Nanoscale stiffness topography reveals structure and mechanics of the transport barrier in intact nuclear pore complexes

The nuclear pore complex (NPC) is the gate for transport between the cell nucleus and the cytoplasm. Small molecules cross the NPC by passive diffusion, but molecules larger than ∼5 nm must bind to nuclear transport receptors to overcome a selective barrier within the NPC1. Although the structure and shape of the cytoplasmic ring of the NPC are relatively well characterized2, 3, 4, 5, the selective barrier is situated deep within the central channel of the NPC and depends critically on unstructured nuclear pore proteins5, 6, and is therefore not well understood. Here, we show that stiffness topography7 with sharp atomic force microscopy tips can generate nanoscale cross-sections of the NPC. The cross-sections reveal two distinct structures, a cytoplasmic ring and a central plug structure, which are consistent with the three-dimensional NPC structure derived from electron microscopy2, 3, 4, 5. The central plug persists after reactivation of the transport cycle and resultant cargo release, indicating that the plug is an intrinsic part of the NPC barrier. Added nuclear transport receptors accumulate on the intact transport barrier and lead to a homogenization of the barrier stiffness. The observed nanomechanical properties in the NPC indicate the presence of a cohesive barrier to transport and are quantitatively consistent with the presence of a central condensate of nuclear pore proteins in the NPC channel

Complexity Theory for a New Managerial Paradigm: A Research Framework

In this work, we supply a theoretical framework of how organizations can embed complexity management and sustainable development into their policies and actions. The proposed framework may lead to a new management paradigm, attempting to link the main concepts of complexity theory, change management, knowledge management, sustainable development, and cybernetics. We highlight how the processes of organizational change have occurred as a result of the move to adapt to the changes in the various global and international business environments and how this transformation has led to the shift toward the present innovation economy. We also point how organizational change needs to deal with sustainability, so that the change may be consistent with present needs, without compromising the future

Neutron irradiation and compatibility testing of Li/sub 2/O

A study was made of the neutron-irradiation behavior of /sup 6/Li-enriched Li/sub 2/O material in EBR-II. In addition, a stress-corrosion study was performed ex-reactor to test compatibility of Li/sub 2/O materials with a variety of stainless steels. Results of the irradiation testing showed that tritium and helium retention in the Li/sub 2/O (approx. 89% dense) lessened with neutron exposure. Helium and tritium retention appear to approach steady-state after approx. 1% /sup 6/Li burnup. The stress-corrosion studies, using 316 stainless steel (Ti-modified) and a 35% Ni alloy, showed that stress does not enhance the corrosion, and that dry Li/sub 2/O is not significantly corrosive, the LiOH content producing the corrosive effects. Corrosion, in general, was not severe as a passivation in sealed capsules seemed to occur after a time, greatly reducing corrosion rates

Irradiation and compatibility testing of Li/sub 2/O materials at EBR-II

A study was made of the neutron-irradiation behavior of /sup 6/Li-enriched Li/sub 2/O material in EBR-II. In addition, a stress corrosion study was performed ex-reactor to test compatibility of Li/sub 2/O materials with a variety of stainless steels. Results of the irradiation testing showed that tritium and helium retention in the Li/sub 2/O (approx. 89% dense) lessened with neutron exposure. Helium tritium retention appeared to approach steady-state after approx. 1% /sup 6/Li burnup. The effect was likely caused by the formation of open porosity in the pellets. The stress corrosion studies, using a 316 stainless steel (Ti-modified) and a 35% Ni alloy, showed that stress does not enhance the corrosion, and that dry Li/sub 2/O is not significantly corrosive, the LiOH content producing the corrosive effects. Corrosion, in general, was not severe as a passivation in sealed capsules seemed to occur after a time greatly reducing corrosion rates