Graphene/M_xWO₃ (M=Na, K) nanohybrids with excellent electrical properties

Liu, B.,Yin, S.,Wu, X.,Wang, Y.,Huang, Y.,Wu, J.,Sekino, T.,Matsushita, J.,Lee, S.W.,Kobayashi, M.,Kakihana, M.,Sato, T. Pergamon Press ; Elsevier Science Ltd 2015 Carbon Vol.94 No.-

Graphene/M<SUB>x</SUB>WO<SUB>3</SUB> (M=Na, K) nanocomposites with different weight ratios were successfully synthesized using MBH<SUB>4</SUB> as a reducing agent in aqueous solution, followed by crystallization of amorphous precursors under calcination in H<SUB>2</SUB> (5vol.%)/N<SUB>2</SUB> atmosphere at 600<SUP>o</SUP>C. The coupled samples showed good shielding properties in NIR wavelength range together with certain visible lights transparency. The as-prepared tungsten bronze nanoparticles are homogeneously anchored on graphene sheets, and the graphene/tungsten bronze nanocomposite showed an enhanced electrical conductivity with good shielding properties in the NIR range together with certain visible lights transparency. With the increment of graphene amount in the composites, the contact between the graphene sheets was enhanced, and the M<SUB>x</SUB>WO<SUB>3</SUB> might enhance the charge transport properties of graphene by generating the short conductive path for electrons over the remained oxygenated functional groups. The synergistic effects could be observed in the composites. When 5wt.% or more graphene were composed into M<SUB>x</SUB>WO<SUB>3</SUB>, the hybrid composite showed the higher electrical conductivity than those of uncoupled graphene and tungsten bronze alone.

The Magnetoresistance in Iron-based Superconductors

B. Lv,R. B. Xie,S. L. Liu,G. J. Wu,H. M. Shao,X. S. Wu 한국자기학회 2011 Journal of Magnetics Vol.16 No.2

The phase transition of vortex matter from solid to liquid was studied in iron-based superconductors. Based on the traditional vortex glass theory, we have examined the magnetoresistivity data of iron-based superconductors using our extended thermal activation model: ρ(B,T) = ρ((T-Tg(B))/(Tc(0)-Tg(B)))<SUP>v(z-1)</SUP>. We predict that the magnetic field-dependent area S + S? which integrates ρ with T is proportional to B<SUP>β</SUP>, where β is the vortex glass transition exponent. From our calculation, the vortex glass transition exponent is 0.33, close to the exponent of area S?+ S is 0.31 in SmO0.9F0.1FeAs; the exponent of area S is 0.63, which is close to the irreversibility line exponent 2/3. Both of the results show the validity of our model. In addition, our model is shown to be effective in describing irreversibility behavior in layered superconductors.

Highly flexible, erosion resistant and nitrogen doped hollow SiC fibrous mats for high temperature thermal insulators

Liu, Y.,Liu, Y.,Choi, W.,Chae, S.,Lee, J.,Kim, B. S.,Park, M.,Kim, H. Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.6

<P>Thermally stable and chemical resistant silicon carbide (SiC) fibrous mats have drawn much attention as a high-temperature thermal insulator in top end equipment and technology. Herein, novel free-standing, flexible, acid/alkali-resistant and nitrogen doped (N-doped) hollow SiC fibrous mats bearing ultralow thermal conductivity are reported. The materials were fabricated via a three-step process: the preparation of core-shell fibers from polymeric precursors by co-axial electrospinning, the thermal or electron beam irradiation curing process and pyrolysis process. The as-obtained continuous fibers manifested an oval-shape hollow structure and the thickness of the cavity wall was approximately 1.5 mu m. The crystal pattern was obtained after pyrolysis over 1300 degrees C under a nitrogen atmosphere. The morphology, composition, curing and formation mechanisms of N-containing hollow SiC fibers with texture and porous surfaces were elaborately analysed. These facilely fabricated N-doped hollow SiC fibrous mats possess good flexibility, noninflammability, high thermal stability, erosion resistance, light weight (0.218 g cm(-3)) and low thermal conductivity at high temperature (0.039 W m(-1) K-1), suggesting promising application as a high temperature thermal insulator.</P>

