13 research outputs found

    Quantitative Assessment of the Connection between Steric Hindrance and Electronic Coupling in 2,5-Bis(alkoxy)benzene-Based Mixed-Valence Dimers

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    The effect of the bridging ligand on electronic delocalization was examined in a series <i>p</i>-bis­(alkoxy)­benzene dimers relevant to conducting polymers used for organic devices. Using spectroscopic methods, the degree of delocalization for an ethylene-bridged <i>p</i>-bis­(alkoxy)­benzene dimer was determined and compared to the electronic coupling for directly coupled and phenylene-bridged <i>p</i>-bis­(alkoxy)­benzene dimers reported previously. Despite a significant increase in distance (53%) between the redox-active sites, the ethylene-bridged compound exhibited a higher electronic coupling than either of the others previously reported. The increased coupling can be attributed to the lower rotational barrier to planarization for the ethylene-bridged dimer. This result highlights the need to minimize both sterics and distance between redox active sites in molecular systems designed for promoting electron mobility and provides quantitative evidence that an optimal balance between these parameters can be achieved

    Identification of Soybean MicroRNAs Involved in Soybean Cyst Nematode Infection by Deep Sequencing

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    <div><p>Soybean cyst nematode (SCN), <em>Heterodera glycines</em>, is the most devastating pathogen of soybean worldwide. MicroRNAs (miRNAs) are a class of small, non-coding RNAs that are known to play important role in plant stress response. However, there are few reports profiling the miRNA expression patterns during pathogen stress. We sequenced four small RNA libraries from two soybean cultivar (Hairbin xiaoheidou, SCN race 3 resistant, Liaodou 10, SCN race 3 susceptible) that grown under un-inoculated and SCN-inoculated soil. Small RNAs were mapped to soybean genome sequence, 364 known soybean miRNA genes were identified in total. In addition, 21 potential miRNA candidates were identified. Comparative analysis of miRNA profiling indicated 101 miRNAs belong to 40 families were SCN-responsive. We also found 20 miRNAs with different express pattern even between two cultivars of the same species. These findings suggest that miRNA paly important role in soybean response to SCN and have important implications for further identification of miRNAs under pathogen stress.</p> </div

    Differential expressed miRNAs in response to SCN.

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    <p>miRNA with expression changes greater than 2 fold and P-value lower than 0.01 at least in one cultirvar.</p

    Novel miRNA candidates predicted from miRNA precursor.

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    <p>Novel miRNA candidates predicted from miRNA precursor.</p

    Step-loop RT-PCR for novel miRNAs.

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    <p>Gma-miR160: the positive control, NC: Water was added instead of RNA in the reverse transcript reaction, the negative control.</p

    Length distribution of soybean roots sRNAs.

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    <p>(a) Ratio of unique sRNAs reads vs size. (b) Ratio of total sRNAs reads vs size.</p

    qRT-PCR results.

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    <p>qRT-PCR confirming express pattern of miRNAs.</p

    Efficient Treatment of Phosphonate-Laden Wastewater by CaO<sub>2</sub>/UV: Partial Oxidation, Complexation, and Coprecipitation

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    Unlike the case for inorganic phosphate (Pi), removing organic phosphorus (Po) is more challenging. Conventional methods for removing Po involve a two-step route, where Po is first converted to Pi by an advanced oxidation process, followed by subsequent chemical precipitation/coagulation. Here, we propose a one-step CaO2/UV method for simultaneous conversion and coprecipitation of phosphonates, a representative type of organic phosphorus compound. We discovered that the total P removal (82.0%) is much higher than the conversion efficiency of Po to Pi (26.7%) under a dose of 1.5 mM CaO2 and 4 h UV irradiation for nitrilotris-methylene phosphonic acid (NTMP) treatment, providing new directions for treating Po compounds without completely breaking down the molecular structure. We further found that a CaO2/Po molar ratio of 1.5 is ideal for inducing the partial breakdown of the NTMP structure, Ca-phosphate formation, and coprecipitation of NTMP and its degradation intermediates. Beyond that, we noted that the presence of Ca2+ enhances the reactivity of NTMP with hydroxyl radicals, as supported by the improved conversion efficiency of Po to Pi, i.e., 37.4% vs 9.1% under pHi 11. We also demonstrated the preliminary feasibility of the CaO2/UV system in treating the reverse osmosis concentrate. Our study offers a robust one-step approach and sheds new insights on the synergistic role of partial oxidation, complexation, and coprecipitation in dealing with phosphonate-laden wastewater

    Sequence Effects in Donor–Acceptor Oligomeric Semiconductors Comprising Benzothiadiazole and Phenylenevinylene Monomers

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    To understand the influence of monomer sequence on the properties and performance of conjugated oligomers, a series of dimers, trimers, and tetramers were prepared from phenylene (<b>P</b>) and benzothiadiazole (<b>B</b>) monomers linked by vinylene groups. Optical and electrochemical studies established the influence of sequence on both the λ<sub>max</sub> and redox potentials of this series of structurally related oligomers. For tetramers with bromo end groups (<b>PBBP</b>, <b>BPPB</b>, <b>PBPB</b>, <b>PPBB</b>), the λ<sub>max</sub> ranged from 493 to 512 nm (Δ = 19 nm), the electrochemical oxidation potential from 0.65 to 0.82 (Δ = 0.17 V) and the reduction potential from −1.45 to −1.31 (Δ = 0.14 V), all of which are sequence-dependent. The effect of end groups (cyano, bromo, and alkyl) was also demonstrated to be important for the properties of these oligomers. DFT calculations of the tetramers were performed and the energy levels were correlated well with the experimentally determined spectroscopic data. Bulk heterojunction (BHJ) solar cells fabricated with selected tetramers as the donor and PC<sub>61</sub>BM as the acceptor exhibited power conversion efficiencies that varied by a factor of 3 as a function of sequence (0.47–1.85%). These results suggest that sequence control is important for tuning optoelectronic properties and photovoltaic performance of these structurally related conjugated oligomers
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