966 results on '"Konstantopoulos, P. A."'
Search Results
2. A Coalitional Game for Demand-Side Management in a Low-Voltage Resistive Micro-Grid with Multiple Electricity Retailers
- Author
-
Mendoza, Fernando Genis, Monasterios, Pablo R Baldivieso, Bauso, Dario, and Konstantopoulos, George
- Subjects
Mathematics - Optimization and Control - Abstract
An existing challenge in power systems is the implementation of optimal demand management through dynamic pricing. This paper encompasses the design, analysis and implementation of a novel on-line pricing scheme based on coalitional game theory. The setting consists of a network with multiple energy retailers competing to attract consumers by announcing a price in a hierarchical leader-follower structure. The process of coalition formation under such a pricing scheme can be viewed as a game for which we show that a Stackelberg equilibrium exists, \ie given a price, consumers will respond by conforming to a reciprocal power consumption quantity. We propose a coalition formation algorithm and perform a game-theoretic stability analysis on the resulting coalitions. We integrate the pricing setting with a resistive micro-grid dynamic model. In this context we analyse the behaviour of the integrated system, bridging the gap between market and physical layers of the problem. Simulations provide a comparison of profits generated by the proposed scheme against a more traditional single retailer scheme, while simultaneously showing convergence towards a steady-state equilibrium. Additionally, we shed light into the system's physical response when subject to our proposed pricing scheme.
- Published
- 2024
3. Predicting Solar Heat Production to Optimize Renewable Energy Usage
- Author
-
Boura, Tatiana, Koliou, Natalia, Meramveliotakis, George, Konstantopoulos, Stasinos, and Kosmadakis, George
- Subjects
Computer Science - Machine Learning ,Computer Science - Artificial Intelligence ,Electrical Engineering and Systems Science - Systems and Control - Abstract
Utilizing solar energy to meet space heating and domestic hot water demand is very efficient (in terms of environmental footprint as well as cost), but in order to ensure that user demand is entirely covered throughout the year needs to be complemented with auxiliary heating systems, typically boilers and heat pumps. Naturally, the optimal control of such a system depends on an accurate prediction of solar thermal production. Experimental testing and physics-based numerical models are used to find a collector's performance curve - the mapping from solar radiation and other external conditions to heat production - but this curve changes over time once the collector is exposed to outdoor conditions. In order to deploy advanced control strategies in small domestic installations, we present an approach that uses machine learning to automatically construct and continuously adapt a model that predicts heat production. Our design is driven by the need to (a) construct and adapt models using supervision that can be extracted from low-cost instrumentation, avoiding extreme accuracy and reliability requirements; and (b) at inference time, use inputs that are typically provided in publicly available weather forecasts. Recent developments in attention-based machine learning, as well as careful adaptation of the training setup to the specifics of the task, have allowed us to design a machine learning-based solution that covers our requirements. We present positive empirical results for the predictive accuracy of our solution, and discuss the impact of these results on the end-to-end system.
- Published
- 2024
4. Tuning extracellular fluid viscosity to enhance transfection efficiency
- Author
-
Ma, Jingyao, Zhu, Yining, Kong, Jiayuan, Yu, Di, Toh, Wu Han, Jain, Milun, Ni, Qin, Ge, Zhuoxu, Lin, Jinghan, Choy, Joseph, Cheng, Leonardo, Konstantopoulos, Konstantinos, Konig, Maximilian F., Sun, Sean X., and Mao, Hai-Quan
- Published
- 2024
- Full Text
- View/download PDF
5. Last passage percolation and limit theorems in Barak-Erd\H{o}s directed random graphs and related models
- Author
-
Foss, Sergey, Konstantopoulos, Takis, Mallein, Bastien, and Ramassamy, Sanjay
- Subjects
Mathematics - Probability - Abstract
We consider directed random graphs, the prototype of which being the Barak-Erd\H{o}s graph $\vec G(\mathbb Z, p)$, and study the way that long (or heavy, if weights are present) paths grow. This is done by relating the graphs to certain particle systems that we call Infinite Bin Models (IBM). A number of limit theorems are shown. The goal of this paper is to present results along with techniques that have been used in this area. In the case of $\vec G(\mathbb Z, p)$ the last passage percolation constant $C(p)$ is studied in great detail. It is shown that $C(p)$ is analytic for $p>0$, has an interesting asymptotic expansion at $p=1$ and that $C(p)/p$ converges to $e$ like $1/(\log p)^2$ as $p \to 0$. The paper includes the study of IBMs as models on their own as well as their connections to stochastic models of branching processes in continuous or discrete time with selection. Several proofs herein are new or simplified versions of published ones. Regenerative techniques are used where possible, exhibiting random sets of vertices over which the graphs regenerate. When edges have random weights we show how the last passage percolation constants behave and when central limit theorems exist. When the underlying vertex set is partially ordered, new phenomena occur, e.g., there are relations with last passage Brownian percolation. We also look at weights that may possibly take negative values and study in detail some special cases that require combinatorial/graph theoretic techniques that exhibit some interesting non-differentiability properties of the last passage percolation constant. We also explain how to approach the problem of estimation of last passage percolation constants by means of perfect simulation., Comment: 79 pages, 12 figures
- Published
- 2023
- Full Text
- View/download PDF
6. Depth-guided Free-space Segmentation for a Mobile Robot
- Author
-
Sevastopoulos, Christos, Hussain, Joey, Konstantopoulos, Stasinos, Karkaletsis, Vangelis, and Makedon, Fillia
- Subjects
Computer Science - Robotics ,Computer Science - Computer Vision and Pattern Recognition - Abstract
Accurate indoor free-space segmentation is a challenging task due to the complexity and the dynamic nature that indoor environments exhibit. We propose an indoors free-space segmentation method that associates large depth values with navigable regions. Our method leverages an unsupervised masking technique that, using positive instances, generates segmentation labels based on textural homogeneity and depth uniformity. Moreover, we generate superpixels corresponding to areas of higher depth and align them with features extracted from a Dense Prediction Transformer (DPT). Using the estimated free-space masks and the DPT feature representation, a SegFormer model is fine-tuned on our custom-collected indoor dataset. Our experiments demonstrate sufficient performance in intricate scenarios characterized by cluttered obstacles and challenging identification of free space.
- Published
- 2023
7. Star Clusters in Tidal Debris
- Author
-
Rodruck, Michael, Charlton, Jane, Borthakur, Sanchayeeta, Chitre, Aparna, Durrell, Patrick R., Elmegreen, Debra, English, Jayanne, Gallagher, Sarah C., Gronwall, Caryl, Knierman, Karen, Konstantopoulos, Iraklis, Li, Yuexing, Maji, Moupiya, Mullan, Brendan, Trancho, Gelys, and Vacca, William
- Subjects
Astrophysics - Astrophysics of Galaxies - Abstract
We present results of a Hubble Space Telescope (HST) UBVI-band study of star clusters in tidal tails, using new WFC3 and ACS imaging to complement existing WFPC2 data. We survey 12 tidal tails across seven merging systems, deriving ages and masses for 425 star cluster candidates (SCCs). The stacked mass distribution across all systems follows a power law of the form $dN/dM \propto M^{\beta}$, with $\beta = -2.02 \pm 0.15$, consistent with what is seen in other star forming environments. GALEX and Swift UV imaging provide star formation rates (SFRs) for our tidal tails, which when compared with ages and masses of our SCCs, allows for a determination of the cluster formation efficiency (CFE). We find the CFE increases with increasing SFR surface density, matching the theoretical model. We confirm this fit down at SFR densities lower than previously measured (log $\Sigma_\text{SFR} \: (\text{M}_\odot \: \text{yr}^{-1} \: \text{kpc}^{-2}) \approx -4.2$), as related to the CFE. We determine the half-light radii for a refined sample of 57 SCCs with our HST WFC3 and ACS imaging, and calculate their dynamical age, finding the majority of them to be gravitationally bound. We also provide evidence of only low-mass ($< 10^4 \: \text{M}_\odot$) cluster formation in our nearest galaxy, NGC 1487, consistent with the theory that this system is a dwarf merger., Comment: 26 pages, 27 figures. Accepted at MNRAS
- Published
- 2023
8. Incorporating Complex Sampling Weights in Multilevel Analyses of Education Data
- Author
-
Shen, Ting and Konstantopoulos, Spyros
- Abstract
Large-scale assessment survey (LSAS) data are collected via complex sampling designs with special features (e.g., clustering and unequal probability of selection). Multilevel models have been utilized to account for clustering effects whereas the probability weighting approach (PWA) has been used to deal with design informativeness derived from the unequal probability selection. However, the difficulty of applying PWA in multilevel models (MLM) has been generally underestimated and practical guidance is scarce. This study utilizes an empirical as well as a Monte Carlo simulation investigation to examine the performance of the multilevel pseudo maximum likelihood (MPML) estimation based on information derived from the Early Childhood Longitudinal Study Kindergarten cohort of 2010-2011 (ECLS-K:2011). Variance components and fixed effects estimators across four estimation methods including three MPML estimators (i.e., weighted without scaling, weighted size-scaled and weighted effective-scaled) and the unweighted estimator are provided. Practical guidance about the use of sampling weights in MLM analyses of LSAS data is also offered.
