Synchronization transition in gap-junction-coupled leech neurons

Real neurons can exhibit various types of firings including tonic spiking, bursting as well as silent state, which are frequently observed in neuronal electrophysiological experiments. More interestingly, it is found that neurons can demonstrate the co-existing mode of stable tonic spiking and bursting, which depends on initial conditions. In this paper, synchronization in gap-junction-coupled neurons with co-existing attractors of spiking and bursting firings is investigated as the coupling strength gets increased. Synchronization transitions can be identified by means of the bifurcation diagram and the correlation coefficient. It is illustrated that the coupled neurons can exhibit different types of synchronization transitions between spiking and bursting when the coupling strength increases. In the course of synchronization transitions, an intermittent synchronization can be observed. These results may be instructive to understand synchronization transitions in neuronal systems.     

Physical characteristics of polyimide films for flexible sensors

Physical characteristics of polyimide films, including optical, micro/nano mechanical, and thermophysical characteristics were investigated using a photometric, a nanoindentation, and a thermomechanical analyzer for applications in flexible sensors. Experimental results show that UV light cannot transmit into the polyimide films. The transmittances, with a maximum of about 86%, at VIS and near IR lights decrease with increasing PI film thicknesses. The mechanical characteristics were determined using tensile, bending moment, and nanoindentation testing. The stress–strain curve approximated bilinear characteristics, the load–unload bending moment exhibited hysteresis, and nanoindentation generated elastic energy dissipation in the loading–unloading region. Nanoindentation showed an almost uniform hardness and a reduced Young’s modulus of about 0.181±0.03 and 3.21±0.06 GPa, respectively, when the penetrating depth was more than about 2 μm. Thermophysical characteristics were greatly influenced on 8.3 and 25 μm specimens due to the higher relaxation of thin PI films. The thermal expansion remained steady when the thickness was over 50 μm. The results show that PI films have potential in flexible sensing and higher temperature fabrication.     

A formula used to subtract the effect of gamma-ray of the others to that of measured reaction in measurement of cross section of nuclear reaction and its application

Abstract According to the regulation of growing and decay of artificial radioactive nuclide, a formula used to subtract the effect of characteristic γ-ray of the others to that of measured reaction was deduced. And then the cross sections of 120Te (n, 2n)119mTe reaction induced by neutrons around 14 MeV were measured by activation relative to the 93Nb (n, 2n)92mNb. In the process of the cross sections measured to be calculated, it was subtracted that the effect of characteristic γ-ray of 126Te (n, p)126Sb to that of measured 120Te (n, 2n)119mTe reaction using the formula deduced. The experimental results were (689±37) and (750±41) mb at the neutron energies of (13.5±0.3) and (14.6±0.3) MeV, respectively. Measurements were carried out by γ-detection using a coaxial HPGe detector. As samples, spectroscopically pure tellurium powder has been used. The fast neutrons were produced by the T(d, n)4He reaction. The neutron energies in these measurements were determined by the method of cross-section ratios between 90Zr (n, 2n) 89m+gZr and 93Nb (n, 2n) 92mNb reactions.     

Liquid polyamorphism: Possible relation to the anomalous behaviour of water

We present evidence from experiments and computer simulations supporting the hypothesis that water displays polyamorphism, i.e., water separates into two distinct liquid phases. This concept of a new liquid-liquid phase transition is finding application to other liquids as well as water, such as silicon and silica. Specifically, we investigate, the relation between changes in dynamic and thermodynamic anomalies arising from the presence of the liquid-liquid critical point in (i) Two models of water, TIP5P and ST2, which display a first order liquid-liquid phase transition at low temperatures; (ii) the Jagla model, a spherically symmetric two-scale potential known to possess a liquid-liquid critical point, in which the competition between two liquid structures is generated by repulsive and attractive ramp interactions; and (iii) A Hamiltonian model of water where the idea of two length/energy scales is built in. This model also displays a first order liquid-liquid phase transition at low temperatures besides the first order liquid-gas phase transition at high temperatures. We find a correlation between the dynamic fragility crossover and the locus of specific heat maxima C_P^max (“Widom line”) emanating from the critical point. Our findings are consistent with a possible relation between the previously hypothesised liquid-liquid phase transition and the transition in the dynamics recently observed in neutron scattering experiments on confined water. More generally, we argue that this connection between C_P^max and the dynamic crossover is not limited to the case of water, a hydrogen bonded network liquid, but is a more general feature of crossing the Widom line, an extension of the first-order coexistence line in the supercritical region. Dedicated to Armin Bunde on the occasion of his 60th birthday.     

