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.

Numerical Predictions of Laminar Forced Convection Heat Transfer with and without Buoyancy Effects from an Isothermal Horizontal Flat Plate to Supercritical Nitrogen

Numerical predictions are made for Laminar Forced convection heat transfer with and without buoyancy effects for Supercritical Nitrogen flowing over an isothermal horizontal flat plate with a heated surface facing downwards.Computations are performed by varying the value ofΔT from5 to 30 K and P_(∞)/P_(cr)ratio from1.1 to 1.5.Variation of all the thermophysical properties of supercritical Nitrogen is considered.The wall temperatures are chosen in such a way that two values of Tw are less than T∗(T*is the temperature at which the fluid has a maximum value of Cp for the given pressure),one value equal to T∗and two values greater than T∗.Three different values of U∞are used to obtain Re∞range of 3.6×10_(4)to 4.74×10^(5)for forced convection without buoyancy effects and Gr_(∞)/Re^(2)_(∞)range of 0.011 to 3.107 for the case where buoyancy effects are predominant.Six different forms of correlations are proposed based on numerical predictions and are compared with actual numerical predictions.It has been found that in all six forms of correlations,the maximum deviations are found to occur in those cases where the pseudocritical temperature TT∗lies between the wall temperature and bulk fluid temperature.

余甘子果实斑点病菌LAMP可视化检测方法的建立

【目的】建立余甘子果实斑点病菌快速、便捷、灵敏、可视的环介导等温扩增技术(loop-mediated isothermal amplification,LAMP)检测方法,为该病害的风险预判和科学防治提供依据。【方法】以余甘子果实斑点病致病菌间座壳菌(Diaporthe phoenicicola)的翻译延伸因子EF-1α基因为靶序列,设计LAMP特异性扩增引物;以余甘子间座壳菌DNA为模板,优化反应温度、反应时间、dNTPs浓度、Mg^(2+)浓度和内外侧引物浓度比,建立LAMP检测最佳反应体系,测试其特异性和灵敏性,并对余甘子发病果实进行实际检测。【结果】适用于余甘子果实斑点病LAMP检测的最佳引物为引物组合4(EF4-F3/EF4-B3和EF4-FIP/EF4-BIP);LAMP检测最佳反应条件为dNTPs浓度1.0 mmol/L,Mg^(2+)浓度4 mmol/L,内外侧引物质量比6∶1,反应温度63℃,反应时间50 min。优化后的LAMP检测方法可特异性地检出余甘子间座壳菌(D.phoenicicola),检测灵敏度可达0.01 ng/μL,且在实际应用中准确率高达100%。【结论】首次建立了余甘子果实斑点病致病菌间座壳菌LAMP可视化快速检测方法,该方法特异性强、灵敏度高,操作简单,可用于田间余甘子果实斑点病菌的快速检测。

基于相场法的非等温气-水两相驱替特征研究

为了阐明在非等温条件下多孔介质中气-水两相动态驱替特征,使用一种基于Navier-Stokes方程、Cahn-Hilliard方程耦合下的两相流数值方法,与表面张力模型、传热模型相结合,完成了对流体动力学和传热的定量计算,同时利用表征真实孔隙特征下的非均质模型,实现了多孔介质内非等温热-流耦合下两相流动过程的精准表征.通过求解Cahn-Hilliard方程精准模拟相分离的演化特征,利用Navier-Stokes方程完成对流体速度及压力的相关计算,结合传热方程获取各个时刻的温度分布;联合流动耦合和温度耦合的节点,实现质量、动量及能量方面的全耦合;算法使用自适应网格法,使网格点分布始终与物理解耦合,提高了解的高精度性.研究表明:大孔中流体压力变化态势平稳,孔喉狭窄处流体速度较大且波动剧烈;注气压力增加,气体突破时间缩短,温度的热传导速率加快,驱替效率在气体突破后呈下降趋势;注气压力较高会加剧水对气体流动能力的干扰,当注气压差满足气相可进入细小孔隙,同时受流动干扰相对较小时,驱水效果最好.

