1,459 research outputs found
Constrained sintering of 8mol% Y 2O 3 stabilised zirconia films
Constrained sintering kinetics of 8 mol% Y2O3/92 mol% ZrO2 (8YSZ) films approximately 10–15 m thick screen-printed on dense YSZ substrates,
and the resulting stress induced in the films, were measured in the temperature range 1100–1350 ◦C. The results are compared with those reported
earlier for 3YSZ films.
Both materials behave similarly, although there are differences in detail. The constrained densification rate was greatly retarded compared with
the unconstrained densification rate due to the effect of the constraint on the developing anisotropic microstructure (3YSZ) and, in the case of
8YSZ, considerable grain growth. The stress generated during constrained sintering was typically a few MPa. The apparent activation energies for
free sintering, constrained sintering, creep and grain growth are found to cover a wide range (135–670 kJ mol−1) despite all probably being mainly
controlled by grain boundary cation diffusion
Constrained sintering kinetics of 3YSZ films
3YSZ green layers approximately 10 μm thick were screen-printed onto 3YSZ substrates and their constrained sintering kinetics were measured at 1100–1350 °C using an optical dilatometer. The densification rates of the same powder in the form of pellets and free-standing films were also measured. The constrained densification rate was greatly retarded compared with the free densification rate at a given temperature and density. The retardation increased with increasing density and temperature and could not be properly accounted for by existing theories of constrained sintering. As a result the apparent activation energy is much lower for constrained sintering (135 ± 20 kJ mol−1) than for free sintering (660 ± 30 kJ mol−1). It is proposed that this is because the constrained microstructure exhibits larger and more widely separated pores at the higher temperatures
Stress induced by constrained sintering of 3YSZ films measured by substrate creep
3YSZ green layers approximately 10 μm thick were screen printed onto 3YSZ substrates up to 300 μm in thickness. The stress induced by constrained sintering of the film (between 1150° and 1350°C) was measured by monitoring the bending displacement of vertical strips of bilayers using a long-distance microscope. In order to deduce the stress it was first necessary to measure the creep properties of the substrates by monitoring the bending of horizontal beams under gravity. The creep strain rate of the 3YSZ substrates was linearly dependent on applied stress at the low stresses and strains involved in the present work. The creep viscosity appeared to increase with strain (time), which might be due to changes in grain-boundary composition, and had higher activation energy at temperatures above approximately 1250°C. The magnitudes of the creep viscosities are in reasonable agreement with other creep data in the literature for 3YSZ.
The in-plane stress induced during constrained sintering of the 3YSZ films had a maximum value of approximately 3 MPa at 1200°C. This behavior is consistent with literature results reported for constrained sintering of bulk alumina. The stress induced by the constraint is of a similar order to the estimated sintering potential
Patient perception of treatment efficacy, disability and health satisfaction
Abstract published in Rheumatology, Volume 55 (Suppl 1), April 2016, page i123
Auditor of State Mary Mosiman today released a reaudit report on the Mason City Community School District (District) for the period July 1, 2014 through June 30, 2015. The reaudit also covered items applicable to the years ended June 30, 2016 and June 30, 2017.
Auditor of State Mary Mosiman today released a reaudit report on the Mason City Community School District (District) for the period July 1, 2014 through June 30, 2015. The reaudit also covered items applicable to the years ended June 30, 2016 and June 30, 2017
Primer registro de anomalía intersexual gonadal de Trachurus mediterraneus (Steindachner, 1868) desde el Mar de Alborán.
