Unexpected Effects of Activator Molecules' Polarity on the Electroreological Activity of Titanium Dioxide Nanopowders.

Titanium dioxide nanoparticles, obtained using the sol-gel method and modified with organic solvents, such as acetone, acetonitrile, benzene, diethyl ether, dimethyl sulfoxide, toluene, and chloroform, were used as the filler of polydimethylsiloxane-based electrorheological fluids. The effect of electric field strength on the shear stress and yield stress of electrorheological fluids was investigated, as well as the spectra of their dielectric relaxation in the frequency range from 25 to 106 Hz. Modification of titanium dioxide by polar molecules was found to enhance the electrorheological effect, as compared with unmodified TiO2, in accordance with the widely accepted concept of polar molecule dominated electrorheological effect (PM-ER). The most unexpected result of this study was an increase in the electrorheological effect during the application of nonpolar solvents with zero or near-zero dipole moments as the modifiers. It is suggested that nonpolar solvents, besides providing additional polarization effects at the filler particles interface, alter the internal pressure in the gaps between the particles. As a result, the filler particles are attracted to one another, leading to an increase in their aggregation and the formation of a network of bonds between the particles through liquid bridge contacts. Such changes in the electrorheological fluid structure result in a significant increase in the mechanical strength of the structures that arise when an electric field is applied, and an increase in the observed electrorheological effect in comparison with the unmodified titanium dioxide.

[The difficulties of diagnosis and treatment of non-occlusive mesenteric circulatory disorders].

AIM: To review one of actual problems of emergency surgery - diagnosis and treatment of patients with non-occlusive mesenteric circulatory disorders. MATERIAL AND METHODS: The article presents the clinical observations showing the ambiguity of clinical picture, features and challenges of diagnosis, treatment of disease and opportunities for positive outcomes. Diagnostic methods are x-ray, abdominal ultrasonography according to which acute abdominal ischemia may be assumed. However, in all unclear cases diagnostic videolaparoscopy is mandatory to determine further tactics. Unfortunately diagnostic videolaparoscopy is not always interpreted comprehensively and not a definitive method of diagnosis. Wide surgical access is usually necessary for non-occlusal acute violation of mesenteric circulation and volume of surgery varies from segmental to subtotal intestinal and colic resection with obligatory enteral intubation and decompression. Thus, complex pre- and postoperative treatment is required.