacillus Subtilis
Geoff P Doherty, Kirra Bailey, Peter J Lewis
BMC Research Notes , 2010, DOI: 10.1186/1756-0500-3-303
Abstract: While observing the recruitment of the transcription machinery into the forespore of sporulating Bacillus subtilis, we noticed the occurrence of stage-specific fluorescence intensity differences between GFP and mCherry. During vegetative growth and the initial stages of sporulation, fluorescence from both GFP and mCherry fusions behaved similarly. During stage II-III of sporulation we found that mCherry fluorescence was considerably diminished, whilst GFP signals remained clearly visible. This fluorescence pattern reversed during the final stage of sporulation with strong mCherry and low GFP fluorescence. These trends were observed in reciprocal tagging experiments indicating a direct effect of sporulation on fluorescent protein fluorophores.Great care should be taken when interpreting the results of protein localisation and quantitative gene expression patterns using fluorescent proteins in experiments involving intracellular physiological change. We believe changes in the subcellular environment of the sporulating cell leads to conditions that differently alter the spectral properties of GFP and mCherry making an accurate interpretation of expression profiles technically challenging.Various Gram positive bacteria can form structures called endospores, which are highly resistant to environmental stress and can remain dormant for thousands of years. The sporulation process can be crudely divided into five stages; Initiation, septation, engulfment, spore and cortex formation and finally maturation and endospore release (Reviewed in [1]). This process is triggered by a stress response such as starvation and results in the expression and repression of a cascade of genes in a tightly controlled temporal manner over several hours in order to form the mature endospore as outlined in Figure 1. After the decision to sporulate has occurred, the rod-shaped cell asymmetrically divides to form a prespore and a much larger mother cell. The mother cell then engulfs the prespore,
Empirical line lists and absorption cross sections for methane at high temperature
Robert J. Hargreaves,Peter F. Bernath,Jeremy Bailey,Michael Dulick
Physics , 2015, DOI: 10.1088/0004-637X/813/1/12
Abstract: Hot methane is found in many "cool" sub-stellar astronomical sources including brown dwarfs and exoplanets, as well as in combustion environments on Earth. We report on the first high-resolution laboratory absorption spectra of hot methane at temperatures up to 1200 K. Our observations are compared to the latest theoretical spectral predictions and recent brown dwarf spectra. The expectation that millions of weak absorption lines combine to form a continuum, not seen at room temperature, is confirmed. Our high-resolution transmittance spectra account for both the emission and absorption of methane at elevated temperatures. From these spectra, we obtain an empirical line list and continuum that is able to account for the absorption of methane in high temperature environments at both high and low resolution. Great advances have recently been made in the theoretical prediction of hot methane, and our experimental measurements highlight the progress made and the problems that still remain.
Bacterial Transfer from Hands While Eating Popcorn  [PDF]
Kimberly A. Baker, Inyee Y. Han, J. Bailey, Lauren Johnson, Edward Jones, Amy Knight, Mollye MacNaughton, Peter Marvin, Katherine Nolan, Rose Martinez-Dawson, Paul L. Dawson
Food and Nutrition Sciences (FNS) , 2015, DOI: 10.4236/fns.2015.615139
Abstract: Popcorn is a very social food, often shared with others and offered at many major sporting events, concerts, movies, and fairs. However, sharing may not be safe since microorganisms found on hands may be transferred onto the shared popcorn. This study was conducted to determine if bacteria are transferred from hands to popcorn during handling. Over 30 samplings revealed that bacterial transfer to popcorn from hands was very low; however transfer did occur with large variation between subjects. Since hands and surfaces can carry bacteria in situations where food is being shared, transferring bacteria from one person to another person is always a risk.
