Synchrotron single-crystal XRD, IR-, Raman spectroscopy and high pressure study of synthetic krieselite.

Spontaneous crystals of krieselite (Ge analogue of topaz) with the chemical formula Al2[(Ge0.75Si0.25)O4](F1.63OH0.37) were synthesized using a thermo-gradient hydrothermal method at a temperature of 600/650 °C and pressure of 100 MPa. The unit cell parameters are: a = 8.9732(8) Å, b = 8.4823(7) Å, c = 4.7379(5) Å, V = 360.62(6) Å3, space group Pnma. The F-/OH- content of the samples was refined by FTIR spectroscopy method. Raman spectroscopy showed the main differences between the spectra of krieselite and topaz at the ambient conditions. The assignment of observed and calculated Ag bands (cm-1) for non-polarized Raman spectra was carried out. Using in situ Raman spectroscopy at high pressures, the dependence of the shift in the position of the main bands of the krieselite Raman spectrum on the pressure was established, and the corresponding paths of pressure induced distortion of crystal structure was assumed. According to the data of Raman spectroscopy, it was revealed that krieselite does not undergo the phase transitions up to 30 GPa. The probable way of crystal structure distortion within the space group Pnma was proposed based on simulation of high-pressure Raman spectra.

Na(2/7)Gd(4/7)MoO4: a modulated scheelite-type structure and conductivity properties.

Scheelite-type compounds with the general formula (A1,A2)(n)[(B1,B2)O(4)](m) (2/3 ≤ n/m ≤ 3/2) are the subject of large interest owing to their stability, relatively simple preparation, and optical properties. The creation of cation vacancies (□) in the scheelite-type framework and the ordering of A cations and vacancies can be a new factor in controlling the scheelite-type structure and properties. For a long time, cation-deficient Nd(3+):M(2/7)Gd(4/7)□(1/7)MoO(4) (M = Li, Na) compounds were considered as potential lasers with diode pumping. They have a defect scheelite-type 3D structure (space group I4(1)/a) with a random distribution of Li(+)(Na(+)), Gd(3+), and vacancies in the crystal. A Na(2/7)Gd(4/7)MoO(4) single crystal with scheelite-type structure has been grown by the Czochralski method. Transmission electron microscopy revealed that Na(2/7)Gd(4/7)MoO(4) has a (3 + 2)D incommensurately modulated structure. The (3 + 2)D incommensurately modulated scheelite-type cation-deficient structure of Na(2/7)Gd(4/7)MoO(4) [super space group I4 (α-ß0,ßα0)00] has been solved from single-crystal diffraction data. The solution of the (3 + 2)D incommensurately modulated structure revealed the partially disordered distribution of vacancies and Na and Gd cations. High-temperature conductivity measurements performed along the [100] and [001] orientation of the single crystal revealed that the conductivity of Na(2/7)Gd(4/7)MoO(4) at T = 973 K equals σ = 1.13 × 10(-5) Ω(-1) cm(-1).

Synthetic brunogeierite Fe2GeO4: XRD, Mössbauer and Raman high-pressure study.

We present complex spectroscopic data of the synthetic brunogeierite (Fe2+)2Ge4+O4 with space group Fd3¯m of spinel structure: a = 8.3783 (6) Å, V = 588.12 (13) Å3. Brunogeierite crystals up to 200 µm in size were crystallized by the interaction of a boric acid solution on a metal iron wire in the presence of germanium oxide (GeO2) at 600/650 °C and 100 MPa. Mössbauer spectrum of synthetic brunogeierite consists of the symmetric doublet with the parameters IS = 1.104(1) mm/s and QS = 2.845(1) mm/s, that corresponds to the octahedral position of iron ions ([VI]Fe2+). The Raman spectra of Fe2GeO4 crystal consist of an intense main band at 756 cm-1 and four less intense bands at ∼644, 472, 302, and ∼205 cm-1 at ambient conditions. All five bands inherent in the spectrum of cubic spinel are present and gradual change in high pressure spectra up to 30 GPa. The color of the crystal changes from brown-orange to reddish at the center at 22.7 GPa and became opaque black up to 30.2 GPa. Herewith, in the high pressure spectra, we observed the splitting of some bands and the appearance of additional bands in a wide pressure range (from 1.6 to 30 GPa). The factor group analysis with the lattice dynamics calculation of potential crystal structure distortions shows the decreasing of the structure symmetry to tetragonal or rhombohedral in this pressure range.

SiC/C nanocomposites with inverse opal structure.

The synthesis, morphology, structural and optical characteristics of SiC/C nanocomposites with an inverse opal lattice have been investigated. The samples were prepared by thermochemical treatment of opal matrices filled with carbon compounds which was followed by silicon dioxide dissolution. The samples were studied by electron microscopy, x-ray diffraction, photoluminescence, IR and Raman scattering spectroscopy. The electron microscopy data revealed a highly porous periodic structure which was a three-dimensional replica of the voids of the initial opal lattice. The hexagonal silicon carbide was found to be non-uniformly distributed throughout the volume, its greater part located in the surface layer up to 50 µm deep. The data of x-ray diffraction, IR and Raman scattering spectroscopy enabled us to assume that the composite had hexagonal diamond fragments. The photoluminescence and optical reflection spectra of the composites have been measured.

Heat capacity and thermal expansion of the itinerant helimagnet MnSi.