造纸法烟草薄片与天然烟叶吸湿-解湿行为差异性研究

采用多种模型对天然烟叶与烟草薄片在制丝生产线环境下的等温吸湿-解湿行为进行拟合,借助最优等温吸湿模型与解湿动力学模型,对其等温吸湿-解湿行为进行分析。结果表明,DLP模型对天然烟叶与烟草薄片的等温吸湿行为拟合效果最好,二者的等温吸湿线分别为Ⅲ型和Ⅱ型,等温吸湿行为有较大差异;烟草薄片的吸湿滞后现象不明显,而天然烟叶在相对湿度较低时,吸湿滞后现象明显。Page模型对天然烟叶与烟草薄片的解湿过程拟合效果最好;在干燥前期,温度升高加快了烟叶的解湿速率,而在干燥后期,温度升高使得解湿速率降低;相同环境下,烟草薄片的失水速率高于天然烟叶。经验证,Page模型对烟草薄片与天然烟叶含水率的理论值和实测值相对误差均在5%内,能够较好地预测其在实际生产环境下的解湿情况。

Microstructural evolution of AZ61 magnesium alloy predeformed by ECAE during semisolid isothermal treatment

The microstructural evolution of AZ61 magnesium alloy predeformed by equal channel angular extrusion（ECAE） during semisolid isothermal treatment（SSIT） was investigated by means of optical metalloscopy and image analysis equipment.The process involved application of ECAE to as-cast alloy at 310 ℃ to induce strain prior to heating in the semisolid region for different time lengths.The results show that extrusion pass,isothermal temperature and processing route have an influence on microstructural evolution of predeformed AZ61 magnesium alloy during SSIT.With the increase of extrusion pass,the solid particle size is reduced gradually.When isothermal temperature increases from 530 ℃ to 560 ℃,the average particle size increases from 22 μm to 35 μm.When isothermal temperature is 575 ℃,the average particle size decreases.The particle size of microstructure of AZ61 magnesium alloy predeformed by ECAE at BC during SSIT is the finest.

Comparative analysis of isothermal and non-isothermal solidification of binary alloys using phase-field model

Based on the entropy function, a two-dimensional phase field model of binary alloys was established. Meanwhile, an explicit difference method with uniform grid was adopted to solve the phase field and solute field controlled equations. And the alternating direction implicit(ADI) algorithm for solving temperature field controlled equation was also employed to avoid the restriction of time step. Some characteristics of the Ni-Cu alloy were captured in the process of non-isothermal solidification, and the comparative analysis of the isothermal and the non-isothermal solidification was investigated. The simulation results indicate that the non-isothermal model is favorable to simulate the real solidification process of binary alloys, and when the thermal diffusivity decreases, the non-isothermal phase-field model is gradually consistent with the isothermal phase-field model.

Effects of isothermal process parameters on semisolid microstructure of Mg-8%Al-1%Si alloy

A Mg-8%Al-1%Si alloy with semisolid microstructure was fabricated by isothermal heat treatment process. The effects of isothermal process parameters such as holding temperature and holding time on the microstructure of Mg-8%Al-1%Si alloy were investigated. The results show that a non-dendritic microstructure could be obtained by isothermal heat treatment. With increasing holding temperature from 560 to 575 °C or holding time from 5 to 30 min, the liquid volume fraction increases, the average size of α-Mg grains grows larger and globular tendency becomes more obvious. In addition, the Mg2Si phase transforms from Chinese script shape to granule shape. The morphology modification mechanisium of Mg2Si phase in Mg-8%Al-1%Si alloy during the semisolid isothermal heat treatment was also studied.

Hydrogen desorption kinetics mechanism of Mg-Ni hydride under isothermal and non-isothermal conditions

The Mg-Ni hydride was prepared by hydriding combustion synthesis under a high magnetic field. The dehydriding kinetics of the hydrides was measured under the isothermal and non-isothermal conditions. A model was applied to analyzing the kinetics behavior of Mg-Ni hydride. The calculation results show that the theoretical value and the experimental data can reach a good agreement, especially in the case of non-isothermal dehydriding. The rate-controlling step is the diffusion of hydrogen atoms in the solid solution. The sample prepared under magnetic field of 6 T under the isothermal condition can reach the best performance. The similar tendency was observed under the non-isothermal condition and the reason was discussed.

