1,212 research outputs found
A superfluid hydrodynamic model for the enhanced moments of inertia of molecules in liquid 4He
We present a superfluid hydrodynamic model for the increase in moment of
inertia, , of molecules rotating in liquid He. The static
inhomogeneous He density around each molecule (calculated using the Orsay-Paris
liquid He density functional) is assumed to adiabatically follow the
rotation of the molecule. We find that the values created by the
viscousless and irrotational flow are in good agreement with the observed
increases for several molecules [ OCS, (HCN), HCCCN, and HCCCH ]. For
HCN and HCCH, our model substantially overestimates . This is likely
to result from a (partial) breakdown of the adiabatic following approximation.Comment: 4 pages, 1 eps figure, corrected version of published paper. Erratum
has been submitted for change
Global MHD Simulations of Cylindrical Keplerian Disks
This paper presents a series of global three dimensional accretion disk
simulations carried out in the cylindrical limit in which the vertical
component of the gravitational field is neglected. The simulations use a
cylindrical pseudo-Newtonian potential to model the main dynamical properties
of the Schwarzschild metric. The disks are initially constant density with a
Keplerian angular momentum distribution and contain a weak toroidal or vertical
field. These simulations reaffirm many of the conclusions of previous local
simulations. The magnetorotational instability grows rapidly and produces MHD
turbulence with a significant Maxwell stress which drives accretion.
Tightly-wrapped low- spiral waves are prominent. In some simulations radial
variations in Maxwell stress concentrate gas into rings, creating substantial
spatial inhomogeneities. There is a nonzero stress at the marginally stable
orbit which produces a small decline in specific angular momentum inside the
last stable orbit. Detailed comparisons between simulations are used to examine
the effects of computational domain and equation of state. Simulations that
begin with vertical fields have greater field amplification and higher ratios
of stress to magnetic pressure compared with those beginning with toroidal
fields. In contrast to MHD, hydrodynamics alone neither creates nor sustains
turbulence.Comment: Submitted to the Astrophysical Journal Web version of paper and MPEG
animations can be found at http://www.astro.virginia.edu/~jh8h/cylinder
Neural origins of basal diencephalon in teleost fishes: Radial versus tangential migration
Teleost fish possess large lateral diencephalic regions such as the torus lateralis, the preglomerular area, and the diffuse nucleus of the hypothalamic inferior lobe. While their developmental origins traditionally were suggested to lie in diencephalic midline ventricular proliferative zones, more remote midbrain origins were reported recently. This review focuses on the preglomerular region and summarizes the data supporting three existing hypotheses on its developmental origins. The conclusion is that lateral torus, diffuse nucleus of hypothalamic inferior lobe, and preglomerular region are part of the diencephalon, but have a multiregional origin provided by both radially and tangentially migrating cells forming these regions in question
A network analysis to identify pathophysiological pathways distinguishing ischaemic from non-ischaemic heart failure
Aims
Heart failure (HF) is frequently caused by an ischaemic event (e.g. myocardial infarction) but might also be caused by a primary disease of the myocardium (cardiomyopathy). In order to identify targeted therapies specific for either ischaemic or nonâischaemic HF, it is important to better understand differences in underlying molecular mechanisms.
Methods and results
We performed a biological physical proteinâprotein interaction network analysis to identify pathophysiological pathways distinguishing ischaemic from nonâischaemic HF. First, differentially expressed plasma protein biomarkers were identified in 1160 patients enrolled in the BIOSTATâCHF study, 715 of whom had ischaemic HF and 445 had nonâischaemic HF. Second, we constructed an enriched physical proteinâprotein interaction network, followed by a pathway overârepresentation analysis. Finally, we identified key network proteins. Data were validated in an independent HF cohort comprised of 765 ischaemic and 100 nonâischaemic HF patients. We found 21/92 proteins to be upâregulated and 2/92 downâregulated in ischaemic relative to nonâischaemic HF patients. An enriched network of 18 proteins that were specific for ischaemic heart disease yielded six pathways, which are related to inflammation, endothelial dysfunction superoxide production, coagulation, and atherosclerosis. We identified five key network proteins: acid phosphatase 5, epidermal growth factor receptor, insulinâlike growth factor binding proteinâ1, plasminogen activator urokinase receptor, and secreted phosphoprotein 1. Similar results were observed in the independent validation cohort.
