Theoretical investigation of triazine based a star shape pyrrole monomer

In this work, we report a comprehensive theoretical investigation of electroactive star shaped pyrrole functionalized triazine monomer with two main goals. First goal of this work is to explore the physical and chemical properties of the monomer, then to investigate correlation between the experimental and the theoretical properties of monomer. The scale factor which is calculated from B3LYP/cc-pVDZ was determined as 0.985 for FT-IR and it is an important and reliable contribution to the literature. It is determined that the most appropriate basis set for this molecule. The other novel objective of this research is to investigate temperature effect on displacement of chlorine atoms in 2,4,6-trichloro-1,3,5-triazine. This method applied for the first time in the literature for triazines is especially crucial to the synthesis of unsymmetrical triazines.     

Response analysis in biochemical chain reactions with negative feedforward and feedbackward loops

Finite difference equations can be used to study the responses of biochemical chain reactions at any step of the chain to an external stimulus. In this study, we developed mathematical models for two hypothetical chain reactions involving loops to study the responses in the chain as the length of the chain gets longer, so called transient and steady state responses. The first model is for a chain with a negative feedforward loop, and the second one is for a chain that has a negative feedback loop. Although both of the models have the same steady state equations and values, we showed that the chain with negative feedforward and negative feedback loops can produce significantly different behaviors. The former can bring the chain into oscillations with various periods and eventually chaos when the feedback is strong enough as the length of the reaction chain increases, whereas the latter is not capable of producing oscillations and more complicated dynamics.     

Electrospinning of polymer-free nanofibers from cyclodextrin inclusion complexes

The electrospinning of polymer-free nanofibers from highly concentrated (160%, w/v) aqueous solutions of hydroxypropyl-β-cyclodextrin (HPβCD) and its inclusion complexes with triclosan (HPβCD/triclosan-IC) was achieved successfully. The dynamic light scattering (DLS) and rheology measurements indicated that the presence of considerable HPβCD aggregates and the high solution viscosity were the key factors in obtaining electrospun HPβCD and HPβCD/triclosan-IC nanofibers without the use of any polymeric carrier. The HPβCD and HPβCD/triclosan-IC solutions containing 20% (w/w) urea yielded no fibers but only beads and splashes because of the depression of the self-aggregation of the HPβCD. The inclusion complexation of triclosan with HPβCD was studied by isothermal titration calorimetry (ITC) and turbidity measurements. The characteristics of the HPβCD and HPβCD/triclosan-IC nanofibers were investigated by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). It was found that the electrospinning of HPβCD/triclosan-IC solution having a 1:1 molar ratio was optimal for obtaining nanofibers without any uncomplexed guest molecules.     

A rapid solid sampling method for determination of nickel and copper along human hair by ETAAS

A procedure for copper and nickel determination in scalp hair by solid sampling electrothermal atomic absorption spectrometric method was described. The hair samples (0.02 to 0.4 mg) were inserted directly on the platforms of solid sampling autosampler. The effects of pyrolysis temperature, atomization temperature, the amount of sample as well as addition of a modifier (Pd/Mg) and/or auxiliary digesting agents (hydrogen peroxide and nitric acid) and/or a surfactant (Triton X-100) on the determination of copper and nickel by solid sampling atomic absorption spectrometry were investigated. After optimization of parameters, the average recoveries of copper in two different certified reference hair samples were 105.7 and 97.6%. The recoveries of nickel in the both certified reference hair samples were in 95.2 and 96.4%. The limits of detection (3σ, N = 10) for copper and nickel were 22 ng/g and 35 ng/g, respectively. Heterogenous distribution of analyte in microscale for segmental analysis could be determined which is important to know that analyte quantity and time of poisoning of a person was exposed. For this purpose, 0.5 cm of pieces were cut along one or a few close strands and analyzed by solid sampling. This process could not be performed by wet-digestion method because 50 mg of sample is needed each time. Finally, the method was applied for the determination of copper and nickel concentrations in the hairs of different persons.     

The use of gold nanoparticles as an effective modifier for the determination of arsenic and antimony by electrothermal atomic absorption spectrometry

Gold nanoparticles (AuNPs) were used as a new chemical modifier for the determination of arsenic and antimony in salt solutions by electrothermal atomic absorption spectrometry. The AuNPs were prepared by reducing chloroauric acid with sodium citrate. The effects of pyrolysis and atomization temperatures, the amounts of interferents and modifier on the sensitivities of arsenic and antimony were investigated. As and Sb remain in the graphite tube up to 1,100°C, which is sufficient for the determination of the two metals in certified reference materials and spiked sea water samples within a 95% confidence level with low RSD (<10%). The detection limits (N?=?10 at 3??) for As and Sb in sea water are 2.3???g?L^-1 and 3.0???g?L^-1, respectively. Almost no background as well as a blank value was detected for AuNPs.

A characterization study on 2,6-dimethyl-4-nitropyridine N-oxide by density functional theory calculations

This study deals with the identification of a title compound, 2,6-dimethyl-4-nitropyridine N-oxide by means of theoretical calculations. The optimized molecular structures, vibrational frequencies, corresponding vibrational assignments, thermodynamic properties and atomic charges of the title compound in the ground state were evaluated using density functional theory (DFT) with the standard B3LYP/6-311G(d,p) method and basis set combination for the first time. Theoretical vibrational spectra were interpreted with the aid of normal coordinate analysis based on scaled density functional force field. The results show that the optimized geometric parameters (bond lengths and bond angles) and vibrational frequencies were observed to be in good agreement with the available experimental results. Based on the results of comparison between experimental results and theoretical data, the chosen calculation level is powerful approach for understanding the molecular structures and vibrational spectra of the 2,6-dimethyl-4-nitropyridine N-oxide. Moreover, we not only simulated frontier molecular orbitals (FMO) and molecular electrostatic potential (MEP) but also determined the transition state and energy band gap. Based on the investigations, the title compound is found to be useful to bond metallically and interact intermolecularly. Infrared intensities and Raman activities were also reported.     

Spectra and Fine Spectra for Factorable Matrices

We obtain the spectra and fine spectra for factorable triangular matrices. Our results contain some previous work of the authors as special cases.     

Spectra for Factorable Matrices on ℓ p

We obtain the spectra and fine spectra for factorable matrices, considered as bounded linear operators over ℓ^p , 1 < p < ∞.     

Experimental and theoretical studies on the functionalization reactions of 4-benzoyl-1,5-diphenyl-1H-pyrazole-3-carboxylic acid and acid chloride with 2,3-diaminopyridine

The 1H-pyrazole-3-carboxylic acid 2 was converted in good yield (69%) into the corresponding 1H-pyrazole-3-carboxamide 5 via reaction of the acid chloride 3 with 2,3- diaminopyridine (4). A different product, the 3H-imidazo[4,5-b] pyridine derivative 6, was formed from the reaction of 3 with 4 and base in benzene for 5 hours. The structures of the synthesized compounds were determined spectroscopically. The mechanism of the reaction between 3 and 4 was examined theoretically.