分类： 天文学 >> 天文仪器与技术 提交时间： 2024-04-18 合作期刊: 《天文技术与仪器（英文）》
摘要：Strong atmospheric turbulence reduces astronomical seeing, causing speckle images acquired by groundbased solar telescopes to become blurred and distorted. Severe distortion in speckle images impedes image phase deviation in the speckle masking reconstruction method, leading to the appearance of spurious imaging artifacts. Relying only on linear image degradation principles to reconstruct solar images is insufficient. To solve this problem, we propose the multiframe blind deconvolution combined with non-rigid alignment (MFBD-CNRA) method for solar image reconstruction. We consider image distortion caused by atmospheric turbulence and use non-rigid alignment to correct pixel-level distortion, thereby achieving nonlinear constraints to complement image intensity changes. After creating the corrected speckle image, we use the linear method to solve the wavefront phase, obtaining the target image. We verify the effectiveness of our method results, compared with others, using solar observation data from the 1 m new vacuum solar telescope (NVST). This new method successfully reconstructs high-resolution images of solar observations with a Fried parameter r0 of approximately 10 cm, and enhances images at high frequency. When r0 is approximately 5 cm, the new method is even more effective. It reconstructs the edges of solar graining and sunspots, and is greatly enhanced at mid and high frequency compared with other methods. Comparisons confirm the effectiveness of this method, with respect to both nonlinear and linear constraints in solar image reconstruction. This provides a suitable solution for image reconstruction in ground-based solar observations under strong atmospheric turbulence.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is the most
sensitive radio telescope for pulsar observations. We make polarimetric
measurements of a large number of faint and distant pulsars using the FAST. We
present the new measurements of Faraday rotation for 134 faint pulsars in the
Galactic halo. Significant improvements are also made for some basic pulsar
parameters for 15 of them. We analyse the newly determined rotation measures
(RMs) for the Galactic magnetic fields by using these 134 halo pulsars,
together with previously available RMs for pulsars and extragalactic radio
sources and also the newly determined RMs for another 311 faint pulsars which
are either newly discovered in the project of the Galactic Plane Pulsar
Snapshot (GPPS) survey or previously known pulsars without RMs. The RM
tomographic analysis in the first Galactic quadrant gives roughly the same
field strength of around 2~$\mu$G for the large-scale toroidal halo magnetic
fields. The scale height of the halo magnetic fields is found to be at least
2.7$\pm$0.3~kpc. The RM differentiation of a large number of pulsars in the
Galactic disk in the Galactic longitude range of $26^{\circ}
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We presented the multiwavelength analysis of a heavily obscured active galactic nucleus (AGN) in NGC 449. We first constructed a broadband X-ray spectrum using the latest NuSTAR and XMM-Newton data. Its column density ($\simeq 10^{24} \rm{cm}^{-2}$) and photon index ($\Gamma\simeq 2.4$) were reliably obtained by analyzing the broadband X-ray spectrum. However, the scattering fraction and the intrinsic X-ray luminosity could not be well constrained. Combined with the information obtained from the mid-infrared (mid-IR) spectrum and spectral energy distribution (SED) fitting, we derived its intrinsic X-ray luminosity ($\simeq 8.54\times 10^{42} \ \rm{erg\ s}^{-1}$) and scattering fraction ($f_{\rm{scat}}\simeq 0.26\%$). In addition, we also derived the following results: (1). The mass accretion rate of central AGN is about $2.54 \times 10^{-2} \rm{M}_\odot\ \rm{yr}^{-1}$, and the Eddington ratio is $8.39\times 10^{-2}$; (2). The torus of this AGN has a high gas-to-dust ratio ($N_{\rm H}/A_{\rm V}=8.40\times 10^{22}\ \rm{cm}^{-2}\ \rm{mag}^{-1}$); (3). The host galaxy and the central AGN are both in the early stage of co-evolution.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is the most
