Virtual scanning keyboards are commonly used augmentative communication aids by persons with severe speech and motion impairments. Designers of virtual scanning keyboards face problems in evaluating alternate designs and hence in choosing the better design among alternatives. Automatic evaluation of designs will be helpful to designers in making the appropriate design choice. In this paper, we present performance models for virtual scanning keyboards that can be used for automatic evaluation. The proposed models address the limitations present in the reported work on similar models. We compared the model predictions with results from user trials and established the validity of the proposed models.
Speech sounds of the languages all over the world show remarkable patterns of cooccurrence. In this work, we attempt to automatically capture the patterns of cooccurrence of the consonants across languages and at the same time figure out the nature of the force leading to the emergence of such patterns. For this purpose we define a weighted network where the consonants are the nodes and an edge between two nodes (read consonants) signify their co-occurrence likelihood over the consonant inventories. Through this network we identify communities of consonants that essentially reflect their patterns of co-occurrence across languages. We test the goodness of the communities and observe that the constituent consonants frequently occur in such groups in real languages also. Interestingly, the consonants forming these communities reflect strong correlations in terms of their features, which indicate that the principle of feature economy acts as a driving force towards community formation. In order to measure the strength of this force we propose an information theoretic definition of feature economy and show that indeed the feature economy exhibited by the consonant communities are substantially better than those if the consonant inventories had evolved just by chance.
Purpose
Angiogenesis, or the formation of new retinal blood vessels is a key feature of many proliferative retinal diseases including diabetic retinopathy, retinal vein occlusions, and retinopathy of prematurity. The aim of the present study was to investigate the role of the serine proteinase inhibitor PAI-1 in facilitating retinal angiogenesis.
Methods
The temporal expression of PAI-1 was examined by real time PCR, western blotting and immunohistochemistry in retinal tissues from mice with oxygen-induced retinopathy. The requirement for PAI-1 in facilitating the retinal angiogenic response in this model was examined by quantitating the angiogenic response using both wildtype and PAI-1 null mice. The mechanism by which PAI-1 mediates angiogenesis was further investigated using isolated human retinal vascular endothelial cells.
Results
PAI-1 expression is up regulated in the retina of mice with oxygen-induced retinopathy. This coincides with a significant increase in the expression of vitronectin in the retina of the experimental mice. There was significant reduction in the angiogenic response of PAI-1−/− mice as compared to wild type mice. PAI-1 promotes endothelial cell migration in vitro and facilitates migration of cells on a vitronectin substrate by regulating αv integrin cell surface expression.
Conclusions
These observations suggest a role for PAI-1 during retinal angiogenesis and point to a potential new therapeutic target in the prevention or treatment of retinal neovascularization seen in many ocular diseases.
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