多原子分子受激光激励后振动分布的模型计算

以SF_6分子为例, 进行了多原子分予受脉冲红外激光激励之后, 其瞬态振动布居的模型计算。本模型可从实验测得的红外荧光或吸收光潜, 反演出与这些光谱相应的振动分布。反之亦然。与同类模型相比, 本模型的计算精度高, 可精确地生成振动跃迁几率矩阵, 且可计算受激光激励后分子在任一时刻的振动分布。用此模型, 首次获得SF_6分子低温条件下(20 K)的可转动分辨的吸收光谱和荧光光谱。     

Vapor-phase synthesis of isoprene from formaldehyde and isobutylene over CuSO4?MOx/SiO2 catalysts

Vapor-phase synthesis of isoprene from formaldehyde and isobutylene over CuSO₄–MO_x/SiO₂ catalysts has been studied. The results show that CuSO₄–MO_x/SiO₂ catalysts exhibit a good catalytic activity; especially when the metal oxides have appropriate basicity, is isoprene yield greatly enhanced. The results of product analysis indicate that there are side-reactions during isoprene production, which are isoprene hydrogenation, polymerization of isobutylene, copolymerization of isobutylene and isoprene, and reaction of C₅ aldehyde and ketone formed during isoprene production. In addition, catalytic behavior of the catalysts and probable mechanism of side-reactions are discussed.

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Synthesis and structure of a novel MoFe4S4 cubane-like cluster (Me3PhCH2N)2 [MoFe4S4 (SC6H11)7]

A novel (Me₃PhCH₂N)₂[MoFe₄S₄(SC₆H₁₁)₇] cubane-like cluster was obtained from a reaction system including (NH₄)₂MoS₄, FeCl₂ and NaSC₆H₁₁ in methanol, and characterized by X-ray crystallography. The title compound crystallizes in triclinic space group witha = 1.523 1(3), b =1.610 5(3),c = 1.838 3(4) nm, α = 77.18 (3)°, β = 75.17(3)°, γ = 64.60(3)°, and Z = 2. Also included in this paper are the discussions on the variation of the reaction products obtained from the participation of cyclohexylthiolate and on the changes of the structural features of the products. Project supported by the National Natural Science Foundation of China and the Climbing Program—State Key Project for Fundamental Research in China, and Hong Kong Research Grants Council (Earmarked Grant No. CUHK. 311/94p).     

On <Emphasis Type="Italic">k</Emphasis>-pairable graphs from trees

The concept of the k-pairable graphs was introduced by Zhibo Chen (On k-pairable graphs, Discrete Mathematics 287 (2004), 11–15) as an extension of hypercubes and graphs with an antipodal isomorphism. In the same paper, Chen also introduced a new graph parameter p(G), called the pair length of a graph G, as the maximum k such that G is k-pairable and p(G) = 0 if G is not k-pairable for any positive integer k. In this paper, we answer the two open questions raised by Chen in the case that the graphs involved are restricted to be trees. That is, we characterize the trees G with p(G) = 1 and prove that p(G □ H) = p(G) + p(H) when both G and H are trees.     

Electronic structures of GaAs/AlGaAs concentric double rings in applied electric and magnetic field

The electronic structures of GaAs/Al_0.35Ga_0.65As concentric double rings are calculated based on the effective mass envelope function theory, with and without the applied electric and magnetic field along the growth direction. The Hamiltonian matrix elements are determined through the Fourier transform method. As the heterostructure evolves from a single ring to the concentric double rings, our simulation is performed on the bound state energies of the electron and the hole. The results show that the energy levels undulate with the evolution of the ring. The applied magnetic field increases the ground state energies both of the electron and of the hole, as well as the transition energy between the first conduction subband and valence subband. However, the electric field decreases the electronic energies linearly.     

Retracts of box products with odd‐angulated factors

Let G be a connected graph with odd girth 2κ+1. Then G is a (2κ+1)‐angulated graph if every two vertices of G are connected by a path such that each edge of the path is in some (2κ+1)‐cycle. We prove that if G is (2κ+1)‐angulated, and H is connected with odd girth at least 2κ+3, then any retract of the box (or Cartesian) product G□ H is S□T where S is a retract of G and T is a connected subgraph of H. A graph G is strongly (2κ+1)‐angulated if any two vertices of G are connected by a sequence of (2κ+1)‐cycles with consecutive cycles sharing at least one edge. We prove that if G is strongly (2κ+1)‐angulated, and H is connected with odd girth at least 2κ+1, then any retract of G□ H is S□T where S is a retract of G and T is a connected subgraph of H or |V(S)|=1 and T is a retract of H. These two results improve theorems on weakly and strongly triangulated graphs by Nowakowski and Rival [Disc Math 70 ( 13 ), 169–184]. As a corollary, we get that the core of the box product of two strongly (2κ+1)‐angulated cores must be either one of the factors or the box product itself. Furthermore, if G is a strongly (2κ+1)‐angulated core, then either Gⁿ is a core for all positive integers n, or the core of Gⁿ is G for all positive integers n. In the latter case, G is homomorphically equivalent to a normal Cayley graph [Larose, Laviolette, Tardiff, European J Combin 19 ( 12 ), 867–881]. In particular, let G be a strongly (2κ+1)‐angulated core such that either G is not vertex‐transitive, or G is vertex‐transitive and any two maximum independent sets have non‐empty intersection. Then Gⁿ is a core for any positive integer n. On the other hand, let G_i be a (2κ_i+1)‐angulated core for 1 ≤ i≤ n where κ₁ < κ₂ < … < κ_n. If G_i has a vertex that is fixed under any automorphism for 1 ≤ i ≤ n‐1, or G_i is vertex‐transitive such that any two maximum independent sets have non‐empty intersection for 1 ≤ i ≤ n‐1, then □_i=1ⁿ G_i is a core. We then apply the results to construct cores that are box products with Mycielski construction factors or with odd graph factors. We also show that K(r,2r+1) □ C_2l+1 is a core for any integers l ≥ r ≥ 2. It is open whether K(r,2r+1) □ C_2l+1 is a core for r > l ≥ 2. © 2006 Wiley Periodicals, Inc. J Graph Theory     

