Abstract In the present study, the sources of thalamic and cortical inputs of thalamic reticular nucleus (TRN) neurons were examined by investigating the responses of the TRN neurons to electrical ...stimulation of different sites in the thalamus and the cortex of the rat. The recurrent excitation of the corticothalamic system that is triggered by electrical stimulation was eliminated by ablating the auditory cortex and by temporarily inactivating the medial geniculate body (MGB), when studying the sources of thalamic and cortical inputs, respectively. Single TRN neurons responded to electrical stimulation of 50–100 μA of the thalamus over a large area (dorsoventrally 1.2–2.4 mm and mediolaterally 1.0–2.3 mm, n =9). Four of 16 auditory TRN neurons responded to electrical stimulation of the lateral geniculate nucleus. The TRN neurons responded to cortical stimulation over a rostrocaudal distance of 2.6±0.5 mm (range: 1.5–3.5 mm, n =24) of the auditory cortex. Visual or auditory TRN neurons also responded to electrical stimulation in the auditory or visual cortices, respectively. The present study revealed that each TRN neuron received a wide range of inputs from both ascending thalamic and descending cortical projections. The projection could be cross-modal. Having a strong and lasting inhibition on the thalamus, the TRN neurons are likely to be involved in adjusting global states relating to awareness and attention in the thalamocortical system.
Researchers have been aiming to replace copper with carbon nanotube/copper nanocomposites, which are lighter and exhibit better electrical, mechanical, and thermal properties. However, the strength ...is far below pure carbon nanotube assembly and even much lower than some copper-based alloys. This disadvantage hinders the extensive application of carbon nanotube/copper nanocomposites. In this study, the carbon nanotube/aluminum–copper nanocomposites with ultra-strength and stiffness were prepared. The strength and elasticity modulus of composite reached as high as 6.6 and 500 GPa, respectively, while a high conductivity of 1.8 × 107 S/m was maintained. This can be attributed to the diffusion of Cu and Al atoms into the carbon nanotube fiber, which enhances friction between the carbon nanotubes by “pinning” and “bridging”. This structure provides us with novel insights into the design of carbon nanotubes/metal nanocomposites with ultrahigh strength and conductivity.
Nanolayered metallic composites usually deform via a transition from homogeneous deformation to major shear banding with decreasing layer thickness, and thus the improvement of strength often ...sacrifices the plasticity of materials. Here, we show two methods to promote brittle-to-ductile transition in nanolayered Ag/Nb pillars. Intrinsically, while keeping the pillar diameter constant, the reduction of layer thickness can increase the strength of multilayers and suppress shear induced failure. Extrinsically, for a constant layer thickness, decreasing the diameter of pillar suppresses shear bands and promotes more uniform plastic deformation. Furthermore, the critical layer thickness at peak strength of multilayers increases monotonically with decreasing pillar diameter. Interface structures evolve from amorphous layer to coherent interface with reduction of layer thickness. Homogeneous co-deformation mediated by heterogeneous interfaces and columnar grain boundaries promotes a unique work hardening behavior. This study indicates that a combination of intrinsic and extrinsic size effect may enable the accomplishment of high strength and uniform deformation simultaneously.
•Brittle-to-ductile transition in nanolayered metals is revealed through changing intrinsic and extrinsic dimension.•Intrinsically, the reduction of layer thickness can increase the strength of multilayers and suppress shear failure.•Extrinsically, decreasing the diameter of pillar suppresses shear bands and promotes uniform plastic deformation.•Homogeneous co-deformation promotes a unique work hardening behavior.
With the rapid development of urban rail transit, the operation companies are plagued by the wear issue of metro pantograph-catenary (PAC) system in the last decades. Abnormal wear not only increases ...the maintenance cost but also seriously affects the stability and safety of the PAC system. In this paper, the models of calculating the wear rate are proposed in the first place, which can be used to approximately predict the wear of the contact wire (CW) and the pantograph strip (PS). After that, the wear distribution on the rigid catenary wire between two adjacent subway stations is analyzed. In addition, the layout of the CW is investigated and a calculation method for estimating and predicting the wear profile on the PS is proposed. The maintenance data recorded by GuangZhou Metro Line 2 and Beijing Metro Line 6 are introduced to validate the proposed models and prediction methods. It shows that the predicted results are in good consistency with the practical wear on the CW and also on the PS. With the help of the wear distribution on the CW, it provides with a reference to take effective measures to extend the service life of the CW and make a differentiated maintenance strategy. In the light of the proposed wear prediction method for PS, a more optimal layout of the CW can be designed to reduce the formation of deep grooves on the PS.
•The two proposed models can be used for the wear rate calculation of rigid contact wire and pantograph strip in metro railway system.•The wear distribution on the contact wire between two adjacent subway stations is approximately estimated, which can serve as a reference for the practical maintenance schedule.•Taking the actual layout of the contact wire into consideration, the wear profile on the pantograph strip is investigated and a calculation method for estimating and predicting the wear profile on the pantograph strip is proposed.
