1,566 research outputs found
Existence and uniqueness results for the Boussinesq system with data in Lorentz spaces
This paper is devoted to the study of the Cauchy problem for the Boussinesq
system with partial viscosity in dimension First we prove a global
existence result for data in Lorentz spaces satisfying a smallness condition
which is at the scaling of the equations. Second, we get a uniqueness result in
Besov spaces with {\it negative} indices of regularity (despite the fact that
there is no smoothing effect on the temperature). The proof relies on a priori
estimates with loss of regularity for the nonstationary Stokes system with
convection. As a corollary, we obtain a global existence and uniqueness result
for small data in Lorentz spaces.Comment: 24 pages. Physica D, in pres
Well-posedness of the Viscous Boussinesq System in Besov Spaces of Negative Order Near Index
This paper is concerned with well-posedness of the Boussinesq system. We
prove that the () dimensional Boussinesq system is well-psoed for
small initial data () either in
or in
if
, and , where
(, , )
is the logarithmically modified Besov space to the standard Besov space
. We also prove that this system is well-posed for small initial
data in
.Comment: 18 page
Existence of global strong solutions in critical spaces for barotropic viscous fluids
This paper is dedicated to the study of viscous compressible barotropic
fluids in dimension . We address the question of the global existence
of strong solutions for initial data close from a constant state having
critical Besov regularity. In a first time, this article show the recent
results of \cite{CD} and \cite{CMZ} with a new proof. Our result relies on a
new a priori estimate for the velocity, where we introduce a new structure to
\textit{kill} the coupling between the density and the velocity as in
\cite{H2}. We study so a new variable that we call effective velocity. In a
second time we improve the results of \cite{CD} and \cite{CMZ} by adding some
regularity on the initial data in particular is in . In this
case we obtain global strong solutions for a class of large initial data on the
density and the velocity which in particular improve the results of D. Hoff in
\cite{5H4}. We conclude by generalizing these results for general viscosity
coefficients
Relationship of glycaemic control and hypoglycaemic episodes to 4-year cardiovascular outcomes in people with type 2 diabetes starting insulin
AIMS: To examine the relationships between glycated haemoglobin (HbA1c) and cardiovascular (CV) events in people beginning insulin in routine clinical practice in Europe, North America and Asia in a non-interventional study, the Cardiovascular Risk Evaluation in people with Type 2 Diabetes on Insulin Therapy (CREDIT) study. METHODS: Data on 2999 people were collected prospectively over 4 years from physician reports. The primary outcome was the composite of stroke or myocardial infarction (MI) or CV-specific death. Events were blindly adjudicated. The relative hazards of CV events were described from Cox proportional hazards models incorporating patient risk factors, with updated average HbA1c as a time-dependent covariate. The relationship of severe and symptomatic hypoglycaemia (collected during the 6 months before yearly ascertainment) with CV and all-cause mortality was examined. RESULTS: A total of 147 primary events were accrued during up to 54 months of follow-up. In all, 60 CV-specific deaths, 44 non-fatal MIs and 57 non-fatal strokes occurred, totalling 161 events. There was a significant positive relationship between updated mean HbA1c and primary outcome: hazard ratio (HR) 1.25 [95% confidence interval (CI) 1.12-1.40; p < 0.0001]. CV death [HR 1.31 (95% CI 1.10-1.57); p = 0.0027] and stroke [HR 1.36 (95% CI 1.17-1.59); p < 0.0001] were both strongly associated with HbA1c, while MI was not [HR 1.05 (95% CI 0.83-1.32)]. One or more severe hypoglycaemic episodes affected 175 participants, while 1508 participants experienced one or more symptomatic hypoglycaemic events. We found no relationship between severe/symptomatic hypoglycaemic events and CV-specific/all-cause death. CONCLUSIONS: Ongoing poorer glucose control was associated with CV events; hypoglycaemia was not associated with CV-specific/all-cause death
