Two-photon live imaging of direct glia-to-neuron conversion in the mouse cortex

Over the past decade,a growing number of studies have reported transcription factor-based in situ reprogramming that can directly conve rt endogenous glial cells into functional neurons as an alternative approach for n euro regeneration in the adult mammalian central ne rvous system.Howeve r,many questions remain regarding how a terminally differentiated glial cell can transform into a delicate neuron that forms part of the intricate brain circuitry.In addition,concerns have recently been raised around the absence of astrocyte-to-neuron conversion in astrocytic lineage-tra cing mice.In this study,we employed repetitive two-photon imaging to continuously capture the in situ astrocyte-to-neuron conversion process following ecto pic expression of the neural transcription factor NeuroD1 in both prolife rating reactive astrocytes and lineage-tra ced astrocytes in the mouse cortex.Time-lapse imaging over several wee ks revealed the ste p-by-step transition from a typical astrocyte with numero us short,tapered branches to a typical neuro n with a few long neurites and dynamic growth cones that actively explored the local environment.In addition,these lineage-converting cells were able to migrate ra dially or to ngentially to relocate to suitable positions.Furthermore,two-photon Ca2+imaging and patch-clamp recordings confirmed that the newly generated neuro ns exhibited synchronous calcium signals,repetitive action potentials,and spontaneous synaptic responses,suggesting that they had made functional synaptic connections within local neural circuits.In conclusion,we directly visualized the step-by-step lineage conversion process from astrocytes to functional neurons in vivo and unambiguously demonstrated that adult mammalian brains are highly plastic with respect to their potential for neuro regeneration and neural circuit reconstruction.

A 1.8V CMOS Direct Conversion Receiver for a 900MHz RFID Reader Chip

A direct conversion receiver with optimized tolerance to local carrier interference is designed and implemented in a 0.18μm 1P6M mixed-signal CMOS process for a 900MHz RFID reader transceiver. A baseband amplifier with series feedback topology is proposed to achieve passive mixer buffering,baseband DC cancellation,and signal amplification simultaneously. The receiver has a measured input ldB compression point of - 4dBm and a sensitivity of - 70dBm when 10dB SNR for digital demodulation is required. The receiver is integrated in a reader transceiver chip and consumes 90mA from a 1.8V supply.

Automatic IQ Phase Calibration Design in a 2.4GHz Direct Conversion Receiver

An automatic IQ phase calibration method implemented in a 2.4GHz direct conversion receiver is proposed. It uses a delay locked loop （DLL） with a proposed quadrature phase detector to greatly reduce the phase error. The receiver is fabricated in a 0.18μm CMOS process. Measurements show that the IQ phase error can be calibrated within 1°,which satisfies the system requirement.

Characterization and Activity of Cr, Cu and Ga Modified ZSM-5 for Direct Conversion of Methane to Liquid Hydrocarbons

Direct conversion of methane using a metal-loaded ZSM-5 zeolite prepared viaacidic ion exchange was investigated to elucidate the roles of metal and acidity in the formation ofliquid hydrocarbons. ZSM-5 (SiO_2/Al_2O_3=30) was loaded with different metals (Cr, Cu and Ga)according to the acidic ion-exchange method to produce metal-loaded ZSM-5 zeolite catalysts. XRD,NMR, FT-IR and N_2 adsorption analyses indicated that Cr and Ga species managed to occupy thealuminum positions in the ZSM-5 framework. In addition, Cr species were deposited in the pores ofthe structure. However, Cu oxides were deposited on the surface and in the mesopores of the ZSM-5zeolite. An acidity study using TPD-NH_3, FT-IR, and IR-pyridine analyses revealed that the totalnumber of acid sites and the strengths of the Broensted and Lewis acid sites were significantlydifferent after the acidic ion exchange treatment. Cu loaded HZSM-5 is a potential catalyst fordirect conversion of methane to liquid hydrocarbons. The successful production of gasoline via thedirect conversion of methane depends on the amount of aluminum in the zeolite framework and thestrength of the Broensted acid sites.

