Modeling Uncertainty in Climate Change: A Multi-Model Comparison

The economics of climate change involves a vast array of uncertainties, complicating both the analysis and development of climate policy. This study presents the results of the first comprehensive study of uncertainty in climate change using multiple integrated assessment models. The study looks at model and parametric uncertainties for population, total factor productivity, and climate sensitivity. It estimates the pdfs of key output variables, including CO2 concentrations, temperature, damages, and the social cost of carbon (SCC). One key finding is that parametric uncertainty is more important than uncertainty in model structure. Our resulting pdfs also provide insights on tail events

Convolutional Neural Net Learning Can Achieve Production-Level Brain Segmentation in Structural Magnetic Resonance Imaging

Deep learning implementations using convolutional neural nets have recently demonstrated promise in many areas of medical imaging. In this article we lay out the methods by which we have achieved consistently high quality, high throughput computation of intra-cranial segmentation from whole head magnetic resonance images, an essential but typically time-consuming bottleneck for brain image analysis. We refer to this output as “production-level” because it is suitable for routine use in processing pipelines. Training and testing with an extremely large archive of structural images, our segmentation algorithm performs uniformly well over a wide variety of separate national imaging cohorts, giving Dice metric scores exceeding those of other recent deep learning brain extractions. We describe the components involved to achieve this performance, including size, variety and quality of ground truth, and appropriate neural net architecture. We demonstrate the crucial role of appropriately large and varied datasets, suggesting a less prominent role for algorithm development beyond a threshold of capability

Stories within Immersive Virtual Environments

[eng] How can we use immersive and interactive technologies to portray stories?How can we take advantage of the fact that within immersive virtual en-vironments people tend to respond realistically to virtual situations andevents to develop narrative content? Stories in such a media would allowthe participant to contribute to the story and interact with the virtualcharacters while the narrative plot would not change, or change only upto how it was decided a priori. Participants in such a narrative would beable to freely interact within the virtual environments and yet still beaware of the main trust of the stories presented. How can we preserve the‘respond as if it is real’ phenomenon induced by these technologies, butalso develop an unfolding plot in this environment? In other words, canwe develop a story, conserving the structure, its psychological and cul-tural richness and the emotional and cognitive involvement it supposes,in an interactive and immersive audiovisual space?In recent years Virtual Reality therapy has shown that an Immersive Vir-tual Environment (IVE) with a predetermined plot can be experienced asan interactive narrative. For example, in the context of Post TraumaticStress Disorder treatment, the reactions of the participants and the thera-peutic impact suggest that an IVE is a qualitatively different experiencethan classical audiovisual content. However, the methods to develop suchkind of content are not systematic, and the consistency of the experienceis only granted by a therapist or operator controlling in real time theunfolding narrative. Can a story with a strong classical plot be renderedin an automated and interactive immersive virtual environment?..[cat] Podem emprar la realitat virtual immersiva per contar històries? Com po-dem aprofitar el fet que dins dels entorns virtuals immersius les personestendeixen a respondre de manera realista a les situacions i esdevenimentsvirtuals per desenvolupar històries? Els participants en aquest tipus denarrativa podrien interactuar lliurement amb els entorns virtuals i noobstant això experimentarien les històries presentades com a plausibles iconsistents. Una història en aquest medi audiovisual permetria als parti-cipants interactuar amb els personatges virtuals i contribuir activamentals esdeveniments escenificats en l’entorn virtual. Malgrat això, la tramaestablerta a priori no canviaria, o canviaria només dins els marges es-tablerts per l’autor. Com podem preservar el fet que hom tendeix a "re-spondre com si fos real" induït per aquestes tecnologies mentre desenvolu-pem una trama en aquests entorns? En altres paraules, podem desenvolu-par una història conservant-ne l’estructura, la riquesa cultural i psicolò-gica i la implicació emocional i cognitiva que suposa, en una realitatvirtual immersiva i interactiva?Recentment la teràpia de realitat virtual ha mostrat que un entorn vir-tual amb un guió preestablert pot ser percebut com una narració inter-activa. Per exemple, en el context del tractament de Trastorns per EstrèsPostraumàtic, les reaccions i impactes terapèutics suggereixen que pro-voca una sensació de realitat que en fa una experiència qualitativamentdiferent als continguts audiovisuals clàssics. No obstant això, la consistèn-cia de l’experiència tan sols pot ser garantida si un un terapeuta o op-erador controla en temps real el flux dels esdeveniments constituint elguió narratiu. Podem representar un guió clàssic en un entorn virtualautomatitzat?..

