Multiplicative maps preserving the higher rank numerical ranges and radii

Let M_n be the semigroup of n×n complex matrices under the usual multiplication, and let S be different subgroups or semigroups in M_n including the (special) unitary group, (special) general linear group, the semigroups of matrices with bounded ranks. Suppose Λ_k(A) is the rank-k numerical range and r_k(A) is the rank-k numerical radius of A∈M_n. Multiplicative maps ?:S→M_n satisfying r_k(?(A))=r_k(A) are characterized. From these results, one can deduce the structure of multiplicative preservers of Λ_k(A).     

Domain wall nucleation and propagation in spin-transfer torque switching with thermal effects

We conduct micro-magnetic simulations to study spin-transfer torque induced magnetization switching in perpendicular magnetic tunneling junctions. The effects of current densities and temperatures on the switching processes are studied in details. We then proposed an approach to compute the deterministic switching time by taking thermal-effect into account. The switching time is less temperature-dependent under higher current density; however, as the current density decreases, the effect of temperature on the switching time becomes more and more significant. The switching process with micro-magnetic simulations is shown to be via domain wall nucleation and propagation. The phenomena are consistent with the recent experimental found-out. We further propose a method to compute the switching time based on domain wall nucleation and propagation theory, and compare the switching time with those from macro-spin approximation. It is found the switching times from the micro-magnetic simulations are much shorter than that from the macro-spin approximations. Macro-spin approximation over-estimates the switching times due to its coherent rotation assumptions.     

Maps preserving the nilpotency of products of operators

Let B(X) be the algebra of all bounded linear operators on the Banach space X, and let N(X) be the set of nilpotent operators in B(X). Suppose ?:B(X)→B(X) is a surjective map such that A,B∈B(X) satisfy AB∈N(X) if and only if ?(A)?(B)∈N(X). If X is infinite dimensional, then there exists a map f:B(X)→C?{0} such that one of the following holds:

(a)

There is a bijective bounded linear or conjugate-linear operator S:X→X such that ? has the form A?S[f(A)A]S^-1.

(b)

The space X is reflexive, and there exists a bijective bounded linear or conjugate-linear operator S : X′ → X such that ? has the form A ? S[f(A)A′]S⁻¹.

If X has dimension n with 3 ? n < ∞, and B(X) is identified with the algebra M_n of n × n complex matrices, then there exist a map f:M_n→C?{0}, a field automorphism ξ:C→C, and an invertible S ∈ M_n such that ? has one of the following forms:

     

Separation of polar mushroom toxins by mixed-mode hydrophilic and ionic interaction liquid chromatography-electrospray ionization-mass spectrometry

Reversed-phase liquid chromatography (RPLC) is commonly used to analyze nonvolatile contaminants and naturally occurring toxins in foods. However, polar compounds, such as hydrophilic polypeptides and quaternary ammonium salts, are often not satisfactorily separated by RPLC and present a challenge for analytical scientists. In this study, hydrophilic interaction liquid chromatography (HILIC), on an amide-based stationary phase in combination with electrospray ionization (ESI) tandem mass spectrometry (MS-MS), is successfully employed to simultaneously separate polar mushroom toxins, including amanitins and phallotoxins, which are cyclic oligopeptides and muscarine, a quaternary ammonium compound, in mushrooms. The sensitivity of different ionization modes is studied, and the positive ionization mode is found to provide a more sensitive and effective tool for the unambiguous identification of the concerned polar toxins because of their characteristic fragmentation patterns. The properties of the mobile phase are also found to have significant impacts on the separation. At a high acetonitrile (ACN) concentration, hydrophilic interaction dominates, and all analytes under study demonstrate a much higher affinity with the stationary phase. The addition of methanol (MeOH) as a modifier could further enhance the HILIC separation for amanitins, phallotoxins, and muscarine. Valley-to-valley separation is achieved upon the optimatizatiqn of the mobile phase (comprising of ACN, MeOH, and ammonium formate buffer at pH approximately 3.5) and the solvent gradient. HILIC coupled with ESI-MS-MS is demonstrated to be a novel technique for the simultaneous separation and confirmatory analysis of the concerned polar toxins by providing an environment of solubility and retention that could not be achieved through the use of RPLC.     

A new route for fast synthesis of copper nanowires and application on flexible transparent conductive films

Journal of Nanoparticle Research - The magnetically assembled chain-like structures of magnetic nanoparticles attract great attention due to their unique properties. In this paper, we studied the...     

以优化方法求解布料无摩擦接触变形问题

利用作者所提出的布料质点模型,用罚函数法解除布料和其它物体之间的接触约束,把接触约束条件下的极值问题转化为无约束极值问题,用F-R共轭梯度法求解,并用三次插值方法进行一维搜索.计算了有缝摺和裁剪开口的布料与球形物体的接触变形问题,得到的结果符合人们的日常实际观察.     

Normally transparent smart window with haze enhancement via inhomogeneous alignment surface

Smart windows which switch between transparent and scattering states can be used not only as privacy window in buildings and cars, but also as information displays, and motorcycle helmet visors. Here, we have proposed a reverse mode polymer-stabilised liquid crystals (PSLCs) smart window based on inhomogeneous alignment surface, which greatly enhances the haze by 42% when compared to device without inhomogeneity treatment. A 100-cm² window that switches between the power-off clear state (~4% haze) and a power-on scattering state (64% haze at 15 V) in less than 3.5 ms is demonstrated. Since no high-temperature treatment (< 80°C) is involved in device fabrication, further development on plastic films is feasible.     

Development of a double-sided micro lens array for micro laser projector application

This paper introduces the development of a double-sided micro lens array (DSMLA) for application in micro laser projectors. For commercial mass production, it is necessary to investigate the concurrent engineering of optical design, mold fabrication, and plastic injection molding at once. This experiment based the design of the micro lens array on the scalar diffraction theory. The proposed DSMLA can simultaneously shape red, green, and blue laser beams into a uniform projection pattern. An ultra precision diamond turning machine using a slow tool servo method fabricated the mold. The study considered optical design constraints from the feedback of mold fabrication and plastic injection molding, measuring and comparing fabricated samples with calculated results. Experimental results show that the fabricated DSMLAs achieve the desired function and application feasibility for micro laser projectors.     

Development of an electrochemical membrane-based nanobiosensor for ultrasensitive detection of dengue virus

A sensitive membrane-based electrochemical nanobiosensor is developed for the detection of dengue type 2 virus (DENV-2) using nanoporous alumina-modified platinum electrode. Its sensing mechanism relies on the monitoring of electrode's Faradaic current response toward redox probe, ferrocenemethanol, which is sensitive toward the formation of immune complexes within the alumina nanochannels. Anti-DENV-2 monoclonal antibody (clone 3H5, isotype IgG) is used as the biorecognition element in this work. The stepwise additions of antibody, bovine serum albumin (BSA) and DENV-2 are characterized by differential pulse voltammetry (DPV). A low detection limit of 1 pfu mL⁻¹ with linear range from 1 to 10³ pfu mL⁻¹ (R² = 0.98) can be achieved by the nanobiosensor. The nanobiosensor is selective toward DENV-2 with insignificant cross reaction with non-specific viruses, Chikungunya virus, West Nile virus and dengue type 3 virus (DENV-3). Relative standard deviation (RSD) for triplicate analysis of 5.9% indicates an acceptable level of reproducibility. The first direct quantitation of DENV-2 concentration in whole mosquito vector is demonstrated using this electrochemical nanobiosensor.