- Published
- 2022
9. Resilient Distributed Integral Control for Multimachine Power Systems with Inherent Input Constraint Satisfaction
- Author
-
Kavvathas, Theodoros E., Konstantopoulos, George C., and Konstantinou, Charalambos
- Subjects
Electrical Engineering and Systems Science - Systems and Control - Abstract
In this paper, a novel distributed controller for multimachine power systems is proposed to guarantee grid frequency restoration and accurate real and reactive power sharing among the generator units, while maintaining the generator inputs (mechanical torque and field excitation voltage) within given bounds. The boundedness of the controller outputs (generator inputs) is rigorously proven using vector field theory. It is additionally shown that even if one generator input reaches its upper/lower limit, the remaining units can still accomplish the desired control tasks without modifying the controller structure or dynamics; hence introducing enhanced system resilience using the proposed approach. This has been accomplished in a unified control structure while using neighbour-to-neighbour communication, thus maintaining the distributed nature of the controller. An example of a 10-bus, 4-machine power system is simulated to verify the proposed controller performance under sudden changes of the load demand., Comment: 2023 31st Mediterranean Conference on Control and Automation (MED2023)
- Published
- 2023
10. Deep Learning Aided Beamforming for Downlink Non-Orthogonal Multiple Access Systems
- Author
-
Konstantopoulos, Georgios and Louet, Yves
- Subjects
Electrical Engineering and Systems Science - Signal Processing - Abstract
In this work, we investigate the optimal beamformer design for the downlink of Multiple-Input Single-Output (MISO) Non-Orthogonal Multiple Access (NOMA), mainly focusing on a two-user scenario. We derive novel closed-form expressions for the Bit Error Rate (BER) experienced by both users when Quadrature Amplitude Modulation (QAM) is employed. Using these expressions, we formulate a fairness-based optimal beamforming problem aiming to minimize the maximum BER encountered by the users. Due to the complexity of this problem and the time-consuming nature of Constraint Optimization (CO) algorithms for real-time telecommunication systems, we propose a deep learning (DL) approach for its solution. The proposed DL architecture possesses specific input and output characteristics that enable the simultaneous training and use of the system by multiple different antenna schemes. By conducting extensive simulations, we demonstrate that our proposed approach outperforms existing beamforming solutions and achieves BER performance close to that given by CO algorithms while significantly reducing the computational time needed. Finally, we conduct simulations to examine the robustness and efficiency of our system in different test scenarios., Comment: This paper was submitted and is under review by IEEE Open Journal of the Communications Society
- Published
- 2023
11. Structural Evolution of the Pharmaceutical Peptide Octreotide upon Controlled Relative Humidity and Temperature Variation
- Author
-
Maria Athanasiadou, Christina Papaefthymiou, Angelos Kontarinis, Maria Spiliopoulou, Dimitrios Koutoulas, Marios Konstantopoulos, Stamatina Kafetzi, Kleomenis Barlos, Kostas K. Barlos, Natalia Dadivanyan, Detlef Beckers, Thomas Degen, Andrew N. Fitch, and Irene Margiolaki
- Subjects
humidity variation ,temperature variation ,X-ray crystallography ,peptides ,polymorphism ,octreotide ,Biology (General) ,QH301-705.5 ,Biotechnology ,TP248.13-248.65 - Abstract
Octreotide is the first synthetic peptide hormone, consisting of eight amino acids, that mimics the activity of somatostatin, a natural hormone in the body. During the past decades, advanced instrumentation and crystallographic software have established X-Ray Powder Diffraction (XRPD) as a valuable tool for extracting structural information from biological macromolecules. The latter was demonstrated by the successful structural determination of octreotide at a remarkably high d-spacing resolution (1.87 Å) (PDB code: 6vc1). This study focuses on the response of octreotide to different humidity levels and temperatures, with a particular focus on the stability of the polycrystalline sample. XRPD measurements were accomplished employing an Anton Paar MHC-trans humidity-temperature chamber installed within a laboratory X’Pert Pro diffractometer (Malvern Panalytical). The chamber is employed to control and maintain precise humidity and temperature levels of samples during XRPD data collection. Pawley analysis of the collected data sets revealed that the octreotide polycrystalline sample is remarkably stable, and no structural transitions were observed. The compound retains its orthorhombic symmetry (space group: P212121, a = 18.57744(4) Å, b = 30.17338(6) Å, c = 39.70590(9) Å, d ~ 2.35 Å). However, a characteristic structural evolution in terms of lattice parameters and volume of the unit cell is reported mainly upon controlled relative humidity variation. In addition, an improvement in the signal-to-noise ratio in the XRPD data under a cycle of dehydration/rehydration is reported. These results underline the importance of considering the impact of environmental factors, such as humidity and temperature, in the context of structure-based drug design, thereby contributing to the development of more effective and stable pharmaceutical products.
- Published
- 2024
- Full Text
- View/download PDF
12. Exploring Serum Copeptin and Hematological Profile: A Comparative Analysis after Intradermal versus Intramuscular Porcine Reproductive and Respiratory Syndrome Virus Vaccination in Piglets
- Author
-
Georgios Maragkakis, Eleni G. Katsogiannou, Georgios I. Papakonstantinou, Laskarina-Maria Korou, Serafeim C. Chaintoutis, Panagiotis Konstantopoulos, Despoina N. Perrea, Georgios Christodoulopoulos, Labrini V. Athanasiou, and Vasileios G. Papatsiros
- Subjects
blood cell counts ,copeptin ,intradermal ,serum ,pig ,PRRSV ,Biology (General) ,QH301-705.5 - Abstract
This study aimed to investigate the impact of intradermal (ID) and intramuscular (IM) vaccination with a porcine reproductive and respiratory syndrome virus (PRRSV)-modified live vaccine (MLV) in piglets on serum copeptin levels and hematological profile. This study included 104 suckling piglets (2 weeks of age) from a commercial farrow-to-finish pig farm suffering from positive unstable PRRSV status. Animals were assigned to four groups, with two replicates (13 piglets/group/replicate); group A: IM vaccination with a PRRSV MLV vaccine, group B: ID vaccination with the same vaccine, group C: ID of Diluvac Forte, and group D: IM of Diluvac Forte. Blood samples were collected from the same three pigs/group/replicate at 4, 7, and 10 weeks of age. Blood samples were used for the performance of the complete blood count, and they were also examined by PCR for PRRSV and by ELISA for copeptin. No significant differences in serum copeptin levels and the number of blood cell counts (packed cell volume—PCV, numbers of white blood cells—WBCs, and platelets number—PLTs) were noticed in the same group over time and among groups. In conclusion, it seems that the vaccination against PRRSV does not affect the levels of the released copeptin. Based on our results, the measurement of serum copeptin could not be proposed as a potential stress biomarker in pigs.
- Published
- 2024
- Full Text
- View/download PDF
13. 2022 consensus conference on diversity, equity, and inclusion: Developing an emergency medicine research agenda for addressing racism through health care research.
- Author
-
Macias-Konstantopoulos, Wendy, Newberry, Jennifer, Patel, Shama, Hess, Erik, Burner, Elizabeth, Davis, Joshua, Sanchez, Leon, and Jarman, Angela
- Subjects
Humans ,Racism ,Health Services Research ,Consensus ,Emergency Medicine ,Evidence Gaps - Abstract
Racism in emergency medicine (EM) health care research is pervasive but often underrecognized. To understand the current state of research on racism in EM health care research, we developed a consensus working group on this topic, which concluded a year of work with a consensus-building session as part of the overall Society for Academic Emergency Medicine (SAEM) consensus conference on diversity, equity, and inclusion: Developing a Research Agenda for Addressing Racism in Emergency Medicine, held on May 10, 2022. In this article, we report the development, details of preconference methods and preliminary results, and the final consensus of the Healthcare Research Working Group. Preconference work based on literature review and expert opinion identified 13 potential priority research questions that were refined through an iterative process to a list of 10. During the conference, the subgroup used consensus methodology and a consensus dollar (contingent valuation) approach to prioritize research questions. The subgroup identified three research gaps: remedies for racial bias and systematic racism, biases and heuristics in clinical care, and racism in study design, and we derived a list of six high-priority research questions for our specialty.
