1731 research outputs found
Sort by
Inter-object grouping in visual processing: How the brain uses real-world regularities to carve up the environment
No full textIn everyday situations humans are continuously confronted with complex and cluttered visual environments that contain a large number of objects. Despite this complexity, performance in real-life tasks is surprisingly efficient. As a novel explanation for this efficiency, we propose that the brain uses typical regularities between objects (e.g., lamps are typically appearing above dining tables) to group these objects to reduce complexity and thereby facilitate behavioral performance. In a series of experiments, we show that object regularities reduce competitive interactions in visual cortex, and we relate this benefit to improved detection of target objects among regular distracter groups. Furthermore, we show that this inter-object grouping also enhances performance in visual working memory and determines how fast objects enter visual awareness in the first place. Altogether, our findings demonstrate that inter-object grouping effectively reduces the number of competing objects and thus can facilitate perception in cluttered, but regular environments
Characterizing the spatiotemporal profile and the level of abstractness of action representations: neural decoding of magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) data
No full textWhen we observe other people's actions, a network of temporal, parietal and frontal regions is recruited, known as action observation network (AON). This network includes areas that have been reported to be involved when we perform actions ourselves. Such findings support the view that action understanding occurs by simulating actions in our own motor system (motor theories of action understanding). Alternatively, it has been argued that actions are understood based on a perceptual analysis, with access to action knowledge stored in the conceptual system (cognitive theories of action understanding). It has been argued earlier that areas that play a crucial role for action understanding should be able to (a) distinguish between different actions, and (b) generalize across the ways in which the action is performed (e.g. Dinstein, Thomas, Behrmann, & Heeger, 2008; Oosterhof, Tipper, & Downing, 2013; Caramazza, Anzelotti, Strnad, & Lingnau, 2014). Here we argue that one additional criterion needs to be met: an area that plays a crucial role for action understanding should have access to such abstract action information early, around the time when the action is recognized. An area that has access to abstract action information after the action has been recognized is unlikely to contribute to the process of action understanding.
In this thesis, I report three neuroimaging studies in which we used magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) to characterize the temporal dynamics of abstract representations of observed actions (Study 1 and 2), meaning that generalize across lower level dimensions, and to characterize the type of information encoded in the regions of the AON (Study 3).
Specifically, in Study 1 we examined where in the brain and at which point in time it is possible to distinguish between pointing and grasping actions irrespective of the way in which they are performed (reach direction, effector) using MEG in combination with multivariate pattern analysis (MVPA) and source analysis. We show that regions in the left lateral occipitotemporal cortex (LOTC) have the earliest access to abstract action representations. By contrast, precentral regions, though recruited relatively early, have access to abstract action representations substantially later than left LOTC. In Study 2, we tested the temporal dynamics of the neural decoding related to the oscillatory activity induced by observation of actions performed with different effectors (hand, foot). We observed that temporal regions are able to discriminate all the presented actions before effector-related decoding within effector-specific motor regions. Finally, in Study 3 we investigated what aspect of an action is encoded within the regions of the AON. Object-directed actions induce a change of states, e.g. opening a bottle means changing its state from closed to open. It is still unclear how and in which brain regions these neural representations are encoded. Using fMRI-based multivoxel pattern decoding, we aimed at dissociating the neural representations of states and action functions. Participants observed stills of objects (e.g., window blinds) that were in either open or closed states, and videos of actions involving the same objects, i.e., open or close window. Action videos could show the object manipulation only (invisible change), or the complete action scene (visible change). This design allowed us to detect neural representations of action scenes, states and action functions independently of each other. We found different sub-regions within LOTC containing information related to object states, action functions, or both. These findings provide important information regarding the organization of action semantics in the brain and the role of LOTC in action understanding
Measuring real-time dynamics underlying online rating processes: Models, methods, applications
No full textThis thesis collects a set of research articles and working papers produced during my doctoral program. Overall, they refer to:
(i) the general problem of collecting measures for the dynamic processes underlying human rating tasks (section Models, methods, instruments)
(ii) the proposal of new statistical methods to analyse data structures arising from the dynamic rating measurements (section Statistical techniques).
