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7
result(s) for
"Pavlou, Georgios E"
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Reconstructing the Magnetic Field in an Arbitrary Domain via Data-Driven Bayesian Methods and Numerical Simulations
by
Pavlidou, Vasiliki
,
Harmandaris, Vagelis
,
Pavlou, Georgios E.
in
Algorithms
,
Astrophysics
,
Bayesian analysis
2025
Inverse problems are prevalent in numerous scientific and engineering disciplines, where the objective is to determine unknown parameters within a physical system using indirect measurements or observations. The inherent challenge lies in deducing the most probable parameter values that align with the collected data. This study introduces an algorithm for reconstructing parameters by addressing an inverse problem formulated through differential equations underpinned by uncertain boundary conditions or variant parameters. We adopt a Bayesian approach for parameter inference, delineating the establishment of prior, likelihood, and posterior distributions, and the subsequent resolution of the maximum a posteriori problem via numerical optimization techniques. The proposed algorithm is applied to the task of magnetic field reconstruction within a conical domain, demonstrating precise recovery of the true parameter values.
Journal Article
Contrary Inferences for Classical Histories within the Consistent Histories Formulation of Quantum Theory
by
Wallden, Petros
,
Zampeli, Adamantia
,
Pavlou, Georgios E
in
Paradoxes
,
Quantum theory
,
Square wells
2024
In the histories formulation of quantum theory, sets of coarse-grained histories, that are called consistent, obey classical probability rules. It has been argued that these sets can describe the semi-classical behaviour of closed quantum systems. Most physical scenarios admit multiple different consistent sets and one can view each consistent set as a separate context. Using propositions from different consistent sets to make inferences leads to paradoxes such as the contrary inferences first noted by Kent [Physical Review Letters, 78(15):2874, 1997]. Proponents of the consistent histories formulation argue that one should not mix propositions coming from different consistent sets in making logical arguments, and that paradoxes such as the aforementioned contrary inferences are nothing else than the usual microscopic paradoxes of quantum contextuality as first demonstrated by Kochen and Specker theorem. In this contribution we use the consistent histories to describe a macroscopic (semi-classical) system to show that paradoxes involving contextuality (mixing different consistent sets) persist even in the semi-classical limit. This is distinctively different from the contextuality of standard quantum theory, where the contextuality paradoxes do not persist in the semi-classical limit. Specifically, we consider different consistent sets for the arrival time of a semi-classical wave packet in an infinite square well. Surprisingly, we get consistent sets that disagree on whether the motion of the semi-classical system, that started within a subregion, ever left that subregion or not. Our results point to the need for constraints, additional to the consistency condition, to recover the correct semi-classical limit in this formalism and lead to the motto `all consistent sets are equal', but `some consistent sets are more equal than others'.
Reconstructing the Magnetic Field in an Arbitrary Domain via Data-driven Bayesian Methods and Numerical Simulations
by
Pavlidou, Vasiliki
,
Harmandaris, Vagelis
,
Pavlou, Georgios E
in
Algorithms
,
Bayesian analysis
,
Boundary conditions
2024
Inverse problems are prevalent in numerous scientific and engineering disciplines, where the objective is to determine unknown parameters within a physical system using indirect measurements or observations. The inherent challenge lies in deducing the most probable parameter values that align with the collected data. This study introduces an algorithm for reconstructing parameters by addressing an inverse problem formulated through differential equations underpinned by uncertain boundary conditions or variant parameters. We adopt a Bayesian approach for parameter inference, delineating the establishment of prior, likelihood, and posterior distributions, and the subsequent resolution of the maximum a posteriori problem via numerical optimization techniques. The proposed algorithm is applied to the task of magnetic field reconstruction within a conical domain, demonstrating precise recovery of the true parameter values.
Remote Microphone Hearing Aid Use Improves Classroom Listening, Without Adverse Effects on Spatial Listening and Attention Skills, in Children With Auditory Processing Disorder: A Randomised Controlled Trial
by
Bamiou, Doris-Eva
,
Iliadou, Vasiliki (Vivian)
,
Pavlou, Menelaos
in
Attention
,
audiology
,
Auditory processing disorder
2020
Children with Auditory Processing Disorder (APD) often have poor auditory processing skills in the presence of normal peripheral hearing. These children have worse listening-in-noise skills compared to typically developing peers, while other commonly reported symptoms include poor attention and distractibility. One of the management strategies for children with APD is the use of Remote Microphone Hearing Aids (RMHAs), which can help improve the signal-to-noise ratio in the child's ears. The aim of this randomised controlled trial was to examine whether RMHAs improved classroom listening in children with APD, and to further test their effects on children's listening-in-noise and attention skills following a 6-month intervention.
Twenty-six children diagnosed with APD, aged 7-12, in primary mainstream education, were randomised into the intervention (
= 13) and control group (
= 13). The primary outcome measure was the Listening Inventory for Education - Revised questionnaire, completed by children to assess their listening using RMHAs under several acoustically challenging situations in the classroom. Secondary outcome measures included the Listening in Spatialised Noise - Sentences test, assessing speech-in-noise perception and spatial listening, and the Test of Everyday Attention for Children, assessing different types of attention skills. Tests were conducted in unaided conditions. Mixed analysis of variance was used to analyse the data. The clinical trial was registered at clinicaltrials.gov (unique identifier: NCT02353091).
The questionnaire scores of self-reported listening skills in the classroom significantly improved in the intervention group after 3,
= 7.31,
= 2.113,
= 0.014, and after 6 months,
= 5.00,
= 1.468,
= 0.016. The behavioural measures of listening-in-noise and attention did not significantly change.
