Homogeneous molybdenum disulfide tunnel diode formed <i>via</i> chemical doping

Liu, Xiaochi,Qu, Deshun,Choi, Min Sup,Lee, Changmin,Kim, Hyoungsub,Yoo, Won Jong American Institute of Physics 2018 Applied Physics Letters Vol.112 No.18

Modulation of Quantum Tunneling <i>via</i> a Vertical Two-Dimensional Black Phosphorus and Molybdenum Disulfide p–n Junction

Liu, Xiaochi,Qu, Deshun,Li, Hua-Min,Moon, Inyong,Ahmed, Faisal,Kim, Changsik,Lee, Myeongjin,Choi, Yongsuk,Cho, Jeong Ho,Hone, James C.,Yoo, Won Jong American Chemical Society 2017 ACS NANO Vol.11 No.9

<P>Diverse diode characteristics were observed in two (2D) black phosphorus (BP) and molybdenum disulfide (MoS2) heterojunctions. The characteristics of a backward rectifying diode, a Zener diode, and a forward rectifying diode were obtained from the heterojunction through-thickness modulation of the BP flake or back gate modulation. Moreover, a tunnel diode with a precursor to negative differential resistance can be realized by applying dual gating with a sad polymer electrolyte layer as a top gate dielectric material. Interestingly, a steep subthreshold swing Of 55 mV/dec was achieved in a top-gated 2D BP-MoS2 junction. Our simple device architecture and chemical doping-free processing guaranteed the device quality. This work helps us understand the fundamentals of tunneling in 2D semiconductor heterostructures and shows great potential in future applications in integrated low-power circuits.</P>

Pile-sinking force modeling and analysis of anti-pull impact pile driver

Shuyi Yang,Deshun Liu,Yaobing Sun 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.8

A "Rigid body - spring - rigid body - elastic rod - rigid body - spring - elastic rod" impact system dynamics model for an anti-pull impactpile driver is established based on the Newton mechanics and stress wave theory. In the developed model, the force, velocity, andstress curves are acquired by solving the dynamic equations. Influences of system dynamics parameters on the maximum pile-sinkingforce are discussed. Results show that mass and velocity of the impact hammer, stiffness of buffer spring and pile cap have significantimpacts on maximum pile-sinking force, while mass of transmission box and platen have less effects. In engineering applications, maximumpile-sinking force can be controlled by rational allocation and design of pile cap and platen’s stiffness. This work can provide someguidelines for the future product optimization design. As a result, impact performance pile drivers with much better can be designed.

Lateral MoS₂ p–n Junction Formed by Chemical Doping for Use in High-Performance Optoelectronics

Choi, Min Sup,Qu, Deshun,Lee, Daeyeong,Liu, Xiaochi,Watanabe, Kenji,Taniguchi, Takashi,Yoo, Won Jong American Chemical Society 2014 ACS NANO Vol.8 No.9

<P>This paper demonstrates a technique to form a lateral homogeneous 2D MoS<SUB>2</SUB> p–n junction by partially stacking 2D h-BN as a mask to p-dope MoS<SUB>2</SUB>. The fabricated lateral MoS<SUB>2</SUB> p–n junction with asymmetric electrodes of Pd and Cr/Au displayed a highly efficient photoresponse (maximum external quantum efficiency of ∼7000%, specific detectivity of ∼5 × 10<SUP>10</SUP> Jones, and light switching ratio of ∼10<SUP>3</SUP>) and ideal rectifying behavior. The enhanced photoresponse and generation of open-circuit voltage (<I>V</I><SUB>OC</SUB>) and short-circuit current (<I>I</I><SUB>SC</SUB>) were understood to originate from the formation of a p–n junction after chemical doping. Due to the high photoresponse at low <I>V</I><SUB>D</SUB> and <I>V</I><SUB>G</SUB> attributed to its built-in potential, our MoS<SUB>2</SUB> p–n diode made progress toward the realization of low-power operating photodevices. Thus, this study suggests an effective way to form a lateral p–n junction by the h-BN hard masking technique and to improve the photoresponse of MoS<SUB>2</SUB> by the chemical doping process.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-9/nn503284n/production/images/medium/nn-2014-03284n_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn503284n'>ACS Electronic Supporting Info</A></P>

