Influence of Diisocyanate on Polyurethane Elastomers Which Crosslinked by β-Cyclodextrin

A series of polyurethane elastomers (PUEs) were synthesized by using β-cyclodextrin (β-CD) as cross-linker from aliphatic, alicyclic, aromatic diisocyanates, and polyol. The PUEs were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), swelling test, hardness test and tensile test. The influence of diisocyanate on microphase separation and properties of PUEs was evaluated.

Nanoindentation Measurements of Mechanical Properties of Polyurethane Elastomers Which Crosslinked by β-Cyclodextrin

A series of PUEs which use β-CD as cross-linker were synthesized. Nanoindentation measurements of mechanical properties of these PUEs were made. Load and depth sensing indentation and nano DMA mode were used to evaluate mechanical properties of PUEs in nano-scale. The difference between the results from two modes proved the microphase separation in PUEs and to investigate PUE from hard domains and soft domains was of great significance.

Gadolinium Enhances Dual-energy Computed Tomography Scan of Pulmonary Artery

Objective To evaluate the feasibility of using gadopentetate dimeglumine(Gd-DTPA)for dual-energy computed tomography pulmonary angiography(CTPA).Methods Sixty-six patients were randomly divided into three groups and underwent CTPA.Group A had a turbo flash scan using an iohexol injection,Group B had a turbo flash scan using Gd-DTPA,and Group C had a dual-energy scan using Gd-DTPA.The original images of Group C were linearly blended with a blending factor of 0.5 or reconstructed at 40,50,60,70,80,90,100,and 110 keV,respectively.The groups were compared in terms of pulmonary artery CT value,image quality,and radiation dose.Results The pulmonary artery CT values were significantly higher in Group C40keV than in Groups B and C,but lower than in Group A.There was no significant difference in the image noise of Groups C40keV,B,and C.Moreover,Group A had the largest beam hardening artifacts of the superior vena cava(SVC),followed by Groups B and C.Group C40keV showed better vascular branching than the other three groups,among which Group B was superior to Group A.The subjective score of the image quality of Groups A,B,and C showed no significant difference,but the score was significantly higher in Group C40keV than in Groups A and B.The radiation dose was significantly lower in Group B than in Groups A and C.Conclusion Gd-CTPA is recommended to patients who are unsuitable for receiving an iodine-based CTPA.Furthermore,a turbo flash scan could surpass a dual-energy scan without consideration for virtual monoenergetic imaging.

Influences of Polyol on the Chemical, Thermal, and Mechanical Properties of Polyurethane Elastomers Crosslinked by <i>β</i>-Cyclodextrin

A series of polyurethane elastomers (PUEs) were synthesized from an aromatic diisocyanate (4, 4’-diphenylmethane diisocyanate);a polyether polyol (polytetramethylene glycol, molecular weight: 1000), polyester polyol (poly-caprolactonediol, molecular weight: 1000, or polycarbonate diol, molecular weight: 1000);and β-cyclodextrin (β-CD) as a cross-linker. The effect of the polyol on the morphologies and chemical, thermal, and mechanical properties of the resultant β-CD-based PUEs were investigated in this study. The obtained films were characterized via solubility and swelling tests (chemical properties), differential scanning calorimetry (crystallinity degree), dynamic mechanical analysis (thermal stability), thermogravimetric analysis (thermal stability), tensile testing (mechanical properties), nuclear magnetic resonance spectroscopy, infrared spectroscopy, atomic force microscopy (morphology), contact angle determination (morphology), and scanning electron microscopy (morphology).

一类受生物启发的双膦双硒镍配合物的合成及其电催化产氢性能

自然界中,[NiFeSe]氢化酶比[NiFe]氢化酶具有更高的催化产氢活性和特殊的耐氧性。其较高的催化活性机制被认为跟[NiFeSe]氢化酶上所取代的硒(Se)原子密切相关。因此,[NiFeSe]氢化酶的特殊结构、性质及催化机制强烈激发科学家们设计并合成各种模拟[NiFeSe]氢化酶活性中心的镍铁硒或镍硒配合物(也即受生物启发的模拟物)。本论文工作首先合成及结构表征了六个基于双硒配体与含二茂铁的双膦配体的镍硒配合物(2a–2c,3a–3b,4);然后将这些镍硒配合物用作[NiFeSe]氢化酶的功能模型物,利用电化学方法,以三氟乙酸为质子给体测定了相应的电催化产氢活性。在相同实验条件下,分别研究了双硒配体上不同的取代基团,及含二茂铁的双膦配体上不同取代基等结构修饰方式对镍硒配合物催化产氢性能的影响。结果表明:这些镍硒配合物的催化产氢活性跟双硒配体及双膦配体的结构有很大关系,对应的催化转化频率(TOF)分别为12182 s^(−1)(2a),15385 s^(−1)(2b),20359 s^(−1)(2c),106 s^(−1)(3a),794 s^(−1)(3b),13580 s^(−1)(4)。其中,1,2-二硒-4,5-二甲基和1,1’-双(二苯膦)二茂铁配体与镍离子配位形成的镍硒配合物2c具有最好的电催化活性(TOF=20359 s^(−1)),其产氢性能已大大超过先前我们课题组所报道的由1,2-苯二硒、1,1’-双(二苯膦)二茂铁所配位形成的镍硒配合物1(TOF=7838 s^(−1))。

Contact Extension and Symplectification

This paper mainly studies the contact extension of conservative or dissipative systems, including some old and new results for wholeness. Then extension of contact system is corresponding to the symplectification of contact Hamiltonian system. This is a reciprocal process and the relation between symplectic system and contact system has been discussed. We have an interesting discovery that by adding a pure variable p,the slope of the tangent of the orbit, every differential system can be regarded as an independent subsystem of contact Hamiltonian system defined on the projection space of contact phase space.

