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981.
在水相体系中, 采用脂肪酶Novozym435对聚丁二酸丁二醇酯(PBS)分子主链中氧醚键在醇段和酸段的不同位置的共聚物聚(丁二酸丁二醇-co-丁二酸二甘醇酯)[P(BS-co-BDGA)]和聚(丁二酸丁二醇-co-二甘醇酸丁二醇酯)[P(BS-co-DEGS)]进行酶促降解研究. 以分子对接模拟探讨了酶对亲水性底物的识别及相互作用机制. 通过对降解前后不同摩尔比的共聚物薄膜的质量损失率、 亲水性、 热性能以及降解产物的分析, 研究了PBS改性共聚物的降解规律. 结果表明, 随着降解时间的推移, 所有共聚物薄膜的质量损失率升高, 亲水性增强, 热分解温度升高; 降解5 d后, P(BS-co-BDGA)降解产生的低聚物种类比P(BS-co-DEGS)的多. 分子对接结果表明, 醚键在酸段的P(BS-co-BDGA)型酯键与Novozym435酶活性位点的结合比醚键在醇段的P(BS-co-DEGS)型酯键更稳定, 因此, 在N435脂肪酶作用下, P(BS-co-BDGA)比P(BS-co-DEGS)的降解效果好. 实验结果表明, 当DGA摩尔分数为20%时, 降解效果最佳. 相似文献
982.
氧气浓度是工业生产过程中重要监测参数,采用可调谐二极管激光吸收光谱法(tunable diode laser absorption spectroscopy,TDLAS),结合波长调制技术,可以实现对现场氧气浓度的高精度在线监测,利用氧气位于760 nm处的特征吸收峰进行了氧气浓度的测量。由于激光具有很强的相干性,所以TDLAS技术的检测灵敏度受到光学干涉噪声的严重制约,特别在低浓度时,光学干涉引起的基线起伏使得提取吸收峰波形信号时出现较大误差,影响了TDLAS分析仪的监测灵敏度。针对这一情况,采用了Levenberg-Marquardt非线性拟合算法,并且利用了吸收谱线线型——洛伦兹线型的导数形式对波长调制后获得的二次谐波波形信号进行拟合,提取波形信息。另一方面Levenberg-Marquardt非线性拟合方法需要有大量的计算,为了使研制的TDLAS分析仪能够实现现场的实时监测,采用了支持浮点运算的DSP的C28系列芯片进行数据处理,实现仪器在现场实时监测的功能。实验结果表明,该算法能够有效提取二次谐波信号的吸收峰特征值、克服背景噪声影响,由算法反演得到的氧气浓度与实际浓度的线性比值为1.01,浓度测量的线性误差为1.18%。 相似文献
983.
Xiuxian He 《Journal of luminescence》2010,130(8):1349-1352
We have investigated the effect of fluorhydric acid (HF) treatment on the photoluminescence (PL) properties of SrTiO3:Pr3+ powders prepared by sol-gel method. The red emission intensity increased significantly up to 18 times when the powders were subjected into a water-diluted 5% HF solution for 10 min. The origin of the PL enhancement was ascribed to the increase of oxygen vacancies in HF-treated SrTiO3:Pr3+ powders. This study also manifested that HF etching is more effective to improve the red PL intensity than vacuum-annealing for the sol-gel made SrTiO3:Pr3+ powders. 相似文献
984.
Methanol Tolerant Non-noble Metal Co-C-N Catalyst for Oxygen Reduction Reaction Using Urea as Nitrogen Source 总被引:1,自引:0,他引:1
机械研磨尿素、氯化钴、乙炔黑混合物并经800 oC热处理后,制备出了非贵金属Co-C-N(800)催化剂. X射线衍射测试表明催化剂中有单质β-Co生成. 用循环伏安法表征了催化剂的电化学特性,结果表明Co-C-N(800)具有良好的催化活性和耐甲醇性能. 45 h浸泡实验表明,催化剂在酸性电解液中具有较好的稳定性. 相似文献
985.
Growth of epitaxial SrTiO3 (STO) films has been examined on H-terminated Si(1 1 1) with SrO buffer layers. The epitaxial SrO buffer layers have reduced stress on H-terminated Si substrates. On the SrO buffer layers, the STO films grow epitaxially with triple domains at low temperature. Each STO domain has equivalent epitaxial relationship to SrO buffer layers, STO(1 1 0)∥SrO(1 1 1) and . 相似文献
986.