Effects of Solution Concentration on the Structural and Magnetic Properties of Ni0.5Zn0.5Fe₂O₄ Ferrite Nanoparticles Prepared by Sol-gel

B. S. Yoo,Y. G. Chae,Y. M. Kwon,D. H. Kim,B. W. Lee,Chunli Liu 한국자기학회 2013 Journal of Magnetics Vol.18 No.3

The Ni0.5Zn0.5Fe₂O₄ nanoparticles about 30 nm were prepared using sol-gel method with metal nitrates dissolved in 2-methoxyathanol. The concentrations of the metal nitrates are adjusted from 0.1 to 0.75 M in order to study the influence on the structural and magnetic properties. The structure and morphology characterization revealed that the crystallinity was improved and the nanoparticle size was increased with the nutrition solution concentrations up to 0.5 M. Degraded crystallinity together with decreased nanoparticle size were observed for concentration of 0.75 M. The saturation magnetization at room temperature reached maximum at 0.5 M, which can be explained by considering the crystallinity and size effect.

Improvement of lower hybrid current drive systems for high-power and long-pulse operation on EAST

Wang M.,Liu L.,Zhao L.M.,Li M.H.,Ma W.D.,Hu H.C.,Wu Z.G.,Feng J.Q.,Yang Y.,Zhu L.,Chen M.,Zhou T.A.,Jia H.,Zhang J.,Cao L.,Zhang L.,Liang R.R.,Ding B.J.,Zhang X.J.,Shan J.F.,Liu F.K.,Ekedahl A.,Gonich 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.11

Aiming at high-power and long-pulse operation up to 1000 s, some improvements have been made for both 2.45 GHz and 4.6 GHz lower hybrid (LH) systems during the recent 5 years. At first, the guard limiters of the LH antennas with graphite tiles were upgraded to tungsten, the most promising material for plasma facing components in nuclear fusion devices. These new guard limiters can operate at a peak power density of 12.9 MW/m2 . Strong hot spots were usually observed on the old graphite limiters when 4.6 GHz system operated with power >2.0 MW [B. N. Wan et al., Nucl. Fusion 57 (2017) 102019], leading to a reduction of the maximum power capability. With the new limiters, 4.6 GHz LH system, the main current drive (CD) and electron heating tool for EAST, can be operated with power >2.5 MW routinely. Long-pulse operation up to 100 s with 4.6 GHz LH power of 2.4 MW was achieved in 2021 and the maximal temperature on the guard limiters measured by an infrared (IR) camera was about 540 C, much below the permissible value of tungsten material (~1200 C). A discharge with a duration of 1056 s was achieved and the 4.6 GHz LH energy injected into the plasma was up to 1.05 GJ. Secondly, the fully-activemultijunction (FAM) launcher of 2.45 GHz system was upgraded to a passive-active-multijunction (PAM), for which the density of optimum coupling was relatively low (below the cut-off value). Good coupling with reflection coefficient ~3% has been achieved with plasma-antenna distance up to 11 cm for the new PAM. Finally, in order to eliminate the effect of ion cyclotron range of frequencies (ICRF) wave on 4.6 GHz LH wave coupling, the location of the ICRF launcher was changed to a port that is located 157.5 toroidally from the 4.6 GHz LH system and is not magnetically connected

Surface segregation and oxidation of Pt₃Ni(111) alloys under oxygen environment

Lee, H.C.,Kim, B.M.,Jeong, C.K.,Toyoshima, R.,Kondoh, H.,Shimada, T.,Mase, K.,Mao, B.,Liu, Z.,Lee, H.,Huang, C.Q.,Li, W.X.,Ross, P.N.,Mun, B.S. Elsevier Science Publishers 2016 CATALYSIS TODAY - Vol.260 No.-

<P>Utilizing ambient pressure X-ray photoelectron spectroscopy (AP-XPS), the surface segregation and oxidation of Pt3Ni(1 1 1) alloys are investigated as a function of temperature and oxygen pressure. The in situ AP-XPS measurements of oxygen oxidation process show that the Pt 'skin' surface is not stable under the exposure of oxygen pressure of 100 mTorr at room temperature. As the temperature and pressure are elevated, the formations of Ni2O3, NiOx, and NiO are observed on surface while Pt atom starts to reduce its adsorbed oxygen, which is a clear sign of surface segregation of Ni to surface. Upon the evacuation of oxygen gas, i.e. ultrahigh vacuum condition, both of NiOx and NiO oxide get reduced and Ni2O3 remains on the surface. The DFT calculation is employed to explain the formation of surface oxides under oxidation condition. (C) 2015 Elsevier B.V. All rights reserved.</P>

