ANTHROPOMETRIC CHARACTERISTICS AND MOTOR ABILITIES IN 13-15 YEARS OLD FEMALE VOLLEYBALL PLAYERS

The goal of this research was to determine whether there is a difference in themanifestation of measured anthropometric characteristics and tested motor abilities offemale volleyball players that are 13-15 years old. The sample of participants consists of 62female volleyball players divided into three groups according to their age. The sample ofvariables has two sub-samples: 18 variables belonging to anthropometric space and 14variables belonging to the space of motor skills. A variance analysis has indicatedsignificant intragroup differences in all the analyzed variables, except the variable forassessment of flexibility in the shoulder angle region. The results of a post hoc test - theBoniferroni procedure - have determined that the level of differences between the groups, inrelation to the examined variables, ranges from those that have statistical significance ofp<0,05, for variables of anthropometric space (Body weight, arm span, Body mass index,the Single arm reach test, Both arm reach test, Upper arm and forearm volume) and thesame value for the motor skills space (Hip joint flexibility, Squat jump with arm swing,Counter-movement jump with, and without the arm swing), to those that reach p<0,00 forvariables of the anthropometric space (Sitting height, Body mass, Chest Volume , Waistvolume, Hips, Upper leg, and Lower leg volume) and for variables of the space of motorskills (the Long jump, Medicine ball throw, “Sit and reach” test, the 5,15 and 20 meter run,T-test, Squat jump without arm swing and Squat jump with arms in the block position).Because the applied instruments validate the assumption that these instruments can be usedto isolate dimensions in experimental sample, and because these dimensions are significantfor success in a motor activity such as volleyball, the results of this research will have broadapplication, and thus are of both theoretical and practical importanc

Analysis of cardiac manifestation and treatment of multisystem inflammatory syndrome in children related to SARS-CoV-2

Cardiovascular manifestations are common (35–100%) in the multisystem inflammatory syndrome in children. Our study aimed to analyze treatment impact and cardiovascular involvement in patients with multisystem inflammatory syndrome in children. The retrospective cohort included 81 patients treated between April 2020 and December 2021 (9.3±4.6 years). Elevated cardiac troponin I and pro-B-type natriuretic peptide were observed in 34.2% and 88.5% of patients, respectively. Myocardial dysfunction was observed in 50.6%. Children older than 10 years had a 4-fold increased risk of myocardial dysfunction (odds ratio [OR] 3.6, 95% confidence interval [CI] 1.4-8.9; p=0.006). A moderate negative correlation was proved between left ventricle ejection fraction and C-reactive protein (rr = - 0.48; p < 0.001). More than one-fifth of the patients presented with shock. Coronary artery dilatation was observed in 6.2% of patients. Mild pericardial effusion was detected in 27.1% of children. On standard electrocardiogram, 52.6% of children had negative T waves in the inferior and/or precordial leads; transient QTc prolongation was registered in 43% of patients. Treatment failure was observed in 19 patients. Patients initially treated with intravenous immunoglobulins had 10-fold higher chances for treatment failure than patients treated with corticosteroids (OR 10.6, 95% CI 3,18 – 35.35; p < 0.001). Cardiovascular manifestations were observed in more than half of the patients, with acute myocardial dysfunction being the most common, especially in children older than 10 years. We established a negative association between the degree of elevation of inflammatory markers and left ventricular ejection fraction. Patients treated with intravenous immunoglobulins who had cardiovascular manifestations had treatment failures more frequently than patients treated with corticosteroids

Mechanistic investigation of hydrogen evolution reaction from multiple proton donors: The case of mildly acidic solutions containing weak acids

© The Author(s) 2019. The present study provides a theoretical framework for mechanistic investigation of the hydrogen evolution reaction (HER) in acidic solutions containing a secondary proton donor in the form of a weak acid. The mechanistic, thermodynamic, and kinetic implications associated with the presence of a weak acid are discussed. The presence of a weak acid was shown to be able to significantly influence the polarization behavior of the HER from H+ through its corresponding chemical dissociation reaction. This effect could lead to an increased limiting current, increased apparent Tafel slope, or even appearance of a secondary limiting current. The theoretical discussions were then applied to the case study of the HER in mildly acidic solutions containing acetic acid, on gold surface. The polarization data showed two Tafel slopes of 65mV at lower current densities and 120mV at higher current densities. A mechanistic mathematical model based on the initial theoretical discussions was developed and used to analyze and quantify the polarization behavior of this system. It was shown that, while in low Tafel slope range the presence of acetic acid has no effect on the HER, at 120 mV Tafel slope range the HER from acetic acid is significant, and it is occurring through a Heyrovsky type electro-desorption reaction

