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Structural and magnetic properties of Si1−xGex thin films implanted with Fe ions
Li Wang,Deng-Lu Hou,Jingsheng Yu,Wengang Wei,Cong-Mian Zhen,Li Ma,Fengchun Hu,Chao Wang 한국물리학회 2013 Current Applied Physics Vol.13 No.4
A series of Si1-xGex (x = 1, 0.848, 0.591, 0.382, 0.209, 0.064, 0) thin films prepared by ion beam sputtering were implanted with Fe ions to different doses using the metal vapor vacuum arc technique. X-ray absorption fine structure (XAFS) was used to characterize the local microstructure around the Fe atoms in Fe-doped Si1-xGex samples. Structural analysis showed that for annealed samples of Ge-rich thin films (including pure Ge) implanted with low doses of Fe ions, almost all the Fe ions substituted at Ge sites. However, an anti-ferromagnetic Fe6Ge5 impurity phase existed in the annealed samples implanted with high doses of Fe. It was also found that the solubility of Fe ions was highest in pure Ge films and that with increasing Si concentration, the solubility decreased. Magnetic analysis showed that for the as-implanted and annealed samples of Ge-rich thin films implanted with Fe ions, room-temperature ferromagnetism was strongest in the pure Ge series of samples and that as the Ge concentration decreased, the ferromagnetism at room temperature weakened. In addition, annealing could increase the number of Fe ions at substitution sites, which resulted in the observed increase in the saturated magnetization after annealing. Experiment and theoretical analysis showed that the ferromagnetism of Fe-doped Ge-rich Si1xGex thin films samples originated from the s, ped exchange interactions between the Si1-xGex matrix and those Fe ions which substituted at Ge sites and that the ferromagnetism was mediated by carriers.
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Zhou, Zhengkui,Jiang, Yu,Wang, Zheng,Gou, Zhiheng,Lyu, Jun,Li, Weiyu,Yu, Yanjun,Shu, Liping,Zhao, Yingjun,Ma, Yanming,Fang, Chao,Shen, Yanting,Liu, Tengfei,Li, Congcong,Li, Qing,Wu, Mian,Wang, Min,Wu, Nature Publishing Group, a division of Macmillan P 2015 Nature biotechnology Vol.33 No.4
Understanding soybean (Glycine max) domestication and improvement at a genetic level is important to inform future efforts to further improve a crop that provides the world's main source of oilseed. We detect 230 selective sweeps and 162 selected copy number variants by analysis of 302 resequenced wild, landrace and improved soybean accessions at >11× depth. A genome-wide association study using these new sequences reveals associations between 10 selected regions and 9 domestication or improvement traits, and identifies 13 previously uncharacterized loci for agronomic traits including oil content, plant height and pubescence form. Combined with previous quantitative trait loci (QTL) information, we find that, of the 230 selected regions, 96 correlate with reported oil QTLs and 21 contain fatty acid biosynthesis genes. Moreover, we observe that some traits and loci are associated with geographical regions, which shows that soybean populations are structured geographically. This study provides resources for genomics-enabled improvements in soybean breeding.
