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Abstract Many attachments to a scanning electron microscope (SEM), such as energy dispersive x‐ray spectroscopy, extend its function significantly. Typically, the application of such attachments requires that the specimen has a planar surface at a specific orientation. It is a challenge to make the plane of a microscale specimen satisfy the orientation requirement since they are visible only in an SEM. An in‐situ procedure is needed to adjust specimen orientation by using stage rotation and tilting functions, in the process of which the key is to determine the initial orientation. This study proposed and tested top‐down and side‐view approaches to determine the orientation of a planar surface inside an SEM. In the top‐down one, the projected area is monitored on SEM images as stage rotation and tilt angles are adjusted. When the surface normal is along the electron beam direction, the area has a maximum value. In the side‐view approach, the stage is adjusted so that the projection appears to be a straight horizontal line on the SEM image. Once the orientation of the specimen for top‐down or side‐view observation is determined, the original can be calculated, and a desired orientation can be realized by manipulating the stage. The procedures have been tested by analyzing planar surfaces of spherical particles in Al‐Cu‐Fe alloy in the form of facets. The measured angles between two surfaces are consistent with those expected from crystallographic consideration within 2.7° and 1.7° for the top‐down and side‐view approaches, respectively. Research HighlightsTop‐down and side‐view approaches have been proposed and tested for in‐situ determination of specimen planar surface orientation in a Scanning Electron Microscope.The measured angles between two surfaces are consistent with those expected from crystallographic consideration within 2.7° and 1.7° for the top‐down and side‐view approaches, respectively.
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Linking global top-down views to first-person views in the brain
Humans and other animals have a remarkable capacity to translate their position from one spatial frame of reference to another. The ability to seamlessly move between top-down and first-person views is important for navigation, memory formation, and other cognitive tasks. Evidence suggests that the medial temporal lobe and other cortical regions contribute to this function. To understand how a neural system might carry out these computations, we used variational autoencoders (VAEs) to reconstruct the first-person view from the top-down view of a robot simulation, and vice versa. Many latent variables in the VAEs had similar responses to those seen in neuron recordings, including location-specific activity, head direction tuning, and encoding of distance to local objects. Place-specific responses were prominent when reconstructing a first-person view from a top-down view, but head direction–specific responses were prominent when reconstructing a top-down view from a first-person view. In both cases, the model could recover from perturbations without retraining, but rather through remapping. These results could advance our understanding of how brain regions support viewpoint linkages and transformations.
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- Award ID(s):
- 2024633
- PAR ID:
- 10465604
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 119
- Issue:
- 45
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1073/pnas.2202024119