El objetivo principal de este trabajo es dar a conocer el primer registro de una anomalía intersexual gonadal de Trachurus mediterraneus desde el mar de Alborán (Mediterráneo occidental). Este espécimen es el primer registro de intersexualidad para un jurel en
el mundo.Postprin
Mechanisms Underlying Pheromone Gradient Tracking in Mating Yeast
Chemotaxis and chemotropism play essential roles in a wide range of biological processes, during which cells interpret extracellular chemical gradients and orient their movement or growth. How cells translate the extracellular chemical gradients into intracellular signaling gradients and accurately orient their cytoskeletons remain unclear. The mating of the budding yeast, Saccharomyces cerevisiae, is the best-studied chemotropic process to date. Haploid yeast cells signal their positions to cells of the opposite mating type by secreting mating pheromones. Upon pheromone binding, the pheromone-responding G protein-coupled receptor (GPCR) activates its cognit Gα subunit, which releases the Gβγ subunit. Free Gβγ gets phosphorylated, signals to the nucleus through a MAP kinase cascade to arrest the cell cycle in G1. Gβγ also positions the polarity complex at the chemotropic growth site (CS). The polarity complex (PC) nucleates actin cables for polarized growth. When cells are treated with isotropic pheromone or pheromone-stimulated cells are unable to sense a gradient, they form mating projections at the default polarity site (DS) determined in G1. How do cells accurately decode the shallow pheromone gradients and orient their growth from the cell-cycle determined DS to the gradient-aligned CS? Numerous models have been proposed to explain yeast gradient sensing, but none of them fully explained how yeast cells overcome the challenges from the shallow and complicated pheromone gradients and the strong intrinsic DS.
Here we propose a deterministic gradient sensing model which answers these questions. We demonstrate that yeast cells accomplish gradient sensing in four phases. Following global internalization of the receptor and G protein (Phase I), mating cells use the DS to assemble a gradient tracking machine (GTM) composed of signaling, polarity, and trafficking proteins (Phase II). Within the GTM, differential activation of the receptor triggers feedback mechanisms that segregate vesicle delivery upgradient and endocytosis downgradient. The segregation of the trafficking machinery redistributes the GTM towards the pheromone source (Phase III, tracking). The GTM stabilizes (Phase IV) when the receptor peak and vesicle delivery align with the pheromone source and are surrounded by the negative GPCR signaling regulator and endocytosis. We also showed that tracking depends on actin-independent – but not actin-dependent – vesicle delivery, and that the DS must be inactivated for budding to allow tracking to start. Together, this model answers the questions of how yeast cells solve the environmental and intrinsic challenges and accurately position the CS. It also provides an additional function of the cell-cycle determined DS. Besides positioning the daughter cell emergence, the DS functions as a platform to assemble the GTM
Analyzing PhD supervision using the competing values framework
This thesis provides an analysis of supervisory interactions between PhD supervisors and their students within social science disciplines, using the Competing Values Framework (CVF). Traditionally, such work has been conducted using a supervisor-centred perspective, and this thesis adds to the literature by adopting a student-centred view to look at supervisor's behaviours during the interaction, from a role performance perspective in light of the CVF.
Drawing primarily on semi-structured interpersonal process recall interview data, the thesis considers a number of interlinking analytical themes. These can be divided into three broad groups. The first focuses on investigating the CVF roles that are adopted by the supervisor during the interaction and recognized by the students as important component parts of the most helpful supervisory moments. In line with the previous literature, I note that the most effective supervisory behaviours reflect the performance of all the eight CVF roles with the producer and the director occupying the dominant position.
The second group is closely linked with the first and investigates CVF managerial roles represented by the least helpful supervision moments selected by the student. I note how PhD supervisors inadequate use, including both overuse and underuse of the CVF roles are related to the least effective supervisory moments. The director and the producer are again the most represented ones which are reported as being mostly underused. The third group analyses students advice on further improvements . In conclusion, I relate my analysis to existing literature and examined the contributions of the thesis to three main areas of research. This research finds that instances of positive and negative supervisee feedback reflect an increased influence of marketorientation and manageralism on research students and correspondingly inadequate use of managerial roles by supervisors
Optimal Design for Nonlinear Model with Random Effect and Information-Based Subdata Selection for LASSO
Optimal designs for nonlinear model with random block effects are systematically studied.
For a large class of nonlinear models, we prove that any optimal design can be based on some
simple structures. We further derive the corresponding general equivalence theorem. This result
allows us to propose an efficient algorithm of deriving specific optimal designs. The application
of the algorithm is demonstrated through deriving a variety of locally optimal designs and
accessing their robustness under different nonlinear models.
Extraordinary amounts of data are being produced in many branches of science as well
as people’s daily activity. Such data are usually huge in both rows and columns. Modeling
such data with limited computation resource has been a challenging problem. We propose an
approach select a very informative subset of the data based on optimal design theory, using
LASSO regression to perform variable selection and estimation. Compare to exist methods like
balanced or weighted sampling, our approach avoids involving sampling error and thus provides
more accurate estimation/prediction, also takes much less time
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