1,243 research outputs found
Tomographic Study of Internal Erosion of Particle Flows in Porous Media
In particle-laden flows through porous media, porosity and permeability are
significantly affected by the deposition and erosion of particles. Experiments
show that the permeability evolution of a porous medium with respect to a
particle suspension is not smooth, but rather exhibits significant jumps
followed by longer periods of continuous permeability decrease. Their origin
seems to be related to internal flow path reorganization by avalanches of
deposited material due to erosion inside the porous medium. We apply neutron
tomography to resolve the spatio-temporal evolution of the pore space during
clogging and unclogging to prove the hypothesis of flow path reorganization
behind the permeability jumps. This mechanistic understanding of clogging
phenomena is relevant for a number of applications from oil production to
filters or suffosion as the mechanisms behind sinkhole formation.Comment: 18 pages, 9 figure
A transdisciplinary and community-driven database to unravel subduction zone initiation
Subduction zones are pivotal for the recycling of Earthâs outer layer into its interior. However, the conditions under which new subduction zones initiate are enigmatic. Here, we constructed a transdisciplinary database featuring detailed analysis of more than a dozen documented subduction zone initiation events from the last hundred million years. Our initial findings reveal that horizontally forced subduction zone initiation is dominant over the last 100âMa, and that most initiation events are proximal to pre-existing subduction zones. The SZI Database is expandable to facilitate access to the most current understanding of subduction zone initiation as research progresses, providing a community platform that establishes a common language to sharpen discussion across the Earth Science community
Impact of repeated percutaneous coronary intervention on long-term survival after subsequent coronary artery bypass surgery
<p>Abstract</p> <p>(Background)</p> <p>In the current stent era, aggressive repeated percutaneous coronary intervention (PCI) has become more common. The aim of this study was to investigate the impact of previous repeated PCI on the subsequent coronary artery bypass grafting (CABG).</p> <p>(Methods)</p> <p>Between January 1990 and January 2008, a total of 894 patients underwent first-time isolated elective CABG. Among the 894 patients, 515 patients had had no PCI (group A), 179 patients had had single PCI (Group B), and 200 patients had had multiple PCI (2-15 times, mean 3.6 ± 2.3 times) (group C) before CABG. These groups were compared in terms of early and late clinical results.</p> <p>(Results)</p> <p>Preoperative left ventricular ejection fraction was significantly higher in group A (group A;58 ± 13%, group B;54 ± 12%, and group C;54 ± 12%). Number of bypass grafts was significantly smaller in group C (A:3.3 ± 1.0, B 3.4 ± 0.9, C 3.1 ± 1.0). Although there was no statistically significant difference among the groups, in-hospital mortality in group C was higher than that in group A and B (A:1.6%, B:1.1%, C:3.5%, p = 0.16). Survival analysis by Kaplan-Meier method (mean follow-up: 58 ± 43 methods) revealed that freedom from all-cause death and cardiac death was significantly lower in group C in comparison with group A. Freedom from cardiac event was significantly higher in group C than that in group A. Multivariate analysis identified a number of previous PCI as an independent risk factor for cardiac death.</p> <p>(Conclusions)</p> <p>Repeated PCI increased risk for long-term prognosis of subsequent CABG.</p
Management of perioperative bleeding risk in patients on antithrombotic medications undergoing cardiac surgeryâa systematic review
Background: Antithrombotic drugs increase the risk of bleeding, especially in patients who need
urgent surgery without an adequate wash-out period. This review aims to evaluate perioperative bleeding
complications in patients on dual antiplatelet therapy (DAPT) or direct-acting oral anticoagulants (DOACs)
undergoing high-bleeding risk cardiovascular surgery and to present currently available potential solutions to
mitigate antithrombotic therapy-related bleeding complications.
Methods: As a first step, we searched for relevant articles, over the last 10 years, in Medline (PubMed) and
abstracted clinical information based on pre-defined criteria for bleeding complications. In the next step,
an additional search evaluating potential solutions to mitigate bleeding complications was performed. The
literature screening and selection process followed the principles derived from the PRISMA statement.
Results: From all reviewed studies, a total of 19 articles could be included evaluating the risk for bleeding
in cardiac surgery related to DAPT or DOACs and 10 papers evaluating antithrombotic drug reversal or
removal in the setting of cardiovascular surgery. Reported bleeding rates ranged between 18% and 41%.
The variability of the reported data is remarkable. Idarucizumab is reported to provide optimal perioperative
hemostasis in up to 93% of patients. It has been observed that andexanet alfa causes unresponsiveness to
the anticoagulant effects of heparin. Antithrombotic removal by intraoperative hemoadsorption is found to
be associated with a significant decrease in re-thoracotomy rate, overall procedure duration, administered
transfusion volumes, chest-tube drainage, and length of hospitalization.
