Necessary and Sufficient Conditions for Oscillations of the Generalized Liénard Systems

In this paper, we study the second-order nonlinear differential systems of Liénard-type x˙=1a(x)[ h(y)−F(x) ], y˙=−a(x)g(x). Necessary and sufficient conditions to ensure that all nontrivial solutions are oscillatory are established by using a new nonlinear integral inequality. Our results substantially extend and improve previous results known in the literature.

苝二酰亚胺共价有机框架超级还原剂用于高效光催化芳基卤化物还原反应

自由基离子型分子光催化剂被证实是具有很强还原能力的可见光超级还原剂,它们在促进惰性的有机反应(例如将芳基卤化物还原为芳基自由基)方面具有突出的催化能力.然而,由于分子聚集严重地降低其催化活性,因而针对非均相超级还原剂的研究较少.本文提出了一种新的方法来解决上述问题,通过溶剂热反应将具有连续光诱导电子转移机制的苝二亚胺超级还原剂(PDI)异质化为二维给体-受体(D-A)共价有机框架(COFs).即以N,N'-双(3-戊基)-2,5,8,11-四(4-甲酰基苯基)苝二酰亚胺(TFPDI)与1,3,6,8-四(4-氨基苯基)芘\(Py-TA)或2,3,6,7-四(4-氨基基苯基)四硫富瓦烯(TTF-TA)为原料,通过溶剂热反应分别制备了两种高晶态二维D-A型COF结构:USTB-21和USTB-22,并用于芳基氯化物、芳基溴化物和芳基碘化物的光催化还原反应.X射线衍射和理论模拟结果表明,USTB-21和USTB-22具有二维共价键连接的层状结构,分别呈现AA和AB的堆积方式.在各自最佳反应条件下,COFs显示出与均相催化剂相媲美的可见光催化性能,可高效地还原一系列芳基氯化物、芳基溴化物和芳基碘化物.其中,USTB-22在可见光驱动不同的芳香卤化物还原时,3 h内的转化率高达99%.瞬态吸收光谱结果表明,相比于均相催化剂(N,N'-双(2,6-二异丙基苯基)苝二酰亚胺),自由基阴离子激发态寿命是150 ps,USTB-21和USTB-22具有更长的激发态寿命,分别为210和260 ps.顺磁共振波谱测试结果证明,自由基阴离子光催化剂异质化成晶态D-A型COFs能够有效地促进电荷分离效率和延长激发态寿命.上述结果说明,USTB-22具有良好的光催化性能主要是因为其激发态寿命较长以及电荷分离效率较好.理论模拟结果表明,所制备的材料具有D-A型的电子结构.对COF的模型片段进行理论计算,揭示了各步反应路径中吉布斯自由能的变化,从而进一步阐明了光催化机理.在催化反应过程中,芳基卤化物还原途径可分为两个阶段:第一阶段为双光子能量输入和光驱电子转移,包括光子捕获和(TTF-PDI•−)^(*)产生以及光驱动电子转移到4-溴苯乙酮底物;第二阶段为能量输出,用于还原4-溴苯乙酮底物生成苯乙酮.综上所述,本文通过溶剂热反应将具有连续光诱导电子转移机制的苝二亚胺超级还原剂异质化为二维D-A型COFs结构.该结构在芳基氯化物、芳基溴化物和芳基碘化物等的光催化还原反应中,可很好地促进电子从光催化剂转移到反应物,进而显著提高光催化反应的活性和选择性;本研究对于未来设计新型自由基离子型高效光催化剂提供了新的思路.

Vibration and noise mechanism of a 110 kV transformer under DC bias based on finite element method

Global energy and environmental issues are becoming increasingly problematic,and the vibration and noise problem of 110 kV transformers,which are the most widely distributed,have attracted widespread attention from both inside and outside the industry.DC bias is one of the main contributing factors to vibration noise during the normal operation of transformers.To clarify the vibration and noise mechanism of a 110 kV transformer under a DC bias,a multi-field coupling model of a 110 kV transformer was established using the finite element method.The electromagnetic,vibration,and noise characteristics during the DC bias process were compared and quantified through field circuit coupling in parallel with the power frequency of AC,harmonic,and DC power sources.It was found that a DC bias can cause significant distortions in the magnetic flux density,force,and displacement distributions of the core and winding.The contributions of the DC bias effect to the core and winding are different at Kdc=0.85.At this point,the core approached saturation,and the increase in the core force and displacement slowed.However,the saturation of the core increased the leakage flux,and the stress and displacement of the winding increased faster.The sound field distribution characteristics of the 110 kV transformer under a DC bias are related to the force characteristics.When the DC bias coefficient was 1.25,the noise sound pressure level reached 73.6 dB.

Construction and validation of a risk-prediction model for anastomotic leakage after radical gastrectomy: A cohort study in China

Objectives:Anastomotic leakage(AL)stands out as a prevalent and severe complication following gastric cancer surgery.It frequently precipitates additional serious complications,significantly influencing the overall survival time of patients.This study aims to enhance the risk-assessment strategy for AL following gastrectomy for gastric cancer.Methods:This study included a derivation cohort and validation cohort.The derivation cohort included patients who underwent radical gastrectomy at Sir Run Run Shaw Hospital,Zhejiang University School of Medicine,from January 1,2015 to December 31,2020.An evidence-based predictor questionnaire was crafted through extensive literature review and panel discussions.Based on the questionnaire,inpatient data were collected to form a model-derivation cohort.This cohort underwent both univariate and multivariate analyses to identify factors associated with AL events,and a logistic regression model with stepwise regression was developed.A 5-fold cross-validation ensured model reliability.The validation cohort included patients from August 1,2021 to December 31,2021 at the same hospital.Using the same imputation method,we organized the validation-queue data.We then employed the risk-prediction model constructed in the earlier phase of the study to predict the risk of AL in the subjects included in the validation queue.We compared the predictions with the actual occurrence,and evaluated the external validation performance of the model using model-evaluation indicators such as the area under the receiver operating characteristic curve(AUROC),Brier score,and calibration curve.Results:The derivation cohort included 1377 patients,and the validation cohort included 131 patients.The independent predictors of AL after radical gastrectomy included age65 y,preoperative albumin<35 g/L,resection extent,operative time240 min,and intraoperative blood loss90 mL.The predictive model exhibited a solid AUROC of 0.750(95%CI:0.694e0.806;p<0.001)with a Brier score of 0.049.The 5-fold cross-validation confirmed these findings with a calibrated C-index of 0.749 and an average Brier score of 0.052.External validation showed an AUROC of 0.723(95%CI:0.564e0.882;p?0.006)and a Brier score of 0.055,confirming reliability in different clinical settings.Conclusions:We successfully developed a risk-prediction model for AL following radical gastrectomy.This tool will aid healthcare professionals in anticipating AL,potentially reducing unnecessary interventions.

“强师计划”背景下地方师范院校高质量发展的困境与出路

高质量的教师队伍是关系到基础教育高质量发展的基础,基础教育教师队伍的高质量要求倒逼地方师范院校的高质量发展。党的十八大以来,国家出台了一系列政策文件,旨在加强国家教师队伍建设,也促进了地方师范院校的高质量发展。地方师范院校在快速发展的同时,其办学定位、人才培养和师资队伍建设等方面的短板和“固疾”依然制约着地方师范院校的高质量发展。2022年,教育部等八部门联合发布《新时代基础教育强师计划》,为地方师范院校的高质量发展带来新契机。精准办学定位,凸显教师教育特色;创新人才培养,服务地方基础教育;提质教师队伍,保障高质量发展。为培养地区优秀中小学、幼儿园师资贡献自己的力量。

A Downsampled SAR-BM3D Despeckling Approach for Single-Look SAR Images in High Resolution

SAR-BM3D is one of the state of the art despeckling algorithms for SAR images. However, when tackling with high resolution SAR images, it often has an unsatisfying despeckling performance in the homogeneous smooth regions, together with a high time complexity. In this paper, a novel downsampled SAR-BM3D despeckling approach combined with edge compensation is proposed. The proposed algorithm consists of two steps. First, despeckle the image which is a downsampled version of original image with SAR-BM3D. Then, compensate edges in each level when upsampling. This approach not only utilizes the good ability of feature preservation, but also improves performance of smoothing homogenous regions. When it comes to high resolution SAR images, the efficiency can be raised by six to seven times, compared to original SAR-BM3D. Experiments on simulated and real SAR images show that the proposed method reaches a high level in terms of visual quality and act more efficiently.

热消融在肝癌免疫治疗中的研究进展

随着肝癌精准医疗与微创理念的不断深入,热消融在肝癌综合治疗中的作用越来越大,它不仅可以直接杀灭肝癌细胞,还能诱导特异性抗肿瘤免疫反应发生,为肝癌治疗提供新途径。但热消融诱导的低水平免疫反应,往往不足以阻止肿瘤的进展。热消融联合肝动脉灌注化疗栓塞(transhepatic arterial chemoembolization,TACE)及免疫治疗可显著提高机体抗肿瘤免疫能力,降低肿瘤复发和转移,为肝癌特别是晚期肝癌的治疗提供新思路,具有广阔的应用前景,本文就热消融在肝癌免疫治疗中的研究进展做一综述。

Factors predicting sensory and motor recovery after the repair of upper limb peripheral nerve injuries

OBJECTIVE： To investigate the factors associated with sensory and motor recovery after the repair of upper limb peripheral nerve injuries. DATA SOURCES： The online PubMed database was searched for English articles describing outcomes after the repair of median, ulnar, radial, and digital nerve injuries in humans with a publication date between 1 January 1990 and 16 February 2011. STUDY SELECTION： The following types of article were selected： （1） clinical trials describ- ing the repair of median, ulnar, radial, and digital nerve injuries published in English; and （2） studies that reported sufficient patient information, including age, mechanism of injury, nerve injured, injury location, defect length, repair time, repair method, and repair materials. SPSS 13.0 software was used to perform univariate and multivariate logistic regression analyses and to in- vestigate the patient and intervention factors associated with outcomes. MAIN OUTCOME MEASURES： Sensory function was assessed using the Mackinnon-Dellon scale and motor function was assessed using the manual muscle test. Satisfactory motor recovery was defined as grade M4 or M5, and satisfactory sensory recovery was defined as grade S3＋ or S4. RESULTS： Seventy-one articles were included in this study. Univariate and multivariate logistic regression analyses showed that repair time, repair materials, and nerve injured were inde- pendent predictors of outcome after the repair of nerve injuries （P 〈 0.05）, and that the nerve injured was the main factor affecting the rate of good to excellent recovery. CONCLUSION： Predictors of outcome after the repair of peripheral nerve injuries include age, gender, repair time, repair materials, nerve injured, defect length, and duration of follow-up.

Expression of neurocan mRNA and ultrastructure of brain tissue after cerebral ischemia and reperfusion in stroke-prone renovascular hypertensive rats treated by electroacupuncture

We established a stroke-prone renovascular hypertensive rat model by bilateral constriction of the renal artery with sliver loop clips. After ten weeks, middle cerebral artery occlusion was induced for 2 hours. The rats then received electro-acupuncture at Baihui （DU 20） and Dazhui （DU 14） after onset of ischemia for 30 days. In situ hybridization study showed that electroacupuncture significantly reduced the number of neurocan mRNA-positive cells in the ischemic penumbra and hippocampal tissues of rats. Electron microscopy results demonstrated that the structure of neurons and blood vessels in the ischemic tissues were restored with electroacupuncture. Overall, these data suggest that electroacupuncture may protect neurons against ischemic reperfusion injury in stroke-prone renovascular hypertensive rats, which may be regulated by downregulation of expression of nerve inhibitory factor neurocan mRNA.

Endostatin enhances antitumor effect of tumor antigen-pulsed dendritic cell therapy in mouse xenograft model of lung carcinoma

Objective： To investigate the antitumor effect of endostatin combined with tumor antigen-pulsed dendritic cell （DC）-T cell therapy on lung cancer. Methods： Transplanted Lewis lung cancer （LLC） models of C57BL/6 mice were established by subcutaneous injection of LLC cells in left extremity axillary. Tumor antigen-pulsed DC-T cells from spleen cells and bone of mice were cultured in vitro. Tumor-bearing mice were randomly divided into three groups, including DC- T＋endostatin group, DC-T group, and phosphate-buffered saline （PBS） control group. Microvessel density （MVD） of tumor tissue in tumor-bearing mice was determined by immunohistochemistry （IHC）. The expressions of vascular endothelial growth factor （VEGF） and hypoxia-inducible factor-1α （HIF-1α） were determined by Western blotting and IHC staining. The proportions of CD8＋ T cells, mature dendritic cells （mDC）, tumor-associated macrophages [TAM （M1/M2）], and myeloid-derived suppressor cells （MDSC） in suspended cells of tumor tissue were determined by flow cytometry. The expressions of inter｜eukin （IL）-6, IL-10, IL-17, transforming growth factor-β（TGF-β） and interferon-γ （IFN-γ） in suspended cells of tumor tissue were detected by enzyme-linked immune sorbent assay （ELISA）. Results： DC-T cells combined with endostatin remarkably suppressed tumor growth. MVD of mice in DC- T＋endostatin group was significantly lower than that of the control group and DC-T monotherapy group. The expressions of VEGF, IL-6 and IL-17 in tumors were markedly decreased, but IFN-γ, and HIF-1α increased after treating with DC-T cells combined with endostatin, compared to control group and DC-T group. In the DC- T＋endostatin group, the proportions of MDSC and TAM （M2 type） were significantly decreased, mDC and TAM （Nil type） were up-regulated, and CD8＋ T cells were recruited to infiltrate tumors, in contrast to PBS control and DC-T monotherapy. DC-T cells combined with endostatin potently reduced the expressions of IL-6, IL-10, TGF-β and IL-17 in tumor tissue, and enhanced the expression of IFN-γ. Conclusions： The study indicated the synergic antitumor effects between endostatin and tumor antigen-pulsed DC-T cells, which may be a prospective therapy strategy to achieve potent antitumor effects on lung cancer.

The Arabidopsis MutS homolog AtMSH5 is required for normal meiosis

MSH5, a member of the MutS homolog DNA mismatch repair protein family, has been shown to be required for proper homologous chromosome recombination in diverse organisms such as mouse, budding yeast and Caenorhabditis elegans. In this paper, we show that a mutant Arabidopsis plant carrying the putative disrupted AtMSH5 gene exhibits defects during meiotic division, producing a proportion of nonviable pollen grains and abnormal embryo sacs, and thereby leading to a decrease in fertility. AtMSH5 expression is confined to meiotic floral buds, which is consistent with a possible role during meiosis. Cytological analysis of male meiosis revealed the presence of numerous univalents from diplotene to metaphase I, which were associated with a great reduction in chiasma frequencies. The average number of residual chiasmata in the mutant is reduced to 2.54 per meiocyte, which accounts for ~25% of the amount in the wild type. Here, quantitative cytogenetical analysis reveals that the residual chiasmata in Afresh5 mutants are randomly distributed among meiocytes, suggesting that AtMSH5 has an essential role during interferencesensitive chiasma formation. Taken together, the evidence indicates that AtMSH5 promotes homologous recombination through facilitating chiasma formation during prophase Ⅰ in Arabidopsis.

Monochromatic green light stimulation during incubation shortened the hatching time via pineal function in White Leghorn eggs

Background:Effect of monochromatic green light illumination on embryo development has been reported in chickens.The avian pineal gland is an important photo-endocrine organ formed by a mediodorsal protrusion during embryonic development.However,the involvement of pineal gland in the light transduction process remains to be elucidated.In the present study,we investigated the influence of monochromatic green light on hatching time and explored the possible mechanism via pineal function.Results:A total of 600 eggs of White Leghorn(Shaver strain)were incubated under photoperiods of either 12 h of light and 12 h of darkness using monochromatic green light(12L:12D group)or 24 h of darkness(0L:24D group)for 18 d.Compared to 0L:24D group,the green light stimulation shortened the hatching time without extending the hatch window or impairing hatchability.The liver of embryos incubated in the 12L:12D light condition was heavier than those of the 0L:24D group on d 21 post incubation which may be linked to the observed increase in the serum concentration of insulin-like growth factor 1(IGF-1);primary secretion of the liver.Histological structure analysis of pineal gland demonstrated that the light stimulation increased follicle area,wall thickness and lumen area on d 10 and d 12 post incubation.Rhythmic function analysis demonstrated that three clock related genes(brain and muscle ARNT-like-1,BMAL1;circadian locomotor output cycles kaput,CLOCK;and cryptochrome-1,CRY1)and a melatonin rate-limiting enzyme related gene(arylalkylamine N-acetyltransferase,AANAT)were rhythmically expressed in the pineal gland of the 12L:12D group,but not in the 0L:24D group.Simultaneously,the light stimulation also increased the concentration of melatonin(MT),which was linked to hepatocyte proliferation and IGF-1 secretion in previous studies.Conclusions:The 12L:12D monochromatic green light stimulation during incubation shortened hatching time without impairing hatching performance.Pineal gland’s early histological development and maturation of its rhythmic function were accelerated by the light stimulation.It may be the key organ in the photo-endocrine axis that regulates embryo development,and the potential mechanism could be through enhanced secretion of MT in the 12L:12D group which promotes the secretion of IGF-1.

A simple model of radial nerve injury in the rhesus monkey to evaluate peripheral nerve repair

Current research on bone marrow stem cell transplantation and autologous or xenogenic nerve transplantation for peripheral nerve regeneration has mainly focused on the repair of peripher-al nerve defects in rodents. In this study, we established a standardized experimental model of radial nerve defects in primates and evaluated the effect of repair on peripheral nerve injury. We repaired 2.5-cm lesions in the radial nerve of rhesus monkeys by transplantation of autografts, acellular allografts, or acellular allografts seeded with autologous bone marrow stem cells. Five months after surgery, regenerated nerve tissue was assessed for function, electrophysiology, and histomorphometry. Postoperative functional recovery was evaluated by the wrist-extension test. Compared with the simple autografts, the acellular allografts and allografts seeded with bone marrow stem cells facilitated remarkable recovery of the wrist-extension functions in the rhesus monkeys. This functional improvement was coupled with radial nerve distal axon growth, a higher percentage of neuron survival, increased nerve fiber density and diameter, increased myelin sheath thickness, and increased nerve conduction velocities and peak amplitudes of compound motor action potentials. Furthermore, the quality of nerve regeneration in the bone marrow stem cells-laden allografts group was comparable to that achieved with autografts. The wrist-extension test is a simple behavioral method for objective quantification of peripheral nerve regeneration.

Comparison of two types of persistent heavy rainfall events during sixteen warm seasons in the Sichuan Basin

Based on hourly precipitation from national surface stations,persistent heavy rainfall events(PHREs)over the Sichuan Basin(SCB)are explored during the warm season(May to September)from 2000 to 2015 to compare synoptic circulations and maintenance mechanisms between different PHRE types.There are two main types of PHREs:one is characterized by a rain belt west of 106°E over the SCB(WSB-PHREs),and the other features a rain belt east of 106°E over the SCB(ESB-PHREs).In total,there are 18 ESB-PHREs and 10 WSB-PHREs during the study period.Overall,the rain belts of WSB-PHREs are along the terrain distribution east of the Tibetan Plateau,while the precipitation intensity of ESB-PHREs is stronger.For the two types of PHREs,the shortwave trough over the SCB and the western Pacific subtropical high act as their favorable background environments,particularly for ESB-PHREs.The water vapor of WSB-PHREs is mainly transported from the South China Sea,whereas for ESB-PHREs the South China Sea and Bay of Bengal are their main moisture sources.The composite vorticity budgets of southwest vortices during their mature stage indicate that the convergence effect is a dominant factor for maintaining the two types of PHREs,and the strong vertical vorticity advection is also favorable,but the relative contribution of vertical advection is larger for WSB-PHREs.

Reconstruction and Dynamics of the Human Intestinal Microbiome Observed In Situ

The human gut microbiome has primarily been studied through the use of fecal samples,a practice that has generated vital knowledge on the composition and functional capacities of gastrointestinal microbial communities.However,this reliance on fecal materials limits the investigation of microbial dynamics in other locations along the gastrointestinal tract(in situ),and the infrequent availability of fecal samples prevents analysis at finer temporal scales(e.g.,hours).In our study,we utilized colonic transendoscopic enteral tubing,a technology originally developed for fecal microbiota transplantation,to sample the ileocecal microbiome twice daily;metagenomic and metatranscriptomic analyses were then conducted on these samples.A total of 43 ileocecal and 28 urine and fecal samples were collected from five healthy volunteers.The ileocecal and fecal microbiomes,as profiled in the five volunteers,were found to be similar in metagenomic profiling,yet their active genes(metatranscriptome)were found to be highly distinct.Both microbiomes were perturbed after laxative exposure;over time,they exhibited reduced dissimilarity to their pre-treatment state,thereby demonstrating resilience as an innate property of the gut microbiome,although they did not fully recover within our observation time window.Sampling of the ileocecal microbiome during the day and at night revealed the existence of diurnal rhythms in a series of bacterial species and functional pathways,particularly those related to short-chain fatty acid production,such as Propionibacterium acnes and coenzyme A biosynthesis Ⅱ.Autocorrelation analysis and fluctuations decomposition further indicated the significant periodicity of the diurnal oscillations.Metabolomic profiling in the fecal and urine samples mirrored the perturbance and recovery in the gut microbiome,indicating the crucial contribution of the gut microbiome to many key metabolites involved in host health.This study provides novel insights into the human gut microbiome and its inner resilience and diurnal rhythms,as well as the potential consequences of these to the host.

A putative bHLH transcription factor is a candidate gene for male sterile 32,a locus affecting pollen and tapetum development in tomato

The tomato(Solanum lycopersicum)male sterile 32(ms32)mutant has been used in hybrid seed breeding programs largely because it produces no pollen and has exserted stigmas.In this study,histological examination of anthers revealed dysfunctional pollen and tapetum development in the ms32 mutant.The ms32 locus was fine mapped to a 28.5 kb interval that encoded four putative genes.Solyc01g081100,a homolog of Arabidopsis bHLH10/89/90 and rice EAT1,was proposed to be the candidate gene of MS32 because it contained a single nucleotide polymorphism(SNP)that led to the formation of a premature stop codon.A codominant derived cleaved amplified polymorphic sequence(dCAPS)marker,MS32D,was developed based on the SNP.Real-time quantitative reverse-transcription PCR showed that most of the genes,which were proposed to be involved in pollen and tapetum development in tomato,were downregulated in the ms32 mutant.These findings may aid in marker-assisted selection of ms32 in hybrid breeding programs and facilitate studies on the regulatory mechanisms of pollen and tapetum development in tomato.

On the formation and wind enhancement mechanisms of a Mongolian cyclone that caused a transmission line galloping trip in Gansu province

Influenced by strong winds associated with a southeastward-moving Mongolian cyclone,a severe transmission line galloping occurred in Baiyin City,Gansu Province,on 14 April 2020.This caused a tripping incident of the transmission line in this region.Based on the hourly,0.5°×0.5°,ECMWF ERA5 reanalysis data,this study investigated the formation mechanisms of the Mongolian cyclone and its associated strong winds.Results from the vorticity budget indicate that the convergence-related vertical stretching and the upward transport of cyclonic vorticity governed formation of the Mongolian cyclone in this event;whereas,tilting and export of cyclonic vorticity from the central region of the cyclone mainly decelerated the cyclone’s formation.The kinetic energy(KE)budget shows that the wind associated with the Mongolian cyclone was mainly enhanced by the positive work of the pressure gradient force.Unlike some typical strong wind events in Northwest China,during this event,no significant downward momentum transportation from the upper troposphere was found.The vertical transport of KE exerted a slightly favorable effect on the KE increase around the location where the transmission line galloping trip appeared.In contrast,the horizontal transport mainly caused an export of KE from this region,which applied an overall negative effect on the wind enhancement associated with the Mongolian cyclone.

泥水盾构砂层掘进防止泥浆箱砂子沉淀装置技术应用——以中俄原油管道二线盾构穿越工程为例

在盾构法隧道穿越工程中,对于泥浆中渣土的处理非常关键,处理不及时就有可能在泥浆箱内沉积,堵塞循环管路,对施工造成巨大影响.根据以往的施工经验,提出对泥水分离系统的泥浆箱进行自主优化设计及适应性改造,并应用到工程实际,得到了良好的效果.

直接铺管施工技术研究——以陕京四线无定河穿越工程为例

直接铺管施工技术具有设备施工占地少,施工周期短的特点,可以一次性完成大口径管道施工,能适应较复杂地质情况,施工可靠性较高.以陕京四线无定河穿越工程为例,介绍了直接铺管施工技术在工程中的应用,克服了穿越管道42m大落差、富含水松散细砂地层、-20℃低温条件下施工等诸多困难.

Grain production space reconstruction and land system function tradeoffs in China

Grain production space reconstruction referred to the changes in the quantity,quality and pattern of grain produc-tion space caused by functional tradeoffs and conflicts between grain production space,urban-rural development space,and ecological service space.Exploring tradeoffs between land system functions caused by grain produc-tion space reconstruction was particularly important for ensuring food security,promoting the construction of ecological civilization,and achieving sustainable development.Therefore,this study identified four relationships of land system functions during the process of grain production space reconstruction(1980-2018)in China by using Set Pair Analysis.Research results showed that the reconstruction of grain production space was achieved mainly through three pathways:Grain for Green,deforestation and reclamation,and urban expansion.Generally,ecological service had spatial negative correlation with grain production,economic development and population carrying capacity(P<0.01),but grain production,economic development and population carrying capacity were positively correlated with each other(P<0.01).In the process of grain production space reconstruction,eco-logical services and economic development,ecological services and population carrying capacity had all shown inverse synergies;there was a tradeoffbetween grain production and ecological services,a codirectional tradeoffbetween grain production and economic development,but a strong synergy between economic development and population carrying capacity.However,the functions of land systems only appeared as synergies or tradeoffs,and there were no inverse synergies and codirectional tradeoffs in the separate processes of Grain for Green,deforestation and reclamation,and urban expansion.It can be concluded that the relationships between land system functions were relatively simple in a single process,but it became complex and diverse when multiple processes were integrated for system analysis.