UV-Activated Luminescence/Colourimetric O2 Indicator
Andrew Mills,Cheryl Tommons,Raymond T. Bailey,M. Catriona Tedford,Peter J. Crilly
International Journal of Photoenergy , 2008, DOI: 10.1155/2008/547301
Abstract: An oxygen indicator is described, comprising nanoparticles of titania dispersed in hydroxyethyl cellulose (HEC) polymer film containing a sacrificial electron donor, glycerol, and the redox indicator, indigo-tetrasulfonate (ITS). The indicator is blue- coloured in the absence of UV light, however upon exposure to UV light it not only loses its colour but also luminesces, unless and until it is exposed to oxygen, whereupon its original colour is restored. The initial photobleaching spectral (absorbance and luminescence) response characteristics in air and in vacuum are described and discussed in terms of a simple reaction scheme involving UV activation of the titania photocatalyst particles, which are used to reduce the redox dye, ITS, to its leuco form, whilst simultaneously oxidising the glycerol to glyceraldehye. The response characteristics of the activated, that is, UV photobleached, form of the indicator to oxygen are also reported and the possible uses of such an indicator to measure ambient O2 levels are discussed.
Functional Enhancement of Electrofusion-derived BRIN-BD11 Insulin-secreting Cells After Implantation into Diabetic Mice
Emma L. Davies,Yasser H. A. Abdel-Wahab,Peter R. Flatt,Clifford J. Bailey
Experimental Diabetes Research , 2001, DOI: 10.1155/edr.2001.29
Abstract: Electrofusion-derived BRIN-BD11 cells are glucosesensitive insulin-secreting cells which provide an archetypal bioengineered surrogate β-cell for insulin replacement therapy in diabetes mellitus, 5x106 BRIN-BD11 cells were implanted intraperitoneally into severely hyperglycaemic (>24mmol/l) streptozotocin-induced insulin-treated diabetic athymic nude (nu/nu) mice. The implants reduced hyperglycaemia such that insulin injections were discontinued by 5–16 days (<17mmol/l) and normoglycaemia (<9mmol/l) was achieved by 7–20 days. Implanted cells were removed after 28 days and re-established in culture. After re-culture for 20 days, glucose-stimulated (16.7mmol/l) insulin release was enhanced by 121% (p<0.001) compared to non-implanted cells. Insulin responses to glucagon-like peptide-1 (10−9mol/l), cholecystokinin-8 (10−8 mol/l) and L-alanine (10 mmol/l) were increased by 32%, 31% and 68% respectively (p<0.05–0.01). Insulin content of the cells was 148% greater at 20 days after re-culture than before implantation (p<0.001), but basal insulin release (at 5.6 mmol/l glucose) was not changed. After re-culture for 40 days, insulin content declined to 68% of the content before implantation (p<0.01), although basal insulin release was unchanged. However, the insulin secretory responses to glucose, glucagonlike peptide-1, cholecystokinin-8 and L-alanine were decreased after 40 days of re-culture to 65%, 72%, 73% and 42% respectively of the values before implantation (p<0.05–0.01). The functional enhancement of electrofusion-derived surrogate β-cells that were re-cultured for 20 days after implantation and restoration of normoglycaemia indicates that the in vivo environment could greatly assist β-cell engineering approaches to therapy for diabetes.
Non-Newtonian behavior and molecular structure of Cooee bitumen under shear flow: a non-equilibrium molecular dynamics study
Claire A. Lemarchand,Nicholas P. Bailey,Billy D. Todd,Peter J. Daivis,Jesper S. Hansen
Physics , 2015,
Abstract: The rheology and molecular structure of a model bitumen (Cooee bitumen) under shear are investigated in the non-Newtonian regime using non-equilibrium molecular dynamics simulations. The shear viscosity, normal stress differences and pressure of the bitumen mixture are computed at different shear rates and different temperatures. The model bitumen is shown to be a shear-thinning fluid at all temperatures. In addition, the Cooee model is able to reproduce experimental results showing the formation of nanoaggregates composed of stacks of flat aromatic molecules in bitumen. These nanoaggregates are immersed in a solvent of saturated hydrocarbon molecules. At a fixed temperature, the shear-shinning behavior is related to the inter- and intramolecular alignment of the solvent molecules, but also to the decrease of the average size of the nanoaggregates at high shear rates. The variation of the viscosity with temperature at different shear rates is also related to the size and relative composition of the nanoaggregates. The slight anisotropy of the whole sample due to the nanoaggregates is considered and quantified. Finally, the position of bitumen mixtures in the broad literature of complex systems such as colloidal suspensions, polymer solutions and associating polymer networks is discussed.
