Echolocation signals of the free-ranging Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientialis)

This paper describes the high-frequency echolocation signals from free-ranging Yangtze finless porpoise in the Tian-e-zhou Baiji National Natural Reserve in Hubei Province, China. Signal analysis showed that the Yangtze finless porpoise clicks are typical high-frequency narrow-band (relative width of the frequency spectrum Q=6.6 &PLUSMN; 1.56, N=548) ultrasonic pulses. The peak frequencies of the typical clicks range from 87 to 145 kHz with an average of 125 &PLUSMN; 6.92 kHz. The durations range from 30 to 122 μ s with an average of 68 &PLUSMN; 14.12 μ s. The characteristics of the signals are similar to those of other members of the Phocoenidae as well as the distantly related delphinids, Cephalorhynchus spp. Comparison of these signals to those of the baiji (Lipotes vexillifer), who occupies habitat similar to that of the Yangtze finless porpoise, showed that the peak frequencies of clicks produced by the Yangtze finless porpoise are remarkably higher than those produced by the baiji. Difference in peak frequency between the two species is probably linked to the different size of prefer-red prey fish. Clear double-pulse and multi-pulse reverberation structures of clicks are noticed, and there is no indication of any low-frequency (< 70 kHz) components during the recording period. © 2005 Acoustical Society of America.

Seismic behaviour of barrel vault systems

In this paper, the experimental study on the rocking behaviour of a full scale barrel vaulted structure undergo cyclic horizontal loading is discussed. The study is the first part of an ongoing experimental and theoretical research program, developed by the University of Brescia, concerning the seismic behaviour of masonry buildings. The scope of the paper is to provide some evidence of the rocking mechanism experienced by barrel vaulted structures undergo horizontal loading. Understanding of the behaviour of such structural systems is fundamental for their seismic vulnerability assessment, as well as for the correct design of possible strengthening techniques. The structural behaviour is also investigated by means of non linear finite element analyses. Numerical results are validated through comparison with experimental results. After validation, the FE model can be applied to different case studies.

Characterisation of a pathogenic virus isolated from marine threadfin fish (Eleutheronema tetradactylus) during a disease outbreak

An unknown virus was isolated from massive mortality of cultured threadfin (Eleutheronema tetradactylus) fingerlings. The virus replicated in BF-2 fish cell line and produced a plaque-like cytopathic effect. Electron micrographs revealed non-enveloped, icosahedral particles approximately 70-80 nm in diameter composed of a double capsid layer. Viroplasms and subviral particles approximately 30 run in diameter and complete particles of 70 nm in diameter were also observed in the infected BF-2 tissue culture cells. The virus was resistant upon pH 3 to 11 and ether treatment. It is also stable to heat treatment (3 h at 56 T). Replication was not inhibited by 5-iododeoxyuridine (5-IUdR). Acridine orange stain revealed typical reovirus-like cytoplasmic inclusion bodies. Electrophoresis of purified virus revealed 11 segments of double-stranded RNA and five major structural polypeptides of approximately 136, 132, 71, 41 and 33 kDa. Based on these findings, the virus isolated was identified to belong to the genus Aquareovirus and was designated as threadfin reovirus. This virus differed from a majority of other aquareovirus by its increase in virus infectivity upon exposure to various treatments such as high and low pH, heat (56 degreesC), ether and 5-IUdR. The RNA and virion protein banding pattern of the threadfin reovirus was shown to differ from another Asian isolate, the grass carp hemorrhage reovirus (GCV). Artificial injection of the threadfin reovirus into threadfin fingerlings resulted in complete mortality, whereas sea bass (Lates calcarifer) fingerlings infected via bath route showed severe mortality within a week after exposure. These results indicate that the threadfin virus is another pathogenic Asian aquareovirus isolate that could cross-infect into another marine fish, the sea bass. (C) 2002 Elsevier Science B.V. All rights reserved.

