Depth of Gingival Sulcus in Healthy Children with Erupting Permanent Teeth

Introduction: Measuring the gingival sulcus depth in children while their permanent teeth erupt is rather difficult especially if using reference norms for adults for a base. Aim: Assessment of the depth of the gingival sulcus during the period of tooth eruption in healthy children. Materials and methods: Thirty children were included in the study (age range 6 – 14 yrs). The children had good oral hygiene and no history of systemic disease. They were clinically examined – their dental statuses were taken, stages of permanent teeth eruption (up to 1/3 of the clinical crown, between 1/3 and 2/3, over 2/3, in occlusion contact), and their gingival sulcus depth was measured at 6 distovestibular, vestibular, mesiovestibular, mesiolingual, lingual, and distolingual sites using an electronic probe Parometer (Orange). It was concluded that the one with the highest value would be considered the maximum depth of the sulcus. Results: The gingival sulcus depth in fully erupted teeth is very similar to that in healthy adults (2.20 – 0.49 mm). The change of sulcus depth in incisors and canines has a variation of 1.5 mm, which at the end of eruption is close to those in adults. Maximum sulcus depth for molars, premolars and incisors was measured distovestibularly, and for canines – mesiovestibularly. Conclusion: At the various stages of eruption, the depth of the gingival sulcus plausibly decreases in all tooth types, and by the end of eruption it reaches a depth similar to that of the adult standard. Most indicative in regard to depth are the vestibular probing point.

Use of Methods of Electronic Microscopy, Mass-Spectrometry and Roentgenospectral Electronic Probe Micro-Analyzer in Ecological and Analytical Studies. Elemental Composition of Blue Micro-Particles of Unknown Nature Observed in Suspended Substance of Lake Baikal

During the period from April till June, 2018, suspended substance of Baikal Lake water from depths up to 25 meters in various distance from the shore (up to 4,000 m) showed presence of hard particles of blue color in size up to 900 mkm of unknown nature with maximum numbers at the nearshore zone, resistant to mineral acids and combustion. The analysis using methods of electronic microscopy with spray application of conducting golden coating, field desorption with inductively connected plasma (mass-spectroscopy) roentgenospectral electronic probe micro-analyzer, along with investigation of the surfaces of the objects studied and the components distributed in them, showed a set of 68 elements entering the composition of the particles. The major composition is marked for Ti, Ca and Si. Comparatively high composition is found for high-density metals: Zn, Pb, Sb, Nb, Cu, As. Suppositions are made about the anthropogenic nature of the blue particles — in forms of products of agglomerating titanium with fuliginous phase, as well as in composition of sorbents on the basis of compounding of titanium and ship paints.

Heteroepitaxial vertical perovskite hot-electron transistors down to the monolayer limit

Two-dimensional heterostructures combined with vertical geometries are candidates to probe and utilize the physical properties of atomically-thin materials. The vertical configuration enables a unique form of hot-carrier spectroscopy as well as atomic-scale devices. Here, we present the room-temperature evolution of heteroepitaxial perovskite hot-electron transistors using a SrRuO3 base down to the monolayer limit (∼4 Å). As a fundamental electronic probe, we observe an abrupt transition in the hot-electron mean free path as a function of base thickness, coinciding with the thickness-dependent resistive transition. As a path towards devices, we demonstrate the integrated synthesis of perovskite one-dimensional electrical edge contacts using water-soluble and growth-compatible Sr3Al2O6 hard masks. Edge-contacted monolayer-base transistors exhibit on/off ratios reaching ∼108, complete electrostatic screening by the base manifesting pure hot-electron injection, and excellent scaling of the output current density with device dimensions. These results open new avenues for incorporating emergent phenomena at oxide interfaces and in heterostructures.

On the microstructure and structure of the polyimide film surface and condensed substances after long-term exposure on the space station

Complex research of polyimide film microstructure and chemical composition has been conducted by scanning electron microscopy, electronic probe microanalysis and infrared spectroscopy. Changes in layers’ surface and in substances condensed on films were studied after long-term exposure (1218 days) on Mir space station. It is shown that during space exposure microstructure and chemical composition of the first layer suffer changes, but other layers of the package located below don’t reveal similar transformations. New phase formations of different shape and size with film and needle structure varying by its chemical composition have been found on an open surface of the first polyimide film layer. It has been established that the condensed substances consist of silicon, iron, copper, zinc, chlorine, potassium and calcium compounds, which are probably deposited from the outer atmosphere of the orbital station.

Heating and cooling of ligand-coated colloidal nanocrystals in solid films and solvent matrices

Infrared pump, electronic probe (IPEP) spectroscopy is used to study matrix-dependent heat transfer processes of colloidal semiconductor nanocrystals.