Navigation methods and apparatus for the visually impaired

Abstract

According to some aspects, a wearable device for estimating a location of the device within a space is provided, the device comprising a plurality of cameras mounted to a structure, at least a portion of the structure being adapted to facilitate a user wearing the device, the plurality of cameras having substantially fixed positions and orientations on the structure relative to each other, and at least one processor configured to receive image data from the plurality of cameras, perform feature detection on the image data to obtain a first plurality of features from the image data, and determine an estimate of the location of the device in the space based, at least in part, on a location associated with a second plurality of features obtained from image data previously captured of the space that matches the first plurality of features.

What is claimed is: 
     
         1 . An in vitro method of developmental toxicity testing comprising the steps of:
 a. micropatterning an extracellular matrix;   b. growing pluripotent stem cells on the micropatterned extracellular matrix in the presence of a mesoendodermal induction medium for forming a geometrical mesoendoderm structure; and   c. testing for change of the geometrical mesoendoderm structure in a presence or an absence of a test compound wherein (1) a decrease in mesoendodermal cell differentiation and/or (2) a change in morphology of the geometrical mesoendoderm structure in the presence of the test compound compared to cells in the absence of the test compound indicates that the test compound is a developmentally toxic agent.   
     
     
         2 . The method of  claim 1 , wherein the mesoendermal induction medium comprises Activin amino acid, bone morphogenic protein, and fibroblast growth factor. 
     
     
         3 . The method of  claim 2 , wherein the mesoendodermal induction medium further comprises vascular endothelial growth factor. 
     
     
         4 . The method of  claim 1 , wherein the change in morphology of the geometrical mesoendoderm structure comprises a change in shape and/or location of the geometrical mesoendoderm structure. 
     
     
         5 . The method of  claim 1 , wherein the micropatterning is achieved by fabricating a stencil of a polydimethylsiloxane (PDMS) sheet having a plurality of geometric shapes cut into the PDMS sheet the PDMS stencil is sealed into a culture container, the matrix is coated over the PDMS stencil within the culture container such that when the PDMS stencil is removed only cells growing in the plurality of geometric shapes remain in the culture container. 
     
     
         6 . The method of  claim 1 , wherein the micropattern is formed by applying a plurality of growth factor gradients on the matrix. 
     
     
         7 . The method of  claim 6 , wherein the plurality of growth factor gradients are printed as a plurality of geometric shapes onto the matrix. 
     
     
         8 . The method of  claim 5 , wherein the plurality of geometric shapes is all the same size and shape, or the plurality of geometric shapes varies in size or shape. 
     
     
         9 . (canceled) 
     
     
         10 . The method of  claim 5 , wherein the plurality of geometric shapes is circular or square. 
     
     
         11 . (canceled) 
     
     
         12 . The method of  claim 5 , wherein the matrix comprises a gelatinous protein mixture secreted by Engelbreth-Holm-Swarm (EHS) mouse sarcoma cells. 
     
     
         13 . The method of  claim 1 , wherein the pluripotent stem cells are human embryonic stem cells (hESCs). 
     
     
         14 . The method of  claim 1 , wherein the pluripotent stem cells are seeded at a density of 4 million cells/ml. 
     
     
         15 . The method of  claim 1 , wherein testing for mesoendodermal cell differentiation is achieved by incubating the cells with antibody against a mesoendodermal marker and imaging the cells for detection of the marker. 
     
     
         16 . The method of  claim 1 , wherein a variation in mesoendodermal cell differentiation at an outer perimeter of the micropattern in the presence of the test compound compared to in the absence of the test compound indicates that the test compound is a developmentally toxic agent. 
     
     
         17 . The method of  claim 6 , wherein the plurality of growth factor gradients are printed as a plurality of geometric shapes onto the matrix, and wherein the plurality of geometric shapes is all the same size and shape, or the plurality of geometric shapes varies in size or shape. 
     
     
         18 . The method of  claim 6 , wherein the plurality of growth factor gradients are printed as a plurality of geometric shapes onto the matrix, and wherein the plurality of geometric shapes is circular or square. 
     
     
         19 . The method of  claim 6 , wherein the plurality of growth factor gradients are printed as a plurality of geometric shapes onto the matrix, and wherein the matrix comprises a gelatinous protein mixture secreted by Engelbreth-Holm-Swarm (EHS) mouse sarcoma cells.