分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present OmniUV, a multi-purpose simulation toolkit for space and ground VLBI observations. It supports various kinds of VLBI stations, including Earth (ground) fixed, Earth orbit, Lunar fixed, Lunar orbit, Moon-Earth and Earth-Sun Lagrange 1 and 2 points, etc. The main functionalities of this toolkit are: (1) Trajectory calculation; (2) Baseline uv calculation, by taking the vailability of each station into account; (3) Visibility simulation for the given uv distribution, source structure and system noise; (4) Image and beam reconstruction. Two scenarios, namely space VLBI network and wide field array, are presented as demonstrations of the toolkit applications in completely different scales. OmniUV is the acronym of "Omnipotent UV". We hope it could work as a general framework, in which various kinds of stations could be easily incorporated and the functionalities could be further extended. The toolkit has been made publicly available.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present VOLKS2, the second release of "VLBI Observation for transient Localization Keen Searcher". The pipeline aims at transient search in regular VLBI observations as well as detection of single pulses from known sources in dedicated VLBI observations. The underlying method takes the idea of geodetic VLBI data processing, including fringe fitting to maximize the signal power and geodetic VLBI solving for localization. By filtering the candidate signals with multiple windows within a baseline and by cross matching with multiple baselines, RFIs are eliminated effectively. Unlike the station auto spectrum based method, RFI flagging is not required in the VOLKS2 pipeline. EVN observation (EL060) is carried out, so as to verify the pipeline's detection efficiency and localization accuracy in the whole FoV. The pipeline is parallelized with MPI and further accelerated with GPU, so as to exploit the hardware resources of modern GPU clusters. We can prove that, with proper optimization, VOLKS2 could achieve comparable performance as auto spectrum based pipelines. All the code and documents are publicly available, in the hope that our pipeline is useful for radio transient studies.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We test the Emergent Gravity(EG) theory using the galaxy-galaxy lensing technique based on SDSS DR7 data. In the EG scenario, we do not expect color dependence of the galaxy sample in the 'apparent dark matter' predicted by EG, which is exerted only by the baryonic mass. If the baryonic mass is similar, then the predicted lensing profiles from the baryonic mass should be similar according to the EG, regardless of the color of the galaxy sample. We use the stellar mass of the galaxy as a proxy of its baryonic mass. We divide our galaxy sample into 5 stellar mass bins, and further classify them as red and blue subsamples in each stellar mass bin. If we set halo mass and concentration as free parameters, $\Lambda$CDM is favored by our data in terms of the reduced $\chi^2$ while EG fails to explain the color dependence of ESDs from the galaxy-galaxy lensing measurement.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The third Antarctic Survey Telescope array instrument at Dome A in Antarctica, the AST3-3 telescope, has been in commissioning from March 2021. We deployed AST3-3 at the Yaoan astronomical station in Yunnan Province for an automatic time-domain survey and follow-up observations with an optimised observation and protection system. The telescope system of AST3-3 is similar to that of AST3-1 and AST3-2, except that it is equipped with a 14K~$ \times$~10K QHY411 CMOS camera. AST3-3 has a field of view of $1.65^\circ \times 1.23^\circ$ and is currently using the $g$ band filter. During commissioning at Yaoan, AST3-3 aims to conduct an extragalactic transient survey, coupled with prompt follow-ups of opportunity targets. In this paper, we present the architecture of the AST3-3 automatic observation system. We demonstrate the data processing of observations by representatives SN 2022eyw and GRB 210420B.
分类: 生物学 >> 生物化学 提交时间: 2020-02-12
摘要: 最近,在中国武汉爆发了肺炎病例,由一种名为2019-CoV的新型冠状病毒引起。我们之前的研究中,根据中国深圳的12例2019-nCoV感染患者的临床特征,所有病例均患有肺炎,一半病例发展为急性呼吸窘迫综合征(ARDS)。本文中,我们针对这12例患者的血浆因子表达谱进行了研究。我们测试了2019-nCoV感染患者血浆中的48个因子的表达,其中38个因子与健康个体相比显着升高;2019-nCoV感染的重症患者血浆中的高细胞因子血症水平显著低于A型流感病毒H7N9感染患者,而略高于细菌感染患者。在这38个细胞因子中,有17个与2019-CoV病毒载量相关,其中的15个(M-CSF,IL-10,IFN-α2,IL-17,IL-4,IP-10,IL-7,IL-1受体拮抗剂,G-CSF,IL-12 (p40),IFN-γ,IL-1α,IL-2,HGF和PDGF-BB)与肺损伤Murray评分高度相关,可用来预测2019-nCoV感染患者的疾病严重程度。我们的研究结果表明,这15种高细胞因子可能是衡量2019-nCoV感染患者疾病严重程度的潜在生物标志物,影响这些信号传递介质的因子可能是针对新型2019-nCoV大流行的潜在药物。
分类: 生物学 >> 生物化学 提交时间: 2020-02-08
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。