Consistency analysis of GRACE and GRACE-FO data in the study of global mean sea level change

Global mean sea level(GMSL) change is one of the important indicators of global climate change and is a crucial scientific issue of continuing interest. As satellite altimeter data, the Gravity Recovery and Climate Experiment(GRACE) and Argo continue to be updated, especially with the release of GRACE Follow-On(GRACE-FO) data, making it necessary to combine these latest data to estimate sea level change. Determinations on whether the GRACE and GRACE-FO observation systems provide unbiased global observation data have not been effectively evaluated. Therefore, this research mainly investigated the consistency of GRACE and GRACE-FO observation data in studying GMSL change. By comparing the sum of the GMSL calculated by the two gravity satellites and Argo data with the GMSL calculated by satellite altimeters, the discrepancy between GRACE-FO + Argo and satellite altimeter data is about 7.9 ± 2.3 mm, which is likely derived from the inconsistency between GRACE and GRACE-FO data.

Low cycle fatigue behavior of zirconium−titanium−steel composite plate

The low cycle fatigue behavior of zirconium−titanium−steel composite plate under symmetrical and asymmetric stress control was studied.The effects of mean stress and stress amplitude on cyclic deformation,ratcheting effect and damage mechanism were discussed in detail.The results show that under symmetric stress control,the forward ratcheting deformation is observed.Under asymmetric stress control,the ratcheting strain increases rapidly with mean stress and stress amplitude increasing.Under high stress amplitude,the influence of mean stress is more significant.In addition,by studying the variation of strain energy density,it is found that the stress amplitude mainly promotes the fatigue damage,while the mean stress leads to the ratcheting damage.In addition,fractographic observation shows that the crack initiates in the brittle metal compound at the interface,and the steel has higher resistance to crack propagation.Finally,the accuracy of life prediction model considering ratcheting effect is discussed in detail,and a high-precision life prediction model directly based on mean stress and stress amplitude is proposed.

Leader-follower Consensus of Upper-triangular Nonlinear Multi-agent Systems

This paper is concerned with the leader-follower consensus problem by using both state and output feedback for a class of nonlinear multi-agent systems. The agents considered here are all identical upper-triangular nonlinear systems which satisfy the Lipschitz growth condition. First, it is shown that the leader-follower consensus problem is equivalent to the control design problem of a high-dimensional multi-variable system.Second, by introducing an appropriate state transformation, the control design problem can be converted into the problem of finding a constant parameter, which can be obtained by solving the Lyapunov equation and estimating the nonlinear terms of the given system. At last, an example is given to verify effectiveness of the proposed consensus algorithms.

Fixed-Time Stabilization of a Class of Strict-Feedback Nonlinear Systems via Dynamic Gain Feedback Control

This paper presents a novel fixed-time stabilization control(FSC)method for a class of strict-feedback nonlinear systems involving unmodelled system dynamics.The key feature of the proposed method is the design of two dynamic parameters.Specifically,a set of auxiliary variables is first introduced through state transformation.These variables combine the original system states and the two introduced dynamic parameters,facilitating the closed-loop system stability analyses.Then,the two dynamic parameters are delicately designed by utilizing the Lyapunov method,ensuring that all the closed-loop system states are globally fixed-time stable.Compared with existing results,the“explosion of complexity”problem of backstepping control is avoided.Moreover,the two designed dynamic parameters are dependent on system states rather than a time-varying function,thus the proposed controller is still valid beyond the given fixedtime convergence instant.The effectiveness of the proposed method is demonstrated through two practical systems.

2000-2019年青海地区植被总初级生产力遥感估算及时空变化分析

青海作为三江源所在地,监测其生态系统变化对我国的生态文明建设具有战略意义。植被总初级生产力(GPP)是陆地生态系统碳循环的重要组分。采用MODIS卫星遥感数据和土壤背景校正NIRv模型,结合3个地面站点的通量观测数据,估算了2000-2019年青海地区的GPP,并结合土地利用数据和气象数据分析了其时空分异特征及对气候变化的响应。结果表明:1)土壤背景校正NIRv模型估算的青海地区GPP与地面实测GPP数据呈良好线性关系(R2=0.91,P<0.001),相较于MODIS GPP产品,估算的GPP在青海地区更具有适用性。2)2000-2019年青海地区植被GPP多年平均值为140.5 Tg C·yr^(-1),年均GPP整体处于上升趋势,年增长率为1.25 Tg C·yr^(-1)(P<0.05)。3)青海地区GPP空间分布呈由西向东显著增加趋势,不同植被类型的GPP值年际变化表现出较大差异。4)整体上,年均气温与GPP变化的相关性高于平均降水量,气象因素对不同植被GPP的影响存在明显空间异质性。

