On the imaginary parts of chromatic roots

While much attention has been directed to the maximum modulus and maximum real part of chromatic roots of graphs of order $n$ (ie, with $n$ vertices), relatively little is known about the maximum imaginary part of such graphs. We prove that the maximum imaginary part can grow linearly in the order of the graph. We also show that for any fixed $\text{◂+▸}p\in \left(0,1\right)$, almost every random graph $G$ in the Erdös-Rényi model has a nonreal root.     

Synthesis,formation mechanism and electric property of hollow InP nanospheres

The present work reports on novel four-layer thermally driven piezoresistive cantilevers implemented in one- and two-dimensional arrays for parallel proximity scanning. There, the heater (metallic meander), the piezoresistive deflection sensor, and the metal actuation film with significantly higher thermal expansion coefficient make up separate layers. Actuation efficiency and cross-talk of the novel cantilever design are studied and compared with two recent designs: thin metallic film and ion-implanted heater. The novel actuator, integrated on a 240 μm long and 3 μm thick silicon cantilever and supplied by V _dc=1 V enables deflections up to 5 μm of the AFM-tip with an actuation efficiency of about 170 nm/mW and suppressed cross-talk between actuator and sensor.     

Controlled growth of uniform nanoflakes-built pyrite FeS<Subscript>2</Subscript> microspheres and their electrochemical properties

Nanoflakes-built pyrite FeS₂ microspheres were synthesized through a simple solvothermal process in mixed solvents of N, N-dimethytformamide and ethylene glycol without using any surfactant. Both the composition of the solvents and urea were key factors for the formation of the uniform products. It was found that the flake-like intermediate products transformed into FeS₂ nanoflakes in situ in the early stage and Ostwald ripening growth mechanism would contribute to the uniformity of the final products. Electrochemical studies revealed that the nanoflakes-built pyrite FeS₂ microspheres exhibited large lithium storage capacities. This method can be easily controlled and is expected to be extendable to the fabrication of other metal chalcogenides with controlled shape and structure.     

Morphology of a silver/polyacrylonitrile nanocomposite

Silver/polyacrylonitrile (Ag/PAN) nanocomposites are synthesized at the stage of simultaneous acrylonitrile polymerization and the reduction of silver ions from a mixture of silver nitrate AgNO₃, acrylonitrile, and a photoinitiator. The synthesized films are transparent in the visible region and are characterized by a uniform dispersion of silver nanoparticles in a PAN matrix without any macroscopic agglomeration. The effects of the metal salt and photoinitiator concentrations on the size and density of metal nanoparticles in a composite are revealed.     

An optimum design and fabrication of lens on luminous uniformity and light extraction of high-power light-emitting diode

The effect of lens inner structure on radiation pattern and light extraction efficiency of light-emitting diode (LED) and the application to artificial light in compact greenhouse is demonstrated. A commercial software package of Trace Pro and one-factor at-a-time (OFAT) method are used to simulate the lens with different inner structure. The optimum parameters of lens inner structure design for the maximum light extraction efficiency and the best uniform luminous are described by the corner radius of curvature, lens width, and lens height, respectively. For a real single LED module, base on the optimum parameters of lens inner structure, the corresponding best luminous uniformity is 62% and corresponding output extraction is 14.11 lm. The maximum uniformity of illumination for LED matrix assembled by LED modules with optimum lens is 88% and corresponding light extraction 1141 lm. In comparison with a commercial artificial light of LED matrix used in agriculture, the high-power LED module with proposed lens inner structure exhibit good improvement in uniformity of illumination and light extraction. This study may provide a practical guideline for design and fabrication of a high-performance lens used in various compact agricultural applications.     

Tomographic implementation of astronomical speckle imaging from bispectra

A bispectral method for astronomical speckle imaging utilizes an average speckle bispectrum of an object to derive its Fourier phase. There has been, however, a problem in conventional bispectral algorithm owing to difficulty in processing bispectral data in a four-dimensional (4D) space. In this paper, we propose an implementation to overcome this problem, where a one-dimensional (1D) object projection is reconstructed from a two-dimensional (2D) average bispectrum of speckle projections, and object projections so obtained at various angles are then tomographically combined into a 2D object image. In this tomographic approach, processes are separable into those for individual projection angles, implying that bispectral data required to be stored at a time are from 4D to 2D and computation time can be substantially reduced by parallelizing angle-by-angle processes. We have performed experiments using simulated and observed data, and have demonstrated the feasibility of the present approach with an achievable accuracy comparable to that of a conventional approach.     

Higher Spin Dirac Operators Between Spaces of Simplicial Monogenics in Two Vector Variables

The higher spin Dirac operator \(\mathcal{Q}_{k,l}\) acting on functions taking values in an irreducible representation space for \(\mathfrak{so}(m)\) with highest weight \((k+\frac{1}{2},l+\frac{1}{2},\frac{1}{2},\ldots,\frac{1}{2})\), with k, l?∈?\(\mathbb{N}\) and \(k\geqslant l\), is constructed. The structure of the kernel space containing homogeneous polynomial solutions is then also studied.     

How can nanobiotechnology oversight advance science and industry: examples from environmental,health, and safety studies of nanoparticles (nano-EHS)

Nanotechnology has great potential to transform science and industry in the fields of energy, material, environment, and medicine. At the same time, more concerns are being raised about the occupational health and safety of nanomaterials in the workplace and the implications of nanotechnology on the environment and living systems. Studies on environmental, health, and safety (EHS) issues of nanomaterials have a strong influence on public acceptance of nanotechnology and, eventually, affect its sustainability. Oversight and regulation by government agencies and non-governmental organizations (NGOs) play significant roles in ensuring responsible and environmentally friendly development of nanotechnology. The EHS studies of nanomaterials can provide data and information to help the development of regulations and guidelines. We present research results on three aspects of EHS studies: physico-chemical characterization and measurement of nanomaterials; emission, exposure, and toxicity of nanomaterials; and control and abatement of nanomaterial releases using filtration technology. Measurement of nanoparticle agglomerates using a newly developed instrument, the Universal NanoParticle Analyzer (UNPA), is discussed. Exposure measurement results for silicon nanoparticles in a pilot scale production plant are presented, as well as exposure measurement and toxicity study of carbon nanotubes (CNTs). Filtration studies of nanoparticle agglomerates are also presented as an example of emission control methods.