An Improved Tet-on System to Tightly Conditionally Regulate Reporter Gene Expression

Yanping Ren,Xiangping Li,Qingyou Liu,Yanfei Deng,Deshun Shi 한국생물공학회 2015 Biotechnology and Bioprocess Engineering Vol.20 No.1

Reporter genes are often used as markers totrack the integration and expression of target genes inanimal genetic engineering. To avoid potential side effectsfrom reporter genes, in this study an improved Tet-onsystem was developed to control reporter gene expression,and its effectiveness was explored in transgenic cells. First,the rtTA protein was fused with Tat and NLS proteins toobtain the prokaryotic expression vector pET32a-Tat-rtTANSL. A eukaryotic transgenic vector was constructed, p-HS4-BPA-TmA-HS4, in which the reporter (mCherry) andtarget (PRL) genes were promoted by TRE and BCN,respectively. After confirming the functionality of thetransgenic vector, purified rtTA protein and Dox wereadded to induce expression of the mCherry gene. Theoptimal amount of purified rtTA protein, its influence ontarget gene expression, and the time of rtTA protein actionwere each investigated separately. The results showed thatrtTA protein was expressed in transformed E. coli with IPTGinduction. TRE could promote mCherry gene expressionby co-transfecting the constructed transgenic vector andprtTA plasmid. When purified rtTA protein and Dox wereadded, red fluorescence was observed in Bcap-37 cellstransfected with the p-HS4-BPA-TmA-HS4 vector, and theexogenous PRL gene was expressed regardless of mCherrygene expression. The optimal amount of rtTA protein was16 μg/mL, and it needed about 6 h to promote mCherrygene expression in transfected cells. These resultsdemonstrate that the expression of the mCherry reportergene can be tightly and conditionally regulated by our Tetonsystem.

Expression pattern of prohibitin, capping actin protein of muscle Z-line beta subunit and tektin-2 gene in Murrah buffalo sperm and its relationship with sperm motility

Zhaocheng Xiong,Haihang Zhang,Ben Huang,Qingyou Liu,Yingqun Wang,Deshun Shi,Xiangping Li 아세아·태평양축산학회 2018 Animal Bioscience Vol.31 No.11

Objective: The aim of the current study is to investigate the relationship between prohibitin (PHB), capping actin protein of muscle Z-line beta subunit (CAPZB), and tektin-2 (TEKT2) and sperm motility in Murrah buffalo. Methods: We collected the high-motility and low-motility semen samples, testis, ovary, muscle, kidney, liver, brain and pituitary from Murrah buffalo, and analysed the expression of PHB, CAPZB, and TEKT2 in mRNA (message RNA) and protein level. Results: Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) result showed that the expression of PHB was higher and CAPZB, TEKT2 were specifically expressed in testis as compared to the other 6 tissues, and that in testis, the expression of TEKT2 was higher than that of CAPZB and PHB. Immunohistochemistry test revealed that all three genes were located on the convoluted seminiferous tubule and enriched in spermatogenic cells. Both qRT-PCR and Western Blot results showed that the expression levels of PHB, CAPZB, and TEKT2 were significantly lower in the low-motility semen group compared to the high-motility semen group (p<0.05). Conclusion: The expression levels of PHB, CAPZB, and TEKT2 in Murrah buffalo sperm have a high positive correlation with sperm motility. And the three genes may be potential molecular markers for the decline of buffalo sperm motility.

