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In addition to excellent surface passivation and carrier selectivity, the structure based on the heavily doped polysilicon layer on an ultrathin silicon oxide interlayer also demonstrates strong impurity gettering effects. Herein, the gettering strength of a range of phosphorus- or boron-doped polysilicon films from different fabrication techniques is assessed and compared. Iron, one of the most common metallic impurities in silicon, is used as a tracer impurity to quantify the gettering strength (segregation coefficient). A comparison of the experimental results to the literature, combined with measurements of the electrically active and inactive dopant concentrations, enables us to suggest the main gettering mechanisms in different polysilicon films. The differences in the segregation coefficients of the phosphorus-doped polysilicon films for iron are within one order of magnitude, in spite of their different combinations of gettering mechanisms. On the other hand, boron-doped polysilicon films show a large variation in their gettering effects, although the predominant gettering mechanisms are all attributed to electrically inactive boron, according to the current understanding of the gettering mechanisms from the literature. Finally, the impact of different polysilicon gettering effects on the efficiency of tunnel oxide-passivated contact (TOPCon) cells is simulated and discussed.

Current demonstration projects show that the power capacity of redox flow batteries can span a large range from kW- to MW-scale. The large-scale, especially MW-scale, flow battery system can usually benefit from cell's large active area, due to that a large cell can reduce the required number of cells and thus assembling difficulties. However, the lack of practical pathways for scaling-up lab-scale toward large-scale flow field designs has been one of the barriers to the commercialization of flow batteries. The present study investigates the interdigitated flow field design for a large-scale (900 cm2 active area) vanadium redox flow battery cell, based on a three-dimensional, multi-physical model. Four pathways for scaling up the flow field are investigated, including (i) geometric similarity, (ii) channel length extension, (iii) same pressure drop, and (v) split-interdigitated flow field. The relation between the width and length of the channel and the concentration overpotential is formulated. The results show that the split-interdigitated flow field outperforms the other scaling-up methods in terms of the overall energy efficiency, while at the cost of the increased pressure drop. To alleviate the high pressure drop, the design can be improved by widening the main channels or adding one extra flow inlet.

Polysilicon/oxide (poly-Si/SiOx) passivating contacts are a promising technology for the next-generation of high-efficiency silicon solar cells. The structure can be realised by a range of fabrication techniques, which can induce very different impurity gettering effects during the formation process. Understanding the different gettering effects will enable tailored solutions to optimise the gettering efficiency in device fabrication. This paper demonstrates a method to separately quantify the impact of each component on the overall gettering effect of the poly-Si/SiOx passivating contact structures. These components consist of the heavily doped poly-Si layer, in terms of its gettering strength; the SiOx interlayer, regarding its potential blocking effect for slowing down the diffusion of impurities; and the dopant in-diffused surface regions of the silicon wafer bulk directly below the SiOx interlayer, which may have a small additional gettering effect due to heavy doping. Phosphorus in-situ doped poly-Si layers from plasma-enhanced chemical vapour deposition (PECVD), coupled with SiOx interlayers from different growth techniques, were used to demonstrate the method. The experimental and simulation results confirm that the heavily doped poly-Si layer acts as the main gettering sink and the presence of different SiOx interlayers determines the overall gettering rate. For the ultrathin SiOx interlayers studied in this work, which have a similar thickness but different stoichiometry, a standard thermally grown SiOx demonstrates the strongest blocking effect, followed by a chemically grown SiOx from hot nitric acid, and a thermal SiOx of a reduced stoichiometry (grown in a pure nitrogen ambient) demonstrates practically no blocking effect.

In this paper, a generalization of differential electromagnetic equations in fractional space is provided. These equations can describe the behavior of electric and magnetic fields in any fractal media. The time evolution of the fractional electromagnetic waves by using the time fractional Maxwell's equations in fractional space has been investigated. Theoretical analysis shows that the amplitude variations of the general plane wave solution not only is related to Bessel functions, but also reveals an algebraic decay, at asymptotically large times.

