Formation and degeneration of scaled capillary notochaetae in Owenia fusiformis Delle Chiaje, 1844 (Oweniidae, Annelida)

Phylotranscriptomic studies of the past decade have repeatedly placed Oweniidae together with Magelonidae, as the sister group to remaining annelids. This newly established placement clearly makes them a key-lineage for understanding annelid evolution and morphology. One of the most prominent morphological features of all annelids are their chaetae. The arrangement and formation process (chaetogenesis) of these chitinous bristles have been studied extensively in hooked chaetae that are arranged in rows. However, the information on other types of chaetae is still scarce. In this study, we investigated the scaled capillary notochaetae of Owenia fusiformis, looking both into the formation process that causes the scaly surface ornamentation and into their arrangement within tight bundles. Our results demonstrate the incredible plasticity of chaetogenesis that allows forming a vast array of three-dimensional structures. The capillary chaetae of Owenia fusiformis are unique in lacking an enamel coating and the scales covering the apical surface of each chaeta are formed by a single microvillus of the chaetoblast. Furthermore, the bundle of chaetae has a peripherally located formative site and a central degenerative site and it appears to result from a secondary curling of the chaetal sac.

THERAPEUTIC METHODS FOR TREATMENT OF DENTAL DISCOLORITIS

The problem of discoloration of teeth, especially accompanied by increased sensitivity, does not lose its relevance in modern dentistry. Despite the presence in the arsenal of dentists of a significant number of means and methods for solving this problem, it does not go away, but, on the contrary, is overgrown with new complaints. In this work, we analyzed the frequency to analyze the frequency of choice of therapeutic methods for treating discoloration of teeth by patients of dental clinics. A questionnaire was developed for a dentist on the patient's choice of a therapeutic method for eliminating dental discoloration and a survey of 30 dentists (10 - therapists, 10 - orthopedists and 10 - general dentists) was conducted for 2019 and 6 months of 2020. It was found that during this period, 184 out of 331 patients who applied to dental clinics with this problem used therapeutic methods for eliminating tooth discoloration: tooth enamel coating with varnish ("Colordent" + adhesive "Single Bond") was carried out in 16.6% of patients, clinical bleaching of enamel in 32.6% of patients with tooth discoloration, intracoronal bleaching followed by direct restoration (replacement of existing fillings with new ones) in 53.8%. The analysis showed that therapeutic methods for eliminating discoloration of teeth predominate slightly, 55%. Of course, in choosing this direction, the doctor is guided by the clinical situation, IROPZ, taking into account the wishes of the patient and his capabilities. However, it seems necessary to develop and test new, gentle and resistant to mechanical stress methods for eliminating discoloration of economy-class teeth with the possibility of solving the problem of increased tooth sensitivity.

Investigation of the Influence of Technological Regimes of High-Temperature Firing on the Structure and Properties of Silicate-Enamel Coatings for Carbon Steels

The silicate-enamel coating becomes the actual coating as a result of firing, which is a process of heating steel products coated with a “biscuit” dried slip layer, until completely melted, and a continuous coating is obtained on a metal substrate. With the constantly increasing requirements for the technical and operational properties of enameled products in the production of steel pipelines, it is advisable to use single-layer enameling, which saves raw materials and energy, due to the reduction in the number of layers and firing cycles of products. Its use for large-sized products, such as pipelines, eliminates their warping that occurs during repeated firing. In addition, the use of single-layer coatings makes it possible to obtain a better surface of products, since with a decrease in the resulting coating thickness it becomes more elastic and impact-resistant. All of the above is predetermined both by the structure of the glass coating itself and the generally formed steel - enamel composition. Therefore, knowledge of the structure, as well as of the physicochemical processes that occur during the firing of the enameled product, is necessary to solve technological issues successfully.

Effects of Biomimetic Press Roller Type, Material, Velocity, and Packing Force on Soil Compaction Characteristics

HighlightsThe performance of biomimetic rollers was better than that of a conventional roller.The biomimetically ridged roller had better soil compaction performance.The resistance order of rollers with different materials was: Fe360A steel > UHMWPE > enamel coating.Packing force was the most significant factor.Abstract. To reduce soil adhesion and rolling resistance during seeding and improve the uniformity of plant spacing, a biomimetically ridged press roller (BRPR) and a biomimetically polyhedral press roller (BPPR) were designed. Moreover, hydrophobic materials, i.e., ultra-high molecular weight polyethylene (UHMWPE) and enamel coating, were applied and compared with uncoated Fe360A steel. Field experiments were conducted to test the effects of the biomimetic press roller type, material, velocity, and packing force on soil compaction characteristics. A conventional press roller (CPR) was used as a reference. Traction resistance (TR), soil bulk density (SBD), soil moisture content (SMC), emergence rate (ER), and percent change of plant spacing (PCPS) were measured. The packing force was the most significant factor affecting each index. For all rollers, the TR, SBD, ER, and PCPS increased with increasing packing force, while the loss of SMC decreased. The TR and SBD decreased with increasing velocity. All rollers achieved proper SBD for corn seeds. The biomimetic press rollers had a significant effect on TR, PCPS, and SMC on the third day after sowing. The BRPR had lower PCPS and TR than the BPPR and higher SMC than the BPPR on the third day after sowing. Compared with the CPR, the PCPS for all biomimetic rollers decreased, and the ER and SMC increased. The BPPR with Fe360A steel had a slightly higher TR than the CPR, but the other biomimetic rollers had a lower TR than the CPR. The BRPR decreased the TR by 2.13% to 22.30%, while the BPPR decreased the TR by 0.35% to 18.59%. Moreover, both types of biomimetic press rollers had the highest TR values when using Fe360A steel, followed by UHMWPE, and the enamel coating had the lowest TR values. The BRPR decreased the PCPS by 19.46% to 48.34%, while the BPPR decreased the PCPS by 9.69% to 36.99%. The biomimetic rollers increased the ER by 2.17% to 11.36%. On the 18th day after sowing, the SMC was 4.21% to 7.75% higher for the biomimetic press rollers compared to the CPR when the packing force was 700 N. This study can provide a reference for the biomimetic design, material, and force selection of press rollers. Keywords: Biomimetics, Compaction characteristics, Enamel coating, Press roller, UHMWPE.

Protective and decorative properties of titanium glass enamels

It is known that enamel coatings with enhanced protective and decorative properties can be fabricated on the basis of boron-silicate glass frits with an increased content of TiO2 in their composition. Opacity and white color of enamel coatings are due to their crystallization at firing temperatures. Titanium glass enamels are not pure white visually, and show yellow and blue shades depending on their chemical composition. The purpose of this work was to establish the influence of basic components on the water resistance and color characteristics of titanium enamel coatings. Our experimental study was focused on the glass frits with the chemical composition described by the generalized formula (76–n–m)SiO2nB2O3mNa2O24MexOy, where MexOy is the total content of TiO2, ZrO2, Al2O3, MgO, СaO, P2O5, and K2O. It was found that the glass frits with the following content of basic components (mol.%): Na2O 12–13, K2O 3, B2O3 10–11, SiO2 49–51 demonstrated the highest water-resistant properties. The color characteristics of titanium enamel coatings prepared on the basis of the mentioned glass frits differ significantly from the reference white light A; the titanium enamel coatings under consideration have a yellow-green tint. The highest deviations of the enamel coating color purity and color tone from a standard of white color were observed when increasing the Na2O content in the glass frits composition at the expense of SiO2. The color of titanium coatings with the highest water resistance has a deviation from the standard of white color within 4–6%.