改进分析化学中常用评价参数教学内容的探讨

分析化学中,定量分析方法的性能评价参数包括:加标回收率、相对标准偏差、校准曲线及其相关系数、线性范围、误差棒、检测限、灵敏度、选择性、稳定性等,深刻理解以上参数的含义并熟练运用是分析化学工作者的基本素养。然而,对大多数高年级本科生和硕士研究生问卷调查发现,掌握常用分析参数用法的学生不足半数,并且无法区分含义相近参数。这是由于目前的教材仅仅介绍分析参数的基本概念,缺乏其实际应用的举例,而且尚无文献以举例的方式系统完整地介绍分析参数应用方式。本文精选分析化学中引用率最高的期刊Analytical Chemistry中多篇前沿文章,通过具体实例生动透彻地讲解各个评价参数的标准应用方式,代替以往单一的理论介绍。本工作旨在引导学生深刻理解基于评价参数直观的评价分析方法和分析结果的有效性,并且能够在以后的科研工作中熟练使用、准确表达,以期为改进更具科学实用的评价参数教学内容提供参考。

Traditional Chinese medicine Pien-Tze-Huang ameliorates LPS-induced sepsis through bile acid-mediated activation of TGR5-STAT3-A20 signalling

Pien Tze Huang(PZH),a class-1 nationally protected traditional Chinese medicine(TCM),has been used to treat liver diseases such as hepatitis;however,the effect of PZH on the progression of sepsis is unknown.Here,we reported that PZH attenuated lipopolysaccharide(LPS)-induced sepsis in mice and reduced LPS-induced production of proinflammatory cytokines in macrophages by inhibiting the activation of mitogen-activated protein kinase(MAPK)and nuclear factor-kappa B(NF-κB)signalling.Mechanistically,PZH stimulated signal transducer and activator of transcription 3(STAT3)phosphorylation to induce the expression of A20,which could inhibit the activation of NF-κB and MAPK signalling.Knockdown of the bile acid(BA)receptor G protein-coupled bile acid receptor 1(TGR5)in macrophages abolished the effects of PZH on STAT3 phosphorylation and A20 induction,as well as the LPS-induced inflammatory response,suggesting that BAs in PZH may mediate its anti-inflammatory effects by activating TGR5.Consistently,deprivation of BAs in PZH by cholestyramine resin reduced the effects of PZH on the expression of phosphorylated-STAT3 and A20,the activation of NF-κB and MAPK signalling,and the production of proinflammatory cytokines,whereas the addition of BAs to cholestyramine resin-treated PZH partially restored the inhibitory effects on the production of proinflammatory cytokines.Overall,our study identifies BAs as the effective components in PZH that activate TGR5-STAT3-A20 signalling to ameliorate LPS-induced sepsis.

Epidemiology of insertional and midportion Achilles tendinopathy in runners:A prospective cohort study

Background:Achilles tendinopathy(AT)is a common problem among runners.There is only limited evidence for risk factors for AT,and most studies have not defined the AT subcategories.No study has compared the incidence and risk factors between insertional AT and midportion AT,though they are considered distinct.This study aimed to assess incidence and risk factors of AT based on data from a large prospective cohort.The secondary aim was to explore differences in risk factors between insertional and midportion AT.Methods:Participants were recruited from among registered runners at registration for running events.Questionnaires were completed at baseline,1 month before the event,1 week before the event,and 1 month after the event.Information concerning demographics,training load,registered events,and running-related injuries were collected at baseline.The follow-up questionnaires collected information about new injuries.A pain map was used to diagnose midportion and insertional AT.The primary outcome was the incidence of AT.Multivariable logistic regression analysis was applied to identify risk factors for the onset.Results:We included 3379 participants with a mean follow-up of 20.4 weeks.The incidence of AT was 4.2%.The proportion of insertional AT was 27.7%and of midportion AT was 63.8%;the remaining proportion was a combined type of insertional and midportion AT.Men had a significantly higher incidence(5%,95%confidence interval(95%CI):4.1%-6.0%)than women(2.8%,95%CI:2.0%-3.8%).AT in the past12 months was the most predominant risk factor for new-onset AT(odds ratio(OR)=6.47,95%CI:4.27-9.81).This was similar for both subcategories of AT(insertional:OR=5.45,95%CI:2.51-11.81;midportion:OR=6.96,95%CI:4.24-11.40).Participants registering for an event with a distance of 10/10.55 km were less likely to develop a new-onset AT(OR=0.59,95%CI:0.36-0.97)or midportion AT(OR=0.47,95%CI:0.23-0.93).Higher age had a significant negative association with insertional AT(OR=0.97,95%CI:0.94-1.00).Conclusion:The incidence of new-onset AT among recreational runners was 4.2%.The proportion of insertional and midportion AT was 27.7%and 63.8%,respectively.AT in the past 12 months was the predominant risk factor for the onset of AT.Risk factors varied between insertional and midportion AT,but we could not identify clinically relevant differences between the 2 subtypes.

