Model for Anisotropic Directed Percolation

We propose a simulation model to study the properties of directed percolation in two-dimensional (2D) anisotropic random media. The degree of anisotropy in the model is given by the ratio $\mu$ between the axes of a semi-ellipse enclosing the bonds that promote percolation in one direction. At percolation, this simple model shows that the average number of bonds per site in 2D is an invariant equal to 2.8 independently of $\mu$. This result suggests that Sinai's theorem proposed originally for isotropic percolation is also valid for anisotropic directed percolation problems. The new invariant also yields a constant fractal dimension $D_{f} \sim 1.71$ for all $\mu$, which is the same value found in isotropic directed percolation (i.e., $\mu = 1$).Comment: RevTeX, 9 pages, 3 figures. To appear in Phys.Rev.

STOCHASTIC EFFICIENCY ANALYSIS USING MULTIPLE UTILITY FUNCTIONS

Evaluating the risk of a particular decision depends on the risk aversion of the decision maker related to the underlying utility function. The objective of this paper is to use stochastic efficiency with respect to a function (SERF) to compare the ranking of risky alternatives using alternative utility functional forms.Research Methods/ Statistical Methods,

Stochastic efficiency analysis with risk aversion bounds: a simplified approach

A method of stochastic dominance analysis with respect to a function (SDRF) is described and illustrated. The method, called stochastic efficiency with respect to a function (SERF), orders a set of risky alternatives in terms of certainty equivalents for a specified range of attitudes to risk. It can be applied for conforming utility functions with risk attitudes defined by corresponding ranges of absolute, relative or partial risk aversion coefficients. Unlike conventional SDRF, SERF involves comparing each alternative with all the other alternatives simultaneously, not pairwise, and hence can produce a smaller efficient set than that found by simple pairwise SDRF over the same range of risk attitudes. Moreover, the method can be implemented in a simple spreadsheet with no special software needed.Risk and Uncertainty,

High-Resolution Analysis of the Efficiency, Heritability, and Editing Outcomes of CRISPR/Cas9-Induced Modifications of NCED4 in Lettuce (Lactuca sativa).

CRISPR/Cas9 is a transformative tool for making targeted genetic alterations. In plants, high mutation efficiencies have been reported in primary transformants. However, many of the mutations analyzed were somatic and therefore not heritable. To provide more insights into the efficiency of creating stable homozygous mutants using CRISPR/Cas9, we targeted LsNCED4 (9-cis-EPOXYCAROTENOID DIOXYGENASE4), a gene conditioning thermoinhibition of seed germination in lettuce. Three constructs, each capable of expressing Cas9 and a single gRNA targeting different sites in LsNCED4, were stably transformed into lettuce (Lactuca sativa) cvs. Salinas and Cobham Green. Analysis of 47 primary transformants (T1) and 368 T2 plants by deep amplicon sequencing revealed that 57% of T1 plants contained events at the target site: 28% of plants had germline mutations in one allele indicative of an early editing event (mono-allelic), 8% of plants had germline mutations in both alleles indicative of two early editing events (bi-allelic), and the remaining 21% of plants had multiple low frequency mutations indicative of late events (chimeric plants). Editing efficiency was similar in both genotypes, while the different gRNAs varied in efficiency. Amplicon sequencing of 20 T1 and more than 100 T2 plants for each of the three gRNAs showed that repair outcomes were not random, but reproducible and characteristic for each gRNA. Knockouts of NCED4 resulted in large increases in the maximum temperature for seed germination, with seeds of both cultivars capable of germinating >70% at 37°. Knockouts of NCED4 provide a whole-plant selectable phenotype that has minimal pleiotropic consequences. Targeting NCED4 in a co-editing strategy could therefore be used to enrich for germline-edited events simply by germinating seeds at high temperature

Deterministic Assembly of Arrays of Lithographically Defined WS2 and MoS2 Monolayer Features Directly from Multilayer Sources into Van der Waals Heterostructures

One of the major challenges in the van der Waals (vdW) integration of two-dimensional (2D) materials is achieving high-yield and high-throughput assembly of predefined sequences of monolayers into heterostructure arrays. Mechanical exfoliation has recently been studied as a promising technique to transfer monolayers from a multilayer source synthesized by other techniques, allowing the deposition of a wide variety of 2D materials without exposing the target substrate to harsh synthesis conditions. Although a variety of processes have been developed to exfoliate the 2D materials mechanically from the source and place them deterministically onto a target substrate, they can typically transfer only either a wafer-scale blanket or one small flake at a time with uncontrolled size and shape. Here, we present a method to assemble arrays of lithographically defined monolayer WS2 and MoS2 features from multilayer sources and directly transfer them in a deterministic manner onto target substrates. This exfoliate-align-release process - without the need of an intermediate carrier substrate - is enabled by combining a patterned, gold-mediated exfoliation technique with a new optically transparent, heat-releasable adhesive. WS2/MoS2 vdW heterostructure arrays produced by this method show the expected interlayer exciton between the monolayers. Light-emitting devices using WS2 monolayers were also demonstrated, proving the functionality of the fabricated materials. Our work demonstrates a significant step toward developing mechanical exfoliation as a scalable dry transfer technique for the manufacturing of functional, atomically thin materials

