Subjects: Biology >> Botany submitted time 2022-08-30 Cooperative journals: 《广西植物》
Abstract： How plants change functional traits to adapt to the environment has always been the focus of ecology. In order to explore the adaptive strategies of plant leaves in different succession stages of Maolan Karst forest, taking the dominant species in five different succession stages ( herb, shrub, shrub-arbor, arbor and climax community) in Maolan Nature Reserve as the research object, the leaf functional properties and soil physical and chemical properties of dominant plants in different succession stages were measured. The results showed that : ( 1 ) With the positive succession of vegetation, soil total nitrogen content ( STN ), soil organic matter content ( SOM ) and soil water content ( SWC ) gradually increased, soil total phosphorus content ( STP ) and soil total potassium content ( STK ) first increased and then decreased, and soil pH value showed a decreasing trend as a whole. ( 2 ) With the positive succession of vegetation, leaf area ( LA ), leaf dry matter content ( LDMC ), leaf thickness ( LT ) and leaf carbon content ( LCC ) gradually increased. On the contrary, specific leaf area ( SLA ) and leaf potassium content ( LKC ), leaf nitrogen content ( LNC ) increased first and then decreased, and leaf phosphorus content ( LPC ) decreased first and then increased.( 3 ) Redundant analysis showed that plants were mainly distributed in the environment of high soil pH and relatively low STK, STP, SWC, SOM and STN in the early succession stage. Plant leaves in the community took high SLA, LNC and LPC, and low LA, LDMC, LT and LWC. Plants in the late succession stage were mainly distributed in the environment of high soil moisture and nutrients. LDMC, LT, LA and LWC showed an upward trend compared with the early succession stage, and SLA, LNC and LPC showed a downward trend compared with the early succession stage. In conclusion, with the forward succession of vegetation, plants adapt to the environment by changing functional traits, and leaf functional traits change from open strategy in the early succession to conservative strategy in the late succession.
Subjects: Geosciences >> Geography submitted time 2022-01-26 Cooperative journals: 《干旱区研究》
Abstract：常年受西风影响的阿尔泰山是古气候研究的重点区域之一。为探究将阿尔泰山泥炭植物碳和氧同位素（13Ccell和18Ocell）的现代过程研究直接运用到百年或千年尺度古气候重建中的合理性，在可靠的210Pb、137Cs测年基础上，分析了19622017年哈巴河气象站冷季（10月次年4月）、暖季（59月）以及年尺度上气温、降水量、相对湿度与黑阳坡泥炭13Ccell、18Ocell的相关关系。结果显示：黑阳坡泥炭13Ccell与58月相对湿度显著负相关（r=-0.52，P），18Ocell与11月次年1月降水量显著正相关（r=0.49，P），黑阳坡泥炭13Ccell、18Ocell变化可以看作分别是58月相对湿度和11月次年1月降水量的代用指标。本研究为阿尔泰山泥炭-纤维素同位素记录的古气候解译提供了多年尺度的数据支撑，不仅丰富了我国关于泥炭地同位素现代器测的过程研究，也对研究区利用泥炭纤维素同位素开展长时间尺度上古气候定量化研究具有重要意义。
Subjects: Astronomy >> Astrophysical processes submitted time 2021-04-14 Cooperative journals: 《天文研究与技术》
Abstract： 2015年9月28日月基光学望远镜在其任务期间经历了唯一一次完整的月全食过程，为研究地球对太阳光的几何遮挡是否会对月面辐射环境产生影响提供了难得机遇。首先，利用月食期间连续长达2小时27分的CCD天文观测图像，统计分析了月食期间的宇宙线事件计数，发现月食期间宇宙线计数不存在明显变化，在30秒曝光时间内，宇宙线事件平均计数为129.27(±15.78)；其次，还分析了8月、10~12月采集的CCD暗场图像中的宇宙线事件计数，分别为119.92(±6.37)次、117.00(±10.90)次、118.61(±8.94)次、123.90(±8.92)次，在1误差分为内，与月食期间的宇宙线事件计数一致，说明地球对太阳的几何遮挡对月面辐射环境没有产生明显影响。最后，文章对以上结果进行了分析讨论。
