The stability of viscous flow between two co-axial rotating cylinders

Summary In this paper a new method is described for solving the characteristic value problem underlying the theory of the stability of viscous flow between two co-axial rotating cylinders. The method depends on solving a simpler adjoint system of equations. It is revealed that the present method which yields a new and more precise secular equation than the one obtained by Steinman, is much simpler and at the same time saves considerable labour in numerical work.     

Absence of biologically related Raman lines in cultures of Bacillus megaterium

Cultures of Bacillus megaterium have been examined with laser-Raman spectroscopy in the 20–300 and 800–1800 cm^?1 ranges. No lines were detected in the 20–300 cm^?1 range, and evidence is presented that sporadic lines observed in the other range can be ascribed to experimental artifacts.     

Spectrophotometric simultaneous determination of rabeprazole sodium and itopride hydrochloride in capsule dosage form

A new simple, economical, rapid, precise and accurate method for simultaneous determination of rabeprazole sodium and itopride hydrochloride in capsule dosage form has been developed. The method is based on ratio spectra derivative spectrophotometry. The amplitudes in the first derivative of the corresponding ratio spectra at 231nm (minima) and 260nm were selected to determine rabeprazole sodium and itopride hydrochloride, respectively. The method was validated with respect to linearity, precision and accuracy.     

Evidence for Multiple Binding Modes in the Initial Contact Between SARS-CoV-2 Spike S1 Protein and Cell Surface Glycans**

Infection of host cells by SARS-CoV-2 begins with recognition by the virus S (spike) protein of cell surface heparan sulfate (HS), tethering the virus to the extracellular matrix environment, and causing the subunit S1-RBD to undergo a conformational change into the ‘open’ conformation. These two events promote the binding of S1-RBD to the angiotensin converting enzyme 2 (ACE2) receptor, a preliminary step toward viral-cell membrane fusion. Combining ligand-based NMR spectroscopy with molecular dynamics, oligosaccharide analogues were used to explore the interactions between S1-RBD of SARS CoV-2 and HS, revealing several low-specificity binding modes and previously unidentified potential sites for the binding of extended HS polysaccharide chains. The evidence for multiple binding modes also suggest that highly specific inhibitors will not be optimal against protein S but, rather, diverse HS-based structures, characterized by high affinity and including multi-valent compounds, may be required.     

Simultaneous HPTLC Determination of Escitalopram Oxalate and Clonazepam in Combined Tablets

A new, simple high-performance thin-layer chromatographic method has been established and validated for simultaneous determination of escitalopram oxalate and clonazepam in a combined tablet dosage form. The drugs were separated on aluminum plates precoated with silica gel 60 F₂₅₄; toluene–ethyl acetate–triethylamine 7:3.5:3 (v/v) was used as mobile phase. Quantitative analysis was performed by densitometric scanning at 258 nm. The method was validated for linearity, accuracy, precision, and robustness. The calibration plot was linear over the ranges 250–2,500 and 50–500 ng band⁻¹ for escitalopram oxalate and clonazepam, respectively. The method was successfully applied to the analysis of drugs in a pharmaceutical formulation.     

Influence of γ-ray-induced effects on dielectric dispersion of CuO-doped calcium fluoroborophosphate glass system

γ-Ray-induced dielectric dispersion in CaF₂–B₂O₃–P₂O₅ glasses doped with different concentrations of CuO was investigated. The glass samples were exposed to γ-rays with dose varying within the range 0–10 kGy. The dielectric dispersion and spectroscopic properties were measured before and after γ-ray treatment. Additionally, thermoluminescence studies were performed on post-irradiated glass samples. The results of dielectric properties and dielectric breakdown strength indicated a substantial increase in the insulating strength of CuO containing glasses due to γ-ray irradiation. The analysis of these results together with UV-vis optical absorption, IR spectra, and thermoluminescence studies have indicated a gradual increase in the concentration of mono-valent copper ions due to γ-ray treatment of the glass network. The additional studies have confirmed that these Cu⁺ ions occupy network-forming positions, increase the polymerization of the borophosphate glass network, and facilitates for the increase of insulating strength of the titled glass.     

Stability-Indicating High-Performance Thin-Layer Chromatographic Method for the Estimation of Ambroxol Hydrochloride and Doxofylline in a Pharmaceutical Formulation Using Experimental Design in Robustness Study

JPC – Journal of Planar Chromatography – Modern TLC - A sensitive, specific, and accurate stability-indicating high-performance thin-layer chromatographic method for the analysis of...