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Critical stability of the metastable bound 2 p 2 3 P e state of two-electron atoms near the critical nuclear charge Z c (smaller than which the bound state ceases to exist) is investigated by employing the explicitly correlated Hylleraas-configuration interaction basis function. Our numerical calculation shows that, when the nuclear charge decreases to Z c , the ionization energy of the system approaches zero linearly and this behavior is fully consistent with the Hellmann–Feynman theorem. Radial and angular physical quantities as well as the inner and outer electron radial density distributions are calculated to reveal the classical geometric structure of the two-electron atom. The inner electron can be well modeled by a hydrogenic model in the 2 p state and its density distribution does not change much as the nuclear charge is changed. The outer electron, which is still localized in a finite region near the nucleus before the system transforms into a well-defined resonance, is shifted notably into a far-distance region. The critical stability of the system near the bound-continuum limit is therefore dominated by the outer electron.

We develop an efficient numerical method to directly calculate the critical screening parameters for one-electron systems with Hulthén and Debye–Hückel screened Coulomb potentials (SCPs). Compared to indirect methods, which locate the critical screening parameters via searching the potential parameters with near-zero energy, the method developed in this work directly calculates the critical screening parameters as eigenvalues of a generalized eigenvalue problem. This feature allows us to simultaneously determine the critical parameters for bound states from low-lying excitation to high-lying Rydberg limit with high accuracy. The method is applied to SCPs to investigate the asymptotic behavior of critical screening parameters as the principal quantum number n approaches infinity. It has been shown that the critical screening parameters in Hulthén and Debye–Hückel potentials follow the 2n −2 and 4n −2/π asymptotic laws, respectively, and that the orbital angular momentum affects the higher-order coefficients linearly.

In order to establish the RT-LAMP detectionmethod of bluetongue virus (BTV), 4 specific LAMP primers were designed and synthesized by using the conservative sequence of the BTV VP7 genome published by GenBank. Through the synthesis of BTV artificial genes, the optimization of the reaction conditions of LAMP, the LAMP sensitivity experiment of BTV and the specific experiments, a preliminary method of BTV LAMP detection was established. The results showed that the BTV gene was successfully synthesized and the LAMP reaction conditions were optimized preliminarily, and the detection limit of the developed BTV LAMP method system could reach 43.7 copies/ ?L of target gene fragment, which could be detected with good sensitivity and specificity. In the experiment, the BTV virus could be amplified with a good specific amplification at 62? and 60min, and the results were negative after the amplification of DNA of Escherichia coli and Escherichia coli under the system constructed by the experiment.