Characterization of Plasma Polymerized Hexamethyldisiloxane Films Prepared by Arc Discharge

Herein, we present a simple method for fabricating plasma polymerized hexamethyldisiloxane films (pp-HMDSO) possessing superhydrophobic characteristics via arc discharge. The pp-HMDSO films were deposited on a soda–lime–silica float glass using HMDSO monomer vapor as a precursor. A detailed surface characterization was performed using scanning electron microscopy and atomic force microscopy. The growth process of the pp-HMDSO films was investigated as a function of deposition time from 30 to 300 s. The non-wetting characteristics of the pp-HMDSO films were evaluated by means of contact angle (CA) measurements and correlated with the morphological characteristics, as obtained from microscopy measurements. The deposited films were found to be nano-structured and exhibited dual-scale roughness with the static CA values close to 170°. Fourier transform infrared spectroscopy analysis was carried out to investigate chemical and functional properties of these films. Methyl groups were identified spectroscopically to be present within the pp-HMDSO films and were proposed to result in the low surface energy of material. The synergy between the dual-scale roughness and low surface energy resulted in the superhydrophobic characteristics of the pp-HMDSO films. A possible mechanism for the pp-HMDSO film formation is proposed.     

Biologically active compounds from Lake Baikal streptomycetes

Data on the biological activity of ethylacetate extracts of Lake Baikal streptomycetes were obtained for the first time. The extracts of isolated actinobacteria of the genus Streptomyces were tested for the presence of compounds that inhibit the growth of pathogenic and conditionally pathogenic microorganisms and that exhibit a cytotoxic effect on Erlich carcinoma tumor cells. The ability of streptomycetes to produce inhibitors of enzymes isolated from marine organisms was also investigated. The production of bioactive compounds as a function of medium composition was given. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 65–69, January–February, 2006.     

Application of orthogonal ultrasonic signals and binaural processing for imaging of the environment

Data acquisition rates in ultrasonic imaging systems are limited by the finite value of the speed of ultrasonic waves. In order to improve the imaging speed, it is proposed to perform simultaneous scanning of the environment in different directions. In order to avoid cross-talk between adjacent channels in different directions, different orthogonal signals are transmitted. Application of cross-correlation processing and non-linear iterative deconvolution enables the reliable separation of signals transmitted by different sources and reflected by multiple targets. The spatial positions of the targets are found using the data obtained after the non-linear deconvolution as the initial data for binaural or tri-aural processing. This approach has been exploited in ultrasonic sonar used for navigation of mobile robots.     

Calibrated Estimators of the Population Covariance

We introduce some calibrated estimators of a finite-population covariance. The estimators are defined by using different calibration equations and different loss functions. The estimators derived are compared by simulation. The study is supported by the Nordplus Neighbour program of the Nordic Council of Ministers.     

Measurement of viscosity of highly viscous non-Newtonian fluids by means of ultrasonic guided waves

In order to perform monitoring of the polymerisation process, it is necessary to measure viscosity. However, in the case of non-Newtonian highly viscous fluids, viscosity starts to be dependent on the vibration or rotation frequency of the sensing element. Also, the sensing element must possess a sufficient mechanical strength. Some of these problems may be solved applying ultrasonic measurement methods, however until now most of the known investigations were devoted to measurements of relatively low viscosities (up to a few Pa s) of Newtonian liquids.     

Development of a new ultrasonic actuator based on Langevin bending transducer

A new ultrasonic actuator based on a bending-type Langevin piezoelectric transducer has been developed. An actuator consists of a half-wavelength Langevin transducer and an aluminum plate that is mounted in the middle of the transducer. The driving tip is located at the bottom of the aluminum plate. Piezoceramic rings with opposite polarity within each half of the ring are divided into two groups. Two harmonic signals with shifted phases by π/2 are used to excite the first bending mode of the Langevin transducer and aluminum plate. Elliptical trajectory of the contact point motion is obtained by combining these two bending modes. Numerical modelling was carried out to analyze harmonic response of the actuator and to investigate the trajectories of the contact point motion. Optimization of the aluminum plate design was performed to maximize the parameters of elliptical motion of the driving tip. A prototype actuator was fabricated, and output characteristics were measured. The results of numerical and experimental study are discussed.     

Flocculation of Bacillus amyloliquefaciens H Disintegrates with Cationized Starch and Aminated Hydroxyethylcellulose

The ability of cationized hydroxyethylated starch (CHES) and aminated hydroxyethylcellulose (DEAE-HEC) to flocculate cell disintegrate of Bacillus amyloliquefaciens H (BamHI) was investigated. The efficiency of flocculation was compared to that of synthetic polymer polyethyleneimine (PEI) and natural polysaccharide chitosan. The influence of salt concentration and biomass concentration on flocculation efficiency was investigated. It was found that the efficiency of flocculation with CHES and DEAE-HEC was similar to that of PEI but better compared to chitosan. Recovery of total soluble proteins at higher than 0.3% concentration of flocculant decreased by more than 18.8% and 42.3% compared to PEI and chitosan, respectively. The yield of BamHI restriction endonuclease activity with all flocculants was similar except for chitosan where 13.1% lower yield was obtained. Meanwhile, efficiency of flocculation with CHES and DEAE-HEC depends drastically on the salt concentration, that is, flocculation diminishes if NaCl concentrations higher than 0.2 M (for CHES) or 0.1 M (for DEAE-HEC) are used. The results have shown that CHES and DEAE-HEC are promising flocculants of cell disintegrates if higher yield of protein is of great concern.     

3D analysis of interaction of Lamb waves with defects in loaded steel plates

The objective of the research presented here is the investigation of the interaction of guided waves with welds, defects and other non-uniformities in steel plates loaded by liquid. The investigation has been performed using numerical simulation for 2D and 3D cases by the finite differences method, finite element method and measurement of 3D distributions of acoustic fields. Propagation of the S(0) mode in a steel plate and its interaction with non-uniformities was investigated. It was shown that using the measured leaky wave signals in the water loading of the steel plate and by application of signal processing, the 3D ultrasonic field structure inside and outside of the plate can be reconstructed. The presence of leaky wave signals over the defect caused by the mode conversion of Lamb waves has been proved using the numerical modelling and experimental investigations. The developed signal and data processing enables to visualise dynamics of ultrasonic fields over the plate, and also to estimate spatial positions of defects inside the steel plates.