Modeling the coupling of reaction kinetics and hydrodynamics in a collapsing cavity

We introduce a model of cavitation based on the multiphase Lattice Boltzmann method (LBM) that allows for coupling between the hydrodynamics of a collapsing cavity and supported solute chemical species. We demonstrate that this model can also be coupled to deterministic or stochastic chemical reactions. In a two-species model of chemical reactions (with a major and a minor species), the major difference observed between the deterministic and stochastic reactions takes the form of random fluctuations in concentration of the minor species. We demonstrate that advection associated with the hydrodynamics of a collapsing cavity leads to highly inhomogeneous concentration of solutes. In turn these inhomogeneities in concentration may lead to significant increase in concentration-dependent reaction rates and can result in a local enhancement in the production of minor species.     

Stereoselective synthesis of chiral tertiary alcohol building blocks via neighbouring group participation from tri-substituted olefins

A regio- and stereoselective preparation of chiral quaternary 1,2/1,3-diols from acyclic tri-substituted alkenes is disclosed. Optically active tertiary alcohols are the constituents of several bioactive natural products, pharmaceuticals and a general method for their preparation is desirable. A sulfinyl moiety has been utilized as an intramolecular nucleophile.     

Structural studies of six and four coordinate zinc(II), nickel(II) and dioxovanadium(V) complexes with thiosemicarbazones

Three Zn(II) complexes of di-2-pyridyl ketone thiosemicarbazone, an octahedral Ni(II) complex of 2-acetylpyridine hexamethyleneiminyl-3-thiosemicarbazone, and a V(V) complex of 2-acetylpyridine morpholyl-3-thiosemicarbazone were prepared and characterized. Crystal structure of Ni(II) and V(V) complexes are reported. The ligand in the nickel complex is found to coordinate in the thione form with a pseudo octahedral geometry and the vanadium(V) complex has trigonal bipyramidal geometry.     

Catalytic determination of silver by means of the 1,2-diaminoethane—peroxodisulphate reaction

A kinetic method for the determination of 5.0 × 10^-3–8.0 × 10^-6 M silver ion is based on the catalysis by silver of the reaction between 1,2-diaminoethane and peroxodisulphate, and titration of the residual oxidant. Copper and manganese interfere at 10:1 mole ratios; zinc and iron are tolerated.     

Eco‐Efficient Synthesis of New Pyrido [2, 3‐c] Coumarin Scaffolds Under Sonochemical Method

We have explored a green and simple approach to assembling of pyrido[2,3‐c]coumarin derivatives via one‐pot multi‐component condensation of 4‐hydroxy‐2H‐chromen‐2‐one, benzaldehyde, acetoacetanilide, and ammonium acetate in the absence of catalyst in ethanol under ultrasound irradiation. Compared with thermal method, this methodology has significant advantages, for example, it can be easily operated, it has an easy work‐up and short reaction times, and it produces satisfactory yields.     

Pharmaceutical Formulation and Characterization of Dipeptide Nanotubes for Drug Delivery Applications

Peptide nanotubes are promising materials for a variety of biomedical applications with ultrashort (≤7 amino acids) forms providing particular promise for clinical translation. The manufacture of peptide nanotubes has, however, been associated with toxic organic solvents restricting clinical use. The purpose of this work is to formulate dipeptide nanotubes using mild techniques easily translated to industrial upscale and to characterize their physiochemical and biological properties. Phenylalanine‐phenylalanine variants can be successfully formulated using distilled water as demonstrated here. Formulations are homogenous in shape (tubular), with apparent size (50–260 nm) and a zeta potential of up to +30 mV. L‐(H₂N‐FF‐COOH), and D‐enantiomers (H₂N‐ff‐COOH) demonstrate no toxicity against glioblastoma cells and are explored for ability to deliver a model hydrophilic molecule, sodium fluorescein, at pH 5.5 (tumor) and 7.4 (physiological). Peptide nanotubes loaded with >85% sodium fluorescein, demonstrate burst release characteristics, fitting the Weibull model of drug release. This research provides important data contributing to the pharmaceutical formulation of peptide nanotubes as drug delivery platforms for hydrophilic drugs.     

Multiple beams surface plasmon interference generation: A theoretical analysis

In this paper, multiple beams surface plasmon (SP) interference generation based on prism coupling technique is theoretically analyzed and presented. The proposed multiple beams SP interference configuration is investigated for nanolithography application for two-dimensional feature fabrication. The configuration is then numerically and experimentally analyzed by employing aluminum metal at 364-nm illumination wavelengths to realize high resolution and high aspect ratio two-dimensional periodic nanoscale dot array patterns on the recording medium.     

Stiffness of contacts between rough surfaces

The effect of self-affine roughness on solid contact is examined with molecular dynamics and continuum calculations. The contact area and normal stiffness rise linearly with the applied load, and the load rises exponentially with decreasing separation between surfaces. Results for a wide range of roughness, system size, and Poisson ratio can be collapsed using Persson's contact theory for continuous elastic media. The compliance due to atomic-scale motion at the interface between solids has little effect on the area and normal stiffness, but can reduce the total transverse stiffness by orders of magnitude. The scaling of this effect with system size is discussed.     

Compatibility study between sitagliptin and pharmaceutical excipients used in solid dosage forms

Differential scanning calorimetry (DSC) is a primary technique for measuring the thermal properties of materials, which reflects the physico-chemical properties of drug substances. In the present study, it is used as a screening technique for assessing the compatibility of sitagliptin with some currently employed pharmaceutical excipients. The influence of processing conditions and their effects (simple blending, co-grinding or kneading) on drug stability was evaluated. Sitagliptin showed a sharp endothermic peak at 212.1 °C with an enthalpy change of 131.5 J g^?1 indicating melting of drug. Facile transformation of dehydrated sitagliptin to monohydrate form was observed in some mixtures, disappearance of sharp melting endothermic peak of sitagliptin was observed in some mixtures. On the basis of DSC results, sitagliptin was found to be compatible with micro crystalline cellulose, croscarmellose, and pregelatinized starch. Some excipient interaction was observed with magnesium stearate, ascorbic acid, and citric acid. X-ray diffractometry and FT-IR were used as supportive tools in interpreting the DSC results. Overall, the excipients selected were compatible with the API and the mixtures are stable within the tested conditions. These results would be useful for formulation development of the film coated tablets of sitaglitptin.     

Desvenlafaxine succinate monohydrate

The title compound {systematic name: [2‐(1‐hydroxycyclohexyl)‐2‐(4‐hydroxyphenyl)ethyl]dimethylammonium 3‐carboxypropanoate monohydrate}, C₁₆H₂₆NO₂⁺·C₄H₅O₄⁻·H₂O, is a succinate salt of O‐desmethylvenlafaxine (desvenlafaxine). The present structure is one of four reported polymorphs of this salt, which is a new antidepressant drug. The carboxyl group of the succinate anion adopts a rare anti conformation and is engaged in a very short O—H...O⁻ hydrogen‐bond contact. Both cations and anions are involved separately in the formation of distinct O—H...O hydrogen‐bonded networks. Desvenlafaxine cations and water molecules self‐assemble to generate a honeycomb layer, while the succinate anions form a linear tape structure. These hydrogen‐bonded networks are interlinked via N—H...O and O—H...O hydrogen bonds. The hydrogen‐bonding network is so strong that desolvation and melting occur together at approximately 402 K. Thus, the crystal structure may be used to understand the thermal stability and solubility of the compound at the molecular level.