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Book ; Online: Competitive Search in the Line and the Star with Predictions

Angelopoulos, Spyros

2023

Abstract: We study the classic problem of searching for a hidden target in the line and the $m$-ray star, in a setting in which the searcher has some prediction on the hider's position. We first focus on the main metric for comparing search strategies under ... ...

Abstract	We study the classic problem of searching for a hidden target in the line and the $m$-ray star, in a setting in which the searcher has some prediction on the hider's position. We first focus on the main metric for comparing search strategies under predictions; namely, we give positive and negative results on the consistency-robustness tradeoff, where the performance of the strategy is evaluated at extreme situations in which the prediction is either error-free, or adversarially generated, respectively. For the line, we show tight bounds concerning this tradeoff, under the untrusted advice model, in which the prediction is in the form of a $k$-bit string which encodes the responses to $k$ binary queries. For the star, we give tight, and near-tight tradeoffs in the positional and the directional models, in which the prediction is related to the position of the target within the star, and to the ray on which the target hides, respectively. Last, for all three prediction models, we show how to generalize our study to a setting in which the performance of the strategy is evaluated as a function of the searcher's desired tolerance to prediction errors, both in terms of positive and inapproximability results. Comment: Conference version in MFCS 2023
Keywords	Computer Science - Data Structures and Algorithms
Subject code	006
Publishing date	2023-12-29
Publishing country	us
Document type	Book ; Online
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Book ; Online: Online Search With a Hint

Angelopoulos, Spyros

2020

Abstract: The linear search problem, informally known as the cow path problem, is one of the fundamental problems in search theory. In this problem, an immobile target is hidden at some unknown position on an unbounded line, and a mobile searcher, initially ... ...

Abstract	The linear search problem, informally known as the cow path problem, is one of the fundamental problems in search theory. In this problem, an immobile target is hidden at some unknown position on an unbounded line, and a mobile searcher, initially positioned at some specific point of the line called the root, must traverse the line so as to locate the target. The objective is to minimize the worst-case ratio of the distance traversed by the searcher to the distance of the target from the root, which is known as the competitive ratio of the search. In this work we study this problem in a setting in which the searcher has a hint concerning the target. We consider three settings in regards to the nature of the hint: i) the hint suggests the exact position of the target on the line; ii) the hint suggests the direction of the optimal search (i.e., to the left or the right of the root); and iii) the hint is a general k-bit string that encodes some information concerning the target. Our objective is to study the Pareto-efficiency of strategies in this model. Namely, we seek optimal, or near-optimal tradeoffs between the searcher's performance if the hint is correct (i.e., provided by a trusted source) and if the hint is incorrect (i.e., provided by an adversary).
Keywords	Computer Science - Data Structures and Algorithms ; Mathematics - Optimization and Control
Publishing date	2020-08-31
Publishing country	us
Document type	Book ; Online
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Article ; Online: Operationalising fairness in medical AI adoption: detection of early Alzheimer's disease with 2D CNN.

Heising, Luca / Angelopoulos, Spyros

BMJ health & care informatics

2022 Volume 29, Issue 1

Abstract: Objectives: To operationalise fairness in the adoption of medical artificial intelligence (AI) algorithms in terms of access to computational resources, the proposed approach is based on a two-dimensional (2D) convolutional neural networks (CNN), which ... ...

Abstract	Objectives: To operationalise fairness in the adoption of medical artificial intelligence (AI) algorithms in terms of access to computational resources, the proposed approach is based on a two-dimensional (2D) convolutional neural networks (CNN), which provides a faster, cheaper and accurate-enough detection of early Alzheimer's disease (AD) and mild cognitive impairment (MCI), without the need for use of large training data sets or costly high-performance computing (HPC) infrastructures. Methods: The standardised Alzheimer's Disease Neuroimaging Initiative (ADNI) data sets are used for the proposed model, with additional skull stripping, using the Brain Extraction Tool V.2approach. The 2D CNN architecture is based on LeNet-5, the Leaky Rectified Linear Unit activation function and a Sigmoid function were used, and batch normalisation was added after every convolutional layer to stabilise the learning process. The model was optimised by manually tuning all its hyperparameters. Results: The model was evaluated in terms of accuracy, recall, precision and f1-score. The results demonstrate that the model predicted MCI with an accuracy of 0.735, passing the random guessing baseline of 0.521 and predicted AD with an accuracy of 0.837, passing the random guessing baseline of 0.536. Discussion: The proposed approach can assist clinicians in the early diagnosis of AD and MCI, with high-enough accuracy, based on relatively smaller data sets, and without the need of HPC infrastructures. Such an approach can alleviate disparities and operationalise fairness in the adoption of medical algorithms. Conclusion: Medical AI algorithms should not be focused solely on accuracy but should also be evaluated with respect to how they might impact disparities and operationalise fairness in their adoption.
MeSH term(s)	Alzheimer Disease/diagnostic imaging ; Artificial Intelligence ; Cognitive Dysfunction/diagnosis ; Humans ; Magnetic Resonance Imaging/methods ; Neural Networks, Computer
Language	English
Publishing date	2022-04-27
Publishing country	England
Document type	Journal Article
ISSN	2632-1009
ISSN (online)	2632-1009
DOI	10.1136/bmjhci-2021-100485
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Article: Digital Resilience Through Training Protocols: Learning To Identify Fake News On Social Media.

