Effects of root dominate over aboveground litter on soil microbial biomass in global forest ecosystems

Background:Inputs of above-and belowground litter into forest soils are changing at an unprecedented rate due to continuing human disturbances and climate change.Microorganisms drive the soil carbon(C)cycle,but the roles of above-and belowground litter in regulating the soil microbial community have not been evaluated at a global scale.Methods:Here,we conducted a meta-analysis based on 68 aboveground litter removal and root exclusion studies across forest ecosystems to quantify the roles of above-and belowground litter on soil microbial community and compare their relative importance.Results:Aboveground litter removal significantly declined soil microbial biomass by 4.9%but root exclusion inhibited it stronger,up to 11.7%.Moreover,the aboveground litter removal significantly raised fungi by 10.1%without altering bacteria,leading to a 46.7%increase in the fungi-to-bacteria(F/B)ratio.Differently,root exclusion significantly decreased the fungi by 26.2%but increased the bacteria by 5.7%,causing a 13.3%decrease in the F/B ratio.Specifically,root exclusion significantly inhibited arbuscular mycorrhizal fungi,ectomycorrhizal fungi,and actinomycetes by 22.9%,43.8%,and 7.9%,respectively.The negative effects of aboveground litter removal on microbial biomass increased with mean annual temperature and precipitation,whereas that of root exclusion on microbial biomass did not change with climatic factors but amplified with treatment duration.More importantly,greater effects of root exclusion on microbial biomass than aboveground litter removal were consistent across diverse forest biomes(expect boreal forests)and durations.Conclusions:These data provide a global evidence that root litter inputs exert a larger control on microbial biomass than aboveground litter inputs in forest ecosystems.Our study also highlights that changes in above-and belowground litter inputs could alter soil C stability differently by shifting the microbial community structure in the opposite direction.These findings are useful for predicting microbe-mediated C processes in response to changes in forest management or climate.

豁痰化瘀利水方对创伤性脑损伤的疗效观察

目的探讨豁痰化瘀利水方对创伤性脑损伤的疗效。方法收集我院2015年7月~2017年10月收治的急性创伤性脑损伤患者110例。均进行头颅CT扫描检查,根据格拉斯哥昏迷计分法(GCS)分级进行系统评估,将患者分为治疗组和对照组,各55例。在常规治疗的基础上,对照组给予单纯西药常规治疗,治疗组采用豁痰化瘀利水方治疗。观察两组治疗的疗效差别。结果治疗组总有效率为93.4%,对照组总有率为64.7%,差异有统计学意义(P<0.05)。结论豁痰化瘀利水方能明显减轻减轻脑损伤的继发性脑改变,明显改善脑损伤预后,降低再出血的危险。

Variation of Environmental Factors and Dominant Population Succession of Microalgae Planktonic in Closed Shrimp Pond

In order to investigate the influence of season changes of environmental factors in closed shrimp ponds on the community structure of planktonic microalgae,this paper conducted isolated tests to the temperature,pH,total nitrogen( TN),total phosphorus( TP) and chlorophyll a in the shrimp culture ponds,analyzed the planktonic microalgae community structure and changes of dominant species in water over the same period,with the aim to explain the responses of microalgae community to changes of environmental factors in the pond without foreign water sources.The results showed that pond water temperature and TP content gradually increased from April to the end of September and then declined in October; water pH first decreased and then increased; TN and chlorophyll a first increased and then decreased.The dominant species in the pond were Cyclotella sp.,Navicula sp.,Oocystis borgei and S.quadricauda in the early stage( Apirl-May),Chlamydomonas sp.,Chlorella sp.,S.quadricauda,Golenkinia radiata and Pseudanabeanain in medium stage( June-July),Microcystis,Pseudanabeana,Chlorella sp.And S.quadricaudain in the mid-late stage( August-September),Microcystis,Pseudanabeana,Oscillatoria sp.and Chlorella sp.in the late stage( October-December),and Chlorella sp.,Golenkinia radiate,S.quadricauda in the last stage.Diatoms and green algae were the dominant species in the early stage when the water had low temperature,low N and P nutrition but high N/P and a certain salinity.With the increase of temperature,water desalination and accumulation of N and P nutrition,algae became the dominant species.Cyanobacteria became the strong dominant stages in the mid-late stage when the water had high temperature in the state of eutrophication,and there were also some green algae which were fond of high temperature and had resistant to pollution.In the late stage,cyanobacteria were the absolute dominant stage,but with the decrease of water temperature in the last stage,green algae became the dominant species,and planktonic microalgae biomass in the pool decreased.