A new computational method to split large biochemical networks into coherent subnets

<p>Abstract</p> <p>Background</p> <p>Compared to more general networks, biochemical networks have some special features: while generally sparse, there are a small number of highly connected metabolite nodes; and metabolite nodes can also be divided into two classes: internal nodes with associated mass balance constraints and external ones without. Based on these features, reclassifying selected internal nodes (separators) to external ones can be used to divide a large complex metabolic network into simpler subnetworks. Selection of separators based on node connectivity is commonly used but affords little detailed control and tends to produce excessive fragmentation.</p> <p>The method proposed here (Netsplitter) allows the user to control separator selection. It combines local connection degree partitioning with global connectivity derived from random walks on the network, to produce a more even distribution of subnetwork sizes. Partitioning is performed progressively and the interactive visual matrix presentation used allows the user considerable control over the process, while incorporating special strategies to maintain the network integrity and minimise the information loss due to partitioning.</p> <p>Results</p> <p>Partitioning of a genome scale network of 1348 metabolites and 1468 reactions for <it>Arabidopsis thaliana </it>encapsulates 66% of the network into 10 medium sized subnets. Applied to the flavonoid subnetwork extracted in this way, it is shown that Netsplitter separates this naturally into four subnets with recognisable functionality, namely synthesis of lignin precursors, flavonoids, coumarin and benzenoids. A quantitative quality measure called <it>efficacy </it>is constructed and shows that the new method gives improved partitioning for several metabolic networks, including bacterial, plant and mammal species.</p> <p>Conclusions</p> <p>For the examples studied the Netsplitter method is a considerable improvement on the performance of connection degree partitioning, giving a better balance of subnet sizes with the removal of fewer mass balance constraints. In addition, the user can interactively control which metabolite nodes are selected for cutting and when to stop further partitioning as the desired granularity has been reached. Finally, the blocking transformation at the heart of the procedure provides a powerful visual display of network structure that may be useful for its exploration independent of whether partitioning is required.</p

The sampling brain

Understanding the algorithmic nature of mental processes is of vital importance to psychology, neuroscience, and artificial intelligence. In response to a rapidly changing world and computational demanding cognitive tasks, evolution may have endowed us with brains that are approximating rational solutions, such that our performance is close to optimal. This thesis suggests one instance of the approximation algorithms, sample-based approximation, to be implemented by the brain to tackle complex cognitive tasks. Knowing that certain types of sampling is used to generate mental samples, the brain could also actively correct for the uncertainty comes along with the sampling process. This correction process for samples left traces in human probability estimates, suggesting a more rational account of sample-based estimations. In addition, these mental samples can come from both observed experiences (memory) and synthesised experiences (imagination). Each source of mental samples has unique role in learning tasks and the classical error-correction principle of learning can be generalised when mental-sampling processes are considered

A generative adversarial network approach to synthetic-CT creation for MRI-based radiation therapy

Tese de mestrado integrado, Engenharia Biomédica e Biofísica (Radiações em Diagnóstico e Terapia), Universidade de Lisboa, Faculdade de Ciências, 2019This project presents the application of a generative adversarial network (GAN) to the creation of synthetic computed tomography (sCT) scans from volumetric T1-weighted magnetic resonance imaging (MRI), for dose calculation in MRI-based radio therapy workflows. A 3-dimensional GAN for MRI-to-CT synthesis was developed based on a 2-dimensional architecture for image-content transfer. Co-registered CT and T1 –weighted MRI scans of the head region were used for training. Tuning of the network was performed with a 7-foldcross-validation method on 42 patients. A second data set of 12 patients was used as the hold out data set for final validation. The performance of the GAN was assessed with image quality metrics, and dosimetric evaluation was performed for 33 patients by comparing dose distributions calculated on true and synthetic CT, for photon and proton therapy plans. sCT generation time was <30s per patient. The mean absolute error (MAE) between sCT and CT on the cross-validation data set was69 ± 10 HU, corresponding to a 20% decrease in error when compared to training on the original 2D GAN. Quality metric results did not differ statistically for the hold out data set (p = 0.09). Higher errors were observed for air and bone voxels, and registration errors between CT and MRI decreased performance of the algorithm. Dose deviations at the target were within 2% for the photon beams; for the proton plans, 21 patients showed dose deviations under 2%, while 12 had deviations between 2% and 8%. Pass rates (2%/ 2mm) between dose distributions were higher than 98% and 94% for photon and proton plans respectively. The results compare favorably with published algorithms and the method shows potential for MRI-guided clinical workflows. Special attention should be given when beams cross small structures and airways, and further adjustments to the algorithm should be made to increase performance for these regions

