[en] The perturbation theory is employed in present Letter to study the transition temperatures of rare-earth magnets. To simplify the model, it is assumed that the ground and first excited crystal-electric-field (CEF) levels are both nonmagnetic singlets, the Heisenberg exchange interaction is only comparable to the energy gap (Δ) between them, and other higher levels are well separated from the first excited one, so their contributions to the bulk magnetization are negligible in low-temperature region. By treating the Heisenberg exchange as a perturbation to the CEF interaction near the critical point, explicit expressions for the Curie and Neel temperatures (T_C and T_N) are derived in terms of the Heisenberg exchange constant (J), the gap Δ and the matrix element of the total spin moment in the ordering direction between the two lowest CEF levels. For completeness and to verify the correctness of the theory, we have also derived the analytical expressions for the magnetic moments at zero temperature for both rare-earth ferromagnet and antiferromagnet, the conditions for the magnetic orderings, and calculated the spontaneous magnetizations and magnetic specific heats at finite temperatures numerically for a hexagonal ferromagnetic Pr compound with the model. This approach can be generalized to real systems to evaluate their transition temperatures and to investigate the mechanisms of magnetic ordering

[en] Mean-field approximation and perturbation theory have been employed in present work to investigate the mechanism of ferromagnetic ordering in PrNi_3.9Cu_1.1. We find that its magnetic behaviors in ordering phase are mainly governed by the three lowest crystal-electric-field (CEF) levels; the indirect mixtures of the excited CEF levels into the ground state due to Heisenberg exchange helps to enhance the magnetic ordering at very low temperatures; but the new excited magnetic states formed by level mixtures impede the ordering near Curie temperature, thus play very crucial and subtle roles in modulating the magnetic process in the region and especially the phase transition

[en] The relationship between the threshold values of ion-temperature-gradient instabilities and the temperature parameters of plasmas is investigated analytically in slab and toroidal geometries separately. It is found that the threshold values increase rapidly when the ion temperature becomes much higher than the electron temperature. The change of the threshold vaues with respect to the ion temperature is quite similar for both geometric models. This finding is consistent with PLT observations. Furthermore, the analytical results also agree with those of the numerical calculations

[en] In dating Peking Man by fission track method, a series of problems have been met. These problems are: what solids can be used to date Peking Man; how can we ascertain mineral annealing degree made by Peking Man; how can we apply self- and extra-detector methods correctly in dating; how can we assess the reliability of measured age through statistical analysis. In this paper, the methods of solving the problems above and dating Peking Man (an age of 0.462 +- 0.045 myr) are described. (author)

[en] This chapter describes the use of an unconventional particle detector of area 10^-3 m², which has been in operation for over 10⁸ years, to look for grand unified theory (GUT) monopoles. Mechanisms which could reduce the significance of the mica result are examined. Topics considered include track etch detectors, mica as a detector of GUT monopoles, track fading, the collisional disruption of the monopole-nucleus system, the catalysis of baryon decay, the reduction of nucleus capture cross sections, diamagnetic repulsion, and monopole carrying positive electric charge. It is concluded that the only significant challenge to the mica flux limit comes from the possibility of a large probability for forming proton-monopole states

[en] Objective: To evaluate the therapeutic effects of internal fixation with support plates and cannulated screws via the posterolateral approach on supination external rotation stage IV ankle fracture. Methods: Eighty-five patients with SER-IV° ankle fracture and large posterior malleolar fracture treated from June 2016 to June 2018 in our hospital, were randomly divided into a support plate group (n=47) and a cannulated screw group (n=38). The treatment outcomes were compared regarding surgical time, amount of bleeding, time of fracture healing, postoperative complications, as well as the American Orthopedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Score and excellent rate one year later. Results: The surgical time and intraoperative blood loss of cannulated screw group were significantly lower than those of support plate group (P<0.05). There were four cases of posterior lateral incision redness complicated with obvious bloody exudation in support plate group on the postoperative 2nd day. One case developed into superficial incision infection subsequently, and one case suffered from deep infection. After dressing and treatment with sensitive antibiotics, stitch removal was delayed, and primary healing was obtained. In cannulated screw group, there were two cases of posterior lateral incision redness complicated with obvious bloody exudation on the postoperative 3rd day, without skin incision infection. One case had cannulated screw loosening two months after surgery, and the posterior malleolar fracture block was slightly displaced. The incidence of surgical complications in support plate and cannulated screw groups were 8.51% and 7.89%, respectively (P>0.05). The AOFAS scores of cannulated screw ((81.71 ± 12.39) points) and support plate groups ((86.62 ± 10.12) points) were significantly different (P<0.05). Conclusion: For patients with posterior malleolar fracture or osteoporosis, fixation using support plate is recommended. Cannulated screw fixation is suitable for for patients with poor conditions of skin soft tissues or basic diseases such as diabetes intolerant to long surgery. (author)