X-RAY CAVITIES IN A SAMPLE OF 83 SPT-SELECTED CLUSTERS OF GALAXIES: TRACING THE EVOLUTION OF AGN FEEDBACK IN CLUSTERS OF GALAXIES OUT TO<i>z</i>= 1.2

Hlavacek-Larrondo, J.,McDonald, M.,Benson, B. A.,Forman, W. R.,Allen, S. W.,Bleem, L. E.,Ashby, M. L. N.,Bocquet, S.,Brodwin, M.,Dietrich, J. P.,Jones, C.,Liu, J.,Reichardt, C. L.,Saliwanchik, B. R.,S IOP Publishing 2015 The Astrophysical journal Vol.805 No.1

<P>X-ray cavities are key tracers of mechanical (or radio mode) heating arising from the active galactic nuclei (AGNs) in brightest cluster galaxies (BCGs). We report on a survey for X-ray cavities in 83 massive, high-redshift (0.4 < z < 1.2) clusters of galaxies selected by their Sunyaev-Zel'dovich signature in the South Pole Telescope data. Based on Chandra X-ray images, we find a total of six clusters having symmetric pairs of surface brightness depressions consistent with the picture of radio jets inflating X-ray cavities in the intracluster medium (ICM). The majority of these detections are of relatively low significance and require deeper follow-up data in order to be confirmed. Further, this search will miss small (<10 kpc) X-ray cavities that are unresolved by Chandra at high (z greater than or similar to 5) redshift. Despite these limitations, our results suggest that the power generated by AGN feedback in BCGs has remained unchanged for over half of the age of the universe (>7 Gyr at z similar to 0.8). On average, the detected X-ray cavities have powers of (0.8-5) x 10(45) erg s(-1), enthalpies of (3-6) x 10(59) erg, and radii of similar to 17 kpc. Integrating over 7 Gyr, we find that the supermassive black holes in BCGs may have accreted 10(8) to several 10(9) M-circle dot of material to power these outflows. This level of accretion indicates that significant supermassive black hole growth may occur not only at early times, in the quasar era, but at late times as well. We also find that X-ray cavities at high redshift may inject an excess heat of 0.1-1.0 keV per particle into the hot ICM above and beyond the energy needed to offset cooling. Although this result needs to be confirmed, we note that the magnitude of excess heating is similar to the energy needed to preheat clusters, break self-similarity, and explain the excess entropy in hot atmospheres.</P>

Ferromagnetism in Zn_1–<i>x</i>Mn_<i>x</i>O Nanoparticles Prepared by Ball Milling

Manh, T. V.,Phan, T. L.,Lee, B. W.,Liu, Chunli,Ho, T. A.,Thanh, T. D.,Vuong, N. M.,Yu, S. C. IEEE 2015 IEEE transactions on magnetics Vol.51 No.11

<P>Previous studies pointed out that ferromagnetism in Mn-doped ZnO was related to exchange interactions between Mn ions mediated by lattice defects. This means that it is possible to modify a Mn-doped ZnO paramagnet to a ferromagnet by creating lattice defects in it. The present work starts from a paramagnetic Zn0.98Mn0.02O sample prepared by solid-state reaction and then creates more defects upon mechanical milling. By changing the milling time (t(m)) from 0.5 to 20 h, we produced nanocrystalline (NC) samples with average crystallite sizes (d) ranging from 30 to 157 nm. The d decrease generated lattice strain and defects. This broadens and blurs the lines of Raman scattering and electron spin resonance (ESR) spectra. Interestingly, magnetization studies versus magnetic field revealed the samples with d <= 150 nm exhibiting room-temperature ferromagnetic (FM) order. The FM order became largest as d = 72 nm, corresponding to a saturation magnetization of M-s approximate to 0.006 emu/g. Apart from this d value, M-s would be gradually decreased. X-ray absorption fine structure (XAFS) spectra revealed a coexistence of Mn2+ and Mn3+ ions in the samples. Their concentration ratio was slightly changed with decreasing d, due to the slight shift of the absorption edge. With the features of Fourier-transformed XAFS and ESR spectra, we believe that ferromagnetism in the NC samples is related to oxygen vacancies residing on the surface of nanoparticles. Local lattice distortions can lead to zinc interstitials for the samples d < 72 nm, which decreases M-s.</P>

