Unifying dark energy and dark matter with the modified Ricci model

In this paper, two modified Ricci models are considered as the candidates of unified dark matter–dark energy. In model one, the energy density is given by r_MR=3M_pl(aH²+b[(H)\dot])\rho_{\mathrm{MR}}=3M_{\mathrm{pl}}(\alpha H^{2}+\beta\dot{H}), whereas, in model two, by r_MR=3M_pl(\fraca6 R+g[(H)\ddot]H^-1)\rho_{\mathrm{MR}}=3M_{\mathrm{pl}}(\frac{\alpha}{6} R+\gamma\ddot{H}H^{-1}). We find that they can explain both dark matter and dark energy successfully. A constant equation of state of dark energy is obtained in model one, which means that it gives the same background evolution as the wCDM model, while model two can give an evolutionary equation of state of dark energy with the phantom divide line crossing in the near past.     

Tailoring A Poly(ether sulfone) Bipolar Membrane: Osmotic‐Energy Generator with High Power Density

Osmotic energy, obtained through different concentrations of salt solutions, is recognized as a form of a sustainable energy source. In the past years, membranes derived from asymmetric aromatic compounds have attracted attention because of their low cost and high performance in osmotic energy conversion. The membrane formation process, charging state, functional groups, membrane thickness, and the ion‐exchange capacity of the membrane could affect the power generation performance. Among asymmetric membranes, a bipolar membrane could largely promote the ion transport. Here, two polymers with the same poly(ether sulfone) main chain but opposite charges were synthesized to prepare bipolar membranes by a nonsolvent‐induced phase separation (NIPS) and spin‐coating (SC) method. The maximum power density of the bipolar membrane reaches about 6.2 W m^?2 under a 50‐fold salinity gradient, and this result can serve as a reference for the design of bipolar membranes for osmotic energy conversion systems.     

Uniform approximation by combinations of Bernstein polynomials

We prove a pointwise characterization result for combinations of Bernstein polynomials. The main result of this paper includes an equivalence theorem of H. Berens and G. G. Lorentz as a special case.     

布喇格条件下二步补偿像差

提出了一种二步记录的全息像差补偿方法,它用短波长(540nm以下)制作,而在长波长(红光或红外光)再现时具有较高的衍射效率和较小的像差,且能适用于任意给定的使用条件,最后给出了计算结果和理论结果.     

Imaging ion-molecule reactions: charge transfer and C-N bond formation in the C(+) + NH3 system

The velocity mapping ion imaging method is applied to the ion-molecule reactions occurring between C(+) and NH(3). The velocity space images are collected over the relative collision energy range from 1.5 to 3.3 eV, allowing both product kinetic energy distributions and angular distributions to be obtained from the data. The charge transfer process appears to be direct, dominated by long-range electron transfer that results in minimal deflection of the products. The product kinetic energy distributions are consistent with a process dominated by energy resonance. The kinetic energy distributions for C-N bond formation appear to scale with the total available energy, providing strong evidence that energy in the [CNH(3)](+) precursor to products is distributed statistically. The angular distributions for C-N bond formation show pronounced forward-backward symmetry, as expected for a complex that resembles a prolate symmetric top decaying along its symmetry axis.     

一种二元整形元件激光直写方法的实验研究

为了实现具有复杂位相结构的二元光束整形元件,提出了采用方光点的激光直写系统来逐点光刻浮雕位相结构的方法,通过双远心投影缩微光路获得5-20 μm方点,光点尺寸对应于最小位相单元,从而获得了位相结构的高质量直写.分析了高斯光点和方光点位相单元结构对二元整形元件衍射效率的影响,方形两台阶二元整形元件的+1级衍射效率达到31%,给出了实验结果.     

Peptide nucleic acid and amino acid modified peptide nucleic acid analysis by capillary zone electrophoresis

A rapid, high resolution, and low sample consumption CZE method is developed for peptide nucleic acid (PNA) analysis for the first time. 30% v/v acetonitrile in PNA sample and 20% v/v acetonitrile in 50 mM borax‐boric acid (pH 8.7) as BGE were employed after optimization. The calibration curves were linear for PNA concentration ranging from 1 to 50 μmol/L. LOD and LOQ of PNA were 0.2 and 1.0 μmol/L, respectively. Since the commercially available reagent gives rise to huge PNA peak and an apparent impurity peak, the purity of PNA was evaluated to be about 81.4% by CZE method, obviously lower than the supplier's purity value of 99.9% evaluated by RP–HPLC, and also lower than 94.8% determined with RP–HPLC by our research group. The CZE method takes only 5 min, needs only 90 nL PNA, much less than 20 min and 20 μL PNA in RP–HPLC method. Moreover, the CZE method is applicable for the analysis of glutamic acid modified and lysine modified PNAs, they show different migration time with their corresponding complementary PNAs. Our results show CZE provides a new choice for PNA and modified PNA analysis, also their purity or quality evaluation.     

Origin of Thermal and Hyperthermal CO2 from CO Oxidation on Pt Surfaces: The Role of Post‐Transition‐State Dynamics,Active Sites,and Chemisorbed CO2

The post‐transition‐state dynamics in CO oxidation on Pt surfaces are investigated using DFT‐based ab initio molecular dynamics simulations. While the initial CO₂ formed on a terrace site on Pt(111) desorbs directly, it is temporarily trapped in a chemisorption well on a Pt(332) step site. These two reaction channels thus produce CO₂ with hyperthermal and thermal velocities with drastically different angular distributions, in agreement with recent experiments (Nature, 2018 , 558, 280–283). The chemisorbed CO₂ is formed by electron transfer from the metal to the adsorbate, resulting in a bent geometry. While chemisorbed CO₂ on Pt(111) is unstable, it is stable by 0.2 eV on a Pt(332) step site. This helps explain why newly formed CO₂ produced at step sites desorbs with far lower translational energies than those formed at terraces. This work shows that steps and other defects could be potentially important in finding optimal conditions for the chemical activation and dissociation of CO₂.     

Simplified processing and characteristic investigation of DCG holographic elements

In this paper,the simplfied procedures of processing dichromated gelatin(DCG)holographic optical elements(HOE's) are presented.Both diffraction efficiency and transmis-sion of DCG grating made by the procedures have been achieved up to 97%.The diffractioncharacteristics of the DCG gratings are measured and analysed,the applications of DCG grat-ings with high quality are also discussed.     

关于Meyer-Knig-Zeller算子的点态逼近定理

本文给出了Meyer-Knig-Zeller算子的点态逼近定理,包含了M.Becker,R.J.Nessel1978年和V.Totik 1984年的结果。