Ultra-trace level determinations of benzidine and dichlorobenzidine residues in surface water by liquid chromatography-electrospray ionization tandem mass spectrometry

A liquid chromatography-electrospray ionization tandem mass spectrometric method (LC-ESI-MS/MS) has been developed for the determination of benzidine (BZ) and 3, 3′-dichlorobenzidine (DCBZ) from surface water. Parent ion of DCBZ gave strong signal with ESI by dissolving with 15?mM ammonium formate, which is also used as mobile phase. Deuterated BZ (d8-BZ) was chosen as the internal standard (IS). BZ and DCBZ were extracted by solid-phase extraction on Oasis hydrophilic-lipophilic balance (HLB) from water at pH 8.0. The coefficients of variation of BZ and DCBZ were less than 13.1% and the detection limits were 0.004?ng?L^?1 for BZ and 0.7?ng?L^?1 for DCBZ using 0.5?L surface water. The detection limit shows fair lower value than the water quality criteria for BZ and DCBZ established by the US EPA. When the proposed method was used to analyze the target compounds in sixteen surface water samples, BZ was detected in a concentration range of 0.15–2.33?ng?L^?1 in four of sixteen surface water samples     

Self-assembled tetramethylbenzidine conductive nanofibers synchronized with gold nanoparticle formation

In this study, for the first time, electrically-conductive tetramethylbenzidine (TMB) nanofibers were synthesized and covered with gold nanoparticles via the in situ redox reaction of TMB and HAuCl₄ in ethanol media. The gold nanoparticles were uniformly bound to the fiber surface through the coordination of the amine atoms in TMB molecules with gold nanoparticles. The conductivity of the composite fibrous membrane was found to be 2.1 × 10⁻³ S cm⁻¹. The developed method described herein is simple and effective for the production of novel electrically-conductive TMB/Au nanofibers. We believed that the composite fibrous materials could be used in various fields such as optoelectronic or sensor applications.     

Analysis of formation and breakup mechanisms in rotary atomization through spray visualization

Abstract  

The spray characteristics of rotary atomization for small gas turbines were investigated using a high-speed camera and Nd:YAG laser flash visualization. To analyze the breakup process of the liquid column and liquid film, spray visualization tests were performed under varied test conditions. Visualization was conducted at rotational speeds from 5,000 to 40,000 rpm and fuel flow rates from 15 to 90 kg/h. From the test results, we discovered that a varicose wave appeared on the surface of the liquid column at rotational speeds below 10,000 rpm. As the rotational speed increases, the column forms a liquid film via a dilatational wave and breaks up via a sinuous wave. Under a gradual increase in rotational speed, the breakup of the liquid column is observed, and the formation of a liquid film is ultimately observed. We conclude that liquid film formation is essential for high spray quality in rotary atomization systems.     

Global strong solution to the Thirring model in critical space

We obtain a strong solution in charge critical space L²(R) of the Thirring system and Federbusch equations in one space dimension by using solution representation of the models. The uniqueness is obtained for the solution Ψ∈L^∞([0,T];L²(R)∩L⁴(R)). A decay of local charge and asymptotic behavior of the field can be shown directly.     

On toric ideals arising from signed graphs

Journal of Algebraic Combinatorics - A signed graph is a pair $$(G,\tau )$$ of a graph G and its sign $$\tau $$ , where a sign $$\tau $$ is a function from $$\{ (e,v)\mid e\in E(G),v\in V(G), v\in...     

Stereoselectivity in nucleophilic additions to 3-azidoalkanals

The stereoselectivity of nucleophilic additions to 3-azidoalkanals was investigated. Non-chelating, BF(3)·OEt(2)-mediated Sakurai addition to 3-azidoalkanals afforded 1,3-anti products, whereas use of a chelating Lewis acid, TiCl(4), resulted in 1,3-syn products with moderate selectivity. A boat-like chelation structure of the 3-azidoalkanal with the Lewis acid is proposed to be consistent with the 1,3-syn selectivity of the reactions. Mukaiyama aldol addition to 3-azidohexanal generated 1,3-anti products regardless of the chelating ability of the Lewis acid.     

Wettability and impact dynamics of water droplets on rice (Oryza sativa L.) leaves

A displacement-shifted approach is introduced to the vision-based particle tracking velocimetry (VB-PTV) technique described in Lei et al. (Exp Fluids 53(5):1251–1268, 2012), using translational and angular displacements. The particle matching algorithm in VB-PTV is based on a proximity matrix, G _ij , which favors short distance particle matches over long distance matches. By modifying the formula used in constructing G _ij , particles that lie at the expected location of the match are favored. Two displacement-shifted methods are introduced: the first of which relies on particle image velocimetry estimates of particle displacements and the second of which relies on both the expected displacement and direction of the correct match to construct the proximity matrix. These displacement-shifted algorithms improve performance in high gradient (0.3 px/px and above), high displacement flows (upwards of 20 pixels), broadening the range of flows for which VB-PTV can be used. RMS errors in PTV results are reduced by 33 % or more when these displacement-shifted algorithms are made to the VB-PTV algorithm which is used to process Oseen vortex images. Experimental images of shear layer and the wake region of vortex shedding were used to verify the performances of the proposed methods, and the results are in agreement with the synthetic tests.     

Nitrogen-doped TiO<Subscript>2</Subscript> nanopowders prepared by chemical vapor synthesis: band structure and photocatalytic activity under visible light

During chemical vapor synthesis of TiO₂ nanopowders, nitrogen atoms were doped into the crystal lattice of TiO₂. The nitrogen atoms were predominantly incorporated substitutionally in the crystal lattice of TiO₂ nanopowders up to the doping level of 1.25 mol% nitrogen, whereas they were in both interstitial and substitutional sites over about 1.43 mol% nitrogen. From the photocatalytic activity of nitrogen-doped TiO₂ estimated by decomposition of methylene blue under visible light, it was found that the substitutional nitrogen anions appearing at the low level doping was beneficial to its photocatalytic activity, whereas the interstitial ones appearing at the high level doping over 1.25 mol% nitrogen were not. The improved photocatalytic activity due to the substitutionally doped nitrogen was attributed to band gap narrowing which was confirmed by the studies of XPS, near edge X-ray absorption fine structure, and UV–Vis absorption.     

Tumor-homing poly-siRNA/glycol chitosan self-cross-linked nanoparticles for systemic siRNA delivery in cancer treatment

The condensed version: Thiolated glycol chitosan can form stable nanoparticles with polymerized siRNAs through charge-charge interactions and self-cross-linking (see scheme). This poly-siRNA/glycol chitosan nanoparticles (psi-TGC) provided sufficient in?vivo stability for systemic delivery of siRNAs. Knockdown of tumor proteins by psi-TGC resulted in a reduction in tumor size and vascularization.