Anisotropic Magnetization and Charge Density Wave in a Na0.78CoO2 Single Crystal

이종수,J. B. Peng,S. M. Lee,C. T. Lin 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.2

Single crystals of γ-Na0.78CoO2 were grown using the floating zone method. The static magnetic susceptibility M/H(T) of Na0.78CoO2 showed significant anisotropic behavior for different crystal orientations of H ∥ (ab) and H ∥ (c). While (M/H)ab(T) for a magnetic field H= 1 T in an ab-plane followed the Curie-Weiss law at high temperatures (T ≥ 100 K), (M/H)c(T) for H ∥ c-axis deviated from Curie-Weiss behavior, which may be understood by using phonon localization from strong electron-phonon coupling. The impurity spin-1/2 effect, dressed by spin fluctuation, was significant at low temperatures (T ≤ 30 K) for both field orientations of H ∥ (ab) and H ∥ (c). The electrical resistivity ρ(T) of Na0.78CoO2 showed a clear metallic character down to 16 K, with a weak increase in the resistivity ρ(T) at low temperatures T ≤ 16 K). The gap-like behavior of ρ(T) was insensitive to applied magnetic fields up to 7 T, which indicates a non-degenerate charge gap. The electrical conductivity σ(T) followed the density wave behavior with a small energy gap (0.64 meV) at low temperatures. We discussed the electrical resistivity ρ(T)$ and the anisotropic M/H(T) behavior of Na0.78CoO2 in terms of the charge density wave and a strong electron-phonon interaction. Single crystals of γ-Na0.78CoO2 were grown using the floating zone method. The static magnetic susceptibility M/H(T) of Na0.78CoO2 showed significant anisotropic behavior for different crystal orientations of H ∥ (ab) and H ∥ (c). While (M/H)ab(T) for a magnetic field H= 1 T in an ab-plane followed the Curie-Weiss law at high temperatures (T ≥ 100 K), (M/H)c(T) for H ∥ c-axis deviated from Curie-Weiss behavior, which may be understood by using phonon localization from strong electron-phonon coupling. The impurity spin-1/2 effect, dressed by spin fluctuation, was significant at low temperatures (T ≤ 30 K) for both field orientations of H ∥ (ab) and H ∥ (c). The electrical resistivity ρ(T) of Na0.78CoO2 showed a clear metallic character down to 16 K, with a weak increase in the resistivity ρ(T) at low temperatures T ≤ 16 K). The gap-like behavior of ρ(T) was insensitive to applied magnetic fields up to 7 T, which indicates a non-degenerate charge gap. The electrical conductivity σ(T) followed the density wave behavior with a small energy gap (0.64 meV) at low temperatures. We discussed the electrical resistivity ρ(T)$ and the anisotropic M/H(T) behavior of Na0.78CoO2 in terms of the charge density wave and a strong electron-phonon interaction.

Mössbauer and MCD spectroscopy of the Fe3S4 nanoparticles synthesized by the thermal decomposition method with two different surfactants

Ivantsov Ruslan D.,Lin Chun-Rong,Ivanova Oxana S.,Altunin Roman R.,Knyazev Yuriy V.,Molokeev Maxim S.,Zharkov Sergey M.,Chen Ying-Zhen,Lin En-Szu,Chen Bing-Yi,Shestakov Nikolai P.,Edelman Irina S. 한국물리학회 2021 Current Applied Physics Vol.25 No.-

Greigite (Fe3S4) nanoparticles (NPs) were fabricated by the thermal decomposition method using two different surfactants: oleylamine (OLA) and 1-hexadecylamine (HDA). In both cases, the synthesized NPs were characterized as the Fe3S4 nanocrystals with minor inclusions of Fe9S11 phase. FT-IR spectroscopy and thermogravimetric analysis allow concluding about OLA or HDA shells covering magnetic core of NPs. M¨ossbauer spectra has revealed deviations of iron ions distribution among crystal positions from that presented in literature for pure greigite. In accordance with these deviations, the pronounce changes are observed in the magnetic circular dichroism (MCD) spectra which manifest themselves as the spectrum shift to higher energies of electromagnetic waves and redistribution of the MCD maximum intensities. These effects are associated with a change in the density of electronic states in the samples due to the redistribution of iron ions between octahedral and tetrahedral positions in nanocrystals under the influence of surfactants.

