Features of high-temperature thermal oxidative degradation of organic-inorganic compositions based on poly(methyl methacrylate) with tetrabutoxytitanium

Thermal oxidative degradation of organic-inorganic compositions based on poly(methyl methacrylate) and the methyl methacrylate-methyl acrylate copolymer with tetrabutoxytitanium was studied by thermo-gravimetric methods.     

Nonlinear propagation of spark-generated N-waves in air: modeling and measurements using acoustical and optical methods

The propagation of nonlinear spherically diverging N-waves in homogeneous air is studied experimentally and theoretically. A spark source is used to generate high amplitude (1.4 kPa) short duration (40 μs) N-waves; acoustic measurements are performed using microphones (3 mm diameter, 150 kHz bandwidth). Numerical modeling with the generalized Burgers equation is used to reveal the relative effects of acoustic nonlinearity, thermoviscous absorption, and oxygen and nitrogen relaxation on the wave propagation. The results of modeling are in a good agreement with the measurements in respect to the wave amplitude and duration. However, the measured rise time of the front shock is ten times longer than the calculated one, which is attributed to the limited bandwidth of the microphone. To better resolve the shock thickness, a focused shadowgraphy technique is used. The recorded optical shadowgrams are compared with shadow patterns predicted by geometrical optics and scalar diffraction model of light propagation. It is shown that the geometrical optics approximation results in overestimation of the shock rise time, while the diffraction model allows to correctly resolve the shock width. A combination of microphone measurements and focused optical shadowgraphy is therefore a reliable way of studying evolution of spark-generated shock waves in air.     

Thermochemical study of a process of complex formation between <Emphasis Type=Italic>D,L</Emphasis>-triptophan and cobalt(II) ions in water solution

Heat effects of the reactions of formation of complexes of the composition CoTrp⁺ and CoTrp₂ were measured by direct calorimetry. Analysis of the effect of the ion force of the solution (0.25, 0.50, and 0.75 M KNO₃) on the heat effects of the processes of complex formation in the D,L-triptophan-Co(II) system at different temperatures (288.15, 298.15, and 308.15 K) was carried out. Standard thermodynamic characteristics of the reactions of formation of complexes in the system under study were evaluated.     

Controlled tissue emulsification produced by high intensity focused ultrasound shock waves and millisecond boiling

In high intensity focused ultrasound (HIFU) applications, tissue may be thermally necrosed by heating, emulsified by cavitation, or, as was recently discovered, emulsified using repetitive millisecond boiling caused by shock wave heating. Here, this last approach was further investigated. Experiments were performed in transparent gels and ex vivo bovine heart tissue using 1, 2, and 3 MHz focused transducers and different pulsing schemes in which the pressure, duty factor, and pulse duration were varied. A previously developed derating procedure to determine in situ shock amplitudes and the time-to-boil was refined. Treatments were monitored using B-mode ultrasound. Both inertial cavitation and boiling were observed during exposures, but emulsification occurred only when shocks and boiling were present. Emulsified lesions without thermal denaturation were produced with shock amplitudes sufficient to induce boiling in less than 20 ms, duty factors of less than 0.02, and pulse lengths shorter than 30 ms. Higher duty factors or longer pulses produced varying degrees of thermal denaturation combined with mechanical emulsification. Larger lesions were obtained using lower ultrasound frequencies. The results show that shock wave heating and millisecond boiling is an effective and reliable way to emulsify tissue while monitoring the treatment with ultrasound.     

Aspects of the super-equivalent sorption of glycine by cation exchanger KU-2-8

The structure formed in a sorbent during the super-equivalent sorption of glycine by cation exchanger KU-2-8 is optimized via quantum chemical simulation. The differential thermodynamic characteristics of ion exchange and super-equivalent sorption in the studied system are calculated using a thermodynamic approach that allows us to describe the simultaneous exchange and super-equivalent sorption of compounds by ion-exchangers.     

Microwave synthesis of vinylphosphonic acid and its derivatives

Microwave Pyrolysis of ??-substituted ethylphosphonic acid derivatives was studied. The resulting mixture of vinylphosphonic acid derivatives is similar to that obtained by convective heating.     

Activity coefficients of components of the sorbent phase in the nonexchange sorption of chloride-containing electrolytes on AN-31 low-basicity anion exchanger in the Cl form

Activity coefficients of components of the sorbent phase in the nonexchange sorption of chloride-containing electrolytes (hydrochloric acid and potassium, sodium, and magnesium chlorides) on AN-31 low-basicity anion exchanger in the Cl form are calculated and analyzed. Peculiarities of the sorption of the investigated electrolytes on the anion exchanger are discussed.     

Counterpropagation of waves with shock fronts in a nonlinear tissue-like medium

A numerical model for describing the counterpropagation of one-dimensional waves in a nonlinear medium with an arbitrary power law absorption and corresponding dispersion is developed. The model is based on general one-dimensional Navier-Stokes equations with absorption in the form of a time-domain convolution operator in the equation of state. The developed algorithm makes it possible to describe wave interactions in the presence of shock fronts in media like biological tissue. Numerical modeling is conducted by the finite difference method on a staggered grid; absorption and sound speed dispersion are taken into account using the causal memory function. The developed model is used for numerical calculations, which demonstrate the absorption and dispersion effects on nonlinear propagation of differently shaped pulses, as well as their reflection from impedance acoustic boundaries.     

Multielement determination of the composition of sulfide ores using X-ray fluorescence analysis

The potentials of the multielement X-ray fluorescence analysis of sulfide ores from one sample are studied. Using cluster analysis, sulfide ores are divided into four groups; within each group, the ores are similar in chemical composition and matrix effects. Calibration equations are obtained for each group. The performance characteristics of the determination results are evaluated.     

Hydrolysis of N,N-Dimethylaminoethyl Methacrylate and Its Salts in Concentrated Aqueous Solutions

The influence exerted by the structure of the ammonium group and anion, pH, and surfactant and polymeric additives on hydrolysis of N,N-dimethylaminoethyl methacrylate and its salts in concentrated aqueous solutions was studied.