Mechanical behavior and failure mechanism of polyurea nanocomposites under quasi-static and dynamic compressive loading

Polyurea is an elastomeric material that can be applied to enhance the protection ability of structures under blast and impact loading.In order to study the compressive mechanical properties of SiC/polyurea nanocomposites under quasi-static and dynamic loading,a universal testing machine and split Hopkinson pressure bar(SHPB)apparatus were used respectively.The stress-strain curves were obtained on polyurea and its composites at strain rates of 0.001e8000 s1.The results of the experiment suggested that increase in the strain rates led to the rise of the flow stress,compressive strength,strain rate sensitivity and strain energy.This indicates that all of the presented materials were dependent on strain rate.Moreover,these mechanical characters were enhanced by incorporating a small amount of SiC into polyurea matrix.The relation between yield stress and strain rates were established using the power law functions.Finally,in order to investigate the fracture surfaces and inside information of failed specimens,scanning electron microscopy(SEM)and micro X-ray computed tomography(micro-CT)were used respectively.Multiple voids,crazes,micro-cracks and cracking were observed in fracture surfaces.On the other hand,the cracking propagation was found in the micro-CT slice images.It is essential to understand the deformation and failure mechanisms in all the polyurea materials.

Preparation and In vitro Evaluation of Polydopamine-coated Immunoadjuvant Nanoparticles

[Objectives]The paper was to prepare immunoadjuvant nanoparticles with good photothermal conversion efficiency and to achieve the synergistic antitumor effect of phototherapy and immunotherapy.[Methods]Poly(lactic-co-glycolic acid)(PLGA)nanoparticles of imiquimod(R837)were prepared by emulsified solvent evaporation method.Dopamine was oxidized and self-polymerized to form polydopamine(PDA)under alkaline conditions,which then adhered to the surface of R837-PNPs(PDA-R837-PNPs).Particle size,Zeta potential and photothermal conversion capacity were used as indicators to select the best polymerization conditions.The photothermal conversion properties and photothermal stability of nanoparticles were investigated by near-infrared light(NIR)irradiation;the encapsulation efficiency and drug loading capacity of R837 were determined by HPLC;the cytotoxicity and cellular uptake of PDA-R837-PNPs were preliminarily investigated using 4T1 cells.[Results]PDA-R837-PNPs were prepared successfully.The optimal polymerization conditions were 0.5 mg/mL dopamine,3 h reaction time and 1.8 mg/mL R837-PNPs.The particle size of PDA-R837-PNPs was(186.7±4.81)nm;the PDI was 0.17±0.02;the Zeta potential was(-21.6±0.56)mV;the encapsulation efficiency was(58.02±0.04)%;and the drug loading capacity was(1.42±0.05)%.PDA-R837-PNPs had good photothermal conversion and photothermal stability in vitro.Cell experiments showed that PDA coating could significantly improve the celluar uptake of PNPs without obvious cytotoxicity,and PDA-R837-PNPs could produce heat to effectively kill 4T1 cells after NIR irradiation.[Conclusions]PDA-R837-PNPs have the characteristics of uniform particle size,good photothermal conversion effect and high cellular uptake rate,thus is expected to achieve efficient antitumor photoimmunotherapic effect.

Study on the mechanism of JiChuanJian in the treatment of slow-transmission constipation based on network pharmacology