- Published
- 2023
14. The SAMI Survey: Evidence for dynamical coupling of ionised gas and young stellar populations
- Author
-
Foster, Caroline, Vaughan, Sam, Fraser-McKelvie, Amelia, Brough, Sarah, Bryant, Julia J., Croom, Scott M., D'Eugenio, Francesco, Groves, Brent, Konstantopoulos, Iraklis S., López-Sánchez, Ángel R., Oh, Sree, Owers, Matt S., Sweet, Sarah M., van de Sande, Jesse, Wisnioski, Emily, Yi, Sukyoung K., and Zovaro, Henry R. M.
- Subjects
Astrophysics - Astrophysics of Galaxies - Abstract
We explore local and global dynamical differences between the kinematics of ionised gas and stars in a sample of galaxies from Data Release 3 of the SAMI Galaxy Survey. We find better agreement between local (i.e., comparing on a spaxel-to-spaxel basis) velocities and dispersion of gas and stars in younger systems as with previous work on the asymmetric drift in galaxies, suggesting that the dynamics of stars and ionised gas are initially coupled. The intrinsic scatter around the velocity and dispersion relations increases with increasing stellar age and mass, suggesting that subsequent mechanisms such as internal processes, divergent star formation and assembly histories also play a role in setting and altering the dynamics of galaxies. The global (flux-weighted) dynamical support of older galaxies is hotter than in younger systems. We find that the ionised gas in galaxies is almost always dynamically colder than the stars with a steeper velocity gradient. In absolute terms, the local difference in velocity dispersion is more pronounced than the local difference in velocity, possibly reflecting inherent differences in the impact of turbulence, inflow and/or feedback on gas compared to stars. We suggest how these findings may be taken into account when comparing high and low redshift galaxy samples to infer dynamical evolution., Comment: 11 pages, 9 figures, 1 table, accepted for publication in MNRAS
- Published
- 2023
- Full Text
- View/download PDF
15. A geospatial source selector for federated GeoSPARQL querying
- Author
-
Troumpoukis, Antonis, Konstantopoulos, Stasinos, and Prokopaki-Kostopoulou, Nefeli
- Subjects
Computer Science - Databases - Abstract
Background: Geospatial linked data brings into the scope of the Semantic Web and its technologies, a wealth of datasets that combine semantically-rich descriptions of resources with their geo-location. There are, however, various Semantic Web technologies where technical work is needed in order to achieve the full integration of geospatial data, and federated query processing is one of these technologies. Methods: In this paper, we explore the idea of annotating data sources with a bounding polygon that summarizes the spatial extent of the resources in each data source, and of using such a summary as an (additional) source selection criterion in order to reduce the set of sources that will be tested as potentially holding relevant data. We present our source selection method, and we discuss its correctness and implementation. Results: We evaluate the proposed source selection using three different types of summaries with different degrees of accuracy, against not using geospatial summaries. We use datasets and queries from a practical use case that combines crop-type data with water availability data for food security. The experimental results suggest that more complex summaries lead to slower source selection times, but also to more precise exclusion of unneeded sources. Moreover, we observe the source selection runtime is (partially or fully) recovered by shorter planning and execution runtimes. As a result, the federated sources are not burdened by pointless querying from the federation engine. Conclusions: The evaluation draws on data and queries from the agroenvironmental domain and shows that our source selection method substantially improves the effectiveness of federated GeoSPARQL query processing., Comment: Published in Open Research Europe
- Published
- 2022
- Full Text
- View/download PDF
16. Mir221/222 drive synovial hyperplasia and arthritis by targeting cell cycle inhibitors and chromatin remodeling components
- Author
-
Fani Roumelioti, Christos Tzaferis, Dimitris Konstantopoulos, Dimitra Papadopoulou, Alejandro Prados, Maria Sakkou, Anastasios Liakos, Panagiotis Chouvardas, Theodore Meletakos, Yiannis Pandis, Niki Karagianni, Maria C Denis, Maria Fousteri, Maria Armaka, and George Kollias
- Subjects
miRNAs ,rheumatoid arthritis ,synovial fibroblasts ,expansion ,cell proliferation ,sc-ATAC seq ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
miRNAs constitute fine-tuners of gene expression and are implicated in a variety of diseases spanning from inflammation to cancer. miRNA expression is deregulated in rheumatoid arthritis (RA); however, their specific role in key arthritogenic cells such as the synovial fibroblast (SF) remains elusive. Previous studies have shown that Mir221/222 expression is upregulated in RA SFs. Here, we demonstrate that TNF and IL-1β but not IFN-γ activated Mir221/222 gene expression in murine SFs. SF-specific overexpression of Mir221/222 in huTNFtg mice led to further expansion of SFs and disease exacerbation, while its total ablation led to reduced SF expansion and attenuated disease. Mir221/222 overexpression altered the SF transcriptional profile igniting pathways involved in cell cycle and ECM (extracellular matrix) regulation. Validation of targets of Mir221/222 revealed cell cycle inhibitors Cdkn1b and Cdkn1c, as well as the epigenetic regulator Smarca1. Single-cell ATAC-seq data analysis revealed increased Mir221/222 gene activity in pathogenic SF subclusters and transcriptional regulation by Rela, Relb, Junb, Bach1, and Nfe2l2. Our results establish an SF-specific pathogenic role of Mir221/222 in arthritis and suggest that its therapeutic targeting in specific subpopulations could lead to novel fibroblast-targeted therapies.
- Published
- 2024
- Full Text
- View/download PDF
17. Investigating the impact of multidisciplinary prehabilitation on deconditioning in patients eligible for haematopoietic allogenic stem cell transplantation: protocol for a feasibility trial
- Author
-
Carol Maher, Ben Singh, Karlee Naumann, Samuel Bushaway, Rhiannon Crane, Swapna Deepak, Amie Hartland, Peter Konstantopoulos, Ella Mansell, Vanessa Marinelli, Vanessa Pallotta, Annabel Tolfts, Alison Virieux, Michelle Wall, Sarah Wilksch, Mabel Zhuang, and Morgan Atkinson
- Subjects
Medicine - Abstract
Background Assessing multidisciplinary prehabilitation strategies becomes crucial to pre-emptively counter the physical, psychological and social negative impacts experienced during an allogenic haematopoietic stem cell transplant (allo-HSCT) among acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS) patients. Current evidence is restricted to studies during induction chemotherapy, omitting rehabilitation interventions and predominantly using exercise-only approaches without a multidisciplinary framework. The aim of this study is to investigate the feasibility, safety and preliminary efficacy of multidisciplinary prehabilitation in adults offered allo-HSCT.Methods and analysis This 8-week single-group pre-post feasibility study aims to pilot a multidisciplinary prehabilitation intervention for participants undergoing allo-HSCT, with a focus on feasibility and safety. Participants, aged 18 or older, diagnosed with AML or MDS, and offered allo-HSCT, will be recruited between June 2023 and July 2024. The multidisciplinary prehabilitation intervention, conducted by the cancer allied health team at the Royal Adelaide Hospital, includes exercise physiology, physiotherapy, dietetics, social work, occupational therapy and psychology interventions. Consistent with a multidisciplinary treatment approach, each component is tailored to address different aspects of patient care, and adherence calculations will assess patient engagement and compliance. In addition, participants will continue to receive usual care from cancer allied health staff. The primary outcome of the study is to assess the feasibility of a multidisciplinary prehabilitation intervention by evaluating intervention uptake, retention, adherence, acceptability and safety. Secondary outcomes are leg strength, upper-body strength, aerobic fitness, falls risk, anthropometry, nutritional status, quality of life, anxiety, depression, self-efficacy for coping with cancer and distress.Ethics and dissemination Ethics approval for this study has been provided by the Central Adelaide Local Health Network (HREC 2022/HRE00284). Recruitment for the study commenced in June 2023 and will continue until July 2024. The methods have been designed and are reported according to the SPIRIT and CONSORT-pilot study checklist.Trial registration number The Australian New Zealand Clinical Trials Registry (ANZCTR): ACTRN12623000052639.