Subjects: Astronomy >> Astrophysical processes submitted time 2020-05-06 Cooperative journals: 《天文研究与技术》
Abstract：为实现宽频带电磁环境实时测量，基于Roach II开发平台，开发设计了数字频谱仪，实时带宽10MHz−2GHz，动态范围达到55dB。首先，分析了数字频谱仪开发设计理念和模块参数设置考虑，实现快速扫描模式、脉冲监测模式测试功能。其次，通过频率响应、动态范围、线性度等关键指标测量及分析，并与商用频谱仪测量结果对比，确定该数字频谱分析仪具有相对准确的测试精度，可应用于射电望远镜台站宽带实时频谱监测及瞬态信号分析。
Subjects: Astronomy >> Astrophysical processes submitted time 2020-04-09 Cooperative journals: 《天文研究与技术》
Abstract：针对新疆奇台110m全向可动射电望远镜(Qi Tai Radio Telescope，QTT)台址电磁环境监测系统，开发监测及数据处理软件，实现电磁环境自动化监测与高效数据处理，具有重要的工程意义。本文依据电磁环境监测系统测量需求，分析了软件开发的主要功能及关键技术问题，设计了基于HDF5数据格式的数据存储流程，采用多仪器并行控制及多线程并行处理技术，基于Microsoft Visual Studio开发平台，实现自动化电磁环境监测与高效数据处理软件的开发，并应用于QTT台址电磁环境监测系统。
Subjects: Medicine, Pharmacy >> Preclinical Medicine submitted time 2017-12-07 Cooperative journals: 《南方医科大学学报》
Abstract： Objective To investigate the effect of stable knockdown of DNA methyltransferase 3b (DNMT3b) on the proliferation and apoptosis of bladder cancer cells. Methods Lentivirus expressing DNMT3b siRNA or the negative control siRNA was infected in human bladder cancer BIU-87 cells. MTT assay and flow cytometry were used to detect cell proliferation and apoptosis, respectively. The inhibitory effect of DNMT3b knockdown on xenograft tumors in nude mice was observed. Real-time PCR and Western blotting were carried out to investigate the expression level of cell apoptosis related genes. Methylation specific PCR was used to examine the methylation in the promoter region of the cell apoptosis related genes. Results The results of real-time PCR and Western blotting showed that DNMT3b mRNA and protein level were stably knocked down in BIU-87 cells. Stable DNMT3b knockdown suppressed BIU-87 cell growth and the tumor formation ability of the cells in nude mice. DNMT3b knockdown promoted the apoptosis of BIU-87 cells, increased the mRNA and protein expression of the cell growth and apoptosis related genes including DAPK, Bax and RASSF1A, and significantly decreased the methylation of these genes. Conclusion Stable DNMT3b knockdown can affect the methylation of the cell growth and apoptosis related genes to regulate their expression, which might be a possible mechanism for suppressed cell growth and enhanced apoptosis of BIU-87 cells.
Subjects: Astronomy >> Astrophysical processes submitted time 2017-09-26 Cooperative journals: 《天文研究与技术》
Abstract：交流伺服系统在工业控制领域得到了广泛应用，但在天文领域的应用仍处于初级阶段。以中法合作天文卫星(Space multi-band Variable Object Monitor, SVOM)的地面观测设备地基广角相机阵(Ground-based Wide-Angle Camera, GWAC)为研究平台，研究了交流伺服系统应用于望远镜转台控制的可行性。测试了望远镜的跟踪速度控制精度、赤经跟踪精度、最大角速度、最大角加速度、重复指向精度等关键技术指标。测试结果表明，和步进电机系统相比，交流伺服系统在低速控制上具有同样高的精度。在高速控制领域，其调速范围更宽，速度调节更快，运行更平稳，具有明显的优势。另外，还具有低噪声、大转矩、高性价比等优点。实验中还测定了交流伺服系统对Apogee CCD U9000、的干扰，结果表明，交流伺服系统对CCD的干扰很小，在可接受的范围内。总之，交流伺服系统完全可用于中小型天文望远镜的转台控制，特别适用于快速转动和指向的系统。
Hits
Hits
Downloads
Comment