Investigation of PCR-RFLPs within Major Histocompatibility Complex B-G Genes Using Two Restriction Enzymes in Eight Breeds of Chinese Indigenous Chickens

R. F. Xu,K. Li,G. H. Chen,B. Y. Z. Qiang,D. L. Mo,B. Fan,C. C. Li,M. Yu,M. J. Zhu,T. A. Xiong,B. Liu 아세아·태평양축산학회 2005 Animal Bioscience Vol.18 No.7

New polymorphism of major histocompatibility complex B-G genes was investigated by amplification and digestion of a 401bp fragment including intron 1 and exon 2 using polymerase chain reaction-restriction fragment length polymorphism (PCRRFLP) technique with two restriction enzymes of Msp I and Tas I in eight breeds of Chinese indigenous chickens and one exotic breed. In the fragment region of the gene, three novel single nucleotide polymorphisms (SNPs) were detected at the two restriction sites. We found the transition of two nucleotides of A294G and T295C occurred at Tas I restriction site, and consequently led to a nonsynonymous substitution of asparagine into serine at position 54 within the deduced amino acid sequence of immunoglobulin variableregion- like domain encoded by the exon 2 of B-G gene. It was observed at rare frequency that a single mutation of A294G occurring at the site, also caused an identical substitution of amino acid, asparagine 54-to-serine, to that we described previously. And the transversion of G319C at Msp I site led to a non-synonymous substitution, glutamine 62-to-histidine. The new alleles and allele frequencies identified by the PCR-RFLP method with the two enzymes were characterized, of which the allele A and B frequencies at Msp I and Tas I loci were given disequilibrium distribution either in the eight Chinese local breeds or in the exotic breed. By comparison, allele A at Msp I locus tended to be dominant, while, the allele B at Tas I locus tended to be dominant in all of the breeds analyzed. In Tibetan chickens, the preliminary association analysis revealed that no significant difference was observed between the different genotypes identified at the Msp I and Tas I loci and the laying performance traits, respectively.

New Evidence of Alleles (V199I and G52S) at the PRKAG3 (RN) Locus Affecting Pork Meat Quality

Chen, J.F.,Dai, L.H.,Peng, J.,Li, J.L.,Zheng, R.,Zuo, B.,Li, F.E.,Liu, M.,Yue, K.,Lei, M.G.,Xiong, Y.Z.,Deng, C.Y.,Jiang, S.W. Asian Australasian Association of Animal Productio 2008 Animal Bioscience Vol.21 No.4

The porcine PRKAG3 (RN) gene encodes the regulatory gamma subunit of adenosine monophosphate-activated protein kinase (AMPK), which is a good candidate gene affecting meat quality. In this study, the effects of two missense mutations A595G (Ile199Val) and G154A (Gly52Ser) in porcine PRKAG3 gene on meat quality traits were studied in M. Longissimus dorsi (LD), M. Semispinalis capitis (SC) and M. Biceps femoris (BF) from different populations of 326 pigs. The PRKAG3 alleles 199I, 199IV, 52S and 52G were identified with PCR-RFLPs and all genotypes - 199I/199I, 199I/199V, 199V/199V, 52S/52S, 52S/52G and 52G/52G - were found. The frequency of V allele was larger than that of I allele in all populations. I allele frequency was zero in Chinese Meishan pigs (population D) especially. G allele frequency was larger than that of S allele in all populations except Large White (population A). Both variations at the PRKAG3 locus significantly affected these meat quality traits. The pork meat quality has not previously been established in Meishan or crosses thereof. The results suggested that generally pH of LD, SC and BF was higher in Meishan pigs than that in other populations. Moreover, Meishan pigs showed higher water-holding capacity and intramuscular fat (IMF), lower water content and water loss percentage compared to other populations in terms of the two variations. The results present here supply new evidence that alleles V199I and G52S at the PRKAG3 locus affect pork meat quality and provide useful information on pork production.