N.M.R. Spectra of the Fuchs0Nes: Structure of Naphthofuchsone

Following the initial synthesis of the fuchsones¹I, (α, η -diphenyl-1,4-benzoquinone methides), numerous substituted members of this series have been described by workers interested in triphenylmethane dyes. The fuchsones have been synthesized by the sulfuric acid condensation of benzilic acid and appropriate phenol¹, by dehydration of 4-hydroxytriphenylcarbinol², by oxidation 4-hydroxytri-phenylmethane and by photochemically induced reactions benzophenones with 2,6-dialkylphenols⁴.     

796 nm二极管泵浦连续波1.88 W Tm∶LYF激光器

用坩埚下降法生长了Tm³⁺掺杂浓度分别为0.8%和1.3%的优质大尺寸LiYF₄(LYF)单晶体。测定了单晶体的吸收光谱、发射光谱,并计算了³F₄能级的的最大吸收截面与最大发射截面分别为0.25×10^-20 cm²和0.33×10^-20 cm²。以796 nm半导体激光器(LD)为泵浦源,采用短平板腔结构模型研究了Tm掺杂LYF单晶体在～2.0μm波段的激光输出性能。当LD泵浦功率为3.4 W时,Tm∶YLF晶体的最大激光输出功率为1.88 W,相应的光光转换效率和斜率效率分别为51%和57%。使用半导体可饱和吸收镜抽运Tm掺杂LYF单晶体,测试其在～2.0μm波段连续波锁模激光运转。当最大抽运功率为3.5 W时,获得锁模激光的最大平均输出功率为200 mW,此时锁模脉冲宽度～20 ps,对应的重复频率63.86 MHz,中心谱线为1.88μm。结果表明,Tm掺杂LYF单晶体是一种具有较好物理性能的～2μm波段超...     

A nonextensive approach to the dynamics of financial observables

We present results about financial market observables, specifically returns and traded volumes. They are obtained within the current nonextensive statistical mechanical framework based on the entropy . More precisely, we present stochastic dynamical mechanisms which mimic probability density functions empirically observed. These mechanisms provide possible interpretations for the emergence of the entropic indices q in the time evolution of the corresponding observables. In addition to this, through multi-fractal analysis of return time series, we verify that the dual relation q_stat+q_sens=2 is numerically satisfied, q_stat and q_sens being associated to the probability density function and to the sensitivity to initial conditions respectively. This type of simple relation, whose understanding remains ellusive, has been empirically verified in various other systems.     

Studies on nano suspensions of silver sol and redispersed nanocrystallite silver in aqueous and alcoholic media

Nanocrystallite silver and silver sol were prepared and characterized by UV-visible spectra, XRD, TEM and HRTEM. The crystallite silver is re-dispersed in two different media, namely, water and alcohol and sonicated before ultrasonic investigation. The silver sol was used as such. Three different models for the propagation of ultrasound through two phase media are compared in these three different types of nano suspensions. Effect of particle size and medium on ultrasonic velocity (U), compressibility (κ) impedance (Z) and viscous relaxation time (τ) is studied. The particle concentration range was 0.2-1 v/v. Density and viscosity of the dispersion and sol are measured at different particle volume fractions. Effective density and ultrasonic velocity are computed by Urick, Kuster and Toksöz and Urick and Ament models and compared with experimental velocities. Values of effective density obtained by using Urick and Urick and Ament equations closely agree with experimental results of density while Urick's equation prediction of velocity is in close agreement with the experimental velocities. This comes as a surprise in view of the large density difference between the medium and suspended particle and suggests the possibility of the balancing effect of the inertial and viscous forces operating in the suspension.     

Enhanced luminescence of GdTaO4:Eu thin-film phosphors by K doping

The effect of K⁺ ions on GdTaO₄:Eu³⁺ thin-film phosphors was investigated in order to improve their luminescent properties. The GdTaO₄:Eu_0.1, K_x thin films were synthesized by sol-gel process, and characterized through measuring their microstructure and luminescence. The results indicated that photoluminescence (PL) intensity of GdTaO₄:Eu³⁺ film was improved remarkably by K doping. There were two maxima in the curve of PL intensity against K⁺ dopant concentration, where one was improved up to 2.1 times at x = 0.001 and the other was enhanced up to 2.7 times at x = 0.05. The first maximum was regarded as the alteration of the local environment surrounding the Eu³⁺ activator by incorporation of K⁺ ions, and the second maximum was due to the flux effect. Additionally, the luminescence increased with the increase of firing temperature from 800 °C to 1200 °C.     

表面绝缘铝平面丝阵Z箍缩实验研究

在"强光一号"装置(1.3 MA,100 ns)上进行了镀2μm聚酰亚胺绝缘膜平面铝丝阵与普通铝丝阵Z箍缩对比实验研究.实验结果表明,表面绝缘能够影响Z箍缩内爆动力学和辐射特性.通过简单理论分析,表面绝缘可能会增加初始阶段的能量沉积和参与内爆的质量;表面绝缘对于抑制平面丝阵多峰现象有明显作用,然而在所进行的实验中,并未观察到对X射线产额的改善作用.     

The world according to Rényi: thermodynamics of multifractal systems

We discuss basic statistical properties of systems with multifractal structure. This is possible by extending the notion of the usual Gibbs-Shannon entropy into more general framework—Rényi’s information entropy. We address the renormalization issue for Rényi’s entropy on (multi)fractal sets and consequently show how Rényi’s parameter is connected with multifractal singularity spectrum. The maximal entropy approach then provides a passage between Rényi’s information entropy and thermodynamics of multifractals. Important issues such as Rényi’s entropy versus Tsallis-Havrda-Charvat entropy and PDF reconstruction theorem are also studied. Finally, some further speculations on a possible relevance of our approach to cosmology are discussed.     

Dependence of the interband transition and the activation energy on the ZnTe spacer thickness in CdTe/ZnTe double quantum dots

Photoluminescence (PL) measurements were carried out to investigate the interband transition and the activation energy in CdTe/ZnTe double quantum dots (QDs). While the excitonic peaks corresponding to the interband transition from the ground electronic subband to the ground heavy-hole (E₁-HH₁) in the CdTe/ZnTe double QDs shifted to higher energy with decreasing ZnTe spacer thickness from 30 to 10 nm due to transformation from CdTe QDs to Cd_xZn_1−xTe QDs, the peaks of the (E₁-HH₁) transitions shifted to lower energy with decreasing spacer thickness from 10 to 3 nm due to the tunneling effects of the electrons between CdTe double QDs. The decrease in the activation energy with decreasing ZnTe spacer thickness might originate from an increase in the number of defects in the ZnTe spacer. The present results can help improve the understanding of the interband transition and the activation energy in CdTe/ZnTe double QDs.     

Phase diagram of a 2D Ising model within a nonextensive approach

In this work we report Monte Carlo simulations of a 2D Ising model, in which the statistics of the Metropolis algorithm is replaced by the nonextensive one. We compute the magnetization and show that phase transitions are present for q ≠ 1. A q - phase diagram (critical temperature vs. the entropic parameter q) is built and exhibits some interesting features, such as phases which are governed by the value of the entropic index q. It is shown that such phases favors some energy levels of magnetization states. It is also shown that the contribution of the Tsallis cutoff is capital to the existence of phase transitions.