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Abstract

Mikołaj Łabowski, Professor Emeritus at the Institute of Acoustics, Adam Mickiewicz University in Poznań, passed away on the 8th of October, 2013. Professor Mikołaj Łabowski was born on the 17th of December, 1935, in Florynka in the southern part of Poland. He graduated from the Faculty of Mathematics, Physics and Chemistry of the Adam Mickiewicz University receiving his Master of Science degree in physics in 1962. Eight years later he obtained his PhD title from the same university. In 1981, on the basis of the book “Ultra- and hypersonic properties of selected liquids and critical mixtures” he obtained the degree of habilitated doctor. The President of Poland awarded him the titles of Associate Professor in Physics in the year 1991 and Full Professor in 1999. From 1985 to 1987,Mikołaj Łabowski held the post of Vice-Dean for Students’ Affairs at the Faculty of Mathematics and Physics of the AdamMickiewicz University. In the years 1996–1999, he was the Director of the University’s Institute of Acoustics. He held many posts in the Polish Acoustical Society, of which he was a HonoraryMember. He always served with advice and assistance in scientific matters to the Committee of Acoustics of the Polish Academy of Sciences. Professor Łabowski was an outstanding scientist, one of the founders of ultrasonic physics in Poland. After returning from scholarship in the Lomonsov University in Moscow, he became an expert in the field of ultrasonic studies of liquids and liquid mixtures. His groundbreaking works on ultrasonic properties of critical binary mixtures opened up new perspectives in the research of dynamic phenomena in the vicinity of critical temperatures. Professor Łabowski’s outstanding scientific achievements were recognized by rewarding him the Minister of Education Prize in the years 1981 and 1987. Throughout his whole professional career associated with the Adam Mickiewicz University in Poznań, Professor Łabowski has published over 100 papers, mostly in renowned international scientific journals, and carried out an intensive teaching activity. Through his profound knowledge and enthusiasm, Professor Mikołaj Łabowski continuously inspired colleagues and collaborators and decisively shaped the development of ultrasonic physics in Poznań. With the death of Professor Mikołaj Łabowski, Polish acoustics has lost a great researcher, teacher, and scholar.
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Abstract

The paper reports the study of the complexation processes in aqueous solution of α-CD and DMSO. Cyclodextrins (CDs) (sometimes called cycloamyloses) are cyclic oligosaccharides formed by glucose units interconnected by α-(1,4) linkages; α-CD is one of three the most common CDs. It consists of six glucopyranose units. The speed of ultrasonic waves has been measured by the resonance method on ResoscanTM System apparatus. Some collateral data, such as density and heat capacity of the system, have also been measured. On the basis of the experimental data the excess adiabatic compressibility was determined. The extremes of the excess adiabatic compressibility function for different mixture compositions allowed us to establish the composition of molecular complexes formed in the solution. The obtained results suggest the formation of the α-CD with DMSO inclusion complexes with chemical stoichiometric ratio value of 1:1.
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Abstract

Ultrasonic emulsifying processes of immiscible liquids can be used to obtain stable emulsions. The authors used an ultrasonic sandwich head with an energy concentrator to obtain a suitable value of the energy density necessary for the emerge of ultrasonic cavitation. Two piezoelectric ring (Dext = 50 mm) transducers of Pz-26 type produced by FERROPERM were used to design the ultrasonic sandwich head. The frequency of the ultrasonic wave was 18.4 kHz and the excitation time of the ultrasonic transducer exiting 5 minutes. Visible bubbles during the generation of ultrasonic waves appeared in the mixture after exceeding the cavitation threshold. The authors determined also the cavitation threshold by measuring the electrical voltage conducted to the transducers. To receive long-lasting emulsion, the electrical voltage attained 300 Vpeak. The dispersion dependence on the emulsifying time was determined. The emulsion of linseed oil and water was stable through some months without surfactants.
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Abstract

The temperature dependence of the particle size distribution (PSD) of the magnetic fluid with an additional biocompatible dextran layer was studied using a ultrasonic method. The measurements of the ultrasound velocity and attenuation were carried out as a function of the volume concentration of magnetite particles at temperatures ranging from 15°C to 40°C. In order to extract the PSD from ultrasonic measurements, the theoretical model of Vinogradov-Isakovich was used. The extraction of PSD from the ultrasonic data requires also the measurements the density and viscosity of the ferrofluid samples. The calculated PSD of the magnetic fluid with an additional biocompatible layer shows a greater thermal stability than that of a magnetic fluid with a single surfactant layer.
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Abstract

Superparamagnetic iron oxide nanoparticles (SPION) synthesised chemically usually need the modification of the particle surface. Other natural sources of magnetic particles are various magnetotactic bacteria. Magnetosomes isolated from magnetotactic bacteria are organelles consisting of magnetite (Fe3O4) or greigite (Fe3S4) crystals enclosed by a biological membrane. Magnetotactic bacteria produce their magnetic particles in chains. The process of isolation of magnetosome chains from the body of bacteria consists of a series of cycles of centrifugation and magnetic decantation. Using a high-energy ultrasound it is possible to break the magnetosome chains into individual nanoparticles – magnetosomes. This study presents the effect of sonication of magnetosome suspension on their acoustic properties, that is speed and attenuation of the sound. Acoustic propagation parameters are measured using ultrasonic spectroscopy based on FFT spectral analysis of the received pulses. The speed and attenuation of ultrasonic waves in magnetosome suspensions are analysed as a function of frequency, temperature, magnetic field intensity, and the angle between the direction of the wave and the direction of the field.
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