大尺寸核/层Co-Pd合金团簇稳定结构研究

纳米尺度合金团簇具有特殊的光学、电、磁和催化等性质,在基础研究和应用领域吸引了广泛的兴趣.使用多体Gupta势函数描述Co-Pd团簇原子间相互作用,应用基于内核构建的自适应免疫优化算法确定最稳定结构.研究结果显示:98原子Co-Pd团簇结构可分为面心立方结构、Mackay二十面体、双二十面体、由双二十面体面面相连构成的结构和十面体结构.序列参数显示Co原子位于内层,而Pd原子位于外层.原子半径和表面能进一步解释了Co和Pd原子的分布规律.原子数目为147的Co-Pd团簇均为完整二十面体结构.     

基于荧光光谱技术研究胶原蛋白溶液中分子的聚集行为

对胶原分子聚集行为的研究,不仅能改善其理化特性,同时也为其在食品、组织工程和生物医药等领域的应用提供理论指导。基于胶原分子中苯丙氨酸(Phe)和酪氨酸(Tyr)的内源荧光特性,采用常规波长、同步荧光和二维(2D)荧光光谱技术研究了不同浓度和温度下胶原分子的聚集行为。研究结果表明：(1)在激发波长275 nm条件下,胶原分子仅在发射波长303 nm处出现了归属于Tyr的特征峰;选取波长差(Δλ)为15 nm的同步荧光扫描胶原分子,发现其在261和282 nm处出现了分别归属于Phe和Tyr的特征峰。(2)特征峰的荧光强度与胶原浓度呈现良好的线性关系,表明了基于常规波长和同步荧光光谱技术对胶原定量分析的可行性。(3)随着胶原浓度的增加,Tyr和Phe的含量逐渐增大,且胶原分子间距逐渐降低并聚集成纤维束,使得Tyr和Phe相互靠近并参与形成大量的氢键,从而导致荧光强度不断增大。然而随着温度的升高,荧光基团与溶剂碰撞的猝灭机会增大,且胶原分子中Tyr和Phe的荧光量子产率逐渐降低,同时胶原分子动能增大,其聚集体逐渐松散,其三股螺旋结构逐渐坍塌,Tyr和Phe参与形成的氢键被破坏,从而导致荧光强度随温度的升高不断降低。(4)275 nm常规波长的2D荧光光谱分析表明,胶原分子在297,303和310 nm处出现了相关峰,其中303 nm归属于Tyr,297 nm归属于胶原分子聚集过程中参与氢键形成的Tyr;310 nm可能归属于Tyr的激发态,其不断的蓝移形成稳定的基团,以便参与氢键的形成,从而促进了胶原分子的聚集。以浓度为外扰的基团响应顺序为303 nm>297 nm>310 nm;以温度为外扰的基团响应顺序为297 nm>310 nm>303 nm。(5)2D同步荧光光谱分析表明,随着胶原浓度和温度的升高,Phe均比Tyr优先响应。综上,采用常规波长、同步荧光光谱技术均能较好的研究胶原分子在不同浓度和温度下的聚集行为,且为胶原的定量分析提供了一种新的方法,但同步荧光光谱技术可将量子产率较低的Phe显现出来,体现了其具有窄化谱带和提升分辨率的优点。此外,结合2D荧光分析技术,可进一步研究胶原分子基团的响应顺序。     

Effect of mutual inductance coupling on superconducting flux qubit decoherence

In the Born-Markov approximation and two-level approximation, and using the Bloch-Redfield equation, the decoherence property of superconducting quantum circuit with a flux qubit is investigated. The influence ou decoherence of the mutual inductance coupling between the circuit components is complicated. The mutual inductance coupling between different loops will decrease the decoherence time. However, the mutual inductance coupling of the same loop, in a certain interval, will increase the decoherence time. Therefore, we can control the decoherence time by changing the mutual inductance parameters such as the strength and direction of coupling.     

Ultrasound-assisted fabrication of a novel nickel(II)-bis-pyrazolyl borate two-nuclear discrete nano-structured coordination compound

Ultrasound was used to synthesize nano-structures of [Ni(bpzB)₂]₂(1), a new two-nuclear discrete-coordination compound of divalent nickel with bis-pyrazolyl borate(bpzB). The nanostructure was characterized by scanning electron microscopy, X-ray powder diffraction, infrared, and elemental analysis. The single-crystal X-ray data show that the coordination number of Ni(II) ions is four (Ni1N₄ and Ni2N₄) with square planar geometry. The supramolecular features in these complexes are guided and controlled by weak directional intermolecular interactions. The discrete molecules interact with each other through labile interactions, creating a 3D supramolecular framework.     

