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Copy this Sentence [article]

Vasileios Lioutas, Andriy Drozdyuk
2019 arXiv   pre-print
Attention is an operation that selects some largest element from some set, where the notion of largest is defined elsewhere. Applying this operation to sequence to sequence mapping results in significant improvements to the task at hand. In this paper we provide the mathematical definition of attention and examine its application to sequence to sequence models. We highlight the exact correspondences between machine learning implementations of attention and our mathematical definition. We
more » ... finition. We provide clear evidence of effectiveness of attention mechanisms evaluating models with varying degrees of attention on a very simple task: copying a sentence. We find that models that make greater use of attention perform much better on sequence to sequence mapping tasks, converge faster and are more stable.
arXiv:1905.09856v1 fatcat:mm36jun42zd4pnnqqm625cbsxa

A Lernaean Hydra [chapter]

Vasileios-Arsenios Lioutas
2016 Stroke  
Data series are a special type of multidimensional data present in numerous domains, where similarity search is a key operation that has been extensively studied in the data series literature. In parallel, the multidimensional community has studied approximate similarity search techniques. We propose a taxonomy of similarity search techniques that reconciles the terminology used in these two domains, we describe modifications to data series indexing techniques enabling them to answer
more » ... o answer approximate similarity queries with quality guarantees, and we conduct a thorough experimental evaluation to compare approximate similarity search techniques under a unified framework, on synthetic and real datasets in memory and on disk. Although data series differ from generic multidimensional vectors (series usually exhibit correlation between neighboring values), our results show that data series techniques answer approximate queries with strong guarantees and an excellent empirical performance, on data series and vectors alike. These techniques outperform the state-of-the-art approximate techniques for vectors when operating on disk, and remain competitive in memory.
doi:10.1093/med/9780190497255.003.0025 fatcat:brqyhtmrpbablhvxs3ihwqdoai

Stroke : Highlights of Selected Articles

Vasileios-Arsenios Lioutas
2016 Stroke  
doi:10.1161/strokeaha.116.014438 fatcat:cwqqrv5ggbfb5cmdiwcjexz2xa

Time-aware Large Kernel Convolutions [article]

Vasileios Lioutas, Yuhong Guo
2020 arXiv   pre-print
Correspondence to: Vasileios Lioutas <contact@vlioutas.com>.  ... 
arXiv:2002.03184v2 fatcat:2zrr75sywrdq7et737syou64zm

MATE-KD: Masked Adversarial TExt, a Companion to Knowledge Distillation [article]

Ahmad Rashid, Vasileios Lioutas, Mehdi Rezagholizadeh
2021 arXiv   pre-print
The advent of large pre-trained language models has given rise to rapid progress in the field of Natural Language Processing (NLP). While the performance of these models on standard benchmarks has scaled with size, compression techniques such as knowledge distillation have been key in making them practical. We present, MATE-KD, a novel text-based adversarial training algorithm which improves the performance of knowledge distillation. MATE-KD first trains a masked language model based generator
more » ... el based generator to perturb text by maximizing the divergence between teacher and student logits. Then using knowledge distillation a student is trained on both the original and the perturbed training samples. We evaluate our algorithm, using BERT-based models, on the GLUE benchmark and demonstrate that MATE-KD outperforms competitive adversarial learning and data augmentation baselines. On the GLUE test set our 6 layer RoBERTa based model outperforms BERT-Large.
arXiv:2105.05912v1 fatcat:22n7p6pnuvb5zh3hsnqrgcftee

Intranasal insulin neuroprotection in ischemic stroke

Vasileios-Arsenios Lioutas, Vera Novak
2016 Neural Regeneration Research  
N-methyl-D-aspartate (NMDA) receptor antagonists, free radical scavengers, cellular membrane stabilizers, monoclonal antibodies all had neutral or, at times negative effects (Lioutas et al., 2015) .  ...  energy failure and ultimately neuronal death: Inflammation, excitotoxicity, apoptosis, reactive oxygen and nitrogen species formation, mitochondrial failure have been implicated in the ischemic cascade (Lioutas  ... 
doi:10.4103/1673-5374.179040 pmid:27127468 pmcid:PMC4828994 fatcat:p5rnmcwuqvegta7zy36ftxycbi

Imagining The Road Ahead: Multi-Agent Trajectory Prediction via Differentiable Simulation [article]

Adam Scibior, Vasileios Lioutas, Daniele Reda, Peyman Bateni, Frank Wood
2021 arXiv   pre-print
We develop a deep generative model built on a fully differentiable simulator for multi-agent trajectory prediction. Agents are modeled with conditional recurrent variational neural networks (CVRNNs), which take as input an ego-centric birdview image representing the current state of the world and output an action, consisting of steering and acceleration, which is used to derive the subsequent agent state using a kinematic bicycle model. The full simulation state is then differentiably rendered
more » ... rentiably rendered for each agent, initiating the next time step. We achieve state-of-the-art results on the INTERACTION dataset, using standard neural architectures and a standard variational training objective, producing realistic multi-modal predictions without any ad-hoc diversity-inducing losses. We conduct ablation studies to examine individual components of the simulator, finding that both the kinematic bicycle model and the continuous feedback from the birdview image are crucial for achieving this level of performance. We name our model ITRA, for "Imagining the Road Ahead".
arXiv:2104.11212v1 fatcat:eqmbvfttyfbejclwti7d2ct3li

