Taugt17b1 Overexpression in Trichoderma atroviride Enhances Its Ability to Colonize Roots and Induce Systemic Defense of Plants.

Trichoderma atroviride, a soil fungus, has important applications in the biocontrol of plant diseases. Glycosyltransferases enhance the root colonization ability of Trichoderma spp. This study aimed to functionally characterize glycosyltransferase Taugt17b1 in T. atroviride. We investigated the effect of Taugt17b1 overexpression in T. atroviride H18-1-1 on its biocontrol properties, especially its ability to colonize roots. Our results demonstrated that the overexpression of the Taugt17b1 increases the T. atroviride colony growth rate, improves its root colonization ability, promotes the growth and activity of the defensive enzymatic system of plants, and prevents plant diseases. This study put forth a new role of T. atroviride glycosyltransferase and furthered the understanding of the mechanisms by which fungal biocontrol agents exert their effect.

A Dissolution/Precipitation Equilibrium on the Surface of Iridium-Based Perovskites Controls Their Activity as Oxygen Evolution Reaction Catalysts in Acidic Media.

Recently, IrV -based perovskite-like materials were proposed as oxygen evolution reaction (OER) catalysts in acidic media with promising performance. However, iridium dissolution and surface reconstruction were observed, questioning the real active sites on the surface of these catalysts. In this work, Sr2 MIr(V) O6 (M=Fe, Co) and Sr2 Fe0.5 Ir0.5 (V) O4 were explored as OER catalysts in acidic media. Their activities were observed to be roughly equal to those previously reported for La2 LiIrO6 or Ba2 PrIrO6 . Coupling electrochemical measurements with iridium dissolution studies under chemical or electrochemical conditions, we show that the deposition of an IrOx layer on the surface of these perovskites is responsible for their OER activity. Furthermore, we experimentally reconstruct the iridium Pourbaix diagram, which will help guide future research in controlling the dissolution/precipitation equilibrium of iridium species for the design of better Ir-based OER catalysts.

Structural Modification of the Cation-Ordered Ruddlesden-Popper Phase YSr2Mn2O7 by Cation Exchange and Anion Insertion.

Calcium-for-strontium cation substitution of the a-b0c0/b0a-c0-distorted, cation-ordered, n = 2 Ruddlesden-Popper phase, YSr2Mn2O7, leads to separation into two phases, which both retain an a-b0c0/b0a-c0-distorted framework and have the same stoichiometry but exhibit different degrees of Y/Sr/Ca cation order. Increasing the calcium concentration to form YSr0.5Ca1.5Mn2O7 leads to a change in the cooperative tilting on the MnO6 units to a novel a-b-c-/b-a-c- arrangement described in space group P21/n11. Low-temperature, topochemical fluorination of YSr2Mn2O7 yields YSr2Mn2O5.5F3.5. In contrast to many other fluorinated n = 2 Ruddlesden-Popper oxide phases, YSr2Mn2O5.5F3.5 retains the a-b0c0/b0a-c0 lattice distortion and P42/mnm space group symmetry of the parent oxide phase. The resilience of the a-b0c0/b0a-c0-distorted framework of YSr2Mn2O7 to resist symmetry-changing deformations upon both cation substitution and anion insertion/exchange is discussed on the basis the A-site cation order of the lattice and the large change in the ionic radius of manganese upon oxidation from Mn3+ to Mn4+. The structure property relations observed in the Y-Sr-Ca-Mn-O-F system provide insight into assisting in the synthesis of n = 2 Ruddlesden-Popper phases, which adopt cooperative structural distortions that break the inversion symmetry of the extended lattice and therefore act as a route for the preparation of ferroelectric and multiferroic materials.

Orbital Dimer Model for the Spin-Glass State in Y_{2}Mo_{2}O_{7}.

The formation of a spin glass generally requires that magnetic exchange interactions are both frustrated and disordered. Consequently, the origin of spin-glass behavior in Y_{2}Mo_{2}O_{7}-in which magnetic Mo^{4+} ions occupy a frustrated pyrochlore lattice with minimal compositional disorder-has been a longstanding question. Here, we use neutron and x-ray pair-distribution function (PDF) analysis to develop a disorder model that resolves apparent incompatibilities between previously reported PDF, extended x-ray-absorption fine structure spectroscopy, and NMR studies, and provides a new and physical explanation of the exchange disorder responsible for spin-glass formation. We show that Mo^{4+} ions displace according to a local "two-in-two-out" rule on each Mo_{4} tetrahedron, driven by orbital dimerization of Jahn-Teller active Mo^{4+} ions. Long-range orbital order is prevented by the macroscopic degeneracy of dimer coverings permitted by the pyrochlore lattice. Cooperative O^{2-} displacements yield a distribution of Mo-O-Mo angles, which in turn introduces disorder into magnetic interactions. Our study demonstrates experimentally how frustration of atomic displacements can assume the role of compositional disorder in driving a spin-glass transition.

La2SrCr2O7: Controlling the Tilting Distortions of n = 2 Ruddlesden-Popper Phases through A-Site Cation Order.