Cells that express the NG2 proteoglycan (NG2+ cells) comprise a unique population of glial cells in the central nervous system. While there is no question that some NG2+ cells differentiate into oligodendrocytes during development, the persistence of numerous NG2+ cells in the mature CNS has raised questions about their identity, relation to other CNS cell types, and functions besides their progenitor role. NG2+ cells also express the alpha receptor for platelet-derived growth factor (PDGF αR), a receptor that mediates oligodendrocyte progenitor proliferation during development. Antigenically, NG2+ cells are distinct from fibrous and protoplasmic astrocytes, resting microglia, and mature oligodendrocytes. Therefore, we propose the term polydendrocytesto refer to all NG2-expressing glial cells in the CNS parenchyma. This distinguishes them from the classical glial cell types and identifies them as the fourth major glial population in the CNS. Recent observations suggest that polydendrocytes are complex cells that physically and functionally interact with other cell types in the CNS. Committed oligodendrocyte progenitor cells arise from restricted foci in the ventral ventricular zone in both spinal cord and brain. It remains to be clarified whether there are multiple sources of oligodendrocytes, and if so whether polydendrocytes (NG2+ cells) represent progenitor cells of all oligodendrocyte lineages. Proliferation of NG2+ cells during early development appears to be dependent on PDGF, but the regulatory mechanisms that govern NG2+ cell proliferation in the mature CNS remain unknown. Pulse-chase labeling with bromodeoxyuridine indicates that polydendrocytes that proliferate in the postnatal spinal cord differentiate into oligodendrocytes. Novel experimental approaches are being developed to further elucidate the functional properties and differentiation potential of polydendrocytes.

OMgp is selectively expressed in CNS by oligodendrocyte. However, its potential role(s) in oligodendrocyte development and myelination remain unclear. We show that OMgp null mice are hypomyelinated in their spinal cords, resulting in slower ascending and descending conduction velocities compared to wild-type mice. Consistent with the hypomyelination, in the MOG induced EAE model, OMgp null mice show a more severe EAE clinical disease and slower nerve conduction velocity compared to WT animals. The contribution of OMgp to oligodendrocyte differentiation and myelination was verified using cultured oligodendrocytes from null mice. Oligodendrocytes isolated from OMgp null mice show a significant decrease in the number of MBP+ cells and in myelination compared to wild-type mice. The dramatic effects of the OMgp KO in oligodendrocyte maturation in vivo and in vitro reveal a new and important function for OMgp in regulating CNS myelination.

Oligodendrocyte-myelin glycoprotein (OMgp) is a myelin component that has been shown in vitro to inhibit neurite outgrowth by binding to the Nogo-66 receptor (NgR1)/Lingo-1/Taj (TROY)/p75 receptor complex to activate the RhoA pathway. To investigate the effects of OMgp on axon regeneration in vivo, OMgp(-/-) mice on a mixed 129/Sv/C57BL/6 (129BL6) or a C57BL/6 (BL6) genetic background were tested in two spinal cord injury (SCI) models - a severe complete transection or a milder dorsal hemisection. OMgp(-/-) mice on the mixed 129BL6 genetic background showed greater functional improvement compared to OMgp(+/+) littermates, with increased numbers of cholera toxin B-labeled ascending sensory axons and 5-HT(+) descending axons and less RhoA activation after spinal cord injury. Myelin isolated from OMgp(-/-) mice (129BL6) was significantly less inhibitory to neurite outgrowth than wild-type (wt) myelin in vitro. However, OMgp(-/-) mice on a BL/6 genetic background showed neither statistically significant functional recovery nor axonal sprouting following dorsal hemisection.

Neurons and glia share a mutual dependence in establishing a functional relationship, and none is more evident than the process by which axons control myelination. Here, we identify LRR and Ig domain-containing, Nogo receptor-interacting protein (LINGO-1) as a potent axonal inhibitor of oligodendrocyte differentiation and myelination that is regulated by nerve growth factor and its cognate receptor TrkA in a dose-dependent manner. Whereas LINGO-1 expressed by oligodendrocyte progenitor cells was previously identified as an inhibitor of differentiation, we demonstrate that axonal expression of LINGO-1 inhibits differentiation with equal potency. Disruption of LINGO-1 on either cell type is sufficient to overcome the inhibitory action and promote differentiation and myelination, independent of axon diameter. Furthermore, these results were recapitulated in transgenic mice overexpressing the full length LINGO-1 under the neuronal promoter synapsin. Myelination was greatly inhibited in the presence of enforced axonal LINGO-1. The implications of these results relate specifically to the development of potential therapeutics targeting extrinsic growth factors that may regulate the axonal expression of modulators of oligodendrocyte development.