Background:Slow-transit constipation remains a functional colonic disorder with the most common gastrointestinal complaint.Although JiChuanJian(JCJ)is used for treatment,little is known about its mechanism of action.We aimed to investigate the mechanism of JCJ in treating slow-transmission constipation based on network pharmacology.Methods:The chemical components and action targets of the six herbs of JCJ were retrieved from the Traditional Chinese Medicine Systematic Pharmacology Analysis Platform.Protein targets of the chemical components were obtained from the UniProt database,whiles the disease targets were retrieved from the Gene Cards database,Disgenet,and TTD databases.A Wayne diagram was drawn and the intersected targets were imported onto the STRING website for analysis to construct protein-protein interaction target interactions.The Cytoscape software constructed protein-protein interaction to identify core targets and drug-active component-target interaction networks.The Kyoto Encyclopedia of Genes and Genomes and gene ontology enrichment analyses were performed through the DAVID analysis website.Results:A total of 55 potential drug-active components of JCJ,233 drug-active ingredient targets,3215 slow-transmission constipation-related targets,and 176 drug and disease targets were identified.The core drug-active ingredients included quercetin,beta-sitosterol,stigmasterol,kaempferol and wogonin.Through enrichment analysis in DAVID database,we obtained 236 biological processes,31 cellular components and 41 molecular functions,mainly involving serotonin binding,G-protein coupled serotonin receptor activity,and neurotransmitter receptor activity,were identified.118 pathway enrichment results were obtained after the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis.Therefore,we hypothesized that the active components in JCJ,such as quercetin,β-sitosterol,and stigmasterol,may treat slow transit constipation by regulating the serotonergic synapse and cyclic adenosine monophosphate signaling pathway.Conclusion:This study showed that JCJ could play a role in treating slow-transmission constipation through multiple components,targets and pathways.

The efficacy and mechanism of fecal microflora transplantation in the treatment of slow transit constipation based on metabonomics anion mode

Background:Fecal microbiota transplantation(FMT)based on the positive ion mode of metabonomics has a good therapeutic benefit for slow transit constipation(STC)patients.However,a piece of comprehensive metabolomics information is yet to be established.The aim of the study was to explore the efficacy and mechanism of FMT in the treatment of STC under metabonomics.Methods:Eight STC patients meeting the set inclusion and exclusion criteria were enrolled and treated with FMT(three times).The Patient Assessment of Constipation-Symptoms(PAC-SYM),weekly total defecation times,and defecation frequency scores of these STC patients were compared before and after treatment.Feces and serum of STC patients before and after treatment were analyzed using 16SrDNA and metabolomics.Results:After FMT treatment,the PAC-SYM score of constipated patients decreased[(5.00±2.94)vs(5.20±2.87)],while the number of complete defecations per week increased[(2.00±1.79)vs(1.69±1.80)].The score of defecation frequency decreased[(0.83±1.03)vs(0.86±0.95)].The metabolites in the feces and serum of patients receiving FMT changed significantly(P<0.05).The results from 16SrDNA analysis showed that theαandβdiversity of the fecal microbiome changed significantly(P<0.05)after transplantation,and the contents of genera Lactobacillus,Bacillus,Succiniclasticum,Cellvibrio,and Escherichia increased in FMT treated patients.Conclusion:FMT may treat STC by increasing the beneficial intestinal flora and metabolites in the anion mode of metabolomics.

喷雾干燥结合紫外交联制备甲基丙烯酸缩水甘油酯改性丝胶中空微球及其性能

为了制备高耐水性光固化丝胶蛋白(SS)微球,采用喷雾干燥与紫外交联相结合的方法,以丝胶为原料制备了甲基丙烯酸缩水甘油酯(GMA)交联SS中空微球(GMA-g-SS),该法赋予了其良好的耐水稳定性和紫外光固化性能。优化的喷雾干燥工艺参数包括:SS浓度、进风温度及进液速度;研究了GMA浓度、二苯甲酮(BP)用量及紫外辐照时间对接枝率的影响。借助扫描电镜、红外光谱及热分析对微球表面形貌结构及稳定性进行了表征与分析。结果表明,喷雾干燥SS微球呈单分散空心结构,直径约5~20μm;GMA-g-SS微球红外光谱在1152 cm^(-1)和764 cm^(-1)处出现环氧基的吸收峰,表明GMA与SS交联成功。交联后微球呈黏连聚集状态,具有较高的紫外光固化性能且耐水稳定性大幅提升,溶失率仅为17.1%。所制备的GMA-g-SS微球具有可调的耐水稳定性和紫外光固化性,是一种有潜力的光固化3D打印生物材料。

