Vitamin C facilitates dopamine neuron differentiation in fetal midbrain through TET1- and JMJD3-dependent epigenetic control manner.

He, Xi-Biao,Kim, Mirang,Kim, Seon-Young,Yi, Sang-Hoon,Rhee, Yong-Hee,Kim, Taeho,Lee, Eun-Hye,Park, Chang-Hwan,Dixit, Shilpy,Harrison, Fiona E,Lee, Sang-Hun AlphaMed Press 2015 Stem Cells Vol.33 No.4

<P>Intracellular Vitamin C (VC) is maintained at high levels in the developing brain by the activity of sodium-dependent VC transporter 2 (Svct2), suggesting specific VC functions in brain development. A role of VC as a cofactor for Fe(II)-2-oxoglutarate-dependent dioxygenases has recently been suggested. We show that VC supplementation in neural stem cell cultures derived from embryonic midbrains greatly enhanced differentiation toward midbrain-type dopamine (mDA) neurons, the neuronal subtype associated with Parkinson's disease. VC induced gain of 5-hydroxymethylcytosine (5hmC) and loss of H3K27m3 in DA phenotype gene promoters, which are catalyzed by Tet1 and Jmjd3, respectively. Consequently, VC enhanced DA phenotype gene transcriptions in the progenitors by Nurr1, a transcription factor critical for mDA neuron development, to be more accessible to the gene promoters. Further mechanism studies including Tet1 and Jmjd3 knockdown/inhibition experiments revealed that both the 5hmC and H3K27m3 changes, specifically in the progenitor cells, are indispensible for the VC-mediated mDA neuron differentiation. We finally show that in Svct2 knockout mouse embryos, mDA neuron formation in the developing midbrain decreased along with the 5hmC/H3k27m3 changes. These findings together indicate an epigenetic role of VC in midbrain DA neuron development. Stem Cells2015;33:1320-1332</P>

Prolonged membrane depolarization enhances midbrain dopamine neuron differentiation via epigenetic histone modifications.

He, Xi-Biao,Yi, Sang-Hoon,Rhee, Yong-Hee,Kim, Hyemin,Han, Yong-Mahn,Lee, Suk-Ho,Lee, Hyunsu,Park, Chang-Hwan,Lee, Yong-Sung,Richardson, Eric,Kim, Byung-Woo,Lee, Sang-Hun AlphaMed Press 2011 Stem cells Vol.29 No.11

<P>Understanding midbrain dopamine (DA) neuron differentiation is of importance, because of physiological and clinical implications of this neuronal subtype. We show that prolonged membrane depolarization induced by KCl treatment promotes DA neuron differentiation from neural precursor cells (NPCs) derived from embryonic ventral midbrain (VM). Interestingly, the depolarization-induced increase of DA neuron yields was not abolished by L-type calcium channel blockers, along with no depolarization-mediated change of intracellular calcium level in the VM-derived NPCs (VM-NPCs), suggesting that the depolarization effect is due to a calcium-independent mechanism. Experiments with labeled DA neuron progenitors indicate that membrane depolarization acts at the differentiation fate determination stage and promotes the expression of DA phenotype genes (tyrosine hydroxylase [TH] and DA transporter [DAT]). Recruitment of Nurr1, a transcription factor crucial for midbrain DA neuron development, to the promoter of TH gene was enhanced by depolarization, along with increases of histone 3 acetylation (H3Ac) and trimethylation of histone3 on lysine 4 (H3K4m3), and decreases of H3K9m3 and H3K27m3 in the consensus Nurr1 binding regions of TH promoter. Depolarization stimuli on differentiating VM-NPCs also induced dissociation of methyl CpG binding protein 2 and related repressor complex molecules (repressor element-1 silencing transcription factor corepressor and histone deacetylase 1) from the CpG sites of TH and DAT promoters. Based on these findings, we suggest that membrane depolarization promotes DA neuron differentiation by opening chromatin structures surrounding DA phenotype genes and inhibiting the binding of corepressors, thus allowing transcriptional activators such as Nurr1 to access DA neuron differentiation gene promoter regions.</P>

The impact of the convex friction distribution on the seismic response of a spring-friction isolation system

Biao Wei,Peng Wang,Xuhui He,Lizhong Jiang 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.4

As for structures with rubber bearings during earthquakes, some firstly damaged bearings and the other normal bearings form atypical spring-friction isolation system. Furthermore, a rough contact surface, due to the stochastic damage of bearing, and the aroundsmooth contact surfaces form a convex distribution of friction coefficient. This paper attempts to analyze seismic responses of aspring-friction isolation system with a theoretically and linearly convex friction distribution, in which the friction coefficientgradually decreases with the distance from the center. The results show that such friction distribution inevitably increases thestructural relative displacement and possibly enlarges the structural acceleration and residual displacement under earthquakes. Theconvex pattern of friction distribution should be avoided in practical engineering, since it reduces the seismic isolation efficiency.