The section Models, methods, instruments contains three chapters on models and methods designed to represent the dynamics of rating evaluations together with some relevant applications. In particular, the latter refer to two different contexts, namely Likert-type questionnaires (Chapters 1 and 2) and two-choice decision making (Chapter 3). Finally, the section also describes two new measurement instruments for dynamic ratings, DYFRAT (Chapter 1) and DYFRAS (Chapter 2). In a similar way, the section Statistical techniques contains three works on novel statistical methodologies to run data analysis in the context of structured data, namely fuzzy numbers (Chapters 4 and 5) and interval-valued data (Chapter 6). The justification for structured-data comes directly from the treatment of the dynamic rating components in the sense that such a kind of data can offer a simple and flexible formal representation to model the information related to the rating properties
Modeling diffraction of nanostructured materials: a combined theoretical and experimental study
No full textThis work reviews, expands upon, tests, and utilizes reciprocal space models of diffraction. In Chapter 2, reciprocal space models are reviewed, moving from strict assumptions of spatial unboundedness and three-dimensional periodicity to more relaxed assumptions of partial periodicity and finite crystals. Throughout the chapter, concepts are illustrated practically through examples of metallic nickel. New expressions are presented and a new approach is shown for approximating the diffraction effect of finite crystal size for a powder ensemble of one-dimensionally disordered crystals. A generalized shape function approach is demonstrated for the first time for the case of a spatially finite one-dimensionally disordered average crystal, without introducing any new definition to the layer electron density. It is explicitly pointed out that care must be taken in choosing models: there is a trade-off between computational expense, accuracy, and physicality. It is essential that the limitations (assumptions) of the models are kept in mind when adopting any specific approach. In Chapter 3, reciprocal space models are tested on synthetic powder diffraction data computed by applying the Debye scattering equation to several atomistic powder specimens. A process for creating atomistic powder ensembles is outlined, and a novel method is proposed for accurately approximating the ensemble-averaged powder diffraction pattern. The minimum library size is determined and compared for each ensemble considered, and it is found that libraries of less than 620 domains are generally sufficient to approximate the ensemble average. The ensemble-averaged powder diffraction data is fit where possible using several different models, and it is found that only the new model for finite, linearly disordered-crystals is successful both at reproducing the powder diffraction data and accurately retrieving the physical characteristics of the samples. It is seen that while a failure to satisfy model assumptions does not necessarily imply that the data fitting fails, it can necessitate that the fitted parameters do not reflect the true characteristics of the sample. In Chapter 4, different RS models are utilizing to fit powder diffraction data from nanostructured boron nitride samples to establish the most likely nanostructure. It is found that models incorporating the powder diffraction effects of stacking disorder and finite crystal size, while not significantly improving the agreement with the observed diffraction data, yielded more accurate and precise refined parameters, and are in better agreement with electron microscopy studies when compared to models assuming a sintered mixture of two nanocrystalline phases. With this result, it is possible to conclude that the most likely nanostructural model is that of sintered bodies composed of a single one-dimensionally disordered nanocrsytalline phase, rather than a two-phase or nanocomposite sintered body. Beyond this, by constructing simulated nanostructures through stochastically sampling refined sample characteristics, it is possible to further conclude that in the samples investigated, the primary manifestation of one-dimensional disorder is the presence of twin boundaries, leading to nanometer scale twin bands or “nanotwins” as proposed by those who synthesized the samples, and ruling out the presence of significantly large bands showing a wurtzite boron nitride structure
Foreign Language Effects on Judgment and Decision Making
No full textI present four studies in which my coauthors and I investigated whether presenting information in a foreign language, as opposed to the native language, influences
judgment and decision-making. Research on judgment and decision-making suggests that there are two routes to judgment and choice: an intuitive, emotional route and an
analytic, controlled route. Research on bilingualism suggests that the use of a foreign language influences the intuitive route. It attenuates emotions and dampens the
activation of moral and sociocultural norms. Merging these lines of research, my coauthors and I predicted that foreign language would influence judgment and decision-making. We found that it influences moral judgment through a deactivation of moral norms, and that it affects the perception of risk and benefit through an attenuation of negative feelings. I discuss the theoretical and practical significance of the present findings, and point out limitations and possible future developments of this research area
Effective Recommendations for Leisure Activities
No full textPeople nowadays find it difficult to identify the best places to spend their leisure time performing different activities. Some services have been created to give a complete list of the opportunities offered by the city in which they live, but they overload people with information and make it difficult for them to identify what is more interesting. Personalized recommendations partially solve this problem of overload, but they need a deeper understanding of the personal tastes of people and of the different ways in which people want to spend their leisure time. In this thesis we identify the requirements for a recommender system for leisure activities, study which data are needed and which algorithm better identifies the most interesting options for each requester. We explore the effects of data quality on recommendations, identifying which kind of information is needed to better understand user needs and who can provide better-quality opinions.