Preparation and Performance of Ce/Zr Mixed Oxides for Direct Conversion of Methane to Syngas

CexZr1-xO2 mixed oxides with different Ce/Zr ratios were prepared by coprecipitation. The characterizations of mixed oxides were studied by X-ray diffraction (XRD) and H2-TPR. And the performances were tested in a fixed-bed quartz reactor. The results indicated that lattice oxygen of CexZr1-xO2 could oxidate methane to syngas and the incorporation of zirconium into the ceria lattice could improve the O2- mobility. The Ce0.7Zr0.3O2 had the best activity in investigative temperature ranging from 600 to 900 ℃. Effects of reaction time on H2/CO ratio were studied at 850 ℃ when using Ce0.7Zr0.3O2 as catalyst. The results indicated that the ratio was closed to 2 values in the first 10 min, however, it rapidly increased with reaction time after >10 min. The possible reason was that the direct partial oxidation of methane reaction was dominant in the first 10 min. However, the methane pyrogenation was responsible for the rapid increase of H2/CO ratio after 10 min. Thus, if syngas with H2/CO ratio of 2 wanted to be obtained, the reaction time needed to be controlled.

Direct conversion of methane to methanol by electrochemical methods

A convenient method for methane(CH_(4))direct conversion to methanol(CH_(3)OH)is of great significance to use methane-rich resources,especially clathrates and stranded shale gas resources located in remote regions.Theoretically,the activation of CH_(4) and the selectivity to the CH_(3)OH product are challenging due to the extreme stability of CH_(4) and relatively high reactivity of CH_(3)OH.The state-of-the-art‘methane reforming-methanol synthesis’process adopts a two-step strategy to avoid the further reaction of CH_(3)OH under the harsh conditions required for CH_(4) activation.In the electrochemical field,researchers are trying to develop conversion pathways under mild conditions.They have found suitable catalysts to activate the C–H bonds in methane with the help of external charge and have designed the electrode reactions to continuously generate certain active oxygen species.These active oxygen species attack the activated methane and convert it to CH_(3)OH,with the benefit of avoiding over-oxidation of CH_(3)OH,and thus obtain a high conversion efficiency of CH_(4) to CH_(3)OH.This mini-review focuses on the advantages and challenges of electrochemical conversion of CH4 to CH_(3)OH,especially the strategies for supplying electro-generated active oxygen species in-situ to react with the activated methane.

Comparison of the Performance of Two Direct Wave Energy Conversion Systems: Archimedes Wave Swing and Power Buoy

Many wave energy conversion devices have not been well received. The main reasons are that they are too complicated and not economical. However, in the last two decades direct conversion systems have drawn the attention of researchers to their widely distributed energy source due to their simple structure and low cost. The most well-known direct conversion systems presently in use include the Archimedes Wave Swing (AWS) and Power Buoy (PB). In this paper, these two systems were simulated in the same conditions and their behaviors were studied in different wave conditions. In order to verify the simulations, results of the generator of the finite element computations were followed. An attempt was made to determine the merits and drawbacks of each method under different wave conditions by comparing the performance of the two systems. The wave conditions suitable for each system were specified.

Tumor cells undergoing direct lineage conversion to neurons: unnatural but useful?

Dear Editor, In 2011, Son et al. （2011） reported that the forced expression of selected transcription factors is sufficient to convert mouse and human fibroblasts into induced motor neurons （iMNs）. The authors used three factors （Ascll, Brn2, and Mytll） to convert fibroblasts into neuronal-like ceils. After confirming that the cells had neuronal morphology, but with absence of motor neuron markers, eight candidate transcription factors were added, which participate in various stages of motor neuron specification. As expected, a significant number of motor cells emerged with known characteristics of cultured embryonic motor neurons.

Decoupled estimation of frequency-dependent IQI and channel for OFDM systems with direct-conversion transceivers

The in-phase and quadrature-phase imbalance (IQI) is one of the major radio frequency impairments existing in orthogonal frequency division multiplexing (OFDM) systems with direct-conversion transceivers. During the transmission of the communication signal, the impact of IQI is coupled with channel impulse responses (CIR), which makes the traditional channel estimation schemes ineffective. A decoupled estimation scheme is proposed to separately estimate the frequency-dependent IQI and wireless channel. Firstly, the generalized channel model is built to separate the parameters of IQI and wireless channel. Then an iterative estimation scheme of frequency-dependent IQI is designed at the initial stage of communication. Finally, based on the estimation result of IQI, the least square algorithm is utilized to estimate the channel-related parameters at each time of channel variation. Compared with the joint estimation schemes of IQI and channel, the proposed decoupled estimation scheme requires much lower training overhead at each time of channel variation. Simulation results demonstrate the good estimation performance of the proposed scheme.