Stories within Immersive Virtual Environments

How can we use immersive and interactive technologies to portray stories? How can we take advantage of the fact that within immersive virtual environments people tend to respond realistically to virtual situations and events to develop narrative content? Stories in such a media would allow the participant to contribute to the story and interact with the virtual characters while the narrative plot would not change, or change only up to how it was decided a priori. Participants in such a narrative would be able to freely interact within the virtual environments and yet still be aware of the main trust of the stories presented. How can we preserve the ‘respond as if it is real’ phenomenon induced by these technologies, but also develop an unfolding plot in this environment? In other words, can we develop a story, conserving the structure, its psychological and cultural richness and the emotional and cognitive involvement it supposes, in an interactive and immersive audiovisual space? In recent years Virtual Reality therapy has shown that an Immersive Virtual Environment (IVE) with a predetermined plot can be experienced as an interactive narrative. For example, in the context of Post Traumatic Stress Disorder treatment, the reactions of the participants and the therapeutic impact suggest that an IVE is a qualitatively different experience than classical audiovisual content. However, the methods to develop such kind of content are not systematic, and the consistency of the experience is only granted by a therapist or operator controlling in real time the unfolding narrative. Can a story with a strong classical plot be rendered in an automated and interactive immersive virtual environment? The thesis developed through this document is that it is possible. Specifically the thesis is that this can be achieved through two principles of interaction that we call ‘ATP’ and ‘Substitution’. ATP stands for ‘Advance The Plot’, and it is an underlying goal of the system to always find the best action possible in any given context that will advance the state of the story being expressed. The second principle, Substitution, states that the human participant in an immersive interactive story can assume the role of any character or, what is equivalent, that if he does not do what the system expects him to do, a virtual character will do it instead. To implement such principles, a story cognitive model named Trama is proposed. The purpose of such a story model is to give artificial agents a guide to decide what to do in an interactive situation in such a way that the human participant has the impression of interacting within one or more narrative plots. To validate such method, three experiments address the main assumptions of the approach.The first one is concerned with whether people interact with virtual characters in a similar way they do with real people, analysing this in a particular aspect of interpersonal communication, namely interpersonal distances. The second assesses whether people identify with their virtual bodies, which is one of the basic assumptions underlying the principles of interaction proposed. The third experiment shows that the story model allows to implement stories in such a way that people can interact within an immersive virtual environment while conserving the impression there is a narrative plot, and that they have assumed a particular role in it. In addition to the experiments, we explore whether the formalism developed within the Trama model captures some aspects of the important role that stories have in cognitive development.Podem emprar la realitat virtual immersiva per contar històries? Com podem aprofitar el fet que dins dels entorns virtuals immersius les persones tendeixen a respondre de manera realista a les situacions i esdeveniments virtuals per desenvolupar històries? Els participants en aquest tipus de narrativa podrien interactuar lliurement amb els entorns virtuals i no obstant això experimentarien les històries presentades com a plausibles i consistents. Una història en aquest medi audiovisual permetria als participants interactuar amb els personatges virtuals i contribuir activament als esdeveniments escenificats en l’entorn virtual. Malgrat això, la trama establerta a priori no canviaria, o canviaria només dins els marges establerts per l’autor. Com podem preservar el fet que hom tendeix a "respondre com si fos real" induït per aquestes tecnologies mentre desenvolupem una trama en aquests entorns? En altres paraules, podem desenvolupar una història conservant-ne l’estructura, la riquesa cultural i psicològica i la implicació emocional i cognitiva que suposa, en una realitat virtual immersiva i interactiva? Recentment la teràpia de realitat virtual ha mostrat que un entorn virtual amb un guió preestablert pot ser percebut com una narració interactiva. Per exemple, en el context del tractament de Trastorns per Estrès Postraumàtic, les reaccions i impactes terapèutics suggereixen que provoca una sensació de realitat que en fa una experiència qualitativament diferent als continguts audiovisuals clàssics. No obstant això, la consistència de l’experiència tan sols pot ser garantida si un terapeuta o operador controla en temps real el flux dels esdeveniments constituint el guió narratiu. Podem representar un guió clàssic en un entorn virtual automatitzat? La tesi principal d’aquest treball és que és possible. En concret, la tesi és que això es pot aconseguir a través de dos principis d’interacció que anomenem ‘ATP’ i ‘Substitució’. ATP significa ‘avançar en la trama’ (Advance The Plot ), i és un objectiu inherent en el sistema per trobar, en qualsevol context, la millor acció possible que farà avançar la història contada. El segon principi, Substitució, formalitza el fet que el participant humà en una trama interactiva pot assumir el paper de qualsevol personatge o, el que és equivalent, que si no fa el que el sistema espera que faci, un personatge virtual ho farà en el seu lloc. Per posar en pràctica aquests principis, he introduït un model cognitiu d’història anomenat Trama. La funció d’aquest model és donar als agents artificials una guia per decidir què fer en una situació interactiva, de manera que el participant humà té la impressió d’interactuar dins d’un o més guions narratius. Introdueixo 3 experiments per abordar els principals supòsits d’aquest mètode. El primer avalua si les persones interactuen amb personatges virtuals de manera similar que fan amb persones reals en un aspecte particular de la comunicació interpersonal: les distàncies interpersonals. El segon estudia fins a quin punt hom s’identifica amb el seu cos virtual, un dels supòsits bàsics subjacents als principis d’interacció proposats. El tercer experiment mostra que el model Trama permet implementar les històries de tal manera que les persones poden interactuar en un entorn virtual immersiu tot conservant la impressió que participen en un guió narratiu subjacent on hi assumeixen un rol concret. També exploro si el formalisme desenvolupat reflecteix o prediu algunes de les moltes funcions que les històries tenen en el desenvolupament cognitiu

