2,452 research outputs found
Volume renormalization for complete Einstein--K\"ahler metrics
For a strictly pseudoconvex domain in a complex manifold we define a
renormalized volume with respect to the approximately Einstein complete
K\"ahler metric of Fefferman. We compute the conformal anomaly in complex
dimension two and apply the result to derive a renormalized
Chern--Gauss--Bonnet formula. Relations between renormalized volume and the CR
-curvature are also investigated.Comment: Minor corrections to the statements and proofs of the main theorem
and corollary. Included the example of the Bergman metric on the ball. To
appear in Differential Geometry and Its Application
Feasibility of training practice nurses to deliver a psychosocial intervention within a collaborative care framework for people with depression and long-term conditions
Background
Practice nurses (PNs) deliver much of the chronic disease management in primary care and have been highlighted as appropriately placed within the service to manage patients with long-term physical conditions (LTCs) and co-morbid depression.
This nested qualitative evaluation within a service development pilot provided the opportunity to examine the acceptability of a Brief Behavioural Activation (BBA) intervention within a collaborative care framework. Barriers and facilitators to engaging with the intervention from the patient and clinician perspective will be used to guide future service development and research.
Methods
The study was conducted across 8 practices in one Primary Care Trust 1 in England. Through purposive sampling professionals (nâ=â10) taking part in the intervention (nurses, GPs and a mental health gateway worker) and patients (nâ=â4) receiving the intervention participated in semi-structured qualitative interviews. Analysis utilised the four Normalisation Process Theory (NPT) concepts of coherence, cognitive participation, collective action and reflexive monitoring to explore the how this intervention could be implemented in practice.
Results
Awareness of depression and the stigma associated with the label of depression meant that, from a patient perspective a PN being available to âlistenâ was perceived as valuable. Competing practice priorities, perceived lack of time and resources, and lack of engagement by the whole practice team were considered the greatest barriers to the implementation of this intervention in routine primary care.
Conclusion
Lack of understanding of, participation in, and support from the whole practice team in the collaborative care model exacerbated the pressures perceived by PNs. The need for formal supervision of PNs to enable them to undertake the role of case manager for patients with depression and long-term conditions is emphasised
Setting priorities for development of emerging interventions against childhood pneumonia, meningitis and influenza
WAcute lower respiratory infections, which broadly include pneumonia and bronchiolitis, are still the leading cause of childhood mortality. ALRI contributed to 18% of all deaths in children younger than five years of age in 2008, and the main pathogens responsible for high mortality were Streptococcus pneumoniae, Haemophilus influenzae and respiratory syncytial virus. In addition, meningitis was estimated to contribute up to
200 000 deaths each year, and influenza anywhere between
25 000 and 110 000. It is widely acknowledged that a major portion of this mortality should be avoidable if universal coverage of all known effective interventions could be achieved. However, some evaluations of the implementation of World Health Organizationâs (WHO) Integrated Management of Childhood Illness (IMCI) strategy, which promotes improved access to a trained health provider who can administer âstandard case managementâ, have shown somewhat disappointing results. Only a minority of all children with life-threatening episodes of pneumonia, meningitis and influenza in developing countries have access to trained health providers and receive appropriate
treatment. Thus, novel strategies for control of pneumonia
that balance investments in scaling up of existing interventions and the development of novel approaches, technologies and ideas are clearly needed
Convergence Properties of Approximate Bayesian Computation
Approximate Bayesian Computation is a family of Monte Carlo methods used for likelihood-free Bayesian inference, where calculating the likelihood is intractable, but it is possible to generate simulated data, and calculate
summary statistics. While these methods are easy to describe and implement, it is not trivial to optimise the mean square error of the resulting estimate.
This thesis focuses on asymptotic results for the rate of convergence of ABC to the true posterior expectation as the expected computational cost increases. Firstly, we examine the asymptotic efficiency of the "basic" versions of ABC,
which consists of proposal generation, followed by a simple accept-reject step. We then look at several simple extensions, including the use of a random accept-reject
step, and the use of ABC to make kernel density estimates.