Gearshift characteristics of a two-speed transmission using new electrically controlled toothed band brakes

Biao Ma,Weichen Lu,He Wang,Liang Yu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.12

In order to realize the miniaturization and electrification of heavy vehicles, this paper innovatively puts forward a two-speed transmission device equiped with electrically controlled toothed band brakes. The dynamic models of the planetary gear and toothed band brake are derived, and the shift strategy is established to achieve the optimal dynamic performance. Moreover, the gearshift characteristics under different working parameters are studied to verify its feasibility. The results demonstrate that the toothed band brake has a short braking time and contributes to good shift performance, thus has potential for application. The effect of synchronous speed and actuator speed on shift performance is also analyzed. The increase of both speeds is beneficial to speed up the shift time, but lead to increased shift impact. The application of such a brake offers the possibility of full-electric and lightweight for electric vehicles.

Effects of shear keys on seismic performance of an isolation system

Biao Wei,Chaobin Li,Xiaolong Jia,Xuhui He,Menggang Yang 국제구조공학회 2019 Smart Structures and Systems, An International Jou Vol.24 No.3

The shear keys are set in a seismic isolation system to resist the long-term service loadings, and are cut off to isolate the earthquakes. This paper investigated the influence of shear keys on the seismic performance of a vertical spring-viscous damper-concave Coulomb friction isolation system by an incremental dynamic analysis (IDA) and a performance-based assessment. Results show that the cutting off process of shear keys should be simulated in a numerical analysis to accurately predict the seismic responses of isolation system. Ignoring the cutting off process of shear keys usually leads to untrue seismic responses in a numerical analysis, and many of them are unsafe for the design of isolated structure. And those errors will be increased by increasing the cutting off force of shear keys and decreasing the spring constant of shear keys, especially under a feeble earthquake. The viscous damping action postpones the cutting off time of shear keys during earthquakes, and reduces the seismic isolation efficiency. However, this point can be improved by increasing the spring constant of shear keys.

Exceptional electrochemical performance of freestanding electrospun carbon nanofiber anodes containing ultrafine SnO_<i>x</i> particles

Zhang, Biao,Yu, Yang,Huang, Zhendong,He, Yan-Bing,Jang, Donghyuk,Yoon, Won-Sub,Mai, Yiu-Wing,Kang, Feiyu,Kim, Jang-Kyo The Royal Society of Chemistry 2012 ENERGY AND ENVIRONMENTAL SCIENCE Vol.5 No.12

<P>SnO<SUB><I>x</I></SUB>–carbon nanofiber (CNF) composites are synthesized using the electrospinning technique for use as freestanding electrodes in Li-ion batteries. The electrodes made from the composites carbonized at 750 °C (SnO<SUB><I>x</I></SUB>–CNF-750) with 14.5 wt% SnO<SUB><I>x</I></SUB> deliver a remarkable capacity of 674 mA h g<SUP>−1</SUP> after 100 cycles when discharged at 0.5 A g<SUP>−1</SUP>. This result is considered the highest among those reported in the literature for anodes made from similar electrospun carbon fibers containing SnO<SUB><I>x</I></SUB> nanoparticles. An increase in carbonization temperature to 950 °C (SnO<SUB><I>x</I></SUB>–CNF-950) results in a significant reduction of the particle content in the fiber due to aggregation of Sn to form nanoparticles external to the fibers, with concomitant degradation of capacities. The presence of amorphous SnO<SUB><I>x</I></SUB> particles at the atomic scale embedded in the conductive CNFs is thought to be responsible for the exceptional electrochemical performance of the SnO<SUB><I>x</I></SUB>–CNF-750 electrodes. These ultrafine particles facilitate the reaction Sn + <I>x</I>Li<SUB>2</SUB>O → SnO<SUB><I>x</I></SUB> + 2<I>x</I>Li<SUP>+</SUP> + 2<I>x</I>e<SUP>−</SUP>, making it highly reversible, which is confirmed by the growing peak currents with increasing scan rate indicated by cyclic voltammetry, and the absence of Sn–Sn bonds in the particles revealed by the extended X-ray absorption fine structure spectroscopy (EXAFS). Both the SnO<SUB><I>x</I></SUB> particle size and content in the fiber play important roles in controlling the rate and cyclic performance of the SnO<SUB><I>x</I></SUB>–CNF composite electrodes.</P> <P>Graphic Abstract</P><P>This paper presents novel SnO<SUB><I>x</I></SUB>–carbon nanofiber composites with embedded ultrafine SnO<SUB><I>x</I></SUB> particles. The composites deliver remarkable power/energy densities as well as excellent cyclic performance due to their high reversibility and stability. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2ee23145j'> </P>