Comparison between visual and passive acoustic detection of finless porpoises in the Yangtze river, China

Recently, sonar signals and other sounds produced by cetaceans have been used for acoustic detection of individuals and groups in the wild. However, the detection probability ascertained by concomitant visual survey has not been demonstrated extensively. The finless porpoises (Neophocaena phocaenoides) have narrow band and high-frequency sonar signals, which are distinctive from background noises. Underwater sound monitoring with hydrophones (B&K8103) placed along the sides of a research vessel, concurrent with visual observations was conducted in the Yangtze River from Wuhan to Poyang Lake in 1998 in China. The peak to peak detection threshold was set at 133 dB re 1 mu Pa. With this threshold level, porpoises could be detected reliably within 300 m of the hydrophone. In a total of 774-km cruise, 588 finless porpoises were sighted by visual observation and 44 864 ultrasonic pulses were recorded by the acoustical observation system. The acoustic monitoring system could detect the presence of the finless porpoises 82% of the time. A false alarm in the system occurred with a frequency of 0.9%. The high-frequency acoustical observation is suggested as an effective method for field surveys of small cetaceans, which produce high-frequency sonar signals. (C) 2001 Acoustical Society of America.

Decoherence of two Josephson charge qubits coupled via sigma(x)sigma(x)-type coupling and exposed to sigma(x) noise

Decoherence properties of two Josephson charge qubits coupled via the sigma(x)sigma(x) type are investigated. Considering the special structure of this new design, the dissipative effects arising from the circuit impedance providing the fluxes for the qubits' superconducting quantum interference device loops coupled to the sigma(x) qubit variables are considered. The results show that the overall decoherence effects are significantly strong in this qubit design. It is found that the dissipative effects are stronger in the case of coupling to two uncorrelated baths than are found in the case of one common bath.

Spontaneous relaxation of a charge qubit under electrical measurement

In this work we first derive a generalized conditional master equation for quantum measurement by a mesoscopic detector, then study the readout characteristics of qubit measurement where a number of remarkable new features are found. The work would, in particular, highlight the qubit spontaneous relaxation effect induced by the measurement itself rather than an external thermal bath.

Exact quantum master equation via the calculus on path integrals

An exact quantum master equation formalism is constructed for the efficient evaluation of quantum non-Markovian dissipation beyond the weak system-bath interaction regime in the presence of time-dependent external field. A novel truncation scheme is further proposed and compared with other approaches to close the resulting hierarchically coupled equations of motion. The interplay between system-bath interaction strength, non-Markovian property, and required level of hierarchy is also demonstrated with the aid of simple spin-boson systems. (C) 2005 American Institute of Physics.

Synthesis and structures of morphology-controlled ZnO nano- and microcrystals

Zinc oxide flower-like bunches were directly synthesized on indium-doped tin oxide (ITO) glass substrates through a simple chemical bath deposition process. By adjusting precursor concentration, other morphologies ( spindles and rods) were also obtained. All of them are hexagonal and single crystalline in nature and grow along the [ 0001] crystallographic direction. The possible growth mechanisms for these nano- and microcrystals were proposed. It was revealed that both the inherent highly anisotropic structure of ZnO and the precursor concentration play crucial roles in determining final morphologies of the products. In addition, vibrational properties of ZnO crystals with different morphologies were investigated by Raman spectroscopy.

Quantum dissipation and broadening mechanisms due to electron-phonon interactions in self-formed InGaN quantum dots

Quantum dissipation and broadening mechanisms in Si-doped InGaN quantum dots are studied via the photoluminescence technique. It is found that the dissipative thermal bath that embeds the quantum dots plays an important role in the photon emission processes. Observed spontaneous emission spectra are modeled with the multimode Brownian oscillator model achieving an excellent agreement between experiment and theory for a wide temperature range. The dimensionless Huang-Rhys factor characterizing the strength of electron-LO-phonon coupling and damping constant accounting for the LO-phonon-bath interaction strength are found to be similar to 0.2 and 200 cm(-1), respectively, for the InGaN QDs. (c) 2006 American Institute of Physics.

超声波对HCFC-141b水合物形成过程的影响研究

针对水合物形成过程中存在成核诱导期长、过冷度大，形成速度慢的问题，本文以HCFC-141b（1，1-dichloro-1-flooroethane）作为研究工质，将超声波引入水合物形成过程中，研究超声波对水合物形成的影响。建立了包括超声波水合反应系统、数据采集和图像采集系统的可视化低温实验系统。利用这套实验系统，分别实验研究了频率为20kHz和15kHz，功率为0-1000w的超声波对HCFC-141b水合物的形成影响。实验结果表明，超声波对水合物的形成有明显的影响。水合物形成过程主要分为三阶段：冷却期、

