Low-filled suspensions of α-chitin nanorods for electrorheological applications.

Highly anisometric α-chitin nanoparticles isolated by TEMPO-oxidation were investigated as filler for electrorheological fluids. The dimensions of rod-like particles were determined by AFM and cryo-TEM methods. The rheological behavior of α-chitin nanoparticles in polydimethylsiloxane changes from viscous to elastic under electric field. The yield stress reaches about 220 Pa at 7 kV/mm for 1.0 wt% fluid. Despite the nanosize of particles, the suspensions sedimentation ratio was found to be low (~23%). The electrorheological behavior of the fluids was discussed in terms of the Mason numbers. The stability of fluids response under switching electric field was shown. The activation energy of polarization processes in suspensions was calculated as 58 ± 2 and 64 ± 1 kJ/mol for 0.5 and 1.0 wt% filler content from the impedance spectra. The high aspect ratio (~70) and dielectric permittivity result in high electrorheological activity of α-chitin suspensions at extremely low concentrations (≤1.0 wt%).

Enhanced electrorheological activity of porous chitosan particles.

Novel porous filler for electrorheological fluids was fabricated from chitosan via freeze drying technique. An exceptional electrorheological effect was discovered in suspensions of polydimethylsiloxane (silicone oil) filled by highly porous chitosan particles. The electrorheological activity was studied by rotational rheometry and visualized by optical microscopy. High porosity of the filler allows preparing highly efficient electrorheological fluids at rather low (< 1 wt%) concentration of dispersed phase. The mechanism of chain-like structure formation was considered. The electrorheological behavior of suspensions and the filler structural organization at different concentration were comprehended in terms of dielectric properties. The rheological data were approximated by Bingham and Cho-Choi-Jhon equations. The sedimentation stability of chitosan suspensions in polydimethylsiloxane was significantly affected by particles porosity.

Effect of exfoliating agent on rheological behavior of ß-chitin fibrils in aqueous suspensions and on mechanical properties of poly(acrylic acid)/ß-chitin composites.

Chitin whiskers are promising reinforcing filler for composites due to their mechanical properties, renewable nature and low cost. A new method for preparation of ß-chitin fibrils from squid pens in ascorbic acid aqueous solutions (AscA) was developed. Stirring of the solution with 2 g/l AscA for 2 h disperses the swollen chitin to individualized fibrils with an aspect ratio > 250. The optimal conditions of ß-chitin exfoliation in acrylic acid (AcrA) aqueous solution were found (0.75-2 g/l, 3-4 h). TEMPO-oxidized ß-chitin fibrils were chosen as a reference sample for comparison of different methods. 0.1% chitin suspensions exfoliated in AscA and AcrA solutions show similar gel-like behavior with a storage modulus (G') of 98 ±â€¯23 and 34 ±â€¯12 Pa, respectively, whereas G' of 0.1% dispersion of the TEMPO-oxidized ß-chitin fibrils was 0.015 ±â€¯0.005 Pa only. Composites based on poly(acrylic acid) comprising 1-3 wt% of ß-chitin fibrils were fabricated by polymerization filling. Mechanical properties of the composites were investigated in dry state in the temperature range of 25-250 °C and at controlled relative humidity in the range from 53.6% to 100%. It was revealed that the maximum reinforcing effect is achieved at high temperature (>120 °C) and high relative humidity (≥75.3%RH).

Colloids of detonation nanodiamond particles for advanced applications.

Nanodiamond (ND) is one of the most attractive allotropic modification of carbon due to their unique physical and chemical properties. In the present review the current state of science and technology in the field of NDs is analyzed. ND can be used in various application and in different form e.g. as a dispersion phase in suspension, as a filler in composites, etc., so the sedimentation stability of ND in different media are under scrutiny. Thus, theoretical aspects of ND suspension coagulation mechanisms and the methods avoiding it were considered. The dependence of rheological behavior on particles modification was discussed as well. Various methods for the preparation and modification of NDs to obtain particles of various sizes on a nanometer scale with different physicochemical properties were reviewed. The area of practical application for NDs was considered on the example of polymer composites. The various manufacturing methods, mechanical properties and medical aspects for thermosetting, thermoplastic and elastomer ND composites were summarized.

[The combined use of ultrasound and the laser in treating patients with osteomyelitis of the ribs and sternum]. / Sochetannoe primenenie ul'trazvuka i lazera pri lechenii bol'nykh s osteomielitom reber i grudiny.

The article deals with the mechanism of low-frequency ultrasound and low-energy laser radiation beneficial influence on the processes of purulent wounds and cavities cleaning and healing. The authors describe the methods and results of their associated usage in 17 cases of costal and sternal osteomyelitis treatment.

[The medical evacuation procedures in slight gunshot wounds]. / Lechebno-évakuatsionnaia taktika pri legkikh ognestrel'nykh raneniiakh.

The article makes a detailed analysis concerning the results of treatment of minimally wounded who were stationed at the separate medical battalion. All the wounded were returned to the ranks in first 55 days from the moment of wounding, and after being examined by the Main Medical Commission. There is a direct dependency between the terms of treatment, number of surgical interventions, development of complications on the one hand, and the size of wound on the other hand. The article stresses that actually the duration of treatment of minor wounded at the separate medical battalion is limited by 10 days. The authors make a conclusion that the possible increase of these terms could return the wounded to their duties without further evacuation to the other medical establishments. There are indications for primary surgical management of gunshot wounds and for further evacuation of this category of wounded from separate medical battalion.

[Dynamic microvascular changes in gunshot wounds]. / Dinamika mikrososudistykh izmenenii v ognestrel'noi rane.

On the basis of the experimental data the authors study the state of microcirculation and tissue breathing on the first day of gunshot injury. It was found out that the state of microvascular channels played the main role in the genesis of morphological disorders of tissues. These changes directly depend on the quantity of the energy that was absorbed from the missile.