On-line solid phase extraction coupled to capillary LC-ESI-MS for determination of fluoxetine in human blood plasma

An instrumental setup including on-line solid phased extraction coupled to capillary liquid chromatography-electrospray ionization-mass spectrometry (SPE-capLC-ESI-MS) has been constructed to improve the sensitivity for quantification of fluoxetine hydrochloride in human plasma. Prior to injection, 0.5 mL of plasma spiked with metronidazole (internal standard) was mixed with ammonium formate buffer for effective chloroform liquid-liquid extraction. The method was validated in the range 5-60 ng mL⁻¹ fluoxetine, yielding a correlation coefficient of 0.999 (r²). The within-assay and between-assay precisions were between (8.5 and 11%) and (6.6 and 7.5%), respectively. The method was used to determine the amount of fluoxetine in a healthy male 14 h after an intake of one capsule of the antidepressant and anorectic Flutin^®, which contains 20 mg fluoxetine per each capsule. Fluoxetine was detected, and the concentration was calculated to 9.0 ng mL⁻¹ plasma. In the preliminary experiments, conventional LC-UV instrumentation was employed. However, it was found that employing a capillary column with an inner diameter of (0.3 mm I.D. × 50 mm, Zorbax C₁₈) increased the sensitivity by a factor of ∼100, when injecting the same mass of analyte. Incorporating an easily automated C₁₈ reversed phase column switching system with SPE (1.0 mm I.D. × 5.0 mm, 5 μm) made it possible to inject up to 100 μL of solution, and the total analysis time was 5.5 min.     

2‐Cyano‐N‐(thiophen‐2‐yl)acetamide in Heterocyclic Synthesis: Synthesis and Antibacterial Screening of Novel Pyrido[1,2‐a]thieno[3,2‐e]pyrimidine‐2‐carboxylate Moieties

A novel series of interesting 6,8‐dicyanopyrido[1,2‐a]thieno[3,2‐e]pyrimidine‐2‐carboxylate compounds were prepared via the reaction of readily accessible 2‐cyano‐N‐(thiophen‐2‐yl)acetamide with arylidene malononitriles in pyridine in the presence of piperidine. Biological screening of the tested compounds as antibacterial agents was also studied.     

Potentiating the antibacterial effect of silver nanospheres by surface-capping with chlorhexidine gluconate

In this work, the commercial polyvinylpyrrolidone (PVP)-capped silver nanospheres (Ag-NSP) were surface decorated with chlorhexidine gluconate (CHXg) for potentiating the antibacterial properties of Ag-NSP. Different formulations of CHXg-loaded Ag-NSP (Ag-NSP/CHXg) were prepared by varying the incubation times (0.5, 1.5, and 3 h). A thorough characterization of Ag-NSP/CHXg nanospheres has been carried out by dynamic light scattering (DLS), transmission electron microscopy (TEM), energy-dispersive surface elemental composition spectral analysis (SEM/EDX), Fourier transform infrared spectroscopy (FTIR), percentage (%) CHXg loading efficiency (LE), in vitro CHXg and Ag⁺ ion release, antibacterial/biofilm inhibition assay, and human mesenchymal stem cells (hMSCs) cytotoxicity evaluation. DLS measured nanospheres to be <160 nm and indicated that CHXg treatment drastically shifted the surface charge from negative to high positive values, with homogenous distribution. TEM revealed spherical Ag-NSP/CHXg nanospheres with a clearly visible surface coating of CHXg. FTIR confirmed association of CHXg with Ag-NSP nanospheres, whereas SEM/EDX data verified presence of spectral peaks specific to silver (Ag), CHXg, and PVP. The %LE gradually increased with increasing incubation times. In vitro CHXg release exhibited a bi-phasic fashion showing maximum release of ~74.83 ± 20.67% from Ag-NSP/CHXg-3h at 14 days. A slow release of Ag⁺ ions was detected; however, the surface decoration of Ag-NSP substantially hampered/restricted the liberation of ions. Agar well diffusion, MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H–tetrazolium), and crystal violet assay suggested good antibacterial/antibiofilm activity of Ag-NSP/CHXg that correlated with the increasing %LE of nanospheres. hMSCs cytotoxicity study showed low toxicity properties of all nanosphere formulations, except for Ag-NSP/CHXg-3h, affecting the cell viability at all proposed concentrations and exposure time points. CHXg accentuated the antibacterial properties of Ag-NSP.     

