167 research outputs found
Daylight saving time, circadian rhythms, and cardiovascular health
No full textVery recently, the European Parliament, called to decide on possible abolition of the Daylight Saving Time (DST), approved a resolution calling the scientific community to conduct a more in-depth evaluation. The question is based on disruption of body's circadian rhythms. We review here the relationship between DST and cardiovascular health. The available evidence suggests the existence of an association between DST and a modest increase of occurrence of acute myocardial infarction, especially in the first week after the spring shift. Possible mechanisms include sleep deprivation, circadian misalignment and environmental conditions. The role of gender and individual preference in circadian rhythms (chronotype) will need further assessment
Direct numerical simulation of forced thermal convection in square ducts up to
No full textWe carry out direct numerical simulation (DNS) of flow in a turbulent square
duct by focusing on heat transfer effects, considering the case of unit Prandtl
number. Reynolds numbers up to are considered which are
much higher than in previous studies, and which yield clear scale separation
between inner- and outer-layer dynamics. Close similarity between the behavior
of the temperature and the streamwise velocity fields is confirmed as in
previous studies related to plane channels and pipes. Just like the mean
velocity, the mean temperature is found to exhibit logarithmic layers as a
function of the nearest wall, however with a different slope. The most
important practical implication is the validity of the traditional hydraulic
diameter as the correct reference length for reporting heat transfer data, as
we rigorously show here. Temperature and velocity fluctuations also have
similar behavior, but apparently logarithmic growth of their inner-scaled peak
variances is not observed here unlike in canonical wall-bounded flows. Analysis
of the split contributions to the heat transfer coefficient shows that mean
cross-stream convection associated with secondary motions is responsible for
about of the total. Finally, we use the DNS database to highlight
shortcomings of traditional linear closures for the turbulent heat flux, and
show that substantial modeling improvement may be in principle obtained by
retaining at least the three terms in the vector polynomial integrity basis
expansion
Aortic coartaction in the elderly: how many errors lie behind an unexpected diagnosis?
No full textA65-year-old woman was admitted to our department
because of chest pain and untreated hypertension. She had
been well until 6 years previously when a diagnosis of
hypertension was made. She reported poor control of blood
pressure associated with leg weakness in coincidence with
tentatively aggressive anti-hypertensive therapy. Aclinical diagnosis of aortic coarctation was made
[1], and a spiral TC study revealed a stenosis of the aorta
2 cm below the origin of the subclavia; a 2 cm aneurysm was present in the proximity of
the stenosis (Fig. 1, white arrow) and epiaortic arteries
were dilated
Please, Sir, pull down your socks!
No full textA 48-year-old male patient presented at the regular followupvisit seven months after a successful kidney transplant.After discussion of blood chemistries with the doctor, thepatient underwent a physical examination. As usual, heunbuttoned his shirt and undid his trouser belt. Inspectionof the limbs, after pulling up his trousers, confirmed thepresence of ankle oedema; the graft was quite firm, with nomurmurs in the area
Differential Influence of Physical Activity on Cardiopulmonary Performance and Stroke Volume Assessed at Cardiopulmonary Exercise Test in Pectus Excavatum: A Pilot Study
No full textBackground: Exercise training increases muscle VO2 by increasing O2 transport and O2 uptake while cardiac output increase might be limited by the conformation of the chest in subjects with pectus excavatum (PE). Aims: The aim of the present study was to investigate the influence of physical activity (PA) on functional parameters of cardiopulmonary performance and stroke volume obtained at Cardiopulmonary Exercise Test (CPET) in PE. Methods and Procedures: A cohort of adolescents (15 with PE and 15 age- and sex-matched healthy controls, HC) underwent Cardiopulmonary Exercise Test (CPET) and administration of the International Physical Activity Questionnaire – Short Form (IPAQ-SF) with estimation of weekly PA (METs h–1⋅week–1). Determinants of CPET parameters were investigated with multivariable linear regression analysis. Results: As expected, when compared to HC, PE had lower VO2 max (37.2 ± 6.6 vs. 45.4 ± 6.4 mL⋅kg–1⋅min–1, p < 0.05), and VO2/HR max (O2 pulse, 12.1 ± 2.4 vs. 16.2 ± 3.6 mL⋅min–1⋅bpm–1, p < 0.05). Importantly, physical activity level was a predictor of VO2 max (adjusted for sex, body mass index, FEV1%, and presence of PE, β = 0.085; 95% Cl 0.010 to 0.160, p = 0.029) whereas O2 pulse was independent from PA level (β = 0.035; 95% Cl −0.004 to 0.074). Conclusion: Physical activity is a determinant of VO2 max (cardiopulmonary performance), whereas it appears not to affect O2 pulse (a measure of stroke volume at peak exercise) related to constrained diastolic filling in PE
STREAmS-2.0: Supersonic turbulent accelerated Navier-Stokes solver version 2.0
