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CO in Protostars (COPS): <i>Herschel</i>-SPIRE Spectroscopy of Embedded Protostars
Yang, Yao-Lun,Green, Joel D.,Evans II, Neal J.,Lee, Jeong-Eun,Jørgensen, Jes K.,Kristensen, Lars E.,Mottram, Joseph C.,Herczeg, Gregory,Karska, Agata,Dionatos, Odysseas,Bergin, Edwin A.,Bouwman, Jeroe American Astronomical Society 2018 The Astrophysical journal Vol.860 No.2
<P>We present full spectral scans from 200 to 670. mu m of 26 Class 0+I protostellar sources obtained with Herschel-SPIRE as part of the 'COPS-SPIRE' Open Time program, complementary to the DIGIT and WISH Key Programs. Based on our nearly continuous, line-free spectra from 200 to 670. mu m, the calculated bolometric luminosities (L-bol) increase by 50%. on average, and the bolometric temperatures (T-bol) decrease by 10%. on average, in comparison with the measurements without Herschel. Fifteen protostars have the same class using Tbol and L-bol/L-smm. We identify rotational transitions of CO lines from J = 4 -> 3to J = 13 -> 12, along with emission lines of (CO)-C-13, HCO+, H2O, and [C I]. The ratios of (CO)-C-12 to (CO)-C-13 indicate that (CO)-C-12 emission remains optically thick for J(up) < 13. We fit up to four components of temperature from the rotational diagram with flexible break points to separate the components. The distribution of rotational temperatures shows a primary population around 100 K with a secondary population at similar to 350 K. We quantify the correlations of each line pair found in our data set and find that the strength of the correlation of CO lines decreases as the difference between J levels between two CO lines increases. The multiple origins of CO emission previously revealed by velocity-resolved profiles are consistent with this smooth distribution if each physical component contributes to a wide range of CO lines with significant overlap in the CO ladder. We investigate the spatial extent of CO emission and find that the morphology is more centrally peaked and less bipolar at high-J lines. We find the CO emission observed with SPIRE related to outflows, which consists of two components, the entrained gas and shocked gas, as revealed by our rotational diagram analysis, as well as the studies with velocity-resolved CO emission.</P>
Fabrication of Nitrogen Doped p-ZnO and ZnO Light-Emitting Diodes on Sapphire
Y. M. Lu,Z. P. Wei,D. Z. Shen,Z. Z. Zhang,B. Yao,B. H. Li,J. Y. Zhang,D. X. Zhao,X. W. Fan,Z. K. Tang 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
Nitrogen-doped p-type ZnO thin films were grown on c-plane sapphire (Al2O3) substrates by plasma-assistant molecular beam epitaxy, where O2 and N2 were introduced via a RF plasma source simultaneously. In situ optical emission spectra of the plasma were employed to monitor the chemical species in the active gas sources, one of the most important growth parameters. By adjusting the growth parameters, we confirm the optimal condition for p-type doping growth. The reproducible p-type ZnO thin films have the hole concentration (NA −ND) up to 1.0 × 1018 cm−3 and the resistivity of 6 cm. A ZnO LED was fabricated by depositing undoped n-type ZnO on the p-type layer. Electroluminescence spectra centered about 430 nm were obtained even at 350 K.
Kang, K. A.,Piao, M. J.,Kim, K. C.,Cha, J. W.,Zheng, J.,Yao, C. W.,Chae, S.,Hyun, J. W. Springer Science + Business Media 2014 In vitro cellular & developmental biology Animal Vol.50 No.1
Hydrogen peroxide (H2O2) can induce cell damage by generating reactive oxygen species (ROS), resulting in DNA damage and cell death. The aim of this study is to elucidate the protective effects of fisetin (3,7,3',4',-tetrahydroxy flavone) against H2O2-induced cell damage. Fisetin reduced the level of superoxide anion, hydroxyl radical in cell free system, and intracellular ROS generated by H2O2. Moreover, fisetin protected against H2O2-induced membrane lipid peroxidation, cellular DNA damage, and protein carbonylation, which are the primary cellular outcomes of H2O2 treatment. Furthermore, fisetin increased the level of reduced glutathione (GSH) and expression of glutamate-cysteine ligase catalytic subunit, which is decreased by H2O2. Conversely, a GSH inhibitor abolished the cytoprotective effect of fisetin against H2O2-induced cells damage. Taken together, our results suggest that fisetin protects against H2O2-induced cell damage by inhibiting ROS generation, thereby maintaining the protective role of the cellular GSH system.