Oral health in relation to all-cause mortality: the IPC cohort study
We evaluated the association between oral health and mortality. The study population comprised 76,188 subjects aged 16–89 years at recruitment. The mean follow-up time was 3.4 ± 2.4 years. Subjects with a personal medical history of cancer or cardiovascular disease and death by casualty were excluded from the analysis. A full-mouth clinical examination was performed in order to assess dental plaque, dental calculus and gingival inflammation. The number of teeth and functional masticatory units 10 missing teeth and functional masticatory units 10 missing teeth (HR = 2.31, [95% CI: 1.40–3.82]) and functional masticatory units <5 (HR = 2.40 [95% CI 1.55–3.73]). Moreover, when ≥3 oral diseases were cumulated in the model, the risk increased for all-cause mortality (HR = 3.39, [95% CI: 2.51–5.42]), all-cancer mortality (HR = 3.59, [95% CI: 1.23–10.05]) and non-cardiovascular and non-cancer mortality (HR = 4.71, [95% CI: 1.74–12.7]). The present study indicates a postive linear association between oral health and mortality
Interaction of vortices in viscous planar flows
We consider the inviscid limit for the two-dimensional incompressible
Navier-Stokes equation in the particular case where the initial flow is a
finite collection of point vortices. We suppose that the initial positions and
the circulations of the vortices do not depend on the viscosity parameter \nu,
and we choose a time T > 0 such that the Helmholtz-Kirchhoff point vortex
system is well-posed on the interval [0,T]. Under these assumptions, we prove
that the solution of the Navier-Stokes equation converges, as \nu -> 0, to a
superposition of Lamb-Oseen vortices whose centers evolve according to a
viscous regularization of the point vortex system. Convergence holds uniformly
in time, in a strong topology which allows to give an accurate description of
the asymptotic profile of each individual vortex. In particular, we compute to
leading order the deformations of the vortices due to mutual interactions. This
allows to estimate the self-interactions, which play an important role in the
convergence proof.Comment: 39 pages, 1 figur
Association Between Clinical Pathways Leading to Medical Management and Prognosis in Patients With NSTEACS.
: A large proportion of patients with non-ST-segment elevation acute coronary syndrome (NSTEACS) are initially selected for medical management (MM) and do not undergo coronary revascularization during or immediately after the index event. The aim of this study was to explore the clinical pathways leading to MM in NSTEACS patients and their influence on prognosis. : Patient characteristics, pathways leading to MM, and 2-year outcomes were recorded in a prospective cohort of 5591 NSTEACS patients enrolled in 555 hospitals in 20 countries across Europe and Latin America. Cox models were used to assess the impact of hospital management on postdischarge mortality. : Medical management was the selected strategy in 2306 (41.2%) patients, of whom 669 (29%) had significant coronary artery disease (CAD), 451 (19.6%) had nonsignificant disease, and 1186 (51.4%) did not undergo coronary angiography. Medically managed patients were older and had higher risk features than revascularized patients. Two-year mortality was higher in medically managed patients than in revascularized patients (11.0% vs 4.4%; P < .001), with higher mortality rates in patients who did not undergo angiography (14.6%) and in those with significant CAD (9.3%). Risk-adjusted mortality was highest for patients who did not undergo angiography (HR = 1.81; 95%CI, 1.23-2.65), or were not revascularized in the presence of significant CAD (HR = 1.90; 95%CI, 1.23-2.95) compared with revascularized patients. : Medically managed NSTEACS patients represent a heterogeneous population with distinct risk profiles and outcomes. These differences should be considered when designing future studies in this population.<br/
The emerging structure of the Extended Evolutionary Synthesis: where does Evo-Devo fit in?