DNA methylation mediated by RdDM pathway and demethylation affects furanone accumulation through regulation of QUINONE OXIDOREDUCTASE in strawberry

Recently,increasing evidence suggests that DNA methylation plays a crucial role in fruit ripening.However,the role of DNA methylation in regulating specific traits,such as flavor,remains unclear.Here,we report a role of DNA methylation in affecting furanone biosynthesis in strawberry.Strawberry quinone oxidoreductase(FaQR)is a key enzyme in furanone biosynthesis.There are four FaQR homologs in strawberry cultivar‘Yuexin’,and one of them,FaQR3,contributes∼50%of FaQR transcripts,indicating a major role of FaQR3 in furanone biosynthesis.Through characterization of levels of DNA methylation and FaQR3 transcript and furanone contents during fruit ripening and after the application of DNA methylation inhibitor,we found that the DNA methylation level of the FaQR3 promoter was negatively correlated with FaQR3 expression and furanone accumulation,suggesting that DNA methylation may be involved in furanone biosynthesis through adjusting FaQR3 expression,and responded to different temperatures consistently.In addition,transient expression of a gene in the RNA-directed DNA methylation(RdDM)pathway,FaAGO4,and enrichment analysis of the 24-nucleotide siRNAs suggested that DNA methylation in the FaQR3 promoter is mediated by the RdDM pathway.Transient RNA interference(RNAi)of FaDML indicated that the demethylation pathway may be involved in regulating furanone accumulation.These findings provide new insights into the role of DNA methylation and demethylation in affecting flavor quality in strawberry during fruit ripening.

Do Geographically Isolated Grasslands Follow the Principle of Island Biogeography in a Landscape Scale? Taking Poyang Lake Grassland as an Example

As one of the basic theories of biodiversity conservation,island biogeography has been widely accepted in the past decades.Originally,island biogeography was put forward and applied in oceanic environments.But later on,it was found out that the application was not only limited to oceanic islands,but also in terrestrial environments with relatively isolated conditions.In terms of biodiversity level,island biogeography generally focuses on a small scale,such as species diversity and genetic diversity.The studies of biodiversity on a large-scale based on island biogeography,such as ecosystem and landscape scales,were seldomly conducted.Taking Poyang Lake,the largest fresh water lake in China as case study area,30 grasslands were randomly selected to study whether island biogeography can be applied to grasslands at a landscape level from three island attributes(area,distance and shape),and the most important ecological variable(flooding)in Poyang Lake.The results showed that in general,grasslands have the property of an island,and follow the basic principle of island biogeography.We found the area and flooding duration were the two most important determinants of landscape diversity.There was a significant positive correlation between the grassland area and the landscape diversity,which could be well expressed by logarithmic function model(R2=0.73).There was a negative correlation between flooding duration and landscape diversity,which could be described by an inverse model(R2=0.206).The distance to mainland and the shape of grassland were correlated with landscape diversity,but the fitting result of the models was not as good as expected.The possible reason could be that Poyang Lake is a seasonal lake,the water level varies with hydrological conditions,so that the grasslands are not strongly isolated and their shape is not stable enough required by island biogeography.Furthermore,it indicates that besides area,distance and shape attributes,flooding strongly affects the biodiversity of grassland vegetation,and should not be ignored when applying island biogeography theory to Poyang Lake.This study is expected to be a supplement for island biogeography in terrestrial environments,and the results are expected to benefit for the biodiversity conservation in Poyang Lake.