A multi-band atomic candle with microwave-dressed Rydberg atoms

Stabilizing important physical quantities to atom-based standards lies at the heart of modern atomic,molecular and optical physics,and is widely applied to the field of precision metrology.Of particular importance is the atom-based microwave field amplitude stabilizer,the so-called atomic candle.Previous atomic candles are realized with atoms in their ground state,and hence suffer from the lack of frequency band tunability and small stabilization bandwidth,severely limiting their development and potential applications.To tackle these limitations,we employ microwave-dressed Rydberg atoms to realize a novel atomic candle that features multi-band frequency tunability and large stabilization bandwidth.We demonstrate amplitude stabilization of microwave field from C-band to Ka-band,which could be extended to quasi-DC and terahertz fields by exploring abundant Rydberg levels.Our atomic candle achieves stabilization bandwidth of 100 Hz,outperforming previous ones by more than two orders of magnitude.Our simulation indicates the stabilization bandwidth can be further increased up to 100 kHz.Our work paves a route to develop novel electric field control and applications with a noise-resilient,miniaturized,sensitive and broadband atomic candle.

超声兰姆波二次谐波发生效应的理论、实验及应用研究进展

材料退化或微损伤的早期无损检测和评价可以保障关键结构的安全服役.因此,开展缺陷演化的早期评价,甚至缺陷产生前的早期检测是非常重要的.通常,线性超声检测方法对材料微观缺陷不敏感.非线性超声技术被广泛认为可以表征材料微观结构变化.二次谐波发生效应作为超声传播过程中的一种典型非线性声学效应,可以用来评价材料的性能退化程度和检测早期的微缺陷.此外,超声兰姆波被广泛应用于大型工业结构的健康监测及材料的无损检测和评价.基于超声兰姆波的无损检测方法能够检测出结构不可达或隐蔽区域,并具有低成本、高效率的优势.兰姆波二次谐波结合了兰姆波的优点和二次谐波对微损伤的高敏感特性,近年来受到越来越多的关注和研究.然而,由于兰姆波的频散和多模式特性,一般认为兰姆波传播过程中不存在强烈的非线性效应,实验上也很难对兰姆波二次谐波进行观察与测量.近年来,虽然兰姆波二次谐波的理论和实验研究取得了重要的进展,但该领域仍存在一系列科学和技术难题.本文系统梳理了超声兰姆波二次谐波发生效应的理论研究历程,综述了兰姆波二次谐波的实验研究进展以及在不同类型损伤评价中的应用,讨论了超声兰姆波二次谐波近年来研究中出现的争议问题,最后展望了兰姆波二次谐波的未来研究重点及发展趋势.

Fast spin squeezing by distance-selective long-range interactions with Rydberg molecule dressing

We propose a Rydberg molecule dressing scheme to create strong and long-ranged interactions at selective distances. This is achieved through laser coupling ground-state atoms off-resonantly to an attractive molecular curve of two interacting Rydberg atoms. Although dephasing due to Rydberg state decay occurs in all dressing schemes, an advantage of the molecule dressing is that a large ratio of dressed interaction to dephasing rate can be realized at large atomic separations. In an optical lattice or tweezer setting, we show that the strong interaction permits the fast generation of spin squeezing for several tens of dressed atoms.The proposed setting offers a new route to study complex many-body dynamics and to realize quantum information processing with non-convex long-range interactions.

Virtual vibration test rig for fatigue analysis of dozer push arms

To obtain accurate fatigue life results for construction machinery components,acquiring load spectra is crucial,as their authenticity and validity directly determine the precision of the analysis.In working conditions,component attitudes change continuously,but they remain static on the vibration test rig(VTR),so the acquired target signals should match with the actual component attitudes in the driving signal generation.This paper proposes an efficient and economical simulation-based virtual VTR for fatigue analysis of dozers.First,the relationship between the push arm rotation angle and the cylinder stroke is established,since the cylinder strokes can be measured easily in data acquisition experiments.Second,load decomposition is used to determine the attitude relationship between virtual VTR conditions and actual conditions,and target signals are calculated based on this attitude relationship and measured data.According to the system's frequency response function,the driving signals are iterated until the system's response signals converge with the target signals.Finally,the iteratively obtained load spectra are utilized for fatigue life analysis.The results show that the virtual VTR can effectively and accurately obtain the results of fatigue analysis and has engineering application significance.