Obtaining of Biologically Soluble Membranes Based on Polymeric Nanofibres and Hydroxyapatite of Calcium

In this paper, the possibility of obtaining a synthetic hydroxyapatite of calcium from a biological waste material is shown. The characteristics influencing the synthesis process are studied. Based on the results of the X-ray analysis and the obtained electron microscope images, it can be concluded that the synthesized HAP has a Ca/P ratio of 1.5 and with crystals with an average size of 2 microns. In work, experiments on obtaining biologically soluble films based on nanoscale polymer fibers and calcium hydroxyapatite were carried out. As a result, the main parameters of the process for the electroforming of nano-sized fibers with HAP are determined. The proposed method allows the laying of strictly directed nanofibers from a polymer with a diameter of 50 to 500 nm. The use of different types of electrodes makes it possible to vary the size of nanofibers. The characteristics such as solution viscosity, high voltage and optimum parameters were selected, which allowed obtaining films from biologically soluble polymer nanofibers and HAP. Also, experiments were conducted to introduce medicines into the film structure

Aerogels Based on Graphene Oxide with Addition of Carbon Nanotubes: Synthesis and Properties

Nowadays numerous sorbents based on graphene and other carbon nanomaterials have been synthesized for the removal or collecting of oil remains due to its unique physico-chemical properties. Obtaining of aerogels based on graphene oxide and carbon nanotubes with addition of chitosan solution as a binder component is shown in this paper. Aerogels were synthesized by reduction of aqueous dispersion of graphene oxide using the reducing agents, followed by ultrasonic and thermal treatment. Ultrasound destroys the graphene layers, decreasing them in size, thereby exposing new layers to form edges that already have no stabilizing carboxyl groups, which are located at the edges, and participate in the formation of bonds. The surface morphology of obtained aerogels was studied by SEM. The study of the sorption capacity showed that graphene/CNTs aerogel is characterized by short absorption time and high sorption ability that depend on densities of the used solvents. All experimental results show the possibility of using the aerogels based on graphene and CNTs as sorbents for collection of oil residues

Study of Operating Characteristics of Pyrotechnic Reserve Power Source Based on Magnesium and Zinс

This paper presents the results of studies of operating parameters of pyrotechnic reserve power source (PRPS). This battery was activated by the pyrotechnic compositions contained in the electrodes. Once the ignition impulse worked, the pyrotechnic compositions took fire immediately and melted the electrolyte. Then the rest pyrotechnic compositions served as anode and cathode. The battery began to discharge. The following characteristics of PRPS were evaluated during the study: release time to operating regime of the electric current, the duration of the PRPS work and initiation temperature of PRPS. A detailed evaluation of the Mg/LiF/PbF2 electrochemical system and Zn/LiF/PbF2 one is undertaken. Test results show that the electric current value using powder of zinc and granular zinc in these experiments was 0.179 A and 0.1 A, respectively, and the operating time at these values of elecrtic current was 40 and 151 sec, respectively

Ionospheric convection response to slow, strong variations in a northward interplanetary magnetic field: A case study for January 14, 1988

We analyze ionospheric convection patterns over the polar regions during the passage of an interplanetary magnetic cloud on January 14, 1988, when the interplanetary magnetic field (IMF) rotated slowly in direction and had a large amplitude. Using the assimilative mapping of ionospheric electrodynamics (AMIE) procedure, we combine simultaneous observations of ionospheric drifts and magnetic perturbations from many different instruments into consistent patterns of high-latitude electrodynamics, focusing on the period of northward IMF. By combining satellite data with ground-based observations, we have generated one of the most comprehensive data sets yet assembled and used it to produce convection maps for both hemispheres. We present evidence that a lobe convection cell was embedded within normal merging convection during a period when the IMF By and Bz components were large and positive. As the IMF became predominantly northward, a strong reversed convection pattern (afternoon-to-morning potential drop of around 100 kV) appeared in the southern (summer) polar cap, while convection in the northern (winter) hemisphere became weak and disordered with a dawn-to-dusk potential drop of the order of 30 kV. These patterns persisted for about 3 hours, until the IMF rotated significantly toward the west. We interpret this behavior in terms of a recently proposed merging model for northward IMF under solstice conditions, for which lobe field lines from the hemisphere tilted toward the Sun (summer hemisphere) drape over the dayside magnetosphere, producing reverse convection in the summer hemisphere and impeding direct contact between the solar wind and field lines connected to the winter polar cap. The positive IMF Bx component present at this time could have contributed to the observed hemispheric asymmetry. Reverse convection in the summer hemisphere broke down rapidly after the ratio |By/Bz| exceeded unity, while convection in the winter hemisphere strengthened. A dominant dawn-to-dusk potential drop was established in both hemispheres when the magnitude of By exceeded that of Bz, with potential drops of the order of 100 kV, even while Bz remained northward. The later transition to southward Bz produced a gradual intensification of the convection, but a greater qualitative change occurred at the transition through |By/Bz| = 1 than at the transition through Bz = 0. The various convection patterns we derive under northward IMF conditions illustrate all possibilities previously discussed in the literature: nearly single-cell and multicell, distorted and symmetric, ordered and unordered, and sunward and antisunward

Riqualificazione e hinterland delle grandi citt\ue0

Il libro costruisce i contributi degli autori sul rapporto tra la riqualificazione e l'hinterland della citt\ue0, che \ue8 attivato per il modificarsi della citt\ue0. Tale mutamento implica la modifica della citt\ue0 verso l'esterno (hinterland) e erso l'interno (riqualificazione). Sono trattate grandi citt\ue0 e citt\ue0 nuove, e al tempo stesso vengono considerate realt\ue0 urbane di molteplici parti del mond