We analyse the possibility of using crowdsourcing as a means for collecting ratings when volunteering is not providing the needed amount of ratings or when a new dataset of ratings is needed to answer some interesting research questions. Finally, we show how the lessons learned can be applied in practice, presenting a prototype of personalized restaurant recommender service
Museum Visits for Older Adults with Mobility Constraints: Sharing and Participation through Technology
No full textThe aim of the thesis is to study how older adults with mobility constrains can enjoy museum experiences of their family members (by providing methods and tools for family members to “save” and share memories of museum visits with older adults at home) and to investigate how older adults can remotely participate in museum visits through technology. We employed face-to-face interviews and questionnaires inside two different museums settings to understand if and what visitors share with non-visitors, and which technology they use for this purpose. The results showed that a low number of visitors share their museum visits with some materials like pictures they took or books bought in the shop. Although visitors have the intention and would like to share information, they rarely do so. In order to support sharing with non-visitors, we provided several ways for “saving” museum content. The visitors were able to bookmark objects during a museum visit, and received by email a link with the bookmarked content in the form of a digital booklet. We tested whether people would use these features, and if they would access and share the “saved” content after the visit. The results suggested that our approach can significantly increase sharing: at least half of the participants shared the digital booklet with someone.
We adapted the booklet for older adults and we performed usability study on it, in order to understand if older adults with and without cognitive decline can use it. We measured and compared the performance on four tasks: opening the booklet, browsing the content, zooming in the content and closing the content after being zoomed in. Results show that the booklet enables older adults to consume content to some extend and it allows additional in-depth exploration.
We studied factors influencing feasibility of remote participation for older adults, where we measured the impact of different designs and interaction techniques on participants ability to understand, follow and engage in remote museum visits. Interactive navigation was found the most suitable interaction paradigm for active older adults, whereas frail adults can participate only through interaction-free tours. While almost all of the participants were able to understand the tours in our experimental setting, the ability to follow a visit was strongly influenced by the interaction type. We investigated levels of experienced presence, social closeness, engagement and enjoyment when older adults join museum visit of onsite visitors in a drama-based approach. The remote participant and onsite participants were connected with audio link, the information about the objects were contained and presented in form of a story connecting all the objects in the exhibition. The constructs of closeness, engagement and enjoyment correlated significantly: we found that both audio channel and interactive story were important elements for creating an affective virtual experience, the audio channel increased the sense of togetherness, while the interactive story made the visit more enjoyable and fun. A virtual tour was designed and developed to engage older adults in an immersive visit through part of the Louvre, by a distant real-life guide. An initial diary study and a creative workshop were conducted to learn how to better support the needs and values of older adults, and which approaches would work better for the scenario of remote participation. Visitors’ experienced levels of social and spatial presence, immersion and engagement were quite high independently of the level of interactivity of the guide, or the presence of others. We discuss further recommendations for video-mediated remote participation for older adults
Bottom-up Tissue Engineering:The Effect of 3D Tissue Fabrication Strategies on Cellular Behavior
Get PDFOrgan failure is one the biggest problems, doctors face every day. Many patients are not able to get a transplant, but even those who recieved it, may undergo painful process of organ rejection and be on the transplant waiting list again. Organ transplants shortage is severe problem in current medicine that has many ethical and medical issues. To solve this problem, the new direction in regenerative medicine was formed, organ prinitng. The main goal of organ printing is fabrication of organ replacements that would mimic the original ones in terms of complexity and functionality. By direct fabrication and maturation of organs in vitro, the problem of organ shortage can be solved, moreover, based on the advances in cell therapy, these organs can be printed with patients own cells, which will eliminte the problem of transplant rejection.