Optical Investigations of Non-polar m-plane InGaN/GaN Multiple Quantum Wells Grown on LiAlO2 (100) by Using MOVPE

D. R. Hang,Mitch M. C. Chou,J. L. Lin,M. Heuken 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1

We investigate the optical properties of m-plane InGaN/GaN multiple quantum wells (MQWs) grown on LiAlO2 substrates by using metal organic vapor phase epitaxy (MOVPE). Polarizationdependent photoluminescence (PL) measurements have been employed to study the optical emission characteristics. We demonstrate that the PL emission has a large polarization anisotropy, which can be attributed to the anisotropic in-plane strain. The degree of polarization is studied as a function of temperature, and the dependence can be explained by using the modified band structure model. The energy splitting of the two uppermost valence bands is obtained from polarized PL spectroscopy and is in good agreement with the activation energy deduced from the Arrhenius relationship. From the excitation-dependent PL measurements, we found the optical emission not to be influenced by the polarization-induced electric field. Our results are important for the design and the fabrication of non-polar InGaN/GaN MQW polarization-sensitive optical devices We investigate the optical properties of m-plane InGaN/GaN multiple quantum wells (MQWs) grown on LiAlO2 substrates by using metal organic vapor phase epitaxy (MOVPE). Polarizationdependent photoluminescence (PL) measurements have been employed to study the optical emission characteristics. We demonstrate that the PL emission has a large polarization anisotropy, which can be attributed to the anisotropic in-plane strain. The degree of polarization is studied as a function of temperature, and the dependence can be explained by using the modified band structure model. The energy splitting of the two uppermost valence bands is obtained from polarized PL spectroscopy and is in good agreement with the activation energy deduced from the Arrhenius relationship. From the excitation-dependent PL measurements, we found the optical emission not to be influenced by the polarization-induced electric field. Our results are important for the design and the fabrication of non-polar InGaN/GaN MQW polarization-sensitive optical devices

Density Functional Theory Study of Conformation-Dependent Properties of Neutral and Radical Cationic <small>l</small>-Tyrosine and <small>l</small>-Tryptophan

Baek, K. Y.,Fujimura, Y.,Hayashi, M.,Lin, S. H.,Kim, S. K. American Chemical Society 2011 The Journal of physical chemistry A Vol.115 No.34

<P>Conformation-dependent properties of <SMALL>l</SMALL>-tyrosine and <SMALL>l</SMALL>-tryptophan in neutral and radical cations were studied by using the density functional theory (DFT) with a new density functional M05-2X. The results are compared with those obtained by using the conventional DFT (B3LYP). Results obtained by both types of DFT were in qualitative accord, including the existence of two conformational subgroups and their subgroup-dependent adiabatic ionization energy and hydrogen bonding. On the other hand, quantitative differences were found between the two DFT methods as well: the M05-2X method successfully reproduced experimental adiabatic ionization energy, whereas the B3LYP functional consistently yielded significantly lower values by 0.2–0.3 eV. More importantly, natural bond orbital (NBO) analysis for cationic conformers showed that all conformers of <SMALL>l</SMALL>-tyrosine and <SMALL>L</SMALL>-tryptophan undergo charge localization upon ionization regardless of the presence of intramolecular hydrogen bonding, unlike the case of <SMALL>l</SMALL>-phenylalanine that was treated earlier by other studies. Different degrees of charge localization among all three aromatic amino acids are explained by employing a simple model in which the aromatic amino acid is assumed to consist of two submoieties of distinct cationic core: the backbone and aromatic side chain. The difference in adiabatic ionization energy between these two submoieties is found to govern the degree of charge localization.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcafh/2011/jpcafh.2011.115.issue-34/jp200826z/production/images/medium/jp-2011-00826z_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp200826z'>ACS Electronic Supporting Info</A></P>

E-Beam Processing of Collagen-Poly(N-vinyl-2-pyrrolidone) Double-Network Superabsorbent Hydrogels: Structural and Rheological Investigations

Maria Demeter,Ion Călina,Cătălin Vancea,Murat Şen,Mădălina Georgiana Albu Kaya,Elena Mănăilă,Marius Dumitru,Viorica Meltzer 한국고분자학회 2019 Macromolecular Research Vol.27 No.3

Collagen (C)-poly(N-vinyl-2-pyrrolidone) (PVP) double-network superabsorbent hydrogels were synthesized by e-beam (electron beam) radiation processing, both with the addition of water-soluble cross-linking agents (CA), as well as without CA. The aim of the study was to develop a hydrogel for future application as wound dressings via e-beam radiation cross-linking of two biocompatible polymers. The formation of C-PVP hydrogels was confirmed by Fourier transform infrared (FTIR) spectroscopy and their performance was determined from morphological and rheological experiments, such as sol-gel analysis, swelling capacity, storage (G') and viscous (G'') moduli, cross-linking density, and pore size. Sol-gel analysis was performed in order to determine the gel properties as function of absorbed dose and it was found that the degradation density (p0)/cross-linking density (q0) ratio indicates a negligible contribution of chain scission processes. The rheological data confirmed that the elastic properties were predominant: G' moduli were larger than G'' moduli, as is specific to elastic solids and indicate the formation of a permanent hydrogel network were cross-links are present. Moreover, the swelling studies indicated that the hydrogels have good stability both in deionized water and phosphate-buffered saline (PBS) solution at 37 oC, and superabsorbent properties. The hydrogels network parameters obtained with lower content of CA, could be controlled by changing the absorbed dose.

