Oxidation behavior of ferrovanadium spinel particles in air:Isothermal kinetic and reaction mechanism

The oxidation behavior of ferrovanadium spinel(FeV_(2)O_(4)),synthesized via high-temperature solid-state reaction,was investigated using thermogravimetry,X-ray diffractometry,and X-ray photoelectron spectroscopy over the temperature range of 450–700℃.The results revealed that the oxidation process of FeV_(2)O_(4)can be divided into three stages with the second stage being responsible for maximum weight gain due to oxidation.Three classical methods were employed to analyze the reaction mechanisms and model functions for distinct oxidation stages.The random nucleation and subsequent growth(A_(3))kinetic model was found to be applicable to both initial and secondary stage.The third stage of oxidation was consistent with the three-dimensional diffusion,spherical symmetry(D_(3))kinetic mode.Both the model-function method and the model-free method were utilized to investigate the apparent activation energy of the oxidation reaction at each stage.It was found that the intermediates including Fe_(3)O_(4),VO_(2),V_(2)O_(3),and Fe_(2.5)V_(7.11)O_(16),played significant roles in the oxidation process prior to the final formation of FeVO_(4)and V_(2)O_(5)through oxidation of FeV_(2)O_(4).

Optimization of Methylene Blue Dye Adsorption onto Coconut Husk Cellulose Using Response Surface Methodology: Adsorption Kinetics, Isotherms and Reusability Studies

In this study, coconut husk cellulose was employed as a cost-effective and environmentally friendly adsorbent to eliminate methylene blue (MB) dye from aqueous solutions. The successful development of response surface methodology paired with a central composite design (RSM-CCD) enabled the optimization and modelling of the adsorption process. The study investigated the individual and combined effects of three variables (pH, contact time, and initial MB dye concentration) on the adsorption of MB dye onto coconut husk cellulose. The developed RSM-CCD model exhibited a remarkable degree of precision in predicting the removal efficiency of MB dye within the specified experimental parameters. This was demonstrated by the strong regression parameters, with an R2 value of 99.79% and an adjusted R2 value of 99.6%. The study depicted that the optimal parameters for attaining a 98.8827% removal of MB dye using coconut husk cellulose were as follows: an initial MB dye concentration of 30 mg∙L−1, contact time of 120 minutes, and pH 7 at a fixed adsorbent dose of 0.5 g. The Freundlich isotherm model provided the most satisfactory description of the equilibrium adsorption isotherms, suggesting that MB dye adsorption onto coconut husk cellulose occurs on a heterogeneous surface. The experimental results demonstrated a strong agreement with the pseudo-second-order kinetics model, indicating that the number of active sites present on the cellulose adsorbent predominantly influences the adsorption process of MB dye. Additionally, the adsorbent made from coconut husk cellulose exhibited the potential to be reused, as it retained its efficiency for a maximum of three cycles of adsorption of MB dye. The results of this study show that coconut husk cellulose has the potential to be an effective and sustainable adsorbent for removing MB dye from aqueous solutions.

Research progress and prospects of nucleic acid isothermal amplification technology

Nucleic acid(DNA and RNA)detection and quantification methods play vital roles in molecular biology.With the development of molecular biology,isothermal amplification of DNA/RNA,as a new molecular biology technology,can be amplified under isothermal condition,it has the advantages of high sensitivity,high specificity,and high efficiency,and has been applied in various fields of biotechnology,including disease diagnosis,pathogen detection,food hygiene and safety detection and so on.This paper introduces the progress of isothermal amplification technology,including rolling circle amplification(RCA),nucleic acid sequence-dependent amplification(NASBA),strand displacement amplification(SDA),loop-mediated isothermal amplification(LAMP),helicase-dependent amplification(HDA),recombinase polymerase amplification(RPA),cross-priming amplification(CPA),and its principle,advantages and disadvantages,and application development are briefly summarized.

