松香基吸附树脂纯化三七总皂苷及吸附机理

该研究以氢化松香（β-丙烯酰氧乙基）酯、甲基丙烯酸为单体,二乙烯基苯为交联剂合成了新型松香基吸附树脂（Rosin-Based AdsorptionResin,RBAR）,采用FT-IR、TGA、粒径分析、SEM和氮气吸附-脱附等温线对RBAR进行了表征,并研究了RBAR对三七总皂苷（Panna notoginseng Saponins,PNS）的吸附。结果表明RBAR具有良好的热稳定性、均一的颗粒粒径、规整的球形、较高的比表面积（563.37m2/g）和丰富的微/介孔结构。在PNS初始质量浓度6mg/m L,温度328K,固液比0.046g/m L,吸附时间180min下,平衡吸附量127.97mg/g,树脂用φ=70%乙醇再生,重复使用10次后吸附率为97%以上。最佳条件下用RBAR对PNS初提物纯化,三七总皂苷质量分数从46%提升到80%,与商业树脂D101相比有更好的解吸和纯化效果。通过吸附动力学、吸附等温线、热力学模型拟合和孔结构分析探讨了吸附机理。吸附动力学符合准一级动力学,主要由液膜扩散控制传质过程;吸附等温线符合Freundlich模型;吸附机理为非均质多层物理吸附,主要...     

阿里云物联网平台的混流泵房远程监控系统设计

针对大型农业园区混流泵房较为分散、可控性和可观测性低等问题,设计并实现了基于阿里云的混流泵房远程监控系统.系统以STM32F429为主控芯片,ATK-M751模块为主要通信模块,利用多种环境监测传感器和霍尔转速传感器实时采集混流泵房的环境以及混流泵转速.系统通过MQTT协议实现设备与阿里云物联网平台的数据交互.用户能够...     

Performance of a 6 mm thick CdTe detector for 166 keV gamma rays

In order to extend the utility of CdTe detectors to higher gamma ray energies, yet avoid increasing the charge collection problems of thick detectors, a 6 mm thick detector configuration has been developed consisting of three crystals 2 mm thick and of 16 mm diameter. The active volume is over 1.0 cm³. The performance of this detector has been evaluated for gamma rays of 166 keV energy by measuring the pulse height spectra and determining the intrinsic peak and total efficiencies over a range of bias voltages and amplifier time constants. A maximum peak and total efficiency of 41% and 80% were obtained with 200 V bias and 2 μs amplifier time constant, although under these conditions the noise width was almost 40 keV FWHM. A Monte Carlo model was used to simulate the gamma ray and electron interaction in this 6 mm detector. Charge collection, including trapping effects, was incorporated into the model. The model pulse height spectra could be approximately matched to the measured data using hole and electron effective mobility values of 60 and 600 cm²/V s, and hole and electron mean trapping times of 25 and 15 μs. Our findings indicate that detectors such as this will not be useful for high resolution spectroscopic applications, but the high gamma ray stopping power will be of interest for applications where the noise width is acceptable. Results from the modelling imply that in this detector shallow trapping sites (reducing the effective mobility) are more important than deep trapping sites in contributing to incomplete charge collection.     

超高压对湿粉条腐败菌的杀菌效果及品质变化

实验研究了不同超高压条件对湿粉条中腐败霉菌黑曲霉（Aspergillus 305.01和Aspergillus 305.02）杀菌效果以及对粉条蒸煮特性的影响。实验结果表明随着处理压力升高和时间延长,超高压对黑曲霉的杀菌效果增强。经400 MPa/10 min的超高压处理后,粉条的Aspergillus 305.01与Aspergillus 305.02均下降了6.01个对数值;与未处理菌悬液相比,Aspergillus 305.01和Aspergillus 305.02的核酸吸光值分别从0.03和0.04增加至0.56和0.48、蛋白质吸光值分别从0.04和0.08增加至0.70和0.44、电导率分别从0.04 mS/cm和0.06 mS/cm增加至0.12 mS/cm和0.20 mS/cm。在400 MPa处理下,提高超高压处理时间,电导率、核酸损失和蛋白质损失增多,表明超高压是通过改变细胞膜的部分功能,引起胞内核酸、蛋白质和电解质等物质流出,从而导致细胞死亡。此外,随着处理时间增加,粉条的煮沸损失、膨润度增大,而断条率变化不显著。综合超高压对湿粉条的杀菌效果和蒸煮特性的影响,400 MPa处理10 min是湿粉条杀菌的较优条件,为超高压改善湿粉条的杀菌效果和品质提供了理论依据。     

3株魏斯氏菌的分离鉴定与生物学特性研究

目的 对泡菜发酵初期魏斯氏菌进行分离鉴定,并探究其安全特性和益生特性。方法 采用平板对细菌进行分离,进行分离菌株生理生化鉴定和16S rDNA测序鉴定,检测其代谢产物毒性,抗生素敏感性,耐药基因,评价细菌的耐酸、耐胆盐、耐人工肠液、黏附能力、对胆固醇及甘油三酯的降解能力、抗氧化能力以及抑菌能力。结果 共筛选出3株魏斯氏菌,命名为融合魏斯氏菌C13、食窦魏斯氏菌G232和W212; 3株菌代谢产物无毒性,对14类21种抗生素表现出不同程度耐药,耐药基因检测C13携带四环素类耐药基因(tetM), G232和W212携带磺胺类耐药基因(sulⅡ); 3株菌能耐受pH 2～4和3.0 g/L以下的胆盐,在人工肠液中3 h后存活率超过76.80%; 3株菌的黏附能力好,疏水性为60.47%～62.69%,自凝聚率为43.76%～52.55%,共凝聚率为43.20%～61.58%;对胆固醇及甘油三酯的降解主要在前15 h;表现出一定的抗氧化能力,对1,1-二苯基-2-三硝基苦肼自由基清除率较高(清除率25.69%～58.12%),对超氧阴离子自由基清除率相对较低(10.08%～35.29%); ...     