Conclusions
Pathophysiological pathways distinguishing patients with ischaemic HF from those with nonâischaemic HF were related to inflammation, endothelial dysfunction superoxide production, coagulation, and atherosclerosis. The five key pathway proteins identified are potential treatment targets specifically for patients with ischaemic HF
Divergences in Real-Time Classical Field Theories at Non-Zero Temperature
The classical approximation provides a non-perturbative approach to
time-dependent problems in finite temperature field theory. We study the
divergences in hot classical field theory perturbatively. At one-loop, we show
that the linear divergences are completely determined by the classical
equivalent of the hard thermal loops in hot quantum field theories, and that
logarithmic divergences are absent. To deal with higher-loop diagrams, we
present a general argument that the superficial degree of divergence of
classical vertex functions decreases by one with each additional loop: one-loop
contributions are superficially linearly divergent, two-loop contributions are
superficially logarithmically divergent, and three- and higher-loop
contributions are superficially finite. We verify this for two-loop SU(N)
self-energy diagrams in Feynman and Coulomb gauges. We argue that hot,
classical scalar field theory may be completely renormalized by local (mass)
counterterms, and discuss renormalization of SU(N) gauge theories.Comment: 31 pages with 7 eps figure
Energetics and Possible Formation and Decay Mechanisms of Vortices in Helium Nanodroplets
The energy and angular momentum of both straight and curved vortex states of
a helium nanodroplet are examined as a function of droplet size. For droplets
in the size range of many experiments, it is found that during the pickup of
heavy solutes, a significant fraction of events deposit sufficient energy and
angular momentum to form a straight vortex line. Curved vortex lines exist down
to nearly zero angular momentum and energy, and thus could in principle form in
almost any collision. Further, the coalescence of smaller droplets during the
cooling by expansion could also deposit sufficient angular momentum to form
vortex lines. Despite their high energy, most vortices are predicted to be
stable at the final temperature (0.38 K) of helium nanodroplets due to lack of
decay channels that conserve both energy and angular momentum.Comment: 10 pages, 8 figures, RevTex 4, submitted to Phys. Rev.
Short- and long-term haemodynamic consequences of transcatheter closure of atrial septal defect and patent foramen ovale
BACKGROUND: Transcatheter atrial septal defect (ASD) and patent foramen ovale (PFO) closure might have opposite short- and long-term haemodynamic consequences compared with restricted interatrial shunt creation, which recently emerged as a potential treatment modality for patients with heart failure with preserved ejection fraction (HFpEF). Given the opposing approaches of ASD and PFO closure versus shunt creation, we investigated the early and sustained cardiac structural and functional changes following transcatheter ASD or PFO closure. METHODS: In this retrospective study, adult secundum-type ASD and PFO patients with complete echocardiography examinations at baseline and at 1âday and 1âyear follow-up who also underwent transcatheter closure between 2013 and 2017âŻat the University Medical Centre Groningen, the Netherlands were included. RESULTS: Thirty-nine patients (mean age 48âŻÂ±âstandard deviation 16 years, 61.5% women) were included. Transcatheter ASD/PFO closure resulted in an early and persistent decrease in right ventricular systolic and diastolic function. Additionally, transcatheter ASD/PFO closure resulted in an early and sustained favourable response of left ventricular (LV) systolic function, but also in deterioration of LV diastolic function with an increase in LV filling pressure (LVFP), as assessed by echocardiography. Age (ÎČâŻ=â0.31, pâŻ=â0.009) and atrial fibrillation (AF; ÎČâŻ=â0.24, pâŻ=â0.03) were associated with a sustained increase in LVFP after transcatheter ASD/PFO closure estimated by mean E/eâ ratio (i.e. ratio of mitral peak velocity of early filling to diastolic mitral annular velocity). In subgroup analysis, this was similar for ASD and PFO closure. CONCLUSION: Older patients and patients with AF were predisposed to sustained increases in left-sided filling pressures resembling HFpEF following ASD or PFO closure. Consequently, these findings support the current concept that creating a restricted interatrial shunt might be beneficial, particularly in elderly HFpEF patients with AF. SUPPLEMENTARY INFORMATION: The online version of this article (10.1007/s12471-021-01543-0) contains supplementary material, which is available to authorized users
Online training courses on Expert Knowledge Elicitation (EKE)
This report summarises the training courses delivered under the contract OC/EFSA/AMU/2021/02 EKE: âDevelop and conduct online training courses on Expert Knowledge Elicitation (EKE)â. The objective of the courses was to develop and conduct online training courses on applying the methodology described in the EFSA Guidance on Expert Knowledge Elicitation in Food and Feed Safety Risk Assessmentâ for EFSA staff and experts, as well as corresponding experts from EU member states. In addition to the three standard EKE methods (Sheffield, Delphi and Cooke), the training included a semi-formal method of EKE. All these methods may be used when EKE is performed within an existing EFSA working group to support uncertainty analysis as outlined in âThe principles and methods behind EFSA\u27s Guidance on Uncertainty Analysis in Scientific Assessmentâ. In total, 12 courses were organised: two on âSteering an Expert Knowledge Elicitationâ, two on âConduct of the Sheffield protocol for an EKEâ, one on âConduct of the Cooke protocol for an EKEâ, one on âConduct of the Delphi protocol for an EKEâ, two on âConduct of a Semi-formal EKEâ, two on âReporting an Expert Knowledge Elicitationâ and two on âWriting an Evidence Dossier for an Expert Knowledge Elicitationâ. The courses had in total 149 participants and received very good feedback from the participants with a mean value of 4.2 of 5 possible, considering all numerical questions in the feedback questionnaire. Recommendations for future activities on training EKE methodologies are provided
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