Ultrathin metal-organic framework nanosheets (Cu-TCPP)-based isothermal nucleic acid amplification for food allergen detection

The rapid and accurate detection of peanuts and soybeans allergen is important to the food safety. In this study, Cu-TCPP nanosheet, a kind of ultra-thin metal-organic framework(MOF)was synthesized and applied in loop-mediated isothermal amplification(named Cu-TCPP@LAMP), which can inhibit the non-specific amplification by absorbing and precise temperature releasing of single primer. As thus, Cu-TCPP@LAMP can achieve high sensitivity and specific amplification of the target gene. As a result, peanut and soybean allergens genes contained in food were successfully detected with a favorable detection sensitivity(5 ng/μL for peanuts and 10 ng/μL for soybeans)and reliable repeatability(The coefficient of variation was 3.38% for peanuts and 3.33% for soybeans). Moreover, the established method was utilized for detection of several commercial products, and had a high consistency with the standard method. Apart from food allergens, this novel assay can be widely used in other areas, such as pathogen detection, tumor nucleic acid detection and so on.

Measurement and prediction of isothermal vapor–liquid equilibrium of a-pinene+camphene/longifolene+abietic acid+palustric acid+neoabietic acid systems

The vapor–liquid equilibrium(VLE)data of a-pinene+camphene+[abietic acid+palustric acid+neoabietic acid]and a-pinene+longifolene+[abietic acid+palustric acid+neoabietic acid]systems at 313.15 K,333.15 K and 358.15 K were measured by headspace gas chromatography(HSGC).These data was compared with the predictions value by conductor-like screening model for realistic solvation(COSMO-RS).Moreover,the calculated data of COSMO-RS and Non-Random Two-Liquids(NRTL)models showed good agreement with the experimental data.It was found that the three resin acids inhibited the volatility of a-pinene,camphene and longifolene and resulted in the decrease of total pressure.Moreover,HE(HB)contributes the most to the excess enthalpy and the hydrogen bonding interaction is the dominant intermolecular force of a-pinene,camphene and longifolene with the three resin acids.In addition,the geometric structures optimization and binding energy were obtained by the DFT to further illustrate the hydrogen bonding interaction and the effects of the addition of the three resin acids on the isothermal VLE.

Heat Characteristics and Viscous Flow in a Moving Isothermal Cylindrical Duct with Nanoparticles

Extrusion, melt spinning, glass fiber production, food processing, and mechanical molding rely on heat transmission. Isothermal techniques have been employed in highly structured equipment and living cell temperature regulators. The flow and heat properties of CuO nanofluids flowing through a moving cylindrical isothermal conduit were examined, in the presence of nanoparticles and viscous dissipation. Two-dimensional flows of an incompressible Newtonian fluid via a cylindrical conduit with uniform surface velocity and temperature were utilized. The flow’s partial differential equations were transformed to a non-dimensional form and numerically solved using a finite difference scheme built in the C++ program. The effect of nanoparticle size (0.0 to 0.6) and viscous dissipation (0, 20, 40) on heat behavior and fluid movement are examined and profiles are used to present the numerical findings. The findings revealed that decreasing the variable nanoparticle parameter increased fluid velocity, stream function, and circulation while decreasing fluid temperature. The temperature of the fluid rises in direct proportion, as the viscous dissipation factor improves. This study improves understanding of the viscous flow and heat behavior of boundary layer problems when a nanofluid is used as the heat transfer working fluid in various engineering isothermal processes such as boiling and condensation.