The heat capacity and thermal expansion of a high quality single crystal of MnSi were measured at ambient pressure at zero and high magnetic fields. The calculated magnetic entropy change in the temperature range 0-30 K is less than 0.1R, a low value that emphasizes the itinerant nature of magnetism in MnSi. A linear temperature term dominates the thermal expansion coefficient in the range 30-150 K, which correlates with an enhancement of the linear electronic term in the heat capacity. A surprising similarity among the variations of the heat capacity, thermal expansion coefficient and temperature derivative of the resistivity is observed through the phase transition in MnSi. Specific forms of the heat capacity, thermal expansion coefficient and temperature derivative of resistivity at the phase transition to a helical magnetic state near 29 K are interpreted as the combination of sharp first-order features and broad peaks or shallow valleys of as yet unknown origin. The appearance of these broad satellites probably hints at a frustrated magnetic state slightly above the transition temperature in MnSi.

[Prevalence of chronic family tonsillitis and its prevention].

To evaluate prevalence, main causes and social factors of chronic tonsillitis (CT), we examined 321 families 335 children (age 1-15 years) from which had diagnosis of CT. The examination detected CT in the other 114 children from these families. Families of 120 healthy children matched for age served control. Family tonsillitis was detected in 171 (53.3%) families of the study group and 15 (17.5%) families of the control group (p < 0.05). Of 307 mothers of reproductive age, 84 (26.3%) were diagnosed to have CT, 36 (11.2%) of them had a history of tonsillectomy. Our data suggest the existence of family CT. To prevent it, early preventive measures should be taken.

[Outcomes of heterobrephomastoidoplasty in surgical treatment of chronic otitis media purulent in children]. / Rezul'taty primenenia geterobrefomastoidoplastiki pri khirurgicheskom lechenii khronicheskogo gnoinogo srednego otita u detei.

Otitis media purulenta chronica (OMPC) in children affects frequently the mastoid process necessitating plastic repair of the mastoid cavity. Taking this in consideration, in the surgery of 66 children with OMPC the authors used implants of demineralized lamb bone tissue. The graft retention occurred in 93.9% of cases.

[Endonasal surgery of posttraumatic dacryocystitis in children]. / Endonazal'naia khirurgiia posttravmaticheskikh dakriotsistitov v detskom vozraste.

Posttraumatic dacryocystitis in children are associated with different anatomic defects of the external nose, nasal cavity, eyelids and adjacent tissues. These injuries may complicate conventional endonasal dacryocystorhynostomy. The first step in the treatment of posttraumatic dacryocystitis should be surgical correction of nasal breathing. It is also necessary to apply bone window at least 1.2 cm in diameter followed by formation of the stoma using intubation tube.

[Timed retrograde catheterization of the nasolacrimal duct as a method of treatment in congenital dacryocystitis and acquired stenosis of the nasolacrimal duct in children]. / Vremennaia retrogradnaia kateterizatsiia nososleznogo protoka kak sposob lecheniia vrozhdennykh dakriatsistitov i priobretennykh stenozov nososleznogo protoka u detei.

The authors propose a procedure of timed catheterization of the nasolacrimal duct for use in children with the duct stenosis and congenital dacryocystitis. The catheter is inserted for 7-10 days. Out of 27 children treated (20 cases of congenital dacryocystitis and 7 cases of the stenosis), a persistent effect was achieved in 24. The authors advocate the method as effective and promising in the above conditions.

[Intranasal dacryocystorhinostomy in children]. / Endonazal'naia dakriotsistorinostomiia u detei.

Endonasal dacryocystorhinostomy performed in 78 children gave a steady favourable effect. Such a surgical operation is also recommended in dacryocysts complicated by phlegmons. Concomitant external fistulae of the lacrimal sac usually spontaneously closed after the operation, large fistulas were sutured.

[Characteristics of clinico-biochemical indicators in obese children with chronic tonsillitis]. / Osobennosti kliniko-biokhimicheskikh pokazatelei pri khronicheskom tonzillite u detei s ozhireniem.

Chronic tonsillitis (CT) was found in 63.1% of 190 obese children aged 3-15 years, 15% of them had no quinsy in the past. Onset of obesity was attributed to frequent quinsy in 18.3% of the examinees. Marked CT exacerbations were more typical for the children aged 6-7 years (10%). In 12-15-year-olds the disease tended to a sluggish course with scarce symptoms (25.8%). Pharyngoscopy discovered edema and hypertrophy of the tonsils in 74.1% of the patients. 35 patients underwent tonsillectomy. Examination of the removed tonsil tissue for phospholipids revealed pathological phospholipids lysophosphatidylcholine and phosphatidylinosite the quantities of which rose with growing obesity. It may be the result of negative action of obesity on tonsil structure.

[Results of endonasal intubation of the nasolacrimal duct in children with congenital dacryocystitis]. / Rezul'taty éndonazal'nogo zondirovaniia slezno-nosovogo kanala u detei s vrozhdennymi dakriotsistitami.

Results of endonasal catheterization of the naso-lacrimal canal of 74 children with congenital dacryocystitis (bilateral problem in 10 of them) are presented. Prior to this manipulation, the patients were exposed to contrast X-ray study of the lacrimal sac for diagnostic purposes. Retrograde catheterization as a method for treating congenital dacryocystitis was very good in 97.3% children of up to 2 years old, 50% children of up to 3 years old, and 33.3% children between 3-4 years old. The patency of the naso-lacrimal canal also recovered in an 8-year-old child. All this gives evidence that, irrespective of children's age, retrograde catheterization should be applied to treat congenital dacryocystitis. After the patency of the naso-lacrimal canal was restored, the external fistula of the lacrimal sac was cauterized with 7% solution of trichloroacetic acid.