NG2 cells (polydendrocytes) comprise an abundant glial population that is widely and uniformly distributed throughout the developing and mature CNS and are identified by the expression of the NG2 proteoglycan at the cell surface. Although recent electrophysiological studies suggest that they are capable of receiving signals from axon terminals, other studies, based on the finding that the NG2 molecule itself induces growth cone collapse, have led to a widely held speculation that NG2 cells themselves also repel and inhibit growing axons. In this study, we have examined the effects of rat NG2 cells on growing hippocampal and neocortical axonsin vitroandin vivo. NG2 cells did not repel growing axons but promoted their growthin vitro, and axonal growth cones formed extensive contacts with NG2 cells bothin vitroand in the developing corpus callosum. Punctate immunoreactivity for fibronectin and laminin was found to be colocalized with NG2 on the surface of NG2 cells. Altering the level of cell surface NG2 expression had no effect on the growth-promoting effects of NG2 cells on growing axons. Thus, our study indicates that NG2 cells are not inhibitory to growing axons but provide an adhesive substrate for axonal growth cones and promote their growth even in the presence of elevated levels of the NG2 proteoglycan. These findings suggest a novel role for NG2 cells in facilitating axonal growth during development and regeneration.

Classic studies recognize two functionally segregated macroglial cell types in the central nervous system (CNS), namely astrocytes and oligodendrocytes. A third macroglial cell type has now been identified by its specific expression of the NG2 chondroitin sulphate proteoglycan (NG2-glia). These NG2-glia exist abundantly in both grey and white matter of the mature CNS and are almost as numerous as astrocytes. It is well established that NG2-glia give rise to oligodendrocytes. However, the majority of NG2-glia in the adult CNS proliferate very slowly and are non-motile. Both astrocytes and NG2-glia display a stellate morphology and express ion channels and receptors to neurotransmitters used by neurons. Both types of glia make intimate contacts with neurons in grey and white matter, and their functional differences and similarities are only beginning to be unravelled. Recent observations emphasize the need to examine the relationship between astrocytes and NG2-glia, and address the question of whether they represent overlapping or two distinct glial cell populations. To be of any relevance, this classification must relate to specific functions in the neural network. At present, the balance of evidence is that NG2-glia and astrocytes are functionally segregated populations.

Oligodendrocyte progenitor cells (OPCs, NG2 glia) play an important role not only as progenitor cells that give rise to myelinating cells in the central nervous system (CNS), but also as an active participant in the neural network. It is necessary to develop a simplified method for generating large quantities of highly purified OPCs for biochemical studies and to establish a neuron-OPC coculture method for functional studies on the mechanism of neuron-OPC signaling. In this study, we have compared the effects of plating density and culture medium on purity, survival, and differentiation of cells collected from primary rat mixed glial cultures by differential adhesion. Comparison of two chemically-defined culture media, Dulbecco's modified Eagle's medium with N1 supplements (N1/DMEM) and Neurobasal medium with B27 supplements (B27/NBM) revealed that while both media successfully maintained greater than 90% pure OPCs after 3 days, B27/NBM was significantly more effective in maintaining viable cells and in supporting oligodendrocyte differentiation than N1/DMEM, and this effect was more pronounced in low density cultures. Furthermore, B27/NBM supported neuron-OPC coculture in which OPCs remained as NG2-positive progenitors and neurons differentiated to form synapses over a period of 3 weeks.

Cells that express the NG2 proteoglycan (NG2+ cells) comprise a unique population of glial cells in the central nervous system. While there is no question that some NG2+ cells differentiate into oligodendrocytes during development, the persistence of numerous NG2+ cells in the mature CNS has raised questions about their identity, relation to other CNS cell types, and functions besides their progenitor role. NG2+ cells also express the alpha receptor for platelet-derived growth factor (PDGF alphaR), a receptor that mediates oligodendrocyte progenitor proliferation during development. Antigenically, NG2+ cells are distinct from fibrous and protoplasmic astrocytes, resting microglia, and mature oligodendrocytes. Therefore, we propose the term polydendrocytes to refer to all NG2-expressing glial cells in the CNS parenchyma. This distinguishes them from the classical glial cell types and identifies them as the fourth major glial population in the CNS. Recent observations suggest that polydendrocytes are complex cells that physically and functionally interact with other cell types in the CNS. Committed oligodendrocyte progenitor cells arise from restricted foci in the ventral ventricular zone in both spinal cord and brain. It remains to be clarified whether there are multiple sources of oligodendrocytes, and if so whether polydendrocytes (NG2+ cells) represent progenitor cells of all oligodendrocyte lineages. Proliferation of NG2+ cells during early development appears to be dependent on PDGF, but the regulatory mechanisms that govern NG2+ cell proliferation in the mature CNS remain unknown. Pulse-chase labeling with bromodeoxyuridine indicates that polydendrocytes that proliferate in the postnatal spinal cord differentiate into oligodendrocytes. Novel experimental approaches are being developed to further elucidate the functional properties and differentiation potential of polydendrocytes.