Lacunar Infarcts and Intracerebral Hemorrhage Differences

Vasileios-Arsenios Lioutas, Alexa Beiser, Jayandra Himali, Hugo Aparicio, Jose Rafael Romero, Charles DeCarli, Sudha Seshadri
2016 Stroke  
and Purpose-Lacunar ischemic stroke (LS) and intracerebral hemorrhage (iCH) are two diverse manifestations of Small Vessel Disease (SVD). What predisposes some patients to ischemic stroke and others to hemorrhage is not well understood. Methods-We performed a nested case-control study within the Framingham Heart Study comparing persons with incident iCH and LIS, to age-and sex-matched controls for baseline prevalence and levels of cardiovascular risk factors. Results-We identified 118 LS (mean
more » ... ified 118 LS (mean age 74 years, 51% male) and 108 iCH (75 years, 46% male) events. Hypertension, diabetes, smoking and obesity were strongly associated with LS. Hypertension, but not diabetes, smoking, or cholesterol levels increased the odds of iCH. Contrary to LS, iCH cases had lower BMI than their controls (26 vs 27); BMI<20 was associated with 4fold higher odds for iCH. In direct comparison, LS cases had higher BMI (28 vs 26) and obesity prevalence (OR 3.1); BMI<20 was associated with significantly lower odds of LS (OR 0.1). Conclusions-LS and iCH share hypertension, but not DM as a common risk factor. iCH cases had lower BMI compared not only to LS but to their controls as well; this finding is unexplained and merits further exploration
doi:10.1161/strokeaha.116.014839 pmid:28008091 pmcid:PMC5288009 fatcat:tyclu4ylaffvvlt7ro5erh6tk4

Young adult patient with headache, fever and blurred vision

Stavroula A Paschou, Konstantinos Tzioras, Vasiliki Trianti, Stavroula Lyra, Vasileios-Arsenios Lioutas, Andreas Seretis, Andromachi Vryonidou
2016 HORMONES  
BAcKgrounD AnD IMporTAncE: This case highlights the fact that acute pituitary apoplexy may be misdiagnosed due to being confused with other entities exhibiting similar symptoms, such as meningitis or subarachnoid hemorrhage. clInIcAl prEsEnTATIon: A patient in his late 30s presented with sudden and severe frontal headache, fever, blurred vision, nausea, confusion, as well as oculomotor palsy (cn III) with partial ptosis of the left eyelid, dilated left pupil and left eye globe deviation
more » ... e deviation inferiorly and laterally. The final diagnosis was acute pituitary apoplexy complicating a pituitary macroadenoma. In this setting, headache is usually present due to stretching and irritation of the dura mater, and fever due to meningeal irritation or upward expansion leading to hypothalamic dysfunction. Decreased visual acuity and defects in visual fields are caused by upward expansion, which compresses the optic chiasm. ophthalmoplegia can also be observed due to lateral expansion with invasion of the cavernous sinus. conclusIon: Medical professionals involved in emergency care should be aware of this clinical entity and collaborate with endocrinologists using a multidisciplinary team approach for prompt diagnosis and optimal treatment of such patients.
doi:10.14310/horm.2002.1701 pmid:28222415 fatcat:ldwz23d5ibgvzbrzwqbyvkwwzq

New Avenues for Treatment of Intracranial Hemorrhage

Shruti Sonni, Vasileios-Arsenios Lioutas, Magdy H. Selim
2013 Current Treatment Options in Cardiovascular Medicine  
The mortality and morbidity from intracerebral hemorrhage (ICH) remain high despite advances in medical, neurological, and surgical care during the past decade. The lessons learned from previous therapeutic trials in ICH, improved understanding of the pathophysiology of neuronal injury after ICH, and advances in imaging and pre-hospital assessment technologies provide optimism that more effective therapies for ICH are likely to emerge in the coming years. The potential new avenues for the
more » ... enues for the treatment of ICH include a combination of increased utilization of minimally invasive surgical techniques with or without thrombolytic usage to evacuate or reduce the size of the hematoma; utilization of advanced imaging to improve selection of patients who are likely to benefit from reversal of coagulopathy or hemostatic therapy; ultra-early diagnosis and initiation of therapy in the ambulance; and the use of novel drugs to target the secondary injury mechanisms, including the inflammatory cascade, perihematomal edema reduction, and hemoglobin degradation products-mediated toxicity.
doi:10.1007/s11936-013-0277-y pmid:24366522 pmcid:PMC3932437 fatcat:piguh6qsb5h6le7em7wjpkacnm