Two new species of Pustula (Albuginales, Oomycota) from Junggar Basin in China based on morphology and molecular data

Xu, Biao,Choi, Young Joon,Song, Jia Ge,Zhang, Shan He,Xi, Ping Gen,Shin, Hyeon Dong,De Jiang, Zi Springer-Verlag 2018 MYCOLOGICAL PROGRESS Vol.17 No.4

Influence of pier height on the effectiveness of seismic isolation of friction pendulum bearing for single-track railway bridges

Weikun He,Lizhong Jiang,Biao Wei,Zhenwei Wang 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.28 No.2

Friction pendulum bearing (FPB) in bridges with different pier heights has various degrees of effectiveness of seismic isolation. To determine the applicability of FPB under different bridge pier height conditions, this paper focuses on the simply supported girder railway bridges that have three types of piers: solid piers with uniform cross-section, solid piers with non-uniform cross-section, and hollow piers with non-uniform cross-section. All of these bridges are first installed with FPB (isolation bearing) and later with non-isolation bearing, modeled by using OpenSEES finite element software. A shake table test is used to verify the related models. Based on nonlinear dynamic time history analysis, the seismic responses of isolated and non-isolated bridges are compared, and their corresponding seismic isolation ratios are calculated. Further, this paper introduces a fuzzy comprehensive evaluation method to determine the seismic isolation effect of FPB on bridges with different pier heights, by weighing and balancing the isolation ratios of different seismic responses of bridges. The results show that the transverse seismic isolation ratios of FPB are generally larger than the longitudinal seismic isolation ratios. In addition, FPB has poorer seismic isolation effect on tall piers compared with short piers.

Foxa2 acts as a co-activator potentiating expression of the Nurr1-induced DA phenotype via epigenetic regulation

Yi, Sang-Hoon,He, Xi-Biao,Rhee, Yong-Hee,Park, Chang-Hwan,Takizawa, Takumi,Nakashima, Kinichi,Lee, Sang-Hun The Company of Biologists Limited 2014 Development (Cambridge) Vol.141 No.4

<P>Understanding how dopamine (DA) phenotypes are acquired in midbrain DA (mDA) neuron development is important for bioassays and cell replacement therapy for mDA neuron-associated disorders. Here, we demonstrate a feed-forward mechanism of mDA neuron development involving Nurr1 and Foxa2. Nurr1 acts as a transcription factor for DA phenotype gene expression. However, Nurr1-mediated DA gene expression was inactivated by forming a protein complex with CoREST, and then recruiting histone deacetylase 1 (Hdac1), an enzyme catalyzing histone deacetylation, to DA gene promoters. Co-expression of Nurr1 and Foxa2 was established in mDA neuron precursor cells by a positive cross-regulatory loop. In the presence of Foxa2, the Nurr1-CoREST interaction was diminished (by competitive formation of the Nurr1-Foxa2 activator complex), and CoREST-Hdac1 proteins were less enriched in DA gene promoters. Consequently, histone 3 acetylation (H3Ac), which is responsible for open chromatin structures, was strikingly increased at DA phenotype gene promoters. These data establish the interplay of Nurr1 and Foxa2 as the crucial determinant for DA phenotype acquisition during mDA neuron development.</P>

Thermal Analysis of High Density Permanent Magnet Synchronous Motor Based on Multi Physical Domain Coupling Simulation

Chen, ShiJun,Zhang, Qi,He, Biao,Huang, SuRong,Hui, Dou-Dou The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.1

In order to meet the thermal performance analysis accuracy requirements of high density permanent magnet synchronous motor (PMSM), a method of multi physical domain coupling thermal analysis based on control circuit, electromagnetic and thermal is presented. The circuit, electromagnetic, fluid, temperature and other physical domain are integrated and the temperature rise calculation method that considers the harmonic loss on the frequency conversion control as well as the loss non-uniformly distributed and directly mapped to the temperature field is closer to the actual situation. The key is to obtain the motor parameters, the realization of the vector control circuit and the accurate calculation and mapping of the loss. Taking a 48 slots 8 poles high density PMSM as an example, the temperature rise distribution of the key components is simulated, and the experimental platform is built. The temperature of the key components of the prototype machine is tested, which is in agreement with the simulation results. The validity and accuracy of the multi physical domain coupling thermal analysis method are verified.