Establishment of a Loop-mediated Isothermal Amplification Method for Rice Bacterial Leaf Brown Spot Disease

Rice bacterial leaf brown spot disease caused by Pseudomonas syringae pv.syringae(Pss)is a major disease on rice.In recent years,Pss has emerged worldwide,seriously affecting rice production.It is very important to establish a rapid detection method of Pss for the diagnosis and prevention of this disease.In order to robust and accurately diagnose the rice bacterial leaf brown spot disease in the field and laboratory,an assay system for the Pss was developed in this study,and the specific sequence of hrcN was used as the target,based on loop-mediated isothermal amplification(LAMP).The best detection system was MgSO 48 mmol·L^(-1),Bst DNA polymerase 8 U,dNTP 1.4 mmol·L^(-1),the ratio of internal and outer primers was 2:1,the reaction temperature was 63℃,the reaction time was 45 min,and the lowest sensitivity was 104 CFU·mL^(-1).This results provided an accurate and robust method for laboratory and field diagnosis of bacterial leaf brown spot disease of rice.

黄铁矿在CO_(2)气氛下非等温氧化转化及动力学分析

针对煤中常见含铁矿物黄铁矿在富氧燃烧典型气氛下转化特性,通过同步热分析结合烟气分析研究了黄铁矿在CO_(2)气氛下的转化行为.结果发现,黄铁矿在CO_(2)气氛下主要经历5个失重阶段且均为吸热过程,首先是黄铁矿颗粒表面硫脱除的起始热解段(相界面反应,n=1/2),活化能低于其在N_(2)气氛下近30 kJ/mol,为220.27 kJ/mol,随后裂解成磁黄铁矿(三维扩散,n=1/2)活化能与其在N_(2)(177.27 kJ/mol)下接近为178.1 kJ/mol;温度高于690℃,随着升温磁黄铁矿缓慢失硫,CO_(2)逐渐参与磁黄铁矿转化且释放SO_(2)和CO;820~1150℃经历双峰失重峰阶段,820~1020℃,氧化气体产物SO_(2)大量生成且在约1000℃达到体积浓度峰值;最后1020~1150℃,坩埚中残留物大量与CO_(2)持续氧化反应失重形成SO_(2)和CO,坩埚中形成复杂物相体系,铁硫化物和铁氧化物共存(或共融).CO_(2)参与黄铁矿产物转化失重阶段活化能分别为180.94 kJ/mol、229.69 kJ/mol和243.46 kJ/mol,动力学机制均为成核与生长(n=1).

球黏土对单及多组分重金属离子的吸附效果

重金属污染水的防范和治理一直是国际上的难点和热点研究课题。吸附法具有经济可行和环境友好等优点,被认为是去除水中重金属离子的最佳技术。球黏土具有潜在的高吸附性能,为进一步探索利用球黏土治理重金属污染水的可行性,该研究通过单组分与多组分重金属离子的批式吸附试验,重点考察球黏土对Pb^(2+)、Cu^(2+)、Zn^(2+)、Cd^(2+)、Cr^(6+)的吸附效果和竞争吸附关系。单组分离子吸附试验表明,球黏土对重金属离子的吸附量遵循先快速增加后缓慢增长,随pH值的增大而增大,随初始浓度增加而增加,直至吸附饱和的规律。最佳吸附平衡时间为90 min;最佳溶液pH值为5。pH值对球黏土吸附5种重金属离子的影响程度由大到小依次为Zn^(2+)、Cd^(2+)、Cr6+、Cu^(2+)、Pb^(2+),当pH值从2增到5时,Zn^(2+)吸附量提高了184%。球黏土对5种离子Pb^(2+)、Cr^(6+)、Zn^(2+)、Cd^(2+)、Cu^(2+)的饱和吸附量分别为311.847、301.437、263.213、195.435和179.635 mg/g。通过动力学模型和等温线模型拟合,吸附数据更加符合准二阶动力学模型和Langmuir等温吸附模型,说明吸附过程为单层吸附,吸附方式为化学吸附,最大吸附量依次为Pb^(2+)(497.593 mg/g)>Cr6+(442.868 mg/g)>Zn^(2+)(339.376 mg/g)>Cd^(2+)(290.039 mg/g)>Cu^(2+)(194.941 mg/g)。多组分离子吸附试验表明,球黏土对4种离子的吸附量同样呈先快速后缓慢增长,直至平稳的趋势。各离子在球黏土的活性位点上表现出的竞争能力由强到弱依次为Cr^(6+)、Zn^(2+)、Cd^(2+)、Cu^(2+)。通过等温线模型拟合,发现多组分重金属离子吸附数据更加符合Langmuir等温吸附模型,吸附方式和吸附过程与单组分一致,各组分的最大吸附量与单组分相比有所下降,但吸附总量却大大增加,说明球黏土对多组分重金属离子具有良好的吸附能力。与其他原生矿物材料相比,球黏土对重金属离子具有更大的吸附量,该研究成果可为球黏土作为吸附剂的利用和推广提供理论依据和数据支持,具有较大的现实意义。