A Practical Mechanistic Model for MIC Based on a Biocatalytic Cathodic Sulfate Reduction Theory,” CORROSION/2009, Paper No. 09390

ABSTRACT Microbiologically induced corrosion (MIC) due to sulfate-reducing bacteria (SRB) is a major problem facing the oil and gas industry as well as other industries such as water utility. Current risk-factor probability models are useful in predicting the likelihood of MIC. However the reliable prediction of the progression of MIC pitting must depend on mechanistic modeling. This paper presents a mechanistic model for the prediction of MIC pitting progression based on a biocatalytic cathodic sulfate reduction (BCSR) theory. The hydrogenase system in the sessile SRB cells at the interface of biofilm and metal surface is treated as a bio-electrocatalyst for sulfate reduction. The model considers both charge transfer resistance and mass transfer resistance. It can be calibrated using an experimentally measured electrochemical parameter recast as &quot;biofilm aggressiveness&quot; for a particular SRB biofilm. Other charge transfer and mass transfer parameters are used as available in the literature or from existing experimental correlations. Computer simulation indicates that charge transfer resistance is important initially when the biofilm thickness is small. However, mass transfer resistance becomes dominant after pit grows to a sizable depth. In fact, the growth of any deep pits will always be mass transfer controlled regardless of how aggressive the biofilm is

A mechanistic model for CO2 corrosion with protective iron carbonate films

The mechanistic model of uniform CO corrosion is presented which covers: electrochemical reactions at the steel surface, diffusion of species between the metal surface and the bulk including diffusion through porous surface films, migration due to establishment of potential gradients and homogenous chemical reactions including precipitation of surface films. The model can predict the corrosion rate, as well as the concentration and flux profiles for all species involved. Comparisons with laboratory experiments have revealed the strengths of the model such as its ability to assist in understanding of the complex processes taking place during corrosion in the presence of surface films

Probabilistic modelling of CO2 corrosion laboratory data using neural networks

The present paper addresses two major concerns that were identified when developing neural network based prediction models and which can limit their wider applicability in the industry. The first problem is that it appears neural network models are not readily available to a corrosion engineer. Therefore the first part of this paper describes a neural network model of CO2 corrosion which was created using a standard commercial software package and simple modelling strategies. It was found that such a model was able to capture practically all of the trends noticed in the experimental data with acceptable accuracy. This exercise has proven that a corrosion engineer could readily develop a neural network model such as the one described below for any problem at hand, given that sufficient experimental data exist. This applies even in the cases when the understanding of the underlying processes is poor. The second problem arises from cases when all the required inputs for a model are not known or can be estimated with a limited degree of accuracy. It seems advantageous to have models that can take as input a range rather than a single value. One such model, based on the so-called Monte Carlo approach, is presented. A number of comparisons are shown which have illustrated how a corrosion engineer might use this approach to rapidly test the sensitivity of a model to the uncertainities associated with the input parameters. (C) 2001 Elsevier Science Ltd. All rights reserved

NAPHTHENIC ACID CORROSION OF MILD STEEL IN THE PRESENCE OF SULFIDE SCALES FORMED IN CRUDE OIL FRACTIONS AT HIGH TEMPERATURE

ABSTRACT Increasing demand on the oil market has raised interest in oils with high naphthenic acid (NAP) concentration. These oils were previously considered of lower quality due to their corrosive character. Processing such oils at elevated temperatures encountered in refineries (300-350°C) may cause aggressive corrosive attack on the inside walls of equipment such as pipes and distillation towers. Naphthenic acid corrosion attack is a nonaqueous corrosion process and can be retarded by sulfur containing compounds inherently present in crude oil fractions in the form of soluble sulfides. Although these sulfides can be corrosive as well, they can also form iron sulfide scale on the metal surfaces potentially offering a degree of protection against naphthenic acid attack. However the iron sulfide scales can be removed from metal surfaces under the combined effects of high velocity flow and NAP attack. This research project has focused on the role of iron sulfide scales formed in different crude oil fractions on samples made from mild as well as chromium containing steels. They were exposed to naphthenic acid attack under high flow rates at high temperature

Turbulent flow around a rotating stepped cylinder

Direct numerical simulation (DNS) of turbulent flow around a rotating cylinder with two backward-facing steps axisymmetrically mounted in the circumferential direction was performed and compared with DNS of plane backward-facing step flow (PBSF) of Le [J. Fluid Mech. 330, 349 (1997)]. The original motivation of this work stemmed from the efforts to design a simple device which can generate flows of high turbulence intensity at low cost for corrosion researchers. It turned out that the current flow shows flow structures quite similar to those of PBSF downstream of the step, even though configurations of the two flows are totally different from one another. The stepped cylinder appears to be a cost-effective tool in the generation of flow structures similar to those of PBSF. (C) 2002 American Institute of Physics