- Published
- 2024
- Full Text
- View/download PDF
18. A new class of solutions to the van Dantzig problem, the Lee-Yang property, and the Riemann hypothesis
- Author
-
Konstantopoulos, T., Patie, P., and Sarkar, R.
- Subjects
Mathematics - Probability ,Mathematical Physics ,Mathematics - Number Theory - Abstract
The purpose of this paper is to carry out an in-depth analysis of the intriguing van Dantzig problem which consists on characterizing the set $\mathbb{D}$ of analytic characteristic functions $\mathcal{F}$ which remains stable by the action of the mapping $V\mathcal{F}(t)=1/\mathcal{F}(it)$, $t\in\mathbb{R}$. % is also a characteristic function. We start by observing that the celebrated Lee-Yang property, appearing in statistical mechanics and quantum field theory, and the Riemann hypothesis can be both rephrased in terms of the van Dantzig problem, and, more specifically, in terms of the set $\mathbb{D}_L \subset \mathbb{D}$ of real-valued characteristic functions that belong to the Laguerre-P\'olya class. Motivated by these facts, we proceed by identifying several non-trivial closure properties of the set $\mathbb{D}$ and $\mathbb{D}_L$. This not only revisits but also, by means of probabilistic techniques, deepens the fascinating studies of the set of even characteristic functions in the Laguerre-P\'olya class carried out by P\'olya, de Bruijn, Lukacs, Newman and more recently by Newman and Wu, among others. We continue by providing a new class of entire functions that belong to the set $\mathbb{D}$ but not necessarily to $\mathbb{D}_L$, offering the first examples outside the set $\mathbb{D}_L$. This class, which is derived from some entire functions introduced by the second author, is in bijection with a subset of continuous negative-definite functions and includes several notable generalized hypergeometric-type functions. Besides identifying the characteristic functions, we also manage to characterize the pair of the corresponding van Dantzig random variables revealing that one of them is infinitely divisible. Finally, we investigate the possibility that the Riemann $\xi$ function belongs to this class.
- Published
- 2022
19. Enhancing shopping experiences in smart retailing
- Author
-
Bourg, Lorena, Chatzidimitris, Thomas, Chatzigiannakis, Ioannis, Gavalas, Damianos, Giannakopoulou, Kalliopi, Kasapakis, Vlasios, Konstantopoulos, Charalampos, Kypriadis, Damianos, Pantziou, Grammati, and Zaroliagis, Christos
- Published
- 2023
- Full Text
- View/download PDF
20. The SAMI Galaxy Survey: The relationship between galaxy rotation and the motion of neighbours
- Author
-
Mai, Yifan, Vaughan, Sam P., Croom, Scott M., van de Sande, Jesse, Barsanti, Stefania, Bland-Hawthorn, Joss, Brough, Sarah, Bryant, Julia J., Colless, Matthew, Goodwin, Michael, Groves, Brent, Konstantopoulos, Iraklis S., Lawrence, Jon S., Lorente, Nuria P. F., and Richards, Samuel N.
- Subjects
Astrophysics - Astrophysics of Galaxies - Abstract
Using data from the SAMI Galaxy Survey, we investigate the correlation between the projected stellar kinematic spin vector of 1397 SAMI galaxies and the line-of-sight motion of their neighbouring galaxies. We calculate the luminosity-weighted mean velocity difference between SAMI galaxies and their neighbours in the direction perpendicular to the SAMI galaxies angular momentum axes. The luminosity-weighted mean velocity offsets between SAMI and neighbours, which indicates the signal of coherence between the rotation of the SAMI galaxies and the motion of neighbours, is 9.0 $\pm$ 5.4 km s$^{-1}$ (1.7 $\sigma$) for neighbours within 1 Mpc. In a large-scale analysis, we find that the average velocity offsets increase for neighbours out to 2 Mpc. However, the velocities are consistent with zero or negative for neighbours outside 3 Mpc. The negative signals for neighbours at distance around 10 Mpc are also significant at $\sim 2$ $\sigma$ level, which indicate that the positive signals within 2 Mpc might come from the variance of large-scale structure. We also calculate average velocities of different subsamples, including galaxies in different regions of the sky, galaxies with different stellar masses, galaxy type, $\lambda_{Re}$ and inclination. Although low-mass, high-mass, early-type and low-spin galaxies subsamples show 2 - 3 $\sigma$ signal of coherence for the neighbours within 2 Mpc, the results for different inclination subsamples and large-scale results suggest that the $\sim 2 \sigma$ signals might result from coincidental scatter or variance of large-scale structure. Overall, the modest evidence of coherence signals for neighbouring galaxies within 2 Mpc needs to be confirmed by larger samples of observations and simulation studies., Comment: 14 pages, 9 figures, accepted for publication in MNRAS
- Published
- 2022
- Full Text
- View/download PDF
21. Public health management of pertussis in adults: Practical challenges and future strategies
- Author
-
C Raina MacIntyre, Jaime Correia de Sousa, Ulrich Heininger, Peter Kardos, Andreas Konstantopoulos, Donald Middleton, Terry Nolan, Alberto Papi, Adrian Rendon, Albert Rizzo, Kim Sampson, Alessandro Sette, Elizabeth Sobczyk, Tina Tan, Catherine Weil-Olivier, Birgit Weinberger, Tom Wilkinson, and Carl Heinz Wirsing von König
- Subjects
Bordetella pertussis ,disease burden ,under-reporting ,Tdap vaccination ,adults ,comorbidities ,Immunologic diseases. Allergy ,RC581-607 ,Therapeutics. Pharmacology ,RM1-950 - Abstract
A panel of 24 international experts met in July 2022 to discuss challenges associated with pertussis detection, monitoring, and vaccination in adults; conclusions from this meeting are presented. There has been a shift in the epidemiology of pertussis toward older children and adults. This shift has been attributed to the waning of infection- or vaccine-induced immunity, newer detection techniques causing detection bias, and possibly the replacement of whole-cell pertussis with acellular vaccines in high-income countries, which may lead to immunity waning more quickly. The burden of adult pertussis is still likely under-ascertained due to widespread under-recognition by healthcare professionals (HCPs), under-diagnosis, and under-reporting in this age group. Non-standardized testing guidance and varied case definitions have contributed to under-reporting. Key barriers to HCP engagement with the tetanus, diphtheria, and pertussis (Tdap) vaccine include low awareness, lack of time/funding, and lack of motivation due to low prioritization of Tdap.
- Published
- 2024
- Full Text
- View/download PDF
22. Understanding the impact of adult pertussis and current approaches to vaccination: A narrative review and expert panel recommendations
- Author
-
Peter Kardos, Jaime Correia de Sousa, Ulrich Heininger, Andreas Konstantopoulos, C. Raina MacIntyre, Donald Middleton, Terry Nolan, Alberto Papi, Adrian Rendon, Albert Rizzo, Kim Sampson, Alessandro Sette, Elizabeth Sobczyk, Tina Tan, Catherine Weil-Olivier, Birgit Weinberger, Tom Wilkinson, and Carl Heinz Wirsing von König
- Subjects
Bordetella pertussis ,disease burden ,underreporting ,Tdap vaccination ,adults ,Immunologic diseases. Allergy ,RC581-607 ,Therapeutics. Pharmacology ,RM1-950 - Abstract
ABSTRACTPertussis has several notable consequences, causing economic burden, increased strain on healthcare facilities, and reductions in quality of life. Recent years have seen a trend toward an increase in pertussis cases affecting older children and adults. To boost immunity, and protect vulnerable populations, an enduring approach to vaccination has been proposed, but gaps remain in the evidence surrounding adult vaccination that are needed to inform such a policy. Gaps include: the true incidence of pertussis and its complications in adults; regional variations in disease recognition and reporting; and incidence of severe disease, hospitalizations, and deaths in older adults. Better data on the efficacy/effectiveness of pertussis vaccination in adults, duration of protection, and factors leading to poor vaccine uptake are needed. Addressing the critical evidence gaps will help highlight important areas of unmet need and justify the importance of adult pertussis vaccination to healthcare professionals, policymakers, and payers.