肉制品中马源性成分重组酶介导链置换等温扩增实时检测方法的建立及应用

目的:建立一种快速鉴定肉及肉制品中马源性成分的重组酶介导链置换等温扩增实时检测方法。方法:以马源性ATpase 6基因为靶基因设计多组特异性引物和Exo探针,通过引物筛选及反应参数优化,建立一种采用重组酶介导链置换等温扩增技术检测马源性成分的方法,并对该方法进行特异性、灵敏度和稳定性验证,同时通过对不同掺入比例混合样品、不同加工工艺模拟样品和市售样品进行检测,分析方法的检出限、适用性和准确性。结果:该方法反应迅速、特异性强、灵敏度高。可在39℃恒温条件下16min内完成反应;对23种非目标源性具有良好特异性;目标DNA的检测灵敏度可达到1.8copies/μL水平;对生肉的检出限为0.01%(质量分数,下同),对熟肉制品的检出限为0.1%;对90份市售样品进行检测,结果与标准方法一致。结论:建立的重组酶介导链置换等温扩增方法可用于肉及肉制品中马源性成分的掺假鉴别检测。

高速列车铜基摩擦材料的氧化行为

高速列车铜基摩擦材料在制动过程中,由于摩擦热的产生和耗散,会发生循环氧化。研究铜基摩擦材料在300、400、500、600和700℃下等温氧化50h的氧化行为。结果表明:铜基摩擦材料的氧化行为呈现多阶段特征;Cu、Fe的氧化与氧的扩散共同控制着低温氧化过程,而石墨的氧化在500℃之后占主导作用;Cu的氧化首先形成Cu_(2)O纳米团簇,然后生成CuO纳米线,最后依次转变为细小的和粗大的等轴晶;氧化温度的升高会促进Fe_(2)O_(3)纳米片的生长和致密化;Cu氧化物由于体积膨胀较大,逐渐将Fe氧化物覆盖;石墨烧蚀后形成的连通孔为内氧化提供氧气扩散通道;材料表面氧化层的形成使得表面硬度提高。

镁改性植物源生物炭的制备及其对磷酸盐的吸附特性

为处理含磷废水和实现农业废弃物的资源化利用,将小麦秸秆制成生物炭,通过MgCl_(2)溶液对其进行浸渍改性,探究改性生物炭对水中磷酸盐的吸附特性。结果表明:热解温度为600℃,0.1 mol/L MgCl_(2)溶液改性得到的小麦秸秆生物炭(WS-0.1Mg-600)在pH=7、初始磷酸盐浓度为10 mg/L时,对磷酸盐吸附效果最好;WS-Mg-600投加量为1.25 g/L时,对磷酸盐吸附量为(4.02±0.46)mg/g;WS-Mg-600吸附磷酸盐最佳pH为10。吸附过程符合拟二级动力学方程以及Langmuir模型,表明该吸附过程是以化学吸附为主,并为单层吸附。

