Avaliação da Diminuição da Força de Ativação de Elásticos Correntes de Diferentes Cores: Estudo in Vitro

O objetivo deste estudo consistiu em comparar a degradação de força de cinco cores diferentes de elásticos corrente, a fim de buscar parâmetros clínicos para o uso desses elásticos nas terapias ortodônticas. Foram avaliados 10 segmentos com 6 elos de elásticos corrente de força média da marca Morelli, das cores preto, cinza, azul, rosa e transparente, provenientes de embalagens seladas e dentro do prazo de validade. Os elásticos foram distendidos até o dobro de seu comprimento e mantidos por dispositivos simples com duas pontas de metal, simulando o uso contínuo dos elásticos por parte dos pacientes. Esses dispositivos foram submersos em saliva artificial a 370C dentro de recipientes mantidos em estufa. As forças dos segmentos de elásticos foram mensuradas com um dinamômetro ortodôntico de precisão ao início e nos intervalos de 1, 7,14, 21 e 30 dias após a imersão, e a média de força para cada grupo e tempo foi calculada. A Análise de variância (ANOVA) a dois critérios (tempo e grupos) e o teste de Tukey foram utilizados para a análise dos dados. Em todos os testes estatísticos foi adotado um nível de significância de 5%. Todas as cores de elásticos degradaram com o tempo, sendo a porcentagem média de degradação após 1 dia de 40,4%; 7 dias 48,2%; 14 dias 56,8%; 21 dias 65% e 81% após 30 dias. Entretanto, há diferença de degradação de força entre as cores dos elásticos. Os elásticos Transparente e Azul apresentaram menor degradação da força, sendo que após 30 dias o elástico Transparente se mostrou mais efetivo, seguido do Azul, Cinza, Preto e Rosa. Mesmo com a diferença na degradação de força entre as cores dos elásticos, esses dados não apresentam relevância clínica se utilizados por até 14 dias, após esse período seria melhor a utilização do elástico Transparente. Palavras-chave: Ortodontia. Látex. Elasticidade Abstract The aim of this study was to compare the force degradation of five different colors of elastomeric chains, in order to achieve clinical parameters for the use of these elastics in orthodontic therapies. The sample was composed by 10 segments with 6 links (medium force) for each color of elastomeric chain (Morelli); black, gray, blue, pink and transparent, from sealed packages and within the expiration date. The elastics were stretched twice their length and maintained by simple devices with two metal tips, simulating the continuous use of the elastics by the patients. These devices were submerged in artificial saliva at 370C to simulate the oral environment. The elastic segments strengths were measured with a precision orthodontic dynamometer at the beginning and at intervals of 1, 7, 14, 21 and 30 days after immersion, and the mean strength for each group and time was calculated. Analysis of variance (ANOVA) with two criteria (time and groups) and the Tukey test were used for data analysis. In all statistical tests, a significance level of 5% was adopted. All the elastics colors degraded over time, with the average degradation percentage after 1 day being 40.4%; 7 days 48.2%; 14 days 56.8%; 21 days 65% and 81% after 30 days. However, there is a difference in force degradation among the elastics colors. The Transparent and Blue elastics showed less force degradation, and after 30 days the Transparent elastic was more effective, followed by Blue, Gray, Black and Pink. Even with the difference in force degradation among the elastics colors, these data are not clinically relevant they are used for up to 14 days, after that period it would be better to use the Transparent elastic. Keywords: Orthodontics. Latex. Elasticity

Fractal signatures of SARS-CoV2 coronavirus, the indicator matrix, the fractal dimension and the 2D directional wavelet transform: A comparative study with SARS-CoV, MERS-CoV and SARS-like coronavirus