通过聚丙烯/聚乙烯二元体系的流变控制制备聚合物多层片材

通过毛细管流变仪研究了二元聚合物体系的分相流动行为,以及在动态外场作用下的演变规律,利用低黏度熔体包覆高黏度熔体的"粘性包覆"现象,筛选出具有满足分相流动条件并特定黏度比的聚乙烯(PE)和聚丙烯(PP),成功地一次成型制备出多层聚合物膜片。利用凝胶色谱仪、偏光显微镜、有限元分析软件等对PP/PE二元体系的形态结构进行了研究,并探讨了分层流动的机理。结果表明,通过PE/PP黏度比可以控制材料流变行为,从而制备"核壳"结构和PP-PE-PP"三明治"结构,并优化出最适宜的加工窗口。同时,发现流动过程中PP和PE的径向速度是不同的,分层流动是材料粘弹性和加工流场共同作用的结果。

Development of a monitoring and warning system based on optical fiber sensing technology for masonry retaining walls and trees

Hong Kong has a long history of applying masonry retaining walls to provide horizontal platforms and stabilize man-made slopes.Due to the sub-tropical climate,some masonry retaining walls are colonized by trees.Extreme weather,such as typhoons and heavy rains,may cause rupture or root failure of those trees,thus resulting in instability of the retaining walls.A monitoring and warning system for the movement of masonry retaining walls and sway of trees has been designed with the application of fiber Bragg grating(FBG)sensing technology.The monitoring system is also equipped with a solar power system and 4G data transmission devices.The key functions of the proposed monitoring system include remote sensing and data access,early warning,and real-time data visualization.The setups and working principles of the monitoring systems and related transducers are introduced.The feasibility,accuracy,serviceability and reliability of this monitoring system have been checked by in-site calibration tests and four-month monitoring.Besides,a two-level interface has been developed for data visualization.The monitoring results show that the monitored masonry retaining wall had a reversible movement up to 2.5 mm during the monitoring period.Besides,it is found that the locations of the maximum strain on trees depend on the crown spread of trees.

Estimation of plasma parameters in the process of micro-scale powder plastic and characteristics of its products

The temperature and density of plasma jets were estimated with a Boltzmann plot and Stark broadening of Ar I(696.54 nm) lines by optical emission spectroscopy(OES) in the process of plasma plastic, and the morphology and microstructure of tungsten(W) powders were investigated by scanning electron microscope(SEM) and x-ray Diffraction(XRD), respectively.The results show that the assumption of local thermodynamic equilibrium(LTE) was invalid at the end of the plasma jets, and earlier than this after the injection of tungsten powder. The temperature and electron density of the plasma jets were up to about T?=?6797 K with Qc?=?50 slpm and ne?=?1.05?×?1016 cm-3 with Qs?=?115 slpm at Z?=?60 mm, respectively, and both dropped rapidly with the injected tungsten powders of 20 μm. After the plasma plastic process,the spherical tungsten powders were prepared and there were some satellite particles on the surface of the spherical products. The tungsten powders were both composed of a single equilibrium α-W phase with a body centered cubic(bbc) crystal structure before and after plasma treatment.

Changes in Imja Lake and Karda Lake in the Everest Region of Himalaya

The Himalaya is a region sensitive to climate change. Changes in the glacial regime are one indicator of global climate changes. There are several studies focusing on analysis of temporal changes of these glacial lakes in the Himalaya region. However, the researches on addressing these trends in relation with surrounding topographical conditions are quite limited. In this study, we analyzed spatio-temporal changes in Imja Lake, located on the southern slope, and Karda Lake, located on the northern slope of the Mt. Everest region, in 1976, 1992, 2000, and 2008. Moreover, we examined whether the topographic conditions differ between the two slopes. Landsat and ASTER GDEM (advanced space borne thermal emission and reflection radiometer, global digital elevation model) data were used to identify boundaries of target glacial lakes and to calculate three indices of growth rate compared to year of 1976 (%, GRa), growth rate compared to preceding year (%, GRb), and growth speed (m2/year, GS) of the two lakes. The topographic conditions in circular buffer zones from the centroid of the two lakes were analyzed. Although the area of two lakes demonstrated linear increase from 1976 to 2008, growth rate compared to year of 1976 (GRa) differed significantly (Kruskal-Wallis test, p squared test for independence on m × n contingency table between 1976, 1992, 2000, and 2008 on growth speed (GS)). The two slopes differed in terms of three topographical variables: altitude, aspect, and angle of inclination (Kruskal-Wallis test,

