Global stability and wavefronts in a cooperation model with state-dependent time delay

This article deals with a diffusive cooperative model with state-dependent delay which is assumed to be an increasing function of the population density with lower and upper bounds. For the cooperative DDE system, the positivity and boundedness of solutions are firstly given. Using the comparison principle of the state-dependent delay equations obtained, the stability criterion of model is analyzed both from local and global points of view. When the diffusion is properly introduced, the existence of traveling waves is obtained by constructing a pair of upper–lower solutions and Schauder's fixed point theorem. Calculating the minimum wave speed shows that the wave is slowed down by the state-dependent delay. Finally, the traveling wavefront solutions for large wave speed are also discussed, and the fronts appear to be all monotone, regardless of the state dependent time delay. This is an interesting property, since many findings are frequently reported that delay causes a loss of monotonicity, with the front developing a prominent hump in some other delay models.     

Development of an integrated metabolomic profiling approach for infectious diseases research

Metabolomic profiling offers direct insights into the chemical environment and metabolic pathway activities at sites of human disease. During infection, this environment may receive important contributions from both host and pathogen. Here we apply an untargeted metabolomics approach to identify compounds associated with an E. coli urinary tract infection population. Correlative and structural data from minimally processed samples were obtained using an optimized LC-MS platform capable of resolving ~2300 molecular features. Principal component analysis readily distinguished patient groups and multiple supervised chemometric analyses resolved robust metabolomic shifts between groups. These analyses revealed nine compounds whose provisional structures suggest candidate infection-associated endocrine, catabolic, and lipid pathways. Several of these metabolite signatures may derive from microbial processing of host metabolites. Overall, this study highlights the ability of metabolomic approaches to directly identify compounds encountered by, and produced from, bacterial pathogens within human hosts.     

Secolignans, neolignans and phenylpropanoids from Daphne feddei and their biological activities

Two new secolignans and one new neolignan, named feddeiphenols A-C (1-3), together with eight known compounds (4-11), were isolated from the leaves and stems of Daphne feddei. Their structures were established on the base of spectroscopic methods, mainly extensive NMR, UV spectroscopy, and MS spectrometry. Compounds 1-11 were tested for their anti-human immunodeficiency virus (HIV)-1 activity and cytotoxicity. The results revealed that compounds 1, 2, 3, 7, and 9 showed therapeutic index (TI) values above 30, respectively, and the other compounds also showed weak anti-HIV-1 activity. Compound 1 showed modest cytotoxic activity. The other compounds also showed weak cytotoxic activity.     

Three silver(I) coordination polymers assembled from 2-sulfoterephthalic acid and N-donor ligands: syntheses, crystal structures, and luminescence properties

The reactions of silver nitrate with 2-sulfoisophthalic acid (H₃stp) in the presence of N-donor ligands produced three coordination polymers; [Ag₃(stp)(pyz)_0.5]_n (1), {[Ag₄(dpp)₄]·2(Hstp)·9H₂O}_n (2), and {[Ag(bpe)]₂[Ag₂(bpe)₂]₂·2(stp)·19H₂O}_n (3) [pyz = pyrazine, bpp = 1,2-bis(4-pyridyl)propane, bpe = 1,2-di(4-pyridyl)-ethylene]. The complexes have been characterized by single-crystal X-ray diffraction, physico-chemical, and spectroscopic methods. Single-crystal X-ray diffraction reveals that complex 1 is a 2D silver carboxylate-sulfonate layered structure, in which the 2D layers are further linked by the N-donor atoms of pyz ligands into a 3D supramolecular structure. Complex 2 is an infinite 1D chain arrangement with the [Ag₂(dpp)₂]²⁺ unit in which weak Ag···Ag or Ag···O interactions extend the chains into 2D structures. Complex 3 has a 3D supramolecular structure constructed by hydrogen bonding, π–π stacking, and Ag···O interactions to link the ligands, metal atoms, and water molecules together. The luminescence properties of the complexes were investigated.     

Preparation, characterization and application of ZnO sol containing quaternary ammonium salts

The zinc oxide sol containing quaternary ammonium salts (DMDAAC-ZnO) was synthesized by zinc acetate and dimethyldiallyl ammonium chloride via the sol–gel process. Effects of zinc acetate concentration, diethanolamine dosage and dimethyldiallyl ammonium chloride dosage on the absorbance-ratio and viscosity of the sol were investigated. Zinc oxide sols were characterized by XRD, TEM and FT-IR. DMDAAC-ZnO was applied to cotton samples and cotton samples treated were tested by antibacterial activity, UV resistance and breaking strength. The antibacterial activity and UV resistance of samples treated by zinc oxide sol containing quaternary ammonium salt were both better than sample treated by zinc oxide sol.     

