EVALUATION OF FORAGING PATTERNS OF LINEPITHEMA HUMILE (MAYR), THE ARGENTINE ANT, TO IMPROVE BAIT PLACEMENT IN NATURAL PARK HABITATS

Linepithema humile (Mayr), the Argentine ant, is an invasive ant species and a significant pest in natural and managed habitats of the southeastern United States. In the natural sites of Lake Greenwood State Park (LGSP) in the Piedmont region of South Carolina, L. humile has invaded. Although park personnel treat problem areas with liquid insecticides, control of L. humile through the park areas is minimal. The primary objectives of this study were to determine the optimal foraging distance of L. humile, evaluate over-wintering nest temperatures and foraging activity of L. humile, and evaluate liquid bait placement to control L. humile. A Double Antibody-Sandwich Enzyme-Linked Immunosorbent Assay (DAS-ELISA) procedure was used to detect individual ants that had consumed rabbit Immunoglobin (IgG) protein (Sigma Chemical Co., St. Louis, MO) for marking and tracking. In this study, the optimal concentration of IgG in an individual ant necessary for detection was determined to be 0.01mg/ml. In both lab and field conditions, there was a significant difference in the detection of IgG in ants fed the protein marker mixed with sugar water compared to ants only fed sugar water. Additional field studies found that an individual ant could retain detectable levels of the protein marker for 3 d and that ants feeding IgG containing bait could be significantly detected up to15 m from the original bait source. In a field at LGSP, Greenwood, SC, bait stations containing 300ml of 30% sugar-water with 0.01 mg/ml of IgG protein were placed in a grid pattern with nine stations placed at 10 m apart and were compared to nine stations in a grid pattern place at 20 m apart. This study was replicated three times. When the distance between the two bait station placements was compared, the amount of IgG detected in L. humile was significantly higher in ants foraging at stations 10 m apart compared to ants foraging at stations at 20 m apart. However, IgG could be detected in ants foraging to stations 20 m. To be cost effective for the amount of bait needed, stations needed and time for labor, 20 m was selected for a later field trial to control L. humile. The over-wintering habitat study showed that mean L. humile nest temperatures were less variable than mean ambient temperatures. From January to March, 2012, the range from lowest to highest temperature was 12.4°C in the nests and 21.7°C in the ambient environment. During this period, the lowest mean temperature recorded in the ambient environment was 8.27°C and 10.01°C in the nests. The highest mean temperature was 30.0°C in the ambient environment and 22.5°C in the nests. Even though ambient and nest temperature fluctuated, the mean foraging activity of L. humile increased from 12 February to 29 February. After 16 March, both the mean ambient temperatures and the nest temperatures continued to be over 15°C. At this temperature, L. humile began to actively forage. This result suggested the optimal bait placement date for control of L. humile was after 16 March due to temperature (ambient and nest) and ant foraging activity. A bait study was conducted in natural areas of LGSP to determine early season control of L. humile using the 20 m bait placement discovered in the earlier study. When temperatures were continuously above 15°C in 2012, three treatment areas were established. These areas included a natural control area with no bait placement, a bait control area with stations containing 200 ml of 25% sugar water, and a bait treatment area with stations filled with 180 ml of 25% sugar water mixed with 20 ml Maxforce Quantum Ant Bait (0.03% imidacloprid). In each area, 10 trees with active L. humile trails were selected to assess foraging activity. The ant trail with the greatest number of individuals on each tree was counted weekly. Liquid bait stations were placed in three rows at 20 m apart. Bait was replaced weekly for three months. The mean number of L. humile was recorded from spring to fall in 2012 and from spring to early summer in 2013. No bait was used after June 2012. Liquid ant bait decreased the L. humile population in the treatment area after one season of baiting as compared with the control areas. It was conclude that early season liquid baiting (mid-March), with a specific placement distance (20 m), was an effective method for controlling L. humile in a natural park habitat in South Carolina

Efficient Triangular Interpolation Method: Error Analysis and Applications

The interpolation errors of bivariate Lagrange polynomial and triangular interpolations are studied for the plane waves. The maximum and root-mean-square (RMS) errors on the right triangular, equilateral triangular and rectangular (bivariate Lagrange polynomial) interpolations are analyzed. It is found that the maximum and RMS errors are directly proportional to the (p+1)’th power of kh for both one-dimensional (1D) and two-dimensional (2D, bivariate) interpolations, where k is the wavenumber and h is the mesh size. The interpolation regions for the right triangular, equilateral triangular and rectangular interpolations are selected based on the regions with smallest errors. The triangular and rectangular interpolations are applied to evaluate the 2D singly periodic Green’s function (PGF). The numerical results show that the equilateral triangular interpolation is the most accurate interpolation method, while the right triangular interpolation is the most efficient interpolation method