Observation-Oriented Causal Discovery for Cultivation Abandonment of Rice Terraces: Focusing on an Effect of Cultural Endemism on Decision-Making in Toraja, Indonesia

Previous discussion about the factors of the expanding trend of abandoned cultivation had focused only on universal factors and lacked evaluation of the regionality of the phenomenon. This paper demonstrated the Toraja’s regional characteristics and the influence of cultural endemism on decision-making about abandoning cultivation by an observation-oriented approach. Based on a causal framework constructed by field observation and geospatial data generation, an adjustment for overt covariates using the multivariate logistic regression model to draw the causal effect from hidden covariates was examined in two rice terraces with different water systems, i.e. irrigated field and rain-fed field. The result of sub-group analysis revealed that decisions about abandoning cultivation in Toraja were greatly associated with disadvantageous factors for intensive farming, i.e. “number of adjacent fields” and “soil erosion” rather than advantageous factors, i.e. “area of field” and “distance to roads”. Moreover, the result of interaction analysis which controlled the effect of topography revealed the powerful effect of particular decision factors only in rain-fed rice terrace: the “distance to roads” factor’s fairly negative contribution on abandoning cultivation (Odds ratio = 9.94E - 01, P value = 2.03E - 11), as well as the “number of adjacent field” factor’s positive contribution on abandoning cultivation (Odds ratio = 1.13E+00, P value = 3.65E - 04). Given the evidence from the explanation of these results by customary laws and land inheritance system for each site, therefore, it could be concluded that the screening and detection of cultural endemism’s influence was achieved using the algorithm this paper proposes.

DNA methylation controlling abscisic acid catabolism responds to light to mediate strawberry fruit ripening

Phytohormones,epigenetic regulation and environmental factors regulate fruit ripening but their interplay during strawberry fruit ripening remains to be determined.In this study,bagged strawberry fruit exhibited delayed ripening compared with fruit grown in normal light,correlating with reduced abscisic acid(ABA) accumulation.Transcription of the key ABA catabolism gene,ABA 8′-hydroxylase FaCYP707A4,was induced in bagged fruit.With light exclusion whole genome DNA methylation levels were up-regulated,corresponding to a delayed ripening process,while DNA methylation levels in the promoter of FaCYP707A4 were suppressed,correlating with increases in transcript and decreased ABA content.Experiments indicated FaCRY1,a blue light receptor repressed in bagged fruit and FaAGO4,a key protein involved in RNA-directed DNA methylation,could bind to the promoter of FaCYP707A4.The interaction between FaCRY1 and FaAGO4,and an increased enrichment of FaAGO4 directed to the FaCYP707A4 promoter in fruit grown under light suggests FaCRY1 may influence FaAGO4 to modulate the DNA methylation status of the FaCYP707A4 promoter.Furthermore,transient overexpression of FaCRY1,or an increase in FaCRY1 transcription by blue light treatment,increases the methylation level of the FaCYP707A4 promoter,while transient RNA interference of FaCRY1 displayed opposite phenotypes.These findings reveal a mechanism by which DNA methylation influences ABA catabolism,and participates in light-mediated strawberry ripening.

