Tobramycin and Nebramine as Pseudo‐oligosaccharide Scaffolds for the Development of Antimicrobial Cationic Amphiphiles

Antimicrobial cationic amphiphiles derived from aminoglycoside pseudo‐oligosaccharide antibiotics interfere with the structure and function of bacterial membranes and offer a promising direction for the development of novel antibiotics. Herein, we report the design and synthesis of cationic amphiphiles derived from the pseudo‐trisaccharide aminoglycoside tobramycin and its pseudo‐disaccharide segment nebramine. Antimicrobial activity, membrane selectivity, mode of action, and structure–activity relationships were studied. Several cationic amphiphiles showed marked antimicrobial activity, and one amphiphilic nebramine derivative proved effective against all of the tested strains of bacteria; furthermore, against several of the tested strains, this compound was well over an order of magnitude more potent than the parent antibiotic tobramycin, the membrane‐targeting antimicrobial peptide mixture gramicidin D, and the cationic lipopeptide polymyxin B, which are in clinical use.     

On a Characterization Theorem on a -adic Solenoids

Doklady Mathematics - According to the Heyde theorem the Gaussian distribution on the real line is characterized by the symmetry of the conditional distribution of one linear form in independent...     

On a Characterization of Idempotent Distributions on Discrete Fields and on the Field of <Emphasis Type="Italic">p</Emphasis>-Adic Numbers

We prove the following theorem. Let X be a discrete field, and \(\xi \) and \(\eta \) be independent identically distributed random variables with values in X and distribution \(\mu \). The random variables \(S=\xi +\eta \) and \(D=(\xi -\eta )^2\) are independent if and only if \(\mu \) is an idempotent distribution. A similar result is also proved in the case when \(\xi \) and \(\eta \) are independent identically distributed random variables with values in the field of p-adic numbers \({\mathbf {Q}}_p\), where \(p>2\), assuming that the distribution \(\mu \) has a continuous density.     

A Geometric Level-Set Formulation of a Plasma-Sheath Interface

In this paper, we present a new geometric level-set formulation of a plasma-sheath interface arising in plasma physics. We formally derive the explicit dynamics of the interface from the Euler-Poisson equations and study the local-time evolution of the interface and sheath in some special cases.     

Nonparametric identification of asymmetric nonlinear vibration systems with the Hilbert transform

The objective of the paper is presenting a simple and more accurate technique for precise identification of nonlinear elastic force functions acting in asymmetric vibration systems. The identification procedure based on the Hilbert transform is a nonparametric one; it does not require a priori information about the system structure or its parameters. The examples of the identification of asymmetric classic vibration nonlinear models – the Helmholtz and the double-well Duffing oscillators – are investigated.     

Effect of fluid flow on cavitation erosion of materials under exposure to vibrations from a hydrodynamic generator

The results of investigation of cavitation erosion of lead in various places of a hydrodynamic-generator submerged jet are presented. Features of erosion caused by the effect of flow are established. It can both strengthen the erosion intensity and weaken it in dependence on the angle of incidence. The stratification of air bubbles under the action of pressure waves is possible in the flow under the interaction with the surface of objects. The flow can change the number of air bubbles participating in the cavitation near the surface. It can also influence the mechanical effect on the surface of the tested materials inducing their nonuniform deformation. All the factors listed affect the cavitation erosion complicating considerably the physics of the process.     

On a characterization of a convolution of Gaussian and idempotent distributions

We prove some analogues of the well-known Skitovich-Darmois and Heyde characterization theorems for a second countable locally compact Abelian group X under the assumption that the distributions of the random variables have continuous positive densities with respect to a Haar measure on X and the coefficients in the linear forms considered are topological automorphisms of the group X.