Rice blast caused by Magnaporthe oryzae is one of the most destructive diseases of rice worldwide. The fungal pathogen is notorious for its ability to overcome host resistance. To better understand its genetic variation in nature, we sequenced the genomes of two field isolates, Y34 and P131. In comparison with the previously sequenced laboratory strain 70-15, both field isolates had a similar genome size but slightly more genes. Sequences from the field isolates were used to improve genome assembly and gene prediction of 70-15. Although the overall genome structure is similar, a number of gene families that are likely involved in plant-fungal interactions are expanded in the field isolates. Genome-wide analysis on asynonymous to synonymous nucleotide substitution rates revealed that many infection-related genes underwent diversifying selection. The field isolates also have hundreds of isolate-specific genes and a number of isolate-specific gene duplication events. Functional characterization of randomly selected isolate-specific genes revealed that they play diverse roles, some of which affect virulence. Furthermore, each genome contains thousands of loci of transposon-like elements, but less than 30% of them are conserved among different isolates, suggesting active transposition events in M. oryzae. A total of approximately 200 genes were disrupted in these three strains by transposable elements. Interestingly, transposon-like elements tend to be associated with isolate-specific or duplicated sequences. Overall, our results indicate that gain or loss of unique genes, DNA duplication, gene family expansion, and frequent translocation of transposon-like elements are important factors in genome variation of the rice blast fungus.

Combined high performance of self-propagating synthesized materials and topological structures optimization, half-Heusler single-stage module and half-Heusler/Bi2Te3 segmented module attained record-high conversion efficiencies of 9.6% and 12.4%.

Van der Waals heterostructures stacked from different two-dimensional materials offer a unique platform for addressing many fundamental physics and construction of advanced devices. Twist angle between the two individual layers plays a crucial role in tuning the heterostructure properties. Here we report the experimental investigation of the twist angle-dependent conductivities in MoS2/graphene van der Waals heterojunctions. We found that the vertical conductivity of the heterojunction can be tuned by ∼5 times under different twist configurations, and the highest/lowest conductivity occurs at a twist angle of 0°/30°. Density functional theory simulations suggest that this conductivity change originates from the transmission coefficient difference in the heterojunctions with different twist angles. Our work provides a guidance in using the MoS2/graphene heterojunction for electronics, especially on reducing the contact resistance in MoS2 devices as well as other TMDCs devices contacted by graphene.

We study the Nernst effect and the spin Nernst effect, that a longitudinal thermal gradient induces a transverse voltage and a spin current. A mesoscopic four-terminal cross-bar device having the Rashba spin-orbit interaction (SOI) under a perpendicular magnetic field is considered. For zero SOI, the Nernst coefficient peaks when the Fermi level crosses the Landau Levels. In the presence of the SOI, the Nernst peaks split, and the spin Nernst effect appears and exhibits a series of oscillatory structures. The larger SOI is or the weaker magnetic field is, the more pronounced the spin Nernst effect is. The results also show that the Nernst and spin Nernst coefficients are sensitive to the detailed characteristics of the sample and the contacts. In addition, the Nernst effect is found to survive in strong disorder than the spin Nernst effect does.Comment: 5 pages, 5 figure

The thermoelectric power, including the Nernst and Seebeck effects, in graphene nanoribbon is studied. By using the non-equilibrium Green function combining with the tight-binding Hamiltonian, the Nernst and Seebeck coefficients are obtained. Due to the electron-hole symmetry, the Nernst coefficient is an even function of the Fermi energy while the Seebeck coefficient is an odd function regardless of the magnetic field. In the presence of a strong magnetic field, the Nernst and Seebeck coefficients are almost independent of the chirality and width of the nanoribbon, and they show peaks when the Fermi energy crosses the Landau levels. The height of n-th (excluding n = 0) peak is [ln 2/|n|] for the Nernst effect and is ln 2/n for the Seebeck effect. For the zeroth peak, it is abnormal with height [2 ln 2] for the Nernst effect and the peak disappears for the Seebeck effect. When the magnetic field is turned off, however, the Nernst effect is absent and only Seebeck effect exists. In this case, the Seebeck coefficient strongly depends on the chirality of the nanoribbon. The peaks are equidistant for the nanoribbons with zigzag edge but are irregularly distributed for the armchair edge. In particular, for the insulating armchair ribbon, the Seebeck coefficient can be very large near the Dirac point. When the magnetic field varies from zero to large values, the differences among the Seebeck coefficients for different chiral ribbons gradually vanish and the nonzero value of Nernst coefficient appears first near the Dirac point then gradually extents to the whole energy region.

We report the investigation of electron transport through a four-terminal graphene-superconductor hybrid system. Because of the quantum interference of the reflected holes from two graphene-superconductor interfaces with a phase difference theta, it is found that the specular Andreev reflection vanishes at theta=0 while the Andreev retroreflection disappears at theta=pi. This means that retroreflection and specular reflection can be easily controlled and separated in this device. In addition, because of the diffraction effect in the narrow graphene nanoribbon, the reflected hole can exit from both graphene terminals. As the width of nanoribbon increases, the diffraction effect gradually disappears and the reflected hole eventually exits from a particular graphene terminal depending on the type of Andreev reflection.

Half‐Heusler (HH) compounds have shown great potential in waste heat recovery. Among them, p‐type NbFeSb and n‐type ZrNiSn based alloys have exhibited the best thermoelectric (TE) performance. However, TE devices based on NbFeSb‐based HH compounds are rarely studied. In this work, bulk volumes of p‐type (Nb0.8Ta0.2)0.8Ti0.2FeSb and n‐type Hf0.5Zr0.5NiSn0.98Sb0.02 compounds are successfully prepared with good phase purity, compositional homogeneity, and matchable TE performance. The peak zTs are higher than 1.0 at 973 K for Hf0.5Zr0.5NiSn0.98Sb0.02 and at 1200 K for (Nb0.8Ta0.2)0.8Ti0.2FeSb. Based on an optimal design by a full‐parameters 3D finite element model, a single stage TE module with 8 n‐p HH couples is assembled. A high conversion efficiency of 8.3% and high power density of 2.11 W cm−2 are obtained when hot and cold side temperatures are 997 and 342 K, respectively. Compared to the previous TE module assembled by the same materials, the conversion efficiency is enhanced by 33%, while the power density is almost the same. Given the excellent mechanical robustness and thermal stability, matchable thermal expansion coefficient and TE properties of NbFeSb and ZrNiSn based HH alloys, this work demonstrates their great promise for power generation with both high conversion efficiency and high power density.

We study the nature of the disorder-induced quantized conductance, i.e., the phenomena of topological Anderson insulator (TAI) induced in HgTe/CdTe semiconductor quantum well. The disorder effect in several different systems where anomalous Hall effect exist, is numerically studied using the tight-binding Hamiltonian. It is found that the TAI phenomena also occur in the modified Dirac model where the quadratic corrections k 2 σ z is included and electron-hole symmetry is kept. It also occurs in the graphene system with the next nearestneighbor coupling and staggered sublattice potential. Comparison between the localization lengths of the 2D ribbon and 2D cylinder clearly reveals the topological nature of this phenomena. Furthermore, analysis on the local current density in anomalous quantum Hall systems where the TAI phenomena can or can not arise reveals the nature of TAI phenomena: the bulk state is killed drastically and only the robust edge state survives in a moderate disorder. When the edge state is robust enough to resist the strong disorder that can completely kills the bulk state, TAI phenomena arise.