Mapping atomic and diffuse interstellar band absorption across the Magellanic Clouds and the Milky Way
Mandy Bailey,Jacco Th. van Loon,Peter J. Sarre,John E. Beckman
Physics , 2015, DOI: 10.1093/mnras/stv2178
Abstract: Diffuse interstellar bands (DIBs) trace warm neutral and weakly-ionized diffuse interstellar medium (ISM). Here we present a dedicated, high signal-to-noise spectroscopic study of two of the strongest DIBs, at 5780 and 5797 \AA, in optical spectra of 666 early-type stars in the Small and Large Magellanic Clouds, along with measurements of the atomic Na\,{\sc i}\,D and Ca\,{\sc ii}\,K lines. The resulting maps show for the first time the distribution of DIB carriers across large swathes of galaxies, as well as the foreground Milky Way ISM. We confirm the association of the 5797 \AA\ DIB with neutral gas, and the 5780 \AA\ DIB with more translucent gas, generally tracing the star-forming regions within the Magellanic Clouds. Likewise, the Na\,{\sc i}\,D line traces the denser ISM whereas the Ca\,{\sc ii}\,K line traces the more diffuse, warmer gas. The Ca\,{\sc ii}\,K line has an additional component at $\sim200$--220 km s$^{-1}$ seen towards both Magellanic Clouds; this may be associated with a pan-Magellanic halo. Both the atomic lines and DIBs show sub-pc-scale structure in the Galactic foreground absorption; the 5780 and 5797 \AA\ DIBs show very little correlation on these small scales, as do the Ca\,{\sc ii}\,K and Na\,{\sc i}\,D lines. This suggests that good correlations between the 5780 and 5797 \AA\ DIBs, or between Ca\,{\sc ii}\,K and Na\,{\sc i}\,D, arise from the superposition of multiple interstellar structures. Similarity in behaviour between DIBs and Na\,{\sc i} in the SMC, LMC and Milky Way suggests the abundance of DIB carriers scales in proportion to metallicity.
On optimality and construction of circular repeated-measurements designs
R. A. Bailey,Peter J. Cameron,Katarzyna Filipiak,Joachim Kunert,Augustyn Markiewicz
Statistics , 2014,
Abstract: The aim of this paper is to characterize and construct universally optimal designs among the class of circular repeated-measurements designs when the parameters do not permit balance for carry-over effects. It is shown that some circular weakly neighbour balanced designs defined by Filipiak and Markiewicz These results extend the work of Magda, Kunert, Filipiak and Markiewicz.
A low-cost portable fibre-optic spectrometer for atmospheric absorption studies
J. Bailey
Atmospheric Measurement Techniques Discussions , 2013, DOI: 10.5194/amtd-6-1067-2013
Abstract: A compact and portable solar absorption spectrometer based on fibre-optic Fabry–Perot technology has been built and tested. The instrument weighs only 4.2 kg and operates from 5 W of power from internal batteries. It provides spectroscopy over the range from 5980–6580 cm 1 (1.52–1.67 μm) at a resolution of 0.16 cm 1. The input to the spectrometer is via single-mode optical fibre from a solar tracking system. Spectral scanning is carried out with a piezoelectrically scanned fibre Fabry–Perot tunable filter. Software has been developed to calibrate the spectra in wavelength and relative flux. The signal to noise ratio in solar spectra is about 700 for a spectrum scanned at 200 milliseconds per spectral point. The techniques used should be capable of being adapted to a range of wavelengths and to higher or lower resolutions.
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