Use of RMHAs improves classroom listening, evidenced by the results of the questionnaire analysis, while a 6-month use did not have adverse effects on unaided spatial listening or attention skills.
Journal Article
Cold vs. Room Temperature: A Comparative Analysis of Platelet Functionality in Cold Storage
by
Dryllis, Georgios
,
Kriebardis, Anastasios G.
,
Valsami, Serena
in
Blood & organ donations
,
Blood platelets
,
Clotting
2025
Background: The platelet functionality of cold-stored platelets remains a subject of debate. Our aim was to investigate the effect of temperature on the hemostatic properties of stored platelets. Methods: Ten split pooled platelets stored at cold and at room temperature were evaluated in vitro on storage days 1, 5, 10, and 15 for metabolic, physiological, and vesiculation parameters, as well as their hemostatic profile using rotational thromboelastometry (ROTEM®). Results: The integrity profile was better preserved in the cold-stored platelets, as lower lactate dehydrogenase levels were documented (e.g., day 10: 261 ± 46 vs. 572 ± 220 U/L, 4 vs. 22 °C, p = 0.004). A time-dependent decrease in hemostatic capacity was evident regardless of the temperature, but the cold-stored units were linked to shorter clot initiation times and increased elasticity, strength, and firmness parameters, especially during extended storage (e.g., maximum clot firmness, INTEM day 15: 81 ± 2 vs. 19 ± 4 mm, 4 vs. 22 °C, p = 0.0008). Additionally, the aggregation of cold-stored platelets was superior after the addition of any agonist tested. Regarding vesiculation parameters, the extracellular vesicles of the units at 4 °C were characterized by a larger size from day 10 onwards, when they also presented higher procoagulant activity (e.g., phospholipid-dependent clotting time of day 15: 21.4 ± 2.3 vs. 25.0 ± 3.0 s, 4 vs. 22 °C, p = 0.016). Conclusion: Our results indicate that cold-stored platelets perform better than those stored at room temperature, demonstrating superior clot formation and stability. This suggests that cold storage may more effectively preserve platelet function, potentially offering advantages for transfusion therapy and the extension of shelf-life. However, the clinical relevance of these findings requires further investigation.
Journal Article
Accelerating the in vitro emulation of Alzheimer’s disease-associated phenotypes using a novel 3D blood-brain barrier neurosphere co-culture model
by
Tsai, Alice
,
Jorfi, Mehdi
,
Spitz, Sarah
in
Alzheimer's disease
,
Alzheimer’s disease (AD)
,
Animal models
2023
High failure rates in clinical trials for neurodegenerative disorders such as Alzheimer’s disease have been linked to an insufficient predictive validity of current animal-based disease models. This has created an increasing demand for alternative, human-based models capable of emulating key pathological phenotypes in vitro . Here, a three-dimensional Alzheimer’s disease model was developed using a compartmentalized microfluidic device that combines a self-assembled microvascular network of the human blood-brain barrier with neurospheres derived from Alzheimer’s disease-specific neural progenitor cells. To shorten microfluidic co-culture times, neurospheres were pre-differentiated for 21 days to express Alzheimer’s disease-specific pathological phenotypes prior to the introduction into the microfluidic device. In agreement with post-mortem studies and Alzheimer’s disease in vivo models, after 7 days of co-culture with pre-differentiated Alzheimer’s disease-specific neurospheres, the three-dimensional blood-brain barrier network exhibited significant changes in barrier permeability and morphology. Furthermore, vascular networks in co-culture with Alzheimer’s disease-specific microtissues displayed localized β-amyloid deposition. Thus, by interconnecting a microvascular network of the blood-brain barrier with pre-differentiated neurospheres the presented model holds immense potential for replicating key neurovascular phenotypes of neurodegenerative disorders in vitro .
Journal Article
Transmural Flow Upregulates PD‐L1 Expression in Microvascular Networks
by
Hirose, Satomi
,
Zhang, Shun
,
Kim, Seunggyu
in
Animals
,
B7-H1 Antigen - genetics
,
B7-H1 Antigen - metabolism
2024
Endothelial programmed death‐ligand 1 (PD‐L1) expression is higher in tumors than in normal tissues. Also, tumoral vasculatures tend to be leakier than normal vessels leading to a higher trans‐endothelial or transmural fluid flow. However, it is not clear whether such elevated transmural flow can control endothelial PD‐L1 expression. Here, a new microfluidic device is developed to investigate the relationship between transmural flow and PD‐L1 expression in microvascular networks (MVNs). After treating the MVNs with transmural flow for 24 h, the expression of PD‐L1 in endothelial cells is upregulated. Additionally, CD8 T cell activation by phytohemagglutinin (PHA) is suppressed when cultured in the MVNs pre‐conditioned with transmural flow. Moreover, transmural flow is able to further increase PD‐L1 expression in the vessels formed in the tumor microenvironment. Finally, by utilizing blocking antibodies and knock‐out assays, it is found that transmural flow‐driven PD‐L1 upregulation is controlled by integrin αVβ3. Overall, this study provides a new biophysical explanation for high PD‐L1 expression in tumoral vasculatures. Elevated endothelial programmed death‐ligand 1 (PD‐L1) in tumor vasculature remains unexplained. Using a microfluidic device, it is found that transmural flow upregulates PD‐L1 in microvascular networks, suppressing CD8 T cell activation. Transmural flow also enhances PD‐L1 expression in tumor microenvironment vessels, controlled by integrin αVβ3. The study provides a biophysical explanation for upregulated PD‐L1 in tumoral vasculature.
Journal Article