Abstract
Physics A material's imperfections can greatly influence how well it conducts electricity. Theoretical physicists have, however, come up with the concept of topological insulators (TIs): materials that conduct only at their surface in a way that makes them “immune” to certain kinds of disorder. The compounds that have been identified as TIs, such as Bi2Se3, fall short of this ideal because they conduct electricity both through the “immune” surface states and the bulk of the material, which is still affected by disorder. Brahlek et al. made thin samples of Bi2Se3, adding copper atoms in precise quantities. When the samples were thick enough and had just the right concentrations of copper, the authors found that the samples were conducting only at their surfaces. This work is a step forward toward making useful TI devices. Phys. Rev. Lett. 113 , 026801 (2014).
Highlights
Primary cells, derived directly from human tissue, exhibit different behaviors in shape and signaling within threedimensional (3D) or 2D spaces
Constant interleukin-7 receptor activation causes T cells to die, so the T cell receptor intermittently blocks the activity of the interleukin-7 receptor
Petrie et al show that when the complex of actin and myosin contracts, it controls the pressure within cells and the shape of those protruding structures
Summary
T cells need to receive signals through both the T cell receptor and the interleukin-7 receptor. Signaling through the interleukin-7 receptor requires the kinase Jak. When researchers activated the T cell receptor, they generated increased amounts of microRNA. The microRNA prevented the T cells from producing new Jak protein and interfered with the ability of the interleukin-7 receptor to signal. Primary cells, derived directly from human tissue, exhibit different behaviors in shape and signaling within threedimensional (3D) or 2D spaces. When the pressure within the cell increases, cells display limb-like bumps, which they use to move through their 3D environment. In the 3D matrix, those cells have higher pressure that differs between the front and back of the cell, which creates a piston effect. In the 3D matrix, those cells have higher pressure that differs between the front and back of the cell, which creates a piston effect. — SMH
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