Structural characterization by neutron diffraction, supported by magnetic, SHG, and µ(+)SR data, reveals that the n = 2 Ruddlesden-Popper phase La2SrCr2O7 adopts a highly unusual structural configuration in which the cooperative rotations of the CrO6 octahedra are out of phase in all three Cartesian directions (ΦΦΦz/ΦΦΦz; a(-)a(-)c(-)/a(-)a(-)c(-)) as described in space group A2/a. First-principles DFT calculations indicate that this unusual structural arrangement can be attributed to coupling between the La/Sr A-site distribution and the rotations of the CrO6 units, which combine to relieve the local deformations of the chromium-oxygen octahedra. This coupling suggests new chemical "handles" by which the rotational distortions or A-site cation order of Ruddlesden-Popper phases can be directed to optimize physical behavior. Low-temperature neutron diffraction data and µ(+)SR data indicate La2SrCr2O7 adopts a G-type antiferromagnetically ordered state below TN ∼ 260 K.

La2SrCr2O7F2: A Ruddlesden-Popper Oxyfluoride Containing Octahedrally Coordinated Cr(4+) Centers.

The low-temperature fluorination of the n = 2 Ruddlesden-Popper phase La2SrCr2O7 yields La2SrCr2O7F2 via a topochemical fluorine insertion reaction. The structure-conserving nature of the fluorination reaction means that the chromium centers of the initial oxide phase retain an octahedral coordination environment in the fluorinated product, resulting in a material containing an extended array of apex-linked Cr(4+)O6 units. Typically materials containing networks of octahedrally coordinated Cr(4+) centers can only be prepared at high pressure; thus, the preparation of La2SrCr2O7F2 demonstrates that low-temperature topochemical reactions offer an alternative synthesis route to materials of this type. Neutron diffraction, magnetization, and µ(+)SR data indicate that La2SrCr2O7F2 undergoes a transition to an antiferromagnetic state below TN ≈ 140 K. The structure-property relations of this phase and other Cr(4+) oxide phases are discussed.

K4Fe3F12: An Fe(2+)/Fe(3+) Charge-Ordered, Ferrimagnetic Fluoride with a Cation-Deficient, Layered Perovskite Structure.

A new mixed-valence iron (Fe(2+)/Fe(3+)) fluoride material with a layered perovskite-related structure has been synthesized and characterized. The material, K4Fe3F12 [K4(Fe(2+))(Fe(3+))2F12], was synthesized using mild hydrothermal conditions. The material exhibits a layered perovskite structure consisting of alternating sheets of apex-linked Fe(2+)F6 and Fe(3+)F6 octahedra; thus, each layer of Fe(2+)F6 centers is sandwiched between two layers of Fe(3+)F6 centers. Magnetization and neutron powder diffraction data show that, upon cooling below 120 K, K4Fe3F12 adopts a magnetically ordered state in which the Fe(3+) and Fe(2+) spins are aligned in an approximately antiparallel manner to each other to yield a pseudoferrimagnetic structure with a net spontaneous moment of 5.41 µB per formula unit at 10 K. Crystal data: K4Fe3F12, trigonal space group R3̅m (No. 166), a = b = 5.7649(9) Å, c = 28.086(9) Å, V = 808.36(3) Å(3), Z = 3, T = 296(2) K.

Ultraviolet to near-infrared downconversion of Y2SiO5: Ce3+, Yb3+ nanobelt-poly-EVA films.

The 1D Y(2)SiO(5): Ce(3+), Yb(3+) nanobelt phosphors and nanobelts-poly-ethylene vinyl acetate (poly-EVA) composite films were fabricated to explore spectral conversion materials for improving the conversion efficiency of c-Si solar cell. Scanning electron microscope, x-ray diffraction, photoluminescence excitation, photoluminescence (PL), transmission and decay curves were employed to characterize the structure, morphology, and optical properties. The nanobelt phosphor exhibits efficient ultraviolet (UV) absorption and gives intense near-infrared (NIR) emission. The UV to NIR downconversion process in Y(2)SiO(5): Ce(3+), Yb(3+) nanobelts was investigated. More importantly, the thickness, transmission and PL spectra of nanobelts-poly-EVA films were also studied in detail. The NIR-emitting one-dimensional nanobelt-composite film may be applied as a promising spectral conversion layer for c-Si solar cell.

[Plasma concentrations of vascular endothelial growth factor and tissue factor in children with acute lymphoblastic leukemia].

OBJECTIVE: To detect plasma concentrations of vascular endothelial cell growth factor (VEGF) and tissue factor (TF) in children with acute lymphoblastic leukemia (ALL) and explore their clinical significance in ALL. METHODS: Thirty-three children with newly diagnosed ALL, including 18 cases of low risk, 7 cases of moderate risk and 8 cases of high risk, were enrolled in this study. Twenty-five patients received a complete remission and 8 cases were in non-remission after conventional remission induction chemotherapy. Plasma concentrations of VEGF and TF in the patients were detected using ELISA before and after treatment. Sixteen healthy children served as normal control group. RESULTS: Plasma concentrations of VEGF and TF in ALL patients before treatment were significantly higher than those in normal controls (P < 0.01). Plasma concentrations of VEGF and TF in the non-remission group before treatment were significantly higher than those in the remission group (P < 0.05) and the control group (P < 0.01). After treatment the plasma concentrations of VEGF and TF in the non-remission group were not significantly reduced and higher than those in the remission and the control groups (P < 0.01). There were significant differences in plasma concentrations of VEGF and TF among the low-risk, moderate-risk and high-risk groups before and after treatment (P < 0.05). Plasma concentrations of VEGF and TF in the high risk group were not significantly reduced after treatment and higher than those in the control group (P < 0.01). A linear correlation was noted between plasma VEGF and TF concentrations in ALL patients before treatment (r=0.50, P < 0.01). CONCLUSIONS: VEGF and TF play an important role in the development of ALL and may be useful to the evaluation of the severity and the outcome in ALL.