No full textWe present STREAmS-2.0, an updated version of the flow solver STREAmS, first introduced in Bernardini et al. (2021) [1]. STREAmS-2.0 has an object-oriented design which separates the physics equations from the specific back-end, making the code more suitable for future expansions, such as porting to novel computing architectures or implementation of additional flow physics. Similarly to the previous version, STREAmS-2.0 supports NVIDIA-GPU and CPU back-ends. Additionally, this version features improvements of the input/output data management, new energy and entropy preserving schemes for the discretization of the convective fluxes, recycling/rescaling inflow boundary condition, and a model for thermally perfect gases with variable specific heats. New version program summary: Program Title: STREAmS CPC Library link to program files: https://doi.org/10.17632/hdcgjpzr3y.2 Developer's repository link: https://github.com/STREAmS-CFD/STREAmS-2 Licensing provisions: GPLv3 Programming language: Fortran, CUDA Journal reference of previous version: M. Bernardini, D. Modesti, F. Salvadore, and S. Pirozzoli. STREAmS: a high-fidelity accelerated solver for direct numerical simulation of compressible turbulent flows. Comput. Phys. Commun. 263 (2021) 107906. Does the new version supersede the previous version?: Yes. Reasons for the new version: New code structure and release of new features. Summary of revisions: • The original solver [1] has been rewritten following an object-oriented design implemented through Fortran derived types that include variables and type bound procedures. The new software architecture has been designed to increase modularity and extensibility of the code, allowing users to add new back-ends and physics equations while maintaining the same code structure. This allows users to reuse portions of the code that are independent of the physics equations, the back-end, or both. The layer of computing procedures maintains a lean structure that can be highly optimized with respect to the implemented back-end. • Input handling is now based on the classic.ini format improving both user readability and input data management. • A family of new kinetic energy and entropy preserving schemes (KEEP) are now available and can be selected for stable, non-dissipative and accurate spatial discretization of the convective terms of the Navier–Stokes equations in smooth flow regions [2]. Concerning the shock-capturing flux, the improved low-dissipative WENO-Z scheme proposed by [3] is now available. • New inflow boundary conditions based on the recycling/rescale approach [4] have been implemented for the simulation of spatially evolving compressible turbulent boundary layers. Moreover, a new inflow condition based on the solution of the compressible Blasius equation is available to take into account the case of laminar boundary layers. • The constitutive relations have been generalized to take into account thermally perfect gases with variable specific heats, approximated with polynomial functions of the temperature that can be specified by the user [5]. • A new stretching function has been implemented to improve the distribution of grid nodes for the computation of wall-bounded turbulent flows. The formulation blends uniform near-wall spacing with uniform resolution in terms of Kolmogorov units in the outer wall layer, guaranteeing accuracy with higher computational efficiency [6]. Nature of problem: The code solves the compressible Navier–Stokes equations in Cartesian coordinates for a thermally perfect gas. The solver is designed for direct numerical simulation (DNS) of compressible supersonic turbulent boundary layers and various canonical configurations are supported, including turbulent channel flow, laminar and turbulent boundary layer and shock-wave/boundary layer interaction. Solution method: The equations are discretized using high-order finite difference approximations with hybrid low-dissipative/shock-capturing capabilities and the time advancement is performed using a Runge–Kutta scheme. References: [1] M. Bernardini, D. Modesti, F. Salvadore, S. Pirozzoli, STREAmS: A high-fidelity accelerated solver for direct numerical simulation of compressible turbulent flows, Comput. Phys. Commun. 263 (2021) 107906. [2] Y. Tamaki, Y. Kuya, S. Kawai, Comprehensive analysis of entropy conservation property of non-dissipative schemes for compressible flows: KEEP scheme redefined, J. Comput. Phys. 468 (2022) 111494. [3] R. Borges, M. Carmona, B. Costa, W. Don, An improved weighted essentially non-oscillatory scheme for hyperbolic conservation laws, J. Comput. Phys. 227 (6) (2008) 3191–3211, https://doi.org/10.1016/j.jcp.2007.11.038 [4] S. Pirozzoli, M. Bernardini, F. Grasso, Direct numerical simulation of transonic shock/boundary layer interaction under conditions of incipient separation, J. Fluid Mech. 657 (2010) 361–393. [5] B. J. McBride, M. J. Zehe, S. Gordon, NASA Glenn coefficients for calculating thermodynamic properties of individual species, NASA/TP 211556, NASA, 2002. [6] S. Pirozzoli, P. Orlandi, Natural grid stretching for DNS of wall-bounded flows, J. Comput. Phys. 439 (2021) 110408.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Aerodynamic
Miglioramento delle proprietà barriera di nanocompositi polimerici PET/PA per packaging alimentare
No full textCardioplegia and angiotensin II receptor antagonists modulate signal transducers and activators of transcription activation in neonatal rat myocytes.