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Mian, Shabeer Ahmad,Yang, Li-Ming,Saha, Leton Chandra,Ahmed, E.,Ajmal, Muhammad,Ganz, Eric American Chemical Society 2014 Langmuir Vol.30 No.23
<P>Mussels have a remarkable ability to bond to solid surfaces under water. From a microscopic perspective, the first step of this process is the adsorption of dopa molecules to the solid surface. In fact, it is the catechol part of the dopa molecule that is interacting with the surface. These molecules are able to make reversible bonds to a wide range of materials, even underwater. Previous experimental and theoretical efforts have produced only a limited understanding of the mechanism and quantitative details of the competitive adsorption of catechol and water on hydrophilic silica surfaces. In this work, we uncover the nature of this competitive absorption by atomic scale modeling of water and catechol adsorbed at the geminal (001) silica surface using density functional theory calculations. We find that catechol molecules displace preadsorbed water molecules and bond directly on the silica surface. Using molecular dynamics simulations, we observe this process in detail. We also calculate the interaction force as a function of distance, and observe a maximum of 0.5 nN of attraction. The catechol has a binding energy of 23 kcal/mol onto the silica surface with adsorbed water molecules.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2014/langd5.2014.30.issue-23/la500800f/production/images/medium/la-2014-00800f_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la500800f'>ACS Electronic Supporting Info</A></P>
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Li, Xiao-Xi,Guo, Mian,Qiu, Bin,Cho, Kyung-Bin,Sun, Wei,Nam, Wonwoo American Chemical Society 2019 Inorganic Chemistry Vol.58 No.21
<P>Mononuclear nonheme manganese complexes are highly efficient catalysts in the catalytic oxidation of hydrocarbons by hydrogen peroxide in the presence of carboxylic acids. Although high-valent Mn(V)-oxo complexes have been proposed as the active oxidants that afford high regio-, stereo-, and enantioselectivities in the catalytic oxidation reactions, the importance of the spin state (e.g., <I>S</I> = 0 or 1) of the proposed Mn(V)-oxo species is an area that requires further study. In the present study, we have theoretically demonstrated that a mononuclear nonheme Mn(V)-oxo species with an <I>S</I> = 1 ground spin state is the active oxidant that effects the stereo- and enantioselective alkane hydroxylation reaction; it is noted that synthetic octahedral Mn(V)-oxo complexes, characterized spectroscopically and/or structurally, possess an <I>S</I> = 0 spin state and are sluggish oxidants. In an experimental approach, we have investigated the catalytic hydroxylation of alkanes by a mononuclear nonheme Mn(II) complex, [(<I>S</I>-PMB)Mn<SUP>II</SUP>]<SUP>2+</SUP>, and H<SUB>2</SUB>O<SUB>2</SUB> in the presence of carboxylic acids; alcohol is the major product with high stereo- and enantioselectivities. A synthetic Mn(IV)-oxo complex, [(<I>S</I>-PMB)Mn<SUP>IV</SUP>(O)]<SUP>2+</SUP>, is inactive in C-H bond activation reactions, ruling out the Mn(IV)-oxo species as an active oxidant. DFT calculations have shown that a Mn(V)-oxo species with an <I>S</I> = 1 spin state, [(<I>S</I>-PMB)Mn<SUP>V</SUP>(O)(OAc)]<SUP>2+</SUP>, is highly reactive and capable of oxygenating the C-H bond via oxygen rebound mechanism; we propose that the triplet spin state of the Mn(V)-oxo species results from the consequence of breaking the equatorial symmetry due to the binding of an equatorial oxygen from an acetate ligand. Thus, the present study reports that, different from the previously reported <I>S</I> = 0 Mn(V)-oxo species, Mn(V)-oxo species with a triplet ground spin state are highly reactive oxidants that are responsible for the regio-, stereo-, and enantioselectivities in the catalytic hydroxylation of alkanes by mononuclear nonheme manganese complexes and terminal oxidants.</P><P>It is theoretically demonstrated that a mononuclear nonheme Mn(V)-oxo species with an <I>S</I> = 1 ground spin state, [(<I>S</I>-PMB)Mn<SUP>V</SUP>(O)(OAc)]<SUP>2+</SUP>, is highly reactive and capable of oxygenating the C−H bond via oxygen rebound mechanism. Thus, it is proposed that a triplet spin state (<I>S</I> = 1) Mn(V)-oxo intermediate is generated as an active oxidant that is responsible for the regio-, stereo-, and enantioselectivities in the catalytic hydroxylation of alkanes by nonheme manganese catalysts and terminal oxidants.</P> [FIG OMISSION]</BR>
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Liang Li,Mian Zheng 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.2
To gain the insights into the influence of the morphology of solid particles on rheological behavior of semisolid metal slurries, the time evolution of Hausdorff dimensionality describing the particle morphology is deduced in order to quantitatively analyze the time evolution of the particle morphology. In consideration of the role of the liquid entrapped by non-spherical solid particles, the non-spherical solid particles with the entrapped liquid are treated as spherical solid particles, and the equivalent solid volume fraction is defined as the sum of solid volume fraction and the volume fraction of the entrapped liquid. This model could be used to analyze the rheological behavior of the semisolid metal slurries containing the non-spherical particles with Hausdorff dimensionality less than 3. Moreover, the rheological behavior of semisolid magnesium alloy AZ91D is theoretically analyzed by this model during isothermal shearing and continuous cooling. The calculated results are found coinciding with the experimental results and the calculated results also reveal that the shear rate and cooling rate could influence the rheological behavior of semisolid metal slurries by changing the morphology of solid particles except by affecting agglomeration degree.
