太阳能两级喷射式制冷系统性能的模拟及其分析

讨论了一种新型的太阳能制冷系统——带回热器的太阳能两级喷射式制冷系统。该系统最大的特点是将两个喷射器串联在一起,以提高整个太阳能制冷系统的性能系数。分别采用R134a、R152a、R245ca和R227ea为制冷工质下系统性能系数COP随两级间总压比分配度不同的变化关系。这四种制冷剂的两级压缩比的变化对总喷射系数的影响各有不同,并提出了气体喷射器的总压缩比1.2—2.8之间两级压缩比的不均匀分配原则。     

Ab initio studies of aspartic acid conformers in gas phase and in solution

Systematic and extensive conformational searches of aspartic acid in gas phase and in solution have been performed. For the gaseous aspartic acid, a total of 1296 trial canonical structures and 216 trial zwitterionic structures were generated by allowing for all combinations of internal single-bond rotamers. All the trial structures were optimized at the B3LYP/6-311G* level and then subjected to further optimization at the B3LYP/6-311++G** level. A total of 139 canonical conformers were found, but no stable zwitterionic structure was found. The rotational constants, dipole moments, zero-point vibrational energies, harmonic frequencies, and vertical ionization energies of the canonical conformers were determined. Single-point energies were also calculated at the MP2/6-311++G** and CCSD/6-311++G** levels. The equilibrium distributions of the gaseous conformers at various temperatures were calculated. The proton affinity and gas phase basicity were calculated and the results are in excellent agreement with the experiments. The conformations in the solution were studied with different solvation models. The 216 trial zwitterionic structures were first optimized at the B3LYP/6-311G* level using the Onsager self-consistent reaction field model (SCRF) and then optimized at the B3LYP/6-311++G** level using the conductorlike polarized continuum model (CPCM) SCRF theory. A total of 22 zwitterions conformers were found. The gaseous canonical conformers were combined with the CPCM model and optimized at the B3LYP/6-311++G** level. The solvated zwitterionic and canonical structures were further examined by the discrete/SCRF model with one and two water molecules. The incremental solvation of the canonical and zwitterionic structures with up to six water molecules in gas phase was systematically examined. The studies show that combining aspartic acid with at least six water molecules in the gas phase or two water molecules and a SCRF solution model is required to provide qualitatively correct results in the solution.     

滇桂艾纳香水溶性多糖BRP-B的分离纯化及止血活性

用蒸馏水溶解滇桂艾纳香浸膏,从中提取多糖,通过膜分离、三氯乙酸法脱蛋白、二乙氨基乙基(DEAE)脱色、SephadexG10、SephadexG50凝胶柱色谱纯化,获得滇桂艾纳香水溶性多糖(BRP-B)。 由凝胶渗透色谱（HPGPC）确定BRP-B为相对分子质量分布均一的多糖,其数均分子量和质均分子量分别为2654和2716 Da。 以血浆复钙时间（PRT）为指标,研究BRP-B的凝血活性,结果显示BRP-B质量浓度为6.25×10-2 g/L时,凝血时间为248.52 s,凝血时间抑制率达22.42%。 小白鼠离体子宫实验结果显示,BRP-B质量浓度为1.67×10-2、1.97×10-2及2.85×10-2 g/L时能明显增加子宫平滑肌的收缩频率。     

Preparation of Polypropylene/Glycidyl Methacrylate Modified n-TiO2-PMMA Composites via the RAFT Process: Grafting “Through” Surface-Modified Nanoparticles

Glycidyl methacrylate (GMA), a functionalized agent that can chemically link to TiO₂ nanomaterial (n-TiO₂), was used to modify the surface of n-TiO₂ via a Ti-ethereal bond, yielding a GMA-modified n-TiO₂ (mn-TiO₂). Then the GMA bonded to the TiO₂ surface was copolymerized with methyl methacrylate (MMA) via a reversible addition-fragmentation chain transfer (RAFT) polymerization in the presence of the RAFT agent S-1-dodecyl-S′-(α, α′- dimethyl -α″-acetic acid)trithiocarbonate (DDACT) to form mn-TiO₂-PMMA nanoparticles. The resulting mn-TiO₂ nanoparticles and mn-TiO₂-PMMA nanoparticle materials were characterized by using infrared spectroscopy (IR), thermal analysis, and electron microscopy. The mn-TiO₂ nanoparticles demonstrated good dispersive capacity in organic solvents. The results of TGA indicated that the amount of PMMA grafted onto the surface of TiO₂ increased with the polymerization time. Additonally, the effects of mn-TiO₂/PMMA on the thermal and mechanical properties of polypropylene were studied.     

