分类: 农、林、牧、渔 >> 土壤学 提交时间: 2024-03-13 合作期刊: 《干旱区科学》
摘要: In the Loess Plateau of China, land-use pattern is a major factor in controlling underlying biological processes. Additionally, the process of land-use pattern was accompanied by abandoned lands, potentially impacting soil microbe. However, limited researches were conducted to study the impacts of land-use patterns on the diversity and community of soil microorganisms in this area. The study aimed to investigate soil microbial community diversity and composition using high-throughput deoxyribonucleic acid (DNA) sequencing under different land-use patterns (apricot tree land, apple tree land, peach tree land, corn land, and abandoned land). The results showed a substantial difference (P<0.050) in bacterial alpha-diversity and beta-diversity between abandoned land and other land-use patterns, with the exception of Shannon index. While fungal beta-diversity was not considerably impacted by land-use patterns, fungal alpha-diversity indices varied significantly. The relative abundance of Actinobacteriota (34.90%), Proteobacteria (20.65%), and Ascomycota (77.42%) varied in soils with different land-use patterns. Soil pH exerted a dominant impact on the soil bacterial communities' composition, whereas soil available phosphorus was the main factor shaping the soil fungal communities' composition. These findings suggest that variations in land-use pattern had resulted in changes to soil properties, subsequently impacting diversity and structure of microbial community in the Loess Plateau. Given the strong interdependence between soil and its microbiota, it is imperative to reclaim abandoned lands to maintain soil fertility and sustain its function, which will have significant ecological service implications, particularly with regards to soil conservation in ecologically vulnerable areas.
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-26
摘要: Two cryogenic systems of high purity germanium detector, liquid nitrogen and mechanical coolers, are expound, together with explanations of merits and demerits for each kind of cooling methods. The resolutions of detector to the characteristic lines of 152Eu under different cooling conditions are studied. The laboratory results indicate that the mechanical cooler (X-Cooler II) is an ideal replacement candidate for the liquid nitrogen cooler that is being utilized by BEMS at BEPC-II.
分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Field Programmable Gate Array (FPGA), combined with ARM (Advanced RISC Machines) is increasingly employed in the portable data acquisition (DAQ) system for nuclear experiments to reduce the system volume and achieve powerful and multifunctional capacity. High-speed data transmission between FPGA and ARM is one of the most challenging issues for system implementation. In this paper, we propose a method to realize the high-speed data transmission by using the FPGA to acquire massive data from FEE (Front-end electronics) and send it to the ARM whilst the ARM to transmit the data to the remote computer through the TCP/IP protocol for later process. This paper mainly introduces the interface design of the high-speed transmission method between the FPGA and the ARM, the transmission logic of the FPGA, and the program design of the ARM. The theoretical research shows that the maximal transmission speed between the FPGA and the ARM through this way can reach 50 MB/s. In a realistic nuclear physics experiment, this portable DAQ system achieved 2.2 MB/s data acquisition speed.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: Using DFT/TDDFT methods, the excited-state lifetimes of Ru(II) polypyridyl complexes were computed accurately and the reason of Ru(II) polypyridyl complexes with long excited-state lifetimes was explained by the electron‑transfer distances and HOMO-LUMO gaps. Finally, the photovoltaic conversion efficiencies of complexes were predicted using DFT and docking methods. This work has provided methods of predicting the excited-state lifetimes and photovoltaic conversion efficiencies of Ru(II) polypyridyl complexes
分类: 计算机科学 >> 计算机科学技术其他学科 提交时间: 2020-06-09
摘要: The chest X-Ray (CXR) is the one of the most common clinical exam used to diagnose thoracic diseases and abnormalities. The volume of CXR scans generated daily in hospitals is huge. Therefore, an automated diagnosis system that is able to save the effort of doctors is of great value. At present, the applications of artificial intelligence in CXR diagnosis usually use pattern recognition to classify the scans. However, such methods rely on labeled databases. They are costly and usually have a high error rate. In this work, we built a database containing more than 12,000 CXR scans and radiological reports, and developed a model based on deep convolutional neural network and recurrent network with attention mechanism. The model learns features from the CXR scans and the associated raw radiological reports directly; no additional labeling required. The model provides automated recognition of given scans and generation of impression. The quality of the generated impression was evaluated with both the CIDEr scores and by radiologists as well. The CIDEr scores were found to be around 5.8 on average for the testing dataset. Further blind evaluation suggested a comparable performance against radiologists.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-11
摘要: In plants, auxin signalling is initiated by the auxin-promoted interaction between the auxin receptor TIR1, an E3 ubiquitin ligase, and the Aux/IAA transcriptional repressors, which are subsequently degraded by the proteasome. Gain-of-function mutations in the highly conserved domain II of Aux/IAAs abolish the TIR1-Aux/IAA interaction and thus cause an auxin-resistant phenotype. Here we show that peptidyl-prolyl isomerization of rice OsIAA11 catalysed by LATERAL ROOTLESS2 (LRT2), a cyclophilin-type peptidyl-prolyl cis/trans isomerase, directly regulates the stability of OsIAA11. NMR spectroscopy reveals that LRT2 efficiently catalyses the cis/trans isomerization of OsIAA11. The lrt2 mutation reduces OsTIR1-OsIAA11 interaction and consequently causes the accumulation of a higher level of OsIAA11 protein. Moreover, knockdown of the OsIAA11 expression partially rescues the lrt2 mutant phenotype in lateral root development. Together, these results illustrate cyclophilin-catalysed peptidyl-prolyl isomerization promotes Aux/IAA degradation, as a mechanism regulating auxin signalling.