吡唑酮衍生物的稀土配合物光致和电致发光性能研究

稀土配合物的发光具有发射带窄、色纯度高、峰发光位置不受配体环境变化的影响、发光不受温度影响等特点，而且发射峰覆盖400-1800纳米的可见区和近红外区，因此可以作为有机电致发光器件的发光层材料。现在的研究大多集中于铕、铽配合物的电致发光器件研究，对于近红外稀土配合物的电致发光以及发白光的镝配合物研究相对较少，但是近红外发光的稀土铒、钕、镱在光通讯、激光技术、生物医学、荧光探针等方面具有特殊的应用前景。在本论文中主要阐述了新型稀土配合物的设计与合成、在器件方面的应用以及器件结构机理的研究。 在本论文中，我们主要研究吡唑酮的衍生物配体对于稀土离子的敏化激发作用。通过配体基团的改性，得到发光更有效的新型稀土配合物。首先，合成了配体PM，并选择TP、Phen、Bipy、Bath做第二配体制备镝、铒、钕、镱、钐等的配合物。解析了配合物的晶体结构，测试得到了各种配合物的光致发光性能，系统分析了几种配合物中配体到中心稀土离子的能量传递过程，研究了配体对稀土的敏化机制。其中镝配合物显示近白光的发射，色坐标为x=0.35，y=0.40，以此配合物为发光层的器件显示明亮的白光，最大发光亮度为527cd/m2，是目前已经报道的镝配合物器件中，性能最突出的一个。 设计合成了配体PT、PC、PF，利用TP和Bath做中性配体与镱离子形成配合物YbPT3Bath、YbPT3TP、YbPC3Bath，它们都显示977纳米的近红外发射。经过分析发现，配体对镱离子的敏化过程是通过电子转移的机制来完成的。通过几种镱配合物发光强度对比发现YbPT3Bath、YbPC3Bath的发射最强。首先将YbPT3Bath用于电致发光器件中，发现其具有较好的电子传输特性，而且YbPM3TP2具有较好的空穴传输特性。因此，我们将这两种配合物结合制备了双发光层电致发光器件，得到的器件比单发光层器件的性能提升了若干倍。我们认为，双发光层器件结构改善了载流子的传输和最终的复合，使得激子在发光层内形成，提高激子激发发光层材料的效率。最后，利用这种双发光层器件结构得到了辐照度比较理想的镱配合物近红外器件。 对ErPM3TP2、NdPM3TP2配合物的发光性能做了系统研究。首先，分析了它们的晶体结构，得到了具体的晶体参数和结构组成。二者在紫外区的吸收光谱都显示为配体的吸收，在紫外区之后出现了稀土离子的特征吸收峰，由此我们利用Judd-Ofelt理论分析计算了Er3+、Nd3+离子在这个配位环境中的振子强度参数，最后得到Er3+、Nd3+离子从激发态能级到下能级的电偶极跃迁辐射几率以及相应的自然寿命值。利用这两种配合物做为发光层材料制备了系列近红外电致发光器件，得到理想的辐照度强度，证明它们在制备近红外器件方面具有潜在应用价值。

稀土配合物光致发光和电致发光性能的研究

有机电致发光器件(organic light-emitting diodes, OLEDs)由于具有全色、低压直流驱动、视角广、高效率和易于制备大屏幕等优点，在平板显示领域具有广阔的应用前景，已引起世界范围内科技界和企业界的广泛重视。稀土配合物作为发光及载流子传输层材料，具有窄带发射和发射波长分布范围广的特点，有利于实现高的色纯度。然而，有机电致发光的机理还未完全弄清楚，稀土配合物电致发光器件距离实际应用还比较远，需要进一步进行研究。本论文研究了Tb~(3+)、Eu~(3+), Sm~(3+)配合物的光致发光和电致发光性质，制备了绿色、红色和橙色电致发光器件，并对稀土配合物的电致发光机理进行了探讨。对于试配合物，以acac为第一配体，研究了第二配体AAP和bath对配合物和器件发光性能的影响并对器件的优化进行了讨论；以Tb(acac)_3bath为发光中心，发现电致发光中~5D_4→~7F_5跃迁相对~5D_4→~7F_5跃迁的增强现象；以Tfacac为第一配体，首次讨论了F取代H对于配体的三重态能级的降低和对配合物以及电致发光器件发光强度的增强作用，对于提高稀土配合物电致发光的性能提供了参考依据。对于铺配合物，以Tfacac为第一配体，以phen和bipy为第二配体，制备了红色电致发光器件并进一步验证了F取代H对于配体的三重态能级的降低作用；以HTH为第一配体，国际上首次报道了室温下Eu~(3+)离子的~5D_1→~7F_J的跃迁，并且其强度依赖于驱动电压的强度，光致发光和电致发光的不同表明二者的发光机理有所不同，并对铺配合物电致发光机理进行了讨论；以HTH为第一配体，国际上首次报道了衫配合物的电致发光现象，并且最大得到了21 cd/m~2的发光强度；为了改善稀土β-二酮配合物光稳定性和热稳定性差的缺点，引入了稀土芳香梭酸配合物，并对配体进行了引入长链的化学修饰，提高了配合物在一般有机溶剂中的溶解度，用旋涂法制备的器件的最大发光亮度达到了174 cd/m~2.