- Published
- 2024
- Full Text
- View/download PDF
23. SCALA: A complete solution for multimodal analysis of single-cell Next Generation Sequencing data.
- Author
-
Tzaferis, Christos, Karatzas, Evangelos, Baltoumas, Fotis, Pavlopoulos, Georgios, Kollias, George, and Konstantopoulos, Dimitris
- Subjects
Automated analysis of single-cell Next Generation Sequencing data ,Integrative analysis of single-cell Next Generation Sequencing data ,Single-cell ATAC-seq analysis ,Single-cell RNA sequencing analysis - Abstract
Analysis and interpretation of high-throughput transcriptional and chromatin accessibility data at single-cell (sc) resolution are still open challenges in the biomedical field. The existence of countless bioinformatics tools, for the different analytical steps, increases the complexity of data interpretation and the difficulty to derive biological insights. In this article, we present SCALA, a bioinformatics tool for analysis and visualization of single-cell RNA sequencing (scRNA-seq) and Assay for Transposase-Accessible Chromatin using sequencing (scATAC-seq) datasets, enabling either independent or integrative analysis of the two modalities. SCALA combines standard types of analysis by integrating multiple software packages varying from quality control to the identification of distinct cell populations and cell states. Additional analysis options enable functional enrichment, cellular trajectory inference, ligand-receptor analysis, and regulatory network reconstruction. SCALA is fully parameterizable, presenting data in tabular format and producing publication-ready visualizations. The different available analysis modules can aid biomedical researchers in exploring, analyzing, and visualizing their data without any prior experience in coding. We demonstrate the functionality of SCALA through two use-cases related to TNF-driven arthritic mice, handling both scRNA-seq and scATAC-seq datasets. SCALA is developed in R, Shiny and JavaScript and is mainly available as a standalone version, while an online service of more limited capacity can be found at http://scala.pavlopouloslab.info or https://scala.fleming.gr.
- Published
- 2023
24. Racial Differences in Triage for Emergency Department Patients with Subjective Chief Complaints
- Author
-
Peitzman, Cassandra, Carreras Tartak, Jossie A., Samuels-Kalow, Margaret, Raja, Ali, and Macias-Konstantopoulos, Wendy L.
- Subjects
Disparities ,Triage ,Emergency Medicine ,Racial Disparities - Abstract
Introduction: Black and Hispanic patients are frequently assigned lower acuity triage scores than White patients. This can lead to longer wait times, less aggressive care, and worse outcomes. In this study we aimed to determine whether these effects are more pronounced for patients with subjective complaints.Methods: We performed a retrospective analysis for all adult visits between 2016-2019 at an urban academic emergency department (ED) with acuity-based pods. We determined rates of initial high-acuity triage both across all patients and among the subset located in the high-acuity pod at time of disposition (either through initial assignment or subsequent up-triage). Analysis was performed for common chief complaints categorized as subjective (chest pain, dyspnea, any pain); observed (altered mental status); numeric (fever, hypotension); or protocolized (stroke, ST-elevation myocardial infarction). We constructed logistic regression models to control for age, race, gender, method of arrival, and final disposition.Results: We analyzed 297,355 adult ED visits. Black and Hispanic patients were less likely to be triaged to high-acuity beds (adjusted odds ratio [aOR] 0.76, 95% confidence interval [CI] 0.73-0.79 for Black, and aOR 0.87, 95% CI 0.84-0.90 for Hispanic patients). This effect was more pronounced for those with subjective chief complaints, including chest pain (aOR 0.76, 95% CI 0.73-0.79 for Black and 0.88, 95% CI 0.78-0.99 for Hispanic patients), dyspnea (aOR 0.79, 95% CI 0.68-0.92 and 0.8, 95% CI 0.72-0.99), and any pain (aOR 0.83, 95% CI 0.75-0.92 and 0.89, 95% CI 0.82-0.97, respectively). Among patients in the high-acuity pod at time of disposition, Black and Hispanic patients were disproportionately triaged to lower acuity pods on arrival (aOR 1.47, 95% CI 1.33-1.63 for Black and aOR 1.27, 95% CI 1.15-1.40 for Hispanic adults), with significant differences observed only for subjective chief complaints. No differences were observed for observed, objective, or protocolized complaints in either analysis.Conclusion: Black and Hispanic adults, including those who ultimately required high-acuity resources, were disproportionately triaged to lower acuity pods. This effect was more pronounced for patients with subjective chief complaints. Additional work is needed to identify and overcome potential bias in the assessment of patients with subjective chief complaints in ED triage.
- Published
- 2023
25. Race, Healthcare, and Health Disparities: A Critical Review and Recommendations for Advancing Health Equity
- Author
-
Macias-Konstantopoulos, Wendy L., Collins, Kimberly A., Diaz, Rosemarie, Duber, Herbert C., Edwards, Courtney D., Hsu, Anthony P., Ranney, Megan L., Riviello, Ralph J., Wettstein, Zachary S., and Sachs, Carolyn J.
- Subjects
health disparities ,social determinants of health ,structural racism ,implicit bias - Abstract
An overwhelming body of evidence points to an inextricable link between race and health disparities in the United States. Although race is best understood as a social construct, its role in health outcomes has historically been attributed to increasingly debunked theories of underlying biological and genetic differences across races. Recently, growing calls for health equity and social justice have raised awareness of the impact of implicit bias and structural racism on social determinants of health, healthcare quality, and ultimately, health outcomes. This more nuanced recognition of the role of race in health disparities has, in turn, facilitated introspective racial disparities research, root cause analyses, and changes in practice within the medical community. Examining the complex interplay between race, social determinants of health, and health outcomes allows systems of health to create mechanisms for checks and balances that mitigate unfair and avoidable health inequalities.As one of the specialties most intertwined with social medicine, emergency medicine (EM) is ideally positioned to address racism in medicine, develop health equity metrics, monitor disparities in clinical performance data, identify research gaps, implement processes and policies to eliminate racial health inequities, and promote anti-racist ideals as advocates for structural change. In this critical review our aim was to (a) provide a synopsis of racial disparities across a broad scope of clinical pathology interests addressed in emergency departments—communicable diseases, non-communicable conditions, and injuries—and (b) through a race-conscious analysis, develop EM practice recommendations for advancing a culture of equity with the potential for measurable impact on healthcare quality and health outcomes.
- Published
- 2023
26. From the Editors – Future Directions to Strengthen the Emergency Department Safety Net
- Author
-
Salhi, Rama, Macias-Konstantopoulos, Wendy L., and Ryus, Caitlin R.
- Published
- 2023
27. Violence and Abuse: A Pandemic Within a Pandemic
- Author
-
Whiteman, Paula J., Macias-Konstantopoulos, Wendy L., Relan, Pryanka, Knopov, Anita, Ranney, Megan L., and Riviello, MD, MS, Ralph J
- Subjects
violence ,abuse ,domestic violence ,gun violence ,COVID 19 - Abstract
Introduction: During the COVID-19 pandemic, as society struggled with increasing disease burden, economic hardships, and with disease morbidity and mortality, governments and institutions began implementing stay-at-home or shelter-in-place orders to help stop the spread of the virus. Although well-intentioned, one unintended adverse consequence was an increase in violence, abuse, and neglect.Methods: We reviewed the literature on the effect the pandemic had on domestic violence, child and elder abuse and neglect, human trafficking, and gun violence. In this paper we explore common themes and causes of this violence and offer suggestions to help mitigate risk during ongoing and future pandemics. Just as these forms of violence primarily target at-risk, vulnerable populations, so did pandemic-related violence target marginalized populations including women, children, Blacks, and those with lower socioeconomic status. This became, and remains, a public health crisis within a crisis. In early 2021, the American College of Emergency Physicians (ACEP) Public Health and Injury Committee was tasked with reviewing the impact the pandemic had on violence and abuse as the result of a resolution passed at the 2020 ACEP Council meeting.Conclusion: Measures meant to help control the spread of the COVID-19 pandemic had many unintended consequences and placed people at risk for violence. Emergency departments (ED), although stressed and strained during the pandemic, remain a safety net for survivors of violence. As we move out of this pandemic, hospitals and EDs need to focus on steps that can be taken to ensure they preserve and expand their ability to assist victims should another pandemic or global health crisis develop.Keywords: pandemic; elder abuse; human trafficking; COVID-19; gun violence; intimate partner violence; child abuse; fear.
- Published
- 2023
28. Optimizing Recruitment and Retention in Substance Use Disorder Research in Emergency Departments
- Author
-
Worth, Lindsay, Macias-Konstantopoulos, Wendy, Moy, Lauren, Perl, Harold, Crandall, Cameron, Chavez, Roberta, Forcehimes, Alyssa, and Bogenschutz, Michael P.
