Multi-analyte HPLC–DAD Method for Concurrent Analysis of Six Antimicrobials and Three Proton Pump Inhibitors Frequently used in Management of Helicobacter pylori Infection: Application to Simulated Intestinal Fluid Samples

Chromatographia - The present work deals with the optimization, validation and application of a versatile HPLC–DAD method for concurrent estimation of nine antimicrobials and proton pump...     

Synthesis and Antiproliferative Activity of Novel Hydrazono Thiazolidene and Thiazole Derivatives Bearing Rhodanine Moiety

Russian Journal of General Chemistry - Some new fluoro-heterocyclic compounds containing thiazole and pyridine moities have been synthesized and studied for their antiproliferative activity....     

Analysis of two stacked cylindrical dielectric resonators in a TE₁₀₂ microwave cavity for magnetic resonance spectroscopy

The frequency, field distributions and filling factors of a DR/TE??? probe, consisting of two cylindrical dielectric resonators (DR1 and DR2) in a rectangular TE??? cavity, are simulated and analyzed by finite element methods. The TE(+++) mode formed by the in-phase coupling of the TE??(δ)(DR1), TE??(δ)(DR2) and TE??? basic modes, is the most appropriate mode for X-band EPR experiments. The corresponding simulated B(+++) fields of the TE(+++) mode have significant amplitudes at DR1, DR2 and the cavity's iris resulting in efficient coupling between the DR/TE??? probe and the microwave bridge. At the experimental configuration, B(+++) in the vicinity of DR2 is much larger than that around DR1 indicating that DR1 mainly acts as a frequency tuner. In contrast to a simple microwave shield, the resonant cavity is an essential component of the probe that affects its frequency. The two dielectric resonators are always coupled and this is enhanced by the cavity. When DR1 and DR2 are close to the cavity walls, the TE(+++) frequency and B(+++) distribution are very similar to that of the empty TE??? cavity. When all the experimental details are taken into account, the agreement between the experimental and simulated TE(+++) frequencies is excellent. This confirms that the resonating mode of the spectrometer's DR/TE??? probe is the TE(+++) mode. Additional proof is obtained from B?(x), which is the calculated maximum x component of B(+++). It is predominantly due to DR2 and is approximately 4.4 G. The B?(x) maximum value of the DR/TE??? probe is found to be slightly larger than that for a single resonator in a cavity because DR1 further concentrates the cavity's magnetic field along its x axis. Even though DR1 slightly enhances the performance of the DR/TE??? probe its main benefit is to act as a frequency tuner. A waveguide iris can be used to over-couple the DR/TE??? probe and lower its Q to ≈150. Under these conditions, the probe has a short dead time and a large bandwidth. The DR/TE??? probe's calculated conversion factor is approximately three times that of a regular cavity making it a good candidate for pulsed EPR experiments.     

Parametric excitation of subharmonic oscillations

Subharmonic oscillations of order one-half for a single-degree-of-freedom system with quadratic, cubic, and quartic nonlinearities under parametric excitation are investigated. Two approximate methods (multiple scales and generalized synchronization) are used for comparison. The modulation equations (reduced equations) of the amplitudes and the phases are obtained. Steady-state solutions (periodic solutions) and their stability are determined. Numerical solutions are carried out, and graphical representations of the results are presented and discussed. The results obtained by the two methods are in excellent agreement.     

Modes and Fields of Two Stacked Dielectric Resonators in a Cavity of an Electron Paramagnetic Resonance Probe

