Catalytic enantioselective synthesis of optically active α-hydroxyl-β,γ-unsaturated acid esters as novel side chains of cerebrosides

Six optically active α-hydroxyl-β,γ-unsaturated acid esters 1a to 1f were synthesised, and they are significant moieties of the cerebrosides. The chiral intermediate alkynol 4 prepared by catalytic asymmetric addition had 99% ee, and which was converted into the target compounds 1a to 1f with high enantiomeric purity.     

Measurements of charge in heated water

In the literature there are reports of static charges appearing with physical (i.e., phase and temperature) changes of water. One of the purposes of the present report is to refine the measurement of charge in heated water. The experiments described in this report confirm the reported phenomenon by comparing the different amounts of charge produced when different amounts of water are heated to the same temperature and in the same setup. When charge differential is correlated to water differential, the source of charge is better isolated to the change in water temperature rather than to any other possible source.     

Rare-earth Doped Nanoparticles with Narrow NIR-II Emission for Optical Imaging with Reduced Autofluorescence

Fluorescence imaging in the second near-infrared region(900-1700 nm, NIR-II) with a high resolution and penetration depth due to the significantly reduced tissue scattering and autofluorescence has emerged as a useful tool in biomedical fields. Recently, many efforts have been devoted to the development of fluorophores with an emission band covering the long-wavelength end of NIR-II region(1500-1700 nm) to eliminate the autofluorescence. Alternatively, we believe imaging with a narrow bandwidth could also reduce the autofluorescence. As a proof of concept, NaYF₄:Yb,Nd@NaYF₄ downconversion nanoparticles(DCNPs) with sharp NIR-II emission were synthesized. The luminescence of DCNPs showed a half-peak width of 49 nm centered at 998 nm, which was perfectly matched with a (1000±25) nm bandpass filter. With this filter, we were able to retain most of the emissions from the nanoparticles, while the autofluorescence was largely reduced. After PEGylation, the DCNPs exhibited great performance for blood vessel and tumor imaging in living mice with significantly reduced autofluorescence and interference signals. This work provided an alternative way for the low-autofluorescence imaging and emphasized the importance of narrow emitting rare-earth doped nanoparticles for NIR-II imaging.     

A versatile A2 + B3 approach to hyperbranched polyacenaphthenequinones

A series of hyperbranched polyacenaphthenequinones has been prepared by superelectrophilic aromatic substitution of (substituted) acenaphthenequinone and 1,3,5‐tris‐(4‐phenoxybenzoyl)benzene via a facile A₂ + B₃ approach. Because of the strongly increased reactivity of the second A functionality, gelation was efficiently avoided during the polymerization. The structure of the resulting polymer was characterized by NMR spectroscopy and gel permeation chromatography. Further modification of the hyperbranched polyacenaphthenequinone was explored both on the acenaphthenequinone and aromatic moieties. Moreover, the polymer modified through sulfonation was investigated as a water‐soluble acid catalyst for the degradation of biomass resources. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2596‐2603     

Darboux integrability of the stretch-twist-fold flow

The stretch-twist-fold (STF) flow, as a special case of Stokes flows, arises naturally in dynamo theory. The paper studies the integrability of the STF flow. The paper provides a complete classification of the irreducible Darboux polynomials for the system with all values of the parameter alpha. When the parameter is zero, the STF flow is integrable. When the parameter is more than zero, it is proved not to be Darboux integrable. The paper also proves the system has neither exponential factors nor polynomial first integrals at the parameter alpha more than zero.