Asymmetric combinational “metal-biocatalytic system”: One approach to chiral 2-subsituted-tetrahydroquinoline-4-ols towards two-step one-pot processes in aqueous media

A novel asymmetric “metal-biocatalytic system”, involving Rh-catalyzed asymmetric transfer hydrogenation and whole cell mediated asymmetric hydroxylation in aqueous buffer, has been achieved. The methodology gives access to 2-subsituted-tetrahydroquinoline-4-ols bearing two stereocenters from 2-subsituted-quinolines in moderate to excellent results (up to 47% yield, 99:1 dr, and >99% ee).     

Error propagation model for microscopic magnetic resonance elastography shear-wave images

Microscopic magnetic resonance elastography is a high-resolution method for visualizing shear waves and assessing the biomechanical viscoelastic properties of small biological samples. In this work, we used error propagation to develop a simple analytical model that relates the signal-to-noise ratio of MR magnitude images to the variance in shear-wave maps collected using gradient-echo and spin-echo phase-contrast pulse sequences. Our model predicts results for shear-wave images in phantoms, which match the experimentally observed phase variance within 8%. This model can be used to optimize MR pulse sequences for elastography studies, as well as other phase-difference techniques in MRI.     

孔板消减气流脉动的数值模拟及实验研究

添加孔板是一种消减压缩机管道系统内气流脉动有效而简便的方法,尽管在工业生产中已被广泛应用,但是其设计和制作所需的各个参数尚处于靠经验取值的阶段.针对这种情况,首先阐述了孔板消减管道内气流脉动的机理;然后使用流体仿真计算软件Fluent建立了管道内气体的二维非稳定流动模型,计算了孔板对管道内气流的压力脉动的影响;并在数值模拟的基础上,搭建了往复式压缩机管道系统实验平台,在进气管线研究了孔板对气流脉动的消减作用.通过数值模拟和实验研究分析了孔板孔径比对气流脉动的影响,并指出选用恰当孔径比的孔板不仅能有效降低主管线和缓冲器至孔板段管线的压力脉动幅度而且对压缩机进口段管线内压力脉动同样具有良好的消减效果.     

Enantioselective organocatalyzed cascade reactions to highly functionalized quinolizidines

An organocatalyzed one-pot Michael addition-Pictet-Spengler sequence of β-ketoamides and α,β-unsaturated aldehydes was developed, which provided access to highly substituted indolo[2,3-α]quinolizidines and benzo[α]quinolizidines in moderate to good yields and good to excellent enantioselectivities. For aromatic α,β-unsaturated aldehydes 1a-j products 10a-r containing a stable enol configuration were obtained.     

Well-Posedness for the Motion of Physical Vacuum of the Three-dimensional Compressible Euler Equations with or without Self-Gravitation

This paper concerns the well-posedness theory of the motion of a physical vacuum for the compressible Euler equations with or without self-gravitation. First, a general uniqueness theorem of classical solutions is proved for the three dimensional general motion. Second, for the spherically symmetric motions, without imposing the compatibility condition of the first derivative being zero at the center of symmetry, a new local-in-time existence theory is established in a functional space involving less derivatives than those constructed for three-dimensional motions in (Coutand et al., Commun Math Phys 296:559–587, 2010; Coutand and Shkoller, Arch Ration Mech Anal 206:515–616, 2012; Jang and Masmoudi, Well-posedness of compressible Euler equations in a physical vacuum, 2008) by constructing suitable weights and cutoff functions featuring the behavior of solutions near both the center of the symmetry and the moving vacuum boundary.     

Effect of H2SO4 Solution Treatment on Adhesion,Charge Transfer,and Catalytic Performance of Screen-Printed PEDOT:PSS

Post-treatment was performed for poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films screen-printed on fluorine-doped tin oxide (FTO) substrates, to improve their charge transfer efficiency. Different H₂SO₄ solutions, including concentrated H₂SO₄ and H₂SO₄ diluted with H₂O or dimethyl sulfoxide (DMSO), were adopted during the post-treatment. The adhesion of the as-treated films was evaluated by adhesive tape peeling tests, the surface morphology and vertical charge transfer from the films to the substrates were investigated by current-sensing atomic force microscopy, and the catalytic activities toward I₃⁻ reduction of PEDOT:PSS films were characterized by electrochemical measurements. It is discovered that selecting proper H₂SO₄ solutions is crucial to improve the charge transfer efficiency and catalytic performance while maintaining reliable adhesion of the film on the substrates, with H₂SO₄/DMSO performing best as the solution for post-treatment. A mechanistic explanationis proposed based on different interactions among solution, PEDOT:PSS, and the substrate for various post-treatment solutions.     

The antifungal activity of essential oil from Melaleuca leucadendra (L.) L. grown in China and its synergistic effects with conventional antibiotics against Candida

To identify the natural antifungal agents, the antifungal activities of Melaleuca leucadendra (L.) L. essential oil (ML-EO) from Fujian Province of China were assayed. Treatment of ML-EO in combination with the front-line using antibiotics against Candida led to synergistic effects. Electron microscopy analysis on the oil treated C. albicans cells revealed the formation of mesosome-like structures, suggesting well the membrane damage caused by the essential oil. The Griess assay by monitoring NO production in LPS-stimulated RAW264.7 cells indicated the potent anti-inflammatory activity of ML-EO. In comparison with the marked essential oil of Melaleuca alternifolia EO, ML-EO had almost the same chemical components. In general, the antifungal activity of ML-EO and its synergistic interactions with conventional antibiotics were able to lead the development of new treatment strategies on Candida infection.