Intrinsic control of axon regeneration

Spinal cord injury disrupts the connections between the brain and spinal cord, often resulting in the loss of sensory and motor function below the lesion site. The most important reason for such permanent functional deficits is the failure of injured axons to regenerate after injury. In principle, the functional recovery could be achieved by two forms of axonal regrowth: the regeneration of lesioned axons which will reconnect with their original targets and the sprouting of spared axons that form new circuits and compensate for the lost function. Our recent studies reveal the activity of the mammalian target of rapamycin (mTOR) pathway, a major regulator of new protein synthesis, as a critical determinant of axon regrowth in the adult retinal ganglion neurons[1]. In this review, I summarize current understanding of the cellular and molecular mechanisms that control the intrinsic regenerative ability of mature neurons

Neuropilin Is a Receptor for the Axonal Chemorepellent Semaphorin III

AbstractExtending axons in the developing nervous system are guided to their targets through the coordinate actions of attractive and repulsive guidance cues. The semaphorin family of guidance cues comprises several members that can function as diffusible axonal chemorepellents. To begin to elucidate the mechanisms that mediate the repulsive actions of Collapsin-1/Semaphorin III/D (Sema III), we searched for Sema III–binding proteins in embryonic rat sensory neurons by expression cloning. We report that Sema III binds with high affinity to the transmembrane protein neuropilin, and that antibodies to neuropilin block the ability of Sema III to repel sensory axons and to induce collapse of their growth cones. These results provide evidence that neuropilin is a receptor or a component of a receptor complex that mediates the effects of Sema III on these axons

Theory of the special Smith-Purcell radiation from a rectangular grating

The recently uncovered special Smith-Purcell radiation (S-SPR) from the rectangular grating has significantly higher intensity than the ordinary Smith-Purcell radiation (SPR). Its monochromaticity and directivity are also much better. Here we explored the mechanism of the S-SPR by applying the fundamental electromagnetic theory and simulations. We have confirmed that the S-SPR is exactly from the radiating eigen modes of the grating. Its frequency and direction are well correlated with the beam velocity and structure parameters, which indicates its promising applications in tunable wave generation and beam diagnostic

Role of Elastic Phonon Couplings in Dictating the Thermal Transport across Atomically Sharp SiC/Si Interfaces

Wide-bandgap (WBG) semiconductors have promising applications in power electronics due to their high voltages, radio frequencies, and tolerant temperatures. Among all the WBG semiconductors, SiC has attracted attention because of its high mobility, high thermal stability, and high thermal conductivity. However, the interfaces between SiC and the corresponding substrate largely affect the performance of SiC-based electronics. It is therefore necessary to understand and design the interfacial thermal transport across the SiC/substrate interfaces, which is critical for the thermal management design of these SiC-based power electronics. This work systematically investigates heat transfer across the 3C-SiC/Si, 4H-SiC/Si, and 6H-SiC/Si interfaces using non-equilibrium molecular dynamics simulations and diffuse mismatch model. We find that the room temperature ITC for 3C-SiC/Si, 4H-SiC/Si, and 6H-SiC/Si interfaces is 932 MW/m2K, 759 MW/m2K, and 697 MW/m2K, respectively. We also show the contribution of the ITC resulting from elastic scatterings at room temperature is 80% for 3C-SiC/Si interfaces, 85% for 4H-SiC/Si interfaces, and 82% for 6H-SiC/Si interfaces, respectively. We further find the ITC contributed by the elastic scattering decreases with the temperature but remains at a high ratio of 67%~78% even at an ultrahigh temperature of 1000 K. The reason for such a high elastic ITC is the large overlap between the vibrational density of states of Si and SiC at low frequencies (< ~ 18 THz), which is also demonstrated by the diffuse mismatch mode. It is interesting to find that the inelastic ITC resulting from the phonons with frequencies higher than the cutoff frequency of Si (i.e., ~18 THz) can be negligible. That may be because of the wide frequency gap between Si and SiC, which makes the inelastic scattering among these phonons challenging to meet the energy and momentum conservation rules