- Subjects
Recruitment ,Retention ,Substance Use Disorder ,Emergency Departmetnt - Abstract
Introduction: Clinical trial recruitment and retention of individuals who use substances are challenging in any setting and can be particularly difficult in emergency department (ED) settings. This article discusses strategies for optimizing recruitment and retention in substance use research conducted in EDs.Methods: Screening, Motivational Assessment, Referral, and Treatment in Emergency Departments (SMART-ED) was a National Drug Abuse Treatment Clinical Trials Network (CTN) protocol designed to assess the impact of a brief intervention with individuals screening positive for moderate to severe problems related to use of non-alcohol, non-nicotine drugs. We implemented a multisite, randomized clinical trial at six academic EDs in the United States and leveraged a variety of methods to successfully recruit and retain study participants throughout the 12-month study course. Recruitment and retention success is attributed to appropriate site selection, leveraging technology, and gathering adequate contact information from participants at their initial study visit.Results: The SMART-ED recruited 1,285 adult ED patients and attained follow-up rates of 88%, 86%, and 81% at the 3-, 6-, and 12-month follow-up periods, respectively. Participant retention protocols and practices were key tools in this longitudinal study that required continuous monitoring, innovation, and adaptation to ensure strategies remained culturally sensitive and context appropriate through the duration of the study.Conclusion: Tailored strategies that consider the demographic characteristics and region of recruitment and retention are necessary for ED-based longitudinal studies involving patients with substance use disorders.
- Published
- 2023
29. Incorporation of a Case-based Health Equity Curriculum into Morbidity and Mortality Conference
- Author
-
Carreras Tartak, Jossie A., Rodriguez, Giovanni, Goralnick, Eric, Macias-Konstantopoulos, Wendy L., and Egan, Daniel J.
- Subjects
morbidity and mortality ,curriculum development ,health equity ,structural competency - Published
- 2023
30. A Teach-the-Teacher Module for Human Trafficking Bedside Instruction
- Author
-
Anthony Young, Shannon Findlay, Michael Cole, James A. Cranford, Michelle Daniel, Harrison Alter, Makini Chisolm-Straker, Wendy L. Macias-Konstantopoulos, Wendi-Jo Wendt, and Hanni Stoklosa
- Subjects
Human Trafficking ,Labor Trafficking ,Public Health ,Sex Trafficking ,Train-the-Trainer ,Case-Based Learning ,Medicine (General) ,R5-920 ,Education - Abstract
Introduction Human trafficking (HT) is a public health issue that adversely affects patients’ well-being. Despite the prevalence of trafficked persons in health care settings, a lack of educational modules exists for use in clinical contexts. We developed a 50-minute train-the-trainer module on HT. Methods After piloting the workshop for faculty, fellows, and residents (n = 19) at the Society for Academic Emergency Medicine (SAEM) national conference, we implemented it in medical students’ curricula during their emergency medicine clerkship at the University of Iowa (n = 162). We evaluated the worskhop by (a) a retrospective pre-post survey of self-reported ability to (1) define HT, (2) recognize high-risk signs, (3) manage situations with trafficked persons, and (4) teach others about HT, and (b) a 3-month follow-up survey to assess longitudinal behavior change. Results In both contexts, results demonstrated improvement across all learning outcomes (pre-post differences of 1.5, 1.3, 1.9, and 1.7 on a 4-point Likert-type scale for each learning objective above, respectively, at the SAEM conference and 1.2, 1.0, 1.3, and 1.3 at the University of Iowa; p < .001 for all). In the 3-month follow-up, we observed statistically significant changes in self-reported consideration of and teaching about HT during clinical encounters among learners who had previously never done either (p < .001 and p = .006, respectively). Discussion This train-the-trainer module is a brief and effective clinical tool for bedside teaching about HT, especially among people who have never previously considered HT in a clinical context.
- Published
- 2024
- Full Text
- View/download PDF
31. A guide to caring for patients who identify as transgender and gender diverse in the emergency department
- Author
-
Logan Jardine, Courtney Edwards, Hannah Janeway, Chance Krempasky, Wendy Macias‐Konstantopoulos, Paula Whiteman, and Antony Hsu
- Subjects
delivery of healthcare ,emergency medicine ,gender‐affirming care ,health inequities ,medical education ,social determinants of health ,Medical emergencies. Critical care. Intensive care. First aid ,RC86-88.9 - Abstract
Abstract Through a review of current research, standards of care, and best practices, this paper serves as a resource for emergency physicians (EPs) caring for persons who identify as transgender and gender diverse (T/GD) in the emergency department (ED). Both patient‐ and physician‐based research have identified existent potential knowledge gaps for EPs caring for T/GD in the ED. T/GD have negative experiences related to their gender identity when seeking emergency medical care and may even delay emergency care for fear of discrimination. Through the lens of cultural humility, this paper aims to address potential knowledge gaps for EPs, identify and reduce barriers to care, highlight gender‐affirming hospital policies and protocols, and improve the care and experience of T/GD in the ED.
- Published
- 2024
- Full Text
- View/download PDF
32. Mitigation of Cyberattacks through Battery Storage for Stable Microgrid Operation
- Author
-
Zografopoulos, Ioannis, Karamichailidis, Panagiotis, Procopiou, Andreas T., Teng, Fei, Konstantopoulos, George C., and Konstantinou, Charalambos
- Subjects
Electrical Engineering and Systems Science - Systems and Control - Abstract
In this paper, we present a mitigation methodology that leverages battery energy storage system (BESS) resources in coordination with microgrid (MG) ancillary services to maintain power system operations during cyberattacks. The control of MG agents is achieved in a distributed fashion, and once a misbehaving agent is detected, the MG's mode supervisory controller (MSC) isolates the compromised agent and initiates self-healing procedures to support the power demand and restore the compromised agent. Our results demonstrate the practicality of the proposed attack mitigation strategy and how grid resilience can be improved using BESS synergies. Simulations are performed on a modified version of the Canadian urban benchmark distribution model., Comment: IEEE SmartGridComm 2022 - Camera Ready
- Published
- 2022
33. A Survey of Traversability Estimation for Mobile Robots
- Author
-
Sevastopoulos, Christos and Konstantopoulos, Stations
- Subjects
Computer Science - Robotics - Abstract
Traversability illustrates the difficulty of driving through a specific region and encompasses the suitability of the terrain for traverse based on its physical properties, such as slope and roughness, surface condition, etc. In this survey we highlight the merits and limitations of all the major steps in the evolution of traversability estimation techniques, covering both non-trainable and machine-learning methods, leading up to the recent proliferation of deep learning literature. We discuss how the nascence of Deep Learning has created an opportunity for radical improvement in traversability estimation. Finally, we discuss how self-supervised learning can help satisfy deep methods' increased need for (challenging to acquire and label) large-scale datasets.
- Published
- 2022
34. Deep Learning Aided Beamforming for Downlink Non-Orthogonal Multiple Access Systems
- Author
-
Georgios Konstantopoulos and Yves Louet
- Subjects
Bit error rate ,deep learning ,MISO ,neural networks ,NOMA ,QAM ,Telecommunication ,TK5101-6720 ,Transportation and communications ,HE1-9990 - Abstract
In this work, we investigate the optimal beamformer design for the downlink of Multiple-Input Single-Output (MISO) Non-Orthogonal Multiple Access (NOMA), mainly focusing on a two-user scenario. We derive novel closed-form expressions for the Bit Error Rate (BER) experienced by both users when Quadrature Amplitude Modulation (QAM) is employed. Using these expressions, we formulate a fairness-based optimal beamforming problem aiming to minimize the maximum BER encountered by the users. Due to the complexity of this problem and the time-consuming nature of Constraint Optimization (CO) algorithms for real-time telecommunication systems, we propose a deep learning (DL) approach for its solution. The proposed DL architecture possesses specific input and output characteristics that enable the simultaneous training and use of the system by multiple different antenna schemes. By conducting extensive simulations, we demonstrate that our proposed approach outperforms existing beamforming solutions and achieves BER performance close to that given by CO algorithms while significantly reducing the computational time needed. Finally, we conduct simulations to examine the robustness and efficiency of our system in different test scenarios.