传统发酵食品中分离的乳酸菌粗提物对耐甲氧西林金黄色葡萄球菌抑菌机制研究

目的 探究乳酸菌HS011(LactobacillusplantarumMG5276)、德氏乳杆菌保加利亚亚种HS023(Lactobacillus delbrueckii subsp. Bulgaricus strain NDO4)、嗜热链球菌HS033 (Streptococcus thermophilus 3233)对耐甲氧西林金黄色葡萄球菌(methicillin-resistant Staphylococcus aureus, MRSA)的抑菌机制。方法 以MRSA为研究对象,探索乳酸菌粗提物对MRSA菌株的最小抑菌浓度(minimum inhibitory concentration, MIC)的影响、抗菌药物复合作用对细菌生长的影响、抽提物对MRSA生物被膜抑制和清除效果,以及抽提物对MRSA细胞膜完整性的破坏作用等。结果 乳酸菌粗提物HS011、HS023、HS033对MRSA的MIC分别为5.75、5.00、6.00mg/mL;指示菌MRSA的生长过程受到粗提物明显抑制,在6h时HS011、HS023、HS033对MRSA的抑菌率分别为28.69%、69.20%和42...     

海菜花结合酚的组成、抗氧化活性及其对DNA损伤的保护作用

采用福林-酚法、亚硝酸钠-氯化铝法分别测定海菜花花、茎、叶中结合酚总酚及黄酮含量,采用高效液相色谱(HPLC)分析结合酚的组成,并研究其抗氧化活性及其对过氧自由基(ROO·)介导的DNA损伤保护作用.结果表明,海菜花结合酚总酚含量为209.72～366.35 mg GAE/g提取物(Extract),黄酮含量为156....     

镁合金表面DCPD涂层的制备及其界面结合机制研究

目的 研究CaHPO4×2H2O(DCPD)与Mg的界面结合机制,以提高DCPD在镁合金表面的界面结合强度。方法 利用电镀法在AZ31镁合金表面制备DCPD涂层,采用SEM、XRD、XPS等对涂层形貌及结构进行表征。同时,运用分子动力学模拟(MD)对DCPD在Mg表面形成机制进行研究,通过统计界面层中不同组分的径向分布函数、密度分布、均力势、总能量等的变化,揭示DCPD/Mg的界面结合能、结合位点及结合方式。结果 通过电镀法形成的DCPD涂层形貌为致密的荷花瓣状晶体,主要成分为CaHPO4×2H2O。模拟结果表明,CaHPO4.2H2O的4个晶面(010)、(−120)、(11−1)、(111)、(−120)与Mg的结合能最强(163.63 kJ/mol)。其中起“铆钉”作用的基团是HPO4²⁻和H2O,结合位点主要为O与Mg,即HPO4²⁻和H2O通过静电作用及范德华力与Mg形成Mg-HPO4²⁻和Mg-H2O偶极对。研究发现,形成的偶极对中HPO4²⁻及H2O的配位数分别为0.75和1.16,Mg-H2O的解离能更大,结构更稳定。结论 提出改善DCPD/Mg结合强度的方法,电镀前可将镁合金置于NH4H2PO4溶液中浸泡片刻,促进CaHPO4×2H2O(−120)晶面的形成。     

2D Ti3C2Tx MXene/aramid nanofibers composite films prepared via a simple filtration method with excellent mechanical and electromagnetic interference shielding properties

Electromagnetic shielding (EMI) materials are becoming more and more important because of the increasingly serious radiation pollution. The preparation of high mechanical strength, ultrathin, lightweight, flexible materials with excellent EMI shielding performance have so far been elusive. Here, we try to prepare an ultrathin, lightweight and flexible film with excellent EMI shielding performance using one-dimensional aramid nanofibers (ANFs) and two-dimensional few-layered Ti₃C₂T_x through a simple filtration method. The ultimate tensile strength and strain of the film are up to 116.71 MPa and 2.64%. The EMI shielding effectiveness and the specific EMI shielding efficiency are 34.71 dB and 21971.37 dB cm² g⁻¹, which will be no recession after 1000 times bending. Our results show that a practical EMI shielding material with excellent performances has been successfully prepared, which will be widely applied in wearable electronics, robot joints, and precision instrument protection and so on.     

MWCNTs-GONRs/Co3O4 electrode with needle-like arrays for outstanding supercapacitors

Multiwalled carbon nanotubes-graphene oxide nanoribbons (MWCNTs-GONRs) exhibit high specific surface area and good electroconductivity because of their unique three-dimensional cross-linking structure with the properties of both CNTs and GONRs. In this study, a hydrothermal method was employed to anchor MWCNTs–GONRs onto a Ni foam (NF) to obtain a precursor substrate. Subsequently, Co₃O₄ arrays were grown on the NF substrate to synthesize a MWCNTs–GONR/Co₃O₄ electrode. The electrode showed a capacitance of 846.2 F g⁻¹ at 1 A g⁻¹ and a capacitance retention of 90.1% after 3000 cycles. Furthermore, MWCNTs–GONRs/Co₃O₄ and active carbon (AC) were used as the positive and negative electrodes, respectively, to assemble a supercapacitor, which delivered a maximum energy density of 38.23 W h kg⁻¹ and a high power density of 6.80 kW kg⁻¹. In addition, the specific capacitance of the device reached a maximum of 91.5% after 9000 cycles. Thus, the MWCNTs–GONRs/Co₃O₄ electrode showed huge potential for supercapacitor applications.