Discussion: Bleeding complications in patients treated with DAPT or DOACs in cardiac surgery are high.
New costly reversal agents are available but have not been sufficiently tested in the cardio-surgical setting
so far. Interestingly, bleeding-related complications seem to be effectively reduced by applying innovative
intraoperative hemoadsorption techniques. Expected results from the ongoing trials should provide better
insights concerning the efficacy and safety of several potential solutions. Currently, the variability of reports
and the deficit of high-quality studies in this specific setting represent the major limitation for the unbiased
conclusion of this review
Green function techniques in the treatment of quantum transport at the molecular scale
The theoretical investigation of charge (and spin) transport at nanometer
length scales requires the use of advanced and powerful techniques able to deal
with the dynamical properties of the relevant physical systems, to explicitly
include out-of-equilibrium situations typical for electrical/heat transport as
well as to take into account interaction effects in a systematic way.
Equilibrium Green function techniques and their extension to non-equilibrium
situations via the Keldysh formalism build one of the pillars of current
state-of-the-art approaches to quantum transport which have been implemented in
both model Hamiltonian formulations and first-principle methodologies. We offer
a tutorial overview of the applications of Green functions to deal with some
fundamental aspects of charge transport at the nanoscale, mainly focusing on
applications to model Hamiltonian formulations.Comment: Tutorial review, LaTeX, 129 pages, 41 figures, 300 references,
submitted to Springer series "Lecture Notes in Physics
The 10th Biennial Hatter Cardiovascular Institute workshop: cellular protectionâevaluating new directions in the setting of myocardial infarction, ischaemic stroke, and cardio-oncology
Due to its poor capacity for regeneration, the heart is particularly sensitive to the loss of contractile cardiomyocytes. The onslaught of damage caused by ischaemia and reperfusion, occurring during an acute myocardial infarction and the subsequent reperfusion therapy, can wipe out upwards of a billion cardiomyocytes. A similar program of cell death can cause the irreversible loss of neurons in ischaemic stroke. Similar pathways of lethal cell injury can contribute to other pathologies such as left ventricular dysfunction and heart failure caused by cancer therapy. Consequently, strategies designed to protect the heart from lethal cell injury have the potential to be applicable across all three pathologies. The investigators meeting at the 10th Hatter Cardiovascular Institute workshop examined the parallels between ST-segment elevation myocardial infarction (STEMI), ischaemic stroke, and other pathologies that cause the loss of cardiomyocytes including cancer therapeutic cardiotoxicity. They examined the prospects for protection by remote ischaemic conditioning (RIC) in each scenario, and evaluated impasses and novel opportunities for cellular protection, with the future landscape for RIC in the clinical setting to be determined by the outcome of the large ERIC-PPCI/CONDI2 study. It was agreed that the way forward must include measures to improve experimental methodologies, such that they better reflect the clinical scenario and to judiciously select combinations of therapies targeting specific pathways of cellular death and injury
Combined in vivo depletion of glycoprotein VI and C-type lectin-like receptor 2 severely compromises hemostasis and abrogates arterial thrombosis in mice
Objectiveâ
Platelet inhibition is a major strategy to prevent acute ischemic cardiovascular and cerebrovascular events, which may, however, be associated with an increased bleeding risk. The (hem)immunoreceptor tyrosine activation motifâbearing platelet receptors, glycoprotein VI (GPVI) and C-type lectin-like receptor 2 (CLEC-2), might be promising antithrombotic targets because they can be depleted from circulating platelets by antibody treatment, leading to sustained antithrombotic protection, but only moderately increased bleeding times in mice.
Approach and Resultsâ
We investigated whether both (hem)immunoreceptor tyrosine activation motifâbearing receptors can be targeted simultaneously and what the in vivo consequences of such a combined therapeutic GPVI/CLEC-2 deficiency are. We demonstrate that isolated targeting of either GPVI or CLEC-2 in vivo does not affect expression or function of the respective other receptor. Moreover, simultaneous treatment with both antibodies resulted in the sustained loss of both GPVI and CLEC-2, while leaving other activation pathways intact. However, GPVI/CLEC-2âdepleted mice displayed a dramatic hemostatic defect and profound impairment of arterial thrombus formation. Furthermore, a strongly diminished hemostatic response could also be reproduced in mice genetically lacking GPVI and CLEC-2.
Conclusionsâ
These results demonstrate that GPVI and CLEC-2 can be simultaneously downregulated in platelets in vivo and reveal an unexpected functional redundancy of the 2 receptors in hemostasis and thrombosis. These findings may have important implications of the potential use of anti-GPVI and antiâCLEC-2âbased agents in the prevention of thrombotic diseases.
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