[en] The main fields of research and achievements in the study of solid state nuclear track detectors (SSNTD) in the Institute of Atomic Energy of the Academy of Sciences of China are presented. The contents include (1) Study of parameters of SSNTD's. A method to calibrate the detection efficiencies of SSNTD's for fission fragments by counting correlated fission fragments has been proposed and used. (2) Fast neutron spectrum and dose measurements. The threshold energy (0.3 Mev) and the detection efficiency curve of polycarbonate foil for 0.085 to 18 Mev neutrons by recoil tracks have been calibrated and other methods are used. (3) Studies of nuclear fission. The angular distributions of fission fragments have been studied with SSNTD's. Non-anomalous angular distributions and obvious structures have been observed near threshold energy of ²³⁸U(n,2n'f) and ²³⁸U(n,f) reactions respectively. (4) Applications in geology, archaeology and analytic chemistry. Muscovite mica, tektites from Hainan Island in China and Peking Man have been dated by fission track method. The contents and microscopic distributions of uranium in minerals and water have been studied. (5) Meteorite study. The track densities and fission track age (3.9 +- 0.3 byr) of Jilin Meteorite were measured and discussed. (author)

[en] Highlights: •We designed the cryogenic experiment to test the Nb₃Sn superconducting magnet performance in the low temperature. •We measured the pressure drop in CICC of Nb₃Sn superconducting magnet at 5 K. •We corrected Katheder’s formula and given the corrected correlation. •The curve of per meter pressure drop in the CICC of Nb₃Sn superconducting magnet was given. -- Abstract: In order to test the performance of experimental advanced superconducting tokamak (EAST) central solenoid (CS) model coil, which was made by the cable-in-conduit conductor using Nb₃Sn strands and a 316 L stainless steel jacket, a cryogenic experiment system was designed. The experimental results showed that the superconducting magnet was cooled down to 5 K, which could meet the test requirements successfully. Meanwhile, we measured the pressure drop in CICC of Nb₃Sn superconducting magnet under the circulating mode of forced flow cooling which used supercritical helium as coolant compared with the result calculated by the Katheder fraction factor correlation, it showed that calculated pressure drop underestimates the experimental data. We corrected the Katheder correlation and compared with the experimental data, it proved that the corrected correlation is much more suitable for the kind of CICC of Nb₃Sn superconducting magnet

[en] We have studied the fission of nuclei with 36< or =Z< or =79 produced in interactions of 1A GeV Au nuclei in CR-39 plastic track detectors. The energy released is typical of fission at lower energies, and the transverse momentum transferred to fissioning species is consistent with a peripheral interaction. The distributions of heavy-to-light fragment mass ratios are very broad, as in fission of nuclei with 28< or =Z< or =83 by 600 MeV and 1 GeV protons

[en] Investigation on bubble detectors started in China in 1989. Five types of bubble detectors have been developed, with LET thresholds ranging from 0.05 to 6.04 MeV mg^-1 cm² at 25 deg. C. The neutron response of bubble detectors made with freon-12 has been investigated with mono-energetic neutrons from 20 keV to 19 MeV. Its effective threshold energy for neutron detection is ∼100 keV at 28 deg. C. The response above this threshold is ∼1.5 x 10^-4 (bubble cm^-2)/(n cm^-2). Bubble detectors are unique not only for neutron dosimetry but also for monitoring and identifying high-energy heavy ions such as cosmic radiation in the space. High-energy heavy ion tracks in large size bubble detectors have been investigated in cooperation with scientists in Japan. The key parameter behind the thresholds of bubble detectors for track registration is the critical rate of energy loss. Three approaches to identify high-energy heavy ions with bubble detectors are suggested. (authors)