氦同位素被溴化氢散射的角分布

基于作者构造的He-HBr体系的各向异性势,采用密耦方法计算了碰撞能量分别为60和100 meV时3He、4He、6He和7He被HBr分子散射的角分布,详细讨论了氦同位素对散射角分布的影响.结果表明:在相同碰撞能量时,随着同位素氯原子质量的增加,总微分截面在0°时的角分布逐渐增大,同一级衍射振荡极小值位置逐渐向小散射角方向移动;弹性与总非弹性截面交界角逐渐减小,总非弹性截面逐渐增加.碰撞能量越低,入射同位素He原子的质量越大,彩虹现象越明显.     

Synchronized Anti-Phase and In-Phase Oscillations of Intracellular Calcium Ions in Two Coupled Hepatocytes System

We study the dynamic behaviour of two intracellufar calcium oscillators that are coupled through gap junctions both to Ca^2＋ and inositol（1,4,5）-trisphosphate （IP3）. It is found that synchronized anti-phase and in-phase oscillations of cytoplasmic cadcium coexist in parameters space. Especially, synchronized anti-phase oscillations only occur near the onset of a Hopf bifurcation point when the velocity of IP3 synthesis is increased. In addition, two kinds of coupling effects, i.e., the diffusions of Ca^2＋ and IP3 among cells on synchronous behaviour, are considered. We fnd that small coupling of Ca^2＋ and large coupling of IP3 facilitate the emergence of synchronized anti-phase oscillations. However, the result is contrary for the synchronized in-phase case. Our findings may provide a qualitative understanding about the mechanism of synchronous behaviour of intercellular calcium signalling.     

Amplified Signal Response by Neuronal Diversity on Complex Networks

The effect of diversity on dynamics of coupled FitzHugh-Nagumo neurons on complex networks is numerically investigated, where each neuron is subjected to an external subthreshold signal. With the diversity the network is a mixture of excitable and oscillatory neurons, and the diversity is determined by the variance of the system＇s parameter. The complex network is constructed by randomly adding long-range connections （shortcuts） on a nearest-neighbouring coupled one-dimensional chain. Numerical results show that external signals are maximally magnified at an intermediate value of the diversity, as in the case of well-known stochastic resonance, burthermore, the effects of the number of shortcuts and coupled strength on the diversity-induced phenomena are also discussed. These findings exhibit that the diversity may play a constructive role in response to external signal, and highlight the importance of the diversity on such complex networks.     

Preparation and crystal structure determination of Eu27Ti20X2S54O12 (X ≈ I0.35 Cl0.65)

The structure of the new compound Eu₂₇T₂₀X₂S₅₄O₁₂ (X ≈ I_0.35 Cl_0.65), prepared by solid state reaction, contains _∞²[(Ti₄S₂O₄)(Ti₂S₁₀)_4/2] planes built up from rutile-like chains that cross perpendicularly. Two [TiS₆] octahedra separate the [Ti₄S₂O₄] clusters at the chain intersections. These planes are separated by a corrugated layer of [Ti₃S₈O₄] triplets of face-sharing Ti-centered octahedra. Five crystallographically independent europium ions are seven- to nine-coordinated.     

新型镉(Ⅱ)配合物荧光探针的合成及性能

以8-氨基喹啉、1,5-萘二磺酸根为配体,NaN₃为pH调节剂,与Cd(NO₃)₂通过水热反应,合成了一个新的一维链状镉配合物:[Cd(8-aql)₂(1,5-nd)]₂·H₂O (1)(8-aql=8-氨基喹啉, 1,5-nd=1,5-萘二磺酸根),并对其进行了元素分析、红外光谱和X-射线单晶衍射表征。配合物1属于单斜晶系,空间群为P2₁/n,不对称结构单元中包含半个Cd(Ⅱ),一个8-aql配体、半个1,5-nd阴离子和一个游离的水分子,中心离子Cd(Ⅱ)采取六配位模式构成畸变的八面体配位几何构型。该配合物具有较高的热稳定性,且在510 nm处发射荧光,属配体的π^*-π跃迁。讨论了此配合物在常见溶剂中的荧光性质。实验结果表明,不同有机小分子对配合物的发射光波长和强度均有不同程度影响,其中硝基苯使配合物荧光猝灭,该配合物可以作为荧光探针检测低浓度的硝基苯。