Post-traumatic splenic cysts treated with laparoscopy: two case reports

Dimitrios V Avgerinos, Christos E Kyriakopoulos, Sophia Konstantinopoulou, Evgenia Gourgari, Vasileios Lioutas
2009 Cases Journal  
Today, laparoscopy tends to become a useful alternative to open procedure for the surgical treatment of spleen disorders, offering at the same time a conservative approach for the management of selected spleen lesions such as posttraumatic cysts. This article describes two cases of posttraumatic splenic cysts, one of which was treated with laparoscopic total splenectomy and the second with laparoscopic cystectomy. The procedure was carried out successfully with no complications in both cases,
more » ... ns in both cases, and the patients were discharged a few days after the operation. Laparoscopy with preservation of functional splenic parenchyma, when feasible, should be the procedure of choice in cases of posttraumatic splenic cysts, as it provides safe and definite treatment with all of the other advantages of minimally invasive surgery.
doi:10.4076/1757-1626-2-7976 pmid:19830034 pmcid:PMC2740124 fatcat:xeug7gnv4jhxdjtihkgtvvwtfa

Predictors of extubation success in acute ischemic stroke patients

Vasileios-Arsenios Lioutas, Khalid A. Hanafy, Sandeep Kumar
2016 Journal of the Neurological Sciences  
Background-Acute ischemic stroke (AIS) patients often undergo intubation and mechanical ventilation (MV). Prolonged intubation and MV have disadvantages and complications. Conventional extubation criteria based only on respiratory parameters are insufficient to guide extubation practices in stroke patients where capacity for airway protection is a major concern. Objective-To identify clinical and neuroanatomical markers of successful extubation in AIS patients requiring MV.
more » ... ethods-Retrospective review of tertiary care hospital patient database from May 2009-November 2012 to identify consecutive patients with AIS intubated during hospitalization. We assessed the effect of age, sex, baseline National Institutes of Health Stroke Scale (NIHSS) score, level of consciousness, facial weakness, dysarthria, neglect, infarct location, dysphagia, respiratory parameters and history of pneumonia on successful extubation by hospital discharge using multivariate logistic regression analysis. Results-112 subjects met study criteria and were included in the analysis. Age and NIHSS scores (mean ± standard deviation) were 74.5 ± 16.1 years and 19 ± 9.8, respectively; 56 % were women. In multivariate analysis, NIHSS score ≤ 15 (Odds Ratio 4.6, 95% Confidence Interval 1.9-11.3, p<0.001) and absence of dysarthria prior to intubation (Odds Ratio 3.0, 95% Confidence interval 1.1-8.3, p=0.04) were independently associated with successful extubation. Conventional respiratory parameters had no effect on extubation success in this cohort. Conclusions-Milder stroke and absence of dysarthria prior to intubation were independently associated with extubation success. Our findings could help inform extubation practices in patients with AIS though prospective validation is necessary.
doi:10.1016/j.jns.2016.07.017 pmid:27538631 pmcid:PMC5328505 fatcat:3dfslbuxjja3vpey76mahq3qli

Utility of Transthoracic Echocardiography in Diagnostic Evaluation of Ischemic Stroke

Jennifer Harris, Jason Yoon, Mohamed Salem, Magdy Selim, Sandeep Kumar, Vasileios Arsenios Lioutas
2020 Frontiers in Neurology  
*Correspondence: Vasileios-Arsenios Lioutas, vlioutas@bidmc.harvard.edu  ...  Google Scholar Keywords: transthoracic echocardiography, ischemic stroke, diagnostics, stroke diagnosis, stroke etiology, resource utilization Citation: Harris J, Yoon J, Salem M, Selim M, Kumar S and Lioutas  ... 
doi:10.3389/fneur.2020.00103 pmid:32132971 pmcid:PMC7040372 fatcat:5pihdmksjjfsfebtoxbglhs3mi

Improving Word Embedding Factorization for Compression Using Distilled Nonlinear Neural Decomposition [article]

Vasileios Lioutas, Ahmad Rashid, Krtin Kumar, Md Akmal Haidar, Mehdi Rezagholizadeh
2020 arXiv   pre-print
., 2017; Lioutas and Guo, 2020) have shown better performance with parameter sharing between the two (Press and Wolf, 2017) .  ... 
arXiv:1910.06720v2 fatcat:7za6klgsrjdknbtc6da4hjoqtq

Mapping Low-Resolution Images To Multiple High-Resolution Images Using Non-Adversarial Mapping [article]

Vasileios Lioutas
2020 arXiv   pre-print
Several methods have recently been proposed for the Single Image Super-Resolution (SISR) problem. The current methods assume that a single low-resolution image can only yield a single high-resolution image. In addition, all of these methods use low-resolution images that were artificially generated through simple bilinear down-sampling. We argue that, first and foremost, the problem of SISR is an one-to-many mapping problem between the low-resolution and all possible candidate high-resolution
more » ... e high-resolution images and we address the challenging task of learning how to realistically degrade and down-sample high-resolution images. To circumvent this problem, we propose SR-NAM which utilizes the Non-Adversarial Mapping (NAM) technique. Furthermore, we propose a degradation model that learns how to transform high-resolution images to low-resolution images that resemble realistically taken low-resolution photos. Finally, some qualitative results for the proposed method along with the weaknesses of SR-NAM are included.
arXiv:2006.11708v2 fatcat:zdhztnadqrgcvnmsfrb7wm7ela
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