Analysis and Design of Adaptive Synchronization of a Complex Dynamical Network with Time-Delayed Nodes and Coupling Delays

This paper is devoted to the study of synchronization problems in uncertain dynamical networks with time-delayed nodes and coupling delays. First, a complex dynamical network model with time-delayed nodes and coupling delays is given. Second, for a complex dynamical network with known or unknown but bounded nonlinear couplings, an adaptive controller is designed, which can ensure that the state of a dynamical network asymptotically synchronizes at the individual node state locally or globally in an arbitrary specified network. Then, the Lyapunov-Krasovskii stability theory is employed to estimate the network coupling parameters. The main results provide sufficient conditions for synchronization under local or global circumstances, respectively. Finally, two typical examples are given, using the M-G system as the nodes of the ring dynamical network and second-order nodes in the dynamical network with time-varying communication delays and switching communication topologies, which illustrate the effectiveness of the proposed controller design methods

Desertification Reversal Promotes the Complexity of Plant Community by Increasing Plant Species Diversity of Each Plant Functional Type

Desertification reversal is globally significant for the sustainable development of land resources. However, the mechanisms of desertification reversal at the level of plant community are still unclear. We hypothesized that desertification reversal has clear effects on plant community composition, plant functional types (PFTs), and other vegetation characteristics, including plant diversity and biomass, and their changes in the early stages of reversal are more dramatic than in later stages. We investigated the vegetation of four to five different stages of desertification reversal at each of seven large study sites in southwestern Mu Us Sandy Land, China. The results show that the dominant species in very severe desertification areas were replaced by perennial grasses in potential desertification areas. The importance values of annual forbs and perennial sub-shrubs decreased dramatically (from 42.59 and 32.98 to 22.13 and 5.54, respectively), whereas those of perennial grasses and perennial forbs increased prominently (from 13.26 and 2.71 to 53.94 and 11.79, respectively) with the reversal of desertification. Desertification reversal increased the complexity of plant community composition by increasing plant species in each PFT, and C3 plants replaced C4 plants to become the dominant PFT with reversal. Plant species richness and species diversity rose overall, and aboveground plant biomass significantly (p < 0.05) increased with the reversal of desertification. Most vegetation characteristics changed more strikingly in the early stages of desertification reversal than in later stages. Our results indicate that the type and composition of the plant community were dramatically affected by desertification reversal. Anthropogenic measures are more applicable to being employed in early stages than in later stages, and Amaranthaceae C4 plants are suggested to be planted in mobile dunes for the acceleration of desertification reversal. This study is useful for designing strategies of land management and ecological restoration in arid and semiarid regions

Do stocking densities affect the gut microbiota of gibel carp (Carassius auratus gibelio) cultured in ponds?

The aim of the present study was to evaluate the intestinal microbial communities of gibel carp (Carassius auratus gibelio) cultivated in two beach ponds at different stocking densities. The two ponds were both ~3.33 hm2 in acreage and ~1.5 m in depth. The stocking densities included one intensive with 2 fish m–3 while the other treated as semi-intensive with 1 fish m–3. The gut microbiota (both allochthonous and autochthonous) were sampled after 135 days of feeding. Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene segments was used to evaluate the bacterial community. Actinobacteria, Cyanobacteria, Firmicutes, Fusobacteria, Proteobacteria and some unclassified_bacteria taxa were identified in gut samples and feed. Similar bacterial communities (Cs=0.83) were observed with respect to the autochthonous and allochthonous gut microbiota of gibel carp cultured in the intensive culture pond. In contrast to these results, some difference (Cs=0.61) was observed in the gut microbiota of fish reared in the semi-intensive culture pond. Our results indicated that the difference in the bacterial communities between allochthonous bacteria and gut associated bacteria of gibel carp was not constant and was modulated by the stocking density