Regulating the d band in WS_(2)@NC hierarchical nanospheres for efficient lithium polysulfide conversion in lithium-sulfur batteries

The performance of lithium-sulfur batteries is deteriorated by the inferior conductivity of sulfur,the shuttle effect of lithium polysulfides(LiPSs),sluggish redox kinetics of polysulfide intermediates and serious volumetric expansion of sulfur.To overcome these challenges,we report a versatile route to prepare multi-functional nanocomposites with tuable hierarchical structure via ammonium hydroxide(NH_(3)·H_(2) O)induced self-assembly.The versatility of the system has been demonstrated that the organization of the hierarchical structure can be regulated by adding different amounts of NH_(3)·H_(2) O,and WS_(2) and Co_(9)S_(8) with nitrogen-doped carbon coating(denoted as WS_(2)@NC and Co_(9)S_(8)@NC)can be prepared by adding different precursor salts.When the as-prepared materials are applied for Li-S batteries,the WS_(2)@NC composite exhibits a reversible capacity of 1107.4 mAh g^(-1) at 0.1 C after 500 cycles and even 728.9 mAh g^(-1) at2 C for 1000 cycles,which is significantly better than the Co_(9)S_(8) counterpart and other reported WS_(2) sulfur hosts.Experimentally,the advantageous performance of WS_(2) could be attributed to its higher surface area and total pore volume,giving rise to the easier access to electrolyte and better ability to buffer the volume change during the charge/discharge process.Theoretically,the density function theory(DFT)calculation reveals that the as-prepared WS_(2) has a higher binding energy towards LiPSs as well as a lower energy barrier for Li^(+)diffusion on the surface than Co_(9)S_(8).More significantly,the density of states(DOS)analysis further confirms that the superior performance is mainly ascribed to the more prominent shifting and the more charge compensation from d band of W than Co,which increase electronic concentration and give more hybridization of d-p orbitals in the Fermi level of the adsorbed Li2 S4 to accelerate the lithium polysulfide interfacial redox and conversion dynamics in WS_(2).By proposing this mechanism,this work sheds new light on the understanding of catalytic conversion of lithium polysulfides at the atomic level and the strategy to develop advanced cathode materials for high-performance lithium-sulfur batteries.

Comparing the Effects of Different Post-Listening Output Tasks on Second Language Incidental Vocabulary Acquisition:Revisiting the Involvement Load Hypothesis

Based on the Involvement Load Hypothesis, the present study investigated the differential effects of three post-listening output tasks(gap-filling, translation, and sentence-making) on immediate acquisition and retention of such vocabulary dimensions as productive knowledge of orthography,receptive recall of meaning and form, and productive knowledge of grammatical functions. Ninety second-year English majors were divided into three groups to finish listening plus one of the postlistening tasks. The results showed that the post-listening output tasks had positive effects on immediate acquisition of productive vocabulary knowledge, partially in agreement with the Involvement Load Hypothesis. However, the effects on vocabulary knowledge retention were found to be largely inconsistent with the Involvement Load Hypothesis. The finding thus challenges this hypothesis in that involvement load is not the only determining factor and suggests that the theoretical construct of involvement load should be constructed with more caution.

Quantifying the Mechanical Properties of White Sandstone Based on Computer Fractal Theory

The work presented in this paper was conducted to quantify the relationship between the pore characteristics and mechanical properties of white sandstone.The study include tests carried out under the coupling effects of chemical corrosion,temperature,nuclear magnetic resonance,and mechanical tests.Computer fractal theory was employed to describe and quantify the characteristics of the growth of pores in white sandstone under the same coupling effect.A custom developed program code,in the MATLAB software platform,was used for calculating the growths of the pores in white sandstone when subjected to coupling effects.The correlation between the computer fractal dimension of the growth of the pores in rock and characteristics of mechanical damage was accordingly analyzed.The results showed that when the temperature was set at a level lower than 100°C,it caused damage to the rock and strength reduction,primarily due to the rates of chemical reactions,the generation,and evolution of pores in the rock mass under the coupling effects of chemical corrosion and temperature.Overall,it was observed that the higher the value of the computer fractal dimension,the higher the growth of the pores,and the lower the uniaxial compressive strength of the white sandstone.