本征可修复的导电聚合物/水凝胶纳米复合薄膜及其独特的体沟道用于实现高性能、柔性和可修复的有机光电晶体管

柔性有机光电晶体管(OPTs)在大机械形变的下一代可穿戴系统中至关重要.然而,目前报道的大多数OPTs都是场效应基结构,其界面电荷传输和本征低跨导的特性限制了OPTs的机械柔性和光电性能的发展.此外,沟道层的p共轭半导体聚合物也缺乏特殊的可修复位点,使其很难实现薄膜的自我修复功能.本文报道了一个具有独特体沟道和强修复功能的柔性高光电性能的OPTs.该OPTs使用有机电化学晶体管架构,由3D体沟道的可修复导电聚合物/水凝胶复合薄膜组成.该器件不仅在遭受损伤后能够在100 ms内有效恢复其机械和电学性能,同时还展现出出色的机械柔性.更重要的是,该器件实现了紫外光波段的高光测性能,其中光响应度高达1.01×10^(5)A W^(-1),探测率达1.01×10^(5)A W^(-1),外量子效率达3.03×104%.结果表明,具有独特体沟道和本征可修复功能的OPTs在下一代可穿戴电子器件的使用中具有潜在应用价值.

Controlled synthesis and optical properties of Ce^(3+)/Tb^(3+) co-doped BaGdF_5 nanocrystals

Based on a hydrothermal method, the Ce3+/Tb3+ co-doped Ba Gd F5 nanocrystals were synthesized by controlling the introduction concentration of Ba2+ and Gd3+. The samples were characterized by X-ray diffraction(XRD), field emission scanning electron microscopy(FESEM) images, photoluminescence(PL) excitation, and emission spectra, as well as the photoluminescence dynamic decay curves. With the increase of the Ba2+ concentration in the synthesis procedure, the positions of diffraction peaks of XRD patterns move toward lower degree, and the case of the samples synthesized with the increase of the Gd3+ concentration is contrary, which consists well with each other. The FE-SEM images suggest that the BaGdF5 nanocrystals are in spherical morphology,and the average diameters decrease with the increase of Ba2+ or Gd3+ concentration. For the 4f–5d transition of Ce3+ is sensitive to the environment of local lattice, the PL excitation and emission spectra of the samples are different. The 4f–4f transition of Tb3+ also presents different optical properties in different host lattices. The variations of the optical properties of Ce3+ and Tb3+ as well as the lifetime of the 5D4+7F5 emission of Tb3+ are also consistent well with each other in the two series of samples.

Microstructure and properties of cerium oxide/polyurethane elastomer composites

In general, inorganic filler/polyurethane elastomer(PUE) composites possess favorable properties, such as modulus, chemical resistance, and heat stability, are promising for broadening the application area of polyurethanes(PU). For the experiments, a series of cerium oxide(CeO_(2))/PUE composites were prepared with different sizes and appearance of CeO_(2), and different mixing methods as well. CeO_(2) particles with different sizes were added into PUs during the formation of urethane linkage and the chain-extend process, respectively. The morphology along with mechanical properties, thermal properties of the composites were studied. The results suggest that the size of CeO_(2) and mixing methods influence the microstructure of PUs which has profound effect on properties of these composites. The composites tend to form more quantity of hard domains(HDs) with small size when CeO_(2) particles were added before the formation of urethane linkage, whereas Ce O2 particles increase the size of HDs when added with chain extender into PU prepolymer.

Preparation of flexible rubber composites with high contents of tungsten powders for gamma radiation shielding

To prepare tungsten/rubber composites with good gamma-ray shielding performances and fine mechanical properties,a composite surface modifier is employed to make surface modification of the tungsten powders.

Photocatalytic hydrogen production from acidic aqueous solution in BODIPY-cobaloxime-ascorbic acid homogeneous system

Iodinated boron dipyrromethene(BODIPY) dyes with 8-hydroxyl-quinoline or phenylamine moiety at the meso-position on the BODIPY core were used as efficient photosensitizers(PSs) of three-component light-driven production of H_2 system from acidic aqueous solution in conjunction with a cobaloxime[CoⅢ(dmgH)_2 PyCl](dmgH = dimethylglyoximate, and py = pyridine) as proton-reducing catalyst and ascorbic acid(H_2 A) as sacrificial electron donor. This is the first example of BODIPYs as homogeneous hydrogen-generating PSs employed in the acidic aqueous conditions. That they are active in the acidic solutions and inactive in the basic conditions may indicate that the extent of competition between intramolecular and intermolecular electron transfer reactions exists. Efficient bimolecular electron transfer reaction between PS and molecular catalyst is needed to make H_2 production, while the intramolecular electron transfer of PS may curb H_2 production. The results underscore that the chemical modification of BODIPYs can be performed, thus allowing for the transformation of acid and base conditions for the light-driven H_2 production.