Odd‐angulated graphs and cancelling factors in box products

Under what conditions is it true that if there is a graph homomorphism G □ H → G □ T, then there is a graph homomorphism H→ T? Let G be a connected graph of odd girth 2k + 1. We say that G is (2k + 1)‐angulated if every two vertices of G are joined by a path each of whose edges lies on some (2k + 1)‐cycle. We call G strongly (2k + 1)‐angulated if every two vertices are connected by a sequence of (2k + 1)‐cycles with consecutive cycles sharing at least one edge. We prove that if G is strongly (2k + 1)‐angulated, H is any graph, S, T are graphs with odd girth at least 2k + 1, and ?: G□ H→S□T is a graph homomorphism, then either ? maps G□{h} to S□{t_h} for all h∈V(H) where t_h∈V(T) depends on h; or ? maps G□{h} to {s_h}□ T for all h∈V(H) where s_h∈V(S) depends on h. This theorem allows us to prove several sufficient conditions for a cancelation law of a graph homomorphism between two box products with a common factor. We conclude the article with some open questions. © 2008 Wiley Periodicals, Inc. J Graph Theory 58:221‐238, 2008     

Relationship Between Stress Modulated Metallicity and Plasmon in Graphene Nanoribbons

Nanoscale quantum plasmon is an important technology that restricts the application of optics, electricity, and graphene photoelectric devices. Establishing a structure–effect relationship between the structure of graphene nanoribbons (GNRs) under stress regulation and the properties of plasmons is a key scientific issue for promoting the application of plasmons in micro-nano photoelectric devices. In this study, zigzag graphene nanoribbon (Z-GNR) and armchair graphene nanoribbon (A-GNR) models of specific widths were constructed, and density functional theory (DFT) was used to study their lattice structure, energy band, absorption spectrum, and plasmon effects under different stresses. The results showed that the Z-GNR band gap decreased with increasing stress, and the A-GNR band gap changed periodically with increasing stress. The plasmon effects of the A-GNRs and Z-GNRs appeared in the visible region, whereas the absorption spectrum showed a redshift trend, indicating the range of the plasmon spectrum also underwent significant changes. This study provides a theoretical basis for the application of graphene nanoribbons in the field of optoelectronics under strain-engineering conditions.     

TE波辐射下超材料椭圆柱电磁斗篷特性分析

 利用有限元方法分析了TE波辐射下,超材料椭圆柱斗篷的电磁特性。研究发现：当超材料的介电常数、磁导率和电导率偏离理论值0.5%时,斗篷外的电场发生了明显变化;当材料的介电常数、磁导率和电导率为理论值时,不论在斗篷内放置什么特性的材料,也不论斗篷内壁上的边界条件如何,超材料椭圆柱斗篷都具有隐形作用。     

新型有机-无机氧化还原复合膜层层组装的无试剂高灵敏电流型 前列腺特异性抗原免疫传感器研究

以前列腺特异性抗原(PSA)和前列腺特异性抗体(anti-PSA)为生物模型分子, 采用电沉积技术和共价键合作用, 研制了新型高灵敏电流型免疫传感器. 利用具有良好导电性和热稳定性的新型有机材料[苝四甲酸二酐(PTCDA)衍生物, 简写为PTC-NH2]膜具有的多孔结构, 该膜可与电沉积制得的冰晶状普鲁士蓝(PB)颗粒进行层层组装镶嵌, 形成多层稳定的有机-无机氧化还原复合膜以增加 PB 的固定量和稳定性, 从而提高电极的电流响应信号; 同时, 通过复合膜表面丰富的氨基吸附大量纳米金以增加抗体的固定量, 从而提高免疫传感器的灵敏度. 利用扫描电子显微镜(SEM)和X射线光电子能谱仪(XPS)对PTC-NH2膜的形貌和结构进行表征, 通过循环伏安法考察了电极修饰过程的电化学特性, 详细研究了该免疫传感器的性能. 该免疫电极对前列腺特异性抗原检测的线性范围为0.5～16.0 ng/mL, 相关系数为0.985, 检测限为0.02 ng/mL. 实验结果表明, 利用该方法制备的免疫传感器具有灵敏度高、稳定性和选择性好等优点.