分类： 生物学 >> 植物学 提交时间： 2018-07-05 合作期刊: 《干旱区科学》
摘要： Climate change is shifting the amount and frequency of precipitation in many regions, which is expected to affect seedling recruitment across ecosystems. However, the combined effects of precipitation amount and frequency on seedling recruitment remain largely unknown. An understanding of the effects of precipitation amount and frequency and their interaction on seedling emergence and growth of typical desert plants is vital for managing populations of desert plants. We conducted two experiments to study the effects of variation in precipitation on Reaumuria soongarica (Pall.) Maxim. First, greenhouse experiments were conducted to examine the effects of three precipitation amount treatments (ambient, +30%, and 30%) and two precipitation frequency treatments (ambient and 50%) on seedling emergence. Second, the morphological responses of R. soongarica to changes in precipitation amount and frequency were tested in a controlled field experiment. Stage-specific changes in growth were monitored by sampling in different growth seasons. Our results showed that precipitation amount significantly affected germination, seedling emergence, and growth of R. soongarica, and there was a larger effect with decreased precipitation frequency compared with ambient. Germination and seedling emergence increased as precipitation increased under the same frequency of precipitation. The highest emergence percentage was obtained with a 30% increase in precipitation amount and a 50% reduction in precipitation frequency. Compared with ambient precipitation, a 30% increase in precipitation amount increased above- and below-ground biomass accumulation of R. soongarica during the growth season. A decrease of 30% in precipitation amount also resulted in an increase in below-ground biomass and root/shoot ratio in the early stages of the growth season, however, above- and below-ground biomass showed the opposite results at the end of the growth season, with larger effects on above-ground than below-ground biomass under decreased precipitation frequency. When precipitation frequency decreased by 50%, values of all growth traits increased for a given amount of precipitation. We concluded that precipitation frequency may be as important as precipitation amount to seedling emergence and growth of R. soongarica, and that understanding the effects of precipitation variability on seedling recruitment requires the integration of both precipitation amount and frequency. In particular, the combination of a 30% increase in precipitation amount and 50% reduction in precipitation frequency increased the emergence and growth of seedlings, suggesting that alteration of amount and frequency of precipitation caused by climate change may have significant effects on seedling recruitment of R. soongarica.
分类： 生物学 >> 动物学 提交时间： 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要： A new skull of Urmiatherium intermedium (Bovidae, Artiodactyla) from the Linxia Basin, Gansu Province is described here. U. intermedium is a large Late Miocene bovid with an odd-looking horn apparatus, consisting of a pair of degenerate, closely situated horn-cores, and a large area of exostoses on the frontal and the parietal bones. Plenty of skulls, teeth, and bone fragments of U. intermedium have been reported from North China, but the skull to be described is the first discovery from the Linxia Basin, expanding the geographic distribution of U. intermedium to the northeast edge of the Tibetan Plateau. Although Urmiatherium is generally thought to be closely related to Plesiaddax, Hezhengia, Tsaidamotherium, and some other Late Miocene “ovibovines”, the phylogenetic position of Urmiatherium is still in debate. The distribution of Urmiatherium is wide, spanning from Iran to North China. Urmiatherium seldom accompanies with other Late Miocene “ovibovines” in North China, but is accompanied by other bovids like Sinotragus.
分类： 地球科学 >> 地质学 提交时间： 2017-08-11 合作期刊: 《古脊椎动物学报》
摘要： A new skull of Urmiatherium intermedium (Bovidae, Artiodactyla) from the Linxia Basin, Gansu Province is described here. U. intermedium is a large Late Miocene bovid with an odd-looking horn apparatus, consisting of a pair of degenerate, closely situated horn-cores, and a large area of exostoses on the frontal and the parietal bones. Plenty of skulls, teeth, and bone fragments of U. intermedium have been reported from North China, but the skull to be described is the first discovery from the Linxia Basin, expanding the geographic distribution of U. intermedium to the northeast edge of the Tibetan Plateau. Although Urmiatherium is generally thought to be closely related to Plesiaddax, Hezhengia, Tsaidamotherium, and some other Late Miocene “ovibovines”, the phylogenetic position of Urmiatherium is still in debate. The distribution of Urmiatherium is wide, spanning from Iran to North China. Urmiatherium seldom accompanies with other Late Miocene “ovibovines” in North China, but is accompanied by other bovids like Sinotragus. 报道并描述了一件来自甘肃临夏盆地的中间乌米兽(Urmiatherium intermedium)头骨化石新材料，该材料产自柳树组上部，属于晚中新世晚期杨家山动物群。中间乌米兽是一种大型的晚中新世牛科动物，角心特化，短且呈薄板状，并且在基部相互靠近。在角心前后方的额骨和顶骨上，发育大片赘生骨疣，这些骨疣与角心一起，合称角器。20世纪初，步林报道了中国北方晚中新世地层中的大量中间乌米兽化石，包括产自山西保德和甘肃庆阳的二十多件头骨以及很多破碎的齿列和骨骼。本文报道的乌米兽头骨化石是乌米兽在甘肃临夏盆地的首次发现，将其在中国北方的分布向西扩展到了青藏高原东北缘地带。乌米兽被普遍认为与近旋角羊(Plesiaddax)、和政羊(Hezhengia)和柴达木兽(Tsaidamotherium)等晚中新世“麝牛类”牛科动物具有较近的亲缘关系，但其系统发育地位仍存有争议。相比其他晚中新世“麝牛类”牛科动物，乌米兽的分布较广，从伊朗至中国北方都有分布，但它鲜与其他晚中新世“麝牛类”牛科动物伴生。在临夏盆地，与其伴生的牛科动物目前仅发现中华羚(Sinotragus)一种。
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： A high luminosity Circular Electron Positron Collider (CEPC) as a Higgs Factory will be helpful to the precision measurement of the Higgs mass. The signal-background interference effect is carefully studied for the Higgs diphoton decay mode in the associated Z boson production at the future e+e− colliders at energy 246GeV. The mass shifts go up from about 20MeV to 50MeV for the experimental mass resolution ranging from 0.8GeV to 2GeV.