sensitive radio telescope for pulsar observations. We make polarimetric
measurements of a large number of faint and distant pulsars using the FAST. We
present the new measurements of Faraday rotation for 134 faint pulsars in the
Galactic halo. Significant improvements are also made for some basic pulsar
parameters for 15 of them. We analyse the newly determined rotation measures
(RMs) for the Galactic magnetic fields by using these 134 halo pulsars,
together with previously available RMs for pulsars and extragalactic radio
sources and also the newly determined RMs for another 311 faint pulsars which
are either newly discovered in the project of the Galactic Plane Pulsar
Snapshot (GPPS) survey or previously known pulsars without RMs. The RM
tomographic analysis in the first Galactic quadrant gives roughly the same
field strength of around 2~$\mu$G for the large-scale toroidal halo magnetic
fields. The scale height of the halo magnetic fields is found to be at least
2.7$\pm$0.3~kpc. The RM differentiation of a large number of pulsars in the
Galactic disk in the Galactic longitude range of $26^{\circ}
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We presented the multiwavelength analysis of a heavily obscured active galactic nucleus (AGN) in NGC 449. We first constructed a broadband X-ray spectrum using the latest NuSTAR and XMM-Newton data. Its column density ($\simeq 10^{24} \rm{cm}^{-2}$) and photon index ($\Gamma\simeq 2.4$) were reliably obtained by analyzing the broadband X-ray spectrum. However, the scattering fraction and the intrinsic X-ray luminosity could not be well constrained. Combined with the information obtained from the mid-infrared (mid-IR) spectrum and spectral energy distribution (SED) fitting, we derived its intrinsic X-ray luminosity ($\simeq 8.54\times 10^{42} \ \rm{erg\ s}^{-1}$) and scattering fraction ($f_{\rm{scat}}\simeq 0.26\%$). In addition, we also derived the following results: (1). The mass accretion rate of central AGN is about $2.54 \times 10^{-2} \rm{M}_\odot\ \rm{yr}^{-1}$, and the Eddington ratio is $8.39\times 10^{-2}$; (2). The torus of this AGN has a high gas-to-dust ratio ($N_{\rm H}/A_{\rm V}=8.40\times 10^{22}\ \rm{cm}^{-2}\ \rm{mag}^{-1}$); (3). The host galaxy and the central AGN are both in the early stage of co-evolution.
分类： 生物学 >> 生物化学 提交时间： 2020-02-08
Yingxia Liu
Yang Yang
Cong Zhang
Fengming Huang
Fuxiang Wang
Jing Yuan
Zhaoqin Wang
Jingxiu Li
Jianming Li
Cheng Feng
Zheng Zhang
Lifei Wang
Ling Peng
Li Chen
Yuhao Qin
Dandan Zhao
Shuguang Tan
Lu Yin
Jun Xu
Congzhao Zhou
摘要： 新型冠状病毒（2019-nCoV）自2019年12月在湖北省武汉市爆发，并迅速传播到中国多地及其他国家。在本研究中，我们报告了来自中国深圳早期的2019-nCoV感染患者的流行病学、临床指标、生化指标和影像学特征，以及可用于预测疾病严重程度的潜在生物标记物。所有12例2019-nCoV感染的肺炎患者均发展为肺炎，其中一半患者进一步发展为急性呼吸窘迫综合征（acute respiratory distress syndrome，ARDS）。最常见的实验室检测生化指标异常是低白蛋白（albumine，ALB）血症、淋巴细胞（lymphocytes，LYM）计数减少，淋巴细胞百分比和中性粒细胞（neutrophils，NEU）百分比降低，C反应蛋白（C-reactive protein，CRP）和乳酸脱氢酶（lactate dehydrogenase，LDH）水平升高，以及CD8细胞计数降低。从患者呼吸道特别是下呼吸道检测到的2019-nCoV病毒滴度与肺部疾病的严重程度正相关。 ALB、LYM、LYM（%）、LDH、NEU（％）和CRP的水平与急性肺损伤程度高度相关。年龄、病毒滴度、肺损伤评分和血液生化指标：ALB、CRP、LDH、LYM（%）、LYM和NEU（%）可能是疾病严重程度的预测指标。此外， 2019-nCoV感染患者的血浆血管紧张素II水平显着升高，并且与病毒滴度和肺损伤程度线性相关。我们的研究结果提供了多种潜在的可用于诊断的生物标志物， 并提出了血管紧张素 II受体阻滞剂（angiotensin II receptor blocker，ARB）药物或可作为治疗2019-nCoV感染的潜在药物进行深入研究。
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