On the efficiency of price competition

We study the efficiency of price competition among multi-product firms in differentiated oligopolies. Under a general affine demand model, we show that total surplus (sum of industry profit and consumers’ surplus) under competition is at least 75% of the maximum total surplus achievable by a centralized planner. We also show, in contrast to more stylized oligopoly models, that price collusion can increase total surplus and that competition does not, in general, yield a Pareto efficient trade-off between industry profit and consumers’ surplus. However, the maximum deviation of total surplus from Pareto optimality is less than 10%. These results have implications regarding the effectiveness of current anti-trust regulations.     

Synthesis and reactions of novel pyridine-bridged-2,6-bis-carboxamide hydrazones

A number of new hydrazones bearing pyridine-2,6-bis-carboxamides were synthesized and elucidated by spectral and elemental analysis. 2,6-Bis-carboxamide pyridine hydrazide was treated with various active carbonyl compounds containing formyl or methanoyl groups to give hydrazones and Schiff bases.     

Antianexiety activity of pyridine derivatives synthesized from 2-chloro-6-hydrazino-isonicotinic acid hydrazide

A series of oxadiazole pyridine derivatives were synthesized by using 2-chloro-6-hydrazinoisonicotinic acid hydrazide as starting material. Treatment of the hydrazide with carbon disulfide to afford the oxadiazole derivative, which was treated with 5-methyl-2-furancarbaldehyde, formic acid, acetic acid/acetic anhydride, or phthalic anhydride to yield the corresponding pyridinodiazoles and on imide. Condensation of the hydrazide with p-fluorobenzaldehyde in ethanol or acetic acid in the presence of sodium acetate afforded hydrazone and oxadiazole derivatives, which were acetylated and cyclized with acetic anhydride to N-acetyloxadiazole derivatives. The hydrazone was treated with acetic acid in the presence of sodium acetate, or bromine water/sodium acetate to give on oxadiazole, while it was cyclized with chloroacetyl chloride in the presence of TEA to oxoazetidinaminoisonicotinamide. Finally, condensation of the hydrazide with acid anhydrides in refluxing glacial acetic acid afforded the corresponding bisimide derivatives. The pharmacological screening showed that many of these obtained compounds have good antianexiety activity comparable to diazepam^® as positive control.     

Parameter identification of fractional-order chaotic systems using different Meta-heuristic Optimization Algorithms

Nonlinear Dynamics - Fractional-order chaotic systems (FOCS) parameter identification is an essential issue in chaos control and synchronization process. In this paper, different recent...     

Further nonlinear dynamical analysis of simple jerk system with multiple attractors

Nonlinear Dynamics - This paper presents an analytical framework to investigate the dynamical behavior of a recent chaotic jerk model with multiple attractors. The methods of analytical analysis...     

Single Crystals of Mixed-Cation Copper-Based Perovskite with Trimodal Bandgap Behavior

Two-dimensional (2D) hybrid perovskites with novel functionalities and structural diversity are a perfect platform for emerging optoelectronic devices such as photodetectors, light-emitting diodes, and solar cells. Here, we demonstrate that excess concentration of Cesium bromide (CsBr) is key to the formation of easily exfoliated 2D Cs₂Cu(Cl/Br)₄ perovskite crystal. Furthermore, by employing this trick to 2D perovskite MA₂Cu(Cl/Br)₄ (MA=methylammonium), we achieve a phase-pure easily exfoliated 2D mixed-cation (MA/Cs)₂Cu(Cl/Br)₄ perovskite crystal, which exhibits reduced bandgap (1.53 eV) with ferromagnetic behavior and photovoltaic property. The resultant mixed-cation structured device reveals enhanced efficiency compared to all MA and all Cs counterparts. These findings demonstrate the importance of cation-engineering in developing innovative materials with novel properties.     

Spectral, electrical conductivity and biological activity properties of some new azopyrimidine derivatives and their complexes

The electronic absorption spectra of 5-(o-substituted phenylazo)-6-amino-2-thiouracils and 6-(o-substituted phenylazo)-5-aminouracils containing different substituents are studied at different pH's. The dissociation constants are evaluated and discussed. Phenomenon of tautomerism is more supported by (1)H NMR and (13)C NMR spectra. The electrical conductivity of some ligands and their Co(II), Ni(II) and Cu(II) complexes in the temperature range 293-150K favoured their semiconducting properties where the metal ion forms a bridge to facilitate the flow of the current. The biological activity of some ligands and their complexes are tested against a number of Gram-positive and Gram-negative bacteria. The results showed that some of the compounds have a well considerable activity against some of the organisms.