Solvent-Free Synthesis of Tertiaryα-Hydroxyphosphates by the Triethylamine-Catalyzed Hydrophosphonylation of Ketones

Abstract

A new, environmentally benign, convenient, and easy method of synthesizing tertiary α-hydroxyphosphonates by the triethylamine-catalyzed hydrophosphonylation of unactivated ketones was developed. In the presence of triethylamine, aromatic or heteroaromatic ketones can react with phosphite to form tertiary α-hydroxyphosphonates under solvent-free and mild conditions. The proposed method was also suitable for functionalized ketones.     

Pt nanoparticles modified Au nanowire array for amperometric and potentiometric detection of glucose

A new glucose biosensor, based on the modification of highly ordered Au nanowire arrays (ANs) with Pt nanoparticles (PtNPs) and subsequent surface adsorption of glucose oxidase (GOx), is described. Morphologies of ANs and ANs/PtNPs were observed by scanning electron microscope. The electrochemical properties of ANs, ANs/GOx, ANs/PtNPs, and ANs/PtNPs/GOx electrodes were compared by cyclic voltammetry. Results obtained from comparison of the cyclic voltammograms show that PtNPs modification enhances electrochemical catalytic activity of ANs to H₂O₂. Hence, ANs/PtNPs/GOx biosensor exhibits much better sensing to glucose than ANs/GOx. Optimum deposition time of ANs/PtNPs/GOx biosensor for both amperometric and potentiometric detection of glucose was achieved to be 150 s at deposition current of 1?×?10^?6 A. A sensitivity of 0.365 μA/mM with a linear range from 0.1 to 7 mM was achieved for amperometric detection; while for potentiometric detection the sensitivity is 33.4 mV/decade with a linear range from 0.1 to 7 mM.     

Characterization and quantification of triacylglycerols in peanut oil by off‐line comprehensive two‐dimensional liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry

The complexity of natural triacylglycerols (TAGs) in various edible oils is prodigious due to the hundreds of set is of TAG compositions, which makes the identification of TAGs quite difficult. In this investigation, the off‐line 2D system coupling of nonaqueous RP and silver‐ion HPLC with atmospheric pressure chemical ionization MS detection has been applied to the identification and quantification of TAGs in peanut oil. The method was successful in the separation of a high number of TAG solutes, and the TAG structures were evaluated by analyzing their atmospheric pressure chemical ionization mass spectra information. HPLC and MS conditions have been optimized and the fragmentation mechanisms of isomers have been validated. In addition, an internal standard approach has been developed for TAG quantification. Then this system was applied in peanut oil samples and there was a total of 48 TAGs including regioisomers that have been determined and quantified.     

Enhanced electrocatalytic oxidation of dyes in aqueous solution using cobalt phthalocyanine modified activated carbon fiber anode

Cobalt tetra(2,4-dichloro-1,3,5-triazine)aminophthalocyanine(CoPc)was immobilized covalently on activated carbon fiber(ACF)felt to obtain CoPc-modified ACF(CoPc-ACF)catalyst,and an electrocatalytic oxidation system using CoPc-ACF as the anode was constructed.The electrocatalytic oxidation of Acid Red 1(AR1)was investigated in aqueous solution by an UV-vis spectrophotometer and UPLC.The results indicated that AR1 could be eliminated efficiently in this electrocatalytic oxidation system.In addition,the results of FTIR,TOC and GC-MS suggested that the electrocatalytic oxidation experienced the decoloration achieved by destroying the azo linkage and the further mineralization due to the cleavages of benzene ring and naphthalene ring.The intermediates were mainly small molecular compounds such as maleic acid and succinic acid,etc.Repetitive tests showed that CoPc-ACF can maintain high electrocatalytic activity over several cycles.The further EPR spin-trap experiments indicated that the hydroxyl radicals did not dominate the reaction in this electrocatalytic system,which was completely different from the traditional electro-Fenton system.Based on the non-radical reaction mechanism,the CoPc-modified ACF electrocatalyst has potential application in treating actual dyestuffs wastewaters,which are accompanied with high concentration of hydroxyl radical scavengers such as chlorine ions and additives in the textile printing and dyeing industry.