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Guo, Mian,Lee, Yong-Min,Seo, Mi Sook,Kwon, Yong-Ju,Li, Xiao-Xi,Ohta, Takehiro,Kim, Won-Suk,Sarangi, Ritimukta,Fukuzumi, Shunichi,Nam, Wonwoo American Chemical Society 2018 Inorganic Chemistry Vol.57 No.16
<P>Mn(III)-iodosylarene porphyrin adducts, [Mn(III)(ArIO)(Porp)]<SUP>+</SUP>, were synthesized by reacting electron-deficient Mn(III) porphyrin complexes with iodosylarene (ArIO) at −60 °C and characterized using various spectroscopic methods. The [Mn(III)(ArIO)(Porp)]<SUP>+</SUP> species were then investigated in the epoxidation of olefins under stoichiometric conditions. In the epoxidation of olefins by the Mn(III)-iodosylarene porphyrin species, epoxide was formed as the sole product with high chemoselectivities and stereoselectivities. For example, cyclohexene oxide was formed exclusively with trace amounts of allylic oxidation products; <I>cis</I>- and <I>trans</I>-stilbenes were oxidized to the corresponding <I>cis</I>- and <I>trans</I>-stilbene oxides, respectively. In the catalytic epoxidation of cyclohexene by an electron-deficient Mn(III) porphyrin complex and <SUP>s</SUP>PhIO at low temperature (e.g., −60 °C), the Mn(III)-iodosylarene porphyrin species was evidenced as the active oxidant that effects the olefin epoxidation to give epoxide as the product. However, at high temperature (e.g., 0 °C) or in the case of using an electron-rich manganese(III) porphyrin catalyst, allylic oxidation products, along with cyclohexene oxide, were yielded, indicating that the active oxidant(s) was not the Mn(III)-iodosylarene adduct but probably high-valent Mn-oxo species in the catalytic reactions. We also report the conversion of the Mn(III)-iodosylarene porphyrins to high-valent Mn-oxo porphyrins under various conditions, such as at high temperature, with electron-rich porphyrin ligand, and in the presence of base (OH<SUP>-</SUP>). The present study reports the first example of spectroscopically well-characterized Mn(III)-iodosylarene porphyrin species being an active oxidant in the stoichiometric and catalytic oxidation reactions. Other aspects, such as one oxidant versus multiple oxidants debate, also were discussed.</P><P>Mn(III)-iodosylarene porphyrin adducts, [Mn(III)(ArIO)(Porp)]<SUP>+</SUP>, were synthesized by reacting electron-deficient Mn(III) porphyrin complexes with iodosylarene (ArIO) and characterized using various spectroscopic methods. In the epoxidation of olefins by the Mn(III)-iodosylarene porphyrin species, epoxide was formed as the sole product with high chemoselectivities and stereoselectivities. The present study reports the first example of spectroscopically well-characterized Mn(III)-iodosylarene porphyrin species being an active oxidant in the stoichiometric and catalytic oxidation reactions.</P> [FIG OMISSION]</BR>
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