A2β-酪蛋白牛奶和普通牛奶的体外消化特性和抗氧化能力评价

[目的]研究体外模拟胃肠消化对A2β-酪蛋白牛奶和普通牛奶的分子量分布及抗氧化能力的影响。[方法]以巴氏杀菌A2β-酪蛋白牛奶、超高温灭菌A2β-酪蛋白牛奶、巴氏杀菌普通牛奶、超高温灭菌牛奶为原料,通过INFOGEST 2.0对牛奶进行体外模拟胃肠消化,采用SDS-PAGE、高效液相色谱仪对体外模拟胃肠消化前后的牛奶样品进行分子量分析,并对体外模拟胃肠消化后各样品的抗氧化能力进行测定。[结果]在体外模拟胃肠消化后,4种牛奶的分子量主要分布于<1000 Da组分,A2β-酪蛋白牛奶小于500 Da组分的比例显著低于普通牛奶。超高温灭菌普通牛奶、超高温灭菌A2β-酪蛋白牛奶表现出较强的铁离子还原能力和1,1-二苯基-2-三硝基苯肼(DPPH)自由基清除能力。[结论]本研究为各类牛奶产品的加工和功能特性提供基础数据。

Hydraulic properties and drought response of a tropical bamboo (Cephalostachyum pergracile)

Bamboo plants are an essential component of tropical ecosystems,yet their vulnerability to climate extremes,such as drought,is poorly understood due to limited knowledge of their hydraulic properties.Cephalostachyum pergracile,a commonly used tropical bamboo species,exhibited a substantially higher mortality rate than other co-occurring bamboos during a severe drought event in 2019,but the underlying mechanisms remain unclear.This study investigated the leaf and stem hydraulic traits related to drought responses,including leaf-stem embolism resistance(P50leaf;P50stem) estimated using optical and X-ray microtomography methods,leaf pressure-volume and water-releasing curves.Additionally,we investigated the seasonal water potentials,native embolism level(PLC) and xylem water source using stable isotope.We found that C.pergracile exhibited strong resistance to embolism,showing low P50leaf,P50stem,and turgor loss point,despite its rapid leaf water loss.Interestingly,its leaves displayed greater resistance to embolism than its stem,suggesting a lack of effective hydraulic vulnerability segmentation(HVS) to protect the stem from excessive xylem tension.During the dry season,approximately 49% of the water was absorbed from the upper 20-cm-deep soil layer.Consequently,significant diurnal variation in leaf water potentials and an increase in midday PLC from 5.87±2.33% in the wet season to 12.87±4.09%in the dry season were observed.In summary,this study demonstrated that the rapid leaf water loss,high reliance on surface water,and a lack of effective HVS in C.pergracile accelerated water depletion and increased xylem embolism even in the typical dry season,which may explain its high mortality rate during extreme drought events in 2019.

肠道菌群介导的不同饮食模式与高尿酸血症相关性研究进展

高尿酸血症(hyperuricemia,HUA)是一种由于尿酸生成与排泄失衡所导致的嘌呤代谢紊乱性疾病,严重时可导致痛风及肾功能损伤。目前我国HUA/痛风的患病率逐年提升,且患病人群越来越年轻化。近年来的研究表明HUA/痛风患者的肠道菌群与健康人相比存在失调现象,而不同饮食模式可介导肠道菌群影响尿酸水平。本文详细阐述了HUA/痛风病人的肠道菌群特征以及肠道菌群对尿酸的代谢机制,为HUA/痛风的预防、提早诊断和辅助治疗提供理论基础;同时总结了不同饮食模式对尿酸水平影响的相关研究进展,旨在指导患者通过调整饮食模式有效预防并延缓HUA/痛风的发生。