The Extended Evolutionary Synthesis (EES) debate is gaining ground in contemporary evolutionary biology. In parallel, a number of philosophical standpoints have emerged in an attempt to clarify what exactly is represented by the EES. For Massimo Pigliucci, we are in the wake of the newest instantiation of a persisting Kuhnian paradigm; in contrast, Telmo Pievani has contended that the transition to an EES could be best represented as a progressive reformation of a prior Lakatosian scientific research program, with the extension of its Neo-Darwinian core and the addition of a brand-new protective belt of assumptions and auxiliary hypotheses. Here, we argue that those philosophical vantage points are not the only ways to interpret what current proposals to ‘extend’ the Modern Synthesis-derived ‘standard evolutionary theory’ (SET) entail in terms of theoretical change in evolutionary biology. We specifically propose the image of the emergent EES as a vast network of models and interweaved representations that, instantiated in diverse practices, are connected and related in multiple ways. Under that assumption, the EES could be articulated around a paraconsistent network of evolutionary theories (including some elements of the SET), as well as models, practices and representation systems of contemporary evolutionary biology, with edges and nodes that change their position and centrality as a consequence of the co-construction and stabilization of facts and historical discussions revolving around the epistemic goals of this area of the life sciences. We then critically examine the purported structure of the EES—published by Laland and collaborators in 2015—in light of our own network-based proposal. Finally, we consider which epistemic units of Evo-Devo are present or still missing from the EES, in preparation for further analyses of the topic of explanatory integration in this conceptual framework
Exploring the equity of GP practice prescribing rates for selected coronary heart disease drugs: a multiple regression analysis with proxies of healthcare need
Background
There is a small, but growing body of literature highlighting inequities in GP practice prescribing rates for many drug therapies. The aim of this paper is to further explore the equity of prescribing for five major CHD drug groups and to explain the amount of variation in GP practice prescribing rates that can be explained by a range of healthcare needs indicators (HCNIs).
Methods
The study involved a cross-sectional secondary analysis in four primary care trusts (PCTs 1–4) in the North West of England, including 132 GP practices. Prescribing rates (average daily quantities per registered patient aged over 35 years) and HCNIs were developed for all GP practices. Analysis was undertaken using multiple linear regression.
Results
Between 22–25% of the variation in prescribing rates for statins, beta-blockers and bendrofluazide was explained in the multiple regression models. Slightly more variation was explained for ACE inhibitors (31.6%) and considerably more for aspirin (51.2%). Prescribing rates were positively associated with CHD hospital diagnoses and procedures for all drug groups other than ACE inhibitors. The proportion of patients aged 55–74 years was positively related to all prescribing rates other than aspirin, where they were positively related to the proportion of patients aged >75 years. However, prescribing rates for statins and ACE inhibitors were negatively associated with the proportion of patients aged >75 years in addition to the proportion of patients from minority ethnic groups. Prescribing rates for aspirin, bendrofluazide and all CHD drugs combined were negatively associated with deprivation.
Conclusion
Although around 25–50% of the variation in prescribing rates was explained by HCNIs, this varied markedly between PCTs and drug groups. Prescribing rates were generally characterised by both positive and negative associations with HCNIs, suggesting possible inequities in prescribing rates on the basis of ethnicity, deprivation and the proportion of patients aged over 75 years (for statins and ACE inhibitors, but not for aspirin)
Hierarchy Theory of Evolution and the Extended Evolutionary Synthesis: Some Epistemic Bridges, Some Conceptual Rifts
Contemporary evolutionary biology comprises a plural landscape of multiple co-existent conceptual frameworks and strenuous voices that disagree on the nature and scope of evolutionary theory. Since the mid-eighties, some of these conceptual frameworks have denounced the ontologies of the Modern Synthesis and of the updated Standard Theory of Evolution as unfinished or even flawed. In this paper, we analyze and compare two of those conceptual frameworks, namely Niles Eldredge’s Hierarchy Theory of Evolution (with its extended ontology of evolutionary entities) and the Extended Evolutionary Synthesis (with its proposal of an extended ontology of evolutionary processes), in an attempt to map some epistemic bridges (e.g. compatible views of causation; niche construction) and some conceptual rifts (e.g. extra-genetic inheritance; different perspectives on macroevolution; contrasting standpoints held in the “externalism–internalism” debate) that exist between them. This paper seeks to encourage theoretical, philosophical and historiographical discussions about pluralism or the possible unification of contemporary evolutionary biology
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