•DC magnetron co-sputtering technology was performed to synthesize (TiVCr)100−xWx alloy films.•Doping W into TiVCr alloys film induces a phase transition from amorphous to quasicrystal and ...nanocrystal.•An ultrahigh strengthening effect where the strength is enhanced by two times was observed.
In this work, we have investigated the effect of W addition on microstructure and mechanical properties of equiatomic TiVCr medium entropy alloy films. It is found that a transition from amorphous phase to quasicrystal and nanocrystal occurs with increasing content of W, showing an improved crystallinity of the films. Hardness drastically increases with increasing W addition and reaches the maximum value of 7.2 GPa at 16.0 at% W content, which is two times higher than that of the initial sample. Amorphous phase strengthening, solid solution and precipitation strengthening become the dominant mechanism, responsible for the ultrahigh strengthening effect.
•Crystalline-to-amorphous transition sequentially take place in incoherent fcc/bcc dual-phase HEAs.•High-entropy interfacial character is strongly dependent on the layer thickness.•Solid-solution ...strengthening and phase interface strengthening are responsible for good combination with high strength and plasticity.
Heterogeneous phase interface with particular microstructure generally plays a key role in the mechanical behavior of nanostructured metals and alloys. Here, we reported a novel high-entropy phase interface with extraordinary property that is strongly dependent on the lattice mismatch and length scale in dual-phase high entropy alloys (DP-HEAs) multilayers. A disorder intermediate layer, fcc-to-amorphous and bcc-to amorphous transition sequentially take place in incoherent fcc/bcc DP-HEAs with decreasing layer thickness (h) owing to the mixture of multiple elements with different atomic radius at interface, producing the evolution from fcc/bcc interface to bcc/amorphous and then amorphous/amorphous interface. Therefrom, yield strength of fcc/bcc DP-HEAs reaches the maximum of 5.6 GPa at h = 10 nm, which is the highest reported strength of the metallic multilayers. However, the superior combination with high strength and uniform plastic strain is achieved through at h > 20 nm. The dominant deformation mechanism crossover from homogeneous co-deformation via interaction of dislocation with interface to catastrophic shear and multiple shear process, leading to the highest strength and good plasticity. This result implies that interfacial character could be accurately manipulated through mediating the interface atomic radius misfit, mixing enthalpy and intrinsic length scale, achieving strong and plastic DP-HEAs.
The carbon nanotube fiber has not shown its advantage and been widely used in many applications due to low conductivity. Depositing a metallic layer on the carbon nanotube fiber surface became an ...effective method. However, the strength of the carbon nanotube fiber decreases with increasing conductivity and coating thickness. Here, we deposited nanocrystalline metal coating on carbon nanotube fibers by magnetron sputtering. The coating consists of an ultrathin Al transitional layer and a Cu layer. After annealing, the Al atoms and Cu atoms diffused into the carbon nanotube fiber to form diffuse interface and chemical reaction interface, leading to the sliding resistance increase and contact resistance decrease between carbon nanotubes. As a result, the new composite fiber with a 2 μm thick Cu layer can exhibit a superhigh effective strength of 996 MPa and electrical conductivity of 2.6 × 107 S/m. This structure achieves both conductivity and strength increasing simultaneously.
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► Effects of LP with different coverage areas on FCG properties were investigated. ► Effects of residual stress and micro-structure on FCG properties were analyzed. ► Crack arrest and fatigue ...striation pattern on fracture cross-sections were studied. ► The reduction of FCG rate by LP in initial and final FCG stage was analyzed.
The effects of coverage area on fatigue crack growth (FCG) properties of 6061-T6 aluminum alloy subject to multiple laser peening (LP) impacts were investigated. Residual stress, micro-structure and fatigue striation pattern on fracture cross-sections were analyzed. Compressive residual stresses and dense dislocation arrangements can be found in the superficial layer after LP. LP coverage area has a direct influence on FCG properties as verified by different size of shell ridges and fatigue striation spacing on fracture cross-sections. Meanwhile, FCG rate decreases with the increase of compressive residual stresses distribution perpendicular to the crack growth direction in the initial FCG stage.
In this work, the hardness of Ag/Nb/Cu/Nb multilayers with Nb amorphous interlayer were investigated as the individual layer thickness of Ag or Cu (hAg or hCu) varies from 5 to 120 nm. The hardness ...values of Ag/Nb/Cu/Nb multilayers improve a lot compared with those of the Ag/Cu multilayers and the length scale effect of strengthening becomes broadening in the range of 5–60 nm. At hAg = 60 nm, the hardness remains high and reaches 95% of the maximum hardness of hAg = 5 nm. The enhancement can be contributed to the modulus mismatch and the crystal/amorphous interfaces (CAIs) due to the addition of Nb amorphous interlayer. These CAIs can both increase resistance of dislocations transmission and inhibit the deformation of the amorphous layer.
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