- Published
- 2024
- Full Text
- View/download PDF
35. Cyber-physical components of an autonomous and scalable SLES
- Author
-
Verba, Nandor, Baldivieso-Monasterios, Pablo, Dong, Siyuan, Braitor, Andrei, Konstantopoulos, George, Gaura, Elena, Morris, Euan, Halford, Alison, and Stephen, Colin
- Subjects
Computer Science - Networking and Internet Architecture - Abstract
Adding renewable energy sources and storage units to an electric grid has led to a change in the way energy is generated and billed. This shift cannot be managed without a unified view of energy systems and their components. This unified view is captured within the idea of a Smart Local Energy System (SLES). Currently, various isolated control and market elements are proposed to resolve network constraints, demand side response and utility optimisation. They rely on topology estimations, forecasting and fault detection methods to complete their tasks. This disjointed design has led to most systems being capable of fulfilling only a single role or being resistant to change and extensions in functionality. By allocating roles, functional responsibilities and technical requirements to bounded systems a more unified view of energy systems can be achieved. This is made possible by representing an energy system as a distributed peer-to-peer (P2P) environment where each individual demand energy resource (DER) on the consumer's side of the meter is responsible for their portion of the network and can facilitate trade with numerous entities including the grid. Advances in control engineering, markets and services such as forecasting, topology identification and cyber-security can enable such trading and communication to be done securely and robustly. To enable this advantage however, we need to redefine how we view the design of the sub-systems and interconnections within smart local energy systems (SLES). In this paper we describe a way in which whole system design could be achieved by integrating control, markets and analytics into each system. We propose the use of physical, control, market and service layers to create system of systems representation., Comment: 14 Pages White paper
- Published
- 2022
36. Two-layer nonlinear control of DC-DC buck converters with meshed network topology
- Author
-
Baldivieso-Monasterios, Pablo R., Sadabadi, Mahdieh, and Konstantopoulos, George C.
- Subjects
Electrical Engineering and Systems Science - Systems and Control - Abstract
In this paper, we analyse the behaviour of a buck converter network that contains arbitrary, up to mild regularity assumptions, loads. Our analysis of the network begins with the study of the current dynamics; we propose a novel Lyapunov function for the current in closed-loop with a bounded integrator. We leverage on these results to analyse the interaction properties between voltages and bounded currents as well as between node voltages and to propose a two-layer optimal controller that keeps network voltages within a compact neighbourhood of the nominal operational voltage. We analyse the stability of the closed loop system in two ways: one considering the interconnection properties which yields a weaker ISS type property and a second that contemplates the network in closed loop with a distributed optimal controller. For the latter, we propose a novel distributed way of controlling a Laplacian network using neighbouring information which results in asymptotic stability. We demonstrate our results in a meshed topology network containing 6 power converters, each converter feeding an individual constant power load with values chaning arbitrarily within a pre-specified range.
- Published
- 2021
37. Superhydrophobicity, Photocatalytic Self-Cleaning and Biocidal Activity Combined in a Siloxane-ZnO Composite for the Protection of Limestone
- Author
-
Panagiotis N. Manoudis, Ioannis Zuburtikudis, Georgios Konstantopoulos, Hadil Abu Khalifeh, Christine Kottaridi, and Ioannis Karapanagiotis
- Subjects
superhydrophobic ,water repellent ,photocatalytic ,biocide ,antibacterial ,zinc oxide ,Technology - Abstract
The erosion phenomena of the natural stone in cultural heritage are induced by various sources. Consequently, the development of multifunctional protective materials that combine two or more useful properties is an effective strategy in addressing the synergistic effects of various erosion mechanisms. A multifunctional coating, consisting of a silane-based precursor and zinc oxide (ZnO) nanoparticles (NPs), is produced and tested for the protection of limestone. The hybrid coating combines the following three properties: superhydrophobicity, including water-repellency, photocatalytic self-cleaning and biocidal activity. The relative concentration of the NPs (0.8% w/w), used for the suggested composite coating, is carefully selected according to wetting studies, colourimetric measurements and durability (tape peeling) tests. The non-wetting state is evidenced on the surface of the composite coating by the large contact angle of water drops (≈153°) and the small contact angle hysteresis (≈5°), which gives rise to a physical self-cleaning scenario (lotus effect). The photocatalytic chemical self-cleaning is shown with the removal of methylene blue, induced by UV-A radiation. Moreover, it is shown that the suggested coating hinders the incubation of E. coli and S. aureus, as the inhibitions are 94.8 and 99.9%, respectively. Finally, preliminary studies reveal the chemical stability of the suggested coating.
- Published
- 2024
- Full Text
- View/download PDF
38. Power Analysis for Moderator Effects in Longitudinal Cluster Randomized Designs
- Author
-
Li, Wei and Konstantopoulos, Spyros
- Abstract
Cluster randomized control trials often incorporate a longitudinal component where, for example, students are followed over time and student outcomes are measured repeatedly. Besides examining how intervention effects induce changes in outcomes, researchers are sometimes also interested in exploring whether intervention effects on outcomes are modified by moderator variables at the individual (e.g., gender, race/ethnicity) and/or the cluster level (e.g., school urbanicity) over time. This study provides methods for statistical power analysis of moderator effects in two- and three-level longitudinal cluster randomized designs. Power computations take into account clustering effects, the number of measurement occasions, the impact of sample sizes at different levels, covariates effects, and the variance of the moderator variable. Illustrative examples are offered to demonstrate the applicability of the methods.
- Published
- 2023
- Full Text
- View/download PDF
39. Class Size and Teacher Effects on Non-Cognitive Outcomes in Grades K-3: A Fixed Effects Analysis of ECLS-K:2011 Data
- Author
-
Konstantopoulos, Spyros and Shen, Ting
- Abstract
This study examines the association between class size, teacher characteristics and five non-cognitive student outcomes (i.e., self-control, interpersonal skills, approaches to learning, externalizing and internalizing problem behaviors) in grades K-3. Individual fixed-effects, that control for observed and unobserved time-invariant factors, including student and school time-constant variables, are employed to analyze national data from the Early Childhood Longitudinal Study, Kindergarten Class of 2010-11 (ECLS-K:2011). Results suggest a significant linear association between reducing class size and interpersonal skills. Teacher experience is saliently, positively and significantly related with student self-control, interpersonal skills, and approaches to learning, and negatively associated with externalizing problem behaviors. Teacher education and certification were not associated with any of the five non-cognitive outcomes. Changing schools had a negative effect on student's self-control.
- Published
- 2023
- Full Text
- View/download PDF
40. Estimation of the last passage percolation constant in a charged complete directed acyclic graph via perfect simulation
- Author
-
Foss, Sergey, Konstantopoulos, Takis, Mallein, Bastien, and Ramassamy, Sanjay
- Subjects
Mathematics - Probability ,82M31, 60K15, 60G10, 05C80 - Abstract
Our object of study is the asymptotic growth of heaviest paths in a charged (weighted with signed weights) complete directed acyclic graph. Edge charges are i.i.d. random variables with common distribution $F$ supported on $[-\infty,1]$ with essential supremum equal to $1$ (a charge of $-\infty$ is understood as the absence of an edge). The asymptotic growth rate is a constant that we denote by $C(F)$. Even in the simplest case where $F=p\delta_1 + (1-p)\delta_{-\infty}$, corresponding to the longest path in the Barak-Erd\H{o}s random graph, there is no closed-form expression for this function, but good bounds do exist. In this paper we construct a Markovian particle system that we call "Max Growth System" (MGS), and show how it is related to the charged random graph. The MGS is a generalization of the Infinite Bin Model that has been the object of study of a number of papers. We then identify a random functional of the process that admits a stationary version and whose expectation equals the unknown constant $C(F)$. Furthermore, we construct an effective perfect simulation algorithm for this functional which produces samples from the random functional., Comment: 17 pages, 3 figures. Final accepted version
- Published
- 2021
- Full Text
- View/download PDF
41. Author Correction: Experimental and theoretical model for the origin of coiling of cellular protrusions around fibers
- Author
-
Sadhu, Raj Kumar, Hernandez-Padilla, Christian, Eisenbach, Yael Eshed, Penič, Samo, Zhang, Lixia, Vishwasrao, Harshad D., Behkam, Bahareh, Konstantopoulos, Konstantinos, Shroff, Hari, Iglič, Aleš, Peles, Elior, Nain, Amrinder S., and Gov, Nir S.