Generation of diverse neural cell types through direct conversion

A characteristic of neurological disorders is the loss of critical populations of cells that the body is unable to replace,thus there has been much interest in identifying methods of generating clinically relevant numbers of cells to replace those that have been damaged or lost.The process of neural direct conversion,in which cells of one lineage are converted into cells of a neural lineage without first inducing pluripotency,shows great potential,with evidence of the generation of a range of functional neural cell types both in vitro and in vivo,through viral and non-viral delivery of exogenous factors,as well as chemical induction methods.Induced neural cells have been proposed as an attractive alternative to neural cells derived from embryonic or induced pluripotent stem cells,with prospective roles in the investigation of neurological disorders,including neurodegenerative disease modelling,drug screening,and cellular replacement for regenerative medicine applications,however further investigations into improving the efficacy and safety of these methods need to be performed before neural direct conversion becomes a clinically viable option.In this review,we describe the generation of diverse neural cell types via direct conversion of somatic cells,with comparison against stem cell-based approaches,as well as discussion of their potential research and clinical applications.

Direct driven wind energy conversion system based on hybrid excitation synchronous machine

A novel direct-drive type wind power generation system based on hybrid excitation synchronous machine（HESM）is introduced in this paper.The generator is connected to an uncontrollable rectifier,and a fully controlled voltage-sourceinverter is used to connect the system to utility grid.An intermediate DC bus exists between the rectifier and inverter.A new control strategy is proposed which achieves the maximum power point tracking（MPPT） with the control of excitation current of HESM and stabilizes the DC link voltage with the control of inverter output current simultaneously.Specially-designed buck circuit is used to control the excitation current of HESM,and grid voltage-oriented vector control strategy is employed to realize the decoupling of the inverter output power.Simulation results and experiment in 3 kW lab prototype show an excellent static and dynamic performance of the proposed system.

Post-transcriptional mechanisms controlling neurogenesis and direct neuronal reprogramming

Neurogenesis is a tightly regulated process in time and space both in the developing embryo and in adult neurogenic niches.A drastic change in the transcriptome and proteome of radial glial cells or neural stem cells towards the neuronal state is achieved due to sophisticated mechanisms of epigenetic,transcriptional,and post-transcriptional regulation.Understanding these neurogenic mechanisms is of major importance,not only for shedding light on very complex and crucial developmental processes,but also for the identification of putative reprogramming factors,that harbor hierarchically central regulatory roles in the course of neurogenesis and bare thus the capacity to drive direct reprogramming towards the neuronal fate.The major transcriptional programs that orchestrate the neurogenic process have been the focus of research for many years and key neurogenic transcription factors,as well as repressor complexes,have been identified and employed in direct reprogramming protocols to convert non-neuronal cells,into functional neurons.The post-transcriptional regulation of gene expression during nervous system development has emerged as another important and intricate regulatory layer,strongly contributing to the complexity of the mechanisms controlling neurogenesis and neuronal function.In particular,recent advances are highlighting the importance of specific RNA binding proteins that control major steps of mRNA life cycle during neurogenesis,such as alternative splicing,polyadenylation,stability,and translation.Apart from the RNA binding proteins,microRNAs,a class of small non-coding RNAs that block the translation of their target mRNAs,have also been shown to play crucial roles in all the stages of the neurogenic process,from neural stem/progenitor cell proliferation,neuronal differentiation and migration,to functional maturation.Here,we provide an overview of the most prominent post-transcriptional mechanisms mediated by RNA binding proteins and microRNAs during the neurogenic process,giving particular emphasis on the interplay of specific RNA binding proteins with neurogenic microRNAs.Taking under consideration that the molecular mechanisms of neurogenesis exert high similarity to the ones driving direct neuronal reprogramming,we also discuss the current advances in in vitro and in vivo direct neuronal reprogramming approaches that have employed microRNAs or RNA binding proteins as reprogramming factors,highlighting the so far known mechanisms of their reprogramming action.

BEST DIRECT AND CONVERSE RESULTS FOR LAGRANGE-TYPE OPERATORS

The aim of this paper is to give direct and converse theorems for the approximation by using a discretely defined method Ln (see D. H. Mache [10], which is a modification of the Lagrange operator. Furthermore we obtain with a matrix construction technique (see M. D. Ye and D. X. Zhou [11]) a Lagrange-type operator n, for which we get a characterization for Lipschitz functions by the approximation rate of these methods.