Vellingiri, K.,Deep, A.,Kim, K.H.,Boukhvalov, D.W.,Kumar, P.,Yao, Q. Elsevier Sequoia 2017 Sensors and actuators. B, Chemical Vol.241 No.-
<P>The amino derivative of the UiO-66 metal organic framework (MOF) was investigated for potential use as a sensing probe for formaldehyde (FA) in an aqueous medium. The sensitivity and specificity of this MOF probe were virtually unaffected by the presence of other tested reference aldehydes, e.g., propionaldehyde( PA), butyraldehyde (BA), and valeraldehyde (VA). The maximum incubation time for the interaction of the MOF probe against 100 ppm of FA standard was estimated at 2 min. The linear detection of FA molecules using the proposed probe was performed in the range of 10-100 ppm with a limit of detection (LOD) at 4 ppm. The stability of the MOF for FA detection was estimated through a series of adsorption-desorption cycles. DFT calculations showed that the selective sensing/capture of FA corresponded to the formation of a stable, non-covalent bond between FA and the C6H3NH2 unit of the MOF. This interaction decreased the HOMO/LUMO gap of FA by approximately 0.8 eV, a trend that was not evident for all other aldehydes. The results of FTIR, TGA, and XPS analysis confirmed a small but visible change in the chemical environment of the N-H and C-H bonds of UiO-66-NH2 upon their interactions with FA molecules. Therefore, the proposed MOF probe appears suitable for sensing FA in an aqueous medium. (C) 2016 Elsevier B.V. All rights reserved.</P>
ERK1 phosphorylates Nanog to regulate protein stability and stem cell self-renewal
Kim, S.H.,Kim, M.O.,Cho, Y.Y.,Yao, K.,Kim, D.J.,Jeong, C.H.,Yu, D.H.,Bae, K.B.,Cho, E.J.,Jung, S.K.,Lee, M.H.,Chen, H.,Kim, J.Y.,Bode, A.M.,Dong, Z. Elsevier 2014 Stem cell research Vol.13 No.1
Nanog regulates human and mouse embryonic stem (ES) cell self-renewal activity. Activation of ERKs signaling negatively regulates ES cell self-renewal and induces differentiation, but the mechanisms are not understood. We found that ERK1 binds and phosphorylates Nanog. Activation of MEK/ERKs signaling and phosphorylation of Nanog inhibit Nanog transactivation, inducing ES cell differentiation. Conversely, suppression of MEK/ERKs signaling enhances Nanog transactivation to inhibit ES cell differentiation. We observed that phosphorylation of Nanog by ERK1 decreases Nanog stability through ubiquitination-mediated protein degradation. Further, we found that this phosphorylation induces binding of FBXW8 with Nanog to reduce Nanog protein stability. Overall, our results demonstrated that ERKs-mediated Nanog phosphorylation plays an important role in self-renewal of ES cells through FBXW8-mediated Nanog protein stability.
Merlin facilitates ubiquitination and degradation of transactivation-responsive RNA-binding protein
Lee, J Y,Moon, H J,Lee, W K,Chun, H J,Han, C W,Jeon, Y-W,Lim, Y,Kim, Y H,Yao, T-P,Lee, K-H,Jun, T-Y,Rha, H K,Kang, J-K Nature Publishing Group 2006 Oncogene Vol.25 No.8
The Nf2 tumor suppressor codes for merlin, a protein whose function is largely unknown. We have previously demonstrated a novel interaction between merlin and TRBP, which inhibits the oncogenic activity of TRBP. In spite of the significance of their functional interaction, its molecular mechanism still remains to be elucidated. In this report, we investigated how merlin inhibits the oncogenic activity of TRBP in association with cell growth conditions. In the human embryonic kidney 293 cell line, the level of endogenous merlin increased, whereas that of endogenous TRBP significantly decreased along with the increase in cell confluence. We demonstrated that the carboxyl-terminal region of TRBP was responsible for this phenomenon using stable cell lines expressing deletion mutants of TRBP. The overexpression of merlin decreased the protein level of TRBP, and the ubiquitin-like subdomain of merlin's FERM domain was important for this activity. We also demonstrated that TRBP is ubiquitinylated and the ubiquitinylated forms of TRBP are accumulated by ectopically expressed merlin or cell confluence in the presence of MG132, a proteasome inhibitor. Furthermore, we showed that the regulation of TRBP in response to cell confluence was abolished upon knockdown of merlin expression by specific small interfering RNA. Finally, we showed that ectopically expressed merlin restored cell–cell contact inhibition in cells stably expressing TRBP but not in TRBPΔc. These results suggest that merlin is involved in the regulation of TRBP protein level by facilitating its ubiquitination in response to such cues as cell–cell contacts.Oncogene (2006) 25, 1143–1152. doi:10.1038/sj.onc.1209150; published online 10 October 2005
A strategy to overcome the limits of carbon-based materials as lithium-ion battery anodes
Yao, F.,Li, B.,So, K.,Chang, J.,Ly, T.H.,Vu, A.Q.,Mun, H.,Cojocaru, C.S.,Yue, H.,Xie, S.,Lee, Y.H. Pergamon Press ; Elsevier Science Ltd 2014 Carbon Vol.79 No.-
The free-standing Si-coated carbon nanofiber (Si/CNF) mat was fabricated for the anode of lithium ion battery through combining electrospun CNF mat with electrodeposited Si layer. Spaghetti or granule-like Si was obtained by varying the deposition conditions. This Si/CNF mat was directly used as an active material and a current collector as well, which involves neither binders nor additional metal substrate. The best performance was achieved in spaghetti-like Si due to its highly porous nature which can accommodate volume expansion and large surface area which benefit the efficient charge transfer both at Si/CNF interface and at the electrode/electrolyte interface. The optimized Si/CNF mat after annealing at 1000<SUP>o</SUP>C delivered a capacity of 870mAhg<SUP>-1</SUP> at 1st discharge and 730mAhg<SUP>-1</SUP> at 50th discharge with a capacity retention of 84%, improving the capacity of pure CNF (280mAhg<SUP>-1</SUP> at the 50th discharge) by almost three times. In addition, corrosion of the current collector no longer exists in our approach. Our X-ray photoemission spectroscopy and electrochemical analysis revealed that the formation of Si-C bond through high temperature annealing can enhance the adhesion between silicon and carbon at the interface which benefits the cyclic performance of anode ultimately.