Analysis of thermal stability and pyrolysis kinetic of dibutyl phosphate-based ionic liquid through thermogravimetry,gas chromatography/mass spectrometry,and Fourier transform infrared spectrometry

Journal of Thermal Analysis and Calorimetry - The impingement of CuO-water nanofluid flows upon a cylinder subject to a uniform magnetic field with constant surface temperature and embedded in...     

Three new biflavonoids from the branches and leaves of Cephalotaxus oliveri and their antioxidant activity

Three new biflavonoids, named oliveriflavones A-C (1–3), together with two known flavonoids (quercetin (4) and rutin (5)), were isolated from the endangered plant Cephalotaxus oliveri. The chemical structures of these compounds were elucidated by comprehensive spectroscopic methods including NMR, HRESIMS, IR, UV, and CD spectra. Compounds 1–5 were first isolated from the genus Cephalotaxus. All the compounds were tested for their antioxidant activity. Compounds 4 and 5 showed excellent activity with IC₅₀ values of 0.03 ± 0.06 μM and 0.02 ± 0.10 μM, respectively.     

Four-Dimensional Newton’s Constant in Brane World with a Sloping Extra Dimension

We show the four-dimensional Newton’s constant obtained naturally from five-dimensional brane world with a tinily sloping extra dimension, which is independent of the bulk Weyl tensor. The corresponding universe is stiff fluid dominated when the slope of extra dimension is very small. Otherwise, the universe may be undergoing a self-acceleration at present epoch and have a decelerated phase in very recent past.     

用三电极体系研究铜在微液滴下的电化学腐蚀

由于大气腐蚀高阻抗的特征, 传统的参比电极难以用于大气腐蚀研究之中. 为了获取准确的大气腐蚀电化学信息, 我们需要对传统的参比电极进行修改. 本文在三电极体系中采用修改的参比电极, 通过电化学阻抗和电化学极化两种方法研究铜在含有(NH₄)₂SO₄液滴下的腐蚀行为, 结果表明液滴下铜的平均腐蚀速率随着液滴体积从1到20 μL增加而减小; 当液滴高度不超过850 μm时, 平均腐蚀速率随着液滴高度的减小却迅速地增大. 此外, 电化学阻抗和电化学极化得出的腐蚀速率相一致, 这证明修改的参比电极可以用于液滴下的大气腐蚀研究.     

A Numerical Study of Jet Propulsion of an Oblate Jellyfish Using a Momentum Exchange-Based Immersed Boundary-Lattice Boltzmann Method

In present paper, the locomotion of an oblate jellyfish is numerically investigated by using a momentum exchange-based immersed boundary-Lattice Boltzmann method based on a dynamic model describing the oblate jellyfish. The present investigation is agreed fairly well with the previous experimental works. The Reynolds number and the mass density of the jellyfish are found to have significant effects on the locomotion of the oblate jellyfish. Increasing Reynolds number, the motion frequency of the jellyfish becomes slow due to the reduced work done for the pulsations, and decreases and increases before and after the mass density ratio of the jellyfish to the carried fluid is 0.1. The total work increases rapidly at small mass density ratios and slowly increases to a constant value at large mass density ratio. Moreover, as mass density ratio increases, the maximum forward velocity significantly reduces in the contraction stage, while the minimum forward velocity increases in the relaxation stage.     

Non-Ionic Water-Soluble Crown-Ether-Substituted Polyfluorene as Fluorescent Probe for Lead Ion Assays

A new non-ionic water-soluble polyfluorene that contains two benzo-18-crown-6 side chains per repeat unit (PFDC) is synthesized and characterized. Upon addition of Pb²⁺ ions to a solution of PFDC, the PFDC fluorescence is strongly quenched. The minor interference from other metal ions, especial from Cu²⁺ and Hg²⁺ions, clearly shows that the PFDC can be used to detect Pb²⁺ ions with high selectivity. The fluorescence quenching of PFDC in solution originates from the multivalent coordination of the crown-ether moieties to Pb²⁺ ions followed by precipitation. In comparison to ionic conjugated polymers, the pH of the medium shows less effect on the binding of non-ionic PFDC to Pb²⁺ ions.

     

纳米结构氧化铁棒束的制备、表征及光学性质

以三氯化铁(FeCl3·6H2O)和氨三乙酸(N(CH2COOH)3)为主要原料,在160℃反应12h得到了空心管状的白色前驱体,再经500℃煅烧2h得到了纳米结构氧化铁棒束.通过热重分析(TG)、光学显微镜、X射线衍射(XRD)、扫描电子显微镜(SEM)、红外光谱(FT-IR)、紫外-可见光谱(UV-Vis)对所得产物进行了表征.结果表明:所得白色前驱体经500℃煅烧后全部转化为六方相的氧化铁(α-Fe2O3),形貌为含微孔结构的棒束,直径约为2μm,其结构单元为含微孔结构的纳米棒,这些棒的直径为30～50 nm,长度约16μm;紫外数据表明所得氧化铁棒束的最大吸收波长为546nm,带宽吸收约在685 nm处,发生红移.     

微下拉晶体光纤生长设备研制及YAG单晶生长

介绍了一种新型单晶生长技术(微下拉:micro-pulling-down),并概述了该方法在Nd∶ YAG单晶光纤生长方面的应用及发展.率先在国内开展了微下拉单晶生长炉的研制工作,填补了该领域的空白.同时,生长了直径3mm,长度100 mm、300 mm的Nd∶ YAG单晶,晶体整体透明、内部无散射点,表现出了良好的单晶性,有望作为激光工作物质使用.     

Nanofibrous Membranes Containing Carbon Nanotubes: Electrospun for Redox Enzyme Immobilization

Summary: Nanofibrous membranes that possess reactive groups are fabricated by the electrospinning process from PANCAA solutions that contain MWCNTs. Field emission scanning electron microscopy is used to evaluate the morphology and diameter of the nanofibers. Potentials for applying these nanofibrous membranes to immobilize redox enzymes by covalent bonding are explored. It is envisaged that the electrospun nanofibrous membranes could provide a large specific area and the MWCNTs could donate/accept electrons for the immobilized redox enzymes. Results indicate that, after blending with MWCNTs, the diameter of the PANCAA nanofiber increases slightly. The PANCAA/MWCNT nanofibrous membranes immobilize more enzymes than that without MWCNTs. Moreover, as the concentration of the MWCNTs increases, the activity of the immobilized catalase is enhanced by about 42%, which is mainly attributed to the promoted electron transfer through charge‐transfer complexes and the π system of MWCNTs.

The covalent immobilization of redox enzymes, such as catalase, on a PANCAA/MWCNTs nanofiber.     

新型萘基卟啉-蒽醌化合物的合成

荧光猝灭;新型萘基卟啉-蒽醌化合物的合成