伞形花内酯的荧光量子产率与电离常数

研究了伞形花内酯在不同酸度下的荧光光谱,测量了荧光量子产率和电离常数。伞形花内酯有2种荧光型体,分别存在于弱酸性和弱碱性溶液中。在pH 3～6的溶液中,伞形花内酯以中性分子型体存在,最大激发波长λex=325nm,最大发射波长λem=455nm;在pH 9～10.5的溶液中,伞形花内酯主要以阴离子型体存在,λex/λe...     

N-2-aryl-1,2,3-triazoles: a novel class of UV/blue-light-emitting fluorophores with tunable optical properties

The N-2-aryl-1,2,3-triazole derivatives (NATs) were developed as a new class of UV/blue-light-emitting fluorophores. Though both N-1-aryl-1,2,3-triazoles and N-2-aryl-1,2,3-triazoles gave strong photo absorption under excitation at 330 nm, only the N-2-analogous showed strong fluorescence emission in the UV/blue range with high efficiency in various solvents (quantum yield Φ around 0.3-0.5). Significant substituted group effects were observed, allowing tunable optical properties with emission (λ(max)) from 350-400 nm and Stokes shift from 38-93 nm. The computational studies along with X-ray crystal structures indicated the significance of the effective conjugation between triazole ring and aryl groups on the N-2 position. The planar intramolecular charge transfer (PICT) mechanism was proposed, which was supported by solvent effect studies. Simple derivatizations gave NAT-modified lysine and strong UV/blue emitting bis-NAT (Φ=0.76, λ(max)=390), which suggested the great potential of this new class of fluorophores in biological and material science research.     

辛酸亚锡对氧化锌催化制备丙交酯的影响

用减压蒸馏法合成了丙交酯,在反应的不同时间段加入辛酸亚锡,可使丙交酯最高馏出温度降低至197 ℃。 采用红外光谱表征了丙交酯,测定了反应体系的表面张力和黏度,结果表明,脱自由水后的乳酸、脱自由水后加氧化锌和脱自由水后加氧化锌和辛酸亚锡体系的表面张力分别为38.8、47.0和40.3 N/m;黏度分别为43.1049、59.6774和48.9376 mPa·s。 辛酸亚锡的加入降低了反应体系表观张力和黏度,有利于低聚物结构中酰氧键断裂生成丙交酯。     

OPTIMAL HARVEST FEEDBACK RULE ACCOUNTING FOR THE FISHING‐UP EFFECT AND SIZE‐DEPENDENT PRICING

Abstract Fishing leads to truncation of a population's age and size structure. However, large‐sized fish are usually more valuable per unit weight than small ones. Nevertheless, these size‐related factors have mostly been ignored in bioeconomic modeling. Here, we present a simple extension to the Gordon–Schaefer model that accounts for variations in mean individual catch weight, and derive the feedback rule for optimal harvest in this setting. As the Gordon–Schaefer model has no population structure, size effects have to be accounted for indirectly. Here we assume a simple negative relationship between fishing effort and mean individual weight, and a positive relationship between mean catch weight and price. The aim is to emulate alterations of size structure in fish populations due to fishing and the influence of size on price per weight unit and eventually, net revenues. This demonstrates, on a general level, how such size‐dependent effects change the patterns of optimal harvest paths and sustainable revenue in single fish stocks. The model shows clear shifts toward lower levels of optimal effort and yield compared to classical models without size effects. This suggests that ignoring body size could lead to misleading assumptions and policies, potentially causing rent dissipation and suboptimal utilization of renewable resources.     

Natural convection of non-Newtonian power-law fluid over axisymmetric and two-dimensional bodies of arbitrary shape in fluid-saturated porous media

Numerical analysis of the free convection coupled heat and mass transfer is presented for non-Newtonian power-law fluids with the yield stress flowing over a two-dimensional or axisymmetric body of an arbitrary shape in a fluid-saturated porous medium. The governing boundary layer equations and boundary conditions are cast into a dimensionless form by the similarity transformation. The resulting system of equations is solved by a finite difference method. The parameters studied are the rheological constants, the buoyancy ratio, and the Lewis number. Representative velocity, temperature, and concentration profiles are presented and discussed. It is found that the results depend strongly on the values of the yield stress parameter and the power-law index of the non-Newtonian fluid.     

The effect of temperature on the photoluminescence ofp-CuGaSe2 single crystals

We studied the temperature dependences of spectral bands and of the outer quantum yield of the edge photoluminescence (PhL) of p-CuGaSe₂ single crystals obtained by the method of chemical transport reactions. We determined the activation energies of acceptor levels and showed that the temperature dependence of the intensity of PhL is determined by an acceptor level of 35 meV below the Debye temperature and of 150 meV above the Debye temperature. The spectra of the edge PhL at 300 and 80 K are determined mainly by band-band optical transitions. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 590–593, July–August, 1998.     

高电荷态离子207Pbq+(24≤q≤36)与Si(110)固体表面作用的电子发射研究

报道了利用兰州重离子加速器国家实验室ECR源引出的高电荷态离子²⁰⁷Pb^q+(24≤q≤36)入射到Si(110)表面产生的电子发射的实验测量结果.结果表明,高电荷态离子与固体表面相互作用产生的电子发射产额Y与入射离子的电荷态q、入射角度ψ和入射能量E都有很强的关联.首次发现,电子发射产额Y与入射角度ψ间有接近1/tanψ的关系.理论分析认为,这些过程与基于经典过垒模型的势能电子发射过程密切相关. 关键词： 高电荷态离子 经典过垒模型 电子发射产额     

Spectral characteristics of luminescence of solutions of complex molecules under conditions of electronic excitation transfer to a saturable acceptor in the case of inhomogeneous broadening of electronic energy levels

Spectral characteristics of solutions of complex molecules under conditions of inhomogeneous broadening of energy levels are considered in the case when the nonlinear dependence of the population of molecular states on the excitation intensity is determined not by saturation of molecular levels but by exchange of the electronic excitation energy with the environment. Calculations have shown that the dependence of the position of the fluorescence spectrum on the excitation frequency is nonmonotonic in solutions of the type and varies substantially with the excitation intensity. Belarusian State University, 4, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 164–168, March–April, 1997.     

Photoelectric behaviour of lattice-matched GaAs/Al x Ga1- x As quantum well electrodes

The photoelectric properties of the lattice-matched GaAs/A1 _x Ga_l - _x As quantum well electrodes and the influence of the electrode structure such as well width, the thickness of outer barrier and the number of period were studied in a nonaqueous electrolyte. A new kind of structure of multiple quantum well electrode with varied well width, possessing the quantum yield three times that of GaAs bulk materials, was designed and fabricated. Project supported by the National Natural Science Foundation of China.     

混合卟啉体系中的光化学烧孔

在有机电子转移型烧孔体系中,混杂两种电子给体-苯并卟啉锌衍生物分子,可增加吸收带的非均匀宽度。本文通过对光谱孔的宽度和烧孔效率的讨论,证明了混杂电子给体的方法对孔宽和烧孔效率无明显影响,可以达到增加此类材料体系的烧孔数目,提高信息存储密度的目的。