分类： 生物学 >> 生物物理学 提交时间： 2016-05-15
摘要： Background: Bladder cancer (BC) is the fifth most common malignancy worldwide. The expression levels of microRNAs (miRNAs) in urine samples of BC patients have been demonstrated to be different from healthy people. Several studies focusing on the diagnostic value of urinary miRNAs for BC detection have been reported. The aim of this meta-analysis was to access the overall diagnostic accuracy comprehensively and quantitatively. Methods: PubMed, Embase, Web of Science, the Cochrane Library, and CNKI were searched without language restrictions for studies about the diagnostic value of miRNAs for BC. The pooled sensitivity, specificity, positive and negative likelihood ratios (PLR and NLR, respectively), diagnostic odds ratio (DOR) were calculated using the random effects model. The summary receiver operating characteristic (SROC) curve was also generated and the area under the curve (AUC) was also reckoned to assess the diagnosis accuracy. Besides, Chi-square test and I-2 test were used to assess the heterogeneity between studies. Publication bias was evaluated by the Deeks' funnel plot asymmetry test. Results: Fourteen studies were included in this meta-analysis, with a total of 1,128 BC patients and 1,057 matched controls. The overall sensitivity, specificity, PLR, NLR and DOR of urinary miRNAs for the diagnosis of BC were 0.71 (95% CI: 0.67-0.75), 0.75 (95% CI: 0.70-0.79), 2.8 (95% CI: 2.3-3.4), 0.39 (95% CI: 0.33-0.46) and 7 (95% CI: 5-10), respectively. The area under the SROC curve was 0.79. Subgroup analyses suggested that the ethnicity and miRNA profiling had an obvious influence on the diagnostic accuracy. Conclusion: The current analysis suggested that urinary miRNA panels may be a promising noninvasive biomarker in the diagnosis of BC.
分类： 核科学技术 >> 粒子加速器 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
LI Yi-Ding
ZHANG Xiao-Ding
WEI Tao
ZHAO Liang-Chao
HE Xiao-Zhong
MA Chao-Fan
YANG Guo-Jun
JIANG Xiao-Guo
摘要： Differing from radiography without lens system, the high-energy proton radiography (PRAD) uses Zumbro lens system to focus the penetrating protons. Since the Zumbro lens system is able to limit the range of multiple Coulomb scattering angles of the protons, the low-energy PRAD with Zumbro lens system is also feasible, although the attenuation of probing protons in the object is negligible. Low-energy PRAD is superior to the high-energy PRAD for diagnosing the objects of small thicknesses. To verify the imaging principle of Zumbro lens system, 11 MeV PRAD experiments were performed at the China Academy of Engineering Physics (CAEP) recently. The experiment results demonstrated that this 11 MeV PRAD was able to radiograph objects of area density less than 2.7�10-2 g/cm2 and the area density discrepancy less than 2.3% could be distinguished.
分类： 核科学技术 >> 粒子加速器 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
ZHANG Xiao-Ding
LI Yi-Ding
YANG Guo-Jun
WEI Tao
HE Xiao-Zhong
LONG Ji-Dong
JIANG Xiao-Guo
MA Chao-Fan
ZHAO Liang-Chao
YANG Xing-Lin
ZHANG Zhuo
WANG Yuan
LI Wei-Feng
SHI Jin-Shui
摘要： Proton radiography experiment with a Zumbro lens system was carried out on an 11 MeV proton cyclotron. The experimental results show that the image blurring is improved markedly. Clear images and good spatial resolution of the density step edges are obtained, which is important for hydrotest experiments, and the spatial resolution can achieve 100 m.
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