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The cytosolic calcium system is inhomogenous because of the discrete and random distribution of ion channels on the ER membrane. It is well known that the spiral tip can be pinned by the heterogenous area, and the field can detach the spiral from the heterogeneity. We use the adventive field to counteract the attractive force exerting on the calcium spiral wave by the heterogeneity, then the strength of the adventive field is used to quantify the attractive force indirectly. Two factors determining the attractive force are studied. It is found that: (1) the attractive force sharply increases with size of the heterogeneity for small-size heterogeneity, whereas the force increases to a saturated value for large-size heterogeneity; (2) for large-size heterogeneity, the force almost remains constant unless the level of the heterogeneity vanishes, the force decreases to zero linearly and sharply, and for small-size heterogeneity, the force decreases successively with the level of the heterogeneity. Furthermore, it is found that the forces exist only when the spiral tip is very close to the heterogenous area. Our study may shed some light on the control or suppression of the calcium spiral wave. [ABSTRACT FROM AUTHOR]

Excited states of the odd-odd nucleus 122I are investigated via the fusion-evaporation reaction 116Cd(11B,5n) at a beam energy of 68 MeV. The two most strongly populated bands in 122I are observed up to excitation energies around 10.5 MeV. Their possible configurations at lower spins are assigned to πh11/2 ... vh11/2 and πh11/2 ... vd5/2 based on the observed population, B(M1)/B(E2) values, alignments and signature splitting. E1 transitions are observed connecting the πh11/2 ... vd5/2 band to the πh11/2 ... vh11/2 band, which may be evidence of octupole collectivity. Band terminations caused by the full alignment of the valence nucleons outside the 114Sn core are observed in both bands. [ABSTRACT FROM AUTHOR]

A target in layered medium can be located by the ridge-like distribution time reversal and reverse time migration (TR-RTM) mixed method. However, this method cannot distinguish between acoustic field distributions of the interface and target for the wider acoustic pulse signals, which may result in inaccurate location of the target. A snapshot TR-RTM mixed method is proposed to solve this problem. The principle of snapshot TR-RTM mixed method is first given. Experiments are then carried out, and a mountain-like acoustic field distribution is obtained by processing experimental data. The results show that the location of the peak is that of the target, and the ratio of the scattered signal and interface reflection signal (signal-to-interference ratio) is improved by about four times after processing. Furthermore, this method can effectively suppress the interface reflection signal and enhance the target scattering signal. Therefore, it can achieve effective detection and location of a target in a layered medium. [ABSTRACT FROM AUTHOR]

A prototype of a laser driven proton accelerator is built at Peking University. Protons exceeding 10 MeV are accelerated from micrometer-thick aluminum targets irradiated by tightly focused laser pulse with 1.8 J energy and 30 fs duration. The beam energy spectrum and charge distribution are measured by a Thomson parabola spectrometer and radiochromic film stacks. The sensitivity of proton cut-off energy to the focusing of the laser beam, the pulse duration, and the foil thickness are systematically investigated in the experiments. Stable proton beams have been produced with an optimized parameter set, providing a cornerstone for the future applications of laser accelerated protons. [ABSTRACT FROM AUTHOR]

An improved indirect scheme for laser positron generation is proposed. The positron yields in high-Z metal targets irradiated by laser produced electrons from near-critical density plasmas and underdense plasma are investigated numerically. It is found that the positron yield is mainly affected by the number of electrons of energies up to several hundreds of MeV. Using near-critical density targets for electron acceleration, the number of high energy electrons can be increased dramatically. Through start-to-end simulations, it is shown that up topositrons can be generated with state-of-the-art Joule-class femtosecond laser systems. [ABSTRACT FROM AUTHOR]

A compact laser plasma accelerator that is a novel accelerator based on the interaction of ultra-intense laser and plasmas is being built now at Peking University. According to the results of experiments and numerical simulations, a beam line combining the advantages of quadrupole and analyzing magnets is designed to deliver proton beams with energy ranging from 1 to 44 MeV, energy spread within ±5% andprotons per pulse. It turns out that the existence of space charge force of protons can be ignored for the increase of transverse and longitudinal envelopes even in the case of 10protons in one pulse. To cope with the challenge to obtain a uniform distribution of protons at the final experiment target in laser acceleration, we manipulate the envelope beam waist in the Y direction to a proper position and obtain a relatively good distribution uniformity of protons with an energy spread of 0±5%. [ABSTRACT FROM AUTHOR]

La(O,F)BiSe2 is a layered superconductor and has the same crystal structure with La(O,F)BiS2. We investigate the electronic structure of La(O,F)BiSe2 using the angle-resolved photoemission spectroscopy. Two electron-like Fermi surfaces around X(π, 0) are observed, corresponding to the electron doping of 0.23 per Bi site. We clearly resolve anisotropic band splitting along both Γ—X and M—X due to the cooperative effects of large spin-orbit coupling and interlayer coupling. Moreover, we observe an almost non-dispersive electronic state around −0.2eV between the electron-like bands. This state vanishes after in-situ K evaporation, indicating that it could be the localized surface state caused by defects on the cleaved surface. [ABSTRACT FROM AUTHOR]

Due to its complicated matrix effects, rapid quantitative analysis of chromium in agricultural soils is difficult without the concentration gradient samples by laser-induced breakdown spectroscopy. To improve the analysis speed and accuracy, two calibration models are built with the support vector machine method: one considering the whole spectra and the other based on the segmental spectra input. Considering the results of the multiple linear regression analysis, three segmental spectra are chosen as the input variables of the support vector regression (SVR) model. Compared with the results of the SVR model with the whole spectra input, the relative standard error of prediction is reduced from 3.18% to 2.61% and the running time is saved due to the decrease in the number of input variables, showing the robustness in rapid soil analysis without the concentration gradient samples. [ABSTRACT FROM AUTHOR]

During the laser foil interaction, the output ion beam quality including the energy spread and beam divergence can be improved by the target ablation, due to the direct laser acceleration (DLA) electrons generated in the ablation plasma. The acceleration field established at the target rear by these electrons, which is highly directional and triangle-envelope, is helpful for the beam quality. With the help of the target ablation, both the beam divergence and energy spread will be reduced. If the ablation is more sufficient, the impact of DLA-electron-caused field will be strengthened, and the beam quality will be better, confirmed by the particle-in-cell simulation. [ABSTRACT FROM AUTHOR]

We investigate the application of the density-matrix renormalization group (DMRG) algorithm to a one-dimensional harmonic oscillator chain and compare the results with exact solutions, aiming at improving the algorithm's efficiency. It is demonstrated that the algorithm can show quite accurate results if the procedure is properly organized; for example, by using the optimized bases. The errors of calculated ground state energy and the energy gap between the ground state and the first excited state are analyzed, and they are found to be critically dependent upon the size of the system or the energy level structure of the studied system and the number of states targeted during the DMRG procedure. [ABSTRACT FROM AUTHOR]