SummaryThe main goal of this paper is to show the 2D fractal signatures of SARS-CoV2 coronavirus, indicator matrixes maps showing the concentration of nucleotide acids are built form the RNA sequences, and then the fractal dimension and 2D Directional Wavelet Transform (DCWT) are calculated. Analysis of 21 RNA sequences downloaded from NCBI database shows that indicator matrixes and 2D DCWT exhibit the same patterns with different positions, while the fractal dimensions are oscillating around 1.60. A comparison with SARS-CoV, MERS-CoV and SARS-like Coronavirus shows slightly different fractal dimensions, however the indicator matrix and 2D DCWT exhibit the same patterns for the couple (SARS-CoV2, SARS-CoV) and (MERS-CoV, SARS-like) Coronavirus. Obtained results show that SARS-CoV2 is probably a result of SARS-CoV mutation process.

THE COMPLEX APPROACH TO THE MODERNIZATION OF BOILERS, HEAT NETWORKS AND CONNECTED BUILDINGS

The mathematical model that allows for a comparative analysis of the technical and economic characteristics of the three scenarios of the thermal modernization district heating system: the replacement of boilers, heat networks and pumps, the replacement of these elements in combination with thermal modernization of buildings, as well as a scenario that includes the implementation of all previous measures and the installation of Individual Heat Points in buildings (complex modernization). The advantages of the complex modernization on the horizon of planning for 50 years have been shown. Calculated analysis of the influence of various factors on the preference for this scenario has been carried out. The developed model can be used for the preparation of feasibility studies of projects energy efficient modernization of district heating systems and buildings. Bibl. 5, Fig. 8, Tab. 2.

CALCULATED ANALYSIS OF SEISMIC SECURITY OF HOISTING CRANES

The choice of methods of the theory of seismic resistance in relation to the assessment of seismic safety of hoisting cranes operated in buildings and structures depends on the availability and the type of a seismic model. In the presence of a seismic input in the form of seismic coefficients of dynamism or their modified variants in the form of seismic response spectra, there is used a linear-spectral method, to be exact, its "flat" version, according to BD 14.13330.2014 "Building in seismic zones" and DS-031-01 "Design standard of earthquake resistant atomic power stations". Dynamic analysis of the theory of seismic resistance of structures is an extension of a linear-spectral method. It simplifies finite-element modelling of real structures, but uses methods of numerical integration of big systems of second-order seismic differential equations.

Digital simulation of physical processes in vehicles engine power units

This article studies the issues of digital simulation of physical operating processes in vehicles transmission. Simulation of dynamic processes is carried out in power transmissions at the design stage. The procedure for using the digital packages such as MATLab – Simulink and Simscape was considered for the numerical simulation of dynamic processes in mechanical systems based on the example of the theoretical calculation of K-744 tractor transmission dynamics. A digital model of K-744 tractor transmission is constructed, its calculation scheme is given, the initial characteristics are determined. A digital model of the tractor engine was created by means of the Simulink package. A nature of change in tractor engine torqueis determined by it. The calculated analysis of normal transmission frequencies is performed. Forced torsional vibrations are calculated in the tractor change gearbox generated by the vehicle engine operation. The conditions of resonance in the transmission are analyzed. The unfavorable modes of joint operation of the engine and the gearbox are determined for K-744 tractor.

Heavy Metals in Soils Affected by Coal Enterprises and Their Impact on Human Health

Concentrations of heavy metals in Southern Kuzbass urban soils affected by coal mining industry and sity boilers were studied. The risks of toxic effects of elements found in soils as a result of geochemical sampling (200 samples) were identified. The hazard ratio during the intake of elements - toxins into the human body orally and via inhalation was calculated. Analysis of uncertainty in the estimation of the average daily doses was carried out. The obtained risk parameters fall into the category of permissible or acceptable. The primary contribution to the total hazard ratio is made by the manganese, cobalt, copper, and arsenic. These elements show special features of the soil in the affected area of coal mining, urban boilers everywhere and the activity of repair — metallurgical and foundry businesses locally. No pronounced differentiation of the city areas according to the value of the hazard ratio was discovered.