Formation of Hollow Solid Microparticles during Interaction of Gas with the Substance Present in Solution Microdroplets Transported by Air Flow

The hollow spherical microparticles are formed on mixing of two air flows of microdroplets of solutions of substances A and B (the substance B is readily transported from solution to gas phase) which react to yield a solid substance C, as found by scanning electron microscopy; air flows are obtained using ultrasonic generators. Outer diameter of the hollow microparticles formed is close to that of the microdroplets of the initial solution. The hollow microparticles of hydrazone are obtained by the interaction of droplets of hydrazide solution and formaldehyde entering into gas phase from microdroplets of its acidic aqueous solution. In addition, the hollow microparticles of iron hydroxycholide were obtained by the reaction of FeCl₃ aqueous solution and ammonia entering into gas phase from the microdroplets of its solution. The hollow microparticles presumably of cobalt hydroxynitrate were obtained by the reaction of microdroplets of Co(NO₃)₂ aqueous solution and ammonia. The outer diameter of the hollow particles obtained is equal to 3–10 m, and wall thickness to 2–2.5 m.     

Numerical modeling of the ascent of a turbulent thermal in an inhomogeneous compressible atmosphere

The ascent of a thermal is investigated on the basis of the compressible medium model. Fairly general dimensionless relations, which make it possible to determine the values of the turbulent transport coefficients for a broad range of initial parameters, are obtained. The effect on the ascent dynamics of the compressibility and the initial height of the thermal above the surface is analyzed.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 72–80, January–February, 1989.The authors are grateful to Yu. A. Gostintsev and Kh. S. Kestenboim for useful discussions.     

BFKL Pomeron in the reaction γ ⊥ * (Q 2)p→ρ ⊥ 0 p at large Q 2 and W

The reaction γ _⊥ ^* (Q ²)p→ρ _⊥ ⁰ p has been studied at large Q ² and W ²/Q ² and low momentum transfers to the nucleon, k _⊥ ² —that is, in the region where the Pomeron exchange mechanism is operative. At sufficiently large Q ², the Pomeron interacts with quarks occurring at small distances, whereby the hard component of the Pomeron is separated, so that the process is governed by the Pomeron of perturbative QCD (BFKL Pomeron). Our calculations indicate that, in vector-meson electroproduction at low k _⊥ ² , the perturbative regime cannot set in fast because, for Q ²≤100 GeV² and, accordingly, for W ²/Q ²≤10⁷, comparatively large distances of $\rho _{q\bar q} > 0.2$ fm are important.     

Study of synthetic hydroxyapatite by the method of high-resolution transmission electron microscopy: Morphology and growth direction

Hydroxyapatite crystals grown from aqueous solutions have been studied by the methods of high-resolution electron microscopy and transmission electron diffraction. Processing of the experimental electron micrographs with the use of the Digital Micrograph program and the study of the corresponding Fourier trans-forms showed that the submicron microcrystals grow mainly along the [0001] direction. The (0001) and the $(01\bar 10)$ planes are perpendicular and parallel to the long edge of the crystals, respectively. The good accord between the experimental electron-microscopy images and the electron microscopy images calculated by the EMS program was attained only for crystals with the thicknesses ranging from one to five lattice periods. This allows us to state that hydroxyapatite grows from aqueous solutions in the form of very thin (with the thickness of the order of several lattice parameters) platelike crystals.     

On the problem of “mysterious” adducts in the Belousov-Zhabotinsky reaction

The formation of an adduct betweeno-phenanthroline and bromine, a feasible intermediate in the Belousov-Zhabotinsky reaction (BZ) catalyzed by ferroin, was studied. The stability constant of the adduct was determined. One of the assumptions on the composition of the “red precipitate,” the substance to which several differences between the behavior of the ferroin and cerium BZ reactions are due, was confirmed.     

On the possibility of obtaining crystalline materials containing extended cylindrical pores

Using the example of studying the behavior of heated crystals of copper sulfate CuSO₄ · 5H₂O that are derived from an aqueous solution and contain three-dimensional inclusions of the mother environment, we show that the heating of these crystals in an inactive medium leads to the discharging of inclusions due to the emersion of their content on the surface. The routes for discharging mother-solution inclusions are determined using optical and electron microscopy and X-ray topography. According to the proposed model, the inclusions are discharged because they expand on being heated and press the crystal matrix. As a result, the solubility of copper sulfate in the mother environment increases, and, along the linear dislocation that passes close to the inclusions and emerges on the crystal surface, a cylindrical pore appears via which the mother solution goes from the bulk of the crystal to its surface. Finally, we obtain a porous material that can reversibly absorb appreciable amounts of an inert fluid (e.g., alcohol) from the ambient environment.     

A nonlinear effect observed during the modification of the structure of polyethylene irradiated by intense soft x-rays

The processes in polymers caused by high-fluence soft x-ray irradiation (on the order of tens of kW/cm²) are considered. Experimental results on the irradiation of polyethylene by soft x-ray radiation at various irradiances are presented. At a fixed fluence, the radiochemical yield of the formation of double bonds is demonstrated to increase with the irradiance. The possible mechanisms of this phenomenon are discussed.