Fabrication of Ge quantum rings from droplets by pulsed laser deposition

Two-dimensional Ge quantum single rings and polyrings were prepared on a Si(100) matrix by using the droplet technique in pulsed laser deposition. The complete rings with well-defined sharp inner and outer edges were formed via an elastic self-transforming process of droplets into nanorings in the presence of Ar gas. The single rings were from the separated droplets while the polyrings were from a few partially overlapped droplets. The self-transformation is likely to be driven by the strain of Ge/Si layers and the surface tension. The planar quantum rings of Ge formed by the deformation of droplets may be useful for investigating growth processes, fundamental physics phenomena, and nanoscale devices. PACS 78.67.Bf; 81.16.Mk; 07.79.-v     

Some nonexistence results for nonconstant stationary solutions to the Gray–Scott model in a bounded domain

In the present paper, we are concerned with a reaction–diffusion system well-known as the Gray–Scott model in a bounded domain and study the corresponding steady-state problem. We establish some results for the nonexistence of nonconstant positive stationary solutions.     

Use of stable isotopes as surrogates for radionuclides for security studies

During the past decade, interest has increased in qualifying and quantifying the threat posed to the public by the illegal use of radionuclides. In order to take investigations beyond the laboratory bench into more realistic scenarios, environmental and safety considerations dictate that these studies be performed on stable and benign surrogates. This paper discusses some of these studies, specifically the use of cerium dioxide for actinide ceramics and calcium and natural strontium ceramics for those based on ⁹⁰Sr.     

An on-line method for determining ATPase bioactivity and its application to human umbilical vein endothelial cell membrane

Based on the determination of inorganic phosphate (the product of ATP dephosphorylation by ATPase), a method for on-line determination of bioactivity of ATPase on cell membrane is presented, in which on-line sampling of cell membrane and separation of inorganic phosphate is employed in a flow injection system. The method has been successfully applied to the investigation of variation of ATPase from human umbilical vein endothelial cell membrane; the results show that ATPase activity decreases with elapsed time studied, which may supply important information for the pertinent studies on cell membrane enzymes bioactivity.     

Threshold control of mutual insurance with limited commitment

We study the optimal premium policy of mutual insurance when the charged premium cannot be higher than a preset rate. We provide a complete solution to the problem and use numerical simulations to illustrate how the optimal premium policy responds to changes of outside factors. The results are useful for mutual insurance firms to design premium policies and can be used to test the behavior of these firms in empirical studies.     

Decomposition and removability properties of John domains

In this paper we characterize John domains in terms of John domain decomposition property. In addition, we also show that a domain D in ℔ ⁿ is a John domain if and only if D\P is a John domain, where P is a subset of D containing finitely many points of D. The best possibility and an application of the second result are also discussed.     

A Raman system for multi-gas-species analysis in power transformer

We have built a complete Raman detection system for multi-trace-gas diagnosis, which is suitable for analyzing the dissolved gases in electric power system. In the system, a high-sensitivity CCD device connected to a spectrometer is used as the detection unit of the Raman system. A near-confocal cavity is used for improving the detection sensitivity of the system. In the effective spectral range of about 570–710 nm, Raman spectra of eight typical gases are achieved by using this Raman system. The detection limits for different gases have been obtained: 126 ppm for CO₂, 21 ppm for CH₄, 63 ppm for C₂H₄, 42 ppm for C₂H₂, 96.6 ppm for H₂. The detectability of the system satisfies the requirements of gas diagnosis in power transformer.     

Closed-form solutions for a mode III radial matrix crack penetrating a circular inhomogeneity

In this research we address in detail a mode III radial matrix crack penetrating a circular inhomogeneity. One tip of the radial crack lies in the matrix, while the other tip of the radial crack lies in the circular inhomogeneity. In addition the two tips of the crack are mutually image points (or inverse points) with respect to the circular inhomogeneity-matrix interface. First we conformally map the crack onto a unit circle C_a in the new ζ-plane. Meanwhile the inhomogeneity-matrix interface is mapped onto C_b, a part of another circle in the ζ-plane. In addition C_a and C_b intersect at a vertex angle π/2. By using the method of image in the ζ-plane, closed-form solutions in terms of elementary functions are derived for three loading cases: (1) remote uniform antiplane shearing; (2) a screw dislocation located in the unbounded matrix; and (3) a radial Zener–Stroh crack.     

Enrichment of the spindle fiber attachments from mouse liver cell nuclei

Spindle fiber attachments (SFAs) were enriched in a fraction of nuclei isolated from mouse livers. The enrichment method combines sonication, treatment with 2 mol/L NaCl and high speed centrifugation. SFA was enriched 27-fold on the average (n = 4) when measured by radioimmunoassay. The basic method offers opportunities for further increases of yield and for the enrichment of SFA of other vertebrates.