Soetekouw, Lisa / Angelopoulos, Spyros

Information systems frontiers : a journal of research and innovation

2022 , Page(s) 1–17

Abstract: We explore whether training protocols can enhance the ability of social media users to detect fake news, by conducting an online experiment ( ...

Abstract	We explore whether training protocols can enhance the ability of social media users to detect fake news, by conducting an online experiment (
Language	English
Publishing date	2022-01-19
Publishing country	United States
Document type	News
ZDB-ID	2015660-1
ISSN	1572-9419 ; 1387-3326
ISSN (online)	1572-9419
ISSN	1387-3326
DOI	10.1007/s10796-021-10240-7
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Article: Laparoscopic repair of large inguinoscrotal hernias with combined use of plug and flat mesh.

Kotidis, E / Tatsis, D / Bitsianis, S / Mantzoros, I / Angelopoulos, S

Hippokratia

2022 Volume 25, Issue 1, Page(s) 38–41

Abstract: Background: This study's purpose was to examine the outcomes of the laparoscopic repair of large inguinoscrotal hernias with the combined use of a plug and flat mesh and to compare them to laparoscopic repair with the exclusive use of a flat mesh.: ... ...

Abstract	Background: This study's purpose was to examine the outcomes of the laparoscopic repair of large inguinoscrotal hernias with the combined use of a plug and flat mesh and to compare them to laparoscopic repair with the exclusive use of a flat mesh. Case series: Fifty male patients with large inguinoscrotal hernias underwent this procedure over two years. Twenty-five patients had a transabdominal preperitoneal (TAPP) hernia repair with the combined use of a plug and flat mesh, and 25 patients had TAPP repair using a flat mesh only. The novelty of this technique lies in the fact that after complete dissection of the hernia sack, a plug mesh is placed reversely, and its top edge is anchored onto the lower edge of the inguinal ligament with a standard fixation device. Next, a flat mesh is fixated, and the two meshes are sutured together with polypropylene sutures to form one combined mesh. One hernia recurrence was recorded during the follow-up period after the combined use of the plug and flat mesh. One patient developed a scrotal hematoma which was treated conservatively. Conclusions: The laparoscopic repair of large inguinoscrotal hernias with the combined use of a plug and flat mesh is a safe and effective technique with excellent short-term outcomes. It is a simple modification of the standard TAPP procedure. The recurrence rate of large inguinoscrotal hernias is also believed to be reduced. HIPPOKRATIA 2021, 25 (1):38-41.
Language	English
Publishing date	2022-02-19
Publishing country	Greece
Document type	Case Reports
ZDB-ID	2491943-3
ISSN	1790-8019 ; 1108-4189
ISSN (online)	1790-8019
ISSN	1108-4189
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Book ; Online: R\'enyi-Ulam Games and Online Computation with Imperfect Advice

Angelopoulos, Spyros / Kamali, Shahin

2023

Abstract: We study the nascent setting of online computation with imperfect advice, in which the online algorithm is enhanced by some prediction encoded in the form of a possibly erroneous binary string. The algorithm is oblivious to the advice error, but defines ... ...