On the Behavioural Profiling of Gamblers using Cryptocurrency Transaction Data

Blockchain technologies enable a number of new ways to gamble online. Very little is known about engagement with one such new way of gambling: decentralised gambling applications, which provide simple casino games like dice rolls and coin flips. This is important as understanding engagement with any type of gambling is a crucial first step to assessing the risk of experiencing gambling related harm within the population. This thesis first surveys existing literature for methods of describing engagement in gambling, and then applies these methods to actual transaction data gathered from several decentralised gambling applications. This replication-oriented approach means results can be grounded against existing findings, and the descriptions of player engagement in this new domain have some context for comparison. It also means that descriptions can be tentatively mapped to similar scenarios, such as risk of experiencing gambling related harm in other studies. The results of several replication oriented studies presented herein find that engagement in the decentralised gambling domain is typically less than in comparable online casino games, but that a heavily involved subgroup is more involved. It also finds that engagement with gambling- like mechanisms in blockchain games is much less than in decentralised gambling applications, guiding future studies in gambling research away from blockchain games despite their mechanical similarities. Finally, behavioural groups in the decentralised gambling domain do not appear to be comparable with existing research in the centralised online casino game domain. The results of these studies provide a first look at engagement in this emerging domain, a comparative description with similar forms of gambling, and a description of behavioural groups, which provides essential context for further research to asses the scale of the risk of experiencing gambling related harm

Proceedings of the 35th International Workshop on Statistical Modelling : July 20- 24, 2020 Bilbao, Basque Country, Spain

466 p.The InternationalWorkshop on Statistical Modelling (IWSM) is a reference workshop in promoting statistical modelling, applications of Statistics for researchers, academics and industrialist in a broad sense. Unfortunately, the global COVID-19 pandemic has not allowed holding the 35th edition of the IWSM in Bilbao in July 2020. Despite the situation and following the spirit of the Workshop and the Statistical Modelling Society, we are delighted to bring you the proceedings book of extended abstracts