Structural changes in martensite foils at the tips of microcracks arising as a result of stress relaxation

Changes in the structure at the tips of microcracks in structural materials with a structure of massive lath martensite are studied by diffraction electron microscopy. It is shown that changes at the tip of a crack occur as a result of successive stress relaxation. At first slip bands form, then reorientation zones (RZ) form, and finally zones free from dislocations (DFZ) form. The final stage is occurrence in DFZ of submicrocracks which then merge with a main crack. The dislocation structure at the tips of cracks is studied and the mechanism of submicrocrack generation is analyzed.Translated from Problemy Prochnosti, No. 12, pp. 94–99, December, 1990.     

Preparing of pellets by extrusion/spheronization using different types of equipment and process conditions

Introduction: The focus of this work was to produce matrix pellets made by extrusion/ spheronization using two types of equipment. The aim was to accomplish the laboratory-scale I process that has been already optimized and accepted with another type of equipment (laboratory-scale II).

Methods: A matrix pellet formulation consisting of MCC, Eudragit NE 30D and diclofenac sodium was used in the two types of equipment. Physico-chemical parameters and the dissolution profiles of the pellets in phosphate buffer pH 6.8 were compared.

Results: Pellets from both processes were similar in shape and tensile strength. They differed in particle size and dissolution profile. This may be contributed to different spheronization conditions.     

Bioavailability of nanoparticles of ferric oxide when used in nutrition. Experimental results in rats

Bioavailability of iron (Fe) introduced in the form of nanoparticles of ferric oxide and ferric sulphate was characterized in rats receiving Fe-deficient semi synthetic diet. Shown that nanoparticles of ferric oxide as well as the traditional form of this trace element (soluble salt of Fe) can restore the status of this trace element disturbances due to its scarcity in the diet.     

Structural changes of milk components during acid-induced coagulation kinetics as studied by synchronous fluorescence and mid-infrared spectroscopy

Dynamic oscillatory experiments and front-face synchronous fluorescence spectroscopy and mid-infrared (mid-IR) spectroscopy have been used to investigate structure evolution, at the macroscopic and molecular levels, during milk acidification kinetics. The studies were performed using skim milk, at two different temperatures (30 °C and 40 °C), to which was added glucono-δ-lactone (GDL) to generate different structural changes in casein micelles and gels. Synchronous fluorescence spectra were recorded in the 250-500 nm excitation wavelength range using an offset of 80 nm between the excitation and emission monochromators for each system during the 300 min acidification kinetics. The change in the fluorescence intensity at 281 nm reflects the pH-induced physicochemical changes of casein micelles and, in particular, structural changes in the micelles in the pH range 5.5-5.0. Regarding mid-infrared spectroscopy, the region located between 1700 and 1500 cm(-1), corresponding to the amide I and II bands, and the 1500-900 cm(-1) region, called the fingerprint region, were considered for the characterization of milk coagulation kinetics. Changes in the absorbance at 1063 cm(-1) as a function of pH for kinetics recorded at 30 °C and 40 °C reflected pH-induced phosphate dissolution in the pH range 5.5-5.0. Compared to rheometry, which reveals microstructure changes only in the gel state, spectroscopic methods make it possible to monitor molecular structure changes in micelles throughout the acidification processes.     

Heat transfer involving the laminar-turbulent transition and the enhanced turbulence of an external flow

Experimental data on heat transfer and friction in the presence of a bypass laminar-turbulent transition in a flow with an increased degree of turbulence Tu_e=3.2–7% are reported. It is shown that several types of bypass transition can occur depending on the turbulence scale: from laminar to turbulent, from pseudolaminar to quasiturbulent, and combination. It is established that the mechanism of the transition is related to the selective properties of the wall boundary layers developed in its presence. A tendency toward the development of an upper thermal transition in turbulized flows is established. Deceased. Institute of Technical Thermophysics, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 6, pp. 958–964, November-December, 1996.     

The mechanism of nonperiodic motion in porous media as a result of the accumulating effect of nonlinear waves

We carried out a theoretical investigation of the nonlinear mechanism of nonperiodic motion in a saturated porous medium under the prolonged action of elastic waves. Within the framework of a generalization of the Frenkel—Biot—Nikolaevskii model, we suggest a technique for constructing a slow (background) solution that takes into account the accumulating effect of fast nonlinear oscillations. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 1, pp. 3–9, January–February 1997.     

Use of high-tensile cast iron packer parts

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 12, pp. 27–28, December, 1990.