Classical mean-variance model revisited: pseudo efficiency

Investigating the inverse problem of the classical Markowitz mean-variance formulation: Given a mean-variance pair, find initial investment levels and their corresponding portfolio policies such that the given mean-variance pair can be realized, we reveal that any mean-variance pair inside the reachable region can be achieved by multiple portfolio policies associated with different initial investment levels. Therefore, in the mean-variance world for a market of all risky assets, the common belief of monotonicity: ‘The larger you invest, the larger expected future wealth you can expect for a given risk (variance) level’ does not hold, which stimulates us to extend the classical two-objective mean-variance framework to an expanded three-objective framework: to maximize the mean and minimize the variance of the final wealth as well as to minimize the initial investment level. As a result, we eliminate from the policy candidate list the set of pseudo efficient policies that are efficient in the original mean-variance space, but inefficient in this newly introduced three-dimensional objective space.     

Observation of a red-blue detuning asymmetry in matter-wave superradiance

We report the first experimental observation of strong suppression of matter-wave superradiance using blue-detuned pump light and demonstrate a pump-laser detuning asymmetry in the collective atomic recoil motion. In contrast to all previous theoretical frameworks, which predict that the process should be symmetric with respect to the sign of the detuning of the pump laser from the one-photon resonance, we find that for condensates the symmetry is broken. With high condensate densities and red-detuned pump light the distinctive multiorder, matter-wave scattering pattern is clearly visible, whereas with blue-detuned pump light superradiance is strongly suppressed. However, in the limit of a dilute atomic gas symmetry is restored.     

Faithful Entanglement Sharing for Quantum Communication Against Collective Noise

We present an economical setup for faithful entanglement sharing against collective noise. It is composed of polarizing beam splitters, half wave plates, polarization independent wavelength division multiplexers, and frequency shifters. An arbitrary qubit error on the polarization state of each photon in a multi-photon system caused by the noisy channel can be rejected, without resorting to additional qubits, fast polarization modulators, and nondestructive quantum nondemolition detectors. Its success probability is in principle 100%, which is independent of the noise parameters, and it can be applied directly in any one-way quantum communication protocol based on entanglement.     

Unidirectional synchronization of Hodgkin–Huxley neurons exposed to ELF electric field

In this paper, a hybrid control strategy, H_∞ variable universe adaptive fuzzy control, is derived and applied to synchronize two Hodgkin–Huxley (HH) neurons exposed to external electric field. Firstly, the modified model of HH neuron exposed to extremely low frequency (ELF) external electric field is established and its periodic and chaotic dynamics in response to sinusoidal electric field stimulation are described. And then the statement of the problem for unidirectional synchronization of two HH neurons is given. Finally H_∞ variable universe adaptive fuzzy control is designed to synchronize the HH systems and the simulation results demonstrate the effectiveness of the proposed control method.     

Near-infrared downconversion through energy transfer from \mathrm{VO}_{4}^{3-} group to Yb3+ in Yb3+ doped YP0.9V0.1O4

Through the study of photoluminescence spectra, fluorescence decay curves, concentration-dependent luminescence and low temperature luminescence, the energy transfer from isolated $\mathrm{VO}_{4}^{3-}$ group to Yb³⁺ is investigated in Yb³⁺ doped YP_0.9V_0.1O₄. The experimental results show that the energy transfer from $\mathrm{VO}_{4}^{3-}$ group to Yb³⁺ is very efficient. Cooperative energy transfer, through which one high-energy photon absorbed by $\mathrm{VO}_{4}^{3-}$ group is converted to two near-infrared photons emitted by Yb³⁺ ions, is proposed to be the energy transfer process. This efficient ultra-violet to near-infrared downconversion could have potential application in improving the efficiency of silicon-based solar cell.     

山茱萸的大孢子发生和雌配子体发育

本文对山茱萸(Cornus officinalis Sieb.et Zucc.)的大孢子发生和雌配子体发育进行了研究,并用组织化学方法对胚珠组织中的RNA、DNA、蛋白质和不溶性多糖进行了测定观察.山茱萸的胚珠为单珠被、薄珠心,并在发育过程中形成结构特殊的珠被绒毡层、承珠盘和珠孔塞.孢原细胞直接起大孢子母细胞作用.合点端大孢子具功能.胚囊发育属寥型.在开花前2个月时,成熟胚囊中的2个极核融合次生核,3个反足细胞退化,形成由一个3-细胞卵器和一个具次生核的中央细胞构成的4-细胞雌配子体.某些助细胞中的核位于近合点端,珠孔端为大液泡所占据,次生核通常位于胚囊的合点端.对珠被细胞的RNA、DNA、蛋白质和不溶性多糖的染色均呈较强的正反应.在成熟后期的珠被各层细胞中,除多糖颗粒外,对其他几种物质的检测结果均表现出由外向内形成一个较明显的浓度梯度,即珠被绒毡层着色最深.在成熟的雌配子体中,以卵细胞对Brachet反应最强,其次是中央细胞.卵细胞含大量淀粉粒,助细胞和中央细胞含淀粉粒少,且颗粒比卵细胞中的小.卵细胞和中央细胞呈Feulgen负反应.     