Organ printing is multistep and complex process, composed of three main steps: tissue design, or theoretical modelling of replacement composition; tissue fabrication, or direct cell encapsulation and controlled assembly of building units; at last, tissue maturation to reach desirable functionality of the replacement. In the past decade, there was developed a variety of methods for the second step of organ printing, cell encapsulation, which is practicaly the main procedure for tissue fabrication. However, all these methods of cell encapsulation are complex and they might affect cells viability and functionality, which will result in changed tissue function. Thus, starting from the detailed analysis of the tissue fabrication process (encapsulation and assembly methods) the list of possible cell behavior affectors was composed. Based on this list, we designed a multistep protocol for coherent evaluation of cells behavior parameters, in terms of viability, functionality and activity during the tissue fabrication and its maturation steps. Three main materials were used for this study, two naturally (alginate and modified gelatin) and one synthetically (polyethilene glycol) derived polymers.3
The encapsulation step was performed with two different methods based on chemical or photo crosslinking of the material. Cell parameteres were evaluated on the molecular level for variety of parameters, including viability, activity, proliferation, stress markers expression, at last ability to adapt artificial environment to the cell functional niche with extracellular matrix markers expression, and proteoglycans. The innovation of the presented study consists in the developing a unique protocol for detailed cell functionality evaluation during the organ printing procedures. In fact, based on the conducted study, it was proved the safety of the encapsulation methods. Moreover, based on the cell parameters post-encapsulation, there was suggested the optimal time for tissue maturation for application of the fabricated structures in organ printing, but also in other fileds, like developmental and pathological biology, or drug screening. Eventully, a novel way of simple blocks assembly into 3D complex structures was developed and proved to be safe for cell parameters.
At last, for the future research in organ printing, a detailed study over a cell behavior and functionality has to be performed for every fabrication method, what will improve the organ production process drastically
Nomos 3: legal compliance of software requirements
No full textLaws and regulations are increasingly impacting the design and development of software systems, as legislations around the world attempt to control the impact of software on social and private life. Software systems need to be designed from the beginning in a law-aware fashion to ensure compliance with applicable laws. Moreover, they need to evolve over time as new laws pass and existing ones are amended. In this interdisciplinary field many challenges remain open. For any given norm, there are alternative ways to comply with it for a system-to-be. Moreover, revising some requirements or adding new ones can have an important impact on what norms apply. To complicate matters, there is a sizeable knowledge gap between technical and legal experts, and this hampers requirements analysts in dealing with the problem on their own. This thesis proposes to use conceptual models of law and requirements to help requirements engineers address these problems by answering questions such as ``Given this set of requirements, which norms are applicable?'', ``Which norms are complied with?'', ``What are the alternative ways I use to comply with a norm?''. The thesis proposes the Nomos 3 framework that includes a modeling language for law and requirements, reasoning support for Nomos 3 models, as well as a systematic process for establishing compliance. The proposed framework is evaluated by means of illustrative case studies, a scalability study for the reasoning mechanism, as well as other specific studies intended to assess the effectiveness of the proposed concepts, tools, and process
Bacterial lipoproteins: sorting mechanisms and biotechnological applications
No full textThe mechanism responsible for lipoprotein sorting is conserved among bacterial species. However, the final
destination of lipoproteins may vary among species. In some species lipoproteins are surface-exposed while in others they are associated to the outer membrane but facing the periplasm. To elucidate whether the difference in lipoprotein location is intrinsic to lipotrotein sequence/structure or rather is due to specific transport systems present in some bacterial species and absent in others lipoproteins were expressed in different species and their compartmentalization analyzed. The data seem to indicate that the destiny of lipoproteins depends upon specific structural signatures but the recognition of such signatures can be species-specific. Interestingly, lipoproteins can be exploited as chaperones to deliver foreign proteins to the outer membrane compartment