Design of Software-Defined Down-Conversion and Up-Conversion: An Overview

In recent years, much attention has been paid to software-defined radio （SDR） technologies for multimode wireless systems SDR can be defined as a radio communication system that uses software to modulate and demodulate radio signals. This article describes concepts, theory, and design principles for SDR down-conversion and up-conversion. Design issues in SDR down-conversion are discussed, and two different architectures, super-heterodyne and direct-conversion, are proposed. Design issues in SDR up-conversion are also discussed, and trade-offs in the design of filters, mixers, NCO, DAC, and signal processing are highlighted.

Impact of Two-Way FDI on the Industrial Structure in Shandong Province Under the Background of “New and Old Kinetic Energy Conversion”

This paper uses the panel data of 17 cities in Shandong Province from 2003 to 2018 to construct a panel model to empirically study the impact of foreign direct investment(FDI)on the industrial structure.The results show that two-way investment,financial industry development,and policy variables have significant roles in promoting the advancement of the industrial structure in the province.In the future implementation of the“Going Global”strategy in Shandong Province,the cooperation between two-way investment and the financial industry should be strengthened,the level of regional financial development should be improved,and the impact of two-way investment on the optimization and upgrading of the industrial structure should be reinforced.

New paths and research directions in CO_(2) conversion by electro-, photoand plasma catalysis

CO_(2) conversion into value-added products by electro-, photoand plasma catalysis under mild operating conditions(ambient temperature and pressure) is an emerging area to achieve carbon circularity by producing chemicals and fuels using directly renewable energy. Among all CO_(2) conversion approaches, the electrocatalytic reduction of CO_(2) is the most mature technology, capable of achieving high productivity(i.e. high current densities) at large scale, especially for producing carbon monoxide(CO), but with many examples showing selectivity to C_(2) carbon products.

Enhanced performance in the direct electrocatalytic synthesis of ammonia from N2 and H2O by an in-situ electrochemical activation of CNT-supported iron oxide nanoparticles

The direct electrocatalytic synthesis of ammonia from N2 and H2O by using renewable energy sources and ambient pressure/temperature operations is a breakthrough technology,which can reduce by over 90%the greenhouse gas emissions of this chemical and energy storage process.We report here an in-situ electrochemical activation method to prepare Fe2O3-CNT(iron oxide on carbon nanotubes)electrocatalysts for the direct ammonia synthesis from N2 and H2O.The in-situ electrochemical activation leads to a large increase of the ammonia formation rate and Faradaic efficiency which reach the surprising high values of 41.6μg mgcat^−1 h^−1 and 17%,respectively,for an in-situ activation of 3 h,among the highest values reported so far for non-precious metal catalysts that use a continuous-flow polymer-electrolytemembrane cell and gas-phase operations for the ammonia synthesis hemicell.The electrocatalyst was stable at least 12 h at the working conditions.Tests by switching N2 to Ar evidence that ammonia was formed from the gas-phase nitrogen.The analysis of the changes of reactivity and of the electrocatalyst characteristics as a function of the time of activation indicates a linear relationship between the ammonia formation rate and a specific XPS(X-ray-photoelectron spectroscopy)oxygen signal related to O2−in iron-oxide species.This results together with characterization data by TEM and XRD suggest that the iron species active in the direct and selective synthesis of ammonia is a maghemite-type iron oxide,and this transformation from the initial hematite is responsible for the in-situ enhancement of 3-4 times of the TOF(turnover frequency)and NH3 Faradaic efficiency.This transformation is likely related to the stabilization of the maghemite species at CNT defect sites,although for longer times of preactivation a sintering occurs with a loss of performances.

Direct transformation of fossil carbon into chemicals: A review

Despite the long tradition of fossil carbon(coal,char,and related carbon-based materials)for fueling mankind,the science of transforming them into chemicals is still demandingly progressing in the current energy scenario,especially when considering its responsibilities to the global climate change.Traditionally,there are four routes of preparing chemicals directly from fossil carbon,including hydrogasification,gasification,direct liquefaction,and oxidation,in the macroscope of gas-solid reaction(hydrogasification and gasification)and liquid-solid reaction(direct liquefaction and oxidation).When the study goes to microscale,the gas-solid reaction can be considered as the reaction between the severe condensed radicals and gas,while the liquid-solid reaction is the direct reaction between the radical and the activated-molecule.To have a full overview of the area,this review systematically summarizes the main factors in these processes and shows our own perspectives as follows,(ⅰ)stabilizing the free radicals generated from coal and then directly converting them has the highest efficiency in coal utilization;(ⅱ)the research on the self-catalytic process of coal structure will have a profound impact on the direct preparation of chemicals from fossil carbon.Further discussions are also proposed to guide the future study of the area into a more sustainable direction.