计算机模拟在物理化学BET多分子层吸附理论教学中的应用

BET多分子层吸附理论抽象但应用广泛,BET公式的推导过程涉及较多数学知识,学生很难透彻理解BET公式的物理意义。面对比表面分析仪输出的吸附脱附等温线和比表面积,学生只能生搬硬套,难以达到预期的教学效果。本文利用计算机模拟气体分子在固体表面的吸附脱附过程,通过调整吸附脱附常数,可分别得到第I、II、III类吸附等温线;结合实时可视化使学生能直观看到气体分子在固体表面的吸附脱附动力学,从而能更好地理解BET理论。计算机模拟辅助教学还能活跃课堂气氛,实现教与学互动,激发学生的求知欲和科研兴趣,提高教学质量。

等温压缩空气储能技术研究综述

压缩空气储能是一种新型的大型物理储能技术,具有很好的发展前景。介绍了等温压缩空气储能的基本原理,以及关键设备与相关技术的原理及发展现状;对液体活塞、水泵和水轮机进行分析和总结;对等温压缩空气储能的基本原理进行了归纳和说明;分析了现有等温压缩空气储能技术研究进展情况,对系统中液体活塞技术以及水泵和水轮机技术进行分析和总结;对已有的压缩空气储能电站数据进行汇总分析。在此基础上,对等温压缩空气储能技术未来发展方向进行了展望,可为等温压缩空气储能系统中动力设备的选用以及示范项目的推进提供一定的数据参考。

应用于食品检测领域的分子即时检测技术研究进展

食品安全问题关系人类民生。为有效预防和控制食品安全风险,减少食品安全经济损失,迫切需要开发出针对食源性病原体、食物掺假、转基因作物的高特异性、高敏感性、快速的核酸检测技术。即时检测(point-of-care testing,POCT)作为一种新兴的快速检测手段,由于其检测速度快、操作简单、现场检查等特点,在食品检测领域应用广泛。本文首先介绍了POCT技术的发展历史,而后根据食品安全事件的特点,从食源性致病菌、食物掺假、转基因作物3个方向分析了食品检测的主要对象,阐述了分子POCT技术在食品检测领域的应用现状,最后对应用于食品检测领域的分子POCT技术存在的问题和解决办法进行了分析总结,对食品检测分子POCT技术的发展方向进行了展望。本文有助于进一步了解分子POCT技术在食品检测中的应用,并为分子POCT技术在食品快速检测中的研究和应用提供参考。

大球盖菇咸味肽的受体感知机制研究

目的探究在不同咸味受体共存体系下,受体的大球盖菇咸味肽识别和结合特性,受体对咸味肽的竞争结合机制。方法采用分子互作技术构建了多受体-肽分子竞争结合体系,研究了咸味受体上皮细胞Na+通道的阿米洛利敏感钠离子通道蛋白(amiloride sensitive sodium channel protein,SCNN)1α、SCNN1β和SCNN1γ3个亚基受体,与咸味受体TRPV1共存体系下,对大球盖菇咸味肽KSWDDFFTR(KR-9P)的竞争结合特性。结果咸味肽KR-9P能够同时被多种咸味受体识别和结合。SCNN1β、SCNN1γ和TRPV1受体共存的多受体-肽分子竞争结合体系中,分子间结合反应遵循焓减放热反应,肽分子数量(饱和/非饱和)和受体结合顺序,对分子间的结合影响不大,受体和肽分子之间发生多位点、多数量的分子结合,分子间结合亲和力处于强结合水平(10^(–9)~10^(–8)M)。多个互作分子共存的混合体系并不利于熵驱动的SCNN1α受体结合肽分子的反应发生,分子间结合亲和力在中等水平(10^(–4)M)。结论不同咸味受体在竞争结合咸味肽时展现出不同的互作机制。SCNN1β、SCNN1γ和TRPV1受体共存会产生咸味肽感知呈味增效的效果,SCNN1α和TRPV1受体之间的肽分子竞争结合,会影响SCNN1α受体感知结合咸味肽。本研究解析了不同咸味受体竞争结合咸味肽的互作机制,为理解咸味肽的受体感知机制提供参考。