We studied computationally the relative stability of PtML/WC(0 0 0 1) [pseudomorphic monolayer of Pt(1 1 1) on WC(0 0 0 1)] interfacial structures using a density functional slab model approach. The work of adhesion was calculated for six different interfacial structures, taking into account both W- and C-terminations of the carbide. The results show that the optimal interfacial structure of PtML/WC(0 0 0 1) is the W-terminated WC(0 0 0 1) with Pt atoms adhesion on the hcp site (W-hcp). The nature of metal/carbide bonding for the W-hcp interfacial geometry was determined on the basis of the partial density of states (PDOS). Adsorption of atomic hydrogen and dissociation of the hydrogen molecule on the W-hcp PtML/WC(0 0 0 1) was investigated and compared to that on Pt(1 1 1). It is found that the most favorable H2 dissociation channels need similar activation energies of 5.28 and 4.93 kJ/mol on PtML/WC(0 0 0 1) and Pt(1 1 1), respectively, with the release of considerable reaction energies. Furthermore, adsorption of CO on the W-hcp PtML/WC(0 0 0 1) and Pt(1 1 1) was also investigated. The results indicate that PtML/WC(0 0 0 1) is much less susceptible to CO poisoning than Pt(1 1 1), especially at the low coverage of CO. 相似文献
987.
Interactions of atomic and molecular hydrogen with perfect and deficient Cu2O(1 1 1) surfaces have been investigated by density functional theory. Different kinds of possible modes of H and H2 adsorbed on the Cu2O(1 1 1) surface and possible dissociation pathways were examined. The calculated results indicate that OSUF, CuCUS and Ovacancy sites are the adsorption active centers for H adsorbed on the Cu2O(1 1 1) surface, and for H2 adsorption over perfect surface, CuCUS site is the most advantageous position with the side-on type of H2. For H2 adsorption over deficient surface, two adsorption models of H2, H2 adsorbing perpendicularly over Ovacancy site and H2 lying flatly over singly-coordinate Cu-Cu short bridge, are typical of non-energy-barrier dissociative adsorption leading to one atomic H completely inserted into the crystal lattice and the other bounded to CuCUS atom, suggesting that the dissociative adsorption of H2 is the main dissociation pathway of H2 on the Cu2O(1 1 1) surface. Our calculation result is consistent with that of the experimental observation. Therefore, Cu2O(1 1 1) surface with oxygen vacancy exhibits a strong chemical reactivity towards the dissociation of H2. 相似文献
988.
ZnO thin films were prepared by pulsed laser deposition at room temperature on glass substrates with oxygen pressures of 10-30 Pa. The structural, electrical, and optical properties of ZnO films were studied in detail. ZnO films had an acceptable crystal quality with high c-axis orientation and smooth surface. The resistivity was in the 102 Ω cm order for ZnO films, with the electron concentration of 1016-1017 cm−3. All the films showed a high visible transmittance ∼90% and a high UV absorption about 90-100%. The UV emission ∼390 nm was observed in the photoluminescence spectra. The oxygen pressures in the 10-30 Pa range were suitable for room temperature growth of high-quality ZnO films. 相似文献
989.
The structural and electronic properties of oxygen molecular adsorbed on the exterior surface of pristine and NC or BC defected (10,0) or (6,6) SiCNT have been investigated systematically using the first-principles projector-augmented wave potential within the density-functional theory under the generalized-gradient approximation. We find that for both pristine tubes the preferred adsorption sites of the O2 molecule are above and nearly parallel to armchair Si-C bond whether physisorption or chemisorption. The strong chemical interaction between O2 molecule and tube leads to not only a vanishing in magnetism of the O2 molecule but also an outward relaxation of the underlying Si-C bond. The C atom substituted by N or B atom assists O2 molecule adsorption above and nearly parallel to zigzag Si-N or Si-B bond as well as imparts a metallic character on the SiCNTs with higher concentration of the defects or a magnetism on the SiCNTs with lower concentration of the defects. Therefore, a combination of N or B doping followed by exposure to air may be an effective way to tune the electronic properties of the semiconducting SiCNTs. Furthermore, the lower binding energies for the pair of oxygen interstitials chemisorbed on NC or BC defected (10,0) or (6,6) SiCNT show that the oxygen molecule will dissociate to the pair of oxygen interstitials at the sidewall of NC or BC defected SiCNTs. 相似文献
990.
Hydrogen Production by Chemical Looping Gasification of Corn Stalk Driven by a tert-Butanol Solution
The purpose of this work is to convert organic wastewater into oxidants(H2O and CO2) to promote biomass gasification during the chemical looping process to achieve high-H2/CO-ratio syngas. A tert-butanol solution was selected as the model organic wastewater to generate enough H2O and CO2 to promote corn stalk chemical looping gasification(CLG). A series of CLG experiments was conducted at 850℃ under various degrees of oxygen excess(Ω). An Ω of approximately 0.9 led to the highest hydrogen yield and fixed carbon conversion compared with the other cases. Chemometrics and thermodynamic analysis further validated the possibility of corn stalk CLG using a tert-butanol solution. The results show that CLG of biomass-organic wastewater can both treat organic waste and promote chemical looping processes. 相似文献