The Potential Roles of Bacterial Communities in Coral Defence: A Case Study at Talang-Talang Reef

Felicity W. I. Kuek,Li-Fang Lim,Lin-Hui Ngu,Aazani Mujahid,Po-Teen Lim,Chui-Pin Leaw,Moritz Müller 한국해양과학기술원 2015 Ocean science journal Vol.50 No.2

Complex microbial communities are known to exert significant influence over coral reef ecosystems. The Talang- Satang National Park is situated off the coast of Sematan and is one of the most diverse ecosystems found off-Sarawak. Interestingly, the Talang-talang reef thrives at above-average temperatures of 28- 30°C throughout the year. Through isolation and identification (16S rRNA) of native microbes from the coral, the surface mucus layer (SML), as well as the surrounding sediment and waters, we were able to determine the species composition and abundance of the culturable bacteria in the coral reef ecosystem. Isolates found attached to the coral are related mostly to Vibrio spp., presumably attached to the mucus from the water column and surrounding sediment. Pathogenic Vibrio spp. and Bacillus spp. were dominant amongst the isolates from the water column and sediment, while known coral pathogens responsible for coral bleaching, Vibrio coralliilyticus and Vibrio shiloi, were isolated from the coral SML and sediment samples respectively. Coral SML isolates were found to be closely related to known nitrogen fixers and antibiotic producers with tolerance towards elevated temperatures and heavy metal contamination, offering a possible explanation why the local corals are able to thrive in higher than usual temperatures. This specialized microbiota may be important for protecting the corals from pathogens by occupying entry niches and/or through the production of secondary metabolites such as antibiotics. The communities from the coral SML were tested against each other at 28, 30 and 32°C, and were also assessed for the presence of type I modular polyketides synthase (PKS) and non-ribosomal peptide synthetase (NRPS) genes which are both involved in the production of antibiotic compounds. The bacterial community from the SML exhibited antimicrobial properties under normal temperatures while pathogenic strains appeared toxic at elevated temperatures and our results highlight the role of the coral SML bacterial community in the coral’s defence.

Design and Analysis of 3D-MAPS (3D Massively Parallel Processor with Stacked Memory)

Dae Hyun Kim,Athikulwongse, Krit,Healy, Michael B.,Hossain, Mohammad M.,Moongon Jung,Khorosh, Ilya,Kumar, Gokul,Young-Joon Lee,Lewis, Dean L.,Tzu-Wei Lin,Chang Liu,Panth, Shreepad,Pathak, Mohit,Minzhe IEEE 2015 IEEE Transactions on Computers Vol. No.

<P>This paper describes the architecture, design, analysis, and simulation and measurement results of the 3D-MAPS (3D massively parallel processor with stacked memory) chip built with a 1.5 V, 130 nm process technology and a two-tier 3D stacking technology using 1.2 \microm-diameter, 6 \micro m-height through-silicon vias (TSVs) and 3.4\nbsp\microm-diameter face-to-face bond pads. 3D-MAPS consists of a core tier containing 64 cores and a memory tier containing 64 memory blocks. Each core communicates with its dedicated 4KB SRAM block using face-to-face bond pads, which provide negligible data transfer delay between the core and the memory tiers. The maximum operating frequency is 277 MHz and the maximum memory bandwidth is 70.9 GB/s at 277 MHz. The peak measured memory bandwidth usage is 63.8 GB/s and the peak measured power is approximately 4 W based on eight parallel benchmarks.</P>

Factors Affecting the Incidence of Angel Wing in White Roman Geese: Stocking Density and Genetic Selection

Lin, M.J.,Chang, S.C.,Lin, T.Y.,Cheng, Y.S.,Lee, Y.P.,Fan, Y.K. Asian Australasian Association of Animal Productio 2016 Animal Bioscience Vol.29 No.6