网络符号消费研究的理论、文化与价值面向

中国知网(CNKI)数据库和Web of Science(WOS)数据库中与网络符号消费相关的有效文献可作为数据来源,借助可视化分析软件CiteSpace,从年度发文量、发文作者、发文机构、关键词共现、关键词聚类等角度进行分析可以发现,国内外学界关于网络符号消费的研究呈现出三个面向:符号消费理论研究、网络消费文化研究以及身体与休闲研究。由此可见,关于网络符号消费的探索和研究日益呈现出多学科跨领域的发展趋势,这为当前及未来国内外学者研究网络符号消费提供一个学术史概览以及渐进式探寻的学术觅迹。

创伤病人早期预警评估工具研究进展

综述创伤病人早期预警相关评估工具的发展过程、主要内容及应用现状,分析各种评估工具的特点及局限性,并进行对比分析,旨在为临床工作者快速选择恰当的评估工具提供借鉴。

草酸钙酸分解的热力学分析

为阐明草酸钙渣酸分解过程的热力学,基于同时平衡原理、质量守恒原理、电中性原则,以盐酸和硫酸为分解药剂,计算和绘制草酸钙酸分解的热力学平衡图,并结合实验验证。研究结果表明:单因素实验结果与热力学计算结果的趋势一致,且部分情况的实验值和计算值吻合;草酸钙是较稳定的沉淀,在pH=4~13的范围内,维持较低溶解水平;在盐酸体系中,氯化钙和草酸对草酸钙的溶解有显著抑制作用,而在硫酸体系中,硫酸钙的生成使溶液钙浓度维持在较低水平,从而促进草酸钙的分解;硫酸参与草酸钙分解的反应率随初始酸度增加而增加,硫酸浓度为4 mol/L时,硫酸的反应率可达39.7%;而盐酸的反应率几乎不受初始酸度的影响,维持在5.4%的较低水平。此外,硫酸参与草酸钙分解的反应率随初始草酸浓度增加而下降,但在相同初始草酸浓度下,硫酸参与草酸钙分解的反应率明显比盐酸的高。

Investigation of fluorescence resonance energy transfer ultrafast dynamics in electrostatically repulsed and attracted exciton-plasmon systems

Following the gradual maturation of synthetic techniques for nanomaterials,exciton-plasmon composites have become a research hot-spot due to their controllable energy transfer through electromagnetic fields on the nanoscale.However,most reports ignore fluorescence resonance energy transfer(FRET)under electrostatic repulsion conditions.In this study,the FRET process is investigated in both electrostatic attraction and electrostatic repulsion systems.By changing the Au:quantum dot ratio,local-field induced FRET can be observed with a lifetime of ns and a fast component of hundreds of ps.These results indicate that the intrinsic transfer process can only elucidated by considering both steady and transient state information.

塔里木盆地绿洲带地下水咸化机制

采用Durov图、PMF模型、Gibbs图、离子比值法和饱和指数法对2016~2018年采集的1326组地下水样品进行分析,揭示研究区地下水中盐分的来源及高盐地下水形成的驱动因素.结果表明:在研究区绿洲带微咸水和咸水占比分别为37.2%和19.1%,水化学类型主要为SO_(4)·Cl型;在微咸水、咸水、盐水和卤水中岩盐、石膏等蒸发盐岩的持续溶解是导致高盐地下水形成的主要驱动因素,Cl^(-)、SO_(4)^(2-)、 Na^(+)与TDS(P<0.001)及岩盐、石膏的SI值与TDS(P<0.001)之间均呈现出极显著的正相关性,也证实了这一点;冲积平原区较差的地下水动力条件、细粒岩性和弱碱性的水化学环境为地下水中盐分的富集创造了有利条件,蒸发浓缩作用和阳离子交换作用是形成高盐地下水的次要因素;由于人类活动的影响,导致承压水区高TDS潜水沿井壁入渗补给承压水含水层,也是加剧深层地下水咸化的潜在因素.