Isolation and Identification of Prepubertal Buffalo (Bubalus bubalis) Spermatogonial Stem Cells

Feng, Wanyou,Chen, Shibei,Do, Dagiang,Liu, Qinyou,Deng, Yanfei,Lei, Xiaocan,Luo, Chan,Huang, Ben,Shi, Deshun Asian Australasian Association of Animal Productio 2016 Animal Bioscience Vol.29 No.10

Isolation and culture of spermatogonial stem cells (SSCs) are attractive for production of genetic modified offspring. In the present study, buffalo spermatogonial stem-like cells were isolated, cultured and expression pattern of different germ cell marker genes were determined. To recover spermatogonia, testes from age 3 to 7 months of buffalo were decapsulated, and seminiferous tubules were enzymatically dissociated. Two types of cells, immature sertoli cell and type A spermatogonia were observed in buffalo testes in this stage. Germ cell marker genes, OCT3/4 (Pou5f1), THY-1, c-kit, PGP9.5 (UCHL-1) and Dolichos biflorus agglutinin, were determined to be expressed both in mRNA and protein level by reverse transcription polymerase chain reaction and immunostaining in buffalo testes and buffalo spermatogonial stem-like cells, respectively. In the following, when the isolated buffalo buffalo spermatogonial stem-like cells were cultured in the medium supplemented 2.5% fetal bovine serum and 40 ng/mL glial cell-derived neurotrophic factor medium, SSCs proliferation efficiency and colony number were significantly improved than those of other groups (p<0.05). These findings may help in isolation and establishing long term in vitro culture system for buffalo spermatogonial stem-like cells, and accelerating the generation of genetic modified buffaloes.

Highly Oriented Monolayer Graphene Grown on a Cu/Ni(111) Alloy Foil

Huang, Ming,Biswal, Mandakini,Park, Hyo Ju,Jin, Sunghwan,Qu, Deshun,Hong, Seokmo,Zhu, Zhili,Qiu, Lu,Luo, Da,Liu, Xiaochi,Yang, Zheng,Liu, Zhongliu,Huang, Yuan,Lim, Hyunseob,Yoo, Won Jong,Ding, Feng,Wa American Chemical Society 2018 ACS NANO Vol.12 No.6

<P>Fast-growth of single crystal monolayer graphene by CVD using methane and hydrogen has been achieved on “homemade” single crystal Cu/Ni(111) alloy foils over large area. Full coverage was achieved in 5 min or less for a particular range of composition (1.3 at.% to 8.6 at.% Ni), as compared to 60 min for a pure Cu(111) foil under identical growth conditions. These are the bulk atomic percentages of Ni, as a superstructure at the surface of these foils with stoichiometry Cu<SUB>6</SUB>Ni<SUB>1</SUB> (for 1.3 to 7.8 bulk at.% Ni in the Cu/Ni(111) foil) was discovered by low energy electron diffraction (LEED). Complete large area monolayer graphene films are either single crystal or close to single crystal, and include folded regions that are essentially parallel and that were likely wrinkles that “fell over” to bind to the surface; these folds are separated by large, wrinkle-free regions. The folds occur due to the buildup of interfacial compressive stress (and its release) during cooling of the foils from 1075 °C to room temperature. The fold heights measured by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) prove them to all be 3 layers thick, and scanning electron microscopy (SEM) imaging shows them to be around 10 to 300 nm wide and separated by roughly 20 μm. These folds are always essentially perpendicular to the steps in this Cu/Ni(111) substrate. Joining of well-aligned graphene islands (in growths that were terminated prior to full film coverage) was investigated with high magnification SEM and aberration-corrected high-resolution transmission electron microscopy (TEM) as well as AFM, STM, and optical microscopy. These methods show that many of the “join regions” have folds, and these arise from interfacial adhesion mechanics (they are due to the buildup of compressive stress during cool-down, but these folds are different than for the continuous graphene films-they occur due to “weak links” in terms of the interface mechanics). Such Cu/Ni(111) alloy foils are promising substrates for the large-scale synthesis of single-crystal graphene film.</P> [FIG OMISSION]</BR>