海马环路中的组合突触可塑性与大鼠情绪研究

海马在某些类型的学习和记忆中起着关键的作用，而突触可塑性（synaptic plasticity）为学习和记忆的模型提供了理论基础。在海马环路中，分布着各种类型的可塑性，包括突触特异的Hebbian形式的可塑性，如长时程增强（long-term potentiation，LTP）和长时程抑制（long-term depression，LTD）；稳态可塑性（homeostatic plasticity），如突触缩放（synaptic scaling）。稳态可塑性是一种整体的调控过程，它可以调节神经元甚至神经网络的平衡；而Hebbian可塑性则是突触特异的，即每个突触进行单独调控的过程。 越来越多的研究提示稳态可塑性和Hebbian可塑性之间存在着空间间隙（spatial gap），那么，如何使得神经元可以通过Hebbian可塑性的过程来维持细胞整体的兴奋性就变得尤为重要。一些报道揭示了LTP和LTD可以在同一突触通路中同时被激活，因此，我们提出组合突触可塑性的概念，即LTP和LTD的组合，它在赋予系统灵活性的同时又可以降低噪音维持系统的稳定性。基于此，本文将围绕这个问题而开展实验工作。 通过对海马CA1区锥体神经元的微小兴奋性突触后电流（miniature excitatory synaptic current, mEPSC）进行测定分析，我们发现mEPSC的幅度分布符合双峰正态分布（double-peak normal distribution）。Theta节律刺激（theta burst stimuli, TBS）诱导后，mEPSC的幅度分布发生改变，呈现右移趋势。随后，采用干扰肽Pep-A2特异地阻断LTP而不影响LTD，我们发现Pep-A2不影响基础状态下mEPSC的幅度分布。在干扰肽Pep-A2存在下，TBS诱导对基础状态下mEPSC的幅度分布也没有影响。结果为揭示LTP和LTD的组合可塑性提供了初步的证据，对进一步理解记忆的编码过程提供了一定的基础。社交隔离可以引起实验大鼠产生焦虑样和抑郁样的行为，而性经历可以改变动物的情绪状态，降低焦虑样和抑郁样的反应。然而，性经历后进行社交隔离对大鼠情绪的影响并没有报道。在这部分工作中，雄性大鼠经历一周的社交活动（male-male paired housing）或者性活动（male-female paired housing），随后进行一段时间的隔离（1天，2天或者7天）。我们发现，经历过性活动的大鼠，无论隔离与否都表现出相似的情绪反应，包括焦虑样和抑郁样行为以及超声波（ultrasonic vocalizations，USVs）发放；而未经历过性活动的大鼠，其情绪反应随着隔离时间的不同而不同。这一现象提示我们，先前的性经历可以对抗实验动物对环境应激事件，如社交隔离的反应。

Real-time counting of single electron tunneling through a T-shaped double quantum dot system

Real-time detection of single electron tunneling through a T-shaped double quantum dot is simulated, based on a Monte Carlo scheme. The double dot is embedded in a dissipative environment and the presence of electrons on the double dot is detected with a nearby quantum point contact. We demonstrate directly the bunching behavior in electron transport, which leads eventually to a super-Poissonian noise. Particularly, in the context of full counting statistics, we investigate the essential difference between the dephasing mechanisms induced by the quantum point contact detection and the coupling to the external phonon bath. A number of intriguing noise features associated with various transport mechanisms are revealed.