The effects of the global structure of the mask in visual backward masking

The visibility of a target can be strongly affected by a trailing mask. Research on visual backward masking has typically focused on the temporal characteristics of masking, whereas non-basic spatial aspects have received much less attention. However, recently, it has been demonstrated that the spatial layout is an important determinant of the strength of a mask. Here, we show that not only local but also global aspects of the mask's spatial layout affect target processing. Particularly, it is the regularity of the mask that plays an important role. Our findings are of importance for theoretical research, as well as for applications of visual masking

Use of spatial information in 2D SEMG array decomposition

A new feature extraction/classification method for High Density surface ElectroMyoGraphy (HD sEMG) Motor Unit Aciton Potential (MUAP) decomposition using 2D shape and energy distribution features is presented and experimentally tested.\u

Invisibility and interpretation

Invisibility is often thought to occur because of the low-level limitations of the visual system. For example, it is often assumed that backward masking renders a target invisible because the visual system is simply too slow to resolve the target and the mask separately. Here, we propose an alternative explanation in which invisibility is a goal rather than a limitation and occurs naturally when making sense out of the plethora of incoming information. For example, we present evidence that (in)visibility of an element can strongly depend on how it groups with other elements. Changing grouping changes visibility. In addition, we will show that features often just appear to be invisible but are in fact visible in a way the experimenter is not aware of

Spatial grouping determines temporal integration

To make sense out of a continuously changing visual world, people need to integrate features across space and time. Despite more than a century of research, the mechanisms of features integration are still a matter of debate. To examine how temporal and spatial integration interact, the authors measured the amount of temporal fusion (a measure of temporal integration) for different spatial layouts. They found that spatial grouping by proximity and similarity can completely block temporal integration. Computer simulations with a simple neural network capture these findings very well, suggesting that the proposed spatial grouping operations may occur already at an early stage of visual information processing

Combining simultaneous with temporal masking

Simultaneous and temporal masking are two frequently used techniques in psychology and vision science. Although there are many studies and theories related to each masking technique, there are no systematic investigations of their mutual relationship, even though both techniques are often applied together. Here, the authors show that temporal masking can both undo and enhance the deteriorating effects of simultaneous masking depending on the stimulus onset asynchrony between the simultaneous and temporal masks. For the task and stimuli used in this study, temporal masking was largely unaffected by the properties of the simultaneous mask. In contrast, simultaneous masking seems to depend strongly on spatial grouping and was strongly affected by the properties of the temporal mask. These findings help to identify the nature of both temporal and simultaneous masking and promote understanding of the role of spatial and temporal grouping in visual perception

A context-aware adaptive feedback agent for activity monitoring and coaching

A focus in treatment of chronic diseases is optimizing levels of physical activity. At Roessingh Research and Development, a system was developed, consisting of a Smartphone and an activity sensor, that can measure a patient’s daily activity behavior and provide motivational feedback messages. We are currently looking into ways of increasing the effectiveness of motivational messages that aim to stimulate sustainable behavioral change, by adapting its timing and content to individual patients in their current context of use

Feature fusion reveals slow and fast visual memories

Although the visual system can achieve a coarse classification of its inputs in a relatively short time, the synthesis of qualia-rich and detailed percepts can take substantially more time. If these prolonged computations were to take place in a retinotopic space, moving objects would generate extensive smear. However, under normal viewing conditions, moving objects appear relatively sharp and clear, suggesting that a substantial part of visual short-term memory takes place at a nonretinotopic locus. By using a retinotopic feature fusion and a nonretinotopic feature attribution paradigm, we provide evidence for a relatively fast retinotopic buffer and a substantially slower nonretinotopic memory. We present a simple model that can account for the dynamics of these complementary memory processes. Taken together, our results indicate that the visual system can accomplish temporal integration of information while avoiding smear by breaking off sensory memory into fast and slow components that are implemented in retinotopic and nonretinotopic loci, respectively

Development of biobased building blocks, polymers and coatings

Coatings are omnipresent in daily life, indispensable in construction and applied everywhere around us to enhance the durability and aesthetics of numerous products ranging from cars to wood to electronics. One of the most conventional sets of building blocks used to build these polymer chains, justified by their high reactivity and broad versatility, are the petrochemical feedstock derived acrylates. Despite their promise, the high demand and the resulting large-scale production from fossil fuels contribute heavily to an unsustainable ecological footprint. As a result of the growing environmental awareness and the desire for a green future, sustainable production of acrylates and the development of acrylate alternatives derived from biorenewable resources have gained increased attention over the last decades. Although great progress has been made, the commercialization of a competing sustainable process has not yet been achieved due techno-economic challenges arising from the underdeveloped larger scale syntheses and expensive starting materials and reagents. In this thesis we implemented both strategies and present several new developments towards sustainable acrylate alternatives (alkoxybutenolides) and biobased acrylic acid, all starting from furfural and using oxygen and visible light for sustainable chemical transformations. In order to account for a larger scale synthesis, a photochemical reactor was developed for the continuous production of our sustainable building blocks. The resulting biobased coatings obtained from these alkoxybutenolides are hard, transparent and resistant to solvent and water, similar to commercial coatings. Above all, the coatings are functional and have tunable properties, based on the different building blocks we developed

A model-based approach to stabilizing crutch supported paraplegic standing by artifical hip joint stiffness

The prerequisites for stable crutch supported standing were analyzed in this paper. For this purpose, a biomechanical model of crutch supported paraplegic stance was developed assuming the patient was standing with extended knees. When using crutches during stance, the crutches will put a position constraint on the shoulder, thus reducing the number of degrees of freedom. Additional hip-joint stiffness was applied to stabilize the hip joint and, therefore, to stabilize stance. The required hip-joint stiffness for changing crutch placement and hip-joint offset angle was studied under static and dynamic conditions. Modeling results indicate that, by using additional hip-joint stiffness, stable crutch supported paraplegic standing can be achieved, both under static as well as dynamic situations. The static equilibrium postures and the stability under perturbations were calculated to be dependent on crutch placement and stiffness applied. However, postures in which the hip joint was in extension (C postures) appeared to the most stable postures. Applying at least 60 N /spl middot/ m/rad hip-joint stiffness gave stable equilibrium postures in all cases. Choosing appropriate hip-joint offset angles, the static equilibrium postures changed to more erect postures, without causing instability or excessive arm forces to occur