分类: 心理学 >> 社会心理学 提交时间: 2023-03-28 合作期刊: 《心理科学进展》
摘要: 工作记忆训练(Working Memory Training, WMT)诱发神经可塑性, 但其具体机制尚不明晰。为探索WMT改变正常人群大脑功能的时空特性, 以“扩展的智力顶额整合理论”和“神经效率假说”为依据, 采用逐层递进的5种方法, 分6个步骤来查究近20年来正常人群WMT的37篇fMRI文献。第一步, 用叙述性综述、频数分析和卡方检验法比较脑区激活模式和脑网络功能连接在WMT前后发生的改变, 发现WMT改变了大脑的5个联合区、7个宏观区和3个子区。其中, 额上回、顶下小叶和扣带回这3个子区各自激活减弱的报道文献数量多于其激活增强的, 且这种差异分别具有统计学意义。第二步, 采用激活似然估计法对其中26篇开展元分析, 发现大脑的3个子区激活减弱水平在WMT前后的差异具有统计学意义, 即额中回(BA6和8)、额上回(BA6)和前扣带回(BA24和32)。第三步, 综合定性和定量分析结果, 提出WMT脑区分布递减时空模型, 产生5个结果和讨论。第四步, 采用非参数检验进一步追踪WMT效应的调节因素, 发现训练的任务类型和时间分别对脑区激活的影响具有统计学意义。第五步, 针对正常人群WMT诱发神经可塑性的时空特性, 得出3个结论:第一, WMT改变了正常人群相应脑区的神经活动, 表现为减弱或增强, 但减弱更加突出, 且更新和较短时间的WMT倾向于诱发较多减弱; 第二, 这些神经活动变化主要发生在额顶叶联合区, 但也包括分别以颞叶、枕叶、扣带回及纹状体为主的联合区, 在一定范围内体现了整脑功能联合。这体现了WMT诱发神经可塑性的空间特性, 且符合“扩展的智力顶额整合理论”; 第三, 额中回、额上回、顶下小叶和扣带回(尤其前扣带回)这4个子区在激活减弱水平上重点展示了WMT神经可塑性的时间特性, 且符合“神经效率假说”, 恰好体现出“聪明的大脑更懒惰”。第六步, 指出WMT诱发神经可塑性的未来研究可能关注脑可塑性中的低活跃性、辨析额中回、额上回、顶下小叶和扣带回(尤其前扣带回)这4个子区在激活减弱水平上体现的时间特性、找寻训练减弱或增强大脑活动的综合性影响因素。
分类: 核科学技术 >> 核材料与工艺技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Amino-type adsorbents (ATAs) were prepared by radiation-induced graft copolymerization of 4-hydroxybutyl acrylate glycidyl ether (HB) onto a polyethylene-coated polypropylene (PE/PP) duplex fiber of a non-woven fabric, and modified with different amines of ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and diethylamine (DEA). The adsorption behavior of uranyl ions onto the ATAs was studied in batch experiments. The effects of the contact time, initial concentration of the ions, temperature, and pH value. The salinity were investigated along with the adsorption kinetics and the adsorption isotherms. The kinetic experimental data followed the pseudo second-order kinetic model, and the adsorption isotherms correlated well with the Langmuir model. The ATAs showed good efficiency in adsorbing uranyl ions, with the best saturation adsorption capacity being 64.26 mg g-1 for ATA-DETA within 120 min. The temperature dependence of ATA-DETA was quite abnormal and the quickest behavior was obtained at 25 ℃. ATAs showed good adsorption capacity over a wide pH range of 4.08.5, and HCl could be used in the elution process. Salinity of the solution had great effect on the adsorption capacity, 3.5% salinity resulted in a 55% loss of capacity from ATA-DETA. The selectivity of ATA-DETA showed an order of: UO22+ Fe3+ > Zn2+ > VO3- > Co2+ > Ni2+.