A comprehensive review of thermally sprayed abradable sealing coatings:Focusing on abradability

Modern aero and stationary gas turbine engines have been designed with much higher compressor-pressure ratios and thrust-weight ratios than earlier models,and these ratios are strongly influenced by the hot-running clearances between the rotating and stationary components.The main benefit of reduction in the clearances is efficiency gains,resulting in lowered fuel consumption and polluting gas emissions,with ecological and economic advantages.However,at these undersized clearances,some rubbing interactions are unavoidable,which can be accommodated by applying Abradable Sealing Coatings(ASCs)on the stationary inner surface.This paper reviews the commercially available abradable materials for thermal spraying at various application positions and temperatures.Emphasis is placed on the abradability and wear mechanisms involved.In addition,considering the tendency of SiC/SiC ceramic matrix composites replacing superalloys as hot section components,the future prospect of ceramic abradables based on Environmental Barrier Coatings(EBCs)in turbine stages is summarized and a new concept of"self-degradable ceramics"based on the corrosive steam environment is proposed for the purpose of high-temperature fillerfree abradables.

Disulfiram enhances the antitumor activity of cisplatin by inhibiting the Fanconi anemia repair pathway

A series of chemotherapeutic drugs that induce DNA damage,such as cisplatin(DDP),are standard clinical treatments for ovarian cancer,testicular cancer,and other diseases that lack effective targeted drug therapy.Drug resistance is one of the main factors limiting their application.Sensitizers can overcome the drug resistance of tumor cells,thereby enhancing the antitumor activity of chemotherapeutic drugs.In this study,we aimed to identify marketable drugs that could be potential chemotherapy sensitizers and explore the underlying mechanisms.We found that the alcohol withdrawal drug disulfiram(DSF)could significantly enhance the antitumor activity of DDP.JC-1 staining,propidium iodide(PI)staining,and western blotting confirmed that the combination of DSF and DDP could enhance the apoptosis of tumor cells.Subsequent RNA sequencing combined with Gene Set Enrichment Analysis(GSEA)pathway enrichment analysis and cell biology studies such as immunofluorescence suggested an underlying mechanism:DSF makes cells more vulnerable to DNA damage by inhibiting the Fanconi anemia(FA)repair pathway,exerting a sensitizing effect to DNA damaging agents including platinum chemotherapy drugs.Thus,our study illustrated the potential mechanism of action of DSF in enhancing the antitumor effect of DDP.This might provide an effective and safe solution for combating DDP resistance in clinical treatment.

Genome-wide characterization of alternative splicing in blood cells of COVID-19 and respiratory infections of relevance

Dear Editor,Alternative splicing of eukaryotic transcripts refers to the posttranscriptional process in which the coding regions(exons)of a precursor transcript are joined in different combinations through the removal or retention of non-coding intervening sequences(introns)to produce distinct mature messenger RNA(mRNA)transcripts and further generate one or more mature mRNAs(Lee and Rio,2015).Alternative splicing is revealed dysregulation in infectious diseases.Many pathogens hijack the splicing mechanism of host cells to complete their replications,accompanied by dysregulated innate immune response or cell damage,leading to the changes of alternative splicing landscape in host cells(Ashraf et al.,2019;Tomezsko et al.,2020;Kremsdorf et al.,2021).The regulation mechanism of alternative splicing by viral pathogens,such as hepatitis B virus(Duriez et al.,2017),human immunodeficiency virus 1(Tomezsko et al.,2020),Zika virus(Bonenfant et al.,2020)and enterovirus 71(Li et al.,2020),have been explored.

Recent developments and progress of inorganic photo-stimulated phosphors

Photo-stimulated luminescence(PSL) is the process in which trapped charges are released by photons and produce luminescence through recombination. The variegated optical characteristics of photostimulated phosphors(PSPs) have drawn increasing attention and a large body of work encompassing mechanism and application of PSPs has been addressed. The optical data storage capacity resulting from abundant defect states enables PSPs to be applied to information storage. Moreover, PSPs provide potential application for anti-counterfeiting, as color changes due to the tunneling process. Recently, near infrared(NIR) light PSPs have been developed, exhibiting enormous potential for in vivo bio-imaging, as the stable and high noise-signal ratio characteristic of PSL. In this review, we devote to introducing the development and process of PSPs, and the challenge and future advance have also been demonstrated.