A density functional theory study on boundary of “superreduced” transition metal carbonyl anions [M(CO)n](M=Cr, n=5, 4, 3, z=2, 4, 6; M=Mn, n=5, 4, 3, z=1, 3, 5; M=Fe, n=4, 3, 2, z=2, 4, 6; M=Co, n=4, 3, 2, z=1, 3, 5)

A nonlocal density functional theory (DFT) method has been applied to the calculations on optimized geometry, Mulliken atomic net charges and interatomic Mulliken bond orders as well as total bonding energies (E) in the binary transition metal carbonyl anions with different reduced states [M(CO)_n]^z− (M=Cr, n=5, 4, 3, z=2, 4, 6; M=Mn, n=5, 4, 3, z=1, 3, 5; M=Fe, n=4, 3, 2, z=2, 4, 6; M=Co, n=4, 3, 2, z=1, 3, 5). For comparison of relative stability, a relative stabilization energy D is defined as D=E([M(CO)_n]^z−)−nE(CO). The calculated C–O distances are lengthened monotonously with the increase of the anionic charge, but the M–C distances are significantly lengthened only in the higher reduced states. The relative stabilization energy calculated is a considerable negative value in the lower reduced states, but a larger positive value in the higher reduced states. The DFT calculations show that with the increase of the anionic charge, the Mulliken net charges on the M, C, and O atoms all increase, however, an excess of the anionic charge is mainly located at the central metal atom. The calculated C–O Mulliken bond orders decrease consistently with the increase of the anionic charge, but the M–C bond orders exhibit an irregular behavior. However, the total bond orders calculated clearly explain the higher reduced states to be considerably unstable. From analysis of the calculated results, it is deduced that the stability of the binary transition metal carbonyl anions [M(CO)_n]^z− studied are associated with the coordination number n and the anionic charge z, further, it is possible for the anions studied to be stable if n≥z, conversely, it is impossible when n<z.     

Highly sensitive hybridization assay using the electrochemiluminescence of an ITO electrode, CdTe quantum dots functionalized with hierarchical nanoporous PtFe nanoparticles, and magnetic graphene nanosheets

We report on a disposable microdevice suitable for sandwich-type electrochemiluminescence (ECL) detection of DNA. The method is making use of CdTe quantum dots functionalized with hierarchical nanoporous PtFe (CdTe@PtFe) nanoparticles and with magnetic graphene nanosheets. The latter were selected as carriers for the capture DNA due to their excellent biomagnetic separation capability and electrical properties. The CdTe@PtFe nanoparticles were used to label the signal DNA which resulted in distinctly enhanced ECL owing to the large specific surface area and good electrical conductivity of the PtFe alloy. A DNA sensor was constructed on a disk-shaped indium tin oxide electrode that was fabricated via etching. Under optimal conditions, the biosensor responds linearly to DNA in the 0.02 fM to 5000 fM concentration range, with a detection limit as low as 15 aM. The electrode is regenerable. The method displays excellent specificity, extremely good sensitivity, and is highly reproducible.

Interface Engineering in Two‐Dimensional Heterostructures: Towards an Advanced Catalyst for Ullmann Couplings

The design of advanced catalysts for organic reactions is of profound significance. During such processes, electrophilicity and nucleophilicity play vital roles in the activation of chemical bonds and ultimately speed up organic reactions. Herein, we demonstrate a new way to regulate the electro‐ and nucleophilicity of catalysts for organic transformations. Interface engineering in two‐dimensional heteronanostructures triggered electron transfer across the interface. The catalyst was thus rendered more electropositive, which led to superior performance in Ullmann reactions. In the presence of the engineered 2D Cu₂S/MoS₂ heteronanostructure, the coupling of iodobenzene and para‐chlorophenol gave the desired product in 92 % yield under mild conditions (100 °C). Furthermore, the catalyst exhibited excellent stability as well as high recyclability with a yield of 89 % after five cycles. We propose that interface engineering could be widely employed for the development of new catalysts for organic reactions.