On Internal Fracture of Solids

Initiation and propagation of internal fracture in solid

Coexistence of gapless excitations and commensurate charge-density wave in the 2H-transition metal dichalcogenides

An unexpected feature common to 2H-transition metal dichalcogenides (2H-TMDs) is revealed with first-principles Wannier functions analysis of the electronic structure of the prototype 2H-TaSe2: The low-energy Ta \red{``$5d_{z^2}$''} bands governing the physics of charge-density wave (CDW) is dominated by hopping between next-nearest neighbors. With this motivation we develop a minimal effective model for the CDW formation, in which the unusual form of the hopping leads to an approximate decoupling of the three sublattices. In the CDW phase one sublattice remains undistorted, leaving the bands associated with it ungapped everywhere in the Fermi surface, resolving the long-standing puzzle of coexistence of gapless excitations and commensurate CDW in the 2H-TMDs.Comment: 4 pages, 5 figure

Bayesian Dose Finding for Combined Drugs with Discrete and Continuous Doses

published_or_final_versio

Genetic diversity and population structure of Chinese honeybees (Apis cerana) under microsatellite markers

Using 21 microsatellite markers and PCR method, the polymorphisms of 20 Apis cerana honeybee populations across China was investigated and the genetic structure and diversity of the populations were explored. The results showed that 507 alleles (mean 24.14 per locus, ranging from 13 to 45) were observed in 842 honeybees. Wuding bee had the highest level of  heterozygosity (0.695), and the lowest estimate was 0.207 for Changbai bee. The global heterozygote deficit across all populations (Fit) amounted to 0.776. About 42.3% of the total genetic variability originated from differences between breeds, with all loci contributing significantly to the differentiation. An unrooted consensus tree using the Neighbour-Joining method and pair-wise distances showed that 6 populations from Eastern China clustered together. The structure analysis indicated that the 6 populations were separated first. These findings demonstrated that the 6 honeybee populations had close genetic relationships.Key words: Apis cerana, microsatellite, polymorphism, genetic structure

Potential Models and Lattice Gauge Current-Current Correlators

We compare current-current correlators in lattice gauge calculations with correlators in different potential models, for a pseudoscalar charmonium in the quark-gluon plasma. An important ingredient in the evaluation of the current-current correlator in the potential model is the basic principle that out of the set of continuum states, only resonance states and Gamow states with lifetimes of sufficient magnitudes can propagate as composite objects and can contribute to the current-current correlator. When the contributions from the bound states and continuum states are properly treated, the potential model current-current correlators obtained with the potential proposed in Ref. [11] are consistent with the lattice gauge correlators. The proposed potential model thus gains support to be a useful tool to complement lattice gauge calculations for the study of $Q\bar Q$ states at high temperatures.Comment: 18 pages, 4 figures, to be published in Physcial Review

Examination on Time-Dependent Soil Models in One-Dimensional Consolidation

This paper reviews the performance of two time-dependent constitutive models in predictions of one-dimensional consolidation. The Soft-Soil Creep model [1] is an example of an elastic-viscoplastic formulation that incorporates a time-dependent state variable to estimate viscoplastic deformation. We show that the SSC model is equivalent to the isotache formulation proposed by Imai [2], as both are based on a unique relationship between stress, void ratio and the viscoplastic component of void ratio rate. Simulations of 1-D consolidation confirm that both models represent Hypothesis B behavior, where the axial strain at the End of Primary (EOP) consolidation is dependent on the depth of the clay layer. The effects of specimen thickness and the phenomenon of pore pressure increase at the start of consolidation are discussed in detail. Our interpretation highlights the importance of assumptions regarding the initial strain rate on the behavior observed at different scales under a given applied increment of loading

Scanning Tunneling Spectroscopy and Vortex Imaging in the Iron-Pnictide Superconductor BaFe1.8_{1.8}Co0.2_{0.2}As2_2

We present an atomic resolution scanning tunneling spectroscopy study of superconducting BaFe$_{1.8}$Co$_{0.2}$As$_2$ single crystals in magnetic fields up to $9 \text{Tesla}$. At zero field, a single gap with coherence peaks at $\overline{\Delta}=6.25 \text{meV}$ is observed in the density of states. At $9 \text{T}$ and $6 \text{T}$, we image a disordered vortex lattice, consistent with isotropic, single flux quantum vortices. Vortex locations are uncorrelated with strong scattering surface impurities, demonstrating bulk pinning. The vortex-induced sub-gap density of states fits an exponential decay from the vortex center, from which we extract a coherence length $\xi=27.6\pm 2.9 \text{\AA}$, corresponding to an upper critical field $H_{c2}=43 \text{T}$.Comment: 4 pages, 4 figure

Thermal and electrical transport in the spin density wave antiferromagnet CaFe4_{4}As3_{3}

We present here measurements of the thermopower, thermal conductivity, and electrical resistivity of the newly reported compound CaFe4As3. Evidence is presented from specific heat and electrical resistivity measurements that a substantial fraction of the Fermi surface survives the onset of spin density wave (SDW) order at the Neel temperature TN=88 K, and its subsequent commensurate lockin transition at T2=26.4 K. The specific heat below T2 consists of a normal metallic component from the ungapped parts of the Fermi surface, and a Bardeen-Cooper- Schrieffer (BCS) component that represents the SDW gapping of the Fermi surface. A large Kadowaki-Woods ratio is found at low temperatures, showing that the ground state of CaFe4As3 is a strongly interacting Fermi liquid. The thermal conductivity of CaFe4As3 is an order of magnitude smaller than those of conventional metals at all temperatures, due to a strong phonon scattering. The thermoelectric power displays a sign change from positive to negative indicating that a partial gap forms at the Fermi level with the onset of commensurate spin density wave order at T2=26.4 K. The small value of the thermopower and the enhancements of the resistivity due to gap formation and strong quasiparticle interactions offset the low value of the thermal conductivity, yielding only a modest value for the thermoelectric figure of merit Z < 5x10^-6 1/K in CaFe4As3. The results of ab initio electronic structure calculations are reported, confirming that the sign change in the thermopower at T2 is reflected by a sign change in the slope of the density of states at the Fermi level. Values for the quasiparticle renormalization are derived from measurements of the specific heat and thermopower, indicating that as T->0, CaFe4As3 is among the most strongly correlated of the known Fe-based pnictide and chalcogenide systems.Comment: 8 pages with 5 figure