Potassium polytitanate gas-sensor study by impedance spectroscopy.

Nanocrystalline potassium polytitanates K2O·nTiO2·mH2O represent a new type of semiconducting compounds which are characterized by a high specific surface that makes them promising for use in gas sensors. In this work, we have studied potassium polytitanate mesoporous nanoparticle agglomerates placed over a SiO2/Si substrate equipped with multiple coplanar electrodes to measure the electrical response to various organic vapors, 1000 ppm of concentration, mixed with air by impedance spectrometry in range of the 10(-2)-10(6) Hz. The recorded impedance data for each sensor segment are associated with RC components of an equivalent circuit which are applied to selectively recognize the test vapors exploiting a "multisensor array" approach.

Tungsten oxo salicylate complexes from tungsten hexachloride reactions systems.

Tungsten hexachloride is a potent halogen-transfer agent, capable of reacting directly with salicylic acid to generate a tungsten oxo fragment and salicoyl chloride. As a result, oxo complexes dominate the chemistry of tungsten(VI) salicylates. Both mono- and disalicylate substituted tungsten oxo complexes are accessible. The Brønsted free acid W(=O)Cl(Hsal)(sal) complex is a sparingly soluble, presumably polymeric material that can be dissolved in THF. The THF adduct has been characterized by NMR spectroscopy, although an X-ray crystallographic study indicates that the product cocrystallizes with a structurally analogous d(1) WCl(2)(Hsal.THF)(sal) byproduct. The remaining chloride ligand in W(=O)Cl(Hsal)(sal) is replaced by a bridging oxo unit when the reaction contains a significant excess of salicylic acid. The product "linear" oxo bridged ditungsten complex, [W(=O)(Hsal)(sal)](2)O, forms intramolecular hydrogen bonds, accounting for its high solubility in noncoordinating solvents. An X-ray study shows that the intramolecular Hsal.sal hydrogen bonding in this complex accommodates a more linear W-O-W arrangement than does a previously observed class of isostructural diolate derivatives. Tungsten oxo tetrachloride, formed in the initial reaction between salicylic acid and WCl(6), also reacts with the salicoyl chloride byproduct to generate tungsten salicoylate (OAr-2-COCl) complexes.

[Mechanisms of incidence and specifics of spondylolysis and spondylolisthesis course in vertebral osteochondropathy]. / Mekhanizmy vynyknennia ta osoblyvosti perebihu spondylolizu ta spondylolistezu pry osteokhondropatiï khrebta.

There were studied up the morphofunctional changes of vertebral motor segments in 21 patients with vertebral osteochondropathy as well as with initial spondylolysis and spondylolisthesis. The patients were from 12 to 21 years old, the average follow-up was 4.5 years. In vertebral deformity in sagittal plane the spondylolystic spondylolisthesis was not revealed in patients, and in particular the leading clinical sign presented was the syndrome of spondyloarthrosis on the level of compensational hyperlordosis; in vertebral osteochondropathy with preserved or the smoothed physiologic vertebral curvatures--dysplastic spondylolisthesis with early occurrence of hyperplastic spondyloarthrosis as a consequence of the Schmorl's hernia in middle lumbar vertebral segments and of instability of the lower lumbar segments due to vertebral sliding shift with subsequent occurrence of hyperplastic spondyloarthrosis predominantly on these levels. The presence of hyperplastic spondyloarthrosis in lower lumbar vertebral segments while overextension causes the risk rise of the vertebral canal stenosis occurrence.

X-ray attenuation coefficients of high-atomic-number, hexanuclear transition metal cluster compounds: a new paradigm for radiographic contrast agents.

RATIONALE AND OBJECTIVES: The purpose of this study was to examine the radiologic attenuation properties of the parent cluster compounds, particularly attenuation as a function of discrete photon energy, before investigating ligand substitutions, which are necessary to improve cluster biocompatibility and to impart desirable physicochemical properties. MATERIALS AND METHODS: The linear attenuation coefficients for solutions of the cluster compounds Ta6Br14, K8Ta6O19, and (H3O)2W6Cl14 were determined at 60, 80, 103, 122, and 140 keV from gamma-ray transmission measurements with americium-241, xenon-133, gadolinium-153, cobalt-57, and technetium-99m radioactive sources. Transmission measurements were obtained for a fixed time interval that ensured a statistically accurate count distribution exceeding 20,000 counts through the sample for each trial. RESULTS: On a strictly mole per liter basis, a 0.075 mol/L aqueous solution of K8Ta6O19 showed 1.08 times the attenuation of 0.063 mol/L aqueous iohexol at 60 keV and 3.30 times the attenuation at 80 keV. Similarly, a 0.05 mol/L methanolic solution of (H3O)2W6Cl4 showed 0.96 times (96%) the attenuation of 0.063 mol/L aqueous iohexol at 60 keV but 3.09 times the attenuation of the iohexol solution at 80 keV. Attenuations of 0.063 mol/L aqueous iohexol and 0.0125 mol/L Ta6Br14 (ie, at approximately one-fifth the iohexol concentration) were comparable at greater than 60 keV. CONCLUSION: These results confirm the theoretic potential for use of early transition metal cluster compounds as radiographic contrast agents. At higher x-ray energies, cluster compounds demonstrate multiplied x-ray attenuation relative to iodinated contrast agents.

[Condition of morbidity and prevention of acute intestinal infections in the USSR]. / Sostoianie zabolevaemosti i profilaktiki ostrykh kishechnykh infektsii v strane.

The article presents original materials characterizing morbidity in acute enteric infections, such as typhoid fever and other Salmonella infections, dysentery, in the USSR. Morbidity registered in recent years is shown to be the consequence of the unsatisfactory solution of problems connected with supplying the population with epidemiologically safe water and foodstuffs. The decisive role played by sanitary and hygienic measures in the prevention and control of acute enteric infections is emphasized.