Formation and evolution characteristics of bcc phase during isothermal relaxation processes of supercooled liquid and amorphous metal Pb

The formation and evolution characteristics of bcc phase during the isothermal relaxation processes for supercooled-liquid and amorphous Pb were investigated by molecular dynamics simulation and cluster-type index method （CTIM）. It is found that during the relaxation process, the formation and evolution of bcc phase are closely dependent on the initial temperature and structure. During the simulation time scale, when the initial temperature is in the range of supercooled liquid region, the bcc phase can be formed and kept a long time; while it is in the range of glassy region, the bcc phase can be formed at first and then partially transformed into hcp phase; when it decreases to the lower one, the hcp and fcc phases can be directly transformed from the glassy structure without undergoing the metastable bcc phase. The Ostwald＇s ＂step rule＂ is impactful during the isothermal relaxation process of the supercooled and glassy Pb, and the metastable bcc phase plays an important role in the precursor of crystallization.

Isothermal section of Mg-rich corner in Mg-Zn-Al ternary system at 335 °C

The phase equilibria and compositions at the Mg-rich corner of the Mg?Zn?Al ternary system at 335 °C were systemically investigated through the equilibrated alloy method by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) assisted with energy dispersive spectroscopy of X-ray (EDS). It is experimentally testified that theα-Mg solid solution is not in equilibrium with the Mg32(Al, Zn)49 (τ) ternary intermetallic compound orq quasicrystalline phase, but only in equilibrium with one ternary intermetallic compound Al5Mg11Zn4 (φ). The whole composition range of theφ phase was also obtained at 335 °C, i.e., 52.5%?56.4% Mg, 13.6%?24.0% Al, 19.6%?33.9% Zn (mole fraction). The solubility of Al in the MgZn phase is remarkably more than that in the Mg7Zn3 phase, and the maximum is about 8.6% Al. Aluminum and zinc are simultaneously soluble in theα-Mg solid solution.

Development of transition condition for region with variable-thickness in isothermal local loading process

Using simple unequal-thickness billet combining isothermal local loading can control the metal flow and improve the cavity fill in manufacturing process of large-scale rib-web titanium alloy component with low cost and short cycle. The beveling transition pattern is well used for variable-thickness region of billet （VTRB） due to its simple and ample range of transition condition. The transition condition development in the local loading process has a significant influence on dynamic boundary of unrestricted portion of VTRB. With the help of reasonable assumptions, a mathematical model of transition condition development was established by theoretical analysis. The predicted results for local loading process of rib-web component using the established model were compared with the numerical and experimental ones, and the results indicated that the model of transition condition development is reasonable. Using the established model could deal with the dynamic boundary of unrestricted portion of VTRB well, and the model is suitable for the analysis of metal flow and cavity fill in local loading process of multi-ribs component.

Effects of supersonic fine particles bombarding on thermal barrier coatings after isothermal oxidation

This work was attempted to modify the current technology for thermal barrier coatings（TBCs） by adding an additional step of surface modification,namely,supersonic fine particles bombarding（SFPB） process,on bond coat before applying the topcoat.After isothermal oxidation at 1000 °C for different time,the surface state of the bond coat and its phase transformation were investigated using X-ray diffraction（XRD）,scanning electron microscopy（SEM） equipped with energy-dispersive X-ray spectrometry（EDS）,transmission electron microscopy（TEM） and Cr3＋ luminescence spectroscopy.The dislocation density significantly increases after SFPB process,which can generate a large number of diffusion channels in the area of the surface of the bond coat.At the initial stage of isothermal oxidation,the diffusion velocity of Al in the bond coat significantly increases,leading to the formation of a layer of stable α-Al2O3 phase.A great number of Cr3＋ positive ions can diffuse via diffusion channels during the transient state of isothermal oxidation,which can lead to the presence of（Al0.9Cr0.1）2O3 phase and accelerate the γ→θ→α phase transformation.Cr3＋ luminescence spectroscopy measurement shows that the residual stress increases at the initial stage of isothermal oxidation and then decreases.The residual stress after isothermal oxidation for 310 h reduces to 0.63 GPa compared with 0.93 GPa after isothermal oxidation for 26 h.In order to prolong the lifespan of TBCs,a layer of continuous,dense and pure α-Al2O3 with high oxidation resistance at the interface between topcoat and bond coat can be obtained due to additional SFPB process.