光纤型宽带可调连续波差频产生中红外激光器转换效率的研究

以掺镱光纤激光器为抽运源、掺铒光纤激光器后接掺铒光纤放大器为信号源,利用周期极化掺镁铌酸锂晶体,研究了全光纤化差频产生中红外激光器的转换效率特性。结果表明,抽运光和信号光偏振态影响差频产生过程的转换效率,利用偏振控制器,可将抽运光和信号光偏振方向调节到与晶体光轴方向平行,以获得高的转换效率。抽运光和信号光的光束质量既影响差频产生过程的转换效率,又决定晶体纵向位置的容限,当聚焦系统由自聚焦透镜和焦距100mm平凸透镜组成时,相对转换效率达0.717mW-2,晶体纵向位置容限为44mm。此外,差频光在3126.36~3529.6nm范围内调谐时,转换效率基本保持不变。     

晶体NiX2(X=Cl,Br,I)的光谱和电子顺磁共振谱研究

在强场耦合图像中,采用双自旋-轨道耦合(SO)参量模型建立了过渡族3d2(3d8)离子的三角对称下全组态光谱能级和电子顺磁共振(EPR)公式.与经典的晶体场理论(仅考虑中心金属离子的自旋-轨道耦合作用)相比较,该公式还包括了配体离子的自旋-轨道耦合作用的贡献,这一模型在应用于计算共价性较强的晶体光谱和电子顺磁共振谱可得到合理的结果.作为验证,用完全对角化方法研究了品体NiX2(X=Cl,Br,I)的光谱和电子顺磁共振谱,结果表明,理论与实验很好地符合.建立的全组态谱能级和电子顺磁共振公式为更精确地计算光谱和电子顺磁共振谱提供了一条可行方法.     

一种投影式激光方向测量方法

为了在激光告警中实现全方位角度探测,且达到一定的探测精度,提出了一种投影式激光方向测量方法.通过计算激光照射在参量给定的遮光板上形成的投影量.求解在探测器上由不同探测象限产生的不同的探测电流的比值.再根据投影面积的比值与角度一一对应的关系可事先编码的原理.由对应程序判断激光入射方向.在软件Matlab仿真中计箅得到产生最小分辨率的四个极限角度分别为(0°,90°)、(33°,21°)、(33°,69°)、(45°,90°),并由实验得到最小分辨电压为0.05 V.通过仿真计算与实验数据证明该设计可达到最小识别角度1°的探测要求.     

Investigation of the influence of extra noises in seed beams on continuous-variable entanglement generation

The influence of the extra classical noises in seed beams on the entanglement between the signal and the idler modes of the output fields generated by a non-degenerate optical parametric amplifier operating at deamplification is investigated theoretically and experimentally.With the increase of the extra classical noises in the seed beams,the correlation degree of the output entangled optical fields,which is scaled by the quantum noise limit,decreases rapidly.The experimental results are in good agreement with the theoretical calculations.     

Cytotoxic effects and in vitro reversal of multidrug resistance by therapeutic ultrasound in human hepatocarcinoma cell line (HepG2)

Multidrug resistance (MDR) is one of the major obstacles to successful chemotherapy of human malignancies. Although many strategies have been explored to overcome MDR, none of them have been proven to be clinically useful until now. The aim of this study was to investigate whether a novel therapeutic ultrasound (US) approach would have useful effects on the reversal of MDR in cancer cells. Wild-type and MDR phenotype (HepG2/ADM) cells of the human hepatocarcinoma cell line HepG2 were exposed to 0.8 MHz US at an intensity of 0.43 W/cm² for a 9 s exposure (total energy density: 3.87 J/cm²). After US exposure, cell number and viability were counted immediately, and flow cytometry was performed to measure retention of rhodamine 123 and adriamycin in HepG2 and HepG2/MDR cells. Both cell lines were then incubated in suspension with adriamycin, vincristine, etoposide, cisplatin and 5-fluorouracil, respectively, and the MTT assay was used to determine cytotoxicity. The results showed that US exposure could significantly increase the uptake of Rh123 and ADM by HepG2/ADM tumor cells. The resistant index for the chemotherapeutic drugs was significantly lower in the US-exposed HepG2/ADM cells than in those not exposed to US. It was therefore concluded that US exposure could enhance the sensitivity of HepG2/ADM tumor cells to these chemotherapeutic agents, and the functional and structural changes induced by previous US exposure in MDR tumor cells may be responsible for it. However, further study is needed to investigate the mechanism behind US-mediated reversal of MDR.     

Study on the temperature distribution of heated falling liquid films

A 2-D theoretical model was derived to present the temperature distribution of falling liquid films flowing over a vertical heated/cooled plate with constant temperature. And the temperature gradients for different flow rates and fluids were also discussed for different liquid films. The temperature distributions for liquid films of water, ethanol aqueous solutions and glycerol aqueous solutions were experimentally investigated with a sensitive thermal imaging system. It is found that the surface temperature of a film flowing over a vertical heated solid plate has a characteristic relationship with the film flow distance. A lower flow rate of the film or a higher temperature of the wall generally leads to a higher surface temperature in the film inception. For films of glycerol aqueous solutions under the same heating conditions, a lower glycerol concentration causes a higher surface temperature of the film, due to the decrease of the liquid viscosity, whereas the ethanol concentration is found to have little influence on the temperature distribution of the film surface. Comparisons of the experimental data and the theoretical model show that the model can adequately describe the surface temperature distribution of a heated falling liquid film.