Interfacial processes and mechanisms of synergistic degradation of dichlorobiphenyl by white rot fungi and magnetite nanoparticles

The rapid increase in the artificial syntheses of organic pollutants has raised widespread concern.However,the mechanisms by which fungi degrade these new organic pollutants in the environment and adapt to environmental stressors remain unclear.In this study,Phanerochaete chrysosporium,a model white rot fungus,was used to explore the interfacial processes and mechanisms for synergistic degradation of 4,4′-dichlorobiphenyl(PCB15)with magnetite nanoparticles.The results showed that after 3 and 5 days of cultivation with Phanerochaete chrysosporium alone,the rates for PCB15 degradation were 32%and 65%,respectively,indicating that the white rot fungus itself was able to degrade the organic pollutant.Moreover,the addition of magnetite nanoparticles significantly enhanced the degradation of PCB15 by Phanerochaete chrysosporium.After cocultivation for 3 and 5 days,the rates for PCB15 degradation increased to 42%and 84%,respectively.Synchrotron radiation-based Fourier transform infrared spectromicroscopy(SR-FTIR)showed that the magnetite particles were tightly adhered to the fungal hyphae and were unevenly distributed on the hyphal surfaces.Furthermore,cocultivation of the fungus and magnetite nanoparticles significantly enhanced the nanozymatic activity of magnetite.A linear regression model provided a significantly negative correlation(r=−0.96,p<0.001)between the nanozymatic activity of the magnetite and the concentration ratio of the PCB15,supporting the hypothesis that white rot fungi degraded the PCB15 by enhancing the nanozyme activity of magnetite.High-resolution X-ray photoelectron spectroscopy(XPS)revealed that the nanozymatic activity of magnetite was mainly governed by oxygen vacancies on the mineral surfaces rather than the iron valence.Together,these findings increase our understanding of the powerful capabilities of fungi in terms of stress resistance and adaptation to extreme environments and provide new insights into fungal-mediated degradation of organic pollutants for soil remediation in contaminated sites.

Increased long-distance and homo-trans interactions related to H3K27me3 in Arabidopsis hybrids

In plants,the genome structure of hybrids changes compared with their parents,but the effects of these changes in hybrids remain elusive.Comparing reciprocal crosses between Col×C24 and C24×Col in Arabidopsis using high-throughput chromosome conformation capture assay(Hi-C)analysis,we found that hybrid three-dimensional(3D)chromatin organization had more long-distance interactions relative to parents,and this was mainly located in promoter regions and enriched in genes with heterosis-related pathways.The interactions between euchromatin and heterochromatin were increased,and the compartment strength decreased in hybrids.In compartment domain(CD)boundaries,the distal interactions were more in hybrids than their parents.In the hybrids of CURLY LEAF(clf)mutants clfCol×clfC24and clfC24×clfCol,the heterosis phenotype was damaged,and the long-distance interactions in hybrids were fewer than in their parents with lower H3K27me3.ChIP-seq data revealed higher levels of H3K27me3 in the region adjacent to the CD boundary and the same interactional homo-trans sites in the wild-type(WT)hybrids,which may have led to more long-distance interactions.In addition,the differentially expressed genes(DEGs)located in the boundaries of CDs and loop regions changed obviously in WT,and the functional enrichment for DEGs was different between WT and clf in the longdistance interactions and loop regions.Our findings may therefore propose a new epigenetic explanation of heterosis in the Arabidopsis hybrids and provide new insights into crop breeding and yield increase.

Divergent total synthesis of marine meroterpenoids(+)-dysidavarones A–C

Here,we report a concise and divergent enantioselective total synthesis of marine sesquiterpene quinone meroterpenoids(+)-dysidavarones A–C(1–3)using predysidavarone 6 as a key common intermediate.The highly strained and bridged eight-membered carbocycle of predysidavarone 6 was constructed by a one-pot intermolecular alkylation and intramolecular arylation of Wieland–Miescher ketone derivative 11 and benzyl bromide 12.The total synthesis of(+)-dysidavarones A–C(1–3)was achieved from predysidavarone 6 in a divergent manner by a late-stage introduction of the ethoxy group,which reveals the possible source of the ethoxy group within(+)-dysidavarones A–C(1–3)and provides a late-stage modifiable route for the synthesis of dysidavarone analogs for further anti-cancer activity evaluation.