汉麻籽多肽靶向抑制胰脂肪酶/胆固醇酯酶的分子作用机制

采用酶活动力学、联合抑制、荧光光谱、等温滴定量热法和分子对接等技术系统探究两种多肽(APAM和RLPA)对胰脂肪酶(pancreatic lipase,PL)和胆固醇酯酶(cholesterol esterase,CE)活性调控效果及分子结合机制。结果表明,RLPA对PL和CE具有更强的抑制活性,其半抑制浓度分别为(79.62±3.20)μmol/L和(301.27±14.40)μmol/L。抑制动力学分析表明APAM对两种酶的抑制机制为竞争性抑制,而RLPA则为混合性抑制。联合抑制表明APAM和RLPA在低浓度下均可与奥利司他协同抑制PL和CE,但在高浓度下协同作用减弱,甚至出现拮抗现象。荧光光谱结果表明两种多肽可以通过与PL和CE发生结合产生静态猝灭,改变了酶中脂肪族氨基酸的疏水环境。等温滴定量热法证明多肽与酶的结合过程是自发且放热,主要通过氢键和静电相互作用实现。分子对接模拟进一步分析表明氢键、盐桥和阳离子-π相互作用在多肽与酶的结合中起着至关重要的作用。这项研究丰富了对多肽与PL和CE的相互作用机制的认识,为开发基于汉麻籽蛋白的功能性食品提供了科学依据。

非饱和黄土的水蒸气吸附特性

为研究非饱和黄土对水蒸气的吸附特性,采用蒸汽平衡法开展不同湿度环境下的等温吸附试验,分析水蒸气在非饱和黄土表面的吸附行为,并探讨温度、矿物成分及含量、干密度对土体吸附性能的影响。结果表明:非饱和黄土水蒸气吸附量随相对湿度的增加而增加,整个过程包含了单层吸附、多层吸附和毛细凝聚3个阶段,且GAB模型可以用来描述非饱和黄土的水蒸气吸附过程;水蒸气吸附量与温度之间存在明显的负相关关系,相对湿度恒定,水蒸气吸附量随温度的升高而降低;非饱和黄土的水蒸气吸附与矿物组成密切相关,黏土矿物含量直接影响其水蒸气吸附能力;此外,干密度对水蒸气吸附量的影响可分为两个阶段,在相对湿度RH<80%时,水蒸气吸附量随干密度的增大而增大,直到进入毛细凝聚阶段,随着干密度的增大,水蒸气吸附量不再增大反而有所降低。

Establishment of Reverse-transcription Loopmediated Isothermal Amplification Method for Detection of Wheat Streak Mosaic Virus

A reverse-transcription loop-mediated isothermal amplification （RT-LAMP） method was established for the detection of wheat streak mosaic virus （WSMV）. Ac-cording to the conservative regions of the genes that encode the coat protein of WSMV, 2 pairs of primers were designed. Final y, the 1st pair of primers was select-ed through the specificity test. The sensitivity test showed the sensitivity of RT-LAMP method was 10 times higher than that of RT-PCR. In addition, the amplifica-tion of target gene could be judged visual y from the presence of fluorescence （cal-cein） in the final reaction system. The RT-LAMP method, established in this study, was rapid, easy, specific and sensitive. Moreover, it did not require sophisticated equip-ment. The RT-LAMP was suitable for the rapid detection of WSMV.