Abstract	We study the nascent setting of online computation with imperfect advice, in which the online algorithm is enhanced by some prediction encoded in the form of a possibly erroneous binary string. The algorithm is oblivious to the advice error, but defines a desired tolerance, namely an upper bound on the number of erroneous advice bits it can tolerate. This is a model that generalizes the untrusted advice model [Angelopoulos et al. ITCS 2020], in which the performance of the algorithm is only evaluated at the extreme values of error (namely, if the advice has either no errors, or if it is generated adversarially). In this work, we establish connections between games with a lying responder, also known as R\'enyi-Ulam games, and the design and analysis of online algorithms with imperfect advice. Specifically, we demonstrate how to obtain upper and lower bounds on the competitive ratio for well-studied online problems such as time-series search, online bidding, and fractional knapsack. Our techniques provide the first lower bounds for online problems in this model. We also highlight and exploit connections between competitive analysis with imperfect advice and fault-tolerance in multiprocessor systems. Last, we show how to waive the dependence on the tolerance parameter, by means of resource augmentation and robustification.
Keywords	Computer Science - Data Structures and Algorithms
Subject code	005
Publishing date	2023-01-04
Publishing country	us
Document type	Book ; Online
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Book ; Online: Search Games with Predictions

Angelopoulos, Spyros / Lidbetter, Thomas / Panagiotou, Konstantinos

2024

Abstract: We study search games between a mobile Searcher and an immobile Hider in which the Searcher aims to minimize some payoff, which is either the time to find the Hider (the search time), or a normalized search time. We consider a new setting in which the ... ...

Abstract	We study search games between a mobile Searcher and an immobile Hider in which the Searcher aims to minimize some payoff, which is either the time to find the Hider (the search time), or a normalized search time. We consider a new setting in which the Searcher has some potentially erroneous information, or prediction on the Hider's position. Specifically, we study tradeoffs between the consistency of a search strategy (i.e., its worst case expected payoff assuming the prediction is correct) and the robustness (i.e., the worst case expected payoff assuming that the prediction is adversarially generated). We show how to apply this framework in search games over both discrete and continuous, as well as bounded and unbounded spaces. Specifically, we prove optimal consistency/robustness tradeoffs for three fundamental search games, namely searching in a number of discrete locations, expanding search in a tree network, and searching in the infinite line. Our study is the first to address the full power of mixed (randomized) strategies; previous work focused only on deterministic strategies, or relied on stochastic assumptions that do not guarantee worst-case robustness in adversarial situations.
Keywords	Computer Science - Computer Science and Game Theory ; Mathematics - Optimization and Control
Subject code	629
Publishing date	2024-01-02
Publishing country	us
Document type	Book ; Online
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Article ; Online: The impact of intersectional racial and gender biases on minority female leadership over two centuries.

Pogrebna, Ganna / Angelopoulos, Spyros / Motsi-Omoijiade, Immaculate / Kharlamov, Alexander / Tkachenko, Nataliya

Scientific reports

2024 Volume 14, Issue 1, Page(s) 111

Abstract: This study scrutinizes the enduring effects of racial and gender biases that contribute to the consistent underrepresentation of minority women in leadership roles within American private, public, and third sector organizations. We adopt a behavioural ... ...

Abstract	This study scrutinizes the enduring effects of racial and gender biases that contribute to the consistent underrepresentation of minority women in leadership roles within American private, public, and third sector organizations. We adopt a behavioural data science approach, merging psychological schema theory with sociological intersectionality theory, to evaluate the enduring implications of these biases on female leadership development using mixed methods including machine learning and econometric analysis. Our examination is concentrated on Black female leaders, employing an extensive analysis of leadership rhetoric data spanning 200 years across the aforementioned sectors. We shed light on the continued scarcity of minority female representation in leadership roles, highlighting the role of intersectionality dynamics. Despite Black female leaders frequently embracing higher risks to counter intersectional invisibility compared to their White counterparts, their aspirations are not realized and problems not solved generation after generation, forcing Black female leaders to concentrate on the same issues for dozens and, sometimes, hundreds of years. Our findings suggest that the compound influence of racial and gender biases hinders the advancement of minority female leadership by perpetuating stereotypical behavioral schemas, leading to persistent discriminatory outcomes. We argue for the necessity of organizations to initiate a cultural transformation that fosters positive experiences for future generations of female leaders, recommending a shift in focus from improving outcomes for specific groups to creating an inclusive leadership culture.
MeSH term(s)	Humans ; Female ; United States ; Leadership ; Intersectional Framework ; Sexism ; Racial Groups ; Minority Groups
Language	English
Publishing date	2024-01-02
Publishing country	England
Document type	Journal Article
ZDB-ID	2615211-3
ISSN	2045-2322 ; 2045-2322
ISSN (online)	2045-2322
ISSN	2045-2322
DOI	10.1038/s41598-023-50392-x
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Article ; Online: Microwave ablation of a solitary colorectal liver metastasis complicated by stomach perforation and gastrocutaneous fistula - a case report.