卷积伏安法实验数据的平方根卡尔曼滤波Ⅰ卷积伏安法实验数据的平滑

本文探讨了平方根卡尔曼滤波在卷积伏安法中的应用．模拟数据实验结果表明，平方根卡尔曼滤波器用于消除噪声的干扰，效果良好，运算速度快，滤波结果具有良好的线性关系．应用于Ｃｄ（Ⅱ）的半微分电分析法实验数据的处理，结果令人满意     

Detailed ab initio studies of the conformers and conformational distributions of gaseous tryptophan

A systematic and extensive conformational search has been performed to characterize the gas-phase tryptophan structures. A total of 648 unique trial structures were generated by allowing for all combinations of internal single-bond rotamers and were optimized at the DFT/B3LYP/6-311G* level of theory. A total of 45 local minima conformers were found. Further optimization of the 45 conformers with B3LYP and MP2/6-311++G** did not produce meaningful structural change, and accurate geometries, dipole moments, rotational constants, harmonic frequencies, and relative energies were then determined. Combined with statistical mechanics principles, the conformational distributions of gas-phase tryptophan at different temperatures are shown. The results clearly support the conclusion drawn by Compagnon et al. that only one dominant isomer existed in the molecular beam at 85 K and add further evidence that the supersonic jet expansion or embedding helium droplets did not produce an equilibrium distribution.     

Preparation of Lignin Carbon/Zinc Oxide Electrode Material and Its Application in Supercapacitors

In this paper, carbon/zinc oxide (LC/ZnO) composites were successfully synthesized and characterized by X-ray powder diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, Raman, thermogravimetry, and N₂ adsorption–desorption, and tested by electrochemical performance. Studies have shown that the morphology of LC/ZnO composites is that lignin pellets are embedded in ZnO microplates. The lignin carbon in the composites mainly exists in an amorphous structure, and the specific surface area and pore channels of metal oxides are increased by the presence of lignin carbon. The electrochemical performance test shows that the carbonization temperature of LC/ZnO with the highest specific capacitance is 550 °C, and the capacitance retention rate reaches 96.74% after 1000 cycles of testing, indicating that the composite material has good cycle stability. Compared with the control group, it is found that the specific capacitance of LC/ZnO-550 °C is 2.3 times and 1.8 times that of ZnO-550 °C and LC-550 °C, respectively. This shows that during the electrochemical test, the lignin carbon and the metal oxide promote each other and act synergistically. In addition, the composite material exhibits the characteristics of a pseudo-capacitance capacitor, indicating that the redox reaction occurred in the electrochemical performance test.     

Spin-Enhanced O−H Cleavage in Electrochemical Water Oxidation

Herein we report the vital role of spin polarization in proton-transfer-mediated water oxidation over a magnetized catalyst. During the electrochemical oxygen evolution reaction (OER) over ferrimagnetic Fe₃O₄, the external magnetic field induced a remarkable increase in the OER current, however, this increment achieved in weakly alkaline pH (pH 9) was almost 20 times that under strongly alkaline conditions (pH 14). The results of the surface modification experiment and H/D kinetic isotope effect investigation confirm that, at weakly alkaline pH, during the nucleophilic attack of Fe^IV=O by molecular water, the magnetized Fe₃O₄ catalyst polarizes the spin states of the nucleophilic attacking intermediates. The spin-enhanced singlet O−H cleavage and triplet O−O bonding occur synergistically, which promotes the O₂ generation more significantly than the strongly alkaline case involving only spin-enhanced O−O bonding.     

滇桂艾纳香多糖BRP的结构解析

以滇桂艾纳香为原料, 经热水抽提、Sevag法除蛋白、醇沉、DEAE-纤维素柱层析、Sephadex G-200、Sepharose 6 F.F.凝胶色谱纯化得到纯品BRP|经HPGPC检测分析表明, BRP为均一多糖, 分子量为3.3×10⁴ Da|用UV、IR、HPLC、HPGPC、GC-MS、甲基化、NMR (¹H NMR、¹³C NMR、HMQC、HMBC)等方法对BRP结构进行表征, 结果表明, BRP仅由呋喃果糖残基组成, 以→2)Fruf (1→ (或→1)Fruf (→2)方式链接, 推导其结构式为: β-D-Fruf-{2[→1)- β-D-Fruf(2→]_n-1}-β-D-Fruf .     

电荷比较法测量液体闪烁体n,γ分辨性能

描述了一种采用CAMAC一微机系统采集数据,电荷比较法测量液体闪烁体的中子、γ射线分辨性能的新方法,同时测量了液体闪烁体NE213或BC519样品在²⁴¹Am–Be或²⁵²C_f中子源照射下的脉冲总电荷及多路不同时间段的部分电荷,对数据的离线分析给出闪烁体n,γ分辨与延迟时间及能量分布的关系,并可利用n,γ鉴别方法测量中子或γ射线的能量分布及闪烁体快或慢脉冲形状.