The present study investigated stocking density and genetic lines, factors that may alter the severity and incidence of angel wing (AW), in White Roman geese. Geese (n = 384) from two genetically selected lines (normal- winged line, NL, and angel-winged line, AL, respectively) and one commercial line (CL) were raised in four pens. Following common commercial practice, low-stocking-density (LD), medium-stocking-density, and high-stocking-density treatments were respectively administered to 24, 32, and 40 geese per pen at 0 to 3 weeks ($1.92m^2/pen$) and 4 to 6 weeks ($13.2m^2/pen$) of age and to 24, 30, and 36 geese at 7 to 14 weeks ($20.0m^2/pen$) of age. The results revealed that stocking density mainly affected body weight gain in geese younger than 4 weeks, and that geese subjected to LD had a high body weight at 2 weeks of age. However, the effect of stocking density on the severity score of AW (SSAW) and incidence of AW (IAW) did not differ significantly among the treatments. Differences were observed among the genetic stocks; that is, SSAW and IAW were significantly higher in AL than in NL and CL. Genetic selection generally aggravates AW, complicating its elimination. To effectively reduce IAW, stocking density, a suspected causal factor, should be lower than that presently applied commercially.

Robust superhydrophobic carbon nanofiber network inlay-gated mesh for water-in-oil emulsion separation with high flux

Lin, X.,Heo, J.,Jeong, H.,Choi, M.,Chang, M.,Hong, J. Royal Society of Chemistry 2016 Journal of Materials Chemistry A Vol.4 No.46

<P>Much progress has been made toward applying super-wetting membranes to various oil-water separation processes with high molecular permeation flux. However, there are still numerous challenges in the simple preparation of extremely durable membranes with super-wetting properties, especially considering the great developments in high-flux membranes with nanometer-scale thickness. Previous membranes have been usually limited to either high durability with low selectivity or enhanced separation performance with low stability. Herein, an extremely robust carbon nanofiber-polydimethylsiloxane (CNFs-PDMS) network inlay-gated stainless steel mesh (SSM) that shows superhydrophobic and superoleophilic properties is presented. Carbon nanofibers are subtly deposited into SSM pores to form network fillers via an improved vacuum-based filtration. Most importantly, the SSM/CNFs-PDMS membrane exhibits excellent resistance to harsh environmental conditions such as acid, salt, organic, biofouling, and mechanical abrasion. In particular, mechanical damage to the inserted membrane can be avoided using the protective SSM, thereby ensuring super-wetting performance. In the present work, we propose a new concept of discrete or partial superhydrophobicity. Moreover, compared to previous superhydrophobic membranes, the thickness is significantly decreased, leading to enhanced oil-in-water emulsion separation flux. The membranes exhibit a gravity-driven water-in-oil emulsion separation with flux up to 2970 L m(-2) h(-1). This work provides a brand new route for designing durable and high-flux separation systems with an inlay-gated structure in the future by combining ultrathin membranes with protective supports.</P>

Comparisons of In vitro Nitrate Reduction, Methanogenesis, and Fermentation Acid Profile among Rumen Bacterial, Protozoal and Fungal Fractions

Lin, M.,Schaefer, D.M.,Guo, W.S.,Ren, L.P.,Meng, Q.X. Asian Australasian Association of Animal Productio 2011 Animal Bioscience Vol.24 No.4

The objectives were to compare the ability of various rumen microbial fractions to reduce nitrate and to assess the effect of nitrate on in vitro fermentation characteristics. Physical and chemical methods were used to differentiate the rumen microbial population into the following fractions: whole rumen fluid (WRF), protozoa (Pr), bacteria (Ba), and fungi (Fu). The three nitrogen substrate treatments were as follows: no supplemental nitrogen source, nitrate or urea, with the latter two being isonitrogenous additions. The results showed that during 24 h incubation, WRF, Pr and Ba fractions had an ability to reduce nitrate, and the rate of nitrate disappearance for the Pr fraction was similar to the WRF fraction, while the Ba fraction needed an adaptation period of 12 h before rapid nitrate disappearance. The WRF fraction had the greatest methane ($CH_4$) production and the Pr fraction had the greatest prevailing $H_2$ concentration (p<0.05). Compared to the urea treatment, nitrate diminished net gas and $CH_4$ production during incubation (p<0.05), and ammonia-N ($NH_3$-N) concentration (p<0.01). Nitrate also increased acetate, decreased propionate and decreased butyrate molar proportions (p<0.05). The Pr fraction had the highest acetate to propionate ratio (p<0.05). The Pr fraction as well as the Ba fraction appears to have an important role in nitrate reduction. Nitrate did not consistently alter total VFA concentration, but it did shift the VFA profile to higher acetate, lower propionate and lower butyrate molar proportions, consistent with less $CH_4$ production by all microbial fractions.