Ultra-high sensitivity of rhodamine B sensing based on NaGdF_4:Yb^(3+),Er^(3+)@NaGdF_4 core-shell upconversion nanoparticles

A series of mono-dispersed hexagon NaGdF_4:Yb^(3+),Er^(3+)@NaGdF_4 core-shell nanoparticles with different shell thickness were synthesized via a co-precipitation method. Nanoparticles with high upconversion fluorescent emissions result in large signal-to-noise ratio, which guarantees the accuracy of the sensitivity. Besides, the maximum sensitivity of these NPs as detection film increases first and then decreases with the shell thickness increasing. When the shell thickness is 2.3 nm(NaGdF_4-2), the maximum sensitivity(0.69959 ppm^(-1)) is reached. A large degree of overlap between the rhodamine B absorption band and the Er^(3+) green emission bands ensures that the NaGdF_4:Yb^(3+),Er^(3+)@NaGdF_4 nanoparticles can be used as fluorescent probe to detect the concentration of rhodamine B based on fluorescent intensity ratio technology. The linear relationship between the rhodamine B concentration and the intensity ratio(R) of green and red emission intensity(I_(S+H) and I_F) were studied systematically. The result shows that the maximum sensitivity can be obtained in low concentration rhodamine B(<4 ppm), which is lower than the reported minimum detection concentration. Thus, the ultra-high sensitivity detection by NaGdF_4:Yb^(3+),Er^(3+)@NaGdF_4 core-shell upconversion nanoparticles in low concentration can be realized,which provides promising applications in bio-detection filed.

Catalyst-free,direct electrochemical trifluoromethylation/cyclization of N-arylacrylamides using TfNHNHBoc as a CF_(3) source

A new electrochemical strategy for trifluoromethylation/cyclization using TfNHNHBoc as a CF_(3)source was established.This approach was realized by the direct electrolysis of Tf NHNHBoc under external oxidantfree and catalyst-free conditions,and afforded various trifluoromethylated oxindoles with good functional group compatibility and broad substrate scope.Preliminary mechanistic studies show that the reaction proceeds by a radical process.

A boronic acid-based fluorescent hydrogel for monosaccharide detection

A boronic acid-based anthracene fluorescent probe was functionalised with an acrylamide unit to incorporate into a hydrogel system for monosaccharide detection.In solution,the fluorescent probe displayed a strong fluorescence turn-on response upon exposure to fructose,and an expected trend in apparent binding constants,as judged by a fluorescence response where D-fructose>D-galactose>D-mannose>D-glucose.The hydrogel incorporating the boronic acid monomer demonstrated the ability to detect monosaccharides by fluorescence with the same overall trend as the monomer in solution with the addition of D-fructose resulting in a 10-fold enhancement(≤0.25 mol/L).

Friedel-Crafts trifluoromethylthiolation of electron-rich(hetero)arenes with trifluoromethylthio-saccharin in 2,2,2-trifluoroethanol(TFE)

A promoter-free Friedel-Crafts trifluoromethylthiolation of electron-rich arenes and heteroarenes with N-trifluoromethylthiosaccharin 5 using 2,2,2-trifluoroethanol(TFE) as the solvent was described.The reactions were conducted at 40℃and a variety of common functional groups were compatible.

Self-twisting for macrochirality from an achiral asterisk molecule with fluorescence-phosphorescence dual emission

Understanding of the role of supramolecular chirality for tuning material optoelectronic properties has been restricted by the limited number of cases. A particular challenge is to impose supramolecular chirality onto multicolor luminescent systems that can emit in aggregation state. Here we present a self- assembly strategy from a well-selected asterisk molecule for generating supramolecular chirality with fluorescence-phosphorescence dual emission. The work takes advantages of （1） achiral chemical structure dependent peculiar self-assembly that can spontaneously undergo symmetry breaking to produce macrochirality, and （2） the assembly process can be monitored by time which due to the crystallization-driven self-assembly by self-twisting, allowing a self-progressing chiral amplification. A multicolor luminescence induced by the fluorescence-phosphorescence dual emission along with such a self-assembly behavior was also observed at a single solution system versus the time. The self-twisting chiral self-assembly fashion provides new prospects for understanding the establishment of nanochirality from achiral molecular building blocks.