等温滴定量热法研究镉离子与GMP的亲合机理

利用等温滴定量热法研究镉离子与鸟嘌呤核糖核苷酸(GMP)的亲合过程,重点分析不同比例的镉离子和GMP结合时的异同,实验结果显示:(1)镉离子和GMP的浓度比不同会对二者的结合过程产生显著影响,在低浓度比下,反应为焓驱动的放热反应;在高浓度比下,反应为吸热反应。从镉离子和GMP浓度比为20∶1时的ITC滴定曲线和OneSite模型拟合结果可知,镉离子和GMP是接近并按照1∶1的比例结合的,二者的亲合力K值为1.21E 4±2.26E 3。(2)推测GMP与镉离子有两个结合位点,一个为放热结合位点,一个为吸热结合位点,在低浓度比下,只有放热结合位点发生结合。当浓度比到达一定值后,会激活吸热结合位点,同时发生吸热结合和放热结合。因为吸热结合位点的结合能力更强,最终可能呈现为吸热反应。(3)通过反滴法和正滴法的比较,同一浓度下,不同的滴加方式也会对结合结果造成较大的影响。该研究所采用的方法可以很好地从宏观的热力学角度分析金属镉离子与GMP的亲合机理,以期为后续镉离子印迹物制备过程中功能单体的筛选提供重要的试验基础和理论指导。

基于RPA等温扩增的松材线虫快速检测技术体系建立

利用松材线虫Bursaphelenchus xylophilus基因组分析和等温扩增技术,设计生产松材线虫野外快速检测技术产品并测试其效果。结果表明:比较分析松材线虫和拟松材线虫Bursaphelenchus mucronatus基因组发现松材线虫特异性基因Bx-gene12,以此为基础设计特异性扩增引物和探针,对采集自不同地区的松材线虫、拟松材线虫和松树内其他线虫株系采用研磨颗粒以1500 r/min转速震荡5 min的破碎方法有效释放线虫DNA,40℃等温扩增15 min反应条件下可有效区分松材线虫和其他线虫,检测灵敏度达到100 fg或1条线虫;该快速检测方法在25 min内有效检测出染病黑松Pinus thunbergii和赤松Pinus densiflora松木内的松材线虫。利用RPA等温扩增技术实现25 min内对野外环境下松材线虫的快速检测,可为松材线虫病及时有效防控提供支持。

炸药爆轰环境中铝粉非等温燃烧模型

为研究铝粉在爆轰环境中的燃烧特性,基于爆轰环境中铝粉燃烧模型,综合考虑了爆轰产物气体组分和爆轰环境体系温度对铝粉燃烧释能过程的影响,建立了爆轰环境中铝粉非等温燃烧模型,提出了包括铝粉燃烧过程、爆轰产物气体组分和爆轰环境体系温度在内的爆轰环境铝粉非等温燃烧控制方程,并通过激光诱导击穿光谱实验进行了验证。结果表明,铝粉非等温燃烧模型控制方程的计算值与激光诱导击穿光谱实验值的偏差在12%以内,验证了理论模型计算的准确性,获得了铝粉粒度和铝氧比对炸药中铝粉燃烧特性的影响规律。

等温扩增技术在水产品寄生虫检测中的应用研究进展

水产品中寄生虫可引起食源性疾病,已成为影响食品安全的重要因素之一。近年来,基于传统分子生物学发展而来的等温扩增技术以其恒温、高效、耗时短、不过度依赖设备和仪器等优点,逐渐应用于分子诊断和疾病检测。该文在介绍等温扩增技术原理与特点的基础上,综述了其在水产品中寄生虫检测方面的应用研究进展,提出存在问题与解决办法,并展望了等温扩增技术的应用前景,以期为快检技术在水产品质量安全控制技术中的研究开发提供理论参考。