The asymptotic convergence rate of the basic versions of ABC decreases as the summary statistic dimension increases. A naive conclusion from this result would be that, for an infinite-dimensional summary statistic, the ABC estimate would not converge. To show this need not be the case, we look at the asymptotic behaviour of ABC in the case of an observation that consists of a stochastic process over a fixed time interval. We find partial results for two
different criteria for accepting proposals.
We also introduce a new variant of ABC, referred to in the thesis as the ABCLOC estimate. This belongs to a family of variants, in which the parameter proposals are adjusted, to reduce the difference between the distribution of the accepted proposals and the true posterior distribution. The ABCLOC estimate does this using kernel regression. We give preliminary results for the asymptotic behaviour of the ABCLOC estimate, showing that it potentially has a faster
asymptotic rate of convergence than the basic versions for high-dimensional summary statistics
Coping with cyclic oxygen availability: evolutionary aspects
Both the gradual rise in atmospheric oxygen over the Proterozoic Eon as well as episodic fluctuations in oxygen over several million-year time spans during the Phanerozoic Era, have arguably exerted strong selective forces on cellular and organismic respiratory specialization and evolution. The rise in atmospheric oxygen, some 2 billion years after the origin of life, dramatically altered cell biology and set the stage for the appearance of multicelluar life forms in the Vendian (Ediacaran) Period of the Neoproterozoic Era. Over much of the Paleozoic, the level of oxygen in the atmosphere was near the present atmospheric level (21%). In the Late Paleozoic, however, there were extended times during which the level of atmospheric oxygen was either markedly lower or markedly higher than 21%. That these Paleozoic shifts in atmospheric oxygen affected the biota is suggested by the correlations between: (1) Reduced oxygen and the occurrences of extinctions, a lowered biodiversity and shifts in phyletic succession, and (2) During hyperoxia, the corresponding occurrence of phenomena such as arthropod gigantism, the origin of insect flight, and the evolution of vertebrate terrestriality. Basic similarities in features of adaptation to hyopoxia, manifest in living organisms at levels ranging from genetic and cellular to physiological and behavioral, suggest the common and early origin of a suite of adaptive mechanisms responsive to fluctuations in ambient oxygen. Comparative integrative approaches addressing the molecular bases of phenotypic adjustments to cyclic oxygen fluctuation provide broad insight into the incremental steps leading to the early evolution of homeostatic respiratory mechanisms and to the specialization of organismic respiratory functio
Resveratrol augments ER stress and the cytotoxic effects of glycolytic inhibition in neuroblastoma by downregulating Akt in a mechanism independent of SIRT1
Cancer cells typically display increased rates of aerobic glycolysis that are correlated with tumor aggressiveness and a poor prognosis. Targeting the glycolytic pathway has emerged as an attractive therapeutic route mainly because it should spare normal cells. Here, we evaluate the effects of combining the inhibition of glycolysis with application of the polyphenolic compound resveratrol (RSV) in neuroblastoma (NB) cancer cell lines. Inhibiting glycolysis with 2-deoxy-D-glucose (2-DG) significantly reduced NB cell viability and was associated with increased endoplasmic reticulum (ER) stress and Akt activity. Administration of 2-DG increased the expression of the ER molecular chaperones GRP78 and GRP94, the prodeath protein C/EBP homology protein (CHOP) and the phosphorylation of Akt at S473, T450 and T308. Combined treatment with both RSV and 2-DG reduced GRP78, GRP94 and Akt phosphorylation but increased CHOP and NB cell death when compared with the administration of 2-DG alone. The selective inhibition of Akt activity also decreased 2-DG-induced GRP78 and GRP94 expression and increased CHOP expression, suggesting that Akt can modulate ER stress. Protein phosphatase 1 alpha (PP1 alpha) was activated by RSV, as indicated by a reduction in PP1 alpha phosphorylation at T320. Pretreatment of cells with tautomycin, a selective PP1 alpha inhibitor, prevented the RSV-mediated decrease in Akt phosphorylation, suggesting that RSV enhances 2-DG-induced cell death by activating PP1 and downregulating Akt. The RSV-mediated inhibition of Akt in the presence of 2-DG was not prevented by the selective inhibition of SIRT1, a known target of RSV, indicating that the effects of RSV on this pathway are independent of SIRT1. We propose that RSV inhibits Akt activity by increasing PP1 alpha activity, thereby potentiating 2-DG-induced ER stress and NB cell death
Compactness properties of operator multipliers
We continue the study of multidimensional operator multipliers initiated in
[arXiv:math/0701645]. We introduce the notion of the symbol of an operator
multiplier. We characterise completely compact operator multipliers in terms of
their symbol as well as in terms of approximation by finite rank multipliers.