An Efficient Multilevel Fast Multipole Algorithm to Solve Volume Integral Equation for Arbitrary Inhomogeneous Bi-Anisotropic Objects

A volume integral equation (VIE) based on the mixed-potential representation is presented to analyze the electromagnetic scattering from objects involving inhomogeneous bi-anisotropic materials. By discretizing the objects using tetrahedrons on which the commonly used Schaubert-Wilton-Glisson (SWG) basis functions are defined, the matrix equation is derived using the method of moments (MoM) combined with the Galerkin’s testing. Further, adopting an integral strategy of tetrahedron-to-tetrahedron scheme, the multilevel fast multipole algorithm (MLFMA) is proposed to accelerate the iterative solution, which is further improved by using the spherical harmonics expansion with a faster implementation and low memory requirement. The memory requirement of the radiation patterns of basis functions in the proposed MLFMA is several times less than that in the conventional MLFMA

Fault estimation for time-varying systems with Round-Robin protocol

summary:This paper is concerned with the design problem of finite-horizon $H_\infty$ fault estimator for a class of nonlinear time-varying systems with Round-Robin protocol scheduling. The faults are assumed to occur in a random way governed by a Bernoulli distributed white sequence. The communication between the sensor nodes and fault estimators is implemented via a shared network. In order to prevent the data from collisions, a Round-Robin protocol is utilized to orchestrate the transmission of sensor nodes. By means of the stochastic analysis technique and the completing squares method, a necessary and sufficient condition is established for the existence of fault estimator ensuring that the estimation error dynamics satisfies the prescribed $H_\infty$ constraint. The time-varying parameters of fault estimator are obtained by recursively solving a set of coupled backward Riccati difference equations. A simulation example is given to demonstrate the effectiveness of the proposed design scheme of the fault estimator

Interfacial Properties of Monolayer and Bilayer MoS2 Contacts with Metals: Beyond the Energy Band Calculations

Although many prototype devices based on two-dimensional (2D) MoS2 have been fabricated and wafer scale growth of 2D MoS2 has been realized, the fundamental nature of 2D MoS2-metal contacts has not been well understood yet. We provide a comprehensive ab initio study of the interfacial properties of a series of monolayer (ML) and bilayer (BL) MoS2-metal contacts (metal = Sc, Ti, Ag, Pt, Ni, and Au). A comparison between the calculated and observed Schottky barrier heights (SBHs) suggests that many-electron effects are strongly suppressed in channel 2D MoS2 due to a charge transfer. The extensively adopted energy band calculation scheme fails to reproduce the observed SBHs in 2D MoS2-Sc interface. By contrast, an ab initio quantum transport device simulation better reproduces the observed SBH in the two types of contacts and highlights the importance of a higher level theoretical approach beyond the energy band calculation in the interface study. BL MoS2-metal contacts have a reduced SBH than ML MoS2-metal contacts due to the interlayer coupling and thus have a higher electron injection efficiency.Comment: 36 pages, 13 figures, 3 table

Does P-type Ohmic Contact Exist in WSe2-metal Interfaces?

Formation of low-resistance metal contacts is the biggest challenge that masks the intrinsic exceptional electronic properties of 2D WSe2 devices. We present the first comparative study of the interfacial properties between ML/BL WSe2 and Sc, Al, Ag, Au, Pd, and Pt contacts by using ab initio energy band calculations with inclusion of the spin-orbital coupling (SOC) effects and quantum transport simulations. The interlayer coupling tends to reduce both the electron and hole Schottky barrier heights (SBHs) and alters the polarity for WSe2-Au contact, while the SOC chiefly reduces the hole SBH. In the absence of the SOC, Pd contact has the smallest hole SBH with a value no less than 0.22 eV. Dramatically, Pt contact surpasses Pd contact and becomes p-type Ohmic or quasi-Ohmic contact with inclusion of the SOC. Our study provides a theoretical foundation for the selection of favorable metal electrodes in ML/BL WSe2 devices