No full textPrevious investigations have shown that the signal transducers and activators of transcription (STATs) signaling pathway play an important role in the modulation of apoptosis after ischemia and reperfusion. The mechanism for this enhanced cardioprotection is unknown, but we believe that alterations STATs may play a role. To investigate this hypothesis, we examined the effects of angiotension II type 1 (AT1) and angiotension II type 2 (AT2) receptor antagonist added to cardioplegia on the downstream response of different STATs, connected with proinflammatory pathways (STAT2, STAT5) and prohypertrophic and antiapoptotic pathways (STAT3). Isolated, nonworking hearts (n = 3 per group) from neonatal rats were perfused aerobically (4°C) for 20 min in the Langendorff mode with the modified St. Thomas' Hospital no. 2 (MSTH2) cardioplegic solution (Group 1), the MSTH2 cardioplegic solution + AT1 receptor antagonist (Group 2), and MSTH2 cardioplegic solution + AT2 receptor antagonist (Group 3). Thus, myocytes were isolated by enzymatic digestion, and STAT2, STAT3, and STAT5 were investigated in Western blot studies. Times to arrest after cardioplegia were 8-12 s for all groups. Total cardioplegia delivery volume was about 300 mL for the 20 min. Perfusion with the MSTH2 cardioplegic solution supplemented with AT1 receptor antagonist (Group 2) induced a significant reduction in STAT2 and STAT5 tyrosine phosphorylation (-58 and -63%, respectively, vs. Group 1, P < 0.05). Conversely, STAT2 and STAT5 activation were unaffected by perfusion with the MSTH2 cardioplegic solution supplemented with AT2 receptor antagonist (Group 3). The decreased activation of STAT2 and STAT5 observed in Group 2 was accompanied by reduction of interleukin-1β (-57% in Group 2 vs. Group 1, P < 0.05). There were no significant differences in STAT3 phosphorylation among all groups. Only the addition of AT1 receptor antagonist to MSTH2 cardioplegia significantly decreases the inflammatory response of the neonatal rat cardiomyocytes without affecting antiapoptotic influence provided by tyrosine phosphorylation of STAT3. AT1 receptor antagonist added to cardioplegia represents an additional modality for enhancing myocardial protection during cardiac surgery and could contribute to optimize the ischemia tolerance of the pediatric heart
PET/PA nanocomposite blends with improved gas barrier properties: effect of processing conditions
No full textThe aim of this research is to develop nanocomposite polyethylene terephthalate-polyamide blends (PET/MXD6 blends) with low oxygen permeability. Particular attention has been paid to the relation between barrier properties and the processing route adopted and therefore four different strategies were considered. Mechanical characterization shows that clay may effectively act as reinforcing filler in PET/MXD6 blends. Morphological characterization shows the strong effect of the processing strategy on clay dispersion and its distribution between the PET and polyamide phases. Barrier properties of PET/MXD6 nanocomposite blends are enhanced with respect to neat PET polymer as well as PET/MXD6 blends. The significant effect of processing techniques on barrier properties is also revealed
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