Frequency-Dependent Attenuation Analysis of Ground-Penetrating Radar Data

In the early 1990s, it was established empirically that, in many materials, ground-penetrating radar (GPR) attenuation is approximately linear with frequency over the bandwidth of a typical pulse. Further, a frequency-independent Q* parameter characterizes the slope of the band-limited attenuation versus frequency curve. Here, I derive the band-limited Q* function from a first-order Taylor expansion of the attenuation coefficient. This approach provides a basis for computing Q* from any arbitrary dielectric permittivity model. For Cole-Cole relaxation, I find good correlation between the first-order Q* approximation and Q* computed from linear fits to the attenuation coefficient curve over two-octave bands. The correlation holds over the primary relaxation frequency. For some materials, this relaxation occurs between 10 and 200 MHz, a typical frequency range for many GPR applications. Frequency-dependent losses caused by scattering and by the commonly overlooked problem of frequency-dependent reflection make it difficult or impossible to measure Q* from reflection data without a priori understanding of the materials. Despite these complications, frequency-dependent attenuation analysis of reflection data can provide valuable subsurface information. At two field sites, I find well-defined frequency-dependent attenuation anomalies associated with nonaqueous-phase liquid contaminants

Penetration of hot electrons through a cold disordered wire

We study a penetration of an electron with high energy E<<T through strongly disordered wire of length L<<a (a being the localization length). Such an electron can loose, but not gain the energy, when hopping from one localized state to another. We have found a distribution function for the transmission coefficient t. The typical t remains exponentially small in L/a, but with the decrement, reduced compared to the case of direct elastic tunnelling. The distribution function has a relatively strong tail in the domain of anomalously high t; the average ~(a/L)^2 is controlled by rare configurations of disorder, corresponding to this tail.Comment: 4 pages, 5 figure

Ground-Penetrating Radar Theory and Application of Thin-Bed Offset-Dependent Reflectivity

Offset-dependent reflectivity or amplitude-variationwith- offset (AVO) analysis of ground-penetrating radar (GPR) data may improve the resolution of subsurface dielectric permittivity estimates. A horizontally stratified medium has a limiting layer thickness below which thin-bed AVO analysis is necessary. For a typical GPR signal, this limit is approximately 0.75 of the characteristic wavelength of the signal. Our approach to modeling the GPR thin-bed response is a broadband, frequency-dependent computation that utilizes an analytical solution to the three-interface reflectivity and is easy to implement for either transverse electric (TE) or transverse magnetic (TM) polarizations. The AVO curves for TE and TM modes differ significantly. In some cases, constraining the interpretation using both TE and TM data is critical. In two field examples taken from contaminated-site characterization data, we find quantitative thin-bed modeling agrees with the GPR field data and available characterization data

A Dense SNP-Based Linkage Map for Atlantic Salmon (Salmo salar) Reveals extended Chromosome Homeologies and Striking Differences in Sex-Specific Recombination Patterns

Background: The Atlantic salmon genome is in the process of returning to a diploid state after undergoing awhole genome duplication (WGD) event between 25 and100 million years ago. Existing data on the proportion ofparalogous sequence variants (PSVs), multisite variants (MSVs) and other types of complex sequence variationsuggest that the rediplodization phase is far from over. The aims of this study were to construct a high densitylinkage map for Atlantic salmon, to characterize the extent of rediploidization and to improve our understandingof genetic differences between sexes in this species.Results: A linkage map for Atlantic salmon comprising 29 chromosomes and 5650 single nucleotidepolymorphisms (SNPs) was constructed using genotyping data from 3297 fish belonging to 143 families. Of these,2696 SNPs were generated from ESTs or other gene associated sequences. Homeologous chromosomal regionswere identified through the mapping of duplicated SNPs and through the investigation of syntenic relationshipsbetween Atlantic salmon and the reference genome sequence of the threespine stickleback (Gasterosteusaculeatus). The sex-specific linkage maps spanned a total of 2402.3 cM in females and 1746.2 cM in males,highlighting a difference in sex specific recombination rate (1.38:1) which is much lower than previously reportedin Atlantic salmon. The sexes, however, displayed striking differences in the distribution of recombination siteswithin linkage groups, with males showing recombination strongly localized to telomeres.Conclusion: The map presented here represents a valuable resource for addressing important questions of interestto evolution (the process of re-diploidization), aquaculture and salmonid life history biology and not least as aresource to aid the assembly of the forthcoming Atlantic salmon reference genome sequence

Stability of Transonic Shock Solutions for One-Dimensional Euler-Poisson Equations

In this paper, both structural and dynamical stabilities of steady transonic shock solutions for one-dimensional Euler-Poission system are investigated. First, a steady transonic shock solution with supersonic backgroumd charge is shown to be structurally stable with respect to small perturbations of the background charge, provided that the electric field is positive at the shock location. Second, any steady transonic shock solution with the supersonic background charge is proved to be dynamically and exponentially stable with respect to small perturbation of the initial data, provided the electric field is not too negative at the shock location. The proof of the first stability result relies on a monotonicity argument for the shock position and the downstream density, and a stability analysis for subsonic and supersonic solutions. The dynamical stability of the steady transonic shock for the Euler-Poisson equations can be transformed to the global well-posedness of a free boundary problem for a quasilinear second order equation with nonlinear boundary conditions. The analysis for the associated linearized problem plays an essential role