分类: 核科学技术 >> 核爆炸工程 提交时间: 2024-02-08
摘要: In high-altitude nuclear detonations, the proportion of pulsed X-ray energy can exceed 70%, making it a specific monitoring signal for such events. These pulsed X-rays can be captured using a satellite-borne X-ray detector following atmospheric transmission. To quantitatively analyze the effects of different satellite detection altitudes, burst heights, and transmission angles on the physical processes of X-ray transport and energy fluence, we developed an atmospheric transmission algorithm for pulsed X-rays from high-altitude nuclear detonations based on scattering correction. The proposed method is an improvement over the traditional analytical method that only computes direct-transmission X-rays. The traditional analytical method exhibits a maximum relative error of 67.79% compared with the Monte Carlo method. Our improved method reduces this error to within 10% under the same conditions, even reaching 1% in certain scenarios. Moreover, its computation time is 48000 times faster than that of the Monte Carlo method. These results have important theoretical significance and engineering application value for designing satellite-borne nuclear detonation pulsed X-ray detectors, inverting nuclear detonation source terms, and assessing ionospheric effects.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The East Asian very-long-baseline interferometry (VLBI) Network (EAVN) is a rapidly evolving international VLBI array that is currently promoted under joint efforts among China, Japan, and Korea. EAVN aims at forming a joint VLBI Network by combining a large number of radio telescopes distributed over East Asian regions. After the combination of the Korean VLBI Network (KVN) and the VLBI Exploration of Radio Astrometry (VERA) into KaVA, further expansion with the joint array in East Asia is actively promoted. Here we report the first imaging results (at 22 and 43 GHz) of bright radio sources obtained with KaVA connected to Tianma 65-m and Nanshan 26-m Radio Telescopes in China. To test the EAVN imaging performance for different sources, we observed four active galactic nuclei (AGN) having different brightness and morphology. As a result, we confirmed that Tianma 65-m Radio Telescope (TMRT) significantly enhances the overall array sensitivity, a factor of 4 improvement in baseline sensitivity and 2 in image dynamic range compared to the case of KaVA only. The addition of Nanshan 26-m Radio Telescope (NSRT) further doubled the east-west angular resolution. With the resulting high-dynamic-range, high-resolution images with EAVN (KaVA+TMRT+NSRT), various fine-scale structures in our targets, such as the counter-jet in M87, a kink-like morphology of the 3C273 jet and the weak emission in other sources, are successfully detected. This demonstrates the powerful capability of EAVN to study AGN jets and to achieve other science goals in general. Ongoing expansion of EAVN will further enhance the angular resolution, detection sensitivity and frequency coverage of the network.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Rare-earth ions doped crystals are of great significance for micro-sensing and quantum information, whilst the ions in the crystals emit light with spontaneous partial polarization, which is, though believed to be originated from the crystal lattice structure, still lacking a deterministic explanation that can be tested with quantitative accuracy. We report the experimental evidence showing the profound physical relation between the polarization degree of light emitted by the doped ion and the lattice symmetry, by demonstrating, with unprecedented precision, that the lattice constant ratio c/a directly quantifies the macroscopic effective polar angle of the electric and magnetic dipoles, which essentially determines the linear polarization degree of the emission. Based on this discovery, we further propose a pure optical technology to identify the three-dimensional orientation of a rod-shaped single microcrystal using the polarization-resolved micro-spectroscopy. Our results, revealing the physical origin of light polarization in ion-doped crystals, open the way towards on-demand polarization control with crystallography, and provide a versatile platform for polarization-based microscale sensing in dynamical systems.
分类: 生物学 >> 生态学 提交时间: 2017-11-17
摘要: Interleukin-15 (IL-15) is a pleiotropic cytokine and a member of the four α-helix bundle family of cytokines which include IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21. IL-15 exhibits a broad biological activity and induces the differentiation and proliferation of T, B and natural killer (NK) cells. In this study, a DNA fragment containing the mature human IL-15 sequence was cloned into pPICZaA vector, generating a fusion protein with the alpha factor signal sequence in the Nterminus and 6×His as well as c-Myc tags in the C-terminus. The resulting plasmid was integrated into the genome of Pichia pastoris strain X-33. Recombinant yeast transformants with high-level recombinant human IL-15 (rhIL-15) production were identified, which secrete as much as 75 mg/L rhIL-15 after 3 days of induction by methanol. The rhIL-15 was purified by Ni+-NTA affinity chromatography, followed by DEAE anion exchange, yielding over 95% highly purified rhIL-15. Mass spectrometry and MALDI-TOF-TOF analysis showed the purified rhIL-15 had larger molecular weights than expected, due to different degrees of N-linked glycosylation. The biological activity of the rhIL-15 proteins was measured by its ability to enhance cellular proliferation of CTLL-2 and NK cells. The results demonstrate that the experimental procedure we have reported here can produce a large amount of active recombinant human IL-15 from Pichia pastoris.
分类: 生物学 >> 生态学 提交时间: 2017-11-17
摘要: Immunodeficient mice engrafted with either normal or cancerous human cells are widely used in basic and translational research. In particular, NOD/SCID/IL2rg−/− mice can support the growth of various types of human cancer cells. However, the hairs of these mice interfere with the observation and imaging of engrafted tissues. Therefore, novel hairless strains exhibiting comparable immunodeficiency would be beneficial. Recently, the CRISPR/Cas9 system has been used for efficient multiplexed genome editing. In the present study, we generated a novel strain of nude NOD/SCID/IL2rg−/− (NSIN) mice by knocking out Foxn1 using the CRISPR/Cas9 system from NOD/SCID/IL2rg−/− (NSI) mice. NSIN mice were deficient in B, T, and NK cells, which showed impaired T cell reconstitution and thymus regeneration after allogeneic bone marrow nucleated cell transplantation, and exhibited improved capacities of grafting both leukemic and solid tumor cells compared with NSI, NOG and NDG mice. Moreover, NSIN mice facilitated the monitoring and in vivo imaging of both leukemia and solid tumors. Therefore, our NSIN mice provide a new platform for xenograft mouse models in basic and translational research.
分类: 物理学 >> 核物理学 提交时间: 2016-09-14
摘要: Following the discovery of the Higgs boson at LHC, new large colliders are being studied by the international high-energy community to explore Higgs physics in detail and new physics beyond the Standard Model. In China, a two-stage circular collider project CEPC-SPPC is proposed, with the first stage CEPC (Circular Electron Positron Collier, a so-called Higgs factory) focused on Higgs physics, and the second stage SPPC (Super Proton-Proton Collider) focused on new physics beyond the Standard Model. This paper discusses this second stage.