Orientation and strain rate dependent tensile behavior of single crystal titanium nanowires by molecular dynamics simulations

Molecular dynamics simulation was employed to study the tensile behavior of single crystal titanium nanowires（NWs）with[112^-0],[1^-100] and[0001]orientations at different strain rates from 10^8s^-1 to 10^11s^-1.When strain rates are above 10^10s^-1,the state transformation from HCP structure to amorphous state leads to super plasticity of Ti NWs,which is similar to FCC NWs.When strain rates are below 10^10s^-1,deformation mechanisms of Ti NWs show strong dependence on orientation.For [112^-0] orientated NW.{101^-1} compression twins（CTs）and the frequently activated transformation between CTs and deformation faults lead to higher plasticity than the other two orientated NWs.Besides,tensile deformation process along [112^-0] orientation is insensitive to strain rate.For [1^-100] orientated NW,prismaticslip is the main deformation mode at 10^8s^-1.As the strain rate increases,more types of dislocations are activated during plastic deformation process.For[0001]orientated NW,{101^-2} extension twinning is the main deformation mechanism,inducing the yield stress of [0001] orientated NW,which has the highest strain rate sensitivity.The number of initial nucleated twins increases while the saturation twin volume fraction decreases nonlinearly with increasing strain rate.

Correspondence:Zero ground clearance dual antenna pair for metal-cased fifth-generation multiple input multiple output smartphone

1 Introduction The fifth-generation(5G)era has already arrived and many applications are prospering.The multi‐ple input multiple output(MIMO)system is the key to enhancing channel capacity for both the fourthgeneration(4G)wireless communication and 5G sys‐tems.For a smartphone,the most challenging task for antenna engineers is to accommodate the numerous 4G and 5G multi-port antennas while avoiding mutual coupling problems(Li Y et al.,2009,2012;Hong,2017;Sharawi et al.,2017).Therefore,implementing multiple antennas within a small space is a worth‐while topic to study,especially for antennas operat‐ing at the same frequency。

Comparing the Effects of Listening Input and Reading Input on EFL Learners' Incidental Vocabulary Acquisition

This study examined the effects of either listening or reading input on 88 first-year non- English-ma）or Chinese university EFL students＇ incidental acquisition in vocabulary form, meaning and production. The students were put into a Listening Group （n = 47） and a Reading Group （n = 41）, each of which finished either two listening activities （each consisting of a dialogic text and an information transfer task） or two reading activities （each consisting of a reading text and five multiple-choice questions）. The four texts all contained five low- frequency target words which a revised Vocabulary Knowledge Test had shown to be only slightly known by the participants before the activities. The results of the post-tests showed that the Reading Group had general acquisition advantage over the Listening Group in terms of all the three vocabulary aspects, and due to the fact of rich target word contexts and repeated access to the texts, the Listening Group manifested vocabulary meaning acquisition nearly equal to the Reading Group. Overall, the study shows the notably advantageous effects of reading input on incidental vocabulary acquisition, and concerning facilitating vocabulary acquisition through listening, it points out the importance of increasing opportunities for learners to process listening input with rich contextual clues through task repetition.

Serosurvey for SARS-CoV-2 among blood donors in Wuhan,China from September to December 2019

The emerging of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)caused COVID-19 pandemic.The first case of COVID-19 was reported at early December in 2019 in Wuhan City,China.To examine specific antibodies against SARS-CoV-2 in biological samples before December 2019 would give clues when the epidemic of SARS-CoV-2 might start to circulate in populations.We obtained all 88,517 plasmas from 76,844 blood donors in Wuhan between 1 September and 31 December 2019.We first evaluated the pan-immunoglobin(pan-Ig)against SARS-CoV-2 in 43,850 samples from 32,484 blood donors with suitable sample quality and enough volume.Two hundred and sixty-four samples from 213 donors were pan-Ig reactive,then further tested IgG and IgM,and validated by neutralizing antibodies against SARS-CoV-2.Two hundred and thirteen samples(from 175 donors)were only pan-Ig reactive,8(from 4 donors)were pan-Ig and IgG reactive,and 43(from 34 donors)were pan-Ig and IgM reactive.Microneutralization assay showed all negative results.In addition,213 screened reactive donors were analyzed and did not show obviously temporal or regional tendency,but the distribution of age showed a difference compared with all tested donors.Then we reviewed SARS-CoV-2 antibody results from these donors who donated several times from September 2019 to June 2020,partly tested in a previous published study,no one was found a significant increase in S/CO of antibodies against SARS-CoV-2.Our findings showed no SARS-CoV-2-specific antibodies existing among blood donors in Wuhan,China before 2020,indicating no evidence of transmission of COVID-19 before December 2019 in Wuhan,China.

