Interfacial long traveling waves in a two‐layer fluid with variable depth

Long wave propagation in a two‐layer fluid with variable depth is studied for specific bottom configurations, which allow waves to propagate over large distances. Such configurations are found within the linear shallow‐water theory and determined by a family of solutions of the second‐order ordinary differential equation (ODE) with three arbitrary constants. These solutions can be used to approximate the true bottom bathymetry. All such solutions represent smooth bottom profiles between two different singular points. The first singular point corresponds to the point where the two‐layer flow transforms into a uniform one. In the vicinity of this point nonlinear shallow‐water theory is used and the wave breaking criterion, which corresponds to the gradient catastrophe is found. The second bifurcation point corresponds to an infinite increase in water depth, which contradicts the shallow‐water assumption. This point is eliminated by matching the “nonreflecting” bottom profile with a flat bottom. The wave transformation at the matching point is described by the second‐order Fredholm equation and its approximated solution is then obtained. The results extend the theory of internal waves in inhomogeneous stratified fluids actively developed by Prof. Roger Grimshaw, to the new solutions types.     

Rosin Derivatives as a Platform for the Antiviral Drug Design

The increased complexity due to the emergence and rapid spread of new viral infections prompts researchers to search for potential antiviral and protective agents for mucous membranes among various natural objects, for example, plant raw materials, their individual components, as well as the products of their chemical modification. Due to their structure, resin acids are valuable raw materials of natural origin to synthesize various bioactive substances. Therefore, the purpose of this study was to confirm the possibility of using resin acid derivatives for the drug design. As a result, we studied the cytotoxicity and biological activity of resin acid derivatives. It was shown that a slight decrease in the viral load in the supernatants was observed upon stimulation of cells (II) compared with the control. When using PASS-online modeling (Prediction of Activity Spectra for Substances), the prediction of the biological activity spectrum showed that compound (I) is capable of exhibiting antiviral activity against the influenza virus. The use of the SWISS-ADME webserver to reveal the drug-like properties of compounds did not directly indicate the presence of antiviral activity. These results indicate the potential of resin acid derivatives as a starting point for extensive research in the study of biological activity.     

Nano‐Ruby: A Promising Fluorescent Probe for Background‐Free Cellular Imaging

Bioprobes based on fluorescent ruby nanoparticles, which are suitable for ultrasensitive imaging, are reported. A stable aqueous/buffer colloid, permitting facile conjugation to proteins, is produced by femtosecond laser ablation of ruby and the nanoparticles (mean size 17 nm) are photostable, with long lifetime (1–4 ms) 694 nm emission. With time‐gating complete (>20 dB) suppression of cell autofluorescence and suppression of exogenous fluorophores is observed. Nanoparticles are imaged in as‐grown cells and those immunolabeled with quantum dots. Immunoassay binding to target biomolecules is also demonstrated.     

Development of a convenient synthetic route to aminochromenes via Buchwald C-N coupling

A convenient new synthetic route to p-aminophenylaminobenzo- and naphthopyrans was developed via palladium-catalyzed C-N coupling. It was demonstrated that novel targeted aminoderivatives reveal photochromic properties. The structure of intermediate p-nitrophenylaminochromenes was confirmed by X-ray crystallographic analysis.     

Functionalization of aminocrown ethers with [2H]-chromene units by Buchwald-Hartwig C-N coupling for constructing of photoswitchable molecular devices

Functionalization of the diaminodibenzocrown ethers with 2H-[1]benzopyrane and 3H-naphtho[2,1-b]pyrane units by Buchwald-Hartwig C-N coupling was developed. It is demonstrated that the novel molecule possesses photochromic properties that can be modified by the complex formation process.     

A new three-component one pot reaction of trinitromethane, epoxides and alkenes via dinitronitronates: synthesis of highly functionalized 3,3-dinitroisoxazolidines

A novel approach to acyclic alkyldinitronitronates using nucleophilic opening of epoxides with the trinitromethyl anion is presented. The scope and limitations of this synthetic procedure are presented. A series of highly functionalized 3,3-dinitroisoxazolidines were synthesized as mixtures of diastereomers.     

Efficient synthesis of racemic β-aminophosphonates via aza-Michael reaction in water

Water as a solvent significantly accelerates the addition of various amines to diethyl vinylphosphonate to yield β-aminophosphonates without any catalyst compared to known procedures for such aza-Michael reactions. The products are obtained in quantitative yields and high purity over short reaction times. Using a reactant ratio (vinylphosphonate/amine) of 2:1 resulted in double phosphorylation of primary amines.     

Stereochemical correlation of diastereomeric 3-amino- with 3-arylamino acids,and their derivatives via stereospecific N-phenylation by diphenylhalonium salts

Diphenylhalonium salts were used in stereospecific N-phenylation of racemic and optically active 3-amino-2,3-diphenyl-1-propanols leading to 3-anilino-2,3-diphenyl-1-propanols. The absolute configurations of the latter and of genetically related compounds were established.

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Stereochemische Korrelation von diastereomeren 3-Amino- mit 3-Arylaminosäuren bzw. ihrer Derivate durch stereospezifische N-Phenylierung mit DiphenylhaloniumsalzenKurze Mitteilung

Zusammenfassung Durch stereospezifische N-Phenylierung mit Hilfe von Diphenylhaloniumsalzen werden racemische sowie optische aktive 3-Amino-2,3-diphenyl-1-propanole in die entsprechenden 3-Anilino-2,3-diphenyl-1-propanole übergeführt. Auf Grund dieser Umwandlung wird die absolute Konfiguration der Aminoalkohole und davon abgeleiteter Derivate ermittelt.