Symeonidis, S / Giankoulof, C / Christidis, P / Anestiadou, E / Loutzidou, L / Bitsianis, S / Ioannidis, O / Tsalis, K / Angelopoulos, S / Petsatodis, E

Klinicka onkologie : casopis Ceske a Slovenske onkologicke spolecnosti

2022 Volume 35, Issue 4, Page(s) 323–327

Abstract: Background: Organ perforation secondary to thermal ablation is a rare but severe complication that can occur in certain patients, in whom tissue dissection and preservation cannot be adequately achieved.: Case description: A 69-year-old man presented ...

Title translation	Mikrovlnná ablace solitární jaterní metastázy kolorektálního karcinomu komplikované perforací žaludku a gastrokutánní píštělí - kazuistika.
Abstract	Background: Organ perforation secondary to thermal ablation is a rare but severe complication that can occur in certain patients, in whom tissue dissection and preservation cannot be adequately achieved. Case description: A 69-year-old man presented with a gastrocutaneous fistula 20 days after a microwave ablation of liver metastases from colorectal cancer. Besides skin rash, local tenderness, and gastric content discharge from a wound where the probe had been placed, no other signs or symptoms were present. The patient was treated surgically, and a wedge-shaped gastric resection was performed. His postoperative course was uneventful. After 8 months, the patient underwent the same procedure for local progression of the same lesion, using a pulsed MW antenna and a dedicated hydrodissection needle, without complications. Conclusions: A gastrocutaneous fistula is a rare complication of microwave ablation. However, adequate hydrodissection can minimize the risk for the development of these complications. Proper treatment of these complications does not preclude repeated usage of microwave ablation in the future.
MeSH term(s)	Aged ; Colorectal Neoplasms/complications ; Colorectal Neoplasms/pathology ; Colorectal Neoplasms/surgery ; Gastric Fistula/etiology ; Gastric Fistula/surgery ; Humans ; Liver Neoplasms/therapy ; Male ; Microwaves/adverse effects ; Stomach/pathology ; Treatment Outcome
Language	English
Publishing date	2022-06-23
Publishing country	Czech Republic
Document type	Case Reports ; Journal Article
ZDB-ID	1217739-8
ISSN	1802-5307 ; 0862-495X
ISSN (online)	1802-5307
ISSN	0862-495X
DOI	10.48095/ccko2022323
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Article ; Online: Packaging and Optimization of a Capacitive Biosensor and Its Readout Circuit.

Georgas, Antonios / Nestoras, Lampros / Kanaris, Aris Ioannis / Angelopoulos, Spyridon / Ferraro, Angelo / Hristoforou, Evangelos

Sensors (Basel, Switzerland)

2023 Volume 23, Issue 2

Abstract: In pipeline production, there is a considerable distance between the moment when the operation principle of a biosensor will be verified in the laboratory until the moment when it can be used in real conditions. This distance is often covered by an ... ...

Abstract	In pipeline production, there is a considerable distance between the moment when the operation principle of a biosensor will be verified in the laboratory until the moment when it can be used in real conditions. This distance is often covered by an optimization and packaging process. This article described the packaging and optimization of a SARS-CoV-2 biosensor, as well as the packaging of its electronic readout circuit. The biosensor was packed with a photosensitive tape, which forms a protective layer and is patterned in a way to form a well in the sensing area. The well is meant to limit the liquid diffusion, thereby reducing the measurement error. Subsequently, a connector between the biosensor and its readout circuit was designed and 3D-printed, ensuring the continuous and easy reading of the biosensor. In the last step, a three-dimensional case was designed and printed, thus protecting the circuit from any damage, and allowing its operation in real conditions.
MeSH term(s)	Humans ; COVID-19 ; SARS-CoV-2 ; Biosensing Techniques/methods ; Electrodes
Language	English
Publishing date	2023-01-09
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2052857-7
ISSN	1424-8220 ; 1424-8220
ISSN (online)	1424-8220
ISSN	1424-8220
DOI	10.3390/s23020765
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