106 research outputs found
Combustion Synthesis of Fe-Incorporated SnO 2
Synthesis of nanomaterials within flames has been demonstrated as a highly scalable and versatile approach for obtaining a variety of nanoparticles with respect to their chemistry, composition, size, morphology, and dimensionality. Its applicability can be amplified by exploring new material systems and providing further control over the particle characteristics. This study focused on iron-incorporated SnO2 nanoparticles generated using an inverse coflow diffusion flame burner that supported a near-stoichiometric methane-air combustion. A liquid organometallic precursor solution of Sn(CH3)4 and Fe(CO)5 was used to produce 11–14 nm nanocrystalline particles. Synthesized particles were analyzed using TEM, XRD, and XEDS to characterize for size and composition. A flame temperature field was obtained to map particle evolution within the flame. A range of conditions and parameters were studied to specifically generate targeted particles. The study augments related research towards increasing the production potential of combustion synthesis
Magnetically warped discs in close binaries
We demonstrate that measurable vertical structure can be excited in the
accretion disc of a close binary system by a dipolar magnetic field centred on
the secondary star. We present the first high resolution hydrodynamic
simulations to show the initial development of a uniform warp in a tidally
truncated accretion disc. The warp precesses retrogradely with respect to the
inertial frame. The amplitude depends on the phase of the warp with respect to
the binary frame. A warped disc is the best available explanation for negative
superhumps.Comment: 11 pages, 10 figures, MNRAS accepte
Effect of pre-existing baryon inhomogeneities on the dynamics of quark-hadron transition
Baryon number inhomogeneities may be generated during the epoch when the
baryon asymmetry of the universe is produced, e.g. at the electroweak phase
transition. The regions with excess baryon number will have a lower temperature
than the background temperature of the universe. Also the value of the quark
hadron transition temperature will be different in these regions as
compared to the background region. Since a first-order quark hadron transition
is very susceptible to small changes in temperature, we investigate the effect
of the presence of such baryonic lumps on the dynamics of quark-hadron
transition. We find that the phase transition is delayed in these lumps for
significant overdensities. Consequently, we argue that baryon concentration in
these regions grows by the end of the transition. We briefly discuss some
models which may give rise to such high overdensities at the onset of the
quark-hadron transition.Comment: 16 pages, no figures, minor changes, version to appear in Phys. Rev.
First-order cosmological phase transitions in the radiation dominated era
We consider first-order phase transitions of the Universe in the
radiation-dominated era. We argue that in general the velocity of interfaces is
non-relativistic due to the interaction with the plasma and the release of
latent heat. We study the general evolution of such slow phase transitions,
which comprise essentially a short reheating stage and a longer phase
equilibrium stage. We perform a completely analytical description of both
stages. Some rough approximations are needed for the first stage, due to the
non-trivial relations between the quantities that determine the variation of
temperature with time. The second stage, instead, is considerably simplified by
the fact that it develops at a constant temperature, close to the critical one.
Indeed, in this case the equations can be solved exactly, including
back-reaction on the expansion of the Universe. This treatment also applies to
phase transitions mediated by impurities. We also investigate the relations
between the different parameters that govern the characteristics of the phase
transition and its cosmological consequences, and discuss the dependence of
these parameters with the particle content of the theory.Comment: 38 pages, 3 figures; v2: Minor changes, references added; v3: several
typos correcte
July 2004 Report of Progress
Progress of each ALS-NSCORT project given by each project lead. 10 pages
Multi organ assessment of compensated cirrhosis patients using quantitative magnetic resonance imaging
Background and Aims: Advancing liver disease results in deleterious changes in a number of critical organs. The ability to measure structure, blood flow and tissue perfusion within multiple organs in a single scan has implications for determining the balance of benefit versus harm for therapies. Our aim was to establish the feasibility of Magnetic Resonance Imaging to assess changes in compensated cirrhosis (CC), and relate this to disease severity and future liver related outcomes (LROs).