Method for Solving Non-specific Amplification Interference of Fluorescence Quantitative PCR in Gene Detection

Objective:To explore a method to solve the issue of interference in fluorescence quantitative PCR non-specific amplification for gene detection.Method:A three-step method was used for amplification,and the quantitative fluorescence signal collection process was set in the extension stage.Results:Three-step amplification has the advantages of wide application range;improved accuracy;and reduced primer design requirements.Conclusion:The interference of non-specific amplification signals was effectively avoided,the melting curve plotting process was omitted,the reaction time was shortened,and the detection accuracy was improved.

传统腌腊肉制品质量安全管理研究

对传统腌腊肉制品质量安全风险及质量管理问题进行了分析,指出应加大研发力度、加快知识效益转化进程,规范标准体系、细化监管标准,规范作坊式生产、优化产品市场,加强社会主体参与意识、推动社会共治等建议,提高传统腌腊肉制品行业整体质量安全水平.

装备数字孪生可信评估框架研究

装备数字孪生大规模落地应用的一个关键瓶颈问题是缺乏系统有效的可信评估方法。本文分析了装备数字孪生的动态演化性、虚实交互性等关键特征,提出了装备数字孪生可信评估框架,包括数字孪生的可信内涵、多维多层次可信评估指标体系和可信评估方法论,并以机械臂数字孪生为例说明了整个评估过程,可以为数字孪生的评估、构建提供方向性指导。

黑河流域水沙通量多尺度变化特征及影响因素

采用小波分析法和累积量斜率变化率法分析了黑河上中游水沙通量的周期性变化特征,定量计算了气候变化和人类活动对水沙通量变化的贡献率。研究结果表明:黑河上中游径流变化周期基本一致,上游输沙量变化周期也基本一致,但中游输沙量在1类和2类时间尺度的变化周期相差较大,且干流两个水文站的径流输沙突变时间存在差异。1981-1989年上游干流影响径流的主控因素为人类活动,但1990年以后主控因素逐渐变为降水,2003年以后主控因素又变为人类活动。影响输沙的主控因素在时间序列上均为人类活动,但影响程度略有不同。干流中游影响径流的主控因素在2005年以后逐渐变为降水影响,而人类活动一直是引起中游输沙变化的主要原因。

聚多巴胺涂层的制备及其衍生碳材料的概述

受贻贝粘蛋白的启发,聚多巴胺因其极强的黏附性、优良碳产率而受到广泛的关注。文章综述了浸涂法、转移法等聚多巴胺涂层的主要制备方法,并对制备过程中的各种影响因素进行了分析,揭示了其对聚多巴胺生成速率和最终聚多巴胺涂层厚度的影响规律;并对其衍生碳材料的制备方法、结构性质以及应用进行了简要概述,类似于石墨烯的层状结构、高导电性等特性促使了其在柔性电子、储能等前沿领域的广泛应用。

水曲柳FmCCoAOMT基因在木质素合成及非生物胁迫中的功能分析

为了明确FmCCoAOMT基因的功能,以水曲柳(Fraxinus mandshurica)为材料,利用qRT-PCR方法分析FmCCoAOMT基因的表达模式,结果显示FmCCoAOMT基因具有组织特异性。在雌株和雄株多年生木质部的表达量最高,其中在雄株中是新生枝皮表达量的9.4倍,在雌株中是叶片表达量的13.1倍。采用叶盘法获取转基因烟草(Nicotiana tabacum)植株,过表达FmCCoAOMT的烟草与野生型相比,木质素含量升高41%,纤维素和半纤维素含量分别降低32%和52%。非生物胁迫处理后过表达FmCCoAOMT烟草相比于野生型,POD和SOD活性增加,MDA含量下降,且活性氧含量减少,其中NaCl处理后,POD活性比对照组升高83%;NaCl、ABA和甘露醇处理后,SOD活性比对照组分别升高56.6%、44.2%和19.0%,MDA含量比对照组分别降低了77.2%、11.7%和47.6%。结果表明FmCCoAOMT基因通过参与木质素合成,促进非生物胁迫适应能力。