Design of robust differential microphone arrays with the Jacobi–Anger expansion

Due to their small size, differential microphone arrays (DMAs) are very attractive. Moreover, they have been effective in combating noise and reverberation. Recently, a new class of DMAs of different orders have been developed with the MacLaurin’s series and the frequency-independent patterns. However, the MacLaurin’s series does not approximate well the exponential function, which appears in the general definition of the beampattern, when the intersensor spacing is not small enough. To circumvent this problem, we propose in this paper to approximate the exponential function with the Jacobi–Anger expansion. Based on this approximation and the frequency-independent Chebyshev patterns, we derive first-, second-, and third-order DMAs. Furthermore, in order to improve the robustness of DMAs against white noise amplification, we propose to use more microphones combined with minimum-norm filters. It is also shown that the Jacobi–Anger expansion is optimal from a mean-squared error perspective. Simulations are carried out to evaluate the performance of the proposed DMAs.     

A simple LC‐MS method for determination of cyasterone in rat plasma: application to a pilot pharmacokinetic study

A simple, specific, and sensitive liquid chromatography–mass spectrometry (LC‐MS) method for determination of cyasterone in rat plasma was developed in our laboratory. Cucurbitacin B was used as an internal standard (IS). After protein precipitation with twofold volume of acetonitrile, the analyte and IS were separated on a Luna C₁₈ column (100 × 4.6 mm, i.d., 3.0 µm; Phenomenex) by isocratic elution with acetonitrile–water (80:20, v/v) as the mobile phase at a flow rate of 0.4 mL/min. An electrospray ionization source was applied and operated in the positive ion mode; selected ion monitoring scan mode was used for quantification, and the target ions m/z 543.3 for cyasterone and m/z 581.3 for IS were chosen. Good linearity was observed in the concentration range of 0.40–400 ng/mL for cyasterone in rat plasma. Intra‐day and inter‐day precision were both <7.4%. This method was proved to be suitable for pharmacokinetic studies after oral (5.0 mg/kg) or intravenous (0.5 mg/kg) administration of cyasterone in rats. Copyright © 2015 John Wiley & Sons, Ltd.     

Hexagonal cobalt oxyhydroxide nanoflakes/reduced graphene oxide for hydrogen peroxide detection in biological samples

Analytical and Bioanalytical Chemistry - Abnormal concentration of hydrogen peroxide (H2O2) in blood plasma and cells may lead to several diseases. Thus, it is important to develop a selective and...     

Two New Nitrogenous Compounds from the Seeds of Brassica napus

Chemistry of Natural Compounds - Two new nitrogenous compounds identified as (2S)-2-sinapoyl-4-pentenenitrile (1) and brassicalkaloid A (2) have been isolated from the seed of Brassica napus L....     

3-O-Sulfation of Heparan Sulfate Enhances Tau Interaction and Cellular Uptake

Prion-like transcellular spreading of tau in Alzheimer's Disease (AD) is mediated by tau binding to cell surface heparan sulfate (HS). However, the structural determinants for tau–HS interaction are not well understood. Microarray and SPR assays of structurally defined HS oligosaccharides show that a rare 3-O-sulfation (3-O-S) of HS significantly enhances tau binding. In Hs3st1^−/− (HS 3-O-sulfotransferase-1 knockout) cells, reduced 3-O-S levels of HS diminished both cell surface binding and internalization of tau. In a cell culture, the addition of a 3-O-S HS 12-mer reduced both tau cell surface binding and cellular uptake. NMR titrations mapped 3-O-S binding sites to the microtubule binding repeat 2 (R2) and proline-rich region 2 (PRR2) of tau. Tau is only the seventh protein currently known to recognize HS 3-O-sulfation. Our work demonstrates that this rare 3-O-sulfation enhances tau–HS binding and likely the transcellular spread of tau, providing a novel target for disease-modifying treatment of AD and other tauopathies.     

The catalytic performance study of polymerized ionic liquid synthesized in different conditions on alkylation of o‐Xylene with styrene

In this work, a series of novel acidic polymerized ionic liquids were used as heterogeneous catalyst for alkylation of o‐Xylene with styrene. And the effect of the amount of initiator and the type of acid used for ion exchange on catalyst structure and the catalytic performance of catalysts for alkylation were studied thoroughly. The experiment results show: when the percentage of the amount of initiator in the total material is 3%, the polymerized ionic liquid catalyst MPM‐SO₃H‐[C₃V][SO₃CF₃] has the most uniform with a specific surface area of 97.30 m²/g and a pore volume of 0.35 cm³/g. Benefiting from the unique structure features, MPM‐SO₃H‐[C₃V][SO₃CF₃] manifested an excellent catalytic performance for alkylation of o‐Xylene with styrene, along with the conversion of styrene was 96.8% and the yield of 1‐Phenyl‐1‐ortho‐xylene ethane was 94.7%. Therefore, this work provides a novel reference to the synthesis of polymerized ionic liquids and clearly explains the advantage of novel acidic polymerized ionic liquids on alkylation.     

Precise Synthesis of Ultra-High-Molecular-Weight Fluoropolymers Enabled by Chain-Transfer-Agent Differentiation under Visible-Light Irradiation

Ultra-high-molecular-weight (UHMW) polymers display outstanding properties and hold potential for wide applications. However, their precise synthesis remains challenging. Herein, we developed a novel reversible-deactivation radical polymerization based on the strong and selective fluorine–fluorine interaction, allowing chain-transfer agents to spontaneously differentiate into two groups that take charge of the chain growth and reversible deactivation of the growing chains, respectively. This method enables dramatically improved livingness of propagation, providing UHMW polymers with a surprisingly narrow molecular weight distribution (Đ≈1.1) from a variety of fluorinated (meth)acrylates and acrylamide at quantitative conversions under visible-light irradiation. In situ chain-end extensions from UHMW polymers facilitated the synthesis of well-defined block copolymers, revealing the excellent chain-end fidelity achieved by this method.