- Published
- 2023
- Full Text
- View/download PDF
42. Experimental and theoretical model for the origin of coiling of cellular protrusions around fibers
- Author
-
Sadhu, Raj Kumar, Hernandez-Padilla, Christian, Eisenbach, Yael Eshed, Penič, Samo, Zhang, Lixia, Vishwasrao, Harshad D., Behkam, Bahareh, Konstantopoulos, Konstantinos, Shroff, Hari, Iglič, Aleš, Peles, Elior, Nain, Amrinder S., and Gov, Nir S.
- Published
- 2023
- Full Text
- View/download PDF
43. P-15 Changing indications for penetrating keratoplasty and 5-years survival outcomes – a single tertiary centre experience
- Author
-
David Anderson, Aristides Konstantopoulos, Parwez Hossain, Harinderjeet Sandhu, and Jan Sniatecki
- Subjects
Ophthalmology ,RE1-994 - Published
- 2024
- Full Text
- View/download PDF
44. P19 Regulation of monocyte intracellular metabolism in the inflammatory environment of systemic lupus erythematosus (SLE)
- Author
-
Prodromos Sidiropoulos, George Bertsias, Despoina Kosmara, Chrysoula Stathopoulou, Konstantina Pambouka, Sofia Papanikolaou, Dimitra Nikoleri, Dimitris Konstantopoulos, and Maria Semitekolou
- Subjects
Immunologic diseases. Allergy ,RC581-607 - Published
- 2024
- Full Text
- View/download PDF
45. P75 Molecular exploration of systemic lupus erythematosus (SLE) sexual dimorphism uncovers a crucial role of SMC1A in transcriptional regulation of inflammation
- Author
-
Prodromos Sidiropoulos, George Bertsias, Despoina Kosmara, Aggelos Banos, Dimitrios Boumpas, Chrysoula Stathopoulou, Sofia Papanikolaou, Dimitris Konstantopoulos, and Giannis Vatsellas
- Subjects
Immunologic diseases. Allergy ,RC581-607 - Published
- 2024
- Full Text
- View/download PDF
46. A novel machine learning method to exploit EBSD and nanoindentation for TRIP steels microstructures analysis
- Author
-
Federico Bruno, Georgios Konstantopoulos, Gianluca Fiore, Edoardo Rossi, Marco Sebastiani, Costas Charitidis, Luca Belforte, and Mauro Palumbo
- Subjects
Machine learning ,High-speed nanoindentation mapping ,Correlative analysis ,Steel ,Microstructure ,Materials of engineering and construction. Mechanics of materials ,TA401-492 - Abstract
The recognition of phases and microstructures in TRIP-assisted bainitic-ferritic steels is challenging and requires sophisticated techniques to gain insights and reveal mechanical features with nanoscale precision. EBSD and nanoindentation have been employed to assess the surface composition and their properties within a reporting depth of 30 nm. Correlative mechanical microscopy and data science were used to overcome the shortcomings associated with the lack of an inclusive solution that combines the metadata from both techniques. A modular methodology is presented, which involves routines for exploiting structural and mechanical data via reproducible Machine Learning models (code and data are shared). The approach is structured to facilitate reuse by research community for correlating characterization mapping data, not limited to nanoindentation and EBSD. Gaussian mixture models are adopted to extract mechanical phases utilizing the nanomechanical properties. The K-means++ method is used for the first time to mine information from Inverse Polar Figure (IPF) mapping about anisotropy and to extract the knowledge from images for each grain, including grain coordinates and size. Moreover, k-nearest-neighbours regression was used to perform data imputation to fill in the values of descriptors related to missing coordinates relative to those of nanoindentation, grain boundary, EBSD phase, and EBSD anisotropy maps.
- Published
- 2024
- Full Text
- View/download PDF
47. The energy revolution: cyber physical advances and opportunities for smart local energy systems
- Author
-
Verba, Nandor, Gaura, Elena, McArthur, Stephen, Konstantopoulos, George, Wu, Jianzhoug, Fan, Zhong, Athanasiadis, Dimitrios, Monasterios, Pablo Rodolfo Baldivieso, Morris, Euan, and Hardy, Jeffrey
- Subjects
Electrical Engineering and Systems Science - Systems and Control - Abstract
We have designed a two-stage, 10-step process to give organisations a method to analyse small local energy systems (SLES) projects based on their Cyber Physical System components in order to develop future-proof energy systems. SLES are often developed for a specific range of use cases and functions, and these match the specific requirements and needs of the community, location or site under consideration. During the design and commissioning, new and specific cyber physical architectures are developed. These are the control and data systems that are needed to bridge the gap between the physical assets, the captured data and the control signals. Often, the cyber physical architecture and infrastructure is focused on functionality and the delivery of the specific applications. But we find that technologies and approaches have arisen from other fields that, if used within SLES, could support the flexibility, scalability and reusability vital to their success. As these can improve the operational data systems then they can also be used to enhance predictive functions If used and deployed effectively, these new approaches can offer longer term improvements in the use and effectiveness of SLES, while allowing the concepts and designs to be capitalised upon through wider roll-out and the offering of commercial services or products., Comment: White Paper on Cyber Physical Advances relevant to Smart Local Energy Systems
- Published
- 2021
- Full Text
- View/download PDF
48. Age of Information for Small Buffer Systems
- Author
-
Kesidis, George, Konstantopoulos, Takis, and Zazanis, Michael
- Subjects
Computer Science - Performance ,Mathematics - Probability - Abstract
Consider a message processing system whose objective is to produce the most current information as measured by the quantity known as "age of information". We have argued in previous papers that if we are allowed to design the message processing policy ad libitum, we should keep a small buffer and operate according to a LIFO policy. In this small note we provide an analysis for the AoI of the P_m system which uses a buffer of size m, a single server, operating without service preemption and in a LIFO manner for stored messages. Analytical expressions for the mean (or even distribution) of the AoI in steady-state are possible but with the aid computer algebra. We explain the the analysis for m=3.
- Published
- 2021
49. Experimental and theoretical model for the origin of coiling of cellular protrusions around fibers
- Author
-
Raj Kumar Sadhu, Christian Hernandez-Padilla, Yael Eshed Eisenbach, Samo Penič, Lixia Zhang, Harshad D. Vishwasrao, Bahareh Behkam, Konstantinos Konstantopoulos, Hari Shroff, Aleš Iglič, Elior Peles, Amrinder S. Nain, and Nir S. Gov
- Subjects
Science - Abstract
Abstract Protrusions at the leading-edge of a cell play an important role in sensing the extracellular cues during cellular spreading and motility. Recent studies provided indications that these protrusions wrap (coil) around the extracellular fibers. However, the physics of this coiling process, and the mechanisms that drive it, are not well understood. We present a combined theoretical and experimental study of the coiling of cellular protrusions on fibers of different geometry. Our theoretical model describes membrane protrusions that are produced by curved membrane proteins that recruit the protrusive forces of actin polymerization, and identifies the role of bending and adhesion energies in orienting the leading-edges of the protrusions along the azimuthal (coiling) direction. Our model predicts that the cell’s leading-edge coils on fibers with circular cross-section (above some critical radius), but the coiling ceases for flattened fibers of highly elliptical cross-section. These predictions are verified by 3D visualization and quantitation of coiling on suspended fibers using Dual-View light-sheet microscopy (diSPIM). Overall, we provide a theoretical framework, supported by experiments, which explains the physical origin of the coiling phenomenon.
- Published
- 2023
- Full Text
- View/download PDF
50. Class size and teacher effects on non-cognitive outcomes in grades K-3: a fixed effects analysis of ECLS-K:2011 data
- Author
-
Spyros Konstantopoulos and Ting Shen
- Subjects
Class-size ,Teacher characteristics ,Non-cognitive skills ,Fixed effects estimation ,ECLS-K:2011 ,Education (General) ,L7-991 - Abstract
Abstract This study examines the association between class size, teacher characteristics and five non-cognitive student outcomes (i.e., self-control, interpersonal skills, approaches to learning, externalizing and internalizing problem behaviors) in grades K-3. Individual fixed-effects, that control for observed and unobserved time-invariant factors, including student and school time-constant variables, are employed to analyze national data from the Early Childhood Longitudinal Study, Kindergarten Class of 2010–11 (ECLS-K:2011). Results suggest a significant linear association between reducing class size and interpersonal skills. Teacher experience is saliently, positively and significantly related with student self-control, interpersonal skills, and approaches to learning, and negatively associated with externalizing problem behaviors. Teacher education and certification were not associated with any of the five non-cognitive outcomes. Changing schools had a negative effect on student’s self-control.
- Published
- 2023
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.