分类: 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间: 2016-05-12
摘要: Recretohalophytes with specialized salt-secreting structures (salt glands) can secrete excess salts from plant, while discriminating between Na+ and K+. K+/Na+ ratio plays an important role in plant salt tolerance, but the distribution and role of K+ in the salt gland cells is poorly understood. In this article, the in situ subcellular localization of K and Na in the salt gland of the recretohalophyte Limonium bicolor Kuntze is described. Samples were prepared by high-pressure freezing (HPF), freeze substitution (FS) and analyzed using NanoSIMS. The salt gland of L. bicolor consists of sixteen cells. Higher signal strength of Na+ was located in the apoplast of salt gland cells. Compared with control, 200 mM NaCl treatment led to higher signal strength of ICE and Na+ in both cytoplasm and nucleus of salt gland cells although K+/Na+ ratio in both cytoplasm and nucleus were slightly reduced by NaCl. Moreover, the rate of Na+ secretion per salt gland of L. bicolor treated with 200 mM NaCl was five times that of controls. These results suggest that K+ accumulation both in the cytoplasm and nucleus of salt gland cells under salinity may play an important role in salt secretion, although the exact mechanism is unknown. (C) 2015 Elsevier Ireland Ltd. All rights reserved.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: The functionalization of multi-walled carbon nanotubes (MWCNTs) by ozone treatment has been sys- tematically investigated by using Raman spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), organic elemental anal- ysis (OEA) and Boehm titration. The results showed that the functionalization process occurred at defective sites (opened mouths, tube caps, debris, etc.) before opening caps and truncating walls, and finally the graphitic structure was deteriorated. The surface oxygen content first increased with the treatment time but kept at around 8.0 wt% after 5 h. The analysis of the distribution of oxygen-containing groups re- vealed that phenolic hydroxyl was gradually converted to carboxyl and lactone. The carboxyl was found to play a pivotal role to reduce the over-potentials when we used the functionalized MWCNTs as the cat- alyst for oxygen reduction reaction (ORR).
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: This study investigates the composition dependence of magnetic structures of (Fe1−xMnx)Pt using first- principles method. A series of possible magnetic configurations are considered in the calculation to compare the relative stabilities after structural optimization, based on which, together with the com- parison between theoretical and experimental magnetic properties, the results largely support the ex- perimental finding in powders. The experimentally found stability of ferrimagnetic state in films with a wide composition range of x ≤ 0.5 is not fully supported by this study. The composition-dependent magnetic structures are discussed according to the exchange interactions.
分类: 物理学 >> 核物理学 提交时间: 2016-09-12
摘要: The Ω baryons with JP=3/2±,1/2± are studied on the lattice in the quenched approximation. Their mass levels are ordered as M3/2+
提交时间: 2017-05-02
摘要: Titanium dioxide is a promising photocatalyst for water splitting, but it suffers from low visible light activity due to its wide band gap. Doping can narrow the band gap of titanium dioxide; however, new charge-carrier recombination centres may be introd
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Gadolinium gallium aluminum garnet (GGAG) is a very promising host for the highly efficient luminescence of Ce3+ and shows potential in radiation detection applications. However, the thermodynamically metastable structure would be slanted against it from getting high transparency. To stabilize the crystal structure of GGAG, Yb3+ ions were codoped at the Gd3+ site. It is found that the decomposition of garnet was suppressed and the transparency of GGAG ceramic was evidently improved. Moreover, the photo- luminescence of GGAG:Ce3+,xYb3+ with different Yb3+ contents has been investigated. When the Ce3+ ions were excited under 475 nm, a typical near-infrared region emission of Yb3+ ions can be observed, where silicon solar cells have the strongest absorption. Basing on the lifetimes of Ce3+ ions in the GGAG:Ce3+,xYb3+ sample, the transfer efficiency from Ce3+ to Yb3+ and the theoretical internal quantum efficiency can be calculated and reach up to 86% and 186%, respectively. This would make GGAG:Ce3+,Yb3+ a potential attractive downconversion candidate for improving the energy conversion efficiency of crystalline silicon (c-Si) solar cells.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Nitrogen-doped carbon nanofibers (MCNFs) with an aligned mesoporous structure were synthesized by a co-confined carbonization method using anodic aluminum oxide (AAO) membrane and tetraethy- lorthosilicate (TEOS) as co-confined templates and ionic liquids as the precursor. The as-synthesized MCNFs with the diameter of 80–120 nm possessed a bulk nitrogen content of 5.3 wt% and bimodal meso- porous structure. The nitrogen atoms were mostly bound to the graphitic network in two forms, i.e. pyridinic and pyrrolic nitrogen, providing adsorption sites for acidic gases like SO2 and CO2 . Cyclic exper- iments revealed a considerable stability of MCNFs over 20 runs of SO2 adsorption and 15 runs for CO2 adsorption. The MCNFs also have a preferable adsorption performance for Cd2+.