We give sufficient conditions for the sets of compact and completely compact
multipliers to coincide and characterise the cases where an operator multiplier
in the minimal tensor product of two C*-algebras is automatically compact. We
give a description of multilinear modular completely compact completely bounded
maps defined on the direct product of finitely many copies of the C*-algebra of
compact operators in terms of tensor products, generalising results of Saar
Evidence suggesting that di-n-butyl phthalate has anti-androgenic effects in fish
This article is the pre-print version of the full and final published article.Phthalate ester plasticizers are anti-androgenic in mammals. High doses of certain phthalates consistently interfere with the normal development of male offspring exposed in utero, causing disrupted sperm production, abnormal development of the genitalia, and in some cases infertility. In the environment, phthalates are considered ubiquitous and are commonly measured in aquatic ecosystems at low ng to mu g per litre concentrations. Given the similarity between mammalian and teleost endocrine systems, phthalate esters may be able to cause anti-androgenic endocrine disruption in fish in the wild. In the present study, adult male three-spined sticklebacks (Gasterosteus aculetaus) (n = 8) were exposed to di-n-butyl phthalate (DBP) (0, 15, and 35 mu g DBP/L) for 22 d and analyzed for changes in nesting behavior, plasma androgen concentrations, spiggin concentrations, and steroidogenic gene expression. Plasma testosterone concentrations were significantly higher in males from the 35 mu g DBP/L group compared with the solvent control, whereas plasma 11-ketotestosterone concentrations were not significantly affected. Expression of steroid acute regulatory protein and 3 beta-hydroxysteroid dehydrogenase remained unchanged. Spiggin concentrations were significantly lower in the males exposed to 35 mu g DBP/L. Nest building appeared to be slower in some males exposed to DBP, but this was not statistically significant. These results suggest that DBP has anti-androgenic effects in fish. However, further research is required to firmly establish the consequences of chronic DBP exposure in fish
Two close large quasar groups of size ⌠350 Mpc at
The Clowes & Campusano large quasar group (LQG) atâinline imageâhas been re-examined using the quasar data from the DR7QSO catalogue of the Sloan Digital Sky Survey. In the 1991 discovery, the LQG impinged on the northern, southern and eastern limits of the survey. In the DR7QSO data, the western, northern and southern boundaries of the LQG remain essentially the same, but an extension eastwards of âŒ2° is indicated. In the DR7QSO data, the LQG has 34 members, withâinline image. A new group of 38 members is indicated atâinline imageâand within âŒ2bsl000640 of the Clowes & Campusano LQG. The characteristic sizes of these two LQGs, âŒ350â400 Mpc, appear to be only marginally consistent with the scale of homogeneity in the concordance cosmology. In addition to their intrinsic interest, these two LQGs provide locations in which to investigate early large-scale structure in galaxies and to identify high-zâclusters. A method is presented for assessing the statistical significance and overdensity of groups found by linkage of points
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