生物合成聚3-羟基丙酸酯的研究进展

聚3-羟基丙酸酯(P3HP)作为聚羟基脂肪酸酯家族(PHAs)中的新型热塑性塑料,具有生物降解性和生物相容性等优点。目前,未见野生微生物可以合成P3HP的报道,生产途径主要为化学法和生物法。其中,通过化学法或添加3-HP单体及其结构类似物作为前体的P3HP合成效率低、成本高且不具环保性;而通过构建和改造工程菌的生物代谢途径,能够利用廉价、可再生的碳源,已经逐渐成为研究热点。文中综述了国内外P3HP生物合成研究进展,并对甘油途径、丙二酸单酰辅酶A(Malonyl-Co A)途径和β-丙氨酸途径等合成方法进行了优缺点分析,为生物合成P3HP的深入研究奠定理论基础。

KHSRP combines transcriptional and posttranscriptional mechanisms to regulate monocytic differentiation

RNA-binding proteins(RBPs)are widely involved in the transcriptional and posttranscriptional regulation of multiple biological processes.The transcriptional regulatory ability of RBPs was indicated by the identification of chromatin-enriched RBPs(Che-RBPs).One of these proteins,KH-type splicing regulatory protein(KHSRP),is a multifunctional RBP that has been implicated in mRNA decay,alternative splicing,and miRNA biogenesis and plays an essential role in myeloid differentiation by facilitating the maturation of miR-129.In this study,we revealed that KHSRP regulates monocytic differentiation by regulating gene transcription and RNA splicing.KHSRP-occupied specific genomic sites in promoter and enhancer regions to regulate the expression of several hematopoietic genes through transcriptional activation and bound to pre-mRNA intronic regions to modulate alternative splicing during monocytic differentiation.Of note,KHSRP had co-regulatory effects at both the transcriptional and posttranscriptional levels on MOGOH and ADARB1.Taken together,our analyses revealed the dual DNA-and RNA-binding activities of KHSRP and have provided a paradigm to guide the analysis of other functional Che-RBPs in different biological systems.

New Gene Variants Associated with the Risk of Chronic HBV Infection

Some patients with chronic hepatitis B virus(HBV)infection failed to clear HBV,even persistently continue to produce antibodies to HBV.Here we performed a two stage genome wide association study in a cohort of Chinese patients designed to discover single nucleotide variants that associate with HBV infection and clearance of HBV.The first stage involved genome wide exome sequencing of 101 cases(HBsAg plus anti-HBs positive)compared with 102 control patients(antiHBs positive,HBsAg negative).Over 80%of individual sequences displayed 209 sequence coverage.Adapters,uncertain bases[10%or low-quality base calls([50%)were filtered and compared to the human reference genome hg19.In the second stage,579 chronic HBV infected cases and 439 HBV clearance controls were sequenced with selected genes from the first stage.Although there were no significant associated gene variants in the first stage,two significant gene associations were discovered when the two stages were assessed in a combined analysis.One association showed rs506121-“T”allele[within the dedicator of cytokinesis 8(DOCK8)gene]was higher in chronic HBV infection group than that in clearance group(P=0.002,OR=0.77,95%CI[0.65,0.91]).The second association involved rs2071676—A allele within the Carbonic anhydrase(CA9)gene that was significantly elevated in chronic HBV infection group compared to the clearance group(P=0.0003,OR=1.35,95%CI[1.15,1.58]).Upon replication these gene associations would suggest the influence of DOCK8 and CA9 as potential risk genetic factors in the persistence of HBV infection.

Stem cells to reverse aging

As human life expectancy continues to increase and the birth rate continues to decline, the phenomenon of aging is becoming more prominent worldwide. Therefore, addressing the problems associated with global aging has become a current research focus. The main manifestations of human aging are structural degeneration and functional decline of aging tissues and organs, quality of life decline, decreased ability to resist diseases, and high incidence rates of a variety of senile degenerative diseases. Thus far, no ideal treatments have been found. Stem cell (SC) therapies have broad application prospects in the field of regenerative medicine due to the inherent biological characteristics of SCs, such as their plasticity, self-renewal, and multidirectional differentiation potential. Thus, SCs could delay or even reverse aging. This manuscript reviews the causes of human aging, the biological characteristics of SCs, and research progress on age reversal.

TGF-β signaling pathway in induced pluripotent stem cells reprogramming

To the Editor:The discovery of the induced pluripotent stem cells(iPSCs)by Takahashi and Yamanaka in 2006 was hailed as a major breakthrough in stem cell research.And a large number of experimental studies have proven that the transforming growth factor-β(TGF-β)signaling pathway is a key signaling pathway in iPSC reprogramming.The TGF-βsignaling pathway can promote or inhibit iPSC reprogramming under different conditions[Figure 1].This article describes the role of the TGF-βsignaling pathway in iPSC reprogramming.