An electron paramagnetic resonance (EPR) probe consisting of two dielectric resonators (DRs) and a cavity (CV) is ideal for EPR experiments where both signal enhancement and tuning capabilities are required. The coupling of two DRs, resonating in their \({\text{TE}}_{01\delta }\) mode and a CV resonating in its \({\text{TE}}_{011}\) mode, is studied using energy-coupled mode theory (ECMT). The frequencies and eigenvectors of the three coupled modes are analytically derived. As predicted numerically, ECMT confirms that the \({\text{TE}}^{ + + - }\) and \({\text{TE}}^{ + - - }\) modes are indeed found to be degenerate at a specific distance between the two DRs \(d_{12}\). Additionally, the condition at which degeneracy occurs is specified. For a considerable range, the calculated frequency of the \({\text{TE}}^{ + + + }\) mode changes linearly with respect to \(d_{12}\). The \({\text{TE}}^{ + + + }\) mode showed a 500 MHz frequency change over a distance of 2 cm, when the resonance frequency is around 9.7 GHz. This enables the experimentalist to linearly tune the probe over this large frequency range. Finally the asymmetric configuration, where one of the resonators (DR2) is kept at the cavity center and the other one is allowed to move along the cavity axis, is studied. It is estimated that the frequency changes by 600 MHz over a distance of 1.5 cm. A formula for the magnitude of the magnetic field along the cavity axis, where the EPR samples are usually placed, is developed. This is crucial in determining the magnetic field in the vicinity of the sample and the probe’s filling factor.     

Harmonic,subharmonic, superharmonic,simultaneous sub/super harmonic and combination resonances of self-excited two coupled second order systems to multi-frequency excitation

Harmonic, subharmonic, superharmonic, simultaneous sub/super harmonic, and combination resonances of the additive type of self-excited two coupled-second order systems to multi-frequency excitation are investigated. The theoretical results are obtained by the multiple-scales method. The steady state amplitudes for each resonance are plotted, showing the influence of the different parameters. Analysis for each figure is given. Approximate solution corresponding to each type of resonance is determined. Stability analyses are carried out for each case.     

Comparative impact of doping nano-conducting polymer with carbon and carbon oxide composites in alkyd binder as anti-corrosive coatings

This study concentrated on producing anticorrosive coating depending on alkyd resin blended with polyaniline-carbon allotropes composites as filler. Polyaniline (PANI) and its composites were produced by doping of PANI with the carbon allotropes (graphene and multi-walled carbon nanotubes) and carbon-oxide allotropes (graphene oxide and multi-walled carbon nanotubes oxide) in different ratios through in situ chemical polymerization. The morphology of PANI and its composites were examined by transmission electron microscope (TEM), which proved that PANI composites appeared as a shell layer in core/shell structure with various overlay thickness depending on the adsorption type for polyaniline. The performance of the prepared coatings in cabinet salt agrees with electrical conductivity values where the best PANI/composite in conductivity value is the most efficient as an anti-corrosive coating.     

Facile synthesis of scheelite-type NdOsO4 directly grown on carbon cloth for oxygen evolution reaction

Journal of Solid State Electrochemistry - In the recent work, the scheelite-type ABO4 compound (A = Nd and B = Os) is synthesized via a hydrothermal route directly...     

Testing new graphene oxide-coated glazing for papyrus manuscripts in museums: Part I

The display of papyrus and paper (as cellulosic materials) in the Egyptian museums is always critical due to the traditional placement of display of sensitive materials between two plates of glass, acrylic, or other types of glazing materials. The sensitivity of the glazing materials to abrasion, ultraviolet rays, dust adhesion, and high light reflectivity are considered concerning issues to conservators, curators, and visitors. In this paper, thin protective coatings of graphene oxide (GO) were synthesized by modified Hummers' method and deposited on selected museums' glazing materials (glass and acrylic) using spin coating. Multi-analytical techniques were employed to assess the applicability of GO-coated glazing including scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman spectroscopy (RS), Fourier transform infrared spectroscopy (FTIR), microhardness testing, NIR VIS, and UV spectrophotometer and static potential measurements. The results showed that the glass glazing hardness was increased by ~10% due to the deposition of the GO coating. Moreover, according to glazing type, the reflectance values of the GO-coated glazing samples, compared with the uncoated samples, confirmed that the thin film of GO improved the UV rays blocking. As is evident in the GO-coated glass where approximately 27% of UV rays have been blocked, likewise, 19% of UV rays were blocked in GO-coated acrylic (TRU VUE). Considering VIS and NIR reflection spectra of GO-coated plexiglass, a higher reflectance is presented by 29%. Furthermore, the static potential measurements showed an energy decline in GO-coated glazing compared with the uncoated samples.