Steady-state dendritic cells expressing cognate antigen terminate memory CD8+ T-cell responses

Antigen stimulation of naive T cells in conjunction with strong costimulatory signals elicits the generation of effector and memory populations. Such terminal differentiation transforms naive T cells capable of differentiating along several terminal pathways in response to pertinent environmental cues into cells that have lost developmental plasticity and exhibit heightened responsiveness. Because these cells exhibit little or no need for the strong costimulatory signals required for full activation of naive T cells, it is generally considered memory and effector T cells are released from the capacity to be inactivated. Here, we show that steadystate dendritic cells constitutively presenting an endogenously expressed antigen inactivate fully differentiated memory and effector CD8+ T cells in vivo through deletion and inactivation. These findings indicate that fully differentiated effector and memory T cells exhibit a previously unappreciated level of plasticity and provide insight into how memory and effector T-cell populations may be regulated. © 2008 by The American Society of Hematology.

Bio-inspired multifunctional metallic foams through the fusion of different biological solutions

Nature is a school for scientists and engineers. Inherent multiscale structures of biological materials exhibit multifunctional integration. In nature, the lotus, the water strider, and the flying bird evolved different and optimized biological solutions to survive. In this contribution, inspired by the optimized solutions from the lotus leaf with superhydrophobic self-cleaning, the water strider leg with durable and robust superhydrophobicity, and the lightweight bird bone with hollow structures, multifunctional metallic foams with multiscale structures are fabricated, demonstrating low adhesive superhydrophobic self-cleaning, striking loading capacity, and superior repellency towards different corrosive solutions. This approach provides an effective avenue to the development of water strider robots and other aquatic smart devices floating on water. Furthermore, the resultant multifunctional metallic foam can be used to construct an oil/water separation apparatus, exhibiting a high separation efficiency and long-term repeatability. The presented approach should provide a promising solution for the design and construction of other multifunctional metallic foams in a large scale for practical applications in the petro-chemical field. Optimized biological solutions continue to inspire and to provide design idea for the construction of multiscale structures with multifunctional integration. Inspired by the optimized biological solutions from the lotus leaf with superhydrophobic self-cleaning, the water strider leg with durable and robust superhydrophobicity, and the lightweight bird bone with hollow structures, multifunctional metallic foams with multiscale structures are fabricated, demonstrating low adhesive superhydrophobic self-cleaning, striking loading capacity, stable corrosion resistance, and oil/water separation.

Kinetics and mechanism of hot corrosion of γ-Y 2Si 2O 7 in thin-film Na 2SO 4 molten salt

γ-Y 2Si 2O 7 is a promising candidate material both for hightemperature structural applications and as an environmental/thermal barrier coating material due to its unique properties such as high melting point, machinability, thermal stability, low linear thermal expansion coefficient (3.9×10 -6/K, 200°-1300°C), and low thermal conductivity (<3.0 W/ṁK above 300°C). The hot corrosion behavior of γ-Y 2Si 2O 7 in thin-film molten Na 2SO 4 at 850°-1000°C for 20 h in flowing air was investigated using a thermogravimetric analyzer (TGA) and a mass spectrometer (MS). γ-Y 2Si 2O 7 exhibited good resistance against Na 2SO 4 molten salt. The kinetic curves were well fitted by a paralinear equation: the linear part was caused by the evaporation of Na2SO4 and the parabolic part came from gas products evolved from the hotcorrosion reaction. A thin silica film formed under the corrosion scale was the key factor for retarding the hot corrosion. The apparent activation energy for the corrosion of γ-Y 2Si 2O 7 in Na 2SO 4 molten salt with flowing air was evaluated to be 255 kJ/mol.

Warfare in stingless bees

Bees are well known for being industrious pollinators. Some species, however, have taken to invading the nests of other colonies to steal food, nest material or the nest site itself. Despite the potential mortality costs due to fighting with an aggressive opponent, the prospects of a large bounty can be worth the risk. In this review, we aim to bring together current knowledge on intercolony fighting with a view to better understand the evolution of warfare in bees and identify avenues for future research. A review of literature reveals that at least 60 species of stingless bees are involved in heterospecific conflicts, either as attacking or victim colonies. The threat of invasion has led to the evolution of architectural, behavioural and morphological adaptations, such as narrow entrance tunnels, mud balls to block the entrance, decoy nests that direct invaders away from the brood chamber, fighting swarms, and soldiers that are skilled at immobilising attackers. Little is known about how victim colonies are selected, but a phylogenetically controlled analysis suggests that the notorious robber bee Lestrimelitta preferentially attacks colonies of species with more concentrated honey. Warfare among bees poses many interesting questions, including why species differ so greatly in their response to attacks and how these alternative strategies of obtaining food or new nest sites have evolved.