FTA-环介导等温扩增技术直接提取变异链球菌DNA的效果评价

背景:变异链球菌是龋病的重要病原菌,及时检测变异链球菌水平对龋病的早发现、早治疗有重要意义。目的:建立并评价FTA-环介导等温扩增(loop-mediated isothermal amplification,LAMP)技术直接提取变异链球菌DNA的应用效果。方法:①制备含有ATCC标准菌株变异链球菌的菌悬液,接种于脑心浸出液培养基,充分混匀后按10倍梯度稀释成7种浓度(4.2×10^(7),4.2×10^(6),4.2×10^(5),4.2×10^(4),4.2×10^(3),4.2×10^(2),4.2×10 CFU/mL),每个稀释级做2个平行对照,并增加无菌水作为空白对照;②分别采用FTA卡、常规煮沸法、试剂盒提取及裂解液提取4种方法直接提取菌株DNA,通过LAMP技术进行扩增,并进行特异性试验,比较4种提取方法的差异。结果与结论:①4种方法提取的DNA均满足LAMP扩增的要求;②特异性试验结果显示,只有变异链球菌才可特异扩增出靶基因;③裂解液提取法最低检测限为4.2×10^(3) CFU/mL,FTA卡提取法最低检测限为4.2×10^(4) CFU/mL,试剂盒提取法和常规煮沸法最低检测限分别为4.2×10^(6) CFU/mL和4.2×10^(7) CFU/mL;④4种提取方法其他方面的比较显示,试剂盒提取法的实验成本、步骤数和时间都是最高;其他3种方法步骤数一致,其中FTA卡所需仪器设备最少,常规煮沸法单次成本最低,裂解液提取法所需时间最少;FTA卡和裂解液提取法仅需少量菌即可提取成功,后者在时间方面优于FTA卡,但相较于FTA卡其单次成本高,所需设备多;⑤结果说明,该研究建立的FTA-LAMP技术具有操作简便、特异性强、灵敏度高、结果可视化等优势,有望为高效提取检测变异链球菌提供新途径。

改性花生壳炭对水体中氮磷的吸附特性研究

采用KOH对花生壳炭(BC)进行改性制备改性花生壳炭(MBC)并优化制备方法。利用傅里叶红外光谱(FT-IR)、扫描电镜(SEM)、比表面积及孔径测定等表征方法分析MBC的理化性质,并考察了MBC投加量、溶液初始质量浓度、吸附温度、吸附时间、溶液pH值等对MBC吸附溶液中氮磷的影响。研究结果表明:MBC制备优选条件为活化温度700℃,活化时间1 h,BC、KOH和去离子水3者之比1∶1∶25(g∶g∶mL)。该优选条件下制备的MBC的比表面积最大(488.830 m^(2)/g),约为BC的11.90倍,平均孔径为2.002 nm。相比于BC,MBC的含氧官能团增加,芳香性增强。在投加量为0.1 g、溶液pH值为7、振荡时间为24 h、吸附溶液质量浓度为100 mg/L、转速160 r/min和吸附温度30℃条件下,MBC对氯化铵溶液中铵态氮的吸附量为6.137 mg/g,比相同条件下的BC对铵态氮吸附量(2.116 mg/g)高约190%;MBC对磷酸二氢钾溶液中总磷的最大吸附量为1.731 mg/g,比相同条件下的BC对总磷吸附量(0.512 mg/g)高约238%。MBC对氮磷吸附类型均符合Langmuir模型,为单分子层吸附;吸附过程更符合准二级动力学,吸附方式主要为化学吸附。

实时荧光环介导等温扩增快速检测黄曲霉毒素产生菌方法的建立

黄曲霉毒素是一种具备强致肝损伤性、致癌性和致畸性的微生物毒素。根据产黄曲霉毒素调节基因aflR、柄曲霉素转甲基酶基因omt-1、杂色曲霉素A脱氢酶基因ver-1分别对实时荧光环介导等温扩增(loop-mediated isothermal amplification,LAMP)引物进行设计,对其建立并优化LAMP体系。结果显示,该文所建立的方法针对aflR、omt-1、ver-1基因设计的引物,黄曲霉菌DNA的检出限分别是1.0×10^(-2)、1.0×10^(-3)、1.0×10^(-4) ng/μL。此体系与黄曲霉及寄生曲霉反应成阳性,与其他菌体反应皆为阴性,该方法耗时短、设备要求低,借助恒温荧光读取设备或根据显色剂颜色变化可在60 min内迅速判定待检菌株是否为黄曲霉毒素产生菌,可满足各机构现场快速高效检测的需要。