The ecological peculiarities of the testate amoebae population in the Middle Ob flood plain

The biodiversity and distribution of testate amoebae in the Middle Ob flood plain soils have been studied. The biodiversity of Testacea in the soils consists of 83 species and varieties from 12 families. The population of Testacea in flood plain habitats is rich in water forms, especially in the flood plain part of the catena, because of annual floods. The study showed that the density of Testacea in the forest plots is approximately 10 times higher than in the meadow ones. The species diversity of Testacea in the meadows of the flood plain includes 40 species and varieties. It was found that there is an enrichment of the fauna of Testacea in the flood plain meadows with water forms and a decrease in the population of Testacea in the soil according to the depth. The decrease in the diversity and number down the soil profile is related to the decrease in the amount of the oxygen available and general induration of soil. On the whole, the population composition of Testacea in the soils of the pine forest consists of typical representatives of humus substrates with low values of pH, small stock of humus and mineral nutrition. The soils of mature pine forests are rich in Testacea; they have a similar complex of morphological types, mainly because of the moss cover and forest litter thickness.     

Miyaura Borylation and One‐Pot Two‐Step Homocoupling of Aryl Chlorides and Bromides under Solvent‐Free Conditions

Solvent‐free protocols for Miyaura borylation and the one‐pot, two‐step homocoupling of aryl halides are reported for the first time. Bis(dibenzylideneacetone)palladium(0) [Pd(dba)₂] is an optimal source of palladium for Miyaura borylation, while for one‐pot two‐step homocoupling palladium(II) acetate [Pd(OAc)₂] gives highest yields. Aryl bromides are coupled most efficiently using the DPEphos ligand. Chlorides are coupled using XPhos. The developed protocols are robust, versatile and easily reproducible on a large scale.

     

Production and Sensitivity Evaluation of Nanocrystalline RDX‐based Explosive Compositions

The initiation sensitivity of cyclotrimethylenetrinitramine (RDX) was investigated as a function of crystal size. For this study, RDX powders with mean crystal sizes of ca. 200 and 500 nm were prepared by rapid expansion of supercritical solutions (RESS) with carbon dioxide as the solvent. Initiation sensitivity testing to impact, sustained shock, and electrostatic discharge stimuli was performed on uncoated as well as wax‐coated specimens. The test data revealed that in a direct comparison to coarser grades the nanocrystalline RDX‐based samples were substantially less sensitive to shock and impact stimuli. Furthermore, the 500 nm RDX‐based specimens exhibited the lowest sensitivity values, an indication that minima in shock and impact sensitivities with respect to crystal size exist.     

Range-only measurements based target following for wheeled mobile robots

We consider the problem of navigation and guidance of a wheeled mobile robot towards a maneuvering target based on the measurements concerning only the distance from the robot to the target. We propose a sliding mode controller that drives the robot to the predefined distance from the target and makes the robot follow the target at this distance. Mathematically rigorous proof of convergence and stability of the proposed guidance law is presented. Simulation results confirm the applicability and performance of the proposed guidance approach.     

Equiangular navigation and guidance of a wheeled mobile robot based on range-only measurements

We consider the problems of a wheeled mobile robot navigation and guidance towards an unknown stationary or maneuvering target using range-only measurements. We propose and study several methods for navigation and guidance termed Equiangular Navigation Guidance (ENG) laws. We give mathematically rigorous analysis of the proposed guidance laws. The performance is confirmed with computer simulations and experiments with ActivMedia Pioneer 3-DX wheeled robots.     

Plasmonic bandgap in random media

We present a dispersion theory of the surface plasmon polaritons (SPP) in random metal-dielectric nanocomposite (MDN) consisting of bulk metal embedded with dielectric inclusions. We demonstrate that embedding of dielectric nanoparticles in metal results in the formation of the plasmonic bandgap due to strong coupling of the SPP at the metal-vacuum interface and surface plasmons localized at the surface of nanoinclusions. Our results show that MDN can replace metals in various plasmonic devices, which properties can be tuned in a wide spectral range. Being compatible with waveguides and other photonic structures, MDN offers high flexibility in the plasmonic system design.     

n-Type Doping of Vapor–Liquid–Solid Grown GaAs Nanowires

In this letter, n-type doping of GaAs nanowires grown by metal–organic vapor phase epitaxy in the vapor–liquid–solid growth mode on (111)B GaAs substrates is reported. A low growth temperature of 400°C is adjusted in order to exclude shell growth. The impact of doping precursors on the morphology of GaAs nanowires was investigated. Tetraethyl tin as doping precursor enables heavily n-type doped GaAs nanowires in a relatively small process window while no doping effect could be found for ditertiarybutylsilane. Electrical measurements carried out on single nanowires reveal an axially non-uniform doping profile. Within a number of wires from the same run, the donor concentrations N _D of GaAs nanowires are found to vary from 7 × 10¹⁷ cm^-3 to 2 × 10¹⁸ cm^-3. The n-type conductivity is proven by the transfer characteristics of fabricated nanowire metal–insulator-semiconductor field-effect transistor devices.     

Mesh deformation-based multi-tissue mesh generation for brain images

Multi-tissue meshing is necessary for the realistic building of a biomechanical model of the brain, which has been widely used in brain surgery simulation, brain shift, and non-rigid registration. A two step multi-tissue mesher is developed. First, a coarse multi-tissue mesh is generated by redistributing labels of a body-centered cubic (BCC) mesh. Second, all the surfaces of the submeshes are deformed to their corresponding tissue boundaries. To deform the mesh, two strategies are developed. One is based on a point-based registration (PBR) and the other is based on a robust point matching (RPM). The PBR method explicitly calculates the correspondence, which takes both smoothing and quality into account, then resolves the displacement vector by minimizing an energy function. Unlike PBR method, RPM does not require the correspondence between the source points and the target points to be known in advance. To simultaneously resolve the displacement vector and the correspondence, the Expectation and Maximization optimization is employed to alternately estimate the correspondence and the displacement vector. To effectively cope with outliers, least trimmed square, a robust regression technique, is employed to correct the regression bias induced by outliers. Both methods are effective in deforming the multi-tissue mesh. However, the PBR method favors quality and smoothing, and the RPM method favors fidelity. The resulting mesh is characterized by its flexible control of four mesh properties: (1) tissue-dependent resolution, (2) fidelity to tissue boundaries, (3) smoothness of mesh surfaces, and (4) element quality. Each mesh property can be controlled on a tissue level. Our experiments conducted on synthetic data, clinic MRI, visible human data, and brain atlas effectively demonstrate these features of this multi-tissue mesher.     

Orientated crystallization in drawn thermoplastic polyimide modified by carbon nanofibers

The solid state crystallization in drawn thermoplastic polyimide films is studied as a function of draw ratio (DR) under the effect of vapor grown carbon fiber nanoinclusions. The nucleating effect of the nanoinclusions coupled with the orientation effect of drawing generates a unique orientated layered lamellar structure, characteristic of smectic‐like mesophase. The degree of draw induced orientated crystallization increases with the content of nanoinclusions and with the DR, and is reflected in the mechanical behavior of the film. Generally, the Young's modulus and the yield point of the drawn crystalline films in the drawing direction are significantly higher compared with the noncrystalline counterparts. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers