区域教育数字化应用场景的设计理念与推进路径

教育数字化改革是推动教育治理现代化的重要抓手和驱动力。浙江以应用场景建设为切入点,不断深挖教育数字化改革的三层需要,在对教育数字化应用场景内涵界定的基础上,创新教育数字化应用场景的实现机制,最终形成以人为本的数字学习新模式、构筑集约高效的数字教育新基建、构建数字驱动的教育治理新格局的三条推进路径,为教育数字治理积累了浙江经验。

Soybean(Glycine max)rhizosphere organic phosphorus recycling relies on acid phosphatase activity and specific phosphorusmineralizing-related bacteria in phosphate deficient acidic soils

Bacteria play critical roles in regulating soil phosphorus(P) cycling. The effects of interactions between crops and soil P-availability on bacterial communities and the feedback regulation of soil P cycling by the bacterial community modifications are poorly understood. Here, six soybean(Glycine max) genotypes with differences in P efficiency were cultivated in acidic soils with long-term sufficient or deficient P-fertilizer treatments. The acid phosphatase(AcP) activities, organic-P concentrations and associated bacterial community compositions were determined in bulk and rhizosphere soils. The results showed that both soybean plant P content and the soil AcP activity were negatively correlated with soil organic-P concentration in P-deficient acidic soils. Soil P-availability affected the ɑ-diversity of bacteria in both bulk and rhizosphere soils. However, soybean had a stronger effect on the bacterial community composition, as reflected by the similar biomarker bacteria in the rhizosphere soils in both P-treatments. The relative abundance of biomarker bacteria Proteobacteria was strongly correlated with soil organic-P concentration and AcP activity in low-P treatments. Further high-throughput sequencing of the phoC gene revealed an obvious shift in Proteobacteria groups between bulk soils and rhizosphere soils, which was emphasized by the higher relative abundances of Cupriavidus and Klebsiella, and lower relative abundance of Xanthomonas in rhizosphere soils. Among them, Cupriavidus was the dominant phoC bacterial genus, and it was negatively correlated with the soil organic-P concentration. These findings suggest that soybean growth relies on organic-P mineralization in P-deficient acidic soils, which might be partially achieved by recruiting specific phoCharboring bacteria, such as Cupriavidus.

精准调控Baeyer-Villiger单加氧酶的底物选择性以避免拉唑亚砜的过氧化

氧化酶催化的分子功能化是非常具有吸引力的研究领域之一,其中,高度选择性氧化反应对手性分子的构建至关重要.大量研究集中在对氧化酶立体选择性和区域选择性的分子改造上,而由于底物选择性差引起的过度氧化问题长期被忽视.Baeyer-Villiger单加氧酶(BVMOs)是一类多功能的生物催化剂,可以在脂肪族或环状酮底物的羰基附近插入一个氧原子,具有较高的区域选择性.BVMOs还可以催化包括硫、氮和磷在内的杂原子的不对称氧化.由于其温和的反应条件和较好的对映选择性,BVMOs催化硫醚不对称氧化生成手性亚砜被认为是一种极具吸引力且绿色清洁的合成方法.BVMOs可以催化硫醚不对称氧化生成有价值的手性亚砜,但亚砜过氧化生成无用的副产物砜限制了其进一步应用.这种过度氧化的本质原因是BVMOs对底物选择性不足,导致目标产物亚砜被进一步氧化.本文建立了一个数学模型,将酶对硫醚和亚砜两种相似底物之间的特异性常数之比(kcat/Km)定义为酶对底物选择性.随后使用蛋白结构引导的底物通道工程方法精准调控了拉唑硫醚单加氧酶AcPSMO的底物选择性,成功地将亚砜的过氧化降至最低.酶促氧化奥美拉唑硫醚24h后,突变体F277L生成的副产物砜含量低于1%(mol/mol),而野生型的砜含量为65%.分子动力学模拟和量子力学/分子力学研究结果表明,黄素氢过氧化物(FADH-OOH)周围改变的氢键网络可以调节亚砜氧化的机制和活性.此外,重新设计的AcPSMO突变体也成功地应用于其它手性拉唑亚砜的可控合成.综上,本文开发的精确控制氧化酶底物选择性的方法对于提高其它杂原子生物氧化反应的底物特异性具有借鉴意义.

柠檬酸接枝苎麻纤维铀吸附及抗菌性能

核能开发会产生大量含铀废水,危害生态环境和人类健康。文中通过酯化法制备了柠檬酸接枝苎麻纤维吸附剂,用于去除水溶液中的铀。研究了铀酰离子初始浓度、溶液pH值、吸附时间、温度等条件对吸附剂性能的影响。结果表明,当铀酰离子初始浓度为20mg/L、溶液pH=6、吸附剂的投加量为0.02g/L、吸附时间为12h时达到吸附平衡,最大吸附容量为397mg-U/g;吸附过程符合Langmuir模型和准二级动力学模型。另外,吸附剂对大肠杆菌具有明显的抑制作用,表现出良好的抗菌性能。

Targeting LncRNA LLNLR-299G3.1 with antisense oligonucleotide inhibits malignancy of esophageal squamous cell carcinoma cells in vitro and in vivo

Accumulating evidence has indicated that long non-coding RNAs(lncRNAs)play critical roles in the development and progression of cancers,including esophageal squamous cell carcinoma(ESCC).However,the mechanisms of lncRNAs in ESCC are still incompletely understood and therapeutic attempts for in vivo targeting cancer-associated lncRNA remain a challenge.By RNA-sequencing analysis,we identified that LLNLR-299G3.1 was a novel ESCC-associated lncRNA.LLNLR-299G3.1 was up-regulated in ESCC tissues and cells and promoted ESCC cell proliferation and invasion.Silencing of LLNLR-299G3.1 with ASO(antisense oligonucleotide)resulted in opposite effects.Mechanistically,LLNLR-299G3.1 bound to cancerassociated RNA binding proteins and regulated the expression of cancer-related genes,including OSM,TNFRSF4,HRH3,and SSTR3.ChIRP-seq(chromatin isolation by RNA purification and sequencing)revealed that these genes contained enriched chromatin binding sites for LLNLR-299G3.1.Rescue experiments confirmed that the effects of LLNLR-299G3.1 on ESCC cell proliferation were dependent on interaction with HRH3 and TNFRSF4.Therapeutically,intravenous delivery of placental chondroitin sulfate A binding peptide-coated nanoparticles containing antisense oligonucleotide(pICSA-BP-ANPs)strongly inhibited ESCC tumor growth and significantly improved animal survival in vivo.Overall,our results suggest that LLNLR-299G3.1 promotes ESCC malignancy through regulating gene-chromatin interactions and targeting ESCC by pICSA-BP-ANPs may be an effective strategy for the treatment of lncRNA-associated ESCC.

对比生物体系以及合成体系中单核铜氧物种对碳氢键和氧氢键活化的理论研究展望

由于具有较好的催化性能,含过渡金属的酶一直备受研究者的关注.其中,铜作为生物体中含量仅次于铁和锌的过渡金属,在新陈代谢过程中发挥着重要作用.铜酶广泛存在于自然界中,该类生物大分子涉及电子转移、氧化还原、氧气的运输与活化等生物化学过程.多种铜酶在氧气活化方面表现出引人注目的性质,例如:颗粒状甲烷单加氧酶(pMMO)、多糖单加氧酶(LPMO)、双铜单加氧酶肽基甘氨酸α-羟基化酶(PHM)和多巴胺β-单加氧酶(DβM),它们均可活化氧气,并生成相应的铜-氧活性物种.铜酶或铜配合物活化氧气可生成多种铜-氧活性物种,包括Cu(II)-O_(2)^(•),Cu(II)-OOH(R),Cu(II)-O^(•)及Cu(III)-OH等.这些活性物种通常具有不同强度的攫氢能力,可能是铜酶C-H/O-H活化的活性氧物种.近几十年来,为了深入揭示铜酶的催化活性和反应机理,阐明关键铜-氧中间体的结构和性质,研究人员合成了众多含铜配合物体系,并模拟探索了铜-氧活性物种的反应活性尤其是对底物C-H/O-H键活化能力.本文聚焦于含有单铜活性位点的酶及其配合物体系.结合密度泛函理论计算,深入比较了铜酶及配合物体系中铜-氧活性物种反应活性,总结得到以下普遍规律:(1)MN15泛函可准确描述单核铜氧配合物的热动力学性质,对各类铜氧物种催化的C-H/O-H键活化计算中,得到的热动力学性质都能与实验结果很好地吻合;(2)Cu(II)-O_(2)^(•)在生物体系和人工合成体系中表现出一致的反应活性:它对O-H键活化表现出高反应活性,但对C-H键反应活性较差,因此不太可能是铜酶中C-H活化的活性中间体;(3)Cu(II)-OOH没有活化C-H键的能力,但其近端氧原子上的自由基特性使其能够攫取中等强度O-H键上的氢原子,另外该物种还可以与另一分子Cu(I)偶联形成双铜物种.因此,在生物体系和合成体系中Cu(II)-OOH均可作为氧气活化路径上的关键中间体,但并不能作为C-H键活化的氧化剂;(4)Cu(II)-O^(•)对C-H键活化具有高反应活性,因此该类物种可能在单铜单加氧酶的C-H键活化中起关键作用;(5)尽管许多实验证明Cu(III)-OH对C-H键的活化有较高的反应活性,但是在单加氧酶中,生成这一物种在热力学上是非常不利的,因此不太可能是单加氧酶中的活性物种.综上,本文的观点可以为生物体系及合成体系中的铜氧物种的反应活性提供新的视角与思考.

Characteristics of alveolar macrophages in bronchioalveolar lavage fluids from active tuberculosis patients identified by single-cell RNA sequencing

Tuberculosis(TB),is an infectious disease caused by Mycobacterium tuberculosis(M.tuberculosis),and presents with high morbidity and mortality.Alveolar macrophages play an important role in TB pathogenesis although there is heterogeneity and functional plasticity.This study aimed to show the characteristics of alveolar macrophages from bronchioalveolar lavage fluid(BALF)in active TB patients.Single-cell RNA sequencing(scRNA-seq)was performed on BALF cells from three patients with active TB and additional scRNA-seq data from three healthy adults were established as controls.Transcriptional profiles were analyzed and compared by differential gene expression and functional enrichment analysis.We applied pseudo-temporal trajectory analysis to investigate correlations and heterogeneity within alveolar macrophage subclusters.Alveolar macrophages from active TB patients at the single-cell resolution are described.We found that TB patients have higher cellular percentages in five macrophage subclusters.Alveolar macrophage subclusters with increased percentages were involved in inflammatory signaling pathways as well as the basic macrophage functions.The TB-increased alveolar macrophage subclusters might be derived from M1-like polarization state,before switching to an M2-like polarization state with the development of M.tuberculosis infection.Cell-cell communications of alveolar macrophages also increased and enhanced in active TB patients.Overall,our study demonstrated the characteristics of alveolar macrophages from BALF in active TB patients by using scRNA-seq.

深水全电采油树控制系统可靠性评估方法

The subsea all-electric Christmas tree(XT) is a key equipment in subsea production systems.Once it fails,the marine environment will be seriously polluted.Therefore,strict reliability analysis and measures to improve reliability must be performed before a subsea all-electric XT is launched;such measures are crucial to subsea safe production.A fault-tolerant control system was developed in this paper to improve the reliability of XT.A dual-factor degradation model for electrical control system components was proposed to improve the evaluation accuracy,and the reliability of the control system was analyzed based on the Markov model.The influences of the common cause failure and the failure rate in key components on the reliability and availability of the control system were studied.The impacts of mean time to repair and incomplete repair strategy on the availability of the control system were also investigated.Research results show the key factors that affect system reliability,and a specific method to improve the reliability and availability of the control system was given.This reliability analysis method for the control system could be applied to general all-electric subsea control systems to guide their safe production.

近十年国内教师信息素养研究述评

"互联网+"时代,信息技术对推动教育教学变革作用巨大,对教师信息素养也提出更高要求。对中国知网数据库近十年发表的教师信息素养研究文献分析发现,已有研究主要内容聚焦于教师信息素养的意义与内涵、不同教师群体信息素养、评价机制、国际比较、问题与策略等方面。呈现出我国教师信息素养研究紧跟信息时代新发展、关注实际问题及提升策略、凸显教师专业发展新内涵的特点。未来研究应拓展研究主题,注重应用价值;辨析概念差异,扩展理论视域;突破思辨范式,加强实证研究。

基于交叉运算的人工蜂群优化BP神经网络的脑电信号分类

为了提高脑电信号的分类准确率,提出一种基于人工蜂群算法和BP神经网络的分类方法。针对反向传播(BP)神经网络存在全局搜索能力差、对初始权重敏感和人工蜂群算法的搜索公式精于探索但疏于开发等问题,采用全局搜索因子来增强人工蜂群算法的开发能力,再加入交叉运算来解决人工蜂群算法的全局搜索。采用改进的算法来优化BP神经网络对初始权重敏感的问题,进而实现对脑电信号的分类。实验结果表明,所提算法对脑电信号的分类准确率更高,分类准确率达到91.5%,而且可以加快收敛速度。

胃食管反流病的免疫机制的研究进展—免疫炎症级联反应正成为新的治疗靶点

胃食管反流病(GERD)是胃十二指肠内容物反流进入食管引起的临床表现和病理变化的一组疾病。近年来针对GERD的发病机制的研究发现,在反流物导致黏膜损伤前,免疫炎症反应早已发生并导致上皮细胞发生变化,继而修复机制被激活。其中,酸/非酸反流是诱导免疫和炎症反应的关键因素。因此,开发一种能够有效地阻断由反流引起的炎症级联反应发生的新靶点,将是一种有前途的GERD治疗方法。

稳定表达MVA途径基因提高番茄红素产量

萜类化合物的直接前体物质异戊烯焦磷酸(IPP)和二甲基烯丙基焦磷酸酯(DMAPP)可以由2-甲基-D-赤藻糖醇-4-磷酸途径(MEP途径)和甲羟戊酸途径(MVA途径)合成。在已经优化MEP合成途径、番茄红素合成途径关键基因表达的重组大肠杆菌LYC101中,引入MVA途径基因,进一步提高重组大肠杆菌合成萜类化合物的能力。质粒pALV23和pALV145是本实验室在研究MVA途径基因协调表达时,用核糖体结合位点(RBS)文库连接MVA途径各基因构建质粒文库,而筛选到的有效提高β-胡萝卜素产量的质粒。首先比较了两个质粒分别在低产和高产番茄红素的菌株中对番茄红素合成的影响。结果表明,两个质粒在高、低产番茄红素的菌株中都可以有效提高番茄红素产量。在高产菌LYC101中pALV23比pALV145使番茄红素产量更高。然后,用CRISPR-Cas9系统辅助同源重组的方法,将MVA途经基因和启动子一共6.7kb的条带整合到LYC101菌株的染色体上,得到遗传稳定的菌株LYC102。LYC102的番茄红素产率达40.9mg/g,是出发菌株LYC101产率的2.19倍,比用质粒表达MVA途径基因的菌株提高了20%。在重组大肠杆菌中同时表达MVA途径和MEP途径,可以有效提高萜类化合物产率;文中构建了不含质粒的、遗传稳定的高产番茄红素菌株,为产业化合成番茄红素提供基础;同时构建平台菌株,可以用于其他萜类化合物合成。

甲羟戊酸途径限速步骤研究及其在产番茄红素重组大肠杆菌中的应用

甲羟戊酸途径(MVA途径)被引入重组大肠杆菌中,能够提高重组大肠杆菌中萜类化合物的合成能力。但因重组大肠杆菌中萜类化合物合成途径中间产物积累,导致细胞生长和萜类化合物合成受到限制。本研究在稳定表达MVA途径以及优化2-甲基-D-赤藻糖醇-4-磷酸途径(MEP途径)、番茄红素合成途径关键基因表达的重组大肠杆菌LYC103中,用质粒高表达MVA途径和番茄红素合成途径关键基因,挖掘该途径的限速步骤。结果表明,ispA、crtE、mvaK1、idi和mvaD基因过表达后,细胞生长没有明显变化,番茄红素产量依次提高了13.5%、16.5%、17.95%、33.7%和61.1%,说明这几个基因可能是合成番茄红素的限速步骤。mvaK1、mvaK2、mvaD三个基因在同一操纵子上,用mRNA稳定区(RNA stabilizing region)进行启动子文库(mRSL)调控mvaK1,相当于对3个基因同时调控。用高效基因组编辑技术(CAGO)对mvaK1基因的mRNA稳定区进行启动子文库的调控,得到菌株LYC104。番茄红素产量与对照菌株LYC103相比增加了2倍,细胞生长提高了32%。然后,利用CRISPR-Cas9技术在染色体lacZ位点整合idi基因,得到LYC105菌株。与出发菌株LYC103相比,细胞生长提高了147%,番茄红素产量增加了2.28倍。本研究在染色体上具有完整MVA途径的基础上,利用质粒高表达单个基因挖掘限速步骤,用同源重组方法整合限速基因、解除限速,为代谢工程构建高产菌株提供新策略。

Uniform Formation of Amorphous Cobalt Phosphate on Carbon Nanotubes for Hydrogen Evolution Reaction

Tremendous efforts have been made to the development of highly active,stable hydrogen evolution reaction(HER)electrocatalysts based on earth-abundant metal compounds.Recently,cobalt phosphorus(Co-P)catalysts have received particular attention owing to their good performances for the HER.

A fluorescent Eu(Ⅲ) MOF for highly selective and sensitive sensing of picric acid

A metal-organic framework [Eu_3L_3(CH_3COO)_2(H_2O)_2(μ_3-OH)]·3 DMF,(EuL, H_2L=9H-carbazole-2,7-dicarboxylic acid,DMF=N,N-dimethylformamide) has been synthesized under solvothermal conditions and structurally characterized. In EuL,Eu_6O_8 clusters are four-bridged by carboxylates to form parallel-aligned Eu–O–C chains, which are further linked by the carbazole moieties of L^(2-) ligands to form the three-dimensional framework with rhombic channels. The EuL material with characteristic emission of Eu^(3+) ion exhibits significant luminescence quenching response for picric acid(PA) and the linear Stern-Volmer plot was observed in the concentration range of 0.05–0.15 mM with K_(sv) of 98074 M^(-1). As far as we know, this Ksv is among the highest values for COFs and MOFs in detection of PA. The excellent anti-interference ability and repeatability were also verified by experiments. Lastly, we investigated the luminescence quenching mechanism in the EuL sensing system.

Polymorphisms of potential drug resistant molecular markers in Plasmodium vivax from China-Myanmar border during 2008-2017

Background:Plasmodium vivax remains the predominant species at the China–Myanmar border,imposing a major challenge to the recent gains in regional malaria elimination.To closely supervise the emerging of drug resistance in this area,we surveyed the variations in genes potentially correlated with drug resistance in P.vivax parasite and the possible drug selection with time.Methods:A total of 235 P.vivax samples were collected from patients sufering uncomplicated malaria at Yingjiang,Tengchong,and Longling counties,and Nabang port in China,Yunnan province,and Laiza sub-township in Myanmar,from 2008 to 2017.Five potential drug resistance genes were amplifed utilizing nested-PCR and analyzed,including pvdhfr,pvdhps,pvmdr1,pvcrt-o,and pvk12.The Pearson’s Chi-squared test or Fisher’s exact test were applied to determine the statistical frequency diferences of mutations between categorical data.Results:The pvdhfr F57I/L,S58R,T61M and S117T/N presented in 40.6%,56.7%,40.1%,and 56.0% of the sequenced P.vivax isolates,and these mutations signifcantly decreased with years.The haplotype formed by these quadruple mutations predominated in Yingjiang,Tengchong,Longling and Nabang.While a mutation H99S/R(56.6%)dominated in Laiza and increased with time.In pvdhps,the A383G prevailed in 69.2% of the samples,which remained the most prevalent haplotype.However,a signifcant decrease of its occurrence was also noticed over the time.The S382A/C and A553G existed in 8.4% and 30.8% of the isolates,respectively.In pvmdr1,the mutation Y976F occurred at a low frequency in 5/232(2.2%),while T958M was fxed and F1076L was approaching fxed(72.4%).The K10 insertion was detected at an occurrence of 33.2% in pvcrt-o,whereas there was no signifcant diference among the sites or over the time.No mutation was identifed in pvk12.Conclusions:Mutations related with resistance to antifolate drugs are prevalent in this area,while their frequencies decrease signifcantly with time,suggestive of increased susceptibility of P.vivax parasite to antifolate drugs.Resistance to chloroquine(CQ)is possibly emerging.However,since the molecular mechanisms underneath CQ resistance is yet to be better understood,close supervision of clinical drug efciency and continuous function investigation is urgently needed to alarm drug resistance.

乳胶清除蛋白LcpK30催化氧气裂解聚顺-1,4异戊二烯机理

乳胶清除蛋白LcpK30是一种内型双加氧酶,其通过活化分子氧催化裂解化学惰性的聚顺-1,4异戊二烯,进而生成醛和酮.实验发现活性区域的谷氨酸148对活性有重大影响,然而其作用机制和整个反应机理仍然存在争议.本研究使用量子力学/分子力学组合方法研究了乳胶清除蛋白催化分子氧氧化裂解天然橡胶模型化合物的反应机理.计算结果显示谷氨酸148在反应过程中为质子化态,并与铁(Ⅲ)-超氧物种形成稳定氢键,因此其作用可能与调节铁(Ⅲ)-超氧物种与底物的位置有关.可能反应机理为:(1)铁(Ⅲ)-超氧物种的远端氧进攻底物碳碳双键,形成过氧烃自由基中间体;(2)近端氧回弹到碳自由基,形成过氧化物中间体和铁(Ⅱ)中心;(3)铁(Ⅱ)调节的过氧化物中间体O–O键还原裂解,生成邻二醇自由基负离子中间体;(4)邻二醇自由基负离子C–C键断裂,生成产物醛和酮.此外,计算发现,过氧化物中间体O–O键直接断裂反应能垒超过160 kJ/mol,表明铁(Ⅱ)的催化对于过氧化物中间体的后续转化至关重要.因此,本研究结果不仅加深对于Lcp_(K30)反应机理的理解,而且为Lcp酶降解合成橡胶材料的设计和工程化提供有用信息.

Plasma membrane calcium ATPase 4b inhibits nitric oxide generation through calcium-induced dynamic interaction with neuronal nitric oxide synthase

The activation and deactivation of Ca^(2+)- and calmodulindependent neuronal nitric oxide synthase (nNOS) in the central nervous system must be tightly controlled to prevent excessive nitric oxide (NO) generation. Considering plasma membrane calcium ATPase (PMCA) is a key deactivator of nNOS, the present investigation aims to determine the key events involved in nNOS deactivation of by PMCA in living cells to maintain its cellular context. Using time-resolved Förster resonance energy transfer (FRET), we determined the occurrence of Ca^(2+)-induced protein-protein interactions between plasma membrane calcium ATPase 4b (PMCA4b) and nNOS in living cells. PMCA activation significantly decreased the intracellular Ca 2+ concentrations ([Ca^(2+)]_(i)), which deactivates nNOS and slowdowns NO synthesis. Under the basal [Ca^(2+)]_(i) caused by PMCA activation, no protein-protein interactions were observed between PMCA4b and nNOS. Furthermore, both the PDZ domain of nNOS and the PDZ-binding motif of PMCA4b were essential for the protein-protein interaction. The involvement of lipid raft microdomains on the activity of PMCA4b and nNOS was also investigated. Unlike other PMCA isoforms, PMCA4 was relatively more concentrated in the raft fractions. Disruption of lipid rafts altered the intracellular localization of PMCA4b and affected the interaction between PMCA4b and nNOS, which suggest that the unique lipid raft distribution of PMCA4 may be responsible for its regulation of nNOS activity. In summary, lipid rafts may act as platforms for the PMCA4b regulation of nNOS activity and the transient tethering of nNOS to PMCA4b is responsible for rapid nNOS deactivation.

Lysosomal chymotrypsin induces mitochondrial fission in apoptotic cells by proteolytic activation of calcineurin

Dear Editor Apoptosis is a fundamental physiological process in mam- mals in which cells die by activating a suicide mechanism. The mitochondria are one of the major checkpoints in apoptotic regulation because they serve as sensors and amplifiers of cellular damage （Green and Kroemer, 2004）. After mitochondrial outer membrane permeabilization （MOMP）, the mitochondria release a number of factors that are critically involved in cell death signaling （Tait and Green, 2010）. Bcl-2 family members are regarded as the key reg- ulators of mitochondria-dependent apoptosis （Moldoveanu et al., 2014）; however, dynamin-related protein 1 （Drpl）, which orchestrates mitochondrial fission, also participates in apoptotic regulation by stimulating Bax oligomerization and thereby enhances MOMP （Montessuit et al., 2010）; accord- ingly, the inhibition of Drpl blocks mitochondrial fission and inhibits apoptosis （Cassidy-Stone et al., 2008）.

Scalping or Line-sitting:The Role of Speculators

Speculative behaviors have burgeoned in various business settings whereby it is costly for consumers to purchase directly from sellers.This paper examines the values of two typical speculative behaviors,scalping and line-sitting,against a backdrop of markets with resale.We establish a two-stage model in which a monopolist seller sells an item(product or service)to consumers in the first stage,and the item can be traded on a resale platform in the second stage.Speculators have no interests in consumption but incur lower costs in pm-chasing and reselling processes than consumers.In the scalping model,they buy the item first and resell it later to make profits.In the line-sitting model,they earn incomes by serving as surrogates of consumers in purchasing.We first find whether the two phenomena emerge critically depends on the value of consumers'entry cost.Our main results indicate that both speculative behaviors can bring benefits to the seller and resale platform by a demand expansion effect,although through different mechanisms.Under scalping,the entry of speculators as additional buyers always boosts demand in both stages,and achieves a win-win outcome for the seller and platform,although less consumers remain in the market and the resale price decreases.Under line-sitting,demand is enlarged and profits rise in both stages,only when consumers find purchasing directly more time-and money-consuming,because they need to pay an extra service fee to speculators.Moreover,the consumer population gets better off from the two speculative behaviors when their entry cost is relatively high.When both models emerge,scalping may be preferable to line-sitting for the seller,resale platform and consumers,if the cost advantage of speculators in resale transactions is more evident.