Methods: 60 CC patients, 40 healthy volunteers and 7 decompensated cirrhotics were recruited. In a single scan session, MRI measures comprised phase-contrast MRI vessel blood flow, arterial spin labelling tissue perfusion, T1 longitudinal relaxation time and volume assessment of liver, spleen and kidneys, heart rate and cardiac index. We explore MRI parameters with disease severity and differences in baseline MRI parameters in those 11 (18%) of CC patients who had future LROs.
Results: In the liver compositional changes were reflected by increased T1 in progressive disease (p<0.001) and an increase in liver volume in CC (p=0.006), with associated progressive reduction in liver (p < 0.001) and splenic (p<0.001) perfusion. A significant reduction in renal cortex T1 and increase in cardiac index and superior mesenteric arterial (SMA) blood flow was seen with increasing disease severity. Baseline liver T1 (p=0.01) and perfusion (p< 0.01), and renal cortex T1 (p<0.01) were significantly different in CC patients who subsequently developed negative LROs.
Conclusions: MRI allows the contemporaneous assessment of organs in liver cirrhosis in a single scan without the requirement of contrast agent. MRI parameters of liver T1, renal T1, hepatic and splenic perfusion, and SMA blood flow were related to risk of LROs
February 2005 Report of Progress
Progress of each ALS-NSCORT project given by each project lead. 8 pages
May 2004 Report of Progress
Progress of each ALS-NSCORT project given by each project lead. 11 pages
Dispersion as an Important Step in the Candida albicans Biofilm Developmental Cycle
Biofilms are dynamic microbial communities in which transitions between planktonic and sessile modes of growth occur interchangeably in response to different environmental cues. In the last decade, early events associated with C. albicans biofilm formation have received considerable attention. However, very little is known about C. albicans biofilm dispersion or the mechanisms and signals that trigger it. This is important because it is precisely C. albicans cells dispersed from biofilms that are the main culprits associated with candidemia and establishment of disseminated invasive disease, two of the gravest forms of candidiasis. Using a simple flow biofilm model recently developed by our group, we have performed initial investigations into the phenomenon of C. albicans biofilm dispersion, as well as the phenotypic characteristics associated with dispersed cells. Our results indicate that C. albicans biofilm dispersion is dependent on growing conditions, including carbon source and pH of the media used for biofilm development. C. albicans dispersed cells are mostly in the yeast form and display distinct phenotypic properties compared to their planktonic counterparts, including enhanced adherence, filamentation, biofilm formation and, perhaps most importantly, increased pathogenicity in a murine model of hematogenously disseminated candidiasis, thus indicating that dispersed cells are armed with a complete arsenal of “virulence factors” important for seeding and establishing new foci of infection. In addition, utilizing genetically engineered strains of C. albicans (tetO-UME6 and tetO-PES1) we demonstrate that C. albicans biofilm dispersion can be regulated by manipulating levels of expression of these key genes, further supporting the evidence for a strong link between biofilms and morphogenetic conversions at different stages of the C. albicans biofilm developmental cycle. Overall, our results offer novel and important insight into the phenomenon of C. albicans biofilm dispersion, a key part of the biofilm developmental cycle, and provide the basis for its more detailed analysis
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A measurement of CMB cluster lensing with SPT and DES year 1 data
Clusters of galaxies gravitationally lens the cosmic microwave background (CMB) radiation, resulting in a distinct imprint in the CMB on arcminute scales. Measurement of this effect offers a promising way to constrain the masses of galaxy clusters, particularly those at high redshift. We use CMB maps from the South Pole Telescope Sunyaev–Zel’dovich (SZ) survey to measure the CMB lensing signal around galaxy clusters identified in optical imaging from first year observations of the Dark Energy Survey. The cluster catalogue used in this analysis contains 3697 members with mean redshift of z¯ = 0.45. We detect lensing of the CMB by the galaxy clusters at 8.1σ significance. Using the measured lensing signal, we constrain the amplitude of the relation between cluster mass and optical richness to roughly 17 per cent precision, finding good agreement with recent constraints obtained with galaxy lensing. The error budget is dominated by statistical noise but includes significant contributions from systematic biases due to the thermal SZ effect and cluster miscentring
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